Patent Application
20250052917
The present invention relates to the field of seismic detection systems and methods for a grid framework structure. The grid framework structure supports remotely operated load handling devices on tracks located on a grid framework structure for handling storage containers or bins stacked in the grid framework structure.
Storage systems comprising a three-dimensional storage grid structure, within which storage containers/bins are stacked on top of each other, are well known. PCT Publication No. WO2015/185628A (Ocado) describes a known storage and fulfilment system in which stacks of bins or containers are arranged within a grid framework structure. The bins or containers are accessed by load handling devices remotely operative on tracks located on the top of the grid framework structure. A system of this type is illustrated schematically in
As shown in
The grid framework structure 14 comprises a plurality of upright members or upright columns 16 that support horizontal members 18, 20. A first set of parallel horizontal grid members 18 is arranged perpendicularly to a second set of parallel horizontal grid members 20 to form a plurality of horizontal grid structures supported by the upright members 16. The members 16, 18, 20 are typically manufactured from metal and typically welded or bolted together or a combination of both. The bins 10 are stacked between the members 16, 18, 20 of the grid framework structure 14, so that the grid framework structure 14 guards against horizontal movement of the stacks 12 of bins 10, and guides vertical movement of the bins 10.
The top level of the grid framework structure 14 includes rails 22 arranged in a grid pattern across the top of the stacks 12. Referring additionally to
A known load handling device 30 shown in
The load handling device 30 is equipped with a lifting device or crane mechanism to lift a storage container from above. The crane mechanism comprises a winch tether or cable 38 wound on a spool or reel (not shown) and a grabber device 39. The lifting device comprises a set of lifting tethers 38 extending in a vertical direction and connected nearby or at the four corners of a lifting frame 39, otherwise known as a grabber device (one tether near each of the four corners of the grabber device) for releasable connection to a storage container 10. The grabber device 39 is configured to releasably grip the top of a storage container 10 to lift it from a stack of containers in a storage system of the type shown in
The wheels 34, 36 are arranged around the periphery of a cavity or recess, known as a container-receiving recess or container receiving space 40, in the lower part. The recess is sized to accommodate the container 10 when it is lifted by the crane mechanism, as shown in
In other examples, the container-receiving space 40 of the load handling device 30 may not be located within the body 32 of the load handling device 30. For example, in some examples, the container receiving space 40 may be adjacent to the body 32 of the load handling device 30, e.g. in a cantilever arrangement with the weight of the body 32 of the load handling device 30 counterbalancing the weight of the container to be lifted. In such embodiments, a frame or arms of the lifting device may protrude horizontally from the body 32 of the load handling device 30, and the lifting tethers 38 may be arranged at respective locations on the protruding frame/arms and configured to be raised and lowered from those locations to raise and lower a container 10 into the container-receiving space 40 adjacent to the body 32.
The grid framework structure is subjected to various external and internal forces. These include but are not limited to ground movement which can be attributed to the composition of the ground or soil type, forces developed by the movement of the load handling devices on the grid framework structure which can weight in excess of 100 kg, movement as a result of nearby constructions or moving vehicles such as trains or even during an earthquake or storm. It is paramount to keep the individual elements within the grid framework structure intact as a result of such external forces experienced by the grid framework.
To ensure stability of the grid framework structure, prior art storage systems are largely dependent on various supports and bracing arranged within or at least partly along the periphery of the grid. However, the use of various supports and bracing (anti-movement braces) to stabilise the grid framework structure from internal and external forces is disadvantageous for a number of reasons. The grid framework structure occupies space or area which could be utilised by the grid to store containers; in that it prevents optimum usage of available space or area for the storage of containers. The need of a supporting structure may limit the available options for positioning of the grid framework structure since any auxiliary grid supporting structure often requires connection to a surrounding structure such as the inner walls of a building and the requirement of a supporting structure that is not cost efficient.
WO2019/101367 (Autostore Technology AS) teaches a grid supporting structures for integration in a storage grid structure of an automated storage system. The grid supporting structure is made up of four storage columns interconnected by multiple vertically inclined support struts. The storage column profiles has a cross-section comprising a hollow centre section and four corner sections, each corner section comprises two perpendicular bin guiding plates for accommodating a corner of a storage bin. The support struts have a width which allows them to fit in between two parallel guiding plates so as to not compromise the ability of the storage columns to accommodate a stack of containers or storage bins.
An alternative grid framework structure is thus required that minimises the impact of the available space or area for the storage of containers so as to provide a free-standing storage grid or at least requiring a less extensive auxiliary grid support structure.
Much of the world's population is located along seismic fault lines or in the paths of powerful storms such as hurricanes and tornadoes. Locating the grid frame structure in such areas are at risk of structural damage from seismic and storm events as the current grid framework structure may not hold the grid structure together. Powerful seismic and storm events may result in the failure of their structural integrity e.g. as a result in the inability of the structural fasteners to keep the grid firmly attached to the upright members. Earthquakes can be labelled into four categorises labelled as Type A, B, C, or D depending on the severity of the earthquake, whereby Type A is considered the least powerful earthquake and Type D is considered the most powerful earthquake. Type A-D can be graded by their spectral acceleration which is the maximum acceleration measured in g that an object, above ground level, will experience during an earthquake. Type D considered to represent the most powerful seismic event and typically, has a measured spectral acceleration in the region 0.5 g to 1.83 g (short period spectral response acceleration SDS see https://www.fegstructural.com/seismic-design-category-101/) and is the result of most failure of buildings. As powerful seismic events act on a structure, the three dimensional dynamic forces compromise the structural fasteners holding the grid framework structure together, causing them to work their way loose or out of the members in which they are embedded or, if they remain in place, they may tear their way through a structural fastener.
Many jurisdictions, such as the US states, have passed laws mandating that all new buildings, residential or commercial be constructed with certain seismic bracing features incorporated therein. A grid framework structure comprises internal bracing features incorporated within the grid framework structure whereby one or more of the upright members are braced together by one or more bracing members or bracing towers is shown in
After a seismic event, the state of the grid framework structure needs to be assessed. Manual inspection after the seismic event is possible, but of course it is preferable to understand the state of the grid framework structure before sending in personnel.
The first step before any damage in the grid framework structure can be rectified is to understand the extent of the damage, in particular to measure the extent of yielding in the grid framework structure. To do this manually would require measuring the position of the structural members at the edge and inside the grid framework structure, which is a labour-intensive and time-consuming process. Another method of measuring displacement is required that does not require manual intervention.
A seismic detection system is therefore needed that can determine whether a seismic event has taken place, and assess the extent of yielding of the grid framework structure without the need for humans to enter the grid and take measurements manually.
One aspect of the invention provides a method for detecting seismic events, the method comprising the steps of:
Acceleration data is acquired from the one or more accelerometers as a signal of acceleration as a function of time. Differential acceleration is calculated by subtracting the ground acceleration data from the acceleration data, and is the difference between the acceleration data and the ground acceleration data. Differential acceleration represents the acceleration of the grid framework structure relative to the ground.
The given period of time represents the time between the start of the seismic event and the end of the seismic event. For example, the given period of time could be the time during which the acceleration measured by the accelerometers is significantly higher than background acceleration, or the period of time during which the differential acceleration is above a minimum acceleration threshold.
The step of determining displacement data may comprise performing double integration on the differential acceleration data. Integrating the differential acceleration once with respect to time gives differential velocity (the velocity of the grid framework structure relative to the ground). Integrating the differential acceleration a second time, i.e. integrating the differential velocity with respect to time, gives the displacement data. The displacement data represents differential displacement (the displacement of the grid framework structure relative to the ground as a result of movement of the grid framework structure), and is a signal of displacement as a function of time. The acceleration data and displacement data represent the acceleration and displacement of the points on the grid structure where each of the one or more accelerometers are located, relative to the ground. The ground acceleration data represents the acceleration of the ground, since the ground acceleration data is acquired from one or more accelerometers located on the ground, and provides a reference point for calculating differential acceleration data.
The one or more accelerometers located on the ground may be attached to a substructure (for example, a concrete foundation or slab) upon which the grid framework structure is built, or alternatively the one or more accelerometers located on the ground may be directly placed on top of the soil (e.g. located inside a hole in the substructure).
The step of determining whether a seismic event has taken place may comprise one or more of the following steps:
In each of these three cases a), b) and c), the step of determining whether a seismic event has taken place may comprise identifying the presence of one or more characteristic oscillation regimes in the displacement data, where the one or more characteristic oscillation regimes comprise:
In each of these three cases a), b) and c), determining whether a seismic event has taken place may comprise comparing the displacement data or a parameter derived from the displacement data to a predetermined threshold. In case a) non-proportional response, the predetermined threshold may comprise a displacement threshold; in case b) period elongation, the predetermined threshold may comprises a predetermined frequency and/or a predetermined period of oscillation; and in case c) residual drift, the predetermined threshold may comprise a predetermined static displacement threshold. Each of these three characteristic oscillation regimes is described in more detail below.
Case a), the non-proportional response regime, may occur when a structural member of the grid framework structure extends beyond its elastic limit and exhibits inelastic behaviour.
The step of determining whether a seismic event has taken place over the given period of time may comprise determining whether the displacement data exceeds a predetermined displacement threshold corresponding to the elastic limit of a member of the grid structure. The step of determining whether a seismic event has taken place may comprise identifying the non-proportional response regime by determining whether the displacement is proportional to the acceleration.
Case b), the period elongation regime, may occur when a structural member yields and the dynamic properties of the grid framework structure have changed as a result.
The step of determining whether a seismic event has taken place may comprise determining a change in a frequency and/or period of oscillation of the displacement data over the given period of time. Determining the change in the frequency and/or period of oscillation of the displacement data may comprise determining whether the frequency and/or period of oscillation differs from a predetermined frequency and/or a predetermined period of oscillation. The step of determining the change in the frequency and/or period of oscillation of the displacement data may comprise calculating a Fourier transform of the displacement data to obtain a frequency spectrum of the grid framework structure. The method may further comprise the step of providing reference displacement data representative of the behaviour of the grid framework structure in the absence of seismic events, and calculating a Fourier transform of the reference displacement data to obtain a reference frequency spectrum of the grid framework structure. The method may further comprise the step of comparing the frequency spectrum of the grid framework structure to the reference frequency spectrum of the grid framework structure. The natural frequency of oscillation of the grid structure can be obtained from the frequency spectrum of the grid framework structure. If the natural frequency obtained from the reference frequency spectrum of the grid framework structure (i.e. the natural frequency in the absence of seismic event) is different to the natural frequency obtained from the frequency spectrum of the grid framework structure, then the change in the natural frequency may be an indication of yielding in the grid framework structure.
Case c), the residual drift regime, may occur when there is a static displacement of the grid framework structure that remains after oscillations die down, i.e. the static displacement indicates that an accelerometer has moved from its initial position.
Displacement data can be divided into two parts: oscillating displacement or dynamic displacement, representing the oscillation of the accelerometer about its centre position, and static displacement, representing movement of the centre position of the oscillating displacement relative to its origin or initial position. Dynamic displacement indicates that the accelerometer's position is oscillating about its centre position, and static displacement indicates that the accelerometer has moved or been displaced from its origin or initial position. The displacement data is a superposition of oscillating displacement and static displacement.
The step of determining whether a seismic event has taken place over the given period of time may comprise determining a static displacement from the displacement data and determining whether the static displacement exceeds a predetermined static displacement threshold.
If the centre position of the oscillating displacement remains at the origin, then the static displacement is zero. However, if a structural member upon which an accelerometer is mounted yields, the accelerometer will move so that the centre position of its oscillating displacement is no longer at the accelerometer's origin or initial position. This movement of the centre position can also be described as residual drift, meaning that once the oscillating displacement has died down or attenuated, the accelerometer is displaced (i.e. has drifted) from its initial position.
Rather than determining whether a seismic event has taken place from the presence of any non-zero static displacement or residual drift, it is advantageous to define a predetermined static displacement threshold that is greater than zero. When the static displacement is above this predetermined static displacement threshold, it is considered that a seismic event has taken place. A predetermined static displacement of zero would pick up small displacements, and cause false alarms due to small displacements that are not caused by seismic events (e.g. measurement errors).
Any or all of the three cases a) b) and c) can be used to determine whether a seismic event has taken place. In some cases it may be advantageous to use more than one of these methods, to ensure that the event is indeed a seismic event, and not a false positive (for example, residual drift/static displacement could be detected if an accelerometer moves relative to the grid framework structure rather than indicating failure of a structural member to which it is mounted).
The method may further comprise the step of filtering the acceleration data to remove or attenuate one or more signals associated with non-seismic events. Non-seismic events that may cause vibration signals may include normal operation of a storage and retrieval system or other machinery in the same building or in the surrounding area. For example, vibrations can be generated by load handling devices moving on the grid framework structure, or conveyor systems, pick stations, movement of vehicles (e.g. fork lift trucks), or other machinery in the same building. Outside the building, vibrations can be generated by passing traffic, roadworks, or movement of the ground. Filtering out these non-seismic signals is advantageous because the filtered data is cleaner and it is less likely that false positives will occur (i.e. the method detects a seismic event when no seismic event has occurred).
The step of filtering the acceleration data may comprise using a high-pass filter, low-pass filter, and/or a band filter. A high-pass filter removes or attenuates signals at a frequency below a threshold frequency and permits signals at a frequency above the threshold frequency to pass through. A low-pass filter removes or attenuates signals at a frequency above a threshold frequency and permits signals at a frequency below the threshold frequency to pass through. A band filter removes or attenuates signals at a frequency below a lower threshold frequency or above a higher threshold frequency, and permits signals at a frequency between the lower threshold frequency and the upper threshold frequency to pass through. Filtering is advantageous because it can remove noise at frequencies other than the frequency range of interest, for example the frequency range within which seismic events occur, or the frequency range within which the signal is likely to change as a result of a seismic event.
The step of the step of filtering the acceleration data to remove or attenuate one or more signals associated with non-seismic events may comprise determining the frequency ranges at which oscillation occurs in the absence of seismic events, and attenuating or filtering out these frequency ranges from the acceleration data.
The step of filtering the acceleration data to remove or attenuate one or more signals associated with non-seismic events may comprise providing reference acceleration data representative of the behaviour of the grid framework structure in the absence of seismic events, determining the frequency ranges in the reference acceleration data at which oscillation occurs in the absence of seismic events, and attenuating or filtering out these frequency ranges from the acceleration data.
Determining which frequency ranges to filter out can be done by taking a Fourier transform of the acceleration and/or the reference acceleration data in order to obtain the frequency spectrum.
The one or more accelerometers located on the grid framework structure may comprise a plurality of accelerometers, and the step of determining whether a seismic event has taken place may be based on displacement data from the plurality of accelerometers.
An advantage of using a plurality of accelerometers located on the grid framework structure is that there is redundancy built into the method. If a first accelerometer fails to detect a seismic event, then a second accelerometer is performing the same task and can detect the seismic event if the first accelerometer does not. If the method relied solely upon a single accelerometer located on the grid framework structure, then any issues with the single accelerometer would mean that seismic events would not be detected.
In some examples with a plurality of accelerometers located on the grid framework structure, a voting system can be used to determine whether a seismic event has taken place. Each accelerometer would vote “yes” or “no” depending on whether or not the data acquired by that accelerometer positively identifies a seismic event. For example, a seismic event can be considered to have taken place if a majority of the plurality of accelerometers vote “yes” (i.e. the data from the majority of the plurality of accelerometers positively identifies that a seismic event has taken place). A threshold for determining whether a seismic event has taken place can be based on a proportion of the plurality of accelerometers voting “yes”; the threshold can be a number of accelerometers (e.g. at least 10 accelerometers) or a proportion of the total number of accelerometers (e.g. a majority or 50%, two in three, 75%).
The step of determining whether a seismic event has taken place may comprise at least two out of three of the plurality of accelerometers detecting a seismic event. In this case, if there are three accelerometers located on the grid framework structure, a seismic event will be considered to have taken place if the first and second accelerometers vote “yes” but the third votes “no”.
The method may further comprise the step of sending a signal to one or more output devices in response to determining that a seismic event has taken place over the given period of time. This is important in order to alert personnel to the seismic event and allow the building to be evacuated. The method may further comprise the step of using the differential acceleration and/or the displacement data to determine whether:
These different states of the grid framework structure will be described in more detail later.
In examples where the one or more accelerometers comprise a plurality of accelerometers distributed across the grid framework structure, the method may further comprise the step of using the differential acceleration and/or the displacement data to determine the extent of damage to different parts of the grid framework structure.
The method may further comprise the step of preparing the grid framework structure for further seismic activity if the method detects the early stages of a seismic event.
The step of preparing the grid framework structure for a seismic event may comprise one or more of the following steps:
Alternatively or additionally, preparatory actions may be taken as a result of an alert from a seismic early warning system, otherwise known as Earthquake Early Warning (EEW) or Early Warning System (EWS). Such systems operate on the principle that electronic alerts from the region of the epicentre of the seismic event can travel more quickly than seismic waves. During a seismic event, P-waves (pressure waves or primary waves) are followed by S-waves (shear waves or secondary waves). P-waves are longitudinal compression waves, travel faster than S-waves, and can be transmitted through the liquid layers of the Earth's interior. S-waves are transverse shear waves, more destructive than P-waves but travel more slowly. When a seismic event occurs, the initial P-waves trigger sensors that detect their presence. The location and magnitude of the seismic event is estimated from the P-waves, and the system sends an alert to affected areas. Locations farther from the epicentre of the seismic event can have some seconds or minutes to prepare before the more destructive S-waves arrive. The combination of early warning systems and automated responses can help to prevent some of the injuries and damage typically associated with major seismic events.
Appropriate actions can be taken as a result of an alert from a seismic early warning system. For example, personnel can be evacuated from the building housing the grid framework structure, vehicles can be parked and power sources (e.g. engines or motors) switched off, and other machinery turned off or shut down. In addition the steps for preparing a grid framework structure as described above are applicable.
In another aspect, the invention provides a method of condition monitoring a grid framework structure following a seismic event, the grid framework structure comprising:
The purpose of condition monitoring is to determine the condition of the grid framework structure after a seismic event, e.g. the extent of damage to different portions of the grid framework structure. Condition monitoring after a seismic event is important in order to assess the extent of damage to different portions of the grid framework structure, and will enable the grid framework structure to be repaired faster and reduce downtime. Without condition monitoring, the entirety of the grid framework structure would need to be assessed for damage, and more importantly there would be no indication of whether the grid framework structure is safe for personnel to enter. The predetermined acceleration threshold is an acceleration value that is used to define the status of a portion of the grid framework structure, i.e. different actions (e.g. inspection, repair) may be required depending on whether or not the differential acceleration exceeds the predetermined acceleration threshold.
The predetermined acceleration threshold may comprise a plurality of predetermined acceleration thresholds, each of the plurality of predetermined acceleration thresholds being indicative of a different level of damage to one or more of the portions of the grid framework structure. This enables different portions of the grid framework structure to be classified or categorised according to the level of damage, so that appropriate action (e.g. inspection and/or repairs) can be undertaken efficiently.
The plurality of predetermined acceleration thresholds may comprise a first acceleration threshold indicative of an elastic limit of a portion of the grid framework structure, such that the differential acceleration of the portion of the grid framework structure exceeding the first acceleration threshold provides an indication that the portion of the grid framework structure has been permanently deformed. If permanently deformed, then the portion of the grid framework structure may not be in a suitable condition to continue operating, for example load handling devices may not be able to travel on deformed or misaligned tracks, and load handling devices may not be able to lift storage containers from the stacks if the vertical uprights are deformed or misaligned. If not permanently deformed, then the portion of the grid framework structure may be in a suitable condition to continue operating, for example the tracks have returned to their original shape and position so load handling devices can still operate on the tracks, and the vertical uprights have returned to their original shape and position so the load handling devices can continue to lift storage containers from the stacks in order to retrieve products for customer orders.
The first acceleration threshold may be substantially 0.6 g.
The plurality of predetermined acceleration thresholds may comprise a second acceleration threshold indicative of a safety limit, such that the differential acceleration of a portion of the grid framework structure exceeding the second acceleration threshold provides an indication that it is not safe for personnel to enter the portion of the grid framework structure. Understanding which portions of the grid framework structure are safe for personnel to enter is advantageous, both for reducing the risk to personnel and for enabling personnel to confidently and safely inspect those portions of the grid framework structure which are safe for personnel to enter.
The second acceleration threshold may be substantially 1.0 g.
The plurality of predetermined acceleration thresholds may comprise a third acceleration threshold indicative of a structural limit, such that the differential acceleration of a portion of the grid framework structure exceeding the third acceleration threshold provides an indication that the portion of the grid framework structure does not have sufficient structural capacity to resist aftershocks. The structural limit is a measure of whether the portion of the grid framework structure has sufficient structural capacity to resist aftershocks, i.e. if the differential acceleration has remained below the structural limit then the portion of the grid framework structure is able to resist aftershocks, and if the differential acceleration has exceeded the structural limit, then the portion of the grid framework structure is not able to resist aftershocks, and is therefore in danger of collapsing as a result of aftershocks. If the third acceleration threshold has been exceeded, then no personnel should enter the grid framework structure.
The third acceleration threshold may be substantially 1.83 g.
The method may further comprise the steps of:
The predetermined displacement threshold may be indicative of an elastic limit, such that the displacement of a portion of the grid framework structure exceeding the predetermined displacement threshold provides an indication that the portion of the grid framework structure has been permanently deformed. If the displacement of the portion of the grid framework structure is below the predetermined displacement threshold, then the elastic limit has not been exceeded, and the portion of the grid framework structure has deformed elastically and returned to its original position. This may indicate that the portion of the grid framework structure can continue operating as usual, i.e. the tracks supporting the load handling devices are not misaligned so can continue to be used.
Knowing which portions of the grid framework structure have not exceeded the elastic limit is advantageous, because some portions may be able to continue operating as usual while other portions are assessed for damage and repaired as necessary. Ensuring business continuity, i.e. being able to continue fulfilling customer orders, is a great advantage.
In another aspect, the invention provides a seismic detection system for a grid framework structure configured to carry out the method of any preceding claim, the seismic detection system comprising:
In some cases, the input module may also supply power to the accelerometers.
The seismic detection system may further comprise an output module configured to allow the controller to send a signal to one or more output devices.
The seismic detection system may further comprise one or more accelerometers located on the ground near the grid framework structure. The one or more accelerometers located on the ground near the grid framework structure may be used to acquire ground acceleration data, to be used as a reference in calculating the differential acceleration data as described above.
The one or more output devices may comprise beacons, alarms, and/or sirens.
In another aspect, the invention provides a grid framework structure, comprising
The one or more accelerometers mounted on the grid framework structure may comprise a plurality of accelerometers arranged along the first direction and/or the second direction of the grid. For example, the first direction may represent an X-direction, and the second direction a Y-direction perpendicular to the X-direction. The accelerometers may be arranged in one or more lines along the X-direction and/or the Y-direction, or arranged in a grid pattern. The plurality of accelerometers may be arranged along at least a portion of the periphery of the grid. For example, the plurality of accelerometers may be arranged in a line along one edge of the grid, or two edges of the grid, or three edges of the grid, or all four edges of the grid. In some examples, a portion of the plurality of accelerometers may be arranged on the periphery of the grid and the remainder of the accelerometers arranged within the grid. At least a portion of the plurality of accelerometers may be arranged diagonally relative to the first and second direction of the grid. For example, a portion of the plurality of accelerometers may be arranged in a diagonal line across the grid. Combinations of these and other arrangements are also possible.
The plurality of accelerometers may lie in a substantially horizontal plane. The accelerometers may be in the same plane as the grid itself (e.g. mounted on the tracks or on the horizontal grid members), or in a parallel horizontal plane. The accelerometers may be located at or near the top of the grid framework structure, in order to measure the differential acceleration between the top of the grid framework structure and the ground.
An advantage of having a plurality of accelerometers distributed horizontally on the grid framework structure is that the accuracy of the data is improved. A greater number of accelerometers enables the displacement of the grid framework structure to be determined with greater accuracy and in more detail.
A further advantage of having a plurality of accelerometers distributed horizontally on the grid framework structure is that the data from the accelerometers can be used to determine which part(s) of the grid framework structure have suffered damage in a seismic event. If one part of the grid framework structure is damaged but another part is intact, then it may be possible for load handling devices to keep operating on the undamaged part of the grid while the damaged part is repaired. Also the accelerometer data can be used to determine the extent of yield/damage to the grid framework structure, for example to determine whether a part of the grid framework structure has not gone beyond the elastic limit and can continue operating as usual, or is damaged but safe for personnel to enter to assess the situation and take remedial action, or is so damaged that it would not be safe for personnel to enter that area of the grid framework structure.
The plurality of accelerometers may consist of between 15 and 28 accelerometers.
The one or more accelerometers mounted on the grid framework structure may be mounted on the horizontal grid members. In some examples, the accelerometers may be mounted on the tracks, or on the track supports, or on the vertical uprights.
The grid framework structure may further comprise an exoskeleton comprising a plurality of vertical frame columns braced by one or more bracing members, the grid being further supported by the exoskeleton to form a seismic force restraint system (SFRS). As will be discussed in more detail later, the exoskeleton provides further support to the grid framework structure and protects the grid framework structure from damage in case of seismic events.
The one or more accelerometers mounted on the grid framework structure may be mounted on the SFRS. In particular, the one or more accelerometers mounted on the grid framework structure may be mounted to the one or more bracing members. The bracing members act as sacrificial members in the case of a seismic event (i.e. the bracing members will yield first and protect the grid framework structure from damage), so by placing accelerometers on the bracing members, the seismic detection system is able to detect whether the bracing members have yielded. If the bracing members have not yielded, then the grid and the supporting framework structure are intact and can continue operating. It is advantageous to be able to determine that parts of the grid are undamaged and can continue operating, because then at least part of the storage system can continue fulfilling customer orders without significant downtime, thus reducing costs and enabling continuity of the business.
The grid framework structure may be subdivided into a plurality of modular frames, such that the grid extends across the plurality of modular frames. In examples where the grid framework structure is modular, some or all of the modular frames may be supported by an exoskeleton. Each of the plurality of modular frames may comprise an exoskeleton comprising a plurality of vertical frame columns braced by one or more bracing members, the grid being supported by the exoskeleton to form a seismic force restraint system (SFRS), wherein adjacent modular frames are arranged such that at least a portion of the SFRS is shared between adjacent modular frames.
Another way of describing a modular grid framework structure is an assembly comprising a plurality of modular frames, wherein each of the plurality of modular frames comprises a grid framework structure and the grid extends across the plurality of modular frames, and at least one of the plurality of modular frames comprises the seismic detection system as described above.
An advantage of subdividing the grid framework structure into a plurality of modular frames is that if one of the modular frames yields due to seismic events, other modular frames may be unaffected and able to continue operating.
The grid framework may further comprise a seismic isolation system for reducing seismic forces acting on the grid framework structure, wherein the grid framework structure is supported by the seismic isolation system, the seismic isolation system comprising a superstructure and a substructure, and at least one base isolation device disposed between the superstructure and the substructure such that the at least one base isolation device suppresses movement of the superstructure relative to the substructure in a seismic event.
The seismic isolation system has the advantage of partially isolating or decoupling the grid framework structure from its foundation, so that horizontal components of ground movement during seismic events are attenuated. The at least one base isolation device enables relative motion of the superstructure and the substructure, so not all of the horizontal movement of the ground is translated into horizontal movement of the grid framework structure.
In another aspect, the invention provides a multi-storey grid framework structure, comprising:
The advantage of a multi-storey grid framework structure is that more storage space is provided for the same footprint. This is particularly useful in territories where usable land is at a premium, so there is an advantage in building upwards rather than outwards so as to make the most efficient use of available space.
In another aspect, the invention provides a storage and retrieval system, comprising
Further features and aspects of the present invention will be apparent from the following detailed description of an illustrative embodiment made with reference to the drawings, in which:
As an alternative to the grid framework structure 114 supporting the two-dimensional grid 50 directly on a plurality of upright columns 116 as described with reference to
The prefabricated modular panels of the grid framework structure described above comprise upright columns 116. For example, a sub-group of the upright columns can be braced by one or more bracing members to form prefabricated panels or frames. For the purpose of the present invention, the plurality of upright columns 116 can also include the upright columns 116 in the prefabricated panels. The grid framework structure 114 can comprise any appropriate supporting framework structure to support the grid, including upright columns 116 directly supporting the grid, and/or prefabricated panels and/or frames incorporating upright columns 116.
A connection plate or cap plate 150 as shown in
The first and the second set of grid members supports a first and a second set of tracks or rails 22a, 22b respectively for a load handling device to move one or more containers on the grid framework structure. In some examples the tracks 22a, 22b may be integral with the grid members. In other examples, the tracks may be mounted on top of the grid members (also known as track supports). For the purpose of explanation of the present invention, the intersections 56 constitute nodes of the grid structure. Each of the rectangular frames 54 constitute a grid cell and are sized for a remotely operated load handling device or bot travelling on the grid framework structure to retrieve and lower one or more containers stacked between the upright columns 116. The grid 50 is raised above ground level by being mounted to the plurality of upright columns 116 at the intersections or nodes 56 where the grid members 118, 120 cross so as to form a plurality of vertical storage locations 58 for containers to be stacked between the upright columns 116 and be guided by the upright columns 116 in a vertical direction through the plurality of substantially rectangular frames 54. For the purpose of the present invention, a stack of containers can encompass a plurality of containers or one or more containers.
The grid framework structure 114 can be considered as a free standing (or self-supporting) rectilinear assemblage of upright columns 116 supporting the grid 50 formed from intersecting horizontal grid members 118, 120, i.e. a four wall shaped framework. Two or more of the upright columns are braced by at least one diagonal bracing member to provide one or more braced towers 80 within the grid framework structure 114. The structural rigidity and moment resistance of the grid framework structure is largely provided by incorporating one or more truss assemblies or braced towers 80 at least partially around the periphery and/or within the body of the grid framework structure (see
The grid framework structure is anchored to the ground, in this case superstructure, by one or more anchor bolts. In an embodiment of the present invention, one or more of upright columns at their lower end are mounted to the superstructure by an adjustable foot (see
In addition to mounting the upright columns making up the grid framework structure by the adjustable foot discussed above, one or more of the upright columns making up the braced towers 80 are anchored to the superstructure by one or more anchor feet 132a, 132b (see
Based on the constraints given by the applied loads, the anchor foot 132b of the present invention comprises a stabiliser 136 comprising a plurality of discrete fingers or digits 138 extending from an upright portion 140 such that loads are distributed amongst the plurality of fingers 138, e.g. separate fingers. In the particular embodiment of the present invention shown in
One or more of the discrete fingers 138 of the anchor foot 132b extend or span out in two or more different directions from the upright portion 140 so as to provide improved stability of the anchor foot 132b. One or more of the fingers 138 are of different lengths to aid with the stability of the anchor foot 132b of the present invention. The length of the fingers 138 can be different so provide different levels of stability of the braced tower 80. One or more connecting webs 142 are used to support the one or more of the fingers 138 from axial movement. The anchor foot 132b is anchored to the concrete foundation by one or more bolts through holes in the fingers 138 of the anchor foot 132b.
In the particular embodiment of the present invention, five fingers 138 of varying length are shown (see
While the current grid framework structure 114 is adequate where the ground is relatively stable, i.e. having a spectral acceleration less than 0.33 g categorised as Type A and Type B events, this cannot be said where the grid framework structure is subjected to powerful seismic events generating strong lateral forces in excess of 0.55 g spectral acceleration categorised as a Type C or D seismic event. Such powerful seismic events compromise the structural fasteners joining the grid elements (e.g. track support elements) at the intersections, causing them to work their way loose or out of the cap plates to which they are bolted to. The result is the weakening or complete loss of structural integrity of the grid framework as the lateral forces no longer are able to be transferred safely down to the structural foundations. Failure may occur at the intersections of the grid members or track support elements making up the grid. The bracing towers 80 described above used to maintain the structural integrity of the grid framework structure may not able to withstand the lateral forces as a result of powerful Type D seismic events well in excess of 0.55 g.
One way of mitigating the above problem is to support the grid framework structure by an exoskeleton, as described in WO2021175873 (Ocado), the contents being herein incorporated by reference. The exoskeleton provides an additional level of support to the grid framework structure from seismic event. More specifically, the exoskeleton comprises a plurality of vertical frame columns 218 braced by at least one bracing member, said grid being further supported by the exoskeleton to form a seismic force restraint system (SFRS).
The present invention as shown in
The SFRS can be imagined to form an exoskeleton around the grid framework structure of the present invention. In the particular embodiment of the present invention, the perimeter bracing structure 215 is supported by at least one vertical frame column 218a at the corners of the grid framework structure and braced by at least one horizontal frame beam 220 extending from the corners of the grid framework structure. In the particular embodiment of the present invention as shown in
At least two of the vertical frame columns 218a, 218b are joined together by at least one diagonal bracing member 222 to form a braced frame to provide lateral support for the grid framework structure in the front and/or the back direction. The braced frame is a structural system which is designed to resist earthquake forces. The diagonal bracing members 222 are designed to work in tension and compression, similar to a truss and are designed to resist lateral loads in the form of axial stresses, by either tension or compression. A braced frame can be arranged around the periphery of the grid framework structure or at least one face of the grid framework structure and designed to absorb the bulk of the lateral forces experienced by the grid framework structure.
Any type of braced frame commonly known in the art to provide lateral support to the grid and/or grid framework structure is applicable in the present invention. In
Each of the plurality of vertical frame columns 218a, 218b can be solid supports of C-shape or U shape cross section, double C or double U. Preferably, each of the plurality of vertical frame columns 218a, 218b are solid supports of I-shape comprising upper and lower beam flanges. At least two of the vertical frame columns 218a, 218b are rigidly joined together by the at least one bracing member 220, e.g. a diagonal bracing member 222 and/or a horizontal frame beam. Each of the at least two of the vertical frame columns 218a, 218b has a top end and a bottom end; the bottom end is anchored to a concrete foundation using one or more anchor bolts. Various methods commonly known in the art to anchor the bottom end of the vertical frame columns to the concrete foundation to provide lateral support to the braced frame against powerful seismic event is applicable in the present invention.
Multiple braced frames of the SFRS can be disposed around the periphery of the grid framework structure (i.e. around each face of the grid framework structure) to form a unitary frame body as shown in
At least one 218b of the plurality of vertical frame columns 218a, 218b can be disposed intermediate of or between two vertical frame columns 218a at the corners of the grid framework structure so as to divide the exoskeleton into a braced frame where at least two vertical frame columns 218a, 218b are braced by at least one diagonal brace 222 and a drag strut or collector 232. A drag strut or collector 232 is where the at least two vertical frame columns 218a, 218b are braced by the horizontal frame beams 220 at the top of the two vertical frame columns 218a, 218b and functions to collect and transfer diaphragm shear forces to the vertical frame columns 218a, 218b. In the particular embodiment of the present invention shown in
In some examples, the seismic grid framework structure 214 can be modularised such that adjacent modules 514 of a grid framework structure in an assembly of two or more modules or modular frames share at least a portion of the SFRS 215 of one or more neighbouring modular frames. Each of the modules 514 comprises a seismic grid framework structure discussed above with reference to
Sharing of the at least a portion of the SFRS by adjacent modules can be envisaged in the top plan view shown in
Also shared between adjacent modules are the vertical frame columns 218a, 218b supporting the at least one bracing member 220, 222. By sharing portions of the SFRS between adjacent modules, the external bracing structures of adjacent modules 514 work together in tandem as a unitary body to deflect lateral forces. Putting it another way, joining grids 50 from adjacent modules by a common bracing member 220, 222, e.g. horizontal frame beam, the multiple adjacent grids 50 can function together to form at least one Vierendeel truss such that lateral forces are transferred across the multiple grids to the vertical frame columns 218a, 218b at the periphery of the modules. The perimeter bracing structure 215 shared between adjacent modules 514 also provide internal bracing within the assemblage of the modules 514. The internal bracing includes adjacent modules sharing a common braced frame 230 and/or a common drag strut 232.
The seismic grid framework structure of the present invention allows a mezzanine 702 to be integrated into the perimeter bracing structure 215 and the vertical frame columns 218 of the present invention. The ability to modularise the seismic grid framework structure discussed above allows the mezzanine 702 to share at least a portion of the SFRS of adjacent modules, i.e. share a common braced frame 230 and/or drag strut 232 with adjacent or neighbouring modules. A cross sectional view of an assembly of modules 514 incorporating a mezzanine 702 integrated within the assembly is shown in
To create the mezzanine, vertical frame columns 218a, b supporting the grid frame structure of adjacent or laterally disposed modules 514 are connected together by one or more bracing members, e.g. horizontal frame beams to create a mezzanine floor and one or more diagonal bracing members 222. The vertical support (frame) columns supporting the mezzanine floor can be braced to provide more support to the mezzanine structure as shown in
In the particular arrangement illustrated in
The grid framework structure is divided into two parts, and a mezzanine 700 extends over a pick aisle 702 between the two parts. The pick aisle 702 can accommodate pick stations or other service areas underneath the grid 50. The perimeter bracing structure 215 extends around the modules 514, the pick aisle 702, and the mezzanine 700. A further mezzanine 704 extends to the side, in order to provide a maintenance area where load handling devices can be de-inducted from the grid in order to perform routine maintenance activities or repairs. The mezzanine 704 also provides more space underneath the grid 50 for storage or service areas.
In an exemplary embodiment, such as that illustrated in
In examples where the grid framework structure 114 comprises an SFRS or perimeter bracing structure 215 as in the example illustrated in
In examples where the grid framework structure is modular and comprises an assembly of modular frames 514 as described above with reference to
The seismic detection system 300 further comprises a controller 306 communicatively coupled to the input module for processing data acquired from the one or more accelerometers 302. The controller 306 may be described as a cDAQ (compact data acquisition), and again may be either specially designed for the purpose or an off-the-shelf component. The controller 306 may be provided with a mains power supply.
The seismic detection system 300 further comprises an output module 308 coupled to one or more output devices 310. The output module is communicatively coupled to the controller 306 and configured to receive a signal from the controller 306 indicative of a seismic event. The output module 308 may be a relay output module. In some examples, multiple relays can trigger based on different criteria. Output devices 310 can include alarms, beacons, sirens, graphical user interface displays, or any other suitable output device. The controller 306 may be located in a maintenance area located adjacent to or near to the grid framework structure. The accelerometers 302 may be connected to the controller 306 wirelessly or via cables (in which case, a junction box may be used). The signal processing and data analysis is carried out by the controller 306.
In some examples, further processing of the data can take place after the event to confirm that a seismic event has occurred, and/or to perform further calculations.
The input modules 304 are connected to input terminals 318, which in turn are connected to connection points 320 on the outside of the outer casing 316. The connection points 320 connect cables from the accelerometers 302 on the grid framework structure and also from the ground accelerometer 302a located on the ground.
The output module 308 is connected to relay output terminals 322, which in turn are connected to an output device 310 (in this case, a beacon with three different colours, and a buzzer). When a seismic event is detected, the beacon can light up to give a visual display and the buzzer can sound to give an audible warning. Different colours can be used to represent the severity of the seismic event (e.g. red for the most severe events, yellow for less sever events, and green for no event detected). After a seismic event, the output device 310 can be reset using an alarm reset key switch 324.
A UPS (uninterruptible power supply) 326 and a UPS battery 330 are provided, which connect to the controller 306 via power input terminals 328. The UPS ensures that the seismic detection system can still operate if mains power is cut off. A UPS is generally used to provide emergency power to a load when the input power source or mains power fails, and will provide near-instantaneous protection from input power interruptions.
A wireless router 332 is provided to transmit data from the controller. Wireless antennae 334 are provided on the outside of the outer casing 316. The data from the controller may be transmitted to a computer stored locally (for example, in the maintenance area) or to the cloud, as described above.
The outer casing 316 is provided with mounting points 336, for mounting the outer casing to a wall or other structure.
In some examples, the controller 306 of the seismic detection system can be integrated into other control systems for the grid framework structure 114.
The one or more output devices 310 can be used by personnel to check the status of the grid framework structure, and determine whether it is structurally safe to access after an event. Visual and audible indicators can be used to communicate the status and to let personnel know whether it is safe to access the grid. For example, visual indicators may indicate a status of red, amber, or green. A red status means that the grid framework structure is unsafe and the building needs to be evacuated; amber status means that the grid framework structure is safe for personnel to enter but needs to be inspected and repaired or realigned before load handling devices can operate on the grid; and green status means that the grid framework structure is safe to continue operating.
In some cases, spectral acceleration thresholds may be used to determine whether the status is red, amber, or green. For example, if the measured acceleration has exceeded a predetermined spectral acceleration threshold, the status of the grid framework structure may be classified as “red”. In some cases there may be more than one predetermined spectral acceleration threshold; for example if a lower spectral acceleration threshold is exceeded the status could be defined as “amber”, and if an upper spectral acceleration threshold is exceeded the status could be defined as “red”.
The one or more output devices 310 may be remote i.e. not located inside the building where the grid framework structure is housed, so that personnel can check the status remotely in case they are unable to access the building.
After a seismic event, the one or more output devices may be reset (e.g. alarms turned off) so that they do not continue to operate after investigation and/or remedial action.
In examples where the grid framework structure comprises an SFRS or external bracing structure, it may be advantageous to place accelerometers on structural members of the bracing structure, since these members are expected to buckle first in a seismic event. In the grid framework structure illustrated in
The accelerometers 302 may be located at or near the top of the grid framework structure. This enables the displacement of the grid to be measured relative to displacement on the ground, and gives an indication of yield at the top of the structure.
The accelerometer 302a located on the ground can be attached to a concrete foundation or slab upon which the grid framework structure is built, or alternatively the accelerometer 302a can be directly placed on top of the soil (for example, located inside a hole in the concrete foundation slab).
A recent study (see https://www.nature.com/articles/s41598-018-37716-y) found that the record of asymmetric vertical accelerations observed during a magnitude 6.3 earthquake could be explained by a “flapping effect”, i.e. the local, elastic bouncing of a foundation slab on which the sensor was installed. The results suggest that the extremely large accelerations recorded did not reflect the actual ground shaking, but were caused by a local, system response around the sensor. This finding has important implications for both the evaluation of seismic hazard and the installation methodology of accelerometers in all earthquake prone countries. A simulation model consisting of the foundation slab and an irregular contact surface between the slab and underlying soil successfully explained both the mainshock and aftershock records. The elastic bouncing of the slab (the “flapping effect” is induced by vertical motion through a system with variation in the horizontal direction, e.g., the foundation slab sitting on an irregular surface. Rather than representing the actual shaking of the ground, the measurements are at least partially a local system response around the sensor.
An irregular contact surface allows local elastic bouncing of the concrete slab during earthquake ground shaking. Such an irregular contact surface, which would have been created by differential settlement of the soil or soil erosion over time, was confirmed by site investigation; some minor gaps (<1 cm) between the concrete slab and soil ground were found.
To prevent similar soil-slab interactions in a grid framework structure, the foundation slab can be firmly attached to the soil ground, for example using piles or anchors. Alternatively or additionally, slab properties (thickness, stiffness) may be designed to minimize the effect of elastic bouncing. Alternatively or additionally, the ground accelerometer 302a may be placed directly onto soil ground, for example through a hole or gap in the foundation slab. The term “located on the ground” in this specification should be interpreted to cover both the situation where the accelerometer 302a is secured to the foundation slab, and the situation where the accelerometer is located directly on the soil ground.
Further examples of possible arrangements of accelerometer locations are illustrated in
In the arrangement illustrated in
In the arrangement illustrated in
In the arrangement illustrated in
In the arrangement illustrated in
In the arrangement illustrated in
These arrangements of accelerometers are examples only, and other arrangements are possible. Although the illustrated examples are applied to a modular seismic grid framework structure, these arrangements of accelerometers could also be used on a standard non-seismic grid framework structure, either modular or non-modular. The number of accelerometers may scale with the size of the grid. In examples where the grid is modular, the number of accelerometers may scale with the number of modules 514.
In some examples, increasing the number of accelerometers beyond a given number will result in diminishing returns, i.e. a further increase in the number of accelerometers will provide no substantial further improvement in accuracy of the acceleration data. Marginal improvements in accuracy from adding more accelerometers to the seismic detection system may not justify the increased cost and increased complexity of a system with a larger number of accelerometers.
The distribution of accelerometers on a grid framework structure is different from that which would be required for other structures, for example for a building. A building might have one or two accelerometers on each floor, whereas the grid framework structure has a larger number of accelerometers at or towards the top of the grid framework structure. The difference in distribution is required because the seismic detection system on a grid framework structure is able to detect which parts of the grid are damaged-a typical grid framework structure for a storage and retrieval system extends over a wide area. A seismic detection system in a building, on the other hand, needs to determine which floors of a building are safe for humans to enter, so the accelerometers are likely to be distributed vertically (one on each floor) rather than distributed horizontally (many accelerometers on the top floor). In a building, the purpose of a seismic detection system is to assess the structural integrity of each floor or each level of the building, whereas in a grid framework structure the purpose of a seismic detection system is to assess the structural integrity of the entire grid framework structure, which is located on the ground in a building.
A typical building in a seismic zone will be a tower block or other tall multi-storey building with many floors, but not extending over a wide area compared to the building's height. This is especially true in locations like Japan where usable land is at a premium, so there is a tendency to build upwards rather than outwards. For this reason, the distribution of the accelerometers is different from what would be typical in a tall building; the accelerometers are distributed horizontally rather than vertically, and are at or near the top of the grid framework structure. The accelerometers may be distributed in a substantially horizontal plane.
For example,
The use of a number of accelerometers in different locations distributed over the grid framework structure, rather than a single accelerometer, is advantageous because it permits the damaged section(s) of the grid to be identified after a seismic event. Arrangements of accelerometers surrounding the grid on two or more edges are particularly useful because they enable identification of which parts of the grid are sufficiently undamaged to keep operating as usual, which parts are too damaged to resume operation immediately but safe enough to send personnel in to fix the damage, and which parts are dangerous to personnel.
In examples where the grid framework structure is a seismic grid framework structure (either modular or a single structure), accelerometers can be mounted directly on the bracing structure. In particular, accelerometers may be mounted on horizontal frame beams 220, which extend horizontally along the edges of the grid. If an accelerometer mounted on a horizontal frame beam indicates a residual drift, then the horizontal frame beam has yielded. Positioning accelerometers on the perimeter bracing structure 215 enables the seismic detection system to determine whether the members of the perimeter bracing structure have yielded. In examples where the grid framework structure is an assembly of modular frames (as in
A seismic event can produce a range of different failure modes or states of the grid framework structure, which have different consequences and require different actions.
The state of the grid framework structure may also be determined based on the spectral acceleration measured by the accelerometers at the top of grid framework structure. The grid framework structure has a natural period and a natural frequency, which will depend on the size, shape, and materials from which the grid framework structure is built. After a seismic event has taken place, the data can be analysed to determine whether the frequency spectrum during the seismic event contained components close to the natural frequency of the grid framework structure; if so, more damage would be expected, since an applied oscillation close to the natural frequency or the natural period would result in resonance, and therefore a higher amplitude of vibration.
Many building codes place a limit of the maximum movement allowed during a seismic event before a structure is classed as “failed”. For example, in the US the maximum permitted lateral displacement measured during a seismic event is 2% of the structure's height, while in Japan the maximum permitted lateral displacement measured during a seismic event is 0.5% of the structure's height. If a structure is classed as “failed” according to building codes, the structure may need to be recertified by an appropriately qualified person before it can be considered as compliant with the building code.
Grid framework structures may be very large structures, with thousands of components that could potentially fail. If there is no means of identifying where damage has occurred, every critical part of the grid framework structure would have to be inspected individually. Visual inspection of parts on the outside of the grid framework structure is relatively straightforward, but inspecting parts inside the grid framework structure, especially given the presence of stacks of storage containers, is extremely time consuming, since the storage containers would need to be moved in order to permit visual inspection of the components within the grid framework structure.
When a storage and retrieval system is taken offline for inspection after a seismic event, this is extremely expensive because the system cannot fulfil customer orders while offline. It is therefore advantageous to minimise downtime and get the storage and retrieval system back up and running as quickly as possible.
On the other hand, if a storage and retrieval system continues to operate when it is damaged, this can affect other systems or threaten safety, so it is important to ensure that the system is safe and capable of normal operation before bringing the system back online.
There is a large difference in costs between “Immediate Occupancy” and “Life Safety” failure modes. If there is no means of distinguishing which state the grid framework structure is in, it is necessary to take a more cautious approach to avoid endangering life.
In some examples, particularly where the grid framework structure is modular, different parts of the grid framework structure may be in different states, for example some parts could be safe to continue operating as normal, some parts could safely be entered by personnel in order to replace damaged parts, and some parts are not safe. Understanding the state or failure mode of different parts of the grid framework structure enables downtime to be minimised while ensuring the safety of personnel and compliance with building codes.
The method of generating displacement data to determine whether a seismic event has taken place is illustrated in
In step 101, the raw data is captured by the accelerometers in the form of a signal of acceleration with respect to time.
The data is filtered in step 102. The first task of the controller upon receiving a signal from an accelerometer is to filter the signal to remove excessive noise. This can be done, for example, by using a band filter to band limit the waveform (i.e. to attenuate or remove oscillations that are above or below the specified frequency band), or by using a high-pass filter to attenuate low-frequency vibrations, or by using a low-pass filter to attenuate high-frequency noise.
Additionally, the controller may filter out other known sources of noise, for example vibrations caused by load handling devices moving on the grid framework structure, or frequencies associated with other components or peripherals on the grid framework structure, or even in the same building. In order to do this, the known sources of noise must be characterised by recording the background acceleration signal in the absence of seismic activity, and then analysing this background acceleration signal to determine characteristic background frequencies, e.g. by calculating the Fourier transform of the acquired signal in the frequency domain. These characteristic background frequencies can then be filtered out or attenuated from the acceleration signals received by the controller from the accelerometers. Alternatively, the Fourier transform of the background acceleration signal can be subtracted from the Fourier transform of the acceleration signal from the accelerometers, so that events due to characteristic background frequencies are removed from the signal. In this way, it becomes easier to detect seismic events because any unusual events can more easily be distinguished from the background noise.
Filtering out known sources of noise is important for a seismic detection system for a grid framework structure, especially for grid framework structures that do not have an exoskeleton to provide further support during seismic events. The load handling devices accelerating and decelerating as they move on top of the grid is an additional movement that must be taken into account. This movement will affect the accelerometer readings more so than, say, people moving within a building, because people in a building are likely to be distributed vertically on different floors rather than all at the top of the structure, and likely to be moving more slowly and not continuously. People in a building are likely to move vertically (e.g. taking lifts up and down between different floors) at least as much as horizontally, and buildings are likely to be empty at certain times of day rather than full of people moving continuously. For this reason, filtering out known sources of noise is advantageous.
A ground accelerometer 302a is provided, located on the ground beside or underneath the grid framework structure. The ground accelerometer measures the acceleration at the ground level. At step 103, the acceleration at ground level is then used to calculate the differential acceleration of the accelerometers at the top of the grid framework structure relative to the ground. The controller subtracts the acceleration signal measured by the ground accelerometer from the acceleration signal measured by the accelerometers at the top of the grid framework structure, in order to calculate the differential acceleration.
At step 104, the controller determines the displacement of the grid framework structure relative to the ground from the calculated differential acceleration. This can be achieved mathematically by performing a double integration on the differential acceleration signal (i.e. integrates with respect to time once to obtain a velocity signal, then integrates with respect to time again to obtain a displacement signal). A displacement signal is therefore obtained from each of the accelerometers.
At step 105, the displacement data can be analysed to determine whether a seismic event has taken place.
The first regime is non-proportional response, characterised by high-amplitude spikes. In this regime, the amplitude (displacement response) is not proportional to the applied force. This indicates that the yield strength of a structural member has been surpassed, and the material is no longer exhibiting linear elastic behaviour. In the absence of seismic events, the material of the structural components behaves linearly and obeys Hooke's law, where the displacement is proportional to the applied force:
F=k x
where F is the applied force, k is the stiffness or spring constant of the material, and x is the displacement. The stiffness k depends on the cross-sectional area, the length, and the Young's modulus of the material. The above equation is true when the material of the structure components is below its yield strength. When the yield strength is exceeded, the material starts behaving non-linearly and the value of k is no longer a constant. In the non-proportional response regime the displacements may be higher than would be expected when the material is behaving elastically.
Non-proportional response can be detected by determining whether the amplitude of the displacement signal exceeds a predetermined displacement threshold corresponding to the elastic limit of a structural member of the grid framework structure. Alternatively, non-proportional response can be detected by comparing the acceleration signal (after filtering) with the displacement signal, and determining whether the amplitudes of the two signals are proportional.
The second regime is period elongation, in which the time period of the oscillation is increased from its usual value. This happens because yielding changes the dynamic properties of the grid framework structure. To determine the period of oscillation, a Fourier transform of the signal in the frequency domain can be calculated. The largest spike in the frequency domain will be the oscillation frequency of the grid framework structure during the period elongation regime of the seismic event. To determine whether the period has changed, the oscillation period can be compared to a reference period, corresponding to the natural frequency of vibration of the grid framework structure. The natural frequency can be determined by taking a Fourier transform of the displacement signal in the absence of any seismic events.
The third regime is residual drift, in which there is a static non-zero displacement remaining once the displacement oscillations have stopped or returned to their usual level. This can be seen as the dashed line on
These three regimes (non-linear response, period elongation, residual drift) provide three different methods to identify failure from the displacement time signal. In practice any one of these three methods can be used, or a combination of two or all three. The simplest method is residual drift, as this simply means that the structure has moved after a seismic event, which suggests failure. It has the advantage that it is straightforward to estimate the extent of the yielding of the structure from the magnitude of the static displacement. However, the residual drift method alone may not be sufficiently accurate, and is subject to the risk of false positives (e.g. if the accelerometers have moved rather than the grid structure itself). Using a combination of methods will yield a more accurate result.
The non-proportional response and period elongation methods are more complex and require more analysis. However, these two methods are more indicative of yield failure in the grid framework structure, as the only time that the non-proportional response and period elongation phenomena occur is when the grid framework structure yields. If non-proportional response and/or period elongation are detected, then it is likely that there has been a yield failure. Determining the extent of the yield failure is more difficult with these methods, whereas the residual drift allows easy estimation of the extent of the yield. It is therefore preferable to use a combination of all three methods.
In some cases, adaptive gain control can be used to compensate for differences between predicted and measured peak-to-peak displacement as a function of frequency, as will be described below. For a range of frequencies, the peak-to-peak displacement of the accelerometer is calculated according to the method described above and illustrated in
In cases where the error in displacement calculation is a fixed percentage of the displacement, this error can be corrected by multiplying the calculated displacement by a gain or scale factor. This procedure is repeated across a range of frequencies, resulting in a reference curve of the gain or scale factor vs. frequency. This reference curve can be applied to calculated peak-to-peak displacements in order to correct the error and more accurately estimate the peak-to-peak displacement of the accelerometers.
To simulate residual drift (see the residual drift regime illustrated in
The accelerometers do not measure exactly zero when at rest, due to background noise and to the equipment input offset voltage on the acceleration measurements. This offset voltage is small, but adds up when double integrated over a long time. To compensate for this effect, offset compensation (e.g. by an averaging algorithm) can be applied to the signal to counteract the offset voltage.
As for dynamic displacement, the calculated static displacements tend to be underestimated at low frequencies. Adaptive gain control can therefore be applied, as described above with reference to the peak-to-peak displacement calculation.
The seismic detection system and method of the invention can equally be applied to a multi-storey storage system located in a multi-storey building. In some examples, as well as having a grid framework structure on the ground floor of a building, further grid framework structures can be located on one or more upper floors of the building. For example, an ambient grid framework structure for ambient-temperature goods can be located on the ground floor, and a (usually smaller) chill grid framework structure for chilled temperature goods can be located on an upper floor. This could be the first floor of the building, i.e. the floor directly above the ground floor, or a higher floor, for example the second or third or fourth floor. In other examples, there may be three or more grid framework structures in the same building, located on different floors. In some examples, a single grid framework structure could be located on a higher floor of a multi-storey building instead of on the ground floor.
The seismic demand is the acceleration or force that the ground movement (represented by the signal illustrated in
The seismic capacity is the acceleration or force that a building or structure can resist, which is a function of the materials and design of the structure. For engineering design, it is a requirement that the seismic capacity is greater than or equal to the seismic demand. The seismic capacity of the upper and lower grid framework structures is illustrated by the left-pointing arrows in
When calculating differential acceleration for a grid framework structure on an upper floor, the same method can be used as described earlier in this application. Differential acceleration can be calculated by taking the difference between acceleration measured by the upper grid accelerometers 108 and the upper floor accelerometer 107, as well as by taking the difference between acceleration measured by the upper grid accelerometers 108 and the ground accelerometer 105. This enables the movement of the upper grid structure 103 to be characterised both relative to the floor that it rests on within the building 100, and to the ground.
In some examples, the grid framework structure comprises a seismic isolation system for reducing the seismic forces acting on the grid framework structure. A cross sectional view of one example of a seismic isolation system 208 is shown in
Inter disposed between the superstructure 202 and the substructure 200 are one or more base isolation devices 204. The distribution of the base isolation devices 204 can be tuned to remove any irregularities or possible torsional issues in the superstructure 202. The one or more base isolation devices 204 decouple the superstructure 202, and thus the grid framework structure 114 mounted thereon, from the motion of the substructure or ground motion during earthquakes. In this way, large deflections and high accelerations are prevented being transmitted to the grid framework structure 114. The number and distribution of the one or more base isolation devices 202 is dependent on the weight of the grid framework structure, the height of the grid framework structure, and the composition of the ground. For example, while the energy of seismic waves with higher frequencies tends to be absorbed by solid rock soil, the seismic waves with lower frequency pass through the solid rock soil without being absorbed but are eventually amplified by soft sediments. Base isolation devices can be distributed in an array having a grid like pattern, each of the base isolation devices 204 being respectively mounted between the substructure 200 and the superstructure 202 by lower and upper mounting plates. The base isolation devices provide the lateral flexibility of the seismic isolation system to attenuate ground movement being transmitted to the grid framework structure. Various known base isolation devices that attempt to get maximum energy dissipation by damping are permissible in the present invention. Options include (but are not limited to) elastomeric bearings, sliding bearings or a combination thereof.
In examples where the grid framework structure is located in a multi-storey building, the grid framework structure may be located on an upper floor rather than on the ground floor. Alternatively, a second grid framework structure could be located on an upper floor, in addition to a grid framework structure located on the ground floor. Usually the seismic demand in a multi-storey building is higher for upper floors, but in examples where the entire building utilises a seismic isolation system (i.e. the building is supported by the superstructure 202, which can move relative to the substructure 200), in some cases the seismic demand may be lower on higher floors than on the ground floor.
In this document, the language “movement in the n-direction” (and related wording), where n is one of x, y and z, is intended to mean movement substantially along or parallel to the n-axis, in either direction (i.e. towards the positive end of the n-axis or towards the negative end of the n-axis).
In this document, the word “connect” and its derivatives are intended to include the 25 possibilities of direct and indirection connection. For example, “x is connected to y” is intended to include the possibility that x is directly connected to y, with no intervening components, and the possibility that x is indirectly connected to y, with one or more intervening components. Where a direct connection is intended, the words “directly connected”, “direct connection” or similar will be used. Similarly, the word “support” 30 and its derivatives are intended to include the possibilities of direct and indirect contact.
For example, “x supports y” is intended to include the possibility that x directly supports and directly contacts y, with no intervening components, and the possibility that x indirectly supports y, with one or more intervening components contacting x and/or y. The word “mount” and its derivatives are intended to include the possibility of direct and indirect mounting. For example, “x is mounted on y” is intended to include the 5 possibility that x is directly mounted on y, with no intervening components, and the possibility that x is indirectly mounted on y, with one or more intervening components.
In this document, the word “comprise” and its derivatives are intended to have an inclusive rather than an exclusive meaning. For example, “x comprises y” is intended to include the possibilities that x includes one and only one y, multiple y's, or one or 10 more y's and one or more other elements. Where an exclusive meaning is intended, the language “x is composed of y” will be used, meaning that x includes only y and nothing else.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2118417.1 | Dec 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/086239 | 12/15/2022 | WO |
