Patent Application
20140325922
Structures, such as buildings, bridges, and underwater superstructures, experience unique loading conditions during adverse weather conditions or seismic events. Such wind or seismic loading imposes constant, periodic, or irregular forces on the frame members of the structure. These forces displace at least a portion of the frame members. A structure may fail (i.e. plastically deform, collapse, etc.) where the displacement in the frame members exceeds a structural limit for the frame members, joints, and other components of the structure. A structure may utilize one or more damping systems to reduce the likelihood of failure.
Traditional methods for preventing a structure from failing include designed elasticity, passive damping systems, and viscous damping. Designed elasticity is often included as part of the initial design process of the structure and involves strategically positioning frame members to create an at least partially flexible structure. For a structure having designed elasticity, an input force may displace frame members without plastically deforming the structure. Passive damping systems similarly prevent a structure from failing but incorporate a passive system designed to reduce displacement of the frame members. By way of example, a building may include a weight positioned in an elevated position to counteract building sway. However, these systems are most efficiently installed during the initial design and construction of the structure thereby rendering them of reduced applicability to previously erected structures.
Other passive damping systems include damping devices (e.g., elastomeric isolators, isolation bearings, etc.) positioned within the structure or between the structure and a ground volume to reduce displacement of the structure. Viscous damping utilizes dampers positioned between frame members to dissipate energy and reduce displacement of the structure. However, these systems are most efficiently installed during the initial construction of the structure, and a structure may require numerous damping devices to reduce the displacement of frame members during adverse weather conditions or seismic events.
One exemplary embodiment relates to a fluid transport system for actively damping oscillations of a structure affixed to a ground surface. The system includes a pipe defining a flow path, a driver in fluid communication with the pipe and configured to provide a fluid flow through the pipe, and a controller. The controller is programmed to send a fluid flow command signal in response to an event signal indicating an oscillation event.
Another exemplary embodiment relates to an active damping system for a structure affixed to a ground surface. The system includes a driver and a fluid outlet, the fluid outlet configured to be coupled along an outer surface of the structure in an elevated location relative to the ground surface. The system also includes a connection pipe extending between the driver and the fluid outlet and defining a flow path and a controller. The controller is programmed to send a fluid flow command signal in response to an event signal indicating an oscillation event.
Still another exemplary embodiment relates to a structure affixed to a ground surface. The structure includes a structural frame, a pipe coupled to the structural frame, the pipe defining a flow path, and a driver in fluid communication with the pipe and configured to provide a fluid flow through the pipe. The structure also includes a controller, and the controller is programmed to send a fluid flow command signal in response to an event signal indicating an oscillation event.
Yet another exemplary embodiment relates to a method for actively damping a structure affixed to a ground surface by transferring fluid. The method includes providing a pipe, the pipe defining a flow path, providing a fluid flow through the pipe with a driver, and sending a fluid flow command signal with a controller in response to an event signal indicating an oscillation event.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here.
The damping systems described herein are intended to reduce the displacement of frame members within a structure during adverse weather conditions and seismic loading. Specifically, a system employing fluid active damping is intended to reduce the displacement of frame members within a structure by providing a force to counter wind and seismic loading. Damping systems may include lengths of pipe, tanks, or other structures that provide a fluid flow therethrough providing a countering force. In other embodiments, damping systems locate a fluid in different positions to change the fundamental period of the building. The fluid damping devices described herein are intended to offer various advantages relative to existing damping systems. Such advantages include, among others, the ability to deliver the fluid into numerous orientations within the structure, provide variable damping forces by changing the fluid flow rate, and utilize the fluid for another purpose (e.g., to provide water to operate fixtures within a building, to provide a fluid as part of a fire suppression system, etc.).
Further, the damping systems described herein may include a sensor (e.g., geophone, accelerometer, etc.) to facilitate real-time engagement of the damping system. Various control schemes may be included to further reduce the displacement of frame members within a structure during adverse weather conditions and seismic loading. Such schemes are intended to actively damp oscillations of a structure. Among other benefits, active fluid damping systems may be installed during the initial construction of a structure or retrofitted into existing structures.
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According to an exemplary embodiment, building 10 includes an elevated portion 14 extending upwards from base portion 12. As shown in
According to an exemplary embodiment, elevated portion 14 includes a frame, shown as super structure 16. In some embodiments, super structure 16 is designed to support the vertical weight loads of building 10 including the weight of floors, occupants, office spaces, structural beams, or still other elements. As shown in
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In some embodiments, flow device 60 is in fluid communication with tube 70 and directs a fluid (e.g., water, hydraulic oil, a mixture including sand and water, etc.) through tube 70. According to an exemplary embodiment, flow device 60 is a centrifugal pump that delivers the fluid at a fluid flow rate (e.g., 100 gallons per minute, 100,000 gallons per minute, 300,000 gallons per minute, etc.). In some embodiments, flow device 60 includes an impeller that is rotated by an input device. Such an input device may be an electric motor, a fossil fuel powered engine, a liquid fueled rocket, a solid fueled rocket, compressed air, or another system. According to an alternative embodiment, flow device 60 is another type of pump. According to still another alternative embodiment, flow device 60 is a compressed fluid (e.g., air, nitrogen, etc.) that propels a fluid through tube 70. In still other alternative embodiments, flow device 60 is a tank that stores a compressed fluid. Once activated, such a flow device 60 releases the compressed fluid into tube 70.
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According to an exemplary embodiment, fluid damping device 50 reduces the oscillations of building 30 by delivering a fluid through damping portion 72. As shown in
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According to an exemplary embodiment, fluid damping device 50 having lift portion 74, damping portion 72, lift portion 78, and damping portion 76 reduces the oscillations of building 30. As shown in
For an incompressible fluid and a constant area damping portion, a portion of the damping force is related to the product of the flow rate, fluid density, and change in velocity of the flowing fluid. Various factors impact the change in velocity of the flowing fluid including, among others, the surface roughness of the interior wall of damping portion 72 or the presence of paddles or interference members within damping portion 72. According to an exemplary embodiment, damping portion 72 includes an interior surface roughness designed to inhibit fluid flow (e.g., cast iron or another material and include an absolute roughness of 260 microns, concrete having a surface roughness of between 0.3 and 3 millimeters, etc.). In other embodiments, damping portion 72 includes at least one of an orifice and a flange to increase the change in velocity across damping portion 72.
While fluid flowing through damping portion 72 provides a damping force in a first direction, the fluid also provides a damping force in the opposite direction as it flows through damping portion 76. According to an exemplary embodiment, such a damping force is incorporated as part of a fluid damping strategy of fluid damping device 50. In other embodiments, the fluid damping strategy reduces damping forces due to fluid flowing through damping portion 76. Such a reduction may occur by reducing the surface roughness of the interior wall of damping portion 76, coupling damping portion 76 to a ground volume, or coupling damping portion 76 to building 30 with isolators (e.g., resilient members, dampers, etc.), among other alternatives.
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According to an exemplary embodiment, a fluid is disposed within the inner volume at least one of tank 112 and tank 114. According to an alternative embodiment, fluid damping device 110 includes an inlet pipe to couple flow device 116 with a fluid supply (e.g., retaining pond, container, etc.). Because of the fluid communication between flow device 116, tank 112, and tank 114, a fluid may be repositioned by flow device 116 into tank 112, into tank 114, emptied from both tank 112 and tank 114, or otherwise delivered through fluid damping device 110. According to an exemplary embodiment, the fluid is initially positioned within tank 112 (serving as the fluid supply), and flow device 116 delivers the fluid from tank 112 into tank 114. According to an alternative embodiment, the fluid is initially positioned within tank 114, and flow device 116 delivers the fluid from tank 114 into tank 112. It should also be understood that flow device 116 may selectively flow a fluid from a fluid supply into at least one of tank 112 and tank 114. Fluid damping device 110 may utilize the motion of the fluid flowing into tank 112 or tank 114 to provide a damping force to building 100 through super structure 108.
According to an alternative embodiment, fluid damping device 110 includes various fluid storage devices located in at least one of different elevations along elevated portion 106 and in different lateral positions relative to super structure 108. Such devices may include additional components (e.g., directional flow valves, check valves, etc.) to facilitate flow between the fluid storage devices. By way of example, fluid damping device 110 may include four fluid storage devices arranged as a first set positioned at a first elevation and a second set positioned at a second elevation. At least one flow device may deliver a fluid between the four fluid storage devices. The pairs of fluid storage devices may be positioned such that fluid flow between the first set of fluid storage devices provides a damping force along a first direction and fluid flow between the second set of fluid storage devices provides a damping force along a second direction. In some embodiments, the first direction is perpendicular to the second direction. Still other arrangements of fluid storage devices and piping may be provided to provide damping forces in still other directions, according to various alternative embodiments.
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Lift pipe 156, first damping branch 160, and second damping branch 170 define a plurality of flow paths between flow device 152, nozzles 162, and nozzles 172. According to an exemplary embodiment, flow device 152 delivers a fluid through lift pipe 156 and out of at least one of nozzles 162 and nozzles 172. In some embodiments, fluid is provided to nozzles 162 and nozzles 172 when flow device 152 is engaged (e.g., during an oscillation event). In other embodiments, fluid damping device 150 includes a valve to selectively deliver the fluid through nozzles 162 and nozzles 172 when flow device 152 is engaged. A controller selectively actuates the valve between a first position and a second position as part of a control scheme. In other embodiments, the valve is manually operable.
In still other embodiments, fluid damping device 150 includes a plurality of valves (e.g., a valve associated with each damping branch, a valve associated with each nozzle, etc.). In some embodiments, flow device 152 pressurizes the fluid (e.g., within a container, within lift pipe 156 and the damping branches, etc.). Upon actuation of the valves, the pressurized fluid is released through at least one nozzle. In some embodiments, flow device 152 continues to provide a fluid flow to the nozzles upon actuation of the valve such that the fluid flow from the nozzles is continuous. In other embodiments, flow device 152 pressurizes the fluid and thereafter disengages such that the fluid is directed from the nozzles in discrete amounts rather than as a continuous flow.
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According to an exemplary embodiment, nozzles 162 and nozzles 172 each include a central axis. In some embodiments, the central axes of nozzles 162 and 172 are perpendicular to a central axis of building 140 (i.e. orthogonal to an outer surface of building 140). In other embodiments, at least a portion of the nozzles are arranged such that the central axes are angularly offset from an outer surface of building 140 to, by way of example, direct the fluid flow downward, upward, or to a side of building 140. In still other embodiments, fluid damping device 150 includes at least one moveable nozzle (i.e. a nozzle not having a fixed orientation relative to a structural frame of building 140 to provide variable damping forces). Regardless of orientation, fluid damping device 150 imparts damping forces from nozzles 162 and nozzles 172 to building 140 along an axis opposite the direction of fluid flow.
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It should be understood that the damping device described herein may include any combination of flow devices, pipes, tanks, nozzles, or other components to provide damping forces during an oscillation event. Specifically, combinations of flow devices, pipes, tanks, nozzles, or other components may be incorporated in a configuration particularly suited for a structure. In some embodiments, the locations and orientations of the nozzles are selected based on knowledge of a selected natural vibrational mode of the structure (e.g., at sites of maximum modal deflection). The selected natural mode may be one whose modal frequency is similar to a potential seismic excitation frequency. The selected natural mode may be chosen based on numerical calculations of oscillations of the structure in response to anticipated seismic excitations. In some embodiments, the damping device includes specific components tailored for a particular loading condition (e.g., sharp seismic loading, dull or rolling seismic loading, wind loading, etc.) of a structure. By way of example, the damping device may include a fluid storage device positioned in an elevated location and a flow device that delivers a fluid from the fluid storage device out from a nozzle. Such a configuration may reduce the response time (i.e. the time between engaging the flow device and the structure experiencing damping forces), and such a reduction may be particularly relevant for sharp seismic loading capable of producing short duration yet large magnitude oscillations. In some embodiments, multiple flow devices are provided and situated at various locations within the damping device.
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According to an exemplary embodiment, fluid damping device 210 delivers a fluid into tank 220 during an oscillation event to change the natural vibration mode of building 200. It should be understood that the natural vibration mode of structures may vary based on, among other factors, the materials used to build the structure, the design of the structure (i.e. the arrangement of structural components), and the distribution of weight within the structure. The weight of the fluid delivered into tank 220 may vary the distribution of weight within building 200 thereby altering the natural vibration mode and the frequency response of building 200 during an oscillation event. According to an alternative embodiment, fluid is delivered from a fluid storage device to alter the natural vibration mode of building 200, changing the mode's frequency and/or spatial shape.
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According to an exemplary embodiment, a fluid damping device includes a controller and a fluid flow device. The controller interfaces with the fluid flow device. The controller may send or receive command signals to engage or disengage the fluid flow device, change the direction of the fluid flow from the fluid flow device, or change the rate that the fluid is discharged from the fluid flow device, among other alternatives. In some embodiments, the controller sends a command signal after receiving an event signal indicating an oscillation event. By way of example, a sensor (e.g., geophone, accelerometer) that detects seismic activity, acceleration, structural stress or strain, structural deflection, fluid mass, volume, or forces, or another phenomena may send the event signal. In some embodiments, the sensor is coupled to a portion of the structure (e.g., the top of a building, a middle point of a bridge, other suitable locations, etc.). In some embodiments, accelerations can be measured along multiple directions, or in different sites. Differential accelerations between different directions or locations may be used to measure modal excitations. Structural deflections may be derived (e.g., from double integration of accelerations) or directly measured relative to external references (e.g., with a global positioning system, a differential global positioning system, interferometers, or other metrology tools), according to various alternative embodiments. In other embodiments, the sensor interacts remotely with a fluid damping device (e.g., sensors positioned at established geographic seismology facilities, etc.).
According to an exemplary embodiment, the controller includes a module coupled to the sensor, and the sensor provides a sensor signal to the module. Such a module processes the sensor signal and determines whether an oscillation event may occur, is occurring, or has occurred. In some embodiments, the module includes various parameters (e.g., a threshold acceleration or displacement, etc.), the parameters allowing the module to identify an oscillation event and provide an event signal. According to an exemplary embodiment, the module provides the event signal to the controller, which provides a command signal to a component of the fluid damping device.
According to an exemplary embodiment, the controller includes a processing circuit to implement a control strategy that damps oscillations within a structure. In some embodiments, the control strategy is computed in real-time based on numerical simulations of the oscillation. In other embodiments, the control strategy is selected from one or more pre-derived control strategies. During an oscillation event, such as an earthquake, a building may sway significantly. Failure to implement a control strategy may impart excessive stresses within the structure. Such excessive stresses may allow a building to experience the first, second, or third failure modes.
In some embodiments, the controller implements a control strategy that incorporates several damping techniques. It should be understood that some earthquakes exhibit loading that provides the largest displacement within the first minute and the largest peak loading within the first half of the seismic event. According to an exemplary embodiment, a sensor coupled to a building senses at least one of a building oscillation and a building displacement. In some embodiments, a controller interprets the sensor data, determines whether the data indicates an oscillation event based on a threshold acceleration (e.g., 1.0 meters per second squared) or a threshold displacement (e.g., 0.5 meters), and interfaces with a fluid damping device (e.g., turn on a fluid flow device, engage a valve to facilitate fluid flow, etc.) to provide damping forces. In other embodiments, the controller engages the damping device to apply predetermined damping forces after receiving various features describing an oscillation event (e.g., location, magnitude, and starting time of an earthquake).
According to an exemplary embodiment, the fluid damping device provides damping forces to particular locations of the building. The distribution of damping forces may be related to the loading imparted during the oscillation event. By way of example, the upper portion of a building experiencing large loading due to wind may sway more than other portions, and a damping force applied to an elevated position of the building may reduce at least one of the displacement and acceleration of the building. According to an exemplary embodiment, the controller operates with an initial damping strategy of applying a single damping force, a plurality of damping forces concurrently, or a plurality of damping forces in a pattern designed to damp structure oscillations (e.g., apply a force to different portions of the building, apply a damping force first using damping pipes or nozzles and then using tanks, etc.), among other potential initial damping strategies.
In some embodiments, the fluid damping device provides only an initial damping force. According to an exemplary embodiment, the fluid damping device provides an initial damping force or changes the natural building mode, monitors a response by the structure, and provides additional damping forces or again change the natural building mode. The fluid damping device may continue this iterative process until a condition is satisfied (e.g., the building no longer experiences loading from the oscillation event, the building no longer accelerates or is displaced, etc.).
As described above, a fluid damping device generates a damping force by delivering a fluid at least one of through a damping pipe, into a fluid storage device, and through a nozzle. In some embodiments, the fluid damping device interfaces with still other damping devices (e.g., passive dampers, fluid viscous dampers, etc.) to operate as part of a coordinated damping system. According to an exemplary embodiment, the building includes a fluid damping system capable of providing damping forces in various directions to, by way of example, reduce oscillations due to loading in various directions.
Additional vibratory energy may be imparted into the structure where loading during an oscillation event excites a natural vibration mode of the structure. A fluid damping device damps the additional vibratory energy that may otherwise damage the structure. According to an exemplary embodiment, the fluid damping device changes the natural vibration mode of the structure to a mode that is offset (e.g., out of phase with, having a different phase angle, etc.) from the frequency of the loading. Such a change in the vibration mode may be effective in various conditions (e.g., where the input from the oscillation event is in a narrow frequency band).
According to an exemplary embodiment, the controller first reduces oscillation due to loading by applying a damping force and thereafter engages a fluid flow device to deliver a fluid (e.g., into or from a fluid storage device) to change the natural vibration mode of the structure. According to an alternative embodiment, the controller interfaces with the damping device to provide only damping forces, only change the natural vibration mode, first change the natural vibration mode and thereafter apply damping forces, or employ still another strategy. While an illustrative control strategy has been described, it should be understood that a fluid damping device may include a particular control strategy for a specific structure. Further, fluid damping devices may be employed in buildings, bridges, or other structures to damp loading due to earthquakes, wind, or other inputs. Such buildings, bridges, or other structures may be affixed to a ground surface (e.g., directly coupled, coupled with pylons, coupled with hydraulic or polymeric isolators, etc.).
It is important to note that the construction and arrangement of the elements of the systems and methods as shown in the exemplary embodiments are illustrative only. Although only a few embodiments of the present disclosure have been described in detail, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited. For example, elements shown as integrally formed may be constructed of multiple parts or elements. It should be noted that the elements and/or assemblies of the enclosure may be constructed from any of a wide variety of materials that provide sufficient strength or durability, in any of a wide variety of colors, textures, and combinations. Additionally, in the subject description, the word “exemplary” is used to mean serving as an example, instance or illustration. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. Accordingly, all such modifications are intended to be included within the scope of the present inventions. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the preferred and other exemplary embodiments without departing from scope of the present disclosure or from the spirit of the appended claims.
The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data, which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.
Although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also, two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.
