Patent Application
20210025164
The present disclosure relates to a composite floor system in large open span in multi-story concrete or steel buildings. More particularly, it relates to a structural floor system comprising pre-stressed intersecting modular truss and concrete decking.
In current building construction, particularly in commercial and residential multistory buildings, there are some common floor systems in long spans in steel and concrete skeleton structures. Usage of poured in place concrete slabs, prefabricated concrete joists with slab or pre-stressed and post-tensioned reinforced concrete decks have been proposed in concrete structures while in steel skeleton structures, composite joist decking is the dominant floor system. Each of which, although having advantages, has limitations on loading, operation and construction.
The drawback of pour in place concrete slab is the high thickness of the slab in long spans which has heavy self-weight and impose the excess amount of weight to the structures. Clearly, more weight means heavier columns and beams to support the floor, higher inertia and earthquake force and as a result, higher consumption of steel and concrete. In some case, it even limits the height of the building for a particular soil bearing capacity.
Composite joist decking system in a large span needs large joist. In these cases, overall floor system is relatively deep and the mechanical and electrical devices which run below the joists leads to decrease the height of the story more (often causing the building to be taller). Moreover, these large joists cannot transport and erect without the help of heavy crane. When it comes to the vibration issue, because of the relatively weak stiffness, vibration under moving load are heavy and the height of the joist should be increased sharply in spans more than 10 meter in regular multi-story buildings.
In steel structures, it is the practice to use one-way slab, which means spanning in one direction. One-way slab tends to deflect more than two-way does specifically at the middle of the span. Needless to say, that the levelness and flatness can improve by using two-way slab. Accordingly, it would be desirable to provide a floor system having enough stiffness to have less deflection and vibration, imposes minimum gravity load due to its low weight, easy to run mechanical ducks, pre-manufactured in a controlled environment and finally has the merits of modularity to ease construction and erection.
The present technology is directed to a structural floor system for multi-story concrete and steel structure buildings. The present framework generally comprises a grid of intersecting modular truss units. Each truss unit is manufactured beforehand in the factory or manufactory in a controlled environment. In the construction field, the short-length truss units are assembled to build the longer girder trusses. In the next stage, the said girder trusses erected and mounted on the main beams.
After that, the other intersecting truss units attached the girder trusses to build a grid of trusses. The connection of each truss to another would be done by using cross-shaped plates and bolted connection. Before pouring the concrete, a wire strand system running from the lower cord to the diagonal members of the said girder trusses and is pulled at the specified force and anchored at the top chord.
The tension induced in the wire strand system pushing the truss grid to run upward leading the reduction in final deflection of the floor system. Next, the wooden or metal formwork is placed between the space of the trusses just below the trusses upper cord such that it completely embeds in the concrete. The truss lower cord can be used as a support for the slab formwork. The mesh reinforcement placed on the upper cord of the truss and the concrete is poured. This system can be installed with or without shoring.
Disclosed herein is a composite floor system for covering long spans in multi-story residential and commercial buildings and a method of its construction and erection. In the following description, for proposes of explanation, numerous specific details are set forth in order to provide though understanding of the present disclosure. It will be evident, however, to one skilled in the art that the present disclosure may be practiced without these specific details. The present disclosure is to be considered as an exemplification of the disclosure and is not intended to limit the disclosure to the specific embodiments illustrated by the figures or description below.
The present disclosure will now be described by referencing the appended figures representing preferred embodiments.
According to one preferred embodiment of the disclosure, each truss-shaped unit 1A made up of upper cord 1, lower cord 2 and vertical 4 and diagonal 3 members as truss web. U or C-shaped cold-formed profile is used to construct the truss units 1A. Although utilizing of hot-rolled members are also under the scope of this disclosure, cold-formed is preferable due to its higher strength to weight ratio. The length of each truss unit 1A depends on the floor span, but for the transportation and modular design consideration, the maximum length would be around 3 meters. Because the upper 1 and diagonal 3 cord are under compression after loading, the minimum suitable thickness for cold-formed members would be 3 mm. The said minimum thickness not only provide acceptable resistance against different modes of buckling, but it also meets the minimum criterion for corrosion.
The vertical members 4 are placed at the specified distance from the edge of each truss unit 1A in such a way that it be possible to install splice assemblies 5. The diagonal members 3 attached to the mid span of the upper cord 1, support the said cord against bending, induced by concrete and gravity weight, transforming the bending to axial compression force because truss members design to withstand against axial forces not bending. Triangular space between the members can be used as mechanical or electrical duct way 22. Furthermore, according to the
The unit trusses 1A pre-manufactured in a factory or manufactory and then are shipped to the workshop for installation. Welded or bolted connection 15 can be chosen for connection. In the upper cord 1 of each truss unit 1A, holes 26 are created in a regular distance along the span of truss units 1A on either side of flange. The hole 26 can be circular or non-circular. Dimension and Center to center hole spacing would be according to the cross-sectional dimension of members. The passage of slab concrete 25 from said holes 26 leads to the composite action of truss and the concrete slab 25.
Once all the truss units 1A were shipped to the construction field, the assemblage operation starts with splicing the truss units 1A to build the main (long) girder truss 1B which, as first stage, is placed diagonally between two columns. Connecting each truss unit 1A to another will be made by using cross-sectional plates 5 and bolted connection 15 in both upper 1 and lower cord 2. It should be noted that attachment of all the cross-sectional edges by splicing assemblies 5 is necessary to accommodate axial force transfer. The said cross-sectional plates 5 are configured four-sided to provide suitable condition for connection in joints. When the said girder truss 1B is assembled, lift up to the column bay and installed at its level.
According to the preferred embodiment of the disclosure, by running the wire strand 6 from the lower cord 2 and the diagonal members 3, the strand 6 is pulled at the specified force and anchored at the top chord 1 of the girder trusses 2B. A number of sleeves 12,13 like steel pipe are fitted inside the diagonal 3 and upper cord 2 truss member to ease the process of the said wire strand 6 crossing. The said specific force can be considered equal to the amount of required force needed to neutralize the deflection of gravity load. Applying forces more than that, may be difficult from the construction and cost view point.
According to the
The wire strand 6 system also tolerates part of the load, increase the bearing capacity of the floor system. Usage of wire strand 6 is to improve the structural performance of the floor system. It is obvious that the system without strand 6 is also stable and have all the said advantageous above, so the floor system without the strand is also in the scope of this disclosure.
In the preferred embodiment, the wooden or metal formwork is placed between the truss quadrangle grid and just below the upper cord 2 so that the upper cord 1 can embed in the slab concrete 25. the lower cord 2 of the truss can be used as supporting for the topping formwork eliminating the overall and large scaffolding under the floor. The mesh reinforcement 14 for concrete deck 25 is placed on the upper cord 1 of the truss. For very large spans, may be two layers of reinforcing grid used instead of a one single layer.
Referring to
While preferred material for the elements have been described, the system is no limited by these materials like steel, aluminum, plastic, metal alloys, wood and other materials in various embodiment of the present disclosure. This disclosure is not also limited to method of construction and the structural component shapes like truss configurations, strand system patterns and connection devices and assemblies as shown in the drawings, Instead, different way of construction, structural member and components may be used without departing from the scope of this disclosure. In addition, other types of deck can be suitable for this system and are in the scope of this disclosure. Therefore, this disclosure is not limited to pour in place concrete slab as decking.
