Patent Application
20200181928
The present invention relates generally to construction steel truss formwork. More particularly, the invention relates to a steel truss false-work system derived from the funicular arch concept, hence reducing the material used within the structure and eliminating the need for stringers.
Generally, it is common to find the terms formwork and false-work used interchangeably within the construction industry. However, they can be differentiated as follows: the formwork is considered to be the horizontal system that supports heavier concrete members while false-work is considered to be the temporary girders and shores and the lateral bracing that is supporting the system until concrete sets. Falseworks are either Job-built or prefabricated. The prefabricated systems are commercially used, with standard sizes and usually made of steel or aluminum. They are usually used more than once, and they require a higher life cycle. On the other hand, the job-built systems are built to suit only one job and often made of wood. They are used when the requirements of a job cannot be met by the commercially available systems. Their lifespans are often small since they are fabricated to suit a specified job.
The conventional (traditional) systems have main components that include: sheathing, joists, stringers and shores. Sheathing is the material in contact with the freshly poured concrete surface. The load supported by the sheathing is transferred to the joists. The joists are beams that transfer the load to the stringers. The stringers are the main beams that transfer the load to the shores. Shores are the vertical or inclined members that support the stringers, joists and the decking. The shores of the system are then braced using the cross-bracing members to withstand the lateral loads, these shores are made of wood within conventional systems while are typically made of steel within commercially used systems.
Heavy-duty systems were the logical development after the first generation of steel shoring. These frames were standardized to have an outer diameter of 60.3 mm or 63.5 mm (2 and ⅜ or 2.5 inch) with a wall thickness of 3.2 mm. This also was accompanied by the development in the shoring accessories. U-heads, screws legs and standard bracing sizes were introduced which made the heavy-duty system more adaptable and easy to use for the contractors. The bracing of the scaffold types available in the market has a variety of spans. It spans a distance between frames that ranges between 0.6 and 3 m. This distance can be expanded to range between 3.6 to 4.5 m when using the long-span horizontal shoring beams.
The tube-and-coupler system includes vertical posts and two horizontal members called Runners to connect the posts together. The system is braced by an inclined member to control sway in the system. All the members in this system are tubes connected together by couplers. Newer systems consist of welded-steel-frames that are put on top of each other in order to reach the desired height of the concrete structure. The frames are put beside each other and are connected with cross-bracing members that are connected to the legs of the frames to provide lateral support for the new system. The welded-steel-frame system is more stable than the older system since most of the members are welded together and the cross bracing is connected to the frames through a small piece of steel welded to the legs of the frames which provides more stability.
The weight of the systems can vary greatly according to the manufacturer of that system. However, an average weight of 160 kg per heavy duty tower of falsework has been reported. On the other hand, a standard normal frame tower will weigh 10 to 20% percent less than the heavy-duty system. Therefore, the standard normal frame tower will have a weight that ranges between 128 kg to 145 kg.
On the other hand, formwork is one of the largest cost components in building structural frames. The cost of the formwork system can exceed the material costs of reinforced concrete in some extreme situations. Hence, formwork design is very important to help in reducing the cost of constructing a floor by 25%. The efficiency of the formwork design can also reduce the cost by reducing the amount of time needed to erect the formwork in addition to the cost of the formwork material itself. This means less direct and indirect cost by decreasing the number of working hours of labor and by saving formwork material. The benefits of an efficient design of the formwork also includes: increased productivity for labor, reduced potential for errors and enhance the safety procedures and conditions.
Since formwork appears in the beginning and the end of the construction process, it is appropriate to say that it has direct impact on the construction cost. Consequently, to choosing the wrong formwork system will have drastic effect on the construction. The formwork system should be chosen while considering some factors such as system's productivity, safety, durability and the site conditions. The components of the formwork system that directly affect its cost have been studied. The factors considered included sheathing, joists, stringer, wood shores and the different combinations available for slab formwork components. These data were fed to an optimization code that its results were compared against the cost of the traditional formwork system. Optimizing different formwork components led to saving 9.9% of the formwork cost. Other studies correlated the layout of the structure to the formwork system choice.
However, researches focusing on development of new falsework systems have been rarely published as most of these efforts are performed by companies working in the industry itself.
What is needed is a design and method of a falsework system that will decrease the axial forces on the members and decrease the mid-span deflection and consequently the cross section of each member in the steel truss to replace several frames of the currently used commercially used shores by only two steel trusses to improve construction ease, time, its effect on the space availability within the construction site and its positive impact on the environment in terms of saving a large amount of steel used in shoring activities.
To address the needs in the art, a device and method of making a support structure is provide that includes detachably or pivotably connecting in opposition, at least one pair of half funicular arched trusses, where each half funicular arched truss includes an exterior vertical member having a footing at a bottom end and a structure mount at a top end, a bottom chord member having a bottom end of the bottom chord member connected proximal to the exterior vertical member bottom end and a top end of the bottom chord member connected to a bottom port of a four-point intermediate connector, where the intermediate connector includes the bottom port connected to a bottom portion of a connector housing and an outer port, a center port, and an inner port connected to a top portion of the connector housing, a diagonal member having a diagonal member bottom end connected to the inner port and a diagonal member top end connected proximal to the exterior vertical member top end, an interior vertical member having an interior vertical bottom end connected to the center port and an interior vertical member top end connected to a second structure mount, a second bottom chord having a second bottom chord bottom end connected to the outer port and a second bottom chord top end connected to a bottom port of a second four-point intermediate connector, a second diagonal member having a second diagonal member bottom end connected to an outer port of the second four-point intermediate connector and a second diagonal member top end connect proximal to the interior vertical member top end, a second interior vertical member having a second interior vertical bottom end connected to a center port of the second four-point intermediate connector and a second interior vertical top end connected to a third the structure mount, a third bottom chord having a third bottom chord bottom end connected to an outer port of the second four-point intermediate connector and a third bottom chord top end connected to a bottom port of a third four-point intermediated connector, a third diagonal member having a third diagonal member bottom end connected to an inner port of a third four-point intermediate connector and a third diagonal member top end connected proximal to the second interior vertical top end, a third interior vertical member having a third interior vertical member bottom end connected to a center port of the third four-point intermediated connector and an interior vertical member top end connected to a fourth structure mount, a fourth bottom chord having a fourth bottom chord bottom end connected to an inner port of the third four-point intermediate connector and a fourth bottom chord top end connected to a truss joiner, and a horizontal member connected to the truss joiner and connected proximal to the third interior vertical member top end and connected proximal to the second interior vertical member top end and connected proximal to first interior top end and connected proximal to the exterior vertical top end, where one half funicular arched truss detachably or pivotably connects to another the half funicular arched truss by detachably or fixedly connecting each truss half funicular arched truss to a truss joiner in opposition to form a funicular arched truss scaffold, where when in a detached or pivoted state, storage and transporting a plurality of the half funicular arched trusses is simplified. Finally, a horizontal tie rod connects the lower end of the exterior vertical member of one half of the funicular arched truss to another half of the funicular arched truss.
According to one aspect of the invention, each vertical member, diagonal member, bottom chord, and horizontal member are a hollow tube.
In another aspect of the invention, the ports and the housing four-point intermediated connector are hollow tubes.
In a further aspect of the invention, the bottom chords, the diagonal members, the interior vertical members and the four-point intermediate connectors include a truss member set, where the truss member set are assembled in a number that is scalable according to an intended height and span in an application.
In yet another aspect of the invention, a plurality of the funicular arched truss scaffolds are connected in parallel.
According to one embodiment, the invention includes a scaffold having an opposing pair of half funicular arched trusses that are detachably or pivotably connected in the middle to establish a funicular arched truss. According to this embodiment of the current invention, the opposing pair of half funicular arched trusses include a hollow metal tubing funicular arched structure. In one aspect of the current embodiment, a plurality of the funicular arched trusses are connected in parallel.
Commercially available systems currently used in construction require high initial cost, take time to be erected and reduce the space in the construction site for the movement of material, equipment and labor as they prevent movement underneath them. The current invention provides a new false-work system derived from the funicular arch; funicular arched steel truss (FAST) system. In one embodiment, the invention decreases the cost of the false-work, where less material is required for the structure and therefore needs lower initial cost than systems currently known in the art. Further, the new system is environmentally friendly as it achieves a range between 45% and 50% savings in the amount of CO2 emitted to air due to the use of less material. The savings in the material used in the FAST system ranges between 45% to 51% depending on the covered area and it also provides more space in the construction site for the materials, equipment and workers to move underneath the system. The system also decreases the time needed for erection by range between 67% and 80% depending on the area and consequently helps in saving time and cost.
A closed form solution is provided with members designed mainly to withstand buckling as they are all under compression. As shown in
Furthermore, the current embodiment includes the upper horizontal chords, the diagonals and the bracing members having an outer diameter of 16 mm, which is the minimum limit for these zero members. In this example embodiment, all of these steel tubes have 1.25 mm thickness. Table 1 summarizes the diameters of all the members in half of the symmetric truss. Its numbering system is as follows: the connection between the upper chord members are given the odd number from (1, 3, 5, 7 and 9) and the connections of the bottom chord members are given the even numbers (2, 4, 6, and 8), however, they meet with the upper chord members in the intermediate hinged which has the number 9.
In order to add structural redundancy to the system, a tie rod with an outer diameter of 19 mm is added to the system in order to withstand the thrusting force that tries to open the arch once it is subjected to high loads instead of depending on the friction with the ground to take the horizontal reactions. Further, it allows the setup of the truss to be easily assembled on site since it holds the two halves together, fixes the span at the desired length since it reduces the risk of the arch to open; and reduces the sway of the truss.
In
As shown in
Turning again to
It is understood that the number of intermediate connectors 122 and that associated connecting members used in a funicular arched truss structure 100 can vary according to the height and span of the overall system.
The present invention has now been described in accordance with several exemplary embodiments, which are intended to be illustrative in all aspects, rather than restrictive. Thus, the present invention is capable of many variations in detailed implementation, which may be derived from the description contained herein by a person of ordinary skill in the art.
The variations of the spans of the designed system have been studied in order to compare the savings in weight that it entails when compared to its commercially available counterparts. Table 2 shows the weights of the commercially available steel formwork systems and compares them to the weight of the designed system. It is clear that the weight of the commercially available system increases significantly in wide spans, however, the weight of the system is increases slightly for the spans from 2.4 meters up to 7.2 meters. This is because the lengths of the bottom chord members and the length of the diagonals increase with the increase in the span. Further, the increase in the diameter of the exterior vertical and bottom chord member (4-6) causes increase in the weight in spans of 6 and 7.2 meters. It was found that, originally, the FAST system has a 33% saving in the weight when the span is 2.4 meters. This means that, according to the previous assumption of the number of frames is used to compare the weight and the number of units in the two systems, that there is a saving of 4.89 kg/m2. This is calculated by dividing the weight of the eight units of the commercially available systems (63.65 kg) used to cover the area of 2.4×1.8 m (4.32 m2) to get the value of the weight of this system needed for each m2 from the floor area which yields a value of 14.73 kg/m2. While the weight needed from the proposed system to cover the same area is calculated by dividing the weight of one unit of the system (42.5 kg) by the area (4.32 m2) which yields a value of 9.84 kg/m2. The difference between these numbers gives the savings in the weight of the systems per unit area.
All such variations are considered to be within the scope and spirit of the present invention as defined by the following claims and their legal equivalents.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/035173 | 5/30/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62516821 | Jun 2017 | US |
