Lower string steel floor support plate

Abstract

The utility model relates to engineering technical field discloses a kind of lower string steel floor slab, to solve the problem of traditional profiled steel sheet floor slab free support span small (≤2.7 meters), secondary beam density high, site process is complicated and structural synergy is poor. Floor slab core structure includes: integrally cold-bent profiled steel sheet (including alternately arranged concave rib, convex rib, and the side wall plate, bottom plate, top plate that form concave rib / convex rib are enclosed), connecting fixing part, lower string longitudinal reinforcement and anchoring device;Lower string longitudinal reinforcement is fixed with connecting fixing part by anchoring device, realize indirect connection with profiled steel sheet and prestress is applied, while concave rib can be provided with transverse pull-in steel, side wall plate is provided with cold-pressed rib, bottom plate / top plate is provided with bent rib, additional truss can be additionally provided above concave rib / convex rib, profiled steel sheet below can be equipped with flat plate. Manufacturing method includes steel sheet pressing rib, roll bending, fixed connecting piece, assembling truss, tensioning reinforcement and other steps. The utility model free support span is improved to more than 4.0 meters, total steel consumption of structure is reduced by 30%-40%, site process is simplified, structural synergy and durability are enhanced, suitable for various engineering floor.

Description

Technical Field

[0001] This utility model relates to the field of engineering technology, specifically a bottom-tensioned steel floor deck, which can be widely used in floor slabs for various projects. Background Technology

[0002] Corrugated steel sheet floor decking, as a core load-bearing and formwork integrated component in steel structure buildings, has been widely used in various projects such as industrial plants, commercial complexes, multi-story parking garages, and convention centers due to its advantages such as convenient construction and outstanding economy. Compared with traditional cast-in-place floor slabs, this technology can shorten the construction period by 30%-40%, reduce the overall cost by 10%-15%, and reduce concrete usage by 20%-30%. Its own steel consumption is typically only 15-25 kg / m², making it one of the key technologies for achieving energy conservation and emission reduction in buildings.

[0003] However, those skilled in the art are well aware that existing profiled steel sheet floor decking suffers from the following long-standing technical defects in practical applications, which severely restrict its performance improvement and engineering economics:

[0004] Limited span and insufficient load-bearing capacity for supportless construction: Due to the conventional finished thickness of floor slabs (usually 100-150mm), the effective height (wave height) of profiled steel sheets is generally only 50-80mm. Simultaneously, to ensure the rigidity of the profiled steel sheet as formwork during construction, its base plate thickness must be maintained at 0.8-1.2mm. These two factors combined result in a small moment of inertia and limited bending load-bearing capacity, making it unable to withstand large-span construction loads. Currently, most supportless spans on the market are generally ≤2.7 meters, which is insufficient to meet the requirements of modern large-space buildings for spans exceeding 4 meters.

[0005] Excessive density of secondary beams increases total steel consumption: To match the unsupported span of the floor slab (≤2.7 meters), the spacing of secondary beams must be controlled within this range. This leads to a significant increase in the number of secondary beams, substantially increasing the total steel consumption and cost of the structure. Taking a 1000㎡ floor slab as an example, the steel consumption of secondary beams in the traditional scheme can reach 80-100kg / ㎡, which is 30%-40% higher than the ideal large-span scheme (secondary beam spacing of 4-5 meters). This not only increases the project cost but also occupies valuable interior space due to the excessive number of beams.

[0006] The on-site procedures are cumbersome and the construction efficiency is low: In traditional floor decking construction, to enhance the load-bearing performance of the floor slab during its service life, it is still necessary to lay additional reinforcing bars at the bottom of the slab on-site. Since the bottom reinforcing bars are not in direct contact with the floor decking itself, a large number of reinforcing bar protective layer spacers (usually 6-8 per square meter) must be added to ensure their designed positions. This process increases material costs (the cost of spacers and auxiliary fasteners is about 5-8 yuan / square meter) and extends construction time (laying spacers and positioning reinforcing bars requires an additional 0.5-1 hour / square meter), seriously affecting the overall construction progress and offsetting some of the efficiency advantages brought by prefabricated construction.

[0007] Poor structural coordination and susceptibility to localized failure: Traditional profiled steel sheets primarily serve a dual role as both "concrete pouring formwork" and "later-stage tensile reinforcement." They fail to form an integrated, coordinated load-bearing system with the subsequently laid bottom reinforcement and concrete, limiting the potential for increased load-bearing capacity. Furthermore, the transition web of the profiled steel sheet (the inclined section connecting the concave and convex ribs) is prone to stress concentration under load due to improper angle design (typically 90°-110°), leading to premature buckling deformation of the web and subsequently causing localized cracking or a decrease in load-bearing capacity, posing safety hazards.

[0008] While some improvement plans have been proposed within the industry to address the aforementioned shortcomings, none have achieved a comprehensive breakthrough.

[0009] Conventional approach 1: Increase the rigidity by increasing the thickness of the profiled steel sheet base plate (to 1.3-1.5mm). Although this can slightly increase the span without supports to about 3.0 meters, it increases the amount of steel used by 20%-50%, directly offsetting its economic advantages. Moreover, it does not solve the fundamental problems of complicated on-site procedures and structural coordination.

[0010] The second conventional approach is to add temporary supports (such as full-span steel pipe scaffolding) under the floor slab to achieve a larger span (≤3.8 meters). However, this does not achieve true "support-free" construction. The erection and removal of temporary supports significantly increases construction costs (approximately 12-15 yuan / ㎡) and construction time (extending by 20%-25%). Moreover, the potential for insufficient structural coordination remains even after the supports are removed.

[0011] In summary, existing technologies cannot simultaneously meet the comprehensive requirements of modern steel structure engineering for "low material consumption, high span, no bracing, and fewer procedures." Therefore, there is an urgent need in this field for an innovative profiled steel sheet floor decking solution that can fundamentally overcome the limitations of bracing-free span, significantly reduce the amount of steel used in secondary beams, greatly simplify on-site procedures, and enhance the overall structural synergy. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of the prior art and provide a down-tensioned steel floor deck and its manufacturing method. This solution, through innovative structural design, deeply integrates down-tensioned prestressed technology with profiled steel sheet-concrete composite structures, effectively solving four core pain points: small span without bracing, high secondary beam density, numerous construction procedures, and poor coordination.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A type of under-tensioned steel floor deck, characterized in that it comprises a profiled steel sheet, connecting fasteners, longitudinal reinforcing bars of the under-tensioned chord, and anchors; the profiled steel sheet has alternating concave ribs and convex ribs, and the profiled steel sheet also includes sidewall panels; wherein the concave ribs are formed by the sidewall panels and the bottom plate, and the convex ribs are formed by the sidewall panels and the top plate, and the bottom plate, the top plate, the sidewall panels, and the concave and convex ribs formed thereby are integrally formed from a single piece of thin steel sheet by a cold bending process, ensuring the integrity and continuity of the structure;

[0015] The connecting fastener is fixedly connected to the bottom plate of the concave rib or to the side wall plates on both sides of the concave rib, serving as a reliable force transmission medium for the tensioned cable system.

[0016] The bottom tensioned steel bar has a dual core function as a "tensioned member during construction" and a "stressed steel bar for floor slabs during service": First, before concrete pouring, it acts as a tensioned member by applying prestress through tensioning to offset the tensile stress generated by construction loads, providing a mechanical basis for large-span floor slabs without bracing; Second, after the concrete hardens, it directly serves as the stress-bearing steel bar for the floor slab, working together with the concrete to bear the permanent loads (such as the floor slab's self-weight and decoration loads) and variable loads (such as personnel and equipment loads) during the building's service life, replacing the traditional on-site laid bottom reinforcement bars and greatly simplifying the construction process.

[0017] From the perspective of structural safety and durability, according to the requirements of the "Code for Design of Concrete Structures" (GB 50010-2010), the "Code for Fire Protection Design of Buildings" (GB 50016-2014, 2018 edition), and the "Code for Durability Design of Concrete Structures" (GB / T50476-2008), the reinforcing steel bars in floor slabs must have sufficient concrete cover thickness. In terms of fire resistance, a 15-30mm cover can ensure the floor slab's fire resistance rating reaches 1.5-2.0 hours, preventing a rapid temperature rise in the reinforcing steel bars due to rapid heat conduction from the profiled steel sheet (Q355B profiled steel sheet has a thermal conductivity of 45W / (m·K)) under high-temperature conditions (such as during a fire). This prevents the steel bar strength from dropping to below 10% of its normal strength at 1000℃, ensuring structural fire safety. In terms of durability, this cover thickness effectively isolates the reinforcing steel bars from air and moisture, controlling the corrosion rate to 0.01mm / km. The steel reinforcement has a service life of less than 50 years, extending the corrosion life of steel bars to more than 50 years, thus meeting the durability requirements of the main building structure.

[0018] Based on the aforementioned protective layer thickness requirements, a distance of 15-30mm must be maintained between the lower tensioned steel bars and the profiled steel sheet bottom plate. They cannot be directly attached to the profiled steel sheet. If they are forcibly attached (protective layer thickness <10mm), not only will there be structural safety hazards due to insufficient fire resistance and durability, but also the prestress during the construction stage cannot be transferred to the profiled steel sheet because there is no effective force transmission path between the steel bars and the profiled steel sheet, thus losing the mechanical advantages of the tensioned structure.

[0019] To address the issue of "force transmission interruption caused by protective layer spacing," a dedicated connecting fastener is required. This fastener, on one hand, uses an integrated, molded positioning protrusion (height matching the protective layer thickness, 15-30mm) to precisely support the lower tension reinforcing bars, ensuring stable spacing between the bars and the profiled steel sheet base plate. This prevents the protective layer thickness deviation from exceeding the ±3mm range specified in the "Code for Acceptance of Construction Quality of Concrete Structures" (GB 50204-2015). On the other hand, the fastener must form a rigid connection with the profiled steel sheet via welding or bolts (connection area ≥500mm², force transmission cross-sectional area ≥300mm²), constructing a complete force transmission path of "lower tension reinforcing bars → connecting fastener → profiled steel sheet." This achieves effective transmission of prestress during construction and tensile loads during service, ultimately reaching the design goals of "dual functionality, fire resistance and durability, and continuous force transmission." The longitudinal reinforcement bars of the lower tension chord are fixedly connected to the connecting fasteners through the anchors, so as to indirectly fix the longitudinal reinforcement bars of the lower tension chord to the profiled steel sheet, and prestress can be applied to the longitudinal reinforcement bars of the lower tension chord to form an efficient self-balancing structure system of the lower tension chord, and establish a beneficial pre-compression stress field in the plate.

[0020] Preferably, a transverse tie steel is provided at the upper or middle part between the two side walls of the concave rib to effectively limit the relative displacement of the side walls and enhance the deformation resistance and cross-sectional stability of the concave rib.

[0021] During concrete pouring, the left and right side plates of the concave rib are subjected to lateral pressure from the concrete, resulting in outward expansion deformation. If the upper edge of the side plate is not tied, an unfavorable boundary condition of free top and fixed bottom will be formed, significantly increasing lateral deformation. Especially when the concave rib is deep, simply fixing the upper and lower edges of the side plate is still insufficient to effectively control deformation. Compared to the high-cost solution of simply increasing the thickness of the steel plate, adding transverse tie steel in the middle or upper part of the side plate can provide intermediate restraint in a more economical and efficient way, significantly enhancing the deformation resistance and overall stability of the side wall, and effectively suppressing lateral deformation during concrete pouring. This ensures the mechanical properties of the profiled steel sheet and the performance of the truss assembly.

[0022] Preferably, the two side panels are provided with cold-pressed ribs, which are vertical, oblique, V-shaped, or cross-shaped. Through the cold work hardening effect and geometric stiffening effect, the local stability, buckling load, and overall out-of-plane stiffness of the side panels are significantly improved. The V-shaped or cross-shaped ribs conform to the force transmission path, further enhancing the load-bearing capacity of the side panels.

[0023] Preferably, the bottom plate or top plate is provided with longitudinal bending ribs as stiffening ribs to improve the local stability of the plate and enhance its bonding and combination with concrete.

[0024] Preferably, the top plate is provided with transverse cold-pressed ribs to further improve the rigidity and deformation resistance of the top plate.

[0025] Preferably, the width of the bottom plate is smaller than the width of the top plate. This asymmetrical design helps optimize the force flow in the concrete slab, allowing pressure to diffuse more effectively to the support area. It also reduces the amount of concrete poured, lightens the structure's self-weight, increases the slab's load-bearing capacity, and reduces the amount of reinforcing steel required.

[0026] Preferably, an additional truss is provided above the concave or convex ribs. This spatial truss structure can greatly improve the stiffness and bending bearing capacity of the floor deck during the concrete pouring construction stage, thereby achieving a larger span without bracing.

[0027] Preferably, the additional truss consists of an upper chord and one or more rows of web members, forming an efficient truss force transmission mechanism.

[0028] Preferably, the web members are made of steel bars or steel pipes that are continuously bent into a wave shape; the upper chord is made of steel of various cross sections; the crests of the web members are fixedly connected to the upper chord, and the troughs are fixedly connected to the profiled steel sheet, so as to effectively transfer the shear force of the truss to the profiled steel sheet and form a spatial combination structure.

[0029] Preferably, the trough of the web member is fixedly connected to the top plate and positioned close to the side wall plate, which facilitates the direct transfer of truss forces to the profiled steel sheet, resulting in greater rigidity, better stress distribution, and a more stable spatial structure.

[0030] Preferably, the trough of the web member is fixedly connected to the sidewall plate. The lower edge of the sidewall plate is connected to the bottom plate, thereby forming a pair of tension-compression combined spatial structures with the upper flange and concave rib bottom plate of the truss. This fully utilizes the shear force of the web member and the sidewall plate, increases the moment of the tension-compression section, and thus improves the bending resistance of the spatial rib.

[0031] Preferably, the troughs of the web members are fixedly connected to the base plate. When the sidewalls are thin and the floor deck span is large, the shear resistance of the sidewalls alone cannot withstand the load, allowing the web members to be directly connected to the base plate. Simultaneously, the tension chord reinforcement can be fixed near the troughs using the web members, reducing the need for additional connecting fasteners.

[0032] Preferably, the connecting fastener is a flat steel, channel steel, steel pipe, reinforcing bar, or the trough portion of the web member of the additional truss, achieving functional integration and material saving.

[0033] Preferably, the anchor is a nut, a prestressed anchor, or a weld, providing reliable prestressed anchorage.

[0034] Preferably, a flat plate is connected below the profiled steel sheet. This flat plate is made of gypsum board, calcium cement board, or fiber cement board, eliminating the need for a suspended ceiling and achieving a smooth, aesthetically pleasing building surface while maintaining fire resistance and sound insulation. This improves on-site construction efficiency and protects the floor decking from direct contact with air, thereby enhancing its fire resistance and durability.

[0035] The beneficial effects of this utility model are as follows:

[0036] ① Significantly increases span and load-bearing capacity without bracing: By applying prestress through the "lower tension longitudinal reinforcement," pre-compression stress is established within the floor slab, significantly offsetting the tensile stress generated by the wet weight of concrete and live loads during construction. This allows the span without bracing to be increased from the traditional 2.7 meters to over 4.0 meters. Combined with the composite truss effect formed by the "additional truss" and the enhanced stability of the plates by various reinforcing ribs (cold-pressed ribs, bent ribs), the cross-sectional stiffness and load-bearing capacity are fundamentally enhanced.

[0037] ② Significantly reduces total structural steel consumption and overall cost: The increased span without bracing allows for a greater spacing between secondary beams, up to 4 meters or more, reducing the number of secondary beams and their steel consumption, manufacturing, and installation costs by 30%-40%. Although the steel consumption of the floor decking itself increases slightly due to reinforcement measures, the total structural steel consumption and overall cost are significantly reduced, resulting in obvious economic benefits.

[0038] Completely simplifies on-site construction procedures and improves efficiency: The "lower tension longitudinal reinforcement" and "additional truss" are pre-assembled with profiled steel sheets in the factory, completely replacing the cumbersome procedures of laying bottom reinforcing bars, distribution bars and installing pads on site, saving a lot of labor and time, increasing construction efficiency by more than 20%, and reducing the quality and safety risks of on-site operations.

[0039] ③ Excellent structural synergy and safety: The longitudinal reinforcement of the under-tensioned chord, the additional truss, and the profiled steel sheet form a robust whole through connecting fasteners and anchors. These three components work together with the post-cast concrete to create a highly efficient, integrated, and synergistic load-bearing system. This system has a clear force transmission path and uniform stress distribution, avoiding the risk of premature buckling of the profiled steel sheet web in traditional composite floor slabs, thus significantly improving structural safety, reliability, and durability.

[0040] ④ Functional integration and architectural aesthetics: By integrating and installing the lower flat plate in the factory, the floor deck and ceiling are integrated, eliminating the need for on-site ceiling installation, saving costs while ensuring the flatness and aesthetics of the building's bottom surface, and facilitating the integration of lighting, pipelines and other facilities.

[0041] Working Principle: The core principle of this floor deck is the comprehensive utilization of under-tensioned chord technology, combined action, and truss effect. During construction, the tensioned under-tensioned longitudinal reinforcement applies a reverse load to the system, offsetting part of the positive bending moment; the additional truss provides significant short-term stiffness and load-bearing capacity, jointly ensuring construction safety under large spans. During service, the prestressed tendons and concrete bond together to bear the load, continuing to provide bending resistance; after the concrete hardens, it forms a composite section with the profiled steel sheet and the truss upper chord, jointly bearing the service load and exhibiting excellent overall performance. Attached Figure Description

[0042] Figure 1 This is a three-dimensional schematic diagram of the under-tensioned steel floor deck of this utility model. Figure 1 (No truss).

[0043] Figure 2 This is a three-dimensional schematic diagram of the under-tensioned steel floor deck of this utility model. Figure 2 (No trusses, but with decorative panels).

[0044] Figure 3 This is a three-dimensional schematic diagram of the under-tensioned steel floor deck of this utility model. Figure 3 (No trusses, but with decorative panels).

[0045] Figure 4 This is a three-dimensional schematic diagram of a typical additional truss in this utility model. Figure 1 .

[0046] Figure 5 This is a three-dimensional schematic diagram of a typical additional truss in this utility model. Figure 2 .

[0047] Figure 6 This is a three-dimensional schematic diagram of a typical additional truss in this utility model. Figure 3 .

[0048] Figure 7 This is a three-dimensional schematic diagram of a typical additional truss in this utility model. Figure 4 .

[0049] Figure 8 This is a three-dimensional schematic diagram of a typical additional truss in this utility model. Figure 5 .

[0050] Figure 9 This is a typical optional cross-sectional form of the upper chord of the additional truss in this utility model.

[0051] Figure 10 This is a typical optional cross-sectional form for the web members of the additional truss in this utility model.

[0052] Figure 11 A three-dimensional schematic diagram of the under-tensioned steel floor deck with truss of this utility model. Figure 1 .

[0053] Figure 12 A three-dimensional schematic diagram of the under-tensioned steel floor deck with truss of this utility model. Figure 2 .

[0054] Figure 13 A three-dimensional schematic diagram of the under-tensioned steel floor deck with truss of this utility model. Figure 3 .

[0055] Figure 14 A three-dimensional schematic diagram of the under-tensioned steel floor deck with truss of this utility model. Figure 4 .

[0056] Figure 15 The diagram shows the numbering of each bent part of the profiled steel sheet of this utility model.

[0057] Figure 16 The diagram shows the numbering of each bent part of the profiled steel sheet of this utility model.

[0058] Figure 17 Typical example of the connection position between the additional truss and the profiled steel sheet in this utility model.

[0059] (In the figure: 1-Corrugated steel sheet; 2-Connecting fastener; 3-Longitudinal reinforcement of the lower tension chord; 4-Anchor; 5-Concave rib; 6-Convex rib; 7-Side wall plate; 8-Bottom plate; 9-Top plate; 10-Transverse tie steel; 11-Cold-pressed rib; 12-Longitudinal bending rib; 12a-Transverse cold-pressed rib; 13-Additional truss; 14-Top chord; 15-Web member; 16-Flat plate; 17-Transverse short reinforcement) Detailed Implementation

[0060] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0061] Example 1:

[0062] As attached Figure 1 As shown, a type of under-tensioned steel floor deck includes a profiled steel sheet (1) formed by cold bending a single piece of thin steel sheet. The profiled steel sheet (1) has alternating concave ribs (5) and convex ribs (6). The concave ribs (5) are formed by side wall plates (7) on both sides and a bottom plate (8); the convex ribs (6) are formed by side wall plates (7) on both sides and a top plate (9). A channel steel is welded in the center of the bottom plate (8) of the concave ribs (5) as a connecting fastener (2). The under-tensioned longitudinal steel bars (3) (usually high-strength prestressed threaded steel bars) pass through the channel steel, and are anchored at both ends by nuts as anchors (4) and prestressed. By tightening the nuts, the under-tensioned longitudinal steel bars (3) are tensioned, thereby establishing effective prestress within the floor deck system, greatly improving its stiffness and span without bracing during construction.

[0063] Example 2:

[0064] Based on Example 1, as shown in the appendix Figure 2 and 3 As shown, transverse tie steel (10) is provided above the side wall panels (7) on both sides of the concave rib (5); this can limit the deformation of the concave rib and reduce the thickness of the profiled steel sheet. Cement fiberboard (16) is provided under the profiled steel sheet (1). This serves both as a decorative effect and as protection for the fire resistance and durability of the profiled steel sheet.

[0065] Example 3:

[0066] Based on Examples 1 and 2, as shown in the appendix Figure 11 As shown, an additional truss (13) is added above the concave rib (5). The additional truss (13) consists of a downward-opening channel steel as the top chord (14) and a web member (15) made of steel bars continuously bent into a wave shape. The crest of the web member (15) is welded to the top chord (14), and its trough is welded to the top plate (9) of the convex rib (6), very close to the side wall plate (7), to optimize force transmission. The additional truss (13) works in conjunction with the longitudinal steel bars (3) of the lower tension chord to significantly increase the span without bracing. To further enhance the stability of the concave rib (5), V-shaped cold-pressed ribs (11) are set in the middle of its two side wall plates (7).

[0067] Example 4:

[0068] Based on Example 3, as shown in the appendix Figure 12 As shown, a transverse short bar (17) is provided at the trough of the web member (15) of the additional truss (13). The upper chord of the additional truss (13) is set as a flat tube. The web member (15) is connected to the profiled steel plate (1) at the junction of the top plate (9) and (7), and a chamfer is provided at the junction.

[0069] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A type of under-tensioned steel floor deck, characterized in that, It includes profiled steel sheet (1), connecting fasteners (2), longitudinal steel bars of the lower tension chord (3), and anchors (4); The profiled steel sheet (1) has alternating concave ribs (5) and convex ribs (6), and the profiled steel sheet (1) also includes a side wall plate (7); wherein the concave ribs (5) are formed by the side wall plate (7) and the bottom plate (8), and the convex ribs (6) are formed by the side wall plate (7) and the top plate (9), and the bottom plate (8), the top plate (9), the side wall plate (7), and the concave ribs (5) and convex ribs (6) formed by them are all integrally formed by bending a single piece of thin steel sheet; The connecting fastener (2) is fixedly connected to the bottom plate (8) of the concave rib (5), or fixedly connected to the side wall plates (7) on both sides of the concave rib (5). The lower tension longitudinal steel bar (3) is fixedly connected to the connecting fastener (2) through the anchor (4) to achieve indirect fixation between the lower tension longitudinal steel bar (3) and the profiled steel sheet (1).

2. The under-tensioned steel floor decking according to claim 1, characterized in that: A transverse tie steel (10) is provided in the upper or middle part between the two side wall panels (7) of the concave rib (5).

3. The under-tensioned steel floor decking according to claim 1, characterized in that: The two side panels (7) are provided with cold-pressed ribs (11), which are vertical, oblique, figure-eight, or cross-shaped.

4. The under-tensioned steel floor decking according to claim 1, characterized in that: The bottom plate (8) or top plate (9) is provided with longitudinal bending ribs (12).

5. The under-tensioned steel floor decking according to claim 1, characterized in that: The top plate (9) is provided with transverse cold-pressed ribs (12a).

6. The under-tensioned steel floor decking according to claim 1, characterized in that: The width of the bottom plate (8) is smaller than the width of the top plate (9).

7. The under-tensioned steel floor decking according to claim 1, characterized in that: An additional truss (13) is provided above the concave rib (5) or convex rib (6).

8. The under-tensioned steel floor decking according to claim 7, characterized in that: The additional truss (13) consists of an upper chord (14) and a single or multiple rows of web members (15).

9. The under-tensioned steel floor decking according to claim 8, characterized in that: The web member (15) is made of steel bars, steel pipes, flat pipes, channel steel or flat steel, continuously bent into a wave shape with alternating crests and troughs; the upper chord (14) is a channel section with an opening facing upwards or a channel section with an opening facing downwards or an elliptical steel pipe, a rectangular steel pipe, a flat steel or a trapezoidal pipe; the crests of the web member (15) are fixedly connected to the upper chord (14), and the troughs are fixedly connected to the profiled steel sheet (1).

10. The under-tensioned steel floor decking according to claim 9, characterized in that: The troughs of the multi-row web members (15) are connected to transverse short ribs (17).

11. The under-tensioned steel floor decking according to claim 9, characterized in that: The trough of the web member (15) is fixedly connected to the top plate (9) and is located close to the side wall plate (7).

12. The under-tensioned steel floor decking according to claim 9, characterized in that: The trough of the web member (15) is fixedly connected to the side wall plate (7).

13. The under-tensioned steel floor decking according to claim 9, characterized in that: The trough of the web member (15) is fixedly connected to the base plate (8).

14. The under-tensioned steel floor decking according to claim 1, characterized in that: The connecting fastener (2) is a flat steel, channel steel, steel pipe, steel bar, or the trough of the web member (15) of the additional truss (13).

15. The under-tensioned steel floor decking according to claim 1, characterized in that: The anchor (4) is a nut, a prestressed anchor, or a weld.

16. The under-tensioned steel floor decking according to claim 1, characterized in that: A flat plate (16) is connected below the profiled steel sheet (1).

17. The under-tensioned steel floor decking according to claim 16, characterized in that: The flat plate (16) is a gypsum board, a cement-calcium board, or a fiber cement board.

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