Regarding the question of how to arrange the reinforcement in steel decking, we will explain it in detail here. We will address the reinforcement calculation for steel decking in two parts: the top reinforcement (including negative moment reinforcement) and the bottom load-bearing reinforcement.

The top reinforcement, also called distribution reinforcement or temperature reinforcement, mainly serves to resist the tensile stress generated in the direction perpendicular to the slab span by seasonal temperature changes and concrete shrinkage. Generally, the diameter of the reinforcement should not be less than 6mm, and the spacing should not exceed 250mm. The calculation method for the top reinforcement of profiled steel sheet slabs is the same as that for ordinary concrete slabs; it can be calculated in the same way.

Steel deck reinforcement distribution diagram

The upper reinforcement also includes negative moment reinforcement, which is used to prevent cracks from appearing at the upper part of the support after the slab is under stress. Tension reinforcement is usually placed at these upper parts; this type of reinforcement is called negative reinforcement. Especially when profiled steel sheets are laid in continuous spans, or when negative moments are generated at the supports of beams, the calculation is based on the negative moment at the supports calculated according to the load, and the corresponding reinforcement is configured accordingly. Its diameter should not be less than 8mm, and the spacing should not be greater than 200mm.

The bottom reinforcement mainly bears the positive bending moment. Depending on the type of profiled steel sheet, it can be considered as either a composite floor slab or a non-composite floor slab.

In non-composite floor slabs, the profiled steel sheet mainly serves as formwork. Therefore, the main load-bearing component is the positive bending moment reinforcement. So, in calculations, it is calculated the same as for ordinary concrete floor slabs. Since the reinforcement is arranged in the ribs of the profiled steel sheet, attention should be paid to the spacing of the ribs of the profiled steel sheet, and the load-bearing reinforcement should be arranged according to the spacing of the ribs.

In composite floor slabs, profiled steel sheets not only serve as formwork but can also replace the bottom reinforcing bars. Therefore, depending on the load and span, additional reinforcing bars may not be necessary. Closed-section profiled steel sheets are primarily used. During normal use, reinforcement calculations for profiled steel sheets mainly involve converting the steel consumption of the profiled steel sheets into the amount of reinforcing bars needed to determine if the bending resistance requirements are met.

On the other hand, in the event of a fire, only the amount of steel used in the effective portion of the profiled steel sheet needs to be considered to ensure it meets the bending resistance requirements during a fire. If it does, then no additional reinforcement is required. However, if it only meets the requirements during the usable stage but not during a fire, then fire-resistant reinforcement is necessary.

Both the top and bottom reinforcing bars must take into account the thickness of the concrete cover of the floor slab. In particular, the bottom reinforcing bars should not be placed directly on the profiled steel sheet. The above are some points regarding the reinforcement calculation of steel decking.

Steel decking is a new generation of green building material. Regardless of the type of steel decking, reinforcement requirements must be met during installation.

1) Floor decking is an anisotropic slab. To determine whether it is a one-way or two-way slab, you need to use the anisotropy coefficient. Calculate the effective (converted) side length based on the anisotropy coefficient, and then determine whether it is a one-way or two-way slab based on the ratio of the effective side lengths.

2) If the slab is classified as a two-way slab, the reinforcement should be placed at the crests of the wave in the direction perpendicular to the ribs and at the troughs in the direction along the ribs. However, it should be noted that there should be a protective layer of not less than 20mm. This protective layer is mainly to ensure the bond strength of the reinforcement. The resistance calculation is based on the thickness of the concrete above the ribs in the direction perpendicular to the ribs, and from the troughs in the direction along the ribs, i.e., the thickness of the composite slab is the slab thickness.

3) Along the rib direction, if the profiled steel sheet (converted to steel reinforcement) meets the requirements for both the normal section bearing capacity and the shear bond bearing capacity, reinforcement along the rib direction is not required. Special attention should be paid to calculating the shear bond bearing capacity, as composite floor slabs are generally controlled by shear bond. The "High-Rise Steel Structure Code" does not include shear bond calculations, which is an oversight.

4) If calculated as a two-way slab, reinforcement must be provided at the crest, and the profiled steel sheet has no effect in the direction of the vertical rib.

5) Most composite floor slabs are one-way slabs. The very special ones, such as the corners, may be two-way slabs. Because there are inclined beams, the span is generally very small. Without calculating, the same configuration as other parts can basically meet the requirements.

6) The distribution reinforcement at the top of the slab must meet the requirements of GB50010.

7) Whether the connection at the beam support along the rib direction is continuous or hinged depends not on the profiled steel sheet, but on the negative moment reinforcement. The compression on the profiled steel sheet is negligible. The connection perpendicular to the rib direction is generally considered hinged, but anti-crack reinforcement should be provided.

8) Steel decking does not require studs to be designed as composite beams, but there must be certain structural studs to ensure the integrity of the deck and beam.

9) If the design involves composite beams, secondary beams are generally calculated as composite beams, but the main beams (frame beams) should not be calculated as composite beams because frame beams bear repeated loads, and composite beams lack seismic test reports—this point is overlooked by the code. GB50017 differs from GB50010; GB50017 does not include seismic content. The deflection of the main beam under service load can be verified as a composite beam (if it meets the requirements for composite beams).

Zhonggou New Materials' steel decking products are mainly used in multi-story and high-rise buildings, municipal engineering projects, light steel villas, and prefabricated buildings. Most of the projects undertaken are landmark buildings in local cities, such as Xiamen International Financial Center, Xiamen Center, Shenzhen Ping An South Tower, Chongqing Raffles City, Xinjiang Yimin Building, Shenzhen International Convention and Exhibition Center, and Wuhan Hannan Airport. The customers are mainly Fortune 500 companies in China and even the world, such as China Construction Steel Structure, China State Construction Engineering Corporation, and China Railway Construction Corporation.