# Study on Mechanical Properties of Multi-Cavity Steel-Concrete Composite Floor
## 1 Introduction  
With the continuous improvement of the degree of industrialization of housing construction, many prefabricated composite floor slabs suitable for construction industrialization have been explored. At present, prefabricated composite floors include profiled steel plate concrete composite floor (Figure 0(a)), steel truss composite floor (Figure 0(b)), reinforced truss concrete composite floor (Figure 0(c)) and precast ribbed floor slab (Figure 0(d)). Although all kinds of composite floors have certain advantages, under certain conditions, the applications of these composite floors are limited in different aspects due to cost and actual service performance [1; 2; 3; 4]. [PERSON] [5] carried out full-scale tests on composite slabs simply supported on four sides, and studied their failure characteristics and compressive bearing capacity. The results showed that the composite floor had better bi-directional mechanical characteristics, and its bearing capacity was greatly improved compared with the ordinary floor. [PERSON] [6] studied the bearing capacity and damage characteristics of four steel bar truss composite slabs through a load test, and improved design and calculation method. They pointed out that compared with the ordinary floor, the section stiffness of the steel truss composite slab system was significantly increased, and the deflection of each part was significantly reduced, while its ultimate bearing capacity was the same as that of the traditional cast-in-place concrete floor. [PERSON] [7,8] conducted a full-scale test on the precast unsupported steel truss floor, and carried out the corresponding numerical simulation. They concluded that the section stiffness of this steel truss floor was large, and the overall bearing capacity of the precast floor can meet the construction requirements. Through the static tests of four groups of open profiled steel sheet concrete composite slabs with different spans, [PERSON] studied the crack distribution, failure characteristics and slip of composite slabs. The test results showed that the failure mode of the composite slab was mainly the longitudinal and horizontal shear-bond failure. The longitudinal shear cracks occurred between the profiled steel sheet and the concrete, and the relative slip at the end was observed. Setting studs and increasing the thickness of the floor improved the bending capacity, and the stud can effectively reduce the relative slip at the end. For the large-span open-ended profiled steel sheet concrete composite floor, the longitudinal tensile reinforcement should be properly equipped to improve its bending performance. Their work showed that the ultimate flexural capacity calculated by the full plastic theory was greater than the experimental results, which indicated that the ultimate bearing capacity of the composite slab was controlled by the horizontal and longitudinal shear capacity. The open composite floor designed according to the ultimate bending capacity was unsafe [9]. [PERSON] made an experimental study on the mechanical properties of four 1:1 closed profiled steel sheets. The load deflection curve method and the ultimate moment method were used to determine the section characteristics. It was found that the results calculated by the load deflection curve method were much larger than the theoretical values. The results calculated by the ultimate  
Figure 1: Pictures of existing precast slabs: (**a**) steel deck-concrete composite floor; (**b**) steel bar truss deck; (**c**) composite floor with steel tubular truss; and (**d**) precast ribbed slab-composite floor slab. moment method agreed well with the theoretical values under positive loading, while their difference under negative loading became large. The reason behind this may be that only part of steel in the compression flange of closed profiled steel played a role under negative loading [10]. A new type of multi-cavity steel plate concrete composite floor has been proposed.