Experimental And Numerical Study Of Prestressed Concrete Tube Truss Composite Plate

Prestressed concrete pipe truss composite slab improves the shortcomings of traditional composite slab,such as low production efficiency,pipeline difficult to cross,transportation vulnerable to damage,and has good economy.Prestressed composite slabs with close joints have the characteristics of two-way slabs,but the calculation method still needs to be studied.In order to study the mechanical properties of the new composite slab and the calculation method of the two-way slab in construction and service stages,experiments and theoretical studies have been carried out.The main research contents and results of this paper are as follows:(1)Two pre-fabricated slabs and one two-span continuous slab of pre-fabricated concrete pipe truss composite slab were tested.The test results show that the steel tube truss significantly increases the stiffness of the prefabricated floor,and the concrete filled steel tube truss has a good synergistic effect with the pre-stressed concrete floor.The cracking of the top concrete of the two-span continuous slab of prefabricated floor is later than that of the middle concrete of the left and right span.The calculation of the temporary support spacing only needs to check the cracking load of the middle slab of the continuous slab.The section of prefabricated floor does not conform to the assumption of flat section when it is bent,and the reduction factor is multiplied by 0.7 in stiffness calculation.Suggestions for setting temporary support in prefabricated floor construction stage are given.(2)Six simply supported slabs of prestressed concrete steel tube truss composite slabs were tested along the direction of prestressing.The test results show that the prefabricated floor of the composite slabs of prestressed concrete steel tube truss is well combined with the laminated concrete.The effect of "secondary force" reduces the cracking load and increases the maximum crack width of the prestressing composite slab,which should be considered in the design.(3)Nine Simply Supported Slabs with vertical prestressing direction of prestressed concrete steel tube truss composite slabs were tested.The results show that the cracks of multi-spliced slabs are uniform except for the two-spliced slabs,and there will be no concentrated crack failure due to the existence of spliced joints.The crack width at the joints can be significantly reduced by the splicing anti-crack bar,but the short splicing anti-crack bar anchorage length is insufficient,which will lead to bond failure,which will cause the splitting of the overlapping layer concrete and the prefabricated floor of the composite slab specimens.The main factors affecting the vertical prestressing direction stiffness are h/H and the width of the floor B.The calculation formula of the vertical prestressing direction stiffness influence.(4)ABAQUS finite element software was used to establish a four-edge simply supported composite plate model to study the effect of prestressing and splicing on the composite plate,and to verify the accuracy of the theoretical calculation of orthotropic plate.The results show that the calculated deflection of composite plates in mid-span calculated by orthogonal anisotropic plate theory is in good agreement with that calculated by finite element method,and is on the safe side.