Research On Mechanical Properties Of Reinforced Truss Floor Slab With Fiber Cement Slab Bottom Form

Steel-bars truss decks with fiber cement slab bottom form is a new type of composite slabs form.The fiber cement slab with thickness of 20 mm is used as the permanent bottom form.The fiber cement slab and steel-bars truss are connected as a whole.In the construction stage,steel-bars truss decks with fiber cement slab bottom form can bear all the weight of poured concrete and other construction loads.In the use stage,the permanent bottom form and the post-pouring concrete form a whole to bear all the service load.Fiber cement slab bottom formwork and steel-bars truss are prefabricated in the factory to replace the traditional formwork,and concrete is poured after on-site installation.Combining the advantages of traditional steel-bars truss composite slab(bottom plate thickness of 60mm)and traditional steel-bars truss deck(bottom plate is shaped steel plate),the on-site assembly rate is more than80%.In this thesis,an experimental study is made on the construction stage and use stage of Steel-bars truss decks with fiber cement slab bottom form,and the ABAQUS finite element software is used to calculate and analyze the mechanical properties of the construction stage and the use stage.(1)Experimental study in the construction stage: 3 specimens were directly loaded with heavy objects for loading test,and 7 specimens were simulated by cast-in-place concrete for loading test.The experimental results show that the fiber cement slab bottom formwork is well combined with the steel-bars truss,and there is no detachment or peeling phenomenon.The setting of temporary support can obviously reduce the deflection of the deck,the support span has a great influence on the deflection of the floor bearing plate.(2)Use stage test: 9 specimens were directly loaded with heavy objects for loading test.The experimental results show that the fiber cement slab bottom formwork is well combined with the post-cast concrete,and there is no detachment and spalling phenomenon.The mechanical properties of the steel-bars truss decks with permanent bottom form are similar to those of the ordinary concrete floor slab,and the location and development of cracks are the same as those of the ordinary concrete floor slab.The installation of mid-span temporary support can effectively reduce the deflection of format-free concrete floor slab in service stage.(3)ABAQUS is used to simulate the construction stage,and the calculation results of fiber-cement slab model and non-fiber-cement slab model are compared.In the construction stage,fiber cement slab bottom formwork and steel-bars truss can interact to participate in the force.By calculating and comparing the influence of the diameter of the upper steel bar,the diameter of the lower steel bar,the diameter of the ventral steel bar and the support span on the mechanical properties of the deck,it is found that the diameter of the upper steel bar has a great influence on the mechanical properties of the deck.In order to increase the stiffness reduce the deflection of the deck and,the diameter of the upper steel bar can be considered to increase.The diameter of lower chord reinforcement and belly bar reinforcement have little effect on the mechanical properties of decks.The temporary support span has a great influence on the mechanical performance of the deck.In the case of different loads,spans and plate types,the support span needs to be determined by calculation.(4)ABAQUS finite element software was used to simulate the whole construction process,and the comparison was made with ordinary reinforced concrete floor slab.On this basis,the influence of chord diameter and support span on the mechanical properties of concrete slab with steel-bars truss decks with permanent bottom form in service stage is analyzed.The calculation results show that the concrete slab with steel-bars truss decks with permanent bottom form formed by the steel-bars truss decks with permanent bottom form and the post-poured concrete can bear the same force as the composite slab,and its mechanical performance is basically the same as that of the ordinary concrete floor slab.The diameter of the upper reinforcement has little influence on the concrete slab with steel-bars truss decks with permanent bottom form,while the stress of the lower reinforcement is the same as that of the bottom reinforcement of the ordinary concrete slab.The installation of temporary support in the construction stage can improve the cracking load of the concrete slab with steel-bars truss decks with permanent bottom form and reduce the mid-span deflection.The supporting span has a great influence on the concrete slab with steel-bars truss decks with permanent bottom form.