Elasto-plastic Analysis And Structure Design About Cast-in-situ Crestressed Concrete Hollow Floor

The cast-in-situ prestressed concrete hollow floor structure is a new form of floor, itcombines the technology of concrete structures prestressed with unbonded tendons and thetechnology of the cast-in-situ concrete hollow floor structure, which have many advantagesuch as large span, light weight，good sound insulation and so on. But the research about it’sspecific performance is extremely rare, majority of them is focus on ordinary cast-in-situconcrete hollow floor structure.In this paper, we respectively analysis the internal force about edge-supported andcolumn-supported cast-in-situ concrete hollow floor structure using the method ofelasto-plastic analysis, summarize it’s method of internal force calculation and structuredesign. At last, the numerical simulation of these examples are carried on using ANSYS finiteelement analysis software. Obtained the following conclusions:Through theoretical calculations and numerical simulations, we found that cast-in-situconcrete hollow floor structure using the technology of concrete structures prestressed withunbonded tendons is feasible, and effectively reducing the total height of hollow floorstructure, improving crack resistance under service ability limit state.Using the method of equivalent load to simulate prestress of cast-in-situ concrete hollowfloor structure with unbonded prestress is reasonable, and greatly reduce the amount ofcalculation. Through numerical simulations, we found it’s distribution of stress and deflectionis similar to common floor under boundary condition simply supported on four sides, sohollow floor structure’s cavity effect could be neglected.Using the elastic method to design the cast-in-situ concrete hollow floor structure withunbonded prestress is advisable, but the elastic method is too conservative at present. Andplastic limit load which come from theoretical calculations and numerical simulations is fourtime more than design load, therefore the moment needs to be multiplied by a reduction factor,when we don’t consider membrane effect, reduction factor is between0.8to0.9, otherwise itis between0.7to0.8.