Mechanical Performance And Bearing Capacity Analysis Of Prefabricated UHPC Formwork And UHPC-RC Slab

Ultra-High Performance Concrete(abbreviated as UHPC)is an ultra-high performance cementitious composites material with high strength,high compactness,high toughness,and high durability.In this paper,the steel fiber and PVA fiber was mixed to develop a fiber reinforced UHPC which is used to make the permanent template,and this UHPC permanent template is used for the template of the RC slab.The RC unidirectional slab and the two-way slab with the UHPC permanent template are designed and manufactured;The UHPC non-removable formwork,as well as such one-way plates and two-way plates,were subjected to experimental research and finite element simulation analysis.The research content and results are as follows:1)In this paper,the mechanical properties of the UHPC formwork were investigated experimentally and analyzed by finite element method.UHPC was used to make a template with a thickness of 10mm.The UHPC template was subjected to loading tests and finite element analysis during the construction stage to evaluate its feasibility as a template for cast-in-situ slabs.The results show that when the UHPC plate with a thickness of 10mm is used as a building template,the supporting distance under the template can be taken as 0.6m,and the uniform load that can be applied under the elastic state of the template is 6kN/m~2,which is approximately 1.7 times of the design value of the distributed live load,with higher safety reserves.This paper uses ABAQUS to simulate the mechanical properties of the UHPC formwork during construction.The software analysis results are consistent with the test results.When the template thickness is 15mm and 20mm,the UHPC template safety support spacing can be set to 700mm and1000mm;ensuring the template being in the elastic state(without damage),different thickness of the template's neutral axis is in the section 1/2h.2)The mechanical performance and bearing capacity of RC unidirectional slabs with UHPC non-removable template were tested and analyzed by finite element analysis.Using UHPC template as the bottom mold,steel reinforcements and ordinary concrete were placed on it,and simple-supported one-way slabs and two-span continuous one-way plates were made respectively and subjected to static loading tests.The results show that when UHPC is used as a template for RC unidirectional slabs,there is no visible bond-slippage between the UHPC template and the RC layer at the time of slab failure;the flexural bearing capacity is about twice that of the RC plate with the same cross-sectional dimensions and reinforcement.Considering the tension effect of UHPC formwork,the calculation model of bending capacity of this RC one-way plate was established,the calculated values of the model accorded well with the experimental values.Finite element analysis shows that the UHPC-RC plate with UHPC template can increase the RC simply supported one-way plate bearing capacity by about 119.3%;through the analysis of the parameters of the RC layer thickness and reinforcement ratio,it can be concluded that within a certain range increasing the thickness of the RC layer or appropriately increasing the reinforcement ratio of the plate can increase the ultimate bearing capacity of the plate.Through the finite element model calculation results of UHPC-RC continuous slab and RC continuous slab,it can be seen that the ultimate load of RC continuous one-way slab can be increased by about 27.7%using UHPC template.3)Experimental study and finite element simulation analysis of the mechanical performance and bearing capacity of RC bidirectional plates with UHPC non-removable formwork.When the slab was destroyed,no visible sticking and sliding phenomenon was observed at the interface between the preformed UHPC template and the post-cast concrete.According to the yield line pattern of two-way slab,the ultimate load of two-way slab is calculated by the principle of virtual work.Considering the tension effect of UHPC,the ultimate load calculation value is about 94.0%of the test value,and the calculated value is in good agreement with the test value.