Study On Compressive Performance Of Ultra-high Performance Concrete Sandwich Wallboard

With building industrialization and the need for energy conservation,the current increasingly thick non-composite sandwich thermal insulation wallboard requires higher stress performance of connectors and overall structural performance.Therefore,it is necessary to study a composite sandwich thermal insulation wallboard with both thermal insulation and stress performance.Based on the 2019 Science and Technology Project Plan(2019-K-085)by the Ministry of Housing and Urban Construction and Anhui Provincial Natural Fund Project(1908085ME144),this paper proposes a kind of prefabricated ultra-high performance composite sandwich thermal insulation wallboard with functional gradient,which can ensure the bearing capacity of the wallboard by means of the gradient changes of strength and thermal conductivity,and makes numerical simulation of and theoretical derivation of the compressive performance of this wallboard.The main work and conclusions are as follows:1、The paper makes numerical simulation of literature experiments,finds out the fact that numerical simulation results are consistent with the experimental values,verifies model correctness and rationality,and analyzes the causes of errors;2、It tests the flexural strength and compressive strength of ultra-high performance concrete,tensile strength and compressive strength of foam concrete,and interface bond strength between ultra-high performance concrete and the foam concrete,and puts the measured values into numerical simulation.It theoretically calculates tensile performance of connectors,shear strength,and relative displacement before simulating experimental numeric values,and concludes that at least 44 connectors are required under the current standard;it makes numerical simulation of connector layout with interface bond strength and non-contact interface property.When the connector is less than 1,000 mm,the ultra-high performance concrete surface is not bent locally,which belongs to material failure;interface bond strength is simulated without connectors.When interface bond strength is greater than 0.3MPa,the surface layer is not separated from the sandwich layer and local bend does not occur,which belongs to material failure.3、It takes the amplitude of the first-order buckling mode of wallboard as L/1,000 as the initial defect and introduces the amplitude into the numerical simulation.The main simulation parameters are concrete strength grade,height-thickness ratio,boundary conditions,connector form and sandwich layer materials and others,and the failure mode is material failure.4、According to numerical simulation results,it draws the following conclusions that:the sandwich wallboard with the surface material of ultra-high performance concrete is with higher bearing capacity(2.15 times as much as C30 concrete wallboard)and and better ductility;the bearing capacity with the boundary condition of consolidation at both ends is 3.93% higher than the boundary hinged condition at both ends,which has almost no effect on vertical displacement,and can greatly reduce lateral displacement;the ultimate bearing capacity of grid connectors is 7.00% higher than that of bar connectors;the ultimate bearing capacity of the sandwich layer with foam concrete is 7.41% higher than that of the EPS board.Therefore,the stress difference between the inner and outer wallboard of test pieces with high bearing capacity is smaller: the smaller lateral displacement leads to the small additional bending moment,and the increased proportion of the vertical load in the total load.5、It introduces the current formula for the bearing capacity of wallboard under axial compression.The main calculation factors are concrete strength grade,boundary condition and height width ratio.With reference to the calculation assumption in Design Standards of Concrete Structures(GB50010-2010),and combined with the characteristics of ultra-high performance concrete,this paper analyzes the compressive process of sandwich thermal insulation wallboard;makes numerical simulation of the in-plane bearing capacity of wallboard under different boundary conditions,takes the ratio of out-of-plane and in-plane bearing capacity of wallboard as the stability coefficient of wallboard,fits and puts the stability coefficient into the calculation formula of wallboard under axial compression,and concludes that the calculated values are consistent with simulated values;puts forward the measures to improve wallboard stability according to numerical simulation results and knowledge of material mechanics.Finally,it summarizes the research results of the compressive performance of the ultra-high performance concrete sandwich wallboard with functional gradient,and points out the problems that need further study.Figure [31] table [20] reference [67]...