车辆荷载作用下微开裂LEM-SHCC路桥连接板受力性能研究

Mechanical performance of LEM-SHCC road-bridge approach slab with micro cracking under vehicle load

为掌握微开裂LEM-SHCC路桥连接板在车辆荷载作用下的受力性能,首先进行混合两种PVA纤维长度(8mm和12mm)LEM-SHCC材料的基本材性(弹性模量、抗压强度及抗拉性能)试验,分析PVA纤维长度对LEM-SHCC材料性能的影响,其次制备混合两种PVA纤维长度的LEMSHCC路桥连接板,研究其在系统温度荷载作用下的吸纳变形能力、裂缝分布规律以及受力特点,随后在微开裂的LEM-SHCC路桥连接板最不利位置模拟车辆荷载作用,研究车辆荷载作用下微开裂LEM-SHCC路桥连接板变形特性,最后进行LEM-SHCC路桥连接板的敏感参数(包括PVA纤维长度、板厚、基层顶面当量回弹模量等)有限元对比分析。研究结果表明:采用混合两种PVA纤维长度LEM-SHCC材料较使用单一纤维LEM-SHCC材料的抗压强度和弹性模量分别提高32%和36%,抗拉初裂应力和极限抗拉强度分别提高51%和8.8%;低周反复拉/压混合两种PVA纤维长度的LEM-SHCC路桥连接板,板面裂缝靠近张拉端多而密,靠近锚固端少而间距大,卸载后表面裂缝可自行闭合,且LEM-SHCC板张拉端和锚固端的内力随着张拉次数的增加而减小;微开裂LEM-SHCC路桥连接板随着车辆荷载增加竖向变形增大,回弹弯沉为0.235mm,小于计算弯沉0.345mm,满足路桥连接板的强度要求;当LEM-SHCC材料的PVA纤维长度为10mm,LEM-SHCC板的设计厚度为150mm,基层顶面当量回弹模量为800MPa时,LEM-SHCC板的最大伸长量、最大应力、拉伸损伤等各项性能最优,该研究成果为LEM-SHCC路桥连接板的设计提供参考。

In order to understand the mechanical performance of LEM-SHCC road-bridge approach slab with micro cracking under vehicle load,the basic material properties including elastic modulus,compressive strength,and tensile performance of LEM-SHCC material fabricated by PVA with two different fiber lengths of 8mm and 12mm were tested,and the influence of PVA fiber length on the properties of LEM-SHCC material was analyzed.Furthermore,the deformation absorption ability,crack distribution law and internal force characteristics of LEM-SHCC road-bridge approach slab fabricated by PVA with two different fiber lengths were studied under thermal load.Subsequently,the vehicle load was simulated at the most unfavorable position of LEM-SHCC road-bridge approach slab with micro cracking,and the mechanical performance and deformation characteristics of the LEM-SHCC road-bridge approach slab with micro cracking under vehicle load were studied.Finally,a finite element comparative analysis was conducted on the sensitive parameters of the LEM-SHCC road-bridge approach slab,including the main influencing factors such as PVA fiber length,slab thickness,and equivalent elastic modulus of topsoil of subgrade.The research results show that compared to those of LEM-SHCC material with single fiber length,the compressive strength and elastic modulus of LEM-SHCC material fabricated by PVA with two different fiber lengths may increase by 32%and 36%,respectively,and the initial cracking stress and ultimate tensile strength may increase by 51%and 8.8%,respectively;for the LEM-SHCC road-bridge approach slab fabricated by PVA with two different fiber lengths under low-cycle reciprocating loads,the cracks on the slab surface are close and dense at the tension end,but are less and the spacing is large at the anchor end,and the surface cracks can be closed by themselves after unloading,and the internal forces of the tension end and the anchor end of the LEM-SHCC slab decrease with the increase of the number of tensions;The vertical deformation of the slightly cracked LEM-SHCC road-bridge approach slab increases with the increase of vehicle load,and the rebound deflection is 0.235mm,which is less than the calculated deflection of 0.345mm,meeting the strength requirements of the road-bridge approach slab;When the length of PVA fiber in LEM-SHCC mixtures is 10mm,the design thickness of LEM-SHCC slab is 150mm,and the equivalent modulus of elasticity of foundation is 800MPa,the maximum elongation,maximum stress,and tensile damage of LEM-SHCC board are the best.This research achievement provides a reference for the design of LEM-SHCC road-bridge approach slab.