基于超高性能混凝土弯曲拉伸特性的二次倒推分析法  

Twice inverse analysis method based on four-point bending test results for UHPC tensile behavior characterization

作　　者：张哲[1] 邵旭东[1,2] 朱平[1,2] 李文光[1] 

机构地区：[1]湖南大学,湖南长沙410082 [2]风工程与桥梁工程湖南省重点实验室,湖南长沙410082

出　　处：《土木工程学报》2016年第2期77-86,共10页China Civil Engineering Journal

基　　金：国家自然科学基金(51178177;51378194);交通运输部重大科技专项(2011318494160)

摘　　要：为简便获得超高性能混凝土(Ultra-High Performance Concrete,简称UHPC)的受拉应力-应变曲线,提出考虑剪切变形和曲率分布非线性的二次逐点倒推分析法。基于不同浇注方式的四点弯曲试验梁的荷载-挠度曲线进行了二次倒推分析,并与直接拉伸试验结果及其他倒推法进行了对比。研究表明:1对于剪跨比和高跨比均为1/3的四点弯曲梁,跨中荷载-挠度曲线达比例极限时,剪切变形引起的剪弯挠度比可达24.8%,倒推分析不能忽略;2基于挠度测试的四点弯曲试验,二次倒推分析得到的UHPC材料应力-应变关系近似呈伪应变硬化特性,梁的荷载-挠度曲线比例极限点大致对应直接拉伸应力-应变曲线的线性偏离点;3二次倒推分析法求得的应力-应变曲线总体应力水平高于直接拉伸试验结果,且水平方向浇注的试件应力比垂直方向浇注的高约10%;4相对于其他倒推法,二次倒推分析法得到的本构曲线的应变特征值与直接拉伸试验结果吻合更好,二次倒推分析法用以获得UHPC材料受拉应力-应变关系的可行性较好。To acquire the stress-strain relationship curve of Ultra-High Performance Concrete （UHPC） easily, a point- by-point Twice Inverse Analysis Method （TIAM） considering the influence of shear deformation and the nonlinear distribution of curvature is proposed. Based on the four-point bending tests, the load-deflection curves of specimens casted by different methods are converted into tensile stress-strain curves by TIAM. Following aspects are demonstrated. Firstly, the shear-moment deflection ratio of a beam （both the shear-span and depth-span ratio 1/3 ）, sums up to 24.8%, indicating that it is unreasonable to neglect shear deformation. Secondly, the tensile stress-strain curves obtained by TIAM exhibit pseudo strain-hardening behaviors and the points of the load-deflection curves at the limit of proportionality correspond approximately to those of direct tension tests at linearity deviations. Thirdly, the stress levels of tensile stress-strain relationship derived by TIAM are slightly higher than those from tensile tests, while the stress of the specimens casted horizontally is 10% larger than that of specimens casted vertically. Lastly, with the direct tensile results as reference, strain characteristics of the stress-strain curves by TIAM show an outperformance than those by other point-by-point inverse analysis methods. Therefore, TIAM is feasible to determine the stress-strain relationship of UHPC.

关 键 词：超高性能混凝土 受拉应力-应变曲线 二次倒推分析法 四点弯曲试验 直接拉伸试验 

分 类 号：U444[建筑科学—桥梁与隧道工程]