基于弯曲比例极限的单个试件抗折强度预测方法

Method for predicting flexural strength of single concrete specimen based on flexural proportional limit

为提高混凝土单个试件抗折强度的预测精度,分析了弯曲应力下变形曲线和弯曲比例极限的特性,阐述了基于弯曲比例极限预测单个试件抗折强度的原理和方法.弯曲应力-应变曲线具有在比例极限荷载处由线性向非线性转变的特征,在不破坏试件的前提下,对试件进行逐级加载至比弯曲比例极限荷载大1-2kN,根据应变增量的变化可确定该试件的弯曲比例极限荷载,且该试验不会对试件造成损伤.相同配合比混凝土的弯曲比例极限基本为常数且其变异性比抗折强度小,同配合比混凝土的弯曲比例极限平均值可作为每个试件弯曲比例极限的预估值,将弯曲比例极限荷载除以比例极限平均值即可预估试件的抗折强度.该方法能显著提高单个试件抗折强度的预测精度,可用于预测弯曲疲劳试件的抗折强度.

To improve the predicting precision of flexural strength,the characteristics of deformation curve and flexural proportional limit of concrete under bending stress are analyzed.The principle and technique of the prediction of single specimen＇s bending strength based on flexural proportional limit are expounded.At the flexural proportional limit point,the stress-strain curve transforms from linearity to nonlinearity.Without destroying the specimens,load increase step by step to the level of 1 to 2 kN higher than the flexural proportional limit load.Therefore,by the transformation of incremental strain,the flexural proportional limit load can be determined.While the gradually loading does not bring damage to the concrete specimens.The flexural proportional limit is almost a constant for the concrete specimens with same mix proportion,and their average can be used as the approximate value for each specimen.The approximate bending strength of this specimen could be predicted with the value of the flexural proportional limit load divided by the average flexural proportional limit.Test results shows that the technique can improve the predicting precision of flexural strength remarkably.And it can be used to predict the flexural strength of specimens subjected to bending fatigue load.