高温后混凝土断裂韧度阻力曲线的权函数求解

Determination of Residual Crack Extension Resistance of Post fire Concrete by Weight Function Method

摘要:

基于虚拟裂缝黏聚应力分布，采用解析法与权函数法，对高温后混凝土断裂全过程的裂缝扩展阻力曲线进行求解.试验采用楔入劈拉法，设置20~600 ℃共10组温度.混凝土断裂全过程划分为四个部分，裂缝黏聚应力按照Petersson及CEBFIP Model 1990两类双线性软化本构曲线分布.结果表明：断裂韧度阻力曲线随裂缝扩展长度的增加而增长，但随温度的上升呈下降趋势；解析法与权函数法计算结果吻合较好；软化本构曲线对断裂韧度阻力曲线的形状有明显影响.

Abstract:

The residual crack extension resistance curves (KR(Δa) curves) of post fire concrete, associated with cohesive force distribution on fictitious crack zone of complete fracture process, were obtained by analytical method and weight function method. Wedge splitting tests of 10 groups at temperatures from 20 °C to 600 °C were made. The cohesive force distribution corresponding to four different crack propagation stages was determined according to Petersson and CEB FIP Model 1990 bi linear softening traction separation law. It is found that the residual fracture toughness increases with the increasing of the crack length, whereas, the KR(Δa) curves decrease with the increasing temperatures for the thermal damage induced. KR(Δa) curves calculated by analytical and weight function method have a good coincidence. The softening curves have an obvious influence on the shape of KR(Δa) curves.