基于阶梯刚度模式的PC梁开裂后挠度分析方法  

A Method for Analysing Deflection of PC Girder after Cracking Based on Ladder Stiffness Mode

作　　者：王磊[1] 杨飞[1] 董水英[1] WANG Lei;YANG Fei;DONG Shui-ying(Research Institute of Highway,Ministry of Transport,Beijing 100088,China)

机构地区：[1]交通运输部公路科学研究院,北京100088

出　　处：《公路交通科技》2018年第10期63-68,81,共7页Journal of Highway and Transportation Research and Development

摘　　要：预应力混凝土梁桥的开裂使得结构安全性、适用性和耐久性降低,对于可靠性降低的桥梁有必要对其承载能力进行评定。主梁开裂会导致结构刚度降低,增加主梁下挠风险。同时,主梁下挠进一步加剧裂缝的产生和发展,降低主梁刚度,二者相互影响,形成恶性循环。在进行开裂后的主梁结构力学性能计算时,不可避免地会遇到开裂后主梁刚度的计算问题。计算主梁开裂后刚度时,目前常见的做法是将原结构构件的刚度按一定规则进行折减,并且整个构件采用统一的开裂后刚度值。这种做法往往与结构的实际刚度偏差较大,且结构在荷载作用下的效应误差亦较大。通过对开裂后主梁的裂缝特征参数进行统计,按照一定规则,将开裂后的主梁划分为若干个开裂区段,采用阶梯刚度简化计算方法分别求出每个开裂区段的有效刚度,形成阶梯刚度模式。阶梯刚度建立后,采用挠度分段积分的方法求出阶梯刚度下的荷载挠度。通过开裂后的PC梁加载试验,对阶梯刚度和阶梯刚度下的挠度计算结果进行了验证。结果表明:采用基于裂缝特征统计参数的阶梯刚度模式,更接近结构开裂后刚度的实际情况;基于阶梯刚度的挠度计算结果与试验挠度值吻合较好;与规范规定的开裂后主梁挠度计算方法相比,在未过分增加计算工作量的前提下,本方法的精度更高,更接近实际情况。The safety,serviceability and durability of PC girder bridge are reduced due to the structural cracking. It is necessary to evaluate the load-bearing capacity of the bridge whose reliability has been reduced. The main girder crack may lead to the decrease of structure stiffness and increase the deflection risk of the main girder. Meanwhile,the lower deflection of the main girder is further aggravating the generation and development of the cracks and reducing the stiffness of the main girder. The two factors affect each other and form a vicious circle. In the calculation of the mechanical property of the main girder after cracking,it is inevitable to meet the calculation of the stiffness of the main girder after cracking. When calculating the cracking stiffness of the main girder,the common practice is to reduce the stiffness of the original structural members according to a certain rule,and the whole component adopts a unified stiffness value after cracking.This approach often has a large deviation from the actual stiffness of the structure,and the error of the load effect is larger. The main girder after cracking is divided into a number of cracking sections through statistical parameters of the characteristics of the cracks in the main girder according to a certain rule,and the effectivestiffness of each section is calculated by using the simplified calculation method of ladder stiffness. As a result,the ladder stiffness model is formed. After the ladder stiffness is established,the load deflection based on the ladder stiffness is obtained by using the method of deflection subsection integral. Through the PC girder loading test,the calculation result of ladder stiffness and deflection based on the ladder stiffness are verified. The result shows that（ 1） the adoption of the ladder stiffness model based on the statistical parameters of crack characteristics is more close to the actual stiffness condition of the structure after cracking;（ 2） the calculated result of the deflection based on ladder stiffness

关 键 词：桥梁工程 开裂后挠度 阶梯刚度模式 开裂后的PC梁 开裂刚度 

分 类 号：U448.33[建筑科学—桥梁与隧道工程]