九桩双薄壁墩厚承台空间桁架模型现场试验研究

为进一步研究大型桥梁工程中常见的大型桩基厚承台的受力性能,根据规范建立新疆伊犁河特大桥九桩双薄壁墩承台空间桁架计算模型,对承台内部应力进行了现场测试,并对测试结果进行分析.结果表明,本工程九桩承台属于厚承台范畴,内部完整应力流可近似为一个理想的桁架,即:以主压应力混凝土区为压杆,桩顶区域的受拉钢筋为拉杆的空间桁架模型;承台开裂之前,混凝土拉杆效应不可忽略,但随着裂缝的开展,受拉区混凝土逐渐退出工作;采用空间桁架模型进行设计符合厚承台受力机理,具有更好的合理性.

Experimental Research on Nine-pile Double Thin-wall Pier's Thick Caps Using Strut-and-tie Model

To make further researches on the load-bearing behavior of large-scaled thick pile caps in bridge engineering,the computation strut-and-tie model of nine-pile double thin-wall pier's thick caps for Xinjiang Yili River Grand Bridge was found according to the specifications.The prototype testing study on the interior stresses was made and the test data were analyzed.The analytic results indicate that (1) the pile caps of this project belongs to thick pile cap, in which the whole interior stress flow can be approximated by an strut-and-tie model, where zones of concrete with primarily unidirectional compressive stresses can be modeled by compression struts and tension ties can be used to model the reinforcements around the pile top region; (2) the concrete contribution to tensile resistance shall not be neglected before cracking, however, reinforcements bear most of tension in the tensile force after cracking; (3) strut-and-tie model are suitable for design of thick pile caps and more rational than the traditional design procedures.