深基坑新型钢斜撑接头承载力试验研究

 提出一种深基坑新型钢斜撑接头形式，它可以即插即用，允许有一定的转动角度，可施加预应力，克服原有斜撑接头焊接施工增加基坑暴露时间、倾斜角度固定给斜撑安装带来不便、焊接后无法施加预应力等缺点，可使软土地区深基坑施工受时空效应影响明显减小。配合接头试验制作自平衡式试验架。按照实际尺寸，对该新型支撑接头进行承载力试验，加载到设计轴力2 500 kN时，接头承载力满足设计要求，加载到3 000 kN时接头局部达到屈服状态，预埋钢匣子前方混凝土局部出现压碎现象，但结构整体稳定。用有限元法进行加载过程数值模拟计算，计算曲线与实测吻合较好，这种新型斜撑接头可以进一步推广应用。

EXPERIMENTAL STUDY OF A NEW WELDED JOINT OF STEEL DIAGONAL BRACING IN DEEP PIT EXCAVATION

A new welded joint of steel bracing is proposed. This new joint can be fixed soon after excavation without second welding，which can be rotated in some degree and can be prestressed. These measures can overcome the disadvantages of traditional welded joint，i.e. time increase of deep foundation exposure when using welding joints of diagonal bracing，inconvenient fixation of the slant angle immobility of diagonal bracing，and the prestress not being born on diagonal bracing after welding. It makes the time-space effects on deep foundation excavation obviously being reduced in soft clay areas. The bearing capacity of welded joints is studied by static load test on a welded steel rack with the same size. The test results reveal that the bearing capacity of the welded joint satisfies the requirements of design with a load of 2 500 kN. The whole structure remains stable only with some parts of the welded joint being yielded when load reaches 3 000 kN，and local concrete ahead of the embedded steel plate is crushed. The performance of the welded joint in the process of loading is simulated by finite element method(FEM). The calculation loading curve is consistent well with the test. The new welded joint of diagonal bracing can be used widely in deep foundation excavation with further processing.