(1 山东建筑大学土木工程学院， 济南 250100；2 山东省建筑结构鉴定加固与改造重点实验室， 济南 250100)

［摘要］既有建筑地下增层时，需要设置托换梁将上部竖向构件的荷载向桩基础传递，该托换梁为内置H型钢的双梁式深受弯构件。为研究托换梁受剪承载力，设计了6个试件，进行对比试验。试验结果表明：6个梁均表现为剪压破坏形态；内置H型钢的钢筋混凝土托换梁比未置H型钢相同截面形式与配筋数量的钢筋混凝土托换梁的受剪极限荷载提高约36.3%；双截面钢筋混凝土托换梁的受剪承载力与相同截面和配筋数量的单截面钢筋混凝土梁相当；支座与梁柱节点连线处的箍筋和型钢在抗剪中起了主要作用，而支座处与梁柱节点附近的箍筋和型钢起次要作用；双截面托换梁同一截面的内肢箍筋比外肢箍筋承担更多剪力。最后，基于试验结果，建立了托换梁受剪承载力计算公式，并对托换梁受剪承载力计算结果和试验结果进行了对比。结果表明，未置H型钢的普通钢筋混凝土梁计算结果和试验结果吻合较好；对于内置型钢的梁，受剪承载力计算结果和试验结果平均相差百分比为18.4%，但计算结果均小于试验结果，偏安全。  

［关键词］既有建筑地下增层；托换梁；受剪承载力；双梁式深受弯构件；内置H型钢 

中图分类号：TU375-1 文献标识码：A文章编号：1002-848X(2021)13-0114-05

Experimental study on shear bearing capacity of underpinning beam for addition basement of existing buildings 

JIA  Qiang1,2,  PAN Yu1,2,  ZHANG  Xin1,2 

(1 School of Civil Engineering, Shandong Jianzhu University, Jinan 250100， China；2 Shandong Provincial Key Laboratory of Appraisal and Retrofitting in Building Structures, Jinan 250100， China) 

Abstract: When adding basement to existing building, the underpinning beam needs to be set to transfer the load of the upper vertical member to the pile foundation. The underpinning beam is a double-beam deep bending member with built-in H-shaped steel. In order to study the shear bearing capacity of underpinning beams, 6 specimens were designed and comparative tests were carried out. The test results show that the 6 beams all show the form of shear pressure failure. The shear ultimate load of reinforced concrete underpinning beam with built-in H-shaped steel is increased by about 36.3% compared with that of reinforced concrete underpinning beam without built-in H-shaped steel with the same section and reinforcement quantity. The shear bearing capacity of double-section reinforced concrete underpinning beam is equivalent to that of single-section reinforced concrete beam with the same section and reinforcement quantity. The stirrup and shaped steel at the connection between the support and the beam-column joint play major role in the shear resistance, while the stirrup and shaped steel near the support and the beam-column joint play minor role. The internal stirrups of double-section underpinning beam bear more shear force than the external stirrups. Finally, based on the test results, the calculation formula for the shear capacity of the underpinning beam was established. The calculation results of ordinary reinforced concrete beams without built-in H-shaped steel are in good agreement with the test results; for the beams with built-in shaped steel, the average percentage difference between the calculation result of shear capacity and the test result is 18.4%, but the calculation results are less than the test results, which is relatively safe. 

Keywords:addition basement of existing building； underpinning beam； shear bearing capacity；double-beam deep bending member； built-in H-shaped steel

*国家自然科学基金重点项目（52038006）。

 作者简介：贾强，博士，教授，Email:jiaqiang@sdjzu.edu.cn。