端板连接普通螺栓群中和轴位置研究

Study on the Neutral Axis Location of Common Bolts in Flush End-Plate Connections

以螺栓群偏心距和端板厚度为研究参数,对梁柱节点中端板连接在偏心拉力作用下(A组)和纯弯矩作用下(B组)的螺栓群进行了受拉性能试验研究。通过对破坏模式、螺栓群受力分布和中和轴偏移率的分析,研究了端板连接普通螺栓群中和轴位置变化的情况;对两组试验开展有限元分析,从荷载-位移曲线和节点抗拉性能两方面进行研究。结果表明:随着荷载逐渐增大,螺栓群中和轴不断向受压区移动;增大螺栓群偏心距可使螺栓力增大,且加快中和轴向受压区偏移;增加端板厚度能够减小螺栓力,并延缓中和轴向受压区偏移;现行偏心受拉和纯弯矩作用下普通螺栓端板连接的计算方法(或公式)较为保守,与试验结果相差较大。给出的端板连接螺栓力修正公式的计算结果与试验结果吻合良好。在保证结构安全的前提下,该修正公式计算结果更接近螺栓端板的实际受力状态,从而达到减小节点钢材用量和降低成本的目的。

The bolt eccentric distance and the end-plate thickness were used as the research parameters,and experimental studies on the tensile properties of the bolts with flush end-plate in the beam-column joints was conducted under the action of eccentric pulling force(group A)or pure bending moment(group B).Through analyzing the failure modes,the force distribution of bolts and the offset ratio of the neutral axis,the variations of neutral axis location for common bolts with flush end-plate connections were investigated.Based on the load-displacement curves and the joints tensile performance,the finite element software ABAQUS was used for numerical simulation of the two sets of tests.By comparing the results from tests with those from FEM,the following conclusions can be drawn.As the load increased,the neutral axis of bolts continuously moved continuously to the compression zone.Increasing the bolt eccentric distance can significantly increase the bolt axial force increment and accelerate the offset of neutral axial to compression zone.Increasing the thickness of end-plate can reduce the bolt axial force increment and delay the offset of neutral axial to compression zone.The current calculation methods for common bolted end-plate connections subjected to eccentric pulling force or pure bending moment are conservative,which are quite different from the experimental results.The modified formulae on the bolt force for flush end-plate connections are discussed,and the calculation results are in a good agreement with the test results.For ensuring the safety of the structure,the calculation results from modified formulae are closer to the actual stress state of the common bolted end-plate,which can result in the reduction of the joints material amount and cost.