考虑传力件分担作用下钢板桩围护结构腰梁轴力计算研究

Research on the Steel Waler Axial Force of the SSPW Structure Considering the Steel Fitting Effected

钢板桩围护结构设计中,钢腰梁按照压弯构件计算还是多跨连续梁计算一直是设计者不可回避的问题,目前认为钢腰梁宜采用压弯构件进行计算。但在实际设计中,如果将斜撑平行于腰梁方向的分力全部作用在钢腰梁上,尤其是遇到深水围堰,钢腰梁强度验算一般很难满足要求。解决上述问题的关键在于腰梁和围护桩之间的传力件能传递多少腰梁轴力到围护桩,从而实际反映钢腰梁的轴力。根据实际钢板桩围护结构的监测和有限元模拟结果,通过分析不同长度传力件下支撑轴力-腰梁轴力-传力件传递轴力的受力特点,发现传力件分担轴力和传力件刚度与支撑轴力的大小有关,并存在临界值。根据上述结果,提出了传力件剪力承载力的计算公式,并发现在双对数坐标下,传力件分担轴力/支撑轴力(F/N)和传力件抗侧移刚度/参考传力件抗侧刚度(k/k_(r))在传力件分担轴力小于其抗剪承载力时,二者呈线性变化。研究给出了叠加支撑轴力水平分力后腰梁实际轴力的计算公式,可在钢板桩围护结构设计时参考使用。

During the design of the steel sheet pile wall(SSPW)support structures,it has always been an unavoidable problem for the designer to calculate the steel waler as a beam with flexure and axial loads or a multi-span continuous beam.In this paper,it is considered that the steel waler should be calculated by a beam forced by flexure and axial loads.However,if the steel waler axial forces superimpose the forces from the bracing struts,especially in the case of deep-water cofferdam,the strength of the steel waler is generally difficult to meet the requirements for practical designs.How much the axial force of the steel waler can be transmitted between the steel waler and the steel pile wall by steel fitting could be critical to actually reflect the axial force of the steel waler.The actual field data measured from the project and a series of 3D finite element method(FEM)analyses were performed to provide insights regarding the struts axial force transmitted by SSPW support systems.The results show that the axial force of steel fitting is related to the stiffness of the parts and the axial force applied on it.Furthermore,shear resistant strength as a critical value for the axial force of steel fitting is put forward,and the relationships of the axial force ratio(F/N)versus lateral stiffness ratio(k/k_(r))are the straight lines in the double logarithmic coordinates when the axial force of steel fitting is less than its shear resistant strength by the results of FEM calculations.As a results of this study,a method to predict the actual axial force for steel waler is given for the design of the SSPW support structure.