内填外包钢管混凝土小偏心受压构件极限承载力分析

Analysis on the Ultimate Bearing Capacity of Small Eccentric Compression Component of Steel Tube with Infilled and Outer Concrete

以大瑞铁路澜沧江特大桥主跨342m上承式劲性骨架钢筋混凝土拱桥为背景,选取拱顶截面构造直杆短柱构件。依据弹塑性力学原理,考虑材料非线性,建立内填外包钢管混凝土小偏心受压短柱构件的截面极限承载力数值迭代算法。运用该算法和ANSYS块体单元有限元法分析构件极限承载力。结果表明:内填外包钢管混凝土偏心受压构件的承载力由外包混凝土控制,内填混凝土的强度虽有一定的提高,但纯钢管混凝土的套箍效应未充分发挥;荷载不变时,构件极限承载力随偏心距增加(保持小偏心受压不变)呈下降趋势,但该结构抗弯矩变化的能力较强;桥拱顶截面极限荷载系数在3.0以上,远高于规范要求的2.0安全系数要求,表明该桥拱顶截面具有足够的安全性;两种算法的误差小于6%,截面极限承载力数值迭代算法的结果略小,但完全能满足工程精度要求,因此,工程应用中完全可以采用截面承载力分析法计算该类构件的承载力。

The reinforced concrete deck arch of Lancang River Da-Rui Railway bridge with a main span of 342 m is taken as background,a straight short column physical model representative of arch top section is designed.Based on elastic-plastic mechanics principle and considering material nonlinearity,an iterative numerical algorithm for analyzing the ultimate bearing capacity of the cross section of the short steel tube with infilled and outer concrete column subject to eccentric compressive loading is developed.The ultimate bearing capacity is determined with the developed algorithm and ANSYS solid-element-based analysis.It is shown that the bearing capacity of the eccentric compression component of steel tube with infilled and outer concrete is controlled by the outer concrete.Although the strength of the inner concrete has been increased to a certain extent,the inner concrete does not represent the confinable effect as developed in the pure concrete filled steel tube.When the load remains constant,the ultimate bearing capacity of the component tends to decrease with the increase of eccentricity（keeping small eccentricity invariant under compression）.But it has higher capacity to resist the bending moment.The ultimate load coefficient at the cross section of bridge arch top is above 3.0,which is far greater than the safety factor of 2.0 required by the design code.It indicates that the cross section of the bridge arch top is safe enough.The difference in the results obtained from the developed algorithm and ANSYS is less than 6%.The results of the ultimate bearing capacity of the cross section obtained by the iterative numerical algorithm are slightly smaller,but can fully meet the requirements for engineering precision.It is concluded that the developed method can be reliably applied to calculate the ultimate bearing capacity of this kind of components in engineering application.