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钢－预应力混凝土组合梁抗弯刚度研究

摘要：针对混凝土翼板配置纵向预应力筋的连续组合梁负弯矩段，在正常使用阶段混凝土开裂受到控制，因此考虑混凝土对抗弯刚度的贡献，提出组合梁挠度计算的变刚度法。在混凝土翼板开裂前，按现行规范的折减刚度法计算抗弯刚度；混凝土开裂后，抗弯刚度随开裂程度而变；变刚度的上限为考虑混凝土工作的折减刚度，下限为混凝土完全退出工作的钢梁加钢筋的抗弯刚度，上、下限刚度对应的荷载分别可取为组合梁计算开裂荷载和计算弹性极限抗弯承载力，在上下限区间内的刚度，近似按荷载进行线性插值确定。这种根据使用荷载大小计算出的抗弯刚度，比现行规范忽略混凝土影响的刚度计算模式具有更高的精度，尤其适用于具有良好抗裂性和裂缝宽度控制的预应力混凝土组合梁。



For the absolute shear connection, inelastic calculation procedure of ultimate positive bending moment that ignoring interface slippage was proved to have enough precision. Measure of shear strain of composite beam cross section in shear span indicated that calculating result of convert cross section procedure was more accurate in elastic phrase, while the result that ignoring shear capacity of concrete was undependable. Stiffness of composite beam in negative bending moment region could be decided according as the converted cross section, while after the concrete is cracked, stiffness changes with the development of the crack. As a result, upper limit of the varying stiffness is that of the converted cross section, and lower limit is that of the steel beam when function of concrete is absolutely removed. Consequently, load according to the upper and lower stiffness limit could be considered as the calculating crack load and elastic ultimate bending strength separately, while stiffness among the upper and lower limit would be decided by linear interpolation. This procedure is especially applicable to the prestressed concrete composite beams that have favorable crack- resistance and control capability.