考虑收缩徐变影响的两跨钢-混凝土连续组合梁长期性能预测方法

为量化混凝土翼板收缩徐变对多跨钢-混凝土连续组合梁长期性能的影响,提出相应的预测方法,基于现有两跨连续组合梁长期试验结果对典型的组合梁设计方法进行适用性评述; 在此基础上,基于龄期调整的有效模量法并考虑混凝土的收缩徐变、开裂及组合梁界面相对滑移的综合影响,提出两跨连续组合梁长期中支座弯矩与跨中挠度的计算公式,并采用长期试验结果验证预测方法的可靠性; 进一步对比不同混凝土翼板类型(收缩徐变分布模型)对组合梁长期性能的影响。结果表明:采用龄期调整的有效模量法模拟混凝土徐变特征,考虑收缩产生的附加弯矩,采用折减刚度考虑混凝土开裂与界面滑移的影响,提出的两跨连续组合梁长期性能计算公式,可有效预测组合梁长期中支座弯矩分布与跨中挠度,计算结果与试验结果最大相差25.3%; 混凝土的收缩变形对组合梁长期性能影响显著,当不考虑混凝土收缩变形时,组合梁中支座弯矩与跨中挠度仅分别为试验值的41.1%和60.6%; 组合梁长期性能设计时,应根据楼板类型采用不同的收缩徐变模型,针对钢筋混凝土楼板采用均匀收缩、均匀徐变模型,针对组合楼板采用非均匀收缩、非均匀徐变模型。

Prediction procedures for long-term behavior of double-span steel-concrete continuous composite beams considering shrinkage and creep effects

To investigate the influence of concrete shrinkage and creep on the long-term behavior of multi-span steel-concrete continuous composite beams and propose the corresponding prediction procedures, the applicability of typical composite beam design procedures was evaluated based on the existing long-term test results of two-span continuous composite beams. On this basis, considering the comprehensive effects of concrete shrinkage and creep based on the age-adjusted effective modulus(AEMM)method, cracking and relative slip at the interface of composite beams, formulas for calculating the mid-span support bending moment and deflection of two-span continuous composite beams were proposed. The reliability of the prediction procedure was verified by the long-term test results. Furthermore, the effects of different concrete flange slab types(shrinkage and creep distribution models)on the long-term behavior of composite beams were compared. The results show that the proposed long-term behavior calculation formula for two-span continuous composite beams can effectively predict the mid-span support bending moment distribution and deflection of composite beams with the maximum error between the calculated and measured results of 25.3%, which considers the features of concrete creep by AEMM method, the additional bending moment caused by shrinkage, and the effects of concrete cracking and interface slip by reduction stiffness. The shrinkage deformation of concrete has a significant impact on the long-term behavior of composite beams. When the shrinkage deformation of concrete is not considered, the mid-span support bending moment and deflection of composite beams are only 41.1% and 60.6% of the test values, respectively. Different shrinkage and creep models should be used according to the type of floor slab when designing the long-term behavior of composite beams. The uniform shrinkage and creep models should be used for reinforced concrete floor slabs, and the non-uniform shrinkage and creep models should be used for composite floor slabs.