非均匀收缩变形对两跨连续钢-混凝土组合板长期性能的影响研究

Influence of non-uniform shrinkage on long-term behavior of double-span composite steel-concrete slabs

与钢筋混凝土板两面传递水份的边界条件不同,压型钢板-混凝土组合板只能单面传递水份,由其产生的混凝土非均匀收缩对组合板的受力性能影响较大。现有研究大多针对该收缩变形分布对单跨组合板长期挠度的影响进行分析,针对其对多跨连续组合板长期性能的影响研究较少,且无相应的设计方法。以两跨连续组合板为研究对象,采用随龄期而调整的有效模量法,提出考虑非均匀收缩变形影响的组合板中支座负弯矩、裂缝宽度和跨中挠度的计算方法,并采用已有试验结果验证该方法的可靠性。在此基础上,对比分析不同收缩变形分布模式(非均匀收缩、均匀收缩、不收缩)对两跨连续组合板长期性能的影响差异。研究结果表明:考虑非均匀收缩分布的计算公式,可有效预测钢-混凝土组合板长期支座负弯矩、裂缝宽度及跨中挠度,预测结果/试验结果的均值分别为1.088、1.026和0.927;不考虑收缩变形和考虑均匀收缩变形将显著低估组合板中支座负弯矩、裂缝宽度和跨中挠度,与试验值分别相差50.0%和24.9%、71.3%和58.6%、46.1%和34.5%;非均匀收缩变形由均匀收缩变形及梯度收缩组成,与均匀收缩相比,梯度收缩对组合板长期性能的影响更为显著,设计时不应忽略梯度收缩变形的影响。

Different from the uniform humidity diffusion in reinforced concrete slabs,composite steel-concrete slabs exhibit non-uniform humidity diffusion due to the impervious steel decks on their soffit,leading to non-uniform shrinkage profiles through the thickness of composite slabs. To date,most research efforts have been focused on the influence of non-uniform shrinkage on the mid-span deflection of single-span composite slabs,however,very limited research has been devoted to their impact on the long-term behavior of multi-span composite slabs,and no prediction methods have been available. In this study,design procedures were proposed to calculate the mid-support hogging moment and cracking width and mid-span deflection of double-span composite slabs,using Age-Adjusted Effective Modulus( AAEM) method. The proposed design procedures were benchmarked against experimental data available in literature. The calculated long-term behavior accounting for different shrinkage profiles( i. e.,non-uniform shrinkage profile,uniform shrinkage profile and non-shrinkage profile) was compared,outlining the importance of considering the influence of non-uniform shrinkage on the long-term behavior of double-span composite slabs. The obtained results show that the newly proposed equations can well predict the long-term mid-support hogging moment,crack width and mid-span deflection of two-span continuous slabs,where the mean ratios of calculated to experimental data are 1. 088,1. 026 and 0. 927, respectively. When considering non-shrinkage profiles( or considering constant shrinkage profiles),there are 50. 0%( 24. 9%) decrement in the mid-support hogging moment,71. 3%( 58. 6%) decrement in the crack width,and 46. 1%( 34. 5%) decrement in the mid-span deflection. The non-uniform shrinkage can be regarded as the sum of constant shrinkage and differential shrinkage,and the influence of differential shrinkage is more critical in predicting the time-dependent behavior of two-span composite slabs,which is needed to be considered in their routine design.