Experimental analysis of longitudinal shear of composite slabs

Abstract The composite concrete slab systems with steel-deck incorporated has become an alternative to conventional slab models, since it often does not require the use of shoring, promoting several constructive practices, beyond operation of the reinforcement as a positive moment. The procedure of verification of composite slabs is based on the semi-empirical method m and k. The purpose of this paper was to investigate the application of the "m-k method" in a group of slabs with alternative dimensions as the usually adopted in the tests, even as to correlate the values obtained with the results found when testing the models as proposed by the ANSI 2011 test standard, since the normative method is costly and expensive. Therefore, four-point flexural tests were performed on slab models considering only one deck module, varying two spans, the same procedure was repeated in slabs with usual construction dimensions (normative models). The linear regression method was applied to the data found in order to obtain the parameters that would be analyzed. The main results show that the alternative model with the adopted dimensions does not present values that can be applied directly to the normative models, since the increase of the shear span reduces in a significant way the theoretical resistance of the slabs. Nevertheless, the values for the m and k obtained of both alternative and normative models can be adopted confidently as part of the sizing process of the respective models. The deviations between theoretical and experimental resistance satisfy the specifications of the ANSI 2011 standard for both models helped in the confirmation of the previous statement. The expectation of this paper is to assist in the search for new procedures for determining parameters m and k.

摘要 内置钢承板（steel deck）的组合混凝土楼板体系已成为传统楼板形式的替代方案，因其通常无需设置临时支撑，且可在承受正弯矩时作为受拉钢筋发挥作用，同时推动了多项施工工艺的革新。组合楼板的验证流程基于半经验m-k法(m-k method)。本文旨在探究该方法在一组采用非标准尺寸（区别于试验常用尺寸）楼板中的应用，并将所获参数与按照ANSI 2011试验标准开展模型试验得到的结果进行关联分析——鉴于现行规范方法成本不菲。为此，本文针对仅包含单个钢承板模块的楼板模型开展四点弯曲试验，设置两种不同跨径；同时针对采用常规施工尺寸的楼板（即规范模型）重复上述试验流程。对试验获取的数据采用线性回归法进行处理，以提取待分析的参数。主要研究结果表明：采用所设计尺寸的非标准模型，其参数无法直接套用至规范模型中，因为剪跨比的增大会显著降低楼板的理论抗力。不过，从非标准模型与规范模型中所得的m、k参数，均可可靠地应用于对应模型的设计流程中。两种模型的理论抗力与试验抗力之间的偏差均符合ANSI 2011标准的要求，这进一步验证了前述结论。本文期望可为后续探寻确定m、k参数的新方法提供参考。