Shear capacity of reinforced concrete one-way slabs without shear reinforcement under single loads

现有的无剪钢筋混凝土板的抗剪承载力计算模型大多是基于对梁的抗剪性能的了解而建立的。在单一荷载作用下，板的承载性能被考虑为不同的有效宽度，这不能充分地反映实际的承载性能。根据最近的研究，对于板和梁，直接压杆对剪跨高比和荷载传递的影响是不同的。特别是，拱化作用与剪力有效宽度之间的相互作用取决于静力体系和弯剪比，似乎具有重要意义。在单一荷载和线荷载同时作用的情况下，弯曲产生的较大压缩力的影响尚不清楚，特别是对于具有倾斜受压支撑的弯曲板，本研究的总体目标是分析没有抗剪钢筋的混凝土单向板在单一荷载下的抗剪性能，并建立一个一致的抗剪承载力模型。特别要研究支承条件、约束程度、静力体系(悬臂板、单跨板、多跨板)、剪跨比和配筋率对单点荷载分担和抗剪承载力的影响。通过对板条和宽板的试验，评价了有效宽度的影响。此外，还应分析多个单一荷载的相互作用。通过实验和理论研究解决了这些悬而未决的问题。理论研究的起点是现有的抗剪设计模型。在已有文献的基础上，建立了单荷载作用下的板抗剪试验数据库，对已有的方法进行了评价。实验研究扩展了数据库的参数，这些参数到目前为止还没有研究过。通过对非线性有限元模型的试验和参数研究的评价，量化了弯矩-剪力相互作用对抗剪承载力的不同贡献。结合试验数据，提供了足够的数据库，从而可以建立混凝土楼板在单一荷载作用下的抗剪承载力扩展模型。

The present models for the shear capacity of reinforced concrete slabs without shear reinforcement were mostly developed based on the knowledge of the shear-bearing behaviour of beams. The slab-loadbearing behaviour under single loads is considered by different approaches for an effective width, which capture the actual bearing behaviour insufficiently. According to recent research, the influence of the shear-span-to-depth ratio and the load transfer due to a direct compression strut differs for slabs and beams. In particular, the interaction between arching action and effective width for shear depending on the static system and the moment-shear ratio seems to be of significance. In case of simultaneously acting single and line loads, the influence of the greater compression force due to bending is not clarified, especially for haunched slabs with inclined compression struts.The overall objective of the research project is to analyse the shear-bearing behaviour of one-way concrete slabs without shear reinforcement under single loads and to develop a consistent model for the shear capacity. In particular, the influences of the support conditions, the degree of restraint and the static system (cantilever slab, single- and multi-span slab), the shear-span-to-depth ratio and the reinforcement ratio on the load spreading of a single load and the shear capacity should be investigated. By tests on slab stripes and wide slabs, the influence of the effective width is evaluated. In addition, the interaction of multiple single loads should be analysed. The open questions are adressed by experimental and theoretical investigations. Starting point for the theoretical investigations are the present models for shear design. Based on the shear tests on slabs under single loads from literature, a database is established in order to evaluate the existing approaches. The experimental investigations extend of the database for parameters, which have not been studied so far. By evaluation of the tests and parameter studies on nonlinear finite-element models, the different contributions to the shear capacity depending on the moment-shear interaction are quantified. In combination with the experimental test data a sufficient database is provided allowing to develop an extended model for the shear capacity of concrete slabs under single loads.