Beam flexural overstrength is an important parameter in seismic design and evaluation of reinforced concrete (RC) moment resisting frames. It affects the column-to-beam flexural strength ratio (CBSR) which is a key parameter to avoid unfavorable column-driven mechanisms. In RC beam-and-slab floors, interaction between beam growth and slab panels is of a very complex nature which significantly alters the beam flexural overstrength. Enhancement of beam flexural capacity in slab floor systems depends on several parameters that should be considered on a case-by-case basis. To include some of the effects that were not considered in previous studies due to physical limitations of experimental works and lack of appropriate computational tools, a generic two-by-two bay archetype story model with a beam-and-slab floor system were considered for further investigations by means of numerical modelling. In order to consider the spatial effects of the floor system, several computational models were assembled by changing the span and cross section of beams in terms of depth, width and reinforcement ratio as well as the thickness of slabs to perform a parametric study on beam flexural overstrength ratio. Multilayer nonlinear shell elements were used for finite element modelling of slab panels to account for the kinematic effects of beam elongation along with the restraining effects of the floor slab. According to the results of analyses, variation of positive and negative flexural overstrength ratios of beams at different performance levels were presented for different parameters. Results demonstrate that the flexural overstrength ratio is greatly affected by the level of chord rotation (beam lateral drift or performance level) reinforcement ratio and the type of connection. However, beam-to-slab flexural stiffness ratio as well as beam length are not overly important parameters for flexural overstrength evaluation. This study reveals that, despite code prescriptions, CBSR should not be considered identical for all cases; hence, it should be revisited based on the desired performance level, type of connection and the beam reinforcement ratio.

中文翻译：

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重现钢筋混凝土梁板楼板系统的抗弯强度，以进行抗震设计和评估

梁的抗弯强度是抗震设计和钢筋混凝土抗弯框架评估的重要参数。它会影响柱梁抗弯强度比（CBSR），这是避免不良的柱驱动机制的关键参数。在RC梁板楼板中，梁的生长与板面板之间的相互作用具有非常复杂的性质，这会显着改变梁的弯曲超强度。平板楼板系统中梁抗弯能力的提高取决于应视具体情况而定的几个参数。包括由于实验工作的物理局限性和缺乏适当的计算工具而在以前的研究中未曾考虑的一些影响，考虑采用带有梁板楼板系统的通用的2×2海湾原型故事模型，以通过数值建模的方式进行进一步研究。为了考虑楼板系统的空间效应，通过改变梁的跨度和横截面的深度，宽度和配筋率以及楼板的厚度来组装几个计算模型，以对梁的挠曲进行参数研究超强度比。多层非线性壳单元用于面板的有限元建模，以考虑梁延伸的运动学效应以及楼板的约束效应。根据分析结果，给出了不同参数下梁在不同性能水平下正，负挠曲超强比的变化。结果表明，弯曲超强度比受弦旋转水平（梁横向偏移或性能水平）的增强比例和连接类型的影响很大。但是，梁与板的弯曲刚度比以及梁的长度对于弯曲超强度评估而言并不是太重要的参数。这项研究表明，尽管有代码规定，但并非在所有情况下都认为CBSR是相同的。因此，应根据所需的性能水平，连接类型和梁的增强比重新进行研究。梁与板的弯曲刚度比以及梁的长度对于弯曲超强度评估而言并不是太重要的参数。这项研究表明，尽管有代码规定，但并非在所有情况下都认为CBSR是相同的。因此，应根据所需的性能水平，连接类型和梁的增强比重新进行研究。梁与板的弯曲刚度比以及梁的长度对于弯曲超强度评估而言并不是太重要的参数。这项研究表明，尽管有代码规定，但并非在所有情况下都认为CBSR是相同的。因此，应根据所需的性能水平，连接类型和梁的增强比重新进行研究。