Failure Assessment Of Floor Slab Systems Under Extreme Loading Conditions

多层建筑物可能会受到各种形式的荷载，其中一些是常见的和频繁的，但另一些则更为极端和罕见。前者包括构件和饰面的自重以及由居住者、家具、雪等引起的常规外加荷载。另一方面，后一种更严重的荷载类型可能是由大爆炸、重大火灾、强烈地震事件或这些影响的组合引起的。显然，工程师在设计和建造建筑物时必须适当考虑结构在其整个生命周期中可能经历的不同荷载条件。然而，根据所考虑的载荷，设计理念可能会有很大的不同。虽然结构可以承受常规荷载而不会受到任何可能影响其功能的显著损坏，但针对极端事件的设计的主要目的是防止不成比例的坍塌和生命损失，即使付出大量维修或更换费用的代价也是如此。本项目研究建筑结构在极端荷载条件下的性能，重点关注楼板的极限行为。防止建筑物不成比例的连续倒塌的关键可能在很大程度上取决于楼板的显著变形能力，从而使其能够通过膜机制而不是传统的抗弯强度来承载重大荷载。这些膜机构对于极端情况下的承载能力至关重要，例如荷载意外增加(例如，由于较高楼层的部分坍塌)、实际跨度增加(例如，由于梁或柱等中间支撑元件的损失)或材料性能的强度降低(由于温度升高)。所有这些影响都可能在不同的意外荷载情况下发生，或者在不同的意外荷载情况下发生。本项目的主要目的是评估楼板在极端荷载条件下的承载能力。本研究对钢筋混凝土和钢/混凝土组合板的性能进行了试验研究，重点研究了导致钢筋断裂的破坏条件。这些测试将检查重要的几何特性、材料特性和边界条件的影响。实验结果将被用来验证可以预测与破坏相对应的变形和载荷水平的分析方法。最后，测试和分析的结果将被用来生成简化的程序，这些程序可以用于在极端荷载情况下设计楼板。详细和简化的方法的适用性也将通过一些实际例子得到证明。拟议的研究将对英国和海外建筑建造业的安全和竞争力产生直接影响，从而通过改善结构安全和有效使用建筑材料来提高生活质量。

Multi-storey buildings can be subjected to various forms of loading, some of which are of common and frequent nature but others are more extreme and infrequent. The former type includes the self weight of the members and finishes as well as conventional imposed loads such as those due to occupants, furniture, snow, etc. On the other hand, the latter and more severe type of loading can be caused by large explosions, major fires, strong seismic events, or a combination of these effects. Clearly, engineers have to design and construct buildings with appropriate consideration of the different loading conditions that may be experienced by the structure throughout its life cycle. However, the design philosophy can vary significantly depending on the loading under consideration. Whereas a structure is expected to resist conventional loads without suffering any notable damage that can affect its function, the main aim of design against extreme events is to prevent disproportionate collapse and loss of life even at the expense of a substantial repair or replacement cost.This project deals with the performance of building structures under extreme loading conditions, focusing on the ultimate behaviour of floor slabs. The key to preventing disproportionate progressive collapse in a building may largely depend on the ability of floor slabs to deform significantly such that it can carry significant loads through membrane mechanisms rather than conventional bending strength. These membrane mechanisms are vital for the load-carrying capacity in extreme situations such as an unexpected increase in load (e.g. due to the partial collapse of higher floors), increase in actual span (e.g. due to the loss of intermediate supporting elements such as beams or columns) or reduction in the strength in material properties (due to elevated temperature). All of these effects may take place under different, or a combination of, accidental loading scenarios.The main aim of this project is to assess the load-carrying capacity of floor slabs under extreme loading conditions. The research involves an experimental investigation into the performance of reinforced concrete and composite steel/concrete slabs, focusing on the failure condition causing fracture of reinforcement. The tests will examine the influence of important geometric properties, material characteristics and boundary conditions. The experimental results will be used to validate an analytical procedure which can predict the deformation and load levels corresponding to failure. Finally, the findings from the tests and analysis will be used to generate simplified procedures that can be used for the design of floor slabs against extreme loading scenarios. The applicability of the detailed and simplified approaches will also be demonstrated through a number of practical examples. The proposed research will have a direct impact on the safety and competitiveness of the building construction industry in the UK and overseas, consequently leading to a better quality of life through improved structural safety and the efficient use of construction materials.