Flat slabs are commonly used in the construction of multi-storey buildings due to their ease of placement and installation, relatively short construction time, minimal structural floor depth and economic credentials. However, flat slabs are vulnerable to punching shear, a failure mode that typically occurs without any warning at slab-column connections. While various methods exist to improve punching shear capacity, the use of ultra-high performance concrete (UHPC) offers a highly buildable alternative to use of shear reinforcement in normal strength concrete (NC). However, UHPC is an expensive material and recent research has focussed on its partial use in column zones only, with NC elsewhere i.e. hybrid NC/UHPC. In this paper, a non-linear finite element (FE) model using ABAQUS was developed to simulate the punching shear performance of hybrid NC/UHPC flat slabs without shear reinforcement. The FE model was validated against experimental results from the literature. The validated model was then used to investigate the influence of slab thickness, column size, UHPC area and UHPC compressive strength. The results show that punching shear capacity of the slabs increases with the area of the UHPC zone. Additionally, the ratio of concrete compressive strength of UHPC to that of NC has a significant effect on the behaviour of the hybrid slabs which should be accounted for in future design guides. In order to understand the performance of existing design guides and codes in this context, a comparison between FE results and code predictions is also presented. The results suggest that the code models including ACI 318-14, Eurocode2 and Model Code 2010 cannot accurately estimate the punching shear capacity of reinforced UHPC slabs and hybrid NC/UHPC slabs. A modification to the existing ACI equation is proposed which yields accurate predictions for reinforced UHPC and hybrid slabs.

平板由于其易于放置和安装，相对短的施工时间，最小的结构地板深度和经济信誉而通常用于多层建筑物的建筑中。但是，扁平板容易受到冲切剪切的破坏，这种破坏模式通常发生在板柱连接处而没有任何警告的情况下。尽管存在多种方法可以提高冲压冲剪的能力，但超高性能混凝土（UHPC）的使用提供了可替代标准强度混凝土（NC）中使用剪力增强材料的高度可构建的替代方法。但是，UHPC是一种昂贵的材料，最近的研究集中在仅将其部分用于色谱柱区域，而将NC用于其他地方，即混合NC / UHPC。在本文中，建立了使用ABAQUS的非线性有限元（FE）模型，以模拟无剪切补强的NC / UHPC混合平板的冲切剪切性能。相对于文献中的实验结果验证了有限元模型。然后使用经过验证的模型研究平板厚度，柱尺寸，UHPC面积和UHPC抗压强度的影响。结果表明，板坯的冲切剪切能力随UHPC区的面积而增加。此外，UHPC与NC的混凝土抗压强度之比对混合板的性能有重要影响，这在以后的设计指南中应予以考虑。为了了解在这种情况下现有设计指南和代码的性能，还介绍了有限元结果与代码预测之间的比较。结果表明，包括ACI 318-14，Eurocode2和Model Code 2010在内的代码模型无法准确地估计增强型UHPC板和混合NC / UHPC板的冲切剪切能力。提出了对现有ACI方程的修改，它可以对UHPC和混合板进行精确的预测。