Membrane effects in reinforced concrete: From experimental evidence to numerical and analytical modelling

The development of membrane effects in reinforced concrete structures allows for significant enhancements in the resistance provided that lateral movements of a structure or sub-assemblage are restricted. First, the restrained dilation of flexural cracking allows developing axial compressive forces, which increase the resistance with respect to an unconfined response, called Compressive Membrane Action (CMA) or Arching Action when referring to linear members. CMA is significant for low levels of displacements and its effect is considered in some design codes (e.g. punching resistance in EN1992–1–1:2023). For higher levels of displacement, the member elongates and the compressive forces reduce, becoming eventually in tension and activating the so-called Tensile Membrane Action (TMA). TMA has traditionally been widely considered for robustness considerations (response after accidental actions such as column removal). In this paper, a consistent treatment of CMA and TMA on reinforced concrete sub-assemblages of linear members is presented. First, a database of 56 tests is compiled, filtered and digitalized in terms of the load-displacement curve (covering a wide range of heights (90–660 mm), reinforcement ratios (0.31–1.3 %) and slenderness ratios (4−27)). By analysis of the test results and interpretation using refined finite element simulations, the phenomena underlying the activation of CMA and TMA are investigated and quantified. On this basis, a general approach grounded on limit analysis is presented, both for CMA and TMA, and providing sound and consistent agreement to the test results. This approach enables simple analytical expressions for design, covering different ranges of displacement and thus providing a consistent transition from CMA to TMA. Its predictions show in addition low scatter when compared to test results, smaller than several other approaches currently available in the literature. • A database of 42 RC sub-assemblage tests is compiled and analysed to study CMA and TMA behaviour. • A unified approach for CMA and TMA is developed using limit analysis and validated with experiments. • Detailed finite element models are used to interpret test results and investigate CMA and TMA mechanisms. • Failure mode depends on axial restraint, geometry, and reinforcement ductility and detailing.