The reinforced concrete (RC) membrane element is recognised as a basic component of a wide range of structures, such as shear walls, deep beams and shells. The shear action of RC membranes, as a major cause of structural failure, is difficult to predict and is of vital importance to building safety. To analyse the shear performance of membrane elements, the truss model theory and membrane model theory are commonly employed, and current representative models include modified compression field theory (MCFT), fixed-angle softened truss model (FASTM), rotating-angle softened truss model (RASTM), cracked membrane model (CMM) and softened membrane model (SMM). Among these, the FASTM is widely regarded as an accurate and efficient means for the shear performance prediction of membrane...[ Read more ]

The reinforced concrete (RC) membrane element is recognised as a basic component of a wide range of structures, such as shear walls, deep beams and shells. The shear action of RC membranes, as a major cause of structural failure, is difficult to predict and is of vital importance to building safety. To analyse the shear performance of membrane elements, the truss model theory and membrane model theory are commonly employed, and current representative models include modified compression field theory (MCFT), fixed-angle softened truss model (FASTM), rotating-angle softened truss model (RASTM), cracked membrane model (CMM) and softened membrane model (SMM). Among these, the FASTM is widely regarded as an accurate and efficient means for the shear performance prediction of membrane elements for its theoretical background and calculation effort. However, the tensile constitutive model for concrete in the existing shear models cannot correctly reflect the non-linear behaviour of concrete under tension. Moreover, the local stress variation at cracks due to the tension-stiffening effect is not well defined, especially under cyclic loading conditions.

In this study, the limited tension-stiffening effect of concrete in membrane elements under shear is evaluated and validated using a number of experimental results obtained from the literature. The post-cracking behaviour of concrete is described with different stages based on the level of crack damage. The limited tension-stiffening model weakens the post-cracking tensile strength of concrete by including the influences of the bond stress-slip relationship, orthogonal reinforcement arrangement in the membrane element, crack accumulation and the tension termination point.

Based on this, an analytical model, named as the tension-stiffening fixed-angle truss mode (TFTM), is proposed by combining the limited tension-stiffening model for concrete in tension with fixed-angle theory. Furthermore, the TFTM is extended to general loading cases and the cyclic tension-stiffening fixed-angle truss model (CTFTM) is proposed by introducing reloading/unloading rules and damage coefficient due to cyclic loads. The accuracy of the TFTM and the CTFTM is testified by producing shear stress-strain curves and peak shear strengths for different series of test panels, and the comparisons show that the TFTM and the CTFTM excel in the prediction accuracy and efficiency for membrane elements in monotonic and cyclic loading conditions.

The application of the proposed models for predicting the shear performance and strength of RC squat shear walls under monotonic and cyclic lateral loads is conducted, where the web panel of the shear wall is simulated as an assembly of membrane elements. The results of prediction and comparison with existing shear models and experiments show that the proposed models can accurately predict the shear performance of squat shear walls as well as the influence of various axial load ratios. Due to the excellent accuracy and efficiency of the TFTM and the CTFTM, the proposed models can be further applied in the shear prediction of a large variety of building structure.