UCLA

A study was conducted to develop a modeling approach that integrates flexure and shear interaction under cyclic loading conditions to obtain reliable predictions of inelastic responses of reinforced concrete (RC) structural walls. The proposed modeling approach incorporates cyclic RC panel constitutive behavior based on an interpretation of the fixed-strut-angle approach into a two-dimensional fiber-based macroscopic model. Coupling of axial and shear responses under cyclic loading is achieved at the fiber (panel) level, which further allows coupling of flexural and shear responses at the element level.

The sensitivity of model results to various modeling parameters (e.g., material constitutive parameters and modeling parameters), wall configuration parameters (e.g., aspect ratio, boundary and web reinforcement ratios), and response parameters (levels of wall axial load and shear) was investigated to demonstrate the ability of the model to predict the behavior or RC walls for a broad range of conditions. The proposed analytical model was validated and calibrated against experimental results obtained from six large-scale, heavily instrumented, cantilever structural wall specimens characterized with different aspect ratios (1.5, 2.0 and 3.0), axial load levels (0.0025 A_{gf'c, 0.07 Agf'c and 0.10 Agf'c) and wall shear stress levels (between approximately 4 and 8 √("f'c" ) psi) tested under combined constant axial load and reversed cyclic lateral loading applied at the top of the wall.}

Comparisons of experimental and analytical model results for moderately slender RC walls (aspect ratio 1.5 and 2.0) revealed that the model successfully captures experimentally observed interaction between nonlinear shear and flexural deformations under cyclic loading and predicts lateral strength and stiffness that is within 10% of experimentally measured values. In addition, the magnitudes and relative contributions of shear and flexural deformations along the wall height were predicted closely at low and moderate drift levels, whereas at drift levels larger than 2.0%, model results were within 25% of experimentally measured deformation components. As well, localized nonlinear responses such as vertical tensile and compressive strains and wall rotations at the wall base were well predicted by the model. The model results were less accurate for the slender (aspect ratio 3.0) RC wall specimen in terms of relative contributions of shear and flexural deformations and magnitudes of compressive strains.

Demonstrated model sensitivity to parameters of the implemented RC panel behavior suggested the need for calibration of these parameters for reliable predictions of nonlinear wall behavior. Given the limited model calibration performed in this study, additional work is needed, particularly for slender RC walls where preliminary results were less accurate. Finally, the implementation of the model into a publicly available computational platform is required to enable more detailed system level studies and future model development.