John W. Wallace

Flexural Modeling of Reinforced Concrete Walls - Experimental Verification

This study presents detailed information on the calibration of a nonlinear wall macromodel by comparing model results with experimental results for slender reinforced concrete walls with rectangular and T-shaped cross sections. Test measurements were processed to allow for a direct comparison of the predicted and measured flexural responses. Responses were compared at various locations on the walls. Results obtained with the analytical model for rectangular walls compare favorably with experimental responses for flexural capacity, stiffness, and deformability, although some significant variation is noted for local compression strains. For T-shaped walls, the agreement between model and experimental results is reasonably good, although the model is unable to capture the variation of the longitudinal strains along the flange.

Damage and Implications for Seismic Design of RC Structural Wall Buildings

In 1996, Chile adopted NCh433.Of96, which includes seismic design approaches similar to those used in ASCE 7-10 (2010) and a concrete code based on ACI 318-95 (1995). Since reinforced concrete buildings are the predominant form of construction in Chile for buildings over four stories, the 27 February 2010 earthquake provides an excellent opportunity to assess the performance of reinforced concrete buildings designed using modern codes similar to those used in the United States. A description of observed damage is provided and correlated with a number of factors, including relatively high levels of wall axial load, the lack of well-detailed wall boundaries, and the common usage of flanged walls. Based on a detailed assessment of these issues, potential updates to U.S. codes and recommendations are suggested related to design and detailing of special reinforced concrete shear walls.

Modeling of Squat Structural Walls Controlled by Shear

Reinforced concrete squat walls are common in low-rise construction and as wall segments formed by window and door openings in perimeter walls. Existing approaches used to model the lateral force versus deformation responses of wall segments typically assume uncoupled axial/flexural and shear responses. A more comprehensive modeling approach, which incorporates flexure-shear interaction, is implemented, validated, and improved upon using test results. The experimental program consisted of reversed cyclic lateral load testing of heavily instrumented wall segments dominated by shear behavior. Model results indicate that variation in the assumed transverse normal stress or strain distribution produces important response variations. The use of the average experimentally recorded transverse normal strain data or a calibrated analytical expression resulted in better predictions of shear strength and lateral load-displacement behavior, as did incorporating a rotational spring at wall ends to model extension of longitudinal reinforcing bars within the pedestals.

Shear Strength of Lightly Reinforced Wall Piers and Spandrels

Between the 1950s and 1970s, a significant number of buildings were constructed using lightly reinforced perimeter walls with openings. Evaluation and rehabilitation of such buildings requires accurate assessment of the expected shear strength, stiffness, and ductility of the wall segments (wall piers and spandrels) that comprise the primary lateral load-resisting elements. Assessing wall shear strength is complicated by factors such as use of a single curtain of distributed reinforcement, lack of hooks, and use of weakened plane joints, which are all common in older construction. To address these issues, a database of existing test results was assembled and reviewed; and tests were conducted on lightly reinforced wall piers and spandrels to address significant gaps in the available test data. Observations indicate that the amount of boundary reinforcement provided, presence of axial load, and the location of a weakened plane joint on the wall are the most important factors in the assessment of nominal shear strength.

Shear-Flexure Interaction for Structural Walls

This paper proposes an analytical model that couples the flexural and shear responses of reinforced concrete (RC) structural walls. The proposed modeling approach involves incorporating RC panel behavior into a macroscopic fiber-based model. Results obtained with the analytical model are compared with test results for a slender wall and four short wall specimens. A reasonably good lateral load-displacement response prediction is obtained for the slender wall. The model underestimates the inelastic shear deformations experienced by the wall; however, shear yielding and coupled nonlinear shear-flexure behavior are successfully represented in the analysis results. The model captures accurately the measured responses of selected short walls with relatively large shear span ratios (e.g., 1.0 and 0.69). Discrepancies are observed between the analytical and experimental results as wall shear span ratios decrease (e.g., 0.56 and 0.35). Better response predictions can be obtained for walls with low shear span ratios upon improving the model assumptions related to the distribution of stresses and strains in a wall.