FLEXURAL BEHAVIOR OF HIGH-STRENGTH CONCRETE SLENDER WALLS – ANALYTICAL STUDY
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The use of reinforced concrete structural walls is very common for resisting lateral forces induced by earthquakes and wind, particularly in medium-rise to high-rise buildings.They provide vertical continuity in the lateral-load resisting system and when designed properly, they have been reported to perform well in the events of earthquakes. With huge advancements in the field of concrete materials over the past few decades, engineers have been able to develop concrete mixes of very high compressive strengths. These special concrete mixes, commonly categorized as high-strength concrete (HSC), have enabled construction of compact and robust structures.This study examines the effects of strategic placement of HSC on the performance of slender walls. A conventional prototype wall, for which test data were available in the literature, was analyzed using the finite element method. The model was validated with test data and was subsequently extended to incorporate HSC in the boundary elements to compare its performance with that of the prototype wall constructed with normal-strength concrete (NSC). Effects of change in the reinforcement and dimensions of the boundary elements of the NSC wall on the force-displacement characteristics were investigated for different axial-load ratios. Finally, cold joints resulting from dissimilar concrete pours in the web and the boundary elements for the HSC wall were modeled and its ensuing effects on performance were reported.The HSC wall was found to perform better than NSC prototype wall in terms of strength and stiffness. The former also allowed for reduction in the longitudinal reinforcement of the boundary elements for matching the target strengths of respective NSC prototype walls. The HSC walls also performed better than barbell-shaped NSC walls, enabling replacing the latter with the former when needed. Finally, the modelling of the cold joints led to a drastic change in the force-displacement characteristics and the stress-transfer mechanism due to the breakdown of composite action between the web and the boundary elements, underscoring the importance of ensuring shear transfer at this interface.