Ultimate Strength of Parabolic Concrete Arches

This investigation is aimed to present a simple analytical approach for predicting the ultimate strength of concrete arch using theory of plasticity. Six models of two-hinged parabolic concrete arches with and without steel reinforcement were tested under concentrated load. The observed behavior of cracking strength and collapse load of the arches tested were compared with those predicted by the analytical procedure proposed here. The arches tested were un-reinforced concrete, lightly reinforced concrete, and concrete with filing iron respectively. A Good agreement is found between the proposed analysis and test results. Tests have shown that the collapse of all arches was mainly due to the formation of two plastic hinges at a point of maximum bending moment which is similar to collapse mechanism adopted in this study. The use of light concentric steel reinforcement resulted into a significant increase in the ultimate load. This increase reaches up to three times of that without reinforcement. Ductility was also found to be greatly improved due to using steel reinforcement in arches. The procedure of analysis in this paper can give a simple guide for design of concrete arch.

Cyclic behavior of lightly reinforced concrete moment frames with partial- and full-height masonry walls

Existing lightly reinforced concrete (RC) moment frames are vulnerable to earthquakes. The seismic behavior of these frames could be affected by the presence of masonry infill walls. The objective of this study was to investigate the seismic behavior of gravity-designed RC frames having partial- and full-height masonry infill walls. For this purpose, experimental and numerical studies were conducted. Three one-story and one-bay gravity-designed RC moment frames with and without partial- and full-height masonry infill walls were made and tested under cyclic lateral loads. Numerical models for RC moment frames and masonry walls were proposed based on test data. Nonlinear static and incremental dynamic analyses (IDAs) were conducted for three-story RC moment frames with and without partial- and full-height masonry infill walls using the numerical models. Both experimental and numerical studies demonstrated that the masonry-infilled RC frames had larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. The partial-height masonry-infilled RC model frame had the least collapse strength among the frames.