Modeling of CHB masonry for seismic analysis of low-rise reinforced concrete frames: Effects of CHB masonry properties

• Main Authors: Mendoza, Rodolfo P., Jr., Cruz, Edgardo S., Senoro, Delia B.
• Format: text
• Published: Animo Repository 2009
• Subjects: Hollow bricks—Compression testing; Reinforced concrete—Compression testing; Civil Engineering
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/8423
• Institution: De La Salle University

This paper presents a practical method of modeling CHB masonry for seismic analysis. CHB walls are commonly used in low-rise buildings as non-structural elements that are usually neglected in the analysis of frames as they are assumed not to carry any lateral forces during seismic activity. The inherent in-plane strength and stiffness of these walls attract substantial amount of in-plane forces which were solely assigned to carry by the compositing frame. These actions deviates the behavior of the frame by decreasing the natural period of the structure and correspondingly increase the applied seismic forces. Hence, the frame behavior cannot just be idealized as a simple bare frame but instead a CHB in-filled frame. It was therefore the objective of the study to model the CHB walls in order to determine its effects on the low-rise reinforced concrete frame. The method used in carrying out this study was the compression strut theory that represents the CHB walls as equivalent pin-jointed compression strut. The model considered the mechanical properties of local CHB masonry. Experimental test was conducted by the use of prism having four types of masonry mortars, two types of CHB units with two variable thicknesses. The resulting data were then used to calculate the equivalent thickness of compression struts which were subsequently modeled as cross-braced-type system for the frame. The assessment of the modeled frames was conducted through static pushover analysis using SAP 2000 in which produced capacity curves. Comparison of the capacity curves followed, i.e., for sixteen frame models with different CHB infill properties with bare frame model. Results showed that modeling CHB walls as infill compression struts in seismic analysis can significantly modify the behavior of the frame by increasing its strength and stiffness compared with the conventional bare frame approach. It was concluded that the effect of compression infill strut to the behavior of the frame had been significantly affected by the properties of CHB masonry. Hence, quality of CHB shall be given attention and shall be considered in the design process of concrete frame. That, failure to consider CHB properties to the frame analysis would potentially lead to property damage and adverse impact to public health.