Abstract
This study was undertaken to study the influence of construction deficiencies on hysteretic behavior of exterior beam-column connections. Building stock survey was conducted in five major cities of Pakistan for identification and quantification of material and detailing disparities between design specifications and construction practices. The effect of these disparities was studied using quasi-static cyclic testing on two exterior beam-column connections; EJ-1A (code-compliant) with no deficiencies and EJ-2A (non-compliant) incorporating all identified deficiencies. Damage patterns and hysteretic force-deformation behavior of these models is presented and the performance of the two specimens is compared. The study found that moderate to high deficiencies exist between design specifications and construction practices for the construction of RC buildings in Pakistan. The study also concluded that significant loss of strength and ductility is observed between code-compliant and non-code-compliant exterior beam-column connections subjected to reverse cyclic loading.Key Words: Building stock survey; Quasi-static testing; Beam-column connections.1 Department of Civil Engineering, University of Engineering & Technology, Peshawar, Pakistan.INTRODUCTIONPakistan is located in moderate to high seismic zones1. The past two decades have seen a rapid growth in con-struction of reinforced concrete buildings in almost all major cities of Pakistan, particularly the federal capital and provincial metropolises. This has led to shift from construction of traditional masonry buildings to the more accommodative reinforced concrete buildings. This trend of shifting from low-rise masonry construc-tion to mid-to-high rise reinforced concrete buildings continues because of shift of population from rural to urban areas. Unfortunately, the construction industry, particularly in small cities, has not been able to cope with the ever growing pressure of maintaining quality control procedures for construction of reinforced concrete buildings. This has resulted in construction of reinforced concrete buildings being constructed far below the design standards. This fact was manifested in the October 8, 2005 Kashmir earthquake wherein many public sector reinforced concrete buildings suffered moderate to severe damage. Several studies have been conducted for char-acterization of damage patterns during the October 8, 2005 Kashmir earthquake2-4. Damage patterns of rein-forced concrete buildings included strong beam-weak column phenomenon, separation of infill panels from the lateral framing system and development of soft-story mechanism, amongst others. These studies pointed out deficiencies in construction practices adopted for con-struction of reinforced concrete buildings, particularly the quality of concrete and reinforcement detailing of beam-column connections. In order to portray a true picture of the construction of reinforced concrete buildings constructed in Pakistan, this study was carried out to identify and quantify the construction deficiencies in construction of reinforced concrete buildings in Pakistan. Furthermore, the effect of these deficiencies on the seismic performance of buildings was studied by subjecting experimental models of exterior beam-column connections to reverse-cyclic loading and studying the hysteretic force-deformation behavior of code-compliant and non-code-compliant models. CONSTRUCTION DEFICIENCIESIn order to identify and quantify the disparities that exist between design specifications and actual construc-tion, a building stock survey was carried out in five major cities of Pakistan. These cities included the four provincial capitals Peshawar, Lahore, Quetta and Karachi and the national capital, Islamabad. The idea behind selection of these cities for survey was that these cities have experienced a steep trend of construction of reinforced