International Journal of Computer Applications (0975 – 8887) Volume 106 – No.9, November 2014 27 Earthquake Pounding Effect on Adjacent Reinforced Concrete Buildings Mariam Ehab Assistant lecturer Postgraduate student Structural Engineering Department Cairo University Hamed Salem Professor Structural Engineering Department Cairo University Hatem Mostafa Professor Structural Engineering Department Cairo University Nabil Yehia Professor of Concrete Structures Cairo University ABSTRACT During earthquakes, pounding of adjacent buildings occurs due to their different dynamic characteristics as well as insufficient separation distance between them. Although earthquake loading is commonly considered in structural design, pounding of adjacent buildings is not usually considered and usually causes highly unexpected damages and failures. Pounding effect was numerically investigated in this study, where adjacent buildings were designed to resist lateral earthquake loads without taking into consideration the additional applied force resulting from pounding. Nonlinear dynamic analysis was carried using the Applied Element Method (AEM). Pounding of buildings of different structural systems, different gravity loading and different floor heights was investigated. Dynamic behavior in terms of additional base shear, base bending moments and pounding forces was investigated for different gap distances less than the safe gap distance specified by the Egyptian Code of Practice (ECP). Effect of gap distance, building’s dynamic characteristics, building’s height and gravity loads on additional straining actions due to impact was discussed. Keywords Pounding, separation distance, applied element method. 1. INTRODUCTION In metropolitan cities, buildings are often very close since a maximum land use is required due to high population density. Therefore, for metropolitan cities located in regions of active seismicity, the pounding of adjacent buildings may pose a potentially serious problem. Pounding of adjacent buildings during earthquake excitation is one of the causes of structural damages. Some of the local damages take place due to the unexpected lateral impact force due to pounding which is not usually considered in building design. Sometimes it may cause building’s collapse under a stronger earthquake. The Mexico City earthquake in 1985 has revealed the fact that pounding was present in over 40% of 330 collapsed or severely damaged buildings, and in 15% of all cases it led to collapse [1] [2]. A survey of pounding incidents in San Francisco Bay area during 1989 Loma Prieta earthquake showed significant pounding cases, over 200, at sites over 90 km from epicenter [3], Several destructive earthquakes, both distant and near, have hit Egypt in both historical and recent times. The annual energy release in Egypt and its vicinity is equivalent to an earthquake with magnitude varying from 5.5 to 7.3 on Richter scale. For example Cairo 1992 earthquake that lead to a catastrophic damages, 350 buildings were completely destroyed and 9,000 other severely damaged and causing 545 deaths, injuring 6,512 and making 50,000 people homeless [4]. After that destructive earthquake, the authorities in Egypt changed the design specifications and included an obligatory for a gap distance between neighboring buildings. The current research is focusing on existing adjacent buildings that are not considering the code limitation gap distance. The effect of pounding that takes place due to the difference in the lateral displacements of the two adjacent buildings at the same level is studied. Different lateral deformations results from the difference in vibration modes of the adjacent buildings, which in their turn, depend on the structural system, height, weight and stiffness of structural elements. Since structural pounding could cause damage, partial collapse or total collapse of pounded structures, in this study, the pounding effect was investigated using nonlinear time history dynamic analysis based on the Applied Element Method (AEM) [5] [6] [7] and [8], which is proved to be capable of simulating structural progressive collapse in an efficient way [9, 10] The Extreme Loading of Structures software (ELS®) [11] was used for this purpose. 2. LITERARTURE REVIEW Many researchers studied the pounding phenomenon due to its importance and its effect on the adjacent buildings. Many models with different software has been employed to study this phenomenon , obtain the resulting impact force, studying and comparing the impact force values with the different parameters that affect the pounding, such as: the gap distance , the peak ground acceleration, different building height and structural systems. Anagnostopoulos [12] used a simplified model of several adjacent buildings in a block to study the pounding of such buildings due to strong earthquakes. The structure was modeled as an SDOF system and simulated pounding using impact elements. Maison and Kasai [13] presented the formulation and solution of the multiple degree of freedom equations of motion for a type of structural pounding. They implemented the theory into microcomputer program to perform a sample analysis of an actual 15-storey building in order to study the response behaviors. Their parametric investigation included pounding location elevation, building separation (gap size), local flexibility spring stiffness and initial sway amplitude. Anagnostopoulos and Spiliospolos [14], analyzed the response of adjacent buildings in city blocks to several strong earthquakes, taking into account the mutual collisions, or pounding, resulting from insufficient or non-existing separation distances. The buildings were idealized as lumped mass, shear, and beam type, multi-degree of freedom (MDOF) systems with bilinear force-deformation characteristics and with bases supported on translational and rocking spring- dashpots. Regarding the studied factors, the effect of system configuration is clear. Jeng et al. [15], presented a method to estimate the likely minimum building separation to preclude