Abstract
Problem statement: Inadequate attention during design and construction of some of Reinforced Concrete (RC) buildings in North Cyprus has raised questions about the performance level of these existing buildings under future earthquakes. Approach: Column jacketing, adding steel braces and new shear walls to an existing building are common strengthening methods used by practical engineers in North Cyprus to increase the performance level of an existing building. Results: The aim of this study was to determine the most effective strengthening method among these three mentioned techniques. As a case study, a four stories RC existing building was selected and assessed using finite element method. To remodel of the existing building, the survey works done included three main steps, detecting the reinforcement bars for beams and columns, actual used concrete strength and soil type. The beams and columns reinforcement bars were determined using Ferro scan method and the soil was sampled in Girne city to determine the soil type. The actual concrete strength was determined using core test. Three common strengthening techniques mentioned above, were applied to the existing building. Then the efficiency of each strengthening method was investigated on the basis of removing of weak columns, not-safe beam-column joints in shear and performance levels based on the FEMA356 and Turkish earthquake code. Conclusion/Recommendations: Results showed that column jacketing is the most effective method to remove the weak columns and not-safe column-beam joints in shear. Nonlinear static pushover results showed that despite that adding shear walls caused an increase in the structural base shear and a reduction in the maximum roof displacement and the number of collapsed elements at FEMA356 performance point, but it caused a remarkable reduction in the building ductility ratio. Finally, results showed that the column jacketing is the most effective and the most economic strengthening technique for the low-rise residential buildings in North Cyprus.
Highlights
After several major seismic events that occurred in the recent past, such as the 1989 Loma Prieta and the 1994 Northridge earthquakes, the structural engineering community and building owners began to question the effectiveness of current building codes to protect property
In structural systems comprised of frames only or of combination of frames and walls, sum of ultimate moment resistances of columns framing into a beamcolumn joint shall be at least 20% more than the sum of ultimate moment resistances of beams framing into the same joint should be satisfied (TEC, 2007): (Mra + Mru) ≥ 1.2(Mri + Mrj)
Where: Mra = The moment resistance calculated at the bottom of column or wall clear height by considering fcd and fyd
Summary
After several major seismic events that occurred in the recent past, such as the 1989 Loma Prieta and the 1994 Northridge earthquakes, the structural engineering community and building owners began to question the effectiveness of current building codes to protect property. FEMA 356 (2000) defines LS and CP for reinforced concrete wall buildings when roof drift is equal to 1 and 2% of the building height respectively. Another assessment procedure was proposed by Sucuoglu (2006), where the performance levels are identified with their damage limits. Damage limits of the structural elements classified as Minimum damage limit (MN), Safety limit (SF) and Collapse Limit (CL). In both steel and concrete structures, the beamcolumn joints play a significant role in the performance of building. In North Cyprus practical engineers do not enough pay attention to joints during design and construction
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