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Seismic Mitigation Designs for Reinforced Concrete Buildings According

Concrete Buildings

The Earthquake can be Concrete Buildings as a natural phenomenon or a disaster based on the seismic response of structures during a severe earthquake that plays a vital role in the extent of structural damage and resulting injuries and losses. It is Concrete Buildings necessary to predict the performance of the existing structures and structures at the design stage when it subjected to an earthquake load. Also, it is needed to predict the repair cost required for the rehabilitation of the existing buildings that is insufficient in seismic resistance, and the construction cost and the expected repairing cost for the structures at the design stage that designed to have a ductile behavior with acceptable cracks. This study aims to propose a method for seismic performance evaluation for existing and new structures depending on the width of cracks resulted from the seismic exposure. Also, it assesses the effect of building performance during earthquakes on its life cycle cost. FEMA 356 criteria were used to predict the building responses due to seismic hazard. A case study of seven-story reinforced concrete building designed by four design approaches and then analyzed by static nonlinear pushover analysis to predict its response and performance during earthquake events using Sap 2000 software. The first design approach is to design the building to resist gravity loads only by using ECP code. The second one is to design the building to resist gravity loads and seismic loads by using static linear analysis according to ECP code. The third one is to design the building to resist gravity loads and seismic loads by using static linear analysis according to the regulations of the Egyptian Society of Earthquake Engineering (ESEE). Finally the fourth one is to design the building as the second approach but with ground acceleration greater by five times than it or by using ductility factor R = 1. The methodology followed in this study provides initial guidelines, and steps required to assess the seismic performance and the cost associated with using a variety of design methods for reinforced concrete structures resisting earthquakes, selecting the retrofitting strategies that would be indicated to repair the structure after an earthquake.

The last earthquake events in various world areas and the resulting harms, especially human fatalities, have shown that the structures cannot withstand the earthquake loads. The large damages caused by the earthquake happened in Cairo in 1992 showed that at the construction time, the structures were designed to sustain only vertical loads and had ineffective horizontal load resistance. That expresses that, there are low ductility elements, shear resistance, and steel confinement in the plastic hinge zone that was founded in columns and beam column connections. So it is urgent to assess the seismic performance of existing structures and to constantly refresh the seismic codes for the design of the new structures.

The design of structures for seismic load resistance forced in the Egyptian design codes that motivated the Ministry of Housing and Buildings to regularly update the Egyptian codes provisions to consider the earthquake loads effect. After October 1992, a set of Egyptian codes has been released to avoid building failure and to control significant damages in structural elements. Earthquake analysis has many considerations that have been formed using the performance assessment of existing structures that have been subjected to a severe earthquake. To get a well-engineered structure, it must satisfy the seismic performance requirements that include the careful attention in analysis, design, reinforcement detailing, and good construction. The successful integration of analysis, design, and construction achieves the safety of the structure.

Krawinkler et al. [1], used the pushover analysis method to assess the building performance to get the inter-story drifts that take into account the changes in stiffness and strength, that can be used for the evaluation of P-∆ effect, determinate the effect of strength deterioration of elements on the behavior of the whole structure, get the sequence of failure of structure members and identify the weakness points in the structural members.

Maske [2], uses the nonlinear static pushover analysis, which is considered a common method for assessment of seismic performance for the new and existing structures. To discriminate the weakness zones in the building and then choose if it can be retrofitted or rehabilitated according to its level of damage. He performed the pushover analysis on multistoried frame structures by using SAP2000 software. He analyzed two framed structures with 5 and 12 floors, respectively. The results concluded from his study display that the behavior of properly reinforcement detailed reinforced concrete frame building is adequate as concluded by the capacity curve with demand curve intersection and the plastic hinges distribution in the structural members.

To perform the performance-based design, one must develop the evaluation method of the seismic resistant performance for the reinforced concrete structural members. The performance limit states are classified into three limit states, serviceability limit state, safety limit states, and damage control limit states. Each state is defined by the damages of the structural members. The yielding of reinforcing steel bars and the width of crack are used as the index of the damages. As the result of the plastic nonlinear frame analysis based on the performance-based design process method, the crack width of each member is calculated at each step [3].

Igarashi [4], developed an approach for assessment of seismic damage in reinforced concrete members which is important for exact selection of the most suitable repairing technique for structures damaged and affected by earthquakes risk. He presents the concepts and outlines of damage assessment steps of ductile reinforced concrete structural members. The suggested analytical models assess the width of crack, the length of crack, and the area of concrete that spalled in ductile column and beam. These models are planned to be applied to pushover analysis of framed structure in practical seismic design.

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