Presented by the instructor: Assistant Lecturer (M.Sc.) Wroud Raouf Abdul Hussein Department of Civil Engineering, Al-Mustaqbal University The resistance of reinforced concrete buildings to seismic loads is a fundamental factor in achieving structural safety and reducing the damage that ground motions may cause. A building’s response to earthquakes depends on the efficiency of the structural system, the properties of the materials, the reinforcement details, and the regularity of the mass and stiffness distribution. Therefore, seismic performance assessment is a necessary step for identifying structural weaknesses and selecting suitable solutions to improve building resistance and reduce the risk of collapse. Seismic Performance and the Factors Affecting It Seismic performance refers to a building’s ability to respond to ground motions while maintaining an acceptable level of structural safety. This performance is influenced by several factors, chiefly the building’s height and geometric shape, the strength of the concrete and reinforcing steel, the efficiency of the columns, beams, and structural joints, as well as the soil properties and the intensity of the earthquake. Irregularity in the building, the presence of a weak story, or deficiencies in the reinforcement details may increase deformations and concentrate damage in specific parts of the structure. Methods of Seismic Performance Assessment Seismic performance assessment is carried out by studying the structural drawings, inspecting the condition of the building, verifying the properties of the materials and reinforcement, and then analyzing the building’s response to seismic loads. Analysis methods include equivalent static analysis, response spectrum analysis, pushover analysis, and nonlinear dynamic analysis when needed. Structural analysis software, such as ETABS and SAP2000, is also used to estimate inter-story drift, internal forces, and potential areas of weakness, based on the requirements of the adopted engineering code. Methods of Improving Seismic Resistance The seismic resistance of reinforced concrete buildings can be improved using a number of strengthening techniques, including adding shear walls to increase resistance to lateral loads, strengthening columns and beams using concrete or steel jackets, and using carbon fiber reinforced polymer (CFRP) composites to improve the resistance of certain structural elements. Base isolation systems and energy dissipation devices can also be used to reduce the effect of ground motion on the building. The choice of the appropriate technique depends on the results of the structural assessment, the condition of the building, economic feasibility, and the compatibility of the proposed solution with seismic design requirements. Conclusions and Recommendations It is evident that the seismic performance assessment of reinforced concrete buildings is an essential step in determining the level of structural safety and diagnosing the weaknesses that may lead to damage during earthquakes. The selection of appropriate strengthening techniques also contributes to improving the structure’s resistance, limiting deformations, and reducing the likelihood of collapse. The article recommends assessing existing buildings, particularly older ones or those showing signs of deterioration, and carrying out the necessary inspections before determining strengthening methods. It is also recommended to rely on precise structural analysis, to take into account soil properties, building regularity, and the efficiency of reinforcement details, and to comply with the adopted engineering codes, thereby contributing to enhancing the safety of structures and achieving their sustainability. References American Society of Civil Engineers (ASCE). (2023). ASCE/SEI 41-23: Seismic Evaluation and Retrofit of Existing Buildings. Reston, Virginia: ASCE. Federal Emergency Management Agency (FEMA). (2018). FEMA P-2018: Seismic Evaluation of Older Concrete Buildings for Collapse Potential. Washington, DC: FEMA. American Concrete Institute (ACI). (2022). ACI CODE-369.1-22: Seismic Evaluation and Retrofit of Existing Concrete Buildings—Code and Commentary. Farmington Hills, Michigan: ACI.