Seismic Force Modification Factor

Question: Discuss about theSeismic Force Modification Factor. Answer: Literature Review: From the research (Samantha, 2010)it can be found that the design of a structure can be made cost efficient and at the same time the safety performance of the structure can also be maintained. The elastic behaviour of a structure is expected. It causes a reduction in the design and this seismic force gets influenced by the application of a factor which is known as Seismic force modification factor. It is denoted as R. it helps to simply the designing process of the structure. With the application of R, only linear elastic static analysis is required in a structure. The behaviour of the reinforced steel is capable of controlling the responses of the structural elements of a reinforced concrete that are subjected to the earth quake loading. Therefore, it is very much important to develop an analytical model so that this problem can be avoided. The model must be capable of predicting the primary characteristics of steel. It must be measured within the specified range. The past records or the history of loads must be analysed in order to predict the characteristics and the impacts. If design base shear is denoted by Vt and design seismic force is denoted by Vs, then Seismic force modification factor ( R ) can be obtained with the help of the following equation: Vs = Vt / R Or, R = Vt / Vs According to the research (Adeel, 2009), R factors are known to be very important seismic design tools that can be used in order determine the degree of inelasticity that can be expected in a structure at the time of an earth quake. R factor has the capability to reflect the structure for dissipating energy using the inelastic characteristic of the structure. From the research it has also been known that it is also used for reducing the design forces of a structure. The seismic codes depend on the ductility and reserve strength and suitable seismic code helps to improve the ability of a structure to dissipate and absorb energy (Denis et al., 2003). Seismic force modification factor is also known as response reduction modification factor and according to the research, the value of R can be obtained with the help of the ductility reduction factor and the over strength factor (Adeel, 2009). The over strength factor is denoted as ? whereas the ductility reduction factor is known as R. The R factor can be obtained with the help of the following equation: R = R x ? The values of the seismic force that are used in the design of a structure are generally computed with the help of the diving forces which are associated with the elastic response of the R factor. The R factor is required in order to develop the lateral strength of a structure and also to sustain inelastic deformations i.e. the ductile behaviour of the structure (Adeel, 2009). Therefore the value of the R factor is very important in order to determine the design specifications of the design of the seismic loading. The response modification factor can be obtained with the help of the following expression also (Adeel, 2009): V = 2.5 x ( pga ) x ( W / R ) Or , R = ( 2.5 x ( pga ) x W ) / V Here, V denotes the design base shear. The weight of the structure is denoted by W whereas pga represents the peak ground acceleration. According to the research (Ferraioli et al., 2012) force reduction factor ( q factor ) is the another name of the response modification factor ( R factor ). There are different expressions that can be used in order to calculate R factor. From the research (Ferraioli et al., 2012), it has been found that the R factor can be calculated with the help of the following equation also: R = RS x R x R Here, Rs denotes the strength reduction factor, R represents the ductility reduction factor and R denotes the damping reduction factor (Ferraioli et al., 2012). From the research it has been known that the over strength reduction factor that is recommended by EC8 for a multi story structure is conservative. From the research paper (Ferraioli et al., 2012) it can be found that the beam column joint is very important zone in case of a frame that is capable of resisting reinforced concrete moment. From the research (Adeel, 2009) it has also been found that a structure is influenced from different types of ground shaking. The nature of the shear failure is brittle. The capability of the structural system for resisting the actions allows the design to prevent the seismic forces and also to helps to provide a elastic response. The reduction can be done with the help of the q factor. References Adeel, Z. (2009). Response Modification Factor Of Reinforced Concrete Moment Resisting Frames In Developing Countries. Denis, M., Robert, T., Erol, K., Patrick, P., Murat, S. and Donald, L. (2003). Seismic force modification factors for the proposed 2005 edition of the National Building Code of Canada. pp.308-327. Ferraioli, M., Lavino, A. and Mandara, A. (2012). Behaviour Factor for seismic design of moment-resisting steel frames. Jorge, V., Jennifer, T. and Richard, K. (2004). Development Of Response Modification Coefficient And Deflection Amplification Factor For Design Of Aac Structural Systems. Samantha, K. (2010). A Study Of The Seismic Response Modification Factor For Log Shear Walls.