A practical method for optimum seismic design of friction wall dampers

Friction control systems have been widely used as one of the efficient and cost effective solutions to control structural damage during strong earthquakes. However, the height-wise distribution of slip loads can significantly affect the seismic performance of the strengthened frames. In this study, a practical design methodology is developed for more efficient design of friction wall dampers by performing extensive nonlinear dynamic analyses on 3, 5, 10, 15, and 20-story RC frames subjected to seven spectrum-compatible design earthquakes and five different slip load distribution patterns. The results show that a uniform cumulative distribution can provide considerably higher energy dissipation capacity than the commonly used uniform slip load pattern. It is also proved that for a set of design earthquakes, there is an optimum range for slip loads that is a function of number of stories. Based on the results of this study, an empirical equation is proposed to calculate a more efficient slip load distribution of friction wall dampers for practical applications. The efficiency of the proposed method is demonstrated through several design examples

An Analytical Research on Determination of Beam and Column Contribution to Plastic Energy Dissipation of RC Frames

Determination of capacities of structural members, both in terms of strength and deformation, and estimation of seismic demand are essential issues in earthquake-resistant design. In energy-based design and evaluation, both the structural capacity and the demand imposed by earthquake are considered in terms of energy and accordingly energy dissipation capacity of the structure is associated with seismic energy demand. Plastic energy dissipation of structures under monotonic lateral loading may be obtained by using the resultant pushover curves of nonlinear static analyses. However, the time variation of individual contribution of structural members to the dissipated plastic energy cannot be determined. In this study, the contribution of beam and column deformations to the plastic energy dissipated in multistory reinforced concrete (RC) frames is determined by using nonlinear time history (NLTH) analysis. It is found that rotational deformations of beams are dominant in plastic energy dissipation. Accordingly, some linear relations considering the contribution of dissipated plastic energy in beam plastic hinges to the total plastic energy dissipation of RC frames are derived. Pushover analysis of frames in conducted and the area under the resultant pushover curve is determined to satisfy the mean value of the maximum plastic energy dissipated in frames during the selected earthquakes. The interstory drift ratios are calculated and compared with the interstory drift ratios directly obtained from NLTH analyses. The results are evaluated and presented by graphs and tables