157 International Journal of Civil and Structural Engineering– IJCSE Volume 1 : Issue 3 [ISSN 2372 – 3971] Publication Date : 30 September, 2014 A kind of repairable steel buildings for seismic regions based on building‟s rocking motion and energy dissipation at base level Mahmood Hosseini and Seyed Sasan Alavi Abstract—Most of current seismic design codes accept heavy damages to the building in case of large earthquakes, provided that the building is prevented against collapse. However, this acceptance leads to some unacceptable consequences in populated cities, like very great number of people who lose their residence or work place for very long time. To overcome these difficulties one approach is design of ‘repairable structures’ for buildings, by using the idea of ‘Deliberate Directing of Damage’ (DDD), which means guiding the damage to some pre-decided parts or elements of the structural system, so that other parts do not experience any plastic deformation. In this study the DDD idea has been employed for design of repairable steel buildings based on creation of building’s rocking motion possibility rather than its shear deformation, by using a central hinge support and circumferential energy dissipating columns at base level. Energy dissipation is done by a Multiple Trapezoidal Yielding Plate Energy Dissipating (MTYPED) device, installed at the bottom of the column, which creates a type of hysteretic behaviour in axial deformation of columns. By performing a set of finite elements analyses on MTYPED devices their initial stiffness as well as their yielding strength were obtained, and then they were modelled in a real size building by using nonlinear springs, and a series of nonlinear time history analysis were performed on both rocking building and the conventional building with the same geometry. Results show that the proposed rocking system equipped with MTYPED devices not only gives the building a longer natural period, leading to lower seismic demand, but also leads to remarkable energy dissipation capacity in the building structure at base level, and therefore, keeping the seismic drifts in elastic range in all stories of the building above the ground floor, so that the building structure does not need any major repair work after a large earthquake. This is while the conventional building suffers from heavy damage and needs to be demolished after an earthquake. Keywords— Seismic Codes, DDD Idea, Nonlinear Time History Analysis, MTYPED Devices Mahmood Hosseini / Associate Professor Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Iran Seyed Sasan Alavi / Graduate Student Civil Engineering Department, School of Engineering, Tehran Central Branch of the Islamic Azad University (IAU) Iran I. Introduction Most of current seismic design codes accept, either explicitly or implicitly, heavy damages to the building in case of large earthquakes, provided that the building is prevented against collapse. However, this acceptance leads to some unacceptable consequences in populated cities, such as very great number of affected people who lose their residence or work place for very long time, very difficult and time consuming demolishing works of the heavily damaged buildings and related debris removal works, and finally very large volume of the required reconstruction works, which need lots of money, expertise and time. To avoid these adverse consequences one approach is design of „repairable structures‟ for buildings, by using the idea of „Deliberate Directing of Damage‟ (DDD), introduced by Hosseini and Alyasin (1996), which means guiding the damage to some pre-decided parts or elements in the system, acting as structural fuses or energy dissipators, so that other parts of the system do not experience any plastic deformation, and therefore, the structure can be easily repaired after an earthquake. Although the DDD idea has been introduced initialy for pipelines, it can lead to a new generation of earthquake- resisting buildings, if applied to the buildings structures. In fact, the idea of using „structural fuse‟ is not so new, and some researchers have introduced and worked on this idea for building systems in late 70s to early 80s (Fintel and Ghosh 1981) [2], and some more detailed studied have been also conducted in recent decade (Vargas and Bruneau 2006) [3]. However, it should be noted that in these studies, although the main idea, similar to DDD idea, is concentration of damage in energy dissipators or fuses, and keeping the main structural members elastic or with minor easily repairable damages, in reality the building can not remain in Immediate Occupancy (IO) Performance Level (PL), and needs to be evacuated, at least partially, for repair works. To overcome this shortcoming, the use of rocking motion of the building has been proposed by some researchers in recent decade (Midorikawa et al. 2002) [4]. They used weak base plates, attached to the bottom of each steel column at the first story, to cause rocking vibration under appropriate control, and conducted more recently an experimental study on a structural frame with rocking motion (Azuhata et al. 2008) [5]. Although their proposed rocking structural system is quite effective is seismic response reduction, their studies is limited to 2-dimensional buildings systems.