Seismic retrofit of low-rise buildings with soft-first-storey using metallic yielding dampers | |
| Author | Sharma, Ved Prakash |
| Call Number | AIT Thesis no.ST-00-25 |
| Subject(s) | Earthquake resistant design Buildings--Vibration |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | The effectiveness and possibilities of applying metallic yielding ADAS dampers to improve the seismic performance of low-rise buildings with soft first storey were explored against three representative ground motions. Different possible layouts and parameters of the damper for best possible improvement in response were investigated for suggesting a guideline. Two nearby markets in Bangkok were surveyed to identify the typical material, geometry, plan and layout properties of the existing soft storey buildings for incorporating them into the practical model of this study. Influence of infill walls at the upper stories was compared to the results of bare frame, which suggested that these infill walls are not the only factor behind the soft storey effect. There are other reasons perpetrating from the conventional construction practices. Various layout schemes were developed for the metallic yielding dampers and were analysed to determine the most effective location of these dampers. Although no clear-cut difference was obtained in response for the small plan symmetrical building model of this study, there were marginal indications that locating the dampers at the four corners of the building, farthest from the centre of rigidity, either on the external or internal frames produced the best response. Analyses were carried out for this location of damper for variations in damping parameters, with a view to optimisation. Stiffness ratios (SR) between 2 to 4 were found most efficient in improving seismic response, whereas a value beyond 4 was ineffective from considerations of structure and device ductility demand. Increase in yield ratio (YR) did not produce significant improvements in response parameters; rather it deteriorated the performance in some cases. From structure point of view, a YR between 0.20 to 0.27 was found desirable. Increase in YR was, however, highly effective in reducing the ductility demand on the metallic dampers for all the values of YR considered in this study from 0.20 to 0.67. Eccentricity in stiffness was introduced through the provision of partial infill walls along only one direction at the first storey and analyses were conducted. Eccentric walls were found undesirable for soft-storey buildings in general. Eccentric provision of dampers to balance the eccentricity due to infill walls was rendered ineffective in case the building properties changed due to the collapse of the first storey walls. Hence, a balanced symmetric distribution of dampers is recommended for Such eccentric soft storey buildings. Base shear was increased due to the provision of ADAS damping elements significantly; by up to 5 times for near elastic performance of the building, but this value was only half of the elastic base shear. Metallic yielding dampers were significantly effective in bringing down the seismic response of soft-first-storey buildings close to the elastic limit against earthquakes of typically high PGA, with careful considerations of damper parameters and location, but with a moderate increase in base shear. |
| Year | 2000 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai; |
| Examination Committee(s) | Pichai Nimityongskul ;Zhu, Hongping; |
| Scholarship Donor(s) | The World Bank ;Joint Japan ;World Bank Graduate Scholarship Program; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2000 |