SEISMIC PROTECTION OF MULTI-STOREY BRICK BUILDINGS BY SEISMIC ISOLATION TECHNIQUE

Abstract

A feasible technical solution of the seismic isolation system for multi-storey brick masonry buildings is presented in the Thesis Solution is based on the previous achievements in the area of base isolation technology, but it is modified for application to masonry buildings and to the low-cost housing problems. Two-level sliding isolation system is selected as a possible solution to the problem by taking into account the basic requirements regarding the seismic isolation of masonry buildings. Discrete isolation system In the form of Teflon/Stainless steel sliders is applied at the base level, and acontinuous isolation system in the form of "sliding joint" at the floor lev.] of the building; The proposed isolation scheme t. verified both experimentally and analytically. As a part of the theoretical study, analytical models are formulated for si.ul.tina the behaviour of si„g,o- and multi-degree-of-froodom base sliding systems under the earthguake-type excitation. Comparative study on the seismic performance of aconventional and abase sliding system shows the effectiveness of sliding isolation strategy in reducing the response acceleration and displacement levels. Besides the conventional approach to the analysis of seismically isolated structures, energy partitioning concept is also considered It is shown that th. amount of lnpu(. cnergy transBltted to tha . system during the earthquake is several times less than that one transmitted to the conventional system of th. same mechanical characteristics. in order to .v.lu.t. the oftsotivsn... of the proposed isolation concept in diminishing the extent of damage to multi-storey masonry buildings during the major earthquakes, behaviour of both a conventional and an isolated test model structure is experimentally nvestigated. For this purpose, one-third scale model of atypical twobay, three-storey high brick building is constructed and tested on a computer controlled shake-table. (iii) From the shake-table tests on the model structure, an important observation is made concerning the relationship between the amount of input energy and the PGA level. For a conventional system, the amount of input energy continuously increases with the increase of PGA level, while for the sliding system an opposite trend is observed. This clearly indicates to the increased effectiveness of the proposed isolation scheme at the higher acceleration levels. Analytical models of multi-degree-of-freedom base sliding system behaviour are finally verified by making the comparison between analytical and experimental results. Study shows a satisfactory agreement between experimental and analytical results, as the difference between these two values is generally less than ten percent