Seismic Damage Analyses Of Masonry Structure Retrofitted By Prefabricated Reinforced Concrete Panels

Masonry structures are widely distributed around the whole country of China.There are two main issues for the existing masonry structures, one is that historicalmasonry structures was built before1990and can’t meet the requirement of the currentdesign code, and the other is that many masonry residential buildings have been builtwithout any seismic design and its constructional columns are often set arbitrarily,which results in poor seismic resistance. Hence, it is necessary to study the failuremechanism of the existing masonry structures and develop related retrofit method.Two specimens, which are typical masonry walls in the transverse and longitudinaldirections, respectively, are designed to investigate the failure mechanism of themasonry structures. Another two specimens, which are similar to their prototype, aredesigned to examine the contribution of the constructional columns. In order to examinethe seismic performance of retrofitted masonry wall, four more specimens are made byretrofitting the masonry walls with prefabricated reinforced concrete (RC) panels. Themajor achievements of this dissertation are as follows:1. Based on the field investigation of masonry buildings after Lushan strongearthquake, this study systematically summarized the seismic damage patterns ofmasonry residential buildings, including the arbitrary distribution of the constructionalmeasures, vertical irregularity of structures, irrational dimension of masonry wall andnon-uniform settling of foundation. Besides, although limited damage was found fromthe enhanced masonry buildings, the integrality of these buildings is poor because of theprecast floor slabs.2. Through the experiment on the basic mechanical behavior of masonry materials,the failure patterns of the materials are studied. To examine the interaction between theexisting wall and prefabricated RC panels, two kinds of cementation tests are conducted,such as grouting agent cementation tests and post-cast bond cementation tests.3. Eight masonry walls are designed, and tested with the quasi-statically test. Theinfluence of seismic constructional measures and the failure patterns are examined bycomparing the four walls w/o constructional columns. Besides, four masonry wallsretrofitted by prefabricated RC panels are tested to examine their failure patterns andseismic performance. The experimental results show that the three techniques ensure theco-action between the masonry wall and prefabricated RC panels. The strength ofexisting walls increases by2-5times.4. To investigate the interaction and the force transfer mechanism between the RCpanels and the masonry wall, finite element model is established to simulate thequasi-static cyclic tests, and nonlinear analyses are conducted. The simulation resultsindicate that the prefabricated RC panels using the proposed retrofitting technology areable to improve the seismic performance of the existing masonry walls effectively. The strength of an existing wall increases by2to5times when retrofitted by theprefabricated RC panels. Among the three connection measures, post-casting concretebands are most effective, which is able to transfer70%load from the masonry wall tothe RC panels at the elastic phase, and upto80%load at nonlinear ultimate phase.5. Based on tests and existing calculation method of masonry wall, this papercalculate the shear bearing capacity of4existing masonry walls. Then, a calculationmethod was proposed to estimate the shear bearing capacity of masonry walls enhancedby prefabricated RC panels. It is found from the comparison between the estimatedresults and experimental results that the proposed can estimate the capacity of wallsreasonably well.