Seismic Risk Assessment of Masonry Buildings in Istanbul for Effective Risk Mitigation

Unreinforced and non-engineered masonry buildings are highly vulnerable to seismic hazard and constitute a significant percentage of earthquake losses, including both casualties and economic losses. This study presents an engineering application on seismic safety assessment of unreinforced masonry (URM) buildings in Istanbul, Turkey, a metropolitan city under very high seismic risk. Nearly 20,000 masonry buildings were examined through a two-stage assessment procedure in order to identify the addresses of those buildings which are under high seismic risk. Furthermore, the obtained database can be employed in the preparation of an earthquake mitigation strategy for the expected major earthquake in Istanbul. In the first-stage evaluation, buildings are examined visually from the street by considering their basic structural parameters and they are ranked within a priority list in terms of the calculated seismic risk. Next, the buildings identified with higher risk are evaluated in the second stage by using a more detailed procedure. The developed procedure is both an optimal and a practical tool in the seismic risk assessment of large masonry building stocks in a short period of time with limited resources. [DOI: 10.1193/1.3464344

Seismic response of autoclaved aerated concrete masonry infill walls under in-plane and out-of-plane seismic demands

Infill walls of reinforced concrete (RC) frames exhibit significant vulnerability when subjected to in‐plane (IP) and out‐of‐plane (OOP) seismic demands. Despite the vast number of tests investigating the behavior of brick masonry infill walls in RC frames, past research is concerned with infill walls made up of autoclaved aerated concrete (AAC) blocks. In this study, six single‐bay, single‐story, half‐scaled RC frames were tested under the action of IP cyclic displacement excursions and/or OOP pressure. The objectives of the tests were to investigate the IP behavior of AAC infilled RC frames constructed with or without fiber mesh reinforced plaster to observe the influence of the OOP loads on the IP deformation capacity. It was found that AAC infill walls increased the strength and stiffness of the test frames compared to the bare frame specimen. The specimens without the plaster overlay experienced cracking at inter‐story drift ratio of about 0.35%. The ultimate drift ratio corresponding to a 20% lateral strength loss occurred at about 2% interstory drift ratio. The presence of plaster, on the other hand, delayed the visual cracking of the walls up until 1% interstory drift ratio. The OOP loads applied on the frame by using an airbag system was found to significantly reduce the IP deformation capacity of AAC framed infill walls. These results show that AAC infill walls may not sustain the IP and OOP seismic demands expected in RC frame buildings and innovative solutions are needed to limit the damage

Potential Use of Locked Brick Infill Walls to Decrease Soft-Story Formation in Frame Buildings

The objective of this study is to investigate the effects of a new type of infillcalled locked brick infill adopting horizontal sliding jointsin reducing the soft-story formation in reinforced concrete (RC) frames with code-conforming seismic detailing. Nonlinear static time-history analyses were performed on multistory planar frames with only the upper stories infilled in order to force the soft-story irregularity. The parameters of frame and infill elements that were used in numerical simulations were obtained from half-scale RC infilled frame tests that had been performed by the author covering single story-single bay frames infilled with standard and locked bricks. The numerical simulations showed that the use of locked bricks to form infill walls has the potential to decrease the soft-story/weak-story formation in comparison to standard bricks due to its shear sliding mechanism and decreased upper-story/first-story stiffness, even in buildings that have noninfilled first stories. (C) 2014 American Society of Civil Engineers

Seismic Performance Assessment of Unreinforced Masonry Buildings with a Hybrid Modeling Approach

This study proposes a hybrid modeling approach for the seismic performance assessment of unreinforced masonry buildings. The method combines finite-element and equivalent-frame approaches such that more powerful features of each approach are utilized. The finite-element approach is used to model the masonry components of different geometrical and material characteristics with a high level of accuracy. Then this numerically simulated database is used in the analytical modeling of masonry buildings with equivalent beams and columns instead of spandrels and piers. Thus it becomes possible to model a masonry building as a frame structure that can simply be analyzed in order to capture the global behavior. The method has been verified by comparing the analytical results with the previous experimental findings. The last part of the study is devoted to the implementation of the method to an existing masonry building that was damaged during a severe earthquake. [DOT: 10.1193/1.4000102