• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.182-192
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• 2023

In this study, the efficacy of Engineered Cementitious Composite(ECC) jacket for masonry fences subjected to lateral dynamic load was experimentally verified through a shaking table test, comparing it with the performance of an unreinforced masonry(URM) fence. Firstly, dominant frequencies, modal damping ratios and deformed shapes were identified through an impact hammer test. URM and ECC-strengthened fences with heights of 940mm and 970mm had natural frequencies of 6.4 and 35.3Hz, and first modal damping ratios of 7.0 and 5.3%, respectively. Secondly, a shaking table test was conducted in the out-of-plane direction, applying a historical earthquake, El Centro(1940) scaled from 25 to 300%. For the URM fence, flexural cracking occurred at the interface of brick and mortar joint(i.e., bed joint) at the ground motion scaled to 50%, and out-of-plane overturning failure followed during the subsequent test conducted at the ground motion scaled to 30%. On the other hand, the ECC-jacketed fence showed a robust performance without any crack or damage until the ground motion scaled to 300%. Finally, the base shear forces exerted upon the URM and ECC-jacketed fences by the ground motions scaled to 25~300% were evaluated and compared with the ones calculated according to the design code. In contrast to the collapse risk of the URM fence at the ground motion of 1,000-year return period, the ECC-jacketed fence was estimated to remain safe up to the 4,800-year return period ground motion.

• Earthquakes and Structures
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• v.9 no.4
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• pp.789-830
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• 2015

The recent re-assessment of the seismic hazard in Europe led for many regions of low to moderate seismicity to an increase in the seismic demand. As a consequence, several modern unreinforced masonry (URM) buildings, constructed with reinforced concrete (RC) slabs that provide an efficient rigid diaphragm action, no longer satisfy the seismic design check and have been retrofitted by adding or replacing URM walls with RC walls. Of late, also several new construction projects have been conceived directly as buildings with both RC and URM walls. Despite the widespread use of such construction technique, very little is known about the seismic behaviour of mixed RC-URM wall structures and codes do not provide adequate support to designers. The aim of the paper is therefore to propose a displacement-based design methodology for the design of mixed RC-URM edifices and the retrofit of URM buildings by replacing or adding selected URM walls with RC ones. The article describes also two tools developed for estimating important quantities relevant for the displacement-based design of structures with both RC and URM walls. The tools are (i) a mechanical model based on the shear-flexure interaction between URM and RC walls and (ii) an elastic model for estimating the contribution of the RC slabs to the overturning moment capacity of the system. In the last part of the article the proposed design method is verified through nonlinear dynamic analyses of several case studies. These results show that the proposed design approach has the ability of controlling the displacement profile of the designed structures, avoiding concentration of deformations in one single storey, a typical feature of URM wall structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.33-40
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• 2014

The final purpose of this study is to evaluate the seismic performance of unreinforced masonry (URM) building more accurately. For that, shear strength and hysteresis model considering failure mode of the URM wall were discussed. The shear strength of URM wall without openings could be calculated by determining on the minimum value between the rocking strength suggested by domestic research and the sliding strength suggested by FEMA. The wall having openings could be predicted properly by the FEMA method. And the nonlinear hysteresis models for flexural and shear behaviors considering failure mode were proposed. As the result of the nonlinear cyclic analysis that carried out using suggested models, these analysis models were proper to represent the seismic behavior of URM walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.116-124
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• 2011

RC frames with unreinforced masonry infiledl walls are common in worldwide. Since infilled walls are normally considered as non-structural elements, their presence is often ignored by engineers. In this study, to improve the seismic performance of masonry walls, hexagonal block was developed and the influence of masonry infilled wall on the seismic performance of reinforced concrete(RC) frames that were designed in accordance with current code provisions without the consideration of earthquake loadings are investigated. Two 1/2 scale, single story, single bay, frame specimens were tested. The parameters investigated included that the strength of infilled wallls with respect to that of the lateral load history. The experimental results indicate that infilled walls can significantly improve the lateral stiffness and strength of RC frames. The lateral loads developed by the infilled frame specimen is higher than that of the bare frame. It also indicates that infilled walls can be potentially used to improve the performance of existing nonductile frames. For this purpose. methods should be developed to avoid irreparable damage and catastrophic failure.

• Earthquakes and Structures
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• v.10 no.4
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• pp.811-828
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• 2016

This study aims to present nonlinear time history analysis results of double leaf cavity wall (DLCW) reinforced concrete structure exposed to shake table tests. Simulation of the model was done by a Finite Element (FE) program. Shake table experiment was performed at the National Civil Engineering Laboratory in Lisbon, Portugal. The results of the experiment were compared with numeric DLCW model and numeric model of reinforced concrete structure with unreinforced masonry wall (URM). Both DLCW and URM models have two bays and two stories. Dimensions of the tested structure and finite element models are 1:1.5 scaled according to Cauchy Froude similitude law. The URM model has no experimental results but the purpose is to compare their performance level with the DLCW model. Results of the analysis were compared with experimental response and were evaluated according to ASCE/SEI 41-06 code.

• Earthquakes and Structures
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• v.5 no.5
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• pp.571-588
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• 2013

Many of the current buildings in Algeria were built in the past without any consideration to the requirements of the seismic code. Among these buildings, there are a large number of individual houses built in the 1980's by their owners. They are Reinforced Concrete (RC) frame structures with unreinforced hollow masonry infill walls. This buildings type experienced major damage in the 2003 (Algeria) earthquake, generated by deficiencies in the structural system. In the present study, special attention is placed upon examining the vulnerability of RC frame houses. Their situation and their general features are investigated. Observing their seismic behavior, structural deficiencies are identified. The seismic vulnerability of this type of buildings depends on several factors, such as; structural system, plan and vertical configuration, materials and workmanship. The results of the vulnerability assessment of a group of RC frame houses are presented. Using a method based on the European Macroseismic Scale EMS-98 definitions, presented in previous studies, distribution of damage is obtained.

• Earthquakes and Structures
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• v.14 no.5
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• pp.449-458
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• 2018

Earthquakes have shown the vulnerability of unreinforced masonry (URM) structures. The aim of this research is to study a technique for in-plane seismic retrofitting of URM walls in which both diagonal and vertical steel strips are added to a single side of a URM wall. Specimens have been tested under quasi-static cyclic lateral load in combination with constant vertical load. The tests show that vertical and diagonal strips cause a significant increase in seismic capacity in terms of both strength (about 200%) and displacement at maximum (about 20%). Furthermore, this technique caused the failure modes of URM walls were influenced.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.312-319
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• 2001

The purpose of this study is to evaluate the strength of piers subjected to earthquake ground motion. In particular, the piers of an unreinforced masonry wall under in-plane seismic loading are considered with emphasis. For this purpose, several pier strength equations in seismic rehailitation provisions such as UCBC, FEMA 178, FEMA 273, and FEMA 306 are compared. This strength equations in different provision are applied for calculating the strength of a pier in building. According to the results of this study, it is shown that the assessment procedure based on FEMA 178 overestimated pier strengths comparing to other provisions when all piers are in Rocking-controlled mode.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.46-49
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• 2006

In general, the shear behavior mode of URM wall expresses four types of modes such as rocking failure, sliding shear failure, toe crushing failure, and diagonal tension failure. From the comparison of each equation according to the shear behavior modes, the failure modes based on the aspect ratio and vertical axial stress can be expected. The objectives of this study is to find out the shear behavior of URM wall with different aspect ratio. The test results show that the aspect ratio is understood as an important variable.

• Earthquakes and Structures
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• v.13 no.3
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• pp.309-322
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• 2017

In this paper, a simplified evaluation method of the skeleton curve for reinforced concrete (RC) frame with unreinforced masonry (URM) infill is proposed in a practical form, based on the previous studies. The backbone curve for RC boundary frame was modeled by a tri-linear envelope with cracking and yielding points. On the other hand, that of URM infill was modeled by representative characteristic points of cracking, maximum, and residual strength; also, the interaction effect between RC boundary frame and the infill was taken into account. The overall force-displacement envelopes by the sum of RC boundary frame and URM infill, where the backbone curves of the infill from other studies were also considered, were then compared with the previous experimental results. The simplified estimation results from this study were found to almost approximate the overall experimental results with conservative evaluations, and they showed much better agreement than the cases employing the infill envelopes from other studies.