• Structural Engineering and Mechanics
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• v.84 no.4
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• pp.479-488
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• 2022

Aiming to examine different failure patterns in multistory URM walls, two 1/3 scaled three-story and three-bay URM models were designed for the quasi-static loading tests to contrastively investigate the failure processes and characteristics of the multistory URM walls. Two different failure responses were observed with special attention paid to the behavior of spandrel-failure mode. By evaluating the seismic performance and deformation behavior of two test walls, it is demonstrated that spandrels, that haven't been properly designed in some codes, are of great significance in the failure of entire URM walls. Additionally, compared with pier-failure mode, spandrel-failure for multistory URM building is more reasonable and advisable as its effectively participation in energy dissipation and its efficiently improvement on seismic capacity and deformation in the overall structure. Furthermore, the experimental results are beneficial to improve seismic design and optimize reinforcement method of URM buildings.

• Earthquakes and Structures
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• v.19 no.6
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• pp.411-425
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• 2020

Unreinforced masonry (URM) walls present low shear strength and are prone to brittle failure when subjected to inplane seismic overloads. This paper discusses the shear strengthening of URM walls with Textile Reinforced Mortar (TRM) jackets. The available literature is thoroughly reviewed and an extended database is developed including available brick, concrete and stone URM walls retrofitted and subjected to shear tests to assess their strength. Further, the experimental results of the database are compared against the available shear strength design models from ACI 549.4R-13, CNR DT 215 2018, CNR DT 200 R1/2013, Eurocode 6 and Eurocode 8 guidelines as well as Triantafillou and Antonopoulos 2000, Triantafillou 1998, Triantafillou 2016. The performance of the available models is investigated and the prediction average absolute error (AAE) is as high as 40%. A new model is proposed that takes into account the additional contribution of the reinforcing mortar layer of the TRM jacket that is usually neglected. Further, the approach identifies the plethora of different block materials, joint mortars and TRM mortars and grids and introduces rational calibration of their variable contributions on the shear strength. The proposed model provides more accurate shear strength predictions than the existing models for all different types of the URM substrates, with a low AAE equal to 22.95%.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.69-72
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• 2006

The objective of this study is to find out the shear capacity of URM wall and the variables that affect the shear capacity of URM wall such as the opening and the aspect ratio, considering four kinds of failure modes, sliding shear failure, toe crushing failure, and diagonal shear failure. The main varialble is the shape of opening of URM walls. First URM has one door, second has one window, third hase one door and one window, the last has two windows. The test results of URM with openings show that the specimens are governed by rocking failure mode.

• 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.

• Earthquakes and Structures
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• v.22 no.4
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• pp.355-372
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• 2022

The study is part of an experimental program on full-scale Un-Reinforced Masonry (URM) wall panels strengthened with Textile reinforced mortars (TRM). Eight brick walls (two with and five without central opening), were tested under the diagonal tension (shear) test method in order to investigate the strengthening system effectiveness on the in-plane behaviour of the walls. All the URM panels consist of the innovative components, named "Orthoblock K300 bricks" with vertical holes and a thin layer mortar. Both of them have great capacity and easy application and can be constructed much more rapidly than the traditional bricks and mortars, increasing productivity, as well as the compressive strength of the masonry walls. Several parameters pertaining to the in-plane shear behaviour of the retrofitted panels were investigated, including shear capacity, failure modes, the number of layers of the external TRM jacket, and the existence of the central opening of the wall. For both the control and retrofitted panels, the experimental shear capacity and failure mode were compared with the predictions of existing prediction models (ACI 2013, TA 2000, Triantafillou 1998, Triantafillou 2016, CNR 2018, CNR 2013, Eurocode 6, Eurocode 8, Thomoglou et al. 2020). The experimental work allowed an evaluation of the shear performance in the case of the bidirectional textile (TRM) system applied on the URM walls. The results have shown that some analytical models present a better accuracy in predicting the shear resistance of all the strengthened masonry walls with TRM systems which can be used in design guidelines for reliable predictions.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.305-313
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• 2012

Unreinforced masonry buildings represent a significant portion of the existing and historical buildings around the world. Recent earthquakes have shown the need for seismic retrofitting for these types of buildings. Various types of retrofitting materials (i.e., shotcrete, ECC and Fiber Reinforced Polymer sheets (FRPs)) for unreinforced masonry buildings (URM) have been developed. Engineers prefer to use FRPs, because these materials enhance the shear strength of the wall without expansion of wall sectional area and adding weight to the total structure. However, the complexity of the mechanical behavior of the masonry wall and the lack of experimental data from walls retrofitted by FRPs may cause problems for engineers to determine an appropriate retrofitting level. This paper investigate in-plane behavior of URM and retrofitted masonry walls using two different types of FRP materials to determine and provide information for the retrofitting effect of FRPs on masonry shear walls. Specimens were designed to idealize the wall of a low-rise apartment which was built in 1970s in Korea with no seismic reinforcements with an aspect ratio of 1. Retrofitting materials were carbon FRP and Hybrid sheets which have different elastic modulus and ultimate strain capacities. Consequently, this study evaluated the structural capacity of masonry shear walls and the retrofitting effect of an FRP sheet for in-plane behavior. Also, the results were compared to the results obtained from the evaluation method for a reinforced concrete beam retrofitted with FRPs.

• Earthquakes and Structures
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• v.11 no.2
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• pp.195-215
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• 2016

Rehabilitation of historical unreinforced masonry (URM) buildings is a priority in many parts of the world, since those buildings are a living part of history and a testament of human achievement of the era of their construction. Many of these buildings are still operational; comprising brittle materials with no reinforcements, with spatially distributed mass and stiffness, they are not encompassed by current seismic assessment procedures that have been developed for other structural types. To facilitate the difficult task of selecting a proper rehabilitation strategy - often restricted by international treaties for non-invasiveness and reversibility of the intervention - and given the practical requirements for the buildings' intended reuse, this paper presents a practical procedure for assessment of seismic demands of URM buildings - mainly historical constructions that lack a well-defined diaphragm action. A key ingredient of the method is approximation of the spatial shape of lateral translation, ${\Phi}$, that the building assumes when subjected to a uniform field of lateral acceleration. Using ${\Phi}$ as a 3-D shape function, the dynamic response of the system is evaluated, using the concepts of SDOF approximation of continuous systems. This enables determination of the envelope of the developed deformations and the tendency for deformation and damage localization throughout the examined building for a given design earthquake scenario. Deformation demands are specified in terms of relative drift ratios referring to the in-plane and the out-of-plane seismic response of the building's structural elements. Drift ratio demands are compared with drift capacities associated with predefined performance limits. The accuracy of the introduced procedure is evaluated through (a) comparison of the response profiles with those obtained from detailed time-history dynamic analysis using a suite of ten strong ground motion records, five of which with near-field characteristics, and (b) evaluation of the performance assessment results with observations reported in reconnaissance reports of the field performance of two neoclassical torsionally-sensitive historical buildings, located in Thessaloniki, Greece, which survived a major earthquake in the past.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.93-101
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• 2001

본 논문은 국내의 비보강 조적조에 대해 내진성능을 조사하기 위하여 재료측성 평가를 위한 실험연구를 수행하였다. 실험결과를 바탕으로 조적용 모르터의 압축강도식을 제안하였다. 또한 조적용 모르터의 배합비에 따른 조적조 프리즘의 압축강도 특성을 비교하였다. 조적조 프리즘의 압축강도로써 조적조의 탄성계수를 구할 수 있는 약산식을 제시하였으며, 약산식을 사인장 조적조 실험을 통하여 구한 전단탄성계수값과 비교하여 볼 때 타당성을 가지고 있다고 판단된다. 실험결과로써 나온 재료특성 값을 바탕으로 2층 조적조 다세대 주택에 대한 유사동적해석을 수행하였다. 해석결과로 얻은 전단응력과 전단파괴가 나타난 사인장 조적조의 허용전단응력은 유사한 것으로 확인되었다.

• Structural Engineering and Mechanics
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• v.42 no.5
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• pp.609-629
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• 2012

This study deals with the assessment of low and mid rise multi-story buildings made of stone and /or brick, composite steel and masonry slabs from the sixties, known to be vulnerable to seismic hazard using the "vulnerability index" method based on buildings survey following Ain Temouchent (1999) and Boumerdes (2003) earthquakes, from where vulnerability curves are constructed using the translation method. The results obtained for the case study confirm what has been observed in situ.

• 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.