• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2010.04a
• /
• pp.746-749
• /
• 2010

본 연구에서는 비보강 조적조에 대한 부재 비선형거동 및 비탄성힌지 속성을 고려할 수 있는 midas GEN Ver.741(해외판) 프로그램에 의한 비보강 조적벽체의 푸쉬오버 해석결과와 실험결과와의 비교를 통하여 비보강 조적조 건축물의 전단강도평가를 비롯하여 내진성능평가를 위한 역량스펙트럼 해석 프로그램을 검증하고자 한다. midas GEN Ver.741(해외판) 프로그램의 사용성 검증을 위하여 조적벽체의 축하중, 형상비, 쌓기방법(두께) 그리고 개구부 유무를 변수로 한 10개의 비보강 조적벽체의 전단강도를 비교 평가한다. 비보강 조적벽체에 대한 실험결과와 해석결과를 비교한 결과 각 시험체별 전단강도 값이 비교적 유사한 것으로 나타나며 국내 기존 비보강 조적조 건축물에 대한 해석방법으로 본 프로그램의 사용이 가능한 것으로 평가되었다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.1
• /
• pp.16-24
• /
• 2021

This experimental study was conducted to evaluate the in-plane and out-of-plane seismic performances of an unreinforced masonry walls (URMs) strengthened with prestressed steel-bar truss systems developed in the present investigation. The truss systems were installed on both faces of the walls. All the wall specimens were subjected to lateral in-plane or out-of-plane cyclic loads at the fixed gravity stress of 0.25 MPa. The seismic performance of the strengthened specimens was compared to that measured in the counterpart URM. When compared with the lateral load-displacement curve of the URM, the strengthened walls exhibited the following improvements: 190% for initial stiffness, 180% for peak strength, 610% for accumulated energy dissipation capacity, and 510% for equivalent damping ratio under the in-plane state; the corresponding improvements under the out-of-plane state were 230% for initial stiffness, 190% for peak strength, 240% for accumulated energy dissipation capacity, and 120% for equivalent damping ratio, respectively. These results indicate that the developed technique is very promising in enhancing the overall seismic performance of URM.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.5
• /
• pp.1-9
• /
• 2022

In this study, the in-plane and out-of-plane seismic performance of the masonry wall strengthened using the steel bar truss system proposed by Hwang et al. (2021a, 2021b) or using FRP sheets were compared and evaluated. The maximum strength of the masonry wall reinforced with FRP sheets for the in-plane and out-of-plane loading was 71% and 85%, respectively, of that of the non-reinforced masonry wall. Meanwhile, the maximum strength of the masonry wall reinforced with the steel bar truss system was approximately 1.8 times higher than that of the non-reinforced masonry wall. Compared with the FRP sheet method, the steel bar truss system was excellent at improving the maximum load capacity, rigidity, and energy dissipation capacity. However, in the case of a masonry wall reinforced with FRP sheets, the masonry wall was overstrengthened with the FRP sheets covering the entire masonry wall, and it is considered that the overstrengthened specimen experienced sliding failure, resulting in a lower strength than the other specimens. A follow-up study is needed to compare the seismic performance of the specimen involving only a part of the masonry wall reinforced with the FRP sheets and the specimen reinforced using the steel bar truss system.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.31 no.6
• /
• pp.283-291
• /
• 2018

This study intends to develop an analytical model of unreinforced masonry(URM) walls for the nonlinear static analysis which has been generally used to evaluate the seismic performance of a building employing URM walls as seismic force-resisting members. The developed model consists of fiber elements used to capture the flexural behavior of an URM wall and a shear spring element implemented to predict its shear response. This paper first explains the configuration of the proposed model and describes how to determine the modeling parameters of fiber and shear spring elements based on the stress-strain curves obtained from existing experimental results of masonry prisms. The proposed model is then verified throughout the comparison of its nonlinear static analysis results with the experimental results of URM walls carried out by other researchers. The proposed model well captures the maximum strength, the initial stiffness, and their resulting load - displacement curves of the URM walls with reasonable resolution. Also, it is demonstrated that the analysis model is capable of predicting the failure modes of the URM walls.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.2 s.20
• /
• pp.93-105
• /
• 2006

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of twelve one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The specimens adopted are two-dimensional (2D) hollow concrete block masonry walls with different parameters such as shear span ratio, inflection point and percent of reinforcement in confining columns and walls. Test results obtained for each specimen include cracking patterns, load-deflection curve, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.1 s.24
• /
• pp.1-9
• /
• 2007

This study does by purpose that propose shear resisting force equation of reinforced masonry wall that is reinforced by GFRP(glass fiber reinforced polymer) based on result that is noted through cyclic loading of masonry wall and a shaking table experiment of mock that reflect identifying marks of masonry building which is constructed in domestic. It was Rocking mode to dominate failure of masonry wall in the experiment results, and the equations of UBC show the most resemblant value with experiment results. Through this study, propose the shear force equation of GFRP strengthened masonry wall as following. $$V_n=0.02A_n{\sqrt{f'_m}}+0.022b_gh_g(1+2{\alpha})^3{\sqrt{f_g}}(N/mm^2)$$.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.3
• /
• pp.28-39
• /
• 2013

The most common housing type in Korea is low-rise buildings with unreinforced masonry walls (UMWs) that have been known as a vulnerable seismic-force-resisting system (SFRS) due to the lack of ductility capacities compared to high lateral stiffness of an UMW. However, there are still a little experimental investigation on the shear strength and stiffness of UMWs and on the seismic performance of buildings using UMWs as a SFRS. In Korea, the shear strength and stiffness of UMWs have been evaluated with the equations suggested in FEMA 356 which can not reflect the structural and material characteristics, and workmanship of domestic UMW construction. First of all, this study demonstrates the differences in shear strength and stiffness of UMWs obtained from between FEMA 356 and test results. The influence of these differences on the seismic performance of UMW buildings is then discussed with incremental dynamic analyses results of a prototype UMW building that were selected by the site survey of more than 200 UMW buildings and existing test results of UMWs. The seismic performance assessment of the prototype UMW building are analyzed based on collapse margin ratios and beta values repesenting uncertainty of seismic capacity. Analysis results show that the seismic performance of the UMW building estimated using the equations in FEMA 356 underestimates both a collapse margin ratio and a beta value compared to that estimated by test results. Whatever the estimation is carried out two cases, the seismic performance of the prototype building does not meet the criteria prescribed in a current Korean seismic code and about 90% collapse probability presents for more than 30-year-old UMW buildings under earthquakes with 2400 return years.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.3
• /
• pp.1-10
• /
• 2002

A series of unreinforced masonry(URM) walls were analytically investigated by FEM for a limited version of seismic in-plane performance. For this, URM walls were assumed to be continum and modeled as isotropic plane stress elements, within which the nature of cracking was propogated. Accordingly, behavioral mode of cracking in URM was modeled by smeared-crack approach. Total of 70 cases were considered for various parameters such as axial load ratio, aspect ratio and effective section area ratio due to the existence of opening, etc. The analysis results indicate that these parameters significantly and interactively influence over the ultimate strength of URM walls. Finally, it is suggested that the response modification factor for URM adopted in the current Korean Standard should be validated considering various forms of brittleness and probable failure modes in URM.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.4
• /
• pp.20-27
• /
• 2021

The present study presents a nonlinear finite element analysis (FEA) approach using the general program of Abaqus to evaluate the seismic response of unreinforced masonry walls strengthened with the steel bar truss system developed in the previous investigation. For finite element models of masonry walls, the concrete damaged plasticity (CDP) and meso-scale methods were considered on the basis of the stress-strain relationships under compression and tension and shear friction-slip relationship of masonry prisms proposed by Yang et al. in order to formulate the interface characteristics between brick elements and mortars. The predictions obtained from the FEA approach were compared with test results under different design parameters; as a result, a good agreement could be observed with respect to the crack propagation, failure mode, rocking strength, peak strength, and lateral load-displacement relationship of masonry walls. Thus, it can be stated that the proposed FEA approach shows a good potential for designing the seismic strengthening of masonry walls.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.5
• /
• pp.17-26
• /
• 2020

This study examined the structural effectiveness of the unbonded technique originally developed for seismic strengthening of unreinforced masonry walls on the basis of the prestressed steel bars and glass fiber (GF) grids. The masonry walls were strengthened by using individual steel bars or GF grids and their combination. Test results showed that the proposed technique was favorable in enhancing the strength, stiffness, and ductility of the masonry walls. When compared with the lateral load capacity, stiffness at the ascending branch of the lateral load-displacement curve, and energy dissipation capacity of the unstrengthened control wall, the increasing ratios were 110%, 120%, and 360%, respectively, for the walls strengthened with the individual GF grids, 140%, 130%, and 510%, respectively, for the walls strengthened with the individual steel bars, and 160%, 130%, and 840%, respectively, for the walls strengthened with the combination of steel bars and GF grids. The measured lateral load capacities of masonry walls strengthened with the developed technique were in relatively good agreement with the predictions by the equations proposed by Yang et al. Overall, the developed technique is quite promising in enhancing the seismic performance of unreinforced masonry walls.