• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.1
• /
• pp.56-63
• /
• 2018

The present study examined the reversal cyclic flexural behavior of walls with jacket section approach for seismic strengthening through forming the boundary elements at both ends of the wall. The prestressed wire ropes were used for the lateral reinforcement to confine the boundary element of the wall. The main parameter investigated was the height of the jacket section for strengthening. The limit height of the strengthening jacket section was determined by comparing the moment distributions between the existing and strengthened walls. Test results showed that the examined jacket section approach was significantly effective in enhancing the flexural resistance of walls, indicating 46% higher stiffness at peak strength and 210% greater work damage indicator, compared with the flexural performance of the unstrengthened wall. The ductility of the strengthened walls was insignificantly affected by the height of the jacket section when the height is greater than twice the wall length. The flexural capacity of the strengthened walls was 22% higher than the predictions obtained using the equivalent stress block specified in ACI 318-14.

• 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 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 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 Korea Concrete Institute
• /
• v.27 no.5
• /
• pp.489-499
• /
• 2015

This study suggested shear strength prediction model for retrofitted single-layered RC squat wall by providing column element as additional boundary element. This model revised existing shear strength prediction model of shear wall to consider detail and shear deformation capacity of column by assuming the length that concentrated shear deformation of the column is occurred. It was able to suggest additional compatibility condition related to shear strain of retrofitted of retrofitted shear wall at the ultimate state by using this length. Therefore, this study proposed a flow chart for predicting shear strength of the retrofitted shear wall considering this additional condition. Moreover, this study also proposed a method for predicting initial stiffness of the retrofitted shear wall by transforming the wall's resisting mechanism against to lateral load to a single diagonal strut mechanism. The proposed methods can predict shear strength and initial stiffness of not only the retrofitted shear wall of this study, also infilled RC shear wall in RC frame.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.875-878
• /
• 2008

This paper summarizes on the state-of-the-art research on the reinforced concrete (RC) walls for evaluating and predicting the performance of RC walls analytically and experimentally. A brief discussion of the research trends is presented to propose the further research direction of RC walls. In the paper, 102 papers published on the ACI, Engineering Structure, KCI journal, and AIK journal are collected and reviewed.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.3
• /
• pp.51-60
• /
• 2008

Soil nailing systems are generally many used to the temporary structure in underground excavations and reinforcements of slopes in Korea. However, large-scaled experimental studies related to soil nailing systems are mostly studies related to performance monitoring and field pullout tests. Specially, there are no researches related in the large scaled load tests of soil nailed walls in Korea. In this study, a case study on the large scaled load tests of soil nailed walls is introduced and the behavior characteristic of them is investigated. Also, they are proposed allowable deformation corresponding to the serviceability limit of soil nailed walls and ultimate deformation corresponding to the collapse state of the walls. These results can be applied to the maintenance management of soil nailed walls. And analysis on the required minimum factor of safety of soil nailed walls using the relation curve of load ratio and deformation ratio are carried out.

• Geotechnical Engineering
• /
• v.14 no.5
• /
• pp.67-76
• /
• 1998

The commonly used method to secure the stability of reinforced retaining structure is the reinfocement of backfill with connection attached or unattached to the geogrid type wall. Laboratory model tests for both cartes were conducted to investigate the effectiveness of geogridreinforcement, length of reinforcement inclusion, failure envelop, and the relationships between the face wall displacement and vertical settlement. The bearing capacity of each case was also determined. According to the model test results, geogrid-reinforced rigid wall is very effective for increasing the bearing capacity and reducing the displacement of retaining wall. The observed sliding line of model test is similar to the theoretical one.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.10
• /
• pp.77-83
• /
• 2012

Recently, excavations using propped walls were popularized in downtown due to reduced settlement of nearby structures. These excavations is induced strain to propped walls or settlement in near ground. In this study, the ground reinforcing effect was proven using NDS, which is an inorganic injection material. Injection tests were performed to compute optimum injection pressure and volume. Next, calibration chamber tests were performed by using computed injection pressure and volume, and wall behaviour was examined for overburden pressures of 50kPa and 150kPa. Ground reinforcing effect was shown when the material behind the propped wall was grouted. From test results, optimum injection pressure was 350kPa and the optimum volume was 10L considering economics. Calibration chamber test results show that after the material was grouted, the maximum settlement was reduced to 19% of the non-grouted condition. For overburden pressures of 50kPa and 150kPa behind the wall, the settlement of the wall increased by 58% and 57% when compared to the case of no overburden pressure.

• 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.