• 한국재료학회지
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• 제27권9호
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• pp.477-483
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• 2017

This present study deals with the microstructure and tensile properties of 600 MPa-grade high strength and seismic resistant reinforcing steels. The high strength reinforcing steel (SD 600) was fabricated by Tempcore processing, while the seismic resistant reinforcing steel (SD 600S) was air-cooled after hot-rolling treatment. The microstructure analysis results showed that the SD 600 steel specimen consisted of a tempered martensite and ferrite-pearlite structure after Tempcore processing, while the SD 600S steel specimen had a fully ferrite-pearlite structure. The room-temperature tensile test results indicate that, because of the enhanced solid solution and precipitation strengthening caused by relatively higher contents of C, Mn, Si and V in the SD 600S steel specimen, this specimen, with fully ferrite-pearlite structure, had yield and tensile strengths higher than those of the SD 600 specimen. On the other hand, the hardness of the SD 600 and SD 600S steel specimens changed in different ways according to location, dependent on the microstructure, ferrite grain size, and volume fraction.

• Structural Engineering and Mechanics
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• 제77권6호
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• pp.735-744
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• 2021

In recent years, the use of new materials and technologies with the aim of developing high-performing and cost-effective structures has greatly increased. Application of high-strength concrete (HSC) has been found effective in reducing the dimensions of frame members; nonetheless, such reduction in dimensions of structural elements in the most cases may result in the lack of accountability in the tolerable drift capacity. On this basis, strengthening of frame members using fiber reinforced polymers (FRPs) may be deemed as an appropriate remedy to address this issue, which albeit requires comprehensive and systematic investigations. In this paper, the performance of properly-designed, two-dimensional frames made of high-strength concrete and strengthened with Carbon Fiber Reinforced Polymers (CFRPs) is investigated through detailed numerical simulation. To this end, nonlinear dynamic time history analyses have been performed using the Seismosoft software through application of five scaled earthquake ground motion records. Unstrengthened (bare) and strengthened frames have been analyzed under seismic loading for performance assessment and comparison purposes. The results and findings of this study show that use of CFRP can be quite effective in seismic response improvement of high-strength-concrete structures.

• Earthquakes and Structures
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• 제25권1호
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• pp.43-56
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• 2023

Banda Aceh is one of the areas that sustains the most damage during a natural disaster because it contains so many houses, office buildings, public facilities, and schools. Public structures in coastal areas are highly susceptible to earthquakes, resulting in high casualties and property damage. Several public structures were reconstructed during the reconstruction and rehabilitation period. Because this building is located in an area with a high risk of earthquakes, its capacity must be analyzed initially. Additionally, history indicates that Aceh Province has been struck by numerous earthquakes, including the largest ever recorded in 1983 and the most recent earthquake with a magnitude of 9.3 SR on December 26, 2004. The city of Banda Aceh was devastated by this earthquake, which was followed by a tsunami. The possibility of a large earthquake in Banda Aceh City necessitates that the structures constructed there be resistant to seismic risk. This study's objective was to evaluate the seismic performance of the existing building by applying the method of strengthening the structure in the form of jacketing columns and the addition of steel bracing in order to estimate the performance of the structure using multiple ground motions. Therefore, several public buildings must be analyzed to determine the optimal seismic retrofitting technique.

• Structural Monitoring and Maintenance
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• 제11권1호
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• pp.57-70
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• 2024

Masonry arch bridges as a vital infrastructure were not designed for seismic loads. Given that masonry arch bridges are made up of various components, their contribution under the seismic actions can be very undetermined and each of these structural components can play a different role in energy dissipation. Iran is known as a high-risk area in terms of seismic excitations and according to the seismic hazard zoning classification of Iran, most of these railway infrastructures are placed in the high and very high seismicity zones or constructed near the major faults. Besides, these ageing structures are deteriorated and thus in recent years, some of these bridges using various retrofitting approaches, including sprayed concrete technique are strengthened. Therefore, investigating the behavior of these restored structures with new characteristics is very significant. The aim of this study is to investigate the cyclic in-plane performance of masonry arch bridges retrofitted by sprayed concrete technique through the finite element simulation. So, by considering the fill-arch interaction, the nonlinear behavior of a bridge has been investigated. Finally, by extracting the hysteresis and enveloping curves of the retrofitted and non-retrofitted bridge, the effect of strengthening on energy absorption and degradation of material has been investigated.

• Geomechanics and Engineering
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• 제31권1호
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• pp.31-52
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• 2022

Investigating and evaluating the long-term creep behavior of historical buildings built on seismic zones is of great importance in terms of transferring these structures to future generations. Furthermore, assessing the earthquake behavior of historical structures such as masonry stone bridges is very important for the future and seismic safety of these structures. For this reason, in this study, earthquake analyses of a masonry stone bridge are carried out considering strong ground motions and various water levels. Tokatli masonry stone arch bridge that was built in the 10th century in Turkey-Karabük is selected for three-dimensional (3D) finite difference analyses and this bridge is modeled using FLAC3D software based on the three-dimensional finite difference method. Firstly, each stone element of the bridge is modeled separately and special stiffness parameters are defined between each stone element. Thanks to these parameters, the interaction conditions between each stone element are provided. Then, the Burger-Creep and Drucker-Prager material models are defined to arch material, rockfill material for evaluating the creep and seismic failure behaviors of the bridge. Besides, the boundaries of the 3D model of the bridge are modeled by considering the free-field and quiet boundary conditions, which were not considered in the past for the seismic behavior of masonry bridges. The bridge is analyzed for 6 different water levels and these water levels are 0 m, 30 m, 60 m, 70 m, 80 m, and 90 m, respectively. A total of 10 different seismic analyzes are performed and according to the seismic analysis results, it is concluded that historical stone bridges exhibit different seismic behaviors under different water levels. Moreover, it is openly seen that the water level is of great importance in terms of earthquake safety of historical stone bridges built in earthquake zones. For this reason, it is strongly recommended to consider the water levels while strengthening and analyzing the historical stone bridges.

• 콘크리트학회논문집
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• 제25권6호
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• pp.667-674
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• 2013

기존 강재 브레이싱 내진보강법은 정착부의 안정성 문제와 브레이싱의 국부좌굴이 발생할 문제가 있으며, 이를 방지하기 위한 추가보강으로 인해 불필요한 자중증가 등으로 경제적인 내진보강성능 확보에 어려움이 있다. 이 연구에서는 지진피해를 받은 건물에 지진피해로 인한 기존 기둥의 연성확보를 위해서 유리섬유시트(glass fiber sheet)로 래핑을 함과 동시에 기존 철골 X-브레이싱 내진보강법에 비교해서 경량의 고강도 재료로 보강 후 추가적인 중량증가가 거의 없으며, 브레이싱 압축 좌굴거동에 자유로운 탄소섬유 앵커 X-브레이싱공법(carbon fiber X-brace)을 조합한 경제적이며 효과적인 새로운 내진보강법(GFS-CFXB)을 제안하였다. 이 연구에서 제안한 GFS-CFXB공법의 유용성을 검증할 목적으로 지진피해를 받은 골조를 대상으로 반복가력에 의한 구조실험을 실시하여 내진성능 및 내진보강 효과를 검증하였다.

• Structural Engineering and Mechanics
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• 제13권1호
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• pp.17-34
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• 2002

The use of local two-sided and three-sided jacketing for the repair and strengthening of reinforced concrete beam-column joints damaged by severe earthquakes is investigated experimentally and analytically. Two exterior beam-column joint specimens ($O_1$ and $O_2$) were submitted to a series of cyclic lateral loads to simulate severe earthquake damage. The specimens were typical of existing older structures built in the 1960s and 1970s. The specimens were then repaired and strengthened by local two-sided or three-sided jacketing according to UNIDO Manual guidelines. The strengthened specimens ($RO_1$ and $RO_2$) were then subjected to the same displacement history as that imposed on the original specimens. The repaired and strengthened specimens exhibited significantly higher strength, stiffness and better energy dissipation capacity than the original specimens.

• Smart Structures and Systems
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• 제2권4호
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• pp.305-312
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• 2006

In the case of hospital buildings, where seismic design requirements are very high, existing structuresand especially those attacked by past earthquakes, appear, often, unable to fulfil the necessary safety prerequisites. In this paper, the retrofitting of hospital buildings is investigated, using alternative methods of repair and strengthening. Analysis of an existing hospital building in Patras, Greece, is performed. The load-bearing system is a reinforced concrete system. Two solutions are proposed: strengthening using concrete jackets around column and beam elements and application of viscoelastic dampers for the increase of the stability of the structure. Adequate finite element models are constructed for each case and conclusions are drawn on the efficiency of each rehabilitation method.

• Structural Engineering and Mechanics
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• 제70권2호
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• pp.133-141
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• 2019

The aim of the present paper is to present the cyclic behavior of strengthened reinforced concrete shear wall test specimen, which was reinforced with cold drawn welded wire mesh fabric. Two reinforced concrete shear wall specimens have been tested in the present study. The walls were tested under reversed cyclic loading with loading applied near the tip of the walls. The control wall is tested in its original state to serve as a baseline for the evaluation of the repair and strengthening techniques. The two test specimens include a control wall and a repaired wall. The control wall test specimen was designed and detailed to simulate non-ductile reinforced concrete shear walls that do not meet the modern seismic provisions. The response of the original wall was associated with the brittle failure. The control shear wall was repaired by addition of the reinforcements and the concrete and then it was reloaded. The effectiveness of the repair technique was investigated. Test results indicate that there can be a near full restoration of the walls' strength. The data from this test, augmenting other data available in the literature, will be useful in calibrating improved analytical methods as they are developed.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.487-498
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• 2023

Unreinforced masonry (URM) buildings are extensively adopted in many of the growing nations, particularly in India. Window or door openings are required for architectural or functional reasons, which pose a threat to the building's safety. The past earthquakes have shown that the seismic capability of these structures was very weak. Strengthening these unreinforced masonry walls using welded wire mesh (WWM) is one of the most commonly and economical methods. The present experimental study investigates the impact of openings on the shear behaviour of URM walls and the effectiveness of WWM in enhancing the shear performance of masonry wall. In the experimental program 16 specimens were cast, 8 unstrengthen and 8 strengthened specimens, under 8 unstrengthen and strengthened specimens, every 2 specimens had 0%, 5%, 10%, and 15% openings and all these walls were tested under diagonal compression. The results show that the shear carrying capacity reduces as the opening percentage increases. However, strengthening the URM specimens using WWM significantly improves the peak load, shear strength, ductility, stiffness, and energy dissipation. Furthermore, the strengthening of the URM walls using WWM compensated the loss of wall capacity caused by the presence of the openings.