• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.434-437
• /
• 2006

Structures tend to become high-rise, large and specialized due to the urban concentration. Technology related to the structure and construction is required to improve, for which the use of high strength concrete(HSC) with better material property, and composite member with the combined advantage of both concrete and steel for better performance, is suggested. Over a half of fires, which increase by over 10% every year recently, come from the architectural structure, causing a loss at national level. However, little study has been conducted on the member at high temperature despite the increase in the use of HSC composite members. In this study, the techniques of modeling for analysing by DIANA (Displacement Analyzer) the fire damaged HSC composite compressive members are researched. We can review the effect of change in the steel ratio, section size and the steel ratio on the residual strength of structural members by parameter analysis study.

• International Journal of High-Rise Buildings
• /
• v.4 no.1
• /
• pp.57-64
• /
• 2015

Recently, new keywords such as "Resilience" and "Repairability" have been discussed from the perspective of the sustainability of damaged structures after a severe disaster. To evaluate the repairability and recovery of structures, it is necessary to establish an analytical method that can simulate the behavior of repaired structures. Furthermore, it is desirable to establish an evaluation method for the structural performance of repaired structures. This study investigates the repairability and recovery of steel members that are damaged by local buckling or cracks. This paper suggests a simple analytical model for repaired steel members, in order to simulate the inelastic behavior and evaluate the recoverability of the structural performance. There is good agreement between the analytical results and the test results. The proposed analytical method and model can effectively evaluate the recoverability.

• Steel and Composite Structures
• /
• v.26 no.6
• /
• pp.745-757
• /
• 2018

The inclusion of a ductile steel bracing as means of repairing an earthquake-damaged bridge bent is evaluated and experimentally assessed for the purposes of restoring the damaged bent's strength and stiffness and further improving the energy dissipation capacity. The study is focused on substandard reinforced concrete multi-column bridge bents constructed in the 1950 to mid-1970 in the United States. These types of bents have numerous deficiencies making them susceptible to seismic damage. Large-scale experiments were used on a two-column reinforced concrete bent to impose considerable damage of the bent through increasing amplitude cyclic deformations. The damaged bent was then repaired by installing a ductile fuse steel brace in the form of a buckling-restrained brace in a diagonal configuration between the columns and using post-tensioned rods to strengthen the cap beam. The brace was secured to the bent using steel gusset plate brackets and post-installed adhesive anchors. The repaired bent was then subjected to increasing amplitude cyclic deformations to reassess the bent performance. A subassemblage test of a nominally identical steel brace was also conducted in an effort to quantify and isolate the ductile fuse behavior. The experimental data from these large-scale experiments were analyzed in terms of the hysteretic response, observed damage, internal member loads, as well as the overall stiffness and energy dissipation characteristics. The results of this study demonstrated the effectiveness of utilizing ductile steel bracing for restoring the bent and preventing further damage to the columns and cap beams while also improving the stiffness and energy dissipation characteristics.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.4
• /
• pp.213-222
• /
• 2016

For a steel structure with long service period, structural performance can be changed or decreased by corrosion damage occurred under severe corrosion environment condition. In this study, to examine compressive strength and behavior of circular steel member depending on corrosion damage, compressive loading tests were conducted using circular steel member with artificial corrosion damage which was applied by mechanical process and hand drill. From test results, local corrosion area and pattern is related to their structural performance. Their lcoal bucklings were occurred near artificially sectional damaged part. Reduction in compressive strength of circular steel member was also suggested according to their corroded part and damage.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.485-488
• /
• 2008

The structure supporting road sign is a road information facility for ensuring the safe transportation and smooth traffic. But, lots of road information facilities were damaged by the typhoon "Maemi" in 2003. Such damaged facilities should be rehabilitated and could increase economic loss by causing traffic accident. Therefore, in this study, behavior that reduce wind load and improve wind resistance of the structure supporting road sign are studied about wind load beyond design specification by abnormal climate as below. The first is wind load reducing technique such that shear key resist wind load that is not greater than design wind speed but in case that it is over the design wind limit, column member is rotated on the inner steel pipe axis by the brittle failure of shear key. The second is the technique such that fail-safe the overturning of road sign panel by equipment installation in the vertical member. The third is the technique of installing stiffening plate inside the vertical member to relieve stress concentration.

• 한국방재학회:학술대회논문집
• /
• 2007.02a
• /
• pp.67-70
• /
• 2007

A methodology to evaluate fatigue vulnerability of steel bridge members affected by corrosion and truck traffic variation is proposed. A fatigue limit state function including corrosion and traffic variation effects is established to make the criterion whether the steel bridge member is damaged by fatigue. Corrosion effects are expressed as increase of the average corrosion depth, and the traffic variation effects are modeled as the accumulated number of stress cycles. Reliability analysis is carried out by Monte-Carlo simulation method for the fatigue limit state function. The methodology Proposed is verified by comparing reference study and applying for the steel bridge in service.

• Smart Structures and Systems
• /
• v.15 no.3
• /
• pp.787-806
• /
• 2015

Due to corrosion, a large number of belt conveyors support structure in industrial plants have deteriorated. Severe corrosion may result in collapse of the structures. Therefore, practical and effective structural assessment techniques are needed. In this paper, damage identification methods based on two specific local vibration modes, named periodic and isolated local vibration modes, are proposed. The identification methods utilize the facts that support structures have many identical members repeated along the belt conveyor and there exist some local modes within a small frequency range where vibrations of these identical members are much larger than those of the other members. When one of these identical members is damaged, this member no longer vibrates in those modes. Instead, the member vibrates alone in an isolated mode with a lower frequency. A damage identification method based on frequencies comparison of these vibration modes and another method based on amplitude comparison of the periodic local vibration mode are explained. These methods do not require the baseline measurement records of undamaged structure. The methods is capable of detecting multiple damages simultaneously. The applicability of the methods is experimentally validated with a laboratory model and a real belt-conveyor support structure.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.04a
• /
• pp.328-333
• /
• 1996

Concrete can be defective for several reasons, including an inadequate design, material selection of workmanship, failure to appreciate the hazards associated with prevailing enviromental conditions. Concrete can also deteriorate or be damaged in use. Thus, it is necessary to evaluate the safety of existing concrete strucutres. On the basis of these reasons, they must be performed for repair or rehabilitation. Presently, strengthening methods of R/C structure used in Korea, are an enlargement of concrete member, strengthening with steel plate or CFRP on the R/C structure. It has been widely estabilished that strengthening effect of CFRP is superior to steel plate in terms of it's lighter unit weight and higher tensile strength. But there are no construction results of CFRP on the civil R/C structure in Korea. The strengthening design technique with CFRP, it's const겨ction, and it's strengthening effect for deteriorated R/C rahmen bridge is introduced in this paper.

• Earthquakes and Structures
• /
• v.8 no.3
• /
• pp.699-712
• /
• 2015

Bracing structures with off-centre bracing system is one of the new resistant systems that frequently used in the frame with pin connections. High ductility, high-energy dissipation and decrease of base shear are advantages of this bracing system. However, beside these advantages, reconstruction and hard repair of off-centre bracing system cause inappropriate performance in the earthquake. Therefore, in this paper, the goal is investigating the behavior of this type of bracing system with ductile element (circular dissipater), in order to providing replacement of damaged member without needing repair or reconstruction of the general system. To achieve this purpose, some numerical studies have been performed using ANSYS software, a frame with off-centre bracing system and optimum eccentricity (OBS-C-O) and another frame with the same identifications without ductile element (OBS) has been created. In order to investigate precisely on the optimum placement of circular elements under monotonic load again three steal frames were modeled. Furthermore, the behavior of this general system investigated for the first time, linear and nonlinear behavior of these two steel frames compared to each other, to achieve the benefit of using the circular element in an off-centre bracing system. Eventually, the analytical results revealed that the performance of steel ring at the end of off-centre braces system illustrating as a first defensive line and buckling fuse in the off-centre bracing system.

• Journal of Korean Society of Steel Construction
• /
• v.11 no.4 s.41
• /
• pp.351-362
• /
• 1999

Damage detection methods which utilize the change in dynamic characteristics are very hard to apply to large civil structures since local damage hardly affects global dynamic characteristics. But, if there is a very important and critical member and we focus only on the local behavior of it, it would be possible to detect damage from the change in local dynamic characteristics, such as natural frequencies and mode shapes .In this study, the cable anchorage part of a cable-stayed bridge under construction is modeled and analyzed by commercial finite element program, ABAQUS. It has both welding and bolting connections with a cable and a stiffening plate, and has a possible high stress concentration portions in it. Several damage scenarios such as crack through the welding or crack through the bolting connection are examined. The result shows that the local natural frequencies of the damaged member decrease up to 16% compared with that of the undamaged member. It is concluded that there is quite a high feasibility that the damage of the cable anchorage can be detected by measuring local dynamic characteristics.