• Smart Structures and Systems
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• v.17 no.1
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• pp.149-165
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• 2016

Floods have been known to be one of the main causes of bridge collapse. Contrary to earthquakes, flood events tend to occur repeatedly and more frequently in rainfall areas; flood-induced damage and collapse account for a significant portion of disasters in many countries. Nevertheless, in contrast to extensive research on the seismic fragility analysis for civil infrastructure, relatively little attention has been devoted to the flood-related fragility. The present study proposes a novel methodology for deriving flood fragility curves for bridges. Fragility curves are generally derived by means of structural reliability analysis, and structural failure modes are defined as excessive demands of the displacement ductility of a bridge under increased water pressure resulting from debris accumulation and structural deterioration, which are known to be the primary causes of bridge failures during flood events. Since these bridge failure modes need to be analyzed through sophisticated structural analysis, flood fragility curve derivation that would require repeated finite element analyses may take a long time. To calculate the probability of flood-induced failure of bridges efficiently, in the proposed framework, the first order reliability method (FORM) is employed for reducing the required number of finite element analyses. In addition, two software packages specialized for reliability analysis and finite element analysis, FERUM (Finite Element Reliability Using MATLAB) and ABAQUS, are coupled so that they can exchange their inputs and outputs during structural reliability analysis, and a Python-based interface for FERUM and ABAQUS is newly developed to effectively coordinate the fragility analysis. The proposed framework of flood fragility analysis is applied to an actual reinforced concrete bridge in South Korea to demonstrate the detailed procedure of the approach.

• Land and Housing Review
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• v.1 no.1
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• pp.67-73
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• 2010

Method of protruding steel bar embedded in PHC pile for connecting with foundation plate is an intermediate form of fixed and hinged connection and has often been used in architectural structures such as apartment complex. However, mechanical properties of this method have not been proved and its construction process is not simple. In this study, therefore, by analyzing previous research and by considering ratio of steel bar and concrete in PHC pile, which is minimum reinforcement of rebar, the newly optimized method of reinforcing joint of PHC pile and foundation plate is suggested with respect to PHC pile type (PHC 450, PHC 500, and PHC 600). To assess mechanical properties (ultimate tensile and shear strength) of joint of PHC pile and foundation plate, full scale experimental tests are performed. As a result, all cases are satisfied with required design criteria and can be practically applied. Our results indicate that reduction of rebar reinforcement compared to previous method would lead cost saving in PHC pile construction.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.279-289
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• 2003

Geosynthetic reinforced earth wall was introduced about 20 years ago and many structures have been constructed. Especially, segmental concrete panel facing and friction tie system are the most popular system in Korea, and this friction tie was composed of high tenacity PET filament and LDPE(Low Density Polyethylene) sheath. Due to the lack of direct-test results, design coefficients of friction tie (creep reduction factor) had been determined by quoting the previous and the foreign reference data. This is an unreasonable fact for the use of friction ties. In this study, the creep tests were performed to evaluate the creep behavior of friction tie, and the reduction factor of creep was calculated for the correct design of geosynthetic reinforced earth retaining walls. From the test results, finally it was found that the allowable creep strength of friction tie is 60% of Tult during service life, and creep reduction factor is 1.67 for each grade of friction ties.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.358-363
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• 2007

Reinforcing steel work plays an important role in terms of its structural performance or weight of construction cost for reinforced concrete structures. Precise estimation of re-bar quantity gives a basis for managing the reinforcing steel work effectively. However, the estimation process is still performed ineffectively based upon the expert's experience or manpower in spite of the advanced technology or improvement efforts. Therefore, the purpose of this research is to develop a prototype system for taking-off the quantity of reinforcing steel bars quickly and accurately in an order consistent with the specific members identified on the drawings. An estimate algorithm considering the connection, settlement and coating thickness of re-bars was suggested regarding to their replacement conditions which places more emphasis on constructibility. Also, this system produces the shop drawings automatically with the calculation results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.122-129
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• 2013

In this study, the risk factors which derive from the ground condition of typical construction sites are put forward. In order to prioritize the risk elements, the analytical method of AHP was used. The result of using a weighting factor for each risk analysis showed that if the constituency index is less than 0.1, then reliable results and priorities for each of the risk elements can be calculated using the AHP method. From now on, if the range of measured value can be established, the risk or safety value of concrete structures for power lines can be applicable.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.1
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• pp.66-72
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• 2007

In order to control waves in coastal zones effectively, multi-cylinder piles as the economical structures are suggested. A three dimensional hydraulic model experiment was performed to investigate the hydraulic characteristics of the structure. An experimental study was carried out research the effect of wave control and harbor tranquility through the wave height analysis for the existing concrete wave breaker and the structure with acrylic multi-cylinder piles type at the same location. In the results, the effective order of harbor tranquility is shown as the wave breaker > the staggered arrangement of multi-cylinder piles > the regular arrangement of multi-cylinder piles.

• Journal of the Society of Disaster Information
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• v.14 no.3
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• pp.343-351
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• 2018

Purpose: Recently, As the size of the structure increased, the necessity of reducing its weight was raised. To reduce weight In concrete structures, a hollow slab is proposed as an alternative for weight reduction effect. Method: It is difficult to construct the hollow body due to buoyancy, and the shear performance is insufficient due to the decreased cross section. Slabs were fabricated using unidirectional hollow bodies such as PVC pipes, and experiments were conducted about construction performance and structural performance. Results: The buoyancy preventive device has been improved the construction performance by preventing floating hollow body, it has been confirmed that it has adequate performance to be used as a hollow slab system because it has enough expected shear performance. Coclusion: Hollow ratio has a little connection with bending performance, but after the yielding load, it is necessary to consider the secondary stiffness of structure, and is is supposed that the decrease of shear performance with the increase of hollow core ratio can be complemented with shear reinforcement.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.621-628
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• 2003

Stud shear connectors are the most commonly used shear connectors: up to 22mm studs are usually used in steel-concrete composite structures. To expand the current design codes for stud connectors, large studs with a diameter of more than 25mm should be investigated. Through push-out tests on large stud shear connectors that transcend the limitation of current design codes, fatigue behavior was investigated and comparisons with design equations performed. The shear stiffness of the connectors in elastic range was evaluated through shear tests on 25mm, 27mm, and 30mm studs and compared with those from static tests. The fatigue behavior of large studs was discussed in terms of residual slip and load-slip curves. The initiation of fatigue cracks in the welding part could be detected through the history of displacement range. Test results showed that the design fatigue endurance of S-N curves in current design codes could be applied to large stud shear connector.

• Nuclear Engineering and Technology
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• v.50 no.6
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• pp.989-995
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• 2018

Argonne National Laboratory of the United States and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have cooperated on the development, design, and construction of a neutron source facility. The facility was constructed at Kharkov, Ukraine, and its commissioning process is underway. The facility will be used for researches, producing medical isotopes, and training young nuclear specialists. The neutron source facility is designed with a provision to include a cryogenically cooled moderator system-a cold neutron source (CNS). This CNS provides low-energy neutrons, which will be used in the scattering experiment and material structures analysis. Cold neutron guides, coated with reflective material for the low-energy neutrons, will be used to transport the cold neutrons to the experimental site. The cold neutron guides would keep the cold neutrons within certain energy and angular space concentrated inside, while most of the gamma rays and high-energy neutrons are not affected by the cold neutron guides. For the KIPT design, the cold neutron guides need to extend several meters outside the main shield of the facility, and curved guides will also be used to remove the gamma and high-energy neutron. The neutron guides should be installed inside a shield structure to ensure an acceptable biological dose in the facility hall. Heavy concrete is the selected shielding material because of its acceptable performance and cost. Shield design analysis was carried out for the CNS guide hall. MCNPX was used as the major computation tool for the design analysis, with neutron and gamma dose calculated separately. Weight windows variance reduction technique was also used in the shield design. The goal of the shield design is to keep the total radiation dose below the $5.0{\mu}Sv/hr$ guideline outside the shield boundary. After a series of iterative MCNPX calculations, the shield configuration and parameters of CNS guide hall were determined and presented in this article.

• Steel and Composite Structures
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• v.29 no.4
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• pp.451-464
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• 2018

This paper presents some quasi-static tests for 4 mixed columns composed of CFST column and RC column. The seismic performance and failure mode were studied under low-cyclic revised loading. The failure mode was observed under different axial compression ratios. The hysteretic curve and skeleton curve were obtained. The effects of axial compression ratio on yield mechanism, displacement ductility, energy dissipation, stiffness and strength attenuation were analyzed. The results indicate that the failure behavior of CFST-RC mixed column with archaized style is mainly caused by bending failure and accompanied by some shear failure. The axial compression ratio performs a control function on the yielding order of the upper and lower columns. The yielding mechanism has a great influence on the ductility and energy dissipation capacity of specimens. Based on the experiment, finite element analysis was made to further research the seismic performance by ABAQUS software. The variable parameters were stiffness ratio of upper and lower columns, axial compression ratio, yielding strength of steel tube, concrete strength and rebar ratio. The simulation results show that with the increase of stiffness ratio of the upper and lower columns, the bearing capacity and ductility of specimens can correspondingly increase. As the axial compression ratio increases, the ductility of the specimen decreases gradually. The other three parameters both have positive effect on the bearing capacity but have negative effect on the ductility. The results can provide reference for the design and engineering application of mixed column consisted of CFST-RC in Chinese archaized buildings.