• Computational Structural Engineering
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• v.11 no.1
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• pp.237-249
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• 1998

In this study the support deflection effects in beam-girder slabs which are broadly being adopted in building structures are studied for both distributed loads and concentrated vehicle loads. Taking the finite element analysis of slabs supported with one or two cross beams, the member forces of slabs including the support stiffness have been calculated. Based on the obtained numerical results and regression analysis of those, correction factors of member forces for slabs supported with girders and cross beams have been proposed. Finally, the validity of the proposed correction factors are demonstrated through a typical design example.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.697-706
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• 2011

There are more than 800 railway steel plate girder bridges which are in use and the total length is approximately 50 km. Among these, it shall be pointed out that non-ballast rail systems which lay on wood sleepers are the most critical members. To strengthen this type of structures, mainly two methods have been applied. The first one is the most typical method which is to replace the girders with slab girder system or steel composite girders and to add ballast. It is not uncommon that the construction cost of substructure is more than ten time higher than that of superstructures and even in this case, the structural uncertainty for the substructures is not diminished. To resolve above mentioned problems, new method was developed to rehabilitate railway steel girder bridge by adding PC-slab using transport equipment. Using this method, substructure strengthen is rarely required because the additional weight to the bridge superstructure is only up to 1.0t/m. Also it was possible to save the construction cost by reducing construction duration and by simplifying the construction process. Experimental construction was performed for Jewon bridge and measurements were performed before and after construction to verify the bridge capacity.

• Structural Engineering and Mechanics
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• v.61 no.1
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• pp.117-124
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• 2017

Load testing is one of the important tests to determine if the structural elements can be used at the intended locations for which they have been designed. It is nothing but gradually applying the loads and measuring the deflections and other parameters. It is usually carried out to determine the behaviour of the system under service/ultimate loads. It helps to identify the maximum load that the structural element can withstand without much deflection/deformation. It will also help find out which part of the element causes failure first. The load-deflection behaviour of the road bridge girder has been studied by carrying out the load test after simulating the field conditions to the extent possible. The actual vertical displacement of the beam at mid span due to the imposed load was compared with the theoretical deflection of the beam. Further, the recovery of deflection at mid span was also observed on removal of the test load. Finally, the beam was checked for any cracks to assert if the beam was capable of carrying the intended live loads and that it could be used with confidence.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.611-620
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• 2006

The composite two plate-girder bridges are generally defined as a non-redundant load path structure because the bridge can collapse if one of the two girders is seriously damaged by a fatigue crack. In this paper, a numerical study on the evaluation of the after-fracture redundancy of the composite two-girder bridges was accomplished. The evaluation has been performed on the simple and three-span continuous bridges with I-section cross beams which serve as transverse bracing, and with or without the bottom lateral bracing system. The load carrying capacities of the intact and damaged bridges with or without lateral bracing were evaluated from material and geometric nonlinear analysis, respectively and the redundancy was evaluated for each case. It was acknowledged from the analytical results that both simple and continuous intact two-girder bridges have sufficient redundancy even without lateral bracing, but it takes an important role to improve the redundancy of damaged bridges.

• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.473-484
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• 2021

Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

• Journal of Ship and Ocean Technology
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• v.7 no.3
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• pp.56-65
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• 2003

The hull monitoring systems of container ships with four long-base gages give enough information for identifying the hull girder loads such as bending and torsional moments. But such a load-identification for container ships has not been known. In this paper, a load-identification method is suggested in terms of a linear matrix equation that the measured strain vector equals to the multiplication of the transformation matrix and the desired strain component vector. The equation is proved to be mathematically complete by the property of positive-definite determinant of the transformation matrix. The method is applied to a hull stress monitoring system for 8100TED container ship during sea trial, and the estimated external loads illustrate reasonable results in comparison with the pre-estimated results. This moment decomposition concept has also been tested in real operation conditions. The typical phenomena over the Suez Canal illustrated very suitable results comparing with the physical understandings. Henceforth, one can effectively use the proposed concept to monitor the hull girder loads such as bending and torsional moments.

• Journal of Korean Association for Spatial Structures
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• v.4 no.2 s.12
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• pp.53-61
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• 2004

Recently, most of residential-commercial buildings and apartment houses which are being constructed in the downtown area mainly adopt hybrid structural systems to compose various spaces. Especially, column-supported wall system which is one of the hybrid systems includes shear wall and rigid frame structure and these structures are connected by the transfer floor. But this system is very disadvantageous from the viewpoint of structural safety and is difficult to find out the stress distribution at the transfer floor. Therefore, this study analyzes the behavior and stress distribution according to the shear wall layout of transfer girder system subject to vertical and static lateral loads. Also, this study recognizes load paths and stress concentration based on the analysis results nearby the transfer floor and presents guidelines for the effective design of wall and transfer girder.

• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.419-426
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• 2017

Recently, the transportation of dangerous explosive goods is increasing, which makes vehicle blasting accidents a potential threat for the safety of bridge structures. In addition, blasting accidents happen more easily when earthquake occurs. Excessive dynamic response of bridges under extreme loads may cause local member damage, serviceability issues, or even failure of the whole structure. In this paper, a new explosion-proof and aseismic system is proposed including cable support damping bearing and steel-fiber reinforced concrete based on the existing researches. Then, considering one 40m-span simply supported concrete T-bridge as the prototype, through scale model test and numerical simulation, the dynamic response of the bridge under three conditions including only earthquake, only blast load and the combination of the two extreme loads is obtained and the applicability of this explosion-proof and aseismic system is explored. Results of the study show that this explosion-proof and aseismic system has good adaptability to seism and blast load at different level. The reducing vibration isolation efficiency of cable support damping bearing is pretty high. Increasing cables does not affect the good shock-absorption performance of the original bearing. The new system is good at shock absorption and displacement limitation. It works well in reducing the vertical dynamic response of beam body, and could limit the relative displacement between main girder and capping beam in different orientation so as to solve the problem of beam falling. The study also shows that the enhancement of steel fibers in concrete could significantly improve the blast resistance of main beam. Results of this paper can be used in the process of antiknock design, and provide strong theoretical basis for comprehensive protection and support of girder bridges.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.345-354
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• 2010

This paper presents an experimental investigation of the structural performance of a large-span girder bridge with an under-tension system. Typical long-span structures with beam and girder members have greater structural member depths and sizes to carry the moment and deflection. An under-tension system can be an effective structural system, as it allows the cables to resist some portions of the vertical loadings and deflections. To evaluate the serviceability and ultimate strength of the under-tension system, two $10m{\times}2.4m$ experimental under-tension systems were built and tested. One was developed with an H-beam section, and the other was made with a PF500 section that had the advantages of fast construction and lower construction cost. In the test, the maximum deflections at the mid-point of both beams were effectively reduced using under-tension systems. Also, the increased tension forces in the cable reduced the deflections. The PF500 members, which had a new shape and were developed using the module systems, performed better than the typical H-beam sections in terms of the deflections and ultimate strength.

• Journal of Ocean Engineering and Technology
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• v.22 no.2
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• pp.85-90
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• 2008

Ships in bad weather conditions are likely to be subjected to accidental loads, such as high bending moment, collision, and grounding. Once she has damage to her hull, her ultimate strength will be reduced. This paper discusses an investigation of the effect of collision damage on the ultimate strength of a ship structure by performing a series of collapse tests. For the experiment, five box-girder models with stiffeners were prepared with a cross section of $720mm\;{\times}\;720mm$ and a length of 900mm. Of the five, one had no damage and four had an ellipse shaped damage area that represented the shape of the bulbous bow of a colliding ship. The amount of damage size was different between models. Among the damaged models, the damage in three of them was made by cutting the plate and stiffener, and in one by pressing to represent collision damage. Experiments were carried out under a pure bending load and the applied load and displacements were recorded. The ultimate strength was reduced as the damage size increased, as expected. The one with the largest amount of damage had damage to 30% of the depth, and its ultimate strength was reduced by 19% compared to the undamaged one. The pressed one has higher ultimate strength than those that were cut. This might be due to the fact that the plate around the pressed damage area contributes to the ultimate strength, whereas the cut one has no plate to contribute.