• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.303-314
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• 2018

Shear walls are a typical member under a complex stress state and have complicated mechanical properties and failure modes. The separated-elements model Genetic Evolutionary Structural Optimization (GESO), which is a combination of an elastic-plastic stress method and an optimization method, has been introduced in the literature for designing such members. Although the separated-elements model GESO method is well recognized due to its stability, feasibility, and economy, its adequacy has not been experimentally verified. This paper seeks to validate the adequacy of the separated-elements model GESO method against experimental data and demonstrate its feasibility and advantages over the traditional elastic stress method. Two types of reinforced concrete shear wall specimens, which had the location of an opening in the middle bottom and the center region, respectively, were utilized for this study. For each type, two specimens were designed using the separated-elements model GESO method and elastic stress method, respectively. All specimens were subjected to a constant vertical load and an incremental lateral load until failure. Test results indicated that the ultimate bearing capacity, failure modes, and main crack types of the shear walls designed using the two methods were similar, but the ductility indexes including the stiffness degradation, deformability, reinforcement yielding, and crack development of the specimens designed using the separated-elements model GESO method were superior to those using the elastic stress method. Additionally, the shear walls designed using the separated-elements model GESO method, had a reinforcement layout which could closely resist the actual critical stress, and thus a reduced amount of steel bars were required for such shear walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.158-166
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• 2008

Member force, strain and stress distribution of a section are obtained for prestressed steel and concrete(PSSC) composite bridge subjected to dead and live load in order to interpret the effect of prestressing and deformation of tendon. The stress and strain distribution and moment capacity are obtained for both noncomposite and composite section and for allowable stress limit state, yield limit state and strength limit state. Reliability analysis is conducted after assuming limit states for deflection, stress and flexural strength. Comparing that the reliability index for stress is near 0 for example section which is designed to satisfy the allowable stress exactly, the reliability indexes for deflection and flexural strength are high. Reliability of PSSC girder which is designed based on allowable stress of bridge design code is high for deflection and flexural strength.

• Journal of Korean Society of Steel Construction
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• v.15 no.5 s.66
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• pp.519-529
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• 2003

In recent years, the use of cold-formed steel roof truss has been increased in the steel houses and high-rise apartments. The design of the roof truss anchor connections has been based on the experience and decision of designers. In this paper, the structural behavior of anchor connections based on experimental and decision is described. In the tests, truss members and connection members were jointed directly with self-drilling screw fasteners and the simple shaped connection member with excellent workability and structural capacity was used to connect roof truss and sub-structure. The connecting method was selected according to the construction material of sub-structure: chemical anchor for reinforced concrete structure and welding or DX-Pin for steel structures. The pull-out tests of various type anchor connection were executed to obtain the strength and the stiffness and the result have been compared with AISI(1996) and AlSC(1989) specifications, Simple formulas for the shear strength of screw connections have been propose and compared with tests.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.296-302
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• 2017

Generally, a parking lot is constructed using asphalt or concrete. Such materials are impermeable, which means that a parking lot will directly release pollutants to any nearby water system during a rainfall event. An increased quantity of nonpoint source pollutants harms the ecohydrological system and causes further environmental damage leading to dysfunctional water circulation systems. Therefore, there is an urgent need for the design and application of Low Impact Development (LID) systems that allow more effective prevention of water circulation problems and management of nonpoint source pollution. This study aims to support such efforts by analyzing a permeable paver parking lot constructed using one of the LID techniques and comparing it to a conventional one in terms of the concentration of pollutants, nonpoint source pollution load and runoff rainfall lag effects during a rainfall event; it could serve as a reference for the construction of permeable paver parking lots in the future.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.259-266
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• 2012

In this paper the seismic performance of a flat plate wall system structure was evaluated based on the ATC-63 approach, and the results were compared with those of a wall slab structure having the same size. As analysis model structures, a twelve story flat plate wall structure and a wall slab structure were designed based on the KBC-2009, and their seismic performances and collapse behaviors were evaluated by nonlinear static and incremental dynamic analyses(IDA). It was observed that the flat plate wall structure was designed with smaller amount of reinforced concrete, and showed slightly larger displacement response compared with those of the wall slab structure. The collapse margin ratios of the two structures obtained from the incremental dynamic analyses satisfied the limit states specified in the ATC-63, and the structures turned out to have enough capacity to resist the design level seismic load.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.513-520
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• 2018

Since Paris Climate Change Conference in 2015, many policies to reduce the emission of greenhouse gas have been accelerating, which are mainly related to renewable energy resources and micro-grid. Presently, the technology development and demonstration projects are mostly focused on diversifying the power resources by adding wind turbine, photo-voltaic and battery storage system in the island-type small micro-grid. It is expected that the large-scaled micro-grid projects based on the regional district and town/complex city, e.g. the block type micro-grid project in Daegu national industrial complex will proceed in the near future. In this case, the economic cost or the carbon emission can be optimized by the efficient operation of energy mix and the appropriate construction of electric and heat supplying facilities such as cogeneration, renewable energy resources, BESS, thermal storage and the existing heat and electricity supplying networks. However, when planning a large residential town or city, the concrete plan of the energy infrastructure has not been established until the construction plan stage and provided by the individual energy suppliers of water, heat, electricity and gas. So, it is difficult to build the efficient energy portfolio considering the characteristics of town or city. This paper introduces an energy mix optimization(EMO) method to determine the optimal capacity of thermal and electric resources which can be applied in the design stage of the real large-scaled residential town or city, and examines the feasibility of the proposed method by applying the real heat and electricity demand data of large-scale residential towns with thousands of households and by comparing the result of HOMER simulation developed by National Renewable Energy Laboratory(NREL).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.411-417
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• 2013

The moment responses of electric pole foundations for a railroad were investigated using real-scale load tests. Large overturning moments were applied to two square rigid piles with a 1.1 m width and a 2.2 m embedded depth. Two different installation methods-with and without a form-were applied to evaluate the influence of the form work on the moment capacities of the foundations. The reduction of ground strength caused by the excavation without a form is more pronounce than the decrease of frictional strength due to the smooth concrete surface with a form. From the test results, it is found that the current design method which applies a proportional coefficient to consider the effect of a form work is not appropriate. When the normal and frictional stressed is considered separately, the effect of a form work can be estimated reasonably by reducing the friction angle between soil and foundation by 20%.

• Advances in Computational Design
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• v.7 no.3
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• pp.229-251
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• 2022

In 2017, an intraplate earthquake of Mw 7.1 occurred 120 km from Mexico City (CDMX). Most collapsed structural buildings stroked by the earthquake were flat slab systems joined to reinforced concrete (RC) columns, unreinforced masonry, confined masonry, and dual systems. This article presents the simulated response of an actual six-story RC frame building with masonry infill walls that did not collapse during the 2017 earthquake. It has a structural system similar to that of many of the collapsed buildings and is located in a high seismic amplification zone. Five 3D numerical models were used in the study to model the seismic response of the building. The building dynamic properties were identified using an ambient vibration test (AVT), enabling validation of the building's finite element models. Several assumptions were made to calibrate the numerical model to the properties identified from the AVT, such as the presence of adjacent buildings, variations in masonry properties, soil-foundation-structure interaction, and the contribution of non-structural elements. The results showed that the infill masonry wall would act as a compression strut and crack along the transverse direction because the shear stresses in the original model (0.85 MPa) exceeded the shear strength (0.38 MPa). In compression, the strut presents lower stresses (3.42 MPa) well below its capacity (6.8 MPa). Although the non-structural elements were not considered to be part of the lateral resistant system, the results showed that these elements could contribute by resisting part of the base shear force, reaching a force of 82 kN.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.587-594
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• 2022

In the 2000s, a lot of cable-type grand bridges are being built in consideration of economic aspects such as the reduction of logistics costs and the distribution of traffic volume due to rapid economic development. In addition, because the recently installed grand bridges are designed in an aesthetic form that matches the surrounding environment as well as the original function of the road bridge, and serves as a milestone in an area and is used as an excellent tourism resource, attracting many vehicles and people, there is an urgent need for a safety structure that can ensure the safety of not only vehicles but also people. In order to make cable-stayed bridge safe on wind for additional five safety structures, main girder models with and without safety structures for wind-tunnel experiments was made, and wind tunnel experiments was carried out to measure aerodynamic force coefficients. Also, wind-resistant analyses of 3D cable-stayed bridge were performed on the basis of wind-tunnel experiment results. From the wind tunnel experiments for the aerodynamic force coefficients of main girder with five safety structures and the wind resistant analyses of cable-stayed bridge without safety structure and with safety structure, it was concluded that the best form of wind-resistant safety was shown in the order of mesh, standard, bracing, hollow, and closed type. And wind-resistant safety of cable-stayed bridge with hollow and closed type on design wind speed 68.0m/sec was not secured. Finally, as five safety structures are installed, maximum rate of stress increments was shown in the order of steel main beam, steel floor beam, concrete floor beam and cables.

• Computers and Concrete
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• v.32 no.1
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• pp.99-117
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• 2023

The crack under the influence of the higher intensities of the stresses grows and the structure gets collapsed with the time when the crack length reaches to critical value. Therefore, the fracture behavior of a structure in terms of stress intensity factors (SIF) becomes important to determine the remaining fracture strength and capacity of material and structure for avoiding catastrophic failure, increasing safety and further improvement in the design. The robustness of the method has been demonstrated by comparing the numerical results with analytical and experimental results of some problems. XFEM is used to model cracks and holes in structures and predict their strength and reliability under service conditions. Further, XFEM is extended with a stochastic method for predicting the sensitivity in terms of output COVs and fracture strength in terms of mean values of stress intensity factors (SIFs) of a structure with discontinuities (cracks and holes) under tensile loading condition with input individual and combined randomness in different system parameters. In stochastic technique, the second order perturbation technique (SOPT) has been used for the predicting the fracture behavior of the structures. The stochastic/perturbation technique is also known as Taylor series expansion method and it provides the reliable results if the input randomness is less than twenty percentage. From the present numerical analysis it is observed that, the crack tip near to the hole is under the influence of the stress concentration and the variational effect of the input random parameters on the crack tip in terms of the SIFs are lesser so the COVs are the less sensitive. The COVs of mixed mode SIFs are the most sensitive for the crack angles (α=45° to 90°) for all the values of c₁ and d₁. The plate with the shorter distance between hole and crack is the most sensitive with all the crack angles but the crack tip which is much nearer to the hole has the highest sensitivity.