• Geomechanics and Engineering
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• v.6 no.3
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• pp.263-275
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• 2014

The development of transportation in large cities requires the construction of twin tunnels located at shallow depth. As far as twin tunnels excavated in parallel are concerned, most of the cases reported in literature focused on considering the effect of the ground condition, tunnel size, depth, surface loads, the relative position between two tunnels, and construction process on the structural lining forces. However, the effect of the segment joints was not taken into account. Numerical investigation performed in this study using the $FLAC^{3D}$ finite difference element program made it possible to include considerable influences of the segment joints and tunnel distance on the structural lining forces induced in twin tunnels. The structural lining forces induced in the first tunnel through various phases are considerably affected by the second tunnel construction process. Their values induced in a segmental lining are always lower than those obtained in a continuous lining. However, the influence of joint distribution in the second tunnel on the structural forces induced in the first tunnel is insignificant. The critical influence distance between two tunnels is about two tunnel diameters.

• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.403-411
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• 2007

CFT (Concrete filled steel tube) column has become popular for building construction due to not only its composite effect but also economic effect. However, the conventional CFT column also has its own disadvantages having plastic buckling at the end of column followed by the reduction of strength by yielding of steel tube. An experiment on TR-CFT (Transversely reinforced CFT) column are conducted for making up for conventional CFT column's disadvantages. The experiment parameters are strength of concrete, the layer numbers of carbon fiber sheet. In this study, hysteretic curve, initial stiffness, strength, plastic deformation capacity, and dissipated energy are compared and analyzed between CFT and TR-CFT columns.

• Computers and Concrete
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• v.25 no.2
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• pp.167-179
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• 2020

Optimal design of structures against earthquake loads is often limited to reduce initial construction costs, while the cost induced to structures during their useful life may be several times greater than the initial costs. Therefore, it is necessary to consider the indirect costs due to earthquakes in the design process. In this research, an integrated methodology for calculating life cycle cost (LCC) of moment-resisting concrete frames is presented. Increasing seismic safety of structures and reducing human casualties can play an important role in determining the optimal design. Costs incurred for structures are added to the costs of construction, including the costs of reconstruction, financial losses due to the time spent on reconstruction, interruption in building functionality, the value of people's life or disability, and content loss are a major part of the future costs. In this research, fifty years of useful life of structures from the beginning of the construction is considered as the life cycle. These costs should be considered as factors of calculating indirect costs of a structure. The results of this work represent the life cycle cost of a 4 story, 7 story, and 10 story moment-resisting concrete frame by details. This methodology is developed based on the economic conditions of Iran in 2016 and for the case of Tehran city.

• Smart Structures and Systems
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• v.24 no.5
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• pp.617-630
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• 2019

Currently most of the vision-based structural identification research focus either on structural input (vehicle location) estimation or on structural output (structural displacement and strain responses) estimation. The structural condition assessment at global level just with the vision-based structural output cannot give a normalized response irrespective of the type and/or load configurations of the vehicles. Combining the vision-based structural input and the structural output from non-contact sensors overcomes the disadvantage given above, while reducing cost, time, labor force including cable wiring work. In conventional traffic monitoring, sometimes traffic closure is essential for bridge structures, which may cause other severe problems such as traffic jams and accidents. In this study, a completely non-contact structural identification system is proposed, and the system mainly targets the identification of bridge unit influence line (UIL) under operational traffic. Both the structural input (vehicle location information) and output (displacement responses) are obtained by only using cameras and computer vision techniques. Multiple cameras are synchronized by audio signal pattern recognition. The proposed system is verified with a laboratory experiment on a scaled bridge model under a small moving truck load and a field application on a footbridge on campus under a moving golf cart load. The UILs are successfully identified in both bridge cases. The pedestrian loads are also estimated with the extracted UIL and the predicted weights of pedestrians are observed to be in acceptable ranges.

• Geomechanics and Engineering
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• v.32 no.2
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• pp.209-232
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• 2023

A comprehensive study was conducted to design economical foundations for a number of buildings on soft cohesive soil in the southern coastal regions of Iran. Both static and seismic loads were considered in the design process. Cyclic experiments indicated that the cohesive soil of the area has potential for softening. Consequently, the major challenge in the design stages was relatively high dimensions of settlement, under both static and seismic loadings. Routine soil-improvement methods were too costly for the vast area of the project. After detailed numerical modeling of different scenarios, we concluded that, in following a performance-based design approach and applying a special time schedule of construction, most of the settlement would dissipate during the construction of the buildings. Making the foundation as rigid as possible was another way to prevent any probable differential settlement. Stiff subgrade of stone and lime mortar under the grid foundation and a reinforced concrete slab on the foundation were considered as appropriate to this effect. In favor of an economical design, in case the design earthquake strikes the site, the estimations indicate no collapse of the buildings even if considerable uniform settlements may occur. This is a considerable alternative design to costly soil-improvement methods.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.411-414
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• 2015

The purpose of this study is to conduct a comparative analysis between Korea and the United States of the supply process of unit modular housing at both the factory production phase and the transportation and lifting phase, as part of an attempt to invigorate the unit modular housing market in Korea. Unlike the practice in the United States, one of Korea's unique characteristics is that the floor is constructed with reinforced concrete and hot water heating system. To do this, the wet method in Korea is used that includes concrete placement, curing and constructing hot water floor heating system at the factory production phase, which results in a longer production time and also requires the lifting of heavier loads. In the United States, interior and exterior finishing works of modular housing are performed by different companies, and the distance between the unit module factory and the construction site is quite far. This kind of dualized production structure may cause confusion when it comes to schedule management, procurement management, and stock management. Moreover, problems caused by external environmental factors such as wind and rainfall were reported in the course of long-distance transportation. The results of this case comparison are expected to provide fundamental data that will reduce the amount of trial and error in the unit module production, transportation and lifting work in Korea, which has a comparatively small number of unit modular housing cases.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.191-192
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• 2023

In recent years, the use of high-strength grout has gained popularity in offshore wind power generation complexes for facility foundations and bridges. These marine wind farms require support for horizontal loads from wind and waves. To ensure the strength of the grout produced in environments similar to the actual placing site, this study investigated the curing of high-strength grout discharged through pump pressure in various environments, and examined the difference in strength according to different variables. Compressive strength measurements revealed that the core specimen collected from the bottom (3cm) and uppermost (50cm) of the specimen exhibited lower strength compared to other height specimens, while the core specimen obtained from the corner exhibited lower strength compared to the center. These findings suggest that the strength difference between the center and the corner is more pronounced when curing at low temperatures. This effect is greater than the strength reduction that typically occurs during low-temperature curing, and thus, necessitates careful attention in similar construction environments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.153-162
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• 2007

The purpose of this study is to suggest structural design guidelines in additional shear-wall construction method for apartment remodeling with understanding the effects of the position, length and thickness of the additional walls. The slab-wall frames under seismic loads are analyzed using effective beam width model, which can practically evaluate the structural performance of existing building system. According to the results, proper design guidelines of additional shear-wall construction method(position, length and thickness) is suggested to get the required seismic performance.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.551-558
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• 2015

Lateral displacement in the most complex-shaped tall buildings is caused by eccentric gravity loads which are induced by the difference in location between a center of mass and a center of stiffness. The lateral displacements obtained from analysis, using conventional procedures, are prone to overestimate the actual values because much of realignment efforts made during construction phase are ignored. In construction sequence analysis, the self-leveling of slab and the verticality of columns/walls could be considered at each construction stage. Moreover, the displacement compensation can be achieved by manual process such as re-centering - locating to global coordinates through surveying. Because the lateral displacement increases with the building height, it is necessary to set up adjustment plan through construction stage analysis in advance in order to result in displacements less than the allowable limits. Because analytical solution includes lots of assumptions, the pre-adjusting displacement should be reasonably controlled with considerations for the uncertainty due to these assumptions.

• Journal of the Korea Construction Safety Engineering Association
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• s.38
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• pp.79-87
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• 2006

Formwork is a temporary structure that supports its weight and that of freshly placed concrete as well as construction live loads. In constructions site, pipe supports are usually used as shores which are consisted of the stab formwork. The strength of a pipe support is decreasing as it is frequently being used at the construction site. Among the accidents and failures that occur during concrete construction, there are many formwork failures which usually happen at the time concrete is being placed. The objective of this study is to find out the strength change of used pipe support and unused pipe supports according to aging. In this study, 2857 pipe supports were prepared. Among these pipe supports, 2337 pipe supports were lent to the construction companies free of charge. 520 pipe supports were kept on the outside. Compressive strength was measured by knife edge test and plate test at each 3 month. Test results show that the strength of unused pipe supports as well as used pipe supports was decreasing according to age, use frequency and load carrier, and the strength of used pipe supports was lower than the strength of unused pipe supports at the same age. So, the strength of used pipe supports from 191 days to present day was not satisfied the specification of KSF 8001. In this study, the strength of pipe support according to age, use frequency and load carrier was predicted using SPSS 12.0. It was known that the strength of pipe support using for 5 years was reduced to 42.8%. According to these results, it shows that attention has to be paid to formwork design using used pipe supports. Therefore, the present study results will be able to provide a firm base to prevent formwork collapses.