• Computers and Concrete
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• v.20 no.5
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• pp.605-616
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• 2017

Concrete filled steel tubular (CFST) composite girder is a new type of structures for bridge constructions. The existing design codes cannot be used to predict the thermal stress in the CFST truss girder structures under solar radiation. This study is to develop the temperature gradient curves for predicting thermal stress of the structure based on field and laboratory monitoring data. An in-field testing had been carried out on Ganhaizi Bridge for over two months. Thermal couples were installed at the cross section of the CFST truss girder and the continuous data was collected every 30 minutes. A typical temperature gradient mode was then extracted by comparing temperature distributions at different times. To further verify the temperature gradient mode and investigate the evolution of temperature fields, an outdoor experiment was conducted on a 1:8 scale bridge model, which was installed with both thermal couples and strain gauges. The main factors including solar radiation and ambient temperature on the different positions were studied. Laboratory results were consistent with that from the in-field data and temperature gradient curves were obtained from the in-field and laboratory data. The relationship between the strain difference at top and bottom surfaces of the concrete deck and its corresponding temperature change was also obtained and a method based on curve fitting was proposed to predict the thermal strain under elevated temperature. The thermal stress model for CFST composite girder was derived. By the proposed model, the thermal stress was obtained from the temperature gradient curves. The results using the proposed model were agreed well with that by finite element modelling.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.2
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• pp.137-144
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• 2020

In this study, we propose a new truss deckplate system, which does not require temporary floor supports during construction, with ultra-high-performance concrete (UHPC) infilled top bars. The increased stiffness and strength of the proposed system were well retained as compared to those of the existing truss deckplate systems, thereby resulting in the reduction of maximum deflection at the span center. Four-point bending tests were performed on five specimens with a net span of 4.6 m to evaluate the structural performance of proposed system in the construction stage. In addition, the load-deflection curve was plotted for each specimen, and the effects of test parameters were analyzed. Further, a rigorous nonlinear three-dimensional finite element analysis was performed, and its results were compared with the test results. From the results, it was observed that the test specimens of the proposed system exhibited superior performance as compared to those of the existing one and also satisfied the serviceability requirement during construction provided by the Korea Building Code 2016.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.6
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• pp.153-164
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• 2019

The presence of thermal bridges in a building envelope cause additional heat loss which increases the heating energy. Given that a higher building insulation performance is required in these cases, the heat loss via thermal bridges is a high proportion of the total heat energy consumption of a building. For the dry exterior insulation system that uses mullions and transoms to fix insulation and exterior materials such as stone and metal sheet, the occurrence of thermal bridges at mullions and transoms is one of the main reasons for heat loss. In this study, a dry exterior insulation system using the truss insulation frame (TIF) was proposed as an alternative to metal mullions. To evaluate the building envelope performance, structural, air-leakage, water-leakage, fire-resistance, thermal, and condensation risk tests were conducted. In addition, the annual energy consumption associated with heating and cooling was calculated, including the linear thermal transmittance of the thermal bridges. As a result, the dry exterior insulation system using TIF achieved the allowable value for all tests. It was also determined that the annual heating load of a building was reduced by 36.7 % when the TIF dry exterior insulation system was used, relative to the dry exterior insulation system using steel pipes without additional insulations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.4
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• pp.403-409
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• 2013

Shear behavior of concrete beams reinforced with steel and/or FRP bar is studied through experimental tests. Experimental parameters includes the mechanical properties of reinforcements in shear and bending, and the ratio of shear reinforcement. The validity of the modified truss analogy, that has been widely accepted as a basis for the practical shear design of concrete beams, has been examined thoroughly by analyzing experimental results. The experimental results indicate that the modified truss analogy cannot be directly adopted to the shear problem of concrete beams reinforced with FRP bar.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.609-614
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• 2001

This paper is to explain reasonable shear behavior that can apply usually to reinforced concrete beams on the basic concepts of existent analysis and experimental research information. This study is succession $paper^{2) 3) 4) 5)}$ of treatise announced in existing and main control variable of reinforced concrete beams with stirrups used internal force state factor($\alpha$). Shear failure of reinforced concrete beams with stirrups is Influenced greatly because of the actual geometrical shape(a/d) of the concrete and flexural reinforcement steel ratio, stirrup reinforcement ratio and concrete compression strength, size effect etc. Therefore, shear behavior of reinforced concrete beams with stirrups that flexural crack is happened can be explained easily through proper extent proposal of internal force state factor($\alpha$) that express internal force state flowing. Use existent variable truss model by analysis model to explain arch action. Also, wish to compose each failure factors and correlation with internal force state factor by function, and when diagonal cracks happens, internal force state factor($\alpha$) study whether shear stress and some effect are.

• Structural Engineering and Mechanics
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• v.36 no.2
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• pp.197-206
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• 2010

The purpose of this paper is to carry out both experimental and theoretical investigations of R.C. short column subjected to horizontal forces under constant compressive loading. Eight specimens with section of 40 cm ${\times}$ 40 cm, height 40 cm and 50 cm and different type hoop were used of the steel cage to detect the seismic behavior of reinforced concrete short columns. Hoop spacing of column, strength of concrete, and the axial load of experiments were the three main parameters in this test. A series of equations were derived to reveal the theory could be used on analysis short column, too. Through test failure model of R.C short column being established, the type of hoop affects the behavior R.C short column in ductility rather than in strength. And the effect of analysis by Truss Model is evident and reliable in shear failure model of short column.

• Steel and Composite Structures
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• v.7 no.1
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• pp.1-18
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• 2007

Additional cutouts in the floorbeam webs of orthotropic plated bridge decks relieve the highly stressed lower flange of the ribs passing through these floorbeam webs from possible fatigue damage. Conversely, the floorbeam webs themselves suffer from high stress concentrations, especially along the free edges of the additional cutouts. These stresses result from a combination of direct introduction of vertical traffic loads in the weakened web and from the truss action of the floorbeam. The latter differs from a simple beam action due to the presence of the openings and corresponds more to the behaviour of a Vierendeel truss. Close assessment of the appearing stresses, highly relevant for fatigue resistance, requires the use of elaborate finite element modelling. However, a full finite element analysis merely provides the results of total stresses, leaving the researcher or designer the difficult task of finding the origin of these stress components. This paper presents a calculation method for cutout stresses based on a combination of a framework analysis and a two dimensional finite element analysis of much smaller parts of the floorbeam. This method provides more insight in the origin of the stress components, as well as it simplifies any comparison of different additional cutout geometries, independent of the floorbeam topology.

• Steel and Composite Structures
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• v.39 no.5
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• pp.511-528
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• 2021

There are recently some advances in solving numerically topology optimization problems for large-scaled trusses based on ground structure approach. A disadvantage of this approach is that the final design usually includes many bars, which is difficult to be produced in practice. One of efficient tools is a so-called filter scheme for the ground structure to reduce this difficulty and determine several distinct bars. In detail, this technique is valuable for practical uses because unnecessary bars are filtered out from the ground structure to obtain a well-defined structure during the topology optimization process, while it still guarantees the global equilibrium condition. This process, however, leads to a singular system of equilibrium equations. In this case, the minimization of least squares with Tikhonov regularization is adopted. In this paper, a proposed algorithm in controlling optimal Tikhonov parameter is considered in combination with the filter scheme due to its crucial role in obtaining solution to remove numerical singularity and saving computational time by using sparse matrix, which means that the discrete optimal topology solutions depend on choosing the Tikhonov parameter efficiently. Several numerical examples are investigated to demonstrate the efficiency of the filter parameter control algorithm in terms of the large-scaled optimal topology designs.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.725-736
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• 2011

In a composite beam, a shear connector is installed to resist the horizontal shear on an interface between steel beams and reinforced concrete slabs. The steel-wire-integrated deck plate slab is commonly used at the wide section beam. Then vertical bars are installed at the upper wire of the ends of the steel truss girder to ensure safety during the construction. The new type of shear connector is made of deformed bar and steel plates, and must function as vertical bars but must have higher shear capacity. This paper examines the ways to develop and utilize this new shear connector. From the push-out experiments, a shear connector made of a continuous deformed bar and steel plate showed a higher shear capacity and ductility than a ${\phi}16$ stud connector, and functioned as a vertical bar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.89-98
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• 2012

A steel wire-integrated deck plate that welds integrated triangle truss steel wires on a galvanized steel sheet is developed to reduce construction costs of slabs or formworks such as shores and supports, and it is already widely applied in many construction fields. In this research, experimental tests for 14 full scale specimens, which are in the same field conditions, are conducted on several parameters such as the diameter of top, bottom and lattice steel wire, cutting methods of ends. According to the result, changes in final destruction types of the test bodies and cutting methods of ends didn't affect structural performance of test specimens, and for a 4.0m-span test specimen, there was no big problems in using bottom bar D7 or D8.