• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.303-312
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• 2007

Steel box girder bridges are being commonly designed for medium-span bridges of span length. Composite truss bridges with steel diagonals instead of concrete webs can be an excellent design alternative, because it can reduce the dead weight of superstructures. One of the key issues in the design of composite truss bridges is the joint structureconnecting the diagonal steel members with the upper and lower concrete slabs. Because the connection has to carry concentrated combined loads and the design provisions for the joint are not clear, it is necessary to investigate the load transfer mechanism and the design methods for each limit state. There are various connection details according to the types of diagonal members. In this paper, the joint structure with group stud connectors welded on a gusset plate is used. Push-out tests for the group stud connectors of were performed. The test results showed that the current design codes on the ultimate strength ofthe stud connection can be used when the required minimum spacing of stud connectors is satisfied. Flexure-shear tests were conducted to verify the applicability of the design provisions for combined load effects to the strength of joint structures. To increase the pullout strength of the connection, bent studs were proposed and utilized for the edge studs in the group arrangement of the joint. The results showed that the details of the joint structure were enhanced. Thereafter, design guidelines were proposed.

• Steel and Composite Structures
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• v.36 no.4
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• pp.369-381
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• 2020

Nowadays, in prefabricated composite construction, composite action between steel beam and concrete slab is often achieved with positioning of shear connectors in envisaged openings of concrete slabs. Prefabricated concrete slabs are used for composite steel-concrete buildings and bridges, both for the construction of new structures and for renovation of existing ones, significantly reducing construction time. Development of different types of shear connectors represent alternative solution to the traditionally used headed studs, considering their shear resistance, stiffness and ductility. New types of shear connectors tend to reduce the construction time and overall construction cost. Mechanically fastened shear connectors represent a viable alternative to headed studs, considering their fast installation process and shear resistance. X-HVB shear connectors are attached to the steel beam with two cartridge fired pins. The first step towards extensive implementation of X-HVB shear connectors in composite construction is to understand their behaviour through experimental investigation. Results of the push-out tests, in accordance to Eurocode 4, with X-HVB 110 shear connectors positioned in envisaged openings of prefabricated concrete slabs are presented in this paper. The experimental investigation comprised three different specimen's layout. Group arrangement of X-HVB shear connectors in envisaged openings included specimens with minimal recommended distances and specimens with reduced distances between connectors in both directions. Influence of different installation procedures on overall behaviour of the connection is presented, as well as the orientation of shear connectors relative to the shear force direction. Influence of variations is characterized in terms of failure mechanisms, shear resistance and ductility.

• Steel and Composite Structures
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• v.36 no.1
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• pp.103-118
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• 2020

The static behavior of grouped large-headed studs (d = 30 mm) embedded in ultra-high performance concrete (UHPC) was investigated by conducting push-out tests and numerical analysis. In the push-out test, no splitting cracks were found in the UHPC slab, and the shank failure control the shear capacity, indicating the large-headed stud matches well with the mechanical properties of UHPC. Besides, it is found that the shear resistance of the stud embedded in UHPC is 11.4% higher than that embedded in normal strength concrete, indicating that the shear resistance was improved. Regarding the numerical analysis, the parametric study was conducted to investigate the influence of the concrete strength, aspect ratio of stud, stud diameter, and the spacing of stud in the direction of shear force on the shear performance of the large-headed stud. It is found that the stud diameter and stud spacing have an obvious influence on the shear resistance. Based on the test and numerical analysis results, a formula was established to predict the load-slip relationship. The comparison indicates that the predicted results agree well with the test results. To accurately predict the shear resistance of the stud embedded in UHPC, a design equation for shear strength is proposed. The ratio of the calculation results to the test results is 0.99.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.595-608
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• 2021

To investigate the mechanical behavior of large stud shear connector embedded in hybrid fiber-reinforced concrete (HFRC), a refined 3D nonlinear finite element (FE) model incorporating the constitutive model of HFRC was developed using ANSYS. Firstly, the test results conducted by the authors (He et al. 2017) were used to validate FE model of push out tests. Secondly, a total of 27 specimens were analyzed with various parameters including fiber volume fractions of HFRC, diameter of studs and HFRC strength. Finally, an empirical equation considering the contribution of steel fiber (SF) and polypropylene fiber (PF) was recommended to estimate the ultimate capacity of large stud shear connector embedded in HFRC.

• Steel and Composite Structures
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• v.26 no.2
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• pp.183-196
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• 2018

The traditional prestressed concrete composite box-girders with corrugated steel webs have several drawbacks such as large deflection and potential local buckling. In this study, two methods were investigated to optimize and improve the prestressed concrete composite box-girders with corrugated steel webs. The first method was to replace the concrete bottom slab with a steel plate and the second method was to support the concrete bottom slab on the steel flanges. The behavior of the prestressed concrete composite box-girders with corrugated steel webs with either method was studied by experiments on three specimens. The test results showed that behavior of the optimized and upgraded prestressed concrete composite box-girders with corrugated steel webs, including ultimate bearing capacity, flexural stiffness, and crack resistance, is greatly improved. In addition, the influence of different shear connectors, including perfobond leisten (PBL) and stud shear connectors, on the behavior of prestressed concrete composite box-girders with corrugated steel webs was studied. The results showed that PBL shear connectors can greatly improve the ultimate bearing capacity, flexural stiffness and crack resistance property of the prestressed concrete composite box-girders with corrugated steel webs. However, for the efficiency of prestressing introduced into the girder, the PBL shear connectors do not perform as well as the stud shear connectors.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.415-425
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• 2016

Load-bearing steel stud wall system is widely used for the middle-to-high rise modular buildings worldwide. Seismic performance is a key issue to apply load-bearing steel stud wall system to modular buildings in Korea. This study proposes a new strap braced steel stud wall system with enhanced seismic performance and design equations considering the flexural behaviour of the vertical outer studs. For the verification, two specimens with different strap braces and vertical outer stud were designed and tested. The test results showed that the total strengths were evaluated to be 1.11 to 1.18 times higher than the predicted values. Usually strap braced walls are considered to have low energy dissipation capacities. The proposed system showed enhanced seismic performance with equivalent damping of 9.42% due to the reduced pinching effects.

• Steel and Composite Structures
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• v.36 no.5
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• pp.507-519
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• 2020

Double skin composite walls are increasingly popular and have been applied to many safety-related facilities. They come from the concept of composite slabs. Conventional connectors such as shear studs and binding bars were used in previous studies to act as the internal mechanical connectors to lock the external steel faceplates to the concrete core. However, the restraint effects of these connectors were sometimes not strong enough. In this research, a recently proposed unique type of steel truss was employed along the wall height to enhance the composite action between the two materials. Concrete-filled tube columns were used as the boundary elements. Due to the existence of boundary columns, the restraints of steel faceplates to the concrete differ significantly for the walls with different widths. Therefore, there is a need to explore the effect of height-to-width ratio on the structural behavior of the wall. In the test program, three specimens were designed with the height of 3000 mm, the thickness of 150 mm, and different widths, to simulate the real walls in practice. Axial compression was applied by two actuators on the tested walls. The axial behavior of the walls was evaluated based on the analysis of test results. The influences of height-to-width ratio on structural performance were evaluated. Finally, discussion was made on code-based design.

• Biomedical Science Letters
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• v.7 no.4
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• pp.211-216
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• 2001

This studs was carried out to evaluate KBrO$_3$-induced acute toxicity by clinical pathological parameters in rats. Fourty rats were divided into 4 groups including normal group and three KBrO$_3$-treated groups with doses of 200, 300, and 400 mg/kg, p. o., respectively. Creatinine and BUN were increased remarkably by KBrO$_3$ at 400 mg/kg, respectively (p<0.05, p<0.01). Phosphorus content increased two times the control at 400 mg/kg (p<0.05). Osmolarity was increased, whereas $CO_2$ content showed decrease at 400 mg/kg, respectively (p<0.01, p<0.05). Histopathological findings also showed dose-dependent renal failure. On the other hand, AST was increased three times the control at 400 mg/kg (p<0.01). WBC was increased by KBrO$_3$ depending on the dosage. Platelet was decreased at 200 mg/kg, whereas it was increased at 400 mg/kg (p<0.05). The results above suggest that clinical pathological parameters could be used as indices for the evaluation of KBrO$_3$-induced acute toxic reponse occuring in not only kidney but other organs including liver, when the dosage is as high as 400 mg/kg.

• Steel and Composite Structures
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• v.49 no.2
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• pp.215-230
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• 2023

Cable-girder anchorage joint is the critical part of cable-supported bridges. Tensile-plate anchorage (TPA) is one of the most commonly used types of cable-girder anchorage joints in steel girder cable-supported bridges. In recent years, it has been proposed by bridge designers to apply TPA to concrete girder cable-supported bridges to form composite cable-girder anchorage joint (CCGAJ). In this paper, the mechanical performance of CCGAJ under tensile force is studied through experimental and numerical analyses. Firstly, the effects of the external prestressing (EP) and the bearing plate (BP) on the mechanical performance of CCGAJ were investigated through three tests. Then, finite element model was established for parametrical study, and was verified by the experimental results. Then, the effects of shear connector forms, EP, BP, vertical rebar rate, and perforated rebar rate on the tensile capacity of CCGAJ were investigated through numerical analyses. The results show that the tensile capacity of CCGAJ depends on the first row of PR. The failure mode of CCGAJ using headed stud connectors is to form a shear failure surface at the end of the studs while the failure mode using PBLs is similar to the bending of a deep girder. Finally, based on the strut-and-tie model (STM), a calculation method for CCGAJ tensile capacity was proposed, which has a high accuracy and can be used to calculate the tensile capacity of CCGAJ.

• Korean Journal of Poultry Science
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• v.29 no.1
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• pp.25-35
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• 2002

Two experiments were conducted to studs the effects of early-life feed restriction, ages and duration on compensatory growth, feed efficiency, and abdominal fat pad deposition in broilers. The chicks were randomly assigned to four treatments (experiment 1) or seven treatments (experiment 2) . Each dietary treatment was replicated with three floor pens in both experiments, and twenty chicks were assigned to each pen. In experiment 1, birds in control group (C) were full-fed throughout the study. For treatments 1, 2, and 3, bards were fed diets containing 0.75 kcal ME/gB $W^{o.67}$/d for 3 d(T1), 1.5 ㎉ ME/gB $W^{o.67}$/d for 5 d (T2), and 2.25 local ME/gB $W^{0.67}$/d for 7 d (T3), all imposed beginning at 7 d of age. The selected value seems appropriate for maintenance feeding because the feed restriction at T1 resulted no growth in virtually. Although the birds previously subjected with restricted feeding significantly (P<0.05) enhanced growth partly (in 22~49 d), the weight gain over the entire growth period (7-49 d) was not influenced by the restricted feeding Programs. Whereas, the restricted feedings had effects with significant (P<0.75) increase in feed intake not only in 22~49 d, but in overall period (7-49 d). The feed conversion for the birds previously subjected with restricted feeding was significantly (P<0.05) improved after 21 d. The birds with restricted feedings (T1,T2,T3) showed better (P<0.05) feed conversion ratio than C both in 22-49 d and in 7-49 d. The restricted feeding programs did not show effects in reducing for abdominal fat pad deposition or mortality In experiment 2, the birds of C were full-fed in overall period. But for treatments 1, 2, 3, 4, 5, and 6 (T1-T6),the birds were fed diets containing 0.75 ㎉ ME/gB $W^{0.67}$/d for 3 or 5 d, starting at either 4, 7 or 10 d of age. The selected value seems appropriate for maintenance feeding because the feed restriction resulted no growth in virtually; which was same as experiment.