• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.109-120
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• 2016

Flexural tests of full-scale concrete-filled U-shape hybrid composite beams were conducted. Ordinary (SS400) and high-strength (SM570) steel plates were used in the web and in the bottom flange of U-shape steel section respectively. The primary objectives were to develop the hybrid section configuration with maximized flexural capacity and to investigate its flexural strength and deformation capacity. All the hybrid test specimens in this study exhibited the plastic moment capacity and resonable deformability. It is shown that the plastic stress distribution can be assumed in calculating the flexural strength of the proposed hybrid composite beams if the plastic neural axis is located within 15% of the total beam depth from the top of the composite slab. The procedure for computing the effective flexural stiffness of hybrid composite beams is also recommended based on test results.

• Steel and Composite Structures
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• v.36 no.4
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• pp.481-492
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• 2020

To study the rail mapped deformation caused by the pier settlement of simply - supported bridges with China Railway Track System III (CRTS III) slab ballastless track (SBT) system under the mode of non-longitudinal connection ballastless track slab, this study derived an analytical solution to the mapped relationships between pier settlement and rail deformation based on the interlayer interaction mechanism of rail-pier and principle of stationary potential energy. The analytical calculation results were compared with the numerical results obtained by ANSYS finite element calculation, thus verifying the accuracy of analytical method. A parameter analysis was conducted on the key factors in rail mapped deformation such as pier settlement, fastener stiffness, and self-compacting concrete (SCC) stiffness of filling layer. The results indicate that rail deformation is approximately proportional to pier settlement. The smaller the fastener stiffness, the smoother the rail deformation curve and the longer the rail deformation area is. With the increase in the stiffness of SCC filling layer, the maximum positive deformation of rail gradually decreases, and the maximum negative deformation gradually increases. The deformation of rail caused by the pier settlement of common-span bridge structures will generate low-frequency excitation on high-speed trains.

• Steel and Composite Structures
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• v.26 no.4
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• pp.485-499
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• 2018

In this paper, a hollow steel tube (HST) shear connector is proposed for use in a slim-floor system. The HST welded to a perforated steel beam web and embedded in concrete slab. A total of 10 push-out tests were conducted under static loading to investigate the mechanical behavior of the proposed HST connector. The variables were the shapes (circular, square and rectangular) and sizes of hollow steel tubes, and the compressive strength of the concrete. The failure mode was recorded as: concrete slab compressive failure under the steel tube and concrete tensile splitting failure, where no failure occurred in the HST. Test results show that the square shape HST in filled via concrete strength 40 MPa carried the highest shear load value, showing three times more than the reference specimens. It also recorded less slip behavior, and less compressive failure mode in concrete underneath the square hollow connector in comparison with the circular and rectangular HST connectors in both concrete strengths. The rectangular HST shows a 20% higher shear resistance with a longer width in the load direction in comparison with that in the smaller dimension. The energy absorption capacity values showed 23% and 18% improvements with the square HST rather than a headed shear stud when embedded in concrete strengths of 25 MPa and 40 MPa, respectively. Moreover, an analytical method was proposed and predicts the shear resistance of the HST shear connectors with a standard deviation of 0.14 considering the shape and size of the connectors.

• Composites Research
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• v.16 no.3
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• pp.32-40
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• 2003

In recent years, the investigation on the development of fiber reinforced plastic(FRP) Re-Bar has been greatly increased due to the attractive physical and mechanical properties of FRP. The primary reason of such a tendency is in the fact that it does not ordinarily cause durability problems such as those associated with steel reinforcement corrosion. This study is an experimental investigation on the flexural behavior of one-way concrete slabs, which can be used to construct bridge deck, reinforced with GFRP Re-Bar bundle. The tensile tests of GFRP Re-Bar produced by domestic industry and third point bending tests of one-way slab specimens reinforced with GFRP Re-Bar bundle are peformed. For all slab specimens, load-deflection relations are predicted by using the ACI committee 440 and the results are compared with experimental ones. In order to establish the design criteria or guidelines of concrete flexural member reinforced with FRP Re-Bar, it is needed to evaluate the serviceability limit state as well as the strength limit state.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.611-620
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• 2003

Shear studs with a diameter of 19mm or 22mm are typically used in steel-concrete composite bridge. For the simplification of details in steel bridges, the convenience of removing concrete slab, and the efficient distribution of shear pockets for precast decks, large studs can be an excellent alternative. Through push-out tests on large stud shear connectors that transcend the limitation of current design codes, static behavior was investigated and comparisons with design equations performed. The shear stiffness of the connectors in elastic range and trilinear load-slip curves were proposed after shear tests on 25mm, 27mm, and 30mm studs. The ultimate slip capacity and ultimate strength of large studs were also evaluated, with the test results revealing conservative values for the design shear strength in Eurocode-4. For 30mm stud shear connectors, the welding quality and bearing capacity of concrete slab should be improved.

• 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.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.209-216
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• 2017

One of the important considerations in structural designing the flat plate system is ensuring the resistance to punching shear caused by axial loads and the ductile ability to follow horizontal deformation under earthquake. In this study, the ECC (Engineered Cementitious Composite) has been placed in the critical section zone of punching shear at slab-column joint to improve ductility and the advanced details of shear reinforced area nearby critical section zone has been developed using stud and steel fiber. The shear performance tests were performed on the specimens with parameters of fiber type mixed with ECC, stud and steel fiber set into the shear reinforced area in which the failure pattern, joint strength, displacement and strain of the specimen were compared and analyzed. The test results showed that the strength and ductility of specimens with ECC applied to joint were better than those of RC flat plate system. Also, the shear reinforcement effect of stud and the ductility improvement of steel fiber concrete were confirmed in the shear reinforcement area.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.503-512
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• 2002

Generally, the girder spacing of the two-girder composite bridge is from 5m up to 15m. To ensure the structural safety according to Korean Bridge Design Specification, the deck depth should be from 33 cm upto 73 cm. Using the transversal prestressing strands in concrete deck, we can reduce its depth about 10％. However, there is little experience on the design and construction of prestressed concrete(PSC) decks in Korea. This paper focuses on the behaviors of PSC deck. A literature survey is performed widely. Considering the characteristics of the two-girder bridge and the construction conditions in Korea, a cast-in-place PSC deck is recommended for the two-girder bridge with 6m girder spacing. To examine its structural behaviors and safety, three partial model deck specimens(3 m$\times$5 m) with real scale are fabricated md tested. One(PS34-RS) is 34cm depth with the stiffness restraint in longitudinal edges for simulating the real bridge deck. Another(PS34-NS) is same depth without the stiffness restraint, and the other(PS28-NS) is 28cm depth with the stiffness restraint. Under the static patch loading, each specimen had a larger ultimate flexural strength than the design value. Specimens with the stiffness restraint (PS34-RS and PS28-RS) showed the punching shear failure mode and specimen without that(PS34-NS) showed the flexural failure mode.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.80-86
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• 2020

In the fabrication process of inverted multi-tee (IMT) slabs, concrete has to be poured twice due to its shape, which is a huge disadvantage as a precast member. To overcome this, a new technique for manufacturing IMT slabs using a slipform method has been recently developed. In this study, flexural and shear tests were carried out to investigate the structural performances of inverted multi-tee (IMT) slabs manufactured using slipform method. To this end, one flexural specimen and two shear specimens with topping concrete were fabricated, and their failure modes and crack patterns, and the slips that occurred between the precast slab and topping concrete were measured and analyzed in detail. In addition, the flexural and shear strengths of the specimens were evaluated by utilizing the structural design code, and a shear strength estimation method, which is suitable for composite IMT slabs with different concrete properties, was proposed for practical design. The IMT slab satisfied the nominal flexural strength calculated by the current design code, and the proposed method provided a good estimation of the shear strength of the specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.139-148
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• 2006

The dynamic characteristics of a bridge deduced by using the modeling techniques depend on its stiffness and mass calculated from its geometric model. This research develops the FE modeling techniques for a steel plate girder bridge with composite section. and proves their validity by comparing the results with those from actual measurement. The FE modeling techniques are divided into two categories--a simplified one and two-dimensional model and a detailed three-dimensional model. In the meantime, the dynamic responses of the bridge tested for this research were measured by the ambient vibration some of accelerometers were been attached to its upper slab girder under normal traffic load. The Cross Power Spectrum obtained from the measurement was used to analyze the dynamic characteristics by natural excitation techniques. The analytic results are compared to those of each FE modeling, and thereby the modeling techniques were proved to be valid.