• Journal of Korean Association for Spatial Structures
• /
• v.21 no.2
• /
• pp.12-17
• /
• 2021

• Journal of the Korea Concrete Institute
• /
• v.14 no.6
• /
• pp.823-829
• /
• 2002

The composite frame system with reinforced concrete column and steel beam has some advantages in the structural efficiency by complementing the shortcomings between the two systems. The system, however has also a lot of problems in practical design and construction process due to the material dissimilarities. Considering these circumstances, this research is aimed at the development of the composite structural system which enables the steel beams to be connected to the R/C columns with higher structural safety and economy. Basically the proposed connection system is composed of four split tees, structural angles reinforced by stiffener, high strength steel rods, connecting plates and shear plates. The structural tests have been carried out to verify the moment transfer mechanism from beam flange to steel rods or connecting plates through the angle reinforced by siffener. The four prototype specimens have been tested until the flange of beam reached the plastic states. From the tests, no distinct material dissimilarities between concrete and steel have been detected and the stress transfer through wide flange beam - structural angle - high strength steel rod or connecting plate is very favorable.

• Journal of Korean Society of Steel Construction
• /
• v.19 no.6
• /
• pp.737-749
• /
• 2007

Flexural design of double composite box girder over the interior pier for three-span continuous bridge was performed by the LRFD method. The maximum span length of the continuous bridge ranged from 80m to 120m and the relative ratio of the span length was assumed to be 1:1.25:1. The girder section was designed for the strength limit state and service limit state with additional design check for constructibility. Before the bottom concrete and compression flange showed a complete composite action, the buckling of lower compression flange was checked. The flexural stiffness and flexural resistance characteristics for the section and for the constituent members such as tension flange, compression flange, and web were analyzed for different thicknesses of the bottom concrete on top of the compression flange. The effect of the distribution ratio of steel between the top and bottom flanges was investigated by analyzing ductility behavior and stress distribution through the girder's depth for several different relative area ratios of steel between the top and bottom flanges. It was found that a total amount of 15% of steel can be saved by applying the double composite system compared with that of the conventional composite system.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.6
• /
• pp.23-32
• /
• 2022

Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1^st type and 2^nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.

• Structural Engineering and Mechanics
• /
• v.72 no.4
• /
• pp.503-512
• /
• 2019

The construction of segmental precast concrete bridge is an increase due to its superior performance and economic advantages. This type of bridge is appropriate for spans within 30 to 150 m (100 to 500 ft), known as mega-projects and the design optimization would lead to considerable economic benefits. A box-girder cross section superstructure of balanced cantilever construction method is assessed here. The depth of cross section, (variable along the span linearly), bottom flange thickness, and the count of strands are considered as design variables. The optimum design is characterized by geometry, serviceability, ductility, and ultimate limit states specified by AASHTO. Genetic algorithm (GA) is applied in two fronts: as to the saving in construction cost 8% and as to concrete volume 6%. The sensitivity analysis is run by considering different parameters like span/depth ratio, relation between superstructure cost, span length and concrete compressive strength.

• Steel and Composite Structures
• /
• v.43 no.3
• /
• pp.327-340
• /
• 2022

A vast amount of experimental and analytical research has been conducted related to the seismic behavior and performance of concrete filled steel tubular (CFT) columns. This research has resulted in a wealth of information on the component behavior. However, analytical and experimental data for structural systems with CFT columns is limited, and the well-known behavior of steel or concrete structures is assumed valid for designing these systems. This paper presents the development of an analytical model for nonlinear analysis of composite moment resisting frame (CFT-MRF) systems with CFT columns and steel wide-flange (WF) beams under seismic loading. The model integrates component models for steel WF beams, CFT columns, connections between CFT columns and WF beams, and CFT panel zones. These component models account for nonlinear behavior due to steel yielding and local buckling in the beams and columns, concrete cracking and crushing in the columns, and yielding of panel zones and connections. Component tests were used to validate the component models. The model for a CFT-MRF considers second order geometric effects from the gravity load bearing system using a lean-on column. The experimental results from the testing of a four-story CFT-MRF test structure are used as a benchmark to validate the modeling procedure. An analytical model of the test structure was created using the modeling procedure and imposed-displacement analyses were used to reproduce the tests with the analytical model of the test structure. Good agreement was found at the global and local level. The model reproduced reasonably well the story shear-story drift response as well as the column, beam and connection moment-rotation response, but overpredicted the inelastic deformation of the panel zone.

• Steel and Composite Structures
• /
• v.35 no.3
• /
• pp.371-384
• /
• 2020

The steel-concrete double composite girder in the negative flexural region combines an additional concrete slab to the steel bottom flange to prevent the local steel buckling, however, the additional concrete slab may lower down the neutral axis of the composite section, which is a sensitive factor to the tensile stress restraint on the concrete deck. This is actually of great importance to the structural rationality and durability, but has not been investigated in detail yet. In this case, a series of 5.5 m-long composite girder specimens were tested by negative bending, among which the bottom slab configuration and the longitudinal reinforcement ratio in the concrete deck were the parameters. Furthermore, an analytical study concerning about the influence of bottom concrete slab thickness on the cracking and sectional bending-carrying capacity were carried out. The test results showed that the additional concrete at the bottom improved the composite sectional bending stiffness and bending-carrying capacity, whereas its effect on the concrete crack distribution was not obvious. According to the analytical study, the additional concrete slab at the bottom with an equivalent thickness to the concrete deck slab may provide the best contributions to the improvements of crack initiation bending moment and the sectional bending-carrying capacity. This can be applied for the design practice.

• Steel and Composite Structures
• /
• v.47 no.3
• /
• pp.423-436
• /
• 2023

In this research, we tested 10 simply supported concrete-encased composite columns under monotonic eccentric loads and investigated their shear behaviour. The specimens tested were two reinforced concrete specimens, three steel-reinforced concrete (SRC) specimens with an H-shaped steel section (also called a beam section), and five SRC specimens with a cruciform-shaped steel section (also called a column section). The experimental variables included the transverse steel shape's depth and the longitudinal steel flange's width. Experimental observations indicated the following. (1) The ultimate load-carrying capacity was controlled by web compression failure, defined as a situation where the concrete within the diagonal strut's upper end was crushed. (2) The composite effect was strong before the crushing of the concrete outside the steel shape. (3) We adjusted the softened strut-and-tie SRC (SST-SRC) model to yield more accurate strength predictions than those obtained using the strength superposition method. (4) The MSST-SRC model can more reasonably predict shear strength at an initial concrete softening load point. The rationality of the MSST-SRC model was inferred by experimentally observing shear behaviour, including concrete crushing and the point of sharp variation in the shear strain.

• Journal of the Korea Institute of Building Construction
• /
• v.5 no.1 s.15
• /
• pp.105-109
• /
• 2005

Classified with concrete as placing ways - direct ways, sheath way - and placing directing flange direction, web direction - is analyzed section and strength of hardened concrete. The results of this study is belows the more fluid of concrete, the more useful to top-down method. To minimize the voids of the reverse placement joints, It is more effect to use the sheath method than direct method in concrete placement. If the joint face is a plane, it is impossible to extract the air bubbles which caused voids, so we should consider about this, and decide to select which type of joints.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.297-302
• /
• 2002

This paper investigated the properties of flexural behavior of composite beams (end-Reinforced concrete, center-Steel concrete) according to attaching length of main bars to flange, shear reinforcing length for different types of structure. In the preceding study, structural properties of composite beams were investigated according to shear span to depth ratio, attaching method of main bars and shear reinforcing method. Based on these results, a series of experiments was carried out according to attaching length of main bar ＆ reinforcing length for different types of structure. Consequently, as attaching length of main bar and shear reinforcing length increased, composite beams represented higher strength, ductility index and stress mechanism distributed in connection zone of different types of structure.