• Journal of Korean Association for Spatial Structures
• /
• v.12 no.4
• /
• pp.81-90
• /
• 2012

The concrete-filled tube (CFT) column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. Its Solution, 2 members of ㄷchennel in which Internal diaphragm is installed were welded beforehand and the method of making Rectangular Steel Tube was proposed. According to upside and downside junction shape, Internal diaphragm suggested as symmetric specimen and asymmetric specimen. The upper and lower diaphragm of the Symmetric specimen used the same horizontal and The upper diaphragm of the Asymmetric specimen used the horizontal plate and the lower diaphragm used the vertically plate. In this research, 4 T-shape column to beam steps connections were tested with cyclic loading experiment in order to evaluate the structural capability of the offered connection. Symmetric specimens be a failure in 0.03rad from beam flange. And Asymmetric specimens be a failure in 0.05rad from column interface. The comparison results of All specimens shown similar to energy absorption capacity in 0.02rad.

• Journal of the Korea Concrete Institute
• /
• v.27 no.1
• /
• pp.55-63
• /
• 2015

Prefabrication technologies are making bridge construction safer and less disruptive to the environment and traveling public, making bridge designs more constructible and, improving the quality and durability by shifting site work to a more controllable environment. Modular bridge substructures with concrete-filled steel tube (CFT) piers and composite pier caps were suggested to realize accelerated bridge construction. The precast segmental pier cap consists of a composite pier table and precast prestressed segments on the table. The pier table has embedded steel section to mitigate stress concentration at the connection by small tubes. Each bridge pier has four or six CFT columns which connect to the pier cap. Shear strength of the pier cap was obtained by extending vertical reinforcing bars from the table to the precast segment. Transverse prestressing was introduced to control tensile stresses by service loadings. Structural performance of the proposed modular system was evaluated by static tests. Design requirements of the composite pier cap were satisfied by continuous reinforcing bars and prestressing tendons. Standardized modular substructures can be effectively utilized for the fast replacement or construction of bridges.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.5
• /
• pp.435-445
• /
• 2015

Concrete filled steel tube(CFT), which has superior ductility and strength, is used for building column, bridge piers of ocean structure. Shear design equations of CFT existing in structural design provisions are excessively conservative. It has an effect on constructability and the economics of CFT. However, to suggest the reasonable shear design equation, experimental studies on the shear capacity of CFT have been rarely conducted. This study is analytical research to suggest improved shear design equations of large-diameter concrete-filled steel tubes. This analytical research was conducted to apply finite element analysis model of CFT based on the prior research. It was verified by comparison with prior test results. The verified model was used for parameter studies to estimate the influence of overhang length, concrete compressive strength and diameter-thickness ratio on shear strength.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.2 no.4
• /
• pp.1-10
• /
• 2011

This study investigates the performance of composite (steel-concrete) frame structures through numerical experiments on individual connections. The innovative aspects of this research are in the use of connections between steel beams and concrete-filled tube (CFT)columns that utilize a combination of low-carbon steel and shape memory alloy (SMA) components. In these new connections, the intent is to utilize the recentering provided by super-elastic shape memory alloy tension bars to reduce building damage and residual drift after a major earthquake. The low-carbon steel components provide excellent energy dissipation. The analysis and design of these structures is complicated because the connections cannot be modeled as being simply pins or full fixity ones they are partial restraint (PR). A refined finite element (FE) model with sophisticated three dimensional (3D) solid elements was developed to conduct numerical experiments on PR-CFT joints to obtain the global behavior of the connection. Based on behavioral information obtained from these FE tests, simplified connection models were formulated by using joint elements with spring components. The behavior of entire frames under cyclic loads was conducted and compared with the monotonic behavior obtained from the 3D FE simulations. Good agreement was found between the simple and sophisticated models, verifying the robustness of the approach.

• 건축구조
• /
• v.8 no.4
• /
• pp.60-61
• /
• 2001

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.217-220
• /
• 2008

Recently, many studies about a high-strength concrete and composite structures are being progressed to get the more economic and stable result in the construction of structure all over the world. One of those studies is about CFTA(Concrete Filled and Tied Steel Tubular Arch) girder that applies an arch structure and a pre-stressed structure to CFT(Concrete Filled Steel Tubular) Structure which is filled with a concrete and improve the stiffness and strength of the structure by the confinement effect of fillers to maximize the efficiency of structure and economic. In this study, non-linear behavior of CFTA girders filled with a general concrete and the high-strength concrete respectively were analyzed by using ABAQUS 6.5-1 and results were compared.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.4
• /
• pp.389-398
• /
• 2013

The structural provisions of rectangular CFT (concrete-filled tubular) columns in the 2005/2010 AISC Specification, ACI 318-08, and EC4 were comparatively analyzed as a preliminary study for establishing the unified standards for composite structures. The provisions analyzed included those related to the nominal strength, the effect of confinement, plate slenderness, effective flexural stiffness, and the material strength limitations. Small or large difference can be found among the provisions of AISC, ACI, and EC4. Generally, the 2010 AISC Specification provides the revised provisions which reflect up-to-date test results and tries to minimize the conflict with the ACI provisions. For example, the 2010 AISC Specification introduced a more finely divided plate slenderness limits for CFT columns. In seismic applications, the plate slenderness limits required for highly and moderately ductile CFT columns were separately defined. However, the upper cap limitations on material strengths in both the AISC and EC4 provisions are too restrictive and need to be relaxed considering the high-strength material test database currently available. This study found that no provisions reviewed in this paper provide a generally satisfactory method for predicting the P-M interaction strength of CFT columns under various material combinations. It is also emphasized that a practical constitutive model, which can reasonably reflect the stress-strain characteristics of confined concrete of rectangular CFT columns, is urgently needed for a reliable prediction of the P-M interaction strength.

• 건축구조
• /
• v.22 no.4
• /
• pp.18-24
• /
• 2015

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.6 no.2
• /
• pp.32-39
• /
• 2015

So far, square concrete filled tubular(CFT) columns have been used in a limited width thickness ratio. The reason is that local buckling occurs in steel tube easily. Once the local buckling occurs, the confinement effect of steel tube on concrete disappears. In this study, we developed welded built-up square steel tube with reinforcement which are placed at the center of the tube width acts as an anchor. 3 specimens of slender welded built-up square CFT columns and 3 specimens of slender welded built-up square steel tube columns were manufactured with parameters of width(B) of steel tube, width thickness ratio(B/t). we conducted a experimental test on the 6 specimens under eccentric load, and evaluated the structural resistance and behavior of 6 specimens.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.2
• /
• pp.161-171
• /
• 2010

Bridges have undergone distinctive development in accordance of the introduction of new materials and structural types. The importance on rapid construction technology is currently attracting more and more attention worldwidely as well as domestically because its effectiveness in reducing the overall construction cost. While a wide ranges of previous researches on rapid construction of super structures are available, the studies on substructures are quite limited. The development of the precast segmental internally confined hollow CFT piers are briefly introduced herein and design formulas are presented for pier segment joints, Also, a extensive parametric studies are carried out for the effect of the constitutive elements of the joints. Finally, the design formulas are verified throughout a series of extensive finite element analyses.