• Computers and Concrete
• /
• v.26 no.6
• /
• pp.547-563
• /
• 2020

In this paper, the influence of axial compression ratio on the mechanical properties of new type joints of side span of rectangular concrete-filled steel tubular column-H-type steel beam is studied. Two new types of side-span joints of rectangular concrete-filled steel tubular column-H-type steel beam are designed and quasi-static tests of five new type joints with 1:2 scale reduction ratios are performed. The axial compression ratio of joint JD1 is 0.3, 0.4 and 0.5, and the axial compression ratio of joint JD2 is 0.3 and 0.5. In the joint test, different axial forces were applied to the top of the column according to different axial compression ratios, and low-cyclic reciprocating load was applied on the beam. The stress and strain distribution, beam and column deformation, limit state, failure process, failure mechanism, stiffness degradation, ductile deformation and energy dissipation capacity of the joint were measured and analyzed. The results show that: with the increase of axial compression ratio, the ultimate bearing capacity of the joint decreases slightly, the plastic deformation decreases, and the stiffness and ductility decrease. According to the energy dissipation curve of the specimen, the equivalent damping coefficient also increases with the increase of axial compression ratio in a certain range, indicating that the increase of axial compression ratio can improve the seismic performance of the joint to a certain extent. The finite element method is used to simulate the joint test, and the test results are in good agreement with the simulation results.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.5
• /
• pp.53-58
• /
• 2002

A recent development, a concrete-filled steel(CFS) pier is an alternative to a reinforced concrete bridge pier in an urban area, because of its fast construction and excellent ductility against earthquakes. The capacity of CFS piers has not been used to a practical design, because there is no guide of a seismic design for CFS piers. Therefore, the guide of a seismic design value is derived from tests of CFS piers in order to apply it to a practical seismic design. Steel piers and concrete-filled steel piers are tested with constant axial load using quasi-static cyclic lateral load to check ductile capacity and using the real Kobe ground motion of pseudo-dynamic test to verify seismic performance. The results prove that CFS piers have more satisfactory ductility and strength than steel piers and relatively large hysteretic damping in dynamic behaviors. The seismic performance of steel and CFS piers is quantified on the basis of the test results. These results are evaluated through comparison of both the response modification factor method by elastic response spectrum and the performance-based design method by capacity spectrum and demand spectrum using effective viscous damping. The response modification factor of CFS piers is presented to apply in seismic design on a basis of this evaluation for a seismic performance.

• Journal of Korean Society of Steel Construction
• /
• v.18 no.5
• /
• pp.543-551
• /
• 2006

Cold-formed steel studs that are being used as load-bearing members of wall panels for steel houses have a problem with their insulation due to the heat bridging of their web. Some additional thermal insulating materials should be used. To solve this problem, the new-concept hybrid stud, which consists of a galvanized steel sheet (t = 1.0 m - 12.0 m) and a GFRP panel (t = 4.0-6.0 mm), has recently been developed. An investigation on the structural behavior and the strength capacity of this new hybrid stud has been conducted so that it can be used in load-bearing wall panels of residential buildings. This paper describes the axial compression-torsion test results of the hybrid studs under both axial compression and torsion using ATTM. The main factors of the test were the stud length, the magnitude of the initial compressive force, and the loading method of the monotonic or cyclic loading. The torsion was applied increasingly while the initial compression was kept constant to the failure of the hybrid section. The advanced analysis results obtained form the finite element procedure that considered the material properties of the high-strength galvanized steel and the GFRP were compared with the test results for verification.

• Advances in concrete construction
• /
• v.9 no.3
• /
• pp.313-326
• /
• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.10
• /
• pp.85-97
• /
• 2005

Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exist concerns over long-term residual deformation when subjected to repeated and/or cyclic loads, especially when used as part of permanent structures. In view of these concerns, in this paper time-dependent deformation characteristics of geosynthetic reinforced soil under sustained and/or repeated loads were investigated using a series of plane strain compression tests on geogrid reinforced weathered granite soil specimens. The results indicate that sustained or repeated loads can yield appreciable magnitudes of residual deformations, and that the residual deformations are influenced not only by the loading characteristics but by the mechanical properties of geogrid. It is also found that the preloading technique can be effectively used in controlling residual deformations of reinforced soils subjected to sustained and/or repeated loads.

• Earthquakes and Structures
• /
• v.15 no.5
• /
• pp.499-511
• /
• 2018

This paper aims to investigate the seismic performance of the prestressed steel strips retrofitted RC beam-column joints. Two series of joint specimens were conducted under compression load and reversed cyclic loading through quasi-static tests. Based on the test results, the seismic behavior of the strengthened joints specimens in terms of the failure modes, hysteresis response, bearing capacity, ductility, stiffness degradation, energy dissipation performance and damage level were focused. Moreover, the effects of the amount of the prestressed steel strips and the axial compression ratio on seismic performance of retrofitted specimens were analyzed. It was shown that the prestressed steel strips retrofitting method could significantly improve the seismic behavior of the RC joint because of the large confinement provided by prestressed steel strips in beam-column joints. The decrease of the spacing and the increase of the layer number of the prestressed steel strips could result in a better seismic performance of the retrofitted joint specimens. Moreover, increasing the axial compression ration could enhance the peak load, stiffness and the energy performance of the joint specimens. Furthermore, by comparison with the specimens reinforced with CFRP sheets, the specimens reinforced with prestressed steel strips was slightly better in seismic performance and cost-saving in material and labor. Therefore, this prestressed steel strips retrofitting method is quite helpful to enhance the seismic behavior of the RC beam-column joints with reducing the cost and engineering time.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.3
• /
• pp.1-9
• /
• 2014

Improving the earthquake resistance of buildings through seismic retrofitting using steel braces can result in brittle failure at the connection between the brace and the building, as well as buckling failure of the braces. In this study, a non-compression cross-bracing system using the Carbon Fiber Composite Cable (CFCC), which consists of CFCC bracing and bolt connection was proposed to replace the conventional steel bracing. This paper presented the seismic resistance of a reinforced concrete frame strengthened using CFCC X-bracing. Cyclic loading tests were carried out, and the maximum load carrying capacity and ductility were investigated, together with hysteresis of the lateral load-drift relations. Test results revealed that the CFCC X-bracing system installed RC frames enhanced markedly the strength capacity and no buckling failure of the bracing was observed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.153-156
• /
• 2008

The objective of the present study is to evaluate the flexural behavior of reinforced concrete columns externally strengthened with wire rope and T-shape steel plate units. Three strengened columns and a control unstrengthened column were tested under cyclic lateral load simultaneously subjected to a constant axial load. All columns had same section size, and the arrangement of longitudinal reinforcement and internal hoop. The spacing of wire rope range from 40 ${\sim}$ 80mm, which corresponds from 1.0 ${\sim}$ 0.5, respectively, times the minium amount of hoop specified in seismic design of ACI 318-05. Test results showed that the proposed unbonded-type strengthening procedure is very effective for improving the flexural ductility of reinforced concrete columns.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.3
• /
• pp.93-104
• /
• 2003

The Disturbed State Concept (DSC) model, with simplified unloading/reloading formulation, is implemented in a nonlinear dynamic finite element program fur porous media named DSC_DYN2D. In this research, the DSC constitutive model is utilized using the HiSS model for relative intact (RI) part and the critical state model for the fully adjusted (FA) part in the material. The general formulation for implementation is developed. The cyclic loading tests from the field load test data on a pile segment were numerically simulated using the finite element program DSC_DYN2D and compared with field measurements and those from the previous analysis with the HiSS model. The DSC predictions show improved agreement with the field behavior of the pile compared to those from the HiSS model. Overall, the computer procedure with the DSC model allows improved and realistic simulation of the complex dynamic soil-structure interaction problems.

• Structural Engineering and Mechanics
• /
• v.73 no.5
• /
• pp.529-542
• /
• 2020

As limited well-documented experimental data are available for assessing the attributes of different deformation components of flanged walls, few appropriate models have been established for predicting the inelastic responses of flanged walls, especially those of asymmetrical flanged walls. This study presents the experimental results for three large-scale T-shaped reinforced concrete walls and examines the variations in the flexural, shear, and sliding components of deformation with the total deformation over the entire loading process. Based on the observed deformation behavior, a simple model based on moment-curvature analysis is established to estimate flexural deformations, in which the changes in plastic hinge length are considered and the deformations due to strain penetration are modeled individually. Based on the similar gross shapes of the curvature and shear strain distributions over the wall height, a proportional relationship is established between shear displacement and flexural rotation. By integrating the deformations due to flexure, shear, and strain penetration, a new load-deformation analytical model is proposed for flexure-dominant flanged walls. The proposed model provides engineers with a simple, accurate modeling tool appropriate for routine design work that can be applied to flexural walls with arbitrary sections and is capable of determining displacements at any position over the wall height. By further simplifying the analytical model, a simple procedure for estimating the ultimate displacement capacity of flanged walls is proposed, which will be valuable for performance-based seismic designs and seismic capacity evaluations.