• Structural Engineering and Mechanics
• /
• v.13 no.3
• /
• pp.313-328
• /
• 2002

Based on the orthotropic hypoelasticity formulation, a triaxial constitutive model of concrete is proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancement is considered using so called the strain enhancement factor. It is also developed a three-dimensional finite element model for reinforced concrete structural members based on the proposed constitutive law of concrete with the smeared crack approach. The concrete confinement effects due to the beam-column joint are investigated through numerical examples for simple beam and structural beam member. Concrete at compression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxial compressive state but also by the biaxial and triaxial compressive states. For the reason of the severe confinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a small distance away from the beam-column joint. These observations should be utilized for the economic design when the concrete structural members are subjected to high confinement due to the influence of beam-column joint.

• Steel and Composite Structures
• /
• v.16 no.1
• /
• pp.97-114
• /
• 2014

This paper deals with a study on ultimate strength behaviour of eccentrically loaded CFT columns with and without shear connectors. Thirty specimens are subjected to experimental investigation under eccentric loading condition. P-M curves are generated for all the test specimens and critical eccentricities are evaluated. Three different D/t ratios such as 21, 25 and 29 and L/D ratios varying from 5 to 20 are considered as experimental parameters. Six specimens of bare steel tubes as reference specimens, twelve specimens of CFT columns without shear connectors and twelve specimens of CFT columns with shear connectors, in total thirty specimens are tested. The P-M values at the ultimate failure load of experimental study are found to be well agreed with the results of the proposed P-M interaction model. The load-deflection and load-strain behaviour of the experimental column specimens are presented. The behaviour of the CFT columns with and without shear connectors is compared. Experimental results indicate that the percentage increase in load carrying capacity of CFT columns with shear connectors compared to the ordinary CFT columns is found to be insignificant with a value ranging from 6% to 13%. However, the ductility factor of columns with shear connectors exhibit higher values than that of the CFT columns without shear connectors. This paper presents the proposed P-M interaction model and experimental results under varying parameters such as D/t and L/D ratios.

• KCI Concrete Journal
• /
• v.12 no.2
• /
• pp.73-84
• /
• 2000

A new form of construction utilizing structural steel as the boundary elements in ductile flexural concrete walls is proposed to solve the bar congestion problems in such a heavily reinforced region, while maintaining the ductility and energy absorption capacity comparable to their traditional form. Two wall specimens containing rectangular hollow structural sections (HSS) and channels at their ends respectively, and one companion standard reinforced concrete wall specimen with concentrated end reinforcement were constructed and tested under reversed cyclic loading to evaluate the construction process as well as the structural performance. Initially, all three specimens were chosen and detailed with some caution to have approximately the same flexural capacity without change of the original shape and dimension of a rectangular cross section correction. Analysis and comparison of test results indicated that the reversed cyclic responses of three walls showed similar hysteretic properties, but in those with steel boundaries, local buckling of the corresponding steel webs and flanges following significant yielding was a dominant factor to determine the hysteretic response. The monotonic and cyclic responses predicted based on a sectional approach was also presented and found to be in good agreement with measured results. Design recommendations considering local instability of the structural steel elements and the interaction between steel chords and a concrete web member in such a composite wall are presented.

• Earthquakes and Structures
• /
• v.8 no.3
• /
• pp.699-712
• /
• 2015

Bracing structures with off-centre bracing system is one of the new resistant systems that frequently used in the frame with pin connections. High ductility, high-energy dissipation and decrease of base shear are advantages of this bracing system. However, beside these advantages, reconstruction and hard repair of off-centre bracing system cause inappropriate performance in the earthquake. Therefore, in this paper, the goal is investigating the behavior of this type of bracing system with ductile element (circular dissipater), in order to providing replacement of damaged member without needing repair or reconstruction of the general system. To achieve this purpose, some numerical studies have been performed using ANSYS software, a frame with off-centre bracing system and optimum eccentricity (OBS-C-O) and another frame with the same identifications without ductile element (OBS) has been created. In order to investigate precisely on the optimum placement of circular elements under monotonic load again three steal frames were modeled. Furthermore, the behavior of this general system investigated for the first time, linear and nonlinear behavior of these two steel frames compared to each other, to achieve the benefit of using the circular element in an off-centre bracing system. Eventually, the analytical results revealed that the performance of steel ring at the end of off-centre braces system illustrating as a first defensive line and buckling fuse in the off-centre bracing system.

• Structural Engineering and Mechanics
• /
• v.10 no.4
• /
• pp.405-426
• /
• 2000

Two approximate methods based on mechanism analysis suitable for seismic assessment/design of structural concrete are reviewed. The methods involve use of equal energy concept or equal displacement concept along with appropriate patterns of inelastic deformations to relate structure's maximum lateral displacement to member and plastic deformations. One of these methods (Clough's method), defined here as a ductility-based approach, is examined in detail and a modification for its improvement is suggested. The modification is based on estimation of maximum inelastic displacement using inelastic design response spectra (IDRS) as an alternative to using equal energy concept. The IDRS for demand displacement ductilities are developed for a single degree of freedom model subjected to several accelerograms as functions of response modification factor (R), damping ratios, and strain hardening. The suggested revised methodology involves estimation of R as the ratio of elastic strength demand to code level demand, and determination of design base shear using $R_{design}{\leq}R$ and maximum displacement, determination of plastic displacement using IDRS and subsequent local plastic deformations. The methodology is demonstrated for the case of a 10-story precast wall panel building.

• Earthquakes and Structures
• /
• v.20 no.4
• /
• pp.417-430
• /
• 2021

Due to functional requirements, SRC column-RC beam abnormal joints with characteristics of strong beam weak column, variable column section, unequal beam height and staggered height exist in the Steel reinforced concrete (SRC) frame-bent main building structure of thermal power plant (TPP). This paper presents the experimental results of these abnormal joints through cyclic loading tests on five specimens with scaling factor of 1/5. The staggered height and whether adding H-shaped steel in beam or not were changing parameters of specimens. The failure patterns, bearing capacity, energy dissipation and ductile performance were analyzed. In addition, the stress mechanism of the abnormal joint was discussed based on the diagonal strut model. The research results showed that the abnormal exterior joints occurred shear failure and column end hinge flexural failure; reducing beam height through adding H-shaped steel in the beam of abnormal exterior joint could improve the crack resistance and ductility; the abnormal interior joints with different staggered heights occurred column ends flexural failure; the joint with larger staggered height had the higher bearing capacity and stiffness, but lower ductility. The concrete compression strut mechanism is still applicable to the abnormal joints in TPP, but it is affected by the abnormal characteristics.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.28 no.1
• /
• pp.11-20
• /
• 2024

The ductility of the system based on the capacity of each structural member constituting the seismic force-resisting system is a significant factor determining the structure's seismic performance. This study aims to provide a procedure to supplement the current seismic design criteria to secure the system's ductility and improve the seismic performance of the steel ordinary moment frames. For the study, a nonlinear analysis was performed on the 9- and 15-story model buildings, and the formation of collapse mechanisms and damage distribution for dynamic loads were analyzed. As a result of analyzing the nonlinear response and damage distribution of the steel ordinary moment frame, local collapse due to the concentration of structural damage was observed in the case where the influence of the higher mode was dominant. In this study, a procedure to improve the seismic performance and avoid inferior dynamic response was proposed by limiting the strength ratio of the column. The proposed procedure effectively improved the seismic performance of steel ordinary moment frames by reducing the probability of local collapse.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.3
• /
• pp.131-140
• /
• 2004

The main objective of the research is to develop an algorithm for the optimum design of two dimensional steel frames using refined plastic hinge analysis which considers material and geometrical nonlinearities. Using developed algorithm, an optimum design was perform without calculating an effective length factor of the column (K-factor). A multi-level discrete optimization technique with two parameters has been developed and employed in the optimum design algorithm. The optimization algorithm is applied to structural design with the objective of minimizing the weight of a structure and with constraints on load limit, frame drift, ductility. Various application example is provided to demonstrate the feasibility, validity and efficiency of the developed program.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.959-964
• /
• 2001

This study investigates the seismic performance of bearing walls with rectangular sectional shape and specific details of reinforcements developed for 10 to 20-story apartment buildings in Korea. To investigate seismic behavior of structural walls, several specimens were experimented by author and laboratory test results by other researchers were collected and analysed. Structural behaviors of walls were evaluated by means of ductility, deformation, and strength capacities. For this purpose, thirty six specimens having different Properties such as aspect ratios and details were considered. Based on the results of this study, deformability of the walls with specific details is discussed. Also this study compares the response modification factor(R) for the bearing wall systems in seismic design provisions between Korea and United States.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2002.09a
• /
• pp.189-196
• /
• 2002

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.