• Earthquakes and Structures
• /
• v.14 no.3
• /
• pp.273-283
• /
• 2018

Previous experimental researches indicate that reinforced concrete beam-column joints play an important role in the mechanical properties of moment resisting frame structures, so as to require proper design. In order to get better understanding of the beam-column joint performance, a rational model needs to be developed. Based on the former considerations, two typical models for calculating the shear carrying capacity of the beam-column joint including the inelastic reinforced concrete joint model and the softened strut-and-tie model are selected to be introduced and analyzed. After examining the applicability of two typical models mentioned earlier to interior beam-column joints, several adjustments are made to get better predicting of the test results. For the softened strut-and-tie model, four adjustments including modifications of the depth of the diagonal strut, the inclination angle of diagonal compression strut, the smeared stress of mild steel bars embedded in concrete, as well as the softening coefficient are made. While two adjustments for the inelastic reinforced concrete joint model including modifications of the confinement effect due to the column axial load and the correction coefficient for high concrete are made. It has been proved by test data that predicted results by the improved softened strut-and-tie model or the modified inelastic reinforced concrete joint model are consistent with the test data and conservative. Based on the test results, it is also not difficult to find that the improved beam-column joint model can be used to predict the joint carrying capacity and cracks development with sufficient accuracy.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.4
• /
• pp.471-479
• /
• 2002

In this paper, 18 square CFT columns filled with high-strength concrete were tested under concentric or eccentric axial loading. Two parameters of the experimental program included the buckling length-section depth ratio ($L_K$/D) and the eccentricity of the appled compressive load (e). In additon, mechanical properties such as the compressive concrete strength and compressive and tensile steel strength were measured and incorporated into the material models for the stress-strain relationships of concrete and steel. This model was used in an elasto-plastic analysis in order to predict the behavior of the slender CFT columns. Observtions of the failure mode during the tests under axial loadig were also presented. The strengths obtained from the analysis. Recommendations for Design, and Constructions of CFT structures were presented, as verified by the experimental results.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.1
• /
• pp.26-33
• /
• 2001

Thrust vector control system is control device which is mounted exit of the nozzle to generate pitch, yaw and roll directional force by deflecting flow direction of the supersonic jet from the nozzle. By obtaining control force, jetvane which is exposed in jet flow is working thermal and aerodynamic load. Axial thrust loss and side thrust is affected by shock patterns and interactions between jetvanes according to jetvane geometry and turning angle. In this study, we designed 6 types of jetvane to evaluate pitch, yaw and roll characteristics of ietvane in supersonic flow, and perform the cold flow test in range of turning angles of jetvanes between $0^{\cire}$ and $25^{\cire}$ by $5^{\cire}$ respectively. Also, calculation is going side by side to analyse flow interaction. Results show that there is no interactions between jetvanes upto turning angle 20$^{\circ}$, chord and lead length ratio is very important parameter to aerodynamic performance and maximum thrust loss is appeard to 17% of axial thrust in roll directional control.

• Steel and Composite Structures
• /
• v.33 no.4
• /
• pp.615-627
• /
• 2019

This paper aims to study the compressive behavior of circular hollow and concrete-filled steel tubular stub columns under simulated marine atmospheric corrosion. The specimens after salt spray corrosion were tested under axial compressive load. Steel grade and corrosion level were mainly considered in the study. The mechanical behavior of circular CFST specimens is compared with that of the corresponding hollow ones. Design methods for circular hollow and concrete-filled steel tubular stub columns are modified to consider the effect of marine atmospheric corrosion. The results show that linear fitting curves could be used to present the relationship between corrosion rate and the mechanical properties of steel after simulated marine atmospheric corrosion. The ultimate strength of hollow steel tubular and CFST columns decrease with the increase of corrosion rate while the ultimate displacement of those are hardly affected by corrosion rate. Increasing corrosion rate would change the failure of CFST stub column from ductile failure to brittle failure. Corrosion rate would decrease the ductility indexes of CFST columns, rather than those of hollow steel tubular columns. The confinement factor ${\xi}$ of CFST columns decreases with the increase of corrosion rate while the ratio between test value and nominal value shows an opposite trend. With considering marine atmospheric corrosion, the predicted axial strength of hollow steel tubular and CFST columns by Chinese standard agree well with the tested values while the predictions by Japanese standard seem conservative.

• Steel and Composite Structures
• /
• v.46 no.6
• /
• pp.773-791
• /
• 2023

Connections with damage concentrated to pre-selected components can enhance seismic resilience for moment resisting frames. These pre-selected components always yield early to dissipate energy, and their energy dissipation mechanisms vary from one to another, depending on their position in the connection, geometry configuration details, and mechanical characteristics. This paper presents behaviour insights on two types of beam-to-beam connections that the angles were designed as energy dissipation components, through the results of experimental study and finite element analysis. Firstly, an experimental programme was reviewed, and key responses concerning the working mechanism of the connections were presented, including strain distribution at the critical section, section force responses of essential components, and initial stiffness of test specimens. Subsequently, finite element models of three specimens were established to further interpret their behaviour and response that were not observable in the tests. The moment and shear force transfer paths of the composite connections were clarified through the test results and finite element analysis. It was observed that the bending moment is mainly resisted by axial forces from the components, and the dominant axial force is from the bottom angles; the shear force at the critical section is primarily taken by the slab and the components near the top flange. Lastly, based on the insights on the load transfer path of the composite connections, preliminary design recommendations are proposed. In particular, a resistance requirement, quantified by a moment capacity ratio, was placed on the connections. Design models and equations were also developed for predicting the yield moment resistance and the shear resistance of the connections. A flexible beam model was proposed to quantify the shear resistance of essential components.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.6A
• /
• pp.625-639
• /
• 2009

Experimental and analytical studies are performed on the mechanical behavior of concrete-filled tubular(CFT) truss girders for different f/L ratios. Bending tests are conducted on two CFT truss girder specimens to determine fundamental structural characteristics such as the strength and deformation properties. Nonlinear material models for CFT members subjected to an axial compressive force are compared in this paper by using the nonlinear finite element program, ABAQUS. Previous researchers have proposed several nonlinear stress-strain models of confined concrete. In this study, the nonlinear analyses are performed applying several stress-strain models for confined concrete proposed by Mander, Sakino, Han, Susantha and Ellobody, and the results are compared with the experimental results in terms of load-deflection and load-strain relationships. Based on the comparisons of the load-deflection relationships, the models proposed by Mander and Susantha provide a maximum load about 12.0~13.8% higher and that by Sakino gives a maximum load about 7.6% higher than the experimental results. The models proposed by Han and Ellobody give a maximum load only about 0.2~1.2% higher than the test results, showing the best agreement among the proposed stress-strain models. However, the load-strain relations predicted by the existing models generally provide conservative results exhibiting larger strains than the experimental data.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.3 s.76
• /
• pp.357-363
• /
• 2005

There is a great need for high-strength steel especially for the high-rise steel building structure. High-strength steels, however, may have mechanical properties that are significantly different from those of the conventional steels. The application of high-strength steels to building structures should be reviewed as to whether the inelastic behavior equivalent to that of conventional steels can be attained or not. In this study, SM570TMC steel was tested to evaluate buckling strength under axial compressive force. The comparison tests for local buckling strength evaluation of box-type and H-shaped welded columns were performed with variable width-thickness ratios. As for the experimental check, the maximum strength of stub column was determined by local buckling as far as the limit of width-to-thickness ratio was satisfied with current design codes. Also, the strength of the stub column did not decrease suddenly by local buckling before maximum strength even when the ratio is not satisfied. The buckling strength of SM570TMC steel was higher than both ASD (Allowable Stress Design) and LRFD (Load and Resistance Factor Design) specifications.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.4
• /
• pp.399-410
• /
• 2015

Concrete filled steel tube(CFT) has outstanding deformation capacity and strength in comparison with reinforced concrete or steel tube. CFT drilled shaft, which is developed large shear force due to seismic load and soil liquefaction, is designed as large diameter. However, shear design equations of the current standards do not consider bond stress of CFT and it results in extremely conservative design. Currently, previous studies for improving shear equations scarcely exist and are impossible applied to large CFT drilled shafts since these studies focus on only small scale experimental research. In this study, eventually to propose improving shear equation of large diameter CFT, it is preliminary research to compare and investigate the previous studies and current standards.

• Steel and Composite Structures
• /
• v.28 no.5
• /
• pp.589-606
• /
• 2018

The previous studies reflected the significant effect of neutral-axis position and coupling of in-plane and out-of-plane displacements on behavior of functionally graded (FG) nanobeams. In thin FG beam, this coupling can be eliminated by a proper choice of the reference axis. In shear deformable FG nanobeam, not only this coupling can't be eliminated but also the position of neutral-axis is dependent on through-thickness distribution of shear strain. For the first time, in this paper it is avoided to guess a shear strain shape function and the exact shape function and consequently the exact position of neutral axis for arbitrary gradation of higher order nanobeam are obtained. This paper presents new methodology based on differential transform and collocation methods to solve coupled partial differential equations of motion without any simplifications. Using exact position of neutral axis and higher order beam kinematics as well as satisfying equilibrium equations and traction-free conditions without shear correction factor requirement yields to better results in comparison to the previously published results in literature. The classical rule of mixture and Mori-Tanaka homogenization scheme are considered. The Eringen's nonlocal continuum theory is applied to capture the small scale effects. For the first time, the dependency of exact position of neutral axis on length to thickness ratio is investigated. The effects of small scale, length to thickness ratio, Poisson's ratio, inhomogeneity of materials and various end conditions on vibration and buckling of local and nonlocal FG beams are investigated. Moreover, the effect of axial load on natural frequencies of the first modes is examined. After degeneration of the governing equations, the exact new formulas for homogeneous nanobeams are computed.

• Steel and Composite Structures
• /
• v.36 no.2
• /
• pp.187-196
• /
• 2020

Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.