• Steel and Composite Structures
• /
• v.35 no.3
• /
• pp.327-341
• /
• 2020

The use of high-strength steel and concrete in the construction industry has been gaining increasing attention over the past few decades. With it comes the need to utilise high-strength structural bolts to ensure the design load to be transferred safely through joint regions, where the space is limited due to the reduced structural dimensions. However, research on the behaviour of high-strength structural bolts under various loading combinations is still insufficient. Most of the current design specifications concerning high-strength structural bolts were established based on a very limited set of experimental results. Moreover, as experimental programs normally include limited design parameters for investigation, finite element analysis has become one of the effective methods to assist the understanding of the behaviour of structural components. An accurate and simple full-range stress-strain model for high-strength structural bolts under different loading combinations was therefore developed, where the effects of bolt fracture was included. The ultimate strength capacities of various structural bolts obtained from the present experimental program were compared with the existing design provisions. Furthermore, design recommendations concerning the pure shear and tension, as well as combined shear and tension resistance of Grade 10.9 high-strength structural bolts were provided.

• Earthquakes and Structures
• /
• v.16 no.1
• /
• pp.97-107
• /
• 2019

The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.

• Steel and Composite Structures
• /
• v.31 no.3
• /
• pp.303-317
• /
• 2019

This paper presents a finite element model for predicting the behaviour of high-strength steel bolted beam-to-column joints under monotonic loading. The developed numerical model considers the effects of material nonlinearities and geometric nonlinearities. The accuracy of the developed model is examined by comparing the predicted results with independent experimental results. It is demonstrated that the proposed model accurately predicts the ultimate flexural resistances and moment-rotation curves for high-strength steel bolted beam-to-column joints. Mechanical performance of three joint configurations with various design details is examined. A parametric study is carried out to investigate the effects of key design parameters on the behaviour of bolted beam-to-column joints with double-extended endplates. The plastic flexural capacities of the beam-to-column joints from the experimental programme and numerical analysis are compared with the current codes of practice. It is found that the initial stiffness and plastic flexural resistance of the high-strength steel beam-to-column joints are overestimated. Proper modifications need to be conducted to ensure the current analytical method can be safely used for the bolted beam-to-column joints with high-performance materials.

• Structural Engineering and Mechanics
• /
• v.77 no.1
• /
• pp.89-102
• /
• 2021

Rapid construction of prefabricated bridges requires minimizing the field work of precast members and ensuring structural stability and constructability. In this study, we conducted experimental and analytical investigations of transverse joints of prefabricated T-girder bridge superstructures to verify the flexural performance and serviceability. In addition, we conducted parametric studies to identify the joint parameters. The results showed that both the segmented and continuous specimens satisfied the ultimate flexural strength criterion, and the segmented specimen exhibited unified behavior, with the flexural strength corresponding to that of the continuous specimen. The segmented specimens exhibited elastic behavior under service load conditions, and the maximum crack width satisfied the acceptance criteria. The reliability of the finite element model of the joint was verified, and parametric analysis of the convexity of the joint section and the compressive strength of the filler concrete showed that the minimum deflection and crack width occurred at a specific angle. As the strength of the filler concrete increased, the deflection and crack width decreased. However, we confirmed that the reduction in the crack width was hardly observed above a specific strength. Therefore, a design suitable for prefabricated bridges and accelerated construction can be achieved by improving the joint specifications based on the required criteria.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.61-64
• /
• 2005

Recently to repair the structure of deteriorated concrete, LMC rehabilitation method is introduced. however, this method has the possible risks of brittle failure depending on bond performance of the interface. the prediction of interfacial behavior becomes essential to protect the failure. all of the studies which have been done about this field are only about material property such as strength, durability, bond. there is not enough data and studies about structural behavior and numerical analysis. therefore, in this study A flexural nonlinear analysis model of ABAQUS was proposed to predict the load-deflection response, interfacial stress, and ultimate strength. The parameter study showed that overlay thickness was a main influencing factor to the behavior of RC beam overlayed by LMC.

• Transactions of Materials Processing
• /
• v.19 no.2
• /
• pp.127-131
• /
• 2010

Carbon-epoxy prepreg has been introduced in the forming of the upper and lower swash plates that control the pitch of rotor blade of unmanned helicopter because of its lightweight. Taguchi experimental method has been used by introducing the variables such as arrangement angle, laminated number and forming temperature, in order to obtain the proper forming method by using prepreg satisfying the required strength of the swash plate. In the evaluation of structural safety for the swash plates, three kinds of models are considered by using FE-analysis. In comparison of the hot forged products with Al6061-T6 and the formed products with prepreg, it was found that ultimate tensile strength of the products with prepreg is three times higher than that of the Al6061-T6, and the weight reduction of 68.5g can be achieved by using prepreg swash plates.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.4
• /
• pp.1-12
• /
• 2017

This paper concerns the structural behavior of high-strength concrete beams with compressive strength of 80 MPa subjected to flexure. Main test variables were nominal yielding strength of longitudinal rebar including normal strength rebar(SD 400) and high strength rebar(SD 600), reinforcement ratio from 0.98 to 1.58% and beam section size with $200{\times}250$, $200{\times}300mm$. The nine beams were cast and tested under flexure. The study investigated ultimate flexural strength, load-deflection relationship, crack patterns, failure patterns and ductility of the test beams. Test results indicate that when rebar ratio increased flexural strength increased and ductility decreased. In addition, the number of cracks increased and the crack width decreased as the reinforcement ratio increased. The yield strength of rebar did not affect significantly load-crack width relationship. Nonlinear analysis of test beams was performed and then test results and analytical results of ultimate load were compared. Analytical results of high-strength concrete beams overall underestimated flexural strength of test beams.

• Structural Engineering and Mechanics
• /
• v.72 no.4
• /
• pp.479-489
• /
• 2019

The corrosion of reinforcement leads to a gradual decay of structural strength and durability. Several models for crack occurrence prediction and crack width propagation are investigated in this paper. Analytical and experimental models were used to predict the bond strength in the period of corrosion propagation. The manner of flexural strength loss is calculated by application of these models for different scenarios. As a new approach, the variation of the concrete beam neutral axis height has been evaluated, which shows a reduction in the neutral axis height for the scenarios without loss of bond. Alternatively, an increase of the neutral axis height was observed for the scenarios including bond and concrete section loss. The statistical properties of the parameters influencing the strength have been deliberated associated with obtaining the time-dependent bending strength during corrosion propagation, using Monte Carlo (MC) random sampling method. Results showed that the ultimate strain in concrete decreases significantly as a consequence of the bond strength reduction during the corrosion process, when the section reaches to its final limit. Therefore, such sections are likely to show brittle behavior.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.1
• /
• pp.81-92
• /
• 2013

The ultimate flexural strength of HSB I-girders, considering the effect of local bucking, was investigated through a series of nonlinear finite element analysis. The girders were selected such that the inelastic local flange buckling or the plastic yielding of compression flanges governs the flexural strength. Both homogeneous sections fabricated from HSB600 or HSB800 steel and hybrid sections with HSB800 flanges and SM570-TMC web were considered. In the FE analysis, the flanges and web were modeled using thin shell elements and initial imperfections and residual stresses were imposed on the FE model. An elasto-plastic strain hardening material was used for steels. After establishing the validity of present FE analysis by comparing FE results with test results published in the literature, the effects of initial imperfection and residual stress on the inelastic flange local buckling behavior were assessed. The ultimate flexural strengths of 60 I-girders with various compression flange slenderness were obtained by FE analysis and compared with those calculated from the KHBDC, AASHTO LRFD and Eurocode 3 provisions. Based on the comparison, the applicability of design equations in these specifications for the flexural strength of I-girder considering flange local buckling was evaluated.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.25 no.4
• /
• pp.47-57
• /
• 1988

A new discrete method using idealized rigid body-spring model is introduced. This rigid element method is known to be more efficient and accurate than the finite element method in the inelastic range of structural analysis owing to simplified stress-strain and strain-displacement relations This kind of physical concept using idealized rigid model has been already applied among structural engineers to some problems such as rigid-plastic analysis or plastic design considering rigid bodies and plastic hinges. However the most rigorous and systematic research has been recently performed by T. Kawai et al.[1]. In this paper, an attempt is made to analyze the collapse behavior of stiffened plates under lateral loading by some modification and expansion of Kawai's rigid element approach to the collapse of plates without stiffener. Stiffened plates are treated as orthotropic plates which have equivalent bending rigidities. By employing Morley's plate element resubdivision technique, variety is given to mesh-division styles which have greate effect on the accuracy of numerical results. Some examples are shown to verify the validity of applying rigid element method to the ultimate strength analysis of stiffened plates. It is clarified that lateral deflections and detailed collapse patterns up to the ultimate state of stiffened plates can be easily obtained by the present approach.