• Steel and Composite Structures
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• v.6 no.3
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• pp.183-202
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• 2006

The behavior of steel-concrete composite beams is strongly influenced by the type of shear connection between the steel beam and the concrete slab. For accurate analytical predictions, the structural model must account for the interlayer slip between these two components. This paper focuses on a procedure for response sensitivity analysis using state-of-the-art finite elements for composite beams with deformable shear connection. Monotonic and cyclic loading cases are considered. Realistic cyclic uniaxial constitutive laws are adopted for the steel and concrete materials as well as for the shear connection. The finite element response sensitivity analysis is performed according to the Direct Differentiation Method (DDM); its analytical derivation and computer implementation are validated through Forward Finite Difference (FFD) analysis. Sensitivity analysis results are used to gain insight into the effect and relative importance of the various material parameters in regards to the nonlinear monotonic and cyclic response of continuous composite beams, which are commonly used in bridge construction.

• Structural Engineering and Mechanics
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• v.67 no.3
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• pp.267-275
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• 2018

A numerical study of soil-foundation system under monotonic and cyclic pushover loading is conducted, taking into account both material and geometric nonlinearities. A complete and refined 3D finite element (FE) model, using contact condition and allowing separation between soil and foundation, is implemented and used in order to evaluate the nonlinear relationship between applied vertical forces and induced settlements. Based on the obtained curve, a simplified model is proposed, in which the soil inelasticity is satisfactorily represented by two vertical springs with trilinear behavior law, and the foundation uplifting is insured by gap elements. Results from modeling soil-foundation system supporting a bridge pier have shown that the simplified model is able to capture irreversible settlements induced by cyclic rocking, due to soil inelasticity and vertical loading, as well as large rotations due to foundation uplifting.

• Steel and Composite Structures
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• v.32 no.6
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• pp.769-778
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• 2019

The specially prefabricated steel moment connections with pyramid head is one of the significant innovations in the steel structures forms to improve the installation time and simplify the construction procedure. The beams in this structure form are supported by two top and bottom angles and web double angles. Such a configuration despite its advantages increases the welding operation and filed installation time and costs. In this paper, the effect of using beams with channel and I section in three classes of seismically compact, seismically non-compact, and slender section according to width-to-thickness ratio on the behavior of the connection was investigated under monotonic and cyclic loading. Modeling was performed by ABAQUS and verified by the results of an experimental specimen. The findings indicated that using I and channel section instead of angle section reduces the amount of welding materials as well as easing the installation procedure. However, it has no significant effect on the ultimate strength and ductility of the connection. Furthermore, if the beam section is seismically compact, this form is considered as a special moment frame that has a rotation capacity up to 0.04 radians without any reduction in connection moment resistance.

• Coupled systems mechanics
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• v.7 no.5
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• pp.555-581
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• 2018

The moment-resistant steel frames are frequently used as a load-bearing structure of buildings. Global response of a moment-resistant frame structure strongly depends on connections behavior, which can significantly influence the response and load-bearing capacity of a steel frame structure. The analysis of a steel frame with included joints behavior is the main focus of this work. In particular, we analyze the behavior of two connection types through experimental tests, and we propose numerical beam model capable of representing connection behavior. The six experimental tests, under monotonic and cyclic loading, are performed for two different types of structural connections: end plate connection with an extended plate and end plate connection. The proposed damage-plasticity model of Reissner beam is able to capture both hardening and softening response under monotonic and cyclic loading. This model has 18 constitutive parameters, whose identification requires an elaborate procedure, which we illustrate in this work. We also present appropriate loading program and arrangement of measuring equipment, which is crucial for successful identification of constitutive parameters. Finally, throughout several practical examples, we illustrate that the steel structure connections are very important for correct prediction of the global steel frame structure response.

• Geotechnical Engineering
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• v.12 no.4
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• pp.21-32
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• 1996

To predict the stress-strain behavior of the soil more approximately, the concept of the critical state soil mechanics was added to the plasticity increment theory in the bounding surface Plasticity model. This model was constituted with two ellipse and one hyperbola in older to describe the behaviour of the isotropically consolidated soil. Thus, this model is very complicate due to the various parameters used. Therefore, the accurate understanding and skill of the theory is required in order to apply this model to the practical geotechnical problems. In the present paper, the bounding surface shape paraiheter R and A, the mapping center parameter C among various parameters used were varied and the results were numerically analized. Finally, each sensitivity with respect to monotonic and cyclic loading was analized and the range of the value of the each parameter was proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2018-2025
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• 2002

It is well known that the strength and the fatigue life of welded steel components are affected extensively by welding residual stresses distributed around their weldments under not only monotonic but also cyclic loads. The externally applied loads are to be superimposed with the welding residual stresses, so that unexpected deformations and failures of the components might occur. These residual stresses are not kept constant, but relaxed or redistributed during in service. Under monotonic loads the relaxation takes place when the sum of external and welding residual stress exceeds locally the yield stress of material used. By the way, it is shown that under cyclic loads the welding residual stress is considerably relieved by the first or the early cycles of loads, and then gradually relaxed with increasing loading cycles. Although many investigations in this field have been carried out, the phenomenon and mechanism of the stress relaxation are still not clear, and there are few comprehensive models to predict amount of relaxed welding residual stress. In this study, the characteristics of the welding residual stress relaxation under monotonic and cyclic loads were investigated, and a model to predict quantitatively amount of welding residual stress relaxation was proposed.

• Steel and Composite Structures
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• v.38 no.3
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• pp.241-255
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• 2021

In order to study the interfacial bond-slip behavior of steel reinforced recycled concrete (SRRC) under cyclic loading, thirteen specimens were designed and tested under cyclic loading and one under monotonic loading. The test results indicated that the average bond strength of SRRC decreased with the increasing replacement ratio of recycled concrete, whereas the bond strength increased with an increase in the concrete cover thickness, the volumetric stirrup ratio, and the strength of recycled concrete. The ultimate bond strength of the cyclically-loaded specimen was significantly (41%) lower than that of the companion monotonically-loaded specimen. The cyclic phenomena also showed that SRRC specimens went through the nonslip phase, initial slip phase, failure phase, bond strength degradation phase and residual phase, with all specimens exhibiting basically the same shape of the bond-slip curve. Additionally, the paper presents the equations that were developed to calculate the characteristic bond strength of SRRC, which were verified based on experimental results.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.143-152
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• 2001

This paper presents are monotonic and cyclic behavior of steel plates. The effects of design parameters, initial deflection and aspect ratio, width-thickness ratio are studied by using FEM analysis. The results obtained from the monotonic loadings show that the aspect ratio(a/b) on the strength is to be neglected in the range of $(a/b){\leq}1.0$. The major cause of the reduction in strength sbbjected to cyclic loadings are width-thickness ratio and displacement amplitude. Based on the results, this paper presents some new strength curve with considering the cyclic deteriorations. The results are also discussed about the deformation capacity accordance with the width-thickness ratio and displacement amplitude.

• Computers and Concrete
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• v.18 no.6
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• pp.1083-1096
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• 2016

Beam-column joints are recognized as the weak points of reinforcement concrete frames. The ductility of reinforced concrete (RC) frames during severe earthquakes can be measured through the dissipation of large energy in beam-column joint. Retrofitting and rehabilitating structures through proper methods, such as carbon fiber reinforced polymer (CFRP), are required to prevent casualties that result from the collapse of earthquake-damaged structures. The main challenge of this issue is identifying the effect of CFRP on the occurrence of failure in the joint of a cross section with normal ductility. The present study evaluates the retrofitting method for a normal ductile beam-column joint using CFRP under monotonic and cyclic loads. Thus, the finite element model of a cross section with normal ductility and made of RC is developed, and CFRP is used to retrofit the joints. This study considers three beam-column joints: one with partial CFRP wrapping, one with full CFRP wrapping, and one with normal ductility. The two cases with partial and full CFRP wrapping in the beam-column joints are used to determine the effect of retrofitting with CFRP wrapping sheets on the behavior of the beam-column joint confined by such sheets. All the models are subjected to monotonic and cyclic loading. The final capacity and hysteretic results of the dynamic analysis are investigated. A comparison of the dissipation energy graphs of the three connections shows significant enhancement in the models with partial and full CFRP wrapping. An analysis of the load-displacement curves indicates that the stiffness of the specimens is enhanced by CFRP sheets. However, the models with both partial and full CFRP wrapping exhibited no considerable improvement in terms of energy dissipation and stiffness.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.63-73
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• 2011

The behavior of laterally cyclic loaded piles is affected by the magnitude and number of cycles of cyclic lateral loads as well as loading method (1-way or 2-way loading). In this study, calibration chamber tests were carried out to investigate the effects of loading method of cyclic lateral loads on the behavior of piles driven into sand. Results of the chamber tests show that the permanent lateral displacement of 1-way cyclic loaded piles is developed in the same direction as the first loading, whereas that of 2-way cyclic loaded piles is developed in the reverse direction of the first loading. 1-way cyclic lateral loads cause a decrease of the ultimate lateral load capacity of piles, and 2-way cyclic lateral loads cause an increase of the ultimate lateral load capacity of piles. The change of ultimate lateral load capacity with loading method of cyclic lateral loads increases with increasing number of cycles. It is also observed that the 1-way cyclic loads generate greater maximum bending moment than 2-way cyclic loads for piles in cyclic loading step and generates smaller maximum bending moment for piles in the ultimate state. It can be attributed to the difference in compaction degree of the soil around the piles with loading method of cyclic lateral loads. In addition, it is founded that 1-way and 2-way cyclic lateral loads cause a decrease in the maximum bending moment of piles in the ultimate state compared with that of piles subjected to only monotonic loads.