• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.73-78
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• 2009

Steel Braced frames are a commonly-used seismic resisting system, and chevron steel braced frames are a frequently used type of steel braced frame. Recent research has indicated that the seismic performance of braced frames can be improved by designing the braced frame gusset plate connections in a manner that direct reflects seismic deformation demands, and by permitting yielding in the gusset plate at select performance levels. A parametric study using Finite Element (FE) models was conducted to examine the influence of the gusset plate and framing elements on the seismic performance of chevron braced frames, and to calibrate and develop improved design models. The impact of the frame details, including frame sizes, clearance requirements, gusset plate thickness and tapered plate, was explored. The results suggested that proper detailing of the connection can result in a significant improvement in the frame performance. The results also show that the gusset plate thickness has a significant impact on frame performance.

• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.507-521
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• 1997

The ultimate behavior of a reinforced concrete hyperbolic paraboloid saddle shell under uniformly distributed vertical load is investigated using an inelastic, large displacement finite-element program originally developed at North Carolina State University. Unlike with the author's previous study which shows that the saddle shell possesses a tremendous capacity to redistribute the stresses, introducing tension stiffening in the model the cracks developed are no longer through cracks and formed as primarily bending cracks. Even though with small tension stiffening effect, the behavior of the shell is changed markedly from the one without tension stiffening effect. The load-deflection curves are straight and the slope of the curves is quite steep and remains unchanged with varying the tension stiffening parameters. The failure of the shell took place quite suddenly in a cantilever mode initiated by a formation of yield lines in a direction parallel to the support-to-support diagonal. The higher the tension stiffening parameters the higher is the ultimate load. The present study shows that the ultimate behavior of the shell primarily depends on the concrete tensile characteristics, such as tensile strength (before cracking) and the effective tension stiffening (after cracking). As the concrete characteristics would vary over the life of the shell, a degree of uncertainty is involved in deciding a specified ultimate strength of the saddle shell studied. By the present study, however, the overload factors based on ACI 318-95 are larger than unity for all the cases studied except that the tension stiffening parameter is weak by 3 with and without the large displacement effect, which shows that the Lin-Scordelis saddle shell studied here is at least safe.

• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.93-103
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• 2018

This study showed that experimental study of inelastic nonlinear behavior of two-way beam string structures. General large span structures consisting of beam members have large moment and long cross section of area. In order to decrease these excessive moment and deflection, the two-way beam string structures composed of H-Beam, strut, and cable elements were proposed. In the two-way string beam, the cable with the prestress improves force distribution of some weight reduction. Two systems made of structural steel and cables were tested. The nonlinear behaviour of the two-way beam string structures studied by using finite element model and compared to experimental results. The displacement of the LVDT in the center of the beam correspond with the ABAQUS results. 2,200MPa cable can afford to bear breaking load than 1,860MPa cable. The two-way beam string structures is correlated to the finite element model and the experimental results. In consequence, It showed that the system with two-way cables exhibits much better structural performances than H-Beam structures and beam with cable.

• Coupled systems mechanics
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• v.8 no.4
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• pp.315-338
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• 2019

The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to $20N/mm^2$ and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.451-462
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• 2023

Lumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre-localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post-localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber-reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks.

• Steel and Composite Structures
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• v.18 no.4
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• pp.873-887
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• 2015

The continuous composite I-girder should have a sufficient rotation capacity (or ductility) to redistribute the negative bending moment into an adjacent positive bending moment region. However, it is generally known that the ductility of the high strength steel is smaller than that of conventional steel, and application of high strength steel can cause ductility problems in a negative moment region of the I-girder. In this study, moment redistribution of the continuous composite I-girder with high strength steel was studied, where high strength steel with yield stress of 690 MPa was considered (the ultimate stress of the steel was 800 MPa). The available and required rotation capacity of the continuous composite I-girder with high strength steel was firstly derived based on the stress-strain curve of high strength steel and plastic analysis, respectively. A large scale test and a series of non-linear finite element analysis for the continuous composite I-girder with high strength steel were then conducted to examine the effectiveness of proposed models and to investigate the effect of high strength steel on the inelastic behavior of the negative bending moment region of the continuous composite I-girder with high strength steel. Finally, it can be found that the proposed equations provided good estimation of the requited and available rotation capacity of the continuous composite I-girder with high strength steel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.4
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• pp.149-155
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• 1983

A numerical procedure based on the finite element method for the nonlinear analysis of planar reinforced concrete frames is presented. Material nonlinearities such as cracking of concrete and yielding of steel are incorporated. This method is capable of providing accurate numerical solutions for the response of planar reinforced concrete frames failing primarily, in flexure throughout elastic, inelastic and ultimate load ranges. A numerical example is presented to demonstrate the validity and applicability of the present method. The results are compared with experimental results and the analytical results obtained by other investigator.

• Structural Engineering and Mechanics
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• v.50 no.4
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• pp.459-469
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• 2014

One of the most important structural components of steel structures is the column-base connections which are obliged to transfer horizontal and vertical loads safely to the reinforced concrete (RC) or concrete base. The column-base connections of steel or composite steel structures can be organized both moment resistant and non-moment resistant leading to different connection styles. Some of these connection styles are ordinary bolded systems, socket systems and embedded systems. The structures are frequently exposed to cycling lateral loading effects causing fatal damages on connections like columns-to-beams or columns-to-base. In this paper, connection of steel column with RC base was investigated analytically and experimentally. In the experiments, bolded connections, socket and embedded connection systems are taken into consideration by applying cyclic lateral loads. Performance curves for each connection were obtained according to experimental and analytical studies conducted and inelastic behavior of connections was evaluated accordingly. The cyclic lateral performance of the connection style of embedding the steel column into the reinforced concrete base and strengthening of steel column in upper level of base connection was found to be higher and effective than other connection systems. Also, all relevant test results were discussed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.475-482
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• 2008

This paper indicates that the use of Euler angles lacks in its consistency and exactness of analysis when it was applied to incorporate the rotational equation of motion for rotor systems by previous researcher. Kinetic energy and angular velocity are different from case to case depending on the way of choosing Euler angles and thus only the linear system has been investigated even though the rotor system has a very nonlinear behavior. A new methodology is applied by using both spherical coordinate and quaternion in the rotor rotation to overcome weaknesses of Euler angles and shows its superiority It is found through numerical examples that the use of quaternion will be a more useful and valid tool to derive the numerical model of the rotor system.

• Structural Engineering and Mechanics
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• v.4 no.1
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• pp.25-35
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• 1996

This paper describes a continuum variational formulation for design optimization of nonlinear structures in the elastic-plastic domain, where unloading and reloading of the structures are allowed to occur. The Total Lagrangian procedure is used for the description of the structural deformation. The direct differentiation approach is used to derive the sensitivities of the various structural response measures with respect to the design parameters. Since the material goes into the inelastic range and unloading and reloading of the structure are allowed to occur, the structural response is path dependent and an additional step is needed to integrate the constitutive equations. It can be shown, consequently, that design sensitivity analysis is also path-dependent. The theory has been discretized by the finite element technique and implemented in a structural analysis code. Mathematical programming approach is used for the optimization process. Numerical applications on trusses are performed, where cross-sectional areas and nodal point coordinates are treated as design variables. Optimal designs have been obtained and compared by using two different strategies: a two level strategy where the levels are defined accordingly the type of design variables, cross sectional areas or node coordinates, and optimizing simultaneously with respect to both types of design variables.