• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2A
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• pp.131-143
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• 2009

Under transverse earthquake shaking, arching action of bridge structures develops along the deck between the abutments thus providing the so-called deck resistance. The magnitude of the arching action for bridge structures is dependent on the number of spans, connection condition between deck and abutment or piers, and stiffness ratio between superstructure and substructure. In order to investigate the arching action effects for inelastic seismic responses of PSC Box bridges, seismic responses evaluated by pushover analysis, capacity spectrum analysis and nonlinear time-history analysis are compared for 18 example bridge structures with two types of span numbers (short bridge, SB and long bridge, LB), three types of pier height arrangement (regular, semi-regular and irregular) and three types of connection condition between superstructure and substructure (Type A, B, C). The arching action effects (reducing inelastic displacement and increasing resistance capacity) for short bridge (SB) is more significant than those for long bridge (LB). Semi-regular and irregular bridge structures have more significant arching action than regular bridges.

• Wind and Structures
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• v.7 no.3
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• pp.145-158
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• 2004

The evaluation of the accumulation of permanent set for inelastic structures due to wind action is important in establishing a criterion to select a reduced design wind load and in incorporating the beneficial ductile behaviour in wind engineering. A parametric study of the accumulation of the permanent set as well as the ductility demand for bilinear single-degree-of-freedom (SDOF) systems is presented in the present study. The dynamic analysis of the inelastic SDOF system is carried out using the method of Newmark for artificially generated time history of wind speed. Simulation results indicate that the mean of the normalized damage rate is highly dependent on the natural frequency of vibration. This mean value is relatively insensitive to the damping ratio if the damping ratio is larger than 5%. The scatter associated with the accumulation of the permanent set is very significant. The consideration of the postyield stiffness can significantly reduce the accumulation of the permanent set if the ratio of the yield strength to the expected peak response is small. The results also show that the ductility demand due to the wind action over a period of one hour for flexible structures can be much less than that for rigid structures or structures with larger damping ratio if the SDOF systems are designed with a reduced peak response caused by the fluctuating wind.

• Earthquakes and Structures
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• v.8 no.2
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• pp.305-377
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• 2015

The problem of earthquake induced torsion in buildings is quite old and although it has received a lot of attention in the past several decades, it is still open. This is evident not only from the variability of the pertinent provisions in various modern codes but also from conflicting results debated in the literature. Most of the conducted research on this problem has been based on very simplified, highly idealized models of eccentric one-story systems, with single or double eccentricity and with load bearing elements of the shear beam type, sized only for earthquake action. Initially, elastic models were used but were gradually replaced by inelastic models, since building response under design level earthquakes is expected to be inelastic. Code provisions till today have been based mostly on results from one-story inelastic models or on results from elastic multistory idealizations. In the past decade, however, more accurate multi story inelastic building response has been studied using the well-known and far more accurate plastic hinge model for flexural members. On the basis of such research some interesting conclusions have been drawn, revising older views about the inelastic response of buildings based on one-story simplified model results. The present paper traces these developments and presents new findings that can explain long lasting controversies in this area and at the same time may raise questions about the adequacy of code provisions based on results from questionable models. To organize this review better it was necessary to group the various publications into a number of subtopics and within each subtopic to separate them into smaller groups according to the basic assumptions and/or limitations used. Capacity assessment of irregular buildings and new technologies to control torsional motion have also been included.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.647-650
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• 2003

Under sustained loads, the deformation of a structure gradually increase with time and eventually may be much greater than its instantaneous value, This inelastic and time-dependent deformation causes increase in deflection and curvature, redistribution of stress and internal action, In this paper, time-dependent analysis with creep and shrinkage of uncracked and cracked partially prestressed concrete flexural members is presented.

• Structural Engineering and Mechanics
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• v.23 no.4
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• pp.369-386
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• 2006

The influence of reinforcement buckling on the flexural response of reinforced concrete members is studied. The stress-strain response of compression reinforcement is determined computationally using a large-strain finite element model for bars of varied diameter, length, and initial eccentricity, and a mathematical expression is fitted to the simulation results. This relationship is used to represent the response of bars in compression in a moment-curvature analysis of a reinforced concrete cross section. The compression bar may carry more or less force than a tension bar at a corresponding strain, depending on the relative influence of Poisson effects and bar slenderness. Several cross-section analyses indicate that, for the distances between stirrups prescribed in modern concrete codes, the influence of inelastic buckling of the longitudinal reinforcement on the monotonic moment capacity is very small and can be neglected in many circumstances.

• Journal of Korean Association for Spatial Structures
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• v.23 no.4
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• pp.89-96
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• 2023

The seismic retrofits of existing structures have been focused on the control of structural responses which can be achieved by providing displacement capacity through inelastic ductile action at supplemental devices. Due to their hysteretic characteristics, it is expected to sustain damage through repeated inelastic behaviors including residual deformation which might increase repair costs. To solve such drawbacks of existing yielding devices, this study proposes a self-centering disc spring brace that sustains large axial deformation without structural damage while providing stable energy dissipation capacity. The hysteretic behaviors of suggested brace are first investigated based on the quasi-static cyclic test procedure. Experimental results present the effective self-centering behavior and an analytical model is then suggested in order to reasonably capture the flag-shaped hysteretic behavior of the disc spring brace.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.301-310
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• 2006

If arches are braced by lateral restraints, the ultimate strength of arches is determined by in-plane buckling and plastic bending collapse. This paper is conducted to investigate the in-plane nonlinear elastic and inelastic buckling behavior and the strength of fixed parabolic arches in uniform compresion, as well as to study arch behaviors against non-uniform in-plane compression and bending. As shown by the results, the limit slenderness ratio is suggested to classify the bucklingmode. Buckling strength of fixed parabolic arches under uniform compresion are evaluated using buckling curve for a straight column. Finally, an interaction e quation for arches under combined axial compresion and bending action is proposed.

• Smart Structures and Systems
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• v.16 no.4
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• pp.725-742
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• 2015

Tuned mass dampers (TMD) are devices employed in vibration control since the beginning of the twentieth century. However, their implementation for controlling the seismic response in civil structures is more recent. While the efficiency of TMD on structures under far-field earthquakes has been demonstrated, the convenience of its employment against near-fault earthquakes is still under discussion. In this context, the study of this type of device is raised, not as an alternative to the seismic isolation, which is clearly a better choice for new buildings, but rather as an improvement in the structural safety of existing buildings. Seismic records with an impulsive character have been registered in the vicinity of faults that cause seismic events. In this paper, the ability of TMD to control the response of structures that experience inelastic deformations and eventually reach collapse subject to the action of such earthquakes is studied. The results of a series of nonlinear dynamic analyses are presented. These analyses are performed on a numerical model of a structure under the action of near-fault earthquakes. The structure analyzed in this study is a steel frame which behaves as a single degree of freedom (SDOF) system. TMD with different mass values are added on the numerical model of the structure, and the TMD performance is evaluated by comparing the response of the structure with and without the control device.

• Coupled systems mechanics
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• v.2 no.1
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• pp.85-110
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• 2013

Generally, mass concrete structural behavior is governed by the strain components. However, relevant guidelines in dam engineering evaluate the structural behavior of concrete dams using stress-based criteria. In the present study, strain-based criteria are proposed for the first time in a professional manner and their applicability in seismic failure evaluation of an arch dam are investigated. Numerical model of the dam is provided using NSAD-DRI finite element code and the foundation is modeled to be massed using infinite elements at its far-end boundaries. The coupled dam-reservoir-foundation system is solved in Lagrangian-Eulerian domain using Newmark-${\beta}$ time integration method. Seismic performance of the dam is investigated using parameters such as the demand-capacity ratio, the cumulative inelastic duration and the extension of the overstressed/overstrained areas. Real crack profile of the dam based on the damage mechanics approach is compared with those obtained from stress-based and strain-based approaches. It is found that using stress-based criteria leads to conservative results for arch action while seismic safety evaluation using the proposed strain-based criteria leads to conservative cantilever action.

• Structural Engineering and Mechanics
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• v.2 no.4
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• pp.313-326
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• 1994

Some structures under the action of some specific loads can be treated as consisting of rigid and deformable parts. The paper presents a way to include rigid elements into a finite element model accounting for geometrical and material nonlinearities. Lagrange multipliers technique is used to derive equations of motion for the coupled deformable-rigid system. Solution algorithm based on the elimination of the Lagrangian multipliers and dependent kinematic unknowns at the element level is described. A follow-up paper(Rojek and Kleiber 1993) complements the discussion by giving details of the computer implementation and presenting some realistic test examples.