• Proceedings of the Korea Concrete Institute Conference
• /
• 1990.10a
• /
• pp.19-22
• /
• 1990

Based on the design concept of a "Strong Column - Weak Beam" in the design of reinforced concrete, recently, a design method which moves the plastic hinging zone of a specific length away from the column face, has been proposed for reducing the degradation of stiffness and strength in the beam-column joint. To analyze reinforced concrete structures designed by this method. It is necessary to establish the analytical model which can simulate the hysteretic behavior depended on the initial positions and enlargements of plastic hinges. In this paper, by the numerical assumptions and the regression of experimental results, an analytical model is proposed. To estimate the accuracy of this model, some example analyses are conducted and compared with experimental results. From these comparision. It is shown that the proposed model is a good to predict the behavior of members subjected go cyclic loads.lic loads.

• Structural Engineering and Mechanics
• /
• v.7 no.3
• /
• pp.331-344
• /
• 1999

This paper provides an analysis of the transient behaviour of a right-angled bent cantilever beam subjected to a suddenly applied force at its tip perpendicular to its plane. Based on a rigid, perfectly plastic material model, a double-hinge mechanism is required to complete the possible deformation under a rectangular force pulse (constant force applied for a finite duration) with a four-phase response mode. The kinematics of the various response phases are described and the partitioning of the input energy at the plastic hinges during the motion is evaluated.

• Earthquakes and Structures
• /
• v.5 no.6
• /
• pp.679-702
• /
• 2013

During an earthquake, soils filter and send out the shaking to the building and simultaneously it has the role of bearing the building vibrations and transmitting them back to the ground. In other words, the ground and the building interact with each other. Hence, soil-structure interaction (SSI) is a key parameter that affects the performance of buildings during the earthquakes and is worth to be taken into consideration. Columns are one of the most crucial elements in RC buildings that play an important role in stability of the building and must be able to dissipate energy under seismic loads. Recent earthquakes showed that formation of plastic hinges in columns is still possible as a result of strong ground motion, despite the application of strong column-weak beam concept, as recommended by various design codes. Energy is dissipated through the plastic deformation of specific zones at the end of a member without affecting the rest of the structure. The formation of a plastic hinge in an RC column in regions that experience inelastic actions depends on the column details as well as soil-structure interaction (SSI). In this paper, 854 different scenarios have been analyzed by inelastic time-history analyses to predict the nonlinear behavior of RC columns considering soil-structure interaction (SSI). The effects of axial load, height over depth ratio, main period of soil and structure as well as different characteristics of earthquakes, are evaluated analytically by finite element methods and the results are compared with corresponding experimental data. Findings from this study provide a simple expression to estimate plastic hinge length of RC columns including soil-structure interaction.

• Structural Engineering and Mechanics
• /
• v.51 no.1
• /
• pp.131-140
• /
• 2014

This study focuses on seismic behaviour of tall piers characterized by high slender ratio. Two analysis models were developed based on elastic-plastic hinged beam element and elastic-plastic fiber beam element, respectively. The effect of the division density of elastic-plastic hinged beam element on seismic demand was discussed firstly to seek a rational analysis model for tall piers. Then structural seismic behaviour such as the formation of plastic hinges, the development of plastic zone, and the displacement at the top of the tall piers were investigated through incremental dynamic analysis. It showed that the seismic behaviour of a tall pier was quite different from that of a lower pier due to higher modes contributions. In a tall pier, an additional plastic zone may occur at the middle height of the pier with the increase of seismic excitation. Moreover, the maximum curvature reaction at the bottom section and maximum lateral displacement at the top turned out to be seriously out of phase for a tall pier due to the higher modes effect, and thus pushover analysis can not appropriately predict the local displacement capacity.

• Structural Engineering and Mechanics
• /
• v.63 no.4
• /
• pp.521-536
• /
• 2017

Reinforced concrete core-wall structures with buckling-restrained brace outriggers are interesting systems which have the ability to absorb and dissipate energy during strong earthquakes. Outriggers can change the energy demand in a tall building. In this paper, the energy demand was studied by using the nonlinear time history analysis for the mentioned systems. First, the structures were designed according to the prescriptive codes. In the dynamic analysis, three approaches for the core-wall were investigated: single plastic hinge (SPH), three plastic hinge (TPH) and extended plastic hinge (EPH). For SPH approach, only one plastic hinge is allowed at the core-wall base. For TPH approach, three plastic hinges are allowed, one at the base and two others at the upper levels. For EPH approach, the plasticity can extend anywhere in the wall. The kinetic, elastic strain, inelastic and damping energy demand subjected to forward directivity near-fault and ordinary far-fault earthquakes were studied. In SPH approach for all near-fault and far-fault events, on average, more than 65 percent of inelastic energy is absorbed by buckling-restrained braces in outrigger. While in TPH and EPH approaches, outrigger contribution to inelastic energy demand is reduced. The contribution of outrigger to inelastic energy absorption for the TPH and EPH approaches does not differ significantly. The values are approximately 25 and 30 percent, respectively.

• Journal of Korean Association for Spatial Structures
• /
• v.7 no.2 s.24
• /
• pp.35-44
• /
• 2007

The characteristics of elasto-plastic responses of a gymnasium building which is a steel braced frame with membrane roof is discussed as a basic research on the performance based seismic design of large span structures, in this paper. Under the strong earthquake motions, the formation of plastic hinges on braces attached by the bottom frame make reduce down the stresses and displacements of upper structures, and vertical acceleration of the membrane is tend to increase but maximum response of strain and corresponding stresses are tend to be reduced.

• Journal of the Korea Concrete Institute
• /
• v.22 no.6
• /
• pp.825-832
• /
• 2010

Although a critical section reaches its flexural strength in reinforced concrete structures, the structure does not always fail because moment redistribution occurs during the formation of plastic hinges. Inelastic deformation in a plastic hinge region results in plastic rotation. A plastic hinge mainly depends on material characteristics. In this study, a plastic hinge length and plastic rotation are evaluated using the flexural curvature distribution which is derived from the material models given in Eurocode 2. The influence on plastic capacity the limit values of the material model used, that is, ultimate strain of concrete and steel and hardening ratio of steel(k), are investigated. As results, it is appeared that a large ultimate strain of concrete and steel is resulting in large plastic capactiy and also as a hardening ratio of steel increases, the plastic rotation increases significantly. Therefore, a careful attention would be paid to determine the limit values of material characteristics in the RC structures.

• Structural Engineering and Mechanics
• /
• v.23 no.4
• /
• pp.387-407
• /
• 2006

A Genetic Algorithm (hereinafter GA) based optimum design algorithm and program for plane steel frames with partially restrained connections is presented. The algorithm was incorporated with the refined plastic hinge analysis method, in which geometric nonlinearity was considered by using the stability functions of beam-column members and material nonlinearity was considered by using the gradual stiffness degradation model that included the effects of residual stress, moment redistribution by the occurrence of plastic hinges, partially restrained connections, and the geometric imperfection of members. In the genetic algorithm, a tournament selection method and micro-GAs were employed. The fitness function for the genetic algorithm was expressed as an unconstrained function composed of objective and penalty functions. The objective and penalty functions were expressed, respectively, as the weight of steel frames and the constraint functions which account for the requirements of load-carrying capacity, serviceability, ductility, and construction workability. To verify the appropriateness of the present method, the optimum design results of two plane steel frames with fully and partially restrained connections were compared.

• Structural Engineering and Mechanics
• /
• v.63 no.5
• /
• pp.669-681
• /
• 2017

The design of reinforced concrete buildings must satisfy the serviceability stiffness criteria in terms of maximum lateral deflections and inter story drift in order to prevent both structural and non-structural damages. Consideration of plastic hinge formation is also important to obtain accurate failure mechanism and ultimate strength of reinforced concrete frames. In the present study, an iterative procedure has been developed for the analysis of reinforced concrete frames with cracked elements and consideration of plastic hinge formation. The ACI and probability-based effective stiffness models are used for the effective moment of inertia of cracked members. Shear deformation effect is also considered, and the variation of shear stiffness due to cracking is evaluated by reduced shear stiffness models available in the literature. The analytical procedure has been demonstrated through the application to three reinforced concrete frame examples available in the literature. It has been shown that the iterative analytical procedure can provide accurate and efficient predictions of deflections and ultimate strength of the frames studied under lateral and vertical loads. The proposed procedure is also efficient from the viewpoint of computational time and convergence rate. The developed technique was able to accurately predict the locations and sequential development of plastic hinges in frames. The results also show that shear deformation can contribute significantly to frame deflections.

• Structural Engineering and Mechanics
• /
• v.39 no.3
• /
• pp.427-447
• /
• 2011

The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other available procedures based on such criteria, the present contribution identifies loading patterns to associate with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.