• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.445-450
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• 2003

The moment-curvature envelope describes the changes in the flexural capacity with deformation during a nonlinear analysis. Therefore, the moment-curvature analysis for reinforced concrete columns, indicating the available flexural strength and ductility, can be conducted providing the stress-strain relation for the concrete and steel are known. The moments and curvatures associated with increasing flexural deformations of the column may be computed for various column axial loads by incrementing the curvature and satisfying the requirements of strain compatibility and equilibrium of forces. Clearly it is important to have accurate information concerning the complete stress-strain curve of confined high-strength concrete in order to conduct reliable moment-curvature analysis to assess the ductility available from high-strength columns. However, it is not easy to explicitly characterize the mechanical behavior of confined high-strength concrete because of various parameter values, such as the confinement type of rectilinear ties, the compressive strength of concrete, the volumetric ratio and strength of rectangular ties, etc. So a stress-strain confinement model is developed which can simulate a complete inelastic moment-curvature relations of a high-strength reinforced concrete column

• Earthquakes and Structures
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• 제11권6호
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• pp.967-982
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• 2016

Current codes design the buildings based on life safety criteria. In a performance-based design (PBD) approach, decisions are made based on demands, such as target displacement and performance of structure in use. This type of design prevents loss of life but does not limit damages or maintain functionality. As a newly developed method, resilience-based design (RBD) aims to maintain functionality of buildings and provide liveable conditions after strong ground movement. In this paper, the seismic performance of plain and strengthened RC frames (an eight-story and two low-rise) is evaluated. In order to evaluate earthquake performance of the frames, the performance points of the frames are calculated by the capacity spectrum method (CSM) of ATC-40. This method estimates earthquake-induced deformation of an inelastic system using a reduced response spectrum. Finally, the seismic performances of the frames are evaluated and the results are compared with a resilience-based design criterion.

• 소성∙가공
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• 제17권8호
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• pp.579-585
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• 2008

Numerous experimental investigations on metallic materials and solid polymers have shown that relaxation behavior is nonlinearly dependent on prior strain rate. The stress drops in a constant time interval nonlinearly increase with an increase of prior strain rate. And the relaxed stress associated with the fastest prior strain rate has the smallest stress magnitude at the end of relaxation periods. This paper deals with the performance of three classes of unified constitutive models in predicting the characteristic behaviors of relaxation. The three classes of models are categorized by a rate sensitivity of kinematic hardening rule. The first class uses rate-independent kinematic hardening rule that includes the competing effect of strain hardening and dynamic recovery. In the second class, a stress rate term is incorporated into the rate-independent kinematic hardening rule. The final one uses a rate-dependent format of kinematic hardening rule.

• Structural Engineering and Mechanics
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• 제10권5호
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• pp.491-504
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• 2000

This paper is a presentation of a physical model for the elastic-partly plastic behavior of rectangular hollow section pinned struts subjected to static cyclic axial loading and the evaluation of the compressive strength of retrofitted damaged struts. Retrofitting is achieved by welding stiffening plates along the webs of damaged struts. The shape of the elastic and permanent deformations of the strut axis satisfy the conditions at the ends and midspan. Continuous functions of the geometric variables of stress distributions in the yielded zone are evaluated by interpolation between three points along each partly plastic zone. Permanent deformations of the partly plastic region are computed and used to update the shape of the unloaded strut. The necessity of considering geometric nonlinearity is discussed. The sensitivity of the results to the location of interpolation points, the shape of the permanent deformation and material hysteretic properties is investigated.

• Computers and Concrete
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• 제3권4호
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• pp.261-284
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• 2006

The flexural behaviour of symmetrically reinforced concrete (RC) columns cast of normal- and high-strength concrete under both monotonic and cyclic loading is studied based on an analytical procedure, which employs the actual stress-strain curves and takes into account the stress-path dependence of concrete and steel reinforcement. The analysis is particularly extended into the post-peak stage with large inelastic deformation at various applied axial load level. The effect of axial load on their complete flexural behaviour is then identified based on the results obtained. The axial load is found to have fairly large effect on the flexural behaviour of RC columns under both monotonic and cyclic loading. Such effects are discussed through examination of various aspects including the moment-curvature relationship, moment capacity, flexural ductility, variation of neutral axis depth and steel stress.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1235-1242
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• 2009

Probabilistic seismic hazard analysis (PSHA) is routinely conducted in the US for nuclear plants, for the determination of appropriate seismic design levels. These analyses incorporate uncertainties in earthquake characteristics in stable continental regions (where direct observations of large earthquakes are rare), in estimates of rock motions, in site effects on strong shaking, and in the damage potential of seismic shaking for engineered facilities. Performance goals related to the inelastic deformation of individual components, and related to overall seismic core damage frequency, are used to determine design levels. PSHA has the ability to quantify and document the important uncertainties that affect seismic design levels, and future work can be guided toward reducing those uncertainties.

• 한국지진공학회논문집
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• 제20권5호
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• pp.311-318
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• 2016

The lead-rubber bearing (LRB) dissipates seismic energy through plastic deformation of lead core. Under large-displacement cyclic motion, the temperature increases in the lead core. The shear strength of a lead-rubber bearing is reduced due to the heating effect of the lead core. In this study, the seismic responses such as displacement increasing, shear strength and vertical stiffness degradations of LRB due to the heating effect are evaluated for design basis earthquake (DBE) and beyond design basis earthquake (150% DBE, 167% DBE, 200% DBE).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.851-856
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• 2000

When subjected to the strong earthquake ground motion, upper-wall lower-frame structures have high possibility of the weak-story failure in the lower frame part. Sufficient strength, energy dissipation capacity and ductility should be provided at the joint between the deep beam and the lower column. In this study, a typical structure was selected for a prototype and four 1:2.5 scaled models, representing the subassemblage including the exterior column and the deep beam, were constructed. The transverse reinforcement was designed according to ACI procedure¹ and the procedure proposed by Sheikh². The inelastic behavior of the subassemblages subjected to the cyclic lateral displacement were evaluated through investigation of the ultimate strength, ductility, load-deformation characteristics. From the test of 4 specimens, it is concluded that the specimens designed according to Sheikh's procedure revealed higher ductility than that by ACI procedure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.61-64
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• 2005

Concrete is one of the principal materials for the structure and it is widely used all over the world, but it shows extremely brittle failure under bending and tensile load. Recently to improve such a poor property, Ductile Fiber Reinforced Cementitious Composites (DFRCC) have been developed, and it are defined by an ultimate strength higher than their first cracking strength and the formation of multiple cracking during the inelastic deformation process. This paper is to estimate experimentally the mechanical properties of ductile concrete with the kinds of used fine and coarse aggregate for purpose of development of high ductile concrete mixing coarse aggregate. As the results, ductile concrete mixed coarse aggregate showed the displacement-hardening behavior under bending load similar to DFRCC, and its compressive and bending performance varied according to the kinds of used coarse aggregate.

• 한국안전학회지
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• 제16권2호
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• pp.1-6
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• 2001

In the case of a crack propagation a portion of the work of inelastic deformation near the crack tip is dissipated as heat. In order to understand the thermal effect on fracture toughness, tensile tests were carried out using thermocouples to monitor the variation of temperature. The experimental results show that the temperature of specimen was increased $5.4^{\circ}C$ at static load condition. And the thermal effect is investigated connected with the steady-state stress in the vicinity of a crack propagation in the elastic-plastic C-T specimen theoretically. And fracture toughness, the energy to make crack surfaces, presented correctively. The fracture toughness with considering heat at the blunting of the crack tip is lower about 16.9％ than that of ignoring heat. So, it is resonable to apply the fracture toughness with considering thermal energy and it would be good explanation for constraint effect depending on the configuration in the presence of excessive plasticity.