• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.795-812
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• 2011

Estimation of damage probability of buildings under a future earthquake is an essential issue to ensure the seismic reliability. Fragility curves are useful tools for showing the probability of structural damage due to earthquakes as a function of ground motion indices. The purpose of this study is to compare the damage probability of R/C buildings with low and high level of strength and ductility through fragility analysis. Two different types of sample buildings have been considered which represent the building types mentioned above. The first one was designed according to TEC-2007 and the latter was designed according to TEC-1975. The pushover curves of sample buildings were obtained via pushover analyses. Using 60 ground motion records, nonlinear time-history analyses of equivalent single degree of freedom systems were performed using bilinear hysteretic model and peak-oriented hysteretic model with stiffness - strength deterioration for each scaled elastic spectral displacement. The damage measure is maximum inter-story drift ratio and each performance level considered in this study has an assumed limit value of damage measure. Discrete damage probabilities were calculated using statistical methods for each considered performance level and elastic spectral displacement. Consequently, continuous fragility curves have been constructed based on the lognormal distribution assumption. Furthermore, the effect of hysteresis model parameters on the damage probability is investigated.

• Earthquakes and Structures
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• v.18 no.4
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• pp.519-526
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• 2020

Non-stationary random seismic response and reliability of multi-degree of freedom hysteretic structure system are studied based on the cumulative damage failure mechanism. First, dynamic Eqs. of multi-degree of freedom hysteretic structure system under earthquake action are established. Secondly, the random seismic response of a multi-degree freedom hysteretic structure system is investigated by the combination of virtual excitation and precise integration. Finally, according to the damage state level of structural, the different damage state probability of high-rise frame structure is calculated based on the boundary value of the cumulative damage index in the seismic intensity earthquake area. The results show that under the same earthquake intensity and the same floor quality and stiffness, the lower the floor is, the greater the damage probability of the building structure is; if the structural floor stiffness changes abruptly, the weak layer will be formed, and the cumulative damage probability will be the largest, and the reliability index will be relatively small. Meanwhile, with the increase of fortification intensity, the reliability of three-level structure fortification is also significantly reduced. This method can solve the problem of non-stationary random seismic response and reliability of high-rise buildings, and it has high efficiency and practicability. It is instructive for structural performance design and estimating the age of the structure.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.95-105
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• 1997

Structures subjected to strong seismic excitation may undergo inelastic deformation cycles. The resulting cumulative fatigue damage process reduces the ability of structures and components to withstand seismic loads. Yet, the present earthquake resistance design methods focus mainly on the maximum displacement ductility, ignoring the effect of the cyclic responses. The damage parameters closely related to the cumulative damage need to be properly reflected on the aseismic design methods. In this study, two cumulative damage assessment methods derived from the plastic fatigue theory are investigated. The one is based on the hysteretic ductility amplitude, and the other is based on the dissipated hysteretic energy. Both methods can consider the maximum ductility and the cyclic behavior of structural response. The validity of two damage methods has been examined for single degree of freedom structures with various natural frequencies against two different earthquake excitations.

• 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.

• Earthquakes and Structures
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• v.10 no.5
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• pp.1089-1109
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• 2016

Modified two-surface model (M2SM) is one of the steel elasto-plastic hysteretic constitutive models that consider both analysis accuracy and efficiency. However, when M2SM is used for complex strain history, sometimes the results are irrational due to the limitation of stress-strain path judgment. In this paper, the defect of M2SM was re-modified by improving the judgment of stress-strain paths. The accuracy and applicability of the improved method were verified on both material and structural level. Based on this improvement, the nonlinear time-history analysis was carried out for a deck-through steel arch bridge with a 200 m-long span under the ground motions of Chi-Chi earthquake and Niigata earthquake. In the analysis, we compared the results obtained by hysteretic constitutive models of improved two-surface model (I2SM) presented in this paper, M2SM and the bilinear kinematic hardening model (BKHM). Results show that, although the analysis precision of displacement response of different steel hysteretic models differs little from each other, the stress-strain responses of the structure are affected by steel hysteretic models apparently. The difference between the stress-strain responses obtained by I2SM and M2SM cannot be neglected. In significantly damaged areas, BKHM gives smaller stress result and obviously different strain response compared with I2SM and M2SM, and tends to overestimate the effect of hysteretic energy dissipation. Moreover, at some position with severe damage, BKHM may underestimate the size of seismic damaged areas. Different steel hysteretic models also have influences on structural damage evaluation results based on deformation behavior and low cycle fatigue, and may lead to completely different judgment of failure, especially in severely damaged areas.

• Earthquakes and Structures
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• v.8 no.3
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• pp.485-509
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• 2015

This paper presents the experimental results obtained by applying frequency-domain structural health monitoring techniques to assess the damage suffered on a special type of damper called Web Plastifying Damper (WPD). The WPD is a hysteretic type energy dissipator recently developed for the passive control of structures subjected to earthquakes. It consists of several I-section steel segments connected in parallel. The energy is dissipated through plastic deformations of the web of the I-sections, which constitute the dissipative parts of the damper. WPDs were subjected to successive histories of dynamically-imposed cyclic deformations of increasing magnitude with the shaking table of the University of Granada. To assess the damage to the web of the I-section steel segments after each history of loading, a new damage index called Area Index of Damage (AID) was obtained from simple vibration tests. The vibration signals were acquired by means of piezoelectric sensors attached on the I-sections, and non-parametric statistical methods were applied to calculate AID in terms of changes in frequency response functions. The damage index AID was correlated with another energy-based damage index -ID- which past research has proven to accurately characterize the level of mechanical damage. The ID is rooted in the decomposition of the load-displacement curve experienced by the damper into the so-called skeleton and Bauschinger parts. ID predicts the level of damage and the proximity to failure of the damper accurately, but it requires costly instrumentation. The experiments reported in this paper demonstrate a good correlation between AID and ID in a realistic seismic loading scenario consisting of dynamically applied arbitrary cyclic loads. Based on this correlation, it is possible to estimate ID indirectly from the AID, which calls for much simpler and less expensive instrumentation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.265-272
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• 2000

Unbond brace hysteretic dampers are generally used to prevent or decrease structural damage in buildings subjected to strong earthquake by its energy dissipating hysteretic behavior. According to a previous research, the optimum ratio of device yield strength to story yield strength of the combined system has been identified as the most important parameter for characterizing the performance of this device. In this research, the validity and the applicability of the previous research has been investigated and a new approach has been proposed through earthquake response analysis of a steel structure installed with unbond brace type hysteretic damper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.517-528
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• 2008

This paper presents a hysteretic damage model for reinforced concrete (RC) joints that explicitly accounts for the bond-slip between the reinforcing bars and the surrounding concrete. A frame element whose displacement fields for the concrete and the reinforcing bars are different to permit slip is developed. From the fiber section concept, compatibility equations for concrete, rebar, and bond are defined. Modification of the hysteretic stress-strain curve of steel is conducted for partial unloading and reloading conditions. Local bond stress-slip relations for monotonic loads are updated at each slip reversal according to the damage factor. The numerical applications of the reinforcing bar embedded in the confined concrete block, the RC column anchored in the foundation, and the RC beam-column subassemblage validate the model accuracy and show how including the effects of bond-slip leads to a good assessment of the amount of energy dissipation during loading histories.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.257-262
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• 2003

Base isolation bearings are known as an effective system to Protect bridges from the earthquake damage. There are many types of base isolation bearings in the market. Among them, steel hysteretic damper, made of mild steel and one of the oldest ones, has some good features. Since steel hysteretic damper is made of steel and has simple structure, it is cheeper and easier to maintain than other types. Despite the advantages, steel hysteretic damper with pin-type elements has no application in Korea. The steel hysteretic damper with pin-type elements are tested to examin the basic characteristics and to evaluate antiseismic performance. In this paper, the results of the test are presented.

• Structural Engineering and Mechanics
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• v.23 no.2
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• pp.177-193
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• 2006

Determining the hysteretic energy demand and dissipation capacity and level of damage of the structure to a predefined earthquake ground motion is a highly non-linear problem and is one of the questions involved in predicting the structure's response for low-performance levels (life safe, near collapse, collapse) in performance-based earthquake resistant design. Neural Network (NN) analysis offers an alternative approach for investigation of non-linear relationships in engineering problems. The results of NN yield a more realistic and accurate prediction. A NN model can help the engineer to predict the seismic performance of the structure and to design the structural elements, even when there is not adequate information at the early stages of the design process. The principal aim of this study is to develop and test multi-layered feedforward NNs trained with the back-propagation algorithm to model the non-linear relationship between the structural and ground motion parameters and the hysteretic energy demand in steel moment resisting frames. The approach adapted in this study was shown to be capable of providing accurate estimates of hysteretic energy demand by using the six design parameters.