• Steel and Composite Structures
• /
• v.1 no.3
• /
• pp.283-294
• /
• 2001

In the present work a constitutive model is developed which permits the assessment of the structural performance through a criterion based on cumulative damage. For it, a damage index is defined and is evaluated through the application of the Miner's rule in low-cycle fatigue. However, the damage index is not considered as a posteriori variable since is incorporated explicitly as an internal variable in the constitutive equations which produces a direct coupling between the damage and the structural mechanical behaviour allowing the possibility of considering as a whole different coupled phenomena. For the elaboration of this damage model, the concepts of the mechanics of continuum medium are applied on lumped dissipative models in order to obtain a coupled simplified model. As a result an elastoplastic model coupled with damage and fatigue damage is obtained.

• Steel and Composite Structures
• /
• v.19 no.5
• /
• pp.1055-1075
• /
• 2015

In order to investigate the accuracy and applicability of steel equivalent constitutive model, the calculated results were compared with typical tests of steel frames under static and dynamic loading patterns firstly. Secondly, four widely used models for time history analysis of steel frames were compared to discuss the applicability and efficiency of different methods, including shell element model, multi-scale model, equivalent constitutive model (ECM) and traditional beam element model (especially bilinear model). Four-story steel frame models of above-mentioned finite element methods were established. The structural deformation, failure modes and the computational efficiency of different models were compared. Finally, the equivalent constitutive model was applied in seismic incremental dynamic analysis of a ten-floor steel frame and compared with the cyclic hardening model without considering damage and degradation. Meanwhile, the effects of damage and degradation on the seismic performance of steel frame were discussed in depth. The analysis results showed that: damages would lead to larger deformations. Therefore, when the calculated results of steel structures subjected to rare earthquake without considering damage were close to the collapse limit, the actual story drift of structure might already exceed the limit, leading to a certain security risk. ECM could simulate the damage and degradation behaviors of steel structures more accurately, and improve the calculation accuracy of traditional beam element model with acceptable computational efficiency.

• Earthquakes and Structures
• /
• v.11 no.4
• /
• pp.649-664
• /
• 2016

A seismic damaged bridge may be hit again by a strong aftershock or another earthquake in a short interval before the repair work has been done. However, discussions about the impact of the unrepaired damages on the residual earthquake resistance of a steel bridge are very scarce at present. In this paper, nonlinear time-history analysis of a steel arch bridge was performed using multi-scale hybrid model. Two strong historical records of main shock-aftershock sequences were taken as the input ground motions during the dynamic analysis. The strain response, local deformation and the accumulation of plasticity of the bridge with and without unrepaired seismic damage were compared. Moreover, the effect of earthquake sequence on crack initiation caused by low-cycle fatigue of the steel bridge was investigated. The results show that seismic damage has little impact on the overall structural displacement response during the aftershock. The residual local deformation, strain response and the cumulative equivalent plastic strain are affected to some extent by the unrepaired damage. Low-cycle fatigue of the steel arch bridge is not induced by the earthquake sequences. Damage indexes of low-cycle fatigue predicted based on different theories are not exactly the same.

• Nuclear Engineering and Technology
• /
• v.56 no.8
• /
• pp.3397-3404
• /
• 2024

The shield building of the AP1000 nuclear power plant serves as a crucial protective barrier against radioactive substances. However, past research indicates that structures are susceptible to experiencing aftershocks, which may lead to unforeseeable damage and potential radioactive material leakage. To address this issue, a finite element model of the shield building was established with the damage indexes of the tensile and compressive damage selected for further model analysis. According to the fundamental theory of reliability, the traditional incremental dynamic analysis method was used to analyze the seismic fragility of the shield building by inputting mainshock and aftershock sequences with three strength ratios. The results indicate that the seismic fragility of shield building may be underestimated without considering the influence of aftershocks and the damage state presents an upward tendency as the strength ratio increases. However, the cumulative damage caused by aftershocks is unlikely to exceed the initial damage induced by the corresponding mainshock. Overall, the aggravation of the compressive damage is less pronounced than the increase of the tensile damage as the strength ratio increases.

• Earthquakes and Structures
• /
• v.22 no.1
• /
• pp.83-94
• /
• 2022

In recent years, some studies have identified and quantified factors that can increase or decrease the seismic vulnerability of buildings. These modifier factors, related to the building characteristics and condition, are taken into account in the vulnerability assessment, by means of a numerical estimation resulting from the quantification of these modifiers through vulnerability indexes. However, views have differed on the definition and the quantification of modifiers. In this study, modifier parameters and scores of the Risk-UE Level 1 method are adjusted based on the Algerian seismic code recommendations and the reviews proposed in the literature. The adjusted modifiers and scores are applied to reinforced concrete (RC) buildings in Boumerdes city, in order to assess probable seismic damage. Comparison between estimated damage and observed damage caused by the 2003 Boumerdes earthquake is done, with the objective to (i) validate the model involving influence of the modifier parameters on the seismic vulnerability, and (ii) to define the relationship between modifiers and damage. This research may help planners in improving seismic regulations and reducing vulnerability of existing buildings.

• Computers and Concrete
• /
• v.8 no.3
• /
• pp.311-325
• /
• 2011

Nowadays, many engineers believe that hybrid structures with reinforced concrete central core walls and perimeter steel frames offer an economical method to develop the strength and stiffness required for seismic design. As a result, a variety of such structures have recently been applied in actual construction. However, the performance-based seismic design of such structures has not been investigated systematically. In the performance-based seismic design, quantifying the seismic damage of complete structures by damage indices is one of the fundamental issues. Four damage states and the final softening index at each state for high-rise hybrid structures are suggested firstly in this paper. Based on nonlinear dynamic analysis, the relation of the maximum inter-story drift, the main structural characteristics, and the final softening index is obtained. At the same time, the relation between the maximum inter-story drift and the maximum roof displacement over the height is also acquired. A double-variable index accounting for maximum deformation and cumulative energy is put forward based on the pushover analysis. Finally, a case study is conducted on a high-rise hybrid structure model tested on shaking table before to verify the suggested quantities of damage indices.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2009.04a
• /
• pp.530-533
• /
• 2009

This study deals with 2D and 3D nonlinear seismic damage analysis of a concrete gravity dam using the finite element program ABAQUS and the concrete damaged plasticity model. 2D and 3D spillway sections of the dam are simulated. First the frequency analysis is conducted to compare the fundamental frequency and estimate the value of damping coefficient. Then the seismic analysis is conducted using the simulated ground acceleration motion. The relative displacement between the crest and bottom of the dam is obtained and compared for the maximum value and occurrence time. The results indicate that the plane-stress assumption gives similar results of maximum relative displacement and final damage distribution with 3D analysis.

• Smart Structures and Systems
• /
• v.12 no.6
• /
• pp.679-694
• /
• 2013

In this paper the application of the Interpolation Damage Detection Method to the numerical model of a suspension bridge instrumented with a network of Micro-Electro-Mechanical System sensors is presented. The method, which, in its present formulation, belongs to Level II damage identification method, can identify the presence and the location of damage from responses recorded on the structure before and after a seismic damaging event. The application of the method does not require knowledge of the modal properties of the structure nor a numerical model of it. Emphasis is placed herein on the influence of recorded signals noise on the reliability of the results given by the Interpolation Damage Detection Method. The response of a suspension bridge to seismic excitation is computed from a numerical model and artificially corrupted with random noise characteristic of two families of Micro-Electro-Mechanical System accelerometers. The reliability of the results is checked for different damage scenarios.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.21 no.6
• /
• pp.311-322
• /
• 2017

In this study, the seismic performance of concrete-steel composite moment frame structures equipped with seismic retrofitting systems such as seismic reinforcement, base isolators, and bracing members, which are typical earthquake damage mitigation systems, is evaluated through nonlinear dynamic analyses. A total of five frame models were designed and each frame model was developed for numerical analyses. A total of 80 ground acceleration data were used to perform the nonlinear dynamic analysis to measure ground shear force and roof displacement, and to evaluate the behavioral performance of each frame model by measuring inter-story drift ratios. The analysis results indicate that the retrofitting device of the base isolator make a significant contribution to generating relatively larger absolute displacement than other devices due to flexibility provided to interface between ground and column base. However, the occurrence of the inter-story drift ratio, which is a relative displacement that can detect the damage of the structure, is relatively small compared with other models. On the other hand, the seismic reinforced frame model enhanced with the steel plate at the lower part of the column was found to be the least efficient.

• Structural Engineering and Mechanics
• /
• v.74 no.2
• /
• pp.201-214
• /
• 2020

This study aims at evaluating composite moment frame structures (CFS) using wavelet analysis of the displacement behavior of these structures. Five seismic damage mitigation systems' models of 9-story CFS are examined namely, basic (Model 1), reinforced (Model 2), buckling restrained braced (BRB) (Model 3), lead rubber bearing (LRB) (Model 4), and composite (Model 5) moment frames. A novel integration between continuous and discrete wavelet transforms is designed to estimate the wavelet power energy and variance of measurements' behaviors. The behaviors of the designed models are evaluated under influence of four seismic loads to study the dynamic performance of CFS in the frequency domain. The results show the behaviors of models 3 and 5 are lower than other models in terms of displacement and frequency performances. Model 3 has been shown lower performances in terms of energy and variance wavelets along the monitoring time; therefore, Model 3 demonstrates superior performance and low probability of failure under seismic loads. Furthermore, the wavelet variance analysis is shown a powerful tool that can be used to assess the CFS under seismic hazards.