• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.875-890
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• 2016

A new structural damage index for seismic fragility analysis of reinforced concrete columns is developed based on a local tensile damage variable of the Lee and Fenves plastic-damage model. The proposed damage index is formulated from the nonlinear regression of experimental column test data. In contrast to the response-based damage index, the proposed damage index is well-defined in the form of a single monotonically-increasing function of the volume weighted average of local damage distribution, and provides the necessary computability and objectivity. It is shown that the present damage index can be appropriately zoned to be used in seismic fragility analysis. An application example in the computational seismic fragility evaluation of reinforced concrete columns validates the effectiveness of the proposed damage index.

• Earthquakes and Structures
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• v.23 no.1
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• pp.35-57
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• 2022

This article presents a computationally efficient framework for multi-objective seismic design optimization of steel moment-resisting frame (MRF) structures based on the nonlinear dynamic analysis procedure. This framework employs the uniform damage distribution philosophy to minimize the weight (initial cost) of the structure at different levels of damage. The preliminary framework was recently proposed by the authors based on the single excitation and the nonlinear static (pushover) analysis procedure, in which the effects of record-to-record variability as well as higher-order vibration modes were neglected. The present study investigates the reliability of the previous framework by extending the proposed algorithm using the nonlinear dynamic design procedure (optimization under multiple ground motions). Three benchmark structures, including 4-, 8-, and 12-story steel MRFs, representing the behavior of low-, mid-, and high-rise buildings, are utilized to evaluate the proposed framework. The total weight of the structure and the maximum inter-story drift ratio (IDRmax) resulting from the average response of the structure to a set of seven ground motion records are considered as two conflicting objectives for the optimization problem and are simultaneously minimized. The results of this study indicate that the optimization under several ground motions leads to almost similar outcomes in terms of optimization objectives to those are obtained from optimization under pushover analysis. However, investigation of optimal designs under a suite of 22 earthquake records reveals that the damage distribution in buildings designed by the nonlinear dynamic-based procedure is closer to the uniform distribution (desired target during the optimization process) compared to those designed according to the pushover procedure.

• Journal of Information Technology Applications and Management
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• v.15 no.2
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• pp.67-82
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• 2008

Risk that breed large size disaster is happening variously for cause at social. natural a management. Incidence and damage scale are trend that increase rapidly than past. In these circumstance, to keep operational continuity of organization, area, society, risk management action that establish systematic counter measure estimating and analyze occurrence possibility and expectation damage of risk is essential indispensable issue and the best countermeasure. Risk management action does by main purpose establish optimum disaster reduction countermeasure. To deduce various countermeasure, process that estimate and analyze occurrence possibility and expectation damage of risk is essential indispensable issue. Therefore, this paper studies process design that can presume risk occurrence frequency and damage scale through distribution of probability.

• Computers and Concrete
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• v.5 no.4
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• pp.375-388
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• 2008

Crack opening governs many transfer properties that play a pivotal role in durability analyses. Instead of trying to combine continuum and discrete models in computational analyses, it would be attractive to derive from the continuum approach an estimate of crack opening, without considering the explicit description of a discontinuous displacement field in the computational model. This is the prime objective of this contribution. The derivation is based on the comparison between two continuous variables: the distribution if the effective non local strain that controls damage and an analytical distribution of the effective non local variable that derives from a strong discontinuity analysis. Close to complete failure, these distributions should be very close to each other. Their comparison provides two quantities: the displacement jump across the crack [U] and the distance between the two profiles. This distance is an error indicator defining how close the damage distribution is from that corresponding to a crack surrounded by a fracture process zone. It may subsequently serve in continuous/discrete models in order to define the threshold below which the continuum approach is close enough to the discrete one in order to switch descriptions. The estimation of the crack opening is illustrated on a one-dimensional example and the error between the profiles issued from discontinuous and FE analyses is found to be of a few percents close to complete failure.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.709-719
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• 2001

In particle or short-fiber reinforced composites, cracking of reinforcements is a significant damage mode because the cracked reinforcements lose carrying capacity. This paper deals with elastic stress distributions and load carrying capacity of intact and cracked ellipsoidal inhomogeneities. Three dimensional finite element analysis has been carried out on intact and cracked ellipsoidal inhomogeneities in an infinite body under uniaxial tension and pure shear. For the intact inhomogeneity, as well known as Eshelbys solution, the stress distribution is uniform in the inhomogeneity and nonuniform in the surrounding matrix. On the other hand, for the cracked inhomogeneity, the stress in the region near the crack surface is considerably released and the stress distribution becomes more complex. The average stress in the inhomogeneity represents its load carrying capacity, and the difference between the average stresses of the intact and cracked inhomogeneities indicates the loss of load carrying capacity due to cracking damage. The load carrying capacity of the cracked inhomogeneity is expressed in to cracking damage. The load carrying capacity of the cracked inhomogeneity is expressed in terms of the average stress of the intact inhomogeneity and some coefficients. It is found that a cracked inhomogeneity with high aspect ratio still maintains higher load carrying capacity.

• Journal of Ocean Engineering and Technology
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• v.35 no.4
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• pp.257-265
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• 2021

Many studies have been performed to predict a reliable and accurate stress-range distribution and fatigue damage regarding the Gaussian wide-band stress response due to multi-peak waves and multiple dynamic loads. So far, most of the approximation models provide slightly inaccurate results in comparison with the rain-flow counting method as an exact solution. A step-by-step study was carried out to develop new approximate spectral moments that are close to the rain-flow counting moment, which can be used for the development of a fatigue damage model. Using the special parameters and bandwidth parameters, four kinds of parameter-based combinations were constructed and estimated using the R-squared values from regression analysis. Based on the results, four candidate empirical formulas were determined and compared with the rain-flow counting moment, probability density function, and root mean square (RMS) value for relative distance. The new approximate spectral moments were finally decided through comparison studies of eight response spectra. The new spectral moments presented in this study could play an important role in improving the accuracy of fatigue damage model development. The present study shows that the new approximate moment is a very important variable for the enhancement of Gaussian wide-band fatigue damage assessment.

• Computers and Concrete
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• v.23 no.5
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• pp.335-349
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• 2019

A low-cycle loading experiment of 16 transfer column specimens was conducted to study the influence of parameters, likes the extension length of shape steel, the ratio of shape steel, the axial compression ratio and the volumetric ratio of stirrups, on the shear distribution between steel and concrete, the concrete damage state and the degradation of lateral stiffness. Shear force of shape steel reacted at the core area of concrete section and led to tension effect which accelerated the damage of concrete. At the same time, the damage of concrete diminished its shear capacity and resulted in the shear enlargement of shape steel. The interplay between concrete damage and shear force of shape steel ultimately made for the failures of transfer columns. With the increase of extension length, the lateral stiffness first increases and then decreases, but the stiffness degradation gets faster; With the increase of steel ratio, the lateral stiffness remains the same, but the degradation gets faster; With the increase of the axial compression ratio, the lateral stiffness increases, and the degradation is more significant. Using more stirrups can effectively restrain the development of cracks and increase the lateral stiffness at the yielding point. Also, a formula for calculating the yielding lateral stiffness is obtained by a regression analysis of the test data.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.308-315
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• 2002

Fragility analysis is widely used for the seismic safety evaluation of a structure. In fragility analysis, damage evaluation is a crucial factor. Most of the present fragility analyses use the representative responses such as displacement and absorbed hysteretic energy as a tool of damage evaluation. But damage evaluation method that can represent the local damage of a structure is required in the case of piers of which the local damage can cause the whole failure of bridge system. Therefore this study proposes a damage index, which can represent the distribution and magnitude of local damage by using the Lee and Fenves'plastic-damage model. Using the proposed damage index, fragility curves and damage probability matrix of pier are produced and fragility analysis is performed.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.6
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• pp.559-565
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• 2003

A spectral element model-based structural damage identification method (SDIM) was derived in the previous study by using the damage-induced changes in frequency response functions. However the previous SDIM often provides poor damage identification results because the nonlinear effect of damage magnitude was not taken into account. Thus, this paper improves the previous SDIM by taking into account the nonlinear effect of damage magnitude. Accordingly an iterative solution method is used in this study to solve the nonlinear matrix equation for local damages distribution. The present SDIM is evaluated through the numerically simulated damage identification tests.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.993-999
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• 2004

The estimation of fatigue life at the design stage of membrane type LNG tank is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the tank. In this study, the practical procedure of fatigue life prediction by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function has been shown with the corner region of Gaz Transport Membrane type LNG tank being used as an example. In particular the parameters of Weibull distribution that determine the stress spectrum are discussed. The main results obtained from this study are as follows: 1. The recommended value for the shape parameter of Weibull distribution for the LNG tank is 1.1 in case of using the direct calculation method proposed in this study. 2. The calculated fatigue life is influenced by the shape parameter of Weibull distribution and stress block. The safe fatigue design can be achieved by using higher value of shape parameter and the stress blocks divided into more stress blocks.