Showing papers by "Homayoon E. Estekanchi published in 2012"

Seismic analysis of steel liquid storage tanks by Endurance Time method

Abstract: Endurance Time (ET) method is a time history based method for seismic evaluation of structures using intensifying dynamic excitation as the loading function. In this paper, application of this method in the analysis of steel tanks has been investigated. A methodology for practical application of ET method in seismic assessment of storage tanks has been presented. This methodology has been applied in three-dimensional nonlinear analysis of a particular anchored steel tank using Finite Element method, and results are compared with conventional codified design procedures. Results of the analyses indicate reasonable accuracy of the proposed method in estimation of seismic responses of steel tanks and its applicability in enhancing the design process of steel tanks considering various sources of complicated behavior. Comparative study of seismic response of the tank in anchored and unanchored states utilizing ground motions has been presented. Advantages and limitations of the procedure have also been discussed.

Endurance time method in the linear seismic analysis of shell structures

Abstract: Endurance Time (ET) method is a response history based analysis procedure that can be used for estimating the seismic response of structures at different excitation levels in each response history. This seismic analysis method utilizes specific intensifying acceleration functions to analyze seismic behaviors. One of the potential applications of the ET method is in the seismic assessment of shell structures. In this study, a procedure for linear seismic analysis of shell structures is proposed and applications of this method is investigated for several cases of shell structures. These structures are analyzed under three ET acceleration functions in one direction and the results are compared to time history analysis considering seven actual earthquake records. Moreover, the results of the ET method are compared to response spectrum analysis method. The outcomes of the study reveal that the ET method predicts the linear seismic performance of shell structures with acceptable precision and significant reduction in analysis time. Furthermore, it is conluded that scattering of results of three ET analysis is very low and one analysis can be used instead of three. Finally, the comparison between THA and RSM results verify that response spectuarm method is a conservative method which occasionally encounters problems to evaluate bending stresses of shell structures.

Significance of effective number of cycles in endurance time analysis

Abstract: Endurance Time (ET) method is a dynamic analysis procedure using intensifying accelerograms which can be used to assess the structural performance at different excitation levels. In generation process of current ET accelerograms , the compatibility between acceleration spectrum produced by the ET accelerograms and acceleration spectrum associated with the real ground motions is applied, whereas the duration consistency is not directly considered. It is generally accepted that the strong-motion duration can strongly influence the response of structures which have stiffness or strength degrading characteristics. In this study, the number of cycles that a structure should resist due to a ground motion is considered as a parameter related to shaking characteristics of that ground motion. In addition, the number of cycles of a structure when is subjected to the ET records and the real ground motions are compared. This study further determines how the ET records should be modified to have the best duration consistency with the real ground motions. Two methods are proposed to achieve this objective. It is shown that determining a specific target time for the ET records alone is not a suitable approach to achieve the best duration consistency.

Collapse analysis by endurance time method

Abstract: Estimation of collapse performance is primarily conducted through Collapse Fragility Curves (CFC’s). The EDP-based approach is the main scheme for attaining such curves and employs IDA. Obtaining CFC’s from IDA results is tremendously time consuming and computationally demanding. Introduction of more efficient methods of seismic analysis, can potentially improve this issue. The Endurance Time (ET) method is a straightforward method for dynamic analysis of structures subjected to multilevel excitation intensities. In this paper, collapse analysis using ET analysis results to obtain EDP-based CFC’s, has been explained and demonstrated by a model. For verification, the resulting CFC has been compared to that obtained by IDA.

Evaluation of seismic behavior of fixed offshore platforms with endurance time method

Abstract: هديكچ هزرل راتفر يسررب صخاش نيرت مهم زا يكي ،ييايرد ياه وكس يا نآ يحارط ياه هزرل قطانم رد اه دوجو نيا اب .دشاب يم زيخ شور يليلحت ياه يم رادروخرب يلوبق لباق تقد زا هنيمز نيا رد هك يا نامز و يگديچيپ ليلد هب ،دنشاب نادـنچ لـمع رد ،ندوب رب تفرگن رارق نيسدنهم هجوت دروم ه يم لكشم نيا لح تهج يبسانم شور ،ماود نامز شور .دنا يم شور نيا رد .دشاب لوبق اب ناوت هظحلام لباق نازيم هب ار ليلحت نامز ،اطخ زا يبسانم هدودحم هزاس راتفر ماود نامز ليلحت كي ماجنا اب هك يروطب ،داد شهاك يا هزرل فلتخم حوطس رد ار با هلاقم نيا رد .درك يبايزرا يا شور يفرعم هب ادت همان نييآ رد ليلحت فلتخم ياه ناـمز شور و اـه ماود راتفر همادا رد و هدش هتخادرپ هزرل زا هدافتسا اب وكس هس يا يفيط ليلحت همان نييآ 2800 باتش عباوت و نامز هـسياقم دروم ماود زا روظنم نيدب .تسا هتفرگ رارق يباتش عبات نامز شور رد هك ط يانبم رب ماود همان نييآ في 2800 و هدـش هدافتـسا ،هتشگ ديلوت نازيم جياتن رد فلاتخا يفيط ليلحت اب هسياقم رد همان نييآ 2800 هئارا هديدرگ يبسانم قباطت زا هك تسا . يم رادروخرب .دنشاب :يديلك تاملك نامز شور ،تباث هياپ يوكس هزرل راتفر ،ماود يفيط ليلحت ،يا

Integrating Constrained Random Waves in Endurance Time Analysis of Offshore Structures Subjected to Sea Waves

Abstract: This paper introduces a novel methodology for design and assessment of offshore structures exposed to irregular sea waves. For this, Constrained NewWave (CNW) is integrated with the Endurance Time Analysis (ETA) methodology, which is basically developed for the performance based analysis of onshore structures to earthquake loads. In this approach, the offshore structure is simulated in time-domain under a set of calibrated intensifying wave functions. They are devised to represent a gradually increasing roughness of the sea state by time. A performance index such as base shear, drift or stress in a critical structural members are monitored until they reach to a predefined maximum value. A higher endurance time (corresponding to a higher wave height) is to be interpreted as a better performance of structure.Ability to consider spectral features of waves, waves’ irregularity, the wave-in-deck impacts, utilizing a relatively simple approach, requiring relatively low computational times and capability to consider any desirable damage indices are the advantages of this novel method. The method can be used in the design stage, collapse analysis and for the assessment of existing offshore platforms.In this paper the effectiveness of this method has been examined on offshore jacket platforms. The results obviously have highlighted the potentials of this approach for the dynamic, time-domain, non-linear analysis and assessment of offshore platforms.Copyright © 2012 by ASME