Effects of higher modes and MDOF on strength reduction factor of elastoplastic structures under far and near-fault ground motions

Gerami, Mohsen; Siahpolo, Navid; Vahdani, Reza

doi:10.1016/j.asej.2015.08.015

Cited by 8 publications

(4 citation statements)

References 5 publications

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“…They discussed the effects of periods, deformation/damage, and soil types on the strength reduction factors and proposed the empirical expression and the corresponding seismic design process. Considering that the strength reduction factor is determined by an SDOF system, Gerami et al (2017) discussed the effects of the high mode and an MDOF on the strength reduction factor of frame structures subjected to far and near-fault ground motions and indicated that these effects could be remarkable for near-field motions. Salimbahrami and Gholhaki (2019) studied the effects of the high mode and an MDOF on the strength reduction factor of reinforced concrete frames equipped with a steel plate shear wall and proposed a practical relation.…”

Section: Introductionmentioning

confidence: 99%

Damage-based strength reduction factor spectra of structures subjected to bidirectional ground motions

Wang

Zhang

et al. 2022

Advances in Structural Engineering

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The current research on the damage-based strength reduction factor has been completely based on the inelastic single-degree-of-freedom systems that are more suitable for two-dimensional analyses. Therefore, it is necessary to construct damage-based strength reduction factor spectra for systems subjected to bidirectional ground motions. In this study, an inelastic single-mass bi-degree-of-freedom (SMBDOF) system subjected to the orthogonal bidirectional ground motions with the hysteretic property of two-dimensional yield-surface plasticity function is presented, and the x-component of the system is used to construct the damage-based strength reduction factor spectra of the system ( R b spectra). The Park-Ang damage model is used to determine the constant damage index of the R b spectra. In addition, 178 ground motion records for site classes C, D, and E are considered as ground excitations of the SMBDOF system to construct the mean R b spectra with the format of R b- D- T for a given ductility capacity and R b- μ u- T for a given damage level. The R b spectra of the SMBDOF system is compared with the corresponding R spectra of the SDOF system. Statistical analysis considering different values of the natural period, ductility capacity, damage index, period ratio, and site condition is conducted. Analysis results show that the coupling of two-component responses of an inelastic system could increase the strength demand of the system in certain cases; the trend of the R b spectra presented in this study is approximately consistent for different site classes, but the spectral values have the characteristic of site conditions. Therefore, the influence of the period ratio should be considered because a large period difference between two components of the SMBDOF system could aggravate seismic damage in certain situations. Based on the statistical analysis, the expression of R b spectra curves with a period ratio γ = 1 is derived using the regression analysis, and the correction expression is obtained considering the influence of the period ratio on the R b spectra. Then, the construction procedure of the R b spectra is introduced. The predicted R b spectra obtained by the proposed procedure is compared with the actual mean spectra, and comparison results indicate a good match.

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Section: Introductionmentioning

confidence: 99%

Damage-based strength reduction factor spectra of structures subjected to bidirectional ground motions

Wang

Zhang

et al. 2022

Advances in Structural Engineering

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“…Recent earthquakes indicate that elastic analysis is not an appropriate tool to evaluate the real seismic performance of RC buildings. While, the nonlinear time history analysis (NTHA) is capable to estimate the probable inelastic response of structures, but it is complex and the results are depending on ground motion contents [4]. So, various seismic codes namely Eurocode-8 [5], ECOL-201 [6], ASCE-7 [7], and IS [8] incorporate response reduction, modification, or behavior factor (R), respectively in their seismic analyses.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Seismic Response Modification Factor (R) for Moderate-Rise RC Buildings with Vertical Irregular Configurations

Ahmed

Abdo

Mohamed

2021

Preprint

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Most international design codes consider the nonlinear seismic performance of a structure by the concept of reduction/modification factor (R). Then, an elastic static force-based method can be normally used for seismic design to create earthquake resistant RC buildings. The response modification factor (R) is sensitive to many aspects such as overall ductility, over-strength, damping, and redundancy levels. Indeed, these factors are severely affected by geometric irregularity of the structural system. So, R-value does not become a constant number for the all types of structures with the same lateral load resisting system, as many standard codes noted. It depends on types, combination, and degrees of geometric vertical irregularity. This research assesses the actual values of R for regular and familiar vertical irregularity cases in RC buildings with moment-resisting frames (MRF) systems. Also, it takes into account the reduction percent that may occurs in R-value due to these studied vertical irregularities. The vertical irregularity cases, such as set-back and soft story, are essentially needed to be studied greater than ever due to the wide propagation of these types of buildings in Egypt, recently. In addition, the potential analytical methods that may be used to calculate R-value in comparison with Egyptian code’s value. Nonlinear static pushover analysis is carried out using ETABS via three-dimensional numerical models. The findings prove that vertical irregular models have poor seismic capacities, in comparison with regular one, due to their sudden change in lateral stiffness than that with regular aspect. So, the response modification factor (R) must be re-calculated or even scaled-down before design stage with 15% and 25% for single and combined vertical irregularity, respectively. In addition, this investigation derives a vital equation between R values with vertical irregularity ratios in each studied model. This equation shall be a guide for seismic design codes, structural design engineers, and researchers. Accordingly, the response modification factor R does not become a fixed value regardless vertical irregularity aspects of the buildings, but it has a variable value that depend on their inelastic seismic performance of the lateral load resisting systems.

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“…Moreover, Tzimas et al [14] established a response databank and then utilized it for the development of empirical formulae providing the behavior factor as a function of the geometrical and dynamic characteristics of the 3D steel moment-resisting frame buildings. Consideration of higher mode (HM) and multidegree of freedom (MDOF) effects in extracting the R factor was studied by Siahpolo et al [15]. ey created almost 1764 nonlinear dynamic analysis of 2D-frames under 30 ordinary and near-field earthquakes.…”

Section: Introductionmentioning

confidence: 99%

A New Empirical Correlation for Estimation of EBF Steel Frame Behavior Factor under Near-Fault Earthquakes Using the Genetic Algorithm

Razavi

Siahpolo

Adeli

2020

Journal of Engineering

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The most important feature of the behavior factor is that it allows the structural designer to be able to evaluate the structural seismic demand, using an elastic analysis, based on force-based principles quickly. In most seismic codes, this coefficient is merely dependent on the type of lateral resistance system and is introduced with a fixed number. However, there is a relationship between the behavior factor, ductility (performance level), structural geometric properties, and type of earthquake (near and far). In this paper, a new and accurate correlation is attempted to predict the behavior factor (q) of EBF steel frames, under near-fault earthquakes, using the genetic algorithm (GA). For this purpose, a databank consisting of 12960 data is created. To establish different geometrical properties of models, 3−, 6−, 9−, 12−, 15, and 20− story steel EBF frames were considered with 3 different types of link beam, 3 different types of column stiffness, and 3 different types of brace slenderness. Using nonlinear time history under 20 near-fault earthquake, all models were analyzed to reach 4 different performance levels. 6769 data were used as GA training data. Moreover, to validate the correlation, 2257 data were used as test data for calculating mean squared error (MSE) and correlation coefficient (R) between the predicted values of (q) and the real values. In addition, the MSE and R were calculated for correlation in the train and test data. Also, the comparison of the response of maximum inelastic displacement of 5 stories EBF from the proposed correlation and the mean inelastic time-history analysis confirms the accuracy of the estimate relationship.

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Effects of higher modes and MDOF on strength reduction factor of elastoplastic structures under far and near-fault ground motions

Cited by 8 publications

References 5 publications

Damage-based strength reduction factor spectra of structures subjected to bidirectional ground motions

Damage-based strength reduction factor spectra of structures subjected to bidirectional ground motions

Evaluation of Seismic Response Modification Factor (R) for Moderate-Rise RC Buildings with Vertical Irregular Configurations

A New Empirical Correlation for Estimation of EBF Steel Frame Behavior Factor under Near-Fault Earthquakes Using the Genetic Algorithm

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