scholarly journals Evaluation of a Modified MPA Procedure Assuming Higher Modes as Elastic to Estimate Seismic Demands

2004 ◽  
Vol 20 (3) ◽  
pp. 757-778 ◽  
Author(s):  
Anil K. Chopra ◽  
Rakesh K. Goel ◽  
Chatpan Chintanapakdee
Keyword(s):  
Structural Engineering ◽  
Pushover Analysis ◽  
Computational Effort ◽  
Attractive Alternative ◽  
Engineering Practice ◽  
Seismic Demands ◽  
History Analysis ◽  
Modes Of Vibration ◽  
Response History Analysis ◽  
Damped Systems

The modal pushover analysis (MPA) procedure, which includes the contributions of all significant modes of vibration, estimates seismic demands much more accurately than current pushover procedures used in structural engineering practice. Outlined in this paper is a modified MPA (MMPA) procedure wherein the response contributions of higher vibration modes are computed by assuming the building to be linearly elastic, thus reducing the computational effort. After outlining such a modified procedure, its accuracy is evaluated for a variety of frame buildings and ground motion ensembles. Although it is not necessarily more accurate than the MPA procedure, the MMPA procedure is an attractive alternative for practical application because it leads to a larger estimate of seismic demands, improving the accuracy of the MPA results in some cases (relative to nonlinear response history analysis) and increasing their conservatism in others. However, such conservatism is unacceptably large for lightly damped systems, with damping significantly less than 5%. Thus the MMPA procedure is not recommended for such systems.

scholarly journals Accuracy of Advanced Methods for Nonlinear Static Analysis of Steel Moment-Resisting Frames

2014 ◽  
Vol 8 (1) ◽  
pp. 310-323 ◽  
Author(s):  
Massimiliano Ferraioli ◽  
Alberto M. Avossa ◽  
Angelo Lavino ◽  
Alberto Mandara
Keyword(s):  
Pushover Analysis ◽  
Nonlinear Static Analysis ◽  
Seismic Demands ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Capacity Spectrum ◽  
History Analysis ◽  
Moment Resisting ◽  
Response History Analysis ◽  
Nonlinear Static

The reliability of advanced nonlinear static procedures to estimate deformation demands of steel momentresisting frames under seismic loads is investigated. The advantages of refined adaptive and multimodal pushover procedures over conventional methods based on invariant lateral load patterns are evaluated. In particular, their computational attractiveness and capability of providing satisfactory predictions of seismic demands in comparison with those obtained by conventional force-based methods are examined. The results obtained by the static advanced methods, used in the form of different variants of the original Capacity Spectrum Method and Modal Pushover Analysis, are compared with the results of nonlinear response history analysis. Both effectiveness and accuracy of these approximated methods are verified through an extensive comparative study involving both regular and irregular steel moment resisting frames subjected to different acceleration records.

On a Process of Rapid Estimation of Seismic Demands for Generic Steel Frame Structures

2005 ◽  
Author(s):  
Chiung-Yueh Lin ◽  
Wei-Zhi Chen ◽  
Tysh-Shang Jan
Keyword(s):  
Pushover Analysis ◽  
Tall Buildings ◽  
Frame Structures ◽  
Seismic Demands ◽  
Higher Mode Effects ◽  
Mode Effects ◽  
History Analysis ◽  
Story Drift ◽  
Response History Analysis ◽  
Nonlinear Response History Analysis

The seismic demands of tall buildings can be evaluated by nonlinear response history analysis with some more representative, site-dependent, earthquakes, or by pushover analysis. However, the process of the evaluation is tedious and time consuming. Therefore, it is desirable to have a simplified process that provides quick and reasonable estimates of seismic demands, especially in the stage of conceptual (preliminary) design. Gupta & Krawinkler (2000) has reached on a process in the estimation of roof and story drift demands for frame structures from the spectral displacement at the first period of the structure, through a series of modification factors, accounting for MDOF effects, inelasticity effects, and P-delta effects. It is found that this process can estimate seismic demands reasonably, provided that no negative post-yield story stiffness exists. Also, the modification factors are uniform or with reasonable dispersion, except for structures dominated by higher mode effects. This study has conducted a similar research by performing simulations on Taiwan code–compliant structures of different heights (2,5,10,20 and 30 stories), located in different seismic zones and subjected to sets of local ground motions. The feature of this study is that the seismic demands are estimated from the SRSS of the elastic, modal roof displacements of the structure, instead of the first mode spectral displacement. The simulation results have shown that the modification factors are more promising — uniform or with more reasonable dispersion — even the structure is dominated by high mode effects. Therefore, it is concluded that the process proposed in this study is a feasible method and the modification factors obtained in this study are useful for local engineer in engineering applications.

scholarly journals Extension of Modal Pushover Analysis to Compute Member Forces

2005 ◽  
Vol 21 (1) ◽  
pp. 125-139 ◽  
Author(s):  
Rakesh K. Goel ◽  
Anil K. Chopra
Keyword(s):  
Response Spectrum ◽  
Pushover Analysis ◽  
Seismic Demands ◽  
Modal Pushover Analysis ◽  
History Analysis ◽  
Response History Analysis ◽  
Standard Response ◽  
Nonlinear Response History Analysis ◽  
Seismic Deformation ◽  
Modal Pushover

This paper extends the modal pushover analysis (MPA) procedure for estimating seismic deformation demands for buildings to compute member forces. Seismic demands are computed for six buildings, each analyzed for 20 ground motions. A comparison of seismic demands computed by the MPA and nonlinear response history analysis (RHA) demonstrates that the MPA procedure provides good estimates of the member forces. The bias (or error) in forces is generally less than that noted in earlier investigations of story drifts and is comparable to the error in the standard response spectrum analysis (RSA) for elastic buildings. The four FEMA-356 force distributions, on the other hand, provide estimates of member forces that may be one-half to one-fourth of the value from nonlinear RHA.

Applicability of Modal Pushover Analysis on Bridges

2011 ◽  
Vol 255-260 ◽  
pp. 806-810
Author(s):  
Biao Wei ◽  
Qing Yuan Zeng ◽  
Wei An Liu
Keyword(s):  
Seismic Analysis ◽  
Pushover Analysis ◽  
Time History ◽  
Seismic Demand ◽  
Seismic Demands ◽  
Modal Pushover Analysis ◽  
History Analysis ◽  
Bridge Structures ◽  
Scope Of Application ◽  
Modal Pushover

Taking one irregular continuous bridge as an example, modal pushover analysis (MPA) has been conducted to judge whether it would be applicable for seismic analysis of irregular bridge structures. The bridge’s seismic demand in the transverse direction has been determined through two different methods, inelastic time history analysis (ITHA) and MPA respectively. The comparison between those two results indicates that MPA would be suitable only for bridges under elastic or slightly damaged state. Finally, some modifications are used to improve the MPA’s scope of application, and the results illustrate that the adapted MPA will be able to estimate bridges’ seismic demands to some extent.

Practical Implementation of Generalized Force Vectors for the Multimodal Pushover Analysis of Building Structures

2015 ◽  
Vol 31 (2) ◽  
pp. 1043-1067 ◽  
Author(s):  
F. Soner Alıcı ◽  
HalÛk Sucuoğlu
Keyword(s):  
Nonlinear Response ◽  
Pushover Analysis ◽  
Practical Implementation ◽  
Building Structures ◽  
Design Spectrum ◽  
History Analysis ◽  
Response History Analysis ◽  
Generalized Force ◽  
Nonlinear Response History Analysis ◽  
The Mean

A practical implementation of generalized multimodal pushover analysis is presented in this study, where the number of pushovers is reduced significantly in view of the number of modes contributing to seismic response. It has been demonstrated in two case studies that the reduced procedure for generalized push-over analysis is equally successful in estimating the maximum member deformations and forces under a ground excitation with reference to nonlinear response history analysis. It is further shown that the results obtained by using the mean spectrum of a set of ground motions are almost identical to the mean of the results obtained from separate generalized pushover analyses. These results are also very close to the mean results of the nonlinear response history analyses, hence motivating the implementation of generalized pushover analysis with design spectrum.

Seismic performance criteria based on response history analysis

2014 ◽  
Vol 47 (3) ◽  
pp. 224-228 ◽  
Author(s):  
Brendon A. Bradley
Keyword(s):  
Seismic Performance ◽  
Performance Metrics ◽  
Performance Criteria ◽  
Art Practice ◽  
Seismic Demands ◽  
Codes Of Practice ◽  
History Analysis ◽  
Response History Analysis ◽  
The Mean

This paper provides a comparison of four different seismic performance metrics which relate to the determination of design seismic demands from seismic response history analyses. The considered metrics include those implemented in New Zealand and international codes of practice, as well as emerging metrics which are well established in related research and state-of-the-art practice, but have yet to find their way into conventional guidelines. The metrics are directly compared and contrasted based on a central example. It is illustrated that the use of the “maximum demand” metric in the NZ loadings standard, and the “mean demand” in international codes of practice are notably conservative and unconservative, respectively. Either of the two emerging metrics provide a significant improvement, and given that they require the same information from an analyst’s perspective, are recommended as replacements.

ENERGY-BASED APPROACH TO ESTIMATE SEISMIC DEMANDS FOR ASYMMETRIC BUILDINGS

2010 ◽  
Vol 04 (03) ◽  
pp. 215-230 ◽  
Author(s):  
RAMIN TABATABAEI ◽  
HAMED SAFFARI
Keyword(s):  
Seismic Response ◽  
Dynamic Properties ◽  
Pushover Analysis ◽  
Three Dimensional ◽  
Lateral Force ◽  
Three Dimensional Model ◽  
Seismic Demands ◽  
Asymmetric Buildings ◽  
Plastic Mechanism ◽  
Response History Analysis

In this paper, an energy-based approach to estimate the inelastic response of buildings is presented. In order to estimate torsional effects on the seismic response of structure, the associated plastic mechanism is developed in the three-dimensional model using an adapted version of the DRAIN-3DX program. The changing dynamic properties due to plastic mechanism are used for the calculation of modal lateral loads. Thus, the effects of both stiffness changes and localized response mechanisms at the structure under modal loading are included. The total input energy due to seismic loading is composed of both work done by (1) lateral force pattern acting through the translation displacement and (2) torsion acting through the rotation of each floor. For assessment of the seismic response of asymmetric buildings, the proposed procedure is shown to provide superior results compared to those obtained through deployment of the other methods commonly used: the adaptive modal combination (AMC) procedure, the modal pushover analysis (MPA), and the response history analysis (RHA) approach.

Generalized Response Spectrum Analysis for Structures with Dampers

2018 ◽  
Vol 34 (3) ◽  
pp. 1459-1479 ◽  
Author(s):  
Yuki Terazawa ◽  
Toru Takeuchi
Keyword(s):  
Spectrum Analysis ◽  
Nonlinear Response ◽  
Response Spectrum ◽  
Combination Method ◽  
Axial Stiffness ◽  
Response Spectrum Analysis ◽  
History Analysis ◽  
Response History Analysis ◽  
Nonlinear Response History Analysis ◽  
Damped Systems

In this study, a computational seismic design routine is proposed based on a generalized response spectrum analysis for highly indeterminate structures with energy-dissipation members, such as viscous or elasto-plastic dampers. Complex stiffness terms are introduced to account for displacement-dependent damping, and a three-dimensional (3-D) element stiffness matrix with complex axial stiffness is proposed for elasto-plastic dampers. A modified complete quadratic combination method previously developed for real symmetric damped systems is extended to complex asymmetric damped systems, based on a theoretical analysis of eigenvalue equations. The response is evaluated by iteratively conducting complex eigenvalue analysis and modal combination. The accuracy is confirmed through comparison to nonlinear response history analysis of 2-D frame models. Finally, an example application is presented of a 3-D truss tower seismically retrofitted by replacing the braces with viscoelastic and then elasto-plastic dampers. The proposed design routine is used to rapidly identify novel and efficient damper arrangements and sizing distributions, avoiding computationally intensive nonlinear response history analysis.

scholarly journals Seismic Assessment of Six Typologies of Existing RC Bridges

2020 ◽  
Vol 5 (6) ◽  
pp. 52
Author(s):  
Pietro Crespi ◽  
Marco Zucca ◽  
Nicola Longarini ◽  
Nicola Giordano
Keyword(s):  
Pushover Analysis ◽  
Computational Effort ◽  
Constitutive Law ◽  
Engineering Practice ◽  
Damage Potential ◽  
Safety Level ◽  
Seismic Safety ◽  
Rc Structures ◽  
Brittle Damage ◽  
Italian Context

Over the last few decades, the attention on the safety of existing reinforced concrete (RC) structures has significantly increased. RC bridges, in particular, are highly relevant for strategic importance. In the Italian context, several of these bridges were built around 1960, when engineering practice commonly ignored or underestimated the presence of seismic actions. Therefore, it is fundamental to quantify as accurately as possible their seismic safety level with state-of-the-art analysis techniques. In this paper, an efficient procedure based on the multi-modal pushover analysis approach is proposed for the risk evaluation of several bridges of the Italian highway network. This procedure, tailored for portfolio level assessment, takes into account the non-linear behavior and the complex dynamic response this type of structure with limited computational effort. Three fundamental aspects are defined for the structural modelling of bridges, i.e., materials’ constitutive law, finite element type and nonlinear hinge models. Flexural and shear nonlinearities of piers are included to account for ductile and brittle damage potential. The standardized procedure guarantees consistent comparisons among different bridges of the same network in the form of risk indexes.

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