scholarly journals Evaluation of Modal and FEMA Pushover Analyses: SAC Buildings

2004 ◽  
Vol 20 (1) ◽  
pp. 225-254 ◽  
Author(s):  
Rakesh K. Goel ◽  
Anil K. Chopra
Keyword(s):  
Los Angeles ◽  
Pushover Analysis ◽  
Lateral Force ◽  
Elastic Response ◽  
Seismic Demands ◽  
Lateral Capacity ◽  
Wide Range ◽  
Response History Analysis ◽  
Fema 356 ◽  
Plastic Rotations

This paper comprehensively evaluates the Modal Pushover Analysis (MPA) procedure against the “exact” nonlinear response history analysis (RHA) and investigates the accuracy of seismic demands determined by pushover analysis using FEMA-356 force distributions; the MPA procedure in this paper contains several improvements over the original version presented in Chopra and Goel (2002). Seismic demands are computed for six buildings, each analyzed for 20 ground motions. It is demonstrated that with increasing number of “modes” included, the height-wise distribution of story drifts and plastic rotations estimated by MPA becomes generally similar to trends noted from nonlinear RHA. The additional bias and dispersion introduced by neglecting “modal” coupling and P-Δ effects due to gravity loads in MPA procedure is small unless the building is deformed far into the inelastic range with significant degradation in lateral capacity. A comparison of the seismic demands computed by FEMA-356 NSP and nonlinear RHA showed that FEMA-356 lateral force distributions lead to gross underestimation of story drifts and completely fail to identify plastic rotations in upper stories compared to the values from the nonlinear RHA. The “Uniform” force distribution in FEMA-356 NSP seems unnecessary because it grossly overestimates drifts and plastic rotations in lower stories and grossly underestimates them in upper stories. The MPA procedure resulted in estimates of demand that were much better than from FEMA force distributions over a wide range of responses—from essentially elastic response of Boston buildings to strongly inelastic response of Los Angeles buildings. However, pushover analysis procedures cannot be expected to provide satisfactory estimates of seismic demands for buildings deforming far into the inelastic range with significant degradation of the lateral capacity; for such cases, nonlinear RHA becomes necessary.

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.

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.

A Seismic Design Lateral Force Distribution Based on Inelastic State of Structures

2007 ◽  
Vol 23 (3) ◽  
pp. 547-569 ◽  
Author(s):  
Shih-Ho Chao ◽  
Subhash C. Goel ◽  
Soon-Sik Lee
Keyword(s):  
Seismic Design ◽  
Lateral Force ◽  
Elastic Response ◽  
Force Distribution ◽  
Relative Distribution ◽  
Inelastic Behavior ◽  
Seismic Demands ◽  
Framed Structures ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses

It is well recognized that structures designed by current codes undergo large inelastic deformations during major earthquakes. However, lateral force distributions given in the seismic design codes are typically based on results of elastic-response studies. In this paper, lateral force distributions used in the current seismic codes are reviewed and the results obtained from nonlinear dynamic analyses of a number of example structures are presented and discussed. It is concluded that code lateral force distributions do not represent the maximum force distributions that may be induced during nonlinear response, which may lead to inaccurate predictions of deformation and force demands, causing structures to behave in a rather unpredictable and undesirable manner. A new lateral force distribution based on study of inelastic behavior is developed by using relative distribution of maximum story shears of the example structures subjected to a wide variety of earthquake ground motions. The results show that the suggested lateral force distribution, especially for the types of framed structures investigated in this study, is more rational and gives a much better prediction of inelastic seismic demands at global as well as at element levels.

A subset of CyberShake ground-motion time series for response-history analysis

2021 ◽  
pp. 875529302098197
Author(s):  
Jack W Baker ◽  
Sanaz Rezaeian ◽  
Christine A Goulet ◽  
Nicolas Luco ◽  
Ganyu Teng
Keyword(s):  
Time Series ◽  
Los Angeles ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Motion Time ◽  
History Analysis ◽  
Response History Analysis ◽  
Simulated Ground Motions

This manuscript describes a subset of CyberShake numerically simulated ground motions that were selected and vetted for use in engineering response-history analyses. Ground motions were selected that have seismological properties and response spectra representative of conditions in the Los Angeles area, based on disaggregation of seismic hazard. Ground motions were selected from millions of available time series and were reviewed to confirm their suitability for response-history analysis. The processes used to select the time series, the characteristics of the resulting data, and the provided documentation are described in this article. The resulting data and documentation are available electronically.

Cost of Speed: Analysis of Capital Cost Estimates for High-Speed Ground Transportation Systems

1997 ◽  
Vol 1584 (1) ◽  
pp. 17-21
Author(s):  
John A. Harrison
Keyword(s):  
Los Angeles ◽  
High Speed ◽  
Capital Cost ◽  
Travel Times ◽  
Department Of Transportation ◽  
High Speed Rail ◽  
Cost Estimates ◽  
Capital Costs ◽  
Trip Time ◽  
Wide Range

The Intermodal Surface Transportation Efficiency Act of 1991 required the U.S. Department of Transportation to evaluate the commercial feasibility of high-speed ground transportation—a family of technologies ranging from incremental rail improvements to high-speed rail and magnetic levitation (Maglev) systems—in selected urban corridors. The evaluation involved estimating travel times, capital costs, operation and maintenance costs, and ridership for proposed service frequencies and then computing the potential return on investment from fares and other potential revenues. The results are documented in a U.S. Department of Transportation report generally referred to as the commercial feasibility study (CFS). Two elements of the CFS are addressed here: travel times and capital costs in four illustrative corridors—Chicago to St. Louis; Los Angeles to San Francisco; Eugene, Oreg., to Vancouver, B.C.; and Miami to Tampa via Orlando. Analysis of the results reveals common cost trends: for average speeds up to about 200 km/hr (125 mph), the initial investment required is generally in the range $1.6 to $3 million per route-kilometer ($2.6 to 4.8 million per route-mile). Above this speed regime (which varies by corridor), the initial investment increases steadily with speed, generally reaching $10 to $12 million per route-km ($16 to $19 million per route-mi) for very-high-speed rail systems and from $14 to $19 million per route-km ($23 to $31 million per route-mi) for Maglev systems. Analysis of the capital cost estimates reveals that despite the wide range of initial costs for the high-speed options, the cost per minute of trip time saved is remarkably consistent in corridors of similar length and with similar terrains. Cost-effectiveness plots are provided, allowing the reader to compare the performance of each of the four corridors in terms of trip time savings and cost per route-kilometer.

SFM and TOF-SIMS Study of Novel Self-Organization phenomena in mixed LB monolayers

2002 ◽  
Vol 738 ◽  
Author(s):  
B. Pignataro ◽  
L. Sardone ◽  
A. Licciardello ◽  
G. Marletta
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Scanning Force Microscopy ◽  
Lateral Force ◽  
Self Organization ◽  
High Mass ◽  
Molar Ratio ◽  
Force Microscopy ◽  
Tof Sims ◽  
Wide Range ◽  
Scanning Force

ABSTRACTMixed monolayers of dimyristoylphosphatidylcholine (DMPC) and quercetin palmitate (QP) in a molar ratio of 25/75 have been transferred on mica and oxygen plasma cleaned silicon by the Langmuir-Blodgett (LB) technique at different subphase temperatures. Scanning Force Microscopy (SFM) in height, phase and lateral force modes has been employed to investigate the structural and mechanical features at nanoscopic level of these samples. Although the two molecules show a wide range of miscibility at 37 °C, they give rise to phase separation at 10 °C. This last system provides a new example of nanometric scale self-organization. In particular spiral shaped domains rising from the wrapping-up of nanoscopic fiber-like structures have been observed. The high resolution achieved by the use of the dynamic scanning force microscopy operating in the net attractive regime allow to visualize characteristic nanoscopic rupture points along the supramolecular fibers. High mass resolution Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) spectra showed DMPC- as well as QP-related peaks. The ToF-SIMS spectra from the nanostructured samples (10 °C) have been compared with those from the homogeneous ones (37 °C). The phase separated samples provides interesting secondary ions that highlight the QP supramolecular condensation within the fiber-like structures.

Sign in / Sign up

Export Citation Format

Share Document