Due to its simplicity, the structural engineering profession has been using the nonlinear static procedure (NSP) or pushover analysis. Modeling for such analysis requires the determination of the nonlinear properties of each component in the structure, quantified by strength and deformation capacities, which depend on the modeling assumptions. Pushover analysis is carried out for either user-defined nonlinear hinge properties or default-hinge properties, available in some programs based on the FEMA-356 and ATC-40 guidelines. While such documents provide the hinge properties for several ranges of detailing, programs may implement averaged values. The user needs to be careful; the misuse of default-hinge properties may lead to unreasonable displacement capacities for existing structures. This paper studies the possible differences in the results of pushover analysis due to default and user-defined nonlinear component properties. Four- and seven-story buildings are considered to represent low- and medium- rise buildings for this study. Plastic hinge length and transverse reinforcement spacing are assumed to be effective parameters in the user-defined hinge properties. Observations show that plastic hinge length and transverse reinforcement spacing have no influence on the base shear capacity, while these parameters have considerable effects on the displacement capacity of the frames. Comparisons point out that an increase in the amount of transverse reinforcement improves the displacement capacity. Although the capacity curve for the default-hinge model is reasonable for modern code compliant buildings, it may not be suitable for others. Considering that most existing buildings in Turkey and in some other countries do not conform to requirements of modern code detailing, the use of default hinges needs special care. The observations clearly show that the user-defined hinge model is better than the default-hinge model in reflecting nonlinear behavior compatible with the element properties. However, if the default-hinge model is preferred due to simplicity, the user should be aware of what is provided in the program and should avoid the misuse of default-hinge properties.
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Effect of Lateral Load Patterns in Pushover Analysis
Author: Abhilash R. Biju V. Rahul Leslie | Size: 0.25 MB | Format:PDF | Quality:Unspecified | Publisher: 0th National Conference on Technological Trends (NCTT09) 6-7 Nov 2009 College of Engineering Trivandrum 138 | Year: 2009 | pages: 5
Pushover analysis is a static, nonlinear procedure in
which the magnitude of the structural loading is incrementally
increased in accordance with a certain predefined pattern. With
the increase in the magnitude of the loading, weak links and
failure modes of the structure are found. Static pushover analysis is an attempt by the structural engineering profession to evaluate the real strength of the structure and it promises to be a useful and effective tool for performance based design. The performance point of the structure depends on the lateral load pattern applied,on the structure. Commonly applied load patterns are inverted triangle and uniformly distributed. Then guidelines like FEMA257 & 356 provide guidelines for lateral loads and doing pushover analysis. Here pushover analysis is done a typical RCC structure by applying different lateral load patterns using ETABS and SAP2000. The lateral load patterns used here are uniform load distribution and equivalent lateral force distribution as per FEMA-257, lateral loads from response spectrum analysis as per IS-1893(2002) and the lateral load pattern as per Upper-Bound Pushover analysis method.
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Pushover Analysis of Medium Rise Multi-Story RCC Frame With and Without Vertical Irregularity
Author: Mohommed Anwaruddin Md. Akberuddin*, Mohd. Zameeruddin Mohd. Saleemuddin ** | Size: 0.93 MB | Format:PDF | Quality:Unspecified | Publisher: M A M Akberuddin et al. Int. Journal of Engineering Research and Application Vol. 3, Issue pp.540-546 | Year: 5, Sep-Oct 2013, | pages: 7
he performance of a structural system can be evaluated resorting to non-linear static analysis. This involves the
estimation of the structural strength and deformation demands and the comparison with the available capacities
at desired performance levels. This study aims at evaluating and comparing the response of five reinforced concrete building systems by the use of different methodologies namely the ones described by the ATC-40 and the FEMA-273 using nonlinear static procedures, with described acceptance criteria. The methodologies are applied to a 3 storey frames system with and without vertical irregularity, both designed as per the IS 456-2000 and IS 1893-2002 (Part II) in the context of Performance Based Seismic Design procedures. Present study aims towards doing Nonlinear Static Pushover Analysis of G+3 medium rise RCC residential building frame which is to be designed by Conventional Design Methodology. A Nonlinear Static Analysis (Pushover Analysis) had been used to obtain the inelastic deformation capability of frame. It was found that irregularity in elevation of the building reduces the performance level of structure there is also decrease in deformation or displacement of the building.
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A QUASISTATIC ANALYSIS METH OD TO IMPROVE COLLAPSE MECHANISM ANALYSES OF MULTISTORY BUILDINGS
Author: Masato SAITOH , Masaki IKEGAME and Shiro TANAMURA | Size: 0.45 MB | Format:PDF | Quality:Unspecified | Publisher: 13th World Conference on Earthquake Engineering Vancouver, B.C., Canada Paper No. 1284 | Year: August 1-6, 2004 | pages: 10
This study proposes a quasi-static analysis method to improve the reliability of conventional collapse
mechanism analyses of multi-story buildings. This method is based on the hypothesis that the incremental
deformations of the buildings subjected to earthquakes are proportional to the eigenvectors evaluated by using equivalent story stiffness and damping. In this method, the incremental displacements proportional to the eigenvectors are accumulated in the story drifts of the buildings; the eigenvectors are estimated by performing modal analyses whenever an inelastic event occurs in the stories. The analytical results indicate that the conventional pushover analysis generally overestimates the first story drift, while the quasi-static method tends to give good agreements with the results evaluated by the time history analysis.
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Pushover analysis for the seismic response prediction of cable-stayed bridges under multi-directional excitation
Author: A. Cámara *, MA Astiz Department of Mechanics and Structures, School of Civil Engineering, Technical University of Madrid, Prof. Aranguren s/n, Madrid, Spain | Size: 5.9 MB | Format:PDF | Quality:Unspecified
Cable-stayed bridges represent nowadays key points in transport networks and their seismic behavior needs to be fully understood, even beyond the elastic range of materials. Both nonlinear dynamic (NL- RHA) and static (pushover) procedures are currently available to face this challenge, each with intrinsic advantages and disadvantages, and their applicability in the study of the nonlinear seismic behavior of cable-stayed bridges is discussed here. The seismic response of a large number of finite element models with different span lengths, tower shapes and class of foundation soil is obtained with different procedures and compared. Several features of the original Modal Pushover Analysis (MPA) are modified in light of cable-stayed bridge characteristics, furthermore, an extension of MPA and a new coupled pushover analysis (CNSP) are suggested to estimate the complex inelastic response of such outstanding structures subjected to multi-axial strong ground motions.
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SING THE NEW SAP2000 OPEN APPLICATION PROGRAMMING INTERFACE TO DEVELOP AN INTERACTIVE FRONT-END FOR THE MODAL PUSHOVER ANALYSIS OF BRIDGES
Author: A. G. Sextos and G. K. Balafas | Size: 0.72 MB | Format:PDF | Quality:Unspecified | Publisher: COMPDYN 2011 3rd ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering M. Papadrakakis, M. Fragiadakis, V. Plevris (eds.) Corfu, Greece, | Year: 25–28 May 2011 | pages: 14
Seismic assessment of bridge structures often requires inelastic (static or dynamic) analysis methods to be used, in order to draw a realistic evaluation of the structural behaviour
beyond the elastic range. While the widely-used non-linear static (pushover) analysis provides a low-computational-cost approach to this direction, it is inherently limited by the assumption that the structure's response is solely controlled by its fundamental mode. This limitation is raised by an extension of the “standard” pushover analysis (SPA) to take into consideration the effect of higher modes , a method known as Modal Pushover Analysis (MPA). This method however, can often prove to be time-consuming and strenuous both for pre- and post processing. The latter, provided the motivation for investigating the feasibility to take advantage of the recently released SAP2000 application programming interface (API) in order to develop a new computational tool that implements the MPA specifications for evaluating the seismic behavior of bridges in an organized and automatic fashion. The paper concludes with the application and demonstration of the software developed, for the case of an existing reinforced concrete bridge located along the Egnatia Highway in Greece.
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