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 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.

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 A macromodel substitute for simple prediction of the lateral behaviour of composite shear walls

2018 ◽  
Vol 51 (3) ◽  
pp. 115-126
Author(s):  
Farhad Behnamfar ◽  
Esmail Shakeri ◽  
Akbar Makhdoumi
Keyword(s):  
Steel Plate ◽  
Three Dimensional ◽  
Shear Walls ◽  
Lateral Force ◽  
Concrete Cover ◽  
Three Dimensional Model ◽  
Composite Wall ◽  
Dimensional Element ◽  
Composite Shear ◽  
Force Displacement

Composite shear wall is a structural component consisting of a steel plate connected using shear tabs to a reinforced concrete cover. The steel plate provides for stiffness, strength, and ductility and the concrete cover prevents the steel plate from buckling. In this paper, effects of steel plate's thickness, compressive strength and thickness of the concrete cover and spacing of the shear tabs on the characteristics of the wall in nonlinear lateral behaviour are evaluated and a macromodel substitute for the wall is developed. The macromodel is a generic lateral force-displacement rule for the wall with its characteristics as developed in this paper. Practical ranges of values are accounted for the parameters involved. Such an approach makes it possible to replace the very complicated and time-consuming three-dimensional model of the composite wall with a simple one-dimensional element following the nonlinear lateral force-displacement path as given in this paper.

Modal Analysis of Helical Milling Unit

2012 ◽  
Vol 482-484 ◽  
pp. 2454-2459 ◽  
Author(s):  
Xu Da Qin ◽  
Cui Lu ◽  
Qi Wang ◽  
Hao Li ◽  
Lin Jing Gui
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Element Model ◽  
Helical Milling ◽  
Mode Shapes ◽  
Three Dimensional Model ◽  
Working Principle ◽  
The Finite Element Model

Based on the analysis of the working principle and structure characteristics of helical milling unit, the prototype’s three-dimensional model was built, the prototype’s finite element modal analysis was conducted, and the first 6 natural frequencies and their mode shapes were obtained. The finite element model is experimentally validated by comparing finite element and experimental modal’s parameters. This paper investigates the dynamic properties of prototype, and provides theoretical references for the subsequent dynamic analysis and structural optimization.

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.

scholarly journals Effect of Damping and Yielding on the Seismic Response of 3D Steel Buildings with PMRF

2014 ◽  
Vol 2014 ◽  
pp. 1-21 ◽  
Author(s):  
Alfredo Reyes-Salazar ◽  
Achintya Haldar ◽  
Ramon Eduardo Rodelo-López ◽  
Eden Bojórquez
Keyword(s):  
Seismic Response ◽  
Three Dimensional ◽  
Lateral Force ◽  
Viscous Damping ◽  
Steel Buildings ◽  
Local Response ◽  
Equivalent Viscous Damping ◽  
Response Parameter ◽  
Mdof Systems ◽  
Crude Approximation

The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

scholarly journals Student Learning about Biomolecular Self-Assembly Using Two Different External Representations

2013 ◽  
Vol 12 (3) ◽  
pp. 471-482 ◽  
Author(s):  
Gunnar E. Höst ◽  
Caroline Larsson ◽  
Arthur Olson ◽  
Lena A. E. Tibell
Keyword(s):  
Student Learning ◽  
Self Assembly ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
External Representations ◽  
Three Dimensional Model ◽  
Written Responses ◽  
Significant Difference ◽  
Model Condition ◽  
The Impact

Self-assembly is the fundamental but counterintuitive principle that explains how ordered biomolecular complexes form spontaneously in the cell. This study investigated the impact of using two external representations of virus self-assembly, an interactive tangible three-dimensional model and a static two-dimensional image, on student learning about the process of self-assembly in a group exercise. A conceptual analysis of self-assembly into a set of facets was performed to support study design and analysis. Written responses were collected in a pretest/posttest experimental design with 32 Swedish university students. A quantitative analysis of close-ended items indicated that the students improved their scores between pretest and posttest, with no significant difference between the conditions (tangible model/image). A qualitative analysis of an open-ended item indicated students were unfamiliar with self-assembly prior to the study. Students in the tangible model condition used the facets of self-assembly in their open-ended posttest responses more frequently than students in the image condition. In particular, it appears that the dynamic properties of the tangible model may support student understanding of self-assembly in terms of the random and reversible nature of molecular interactions. A tentative difference was observed in response complexity, with more multifaceted responses in the tangible model condition.

Structural dynamic properties of a reinforced concrete high-rise building during construction

1996 ◽  
Vol 23 (4) ◽  
pp. 950-972 ◽  
Author(s):  
Carlos E. Ventura ◽  
Norman D. Schuster
Keyword(s):  
Reinforced Concrete ◽  
Structural Dynamics ◽  
Dynamic Properties ◽  
Three Dimensional ◽  
Lateral Force ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Structural Dynamic ◽  
High Rise ◽  
High Rise Building

This paper presents the results of a study on the variability of the dynamic properties of an irregular high-rise building during its construction. Most of the knowledge about structural dynamics of high-rise reinforced concrete buildings is based on uniform structures. Hence, there is concern about extrapolating this knowledge to the behaviour of nonuniform building that emerge from current architectural trends. A clear example of these trends is the building selected for this study. This 30-storey reinforced concrete building is representative of the type of current construction in Vancouver, British Columbia. The lateral force resisting system in this structure is uniform in plan and elevation, while the distribution of storey mass is asymmetrical owing to its geometry as well as a major setback at one corner. Dynamic characteristics were determined by analyzing ambient vibrations of the structure. The objectives of this study included determining natural frequencies and corresponding mode shapes, determining the effect of architectural components, assessing base motion, and assessing the manner of the core's deformation. In addition, a three-dimensional dynamic analysis was performed to assess the accuracy of modeling techniques. Finally, base shears and overturning moments during different stages of construction were assessed in accordance with current building codes. Key words: structural dynamics, ambient vibration measurements, earthquakes, building construction, mode shapes and frequencies.

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 Optimization model for polycrystalline diamond compact bits based on reverse design

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878149 ◽  
Author(s):  
Zhijiu Ai ◽  
Yiwei Han ◽  
Yuchun Kuang ◽  
Yuanji Wang ◽  
Mingming Zhang
Keyword(s):  
Design Method ◽  
Three Dimensional ◽  
Polycrystalline Diamond ◽  
Lateral Force ◽  
Design Parameters ◽  
Three Dimensional Model ◽  
Cloud Data ◽  
Cutter Design ◽  
Unbalance Force ◽  
Polycrystalline Diamond Compact

To improve the effectiveness and efficiency of bit cutter design, a new reverse design method is put forward based on the geometry of a polycrystalline diamond compact bit. The polycrystalline diamond compact bit design parameters (cutter parameters and polycrystalline diamond compact bit profile) are calculated based on the data obtained by three-dimensional scanning technology. The main calculation work is realized using MATLAB. Compared with using point cloud data, using the three-dimensional model based on calculated cutter parameters also provides accurate results. Then, the cutter parameters are optimized according to the minimum lateral force principle, minimizing the maximum wear rate principle. The lateral unbalance force of the bit decreases from 7.55%, for the original bit, to 3.17%, for the optimized bit, and the wear of the optimized drill bit is more uniform. The field data show that the optimization models create bits with a longer life and a higher rate of penetration.

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