Session 6.1 - Dynamic Analysis

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A New Algorithm for Non-linear Dynamic Structural Analysis

B.W. Golley, A.D. Mitchell and J. Petrolito

The analysis of structures under dynamic loading is generally carried out using time stepping methods, of which the most popular is Newmark's method. In most non-linear methods, dynamic equilibrium is satisfied at the ends of the time step, although in some methods it is satisfied at the midpoint. In this paper, linear structures are first considered, and properties of the exact amplification matrix are noted. An approximate procedure is then developed using cubic interpolation, with coefficients being chosen using weighted residuals with unspecified weight functions. Properties of the weight functions are then determined such that the amplification matrix is of a similar form to the exact matrix, and are unconditionally stable, permits controlled algorithmic damping and is of the maximum available accuracy. The procedure is shown to be equivalent to a weighted sum procedure based on two pairs of sampling points, thus satisfying dynamic equilibrium in an average sense. The weighted sum procedure is ideal for solving non-linear problems.

Paper 020: [Read][Print]

Keywords: time stepping, unconditional stability, weighted integrals

Probabilistic Seismic Hazard Analysis of Semi-active Control of Tall Structures

J.G. Chase, L. Barroso and S. Hunt

The structural engineering community has been making great strides in recent years to develop performance-based earthquake engineering methodologies for both new and existing construction. Structural control can provide an additional method to meet desired performance objectives. Design of a structure/controller system should involve a thorough understanding of how various types of controllers enhance structural performance, such that the most effective type of controller is selected for the given structure and seismic hazard. This research develops probabilistic seismic demand curves to evaluate the performance of semi-active control systems under seismic excitations, so that the probability that any damage measure exceeds a pre-determined allowable limit can be determined. This study focuses on steel moment resisting frames, specifically the nine-story SAC Phase II structure designed for the Los Angeles region. Several controllers are developed for each structure, and their performance is judged based on the drift, dissipated hysteretic energy, and floor acceleration demands. The use of a probabilistic format allows for a consideration of structural response over a range of seismic hazards. The resulting annual demand hazard curves can be used to evaluate the effect of different control parameters as well as provide a basis for comparison between different control strategies.

Paper 028: [Read][Print]

Keywords: seismic hazard analysis, performance based design, structural control, semi-active control

Seismic Engineering for Replacement Research Reactor in Australia

K. Kayvani, B. Schmidt, J. Steele and G. Sidwell

This paper describes various aspects of the seismic engineering of the Replacement Research Reactor Project (RRRP) at Lucas Heights near Sydney, Australia. They include: seismic hazard studies; codes and criteria; 3D response spectral analyses of the Reactor Building and design of shear walls; 3D time history analysis of the Reactor Building under synthetically generated ground accelerations; derivation of floor spectra for equipment design; seismic qualification of the Reactor Block; and Beyond Design Basis assessment of the Reactor Building using push over analysis.

Paper 105: [Read]

Keywords: Research Reactor,Seismic, Nuclear, Time History Analysis, Floor Spectra

An Efficient Model for Seismic Analysis of Building Structures with the Effect of Floor Slabs

D-G Lee, S-K Ahn and D-K Kim

Most building structures consist of structural elements such as beams, columns, braces, shear walls, foundations, and floor slabs. In general, the models used for the analysis of building structures are prepared without the floor slabs, assuming that they would have negligible effects on the response of a structure. Therefore, the floor slabs are simply replaced by rigid floor diaphragms for efficiency in the analysis. Several researchers attempted to study the effects of floor slabs using finite element models with refined plate element meshes to account for the flexural stiffness of floor slabs. Since beams and floor slabs are not located in a common plane, in general, rigid bodies shall be introduced to represent the T-beam effects. Therefore, the model used in the analysis of building structures with floor slabs would have refined finite element meshes with too many degrees of freedom to be used for the practical engineering purpose. The analytical model was proposed in this study for the efficient seismic analysis of building structures considering the flexural stiffness of floor slabs. The proposed models employ super elements, rigid diaphragms, and the substructuring technique to minimize the number of degrees of freedom to be used in the analysis. Analyses of several example structures were performed to verify the efficiency and the accuracy of the proposed model in the seismic analysis of multistory building structures. The proposed model could provide seismic response of the example structures in significantly reduced computational times while the accuracy in the analysis results such as vibration periods and response time histories were very close to those obtained from the refined model.

Paper 045: [Read][Print]


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