A new lateral force distribution formula for base-isolated structures

The seismic design of new seismically isolated structures is mainly governed by the Uniform Building Code (UBC-97). In the UBC code, the distribution formula of the inertial (or lateral) forces leads to a triangular shape in the vertical direction. It has been found to be too conservative for most isolated structures through experimental, computational and real earthquake examinations. In this paper, four simple and reasonable design formulae, based on the first mode of the base-isolated structures, for the lateral force distribution on isolated structures have been validated by a multiple-bay three-story base-isolated steel structure tested on the shaking table. Moreover, to obtain more accurate results for irregular structures in which higher mode contributions are more likely expected during earthquakes, another four inertial force distribution formulae are also proposed to include higher effects.

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Lateral force distribution on base-isolated structures under near-field earthquakes

Proceedings of the Institution of Civil Engineers - Structures and Buildings ◽

10.1680/stbu.11.00053 ◽

2013 ◽

Vol 166 (7) ◽

pp. 342-354

Author(s):

Faramarz Khoshnoudian ◽

Saeed Esrafili

Keyword(s):

Near Field ◽

Lateral Force ◽

Force Distribution ◽

Isolated Structures

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Developing a simplified method for analysis and design of isolated structures with the novel quintuple friction pendulum system under bidirectional near-field excitations

Journal of Vibration and Control ◽

10.1177/10775463211048261 ◽

2021 ◽

pp. 107754632110482

Author(s):

Hamed Keikha ◽

Gholamreza Ghodrati Amiri

Keyword(s):

Nonlinear Response ◽

Near Field ◽

Lateral Force ◽

History Analysis ◽

Special Cases ◽

Simplified Method ◽

Response History Analysis ◽

Nonlinear Response History Analysis ◽

Isolated Structures ◽

Friction Pendulum

Simplified analysis methods for seismically isolated structures proposed in recent structural codes and specifications are frequently used to reduce the computational effort and to simplify the design procedure, either directly for special cases or for checking the results of nonlinear response history analysis. Of the approximate methods, the equivalent lateral force procedure using the effective stiffness and effective damping is one of the best known. In this study, the simplified method is developed by combining the equivalent lateral force procedure with the capacity spectrum method and evaluated in terms of maximum isolator displacements and base shears for isolated structures with recently invented quintuple friction pendulum isolators , with different geometrical and frictional properties, under two different response spectra with corresponding two different sets of bidirectional near-field ground motions for stiff and soft soils site classes. In order to assess the accuracy of the simplified method, the delivered results of the ELF procedure are compared to those of nonlinear response history analysis, by modelling the quintuple friction pendulum isolator 3D element in OpenSees. Eventually, comments on the accuracy of the simplified method are given to make its applications more appropriate in practical design of base isolation systems.

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Simultaneous Optimal Distribution of Lateral and Longitudinal Tire Forces for the Model Following Control

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.1850533 ◽

2004 ◽

Vol 126 (4) ◽

pp. 753-763 ◽

Cited By ~ 157

Author(s):

Ossama Mokhiamar ◽

Masato Abe

Keyword(s):

Lateral Force ◽

Longitudinal Force ◽

Equality Constraints ◽

Steering Wheel ◽

Slip Angle ◽

Force Distribution ◽

Distribution Method ◽

Tire Force ◽

Model Following Control ◽

Tire Forces

This paper presents a proposed optimum tire force distribution method in order to optimize tire usage and find out how the tires should share longitudinal and lateral forces to achieve a target vehicle response under the assumption that all four wheels can be independently steered, driven, and braked. The inputs to the optimization process are the driver’s commands (steering wheel angle, accelerator pedal pressure, and foot brake pressure), while the outputs are lateral and longitudinal forces on all four wheels. Lateral and longitudinal tire forces cannot be chosen arbitrarily, they have to satisfy certain specified equality constraints. The equality constraints are related to the required total longitudinal force, total lateral force, and total yaw moment. The total lateral force and total moment required are introduced using the model responses of side-slip angle and yaw rate while the total longitudinal force is computed according to driver’s command (traction or braking). A computer simulation of a closed-loop driver-vehicle system subjected to evasive lane change with braking is used to prove the significant effects of the proposed optimal tire force distribution method on improving the limit handling performance. The robustness of the vehicle motion with the proposed control against the coefficient of friction variation as well as the effect of steering wheel angle amplitude is discussed.

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SEISMIC LATERAL FORCE DISTRIBUTION FOR DUCTILITY-BASED DESIGN OF STEEL PLATE SHEAR WALLS

Journal of Earthquake and Tsunami ◽

10.1142/s1793431112500042 ◽

2012 ◽

Vol 06 (01) ◽

pp. 1250004 ◽

Cited By ~ 4

Author(s):

SWAPNIL B. KHARMALE ◽

SIDDHARTHA GHOSH

Keyword(s):

Steel Plate ◽

Shear Walls ◽

Shear Wall ◽

Lateral Force ◽

Performance Based Design ◽

Force Distribution ◽

Steel Plate Shear Walls ◽

Steel Plate Shear Wall ◽

Design Requirements ◽

Ductility Ratio

The thin unstiffened steel plate shear wall (SPSW) system has now emerged as a promising lateral load resisting system. Considering performance-based design requirements, a ductility-based design was recently proposed for SPSW systems. It was felt that a detailed and closer look into the aspect of seismic lateral force distribution was necessary in this method. An investigation toward finding a suitable lateral force distribution for ductility-based design of SPSW is presented in this paper. The investigation is based on trial designs for a variety of scenarios where five common lateral force distributions are considered. The effectiveness of an assumed trial distribution is measured primarily on the basis of how closely the design achieves the target ductility ratio, which is measured in terms of the roof displacement. All trial distributions are found to be almost equally effective. Therefore, the use of any commonly adopted lateral force distribution is recommended for plastic design of SPSW systems.

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