An approach for shake table performance evaluation during repair and retrofit actions

Abstract

SummaryLarge-scale, servo-hydraulic shake tables are a central fixture of many earthquake engineering and structural dynamics laboratories. Wear and component failure from frequent use may lead to control problems resulting in reduced motion fidelity, necessitating repairs and replacement of major components. This paper presents a methodology to evaluate shake table performance preand post-repair, including the definition of important performance metrics.The strategy suggested is presented in the context of the rebuilding of a 4.9 × 3.1 m, 350-kN-capacity uniaxial shake table. In this case, the rebuild consisted of characterization of wear to table components, replacement of worn bearing surfaces, and replacement of hydraulic accumulators. To assess the effectiveness of the repair actions, sinusoidal and triangular waves, white noise, and earthquake histories were run on the table before and after the rebuild. The repair actions were successful in reducing the position and velocity dependence of friction, improving the ability of control algorithms to accurately reproduce earthquake motions. The maximum and average response spectral misfits in the period range of 0.1-2 seconds were reduced from approximately 50% to 15%, and from 5% to less than 2.5%, respectively.

Design, static analysis and development of a new three-legged shake table

“…The static forces in Horizontal plane exhibit similar characteristics for both the manipulator (Figure 10(a) and (b)). The VMA forces are independent of the forces acting in the X-Y plane just as the HMA forces are independent of the forces acting in the Z-axis (discussed using equation (12). The VMA forces are also equal and each VMA force quantify to onethird of the input force (Figure 10(c)).…”

“…The need for such lighter actuators is indicated in the recent shake table literatures, which mention about the future of the shake table technology geared towards utilizing the potency of electro-mechanical actuators 1 because most shake table users prefer lighter actuators. The benefit of such actuation is that they have high frequency response 12 and mechanically compliant system compared to that of hydraulic actuators.…”

“…For steel, the value is 7850 kg/m 3 and for aluminium it is 2700 kg/m 3 R c is the radius of link's circular cross section R top is the radius of the top mobile platform t is the thickness of the mobile platform 2. Actuator static torques are given by equation (12). As discussed in an earlier section, only the HMA forces are considered for optimizing the design parameters because the VMA forces are invariable with regard to the design parameters.…”

Physical Model Tests of Half-Scale Geosynthetic Reinforced Soil Bridge Abutments. I: Static Loading

“…The GRS bridge abutment specimens were constructed on the indoor uniaxial servohydraulic shaking table in the Charles Lee Powell Structural Research Laboratory at the University of California, San Diego (UCSD), which was refurbished prior to this study to increase the fidelity of dynamic motion (Trautner et al 2017). Details of the experimental design and specimen construction are provided by Zheng et al (2018c).…”

Transverse shaking table test of a half-scale geosynthetic reinforced soil bridge abutment

“…The shaking table tests were conducted using the indoor shaking table at the University of California, San Diego (UCSD) Powell Structural Laboratory, which was refurbished prior to this study to increase the fidelity of dynamic motion (Trautner et al 2017). The shaking table has areal footprint dimensions of 5 m × 3 m and a maximum payload capacity of 356 kN.…”