NHERI @ UC San Diego

Shake Table Specifications

Large High-Performance Outdoor Shake Table - OverheadFull Size

The design criteria and main specifications of the shake table system were dictated by consideration of a number of potential research applications involving large or full-scale shake table experiments and a variety of earthquake ground motions. The resulting performance parameters including specifications for actuator stroke, velocity and force capacities, and frequency bandwidth of the earthquake simulator are summarized in the table below.

Size 7.6 m × 12.2 m
Peak acceleration: bare table, 400 ton payload 4.2 g, 1.2 g
Peak velocity 1.8 m/s
Stroke ±0.75 m
Maximum gravity (vertical) payload 20 MN
Force capacity of actuators 6.8 MN
Maximum overturning moment: bare table, 400 ton specimen 35 MN-m, 50 MN-m
Frequency bandwidth 0 — 33 Hz
Performance envelope view [pdf]
Shake Table 3D view [dwg]
EFS Building view [dwg]
Safety Tower Footprint view [dwg]

In deciding on these parameters, far-source (or "ordinary") and near-source earthquake ground motions to be reproduced by the shake table were considered. A maximum horizontal peak ground and peak table acceleration of just over 1g was selected based on the upper bound for the vast majority of recorded ground motion records. To determine the maximum force of 6.8 MN to be imparted by the shake table actuators and a maximum overturning moment of 50 MN-m to be accommodated by the platen and its support mechanism, many factors were considered. A suite of desired large or full-scale specimens for the shake table experiments was taken into account, as well as the assumed mass of the platen including elastic and inelastic dynamic amplification effects (230 Ton), the assumed effective height of the specimen (10 m), as well as dynamic similitude requirements.

It was essential that the LHPOST be able to accurately reproduce near-fault ground motion effects. The reproduction capability of near-source ground motions by the shake table is controlled by the peak table velocity parameter. A peak table velocity of 1.8 m/s was selected by considering a set of representative near-source records used extensively in numerical earthquake engineering research. When the laminar shear box is mounted on the table, additional amplification takes place within the soil box and the peak velocity on the soil surface can exceed 1.8 m/sec.