The table supports the specimen that is to be tested and provides threaded mss with minimounting holes for securing the specimen to the table. The table is constructed to provide high stiffneum possible weight. Reinforced sections of the table accommodate attachment of the hydraulic actuators. Two table assemblies are provided. Each table assembly consists of the table, four base plate-bearing assemblies, bumper boxes, and preloader assemblies. The biaxial table assembly also has a crossbrace assembly.

Three hydraulic power units (MTS 506.82, MTS 506.62, and MTS 506.41) provide the pressurized hydraulic fluid to the hydraulic distribution system in direct response to control signals received from the Remote Pump Control Panel.

The hydraulic service manifolds use check valves, pressure relief valves, accumulators, and solenoid controlled valves to adjust the hydraulic pressure to the MTS multi-stage servovalves and blowdown system.

The blowdown accumulators are used to maintain system performance during short-term, high-demand test conditions. There is one blowdown system for each actuator.

Flow averaging accumulators mounted on each leg of the main pressure piping and the main return piping reduce the pressure fluctuations in the hydraulic system.

A sump pump returns hydraulic fluid that has accumulated in the sump reservoir to the hydraulic fluid reservoir through the main return pipe.

The actuators provided for the seismic test system are specially designed for high performance. Externally mounted actuators are attached to the seismic table and external buttresses with swivel mounting fixtures. An internally mounted actuator is located under the table and is attached to the table and internal buttress. A linear variable differential transformer (LVDT) is mounted inside the actuator to provide an electrical feedback signal that indicates the actuator position. The Series 244.50S actuator has a dynamic stroke of 12 inches (300 mm).

The actuators are equipped with multistage servovalves which control the direction and amount of fluid flow to the actuators. The actuators have two Series 256.25 servovalves which provide a total rated flow of 500 gpm (1890 lpm).

The 469D digital real-time controller provides closed-loop control of table motion and the operator interface to the system. The controller provides programming and feedback summing to ensure faithful reproduction of the desired waveform on the shaking table surface so that accurate tests on the specimen can be conducted and evaluated.

The Digital Computer Subsystem is used for table programming, control and compensation, and data acquisition and analysis. It consists ofcomputer systems, data acquisition system, and software packages.