in Civil Engineering 

The seismic laboratory testing facility at California State University, Fresno, is under the supervision of Prof. Thomas Attard, whose research areas include earthquake engineering, nonlinear structural control, and nonlinear structural dynamics.  Dr. Attard’s research program currently includes 7 graduate student researchers.  Dr. Attard is also grateful to friend and colleague Dr. Michael Symans of Rensselaer Polytechnic Institute (RPI) for his valuable input that was used in the design of the shaking table. 

The shaking table "Atlas" shown was manufactured by D.A.D. Welding in Fresno, California.  A SolidWorks rendition is also shown below.  The table is 8 feet long and 6-3/4 feet wide and can accommodate testing of a variety of structures subjected to various types of excitations.  The maximum allowable weight that can be placed on the table is 40,000 pounds.  The testing of medium-scale two and three story buildings under various uni-axial earthquake feeds is supplied through a displacement-controlled actuator that are monitored and compensated through a multi-stage servo-valve controller.

An MTS hydraulic actuator (55 kips, +/- 5 inch stroke) imparts the simulated ground force to the table in order to generate the desired earthquake motion.  The pump is equipped with two 100 HP electric motors capable of delivering 100 gallons per minute of hydraulic fluid flow at 3000 psi. The hydraulic delivery system is capable of shaking a 40,000lb structure at +/-3 inches and 1.5 g’s at a frequency of 2.2 Hz.

The hydraulics system also includes 5 gallons of accumulation used for in-line pressure and a new Hydraulic Service Manifold (HSM 293.32) purchased from MTS.  These items were the result of grant support from several local engineering companies and individuals.  The servo-hydraulics controller also includes capability to feedback the corrected error back to the table to match the various excitations and to ultimately mimic various ground frequency spectra. 

Some of the manufacturing details are discussed below.

Seventy holes were drilled in 2-inch thick supporting plates with a 1/2 inch countersink to ensure a flush connection.  This was accomplished using a magnetic drill and a modified milling machine attachment.

A "slider" rail is mounted on the above plate and includes 52 drilled countersunk holes.  

The table includes 192 holes and has nuts welded to the underside of the table top, which was done in lieu of tapping the holes.

This is the manufactured raw shaking table top where the 192 holes are drilled in an array format to enable various structural base connections.