Civil Engineering's Seismic Shaker Table

The seismic laboratory testing facility at the California State University Fresno is under the supervision of Prof. Thomas Attard, whose primary research areas are in earthquake engineering, structural control, and nonlinear structural dynamics.  Dr. Attard’s research program currently includes 3 graduate student researchers and 2 undergraduate researchers. Scroll down for photos.

The image above is of a Solidworks rendering of the Final Design. DAD Welding will be fabricating the table and all associated hardware. The table will be 8 feet in length and 6-1/2 feet wide with a flat steel top used for testing various structures under seismic load. When completed, the facility will have the capability to test medium-scale two and three story buildings under various uni-axial earthquake feeds supplied through a displacement-controlled actuator that will be monitored and compensated through a multi-stage servo-valve controller (See description below).

 

In addition to the 70 holes that were drilled in the 2 inch beam, each hole will have to be countersunk 1/2". This has to be done to allow the 2 inch bar to lie flat against the 27" base I Beams. We are using a magnetic drill and a modified milling machine attachment.

 

 

On the bottom of the table top, we have welded 192 nuts. Instead of tapping the holes drilled in the table top, we opted to weld nuts to the underside. This eliminates the potential cross-threading issue and actually makes for a stronger connection.

 

This is the table top for the Seismic table. It has 192 holes drilled in a 12 by 14 array. These holes will allow for a wide variety of structures or structural parts to be attached to the table for testing and experiments.

An MTS Actuator will be used to operate the table to simulate earthquakes. The capacity of the actuator is 90 gallons per minute, and the maximum actuator stroke is +/- 5 inches.  The capacity of the MTS hydraulic actuator is 55 kips.  We are currently attempting to increase the pressure accumulator capacity through local support and also looking to expand to a dual-station manifold system for additional testing capabilities. There is also a second Actuator that will eventually be used to test bridge type structures.

The slider rail will be mounted on this 2 inch by 8 inch by 10 foot structural steel beam. There are 52 holes drilled and countersunk for the attachment of the machined rails. (see below). In addition to this there are also 18 drilled and countersunk holes to attach the entire assembly to the main I Beam support.

These are the I-Beams after DAD Welding filled all the holes, repaired the gouges and added 12 stiffiners to them. The addition of the stiffiners adds about 500 pounds of weight to each I-Beam.

 

This is one of the two beams that we were able to salvage from the library during the desconstruction phase. The two I-Beams weigh about 3,000 pounds each and are 27 inches tall and 10 feet long. They will be the base of the table and will be anchored to the Lab floor with 10-1 inch anchors, drilled 6 inches into the concrete floor.

 

 

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