Left Side of Organ Case Anchor

The St. Cecilia organ was originally constructed in the workshop of Frans W. M. Bosman and associates. It was disassembled and trucked St. Cecilia where it was assembled in place. No provision had been made to prevent the 6000 pound 19 foot case from falling on the congregation in the event of a major earth tremor.

In July of 1996, the case was seismically anchored to the concrete floor under direction of the builder and the the engineering supervision of Mr. Paul Hennessy, civil engineer and member of the parish.

The left side of the organ case frame was bolted to a 4" x 4" structural grade Douglas fir timber which was secured to the floor with four 8.5 inch expanding steel concrete anchor bolts. A 2" x 6" structural grade timber was diagonally bolted to the frame to add rigidity and spread the stress of the tipping moment. Two angle irons were also used to bolt the frame to the secured floor timber.

Right Side of Organ Case Anchor

The right side of the case was attached to two 4" x 4" timbers. One was placed in a similar position to the left side. However, space constraints due the the existence of an electronic power supply and wiring boards made it necessary to use a 3" x 3/16" steel bar to attach the floor anchor timber to the case structural frame in the rear at a point about 40" off the floor. The case frame was attached to the timber in the front directly with bolts. This timber was attached to the floor with three steel concrete bolts.

The third timber, attached to the floor with three steel concrete bolts, was bolted to the exterior case. Although the exterior case is more decorative than structural, its added shear strength augments resistance to tipping motion as well as torsional movement.

The resulting seismic mitigation has no effect on the tonal characteristics of the instrument. The main objectives were greater safety to the congregation while minimizing physical damage to the instrument in the event of an earthquake. This is the first seismic mitigation project undertaken by the parish since the church was constructed in 1987.