Disagreement with PT

June, 2009

Editor, Parking Today:
Re: “Temperature can affect upper floors of precast garages” (March 2009)
The aspect of camber increasing in the top level of parking structures because of the sun’s heating is hardly a new topic, and it exists in all parking structures regardless of the construction material.
The problems described by the authors are rare in well-designed precast parking structures. Indeed, in over 300 parking structures that I have designed or built, I have yet to experience such problems.
While the solutions presented by the authors may work, they are expensive and needless in properly detailed and designed precast structures. The authors also fail to recognize that without a proper bearing pad, the Cazaly hanger can create beam-edge spalling.
Two typical details will provide the rotation needed at the end of the double tees to prevent damage to the tees and beams.
The first is the application of a good quality 3/8” thick Masticord or equal bearing pad under the tee bearing. This pad will allow rotation and movement of the double tee end bearing without cracking or spalling of the beam or tee.
The second is the well-known warning not to weld both ends of the double tee at its bearing. Such a rigid connection will lead to damage to both the tee and the beam.
Parking structures are exposed to the full range of temperatures, and therefore must be allowed to “breathe” or move with temperature extremes.
Paying attention to correct detailing will eliminate any concern for sun camber effect and will not require expensive repairs or secondary strengthening. However, when poor detailing is employed or careless erection happens, damages to beams or tees can occur. CFRP wraps, epoxy injection or stem strengthening can be an effective remedy.
Respectfully submitted,
Thomas J. D’Arcy, P.E.S.E.