Dynamic Design Procedure for HVAC Ducts

Design layout of ducts and supports systems which make up the heating, ventilating and air-conditioning systems (HVAC) is based upon the Japanese Industrial standard (JIS)[1] for hanger support systems conforming to SMACNA[2] standards of high-rigidity design, where emphasis is placed on buildings containing duct systems. However, since high-rigidity systems involve raising the rigidity of the total system, the weight and number of support structures have to be increased, thus posing economic problems. On the other hand, hanger systems are problematic due to their structural weakness. Therefore, we have tried to apply low-rigidity ducts and a support system which rely heavily on the strength of the ducts themselves. To accomplish this we tried to lengthen the duct support span, to lighten the support structures, and to establish a reasonable design method for the duct system. Further, the effectiveness of the present design margin can be confirmed by a duct system test using a shaker table. Our study mainly consisted of experiments: performing duct element tests to study rigidity and strength, using the shaker table to estimate dynamic characteristics and response characteristics of a duct system model, and studying the calculations of the duct beam model.