Document Type
Thesis
Date of Award
9-30-1983
Degree Name
Master of Science in Mechanical Engineering - (M.S.)
Department
Mechanical Engineering
First Advisor
Benedict C. Sun
Second Advisor
Harry Herman
Third Advisor
Bernard Koplik
Abstract
"HVAC" ducts are made of thin gauge sheet metal. They are usually reinforced with transverse stiffeners. These stiffeners are usually made of hot rolled steel sections, such as equal leg angles or channels.
When the size of an "HVAC" duct exceeds 72 inches, additional stiffeners in the axial direction are used to reinforce the duct sheets. Tie rods are also installed, between the axial stiffeners, across the duct cross-section, to support these stiffeners. The "HVAC" ducts are subjected to either external or internal pressure. The transverse stiffeners have one or two tie rods installed, and they become statically indeterminate structures. A digital com-puter has been employed as an aid in designing the transverse stiffeners.
The reactions were determined by the flexibility method. The axial forces were determined iteratively using the computer. The deflections were found out by the principle of superposition. The design criteria are: maximum deflection should not exceed 360 or 0.25 inches, whichever is smaller; the combined normal stress should not exceed 600 of the structural steel's yield strength.
The optimum stiffener size was designed for the following:
- pressures ranging from 0.1 psig to 3.0 psig
- stiffener lengths (duct widths) ranging from 72 inches to 216 inches with 12 inch increments
- stiffener spacings are 24, 30, 40 and 60 inches
The optimum stiffener sizes for these various combinations of pressures, stiffener spacings and stiffener lengths have been tabulated in aid of the design.
Recommended Citation
Somayaji, Raviraj, "Design of HVAC duct stiffeners with tie rods" (1983). Theses. 3642.
https://digitalcommons.njit.edu/theses/3642
