A PARAMETRIC STUDY ON STIFFENED PLATE PANELS OF RECTANGULAR INDUSTRIAL DUCTS

Stiffened steel plate system is often used to form large rectangular industrial duct structures. The design pressure and the deflection limit dictate the plate thickness and the stiffener spacing. Often elastic large deflection plate theory is used to determine these values. A recent investigation on the plate panel design illustrated that allowing for partial yielding of the panel will lead to economical and efficient duct,system. The investigation presented in this paper focuses on the stiffener requirements associated with the partially yielding plate panels. Such stiffeners are often wide flanged steel beam sections, where one flange is connected to the duct plate panel and the other flange is unsupported. Under suction type pressure situation, the unconnected flange of the stiffener is in compression, and the tension flange is fully connected to the duct panel, which, along with the web, may provide a partial rotational restraint to the compression flange of the stiffeners. This study used a finite element method based analysis model and a parametric study to establish design recommendations for the stiffeners associated with such a plate system. Investigations discovered that the stiffener web slenderness (h(w)/t(w)). (root(f(ys)/(E))) and the stiffener length slenderness (L/r(ys)) .(root(f(ys)/(E))) dominate the behaviour and the flexural capacity of stiffened plate system associated with the industrial ducts. The associated failure modes may be :stiffener lateral-torsional buckling, stiffener distortional buckling, stiffener local buckling or stiffener end crippling. This paper establishes the ranges of parameters for different failure modes and it establishes the bending capacity of the stiffeners primarily undergoing stiffener distortional buckling associated with partially yielding steel plate panels.