The Effects of Engineering Assumptions when Designing a Plate Panel/Stiffener System Under a Uniformly Distributed Load Bernard Nasser Master of Engineering in Mechanical Engineering Rensselaer Polytechnic Institute Hartford, Connecticut December, 2011 (For Graduation May, 2012)

Purpose Study focuses on the effect of engineering assumptions made when designing a plate panel/stiffener system under a uniformly distributed load. Initial engineering assumptions design the panel using Classical Deflection Theory (small deflection theory) for a flat rectangular plate under a uniformly distributed load that is either fixed or clamped around the edges. Stiffeners are initially designed as beams under a uniformly distributed load that are either simply supported or fixed at the ends. Initial panel and stiffener sizes generated are an approximation, as a finite element analysis is required to evaluate and authorize the final configuration. Final configurations can be very different from the simple initial closed form evaluations, as stress issues and fabrication constraints are accounted for. Comparative analysis between the closed form solutions (stress and deflection for a fixed or pinned rectangular plate with a uniformly distributed load) and the values generated by a finite element analysis. How close are FEA results to initial assumptions?

Panel System Figure 1: Pressurized Tank with top plate stiffened

Panel System Figure 3: Section view showing stiffener design “butting” into shell side plate Figure 4: Section view showing stiffener design sniped prior to reaching shell side plate Figure 5: Section view showing stiffener design wrapped around plates

Numerical Analysis Clamped Rectangular Plate Under Uniformly Distributed Load α = (given, for a/b = 1) po = 100 psi b = 30in E = 30 x 106 psi t = 0.75in β1 = (given, for a/b = 1) po = 100 psi b = 30in t = 0.75in

Numerical Analysis Simply Supported Plate Under Uniformly Distributed Load α = (given, for a/b = 1) po = 100 psi b = 30in E = 30 x 106 psi t = 0.75in β1 = (given, for a/b = 1) po = 100 psi b = 30in t = 0.75in

FEA Analysis