Graduation Year

2009

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Major Professor

Autar Kaw, Ph.D.

Committee Member

Glen Besterfield, Ph.D.

Committee Member

Muhammad Rahman, Ph.D.

Keywords

Finite element analysis, ANSYS, Design of experiments, OMCCL, OMSR

Abstract

Many different hub assembly procedures have been utilized over the years in bascule bridge construction. The first assembly procedure (AP1) involves shrink fitting a trunnion component into a hub, followed by the shrink fitting of the entire trunnion-hub (TH) assembly into the girder of the bridge. The second assembly procedure (AP2) involves shrink fitting the hub component first into the girder, then shrink fitting the trunnion component into the hub-girder (HG) assembly. The final assembly procedure uses a warm shrink fitting process whereby induction coils are placed on the girder of the bridge and heat is applied until sufficient thermal expansion of the girder hole allows for insertion of the hub component. All three assembly procedures use a cooling method at some stage of the assembly procedure to contract components to allow the insertion of one part into the next. Occasionally, during these cooling and heating procedures, cracks can develop in the material due to the large thermal shock and subsequent thermal stresses.

Previous works conducted a formal design of experiments analysis on AP1 to determine the overall effect of various factors on the critical design parameters, overall minimum stress ratio (OMSR) and overall minimum critical crack length (OMCCL). This work focuses on conducting a formal design of experiments analysis on AP1, AP2 and AP3 using the same cooling methods and parameters as in previous studies with the addition of the bridge size as a factor in the experiment.

The use of the medium bridge size in AP1 yields the largest OMCCL values of any bridge and the second largest OMSR values. The large bridge size has the largest OMSR values versus all factors for AP1. The OMCCL and OMSR increases for every bridge size with an increase in the alpha ratio for AP1. The smallest bridge showed the largest OMCCL and OMSR values for every cooling method and every alpha ratio for AP2 and AP3. The OMCCL and OMSR decrease for every bridge size with an increase in the alpha ratio for AP2 and AP3.

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