Trunnion-Hub-Girder Bolt Assembly Design Program (Grant 1)

This beta-version program and the accompanying manual is for designing trunnion-hub-girder assemblies for bascule bridges. This program should only be used as a theoretical tool. There are four design tools available in this program:

1. The first design tool simulates an actual bridge layout, and finds the actual torque necessary to raise the bridge leaf, given various parameters (for example, material properties and wind loading).

2. Due to the shrink fitting done to the system, and based on the type of standard fits at the interfaces of the trunnion-hub and hub-girder, interferences are created at the two interfaces.  These interferences cause pressures at the interfaces and, correspondingly, develop hoop (also called circumferential and tangential), radial, and von Mises stresses in the THG assembly.  The second design tool finds all of these stresses, as well as the radial displacements in each member (trunnion, hub, and girder). The results provide the design engineer with an idea of how the given diametrical interferences (from shrink fitting) affect the stresses in the various members of the THG assembly.

3. A third tool is developed to find all of the critical stresses (radial, hoop, and von Mises) in the THG assembly at steady state.   The results from this tool are tabulated to show these stresses for various combinations of the material properties and geometric dimensions of the trunnion, hub, and girder.   The design engineer can then use these as design parameters.

4. The fourth design tool is for developing the bolt pattern used to supplement the hub-girder interference fit.  The amount of torque resisted by the hub-girder comes from two sources – hub-girder interference and the bolts. The torque resisted by the bolts is based on the number of bolts, diameter of bolt circles, bolt material and size, material and geometric dimensions of the hub and girder, etc.  This design tool allows the user to test various bolt patterns. The designer then tabulates results for direct use.

Instructions to setup THG Assembly Program:

The downloadable programs are zipped files. Download the zipped file to your computer. Unzip the file using winzip program available free for 30 days at http://www.winzip.com. From the unzipped files, click on the setup.exe file in the Windows Explorer. Follow the onscreen directions. The author has made every effort to keep these files virus free but check it for yourself! No liability of any nature will be assumed by the author or their affiliations.

The manual is in pdf format and can be read and printed using the Adobe Acrobat Reader.  The software for Acrobat Reader is available free of charge at http://www.adobe.com/acrobat/