GT STRUDL was used to model the L-shaped Turbine Generator Building that is essentially an open bay structure with a 7 million pounds Steam Condenser Unit mounted on the roof. The location and extension of the Condenser above the roof on one leg of the L shaped building induces eccentric wind/seismic loads and torsion loading of the TGB.  The design challenge and the use of GT STRUDL in the design analysis process are discussed.

The geometry of the framing is developed using FRAMEWORKS add-on package to Microstation PDS. The use of these programs allowed the development of production drawings and interface with a 3-D plant viewer package.  The FRAMEWORKS add-on package contains an option for generating a GT STRUDL input file.  The GT STRUDL input file provides the model geometry, member properties, materials, releases and some of the loading conditions.  The FRAMEWORKS generated GT STRUDL steel frame model was enhanced to model a 9-inch thick concrete slab on the TGB roof and to model the ACC loads. The interface between the ACC unit and the turbine building roof also added to the complexity of the GT STRUDL model due to the mismatch in ACC unit columns and the structural building steel.

The major design challenge is this building design is the eccentric wind/seismic loading due to the torsion loading and limited bracing areas.  The key design considerations include:

1. Unsymmetrical L shaped building
2.  Large eccentric mass on the roof of one leg of the building
3.  Large sail area from the ACC unit on the roof of one leg of the building
4.  Limited areas for the brace members
5.  The construction sequence requires verification of building stability as the building shell large open areas required for construction access for installation of the combustion and steam turbine