Archon Engineering, PC

Stair Tower

Archon has designed several platform stairways.

This project was performed for a contractor at a fossil power plant. The existing stair tower that was attached to a tall silo structure was considered too flexible by the utility and was considered unsafe. The project had several challenges. The design was not allowed to use curved members; only normal structural shapes were to be used. The wall on the Silo was very thin and not capable of supporting high concentrated support loads. Pipes that penetrated the Silo caused limitations on the position of the stairs and platforms.

A detailed review of the silo drawings was performed as well as a site walk-down to obtain unknown dimensions. Once the required position of platforms was established, a detailed Finite Element Analysis (FEA) was performed on the main stair tower structure. An additional FEA analysis was performed on the support attachments that connected to the wall of the silo. Based on results of the analysis several design iterations were required until stress and deflection requirements were satisfied. In addition to the stress analysis, a natural frequency analysis was performed to ensure that wind induced vibration would not be a concern. Prior to issuing the final design, the design was presented to the contractor for a constructability review.