A Steel Tree Canopy project
The architectural project objective was to construct a sculpture that resembled a tree. The structural result was a steel frame pavilion/bandshell with a tiered canopy and branch system. However, the project iterated several times through various configurations, including a glass geodesic dome and steel fin leaves, before ultimately ending up as an HSS and steel pipe frame with wood decking.
Due to the geometry of the desired structure, there were complex HSS and steel pipe connections, with several instances of many members coming into one location. The eccentric nature of the wind loading on the structure, especially given the need to leave a face without columns to act as a bandshell, created some complex loading conditions at congested locations.
HSS connection challenge
When designing HSS-to-HSS connections, using AISC 360 code formulas is almost impossible because the connections must fall within the limits of applicability. These limits can be found in Chapter K of the AISC 360 Specification for Steel Buildings. In summary, the limits are related to the angle between the members, width ratio, connection eccentricity, gaps, wall thickness, etc. However, the code allows the use of Finite element analysis instead.
Stability Engineering used the IDEA StatiCa Connection application for these connections, allowing them to model all the connections in the project, from very simple to complex joints, with no limitations.
It was surprisingly easy to create various connections even when coming into the software cold for this project. After a short time reviewing tutorials and documentation it went fairly quickly.
Justin Downey
Project Engineer – Stability Engineering
United States
