Finite element analysis of stress-strain state of lightning mast for Granary Square – King Cross (central London)
Area of expertise:
|Keywords||Lighting mast, steel structure, wind load, the stress-strain state, eigenfrequencies, reaction in bolts|
|Programs in use||SolidWorks, ANSYS/Mechanical|
Within the frames of the 5th International Symposium on Computational Mechanics CompMechWorkShop (CompMech'2010) Computational Mechanics Laboratory (CompMechLab) of SPbSTU employees together with experts from the Research Centre YTI of the Mikkeli University of Applied Sciences (Finland), performed finite element analysis of stress-strain state of a steel lighting mast by the request of Siteco Lighting Systems (UK) and Tehomet (Finland). This lightning mast is planned to be mounted in central London.
Architectural modules of urban design and lighting equipment installed in the UK, should be designed and manufactured in accordance with the requirements of numerous regulations and standards. In particular, the metal structure analysis described here was done considering the wind load influence in accordance with the international standards ANSI / ASCE 7-88 and ANSI A58.1-82.
Lighting mast modeled in this project is the structure consisting of the two tubes of rectangular sections connected by jumpers; projectors and reflectors are mounted on the tubes. Mast height is about 13 meters, typical cross-sectional dimensions of the mast is 500 X 400 mm.
To calculate the wind load affecting the metal structure, the first natural frequency and the respective mode shape of the lighting mast were found.
The possibility of reducing the pipes' thickness was considered: three different modifications were reviewed. Wind pressure (in accordance with the standards ANSI / ASCE 7-88 and ANSI A58.1-82) and the gravity force taken with a safety factor 1.2 were considered as factors affecting the structure.
Deformed state of the structure with different pipes' thickness and equivalent von Mises stress distribution were defined as a result of the finite element solution. Particular attention was paid to reactive forces and moments arising in the bolted connections between the lighting mast and foundation.
The results of the finite element simulation allow to define optimal values of the pipes’ thickness used in the construction of the lighting mast, the diameter of bolts for fastening the construction to the foundation and the type of foundation required for the considered design.