Bike-Foot Bridge of Barberino del Mugello – Firenze
General Data
- Length: 76 m
- Width: 2.25 m
- Planning Engineer: Stefano Capretti
- Static Layout: three hinged arches
The Bike-Foot Bridge of Barberino del Mugello in Firenze is a bridge joisted with wing profiled aerodynamic appendages.
The highly technological structure has been built in the Natural Park surrounding the artificial lake of Bilancino as a crossing bridge over the streams Lora and Stura.
Planning the bike-foot bridge structure in laminated wood has involved Habitat Legno, as a company specialising in the sector of planning and constructing laminated wood works, Studio Lombardi Italia Engineering Consultants for an in-depth static and dynamic structural analyses and lastly the Politecnico di Milano (Department of Mechanics, Milano Bovisa, Professor Engineer Alberto Zasso) for an extended test and numerical research for the study of dynamic interaction between the bridge and wind.
To resolve all the problems that could have risen, some targeted scientific- technological tests have been conducted in the Wind Tunnel at the Politecnico di Milano. The results achieved are gathered in three reports drafted by the Department of Mechanics dated: (one) March 6 2001 and (two) June 22 2001.
The bike-foot bridge spanning 76 metres features a bearing structure made by three hinged laminated wood arches, braced by a system of laminated wood rafters and by diagonal steel tensioners. A series of steel suspension rods suspend the deck made of a trellis of laminated wood beams and steel.
The project envisioned several phases:
- tests in the wind tunnel on sectional models of the deck and arched truss with characterisation of the stress diagrams, bearing capacities, and their torque
- numerical calculations of dynamic stability and breakaway stress of vortex under wind effects
- definition of the adimensional damping for laminated wood structures through real test with dynamic exciter
- aerodynamic optimisation of the deck section and torque of the bearing beams through Wind Tunnel tests, of appropriate aerodynamic appendages, and/or reduction of the ratio full/empty on the side protective barriers
- numerical calculation of the bridge improved version
Test verifications of the Completed Structure
Search for structure frequencies with wobbling masses:
Bridge L = 76m F0 = 1.61 Hz (1.35 Hz)
Compared to the calculations we have noticed a higher rigidity.
Damping Coefficient
Measuring damping of free wobbling:
Bridge L = 76m xi = 1.50%
Overall the structure has a damping coefficient higher than the material, most likely by effect of the metal joints.
The main objective of the planning is to increase the structure damping in order to limit the vibrations induced to the pedestrians.
To admire this wonder of science and technology means to acknowledge the great leaps made by human civilisation.