Field tests and analysis of π-type rigid frame timber highway bridge

Field-tests on the performance of a timber highway bridge, the "Midori-bashi", under dynamic and static loads and on its vibration characteristics were conducted. The "Midori-bashi", a glued laminated timber (glulam) bridge located on the forest roadway in Nagano, Japan was completed in November 1996. The bridge has a 30.0m span length, two-hinged x-type rigid frame structure using stress-laminated glulam deck. The total width of the stress-laminated deck is 9.25m. The field tests were conducted using two dump trucks having a gross weight of 196kN each. The deflection, velocity, and acceleration of the bridge were measured at various truck speeds. From these data, the impact factor and the damping factor were obtained and compared with the conventional values employed in Japan. Vibration mode shapes and natural frequencies were also calculated and compared with the results of dynamic analyses.