Inman Park Pedestrian Bridges Renovations, Metropolitan Atlanta Rapid Transit Authority (MARTA), Atlanta, Georgia
Metropolitan Atlanta Rapid Transit Authority (MARTA) received complaints of the vibration issues with the Inman Park Pedestrian Bridges. The vibration issues were originated from pedestrians walking on the bridges. Both the south and north bridges included vierendeel truss steel framing system, and their span length ranged from 63 feet to 138 feet with serval spans.
WDP performed site investigation regarding the vibration issues associated with the pedestrian bridges and performed dynamic structural analyses to determine the dynamic characteristics of the structures. It was found that both north and south pedestrian bridges are susceptible to vibrations due to pedestrian traffic, and the original design did not satisfy the vibration requirement recommend by the current industry.
WDP further analyzed the bridge structures and developed multi-solutions to reduce the vibration issues which can be implemented during the upcoming Owner-developed renovations. The multi-solutions included member stiffening, framing stiffening, structural damping, and mass tuned dampers, and their effectiveness was analytically examined with the numerical models. MARTA selected the framing stiffening option of adding diagonal members in the existing truss system to remediate the bridge vibration. WDP further optimized the configuration and section size of the additional diagonal members.