GTR provided geotechnical and structural design, and technical support for temporary pedestrian bridges during the replacement of the Hungry Hollow, Scotland Hill Road, and College Road Bridges in Rockland County, New York. The bridges, built between 1953 and 1955, had vertical clearances that were below modern standards, had reached the end of their service life, and had been struck by over height vehicles numerous times in the past seven (7) years. It is estimated that the bridges carry a combined 22,000 vehicles daily. In order to maintain foot traffic in, temporary pedestrian bridges were installed. Unique design challenges included designing a pier footing system that could be transported and re-used during the construction of the three (3) bridges, while being stable enough to withstand lateral and uplift pressures from high winds. Additionally, temporary abutments were needed for the pedestrian bridges with tight geographical and right of way restrictions.
To overcome these challenges, GTR worked closely with the general contractor to develop a modular spread footing with deadweight that could resist the overturning and uplift forces from a bridge deck over sixteen (16) feet above the highway surface that could de deconstructed and moved after completion of the permanent bridges. GTR also designed a Geosynthetic Reinforced System (GRS) Abutment Wall to support the temporary bridge abutments along the pedestrian roadway alignment. This involved analyzing several special cases for GRS wall design including overlapping and back-to-back designs to develop a stabile design within the constrictions of the available footprint area. GTR evaluated global stability of the entire system and designed GRS Wall with uniaxial polymer geogrid and weld-wire facing baskets to create a near vertical abutment face (1H:10V) backfilled with compacted dese grade fill. GTR’s design was successfully implemented to facilitate replacement of the bridges without interruption to pedestrian traffic.
- Check bearing capacity, global stability, slope stability
- Includes center pier, pier tower approaches and abutments
