Riverside Road Bridge Replacement

KANTONE AND CARROLL, NEW YORK

Dente Engineering was contracted to conduct a Geotechnical Investigation for the planned replacement of a four-span bridge crossing the Conewango Creek in Chautauqua County, New York. This bridge, which was a replacement for an earlier river crossing, was reportedly constructed in the 1930's. The single lane structure, with an overall span length of about 270 feet, was supported by a combination of 30 foot long rail piles with a capacity of 5 tons at the abutments and 35 foot long wood piles with a capacity of 12.5 tons at the three piers. The bridge was restricted to vehicles exceeding a weight of 8 tons.

The replacement bridge, with a planned length of 250 feet and a width of 31 feet, was evaluated as both a two-span steel plate girder structure and a three-span precast concrete girder structure. Abutment loads for the new bridge were estimated to be in the range of 680 to 850 kips, with pier axial loads ranging between 1,900 and 2,050 kips. The overburden soils at the bridge site generally consisted of soft to very soft silty clay, with occasional traces of sand and gravel extending to a depth of about 173 feet. Beneath these alluvial soils, the test borings encountered more competent soils composed of Sand, Silt and Gravel, with lessor amounts of clay. These generally granular soils were moist and graded from a firm to compact relative density.

The design of the new larger bridge structure was complicated by the deep, soft soil conditions and the relatively large increase in design axial loadings on the abutments and piers over those of the existing structure. These load increases resulted, in part, from the bridge widening, reduction in the number of spans and loadings adopted from the current codes, including seismic. Considering the design axial and lateral loads on the abutments and piers, it was recommended that the bridge be supported by H-Piles bearing in the compact soils that existed at a depth of about 180 ft.

Dente Engineering provided geotechnical engineering services in connection with the bridge replacement. These services included conducting a site reconnaissance; performing axial and lateral loading analyses of pile groups to assist the structural engineer with design; and providing recommendations relative to abutment and wingwall design and construction, including installation criteria for driven piles.

The design considerations and scope of services we provided for the above referenced project are typical to numerous projects that we have completed. Some of the other more recent bridge projects that we have provided design services for include: