Cracking of buttresses in an Ambursen Dam Spillway

ABSTRACT ONLY - Ambursen dams often exhibit buttress cracks that have been attributed to thermal expansion of the upstream slabs. At the Colliersville Dam in New York State, all of the buttresses cracked shortly after construction. At this dam, the reservoir submerges the upstream slabs and the downstream rollway faces south. This paper aims to assess the role of thermal expansion of the downstream rollway slab in contributing to the buttress cracking phenomenon.

To analyze this Ambursen dam, a finite element analysis was conducted utilizing the SAP2000 software. One typical buttress of the buttresses of the Colliersville dam was analyzed. The buttress was modelled as a 3-D shell element to realistically describe the deformation and possible cracking of concrete. The analysis investigated the potential formation of tensile cracks within the buttresses due to the temperature variations on the downstream slab. A temperature variation load was applied to the buttress on the downstream side, in addition to dead load, hydrostatic load, and uplift.

The results of the finite element analysis indicate that temperature fluctuations in the downstream rollway slab can cause expansion and shrinking of the slab that can lead to the development of tensile cracks in the buttresses of the Ambursen dam. The results of the analysis showed that in the areas where the buttresses exhibited cracking, the tensile stress exceeded the tensile capacity of the concrete. The buttresses are minimally reinforced and the tensile resistance from the reinforcing bars was not considered in the analysis. The results of analysis suggest that the thermal expansion of the downstream rollway slab is significantly contributing to the observed buttress cracking phenomenon at the Colliersville Dam.