Calculations to the design of a thrust buttress masonry dam

IN a paper read before the Concrete Institute on March 14, 1912, there was included a brief description of the writer's type design for a dam of arches supported by buttresses in direct thrust. While there is no theoretical objection to the substitution of reinforced concrete spans for the arches, the fact that the whole of the structure is subjected to compression stresses points to the probability that for large works the most suitable material will usually be plain masonry, and the most suitable form for the waterproof wall a segmental arch. The following calculations for a dam of plain masonry would apply in the case of a similar dam made of reinforced concrete, regarded as a material, and in such a case the actual stresses allowed at different depths in the arched wall and in different layers of the buttresses might be varied according to the proportion of reinforcement and its distribution as designed for the development of high compressive strength. A design intended to economise in the quantity of aggregate used in the concrete might, in the case of a highly stressed reinforced concrete dam, have to include the provision of inverts, parallel to the water face, connecting the bases of the buttresses and distributing the load upon the rock. Footing out or battering out the foundations might in such a case involve either the carrying of the bottom ends of the buttresses to considerable depths in the rock, involving the provision of a good deal of masonry for,this purpose alone, or such an angular divergence from the line of direct thrust as would amount to a secession from the principle on which the design is based, and might involve the introduction of tensile stresses such as those in the bases of reinforced concrete columns. Reginal Ryves