Shear strength along construction joints in concrete dams

Conclusions

• 1. Shear strength of concrete along the construction joint should be established with regard to surface roughness and strength of concrete. The present method of selecting the coefficient of friction between 0.6 and 0.65 for the determination of frictional resistance when concrete slides on a concrete surface will certainly not serve for all cases.

• 2. During the study, it was observed that with small normal stresses (σ_av < kg/cm²) the equation r_av = c + tanϕ · σ no longer agrees with Coulomb's linear equation r_av=c+tanφ·σ and that the parameter c tends to zero as σ av approaches to zero. However, further study would be required in order to establish the actual relationship.

• 3. If the surfaces of contact are rough, the sliding of the upper concrete block is accompanied by a vertical motion. The resultant motion is inclined along an angle α which on the average is equal to the mean angle of inclination of the roughness projections on the surface of the block. The shear strength is determined by the stresses σ_± and τ_±.

• 4. It will be necessary to study the shear strength between different classes of concrete and for different kinds of roughness. The results of such a study should be published in construction manuals.