Determination of temperature stresses in concrete blocks of hydraulic structures by influence lines

Abstract

1. The type of thermal stress conditions for plane and prismatic blocks for the same temperature fluctuation patterns remains the same. 2. The variations in numerical values of stresses depend on relative block dimensions and on their cross sections. With the same relative height H/B the minimum tension stresses are found in cooling blocks of square cross section (Fig. 6), and with E/Ef=1 and H/B=1 they are 25 to 30% less than for the blocks subject to a plane thermal deformation. With decrease of the relative block heights the rate of variation decreases. 3. The temperature variation pattern along the height of blocks has the maximum effect upon the resulting stresses. The stress state of tall blocks appears to be in a more favorable condition when the block is cooled so that the higher layers are cooled more intensively than the lower. This circumstance should be taken into consideration when planning the cooling pattern of tall blocks. 4. The relative rigidity of block foundations affects their stress state to a great extent [11]. The increase in the foundation elastic modulus Ef causes an increase of stress at the contact plane. Thus, for the blocks with H/B>0.2 at E/Eoc=1/2 to 2 the stresses at the contact plane vary by 20 to 30%. The effect of foundation rigidity on points at the top and bottom surfaces of blocks with a height H/B<0.4 is more pronounced; here the variation in stiffness can even change the sign of the stress.