Uplift pressure of water in a system of cracks of eccentrically compressed reinforced-concrete elements

Conclusions

• 1. In the tensioned zone equal to the depth of the cracks observed in the experiments a rectangular water pressure diagram is at first established, but after several days due to losses of pressure as a consequence of seepage along partially clogged cracks the pressure diagram becomes less rectangular, and pore water pressure equal to 30–50% of the pressure head occurs in the compressed zone.

• 2. Investigations of the reinforced-concrete elements under the effect of the uplift pressure of water in one crack showed that in this case the change in stresses in the reinforcement occurs only in the section along this crack and has a local character, so that outside the zone of action of the water pressure its effect on the internal forces in the reinforced concrete element rapidly diminish on a length of 0.3–0.4 h.

• 3. In the zone of action of water pressure encompassing a system of 7–9 normal cracks changes in the stress state were observed mainly in sections along the extreme cracks. In the other sections the changes were 2–5 times less. The measured values of the increments of stresses in the reinforcement in sections along the extreme cracks from the effect of a water pressure of 5–8 gauge atm were close to the calculated values of such increments obtained according to the existing standards, in conformity with which these increments should be taken into account in any section of non-crack-resistant reinforced-concrete elements. At the same time, the values themselves of the stresses in the reinforcement obtained from experiments substantially differ from the calculated values obtained both with and without consideration of the water pressure.