Study on the influence of long intermittent periods on the temperature and stress of upper and lower layers in L-shaped concrete structures
Regarding the issue that long intermittent periods exceeding 28 days often occur during the concrete pouring process of the lock bottom slab-guide angle(L-shaped structure),and that the new concrete is strongly constrained by the old concrete,easily causing cracks in the lock concrete structure,a large lock project was used as a basis.A three-dimensional finite ele-ment model of the typical lock chamber bottom slab-guide angle was established to simulate the temperature field and creep stress field of the bottom slab-guide angle concrete under different construction intermittent periods(30 to 180 days).The results showed that as the concrete pouring season shifts from spring to autumn,due to changed in the external climatic environment,the maximum temperature of the guide angle concrete increased from 50.80℃ to 60.77℃,then decreased to 52.85℃.The tem-perature influence ranged of the upper layer concrete on the lower layer concrete was about 1.5 meters in depth.The tempera-ture gradient near the contact surface of the new and old concrete first increased and then decreased,but the intermittent peri-od itself had no impact on the concrete temperature changes.The maximum tensile stress of the guide angle concrete at 28 days increased from 0.93 MPa to 1.71 MPa as the intermittent period extends from 30 days to 180 days,significantly increasing the risk of cracking.
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