Abstract: To study the influences of temperature variation and thermal insulation on the cracking state of dam-embedded steel penstock encircled by cushion layer at runtime in cold region

the concrete damage and bearing characteristics of one penstock under temperature action were analyzed by nonlinear finite element method based on the concrete plastic-damage model. The results indicated that due to the cushion layer there was little damage on the concrete and no macro-cracks would appear on the concrete surface under normal operation condition. Temperature drop leaded to serious damage at the top of pipe

and temperature rise leaded to damage at the bottom of the pipe

in the meantime the stresses of reinforcement within damage zone increased apparently; thermal insulation slab could help reduce temperature load

concrete damage and reinforcement stress efficiently

and the thicker the better

but after the thickness of the slab increased to a certain extent

its effect would tend to be stable. In different engineering the thickness of thermal insulation slab can be controlled by the width of the cracks.