Pre-Stress Loss Due to Creep in Precast Concrete Decked Bulb-Tee Girders Under Cold Climate Conditions

Abstract

Accurate estimation of pre-stress losses is one of the important issues for the design of precast, pre-stressed concrete bridge girders. While this subject has been long studied by many researchers, studies on pre-stress losses in cold climates are minimal. In the present research, long-term pre-stress loss due to concrete creep was studied based on concrete creep test. Two concrete creep test frames were fabricated and placed indoors and outdoors. Concrete strains were measured by Demountable Mechanical Strain Gauge (DEMEC) from two 612 high-strength concrete cylinders in each frame. The concrete strains were collected for 11 months (7/26/2017 – 6/21/2018) after loading, and outdoor ambient temperature dropped below 0C between 100 and 250 days. Between 50 and 100 days, two curves from the two frames are similar in their patterns and values. After 100 days, the total strain from the indoor frame slowly increased reaching 1,600 and 1,700 after 250 days. However, the total strain from the outdoor frame varied between 1,000 and 1,500 and the averaged total strain was 1,300 after 250 days. In cold temperature, the occurrence of concrete creep and shrinkage was suppressed.