Tests and Analysis on Thermal Expansion Behaviour of Steel Strand used in Prestressed Concrete Structure under Low Temperatures

This paper presents the results of the tests and analysis on the coefficient of thermal expansion for the steel strand under combined low temperatures and prestressing forces. A test program was firstly carried out to study the thermal expansion behaviour of the seven-wire strand under combined different low temperatures ranging from 20 to 165 C and different prestressing levels ranging from 0 to 0.75 ft/ftk. The test results exhibited the thermal expansion behaviours of the steel strand under low temperatures in terms of thermal strain versus temperature curves, transit linear thermal expansion coefficient, and average thermal expansion coefficient. The influences of the low temperature and prestressing levels on the thermal expansion behaviours of the steel strand were separately discussed and analysed. Based on the test data, mathematical models were developed to predict the thermal expansion coefficients including transit and average of the steel strand. The developed regression models fully considered the influences of the low temperature and prestressing stresses acted on the strand. Finally, design equations were proposed to predict the transit and average thermal expansion coefficient of the steel strand under combined low temperature and prestressing forces.