Title: Compressive Strength Relationships for Concrete under Elevated Temperatures
Author(s): Adam M. Knaack, Yahya C. Kurama, and David J. Kirkner
Publication: Materials Journal
Appears on pages(s): 164-175
Keywords: compressive strength; design; temperature.
This paper focuses on compressive strength relationships for the design of concrete structures under elevated temperatures from fire. The development of a database of previous experimental research on the temperature-dependent properties of unreinforced concrete is described. A comprehensive statistical analysis of the concrete strength data from this database is conducted using the method of multiple least-squares regression with coded variables. High-strength concrete (HSC) and normal-strength concrete (NSC) with normalweight and lightweight North American aggregates are considered in the investigation. The results are used to develop predictive relationships for the concrete strength loss under fire. Compared with existing strength loss relationships, the proposed relationships are based on a much larger data set, thus increasing statistical robustness. It is shown that a reasonable statistical fit is achieved with the available data, especially considering that the proposed relationships use relatively simple regression models suitable for design. The most significant parameters affecting the concrete strength loss with temperature are the concrete strength at room temperature, aggregate type, and heating test type. Through a critical evaluation of the current database, recommendations are presented for areas where future research should be directed. Recommendations are also made for presenting the results from future fire tests so that researchers can most effectively use this data.