INFLUENCE OF MATERIAL MODELS ON PREDICTING THE FIRE BEHAVIOR OF STEEL COLUMNS

Modern Dimensional Analysis-Based Steel Column Heat Transfer Evaluation Using Multiple Experiments

In order to foresee the response during the fire of a real symmetrical structure (prototype), nowadays engineers apply methods which involve the associated reduced-scale model’s behaviors, mainly dimensional analysis behaviors. Between the dimensional analysis methods, the so-called Modern Dimensional Analysis (MDA), developed by Szirtes, fulfills all engineering requirements compared with the classical one. The authors used this new proposed method to describe their original electric fire simulation testing bench, as well as the Model Law (using MDA) for the heat transfer in tubular rectangular bars. So, a validation of the Model Law was performed based on several scrupulous experimental investigations both on a real column’s segment and its associated reduced-scale models manufactured at 1:2; 1:4, as well as 1:10 scales. The original heating system, the elaborated protocol, the deduced Model Law, and the results of the experimental investigations represent the contributions of the authors in the field of metallic structures subject to fires. The results validate the possibility of using MDA in the case of heat transmission.

High Temperature Mechanical Properties of High Strength Structural Steels Q550, Q690 and Q890

This paper reports the results of an experimental study on high temperature mechanical properties of high strength structural steel (HSSS) produced in accordance with Chinese materials standards. Steady-state tensile coupon tests were carried out on specimens made of China grade steels of Q550, Q690 and Q890. Nine elevated temperature levels up to 800 °C were considered. The elastic modulus, yield strength, ultimate strength and ultimate strain were derived from the measured stress-strain curves. A model was developed to predict the high temperature properties of these steels using an approach developed by the National Institute of Standards and Technology (NIST) and by calibrating the model parameters to the test data. The test results are compared to other tests on high strength steels reported in literature. The test results are also compared to predictions of high temperature properties from various building codes and other standards. The study found that steel grade has significant effect on the reduction factors. The difference between the reduction factors of elastic modulus for Q690 and Q550 was 30% at 600 °C. In this study, reduction factor is defined as the ratio of the high temperature property to the corresponding room temperature property. The study also found that the material models in current codes are not applicable to the investigated high strength steels.