Structural fire safety capacity of concrete is very complicated because concrete materials have considerable variations. In this paper, constitutive models and relationships for concrete subjected to fire are developed, which are intended to provide efficient modeling and to specific fire-performance criteria of the behavior of concrete structures exposed to fire. They are developed for unconfined concrete specimens that include residual compressive and tensile strengths, compressive elastic modulus, compressive and tensile stress-strain relationships at elevated temperatures. In this paper, the proposed relationships at elevated temperatures are compared with experimental result tests and pervious existing models. It affords to find several advantages and drawbacks of present stress-strain relationships and using these results to establish more accurate and general compressive and tensile stress-strain relationships. Additional experimental test results are needed in tension and the other main parameters at elevated temperatures to establish well-founded models and to improve the proposed relationships. The developed models and relationships are general, rational, and have good agreement with experimental data.

Self Compacting Concrete (SCC) specimens with limestone (L) and quartz (Q) powders were formulated. The influence of the type

of the powder on the properties of fresh and hardened concrete was evaluated. Dense packing theories were used for mix design

of samples. The equation of Fuller and Thompson for particle size distribution (PSD) of aggregates was modified with considering

fine particles and a proper PSD curve was obtained for SCC. Experimental results showed that this method needs use of less

powder content and results in higher strength/cement ratio compared to traditional mixing methods. No significant difference was

observed between the compressive strengths of specimens containing limestone (L-specimens) and quartz (Q-specimens) powders,

with similar proportions of materials. The residual compressive strength of specimens was examined at 500°C and contradictory

behaviors were observed. One Q-specimen suffered from explosive spalling, while no spalling was occurred for L-specimens. On

the other hand, the residual strength of remained Q-specimens showed considerable increase compared to L-specimens. The results

show the necessity for more detailed investigations considering different effective parameters.

Observations and investigations have proved that using traditional fire curves such as stand-ard fire curves and natural fire curves should be limited to small/medium compartments. In addition, when using the traditional fire curves, a uniform temperature is assumed throughout the compartment. However, for large open compartments, assuming uniform temperature is not compatible with real fires. To overcome this limitation, a non-uniform fire method named as travelling fire is employed as an alternative. A study is performed here on a seismic-damaged large plan 3-story reinforced concrete structure designed to meet the life safety level of performance when exposed to a travelling fire. To draw a comparison, the structural fire analysis is also performed using the traditional methods. The results show a notable difference – while the fire resistance based on the travelling fire is around 91 minutes, it is around 140 minutes when based on a uniform temperature. This shows that the structure studied is more susceptible to failure when subjected to the non-uniform fire than the uniform fire.