Post-fire performance of structural steel

Qahtan Adnan Sulayman; Mohammed  Mahmood

doi:10.24237/djes.2021.14203

Authors

Qahtan Adnan Sulayman
eng_grad_civil023@uodiyala.edu.iq
Department of Civil Engineering, College of Engineering, University of Diyala
Mohammed Mahmood Department of Civil Engineering, College of Engineering, University of Diyala

Keywords:

Post-fire behaviour, Structural steel, Coupon test, Structural safety

Abstract

Carbon steel is widely used in building industry. The different structural element might be exposed to high temperature during fire. The structural safety of steel buildings must be evaluated after they have suffered a fire. The assessment requires understanding the behaviour of carbon steel after heating. Therefore, this paper is aimed at studying the post-fire behaviour of carbon steel. A total of seventeen coupon specimens were tested by uniaxial tensile test. One of them was tested without heating and considered as a reference. Sixteen specimens were heated at a temperature of either 400°C or 700°C for different durations. Eight specimens were cooled in air and the others cooled in water. Heating durations were 30 min, 60 min, 90 min and 120 min. Results showed that the high-temperature has a great influence on decreasing the ultimate and yield stress and elongation for specimens cooled in the air. For specimens cooled in water, the decreased in yield and ultimate stress was minor comparing to the reference specimen. The ductility of water-cooled specimens showed a noticeable reduction comparing to specimens cooled in air. Increasing the heating time results in higher elongation for specimens heated to 400oC and lower elongation for specimens heated to 700^oC, but the specimen loses strength in both cases.

Conclusions

An experimental investigation was conducted in this study on the behaviour of carbon steel after elevated temperatures. The main conclusions of the study can be summarized as follows:

The physical change, especially after the coupons were exposed to high temperatures, was only in thickness and did not affect another dimension another.
Corrosion starts showing clearly in water-cooled specimens, that was heated to 700° C, whereas for specimens heated to 400° C no corrosion appears on the surface of specimens.
A clear reduction in the yield stress and ultimate strength can occur due to heating the steel to 400° C whether it was cooled in air or water. The maximum percentage of reduction in the yield strength and the ultimate strength are 21% and 16% respectively for the specimens cooled in air. For the water-cooled specimens, the decrease in the yield stress and the ultimate strength are 14% and 17% respectively. These ratios are after heating the specimens for 120 minutes.
Heating the carbon steel to 700^o C can reduce the yield stress and ultimate strength 19% and 13% respectively for the specimens cooled in air. For the water-cooled specimens, the decrease in the yield stress and the ultimate strength was in significant. These ratios are after heating the specimens for 120 minutes. It is recommended to cool the carbon steel using water to avoid strength reduction.
There is no significant difference in the yield strength and ultimate strength of steel heated to 400 °C or 700°C and cooled in air.
The yield strength and the ultimate strength of steel heated to 700°C and cooled in water can be higher than that heated to 400°C and cooled in water.
The elongation of steel heated to 700°C and cooled in water can be lower than that heated to 400°C and cooled in water.

Downloads

Download data is not yet available.

References

A. Al-manoufi , The Use of Met al. Skelton in the Multi-story Building Constructions , Damascus University , Faculty of Architecture Department of Building Science and Construction 2016 P(2).

The structural stability of steel buildings must be maintained in case of fire. To save lives and reduce property losses. Checking the behaviour of frame steel buildings at fire conditions (Swinden 1999).

Marwan Sarraj , The Behaviour of Bolted Connections in Fire, Department of Civil and Structural Engineering, The University of Sheffield (2007) p27.

A . Tamboli ,Han, book of structural steel connection design and details (Third edition ) , 2009 . p (24).

F,Wald, L. Simoes da Silva, D.B. Moore, T. Lennon, M. Chladna, A. Santiago, M. Benes, L. Borges, Experimental behaviour of a steel structure under natural fire, Fire Saf. J. 41 (2006) 509–522.

Marwan Sarraj , The Behaviour of Bolted Connections in Fire, Department of Civil and Structural Engineering, The University of Sheffield (2007).

Jinwoo Lee, Elevated-Temperature Properties of ASTM A992 Steel for Structural-Fire Engineering Analysis, Presented to the Faculty of the Graduate School of The University of Texas at Austin(2012).

S. Selamet , M. Garlock , Fire resistance of steel shear connections , fire safety journal (2014).

Y . Cai , B . Young, Effects of end distance on thin sheet steel single shear bolted connections at elevated temperatures ,Thin-walled structure 148(2020)106577.

K . Yang , R . Hsu, C . Hsu, Strength criteria for bolted connections at elevated temperature, Journal of Constructional Steel Research 88 (2013) 43–52.

Z . Huang ,connection element for modelling end-plate connections in fire, journal of construction steel research 67(2011) 841-853.

Gewain, R. G., Iwankiw, N. R., & Farid, A. (2003). Facts for Steel Building : Fire. United States: American Institutre of Steel Construction

Gebril M.A., Aldlemey M.S., Kablan A.F. (2014) Effect of Austenization Temperatures and Times on Hardness, Microstructure and Corrosion Rate of High Carbon Steel. In: Öchsner A., Altenbach H. (eds) Design and Computation of Modern Engineering Materials. Advanced Structured Materials, vol 54. Springer, Cham. https://doi.org/10.1007/978-3-319-07383-5_30

J. Nagie (2014) The effect of cooling rate on mechanical properties of carbon steel St 35 , Diyala Journal of Engineering Sciences, Vol. 07, No. 01, pp. 109-118, March.

Aziz, E. M., Kodur, V., Glassman, J. D., & Moreyra Garlock, M. E. (2015). Behavior of steel bridge girders under fire conditions. Journal of Constructional Steel Research, 106, 11–22.

Fan, Shenggang, Xiaofeng Ding, Wenjun Sun, Liyuan Zhang, and Meijing Liu. (2016). Experimental investigation on fire resistance of stainless-steel columns with square hollow section. Thin-Walled Structures, 98, 196-211.

Choi, J., Seok, C. S., Park, S., & Kim, G. (2019). Effect of high-temperature degradation on microstructure evolution and mechanical properties of austenitic heat-resistant steel. Journal of Materials Research and Technology, 8(2), 2011-2020.

Cai, Y., & Young, B. (2020). Effects of end distance on thin sheet steel single shear bolted connections at elevated temperatures. Thin-Walled Structures, 148, 106577.

CEN (European Committee for Standardization , Method of test at Ambient Temperature ,in Met al.lic materials -tensile testing , part1 :E.N 10002:2001,CEN Brussels ,Beligum .

Y .Cho , L. Teh , B . Young , A . Ahmed, Net section tension strength of bolted connections in ultra-high strength sheet steel during and after fire, Journal of Constructional Steel Research 172 (2020) 106237 .

A. Çalik , Effect of cooling rate on hardness and microstructure of AISI 1020, AISI 1040 and AISI 1060 Steels, International Journal of Physical Sciences Vol. 4 (9), pp. 514-518, September, 2009 .