The Imperial College London tested Dextra Bartec/Fortec and Griptec couplers at elevated temperatures to evaluate how the couplers would perform in case of a fire.
Highlights of the test include:
The findings indicate that current codified rules can be used for assessing the strength and stiffness properties of both non-spliced rebar and rebar connected with Bartec/Fortec or Griptec couplers.
At temperatures below 400°C the ultimate tensile strength and stiffness of Bartec/Fortec and Griptec splices, as well as un-spliced rebar is not significantly affected.
When tensile tested at temperatures below 500°C, failure still generally occurred in the rebar outside of the Bartec/Fortec or Griptec coupler region.
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Dextra Bartec/Fortec and Griptec rebar couplers at elevated temperatures
Dextra have recently collaborated with Imperial College London to investigate the performance of rebar couplers at elevated temperatures, simulating temperatures which could occur in rebar due to fire, both before and after concrete spalling.
Standard 16mm and 20mm Bartec/Fortec and Griptec couplers were used, as well as non-spliced reinforcement and tests conducted at ambient, elevated steady state and transient elevated temperatures.
a) testing machine, b) schematic representation of the testing arrangement
Codified procedures for the fire design of reinforced concrete structures typically give prescriptive recommendations for rebar/coupler cover with the aim of protecting the reinforcement from reaching temperatures above a critical value of around 500°C.
The test results show that:
For both spliced and un-spliced specimens there is a gradual decrease in yield strength as temperature increases.
At temperatures below 400°C the ultimate tensile strength and stiffness of the spliced and un-spliced specimens is not significantly affected.
When tensile tested at temperatures below 500°C, failure still generally occurred in the rebar outside of the coupler region.
The findings also indicate that current codified rules can be used for assessing the strength and stiffness properties of both non-spliced rebar and rebar connected with Bartec/Fortec or Griptec couplers.
However, the code assumptions regarding the ultimate strain characteristics at elevated temperatures were found to be unrealistic for hot rolled rebar, as well as rebar connected by couplers.
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参考文献
Bompa, D. V., & Elghazouli, A. Y. (2019). Elevated temperature characteristics of steel reinforcement incorporating threaded mechanical couplers. Fire Safety Journal, 104, 8–21. https://doi.org/10.1016/j.firesaf.2018.12.006
