ACI 216R-89 Guide for Determining the Fire Endurance of Concrete Elements.
1.3-Standard fire tests of building construction and materials ASTM E 119 specifies the test methods and procedures for determing the fire resistive properties of building compo- nents, and is a generally accepted standard for performing fire tests. 1.3.1 – Endpoint criteria of ASTM E I19 18.104.22.168-The test assembly must sustain the applied load during the fire endurance test (structural end point). 22.214.171.124-Flame or gases hot enough to ignite cotton wasie must not pass through the test assembly (flame passage end point). 126.96.36.199-Transmission of heat through the test assembly shall not increase the temperature of the unexposed surface more than an average of 250 F (139 C) or 325 F ( 181 C) at any one point (heat transmission end point). 188.8.131.52-There are additional end point criteria for special cases. Those applicable to concrete are as follows: 184.108.40.206.1-Unrestrained concrete structural members: average temperature of the tension steel at any section must not exceed 1100 F (593 C) for reinforcing bars or 800 F (427 C) for cold-drawn prestressing steel. 220.127.116.11.2-Restrained concrete beams more than 4 ft (1.2m) on centers: the temperatures in18.104.22.168.1 must not be exceeded for classifications of 1 hr or less; for classifications longer than 1 hr, the above temperatures must not be exceeded for first half of the classification period or 1 hr , whichever is longer. 22.214.171.124.3-Restrained concrete beams spaced 4 ft ( 1.2 m) or less on centers and slabs are not subjected to the steel temperature limitations. 126.96.36.199.4-Walls and partitions must meet the same cri- teria as in188.8.131.52, 184.108.40.206, and 220.127.116.11. In addition, they must sustain a hose stream test.
During the course of a fire, the negative moment reinforce- ment (Fig. 2.2.1) remains cooler than the positive moment reinforcement because it is better protected from the fire. Thus, the increase in negative moment can be accommo- dated. Generally, the redistribution that occurs is sufficient to cause yielding of the negative moment reinforcement. The resulting decrease in positive moment means that the positive moment reinforcement can be heated to a higher temperature before failure will occur. Thus, it is apparent that the fire en- durance of a continuous reinforced concrete beam is gener- ally significantly longer than that of a similar simply sup- ported beam loaded to the same moment intensity. 2.2.2 Detailing precautions-It should be noted that the amount of redistribution that occurs is sufficient to cause yielding of the negative moment reinforcement. Since by in- creasing the amount of negative moment reinforcement, a greater negative moment will be attracted, care must be exer- cised in designing the member to assure that flexural tension will govern the design. ACI 216R pdf download.