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 test assembly must sustain the applied load during the fire endurance test (structural end point). or gases hot enough to ignite cotton wasie must not pass through the test assembly (flame passage end point). 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). are additional end point criteria for special cases. Those applicable to concrete are as follows: 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. concrete beams more than 4 ft (1.2m) on centers: the temperatures in1. 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. concrete beams spaced 4 ft ( 1.2 m) or less on centers and slabs are not subjected to the steel temperature limitations. and partitions must meet the same cri- teria as in1.3.1.1,, and 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.