تحليل حساسيت زمان گسيختگي قاب بتن آرمه ي در معرض آتش سوزي پس از زلزله نسبت به پارامترهاي طراحي و بارگذاري

SENSITIVITY ANALYSIS OF RC FRAME FAILURE TIME UNDER POST-EARTHQUAKE FIRE TOWARD DESIGN an‎d LOADING PARAMETER

آتش سوزي پس از زلزله (PEF) يكي از رخدادهاي نادر با عواقب ناخوشايند است. زمان مقاومت سازه ها در برابر آتش سوزي در سازه هاي آسيب ديده ي ناشي از زلزله مي تواند متفاوت از سازه هاي سالم باشد. در اين تحقيق اهميت پارامترهاي طراحي و بارگذاري بر مقاومت قاب هاي بتن آرمه تحت بار آتش سوزي پس از زلزله بررسي شده است. براي اين منظور حساسيت پارامترها با استفاده از روش تحليل حساسيت FOSM مبتني بر متغيرهاي تصادفي بررسي شده است. زمان اولين گسيختگي در قاب بتن آرمه به عنوان مقاومت قاب بتن آرمه در برابر بار PEF در نظر گرفته شده است. نتايج نشان مي دهد در بين پارامترهاي طراحي تنش تسليم ميلگرد مهم ترين پارامتر در مقاومت قاب بتن آرمه است. در بين پارامترهاي بارگذاري شدت بار لرزه يي بيشترين اهميت را در مقاومت قاب هاي بتن آرمه در آتش سوزي پس از زلزله دارد.

Several loads over the lifetime of buildings threaten the safety of structures. Earthquake, fire, explosion and ... hazards that jeopardize the safety of the structure.Post-earthquake fire (PEF) is one of the rare occurrences with high consequences.Resistance time of structures against fire in damaged structures caused by earthquake can be different from intact structures.In this research, the importance of designing and loading parameters on the resisting of reinforced concrete frames under post-earthquake fire loads has been investigated.For this purpose, the sensitivity of the parameters was investigated using the FOSM sensitivity analysis method based on random variables.The time of the first failure in the reinforced concrete frame is considered as the reinforcement frame resisting against the PEF load.The thermal load provided by ISO 834 is considered to thermal loading.The results show that, among the design parameters, the reinforcement yielding stresses are the most important parameter in the resistance of the reinforced concrete frame.Concreteresistance and dead load is also one of the most sensitive random variables.The modulus of the elasticity of the armature and the length of the span (if the armature cover is ignored) will produce the least sensitivity for the failure time.In the further analysis of PEF for ten earthquake records, the sensitivity of the failure time to seismic loads is investigated.The results show that seismic load in concrete frames (unlike steel frame) is the most sensitive to failure time.Among the loading parameters, the intensity of seismic load is most important in the resistance of reinforced concrete frames in post-earthquake fires loading.For example, in Sa = 0.7g, the response swing (mean plus minus two standard deviations) for a failure time of 145 minutes have been calculated.The highest swing for the reinforcement yield stress, concrete cover and concrete strength was calculated 60, 53 and 40 minutes, respectively.