بررسي رفتار سقف كامپوزيت با تير لانه زنبوري در آتش سوزي

Behaviour of Castellated Composite Floor Beams in Fire

مقاومت و سختي فولاد در حرارت هاي بالا كاهش مي يابد و بررسي رفتار سازه هاي فولادي را در حرارت هاي بالا ضروري مي‌سازد. در ايران، ساخت سازه هاي فولادي و اجراي سقف كامپوزيت بسيار مورد توجه است و در اين پژوهش از نرم افزار اجزا محدود ABAQUS براي مطالعه‌ي رفتار سقف كامپوزيت با تير لانه زنبوري در دماهاي بالا استفاده شده و تحت آناليز كوپله‌ي مكانيكي– حرارتي براي درنظرگرفتن اثر نيروهاي مكانيكي و بار حرارتي قرار گرفته است. بعد از صحت‌سنجي نتايج مدل‌سازي عددي با نتايج آزمايشگاهي، مقدار تغييرمكان نمونه هاي مختلف تحت بارگذاري در حرارت‌هاي بالا با هم مقايسه و به بررسي ابعاد تير در ميزان مقاومت آن در آتش پرداخته شده است. نمودارهاي نيرو- تغييرمكان نمونه ها در ترازهاي حرارتي مختلف به‌دست آمده است. با مقايسه‌ي نمودار ها در ترازهاي حرارتي مختلف ديده مي شود كه سقف كامپوزيت با فولاد و بتن معمول ساختماني امكان مقاومت در برابر حرارت هاي بالاي 800 درجه سانتي‌گراد را ندارد.

Every year, immense economic and personal costs are imposed as a result of fire damage. It is unlikely that we will ever be able to completely prevent fires from occurring, so, the aim of fire engineering is to reduce the risk presented by fire to acceptable levels. The mechanical strength and stiffness of unprotected steel reduces drastically at elevated temperatures, and the behavior of steel structures is of particular concern. Castellated composite floor beams have been used in structures in Iran for many years, because of their simplicity and economic advantages. Thus, it is important to further work on this topic in Iran. In the present study, finite element models of the composite beams are developed by the FE code, ABAQUS, and the results of the models are compared to that of experimental tests under standard fire conditions to verify the finite element models. Fair agreement was achieved between the model and the experiment, confirming that the finite-element model used is capable of predicting the behavior of the connections at elevated temperatures. Four different sizes of castellated beam were chosen to study the effect of high temperature on the mid-span displacement of composite beams. Also, four different levels of temperature are studied on the load capacity of the beams. Since the behavior of the beam and concrete floor is studied under static and thermal loading, coupled temperature-displacement analysis is used to increase the accuracy of the analyses. “Temperature–displacement” and “displacement–force” curves were derived from these analyses. The results show that increasing the size of castellated beams reduces displacement at the mid-span of the beam due to its increase in stiffness. The stiffness of mild steel, as well as the load bearing capacity of composite beams at elevated temperature, decreases, which causes large displacement at mid-span. The results show that castellated beams cannot withstand temperatures over 800 ?C.