Abstract: understand the behavior of steel at fire. To

Abstract: This paper deals with the study of effect on steel structures in case of fire occurrences.The material properties that affect the behavior of structural steel , members exposed to fire havebeen observed. The performance of steel structures at raised temperature is determined. by manyways. The changes in the properties are studied using different machine. The specimens aretested for 27?C,, 100?C to 900?C at the interval of 100?C Because of temperature effect it seen thatthe load carrying capacity of steel specimen decreases, also steel specimen becomes hard attemperature more than 600?C.Keywords: Temperature; Steel structures; Fires; Thermal expansion; Raised temperatures;Thermal properties; Tensile and torsion strength; Mechanical properties.1. INTRODUCTION: The behavior of mechanical properties of steel grades at raisedtemperatures should be known to understand the behavior of steel at fire. To study the behavior ofsteel structure at raised temperatures, one should use the material data of the used steel materialobtained by testing. The tests have to be conducted so that the results can be used to find the behaviorof the structure. Steel has been widely used in the world. It is one of a designers best options in viewof its advantages. Steel is available in a range of discrete size; its ductile behavior allows plasticdeformation upon yielding, therefore avoiding brittle failure. Fires are destructive; it causes injury,death & loss of property followed by negative environmental consequences. Design of structuresshould incorporate measures to prevent destruction of the structure safeguarding safety issues relatedto human occupancy. Steel elements are commonly used for structures in the building andconstruction industry. However, it has relatively low resistance to raised temperatures thus causingfailure of the structure. The expected behavior is dependent upon the severity of the fire, materialproperties and the degree of protection provided. Therefore, studying the behavior of steel structuresunder temperature becomes an important issue. Thus the study is required to analyze the steelsubjected to high temperature & than its relative strength at high temperature. Some structures aresubjected to accidental fire, due to heat steel member undergo changes in its physical, mechanicaland sometime chemical properties. There are many examples in past, fire always cause hazard.Because of fire the countless loss of valuable materials, goods & human beings. In this work attempthas been meet to investigate the properties of steel under the raised temperature.Need to study behavior of steel under fire “Buildings shall be constructed to maintain structuralstability during fire:i. Allow people adequate time to move safely.ii. Allow fire service personnel adequate time to undertake rescue and fire-fighting operationsiii. Avoid collapse and consequential damage to adjacent household units or other property.2 METHODS2.1 Experimental ProgramThere are three specimens tested each test. Five different tests are conducted on steel, which aretensile testing on mild steel 16 mm ø bar and 25 mm x 5 mm mild steel plate. Torsion test on mildsteel 16 mm ø bar and 22 mm ø pipe which having 2mm thickness, also bending test on 22mm øpipe which having 2mm thickness. In tensile testing there is study of load carrying capacity of thatspecimen under raised temperature, elongation of that specimen and diameter of bar after breakingdue to loading. First two steps are same for the tensile testing of plate third step for plate is studyof plate thickness after breaking, and elongation is measured with help of extensometer.The electric furnace is used for the heating the specimens. The rate of heat is 60°C per minute.The specimen is kept in the furnace and the required temperature. The temperature rate setting donewith the help of controller of furnace. The inner depth of the furnace is 0.45m X0.45m. Thespecimens are kept for duration of 2 hour inside the furnace and later specimens are taken out andcooling of specimen is done under natural atmospheric environment. Each time three specimen arekept at temperatures of Room temperature(27°C), 100°C, 200°C, 300°C, 400°C, 500°C, 600°C,700°C, 800°C and 900°C.2.2 EquipmentUniversal Testing Machine- UTM is used to find the compressive, tensile and flexure strength of thespecimen. The specimen is fixed on the machine. Here tensile loading is carried out to find thetensile strength on steel specimens (mild steel bar, and steel plate).Torsion Testing Machine- TTMis used to find the Torsion of the specimen. The specimen is fixed on the machine. Here torsion testis carried out to find the torsion of steel specimens (mild steel bar, steel hollow section). ElectricalFurnace- The electric furnace is used to heat the specimens. The maximum temperature attained inthe furnace is 1000°C. Then specimens will be kept inside with the door closing tightly so that noair enters inside. Each specimen is kept for duration of 2 hour inside the furnace for an each specifiedcontrolled temperature Extensometer-These extensometers are used for direct extensionmeasurement in tensile tests, flexure tests and alternating load tests. They all possess a largemeasurement range featuring step less adjustment to suit the specimen being tested. Attachextensometers and extensometers with sensor arms are in direct mechanical contact with thespecimen via knife-edges positioned at right angles to the gauge length.3. RESULT AND DISCUSSION3.1 The results of Tensile testing of 16 mm ø bar are plotted on graphThe test is carried out on 16 mm ø bar, which was heated in furnace for two hour at rate of 9°C/min. After heating, the gauge length is marked on bar which is 5xDiameter of bar and thentests were carried out. For testing, total thirty numbers of specimens were taken. The procedureof testing was carried out at various temperatures as for 270C, 1000C, 2000C, 3000C, 4000C,5000C, 6000C, 7000C, 8000C and 9000C while for each temperature testing three specimenswere taken.Temperature in ?C Elongation (%)27 41.25100 40.00200 36.25300 36.25400 35.00500 33.75600 31.25700 30.00Temperature in ?C Diameter afterfailure (mm)27 9.45100 9.50200 9.90300 10.15400 10.35500 10.35600 10.9700 10.95800 11.65Table No 3.1 Bar elongation at timefailure and Temperature.Figure No. 3.1 Elongation Vs Temperature for 16 mm ø bar.From fig 3.1, It can be observed that the elongation of bar decreases with respect to temperature.At room temperature elongation of bar is 41.25%, but after 900?C temperature the elongation ofbar is 15%. Elongation of bar is decrease by 26.25%.Table No 3.2 Bar-Diameter after failure and Temperature.41.25 4036.25 36.25 35 33.7531.25 3018.75150510152025303540450 100 200 300 400 500 600 700 800 900 1000Elongation (%)TemperatureElongation (%)800 18.75900 15.00Figure 3.2 Bar-Diameter after failure Vs Temperature graph.From fig 3.2, It can be saying that the Diameter of bar increases with respect to temperaturebecause of hardness of bar. Original diameter of bar is 16mm, diameter afterbreaking at room temperature is 9.45mm and at 900?C it is 11.9mm.3.3 The results of Tensile testing of plate are plotted on graphThe test is carried out on 25 x 5 mm plate, which is heat in furnace for two hours at rateof 9°C per minute. After heating the gauge length is marked on bar which is 5.65xCrosssectional area of rectangular specimenTable No 3.3 Plate Temperature and elongation09.45 9.5 9.9 10.15 10.35 10.35 10.9 10.9511.65 11.9024681012140 2 4 6 8 10 12Diameter(mm)TemperatureDiameter after after failureTemperature(?C)Elongation(%)27 153.72100 150.55200 145.80300 144.22400 142.63500 139.46600 137.08700 134.70800 123.61900 115.69Figure 3.3 Plate-Elongation Vs Temperature graph.From fig 3.3, It can be observed that the elongation of bar is decreases with respectto temperature. At room temperature elongation of bar is 153.72%, but after 900?Ctemperature the elongation of bar is 115.69%. Elongation of bar is decrease by38.03%.Table No 3.4 Plate Temperature and Thickness of plate after failure153.72150.55 145.8 144.22 142.63 139.46 137.08 134.7123.61 115.690204060801001201401601800 200 400 600 800 1000Elonation(%)TemperatureElongation (%)Temperature(?C)Thickness ofplateAfter breaking(%)27 25.00100 31.00200 30.00300 32.00400 32.00500 36.00600 39.00700 39.00800 40.00900 41.00Figure 3.4 Thickness Vs Temperature for plate.From fig 3.4, It can be observed that the thickness of plate is increases with respect totemperature. At room temperature thickness of plate is 25%, but after 900?C temperature the thickness ofplate is 41%. Elongation of bar is increase by 16%.In this graph, it is seen that the elongation of plateis decreased to raised temperature