Material selection and product specification. Steel material is supplied in two product forms flat products steel plate and strip and long products rolled sections, either open beams, angles, etc or hollow sections. For structural use in bridges these products are inevitably cut to size and shape and welded, one component to another. In the structure, the material is subject to tensile and compressive forces. Structural steel generally responds in a linear elastic manner, up to the yield point and thereafter has a significant capacity for plastic straining before failure. Reinforced Concrete Design Articles Eurocode 8 Structural types Eurocode 8 Ductility clas. PrestressedConcreteDesign 6. Thermalstress calculation heating 139 6. Thermalstress calculation cooling 142 6. Reductionofmomentoversupportin. SteelConstruction. The free encyclopedia for UK steel construction, covering steel design, Eurocodes, steelwork costs, thermal mass, fire engineering, embodied. BETONexpress Design of concrete structures according to Eurocode 2. Crack Width Calculation Eurocode 2' title='Crack Width Calculation Eurocode 2' />All these aspects of steel material are utilised by the designer of a steel bridge. The selection of an appropriate grade of steel for a bridge requires an awareness of the steel manufacturing process, an appreciation of the relevant product standards and design specifications, and an understanding of several issues including material properties, availability and cost. Cmd Commands For Hacking Facebook Account. This article provides designers with background information and specific guidance on how to select an appropriate steel grade and quality, and on how the structural steel products for a bridge are specified in accordance with the Structural Eurocodes. Schematic stress strain diagram for steeltopMaterial propertiestopGeneral. Steel derives its material properties from a combination of chemical composition, mechanical working and heat treatment. The chemical composition is fundamental to the mechanical properties of steel. Adding alloys such as Carbon, Manganese, Niobium and Vanadium can increase the strength. However, such alloy additions increase the cost of the steel, and can adversely affect other properties i. Keeping the sulphur level low can enhance the ductility, and the toughness can be improved by the addition of Nickel. Hence, the chemical composition for each steel specification has been carefully chosen to achieve the required properties. Crack Width Calculation Eurocode 2' title='Crack Width Calculation Eurocode 2' />Plate mill control room. Plates and sections are produced by rolling steel slabs, blooms or billets at a high temperature until the required plate or section size is achieved. This rolling is the mechanical working that refines the grain structure and determines the mechanical properties. The more steel is rolled, the stronger it becomes. This effect is readily apparent in material standards, which specify reducing levels of minimum yield strength with increasing material thickness. However, although rolling increases the strength, it also reduces the ductility of the steel. Crack Width Calculation Eurocode 2' title='Crack Width Calculation Eurocode 2' />The effect of heat treatment is best explained by reference to the different production processes or rolling regimes that can be used in steel manufacturing, the main ones being. As rolled steel. Normalized steel. Normalized rolled steel. Thermomechanically rolled TMR steel. Quenched and tempered Qand. T steel. Steel cools as it is rolled, and the typical rolling finish temperature is 7. C, after which the steel cools naturally. Steel produced through this route is termed As rolled. Curtain walls wall claddings windows and slope roof glazing Part 1 Design considerations Gill J, JGA Publications Ltd ISBN None, pp 23, 1992. Coldformed steel CFS is the common term for products made by rolling or pressing steel into semifinished or finished goods at relatively low temperatures cold. BIP 20222003. 2 Building Services Handbook 2nd edition BIP 20372004. Structural sections generally achieve the required mechanical properties through this efficient production route, but plates usually require further heat treatment. Normalizing is the process where an as rolled plate is heated back up to approximately 9. C, and held at that temperature for a specific time, before being allowed to cool naturally. This process refines the grain size and improves the mechanical properties, specifically the toughness. It renders the properties more uniform, and removes residual rolling strains. Normalized rolled is a process where the rolling finish temperature is above 9. C, and the steel is allowed to cool naturally. This has a similar effect on the properties as Normalizing, but it eliminates a process. Normalized and Normalized rolled steels are denoted N. Thermomechanical rolled steel utilises a leaner chemistry, which requires a lower rolling finish temperature of 7. C to put the strength in, before the steel cools naturally. Note that greater force is required to roll the steel at these lower temperatures, and that the properties are retained unless reheated above 6. Rare Drum Breaks Rar Files. C. Thermomechanical rolled steel is denoted M. The process for Quenched and Tempered steel starts with an as rolled plate, heats it back to 9. C and holds it at that temperature, as for normalizing, but then the steel is rapidly cooled or quenched to produce steel with high strength and hardness, but low toughness. The toughness is restored by reheating it to 6. C, maintaining the temperature for a specific time, and then allowing it to cool naturally tempering. Quenched and tempered steels are denoted Q. Schematic temperature time graph of rolling processestopMechanical properties. The mechanical properties of particular importance to the bridge designer include. Weldability. Welding on stiffenersImage courtesy of Mabey Bridge Ltd. All structural steels are essentially weldable. However, welding involves locally heating the steel material, which subsequently cools. The cooling can be quite fast, because the material offers a large heat sink and the weld and the heat introduced is relatively small. This can lead to hardening of the heat affected zone and to reduced toughness. The significance of this effect increases as the plate thickness increases. The susceptibility to embrittlement also depends on the alloying elements, principally, but not exclusively, on the carbon content. This susceptibility can be expressed as the Carbon Equivalent Value CEV. The CEN product standards e. EN 1. 00. 25 11 give an expression for determining this value, and specify mandatory limits on the maximum CEV. Welding standards e. EN 1. 01. 1 22 will indicate what preheat, if any, is needed for a given CEV, material thickness and weld size. All structural steels, with the exception of weathering steel, have a similar resistance to corrosion. In exposed conditions they need to be protected by a coating system. There are no special requirements of the steel material for ordinary coating systems, including both aluminium and zinc metal spray. Global Mapper (64-Bit) there. However, if the steel is to be galvanized, then there is a need to control the alloy content notably the Silicon content, this can be achieved simply by specifying that the steel be suitable for hot dip zinc coating option 5 in EN 1. Coating applicationImage courtesy of Mabey Bridge Ltd. A weathering steel bridgeWestgate Bridge, Gloucester. Weathering steel is a high strength low alloy steel that in suitable environments forms an adherent protective rust patina, to inhibit further corrosion. The corrosion rate is so low that bridges fabricated from unpainted weathering steel can achieve a 1. Design requirements. EN 1. 99. 3 23, Section 3, Materials describes the requirements for structural steel for bridgeworks, and contains the following clauses. EN 1. 99. 3 23 makes the assumption that execution is carried out in accordance with EN1. General Product standards. All new structural steel for use in bridges should be manufactured to a CEN European Standard EN. These product standards are issued in the UK by BSI, with a short National Foreword that occasionally makes minor modifications to the Standard, and consequently bear the BS EN designation before the reference number. The following CEN product standards are relevant to bridge steelwork. EN 1. 00. 25 For plates and open sections. Part 25 Non alloy structural steels.