Eurocode 4: Design of composite
steel and concrete structures
Dr Stephen Hicks, Manager Structural Systems, Heavy Engineering
Rearch Association, New Zealand
Introduction
BS EN 1994 (Eurocode 4) is the Structural Eurocode that deals with composite steel and concrete structures. It replaces the following national standards: BS 5400-5, BS 5950-3.1 and BS 5950-4. Eurocode 4 consists of three Parts:• Part 1-1, General rules and rules for buildings (BS EN 1994-1-1);
• Part 1-2, General rules — Structural fi re design (BS EN 1994-1-2); and • Part 2, General rules and rules for bridges (BS EN 1994-2).
To enable Eurocode 4 to be ud, designers also need to make reference to the national annex, which includes the national decision for Nationally Determined Parameters (NDPs), the national decision regarding the u of informative annexes and reference to N on-Confl icting Complementary Informati
on (NCCI). For BS EN 1994-1-1 and BS EN 1994-1-2, the website www. s teel- uk will provide all the necessary NCCI, whilst for BS EN 1994-2 NCCI is given in PD 6696-2. In the interests of improving free circulation o f p roducts a nd s ervices i n E urope, i t i s i ntended t o r educe t he n umber of NDPs in the future, thereby leading to a gradual alignment of safety levels across the member states. As a fi rst step in this process, the European Commis-sion Joint Rearch Centre (JRC) has commenced a pilot project that is consider-ing the harmonization of NDPs, who initial focus is Eurocode 2, Eurocode 3 and Eurocode 4 (uropa.eu/showpage.php?id=52).
To assist designers in understanding Eurocode 4, references [1], [2] and [3] provide background information on the origin and objectives of the code provisions, which are supplemented by a lection of worked
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The esntial guide to Eurocodes transition
examples that illustrate the u of a particular clau. In addition, background information is freely available through the Eurocodes website of the JRC (uropa.eu/).
The objective of this chapter is to provide an overview of the key aspects to Eurocode 4 and consider the principal changes for UK designers. The convention ud is that, when the provisions are similar in different parts of this Structural Eurocode, Eurocode 4 is referenced. However, when the rules are specifi c to a certain type of structure, the relevant part is identifi ed (e.g. BS EN 1994-1-1 for buildings).
Materials
Structural steel
Although the u of structural steel with a nominal yield strength of not more than 460 N/mm2 is permitted in bridge designs conforming to B S 5400-5, Eurocode 4 offers opportunities for building designers, where previously a yield strength of not greater than 355 N/mm2 was allowed in BS 5950-3.1. According to Eurocode 3, the modulus of elasticity for steel should be taken as 210 kN/mm2, rather than the value of 205 kN/mm2 given in BS 5400 and BS 5950.
Concrete
The strength and deformation characteristics for normal weight and light-weight concrete are given i
金鱼论坛n Eurocode 2. The compressive concrete strengths ud in the design rules in according to Eurocode 4 are bad on cylinder strengths. Strength class are defi ned as C x/y for normal weight concrete and LC x/y for lightweight concrete, where x and y are the characteristic cylinder and cube compressive strengths respectively. For example, C25/30 denotes a normal weight concrete with a characteristic cylinder strength of 25 N/mm2 and a corresponding cube strength of 30 N/mm2.
While BS 5950-3.1 covers the u of concrete grades C25/30 to C40/50 and LC20/25 to LC32/40, the range of concrete grades that are permitted in designs conforming to Eurocode 4 are much wider at C20/25 to C60/75 and LC20/22 to LC60/66 respectively. Although Eurocode 2 provides guidance for 106歌颂英雄的诗句
Eurocode 4: Design of composite steel and concrete structures lightweight concrete with dry densities of between 800 kg/m2 and 2000 kg/m2, it is unlikely that a density of less than 1750 kg/m3 will be ud in composite design, owing to the fact that this is the lowest value that is permitted in the Eurocode 4 equations for evaluating the resistance of headed stud connectors.龙之谷冰灵
Profi led steel sheeting
Yield strengths of 280 N/mm2 and 350 N/mm2 are the common grades for steel strip in the UK. Typically, profi led steel sheeting (or decking) is galvanized for durability purpos and, for internal environments, a total zinc coating of 275 g/m2 is normal. Grades of steel for profi led steel sheeting are specifi ed in BS EN 10326 (this replaces BS EN 10147, which is the reference given in the current version of BS EN 1994-1-1), which distinguishes both the yield strength and the level of zinc coating. For example, the designation S 280 GD + Z 275 means 280 N/mm2 yield strength and 275 g/m2 of zinc coating.
The rules in BS EN 1994-1-1 are only appropriate for profi led steel sheeting thickness above a certain bare metal thickness. The UK national annex us the recommended value of t ≥ 0.70 mm. Although an identical minimum sheet thickness is given in BS 5950-4, bare metal thickness of between 0.86 mm to 1.16 mm have generally been ud in the UK to date. The thickness of a 275 g/m2 zinc coating is equivalent to approximately 0.02 mm on each face, resulting in overall sheet thickness commonly ud in the UK of between 0.9 mm to 1.2 mm. For design calculations the smaller bare metal thickness should be ud.
Reinforcement
In a similar way as BS 5950-3.1, to simplify calculations the modulus of elas-ticity of the reinforcement may be taken as equal to the value for structural steel in Eurocode 4 (i.e. 210 kN/mm2 rather than 200 kN/mm2 given in Eurocode 2). Shear connectors
写竹子的古诗Headed stud connectors should be supplied according to BS EN ISO 13918 (rather than EN 13918, which is the reference incorrectly given in Eurocode 4).
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The esntial guide to Eurocodes transition
To distinguish studs ud for shear connectors, the designation SD is ud, for example, SD 19 × 100, is a headed stud shear connector with a 19 mm diameter shank and a nominal height of 100 mm. Due to the limitations to the Eurocode 4 design equations for calculating the resistance of headed stud connectors, the stud shank diameters that will be ud in practice are likely to be between 16 mm and 25 mm for solid concrete slabs, and not greater than 19 mm for studs t hrough- d eck welded within the ribs of profi led steel sheeting. The performance of other types of shear connector may be evaluated from standard tests given in the informative Annex B.2 of BS EN 1994-1-1, in the abnce of guidelines for a European Technical Approval (ETA).
In Eurocode 4, the nominal height of the stud rather than the l ength- after- w elding (LAW) is ud in the design equations. However, LAW is needed for detailing purpos, and is sometimes ud to ensure that limits to design rules are satisfi ed (e.g. LAW is required to determine whether a stud may be taken as ductile in the rules for partial shear connection). As a conquence of this, two values of stud height need to be considered by the designer: the nominal height for calculating resistance; and LAW when detailing the shear connection. Traditionally, the LAW is taken as 5 mm shorter than the nominal height.
Composite beams
画女孩Effective width of concrete fl anges to composite beams for shear lag The rules for the effective width in Eurocode 4 are simpler than BS 5400-5, but similar to tho in BS 5950-3.1. The effective width at the ultimate limit state is taken as a constant value for the middle portion of the span and tapers towards the points of zero moment, as shown in Figure 4.1 (as oppod to B S 5950-3.1 where a constant width is taken along the full length for s imply- s upported beams); similar results for effective widths of steel plated structural elements can be calculated from B S EN 1993-1-5. In addition, when multiple shear connectors are provided, the effective width may be incread by the distance between the outermost shear connectors measured from their c entre- l ines, b0 (e Figur
瑜伽伸展带>功败垂成是什么意思啊
e 4.1). However, for the rviceability limit state, the Eurocode 4 provisions are similar to BS 5950-3.1 in that a constant effective breadth may be assumed to act over the entire span, bad on the m id- s pan value.
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Eurocode 4: Design of composite steel and concrete structures
109
F i g u r e 4.1. E q u i v a l e n t s p a n s , f o r e f f e c t i v e w i d t h o f c o n c r e t e fl a n g e
K e y 1 L e = 0.85L 1 2 L e = 0.25(L 13 L e = 0.70L 2 4 L e = 2L 3 f o r
