Reinforced Concrete Design: to Eurocode 2

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It shall be designed to have adequate stability, structural resistance, serviceability and durability. In the case of fire, the structural resistance shall be adequate for the required period of time. A structure shall be designed and executed in such a way that it will not be damaged by events such as explosion, impact and the consequences of human errors, to an extent disproportionate to the original cause. cction \\ ith a kno'' n area of \lee! retnforcement. For equilibrium of the compres-.tve force 111 the concrete and the tensile force in the \tcl'l tn figure 4.4: or W. H. Mosley and J. H. Bungey 1976, 1982, 1987, 1990 f ' W. H. Mosley, J. H. Bungey and R. Hulse 1999, 2007 commonly used for reinforcement. may behave in a similar m;mner or may, on the other hand, not have such a definite y ield point but may show a more gradual l:hange from elastil: to pla:-:tic behaviour and reduced ductility depending on the manufacturing prol:css. A ll mater.ials have a simi lar slope of the clastic region with elastic modul us Es 200 kN/mm 2 approximately. The speciricd strength used in design is based on either the y ield stress or a speci ried proof' stress. A 0.2 per cent proof stress is defined in 1'\gurc 1.5 by the broken line drawn parallel to the linear part of the stress-strain curve. Removal of the load within the plastic range would result in I he stress- strain diagram following a line approximately parallel to the loading pori ion - sec line BC in fi gure 1.6. The steel will be left wi th a permanent strain AC. which is known as ' t-.lip'. If the steel is again loaded. lhe su·ess-strai n diagram will follow the unlonding curve unti l it almost reaches the original stress at B and then it will curve i n the direction of the first loading. Thus, the proportional limit for the second loading is higher I han for the in itial loading. This action is rel'tm-ed tO as ·strain hardening' or 'work hardening'. The load deformntion of the steel is also dependent on the length of' time the load is applied. Under a constant stress the strains will gradually increase - this phenomenon is known as ·creep' or 'relaxation'. The mnount of creep that takes place over a period of ·time depends on the grade of steel and the magnitude of the stress. Creep of the steel is of little significance in normal reinforced concrete work, hut i1 is an important factor in prestres:-:ed concrete where the prestressing steel is very highl y stressed.

Completely revised to reflect recent experience of the usage of Eurocode 2 since its introduction in 2004 and its adoption in the UK as a design standard in 2010 The width may have to be very much greater in some cases, especially when a larger width is needed to reduce the shear stress in the beam. As said earlier, the size is generally chosen from experience. Many design guides are available which assist in design. Efective flange width of beams Mean width of the tension zone. For a T beam with the flange in compression, only the width of the web is taken into account For spans longer than 7 m (except tlat slabs) and where it is necc1-sary to limit dellcr.;tions to ensure that finishei>, such as partitions. are not damaged. the basic values -,hould be multiplied by 7/ span.For bent bars, the basic tension anchorage length is measured along the centreline of the bar from the section in question to the end of the bar, where:

b) Internal ties lntcmal tie ... should abo h~ provided at each noor in two perpendicular directions anu he anchored a ii) Design of steel area, As, with stresses fn and fcc specified 1 e depth of the neutral axi~ can abo be expres~cu in tcnm. ollh~.: ~tr~uns and sucsses ol tl ~ concrete anu \!eel. I rom the ltnear Mrain distribution of figure 4.27: ~--·T)plcal valucll of k arc given in table 6.14 for varioull common shape!> of bendingment diagramll. If the loading is complex. then a value of k muM be estimated for the c :nplete load smce summing deflection" of simpler components will y1eld incorrect 1. ults. Consultant (Chairman) British Precast Concrete Federation British Cement Association The Concrete Society Construct The Concrete Centre BRE DCLG Quarry Products Association Arup Alan Baxter & Associates Powell Tolner Associates Clark Smith Partnership DCLG Consultant W S Atkins Concrete Innovation and Design negligible. ■ Accidental actions are actions of short duration but of significant magnitude that are unlikely to occur on a given structure during the design working life. The characteristic value of an action is defined by one of the following three alternatives. Note The numerical values given above are in accordance with BS EN 1990 and its UK National Annex Key a See also BS EN 1991 Further infonnation on the pmctieal details of design fo1 tor~ion and a de11ign example arc given in charter 7.