paper: moss/webster
EC2 and BS 8110 compared Synopsis This paper is intended to raise awareness amongst the structural engineering profession of the forthcoming Eurocode for the Design of Concrete Structures EC2 which will, in a few years time, replace the existing British code BS 8110. The two codes are compared in the context of design of primary structural elements and information is given on the availability of design aids to assist the practitioner in becoming familiar with and using the new code. The results of a comparative design exercise on a whole building are also briefly reviewed.
Introduction The ENV version of Eurocode 2 Part 1-1 General Rules and Rules for Buildings has been around for some years as a draft for development. A National Application Document (NAD) was prepared prepared to be used in conjunction with the ENV and together with the main document was published by BSI in 19921. The intention was that this document would be trialled on real structures and it is referred to in Approved Document A of the Building Regulations. Regulations. However use of the existing ENV is believed to have been very limited. As part of the wider European Harmonisation process and linked to the requirements of the Construction Products Directive, considerable effort has been expended in recent years in converting the ENV version of the code into a full EN. The EN status means that eventually the code will become normative if and when it is accepted by formal voting. For practical purposes purposes normative in the UK means that it will have the same status as and eventually replace BS 8110.
Timetable for the introduction of EC2 The EN versions of Part 1-1 and Part 1-2 of the code dealing with fire have been through several draft revisions and are now being finalised†. The target date for publication of these Parts of the the code is early 2004. There will be National Annexes to accompany each part of the code, which will include values values for what are called Nationally Determined Parameters.In Parameters. In a similar way to the NAD the intention is that the code will be used with the appropriate National Annex in each member state. These National Annexes are in course of preparation and it is intended to make them available for Public Comment through BSI when the main code is issued.
Grades of concrete EC2 allows benefits to be derived from using high strength concretes concr etes,, which BS 8110 8110 does not. not. Concr Concrete ete strength strengthss are referred to by cylinder strengths,which strengths, which are typically 10-20% less than the corresponding cube strengths. The maximum characteristic cylinder strength f strength f ck permitted is 90N/mm2, which correcorresponds to a characteristic cube strength of 105N/mm2.
Materials and workmanship Part 1-1 of EC2 specifically does not cover this and a separate standard (termed an Execution Standard) has been prepared. This is currently in ENV form and a national document based on the existing National Structural Concrete Specification 2 is in preparation. One issue, which however is specifically referred to in Part 11 of EC2, is the tolerance on cover. Cover to meet durability durability and bond requirements is specified as a minimum value with a tolerance of up to 10mm to be added on top.This is in contrast to BS 8110 where cover is specified as a nominal value and a tolerance of 5mm accepted. In situations situations where good quality quality control is exercised there is scope for reducing the tolerance. †
The full references are EN 1992-1-1 Eurocode Eurocode 2: Design of concrete structures Part 1-1: General rules and rules for buildings and EN 1992-1-2 Eurocode 2: Design of concrete structures Part 1-2: General rules – structural fire design
Note that cover for fire requirements needs to be considered separately and is dealt with in Part 1-2 of EC2.
Design for fire This paper does not consider this topic,and in making comparisons between BS 8110 and EC2 assumes that covers and dimensions of members are largely unaffected by the changed design process. In Part 1-2 of EC2 there is a prescriptive method encompassing simplified approaches based on covers and member dimensions, which is broadly similar to the approach taken in BS 8110. There are however also more sophisticated performance based methods that can be used and the information is much more extensive than in Part 2 of BS 8110. It is envisaged that a specific How to design leaflet4 will be prepared to assist engineers in relation to this topic. Some further guidance on this topic can be found in a paper prepared by Professor Narayanan3.
Design for durability Comparisons between BS 8110 and EC2 made in this paper have assumed that the required covers to be provided are essentially unaltered. unaltered. Simplified guidance guidance to enable engineers to determine the required cover to be provided in different circumstances is in course of preparation and will be included within the National Annex to the code. There is a difference in approach with theoretically at least durability issues being considered more explicitly. explicitly. For example the code has classifications based around potential deterioration mechanisms and the designer should identify the most severe conditions in any particular case, case, rather than simply assessing the environmental exposure. The concept of an explicitly defined design life and the recognition of the need to take additional measures if this design life is required to be significantly exceeded must be seen as a positive step forward.
Richard Moss BSc, PhD, CEng, MICE, MIStructE Building Research Establishment
Rod Webster CEng, FIStructE Concrete Innovation & Design
Received: 06/02 Modified: 11/03 Accepted: 12/03 Keywords: Eurocode 2, BS 8110, Comparing, Concrete structures, Design ©Richard Moss, Rod Webster
Material partial safety factors As with BS 8110 EC2 uses a basic material partial safety factor years ago the material partial partial γ m for concrete of 1.5. Several years safety factor for reinforcing steel in BS 8110 was reduced from 1.15 to 1.05. EC2 uses a value of 1.15 although this is subject to a National Annex. This is unlikely to have any practical impact however as steel intended to meet the existing yield strength of 460N/mm2 assumed by BS 8110 is likely to be able to meet the 500N/mm2 assumption made by EC2, so that the design yield strength f strength f yd will be virtually identical.
Design values for loading In due course these will be given by EC1.The comparisons made in this paper in general consider only the resistance side of the equation although some mention is made of the partial load factors to be used. It is worth noting that a value value of 25kN/m3 is taken for the density of normal weight we ight concrete as opposed to the currently assumed value of 23.6 kN/m3. The combined impact of the partial load factors in conjunction with values for basic design loads and other items such as column load reduction factors and the assessment of slenderness in column members has been considered as part of a separate smallscale study in relation to to a whole building design. The building studied was a typical RC framed flat slab structure. The conclusions from this study were that, at least for the particular building building studied, the overall impact of using EC2 EC2 instead of BS 8110 was minimal.Further minimal. Further details of this study are given below.
Design of flexural elements at the ultimate limit state The design of flexural elements to EC2 is in practice very similar to that of BS 8110. Where EC2 differs, differs, as with the ENV, ENV, is that it does not generally give element specific design guidance, but
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more the general principles to be be applied. This approach should be welcomed, as it is less restrictive and may encourage innovative design methods. Several options are given for the type of stress-strain relationship that may be assumed assumed for concrete. In many cases the designer is likely to opt for the simple rectangular stress block. The stress block used in EC2 is compared with that in BS 8110 in fig 1a and 1b. There has been some debate as to what is the most appropriate value to take for α cc cc. The recommended value in the code is 1.0 but it is likely that the UK National Annex will require a value of 0.85 to be used. The parameter η has been introduced into EC2 and in combination with modification of the value for λ has the effect of reducing the allowable concrete force for higher strength concretes (above C50/60). For concrete strengths up to this value λ =0.8 =0.8 and η=1.0. The following basic equations may be derived for the design of elements in flexure. M 2 bd f ck
K =
l
K =
R
z =
a cc x max hm mx max d 2 2 d c c
d
cc d S 1 + 1 - 2 ha min K, K cc 2 S
_
T
_
i
M2 = bd2 fck K - K As2 =
As =
l
$
n
V
l
i WW
b #
0 .95d
X
0
M 2 fsc d - d2
_
a
i
Fig 1. a) EC2 stress block b) BS 8110 stres stresss block
f sc M - M 2 + As2 f yd z f yd
In these equations x equations xmax is the maximum neutral axis depth permissible before compression steel is to be provided. This in turn depends on the amount of redistrib redistribution ution assumed.The effect of redistribution is dependent on the concrete strength with one set of values up to and including C50/60 and a differing set of values for higher concrete strengths. The values are subject to a National Annex,and Annex, and the UK recommended values for strengths up to C50/60 lead to the following equation:
Beam shear
xmax = (δ – 0.4)d where for example δ =1.0 means no redistribution and δ = 0.8 means 20% redistribution.This is basically the same equation as in BS 8110. It may also be considered advisable advisable to set some upper limit on x on xmax regardless of the amount of negative redistribution (i.e. redistributed M being greater greater than elastic M). The effect of redistribution is also dependent on the ultimate compressive strain of the concrete, which for strengths above C50/60 reduces from 0.0035. M2 is the additional moment to be carried by the compression steel. stress in the compression steel, steel, which for f sc is the design stress concrete strength grades up to C50/60 may be calculated from: f sc = 700(( x– x–d2)/ x)) ≤ f yd x Parametric studies have been carried out looking at the impact of the different stress block on the design of rectangular beams using linear elastic analysis with limited redistribution.In these studies α cc was taken as 1.0 and the redistribution formula was taken as x as xmax = (δ – 0.4)d 0.4)d with with x 0.6d. The conclusion conclusion xmax limited to 0.6d from this study was that there was very little practical difference between EC2 and BS 8110. This conclusion can also be reasonably extended to solid slabs designed using linear elastic analysis with limited redistribution.
Span/depth ratios In both BS 8110 and EC2 the allowable span/depth ratio depends on concrete strength and tension and compression reinforcement ratios. The attached attached flowcharts flowcharts show how the permissible permissible span/depth ratio is arrived at in each case. A detailed parametric study on span/depth ratios has been carried out comparing the provisions of the two codes in relation 34|The Structural Engineer – 16 March 2004
to the minimum permitted depth of rectangular beams for a given span. The influence of increasing the allowable allowable tension steel was considered by allowing a maximum increase of 100% (i.e. double) that required for the ultimate limit state, although there is no upper limit stated in EC2. 20% redistribution was assumed for all continuous spans. The study showed that EC2 tended to be more conservative at low concrete strengths. strengths. However EC2 permits permits much higher span/depth ratios for cantilevers where a low reinforcement percentage is used, even restricting the maximum enhancement in steel area.In area. In practice however, however, economic rather than minimum permissible depths will generally be used, and these are very similar in both codes.
Fig 2. Variable strut inclination method which is based on a truss model
When checking beam shear, shear, EC2 is the same as BS 8110 in that there is a shear stress below which only minimum shear reinforcement need be provided. In EC2 as in BS 8110 this shear stress depends on concrete strength, effective depth and tension steel ratio. The recommended design shear stress of the concrete alone for comparison with the values of v of vc given in Table 3.8 of BS 8110 is:
_
0.18 v Rd, c = c k 100t l f ck c
i
1
3$
v min = 0.035k
3 2
f ck
paper: moss/webster
Where k = 1 + √(200/ d) ≤ 2 /(bd ρ l = As /( bd)) ≤ 0.02 The value 0.18/ γ γc and the expression for the minimum concrete shear stress vmin are subject to the National Annex. Choosing a value of 0.12 for 0.18/ γ above equation, and γc in the above the expression for vmin as given above, BS 8110 generally allows a higher shear stress before shear steel is required. Because of the minimum shear stress that can be carried, EC2 can however allow higher shear stresses for low reinforcement percentages and this effect is accentuated the higher the strength of the concrete. EC2 differs from BS 8110 in that above the limit at which the concrete alone has sufficient capacity, capacity, the designed shear steel to be provided is determined ignoring the contribution from the concrete. The design method used is known as the variable strut inclination method and is based based on a truss model, fig 2. For members not subjected to axial forces the required area of shear steel needing to be provided in the form of links at a distance d from the support face is given by: /(0.9d Asw / s = V Ed /(0.9 d f ywd cotθ )
Fig 3. Comparison of maximum permissible shear stresses
This compares with the BS 8110 equation:
Despite the approaches referred to above the two codes can in general be expected to give similar results in terms of the number and spacing of links to be provided.
Design of compression elements at the ultimate limit state EC2 does not give separate guidance on the approach to be used to designing a column under a known combination of moment and axial force. For practical practical purposes as with BS 8110 the the rectangular stress block used for the design of beams may also be used for the design of columns. However unlike with BS 8110 the maximum compressive strain when designing to EC2 will be less than 0.0035 if the whole section is in compression and will fall to half this value ( f f ck ≤ 50N/mm2) if the section is subject to pure compression as illustrated in fig 4. This will affect the steel strains and hence forces which the steel can carry carry.. N-M interaction charts for a 300mm×300mm section with these assumptions have been produced taking a value of α cc= 0.85 and give close agreement between EC2 and BS 8110 as illustrated in fig 5. The horizontal cut-off line on the EC2 curve has little practical effect, as it will normally fall within the zone of minimum applied moment.
/ yvd Asv / s v = b v(v–vc) f The designer should choose an appropriate angle θ (the angle between the assumed concrete compression strut and the main tension chord) to use in the model. The limits on θ are between 22° and 45° 45° suc such h that cot cotθ is greater than or equal to 1 but less than or equal to 2.5. The maximum shear capacity depends on θ . The lowest possipossible value of θ (maximum cot θ ) should therefore be chosen within the limits above. As with BS 8110 there is also an upper shear stress that cannot be exceeded. In BS 8110 this limit is 0.8 √ f cu ≤ 5 N/mm2. In EC2 this corresponds to taking θ = 45°, which gives gives a recommended upper limit to the shear stress for non-prestressed members of:
Dealing with slenderness 0.45 ν f f cd where ν = 0.6(1– f ck /250) γc f cd = α cc f ck / γ If the design stress of the shear reinforcement reinforce ment is below 80% of the characteristic yield stress f stress f yk, ν may be taken as:
ν = 0.6 up to C60 – f ck /200 > 0.5 for grades above C60 ν = 0.9 – f The two codes have been compared choosing values of α cc = 0.85 and γ c =1.5 and ignoring the increase allowable for ν if the stress in the shear steel is restricted. EC2 will allow a smaller maximum shear capacity at low strengths but a higher capacity at higher strengths principally arising from the cut off of 5N/mm2 in BS 8110. The increase in the allowable shear stress becomes quite significant when increased values of ν are permitted even ignoring the cut-off in BS 8110 as illustrated in fig 3. For a given required shear capacity the amount of shear steel to be provided when designing to EC2 is dependent on cot θ which should be maximised maximised as stated above. above. In practice the following inequality needs to be satisfied: 1
#
cot i =
~ + ~2 - 4 2
where ~ = cot i + tan i =
#
Fig 4. Strain distributions to be assumed when using EC2 under different combinations of bending and axial load
The first step in deciding whether a column is slender is to determine the effective lengths in both directions.The effective lengths are in turn dependent on whether the column may be assumed to be braced or unbraced (‘non-sway’ or ‘sway’ in EC2 terminology). BS 8110 provides tables of values of β with assessment of the end conditions that are appropriate. β can range from 0.75 to 2.2. EC2 appears more complicated in that an assessment needs to be made of the relative flexibilities of the rotational restraints at each end of the column. However this process can be simplified by making conservative assumptions. Having determined the effective lengths the slenderness ratios can then be calculated.In BS 8110 the limits on slenderness ratio lex / h and ley / b are 15 (braced) and 10 (unbraced). In EC2 the allowable slenderness ratio λ is calculated from l0 / i where i is the radius of gyration of the uncracked cross section. For a rectangular section ignoring the reinforcement this simplifies to λ = 3.464 l0 / h where l0 is the effective length. length. The slenderness should be checked in both directions. Where the column is slender when designing to EC2 and using the nominal curvature method which it is probably the most
2.5
0.9 bw dv dvf f cd V Ed
Indirectly the concrete strength can therefore influence the amount of shear steel provided if cot θ needs to be less than 2.5 to satisfy the criterion on maximum shear capacity.
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The other major issue when designing flat slabs is dealing with punching shear. shear. The calculation of punching shear is basically similar to BS 8110, except that the control perimeter is at 2d 2d, rather than 1.5d 1.5d from the column face, and follows a locus from the column face,rather face, rather than being rectangular in shape, fig 6. The effective shear force VEd may be determined using simple enhancement factors similar to those in BS 8110 subject to certain conditions* and the corresponding values are given below. Flat slab shear enhancement factors Internal: 1.15 1.15 Edges: 1.4 1.4 or 1.25 Corners: 1.5 1.25
straightforward, the final design moment is increased by the additional moment to account for second order effects. effects. Once this adjustment has been made the N-M interaction charts may be used as before. The same approach is used for BS 8110 except that the second order moments will be calculated differently. differently.
Fig 5. N-M interaction charts for C35/45 concrete d/h = 0.82 (alpha cc = 0.85)
When links are required, EC2 allows a contribution of 75% 75% of the concrete shear resistance (unlike (unlike beam shear), radiall shear), and a radia distribution of links is assumed. The shape of the outer perimeter,, at which no further links are required, is related to the link ter arrangement, unlike the basic control perimeter. The much higher enhancement factor of 1.5 for corner columns may prove critical in some circumstances,when circumstances, when sizing flat slabs for shear. shear. However However,, the method as a whole seems very logical and may result in fewer links and be simpler to detail than the BS 8110 method.
Biaxial bending
Simplified load combinations and load cases
EC2 states that a separate design may initially be carried out in each principal direction. Imperfections need be taken into account only in the direction where they will have the most unfavourable effect. No further check is necessary if:
The complete set of possible load combinations and load cases is obtained from EN1990 Basis EN1990 Basis of Structural Design. prac-Design. In prac tice these can be simplified greatly for the design of everyday building structures. For practical purposes the UK National Annex is currently permitting the simplified load combinations of all spans and alternate spans loaded as per BS 8110 to be considered sufficient in the majority of cases. For slabs the UK National Annex is currently permitting the all spans loaded condition to be considered sufficient subject to the restrictions as currently imposed in BS 8110. A major difference between the two codes is the partial safety factor appropriate to the dead load for unloaded spans. Three load combination equations are permitted in EN1990 dubbed dubbe d 6.10, 6.10a and and 6.10b. 6.10b. Which equation equation is used has a bearing on the load factors and the more complicated expressions 6.10a and 6.10b can offer some additional potential economies to the designer designer.. In the simplest case using the basic equation 6.10 the values may be summarised as below. below. In the table γ G is the partial load factor appropriate to dead loads and γ Q that appropriate to imposed (live) loads.
λy / λx ≤ 2 and λx / λy ≤ 2 and ( e )/( e ey / h)/( e ex / b) ≤ 0.2 or ( e ex/b /b)/( ey/h /h)) ≤ 0.2 and e ex and ey are the effective total eccentricities including second order effects. If biaxial bending needs to be considered the following simplified criterion may be used: ( M M Edx/M Rdx)a + M (M Edy/M Rdy)a ≤ 1.0 M Edx,y = Design moment of resistance in the respective direction including second order effects M Rdx,y = Moment of resistance in the respective direction a = exponent dependent on geometry When it is necessary to consider biaxial bending BS 8110 states that symmetrically reinforced rectangular sections may be designed to withstand an increased moment about one axis. axis. It is known that this approach can be unsafe in extreme circumstances, so the introduction of the above equation in EC2 should be welcomed.
Strut and tie models
Loaded spans Unloaded spans
Fig 6. Punching shear comparisons for EC2 and BS 8110
EC2
BS 8110
γ G=1.35, γ Q=1.5 γ G=1.35
γ G=1.4, γ Q=1.6 γ G=1.0
Strictly speaking the table above relates only to the design of loaded spans. The design of unloaded spans should theoret-
These are beyond the scope of this paper. However it is hoped to include some guidance on this in a future paper underpinning the provisions within the National Annex for the code.
Robustness and tying requirements This is currently covered in the section dealing with detailing requirements. requireme nts. The UK has pushed for and has had accepted National Annex provisions provisions for all forms of ties except vertical ties, allowing the requirements to be brought into line with BS 8110. This issue will need to be revisited in the light of the current proposed revisions to Approved Document A of the Building Regulations.
Flat slabs and design for punching shear EC2 Part 1-1 now has an Informative Annex dealing with flat slabs which was noticeably absent from the ENV version. The widths of column and middle strips are the same as in BS 8110. The percentages of moments carried by these strips are given as ranges but the BS 8110 values fall within these ranges and hence may still be used. 36|The Structural Engineer – 16 March 2004
Basic control perimeter Control perimeter shape
EC2 at 2d rounded corners
BS 8110 at 1.5d rectangular
*These are nominal values for braced structures. Calculation of shear enhancement factors from equations given in EC2 or BS 8110 may result in less conservative values.
paper: moss/webster
Fig 7. Floor plan for building design study
is 6% (10% at laps) and to EC2 4% (8% at laps). This resulted in actual column sizes being very similar. EC2 does permit the 4% limit to be exceeded where the concrete can still be placed and compacted successfully successfully.. Making assumptions about costs of concrete rebar rebar,, formwork and excavation, overall construction costs were found to be quite similar using using EC2 instead of BS 8110. 8110. The study employed Equations 6.10a and 6.10b as mentioned above. above. If Equation 6.10 alone had been used construction costs using EC2 would have been slightly higher (of the order of 2-3%).
Availability of design aids A suite of practical design aids to assist practising engineers to become familiar with and apply the code is currently in course of preparation. preparation. These include: • A set of Excel based based spreadsheets spreadsheets,, to complement complement the existexisting highly popular set of spreadsheets to BS 8110 produced by the Reinforced Concrete Council (RCC) • A series of How to Design Leaflets Leaflets explaining explaining the basic basic design concepts for primary structural elements available on-line and to be freely distributed. • A concise code summarising summarising the key informati information on within the code required for everyday use and appropriate values from and references to other supporting codes • Wor Worked ked Examples Examples for the Design of Concrete Buildings Buildings A helpline facility is planned to be set up so that frequently asked questions can be answered and a dedicated website www.eurocode2.info www .eurocode2.info is now on-line and will be expanded to provide links to available available sources of information. information. This will complement other activities such as the RCC’s Calcrete Computer Aided Learning package.
ically be considered separately taking γ G = 1.0 on all spans,but spans, but in practice this is very rarely likely to prove the governing load case.
Conclusions Detailing issues It is believed that spacing rules may lead to more and smaller bars, unless crack widths are checked. There is a requirement that beam top steel should be distributed across flanges (both tension and compression).
Comparative design study In this section the results of a separate design study undertaken on a typical flat slab building are reviewed. The floor plan chosen for the study was based on a structure already designed to BS 8110. It had a slightly irregular layout with fairly typical spans of 8.4 and 7.2m (fig 7). Finite element analysis was used for the design of the slabs, mainly because of the irregular column layout. The deflections affecting the perimeter cladding proved to be critical in determining slab thickness. The final slab depths, required to satisfy satisfy the perimeter perimeter deflection limit, limit, were 260mm for EC2 EC2 and 280 mm for BS 8110. There are several reasons for this difference; difference; the principal reasons being: • The instantaneous instantaneous modulus of elasticity EC for a given concrete grade is higher to EC2 than to BS 8110. • The cracking cracking stress stress is much higher to EC2 EC2 and increases increases with concrete strength, but is limited to only 1.0N/mm 1.0N/mm2 in BS 8110. • To EC2, EC2, the modelling modelling of tension tension stiffenin stiffening g built into into the code increases with age, but to BS 8110 it reduces.
Span/depth check flowchart to BS 8110: Part 1
The advent of EC2 as for the other Eurocodes will have a big impact on the design of all types of structures. There will be a learning curve associated with gaining familiarity and using the new code. To make this as painless an exercise is possible, the concrete industry in conjunction with BRE, are producing design aids and information to assist the the profession, and can answer detailed queries, by way of answers to frequently asked questions posted on the above website. In general EC2, EC2, used in conjunction conjunction with the National National Annex, is not wildly different from BS 8110 8110 in terms of the design approach. It gives similar answers and offers scope for more economic structures.
All of these tend to produce smaller displacements to EC2, although these effects are partially offset by a greater density for concrete (25kN/m3 as opposed opposed to 24), 5mm more bottom bottom cover,, and the slightly different relationship between support cover and span steel. In everyday practice, the above selected slab depths may have been rounded up to the nearest 25mm, giving 275mm and 300mm respectively. The column load reduction factors given in EC1 we re found not to be as generous as in BS 6399. Column sizes were determined by the maximum amount of vertical reinforcement permitted by each code.In BS 8110 this
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Span/depth check flowchart to EN 19921992-1 1 (EC2 stage 49 draft)
There will be an opportunity for comment on the values proposed for the Nationally Determined Parameters to be included within the National Annex, before it is published. Overall EC2 is less prescriptive and its scope is more extensive than BS 8110 for example in permitting higher concrete strengths. In this sense the new code will permit designs not currently permitted in the UK, and thus give designers the opportunity to derive benefit from the considerable advances in concrete technology over recent years. years. The authors believe that, after an initial acclimatisation period, EC2 will be generally regarded as a very good code and a step in the right direction.
Acknowledgments The authors would like to acknowledge the funding for this work provide provided d by the ODPM ODPM and the BCA, BCA, and the comments made and assistance provided by members of the Concrete Industry Eurocode 2 Group (CIEG) referred to in Reference 4.
REFERENCES 1. DD ENV ENV 199 19922-11-1: 1:19 1992 92 Eurocode 2: Design of concrete structures Part 1-1. General rules and rules for buildings , BSI 1992 2. National Structural Concrete Specification for Building Construction, Second Edition, BCA Publication 97.378 , July 2000 3. Eur uro ocodes, Proc. Inst. Civ. Eng. , Civil Engineering, 144/Special 144/ Special issue, 2 Nov 2001 4. Chana, P. S.: ‘Making the change: change: implementin implementing g Eurocode Eurocode 2’, Concrete , May 2002, 36 /5, p 21-23 36/5, 5. Web Webster, ster, R.: ‘Reinfor ‘Reinforced ced concrete framed structure: Comparative design study to EC2 and BS 8110’, BRE Report BR455, 2003
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