Comparison between the Provisions of the Egyptian Code of Practice and the Eurocodes for Reinforced Concrete Structures Design

Transcription

1 Comparson between the Provsons of the Egyptan Code of Practce and the Eurocodes for Renforced Concrete Structures Desgn El-Shennawy, Ahmed (ASH) 1 ; Boros, Vazul (VB) 2 ; Novák, Balthasar (BN) 3 1 German Unversty n Caro, Caro, Egypt 2 Stuttgart Unversty, Stuttgart, Germany 3 Stuttgart Unversty, Stuttgart, Germany Abstract: Concrete s the second most consumed materal n the world. However, the concrete ndustry has enormous envronmental footprnt, resultng n hgh energy consumpton and CO 2 emssons. The challenge for the structural desgners s to reach optmal dmensons for structural elements wthout compromsng ts saftey. In ths paper the goal s to evaluate the dfferent phlosophy between the Egyptan Code of Practce and the Eurocodes. As a case study a renforced concrete structure s compared n vew of three aspects: sustanablty, economy and relablty. Frst a fnte element model s developed to desgn the structure accordng to both codes. Then a detaled bll of quanttes for the structure s conducted to calculate the envronmental footprnt and the cost of the buldng. In addton, an advanced probablstc model s establshed to provdes a framework for the relablty analyss of the structure. Fnally the results of the sustanablty and economy comparson are presented. Keywords: CO 2 emssons, codes comparson, economy, renforced concrete, sustanablty. Introducton Economcally utlzng the materals and forces of nature to the beneft of manknd s the responsblty of scentsts n general and cvl engneers n specfc. Through the proper management of the envronment we can ensure a sustanable development. For that reason our am s to reach the optmum structural desgn by mnmzng the usage of buldng materals, wthout compromsng ts safety. All over the world buldng codes are tryng to fnd the mddle ground between these two opposng ams. The German Unversty n Caro and the Unversty of Stuttgart ntated a jont research project to examne, how the respectve standards of ther countres address ths mportant topc. As concrete s the most commonly used constructon materal worldwde (1) and the majorty of the nfrastructure and buldngs of our modern cvlzaton s usng concrete, due to ts durablty, adaptablty and low cost. Therefore t was decded to perform a case study on a renforced concrete resdental buldng. Frst the selected structure s desgned accordng to the provsons of the Egyptan Code of Practce (2) and the Eurocodes (3). Thereafter these buldngs are compared consderng the aspects of sustanablty, economc and safety. Theoretcal Background The am of the tradtonal desgn codes of concrete buldngs s to create a safe structure that can sustan the loads and deformatons t s subjected to. Nowadays modern computatonal technques enable the optmzaton of the cross sectons throughout the desgn process (4). Buldngs constructon has a major envronmental mpact (5). It s the man consumer of land and raw materal. It s also responsble for large amounts of CO 2 emssons. For these very 1

2 reasons sustanablty was chosen as the frst aspect n the current comparson. One tool for evaluatng sustanablty s the lfe cycle assessment (LCA) of the structure. The LCA s a methodology for evaluatng the envronmental footprnt of products or processes (6). The nventory of lfe cycle, one phase of the LCA, enables us to quantfy the total emboded energy of used constructon materal and ther CO 2 emssons (7). Ths assessment allows for the comparson of dfferent structural alternatves from an envronmental pont of vew. The constructon ndustry has a dfferent effect on the economy of each country, because of the dfferent prces of constructon materals. Moreover, Germany has much hgher labour rates than Egypt. Therefore the am of the economc comparson was not only to assess the total cost of each buldng, but also to nvestgate the proporton of labour cost to the materals costs for each country. An advanced probablstc model for the structure was created to assess ts relablty. Dependng on two nternatonal documents: fb Model Code (8) for the mechancal models and Probablstc Model Code (9) for the basc varables. Methodology The chosen buldng s a four storey (12 m heght), resdental buldng wth a floor area of 97 m 2. The structural system of the buldng s a renforced concrete skeleton as shown n Fgure 1. It contans all the common types of structural elements; horzontal beams (smple, contnuous and cantlever) and vertcal columns (corner, edge and nteror), that are requred to sustan the vertcal and horzontal loads on the structure. Frst the nvestgated buldng s desgned accordng to the Egyptan Code of Practce, whch wll be nomnated n the current paper as the ECP-buldng. Then t s desgned accordng to the Eurocodes, whch wll be nomnated n ths paper as the EC-buldng. Fnally a detaled comparson for both codes s carred out, n order to examne how they perform wth respect to the three dfferent aspects: sustanablty, economc and relablty. In the current paper, the results of the sustanablty and economc comparson are presented. Relablty results are dscussed by Boros (10). Fgure 1: Model for the nvestgated renforced concrete resdental structure 2

3 Structural Desgn In ths study the structure was desgned usng fnte element software. Frst the dmensons of structural elements were estmated by prelmnary conceptual desgn and then the fnte element model was created. Thereafter the vertcal and horzontal loads were defned accordng to the provsons of the Egyptan Code of Practce and the Eurocodes separately, as shown n Table 1. Wnd loads were the only parameters nfluenced by the buldngs locaton. It was agreed to consder wnd loads n Caro, Egypt for both codes. Lnear elastc analyss usng the gross secton propertes was used. After obtanng the deformatons and the envelope of stress resultants, the structure was desgned accordng to common desgn rules for both codes and all the servceablty lmt states and ultmate lmt states were checked. The desgn and geometrc parameters of the structure were dentcal for both codes. The type of concrete used was C 20/25 (characterstc cylnder/cubc compressve strength after 28 days). The types of steel used were dfferent for each code, steel 360/520 (characterstc yeld stress of 360 MPa) was chosen for the Egyptan Code of Practce and steel B500A (characterstc yeld stress of 500 MPa) was chosen for the Eurocodes. Table 1: Actons consdered accordng to the Egyptan Code of Practce and the Eurocodes Descrpton Unt Egyptan Code of Practce value Eurocodes value Typcal floor Roof floor Typcal floor Roof floor Self weght of concrete kn/m Self weght of masonry kn/m Floor cover kn/m Lve loads kn/m Wnd loads kn/m Sustanablty Aspect The LCA assessments enabled us to quantfy the two sustanablty ndcators. Frst, the emboded energy was assessed as defned n equaton (1), where e are the emboded energy of the constructon materals and the m are the quanttes of constructon materals. Second, the CO 2 emssons were calculated as defned n equaton (2) where c are the CO 2 emssons of the constructon materals. In order to assess the emboded energy and CO 2 emssons for constructon materals data from (11) was used. The values of e,c and some other ecopropertes for the constructon materals are gven n Table 2. EE = e m = (1) 2 CO = c m = (2) Table 2: Eco propertes of concrete, renforcement steel and brcks Descrpton Unt Concrete Renforcement steel Brcks Emboded energy (e ) MJ/kg CO 2 emssons (c ) kg/kg

4 Cost aspect Cost analyss was performed to determne the total cost of the structure, whch s the sum of the materals cost and labour cost as defned n equaton (3). Materals cost s defned n equaton (4), where m are the quanttes of constructon materals and u are the materals unt prces. The unt prces of the materals are gven n Table 3. Labour cost s defned n equaton (5), where w are the labour rates (gross hourly cost of the labour ncludng nsurance, statutory, contrbutons and taxes), p are the producton rate of labour for each actvty n the constructon of the buldng. Producton rate of labour for constructon actvtes are gven n Table 4. These values were obtaned from a web-based constructon estmatng software (12). Materals unt prces and labour rates were obtaned from an Internatonal Constructon Cost Survey (13), prepared by the worldwde offces of Gardner and Theobald. Total Cost = Labour Cost + Materal Cost (3) MC = u m = LC = w p m = Table 3: Unt prces of constructon materal n Egypt and Germany (4) (5) Descrpton Unt Egypt cost ( ) Germany cost ( ) Concrete C20/25 m Steel 360/520 t Steel B500A t - 1,314 Brcks 1000 brcks Table 4: Producton rate of labour for constructon actvtes Actvty Unt Producton rate (p ) Concrete placement (slabs, beams and columns) h/m 3 (2.00, 2.25 and 2.90) Renforcement steel (slabs, beams and columns) h/t (20.60, and 26.40) Formwork (slabs, beams and columns) h/m 2 (1.25, 0.90 and 0.48) Scaffoldngs h/m 0.10 Brckwork h/1000 brcks Results and Dscusson Structural Element Desgn In Tables 5, 6, 7 and 8 the man dmensons and renforcement detals of structural elements are shown (φ s the renforcement bar dameter n mm). Comparng beams and columns t can be stated that the ECP-buldng has bgger dmensons and heaver renforcement for 4

5 structural elements than the EC-buldng. Ths result s due to the hgher values of the Egyptan Code of Practce for lve loads as can be seen n Table 1. The hgher values for the factors of safety used n the ultmate lmt state desgn combnatons n the Egyptan Code of Practce (1.4 for dead and 1.6 for lve loads) compared to the Eurocodes (1.35 and 1.5 respectvely) also nfluences the results. Fnally t has to be mentoned, that two dfferent types of renforcement steel have been used n the two structures, the yeld stress of renforcement steel used n the ECP-buldng (360 MPa) s lower than n the EC-buldng (500 MPa). Table 5: Beam dmensons and renforcement ECP-buldng Beam Dmensons (m) Bottom renforcement Top renforcement Shear End Md Interor Wdth Depth Base Addtonal renforcement support span support B φ 16 2 φ 16 2 φ 16 2 φ 12 2 φ 16 6 φ 8 /m B φ 16 2 φ 16 4 φ 16 5 φ 8 /m B φ 16 3 φ 12 2 φ 12 2 φ 16 5 φ 8 /m CA φ 16 2 φ 16 5 φ 8 /m Table 6: Beam dmensons and renforcement EC-buldng Beam Dmensons (m) Bottom renforcement Top renforcement End Md Interor Wdth Depth Base Addtonal support span support Shear renforcement B φ 12 3 φ 12 2 φ 12 2 φ 10 2 φ 12 5 φ 8 /m B φ 12 2 φ 12 4 φ 12 4 φ 8 /m B φ 12 2 φ 12 2 φ 10 3 φ 12 4 φ 8 /m CA φ 12 3 φ 12 4 φ 8 /m Table 7: Column dmensons and renforcement ECP-buldng Column Ground and frst floor Second and thrd floor Renforcement Dmensons (m) Renforcement Dmensons (m) Renforcement tes Corner (C1) 0.25 x φ x φ 16 5 φ 8 /m Edge (C2) 0.25 x φ x φ 16 5 φ 8 /m Interor (C3) 0.25 x φ x φ 16 5 φ 8 /m Table 8: Column dmensons and renforcement EC-buldng Column Ground and frst floor Second and thrd floor Dmensons (m) Renforcement Dmensons (m) Renforcement Renforcement tes Corner (C1) 0.24 x φ x φ 12 5 φ 8 /m Edge (C2) 0.24 x φ x φ 12 5 φ 8 /m Interor (C3) 0.24 x φ x φ 16 5 φ 8 /m Envronmental and Cost Assessment of the Two Buldngs The values of the total emboded energy, CO 2 emssons and cost (materal and labour) are presented n Table 9. The envronmental parameters (emboded energy and CO 2 emssons) of the ECP-buldng are greater compared to the EC-buldng by approxmately 11%, as shown 5

6 n Fgures 2 and 3. By examnng the results of the cost analyss, t was observed, that the total cost of the EC-buldng s approxmately sx tmes hgher than the ECP-buldng, as shown n Fgure 4. The labour cost represents 16.67% of the total cost for the ECP-buldng. On the other hand the labour cost for the EC-buldng consttutes a domnate proporton of the total cost, representng 59.75%. The great dfference n the labour cost between the ECPbuldng and the EC-buldng, can be traced back to the hgh dfference of labours rates between Germany (28.59 /h) and Egypt (1.42 /h) (13). In Fgure 5 the overall rato comparson between both buldngs s presented. Table 9: Emboded energy, CO 2 emssons, materal cost and labour cost of the ECP and EC buldngs Emboded energy Materals cost Labour cost Total cost CO (GJ) 2 emssons (t) ( ) ( ) ( ) ECP-buldng 1, ,065 2,813 16,879 EC-buldng ,563 57,255 95, Total emboded energy (GJ) ECP-buldng EC-buldng Total CO2 emssons (t) ECP-buldng EC-buldng Fgure 2: Total emboded energy of both buldngs Fgure 3: Total CO 2 emssons of both buldngs Mllares Total cost ( ) Labour cost Materals cost Labour cost Emboded energy ECP-buldng EC-buldng Materals cost - ECP-buldng EC-buldng CO 2 emssons Fgure 4: Materal and labour cost of both buldngs Fgure 5: Overall comparson of both buldngs Conclusons Ths research compares a renforced concrete resdental buldng desgned by two dfferent codes, the Egyptan Code of Practce and the Eurocodes n vew of sustanablty, economy and relablty. The obtaned results show, that the envronmental parameters (emboded energy and CO 2 emssons) of the ECP-buldng are greater that the EC-buldng by 6

7 approxmately 11%, whle the total cost of the EC-buldng s approxmately sx tmes hgher than the ECP-buldng. The labour cost represents 16.67% of the total cost for the ECP-buldng, whle for the ECbuldng t consttutes wth 59.75% a sgnfcantly hgher proporton of the total cost. The great dfference n the labour cost between the ECP-buldng and EC-buldng s due to the hgh dfference of labour rates n Germany (28.59 /h) compared to Egypt (1.42 /h). Structural elements of the ECP-buldng have bgger dmensons and heaver renforcement than the EC-buldng. The reason for ths s most lkely the hgher value of the factored lve loads n the Egyptan Code of Practce and the dfference n renforcement types used. Fnally t can be stated that the desgn of renforced concrete structures s a dffcult process, whch requres engneerng judgement to mnmze the usage of buldng materals and labour, wthout compromsng the safety of the structure. The present artcle shows that buldngs desgned by the provsons of the Eurocodes are generally more envronmentally frendly, yet also more expensve than ther counterparts n Egypt. Refrences (1) Metha, P.K. and Merman, H. (2009). Tools for reducng carbon emssons due to cement consumpton. Structure, pp (2) Egyptan Code of Practce (2007). ECP , Desgn and Constructon for Renforced Concrete Structures. Mnstry of Buldng Constructon, Research Center for Housng, Buldng and Physcal Plannng, Caro, Egypt. (3) DIN EN (2010). Eurocode: Desgn of Concrete Structures. (4) Srram, R. (2006). Artfcal ntellgence n engneerng: personal reflectons, Advanced Engneerng Informatcs, 20, pp: 3 5. (5) Metha, P.K. (2002). Greenng of the concrete ndustry for sustanable development.concr Int, pp (6) Hauschld, M.Z. (2005). Assessng envronmental mpacts n a lfe-cycle perspectve. Envron Sc Technol. (7) Internatonal Standardzaton Organzaton (2006). ISSO 14040, Envronmental management lfe cycle assessment prncples and framework. (8) fb (2010). Model Code Frst complete draft Volume 2. fb Bulletn 55. (9) JCSS (2001). Probablstc Model Code JCSS.Avalable from: (10) Boros, V., Novàk, B. and El-Shennawy, A. (2013). Applcaton of relablty analyss n structural engneerng. The 3rd Annual Internatonal Conference on Cvl Engneerng. Athena, Greece, June (11) Ashby, M.F. (2012). Materals and the envronment: eco-nformed materal choce. 1st edn. Access Onlne va Elsever. (12) Methvn (2013). Web-based Constructon Estmatng Software. Avalable from: (13) Gardner and Theobald LLP (2011). Internatonal Constructon Cost Survey. Avalable from: 7