Introducing an Economic Plan of Optimum Designing in the Joist Floor Slabs Construction. Dr. Ahmad Akbarlou

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1 Life Science Journal 0;9() Introducing an Econoic Plan of Optiu Designing in the Joist Floor Slabs Construction Dr. had kbarlou Faculty of Engineering, Tabriz Branch, Islaic zad University, Tabriz, Iran E-ail: bstract: In the present paper, considering joisted floor overuse in ost of the residential, office and other types of buildings, nuerous researches have been carried out into technical and theoretical probles. The results have been copiled as article and it has becoe clear that there is a drastic gap concerning financial atters of a variety of structures in building regulations. steel building with joisted floor was considered to coence this technical and econoic research. The effect of shifting floor fraing direction of the joists on floor spans has been calculated and copared (frist on big span, next on sall span) in the aount of used steel including the ain steel girder weight and used bar weight in joist and the total cost of floor construction calculated according to it. The results show that in the case of building with joisted floor along the big span of floor span (fro both direction of fraing), 0% - 9% and 8% - 8% are saved in the case of steel use and floor construction costs, respectively. ccording to statistics concerning the city of Tabriz, 000 tons of steel on average and about 0 billion Rials that is equal to 9.8 illion $ would be saved in the cost of floor construction. These aounts of saving for the whole country(for Iran) are tons of steel and 000 billion Rials that is equal to 0 illion $. [had kbarlou. Introducing an Econoic Plan of Optiu Designing in the Joist Floor Slabs Construction. Life Sci J 0;9():-]. (ISSN: 09-8).. Key words: Joisted floor, optial choice of fraing direction, optial steel use, financial saving.. Introduction Utilizing joisted floor in country buildings is a coon task because of its advantages such as using less steel, concrete, fraing, possibility of anual installation, being theral insulator, less weight, quick installation, and reasonable strength. This study deals with the uncontrolled steel use in order to save financial expenses in building industry. This sees to be necessary because of the increasing deands of the society for appropriate building construction with less total cost. On the other hand, because of insufficient technical and econoical studies in the field of building construction ethods ainly residential buildings, this research ethod ay play a role in changing research issues and ethods. lthough quality and strengthen of structures, have been iproved, it is obvious that less attention has been paid to the engineering econoy. So far, no regulations or codes have been copiled and published by technical organizations or legal authorities. Moreover, uncontrolled and exceptional use of steel in country buildings, leading to increasing need for steel iportation and expense increent, shows this research atters iportance. In the present paper, it has been proposed that related organizations such as Housing and Urbanization Organization, Engineering Constitution, etc., should care about econoic atters in designing and constructing of building in addition to inspection probles, quality control and theoretical probles through copiling necessary regulations and codes.. Research Method residential building with steel structure and joisted floor, according the following plan, in two odes of fraing, i.e. odes a and b, has been selected. fter floor designing, the weight of used steel in the ain girder and bar of the joist estiated and total weight of used steel has been calculated and copared in two cases of a and b. Then the costs of floor construction including the cost of ain girder and joisted floor have been calculated and copared with to the price list of the year 00 ( the last official prices ) that exchanged to the prices of year 0. In floor calculations, the design of steel girder considering vertical loads has been done by allowable stress ethod and based on Iranian steel code. The joist has been designed by ultiate strength ethod based on the code CP 0, rule /0, dated on 9/0/ (leaflet no.9) published by strategic planning and supervision organization. Case a) the ain steel girder in axes and B, and the direction of floor joist in L direction are as following figure (L >L ) Case b) the ain steel girder in axes and, and the direction of floor joist in L direction are as following figure (L >L ) - Floor eleents design and total cost of their preparation and construction. The study continues as follows with an exaple. L =, L = PL=0 /, LL=00 / lifesciencej@gail.co

2 Life Science Journal 0;9() Case a: --a: Design of steel girder in case (a), with a span of L =. L B Section of the joisted floor L α Case a t L B Stirrup section L Case b q = 0+00? ql? M = = = M 900 W = = = c use : IPE 8 F 8 b G =? 8.8 = the weight of ain steel girders. -- a: Design of the floor joist (tensile bar) in case (a), with a span of L =. q L = L = L H = = c 0 h f = c b w = 0 c h e = 0 c Z = 0.9h e Defining of the signs Joist span Thickness of floor Thickness of concrete slab Width of heel Effective height Elastic ar f copressive stress of the joist concrete cu t = 0 c The distance of stirrups f = 00 y c tesile bar yield stress σ = 00 a c Stirrup allowable stress f = 00 c c 8- day concrete copression lifesciencej@gail.co

3 Life Science Journal 0;9() strength o α = 8 B = 0 c Stirrup s angle Distance of the joists = = tensile bar rea S Design based on the USD (ultiate stress design) ethod using CP0 code: q =.DL +.LL?. L = q q =.? 0 +.? 00?. = q L? M = = = h M = 0.8F h - f u y s e 900 = 0.8? 00 譇 s? - s =. c use Φ III h M = 0.f Bh h - f u cu f e 900 = 0. 譮 cu? 0?? - f cu = 9 < 00 o.k. c c V.t Z. σ (sina cosa) (0.8 0.) 0.c use Φ8 --a: Design of copressive bar according to the code. : use Φ0 --a: Theral bar perpendicular to joist direction.. =? 000 Concrete slab rea. =? 00? = 0.8 c 000 use Φ --a: design of theral bar parallel to joist direction.. =? 00? = 0. c 000 use Φ --a: Shear reinforcing bar : use Φ8 L = c --a: Negative oent bar --a: Design of joist stirrups using (llowable stress design) ethod q = DL + LL?. = o q L α = 8 V ax = =? 0 Vax 0 τ = = =. Z. bw 0.9?? 0.. / c Stirrup is need SD = 0. S = 0.??. = 0. c use Φ8 L = 0 c 8--a: Joist rib bar Live load q = 00 < 0, L > 8 = S =??. =. use Φ0 9--a: Calculating the weight of bar used in joist lifesciencej@gail.co 8

4 Life Science Journal 0;9() Table : Calculating the weight of bar POS N L G (/) W () Φ III.. Φ8 I Φ0 II Φ I Φ I 0.. Φ8 I Φ8 II Φ0 II Weight (I =, II = 8, III = ) Total weight of bar = Total steel use = Case b: --b: design of steel girder in ode b with span of L =. q = 80?. =? M = = W = c use IPE G = 0?. = 0--a: Calculating the cost of providing and constructing the floor using Iranian price list of construction field published in 009(the last official price list) Table : Row Operation description nuber of price list unit aoun t () unit price (Rial) Total price (Rial) I bar II bar III bar dditional price of joist truss joisted floor whit c thickness bearing girder Su of total value= = The exchange coefficient of prices of year 00-0 based on the cost coefficient and daily prices =.8 --b: design of floor joist (tensile bar) in ode b with span of L =.? q = M = = 9. 8 M u = 0.8? 00 譇 S? -. = S = 0.9 c use Φ8 III lifesciencej@gail.co --b: design of joist stirrup using SD (llowable stress design)ethod. 9 q = V =? 8 Shear stress : 8 τ = =. <. 0.9?? 0 c ccording to the code : in = 0.00 bw t = 0.00? 0? 0 = 0. c use = Φ I --b: design of copressive bar according to the code. : Φ8 II --b: theral bar perpendicular to joist : Φ I

5 Life Science Journal 0;9() --b: design of theral bar parallel whit joist : Φ I --b: shear reinforcing bar : Φ8 I L = c --b: negative oent bar : 0. = 0.??. = 0. c use Φ II 8--b: Joist's rib bar: according to the code joist's rib is not need. L = < 9--b: Calculating the weight of the bar used in the joist. Table POS G W N L (/) () Φ8 III Φ I Φ0 II Φ I 0.. Φ I Φ8 I Φ II (III = ) و (II = ) و (I = ) Total weight of bar = 8 0--b: Calculating the cost of providing and constructing the floor with Iranian price list of construction field published in 009 Table Row Operation description nuber of price aount unit price Total price unit list () (Rial) (Rial) I bar II bar III bar dditional price of joist truss joisted floor whit c thickness bearing girder Su of total price with operating overhead coefficient (Rial) = ( 89.8= 8 ) The exchange coefficient of prices of year 00-0 based on the cost coefficient and daily prices =.8. In the table the weight of steel use for different spans is presented after designing and calculating like upper ethod. Table : the weight of used steel and the percent of the steel use reduction in 0 odes with different spans and two different odes of joist position (a & b). Row Span of joist () Span of the ain girder () Weight of used bar () Weight of used steel () Su of the weight of steels () Decrease percent of steel use % 8 8 % %9 9 9 % 9 % % % % % % In the plan of the joists and girders, L is the bigger span and L is the saller span. L L lifesciencej@gail.co 0

6 Life Science Journal 0;9() Table : calculating the cost of construction of the floor. Row Joist, s span () ain girder span () Total cost of the floor (Rial) Percent of the cost decrease L L % 89 0 % 000 % % % 8 8 % % 88 % 9 90 %8 0 9 %8 In the plan of the joists and girders, L is the bigger span and L is the saller span. - The diagra of coparing steel use in different odes of floor fraing: The diagra of steel use joist in big span() joist in sall span() steel use () * * * * * * * * * * joist in big span() joist in sall span() Diagra : the curve of steel use. The upper diagra indicates that in all cases when joist is located in bigger span, the use of steel decreases considerablely.

7 Life Science Journal 0;9() The diagra of steel use reduction in floor with the variation of L /L decrease of steel use percent ratio steel use decrease Diagra : The curve of steel use reduction with the variation of L /L s it is seen, when the ratio of L /L increases, steel use percent decreases. Floor construction cost reduction percent (FCCDP) floor cost reduction ratio ( FCCDP ) Diagra : Floor cost reduction percent (FCCDP) s the above diagra indicates, by increasing L /L ratio, floor construction cost percent decreases (except two cases).

8 Life Science Journal 0;9(). Conclusions ) ll the studied cases being the coon spans used in joisted floor have been copared with the obtained results on diagra () which indicates that when the joist is constructed on the big span, steel use decreases considerably. ) Considering diagra, it can be observed that when L /L (ratio of big span to sall span) increases, the steel use decreases, and when L /L =, the axiu decrease can be observed. ) Considering diagra (), it can be deduced that in all cases when the joist is designed on the big span, the cost of joisted floor construction decreases. ) Based on the obtained results on diagra (), when L /L increases, the cost decreases; and the axiu decrease is when L /L =. ) Econoical result of the research: ) The average aount of steel reduction (%) and the average aount of the floor cost reduction (.%) can be obtained fro diagra (). Through calculating the average aount of used steel in joisted floor which is /,. less steel will be used per squre eter of joisted floor. Therefore, according to the statistics on average building construction of the one year for a city such as Tabriz, there has been ore than square eter and assuing 98% of construction whit joisted floor, 000 tons of steel would be saved which aounts to 0 billion Rials saving(equal to 0 illion $). Thus, for the whole country(for Iran) it would be tons of steel use reduction and 000 billion Rials saving(equal to 0 illion $). With such saving for a city such as Tabriz, we can construct 00 residential building units, and for the whole country about 0000 residential building units, each unit with 80 of area. Therefore, with serious attention to this plan, there will be less need to steel iportation and there will be huge savings on cost of constructing the buildings. References:. Iranian building national code, code nuber: 0, "designing and constructing steel structure Buildings".. Iranian price list of construction field published in 009, "porg" organization, precast joist floors, published fro "porg" organization, Engineering constitution organization of East zerbayjan in Iran hoe page for deriving the statistics of buildings construction in tabriz Iran ( Statistical center of Iran for deriving the buildings constructions statistics of in Iran published in 009 ( Leaflet no. 9, published fro "porg" organization in 99.( //0