Effect of Construction Joints on Performance of Reinforced Concrete Beams

Transcription

1 Al-Kwarizmi Engineering Journal Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Effect of Construction Joints on Performance of Reinforced Concrete Beams Zena Waleed Abass Department of Civil Engineering/ College of Engineering/ University of Al- Mustansirya (Received 18January 2011; Accepted 31 May 2011) Abstract Construction joints are stopping places in te process of placing concrete, and tey are required because in many structures it is impractical to place concrete in one continuous operation. Te amount of concrete tat can be placed at one time is governed by te batcing and mixing capacity and by te strengt of te formwork. A good construction joint sould provide adequate flexural and sear continuity troug te interface. In tis study, te effect of location of construction joints on te performance of reinforced concrete structural elements is experimentally investigated. Nineteen beam specimens wit dimensions of mm were tested. Te variables investigated are te location of te construction joints (at midspan or at tird point of te specimens), type of construction joints (vertical, inclined, and key construction joints), and presence of stirrups at tese joints. Te specimens were tested using 1000 kn computer controlled versatile electronic testing macine. Te specimens were positioned in te macine so tat te deflection at center and\or at te location of construction joint was measured at eac load step. Te results of te experimental program indicated tat te best location of te construction joint is at te point of minimum sear. It was found tat te use of vertical construction joint as little effect on te overall beavior of beam specimens (te percentage of reduction in ultimate load capacity is in te range of 0% - 5%). Wile inclined construction joints results in a noticeable reduction in strengt of beams relative to te strengt of beam witout construction joint te percentage of reduction in ultimate load capacity is in range of 8% - 20%.Te presence of stirrups at te construction joints is an important variable, wic affect te type of failure and load carrying capacity. It is found tat adding of stirrups across te joint results in an increase in capacity in te range of (7%- 15%) and a decrease in deflection in te range of (20%- 48%). Keyword: Construction joint, reinforced concrete, beams, cracks in concrete. 1. Introduction Joints are necessary in concrete structures for variety of reasons. Not all concrete in a given structure can be placed continuously, so tere are construction joints tat allow for work to be resumed after a period of time. Since concrete undergoes volume canges, it can be desirable to provide joints and tus relieve tensile or compressive stresses tat would be included in te structure. It is necessary ten to provide various types of joints in most concrete structures, and in order tat tese joints adequately perform te functions for wic tey are intended, it is essential tat tey be installed and located correctly (1) Joints in Concrete Structures Wen joints are installed in a concrete structure, it is essential tat tey do not impair te normal functions of te structure and usually it is desirable tat tey sould blend wit te general appearance. In general, it is convenient to classify te various types of joints in two groups (2) :

2 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) A. Functional joints Tese joints are installed to accommodate movement (volume cange) due to temperature, srinkage during setting, expansion, sliding, warping... etc. B. Construction joints Tese joints are made wen tere is a break stoppage in te construction program. Construction joints are stopping places in te process of placing concrete and tey are provided to simplify construction of a structure. Te location of construction joints depends on te type of work, te site condition and te production capacity of te plant or labor employed. It frequently appens; wen large volume of concrete are being placed tat tere is a break in te construction work. Pure construction joints are not intended to accommodate movement but tey are merely separation between consecutive concreting operations and in fact, every effort is directed towards preventing movement from occurring at tese joints. Construction joints sould not be confused wit expansion joints. Expansion joints are usually used to allow for free movement of parts of a structure and wic are normally designed for complete separation. Construction joints are nearly always te weakest points in a structure. Te main problem tat remains terefore in te formation of a good construction joint is te capability of providing a well bonded medium between te ardened and te fres concrete. Tus construction joints in concrete structure sould be placed were sear forces are expected to be low. Bot te location and te size of joint sould in general be cosen according to te type of structure to ensure good performance of te structure and to provide acceptable appearance. In te case of reinforced concrete beams, construction joints may run orizontally, vertically, inclined or key joints; depending on te placing sequence prescribed by te design of te beam, Fig.(1). Te main concern in joint construction is in providing adequate sear transfer and flexural continuity troug te joint. Flexural continuity is acieved by continuing te reinforcement troug te joint, wile sear transverse is provided by sear friction between old and new concrete, and dowel action in reinforcement troug te joint. Construction joints may result in less tan100 of sear capacity. Te Construction joints sould be made in te following manner (3,4) : 1- Te surface of ardened concrete along te joint sould be torougly rougened. 2- Te surface of te concrete sould ten be cleaned torougly to remove all foreign and attaced matter suc as waste. 3- Hardened concrete sould be moistened torougly before new concrete is placed on it. 4- No pool of water sould be left standing on te wetted surface wen new concrete is placed. Vertical construction joint Horizontal construction joint Inclined construction joint Key construction joint Fig. 1. Types of Construction Joints. 49

3 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) 1.2. ocation of Construction Joint ocation of construction joints is usually predetermined by agreement between te arcitectural engineer and te contractor, so as to limit te work tat can be done at one time to a convenient size, wit te least impairment of te strengt of te finised structure. Generally, it is impractical to place concrete in lifts iger tan one story. Designer sould recognize tis wen locating orizontal construction joints. For building in wic te concrete walls are to be exposed, joints may be located at bends of ornamentation, ledge, rustications, or oter arcitectural details. It is convenient to locate orizontal joints at te floor line in line wit window sills. In te design of ydraulic structures, construction joints usually are spaced at sorter intervals tan in non-ydraulic structures to reduce srinkage and temperature stresses. Construction joints sould be located by te designer to provide logical separation between segments of te structure. As a rule, construction joints are allowed only were sown on te drawings. If te placing of concrete is involuntarily stopped for a time longer tan te initial setting time of te concrete used, te old surface is to be considered as a construction joint, and treated as suc before casting is resumed. Te appearance of a structure can be influenced by te location of te construction joint, and te aim sould be to install tem in apposition tat renders tem as inconspicuous as possible; te alternative is to make tem clearly visible as a feature of te structure. Te joint sould fit into te arcitectural design, and teir location sould facilitate te construction of forms and placing of concrete. However, from a point of view of strengt of te structure, it is desirable to position construction joint at point of minimum sear. For slabs and beams it is, terefore, usual to ave construction joint at mid span or in te middle tird of te span. Tese rules are based on te assumption tat a construction joint may result in less tan 100% of sear capacity in te interface. If tere were practicable to ave suc joints at te supports for slabs and beams, it improves appearance and result in a considerable saving in te cost of te formwork (5). 2. Variables of te Test Program Te variables affecting te location of construction joints of reinforced concrete structure elements are studied experimentally. Tese variables include te location and type of te construction joint and weter or not stirrups are present at te joint. A. ocation of Construction Joint Te effect of location of te joint is te main variable in tis study. Two different locations are considered: at te middle of te beam specimen and at te tird point as sown in Fig.( 2 ). Te reason for coosing te two locations is to investigate te beavior of te reinforced concrete beams wen te construction joint is at zero sear and maximum moment and at te zone of small sear and small moment. Construction joint Construction joint First pour Second pour Second pour First pour /2 /3 a- Construction joint at te middle of te specimen (V=0, M=Mmax.) Fig. 2. ocation of Construction Joints. 50

4 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) B. Types of construction joint Tree types of construction joints were investigated in tis study: B.1. Vertical construction joint Tis type of construction joint is made by using stop-board of wood placed vertically after casting te first part of te beam. Te stop-board as to be scatted to all longitudinal reinforcement to extend from te old concrete to new one, as sown in Fig. ( 3 ). B.2. Inclined construction joints In tis type of construction joints, te stopboard is cut so tat various inclinations of te construction joints can be maintained. Tree inclinations were used, 30, 45 and 60 wit te vertical axes, as sown in Fig. (4). Te reason for coosing tese tree inclinations is to investigate te effect of suc inclinations on te performance of te beam. Vertical construction joint Fig. 3. Vertical Construction Joint. Construction Joint Second Pour First Pour Second Pour Construction Joint a- 30 inclined construction joint wit b- 45 inclined construction joint wit vertical axes vertical axes First Pour Construction Joint Second Pour First Pour 60 0 c-60 inclined construction joint wit vertical axes Fig. 4. Types of Inclined Construction Joints. 51

5 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) B.3. Key construction joints Te key is normally formed by fixing beveled edge strip of wood to a stop board. Te stop-board as to be scatted to all reinforcement to extend from te old concrete to te new one. Te details of key construction joints used in tis investigation are sown in Fig. (5). First pour Construction joint Second pour Construction joint Second pour a- Key construction joint type I b- Key construction joint type Π Fig. 5. Types of Key Construction Joints. C. Presence of stirrups at te construction joint One of te groups contains stirrups at te construction joint located at tird point of te beam it is used to compare te efficiency of suc joint wit oter groups aving joint at tird point of te beam but witout stirrups at tat joint, see Table (1).(Note tat in key joint, () Sape stirrups was used trougout te joint). Table1, Test Parameters of Beam Specimens. Series No. Specimen No. ocation of te joint Stirrups at joint Types of Construction joint Reference beam Witout Construction joint 1 Vertical 2 Inclined by 30 0 Series 3 At te middle Witout stirrups at Inclined by 45 0 one 4 of te specimen te joint Inclined by Key joint I 6 Key joint II 7 Vertical 8 Inclined by 30 0 At te tird Series 9 Witout stirrups at Inclined by 45 0 point of te two 10 te joint Inclined by 60 0 specimen 11 Key joint I 12 Key joint II 13 Vertical 14 Inclined by 30 0 At te tird Having ø 10 Series 15 Inclined by 45 0 point of te mm stirrups tree 16 Inclined by specimen at te joint Key joint I 18 Key joint II * Note:Te concrete compressive strengt for all beam specimens was 20 Mpa (using cylinder mold). 52

6 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) 3. Experimental Work Te experimental work includes 19 simply supported reinforced concrete beams wit dimensions of ( 200x 200x950mm), as sown in Fig. (6) and plate(1a,1b). Te specimens were reinforced wit four longitudinal bars ( 2-ø12 mm bars at bottom and 2-ø10 mm bars at top), and (ø10mm ) closed stirrups located at 80mmc/c along te beam. Table (2) sows te properties of te reinforcement bars used. In all mixes, te cement was Ordinary Portland cement, Type I, wic was manufactured by te United Company Cement factory/iraq. Al- Ukaider natural sand of (4.75mm) maximum size was used as fine aggregate. wile te coarse aggregate was crused gravel wit max size of (19mm).Table (3) sows te quantities of concrete mix used in beam specimens. A P Symm. A 2Ø10Top bars Ø10@80mmc/c 2Ø12Bot. bars 200 Sec. (A-A) All dimensions are in (mm) Fig. 6. Dimensions and Reinforcement Details of Beam Specimens. 1A 1B Plate1: Beam Specimens before Testing (A) and (B). 53

7 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Table 2, Properties of Reinforcement Bars. Bar size(mm) Area Ab in (mm 2 ) Yield strengt Tensile strengt in (MPa) in (MPa) Table 3, Quantities of Concrete Mix. Concrete compressive strengt (MPa) W/C ratio Cement content (kg/m3) Aggregate content (kg/m3) Sand content (kg/m3) Two slandered cylinders 150x300mm were cast from eac batc of concrete during te casting of te first part of te specimen. Anoter two cylinders were cast wit second part of te specimen for eac casting operation. Tus, four cylinders for eac specimen were made. Te cylinders stored and cured under te same condition as te beam specimens and teir compressive strengt were measured at te time of testing. Table (4) sows te concrete compressive strengt for te beam specimens. Table 4, Actual Concrete Compressive Strengt for te Beam Specimens. Series No. Series one Series two Cylinder No. oad (kn) Part 1 Part 2 Compressive oad Compressive Strengt (MPa) (kn) Strengt (MPa) Average 19.7 Average Average 19 Average 18.7 Series tree Average 20.2 Average 19.5 Te beam specimens wit a construction joint were manufactured by casting one part of te specimen in an oiled plywood forms, and after 7 days te second part was cast to make te beam specimen as a one unit wit construction joint between tem. No attempt was made to improve te bond at te joint by degreasing or rougening te old face of concrete. Electrical vibrator was used to vibrate te specimens. Vibration process continued for 60 sec. Te test specimens were removed from te mould after10 days. All te specimens were cured for 14 days by sprinkling. Eac specimen was loaded to failure in 1000 kn computer controlled VERSTIE EECTRONIC TEST MACHINE. Te beam specimen is seated on te bending testing table for te macine. Te concentrated load was applied at te center of te specimen gradually and te deformation was measured wit 0.01 mm dial gauges located at te center of specimen, and at te construction joint wen its location is at tird point of te specimen. Te displacement was recorded by te dial gauge groups at eac 10 kn of load until failure occur eiter by cracking troug te construction joint or troug te concrete. 54

8 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) 4. Results, Discussion and Conclusions Te load deflection curves for beams aving construction joints are compared wit load deflection curves for beams witout construction joints, as sown in Fig.(7) to Fig.(24). Deflections at center and / or at location of te construction joint are listed in table (5). Witout const. joint Vertical const. joint at middle Witout const. joint 30 degree inclined const. joint at middle Fig. 7. oad Deflection Beavior of Beam No. (1) (Series one). Fig. 8 oad Deflection Beavior of Beam No. (2) (Series one). Witout const. joint Witout const. joint 45 degree inclined const. joint at middle 60 degree inclined const.joint at middle Fig. 9. oad Deflection Beavior of Beam No. (3) (Series one). Fig. 10. oad Deflection Beavior of Beam No. (4) (Series one). 55

9 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Witout const. joint Key const. joint type 1 at middle Witout const. joint Key const. joint type 2 at middle Fig.11. oad Deflection Beavior of Beam No. (5) (Series one). Fig.12. oad Deflection Beavior of Beam No. (6) (Series one). Witout constjoint Vertical const. joint at tird point Witout constjoint 30 degree inclined const. joint at tird point Fig. 13. oad Deflection Beavior of Beam No. (7) (Series two). Fig. 14. oad Deflection Beavior of Beam No. (8) (Series two). 56

10 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Witout constjoint 45 degree inclined const. joint at tird point Witout constjoint 60 degree inclined const. joint at tird point Fig.15. oad Deflection Beavior of Beam No. (9) (Series two). Fig.16. oad Deflection Beavior of Beam No. (10) (Series two). Witout constjoint Key const. joint type 1 at tird point Witout const joint Key const. joint type 2 at tird point Fig. 17. oad Deflection Beavior of Beam No. (11) (Series two). Fig. 18. oad Deflection Beavior of Beam No. (12) (Series two). 57

11 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Witout const joint Vertical construction joint wit stirrups at tird point Witout const joint 30 degree inclined cons.joint wit stirrups at tird point Fig. 19. oad Deflection Beavior of Beam No. (13) (Series tree). Fig. 20. oad Deflection Beavior Of Beam No. (14) (Series Tree). Witout const joint 45 degree inclined const. joint wit stirrups at tird point Witout const joint 60 degree inclined const. joint wit stirrups at tird point Fig. 21. oad Deflection Beavior of Beam No. (15) (Series tree). Fig. 22. oad Deflection Beavior of Beam No. (16) (Series tree). 58

12 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Witout const joint Key construction joint type 1 wit stirrups at tird point Witout const joint Key construction joint type2 wit stirrups at tird point Fig. 23. oad Deflection Beavior of Beam No. (17) (Series tree). Fig. 24. oad Deflection Beavior of Beam No. (18) (Series tree). Table 5, oad, Type of Failure and Ultimate Deflection of te Tested Beam Specimens. Series No. Specimens No. Type of failure Ultimate deflection at center (mm) Reference beam Series One Series Two T Series Tree 19 Flexural failure Flexural failure Flexural failure Joint failure Joint failure Flexural failure Flexural failure Joint failure Joint failure Joint failure Joint failure Joint failure Joint failure Flexural failure Flexural failure Joint failure Joint failure Flexural failure Flexural failure Failure oad (kn) Te load was applied to te beam specimens until failure occurred troug te construction joints or flexural failure developed. Close to failure, te flexural cracks cange into inclined sear cracks pointing toward te compression zone. During tests, specimens were examined for cracks. Te load at wic eac crack becomes visible was marked. Te beavior of te reference beam (beam witout construction joint) as sown in plate (2) and (3) is similar to ordinary reinforced concrete beams failing in flexure. Te first crack develops at te beam center at stress wic is close to flexural strengt of concrete. As te load increased, several oter flexural cracks on 59

13 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) bot sides of te central region developed. Near failure wic occurs at about 80 kn, tese flexural cracks cange direction toward te load location. Te measured ultimate deflection was 3.6 mm. primary type of failure depends on te type of construction joint. Te joint failure (crack troug te joint) occurs wen te construction joint is inclined at an angle greater tan or equal 45 wit vertical axis, as sown in plate (4). Flexural crack failure similar to te failure of te reference beam was observed to occur wen te inclination angle is less tan 45 wit vertical axis. Te primary type of failure for series two (specimens wit construction joints at tird point) was by cracking troug te construction joint (joint failure). No cracks outside te joint location were observed in tese specimens during te test. Te load-deflection curves indicate tat te deflection at all load levels is greater tan te deflection of te reference beam. For series tree it is obvious tat te presence of stirrups at te construction joints improves te performance of tese beams relative to similar beams wit construction joints but witout stirrups. Plate (2) Testing Macine. Plate(4) Beam Wit 60 Inclined Construction Joint at Midspan After Testing. Plate (3) Beam witout Construction Joint (Reference Beam) After Testing. Te beams wit stirrups at te construction joint failed by flexural cracking at iger load level wen compared wit beam specimens wit construction joints but witout stirrups at tese joints. Specimens wit construction joints at tird point failed by cracking troug te joints as sown in plate (5) at lower load levels of comparable specimens wit construction joint at middle of te beam specimens. As sown in Table (5), and Figs. ( 25 ) and ( 26 ). For beam specimens wit construction joint at middle section of te specimens (series one) te 60

14 oad(kn) oad (kn) oad (kn) Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Plate (5) Beam wit Vertical Construction Joint at Tird Point witout Stirrups after Testing Vertical const. joint at middle Vertical construction joint at tird point Deflection(mm) Fig. 25. Effect of ocation of Vertical Construction Joint degree inclined const. joint at middle 45 degree inclined const. joint at tird point Deflection (mm) Te reason for failure troug te construction joints located at tird points may be explained on te basis of presence of greater tension in concrete at tese locations as compared to no tension at mid span. Te presence of suc tension reduces te sear capacity possibly because adesion and friction at te interface between new and old concrete may be affected. For beams and slabs it is usual to ave construction joints at mid span or in te middle tird of te span. Tese rules are based on te assumption tat a construction joint may result in less tan 100% of sear capacity at te interface. Te type of construction joints was found to be an important factor affecting te beavior of te tested beams. Te vertical and key construction joints ave similar performance and te capacity and deflection of tese beams are close to tat of te reference beam. Te effect of inclined construction joints depends primarily on te degree of inclination of te surface of concrete; lower inclination wit vertical axis gives iger strengt joints. As sown in Table (5) and Figs. (27) and (28) Vertical const. joint at middle 45 degree inclined const. joint at middle Key const. joint type 1 at middle Deflection (mm) Fig. 27. Effect of Type of Construction Joint at Middle. Fig. 26.Effect of ocation of 45 0 Inclined Construction Joint. 61

15 oad( kn) oad (kn) oad (kn) Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) Vertical construction joint at tird point 45 degree inclined construction joint at tird point Key construction joint at tird point Deflection (mm) Vertical const. joint at tird point witout stirrups Vertical construction joint at tird point wit stirrups Deflection (mm) Fig. 28. Effect of Type of Construction Joint at Tird Point. Fig. 29. Effect of Presence of Stirrups at Vertical Construction Joint. Wen stirrups were added at te construction joints, te strengt of beams increases wit te increase in percentage of steel across te construction joint. Te beavior of tese beam specimens during tests was similar to te beavior of beam specimens of series one were te construction joints at midspan. Table (5) sows tat tese specimens fail at iger levels of loads wen compared wit beam specimens wit construction joints at tird point witout stirrups. Table (5) sows tat te type of failure of vertical, 45 inclined construction joint and less wit vertical axis, and key construction joints for series tree specimens failed by flexural failure wic is different from te type of failure of beam specimens of series two wic failed by joint failure. It can be concluded tat te presence of stirrups at te construction joint ave improved te beavior of beam specimens. Figs. (29 ) and (30 ) sows te effect of te presence of stirrups at te construction joints wit similar beams aving no stirrups at te construction joints degree inclined const. joint at tird point witout stirrups 45 degree inclined construction joint at tird point wit stirrups Deflection (mm) Fig. 30. Effect of Presence of Stirrups at 45 0 Inclined Construction Joint. 62

16 Zena Waleed Abas Al-Kwarizmi Engineering Journal, Vol. 8, No. 1, PP (2012) From te experimental results conclusions can be drawn: te following 1- It is preferable to locate te construction joint at te point of zero sear perpendicular to te main reinforcement. In tis investigation it is found tat beams wit construction joints at zero sears perform better tan beams wit construction joint at te tird points of specimens (te percentage of reduction in ultimate load capacity is in range of 2% -15%). 2- Vertical construction joints ave a sligt effect on te overall beavior of reinforced concrete beams under flexural mode wen tey are placed at te middle of te beam span (zero sears). Te load carrying capacity for te tested beam wit vertical construction joints is about95% of te capacity of te reference beam witout construction joint. 3- Te effects of inclined construction joints depend primarily on te degree of inclination of te surface of concrete, lower inclination wit vertical axis gives iger strengt joints. Te load carrying capacity of beam wit construction joints inclined by 45 is in te range between(8%- 20%) lower tan tat of beam witout construction joint. 4- Te percentage of steel across te joint (i.e. amount of stirrups at te construction joints) affects te overall load-deflection beavior of reinforced concrete beams aving construction joint. As te amount of suc steel is increased, te ultimate load-carrying capacity increased. For te studied cases, it is found tat increasing te amount of steel across te joint in te range of (50%- 100%) causes an increase in capacity in te range of (7%- 15%) and a decrease in te ultimate deflection in te range of (20%- 48%). 5- Te performance of beam wit vertical or key construction joints is similar to te performance of beams witout construction joints. 5. Refrences [1] ACI Committee Report 224.3R-95 "Joints in Concrete Construction", pp. 1-44, [2] P. Critcell, "Joints and Cracks in Concrete", CR Books (A Maclaren Company), ondon, [3] M. Fintel, "Joints in Buildings", Handbook of Concrete Engineering, 2nd Edition, pp.121, 1985 [4] A. Mattock, "Cyclic Sear Transfer and Type of Interface", Journal of te Structural Division, ASCE, vol.107, no. ST10, pp , [5] C. Desai and M. Zaman, "Tin-ayer Element for Interface and Joints", International Journal for Numerical and Analytical Metod in Geometrical, vol.8, pp.19-43,

17 زينة وليذ عباس مجلة الخىارزمي الهنذسية المجلذ 8 العذد 1 صفحة (2012) تاثير المفصل االنشائي على تصرف العتبات الكىنكريتية المسلحة زينة وليذ عباس لسم ان ىذست انمذو ت / انجامعت انمسخىصش ت الخالصة إن انمفاصم اإلوشائ ت عباسة عه مىاطك انخ لف ف عمه ت صب انخشساوت ضش س ت ف عذ ذ مه انمىشاث انخ ال مكه ف ا صب انخشساوت عه مشدهت ادذة. إن ممذاس انخشساوت انخ مكه صب ا عخمذ عه انسعت اإلوخاج ت سعت انخهظ ف انم الع عه و ع ت انم انب انمسخخذمت. انمفصم اإلوشائ انج ذ فش اسخمشاس ت نهمص االوذىاء خالل انسطخ انب ى. ف زا انبذث حم دساست حأث ش أو اع م الع انمفاصم اإلوشائ ت عه أداء األجضاء انخشساو ت عه طش ك فذص ومارج عمه ا ف انمخخبش. حم فذص 91 وم رج باألبعاد 152*022*022 )مهم(. إن انمخغ شاث انخ حم اعخماد ا م لع انمفصم اإلوشائ )ف مىخصف أ ثهث انىم رج( و ع انمفصم اإلوشائ )عم د مائم بضا ت مع انمذ س انعم د لفم مفخاح( إضافت أط اق ف انمفصم اإلوشائ. حم فذص انىمارج ب اسطت ماكىت فذص راث سعت 9222 ك ه و حه. ضعج انىمارج بشكم سمخ بم اط ممذاس االوذشاف ف مىخصف أ حذج انمفصم نكم مشدهت دمم. حش ش انىخائج انعمه ت إن إن أفضم م لع نهمفصم اإلوشائ ف انمىاطك انخ ف ا ل لص له هت حش ش أ ضا إن إن انمفصم انعم د ر حأث ش بس ظ عه ل ة انىمارج )وسبت االوخفاض جاءث ب ه) صفش% -%5( نكه جذ ومصان را حأث ش مهذ ظ عه ل ة انىمارج مع ص ادة دسجت م م انمفصم اإلوشائ مع انمذ س انعم د وسبت االوخفاض كاوج ب ه )%8-%20(. جذ ف زي انذساست أ ضا إن إضافت دذ ذ انخسه خ عه شكم أط اق ف مىطمت انمفصم اإلوشائ مخغ ش م م ن حأث ش عه و ع انفشم انذاصم مما مت انخذمم انمص جذ إن ص ادة كم ت انذذ ذ ف مىطمت انمفصم ؤد إن ص ادة ف مما مت انخذمم انى ائ ت ما ب ه )%7-%15( ومصان ف ممذاس االوذشاف ما ب ه )%20-%88 ). 64