Reinforcement in concrete piles embedded in sand

Transcription

1 International Journal of te Pyical Science Vol. 5(15), pp , 18 November, 2010 Available online at ttp:// ISSN Academic Journal Full Lengt Reearc Paper Reinforcement in concrete pile embedded in and Fira A. Salman*, Moammed M. Moammed, S. M. Sirazi and Moammed Jameel Department of Civil Engineering, Faculty of Engineering, Univerity of Malaya, uala Lumpur, Malayia. Accepted 29 October, 2010 In ti tudy, te neceity of reinforcement in concrete pile (bored or driven) i aeed. Te oil wa aumed to be unaturated and omogeneou andy oil. Trougout te tudy, a finite element computer program wa ued and te pile wa modeled a a beam-on-elatic foundation. Te oil i repreented by dicrete pring. Te tiffne of eac pring i conidered to be linearly variable wit dept. Te moment loading, lateral loading, pile lengt, pile diameter, in addition to te angle of internal friction and oil denity were taken a parameter to tudy teir effect on te extent of reinforcement along te pile aft. It i concluded tat for pile embedded in and, a lengt of reinforcement not le tan 40% of pile lengt for bored pile and 20% for driven pile i needed. ey word: Sand, reinforcement requirement, bored pile, driven pile, pile reinforcement. INTRODUCTION Te cot of teel reinforcement i increaing and te demand i alo ig. Hence, it i neceary to tudy te poibility of reducing ti material to te minimum during pile contruction. In te pat, pile were fully reinforced. Nowaday, te deigner prefer to minimize te lengt of reinforcing bar o tat tey may reduce te cot of pile. Ti minimization require well eparation for te cae were te pile need fully or partially reinforcement and te cae were te reinforcement can be completely eliminated. After making a urvey on te code of practice and tudying teir recommendation in uc field, it wa found tat all te code of practice give pecification and limitation for te percentage of bar tat ould be provided in te pile cro-ectional area. But te dept of extenion of ti reinforcement along te pile i not pecified and tu left to te deigner dicretion. Te main objective of ti tudy can be divided into two main categorie, tat i, (a) make a urvey on te code and teir requirement on pile reinforcement, and (b) invetigating weter te pile need to be provided wit reinforcement or not, and to wat lengt te pile reinforcement i needed. Pat tudie of pile reinforcement Te reinforcement are required in concrete pile to *Correponding autor. firaalman@otmail.com. reit bending and tenile tree, but may be ued to carry a portion of te compreion load. Te extenion of te reinforcement required at any ection of te pile depend upon te load and tree applied to tat ection. Reinforcement i required if te pile i ubjected to bending moment. Te bending moment and earing force in a pile ubject to lateral loading may be aeed uing te metod of Matlock and Reee (1960) a given in Figure (1). Ti metod model te pile a an elatic beam embedded in a omogeneou or nonomogeneou oil. Te tructural capacity along flexible pile i likely to govern te ultimate capacity of a laterallyloaded pile. Te pile reinforcement undergoe te need and te requirement. Terefore, tere i no pecific limit were te pile ould be reinforced. Te need are determined by one of te pile analyi teorie, were field obervation and ome teoretical conideration pecify te requirement. REINFORCEMENT REQUIREMENTS Precat concrete pile Te reinforcement ould be provided in all precat concrete pile to take up te tree caued in andling, pitcing and driving and ti greatly exceed wat i needed once te pile i in te ground (Saurin, 1949; Witaker, 1976; Moan, 1990). Indian Standard (IS part I, 1964-ti code of practice i more tan 40 year old, and it relevance in today practice may

2 2260 Int. J. Py. Sci. Deflection coefficient F for applied moment M Deflection coefficient F for applied lateral load H Moment coefficient F M for applied moment M Moment coefficient F M for applied lateral load H Sear coefficient F v for applied moment M Sear coefficient F v for applied lateral load H Figure 1. Influence coefficient for pile wit applied lateral load and moment (flexible cap or inged end condition) (Matlock and Reee, 1960). not be ignificant) recommended tat te area of te main longitudinal reinforcement all be not le tan te following percentage of te cro-ectional area of te pile: T = Note: (1) Stiffne factor, 5 EPI n P (a) 1.25% for pile wit lengt le tan 30 time te leat widt (b) 1.5% for pile wit lengt between 30 to 40 time te leat widt (c) 2.00% for pile wit lengt greater tan 40 time te leat widt were E p, I p = bending tiffne of pile and n = contant of orizontal ubgrade reaction. (2) Obtain coefficient F, FM and Fv

3 Salman et al at appropriate dept deired and compute deflection, moment and ear repectively uing te given formula. Were te lateral reinforcement all be in te form of oop or link and all be not le tan 5 mm in diameter. Te volume of lateral reinforcement all be not le tan te following percentage of te gro volume of te pile: (a) 0.20% in te body of te pile, (b) 0.60% at eac end of pile for a lengt of about 3 time te leat widt. Te tranition between te cloer pacing and te maximum all be gradual over a lengt of 3 time te leat widt. Sout African Bureau of Standard (SABS 088, 1972) recommended tat te cro-ectional area of longitudinal reinforcement ould be at leat 0.8% of te cro ectional area of te pile, and lateral tie ould be at leat 6 mm in diameter, cloely pacing at bot end of te pile. American Concrete Intitute (ACI 543R, 1974) recommended tat te longitudinal teel cro-ectional area ould not be le tan 1.5% or more tan 8% of te cro-ectional area of te pile. At leat ix longitudinal bar ould be ued for round or octagonal pile and at leat four bar for quare pile. Te lateral teel ould not be le tan 0.25 in. (6 mm) in diameter and paced not more tan 6 in. (150 mm) on center except tat te pacing ould be cloer at eac end of te pile. Wat i DIN? German Intitute for Standardization (DIN ) recommended tat te longitudinal reinforcement of te pile, at lengt not exceeding 10 m, all be not le tan 0.8% of te cro-ection of te pile. For olid rectangular pile, at leat 4 longitudinal bar of 14 mm diameter mut be arranged in te corner; for round pile, at leat 5 longitudinal bar of 14 mm diameter ave to be placed and evenly paced, witout end ook. Te tranvere reinforcement ould be at leat 5 mm in diameter. Te axial pacing (pitc) of a elix ould be not exceed 120 mm and reduced to about 50 mm over a lengt of 1 m at top and bottom of te pile. Japanee Indutrial Standard (JIS A5310, 1987) recommended tat te longitudinal reinforcement all conit of 6 mm or more bar, wit a teel ratio not le tan 0.8% and it i deirable tat tey are arranged uniformly along te circumference of te concentric circle in te repective cro ection of reinforced concrete pile. Te minimum pacing all not be maller tan 0.75 time te maximum dimenion of te coare aggregate. Te piral bar all be arranged outide te longitudinal reinforcement. Te additional bar all ave a diameter not maller tan 3 mm, and a pitc not larger tan 110 mm. Many literature recommended te ame pecification for te reinforcement of precat concrete pile (Celli, 1961; Rennie, 1986; Ja and Sina, 1995). Cat in-itu concrete pile Te extent of reinforcement in cat-in-itu concrete pile i governed by te load involved and te deign analyi. Some code differentiate between te recommendation of reinforcement in bot driven and bored cat-in-itu concrete pile (BS 8004, 1986, and DIN 4014-part I, 1975), were oter conider tem a one unit under te main article, cat-in-itu concrete pile, (IS 2911-part I, 1964, and ACI 543R, 1974). IS 2911-part I (1964) recommended tat any reinforcement in cat-in-itu concrete pile ould be made up into cage ufficiently well wired to wittand andling witout damage. Te bar ould be o paced a not to impede te placing of te concrete and te lateral tie or piral ould not be cloer tan 150 mm center to center. Reinforcement in te pile may reflect te manner of te tranmiion of te load by te pile to te oil, and need not normally exceed 0.8% of te cro-ectional area of te pile. ACI 543R (1974) recommended tat te reinforcement i ued in cat-in-itu concrete pile for any unupported ection of te pile, uplift load, or lateral load wen te analyi indicate. Unupported ection (wic extend troug, air, water, or even troug very fluid oil) ould be deigned to reit buckling under te impoed load. Sufficient longitudinal and lateral teel ould be ued for te load and tree to be reited. For lateral load, te pile ould be deigned and reinforced to take load and tree involved. In general, te amount of reinforcement required will be governed by te load involved and te deign analyi. Except for uplift load, it i recommended tat not le tan four longitudinal bar be ued. Te extent of reinforcement below ground urface depend on te flexural and load ditribution analyi. DIN 4014-part I (1975) recommended tat bored pile normally contain bot longitudinal and tranvere reinforcement extending over te entire lengt of te pile. Te reinforcement all be made in te form of a reinforcing cage and intalled in te caing pipe in uc a way tat it cannot be diplaced during te concreting or lifted wit te caing wen te latter i being extracted. A reinforcement extending over te full lengt of te pile may be dipened wit if te pile are vertical and are not le tan 300 mm in diameter and not more tan 7.5 m in lengt. Provided tere i no likeliood of te pile being ubjected to bending by eiter eart preure, te lateral preure of platic oft oil, eccentric loading or any oter caue. Te longitudinal reinforcement all comprie not le tan five reinforcing bar of 14 mm diameter, paced at interval of not more tan 200 mm. Te total of te cro-ection area of te longitudinal reinforcement mut be not le tan 0.8% of pile cro-ection. If any permanent caing i ued, it all not be reckoned a part of te reinforcement becaue of te rik tat it may rut troug. Te tranvere reinforcement all be arranged in elical form wit a bitc between 150 to 200 mm. It mut ave a diameter of not le tan 5 mm, wen te pile diameter i not more tan 350 mm, or 6 mm wit ticker pile. BS 8004 (1986) and CP 2004 (1972) recommended tat te reinforcement ould normally be carried down for te full lengt for bored pile and into te enlarged bae, if pile are required to reit tenile force. Were te tenile force are mall, te reinforcement need only be of te lengt neceary to tranmit fully te tenile force. Reinforcement ould be provided for tenile force, wic are not expected to exit wen te tructure i completed. For driven cat-in-itu concrete pile, it wa recommended tat te reinforcement may be provided over te wole of teir lengt, over part of teir lengt, or merely provided wit ort plice bar at te top for bending into te pile cap. Te extent of te reinforcement will depend on weter te pile i ued to reit tenile or bending force, on te type of foundation, and on te poibility on orizontal or vertical movement due to te intallation of oter pile nearby or to moiture cange in te oil. Derrington (1966) tated tat if pile of 3 ft (0.9 m) diameter and over do not generally require reinforcement unle paing troug a coniderable dept of very oft ground. Only nominal reinforcement i required at te pile ead for connection to pile cap or column. In 2 ft (0.6 m) and 2.5 ft (0.75 m) diameter pile it may be conidered deirable to reinforce te upper part of te pile aft if ti pae troug weak ground. Large diameter pile may be reinforced to reit bending moment reulting from orizontal force, tee force being balanced by te paive reitance of ground againt te pile. Fleming et al. (1985) recommended tat for bored pile loaded in compreion alone, it i only neceary to reinforce te aft to a dept of 2 m greater tan te dept of temporary caing, to prevent any tendency for concrete lifting wen pulling te caing. Pile ubjected to tenion or lateral force and eccentric loading (poibly

4 2262 Int. J. Py. Sci. being out of poition or out of plumb) require uitable reinforcement to cope wit tee force. Nominal reinforcement for pile in compreion only would comprie about four 12 mm diameter bar for a 400 mm diameter pile to five 16 mm diameter bar for a 550 mm diameter pile. A pecial cage of 5 mm teel, or oop of flat teel, are employed a lateral tie. Bar ould not be o denely packed tat concrete aggregate cannot pa freely between tem and oop reinforcement i not recommended at cloer tan 100 mm center. Provided te cage can be oriented, maximum teel need only be placed over tat part of te pile ubjected to maximum tre, and a reduced denity can be ued in te plane of te natural axial. For driven cat-in-itu concrete pile, Fleming et al. (1985) recommended tat widely paced reinforcement bar being neceary to allow te low workability mix to penetrate to te interior of te pile. If te pile i to reit compreive force only, te reinforcement may be retricted to te upper ection. Bowle (1988) tated tat, for bored pile, te reinforcing bar may be required only in te upper region for moment tat are carried by te aft, becaue tee moment diipate wit dept are ence te aft load i primarily axial at about L/2. At ti dept, temperature cange are not great; terefore, longitudinal and piral reinforcement are not required. Tomlinon and Woodward (2008) tated tat reinforcement i not needed in bored pile unle uplift load are to be carried (uplift may occur due to te welling and rinkage of clay). Reinforcement may alo be needed in te upper part of te aft to wittand bending moment caued by any eccentricity in te application of te load, or by bending moment tranmitted from te ground beam. Deign apect Laterally loaded pile are analyzed by mean of two main categorie, one uing Winkler modulu of ub-grade reaction concept a te oil model, and te oter uing and elatic continuum a oil model. Eac one a it advantage and diadvantage. Matlock and Reee (1960) formulated and olved te differential equation for te deflection of te pile uing a beam-on-elatic foundation approac. Te oil trengt i caracterized uing coefficient of ub-grade reaction. Tey obtained a erie of nondimenional curve o tat a uer could enter te appropriate curve wit te given lateral load and etimate te ground-line deflection and maximum bending moment in te pile aft. Brom (1965) preented metod for te calculation of lateral deflection at working load baed on te concept of a coefficient of ubgrade reaction. It a been aumed tat te coefficient of ubgrade reaction increae linearly wit dept in cae of coeionle oil, and tat it i contant wit dept for coeive oil. Poulo (1971) analyzed te beavior of pile tat were ubjected to lateral load and moment uing te continuum teory. It wa found tat te major factor influencing te pile beavior are te lengt to diameter ration, L/D, and te pile flexibility ratio, R, wic i defined a: R = E ( EI ) P 4 L were R i te pile flexibility ratio, E i te modulu of elaticity of te pile, I i te moment of inertia of te pile, E i te modulu of elaticity of oil, and L i te lengt of pile embedded in oil. (1) Randolp (1981) tudied te repone of flexible pile to lateral loading uing finite-element metod and treated te oil a an elatic continuum wit a linearly varying oil modulu. It wa found tat te maximum bending moment induced in a free-eaded pile ubjected to lateral force, H, can be etimated a: 0.1 M max = H lc (2) ρ c were M max i te maximum bending moment induced, H i te lateral force, ρ c i te factor giving relative omogeneity of oil, and i te critical lengt of te pile. l c Gleer (1984) uggeted a generalized olution applicable to laterally loaded vertical pile of any configuration of tiffne trougout teir lengt, embedded in foundation compriing any arrangement of layer of any type of oil. Te oil beavior at any point along te lengt of te pile can vary from elatic troug emielatic to platic a a known function of te applied tre at tat point. He took full recognizance of te beavior of oil aving nonlinear p-y repone curve in predicting te beavior of pile in uc oil wen ubjected to lateral load. Horvat (1984) preented te teoretical development of te application of te implified continuum approac to te laterally loaded pile problem, uing te analyi procedure, uggeted by Reiener (1958). He owed tat olving uc problem could be implified if certain tre component (σ y, σ z, and τ yz) were aumed to be equal to zero. In addition, all diplacement were aumed to be equal to zero at ome orizontal ditance from te pile. He alo demontrated tat tere were difficultie in adapting ti approac to andle nonlinear beavior, a Young modulu tat varie linearly wit dept, and oter practical conideration. Amir (1985) analyzed te beavior of ear pile in rock by te pring model metod, auming an exponential relationip between idewall ear and diplacement. Te reulting nonlinear differential equation, in term of dimenionle force, may be olved by iterative finite-difference. Te load ettlement curve and axial force ditribution obtained from ti olution ow good agreement wit field meaurement. Budu and Davie (1987) preented reult of a numerical analyi of ingle laterally loaded pile embedded in coeionle oil. Te oil i modeled a an elatic material. Tey ued te reult of intrumented lateral load tet carried by Cox et al. (1974), to compare between teir reult and te reult obtained from te analyi of te tet pile, carried by Reee et al. (1974). By modeling te laterally loaded pile a a beam element and te oil preure a independent nonlinear pring (p-y metod). Te tet pile, 610 mm diameter teel pile wit flexural rigidity 172 MN.m 2, wa embedded 21 m in a depoit of medium dene to dene fine and. Lateral load wa applied at a eigt of 305 mm above ground level. Te ground water level wa kept above ground level during te tet. Te propertie of and a reported by Budu and Davie (1987) are: φ= 39 o,γ = 10.5 kn/m 3.Te agreement between te reult are quite good. Bowel (1988) generalized a computer program to analyze laterally loaded pile uing Winkler foundation approac and aumed te modulu of ub-grade reaction increae linearly wit dept. Verruijt and ooijman (1989) preented a numerical model for a laterally loaded pile in a orizontally layered elatic continuum, and obtained a quai-tree-dimenional analyi. Tey combined te finite-element and finite-difference metod wit a relatively imple and compacted metod of analyi. A comparion between teir olution and te olution obtained by Poulo (1971) and te ub

5 Salman et al grade teory owed a good agreement for intermediate and large value of flexibility ratio. In general, te value of ub grade teory are omewat larger tan toe obtained by Poulo; te agreement i good over te entire range of flexibility factor. Teoretical approace for determination of Many teoretical approace were ued to determine te value and variation of ub-grade reaction. Some of tee tudie are given in ti ection. Palmer and Tompon (1948) uggeted te following expreion for te variation of wit dept: n Z = L L were i te orizontal modulu of ub-grade reaction, Z i any dept along te pile, L i te pile embedded lengt, L i te value of at te pile bae (Z = L) and n i an empirical index equal to or greater tan zero. Te mot common aumption are tat (n = 0) for clay were te modulu i contant wit dept and (n = 1) for granular oil were te modulu increae linearly wit dept. For te cae (n = 1), it i convenient to expre te variation of a: Z B = n (4) were B i te diameter or widt of te pile, and n i an empirical value ranging from ( ) kn/m 3 for oft normally conolidated clay. Glick (1948) propoed te following equation to find : = 22.4E 1 ( ν ) ( ν )( ) ( 2 ν ) ln L B were: E i te oil modulu of elaticity, and ν i te oil Poion ratio. Alizade and Davion (1970) analyzed te reult of te field tet on laterally loaded pile by mean of te teoretical expreion preented by Matlock and Reee (1960). Ti expreion i baed on te triangular ditribution of orizontal ubgrade modulu,, wit dept, in wic: = nz (6) For deign purpoe, n ould be elected compatible wit te anticipated deflection. Sogge (1981) propoed te following imple relationip to obtain a range of n value for allow pile: ( 2 to 30) Z B = (in kcf unit (kcf = 159 kn/m 3 )) (7) Bowle (1996) gave te mot general form for eiter orizontal or (3) (5) vertical modulu of ub-grade reaction, wic i: A B Z n = + (8) Were A i a contant for eiter orizontal or vertical member, B i a coefficient for dept, and n i an exponent to give te bet. At te ground urface, A i zero for orizontal, but at any mall dept A will be greater tan zero. For footing and mat, A > 0 and B 0. Ti mean tat i conidered contant becaue te dept of influenced zone i mall compared to pile. THE COMPUTER PROGRAM If te pile i not deigned for buckling, ten te main caue of tenile tree in a pile ection are te lateral load and/or bending moment, tat i, te reinforcement ould be provided for all ection ubjected to tenile tre. For ti reaon, a computer program (PLRN) i modified from tat given in Bowle (1988) to ceck te dept troug wic te reinforcement will only be required to cover te tenion zone of te pile. (PLRN) program i coded in Fortran-77 language and baed on Winkler foundation model were te pile i treated a beam element and te uniaxial oil reitance i repreented by independent pring. Problem decription and modeling Te baic parameter tat are ued in ti tudy are a follow: (expand te abbreviation) For pile: Moment, M = 0.1 B Q a (kn.m) Horizontal load, H = 0.1 Q a (kn) Q a = 100 kn L= 25.0 m B= 1.0 m (for bored pile) B= 0.5 m (for driven pile) For oil: Unit weigt of oil, γ = 15 kn/m 3 Angle of internal friction, φ= 30 o Coeion, c u = 0 kn/m 2 Bored pile are uually contructed wit larger diameter compared to driven pile. Terefore, for a contant dept, te dept ratio in bored pile will be maller tan tat in driven pile. Ti paper doe not deal wit te effect of contruction of te pile on it beaviour, but wen te pile i loaded laterally, it beaviour will depend on weter it a large diameter (bored) or mall (driven). ANALYSIS AND DISCUSSION Te effect of different parameter on te tre ditribution and, ence, on te extenion of reinforcement below te ground urface are tu explained. Effect of pile type Figure 2 preent a relationip between te minimum

6 2264 Int. J. Py. Sci. Dept ratio (/B) Figure 2. Stre ditribution for driven and bored pile embedded in and. Dept ratio (/B) Figure 3. Effect of moment loading on te tre ditribution along te aft of bored pile in and. bending tre (tenion or compreion) witin te pile ection under te general working load and te dept ratio for bot bored and driven pile embedded in and. Te pile will no longer be ubjected to tenile tre and, terefore, it will act a a compreion member. Te variation in te tre ditribution along te pile aft i due to te cange in te ditribution of bending moment along te aft and te decreae in te allowable load wit dept,. Te tenile tree in bored pile are maller tan in driven pile becaue te diameter and ence te moment of inertia of te pile ection are greater wic lead to decreae in te tree. Bored pile Effect of moment loading Figure 3 ow te effect of moment loading on te

7 Salman et al Figure 4. Effect of lateral loading on te tre ditribution along te aft of bored pile in and. Figure 5. Effect of pile lengt on te tre ditribution along te aft of bored pile in and. tre ditribution along te pile aft, a te applied moment increae te tenile tre will increae at te pile top and decreae or vanie a it goe down. It wa found tat te zero tenile tre occur at a dept of about 6.5 diameter for 10% of te applied moment loading. A uc, te teel reinforcement need to be extended along ti dept only. Effect of lateral loading Figure 4 ow te effect of lateral load on te tre ditribution along te pile aft, a te applied lateral load increae te tenile tre increae to it maximum value at a dept ratio of 4 wit 30% of te applied load, ten decreae wit dept to reac a contant value in te compreion ide. Te contant value in te tre ditribution curve i te ame a for all value of te applied lateral load. Te maximum tenile tre, for all curve, located at about 4 diameter. Te dept were te tenile tre equal to zero will increae a te lateral load increae. Te effect of applied moment vanie at a dept ratio of about 10 wile ti dept ratio i about 15 for lateral load. Effect of pile lengt Figure 5 repreent te effect of pile lengt on te tre ditribution along te pile aft, a te pile lengt

8 2266 Int. J. Py. Sci. Figure 6. Effect of diameter on te tre ditribution along te aft of bored pile in and. Figure 7. Effect of friction angle on te tre ditribution along te aft of bored pile in and. increae, te tre will increae too in bot compreion and tenion ide, but will not affect te dept of zero tenile tre nor te location of it maximum value. Te maximum tenile tre appear at approximately 5 diameter and it will be equal to zero at about 6 diameter. Effect of pile diameter Figure 6 ow te effect of pile diameter on te tre ditribution along te pile aft, te increae in pile diameter, increae te pile tiffne, and accordingly will decreae te value of te tenile tree along te aft. Te maximum tenile tre will occur at a dept ranging between 4 to 5 diameter for a pile diameter of 2.0 to 0.8 m, repectively. Te dept of zero tenile tre decreae a te pile diameter increae. But generally it doe not exceed 7 diameter. Wen te pile diameter increae, te moment of inertia of it ection will increae too, wic caue reduction in tree. Effect of angle of internal friction Figure 7 ow tat te effect of angle of internal friction on te tre ditribution for bored pile embedded in

9 Salman et al Figure 8. Effect of unit weigt of oil on te tre ditribution along te aft of bored pile in and. Figure 9. Effect of moment loading on te tre ditribution along te aft of driven pile in and. and. Te angle of internal friction a a ignificant effect on te tre ditribution. A it increae in value, increaing oil tiffne, te bending moment will decreae and te tenile tre will not appear. For minimum value of te angle, 25, te zero tenile tre appear at about 8 diameter wit maximum tenile tre located at about 5 diameter. Effect of oil unit weigt Figure 8 ow te effect of oil denity on te tre ditribution along te pile aft embedded in and. Te beavior i omewat imilar to te effect of angle of internal friction, increaing in compreion tree, decreaing to reac a maximum tenile tre ten increaing again to reac a contant compreion value. Te oil denity a little effect on te tre ditribution, at leat in te upper portion. Te maximum tenile tre located at approximately 5 diameter were it reace zero at about 5.5 to 6.5 diameter. Driven pile Effect of moment loading Figure 9 ow te effect of moment loading on te tre ditribution along te aft of driven pile embedded in and. Te beavior i imilar to toe of

10 2268 Int. J. Py. Sci. Figure 10. Effect of lateral loading on te tre ditribution along te aft of driven pile in and. Figure 11. Effect of pile lengt on te tre ditribution along te aft of driven pile in and. bored pile in and, but wit greater value of tre in bot compreion and tenion and le dept for maximum and zero tenile tree. Generally, te dept of zero tenile tre i located at about 8 diameter for te moment of 10% of te applied load. Effect of lateral loading Figure 10 ow te effect of lateral loading on te tre ditribution along te pile aft. Te beavior i imilar to tat of bored pile but wit greater value of tre and le dept. In general, te maximum tenile tre appear at approximately 4 to 6 diameter for a range of lateral load from 30 to 10% of te applied load, repectively. Te dept of zero tre increae wit increaing lateral load. Value ranging between 8 and 11 diameter for lateral loading caued by 10 to 30% of te applied load repectively. Effect of pile lengt Figure 11 ow te effect of pile lengt on te tre ditribution along te aft of driven pile in and. It i clearly een tat te tre increae a te pile lengt

11 Salman et al Figure 12. Effect of diameter on te tre ditribution along te aft of driven pile in and. Figure 13. Effect of friction angle on te tre ditribution along te aft of driven pile in and. increae, but te pile lengt a no effect on te location of te maximum tenile tre or on te dept of it zero value, imilar to bored pile te dept of maximum tenile tre i at approximately 6 and 8 diameter for te dept of zero tenile tre. tenion and compreion, due to increaing pile tiffne. Subequently te dept of zero tenile tre i at about 6 diameter were te dept of it zero value varie between 8 to 10 diameter for a diameter of 0.5 to 0.3 m, repectively. Effect of pile diameter Figure 12 repreent te effect of pile diameter on te tre ditribution of driven pile embedded in and. Te tree decreae a te diameter increae for bot Effect of angle of internal friction Figure 13 ow te effect of te angle of internal friction on te tre ditribution for driven pile in and. Te value of te tenile tree will decreae a te oil

12 2270 Int. J. Py. Sci. Figure 14. Effect of unit weigt of oil on te tre ditribution along te aft of driven pile in and. tiffne increae, baed on te increae in te angle of internal friction, imilar to bored pile. Te location of maximum tenile tre will increae a te oil tiffne decreae and it range between 4 to 6 diameter. Te ame ting i alo true for te dept of zero tenile tre, wic i located at about 7 to 10 diameter for φ = 35 and 25 repectively. Effect of oil unit weigt Figure 14 repreent te effect of oil denity on te tre ditribution along te aft of driven pile embedded in and. Similar to bored pile, te oil denity a little effect on te tre ditribution. Te maximum tenile tre i located at about 5 diameter wile te zero tenile tre i at approximately 8 diameter for different oil denity ranging from 15 to 20 kn/m 3. Concluion A beam-on-elatic foundation model wa ued to analyze a loaded pile in order to invetigate it need and neceity for reinforcement. Ti model i performed uing te finite element metod a a numerical tool for te analyi. Te pile i dicretized into a number of element wile te oil i repreented by a number of pring. Te tiffne of tee pring i conidered to be variable wit dept. Baed on te reult obtained, te following concluion can be drawn: 1. For cat-in-itu bored or driven pile, te code did not recommend a pecific dept for te reinforcing bar tat ould be provided to reit te tenile tree. Ti iue i left to te deigner. 2. Bored pile embedded in and mut be provided wit reinforcing bar extending to a dept of not le tan 0.4 time te pile lengt. Wile for driven pile ti lengt may be reduced to 0.2 time te pile lengt, approximately. 3. For bored pile in and, te pile will not be ubjected to tenile tree below an approximate dept ratio of 10; accordingly reinforcement i not needed below ti dept. 4. For bored pile, te dept of zero tre in and i greater for mall value of friction angle and ti dept will be about 8 diameter. 5. Driven pile in and need a dept of reinforcement to be extended to approximately 8 diameter to reit te tenile tree, wile it doe not need any reinforcement at a dept of about 11 diameter becaue te zero moment will tart at tat dept. ACNOWLEDGEMENT Te autor would like to acknowledge and extend gratitude to te Univerity of Malaya for te encouragement, tecnical upport, and epecially for te financial upport by te Intitute of Reearc Management and Monitoring (IPPP), Univerity of Malaya (UM) under UMRG grant number (RG086/10AET).

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