Efficient Splicing Techniquefor Precast PrestressedConcrete PilesO0000a00000a000000

William J. VenutiProfessorDepartment of Civil Engineering

and Applied MechanicsSan Jose State UniversitySan Jose, California

F requently it is necessary, or atleast desirable, to splice pre-

cast prestressed concrete piles.The advantages of reducing thelengths of long piles into shortersections are that it.

I. Results in easier handlingduring transportation and inthe pile driver leads.

2. Minimizes the chance ofcracking during handling.

3. Permits greater flexibility indetermining required lengthof pile.

4, Allows extensions of pileswhen necessary.

5. Reduces cost in transporta-tion.

6. Simplifies storage at the pre-casting yard and at the con-struction site.

These advantages can only beachieved if the splice is economi-caI, can develop the structural.capacity of the pile section andthe connection can be madequickly and without the require-ments of special trade skills in thefield.

This report presents the resultsof an extensive investigation ofthe structural capacity of awedge-type splice for 12-in. (305mm) square precast prestressedconcrete piles.'

Literature Review

Only a limited number of referenceson prestressed concrete pile spliceshave appeared in the literature in thepast decade, a few of which have dealt

102

with laboratory or field testing ofsplices,

In June 1968, Gerwick 2 presented areview which includes historical in-formation and the utilization, design,manufacture, and installation of pre-stressed concrete piles. Problem areasand failures are discussed. Epoxy-dowelled splices were mentioned asbeing the most desired type in meet-ing the necessary requirements ofhigh flexure resistance, although me-chanical splices were considered to bethe most economical. An account ofthe entire presentation appeared in asubsequent PCI JOURNAL. 3 Kil-bridge 4 later summarized Gerwick'spresentation in Concrete (London).

An excellent state-of-the-art reporton design practice and recommen-dations of prestressed concrete pilingwas presented by Li and Lius in 1970.The paper first reviews major factorsinherent in prestressed concrete piles.It discusses required concretestrengths for splices and build-ups forconditions with and without driving.Included are considerations of pileprestress levels, driving stresses, headand tip design practice, and require-ments for an ideal splice.

Alley6 discusses the successful useof a combination sleeve and wedgesplice which was developed and pat-ented by Raymond International, Inc.It was used for splicing 16 ya-in. (420mm) octagonal piles for a cementplant in Seattle, Washington. Thesplice consisted of an outer and innersteel sleeve connected with four steelwedges which were driven andwelded to form piles with a totallength of 175 ft (53.4 m).

A technique of splicing piles,whereby high strength steel bars areembedded in the driven pile withsleeve anchorages, is discussed byBritt. 7 Since the bars extended beyondthe top of the driven pile, a specialhelmet was required during driving.The upper pile section, with high

SynopsisThis paper summarizes the

results of a comprehensive labo-ratory investigation of the struc-tural integrity of a wedge-typesplice for prestressed concreteplies.

A series of tests were con-ducted in tension, compression,bending, and shear. In addition,tests were made to determinethe corrosion rate of the splice.

Conclusions from the test re-sults indicate that the splice hasthe structural characteristics re-quired for spliced precast con-crete piles. Design recommen-dations are made for the use ofthe splice in buildings andbridges.

strength bars threaded through its en-tire length, is then lowered into posi-tion over the driven pile. The bars ofthe two pile sections are then cou-pled. After hardening of an epoxy atthe end surfaces of the connectedpiles, the high strength (Macalloy)bars are post-tensioned, after whichthe extended pile is then ready forfurther driving.

An excellent textbook" on the con-struction of prestressed concretestructures devotes an entire chapter toprestressed concrete piling. Discussedare typical details of prestressed con-crete pile splices used in the UnitedStates, Norway, Sweden, Great Brit-ain, and Japan.

An example of a special pile splic-ing technique used for the construc-tion of a Florida expressway is dis-cussed by Cook. 9 Due to the very se-vere foundation problems, piles with

PCI JoURNAL'september-October 1980 103

total lengths ranging up to 355 ft (108in) were used. The splices for the36-in. (914 mm) diameter hollow-coreprecast prestressed concrete pile sec-tions utilized a 10-ft (3.05 m) long ex-ternal splicing collar which wasclamped to the upper and lower pilesections. The collar remained in placewhile an epoxy, which envelopedreinforcing bars inserted into the pilesections, hardened overnight.

In 1973, AC! Committee 543 10 pub-lished recommendations for the de-sign, manufacture and installation ofconcrete piles. The objective of thereport is to assist the design engineer,the manufacturer, the field engineer,and the contractor in the design andutilization of various types of concretepiles. Although only a minimal refer-ence is made to splices, it does rec-ommend that epoxies and otherquick-setting compounds used forsplices should have strength anddurability at least equivalent to that ofthe concrete materials in the pile. Re-grettably, the extensive revisions" tothis committee report, which werepublished the following year, do notrefer to splices.

A comprehensive review and evalu-ation of prestressed concrete pilesplices were made in 1974 by Bruceand Hebert of Tulane University. 12.13

Twenty splices used in various partsof the world are discussed. They in-clude welded, bolted, mechanicallocking, connector ring, wedge,sleeve, dowel, and post-tensionedsplices. Excellent details of thesplices and a summary of the splicestrengths are presented. The secondpart of the report gives the results ofthe testing and analysis of a cement-dowel splice.

The S-M splice, which consists of amale-female connection, was testedby Houde 14 for Western Caissons(Quebec) Limited. The two parts arelocked together with a circular lockingbar after they are brought together.

The male and female plates, whichare cast on the ends of the pile sec-tions, are anchored with deformedbars which are welded to the platesand embedded in the concrete. Thisreport gives the results of push-out,torsion, compression, and bendingtests made on a 14-in. (356 mm)square pile splice.

Camble 15 made similar but moreextensive tests on the same splice aspart of an acceptance requirement forpiles to be used in the foundation of asewage treatment plant in Syracuse,New York.

The PCI Committee on PrestressedConcrete Piling' published a usefulreport on recommendations for thedesign, manufacture, and installationof prestressed concrete piles in 1977.Included is a discussion on consid-erations that should be made in se-lecting a splice.

A practical manual by Hunt' 7 pre-sents information on pile foundationsand various kinds of pile accessories.It also includes a brief description ofsome prestressed concrete pilesplices.

Regrettably, current codes andspecifications lack detailed require-ments for the design, manufacture,and installation of prestressed con-crete pile splices; hence, there is apressing need for the ACI and PCIrecommendations to be fully recog-nized. As an example, the currentAASHTO' R specifications for bridgesmerely indicates that full-length pilesshall be used where practicable, butin exceptional circumstances, splicingof piles may be permitted.

The Uniform Building Code'° con-tains no reference to pile splices. Infact, the first research report to be is-sued for a pile splice by the Interna-tional Conference of Building Offi-cials is for the Dyn-A-Splice, the testresults for which are presented here.

The Swedish Building Code20 re-quires that a driving test of a spliced

104

WEDGE ALIGNMENTCONE

SPLICEPLATE

BOLT

Fig. 1. Major components of wedge-type splice.

pile be made prior to approval. Thenumber of blows, as well as the size ofthe pile hammer, is specified. Sub-sequent to the driving, the pile isextracted, the splice examined, andthen subjected to a standardizedbending test.

Description of SpliceThe mechanical wedge splice tested

is used primarily for square piling butmay also he used with round, octa-gonal, and hollow cross sections. Thesplice is currently being used suc-cessfully with precast reinforced con-crete piles in Scandinavia and West-ern Europe but has been adapted toprecast prestressed concrete piles forthe purpose of this investigation.

The parts of the splice in the upperand lower pile sections are identical,as shown in Fig. 1. Only one of thefour wedges is shown.

During fabrication, the splice is as-sembled by placing the four internally

threaded bolts into the holes of thesplice plate. Reinforcing bars are thenthreaded into the bolts and positionedinto place (Fig. 2). Preformed holes inthe splice plate allow far placement ofthe prestressing strands. The ends ofthe splice are shown in Fig. 3.

In the field, the splicing procedureis quite simple. The alignment cone isfirst placed into the centering hole ofthe lower pile section. The upper pilesection is then lowered onto the lowerpile section until the splice plates arein direct contact. (See Fig. 4; note thatthe cone had not been installed at thispoint.) This is followed by driving awedge into each of the four carriers ofthe splice with a sledge hammer (Fig.5). The tapered wedge then becomeslocked in the splice plate with eachprotruding bolt- This operation pullsthe two pile sections towards eachother and forms a tight connection.The splice is completed by tappingdown splice plate tabs over the out-side face of the wedge to assure that

PCL JOURNALJSeptember-October 1980 105

6- 716"DIA. STRANDS WITr7"DIA. CIRCLE.

12 00

O^yl 0

I I.62"

33 TIES4 #8 REINFORCING BARS

W3.5 STEEL SPIRAL

CONVERSION FACTORI in = 25.4mm

Fig. 2. Splice details showing principal dimensions and reinforcement.

the wedge will remain in place duringdriving and under service conditions.The time needed to complete thesplice is minimal.

Force Paths

The splice is designed to transmitthe full capacity of the pile section incompression, tension, bending, shear,and torsion.

Compressive forces are transmittedfrom the upper pile section to theupper splice plate, the lower spliceplate, and then to the lower section ofpile. No contact is made betweenmating bolts. Tensile forces aretransmitted from the upper pile sec-

tion to the upper four reinforcing bars,the upper four bolts, the four wedges,the four lower bolts, and finally to thefour lower reinforcing bars which arebonded to the lower pile section.Shearing forces are transmitted bymeans of the four wedges at the spliceinterface. The forces are in turntransmitted to the bolts, reinforcingbars, and then to the concrete.

Although torsion tests were notconducted on the splice, it does havethe capability of transmitting torsionin either rotational direction about thelongitudinal axis of the pile. Torque istransmitted by means of the wedges ateach of the four corners of the splice.

106

Fig. 3. Piles with wedge-type splice. Fig. 4. Positioning of upper pile section.

Fig. 5. Workman driving in splice wedge.

PCI JOURNAL/September-October 1980 107

2-9' 2P

9 -_ - STEEL BEAMSSPLICE — SPECIMEN

3" 5'.. 9 PLATEN

A. 12 FT, BENDING SPECIMEN

2P

STEEL BEAMS

SPECIMEN

B. 9 FT. BENDING SPECIMEN

6' 5'- 0" P.^LOAD CELLS - IB

STEEL BEAM

AII SPECIMEN

II-6" II'-6" _ .

C.24 FT. BENDING SPECIMEN

29.. 2P

— STEEL BEAMSSPECIMEN

3"jI 5`-9°

D. 12 FT. UNSPLICED BENDING SPECIMEN

P

LI —STEEL BEAM

SPECIMEN IIIiIIII STEELBLOCKS

4 - 6 9-0" 4 - 6"

E. SHEAR SPECIMENCONVERSION FACTORSIin.= 25.4 mmHI = 0.305 m

Fig. 6. Loading arrangements of specimens.

108

Test Specimens

Inasmuch as the splice was origi-nally designed for precast reinforcedconcrete sections, it was consideredessential that the splice be modifiedand subjected to various tests prior toits use in precast prestressed concretepiles. Consequently, the newly de-signed splice was incorporated intopiles of various lengths and subjectedto tests in tension, compression,bending, and shear.

The bending specimens were of 12,9, and 24 ft (3.66, 2.75, and 7.32 in) asshown in Figs. 6A, 6B, and 6C, re-spectively. Unspliced pile specimens( 12 ft (3.66 m) long), (see Fig. 6D)were also tested for comparison pur-poses. Tension specimens were of thesame length and type as shown in Fig.6C. Shear specimens included twosplices (see Fig. 6E).

Fabrication of SpecimensThe specimens were cast at the pre-

stressing plant of Santa Fe-Pomeroy,Inc., Petaluma, California. The speci-mens were cast in steel forms alongwith a normal production run of 12-in.(305 mm) square piles, using the longline method for pretensioning. Fig. 7shows the splice plate, reinforcingbars, ties and spiral in place prior tocasting of the concrete.

The cement content of the concretemix was 7 sacks per cu yd (389 kg ofcement per m 3 ). The concrete mix wasproportioned for a compressivrstrength, f, of 6000 psi (41.4 MPa) at28 days. Type 11 prestress KaiserPennanente cement was used and the1-in. (25.4 mm) maximum size aggre-gates were Russian River run obtainedfrom the Kaiser Sand and Gravel Co.in Windsor. The admixture used wassupplied by Zeecon.

For prestressing, the initial ten-sioning force was 22,600 lbs (101 kN)per strand. After prestress losses, the

total working force of 111,600 lbs (496kN) for the six strands provided aneffective prestress of 785 psi (5.41MPa) in the concrete.

The average compressive strengthof the concrete at 30 days, based onthree cylinder tests, was 7560 psi (52.1MPa). The average split cylinder ten-sile strength, based on two cylindertests, was 670 psi (4.62 MPa).

Testing Program

As previously stated in the literaturereview, there is virtually no publishedguidance for the design of prestressedconcrete pile splices, Nor are thereany specific requirements in nationalcodes or specifications. In the absence,of such references, a designer eitherestablishes his own requirements for

Fig. 7. Splice assembly of specimenprior to casting.

PCI JOURNAL/Seplember-October 1980 109

the performance of a prestressed con-crete pile splice or conservativelyspecifies that the splice should havean ultimate capacity in tension, com-pression, bending, shear, and torsionequivalent to the unspliced pile.Other considerations must also bemade such as excessive relativemovements, possible corrosion, in-duced brittleness due to welding, in-stallation method, cost, behaviorunder impact Ioads due to driving,and other criteria.

Another consideration is the effectof a splice on the curvature of a pilewhen subjected to bending in a seis-mic zone. Margason and others21-24discuss the basic assumption that pilesgenerally move with the surroundingsoil during an earthquake and that ifno soil failure occurs, a rational pre-diction of the pile curvature can bemade for a given site and specificearthquake. It is stated that the pilebending problem is one of ductilityrather than of strength with resultingradii of pile curvatures ranging from200 ft (61 m) for strong earthquakes to

1000 ft (305 m) for small to moderateearthquakes.

However, the introduction of asplice in a pile should have a minimaleffect on pile curvature because anyincrease in flexural stiffness due to thepresence of reinforcing bars in thesplice would be small considering thesplice length of about 8 ft (2.44 m) in atotal length of spliced pile of ap-proximately 100 ft (30 m).

Because of these various consid-erations, the objective of the tests wasto determine if the splice had struc-tural characteristics equivalent tothose of the unspliced pile. Therefore,tests were made in tension, compres-sion, bending, and shear. No torsionaltests were made because torsionalloading on a pile foundation does notappear to he critical even tinder ex-treme conditions such as seismicloading. However, because of the me-chanical features of the splice, it isbelieved that the ultimate torsionalmoment is greater than that of a typi-cal 12-in. 305 mm) square prestressedconcrete pile.

Fig. 8. Test bed for tension testing,

110

Test ResultsIn this section a summary is given

of the results of tension tests of thesplice and assembly parts, bendingtests of spliced and unspliced beams,and shear, compression and corrosiontests.

Tension Tests of Bars,Bolts, and Wedges

In order to estimate the tensile andflexural capacity of the splice, fivespecimens, each consisting of tworeinforcing bars, two bolts and awedge, were tested in tension. Eachassembly was put together in a man-ner similar to how it would be ar-ranged within a splice, with the ex-ception of the splice plate. The aver-age tensile strength of the five speci-mens was 54.8 kips (244 kN). In eachcase, failure was in the wedge.

Tension Tests of SpliceThe tension specimens were tested

in a prestressing concrete bed whilein a horizontal position, as shown inFig. S. No longitudinal displacementmeasurements were made during the

Table 1. Tensile capacity and type offailure of tensile specimens.

Spec- Age, Tensile Type ofimen days capacity, failure

kips

Ti 26 165.0 splice*T2 29 180.0 StrandsT3 32 186.0 Strands

• Failure otthree wedge.. and one bolt.Note: l kip = 4.448 kN.

tests. At increments of 25 kips (111kN), the specimen was examined forcracks.

The tensile strengths of the tensilespecimens (Specimens T1, T2, andT3) are tabulated in Table 1.

Specimen TI was gradually loadedand inspected for cracks periodically.No cracks were visible at 115 kips(512 kN), the last load at which crackexaminations were made. The splicefailed at a tensile force of 165 kips(734 kN).

Specimen T2 did not experience asplice failure. At 150 kips (667 kN),transverse cracks, spaced at approxi-mately 2 ft (0.6 m), were observed.

Fig. 9. Arrangement for bending tests of 24-ft (7,32 m) long specimens.

PCI JOURNAUSeptember-October 1980 111

^I■ in the splice. An examination of thesplice after the strand failure of 186kips (827 kN) indicated that the splicewas completely intact with no evi-dence that it had been loaded. As withthe other tensile specimens, trans-verse cracks developed before failure.The estimated breaking strength of sixstrands, based on the mill test reports,is 191.8 kips (853 kN),

Bending Tests of 24-ft(7.32 m) Beams

Fig. 10. Splice of Specimen T2 afterflexural failure.

Many of the tensile cracks in the con-crete closed after release of the tensileforce at failure.

Specimen T3 likewise did not ex-perience a splice failure. As withSpecimen T2, the six strands failedwithout causing any structural distress

Specimens T2, T3 (which had beentested in tension but did not experi-ence a splice failure), T4 and T5, weretested in bending, as shown in Fig.6C. Hydraulic rams were used toapply the load and SR-4 strain gageload cells were utilized to measurethe load at each of the two load points,as shown in Fig. 9. Deflection read-ings at the %, '/4, and midpoints of theleft half of the specimen were re-

Table 2. Summary of test data and type of failure for bending specimens.

Specimen Age,days

Per,kips

MI,kip-ft

P,kips

M,,,kip-ft

Type offailure

T2 50 - - 23.0 127.6 CompressiveT3 48 - - 16.5 95.1 CompressiveT4 49 6.0 42.6 17.1 98.1 CompressiveT5 49 4.5 35.1 21.8 121.6 CompressiveB1S 26 14.0 41.0 32.5 91.9 WedgesB2S 29 15.0 43.8 25.1 71.4 WedgesB3S 32 16.2 47.2 34.0 96.0 CompressiveB4S 35 13.8 40.3 22.5 64.4 BoltsB55 37 13.8 40.3 32.5 91.9 Wedge and bolt

BSS 40 12.5 35.8 38.3 106.6 CompressiveB7S 40 I3.8 39.1 38.1 106.2 WedgesB8S 40 13.8 39.1 24.1 67.7 Bolts

B1 U 30 15.0 43.8 30.3 85.7 CompressiveB2U 31 16.5 47.9 28.9 82.0 CompressiveB3U 34 1.5.0 43.8 29.0 82.2 Compressive84U 37 16.2 47.2 30.0 85.0 CompressiveB5U 39 16.2 47.2 31.1 88.0 Compressive

Symbols; P^,. = cracking load; P„ = ultimate load; M,, = cracking moment; and M, = ultimate moment,Note: I kip = 4.448 kN; I kip-ft = 1.356 kN • m.

112

corded at load increments of 2 kips(8.9 kN) (on one ram). Deflectionswere read to the nearest 0.001 in.(0.025 mm).

The load at the appearance of thefirst crack, P c „ the correspondingmoment, M cr , the ultimate load, P,and the ultimate moment, M a , forSpecimens T2, T3, T4, and T5 aretabulated in Table 2. The tabulatedloads are those read directly from theload cell. The tabulated moments in-clude the bending moment due to theapplication of the external loads andthe bending moment due to thebeam's own weight [ 12.6 kip-ft (17.1kN • m)].

Specimen T2, although previouslyloaded in tension to 165.0 kips (734kN), displayed the maximum bendingstrength, failing in flexural compres-sion at 52 in. (1.32 m) from the splice

plate, within the zone of constantmoment, but beyond the end of thesplice reinforcing bars. Fig. 10 showsthe excellent condition of the spliceafter flexural failure of the beam. Aplot of deflection curves for load in-crements of 2 kips (8.9 kN) up toP = 20 kips (89 kN), is shown in Fig.11.

Specimen T3 also failed in flexuralcompression in the zone of constantbending moment. Subsequent to thecompressive failure in the top fibers at45 in. (1.14 m) from the splice, somestrands ruptured. The diagonal crackat failure, as shown in Fig. 12, ex-tended to 62 in. (1.558 m) from thesplice, at the bottom surface. Thesplice was in excellent condition afterfailure.

Specimens T4 and T5 were the two24-ft (7.32 m) long flexural specimens

C 3/8L2 tI9KN1

P = 4 K 18 MP = 6 K (27KN

0.5 P = 8 K (36KN)

P = I0 K (44 KN}20)1.0

P=12K (5

1.540) p = 14 K (62KN)

2.0 P = 16x{71 KN)

60) Q = 18 K (80 KN)2.5

P - 20x (89 KN}^

I/4L 1 P 1/8L

CONVERSION FACTORSI in.= 25.4 mmIft = 0.305 m1K = 4448KN

rE SYM.

P P 5'-0"

reL - 23'-0" 6..

Fig. 11. Load vs. deflection (Specimen T2).

PCI JOURNALSeptember-October 1980 113

Fig. 12. Specimen T3 after flexural failure.

. SYM.P I P 5-0

20

(80)

15

(60)

0

10a (40)

0J

(20)

0

12

rORS

0.5 (20) 1.0 1.5 (40) 2.0 (60) 2.5 3.0 (80)

Q DEFLECTION- INCHES (mm)

Fig. 13 Load vs. centerline deflection (Specimens 12, T3, 14. and T5).

114

Fig. 14. Testing arrangement for testing of 12-ft (3.66 m) long spliced specimens.

which were riot previously loaded intension. Both specimens experienceda flexural compressive failure with nodamage to the splices.

It should be noted that in all fiaurcases, the unspliced section of the pilefailed while the splice retained itsstructural integrity. This would inferthat the splice capacity of thesespecimens was in excess of the aver-age ultimate moment capacity of! 10.6kip-ft (150 kN • in).

A plot of load, P. vs. centerline de-flection for all four test specimens(Specimens T2, T3, T4, and T5) isshown in Fig. 13. (Note that deflectionreadings were not taken to ultimateload.)

Bending Tests of ShorterSpecimens

Specimens B1S, B2S, B3S, B4S, andB5S were tested in bending on a 11 ft6 in. (3.51 in) span, as shown in Fig.6A.

Specimens B6S, B7S, and B8S weretested in bending on an 8 ft 6 in. (2.59

m) span, as shown in Fig. 6B. With ashear span of 2 ft 9 in. (0.84 in), themaximum moment for a given load isthe same as for the 12-ft (3.66 m) longbeams.

Specimens B1U, B2U, B3U, B4U,and B5U (pile specimens withoutsplice) were tested in the same man-ner as the 12-11 (3.66 m) long splicedspecimens, as shown in Fig. 6D.Beams were loaded in the same p051-

lion as they were cast.

Bending Test Results of 12-ft(3.66 m) Spliced Beams (Fig. 14)

The values of P n., Mer , P, and Wfor Specimens BIS, B2S, B3S, B4S,and B5S are tabulated in Table 2. Thelisted moments include the bendingmoment due to the application of themachine load and that due to thebeam's own weight of 2.5 kip-ft (3.4kN • m).

The failure of Specimen B5S is at-tributed to rupture of one bolt and theopposite wedge at the bottom of thesplice. A view of a splice and some

PCI JOURNAL/September-October 1980 115

-ass

)--o ^o

Fig. 15. Flexural failure of Specimen B5S.

concrete crushing at the top adjacentto the splice is seen in Fig. 15.

The mean ultimate moment for thefive 12-ft (3.66 m) specimens is 83.1kip-ft (113 kN • m).

A plot of moment at the splice vs.beam rotation is shown in Fig. 16 forthe five 12-ft (3.66 m) specimens. Inthese tests deflection readings wereterminated prior to reaching ultimatemoment.

Specimens B6S, B7S, and B8S weretested in bending as shown in Fig. 6B.The values ofP Mn., P., and M, aretabulated in Table 2. The listed mo-ments include the additional momentdue to the beam's own weight of 1.4kip-ft (1.9 kN • m). The mean ultimatemoment for the three 9-ft (2.75 m)specimens is 93.5 kip-ft (127 kN . m).The mean ultimate moment for alltwelve spliced specimens is 94.9kip-ft (129 kN - m). Note that in six ofthe twelve specimens, the splice didnot fail at ultimate moment.

Bending Tests of 12-ft(3.66 m) Unspiiced Beams

Tire values of Par, Mer Pu, and M.for Specimens B1U, B2U, B3U, B4U,and B5U are tabulated in Table 2_ Themoments M. and M. include the mo-ment due to the machine load and the

specimen's own weight of 2.5 kip-ft(3.4 kN. m).

All specimens failed due to crush-ing of the concrete fibers in the zoneof maximum moment. A typical failureis shown in Fig. 18.

The mean ultimate moment of theunspliced specimens is 84.6 kip-ft(115 kN • m). This compares with arecommended allowable moment of32 kip-ft or 384 kip-in. (43.4 kN • m)for a permissible concrete tensilestress of 600 psi (4.14 MPa). is Thetheoretical ultimate moment of theunspliced 12-in. (305 mm) square pilewithout an axial load, using a strengthreduction factor, 46, 0.90, is 55 kip-ft(74.6 kN • m).2B

The actual pile capacity of 84.6kip-ff (115 kN • m), based on the testresults, is 54 percent greater than thetheoretical value. It is also to be notedthat the mean ultimate moment of thetwelve spliced specimens of 94.9kip-ft (129 kN • m) is 73 percentgreater than the theoretical pilecapacity and 12 percent greater thanthe actual pile capacity.

A plot of moment at the splice vs.beam rotation for the five unsplicedspecimens is shown in Fig. 17. Acomparison of Fig. 16 with Fig. 17shows that the flexural stiffness of the

116

80

(100) B 45

70- B2S

60(80) BIS

3S

SYM.

2 1 - 9" PP

3"„^^, 5'-9" 4, 5'-9" 3

CONVERSION FACTORSI in = 25.4 mmIf1=0.305mI K = 4.448 KN

5 10 15 20 25 30

ROTATION 8 (IO-3 RAD)

z 5O

L~i (60}

40

Iw 302 (40)O

20

(20)

10

0

Fig. 16. Moment vs. rotation of 12-ft (3.66 m) specimens with splice.

spliced specimens is approximatelyequivalent to that of the unsplicedspecimens. This is probably attributedto the fact that the elastic movementof the splice components due to ten-sion is balanced by the increasedflexural stiffness of the pile section inthe vicinity of the splice owing to thepresence of the No. 8 (25 mm) rein-foruing bars.

Shear TestsTwo complete shear specimens

were tested in shear as shown in Fig.6E. With this arrangement, twosplices were tested simultaneously.

Due to the capacity of the loadingbeams and a desire to later reuse theshear specimens for flexural or com-pression tests, each test was stoppedat a total load of 225 kips (1000 kN), orwith 112.5 kips (500 kN) of shearingforce on each splice. The splices werefound to be in excellent condition atthe conclusion of the tests, as shownin Fig. 19.

PCI JOURNALJSeptember-October 1980 117

60(8 0)

z 50Y

t (60)

a 40

F-Z 30U(40)20M

(20)

El

B4U rBIU80

(100)

70

M

2U a B3U

CL SYM.

P2

3I 51 _ g" 5' 9" 3"

CONVERSION FACTORS1 in, = 25 4 mmIft=0.305mI K = 4,448 KN

5 10 15 20 25 30

ROTATION e (I 0 -3 RAD )

Fig. 17. Moment vs. rotation of 12-ft (3.66 m) specimens without splice.

Fig. 18. Flexural failure of Specimen B3U.

118

Fig. 19. Arrangement for shear tests.

Compression TestsThree compression specimens,

similar to the 9-ft (2.75 m) long bend-ing specimen as shown in Fig. 6B,were tested in axial compression asshown in Fig. 20. The average ulti-mate load was 877 kips (3900 kN),27which corresponds to a compressivestress of 6180 psi (42.6 MPa). Therewere no failures of the splice. Allspecimens failed due to concretecrushing in the upper section just be-neath the machine loading head.

Corrosion TestsIn order to assess the corrosion re-

sistance of the splice when subjectedto a harsh environment, corrosion testswere conducted on the individualparts of the splice and on a complete9-ft (2.75 in) specimen with the spliceat mid-length. The 9-ft (2.75 m)specimen was subjected to a sustainedcompressive loading of 150 kips (667kN), the magnitude of which repre-sents a reasonable level of sustainedforce that a 12-in. (305 mm) pile willhe subjected to in a building or bridge

Fig. 20. Arrangement for testing ofcompression specimens.

PCI JOURNAL/September-October 1980 119

and is equal to 60 percent of the rec-ommended allowable compressiveforce. The load was sustained for aperiod of three days prior to the corro-sion test and during the entire periodof the corrosion test (approximately 10hours). The reason that the corrosionreadings were taken under loading isthat it is recognized that the corrosionrate increases with increased stress ofthe component.

The technique involved taking aseries of potentiostatic measurementsof the complete splice while im-mersed in a saline solution. A secondmethod involved subjecting the spliceto an aggressive environment for agiven period of time and thenmeasuring the weight of the corrosionproducts formed during this time.

The results2s indicate that the spliceexhibited negligible corrosion and isserviceable for use in most soils with-out restrictions. This low corrosionrate is attributed to the presence ofthe zinc alloy alignment cone whichserves as a sacrificial part.

Conclusions

The following conclusions arebased on the experimental data ob-tained from this project.

1. The minimum ultimate momentcapacity of the splice is 95 kip-ft (129kN . m). Since one-half of the flexuralspecimens failed outside the pilesplice region, the actual mean ulti-mate moment capacity of the splicewas not attainable.

2. The ultimate moment capacity ofthe splice is greater than that of atypical unspliced pile [85 kip-ft (115kN . m)].

3. The negligible movement be-tween two pile sections at the spliceand the presence of the reinforcingbars of the splice do not significantlyalter the moment-curvature or load-deflection characteristics of the pile.

4. The tensile strength of the spliceis greater than that of the pile. The48-in. (1.2 m) embedment length ofthe reinforcing bars is more than ade-quate in developing the tensilecapacity of the pile or splice.

5. Under an axial compressiveforce, the splice is capable of de-veloping the compressive strength ofthe pile.

6. The splice has a shear capacitywhich is in excess of that required formost severe loading conditions.

7. The splice should exhibit neg-ligible corrosion and is serviceable foruse in most soils without restrictions,

Design Recommendations

The design requirements for a pre-cast prestressed concrete pile shouldapply equally to splices. The spliceshould be capable of resisting forcesinduced during handling and drivingand when subjected to design loads.Inasmuch as the splice is equally asstrong as the pile, the design of thepile need not be limited by the in-stallation of a splice.

Pile design recommendations25given by Santa Fe-Pomeroy, Inc.,manufacturers of the piles which weretested with the splice, allow an axialcompressive force of 250 kips (1112kN) for a 12-in. (305 mm) square pile.This allowable load is based on thecommonly accepted building codeform ulaY9 for concentrically loadedshort column prestressed piles. With apile capacity of 877 kips (3900 kN) incompression, the safety factor of 3.50is more than adequate.

The theoretical ultimate moment ofthe 12-in. (305 mm) pile with no axialforce is 55 kip-ft (74.6 kN • m).N Usinga load factor of 1.7, the design allowa-ble moment is 32 kip-ft (43.4 kN . m).With a splice ultimate moment capac-ity of 95 kip-ft (129 kN • m), the safetyfactor is 3.0, which is much higher

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Table 3. Summary of recent applications of pile splice.

Structure Location Pile Driving Contractor

Liberty House—Department Sacramento, California Jensen & ReynoldsStore Benicia, California

Golden Gateway III— San Francisco, Santa Fe-Pomeroy, Inc.Condominiums California Petaluma, California

Hines Building— San Francisco, Santa Fe-Pomeroy, Inc.High-rise office building California Petaluma, California

San Francisco International San Francisco, Kie-Con, Inc.Airport—Central California Pleasanton, CaliforniaTerminal modernizations

Bridge Hayward, California Kie-Con, Inc.Pleasanton, California

than normally required. For higherstrength 12-in. (305 mm) piles, an al-lowable moment in the splice of 47kip-ft (63.7 kN • m) (50 percent of theultimate moment) should be permis-sible.

For combined axial and flexuralloading, an interaction formula shouldbe used to check the adequacy of thepile and splice, due to the infinitenumber of combinations of loadingsthat could exist.

The details of the splice (Fig. 2)should be kept the same for all 12-in.(305 mm) piles. Although the 48-in.(1.2 m) long reinforcing bars arelonger than required to develop thetensile capacity of the pile, the addi-tional length assists in extending thehigh impact forces near the pile head,due to driving, over a greater length.

To date, three agencies have giventheir acceptance or approval of thesplice.

In a report9° of the Technical Di-rector of the International Conferenceof Building Officials to its ResearchCommittee, it was stated that "theDyn-A-Splice device for splicing pre-stressed concrete piles is an alternatemethod of design to that required bythe 1979 Uniform Building Code,' 'Section 2909 (e)."

A recently published ICBO Re-search Report states that the assem-

bled Dyn-A-Splice is capable oftransmitting the following designloads and bending moments:

Compression: 525 kips (2335 kN)Tension: 100 kips (445 kN)Shear: 70 kips (311 kN)Bending: 32 kip-ft (43.4 kN . m)These limiting values are primarily

based on the test results of the ex-perimental investigation of the splice.

The City of San Francisco hasgranted approval" for the use of the10, 12, 14, and 16 in. (254, 305, 356,and 406 mm) square splice in the con-struction of pile foundations in thecity. No design values for the varioussize splices are specified. However,one condition is that special inspec-tion shall be required for installationof the wedges,

The State of California Departmentof Transportation (Caltrans) has alsogranted approval of the splice for usein pile foundations of bridges. Theultimate design loading require-ments'2 for a 12-in. (305 mm) squaresplice are as follows:

Tensile force: 115 kips (512 kN)Compressive force: 500 kips (2224

kN)Shearing force: 70 kips (311 kN)Bending moment: 75 kip-it (102

kN • m) (with zero axial load).To date, the splice has been used in

the projects shown in Table 3.

PCI JOURNAL/September-October 198D 121

Advantages andDisadvantages of Splice

Based on the results of the experi-mental program and observation of thefabrication and installation of thesplice, the advantages of the splice areas follows:

1. The splice can develop the fullcapacity of the pile in tension, com-pression, and bending.

2. The shear and torsional strceigtIisare the same in all directions. Thesplice cannot unlock due to torsion.

3. Prior to fabrication, the rein-forcing bars, bolts, and splice platescan be stored separately thus requir-ing a minimum of storage space.

4. Parts of the splice are identical ineach pile section which simplifieshandling and avoids errors in themanufacture of the piles.

5. The splice is installed easily andquickly with unskilled labor and asledge hammer. No welding or epoxymaterials are needed.

6. The pile head with an installedsplice needs no special helmet duringdriving. Only normal pile cushioningmaterials or other cushioning de-vices"' are required.

7. There are only two kinds ofcomponents to install in the field: fourwedges and an alignment cone.

S. Plate-to-plate contact of thesplice assures longitudinal alignment.

9. The zinc alloy alignment coneserves as a sacrificial element in theevent of corrosion thus prolonging the

life of the structural components ofthe splice.

The only apparent disadvantage ofthe splice is that careful fabrication atthe prestressing plant is required toinsure longitudinal alignment of thereinforcing bars. However, this is eas-ily accomplished by use of speciallydesigned jigs,

Further Research

Plans are currently being made toextend the structural testing programto include:

1. Bending about a diagonal (45deg) axis.

2. Response of the splice whensubjected to combined axial compres-sion and bending.

3. Structural behavior of 16-in. (406mm) square splices.

4. Structural behavior of splicedoctagonal piles.

5. Torsional capacity of the splice.6. Dynamic response of the splice

and pile during driving.

Acknowledgment

The author wishes to express his ap-preciation to Herbert A. Bratiner, SantaFe-Pomeroy, Inc., for his valuable assis-tance in planning the test program; DavidA. Sheppard, Prestressed Concrete Insti-tute, fir the photographs o1 Figs. 3, 4, and5; and Bengt 0. Cardell, A-Joint Corpora-tion, for permission to publish the testdata.

Discussion of this paper is invited. Please forwardyour comments to PCI Headquarters by May 1, 1981.

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REFERENCES

1. Venuti, W. J., "Structural Characteris-tics of the Dyn-A-Splice," San JoseState University, California, February1980, 36 pp.

2. Gerwick, Ben C., Jr., "General Reporton Prestressed Concrete Piles," Pro-ceedings, Federation Internationale dela Precontrainte Internationale, Sym-posium on Mass-Produced PrestressedPrecast Elements, Madrid, June 1968.

3. Lerwick, Ben C., Jr., "PrestressedConcrete Piles," PCI JOURNAL, V.13, No. 5, October 1968, pp. 66-133.

4. Kirkhridge, T. W., "The World Utili-zation of Prestressed Precast ConcretePiles," Concrete (London), V. 5, No. 1,January 1971, pp. 5-8.

5. Li, Shu-Tien, and Liu, Tony Chen-yeh, "Prestressed Concrete Piling—Contemporary Design Practice andRecommendations," ACI Journal, No,3, Proceedings, V. 67, March 1970, pp.201-220.

6. Alley, E. F., "Long Prestressed Piles,"Civil Engineering, ASCE, April 1970,pp. 50-52.

David C., "Splicing of Precast Pre-stressed Concrete Piles: Part 1—Re-view and Performance of Splices,"PCI JOURNAL, V. 19, No. 5, Septem-ber-October 1974, pp. 70-97.

13. Bruce, Robert N., Jr., and Hebert,David C., "Splicing of Precast Pre-stressed Concrete Piles: Part 2—Testsand Analysis of Cement-DowelSplice," PCI JOURNAL, V. 19, No. 6,November-December 1974, pp. 40-66.

14. Houde, Jules, "Report on Tests on S-MConcrete Pile Splices," Centre de De-velopment Technologique de l'EcolePolytechnigne de Montreal, Montreal,Ontario, March 1975, 6 pp.

15. Gamble, William L., "Bending, Ten-sion, and Torsion Tests of PrestressedConcrete Pile Segments Joined by S-MSplices," University of Illinois, Sep-tember 1975, 14 pp.

16. PCI Committee on Prestressed Con-crete Piling, "Recommended Practicefor Design, Manufacture and Installa-tion of Prestressed Concrete Piling,"PCI JOURNAL, V. 22, No. 2, March-April 1977, pp. 20-49.

7. Britt, G. B., "Rapid Extension of 17Reinforced and Prestressed ConcretePiles," Concrete (London), V. 5, No. 1,January 1971, pp. 9-12.

8. Gerwick, Ben C., Jr., Construction of 18.Prestressed Concrete Structures, JohnWiley & Sons, Inc., New York, 1971,pp. 167-208.

9. Cook, Jack R., "Severe FoundationProblem Solved Using Long Precast 19.Prestressed Concrete Piles," PCIJOURNAL, V. 19, No. 1, January-Feb-ruary 1974, pp- 62-72.

10. ACI Committee 543, "Recommen- 20.dations for Design, Manufacture, andInstallation of Concrete Piles," ACIJournal, Proceedings, V. 70, No. 8,August 1973, pp. 509-544.

11. ACI Committee 543, "Revisions to:Recommendations for Design, Man- 21ufacture, and Installation of ConcretePiles," ACI Journal, Proceedings, V.71, No. 10, October 1974, pp. 477-492.

12. Bruce, Robert N., Jr., and Hebert,

Hunt, Hal W., Design and Installationof Driven Pile Foundations, AssociatedPile and Fitting Corporation, Clifton,New Jersey, 1979. 200 pp.AASIITO, Standard Specifications forHighway Bridges (Twelfth Edition,1977), The American Association ofState Highway and Transportation Of-ficials, Washington, D.C., 1977, p. 295.ICBO, Uniform Building Code (1979Edition), International Conference ofBuilding Officials, Whittier, California,734 pp.Royal Swedish Academy of Engineer-ing Sciences—Commission on Pile Re-search "Swedish Building Code 1975Approval Rules No - 1975.8 Piles,"(Translated by Bengt Broms) Report57, Stockholm, 1979, pp. 24-30.Margason, Edward, "Pile BendingDuring Earthquakes," one of six lec-tures presented at the University ofCalifornia, Berkeley, and sponsored bythe ASCE San Francisco Section,

PCI JOURNAUSeptember-October 1980 123

Continuing Education Committee, 27March 1975.

22. Margasou, Edward, "Earthquake Ef-fects on Embedded Pile Foundations,"paper presented at PILETALK Semi-nar, San Francisco, California, March1977.

23. Bertero, V. V., Lin, T. Y., Seed, H. B.,Lerwick, B. C., Jr., Brauner, H. A., andFotinos, G. C., "Aseismic Design ofPrestressed Concrete Piling," pre-sented at the Federation Internationalede la Precontrainte Congress, NewYork, May 1974.

24. Gerwick, B. C., Jr., and Brauner, H. A.,"Design of High Performance Pre-stressed Concrete Piles for DynamicLoading," American Society for Test-ing and Materials, STP 670, 1979.

25. "Properties of Pretensioned Pre-stressed Concrete Piles," DesignSheet, Santa Fe-Pomeroy, Inc., Peta-luma, California.

26. "Pretensioned Prestressed ConcretePiles—Pile Interaction Curves," De-sign Sheet, Santa Fe-Pomeroy, Inc.,Petaluma, California.

Stephen, R. M., Letter report on thecompression test results of the Dyn-A-Splice, University of California,Berkeley, California, February 1980.

28. Anderson, R. N., "Report of CorrosionTest on the Dyn-A-Splice System,"Palo Alto, California, February 1980.

29. PCI Design Handbook—Precast Pre-stressed Concrete, Prestressed Con-crete Institute, 2nd Edition, 1978, p.3-39,

30. Report of the Technical Director to theResearch Committee, InternationalConference of Building Officials,Whittier, California, May 28, 1980.

31. Letter from Robert C. Levy, Superin-tendent, Bureau of Building Inspec-tion, Department of Public Works, Cityand County of San Francisco, datedMay 16, 1980.

32. Bridge Planning and Design Manual,Caltrans, "Prestressed Concrete PileSplice Detail," V. IV, Detailing, Oc-tober 1977, pp. 20-21.

33. "Effective Pile Driving—Dyn-A-Cap,"Brochure by A-Joint Corporation, SanJose, California, 1979.

NOTE: Further information on the patented Dyn-A-Splicemay be obtained from the author or Bengt O. Cardell,President, A-Joint Corporation, 335-D Turtle Creek Court,San Jose, California 95125.

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