Presents the highlights of the recent UnitedStates-Japan Seminar on Precast ConcreteConstruction in Seismic Zones from two viewpoints.In the introductory part, Professor Neil M. Hawkinsgives an overview of the Seminar together with theprincipal findings from the conference sessions.In the second part, Dr. Robert E. Englekirk offershis impressions of the Seminar from a designengineer's viewpoint.

U.S.-Japan Seminar onPrecast Concrete Construction

in Seismic Zones

Neil M. HawkinsActing Associate DeanCollege of EngineeringUniversity of WashingtonSeattle, Washington

Robert E. Englekirk*President

Robert Englekirk Consulting Engineers Inc.Chief Executive Officer

Englekirk & Hart Consulting Engineers, Inc.and Adjunct Processor

Civil Engineering DepartmentUniversity of California

Los Angeles, California

Dr. Englekirk serves on PCi's Board of Directors and Technical ActiviesCommittee and is a member of the PC I Seismic Committee.

PCI JOURNALIMarch-April 1987 75

Overview of Seminar

by NEIL M. HAWKINS

The fifth American Concrete Insti-tute-Japan Concrete Institute Semi-

nar on Concrete was held in Tokyo.October 27 through November 1, 1986.The subject of the Seminar was PrecastConcrete Construction in SeismicZones.

On the United States side, the Semi-nar was supported financially by theNational Science Foundation, Divisionof International Programs; and the Pre-stressed Concrete Institute. On theJapan side, the Seminar was supportedby the Japan Society for Promotion ofScience, the Japan Precast ConcreteContractors, and many other construc-tion related organizations. Additionaltechnical support for the Seminar wasprovided on the United States side bythe American Society of Civil Engineersand on the Japanese side by the Ar-chitectural Institute of Japan and theJapan Society of Civil Engineers.

There were 12 United States dele-gates drawn from consulting firms, pre-casting organizations, and universities,headed by Professors Neil M. Hawkinsand Alan H. Mattock from the Univer-sity of Washington, Other United Statesparticipants were Dr. Samy Adham, Ag-babian and Associates, Los Angeles;Professor Ned H. Burns, University ofTexas at Austin; Dr. Douglas P. Clough,ABAM Engineers, Seattle; Dr. Robert E.Englekirk, Robert Englekirk ConsultingStructural Engineers Inc., Los Angeles;Professor Harry G. Harris, Drexel Uni-versity, Philadelphia; Professor WilliamL. Gamble, University of Illinois; Mr.Francis J. Jacques, Stanley Structures,Denver; Professor Peter Mueller, Le-high University, Bethlehem, Pennsyl-vania; Professor John F. Stanton, Uni-

versity of Washington; and Dr. Alfred A.Yee, Honolulu. Six of the American del-egates were accompanied by theirwives.

On the Japanese side, there were 16delegates drawn from the same mix oforganizations as on the United Statesside, headed by Professor YasuyoshiSuenaga of Yokohama National Univer-sity, and assisted by Professor JunYamazaki of Tokyo Metropolitan Uni-versity. While an unfortunate illnessprevented Professor Suenaga's atten-dance at the Seminar, the depth of hisplanning was demonstrated by the suc-cess of the Seminar and the ease withwhich Professor Yoshikazu Kanoh fromMeiji University and Professor SigeruMochizuki from Musashi Institute ofTechnology could step in and takeleadership on the Japanese side.

In addition to the American andJapanese participants, there were fiveThird Country participants drawn fromCanada (Professor Richard Spencer);People's Republic of China (Mr. WeiLian); Mexico (Professor Francisco Ro-bles); New Zealand (Professor RobertPark); and Norway (Mr. Per Jahren).

The Seminar was divided into threephases so that events were consistentwith supporting agency constraints. Themajority of the United States and ThirdCountry papers were presented at atwo-day long pre-Seminar attended bysmIne 250 Japanese engineers and heldin the auditorium of the ArchitecturalInstitute of Japan. The remainingAmerican and Third Country papers andthe Japanese papers were presented at athree-day long closed Seminar held inthe offices of the Japan Society of CivilEngineers.

76

Finally, the Seminar concluded witha four-day post-Seminar tour that in-cluded a survey of construction for thewidening of the Tohmei Expresswaylinking Tokyo and Osaka, and a visit tothe second Honshu-Shikoku BridgeCrossing. There was also an active socialprogram: a conference banquet involv-ing a welcoming reception at the pre-Seminar in Happoen and a farewell re-ception at the Fujiya Hotel in Hakone.

In the technical program some 45 pa-pers were presented of which 12 werestate-of-the-art reports; 6 were earth-quake response reports; 10 were con-cerned with members' properties forearthquake loadings; 5 with joint prop-erties for earthquake loadings, and 12with mixed gravity and earthquake useconsiderations as likely with bridgedecks, girders and off-share structures.The more significant contributions willbe included in a Special Publication tohe produced by the ACI. 1'he followingare the principal findings from theSeminar:

1. Information on the actual dynamicresponse of precast concrete construc-tion in earthquakes is lacking and,thus, there is inadequate correlationbetween computer predictions ofdynamic behavior and actual behavior.

2. Japanese investigators have beenconcerned primarily with what occursbetween interfaces, while non-Japaneseinvestigators have been much moreconcerned with what happens on eachside of the interface. There is a need tointegrate the results of the two programsso that future investigators can use theunderstanding generated by both pro-grams.

3. There is much more interest inpossible bridge structure innovations inJapan than in the United States. Much ofthat Japanese effort is directed towardspossible precast concrete bridge deckdevelopments while the primary Ameri-can concern is with bridge deck dur-ability.

4. In Japan, precast prestressed con-

crete structures are essentially an exten-sion of concrete structures in generaland the overall design objective can bedescribed as attempting to make precastconcrete structures behave as mono-lithic structures. The exception is low-rise housing structures where adjust-ments in design loads are permittedwhen there is laboratory documentationof the available ductility. By contrast, inthe United States, because of the dif^fering seismic zones, details have beendeveloped for precast prestressed con-crete that differ from those for mono-lithic construction. In the United States,the primary emphasis is on readily con-structible, dry joints. Technological ad-vancements could result from themarrying of these two concepts.

S. Over the last decade, in both Japanand the United States, the prime interestfor precast concrete construction inseismic zones has shifted from panelstructures to frame structures. For pre-cast prestressed concrete frame struc-tures, there is a need for a code com-patible research program that examinesthe significance of variations in globalductility forms on dynamic response andthe interrelation between such globalductility forms and ductility responsecharacteristics. The significance ofvariations in the area and shape of thehysteresis loops for reinforced concreteversus partially prestressed concrete,versus prestressed concrete structures,versus other material forms needs to beexamined through correlation oftheoretical studies, shaking table dataand real earthquake data.

In conclusion, this Seminar on Pre-cast Concrete Construction in SeismicZones was two years in planning. It wasofficially part of the ACI-JCI SeminarProgram and the U.S.-Japan ScientificExchange Program. It is hoped that thefollow-up to this successful interna-tional conference will also includeNSF-JSPS funding of a joint researchprogram on precast construction inseismic zones.

PCI JOU9NAL1March-April 1987 77

Designer's Viewpoint of Seminar

by ROBERT E. ENGLEKIRK

The importance of exchanging designand construction ideas cannot be

overemphasized. Though there mayexist enough difference in our respec-tive construction industries and socialgoals to preclude a direct system trans-fer, the ideas conceived by designers toeffectively develop systems are readilytransferable.

In the overview which follows, an at-tempt has been made to focus on sup-porting ideas and concepts in the hopesthat the reader will not summarily dis-miss a system but rather endeavor tounderstand the supporting ideas andintroduce them into our construction in-dustry . Many intriguing concepts werepresented at the United States-JapanSeminar on Precast Concrete Construc-tion in Seismic Zones and subsequentlydiscussed.

Several parallel trends exist in themarketplace for precast concrete inJapan and the United States. The in-dustries of both countries appear to beemerging from a long period of inactiv-ity where the economies of cast-in-placeconcrete severely reduced the structuralmarket share of precast concrete. Bothcountries appear to understand the di-rection required of precast concrete if itis to once again become a viable prod-uct.

Japan, however, is significantly aheadof the United States in terms of devel-oping the tools necessary to implementthe supporting program. The Japaneserecognize the importance of a systemsapproach, wherein the amount of pre-cast concrete is maximized. As a conse-quence, their tests have focused on as-sembly methodologies which give theconstructor the flexibilities necessary to

embark upon an imaginative and costeffective use of precast concrete.

Further, though the composition ofthe construction industries in theUnited States and Japan appear at leastsuperficially to be significantly dif-ferent, many basic similarities exist.Large Japanese constructors utilize staffengineers and architects to developbuilding designs which they market on aturnkey basis. This does not, however,represent the major part of their work forthe community of independent consul-tants is reported to be three or four timeslarger than that employed by con-structors.

Since the effective development ofprecast concrete systems requires ateam approach, the designer and con-striictor must combine their talents andbackgrounds if a well designed, cost ef-fective system is to be developed. TheJapanese system is well suited to thisprocess and has, as a consequence, pro-duced some challenging precast pre-stressed systems.

Many American constructors are pro-moting with considerable success thedesign/construct approach to project de-velopment. As a consequence, moreimaginative precast prestressed con-crete systems are being developed andrefined in the United States. The rate ofdevelopment is considerably slowerthan in Japan as will readily be seen inwhat follows.

Fundamental ConsiderationsThe quantification of ductility de-

mands and availability of ductility inprecast concrete systems is basic to anyengineering decision relating to seismic

78

design. A simple method for quantifyingcomponent ductility demand was pre-sented by Clough. I Clearly, connector lo-cation and the ductility demand placedon the connector plays an important rolein the evaluation of systems. 2 Threebasic connector/deformation conditionsare characteristic of precast concretesystems:

(a) Precast concrete connectionswhich require post yield deformationcapabilities or energy dissipation.

(b) Precast concrete connections inwhich stress demands are high but elas-tic behavior is anticipated.

(c) Precast concrete connections inwhich moment demand is low.

Examples of Type "a" connectors aretypically those which occur in beams atthe beam-column interface and those lo-cated at the base of a shear wall. In theUnited States neither code nor practiceaccepts connectors or splices in beamsor columns of ductile frames if post yielddeformations are likely. On the otherhand, joints in precast wall panels areaccepted regardless of whether or notthey possess any ductility.

The Japanese Code permits the de-signer/constructor considerably morefreedom. The design proposed must beshown to possess acceptable levels ofductility. The Japanese have developeda procedure for prequalifying connec-tors which are to be used in regions ofstress reversal where the connectormust be capable of post yield deforma-tions, The design proposed must beshown to possess acceptable levels ofductility. As a consequence, theJapanese Code permits this type of con-nection.

Acceptability is accomplishedthrough the prequalification of sub-assemblies proposed for a project.Japanese prequalification proceduresrequire four cycles of strain to 2 e„ and5e,,. a Japanese codes prescribe higheryield load levels and, as a consequence,ductility demands will be lower thanthose anticipated in United States

PRECASTCONCRETE C

CAST-IN-PLACE CONCRETE

Fig. 1. Precast unit in frame system.

codes. Most of the participants felt that astandardization of test programs whichidentified post yield load level and thenumber of cycles at that load levelwould facilitate technology transfer.

Connections most commonly used inJapan on ductile frames use a cast-in-place joint.' From a philosophical per-spective, the joint shown in Fig. 1 (takenfrom Ref. 4) is of particular interest.Whether or not an assembly of this typehas been tested was not clear. Presum-ably the adverse implications associatedwith performance and constructibilityhave discouraged extensive testing ofthis system. Of significance, however, isthe fact that it is not categorically for-bidden and if a contractor were to dem-onstrate an acceptable level of availableductility in this assembly, it could beused and the reinforcing bar splice ac-cepted, presuming it had been prequal-ified.

Discussions focused on the hystereticbehavior of connectors subjected tocyclic loads significantly beyond yield.The importance of the shape of the hys-teretic loop must be established. Pre-cast concrete joints are characterized bypinched hysteresis loops and, as a con-sequence, presumably dissipate lessenergy than cast-in-place assemblieseven though curvature and displace-ment ductilities are comparable (Fig. 2).

The Japanese felt that energy dissipa-tion was the key to comparability whileNew Zealand and United States partici-pants considered ductility as measuredby deformation to be most important and

PCI JOURNAUMarch-April 1987 79

-D,DISPLACEMENT

NCHED HYSTERESISiOP CHARACTERISTIC OFtESTRESSED CONCRETE

uvSTERESIS LOOP'RESENTATIVE OF DUCTILE;T-IN-PLACE CONCRETE

Fig. 2. Hysteretic behavior of concrete Systems.

energy dissipation not a significantissue. Clearly, work in this area is ofparamount importance if joints in pre-cast assemblies are to be located whereyielding is anticipated since thepinched hysteresis loop is a characteris-tic feature of these assemblies.

Precast ConcreteApplications

joints in regions of high stress do notappear to concern Japanese engineers asmuch as they do engineers in the UnitedStates. This is evidenced by the fact thatJapanese engineers have constructedframe buildings of up to 24 stories usingprecast beams and cast-in-place col-umns. All column reinforcing steel isspliced immediately above the beam-column joint (Fig. 3).

Constructibility requires that the em-bedment of beam bars in the beam-column joint be reduced significantlyfrom what is considered acceptable byUnited States codes. Beam joints thatfurther reduce the splice and embed-ment length (Fig. 4) have been prequal-ified for low rise buildings.

Ohbayashi-Gumi Corp., ,, in the con-struction of a 24-story apartment build-ing, elected to use a longer precast unit

continuous through one column andspliced at midspan with an adjoiningprecast segment (Fig. 5). Bottom barswere continuous through one jointwhile at the discontinuous beam end thereinforcing steel was continuous with a180 degree loop connecting top andbottom bars. Top bars were then placedin the poured topping slab. Slab unitswere precast. Columns were splicedabove the floor, all bars being welded atthis point. A floor cycle was accom-plished every 8 days (6-day work week).Columns were spaced at 15 ft (4.6 rn)centers [12 ft (3.7 rn) clear].

Taisei and Shimizu have con-structed 3,840,000 and 240,000 sq ft(357,000 and 22,300 m l), respectively,using a variety of precast/poured sys-tems utilizing precast column forms,beam shells or half beams and formingslabs. Recent American experience inareas of comparable seismicity is limitedand typically does not use precast com-ponents to the extent used by the Jap-ane se. 5.7

Using post-tensioning to assembleprecast concrete units in Japan is ac-cepted. Low rise housing units com-prised of precast units may he as-sembled using post-tensioning but moreoften appear to be assembled using

80

CONCRETE PLICEIN SITU` ILEEVE

JOINT

PRECAST BEAMi

II If '•11. JI ,;ll

PRECAST Hr. .. . I 1 . "11' • CAPITALCOLUMN rl' - II II'-

Fig. 3. Panel zone of column beams.

SPLICESLEEVE CAST YN PLACE SPLICL SLEEVE

CONCRETE BED MORTAR

PRECAST PRECASTBEAM UNIT :. ..y BEAM UNIT

t- 1 1Ii PRECAST PRECAST

COLUMN COLUMN

Fig. 4. Left: Type A for buildings with small stress (two to three stories). Right: Type B forbuildings with large stress (fourto seven stories).

bolts. Housing units of up to 10 stories" do not appear to be the practice. 9 Wet[102 ft (31 m) I may he joined using joints with hoop connectors are commonpost-tensioning or splice sleeves. Spe- (Fig. 6) although dry joints are also usedcial boundary elements typically re- (Fig. 7).quired by current United States codes The area of wet concrete transferring

PCI JOURNAL/March-April 1987 8i

(b) NAM Inner Beam—4 ItM P C== i 9

Precast Unit of Beam

Fig. 5. Continuous beam spliced at midspan.

Fig. 6. Example of wet joint (eight stories) (Ref. 9).

shear from panel to panel does not ap-pear to concern either the Japanese orAmerican research group (see Fig. 8)."Shear transfer mechanisms permitted bycurrent United States codes require theuse of shear friction (at least by usualinterpretation). As a consequence, thethroat area and quantity of reinforce-ment crossing this joint is larger than ap-pears to be required.'°

Professor Park (New Zealand) pre-

sented a report on joining precast con-crete frame members with groutedpost-tensioning." Limited testing, nowover 15 years old, indicates good be-havioraI characteristics within the re-gion of plastification which appears tobe only slightly smaller than that whichoccurs in comparable cast-in-place sys-tems.

Tests performed at Lehigh University(as yet unpublished) indicate that the

82

BEARING WALL(UPPERI

CONCRETE BED MORTAR

'"' FLOOR SLAB

I IyII

.`^ FLOOR SLABIn

L I/BEARING WALL

ILOWER)

Fig. 7. Left: Dry joint (splice sleeve) (Ref. 9). Right: Dry joint (SPH type) (Ref. 9).

Fig. 8. Platform type horizontal connection with Grade 60 reinforcement (left): andpost-tensioning bars (right).

PCI JOURNAL/March -April 1987 83

performance of precast concrete wallsystems joined with MTB splice sleevesis comparable to the performance ofcast-in-place systems. Significant im-provement has been observed in con-nection with the inclusion of spiral eon-finement reinforcement of the splicesleeve.

Joining precast concrete componentswith epoxy and post-tensioning is beingstudied in Japan. E2 If post-tensioninglevels are reasonably high [600 psi (4.1MPa)1, joint behavior appears to becomparable to cast-in-place construc-tion. Test programs planned by bothJapanese and New Zealand researcherswill use epoxy based grout joints ap-proximately 1 in. (25.4 mm) thick toconnect precast members' joints bypost-tensioning. Japanese tests willprobably focus on shear transfer whileNew Zealand tests will be concernedwith cyclic behavior of joints in thepost-elastic range.

Precast concrete floor slabs have beenassembled with post-tensioning inJapan. Composite action between pre-cast concrete slabs, joined by post-ten-sioning, and steel supports has also been

accomplished. 1:J Bridge decks of precastslabs (noncomposite) supported byprestressed girders have been usedby the Japan Highway Public Cor-poration.' 4 Diaphragm shears wereattained with grouted shear keys andpost-tensioning.

ConclusionDevelopment of a methodology for

the design of precast concrete to resistseismic loading is well underway inJapan as evidenced by the publication ofthe new Japan Code governing precastconcrete construction. [Unfortunately,this document (Ref. 15) has not beentranslated into English.]

American procedures are still in theconceptual stages 6 though ideas andimaginative use of precast concrete inareas of moderate seismicity abound. 16,17

Quality control, construction econ-omies, and speed of construction makethe effective use of precast concrete as aseismic bracing element a desirablegoal. A cooperative effort is the mostcost effective way of accomplishing thisobjective.

NOTE: Discussion of this joint article is invited. Please submityour comments to PC] Headquarters by December 1, 1987.

84

REFERENCES

Clough, D. P., "A Seismic DesignMethodology tar Medium-Rise PrecastConcrete Buildings," Proceedings,US/Japan Seminar on Precast ConcreteConstruction in Seismic Zones, V. 1,Tokyo, Japan, October 29-31, 1986, pp.101-126.

2. Englekirk, R. E., "Concepts for the De-velopment of Earthquake ResistantDuctile Frames of Precast Concrete,"Proceedings, US/Japan Seminar on Pre-cast Concrete Construction in SeismicZones, V. 1, Tokyo, Japan, October29-31, 1986, pp. 171-190.

3. Imai, H., Kanoh, Y., "Standard for Per-formance Evaluation of Rehar Joints,"Proceedings, US/Japan Seminar on Pre-cast Concrete Construction in SeismicZones, V. 2, Tokyo, Japan, October29-31, 1986, pp. 137-156.Kanoh, Y., "Review of Japanese PrecastConcrete Frame Systems Used asBuilding Structures," Proceedings, US/Japan Seminar on Precast Concrete Con-struction in Seismic Zones, V. 2, Tokyo,Japan, October 29-31, 1986, pp. 35-54.

5. Takeda, T., "Design and Construction ofHigh Rise Precast Concrete Structures inJapan," Abstract of Special LecturesAmong Pre-Seminar Lectures on PrecastConcrete Construction in Seismic Zones,Japan Concrete Institute, Tokyo, Japan,October 27-28, 1986, pp. 5-8.

6. Englekirk, R. E., "State-of-the-Art De-sign Perspective," Seminar on PrecastConcrete Construction in SeismicZones, Japan Concrete Institute, Tokyo,Japan, October 27-31, 1986, V. 1-1.Hawkins, N. M., "Research Considera-tions for Precast Concrete Constructionin U.S.A.," Seminar on Precast ConcreteConstruction in Seismic Zones, JapanConcrete Institute, Tokyo, Japan, Octo-ber 27-31, 1986, V. 1-1, pp. 295-310.

8. Sonobe, Y., "State of the Art of LowrisePrecast Reinforced Concrete Structuresin Japan," Proceedings, US/Japan Semi-nar on Precast Concrete Construction inSeismic Zones, V. 2, Tokyo, Japan, Oc-tober 29-31, 1986, pp. 21-34.

9. Suenaga, Y., "Design Guideline for Pre-

cast Concrete Structures in Japan," Pro-ceedings, US/Japan Seminar on PrecastConcrete Construction in Seismic Zones,V. 2, Tokyo, Japan, October 29-31, 1986.pp. 1-20.

10. Mueller, P., "Hysteretic Behavior of Pre-cast Panel Walls," Proceedings, US/JapanSeminar on Precast Concrete Construc-tion in Seismic Zones, V. 1, Tokyo,Japan, October 29-31,1986, pp. 127-142.

11. Park, R., "New Zealand Research intothe Seismic Design of Building FramesIncorporating Precast Prestressed Con-crete," Proceedings, US/Japan Seminaron Precast Concrete Construction inSeismic Zones, V. 1, Tokyo, Japan, Octo-ber 29 -31, 1986, pp. 39-59.

12. Izumi, M., and Abe, C., "Shear Strengthof Precast Prestressed Concrete Joints,"Proceedings, US/Japan Seminar on Pre-cast Concrete Construction in SeismicZones, V. 2, Tokyo, Japan, October29-31,1986, pp. 97-110,

13. Fujii, M., Nakai, E., Watanabe, E., Ta-kenaka, H., "Studies on Composite Gird-er Bridges Using Prestressed PrecastConcrete Slabs," Proceedings, US/JapanSeminar on Precast Concrete Construc-tion in Seismic Zones, V. 2, Tokyo,Japan, October 29 -31, 1986, pp. 239-258.

14. "Construction Work of Deck Slab on theShin-Tsuburano Bridge," Matsuda Con-struction Office, Tokyo First Con struc-tion Bureau, Japan Highway Public Cor-poration, October, 1986.

15. "Guide for Design and Prefabrication ofPrecast Reinforced Concrete Structures,"Japanese Architecture Association, 1986.

16. Yee, A. A., "Seismic Considerations forPrecast Concrete Construction," Pro-ceedings, US/Japan Seminar on PrecastConcrete Construction in Seismic Zones,V. 1, Tokyo, Japan, October 29-31, 1986,pp. 143-152.

17. Jacques, J., and Aawad, A., "Seismic De-sign of Panel Wall Systems Using Verti-cal Post-Tensioning," Proceedings, US/Japan Seminar on Precast ConcreteConstruction in Seismic Zones, V.1, Tokyo, Japan, October 29-31, 1986,pp. 225-246.

PC! JOURNAL/March-April 1987 85