_ Recent Development of Seismic Retrofit Methods in Japan

7/27/2019 _ Recent Development of Seismic Retrofit Methods in Japan

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Recent Development of

Seismic Retrofit Methods in Japan

Japan Building Disaster Prevention Association

January 2005


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Preface

The Great Hanshin-Awaji Disaster (Kobe Earthquake) caused huge damages to building

structures, especially to old or non-engineered buildings. It has strongly beenrecognized that the strengthening of these seismic vulnerable buildings is one of urgent

issues for the reduction of earthquake disaster. Thus, in response to the precious lessons

from the Kobe Earthquake, the Japanese government enacted "the Law for Promotion of

Seismic Retrofit of Buildings," in December 1995. In accordance with the law, existing

buildings of more than certain floor area for public use shall be retrofitted to satisfy the

seismic performance level equivalent to the current code requirement at the time of

renovation.

Practical evaluation of seismic performance and retrofit design of existing buildings has

been based on The Standard for Seismic Evaluation of Existing Buildings, and

Guidelines for Seismic Retrofit Design, before and after the enacting of the law,

which are published from the Japan Building Disaster Prevention Association.

Conventional methods for seismic retrofit of building structures are provided by the

guidelines in detail, the effectiveness of which has been verified through past

experimental research.

On the other hand, various efficient methods of seismic retrofit have been developed or

invented especially after the Kobe Earthquake. Although the effectiveness of the new

methods was verified through various performance tests by the researchers in the

developers group, neutral and standardized evaluation of the methods was necessary

information to users such as structural designers or clients.

For this purpose, the Japan Building Disaster Prevention Association (President: Tsuneo

Okada) has set up a technical committee for evaluation of methods for building disaster

prevention. The committee (Chairman: Shunsuke Otani) officially started in 1996, and

evaluated 28 methods in total until 2004. The members of the committee from 2004 are

listed below.

Most of the methods for evaluation are recently developed techniques for seismic

retrofit or strengthening of old reinforced concrete buildings in Japan. Requirements

and guidelines for design and construction by the new retrofit methods are prescribed as

a manual in practice. The validity of the manual is evaluated, such as in the viewpointsof reliability of material properties, member performance, design equations, detailing

and construction work. The scope of the method is also clearly restricted by reviewing

background research. The details on the new methods could be available from the

manuals in Japanese. However, the comprehensive information in English on the

methods was not available.

January 17, 2005, is the tenth anniversary of the Kobe Earthquake. Commemorating the

anniversary, various international events are planned, such as the International

Symposium on Earthquake(ISEE Kobe 2005) and at United Nations World Conference

on Disaster Reduction in Awaji and Kobe, in order to reduce seismic disaster in the

future. The promotion of seismic retrofit of structures worldwide is one of the major


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topics to be discussed there. To contribute to the symposium of the conference above by

introducing the seismic retrofit technologies recently developed in Japan, 22 methods

out of 28, evaluated by the JBDPA committee, are outlined in English and compiled in

this volume.

This volume is prepared voluntarily by each developers group according to the given

standard format for distribution at above meetings. Note that the views shown in this

volume do not reflect those of the committee members but those of the developers.

Also please note that some of these outlines in English introduce broader scope of

application than approved by the JBDPA evaluation procedure. The contents is to be

uploaded to the website of JBDPA (http://www.kenchiku-bosai.or.jp) soon and will be

updated periodically in the future. The sincere cooperation and efforts of the developers

for drafting the volume are gratefully acknowledged.

EditorToshimi Kabeyasawa
http://www.kenchiku-bosai.or.jp/http://www.kenchiku-bosai.or.jp/


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Technical Committee on Evaluation of Building Disaster Prevention Methods

(from April 2004 to present)

Shunsuke Otani (Chiba University, Chairman)Yoshihoro Abe (Tohoku Institute of Technology)

Toshikatsu Ichinose (Nagoya Institute of Technology)

Daisuke Kato (Niigata University)

Toshimi Kabeyasawa (University of Tokyo)

Takashi Kaminosono (MLIT)

Kazuhiro Kitayama (Tokyo Metropolitan University)

Hiroshi Kuramoto (Toyohashi University of Technology)

Takeyoshi Korenaga (Taisei Corporation)

Hiroyasu Sakata (Tokyo Institute of Technology)

Osamu Joh (Hokkaido University)

Shinichi Sugawara (Science University of Tokyo)Norio Suzuki (Kajima Corporation)

Matsutaro Seki (Ohibayashi Corporation)

Hideo Tsukagoshi (Shimizu Corporation)

Shigemitsu Hatanaka (Mie University)

Shizuo Hayashi (Tokyo Institute of Techonology)

Masaki Maeda (Tohoku University)

Fumio Watanabe (Kyoto University)


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List of Seismic Retrofit Methods

1. CRS-CL Method (Carbon fiber Retrofit System for CoLumns) 12. CRS Method (Carbon fiber Retrofit System for Chimney) 53. MARS system (Mending Application of Reinforced Sheets) 94. AF System (Aramid Fiber retrofitting system) 135. -- Not translated6. -- Not translated7. Precast Retrofit Shear Wall System (PRSW) 198. -- Not translated9. -- Not translated10. CRS-BM Method (Carbon Fiber Retrofit System for BeaMs) 2311. Acrypair System 2712. SR-CF System (Seismic Retrofit by Carbon Fiber sheet) 3113. -- Not translated14. CFRP Sandwich Panel Roof 3515. Pitacolumn Method 3916. Aoki Seismic Retrofit Method by means of Energy Dissipation Braces 4317. Seismic Retrofitting Technology of Existing RC Frame Structures

by External Steel Brace Reinforcement 47

18. Tufnes method 5119. -- Not translated20. SRF (Super retrofit with flexibility) 5721. -- Not translated22. Seismic Retrofit for Existing R/C Buildings using SNE-Tru 6123. TARS (Taisei Anchor-less Retrofit System) 6524. OFB (Outer-frame brace) 6925. Seismic retrofit technology for steel structures using

(Tomoe Friction Damper) 73

26. PPMG-CR (Seismic Retrofit Technology of Columns with a SpecialPolymer-cement Mortar) 75

27. PCa Brace System 7928. PCaPC External Frame Aseismic Strengthening System 83


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1. Title

CRS-CL Method (Carbon fiber Retrofit System for CoLumns)

2. OutlineCRS-CL Method is a seismic retrofit technique for existing reinforced concrete columnsand concrete-encased steel composite columns using carbon fiber reinforced plastic(CFRP) sheet or strand. Shear strength, lateral deformability and axial capacity of thecolumn members can be improved by confining with CFRP sheet or strand.

3. Specifications for materialsCRS-CL Method uses carbon fiber (CF) sheet or strand as the reinforcing material.Table 1 lists their design specification values.

Table 1 Specifications of the reinforcing materials

(a) carbon fiber sheet

weight thicknessElastic

modulusFracture

stressStress

for design

g/m2 mm kN/mm2 N/mm2 N/mm2

200 0.111300 0.167

230 3400 1750

(b) carbon fiber shrand

number offilament

areaElastic

modulusFracurestress

Stressfor design

mm2 kN/mm2 N/mm2 N/mm2

12000 0.435 230 3400 1750

4. Typical construction detailsThe construction process of CRS-CL Method is as follows: removal of existingfinishing, rounding of corners, wrapping CF sheet or winding CF strand withsimultaneous impregnation of epoxy resin, and finishing of the retrofitted column.Figure 1 shows cross sections according to the construction process. Figure 2 illustrateswrapping CF sheet (Sheet Method) and winding CF strand (Strand Method).

Figure 1 Typical construction details

exsiting

finishing

existingcolumn

glinding

mortarmortar

CFRP finishing


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(a) wrapping CF sheet (Sheet Method) (b) winding CF strand (Strand Method)

Figure 2 Two methods for providing CFRP

5. Research for verification

The effectiveness of CRS-CL Method for strengthening reinforced concrete columnshas been verified through a series of seismic tests. Static loading tests on columns or

beams were conducted for the total of 78 specimens in the first to tenth phase, whichrepresents reinforced concrete or concrete-encased steel composite columns in old

buildings of Japan or bridge columns of highway and railway. Many of the columnswere strengthened using carbon fiber sheet or strand. The columns strengthened by thenew method could maintain lateral and axial load capacity until more than eight percentinter-story drift, while the bare specimens without strengthening failed in shear or bondat small drift and graduately lost axial load capacity. The typical hysteresis relations arecompared for a bare reinforced concrete specimen and a CRS specimen as shown inFigure 2. The specimens after tests are shown in Photo 1. Concrete prisms and cylindersconfined with the CFRP material were also tested to grasp the confinement by CFRP.Through these test series, the method is verified to be effective for prevention of theloss of lateral and axial load capacity under various structural conditions. And also, astructural design guideline for CRS-CL Method was established.

A shaking table test was conducted for the verification of the new strengthening methodunder dynamic loading. Each specimen consists of four reinforced concrete columnsand a loading steel slab and tested on the shaking table at the Institute of Obayashi. Onewas a bare reinforced concrete column specimen designed to fail in a brittle manner,while the other was strengthened by the CRS-CL Method. The bare columns withoutstrengthening failed in shear resulting in collapse associated with loss of the axial loadcapacity. On the other hand, the columns strengthened by CRS Method survived againstthree times of the same input motion. The bare reinforced concrete columns andCRS-CL columns after the shaking table test are shown in Photo 2.

existingcolumn

carbon fiber

sheet

carbon fiberstrand

existing

column


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(a) RC (without CFRP) (b) CRS-CL (with CFRP)Figure 2 Typical hysteresis relations of RC and CRS columns

(a) RC column (b) CRS-CL columnsPhoto 1 Specimens after static a loading test

(a) RC column (b) CRS-CL columnsPhoto 2 RC column and CRS-CL column after a shaking table test

LM00

- 500

- 300

- 100

100

300

500

- 50 - 25 0 25 50 75 100

Displacement(mm)

Load(kN)

LM18

- 600

- 400

- 200

0

200400

600

- 50 - 25 0 25 50 75 100

Displacement(mm)

Load(kN)


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6. Examples in practice

At least, more than 200 of structures (buildings and publicworks) in all over Japan have been retrofitted with

CRS-CL Method, including highway piers, a water tanktower, old office buildings, school buildings, hospitalbuildings and museums, etc.

Photo 3 Examples of application

7. References1) Hideo Katsumata, Yoshirou Kobatake, and Toshikazu Takeda: A study on

strengthening with carbon fiber for earthquake-resistant capacity of existingreinforced concrete columns, proc. of 9WCEE, Vol. VII, pp.517-522, 1988

2) Hideo Katsumata and Yoshirou Kobatake: Seismic retrofit with carbon fibers for

reinforced concrete columns, proc. of 11WCEE, paper No. 293, 1996.3) Hideo Katsumata, Kohzo Kimura, and Hisahiro Murahashi: Experience of FRPStrengthening for Japanese historical structures, Elsevier Science, FRP composite incivil engineering, Vol. II, pp.1001-1008, 2001

4) Obayashi Corporation, et al.: The design and construction guideline for CRS-CLMethod (revised 2003), Obayashi Corporation (in Japanese)

8. Ownership organizationObayashi Corporation (Head Office), 1088502, Minato-ku, Tokyo.Obayashi Corporation (Technical Research Institute), 2048558, Kiyose-shi, Tokyo.Tel: +81-424-95-1111

Fax: +81-424-95-0901URL: www.obayashi.co.jp/virtual/index.html

9. Certification

JBDPA Certification No.1675(current), No.1166(previous in 1998, 1995, 1991)BCJ Evaluation No.C-1985 and Fire Safety-1561, Approval of Minister ofConstruction: 1999 Apr. 6 and 1997 Jun. 12Patent No.: 1865468(Japan), 1880461(Japan), 1865467(Japan), 2078774(Japan),

3119129(Japan), 3185640(Japan), 3249736(Japan), 3246341(Japan)

(a) column in an old office building

(Sheet Method)

(b) column in a museum

Strand Method


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1. Title

CRS Method (Carbon fiber Retrofit System for Chimney)

2. OutlineCRS Method for chimney is a seismic retrofit technique for existing reinforced concretechimney using carbon fiber reinforced plastics (CFRP) sheet and strand. Flexuralstrength of the chimney is improved by gluing with CFRP sheet and safety margin forthermal stress is increased by winding with CFRP strand.

3. Specifications for materialsCRS Method for chimney uses carbon fiber (CF) sheet and strand as the reinforcingmaterial. The design specification values of carbon fiber and Carbon Fiber ReinforcedPlastics (CFRP) show below:

Tensile strength: 2,650N/mm2 (270kgf/mm2)

Tensile modulus: 216 255kN/mm2 (2.2 2.6 104kgf/mm2)

4. Typical construction detailsThe construction process of CRS Method for chimney is as follows: (1) removal oflightning conductor and ladder, (2) substrate treatment and/or arrangement of concretesurface, (3) gluing carbon fiber sheet in the longitudinal direction, (4) winding carbonfiber strand impregnated with epoxy resin along the hoop direction, (5) restoration ofthe lightning conductor and ladder, (6) painting according to provisions for safety ofairplanes. Figure 1 illustrates the basic concept of CRS Method for chimney by gluingCF sheet and winding CF strand. Photos of Figure 2 show the general view by ascaffold lift and the retrofitting works on the scaffold lift.

(a)General view of execution by scaffold lift

Figure 1 Basic concept Figure 2 Typical construction details


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(b) gluing CF sheet (c) winding CF strand

Figure 2 Typical construction details (continued)


The effectiveness of CRS Method for strengthening reinforced concrete chimney hasbeen verified through a series of flexural tests. Six flexural loading tests on hollowreinforced concrete cylinder specimens modeled on an existing reinforced concretechimney were conducted. The experimental setup is shown in Figure 3. Monotonousload was applied steadily at two points of the specimen until a load drop occurred due tofracture of CFRP. The load-displacement relationship is shown in Figure 4. This figureshows that the maximum strength is much improved and the displacement at maximumstrength become large as the amount of longitudinal CF is increased.

Following fundamental tests on adhesion properties between CFRP and concretesurface were also carried out: (1) adhesion length of CF sheet to concrete surface, (2)

lap joint length of CF sheet, (3) durability of the adhesive strength by acceleratedartificial exposure. The adhesion tests (1) and (2) suggest that the development length ofCF sheet should be more than 20cm and the length of lap joint needs more than 10cm.The specimen of durability test, as shown in Figure 5, consists of two concrete blocks,40 40 100mm, which were jointed with CF sheet. After exposure, the specimen was

pulled at each end. Results of the tensile tests after exposure are shown in Figure 6 andindicate that the adhesive strength between concrete surface and CF sheet decreaseswith the time of accelerated artificial exposure, a decrease of about 10% at 2,000 hoursand about 15% at 4,000 hours compared with the non-exposure specimen.

Figure 3 Specimen and experimental setup


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Figure 4 Load-displacement relationship

Figure 5 Specimen of exposure test

Figure 6 Maximum load-accelerated exposure time relationship


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In Japan, over 60 chimneys have been retrofitted by CRS Method, including high-risechimney.

Figure 7 Example of application

7. References

1) Yoshiro Kobatake, Kohzo Kimura, and Hideo Katsumata A retrofitting method forreinforced concrete structures using carbon fiber Fiber-reinforced-Plastic(FRP)Reinforcement for Concrete Structures: Properties and Applications ElsevierScience Publishers, 1993.

2) Kohzo Kimura, Yoshiro Kobatake, Hideo Katsumata, Kensuke Yagi, TakeoSawanobori, and Tsuneo Tanaka A study on seismic retrofit of reinforced concretemembers using carbon fiber (part.2), p.821-p.822, AIJ, 1988 (in Japanese)

3) Yoshiro Kobatake, Kohzo Kimura, and Hideo Katsumata A retrofitting method forreinforced concrete structures using carbon fiber AIJ J. Technol. Des.No.2,

p.62-p.67, Mar., 1996 (in Japanese)

8. Ownership organizationObayashi Corporation (Head Office), 1088502, Minato-ku, Tokyo.Tel: +81-3-5769-1111URL: www.obayashi.co.jp

9. Certification

The Japan Building Disaster Prevention Association Certification No.1597 (current),

1997 Sep. 17, 1991 Sep. 17 (previous)

Patent No.: 2130247(Japan), 02718459(Japan)


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1. Title

MARS system (Mending Application of Reinforced Sheets)

2. OutlineMARS system is the method of reinforcing existing concrete structures with FRP

(fiber-reinforced plastic) sheets that are strong, lightweight, and superior anti-corrosive.

FRP sheets, by wrapping around surfaces of concrete structures, increase the durability

and the ductility of structural members.

3. Specifications for materials

MARS uses carbon fiber sheet which are arranged in regular order, and made to carbonfiber dry sheet.. Table 1 lists their design specification values.


Maker Name Tensile strength Tensile modulus of elasticity

TOHO TENAX BesfightHTA-12

3400N/mm2over 2.27 105N/mm2over

4. Typical construction detailsFigure 1 shows a cross section and view.

Concrete surface treatment(edge cutting more than r=20mm)Primer coatingMatrix resin coatingCFRP sheet gluingMatrix resin coating


1 2 3 4 51 2 3 4 5


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The effectiveness of MARS for strengthening reinforced concrete columns has beenverified through a serious of seismic tests. Tests on columns were conducted fornineteen specimens, which represents reinforced concrete columns in old buildings ofJapan or worldwide. Some of the columns were strengthened using carbon fiber sheet.The columns strengthened by the new method could maintain relatively high gravityload until more than ten percent inter-story drift, while the bare specimens withoutstrengthening failed in shear at small drift simultaneously losing axial load capacity.The typical hysteresis relations are compared for bare reinforced concrete specimen andMARS specimen as shown in Figure 2 with after tests photograph. Various types ofconcrete prisms and cubes confined with the sheet were also tested, based on which theresistance mechanisms of the columns were interpreted. Through these test series, the

method has been improved to be effective to prevent the loss of capacity not onlyagainst axial load but also against lateral load reversals.

(a) RC (without carbon fiber sheet)

(b) SRF (with carbon fiberr sheet)

Figure 2 The typical hysteresis relations and photograph

of RC column and MARS column

-400

-300

-200

-100

0

100

200

300

400

-40 -20 0 20 40 60 80 100

+1/10

-1/ 100-1/ 30-1/ 50

(rad)

Qmax=294.6kN, 8.55mmQmi n=-295.6kN, -6.02mm

P-

(rad)

+1/ 100 +1/30+1/50

-400

-300

-200

-100

0

100

200

300

400

-40 -20 0 20 40 60 80 100

+1/10

-1/100-1/ 30-1/ 50

(rad)

Qmax=294.6kN, 8.55mmQmi n=-295.6kN, -6.02mm

P-

(rad)

+1/ 100 +1/30+1/50

No reinforcement Axial force rate=0.4

Shear force(kN)

Displacement(mm)

-400

-300

-200

-100

0

100

200

300

400

-40 -20 0 20 40 60 80 100

Qmax= 275.5kN, 12. 60mmQmi n=-285.5kN,- 9.02mm

+1/10

-1/100-1/ 30-1/50

(rad)

P-

(rad)

+1/100 +1/30+1/50

-400

-300

-200

-100

0

100

200

300

400

-40 -20 0 20 40 60 80 100

Qmax= 275.5kN, 12. 60mmQmi n=-285.5kN,- 9.02mm

+1/10

-1/100-1/ 30-1/50

(rad)

P-

(rad)

+1/100 +1/30+1/50

Displacement(mm)

2 sheets reinforcement Axial force rate=0.4

Shear force(kN)


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6. Application ExampleMany of constructed facilities have been retrofitted with MARS system.

Columns in buildings


7. References

4) Norimitsu Hayashida and Tomoaki Tsujimura: A strength method using carbon fibersheets for improving the earthquake resistance of existing reinforced concretecolumns Kumagaigumi Technical Research Report NO.55 1996.

8. Ownership organization

Kumagai Gumi Co., Ltd., Shinjyukuku, Tokyo.Tel: +81-3-3235-8617Fax: +81-3-3235-9215E-mail: [email protected],jpURL: www.kumagaigumi.co.jp

9. Certification


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1. Title

AF System (Aramid Fiber retrofitting system)

2. OutlineAF System is a seismic retrofit technology for existing reinforced concrete columnsusing aramid fiber sheets against earthquake loading and was certified by JBDPA (TheJapan Building Disaster Prevention Association). Deformability of the column memberscan be improved by confining with aramid fiber sheets.

3. Specifications for materialsAF System uses woven aramid fiber sheets as the reinforcing material. Aramid fibersare arranged to the axial direction of the sheets. Figure 1 shows an aramid fiber sheetand Table 1 lists their design specification values. Aramid fiber sheets are characterized

by light weight, high strength, no corrosion, and non-conductivity.

Figure 1 Aramid fiber sheet


Type Weight(g/m2)

Thickness(mm)

Width(mm)

Tensilestrength(N/mm2)

Youngsmodulus

( 103 N/mm2)40tf 280 0.19360tf 415 0.286Aramid 190tf 623 0.430

2060 118

40tf 235 0.16960tf 350 0.252Aramid 290tf 525 0.378

100

300

500 2350 78

4. Typical construction details

Figure 2 shows a typical construction procedure of AF System. Epoxy resin is used formatrix of the sheets.


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Figure 2 Typical construction prcedure

Figure 3 Attaching aramid fiber sheet


The effectiveness of AF System for strengthening reinforced concrete columns has beenverified through a serious of seismic tests. Static tests on columns were conducted formany specimens varying amount of fibers to establish design methods. Figure 4 (a)shows a bare RC column without aramid fiber sheet which represents columns in old

buildings. The columns strengthened by AF System (Figure 4 (b)) could carry higherlateral load and show ductility with flexural failure while the bare RC columns failed inshear with relatively low deformation. The typical hysteresis relations are compared for

bare reinforced concrete specimen and AF specimen as shown in Figure 4.

Surface treatment Coating primerand epoxy resin

Wrapping sheet andremoving air with roller

Coating epoxy resinFinishing with mortalor painting


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(a) RC (without aramid fiber sheet)

(b) AF (with aramid fiber sheet)

Figure 4 The typical load-deformation relations of RC column and AF column

Further research have been continued to develop applications of aramid fiber retrofittingmethod after the certification of AF System by JBDPA. Research themes about aramidfiber sheet developed by many organizations are listed as follows:

Shortened columns by spandrel wallColumns subjected to high axial force (N/bd=0.6)Columns with finishing mortalColumns with wing wallColumns with low strength concrete of fc=6N/mm2

Lateral deformation (cm)

Load

(tf)

Lateral deformation (cm)

L

oad

(tf)


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Axial behavior of axially loaded columnsT-shaped girders with slabAnchorage for aramid fiber sheet with steel plate and bolt

Application of super high quantity sheets up to 1500g/m2

Steel plate and aramid fiber sheet composite method

For example, Figure 5 shows a shortened column by spandrel wall reinforced witharamid fiber sheets after lateral loading tests. The specimen under constant axial loadmaintains maximum lateral force up to deformation of 10% of column height.

Figure 5 Short column with aramid fiber sheet


AF system is certified by JBDPA for existing building columns that requirestrengthening for shear. But applications of aramid fiber sheets have been widelyexpanding not only for building columns but also for bridge piers, tunnels, andchimneys etc. More than 500 structures have been retrofitted with aramid fiber in Japan.

Figure 6 Shear strengthening of building columns


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Figure 7 Strengthening and repair for girders and slabs

Figure 8 Strengthening for bridge pires

Figure 9 Repair for chimney


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7. References5) Minoru Oda, Tadashi Okamoto, Hisayuki Yamanaka and Akira Asakurua: Shear

strengthening of existing RC columns wrapped witharamid fiber , Proceedings ofJapan Concrete Institute vol.15 No.2, 1993

6) Kiyoshige Suzuki, Tomoya Nagasaka, Tadashi Okamoto and Masaharu Tanigaki:An experimental study on shear capacity of existing RC columns strengthened withcontinuous fiber tapes, Summaries of technical papers of annual meeting ,Architectural Institute of Japan, vol.C-2 , Sept. 1996

7) Masaharu Tanigaki, Kazuhiko Ishibashi and Hideaki Ibuki: Shear strengtheningshortened columns by spandrel using aramid fiber sheets, Proceedings of JapanConcrete Institute vol.22 No.3, 2000

8. Ownership organizationAF System AssociationAIG Nihombashi Hommachi Bld. 1-1-1 Nihombashi Hommachi, Chuoku, Tokyo.DU PONT-TORAY Co.,Ltd.Tel: +81-3-3245-5082Fax: +81-3-3242-3183E-mail: [email protected]

9. Members of AF System Association

Administration: DU PONT-TORAY Co.,Ltd.OBAYASHI Corporation, KAJIMA Corporation,SHINKO WIRE Co.,Ltd., SHO-BOND Corporation,TEIJIN TECHNO PRODUCTS Limited, TOKYU Construction,SUMITOMO MITSUI Construction Co.,Ltd.

10. CertificationAF System was certified by JBDPA in 1997 ( No.1624) and revised in 2002


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1. Title

Precast Retrofit Shear Wall System (PRSW)

2. OutlineThis system is a seismic retrofit technology, which installs a precast concrete wall in an existingreinforced concrete flame. The characteristic point of this system is the connection method

between the precast wall and the reinforced concrete flame. The connection method is shown inFig. 1.

Fig.1 Outline of precast retrofit shear wall system and a connection detail


Specifications for materials are shown in Table. 1.

4. Construction detailsThis system consists of three types of precast concrete walls as shown in Fig. 2.

Fig. 2 Three types of Precast concrete walls

Materi al s Speci f i cati ons

Concrete 21Pa36Pa

Rei nforcement SR235, SD295A, SD345,SD390

Prestressi ng SBPR 785/1030,SBPR 930/1080,

steel bar SBPR 1080/1230

Table. 1 Specifications for materials


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The seismic loading tests were done for explained the behavior of precast retrofit shear wall.Figure 4 shows main test specimens.

RCW-1(retrofit reinforced concrete wall) PCW-3(Retrofit precast concrete wall)Fig. 4 Test specimens

Test specimens are on a scale of 1/3. RCW-1 is that the resisting wall is consisted of concreteplacing in existing reinforced concrete frame, while PCW-3 is that the shear wall is consistedof setting precast retrofit wall in existing concrete frame. Loading method is shown in Fig. 4.Loading cycle is shown in Fig. 5. Figure 6 describes the behavior of test specimens.

Fig. 4 Seismic loading method

Fig. 5 Loading cycle


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Fig. 6 The behavior of test specimens


Precast Retrofit Shear Wall System haves 13 examples in practice. Fig. 7Fig. 18 show theexample of practice.

Fig. 7 Interior before retrofit Fig. 8 Removal of existing RC wall

Fig. 9 in-situ of anchoring Fig. 10 Carrying in of precast wall

Fig. 11 Move of precast wall inside Fig. 12 Setting of precast walls


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Fig. 13 Setting of prestressing steel bars Fig. 14 Prestressing by oil jack

Fig. 15 Connection reinforcement Fig. 16 Finish of connection reinforcing

Fig. 17 Grouting Fig. 18 nterior finishing

7. References1) The Japan building disaster prevention association: Guidelines for Seismic Retrofit ofExisting Reinforced Concrete Buildings, 2001

8. Ownership organizationPre-cast Retrofit Shear Wall Society Chuoku Tokyo.Tel : +81-3-5651-8232Fax : +81-3-5651-8229


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1. Title

CRS-BM Method (Carbon Fiber Retrofit System for BeaMs)

2. OutlineCRS-BM is a seismic retrofit technique for existing reinforced concrete beams usingcarbon fiber reinforced plastic (CFRP) sheet. Shear strength and lateral deformability ofthe beam members can be improved by wrapping with CFRP sheet.

3. Specifications for materialsCRS-BM Method uses carbon fiber (CF) sheet as the reinforcing material. Table 1 liststheir design specification values.


weight thickness

Elastic

modulus

Fracture

stress

Stress

for designg/m2 mm kN/mm2 N/mm2 N/mm2

200 0.111300 0.167

230 3400 1750


The construction process of CRS-BM Method is as follow: removal of coating,preparation of surfaces with chamfering of corners, setting of bolts, application ofprimer, wrapping CFRP, setting plates, and finishing with coatings. Figure 1 illustrateswrapping CF sheets.

CF sheets

bolt

boltflat bar

flat bar

chamfering

Type 1

Type 2

ExistingRC Beam

bolt

flat bar



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The effectiveness of CRS-BM Method for strengthening reinforced concrete beams has

been verified through a series of seismic tests. Static loading tests on beams wereconducted for eight specimens in the first phase, and eight and five in the second andthe third, which represent reinforced concrete beams in old buildings of Japan. Many ofthe beams were strengthened using CF sheet. The beams strengthened by the newmethod could maintain lateral load capacity until more than 5% drift, while the barespecimens without strengthening failed in shear at small drift. The typical hysteresisrelations are compared for a bare reinforced concrete specimen and a CRS-BMspecimen as shown in Figure 2. The specimens after tests are shown in Photo 1.

200

400

600

0.02 0.04 0.060

RC (Unretrofit)

RC (Unretrofit)

CF2-P (Two layers)

CF2-P (Two layers)

CF1-A1(One layer)

CF1-A 1 (One layer)

Shearforce(kN)

deflection angle (rad.) (a) Anchoring methods of CF sheets (b) Relationships between shear force

and deflection angleFigure 2 The typical hysteresis relations of RC beam and CRS-BM beam

(a) unretrofit beam (b) retrofit beamPhoto 1 Specimens during and after tests


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Some buildings that had weak beams were retrofitted with CRS-BM Method. Anexample for a school building in Kobe is shown in Photo 2.

Photo 2 Examples of application (beams in a school building)

7. References

1) Hagio Hiroya, Katsumata Hideo, and Kimura Kohzo: The Beam Retrofitted by

Carbon Fiber - Experiment and Designs 12WCEE Feb. 2000.2) Obayashi Corporation, et al. : The design and construction guideline for CRS-BMMethod (revised 2004), Obayashi Corporation (in Japanese)


Obayashi Corporation (Head Office), 1088502, Minato-ku, Tokyo.Tel: +81-3-5769-1111URL: www.obayashi.co.jpObayashi Corporation (Technical Research Institute), 2048558, Kiyose-shi, Tokyo.Tel: +81-424-95-1111

Fax: +81-424-95-0901URL: http://www.obayashi.co.jp/virtual/index.html

9. Certification(Current ) JPDPA Certification No.1776(Previous) JPDPA Certification No.1280Patent No. : 3301288(Japan)


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1. Title

Acrypair System

2. OutlineAcrypair System is an advanced technology for strengthening reinforced concretestructures using carbon fiber sheets and methyl methacrylate (MMA) resin. It is effectivefor concrete and RC materials and provide the ease and speed of applications construction.

3. Specifications for materialsThe specifications for the CF sheet used to make the specimens are shown in Table 1. The

properties of the MMA resin and those of the reference epoxy resin are shown in Table 2.

4. Research for verificationRehabilitation and maintenance of existing RC structures recently become the subject ofwide interest. The use of composite wraps on concrete materials presents an economicaland efficient means of strengthening the structures. Means using continuous fiber materials,

particularly carbon fiber sheets, are one of the effective approaches. The CF sheet methodinvolves attaching the sheets to RC and epoxy resins typically use as matrix and adhesives.However the method using epoxy resins have restriction on field application because of

slow curing reaction, especially at low temperatures such as below 5. To eliminate suchrestriction, alternative resin systems, which are acrylic resins, have been developed. Thenew resin systems have excellent curing properties such as rapid reaction andlow-temperature curing ability.The acrylic resins are specially designed to cure within an hour at required temperatures.These short curing times cause limitation of attaching operation area at a time. To secure asufficient amount of time for the operation, ABA Two-Component method (ABA-TCM)was developed. The concept of ABA-TCM is represented in Fig 1. Two types of resinfluids, one containing only a hardener and the other containing only an accelerator, are

prepared. These fluids are brought into contact and mixed together at applied surface

during impregnation to CF sheets. ABA-TCM has been already confirmed on mechanical

1 Specifications for carbon fiber sheets

Unit Weight Design Fiber Tensile Tensile

of sheet thickness density strength modulus(g/m2) (mm/sheet) (g/mm3) (N/mm2) (N/mm2)

300 0.167 1800 3432 2.36 105

Table 2 Properties of the resin used for impregnarion and bonding

Resin Ambient temperature Viscosity Curing time Flexural strength Flexural modulus

() (Pas) (min) (N/mm2) 103(N/mm2)

MMA 30 0.2 43 63 2.77

20 0.26 50 64 2.76

10 0.52 41 60 2.4

0 0.72 42 64 2.64

Epoxy1) 20 10 or more 600 98 3.331) Room-temperature-curing epoxy resin commonly used in the CF sheet strengthening method


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properties of the composites.

RC pillars wrapped with CF sheets were tested for shear. The test variables consisted of thenumber of CF sheet piles and two load conditions as summarized in Table 3. The test seriesspecimens were applied a static axial load and a cyclic lateral load and symbolized. Thedetails of the tests are illustrated in figure 2. CF sheets were wrapped around RC pillars inthe hoop direction and the lap joint lengths were 200 mm.

The load-deformation curves of the test series specimens are shown in Fig 3. Themaximum forces and the ultimate deformations on specimens wrapped with CF sheets

Apply primer Cure primer Apply A resin fluid

Impregnate by roller F inishApply A resin fluidApply B resin fluid

Figure 1 Concept of ABA-TCM

Apply primer Cure primer Apply A resin fluid

Impregnate by roller F inishApply A resin fluidApply B resin fluid

Figure 1 Concept of ABA-TCM

Table 3 Details of shear test specimensSpecimen Load Hoop steel CF sheet

pf : CF volume percentage of specimen

pw : hoop steel volume percentage of specimen

C-08-0

C-08-3

C-08-6

1 ply (pf=0.0835%)

None

2 plies (pf=0.111%)

Cyclic lateral load

&

Axial load : 530kN

pw=0.08%

(D6-@200)

1200

Axial load

Lateral load

400

400

C series specimen

Figure 2 Schematics of RC strengthening test and specimens geometry (mm)

1200

Axial load

Lateral load

400

400

C series specimen

1200

Axial load

Lateral load

400

400 1200

Axial load

Lateral load

1200

1200

Axial load

Lateral load

400

400

400

400

C series specimen

Figure 2 Schematics of RC strengthening test and specimens geometry (mm)


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were extremely improved as shown in Table 4.

The acceptability of CF sheets/MMA resin system for strengthening concrete wasconfirmed. This system exhibited superior strengthening effect for concrete subjects oncompression and shear. The acrylic resins for matrix and primer in this system had rapidcuring and low-temperature curing ability without reduction of mechanical properties ofthe composites. Thus the availability and the versatility of CF sheets strengthening methodfor construction applications could increase by using this system. Evaluation of durabilityof this system on mechanical properties has progressed.

5. Examples in practiceThe concrete pillar exceeding 10 affairs was reinforced with Acrypair system. Moreover,30 or more reinforcement was performed in structures other than a pillar.

1) Reinforced pillar of the station building. 2) Reinforced pillar of factory.

4 Results of RC pillar shear test

Specimen aximum shea Shear strength

force (kN) (MPa)

C-08-0 303 1.89

C-08-3 434 2.72

C-08-6 513 3.21

-600

-300

0

600

300

-50 0 50

Deformation d (mm)

Shearfor

ce(kN)

Deformation d (mm)

200-20-600

-300

0

600

300C-08-0 C-08-3

-600

-300

0

600

300

1000 50-50

Deformation d (mm)

C-08-6

Figure 3 Relationship of deformation and shear force at shear test

-600

-300

0

600

300

-50 0 50

Deformation d (mm)

Shearfor

ce(kN)

Deformation d (mm)

200-20-600

-300

0

600

300C-08-0 C-08-3

-600

-300

0

600

300

1000 50-50

Deformation d (mm)

C-08-6

Figure 3 Relationship of deformation and shear force at shear test


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6. References

1) Y.Sakai, S.Ushijima, S.Hayashi and T.sano, Mechanical characteristics of carbon fibersheet with methyl methacrylate resin, Proceedings of the third International Symposiumon Non-metallic(FRP) Reinforcement for Concrete Structures. Vol.2, 1997, pp.243-250.2) T.Sano, S.Hayashi and T.Furukawa, Studies on applicability of CF sheets/MMA resinsystem for strengthening concrete structures, 43rd International SAMPE Symposium,1998.


Ryoko Co., Ltd. Construct Chemicals Division14-1 Koami-cho, Nihonbashi Chuo-ku, Tokyo, 103-0016 JAPANPHONE:03-5651-0656

FAX :03-5651-0055URL: http://www.kkryoko.co.jp/

8. Certification

Patent No. 10-110536(Japan)


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1. Title

SR-CF System (Seismic Retrofit by Carbon Fiber sheet)

2. OutlineThe SR-CF system 1) is a seismic retrofitting technology for existing reinforced concrete

buildings by adhering carbon fiber sheets with epoxy resin on the concrete surfaces.This system can improve the structural properties of independent columns, columnswith wing-walls 2), beams 3), and walls 4) by using special devices called CF-anchors,while conventional seismic strengthening by carbon fiber sheets has been considered to

be effective only to independent columns. The use of the CF-anchor is the mostcharacteristic in this system.


PAN type unidirectional carbon fiber sheets and carbon fiber strands are used in the

SR-CF system. Carbon fiber strands are used as materials of the CF anchors. Sizinglevel of the carbon fiber strand is regulated smaller in order that the epoxy resin can beeasily impregnate into the strand. Table 1 lists their design specification values.

Table 1 Specifications of the carbon fiber sheets

Fiber areal weight (g/m2) 200 300Thickness (mm) 0.111 0.167

Tensile strength (MPa) 3400 3400Young's modulus (GPa) 230 230

Table 2 Specifications of the carbon fiber strands

Type 12K 24KCross section (mm2) 0.435 0.870

Tensile strength (MPa) 4500 for strands3400 for CF-anchor

4500 for strands3400 for CF-anchor

Young's modulus (GPa) 230 230

4. Typical construction detailsFigure 1 shows a schematic diagram of the SR-CF system. The innovative techniquecalled CF-anchor is used in this system. The CF-anchor is a bundle of carbon fiber

strands which are strings of 2 to 3 mm in diameter consisting of 24,000 or 12,000filaments. There are two types of CF-anchors. One is penetrating type, and another thefixing type.The penetrating anchors are used for the shear strengthening of columns with wingwalls. A bundle of carbon fiber strands is penetrated through a hole drilled at the wingwall. The ends of the bundle are spread like a fan and adhered to the carbon fiber sheetwhich is previously applied on the column. The bundle joins the both ends of the carbonfiber sheet, which was separated by the side wall. Consequently, it is made possible toenvelop the column by the carbon fiber without demolishing a part of wing walls.Beams with slabs can be strengthened by the same method.The fixing- type CF-anchors are used for the shear strengthening of walls. The carbon


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fiber sheet is adhered on the wall surface diagonally. An end of the CF-anchor is spreadlike a fan and adhered to the carbon fiber sheet. The other end is inserted into a holedrilled on the peripheral reinforced concrete frame and is fixed with injected epoxy

resin. The CF-anchors fix the edges of the carbon fiber sheets on the wall to theperipheral columns and beams.

Figure 1 Schematic diagram of the SR-CF System

5. Research for verificationA number of specimens were tested to evaluate the effect of strengthening for each typeof structural members, such as independent columns, columns with side-walls, beamswith slabs, and walls. Photo 1 shows specimens of columns with side-walls after thetests. (a) is a specimen without strengthening and (b) is a specimen strengthened by theSR-CF system. The specimen without strengthening failed in sheer at small drift angle.On the other hand, the column of the strengthened specimen was not so much damaged

even at 3.0% of drift angle while the wing walls were considerably damaged. Figure 2shows the test results of the wall specimens. It shows that the shear strength of thestrengthened walls increase in proportion to the amount of the carbon fiber sheets on thewall surfaces.

6. Examples of ApplicationPhoto 3 show the execution of CF-anchors to the column with spandrel walls andwindows. The CF-anchors are penetrated through the walls at the narrow space betweenthe column and the window frame (a). As a result, the strengthening was completedwithout temporally removing the windows (b). Photo 4 shows a strengthening of abeamand Photo 5 shows a strengthening of a wall.


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(a) Specimen not strengthened (b) Specimen strengthened by SR-CF systemPhoto 1 Failures of column with wing-walls specimens after tests

Photo 2 Beam specimens after tests Figure 2 Test results of wall specimens

(a) The CF-anchor under installation (b) Strengthening completedPhoto 3 Application to the column with wing walls


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Photo 4 Application to the beam with slabs Photo 5 Application to the wall

7. References

3) SR-CF System Research Association Design Guidelines for SR-CF System, Feb.

2002 (in Japanese)4) K.Masuo, S.Morita, Y.Jinno, H.Watanabe Advanced Wrapping System with

CF-anchor -Seismic Strengthening of RC Columns with Wing Walls-, FRPRCS-5,Vol.1, pp.299-308 May 2001

5) Y.Jinno, H.Tsukagoshi Seismic Strengthening of Reinforced Concrete Beams withSlabs by Carbon Fiber Sheet and CF-anchor, Proceedings of Structural EngineersWorld Congress 2002, Session T8-3-a-1, pp.1-8, Oct.2002

6) Y.Jinno, H.Tsukagoshi Seismic Strengthening of Reinforced Concrete Walls bySR-CF System, Proceedings of the first fib congress 2002, Session 6, pp.109-118,Oct.2002

8. Ownership organizationSR-CF System Research Association, Tokyo, JapanTel: +81-3-5623-5558Fax: +81-3-5623-5551E-mail: [email protected]

9. CertificationJPDPA Certification No.1399Patent No.: US 6330776 B1(USA), 10-2000-7002781(Korea) , 121278(Taiwan)

Patent Application No.(Published): 10-206983(Japan) etc.


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1. Title

CFRP Sandwich Panel Roof

2. OutlineThe CFRP sandwich panel roof is the lightweight monocoque roof which is made byCFRP (Carbon Fiber Reinforced Polymer) sandwich panel. Its weight is about one-forthas heavy as existent prestressed precast concrete shell. Due to the lightness, it is

possible to improve the earthquake resistance of many steel reinforced concretegymnasiums in Japan by replacing precast concrete shell with the CFRP sandwich panelroof while it is possible to reduce reinforcing sub-structures.

3. Specifications for materials3.1 Components and Materials

CFRP sandwich panel is composed of skins, core and ribs (see Fig.1). Skin is made of

CFRP. The cubic ratio of CF is 5%, GF(Glass Fiber) 45% and phenol polymer 50%. Thethickness of the skin is 4mm. Core is made of phenol foam. The thickness of the core is75mm. Rib is made of GFRP. The thickness of the rib is 2.2mm. These components areformed into one piece with VARTM (Vacuum Assisted Resin Transfer Molding).

3.2 Material PropertiesThe material properties of the components are showed in Table 1.

3.3 Allowable Unit StressThe sandwich structure can exhibit local buckling of the skin under bending orcompression. In case of an one-way hyperbolic paraboloidal shell, the design criterion isusually due to compressive stress of the skin. Table 2 shows material strengths, standardstrengths and allowable unit stresses. Material strengths are decided by coupon tests.Standard strengths (F) are decided by the product of the average of coupon tests and thestatistical coefficient of 0.72. This coefficient is more wide range than three-sigma. Thedesign of CFRP sandwich panel roof is based on allowable stress design. Because of the

brittleness of CFRP materials, the safety factors are decided as 4 for sustained loads and2 for temporary loads.

Figure 1Section of CFRP

sandwich panel

83

unit mm

4

75

4

GFRP rib CFRP skin

CFRP skin

phenol foamcore

Table 1 Material Properties

Young's modulus

N/mm2

Shear

modulus N/mm

2

Poisson's

ratio

EL ET GLT

Skin 30300 30300 5390 0.13

Ri b 19600 12700 8160 0.42

Core 20.6 7.80 0.01


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Unit: mm


The specifications of CFRP sandwich panel roof is showed in Table 3. Figure 2 showsthe shape of the shell. The original shape is out of a hyperbolic paraboloidal surface.Figure 3 and 4 show the connections of shell-tie beam and shell-shell respectably.Figure 5 shows a roof plan and a section.

Bol tCFRP Sandwi chPanel

Ti e Beam

CFRP Sandwi chPanel

Ti e Beam

Grouti ng

Fastener PL

Bol tFastener PL

Table 2 Standard Strength and Allowable Unit Stress

Allowable unit stress

Stress Strength

Standard

strength( F )

for sustained

loads

for temporary

loads

Compression 230 165 F/4 F/2Local Buckling Stress

(rib space: 450 400)78 56 F/4 F/2

Local Buckling Stress

(rib space: 450 200)105 75 F/4 F/2

Tension 300 215 F/4 F/2

In-plane Shear 45 32 F/4 F/2

Skin

Bearing 320 230 F/4 F/2

Rib In-plane Shear 170 122 F/4 F/2

Table 3 Specifications of

CFRP sandwich panel roof

Shape Figure 2Radius of Curvature 180 m

Maximum Span 24.5 mWidth 2.5 mHeight 0.9 m

Structural Weight 500 N/m2Fireproofing etc. Weight 100 N/m2

Shell-Tie BeamConnection

Bolt (Fig.3)

Shell-Shell Connection Bolt (Fig.4)Roof Plan Figure 5

Figure 2 Shape of CFRP sandwich

panel shell

Figure 3 Shell-Tie Beam ConnectionsFigure 4 Shell-Shell

Connections

Fi l l er PL

Bol t

PanelCFRP Sandwi ch


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5. Research for verificationThe coupon material tests and the structural experiments were conducted. The structuralexperiments were compression tests and bending tests about the elements of the flat

panels. It was found on these experiments that local buckling (wrinkling) of skin wascritical. The various strengths (Table 2) were decided upon these experiments. On theother hand, the sandwich shells which had a real section were tested under bendingforce. About the real size shell, local buckling of the skin occurred at the stressconcentrated point. Reference 1 and 3 show the details about the structural experiments.Reference 2 and 4 show the comparisons between the theory and the experiments aboutlocal buckling.

(a) Compression Tests on Panel Element (b) Bending Tests on Real Size Shell

Photo 1 Structural Experiments

6. Examples in practiceThe CFRP sandwich panel roofs have been applied to ten schools gymnasiums in Japan.In the case of the 24m 35m plan which had fourteen shell roofs, the roof replacingwork including scaffold cost only three weeks. It is enough less time than a summervacation term.

Figure 5 Roof Plan and Section

convexity

concavity


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(a) Under construction (b) After replacing

Photo2 Examples of application

7. References1) Tateishi Y., Sugizaki K., Fujisaki T., Kanemitsu T., and Yonemaru K., Experimentand Application of CFRP Sandwich Panel, CD-ROM Proc. IASS symp., NAGOYA,2001, TP037.2) Tateishi Y. and Yamada S., Theory and Experiment of Local Buckling in CFRPSandwich Panel, CD-ROM Proc. IABSE symp., Shanghai, 2004, (IABSE reports vol.88,

pp376-377 (short version))3) Tateishi Y., Sugizaki K., Fujisaki T., Kanemitsu T., and Yonemaru K., and Kondo T.,Development of CFRP Sandwich Panel (in Japanese), AIJ Journal of Technology andDesign, No.14, pp133-138, Dec., 20014) Tateishi Y. and Yamada S., Local Buckling of CFRP Sandwich Panels with LatticedRibs (in Japanese), Journal of Structural and Construction Engineering, AIJ, No.573,

pp119-127, Nov., 2003


Toray Industries, Inc. 2-2-1, Muromachi, Nihonbashi, Chuo-ku, TokyoTel: +81-3-3245-5736Fax: +81-3-3245-5726E-mail:[email protected]: http://ns.toray.co.jp/composites/application/app_g002.html

Shimizu Co. 1-2-3, Shibaura, Minato-ku, Tokyo.Tel: +81-3-3820-6644Fax: +81-3-3820-5955E-mail: [email protected]

9. CertificationPatent Application No. (Published): 2000-322829(Japan), 2000-197036(Japan),2000-120227(Japan), 2000-336854(Japan), 2001-207597(Japan), 2001-058319(Japan),2001-254456(Japan)


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1. Title

PITACOLUMN Method

2. Summary of the MethodThe PITACOLUMN method is a completely external type earthquake-proof reinforcing

method targeted at low- to mid-rise reinforced concrete buildings. This method is a low cost,

short construction period, and environmentally friendly method. Since it is not required to

works inside a building for reinforcement physically at each phase, no transportation of interior

equipment and removal and/or installment of existing fixtures are needed. Therefore it allows

continuous use of the building. Reinforcing structure is a reinforced concrete member

containing a steel plate, and the method is surpassing in maintenance and does not require any

special finish comparable to that of the existing structure. The reinforcement working procedure

is as follows; drive post-installed anchors into the external surface of the existing structure,attach a steel plate by using these anchors and arrange reinforcing bars around the plate, and

then cast concrete to complete.

One of two types of reinforcing pattern can be selected according to performance based

reinforcement volume or reinforcement target. That is a frame reinforcement is targeted at

ductility reinforcement and a frame reinforcement with braces is targeted at strength

reinforcement. ( Fig. 1)

Figure. 1 - Summary of the Method

Steel Pl ate

Rei nforci ng MemberExi st i ng (RC) Column

Post- i nstal l ed Anchor

Approx. 200 mm

Cl eavage Preventi ng Bar

c) Detai l of the Secti on of Member

Steel Pl atePost -i nstal l ed Anchor


Exi st i ng (RC) Column

Rei nforci ng Member

f rame Rei nforcement frame Rei nforcement wi th Braces

BraceSteel Pl atePost -i nstal l ed Anchor


Exi st i ng (RC) Column

Rei nforci ng Member


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3. Specifications of Materials

The standards for the specifications of materials for the PITACOLUMN method are

shown in Table 1.

Table 1 Standards for Specifications of Materials

Post-installed

Anchor

Use adhesive type anchor

Steel Plate J IS G 3136 Rolled Steel for Building Structure - SN400B, SN400C

J IS G 3101 Rolled Steel for General Structure - SS400

J IS G 3106 Rolled Steel for Welded Structure - SM400B, SM400C

Anchor Bar D16,D19,D22 SD345

Assembly Bar D13,D16,D19 SD345 SD295A,B

Reinforcing Bar

Cleavage

Preventing Bar

D6, 6 SD295A, B, SMW-P, R, I

Concrete Normal concrete or super -plasticized concrete

Specified-design strength is more than or equal to 24N/mm2 and less

than or equal to 36N/mm2.

4. Detail of Standard Structure for the PITACOLUMN method

The PITACOLUMN method means a method in which post-installed anchors are

driven into an existing structure at uniform space, a steel plate is attached using these

anchors, cleavage preventing bars are arranged around the plate, and concrete is cast.The construction process is described below and the details of section of this method are

shown in Fig. 2.

(1) Drive post- installed anchorsinto existing structure

(2) Removal of existing finishing material

(3) Installment of reinforcing steel plate

(4) Arrangement of cleavage preventing bars

(5) Assembly of mold form

(6) Casting of concrete

(7) Disassembly of mold form(8) Finishing

Figure. 2 Section of the Method

Exi sti ng

Structure

Fi ni shi ng

( )Dri ve anchor ( )I nstal l ment of

steel pl ate

( )Arrangement of

cl eavage preventi ng bars

( )Casti ng of concrete

Exi sti ng

Structure

Exi sti ng

Structure

Exi sti ng

Structure


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5. Experimental Verification

The test specimens of 1/3 size model of 2 layers and 1 span were made and were

tested with static loading to confirm the effectiveness of this method. The test results of

the brace type reinforcement are shown here as the representative example.The view of testing are shown in Photo 1 and the final state of cracking is shown in

Fig. 3. The cracks in the existing parts were due to shear failure (accompanying bond

splitting failure) of columns as with a test specimen without reinforcement, and it was

observed that there is no change in the failure modes. And all cracks on the reinforced

side are bending cracks only.

The relationship between load and displacement is shown in Fig. 4. The vertical axis

is load and the horizontal axis is displacements of 2 layers. A dashed line in the figure

indicates the test specimen without reinforcement. The test specimen with

reinforcement was improved in both strength and ductility significantly compared to thetest specimen without reinforcement and it was confirmed that it showed stable

hysteresis up to drift angle of R = 1/60. Maximum strength (Max load) was 500 kN at

drift angle R = 1/60. Though the brace of 2nd floor was buckled at R = -1/460 with Q

=-183 kN during loading of R =-1/60, it sustained the increase of load and showed Q

=-340 kN at R =-1/60. After that the brace of 1st floor was buckled at R = 1/44 with Q =

477 kN during loading of R = 1/30, and then its deformation progressed rapidly and led

to a failure. It was also confirmed that the yielding process of members was preceded by

the yielding at reinforced part and then the existing part was yielded.

Figure.3 Final State of Cracking

Photo 1 Loading Situation Figure. 4 Load - Displacement Relationship

Buckl ed

West to East East to WestSide

Rei nforced Si de Exi sti ng Si deWEST EAST EAST WEST

East to West West to East

West to EastEast to West

West to EastEast to West

Buckl ed

SideRi ghtLef t

Si deSideRi ghtLef t

-600

-400

-200

0

200

400

600

- 100 -80 - 60 -40 - 20 0 20 40 60 80 100

DISP(mm)

LOAD(kN) Brace buckled

Bracebuckled

//

/ /

Drift Angle R

Non-ReinfocedSpecimen


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6. Construction Examples

There are 120 construction examples reinforced by this method, mainly applied for

school buildings, to date.

a)J unior High School Building (School Colored) b) J unior High School Building (Designed by Students)

c)University Building (with Exterior Panels) d)Elementary School Building (with Balconies)

Photo 2 Examples of Reinforcement

7. Reference

Y. Ban, T. Yamamoto, M. Kato and Y. Ueda: New Outside Retrofitting Method

Contained Steel Plate in Concrete Member (Test Results of One-bay and Two-Layersframe). The 10th Japan Earthquake Engineering Symposium, K-15, 1998.11

8. Company

Yahagi Construction Co., Ltd. 3-19-7, Aoi, Higashi-ku, Nagoya-shi, Aichi, Japan

TEL: +81-(0)52-935-2351

9. Patent

Patent No. 3022335(Japan)




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1. Title

Aoki Seismic Retrofit Method by means of Energy Dissipation Braces

2. OutlineIn this seismic retrofit method, external energy dissipationbraces (braces consisting ofsteel pipes and friction dampers embedded in the pipes) are installed on the externalwalls of an existing building to be retrofitted so as to absorb earthquake energy input tothe building and thereby enhance its seismic performance (Photo 1). One advantage ofthis method is that by using friction dampers as response control devices, earthquakeenergy can be absorbed efficiently even under small amplitudes of the story drift angle(around 1/2000 to 1/1500 rad). This makes it possible to reduce the maximum responsestory drift angle of existing buildings to about 1/200 rad. Since friction dampers absorbearthquake energy efficiently, damper strength; frictional force of the damper, can bespecified to 200 to 400 kN per unit so that the expected effect of strengthening can be

attained simply by installing external damping braces to the external walls of thebuilding. Although the conventional strengthening methods require removing sashesand interior and exterior finishes and reinstalling them, the newly developed methodmakes it possible to use the building without interruption while retrofit work is in

progress. Thus, manpower requirements can be reduced significantly, and both cost andconstruction period can be also reduced. In addition, this retrofit method isenvironmentally considerate because the volume of waste materials to be disposed atwhich the interior and exterior parts are removed is small and noise level is low.

3. Performance of friction dampersFig. 1 shows the configuration, mechanism and the hysteretic properties of the frictiondamper. The friction damper consists of a die, a rod, an outer cylinder and an innercylinder. The diameter of the close- fitting rod in the die is slightly larger than the insidediameter of the die so that the rod is able to move in the axial direction whilemaintaining a constant frictional force. Earthquake energy causing dynamic motions ofthe building is transformed into frictional heat and is thus absorbed while the frictiondamper built into the damping brace is moving forth and back in the axial direction. Asshown Fig. 1(b), the damper shows hysteresis loops of the perfectly elasto-plastic type.Frictional forces show a slight variation as damper strokes are repeated, andenergy-absorbing performance of the damper is clearly observed.

Photo 1 Example of application of Aoki seismic retrofit method


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Photo 2 shows an example of the external damping brace installation. External dampingbraces are installed on the existing structural frame (main structure) through anchoragebases. The space between the anchoring base and the side of the existing structuralframe is filled with grout and the anchorage base is fastened to the main structure byusing prestressing steel bars.


The effect of the damping retrofit method has been confirmed through the full-scaleseismic tests using a three-story R/C school building planned to be demolished. Thecentral part of the building in the longitudinal direction (three stories, 1 x 2 span) wasused as a specimen, and concentrated loads were applied to the rooftop by the pseudodynamic testing method. The effect of the damping retrofit on the building wasconfirmed by comparing the test results obtained without retrofit and the pseudodynamic test results obtained by using the external damping braces with friction

Fig. 1 Friction damper

DieRod

Inner cylinder Outer cylinder

Force acting on circumference

(tightening force from die)

Damper axial force

Friction force

Rod

Die -500-400

-300

-200

-1000

100

200

300

400

500

-15 -10 -5 0 5 10 15

stroke[mm]

load

[kN]

(a) Configuration and mechanis (b) Hysteresis loops of damper

Photo 2 Installation method of external energy dissipation braces

Connection: secured in place with

four prestressing bars ( 23 mm dia.)

Steel i e brace: 190.7 t 19

Friction dam er 400kN

Connection with foundation: connected indirectly by post-construction anchors


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dampers. Photo 3 shows the test setting. Fig. 2 compares the results of the retrofit andnon-retrofit tests regarding the time history of response displacement and the maximumresponse. Fig. 3 shows the load-displacement relationships at the top of the building inthe retrofit and non-retrofit tests.


This retrofit method has been used in a total of 20 projects consisting of sixteen schoolbuildings, one hospital, one city office, and two apartment buildings. Photo 4 shows anexample of the installation on a school building with balconies. Photo 5 shows an

example of the application to an apartment building.

7. References1) Keiji Kitajima, Hideaki Ageta, Mitsukazu Nakanishi and Hiromi Adachi: Research

and Development of Response-Control Retrofitting Techniques by means of FrictionDamper, 12th World Conference on Earthquake Engineering, Paper No.0868, Jan.2000

2) Hajime Yokouchi, Keiji Kitajima, Hideaki Ageta, Hideaki Chikui, MitsukazuNakanishi and Hiromi Adachi: Pseudo-Dynamic Test on An Existing R/C SchoolBuilding Retrofitted with Friction Dampers, 13th World Conference on EarthquakeEngineering, Paper No.2111, Aug. 2004

Photo 3 Full view of the test

(a) Retrofit (b) Non-retrofit

Fig. 3 Load-disp. relationship at the top

- 3000

3000

-80 80

Di sp [mm]

[kN]

-3000

3000

-80 80

Di sp [mm]

[ kN]

Fig. 2 Comparison of the retrofit and non-retrofit test results

a Time histor of res onse dis lacement

-80

-60

-40

-20

0

20

40

60

80

0 1 2 3 4 5 6 7 8

Ti me [sec]

Disp[m

m]

Retrofit

Non-retrofit

(b) Maximum storydeformation angle

0

1

2

3

4

0 0. 2 0. 4 0. 6 0. 8 1R [%]

Retrofit

Non-retrofi

FL .Input ground motions; El Centro 1940 N-S record 65cm/sec


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3) Keiji Kitajima, Hideaki Chikui, Hideaki Ageta and Hajime Yokouchi: Application toResponse Control Retrofit Method by means of External Damping Braces usingFriction Dampers, 13th World Conference on Earthquake Engineering, Paper

No.2112, Aug. 2004

8. Ownership organizationAsunaro Aoki Construction Co. Ltd, 1050014, Minatoku, Tokyo.Tel: +81-3-5439-8513Fax: +81-3-5439-8531E-mail: [email protected]: www.aaconst.co.jp

9. CertificationJDPBA Certification No.1498Patent No.: 3341822(Japan)

Photo. 4 Application to an balconied school building

Friction damper

Connection

Steel Pipe Brace

Photo. 5 Application to an apartment building


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1.Title

Seismic Retrofitting Technology of Existing RC Frame Structures by External SteelBrace Reinforcement

2.OutlineFor seismic retrofit of existing reinforced concrete structure in Japan, steel braces areusually inserted into the existing reinforced concrete frame and joined to it using mortarfilling of high compressive strength. This is called the conventional retrofit method.According to this construction method the outer finishing materials such as existingwindows and sashes must be removed, after the reinforcing work is finished. This isdisadvantageous in that it lengthens the construction period, and that construction costalso becomes expensive. A new method, which installs the steel braces to the outside ofthe existing reinforced concrete frame, was considered in order to improve these defectsin the conventional method. This new method is known as the Yokosuka Type seismic

retrofit method. Comparing the new seismic retrofit method with the conventional, theprimary merits are as follows;(1)The time necessary for construction is shorter because the steel braces are directlyinstalled in the existing reinforced concrete frame structure.(2)The retrofitting can be carried out while the building is in use.(3)The cost for retrofitting is reduced by approximately thirty percent compared toconventional retrofitting.

Fig 1. Seismic retrofit methods for existing RC frame structure


The present seismic retrofitting is consists of a steel frame structure with studs in whichsteel braces are connected, resin bolts inserted into the existing RC frame structure, andgrout mortar which is filled between the steel frame and the existing RC frame.H-shaped steel members are ordinarily used for the vertical members of the framestructure and the braces. Channel and angle shaped steels are used for the lateralmembers on the outer side of the floor and roof beams, respectively. Also, the studs areconnected along the inside of the web portion of the steel frame structure for the

purpose of enhancing the bond with the steel frame by means of grout mortar. Resin

bolts are driven into the existing RC frame structure to which the steel frame structure

(a)Conventional retrofit method (b)Yokosuka Type seismic retrofit method.

Hanging wall

Skirting wall

Existing RC frame structure

Steel brace

Stud bolt

Steel frame for retrofitting

Resin anchor installedto RC frame

grout mortar

Installation of

Resin bolt

Hanging wallSkirting wall

Steel brace

Existing RC frame structure Steel frame for retrofittin

Resin anchor installed to RC frame Installation of

Resin bolt


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with braces is connected so that they may lap with the studs connected along the web insteel frame. The grout mortar, which is filled between the existing RC frame and steelframe structures, possesses the property of non-shrinkage and high compressive strength

above 30N/mm2

.

Table 1.Main materials used for seismic retrofitting

Item Materials and its specification

Steel frameVertical member, H-shaped steel; Lateral member, channel and angleshaped steel

Steel Braces H-shaped steel with larger size than 175 175Stud bolt Two kinds of 16 and19 studsResin bolt Three kinds of deformed bar with diameter of 16,19 and22mm

Grout mortar

Mortar is constructed by mixing Portland cement and fine aggregate as

well as add-mixtures. It has compressive strength over 30N/mm2 and isreinforced by spiral and mesh hoops.

4. Typical construction detailsThe main construction for the seismic retrofitting begins with driving resin bolts into theexisting RC frame structure. They are driven into the outer side of the column and beamof the story in which seismicretrofitting is necessary. Next the steelframe structure with braces and stud

bolts is installed to the outer side ofthe existing RC frame structure for

each individual story. As thechannel-shaped lateral steel in theframe is divided into two parts in thehorizontal direction, both steel partsare welded at the site along the central

portion. After installation of, the steelframe structure to the existing RCframe, form work is fixed to bothstructures so that the grout mortar doesnot flow out. Spiral and meshreinforcement are placed

simultaneously into the grout mortarfor the purpose of crack control whichmay be caused by the bolts. Anapplicable example of seismicretrofitting for one existing RC framestructure with three stories is shown infig .2.

Fig. 2 Typical details

5. Research for verification5.1 Outline of testOne-span and mono-layer frame models for the first floor and ridge direction of a

reinforced concrete school building as well as one-span and two-layer frames for the

Roo

3rd floor

2n oor

1st oor

GL

B-B section

op o eam nto groun

H-150

15

0710

H-150

15

0710

H-200200812

+2PL

-9

Site welding

Site welding

A-A section


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upper most and next lower floors were considered, and test specimens at 1/3 scale weremanufactured.The beam in the reinforced

concrete frame is joinedtogether in the plane which isidentical with the centroid ofthe column. Consequently, thecolumn-beam connection

becomes eccentric. Theconnection system thatintegrates the reinforcedconcrete frame with the steelframe built up from V typesteel braces is constituted from

anchor bolts (D13) behindresin systems and stud bolts (9 ) welded to the steel brace and filling mortar. Specimen (1FB-2), which installed thesteel brace system using this joining method from the outside of the reinforced concreteframe and, a specimen of shear wall (1FB-2W) were produced. Specimen (1FO), a bareframe without the steel brace, was also produced. A total of 3-test specimens were

produced. The detail drawing of specimen (1FB-2) is shown in Fig.3.5.2 The test method.In order to apply a horizontal force to the reinforced concrete frame reinforced by steel

braces, a PC steel bar fixed in the beam is joined to an oil jack (1000kN and 500kN).For push and pull loadings these they were amounted at right and left sides, and theloading is given for the test specimen by a half push and half pull. A level steel memberfor the mono-layer specimen was joined together in the capital portion of the column inorder to load the column with axial force, in which the two-layer specimen was given afixed axial force 0.15FcbD by a 1000kN oil jack. The horizontal loading schedule wascarried out by each cycle alternating repetition for 1/1000, 1/400, 1/200, 1/100, 1/50,1/25 radian as joint translation angle. The horizontal loading was applied only to the topof the second layer. The axial force of the column of 0.12FcbD was applied by a PCsteel bar installed in a sheath tube in the column and 300kN center hole jacks.5.3 Test resultThe envelope curves for the hysteresis loop of load-horizontal displacement of the

mono-layer specimen are shown in Fig.4. The following are also shown in the figure:cracking load, load at the yield of main longitudinal steel bar in column, maximum loadand curves for steel brace yield as well as load of plastic buckling. It was found that, themaximum load for specimens 1F0, 1FB-2, 1FB-2W occurs at 1/100rad joint translationangle. These specimens with out-of-plane deformation due to torsion were remarkable.The column also produced shear failure in each specimen. Therefore, the load alsodecreases after the maximum load. Still, it is based on the out-of-plane deformation bythe torsion increasing on specimen 1F0 and 1FB-2W where the ultimate state occurredon 1/50rad or less, after which loading became impossible. The load at which thereinforcement brace reaches the yield strength has appeared in the maximum loadvicinity. Joint translation angle is also arising on the plastic buckling at 1/50rad. The

envelope for the hysteresis loop of load-first layer horizontal displacement was obtained

Fig.3 Details of Specimen(1FB -2)

250

190

140

250

375

575300 250

625 625CL

1250 250 3002350

375

1075

125

200

1775

BH-7575107

Stiffner 4,5

Resin anchor

Stud bolt

Filler morutar

BC-300120555

PL -4 5

BH

-75754

.58


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form the horizontal loading test atwo-layer specimen in Fig.6. From this,

joint translation angle shows the

maximum load at 1/100rad. Since thesecond layer column shows a resistancemechanism by the flexural failure, thedeterioration of the strength aftermaximum load is not observed.

6. Examples in practiceThe present seismic retrofitting method

has been applied mainly to existing RCschool and office buildings since 2001. Two examples of a four-story school and athree-story office buildings which were constructed in 1970 and 1967 respectively, are

indicated by photographs 1 and 2. Damper devices are installed into the steel braces forseismic retrofitting in the latter building. The cost necessary for retrofitting by the

present method is decreased about thirty percent in comparison with that of theconventional seismic method.

7. References

(1)Structured design manual for retrofit by steel braces: development and test report,by the Architectural Division, Yokosuka City Hall, 2001.(2)E. Makitani, H. Arima and S. Marumo, Aseismic structural performance of existing

RC frame structures by external steel brace reinforcement, Proceedings of 6th ASCCSConference, Los Angeles, USA, 2000.

8. Owner ship organizationArchitectural Division of Yokosuka City Hall, Ogawa-cho, YokosukaTEL: +81-46-822-8412FAX: +81-46-822-8537E-mail:[email protected]

9. Certification

JBDPA Certification NO. 1499

Patent NO: In application

Fig.4 Envelope Curves for Mono-layer Specimen

Photo1. Retrofitted school building Photo2. Retrofitted office building


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1. Title

Tufnes method

2. OutlineThe Tufnes method uses U-shaped Tufnes forms lined with carbon fiber sheets. Theform is installed around the column, and grout is injected into the interstice between theform and column, to make an integrated structural member. This improves the shearstrength and toughness of the column.

3. Specifications for materialsTable 1 lists the specimens. Fifteen specimens in total were used. Series I includesspecimens reinforced with Tufnes forms made of 20 mm thick preformed mortar board(GFRC board), a non-reinforced specimen, and specimens lined directly with carbonfiber sheet layers. The test parameters are joint position and number of carbon fiber

sheets. Series II includes specimens reinforced with Tufnes forms made of 13-mmthick lightweight calcium boards (PB form). The joints of carbon fiber sheets are

provided in both directions, that is, parallel and normal to the loading direction. Thecarbon fiber sheet joint lap is 100 mm long for both series.

Table 1 Specimen List

CFRPlayers

pw(CF)

( )pw( )

No.1 RC-14 None None None 0.14 25.5 None

No.2 CRC-20 1 0.07 0.21 27.0

No.3 CRC-26 2 0.13 0.27 27.9

No.4 GRC-20 1 0.06 0.2 33.8

No.5 GRC-26 2 0.12 0.26 36.8 0.2

No.6 GRC-32R 3 0.18 0.32 27.8

No.7 GRC-26P 2 0.12 0.26 29.6

No.8 GRC-32P 3 0.18 0.32 29.9

No.9 GRC-38P 4 0.24 0.38 29.3

No.10 PB-20 1 0.06 0.2 36.0

No.11 PB-26 2 0.12 0.26 36.0

No.12 PB-20-FC 25.7 0.2

No.13 PB-20-S12-D29

3.084-D29 (1.03) 35.8

No.14 PB-20-RB 12-22 (1.82) 4-22 (0.61) 35.8

No.15 PB-26-N12-D22

1.864-D22 (0.62) 2 0.12 0.26 36.0 0.4

Notes:

-No.6 (GRC-32R) is a specimen made by repairing and reinforcing No.1.

Series

Series

Bothdi recti ons

B

(MPa)J oi n posi ti on

-(Common for both series) :Column section bxD=50x50 (cm), Internal height ho=150 (cm), M/QD=1.5, Amount of ties D10at 200 mm

intervals

Secti on

Normal to thel oadi ng

di recti on

Paral l el tothe l oadi ngdi recti on

Axialforcerati o

Series No Speci menRei nforci ng

method

All mainreinforcement

pg( )

Tensile mainreinforcement

pt( )

Tufnes(PB form)

12-D22(1.86)

4-D22 (0.62)

Di rect

l i ni ng

Tufnes(GFRC form)

12-D22(1.86)

4-D22 (0.62)

1 0.06 0.2

Hoop


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Fig. 1 shows the reinforcement details of the specimens of both series.

Fig. 1 Reinforcement details

5. Research for verificationThe test results of a non-reinforced specimen and specimens lined directly with carbonfiber sheets, were compared with those of the specimens using the Tufnes forms. Thecomparison verified that the reinforcement effect of the Tufnes method was equivalentto that of the direct lining method.The specimens compared were No. 10 and No. 11 of series II (Tufnes method withlightweight-calcium-board form) and No.2 and No.3 of series I (directly lined withcarbon fiber sheets). The load-deformation relationships of these specimens are shownin Fig. 2. The test parameters are the same for both types of specimens, except thereinforcement methods. Since the concrete strengths of these specimens are

significantly different, the loads in the test were divided by the shear force calculatedfrom bending strength for comparison. However, since No.2 and No. 12 have almostthe same concrete strength, their test results were compared directly.

As shown in Fig. 2, the strength of the Tufnes specimens declined when deformationwas high (R=1/33 to 1/25) because the carbon fiber sheet broke. But, the behavior upto failure was almost the same for both types of specimens. From the fact that No.2and No.12, which have almost the same concrete strength, showed a similar behavior,we can conclude that the Tufnes method provided a reinforcement effect equivalent tothe direct lining method.

CFRPCFRP

600

250

600

600

600

250

r=30

CFRP

20

L=100

30

L=100

r=30

20

30

L=100

150

13

30

150

r=30

586

586

grout

grout grout

joint lapL=100

joint lapL=100

joint lapL=100


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(a) Reinforced with 1-layer carbon fiber sheet

(b) Reinforced with 2-layer carbon fiber sheet

(c) Reinforced with 1-layer carbon fiber sheet

Fig. 2 Q- relationships (with different reinforcement methods)

- 1. 5

- 1

- 0. 5

0

0. 5

1

1. 5

No. 2( 1 )

No. 10 1

e

c

cmu

10 20 30 40

- 10- 20-30-40

R x10- 3r ad. 67

No. 2 (1-layer direct lining)No.10 (1-layer Tufnes )

- 1. 5

- 1

- 0. 5

0

0. 5

1

1. 5

- 90 - 60 - 30 0 30 60 90 120

No. 3( 2

No. 11( 2

e

c

cmu

c m m

10 20 30 40

- 10-20-30-40

R x10- 3r ad. 67

No.3 (2-layer lining)No.11(2-layerTufnes )

- 900

- 600

- 300

0

300

600

900

- 90 - 60 - 30 0 30 60 90 120

No. 2 1 B= 2

No. 12 1 B=25

e

c

kN

c m m

10 20 30 40

- 10- 20-30-40

R x10- 3r ad. 67

No.2 (1-layer direct lining B=27.0)

No.12 (1 layer Tufnes B=25.7)


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1-layer reinforcement 2-layer reinforcement

(a) Direct lining method

1-layer reinforcement 2-layer reinforcement

(b) Tufnes method (Primer mold)

Photo 1 Views of final failure


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Used for reinforcing independent columns (about 580 m2 in total) of eight buildingsincluding multifamily residential buildings, department stores and office buildings.

(a) Erection of Tufnes form (b) Seismic retrofit completed

Photo 2 Example of appli

_ Recent Development of Seismic Retrofit Methods in Japan

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