CF Anchors

SEISMIC STRENGTHENING OF REINFORCED CONCRETE WALLS

BY SR-CF SYSTEM

- Methods and Effects of Shear Strengtheningby Carbon Fiber Sheets and CF-anchors -

Yasuo Jinno Hideo TsukagoshiShimizu Corporation

JAPAN

Keywords: strengthening, reinforced concrete wall, carbon fiber sheet, CF-anchor, shear

1 INTRODUCTION

The SR-CF system[1] is a method for retrofitting existing reinforced concrete buildings againstearthquakes by laminating carbon fiber sheets. The method improves the shear strengths ofindependent columns[2], columns with side walls[3],[4], beams[5], and walls[6]. Strengthening of reinforced concrete structures with carbon fiber sheets is the best method forretrofitting existing buildings since it features small and light materials, little noise and vibration, shortworking periods, and no welding works. Carbon fiber sheets, very strong against tensile forces, arelittle adhesive to concrete surfaces and prone to peeling from concrete when a force is applied. Forthis reason, the method has been effective as long as the peeling-off is prevented, such as bywrapping a carbon fiber sheet around an independent column and forming a hoop of carbon fiber. On the other hand, the SR-CF system is effective to retrofit columns with side walls, beams, andwalls, around which hoops of carbon fiber sheets are difficult to form. The SR-CF system uses specialdevices called the CF-anchors to join the carbon fiber sheets which are separated by side walls and tofix carbon fiber sheets to reinforced concrete building frames. The use of the CF-anchor is the mostcharacteristic in this system. This paper describes the shear strengthening of walls by the SR-CF system and shear tests on thereinforced walls, and then proposes methods for assessing the shear resistance.

Fixing to the peripheral frame

Carbon fiber sheetAdhering to the carbon fiber sheet

Penetrating-type CF-anchor

Carbon fiber sheet

Adhering to the carbon fiber sheet

Penetrating the wall

Fixing-type CF-anchor

Strengthening a beam

Strengthening an independent column

Strengthening a column with a side wallStrengthening a wall

Fig 1 Outline of the SR-CF System

109

Seismic design of concrete structuresSession 6

2 METHODS FOR STRENGTHENING A WALL

2.1 Outline of CF-anchors Carbon fiber strands used in the SR-CF systemare strings of 2 to 3 mm in diameter consisting of24,000 (called the "24K" strings) or 12,000 (calledthe "12K" strings) carbon fibers, each of which isseveral microns in diameter. The CF-anchor is abundle of such carbon fiber strands, and isimmersed into epoxy resin and hardened beforeuse as in carbon fiber sheets. The CF-anchors may be classified into twocategories by the usage. One is penetrating type,and another the fixing type. The penetratinganchors are used for the shear strengthening ofcolumns with side walls. A bundle of carbon fiberstrands is passed through a hole drilled at the sidewall. The ends of the bundle are spread like a fanand glued to the carbon fiber sheet pasted on thecolumn. The bundle joins the two ends of thecarbon fiber sheet, which was separated by theside wall. Consequently, it is made possible toenvelop the column by the sheet. The fixing-type CF-anchors are used for theshear strengthening of walls. An end of the CF-anchor bundle is spread like a fan and glued to acarbon fiber sheet. The other end is inserted into ahole drilled on the concrete wall and is fixed withinjected epoxy resin. The anchors fix the edges ofa carbon fiber sheet on a concrete wall.

2.2 Methods for strengthening walls The SR-CF system strengthens walls by thecarbon fiber sheet diagonally glued on the surfaceof the wall with its edges fixed to the peripheralcolumn, beam, and floor using CF-anchors. Thismethod gives the carbon fiber sheet theperformance of a tensile brace, and increases theshear resistance of the wall. The process of strengthening a wall using CF-anchors is shown in Figure 2.(1) Smoothen the surface of the concrete wall byremoving soft section. Drill holes for installing CF-anchors on the peripheral frame (side columns,beam, and the floor).(2) Apply primers on the surface of concrete.(3) Laminate carbon fiber sheets on the wallsurface. The fibers of the sheets should bediagonally installed. Apply sheets so that the fibersof each sheet are diagonal along the oppositeangle to each other. The two carbon fiber sheetsare counted as one layer. Laminate the necessarynumbers of layers.

(1) Smoothen the surface of the wall Drill holes on the peripheral columns, beam, and floor for inserting CF-anchors

(2) Apply primers on the surface of the wall

(3) Adhere carbon fiber sheets on the surface of the wall

CF-anchors

(4) Bundle CF strands to prepare a CF-anchor(5) Insert the CF-anchor that is immersed with epoxy resin into a hole

(6) Spread the CF strands and adhere to the carbon fiber sheet

Fig.2 Process of strengthening walls

Proceedings of the 1st fib Congress

110

(4) Prepare CF-anchors by bundling the sameamount of carbon fiber strands as those containedin the carbon fiber sheets. (For example, a carbonfiber sheet of 300 g/m2 in fiber area weightcontains carbon fibers that are almost equivalentto 19 "24K" strands per a width of 100 mm. To fixtwo layers of such carbon fiber sheets byspreading the end of a CF-anchor to a width of200 mm, the CF-anchor should be prepared bybundling 19 x (200 / 100) x 2 = 76 strands.)(5) Immerse the upper halves of the CF-anchorsinto epoxy resin, and insert the ends into the holesdrilled on the columns and beam.(6) Apply epoxy resin on the edges of the carbonfiber sheets, spread the remaining halves of theCF-anchors like fans, and paste the anchors to thesheets by immersing epoxy resin. The central lineof each fan should be along the direction of fibersof a carbon fiber sheet. Since the carbon fibersheets are diagonally applied along the twodifferent opposite angles, divide the CF-anchorsinto two groups from the center of the beam, andspread and paste the anchors to the direction ofthe opposite corner. The CF-anchors for fixing thesheets to a column are similarly fixed by changingthe directions at the center of the column.

3 TEST PROGRAM

The bending shear resistance of wall specimens,that were reinforced by the SR-CF system, wastested to examine the shear strengthening effectof the SR-CF system on existing reinforcedconcrete walls. Table 1 shows the specimens, and Table 2shows the properties of the materials used. Theexperimental parameter was the method forstrengthening walls. Series 2 tests wereconducted by changing the number of carbon fibersheet layers, the angle of installing carbon fibersheets, and the kind of carbon fiber sheets. InSeries 1 tests, the authors also examined wallspecimens on which the carbon fiber sheets wereinstalled horizontally and vertically. The carbonfiber sheets used in the experiments were mainlyPAN sheets and partly carbon fiber sheets of largeYoung s modulus. Figure 3 shows the rebar arrangement and themethods for strengthening the walls, and theloading configuration. Each specimen was a wallwith columns at both sides. In Series 1 tests, thethickness of the walls at the sections to be testedwas 100 mm, the internal height was 1,200 mm,

300

590 kN590 kN

A CF-anchor is embedded for a depth of 150 mm, and is adhered to the sheets for a length of 200 mm.

R=20

Axial load of 470 kN

Lateral load

300 1800 300

2 layers of CF sheetsWallColumn

Finishing mortar ( WM-series)

1 layer of CF sheets

Adhering length=200mm

Longitudinal reinforcement of columns : 8-19 Hoops of columns : 4-@100Wall reinforcement :4-@200 double for both vertical and horizontal directions

300

CF-anchors

Wall:1 layer of CF sheet for both the face and back surfaces

Columns:2 layers of CF sheets

R=20

Lateral load Lateral load

300 2700 300

300

CF-anchorsCF sheets installed on the wall

2 layers of CF sheetsCF-anchors

CF sheets are installed along the two opposite angles (the figure shows installation of 2 layers for each angle).

Fixing CF-anchor

Penetrating CF-anchor

Angle of CF sheet

Series 1 (for WM-D-CI)

Series 2 (for No.2)

2010020

100

100

300100

1200

900

470 kN

Lateral load

Longitudinal reinforcement of columns : 8-19Hoops of columns : 4-@100Wall reinforcement :4-@150 double for both vertical and horizontal directions

WallColumn

200

2 layers of CF sheets

Fig.3 Configuration of specimens and strengthening methods

111


Table 2 Mechanical properties of materials

(a) Concrete (b) Rebar

(c) Carbon fiber sheet

(d) Carbon fiber strand

Fiber weight(g/m )

PAN type 300300

Tensile strength(MPa)34802640Pitch type

2Design thickness

(mm)0.1670.142

Type of CF sheet

PAN type (24K)

Tensile strength(MPa)4500

Density(kg/m )

1800

Type of CF strand3

Size amount(%)0.2

Compressive strength(MPa)

Series 1No.1No.2No.3No.4

27.925.626.324.728.6

Series 2

No.5 30.5No.6 26.0No.7 29.5No.8 30.5

Tensile strength(MPa)2.382.492.522.192.652.302.432.852.86

Yield strength(MPa)

Series 1

19

419

474330438344

Series 2

Tensile strength(MPa)

519450498

539

4

.

and the internal length was 1,800 mm. The side column was 300 mm x 300 mm in section. The Series2 specimens were walls of 100 mm in thickness, 900 mm in internal height, and 2,700 mm in internallength with side columns of 300 mm x 300 mm in section. Fundamentally, the specimens were modelsof walls in buildings that have been designed according to the Japanese Building Code before 1971,and used round bars as reinforcement. The ratio of shear reinforcing bar of the columns was 0.084%,and the ratio of wall reinforcement was 1.26%. To ensure shear failure in the walls, the walls weredesigned to be flexurally strengthened by increasing the longitudinal reinforcement in columns.

4 TEST RESULTS

Table 3 shows the results of the experiments. Figure 5 shows the final failure states of SpecimenNo.1, which was not strengthened, and Specimen No.2, which was strengthened. Load-deformationcurves are shown in Figure 4. All of the Series 2 specimens showed the ultimate strength and failed inshear at drift angles of around 1/200 rad. All specimens showed sharp drops in load after the fracture.In Specimen No.1, which was not reinforced, the wall and columns failed in shear as one body.

Table 1 List of specimens

Strengthening of the wallSpecimenSeries

W-NW-B-C1WM-N

WM-D-C1No.1No.2No.3No.4No.5

No.6

No.7No.8

Strengthening of columns Notes

No strengthening

1Front:1 layer, rear:1 layer 2 layers

No strengtheningWith finishing mortarFront:1 layer, rear:1 layer 2 layers

No strengthening

2

Front:2 layersFront:4 layersFront:3 layers, rear:3 layers

(2 layers of PAN sheets and 2 layers of pitch sheets)2 layers

(2 layers of PAN sheets and 2 layers of pitch sheets)Front:4 layers No CF-anchorsFront:2 layers, rear:2 layers

Vertically and horizontally

Diagonally

DiagonallyDiagonally

Diagonally

45 degrees

DiagonallyDiagonally

Diagonally Front:4 layers

Front:4 layers


112

-2.0

-1.0

0.0

1.0

2.0

-30 0 30 60

Late

ral L

oad

(MN

)

Horizontal deformation (mm)

WM-D-C1(2 layers)

-2.0

-1.0

0.0

1.0

2.0

-30 0 30 60

Late

ral L

oad

(MN

)

Horizontal deformation (mm)

WM-N(no strengthening)

-3.0

0.0

3.0

-6 0 6 12

Late

ral L

oad

(MN

)

Horizontal deformation (mm)18

No.1(no strengthening) -3.0

0.0

3.0

-6 0 6 12

Late

ral L

oad

(MN

)


No.8(4 layers)

-3.0

0.0

3.0

-6 0 6 12

Late

ral L

oad

(MN

)


No.4(6 layers)

-3.0

0.0

3.0

-6 0 6 12

Late

ral L

oad

(MN

)


No.2(2 layers)

Fig.4 Load-deformation curves

Specimen No.1, drift angle of 1/400 rad

Specimen No.1, final state of failure

Specimen No.2, drift angle of 1/400 rad

Specimen No.2, final state of failure

+-

(Specimen No.2 was observed from the back surface, which was not strengthened)

Fig.5 Crack patterns

-2000

0

2000

4000

-1100 -550 0 550 1100Location (mm)

-2000

0

2000

4000

6000

-2000

0

2000

4000

+1/1200+1/800+1/400+1/200+1/100

Stra

in (1

0 )-6

Stra

in (1

0 )-6

Stra

in (1

0 )-6

Fig.6 Strain distribution on carbon fiber sheet

113


On the other hand, the columns of the reinforced specimens showed no external change when the wallsections failed and maintained a shear strength that was equivalent to a resistance of up to adeformation angle of 1/25 rad. All of the specimens that were strengthened with diagonally installed carbon fiber sheets showedmaximum resistance values larger than the non-reinforced specimen. The shear resistance was moresignificantly increased in specimens with higher degrees of strengthening. On the other hand, Specimen W-C1-B of Series 1, to which carbon fiber sheets were vertically andhorizontally applied, showed no increase in resistance compared to the non-reinforced specimen W-N. Figure 6 shows the strain distribution on carbon fiber sheets laminated on the wall surface ofSpecimen No.2. The CF-anchors were glued to the carbon fiber sheets by changing the directions atthe centers of the beam and the columns. Therefore, the direction of the CF-anchor fibers agreed withthe direction of the sheet fibers at a half of the carbon fiber sheets on the wall. However, the strain onthe carbon fiber sheets was uniformly distributed regardless of the directions of CF-anchors. In all Specimens Nos. 2 to 8, the strain on the carbon fiber sheets on columns did no reach200x10-6 before they were fractured. Therefore, the strengthening of the columns does not affect theshear resistance of walls.

5 DISCUSSION

5.1 Estimation of ultimate strength To estimate the shear force that acts on the carbon fiber sheets, the authors assumed that the wallsdeformed as shown in Figure 7. The authors ignored bending deformation and assumed that sheardeformation was dominant and the walls deformed into parallelograms. The carbon fiber sheets,diagonally laminated on the walls, were regarded as tensile braces installed along existing walls.Assuming that the strain on the carbon fiber sheets is uniform over the entire wall surface, the shearforce working on the sheets is expressed with Equation (1). The tensile force of the carbon fiber sheetsis transmitted to the upper and lower beams and the columns on both sides. The horizontal componentof the force that is transmitted to the upper beam is the imposed shear force.The value of cf and Ecf are different from material test values, and should be determined fromexperiments.

Table 3 Test results

* : Qcf denotes the difference in shear force between the specimens with/without strengthening at a drift angle of 1/400 rad

Shear force at each drift angle (kN)

No.1No.2No.3No.4No.5No.6No.7No.8

Maximum load(MPa)

WM-D-CWM-N

W-B-C1W-N

Specimen Qcf *(MPa)1/800 (rad) 1/400 (rad) 1/200 (rad)

1363 1903 24391407 1938 24881586 2152 27981606 2096 26231419 2074 24211464 1920 24191465 1942 2602

1108 1551 20911363 1733 1851908 1247 1511998 1321 1577910 1255 1584

352386600544523369390

-485

-66-

2439248827982623242124192602

21751851151115771584


114

Qcf = Ltcfcfsincos (1)cf = Ecf(/h)sincos (2)

where,Qcf: shear force imposed on the carbon fiber sheets,L: internal length of the wall (1,800 mm for Series 1 and 2,700 mm for Series 2),h: height of the wall (1,200 mm for Series 1 and 900 mm for Series 2),tcf: thickness of the carbon fiber sheetscf: apparent strength of the carbon fiber sheetsEcf: apparent Young s modulus of the carbon fiber sheets,: horizontal deformation at the top of the wall, and: offset angle of the carbon fiber sheets (sin=0.555 and cos=0.832 for Series 1, and sin=0.316 and cos=0.949 for Series 2).

Figure 8 shows changes in apparent stress of the carbon fiber sheets. Regarding the difference inload during deformation between strengthened specimens (Nos. 2, 8, and 4) and non-strengthenedspecimen (No.1) as the horizontal shear force Qcf working on the carbon fiber sheets, cf value wasdetermined using Equations (1) and (2) as plotted on the Y axis.

Assumed deformation of a wall and strain of carbon fiber (CF) sheets

L

h

dL

dLsin

dLsintcfEcfcfFixed to the beam

Force equilibrium of CF sheet

dLsintcfEcfcfFixed to the beam

dLsintcfEcfcfFixed to the column

dLsintcfEcfcfFixed to the column

Strain of CF sheets cfElastic modulus Ecf

Fig.7 Model for calculating the shear force imposed on carbon fiber sheets

0

400

800

1200

1600

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Exp

erim

enta

l stre

ss v

alue

s of

carb

on fi

ber

shee

ts (M

Pa)

No.2 (2 layers)No.8 (4 layers)No.4 (6 layers)Equation(2) (Ecf=230GPa)

Drift angle (10 rad)-3

Fig.8 Changes in apparent stress of carbon fiber sheets

0

1000

2000

3000

0.0 0.3 0.6 0.9 1.2

She

ar fo

rce

at e

ach

drift

ang

le Q

(kN

)

Thickness of carbon fiber sheets tcf (mm)

Q = 2138 + 0.842Ltcfsincos(R= 0.9845)

Q = 1610 + 0.680Ltcfsincos(R= 0.9539)

Shear force at 1/400 radShear force at 1/200 rad

No.7(No CF-anchors)No.3(4 layers on one side only)

(No.1,2,8,4)

Fig.9 Relationship between shear force and amount of strengthening

115


The figure also shows values calculated by substituting Ecf = 230 GPa in Equation (2), whichrepresent a state of complete detachment of the carbon fiber sheets from the concrete surface. Whenthe deformation was small, the apparent rigidity of the carbon fiber sheets was high, and the apparentstrain was larger than the value calculated using Ecf = 230 GPa. The difference is likely attributable tothe adhesion of the carbon fiber sheets to the concrete surface. As the deformation progressed, theapparent strain of the carbon fiber sheets approximated the calculated values since the sheets wereincreasingly peeled off from the concrete surface. Figure 9 shows the experimental shear forces at drift angles of 1/400 and 1/200 rad as a function ofthe amount of carbon fiber sheets, and the linear regression equations as well. The factor of thesecond term corresponds to the apparent strength of the carbon fiber sheets cf of Equation (1).cfwas 680 MPa at a drift angle of 1/400 rad, and 842 MPa at 1/200 rad. Generally, the drift angle at the ultimate strength for the potential shear failure mode is reportedlyabout 1/250 rad [7]. However, the authors used the strength at a drift angle of 1/400 to calculate theultimate strength of the walls since cf may remain almost constant after a drift angle of 1/400 rad asshown in Figure 8 (No.2), and the equations ignore bending deformation. Therefore,

cf = 680 (MPa) (3)

is used for Equation (1). The ultimate strength of a wall is determined asthe sum of the yielding strength of the wall beforestrengthening and the shear force Qcf that isimposed to the carbon fiber sheets, as derived byEquation (1). The yielding strength of the non-strengthened wall is the smaller of its flexural andshear strengths (Any equation is available as longas the one can appropriately estimate thestrength). Since this strengthening system doesnot improve the structural characteristics ofexisting walls but forms braces of carbon fibersheets along the walls, Qcf values aredetermined using Equation (1) regardless offailure modes. It should be noted that strengthening of a wallwith shear failure mode using this system mayincrease the shear strength to exceed its flexuralstrength, but this system does not necessarilyconvert the shear failure mode into flexural failuremode. Since carbon fiber sheets and CF-anchorssuffer brittle failure, laminated carbon fiber sheetson flexural failure mode walls may cause suddendrops in strength due to Qcf values when thecarbon fiber sheets fail. Therefore, this systemshould only be implemented to strengthen shearfailure mode walls, and the strengthening designshould be preferable to strength resistant typestructures. Figure 10 compares the Qcf values calculatedusing Equation (1) and experimental values. Theexperimental values are the difference between theshear strength values of the strengthened and non-strengthened specimens. Figure 10(a) showsexperimental Qcf values from the shear strength

0

200

400

600

800

0 200 400 600 800

Exp

erim

enta

l Qcf

val

ues

at 1

/200

rad

(kN

)

Qcf values calculated from cf=680MPa (kN)

(b) Qcf estimated for ultimate strength

0

200

400

600

800

0 200 400 600 800

Exp

erim

enta

l Qcf

val

ues

at 1

/400

rad

(kN

)

Qcf values calculated from cf=680MPa (kN)

(a) Qcf estimated for 1/400 rad

Series 1Series 2

Pitch fiberNo CF-anchorscal=exp

4 layers on one side

Fig.10 Comparison between calculated and experimental Qcf values


116

during a drift angle of 1/400 rad, and Figure 10(b) derived the Qcf values from the shear strengthduring a drift angle of 1/200 rad, when the ultimate strength was almost reached. Excluding specimensthat used pitch carbon fiber sheets, strengthened with 4 layers only at one side, or did not use CF-anchors, the experimental data showed a good agreement with the calculated values.

5.2 Upper limit of strengthening This system strengthens a wall by increasing the apparent rigidity of the laminated carbon fibersheets by gluing the carbon fiber sheets to the concrete surfaces of the wall. Laminating carbon fibersheets with over a certain number of layers does not increase the strengthening effect since suchlamination causes the carbon fiber sheets to detach from the concrete surfaces. Specimen No. 4 with 3 layers at each side and 6 layers in total, was on the regression line as shownin Figure 9, showing that 3 layers on one side or 6 layers in total is not the upper limit of strengthening.On the other hand, Specimen No. 3, which had 4 layers on one side, showed the ultimate strength of2.49 MN. This was significantly lower than the regression line although the total number of layers was4, less than 6 as in No. 4. This suggests that the upper limit of strengthening exists between 3 and 4layers of carbon fiber sheets per side of a wall. Since the peeling of carbon fiber sheets from the concrete surface affects the upper limit ofstrengthening, the upper limit is not a value converted into ratio of wall reinforcement but is given as afunction of the thickness of carbon fiber sheets. In this study, the upper limit of strengthening wascalculated using Equation (1) and as follows: 3 layers of 300 g/m2 sheets (design thickness: 0.501 mm) per side, or for both sides of a wall to bestrengthened; 6 layers of 300 g/m2 sheets (design thickness: 1.00 mm) in total.

5.3 Effects of CF-anchors Figure 9 shows the experimental results of No. 7, which was laminated with carbon fiber sheetsusing no CF-anchors, marked with dark circles (). At a drift angle of 1/400 rad, no difference in shearstrength was observed by the presence of CF-anchors. The carbon fiber sheets were effective inretrofitting the walls. The effects of CF-anchors were not significant at drift angles of less than 1/400rad. On the other hand, at a drift angle of 1/200 rad, the shear strength of No.7 was lower than that ofNo. 4, showing the effects of CF-anchors to increase the strength at drift angles of over 1/400 rad.Considering that walls are prone to failure near the peripheral frames, CF-anchors are morenecessary.

6 CONCLUSION

The authors proposed a method for shear strengthening reinforced concrete walls using carbonfiber sheets and CF-anchors, and tested their effects. The authors obtained the following results:(1) The shear strength of a wall is improved by diagonally laminating carbon fiber sheets and fixing the

edges to the peripheral frame with CF-anchors so that the carbon fiber sheets act as tensile braces.The contribution of the carbon fiber sheets is calculated as:

Qcf = Ltcfcfsincos (1)where, cf = 680 MPa, and tcf < 0.5 mm for one side and 1.0 mm for two sides combined.

(2) CF-anchors are necessary to maintain the strengthening effect at drift angles of over 1/400 rad, atwhich the peeling-off of the carbon fiber sheets from the concrete surface may be significant, and itis also necessary even if failure may occur near the peripheral frame.

ACKNOWLEDGMENTS This report includes some of the results obtained in a project of the Petroleum Energy Center,entitled "Development of pitch carbon fiber reinforcement materials for concrete structures."

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REFERENCES[1] SR-CF System Research AssociationDesign Guidelines for SR-CF System, Feb. 2002 (inJapanese)[2] Y.JinnoStructural Behaviors of Reinforced Concrete Columns Strengthened by Carbon FiberBlanket, 42nd International SAMPE Symposium, Vol.42, No.1, pp.117-124, May.1997,[3] K.Masuo, S.Morita, Y.Jinno, H.WatanabeAdvanced Wrapping System with CF-anchor -Seismic Strengthening of RC Columns with Wing Walls-, FRPRCS-5, Vol.1, pp.299-308May 2001[4] Y.Matsuzaki, K.Nakano, H.Fukuyama, S.WatanabeAdvanced Wrapping System with CF-anchor -Shear Strengthening of RC Columns with Spandrel Wall-, FRPRCS-5, Vol.2, pp.813-822May 2001[5] Y.Jinno, H.Tsukagoshi, Y.YabeRC Beams with Slabs Strengthened by CF Sheets and Bundlesof CF Strands, FRPRCS-5, Vol.2, pp.981-988May 2001[6] Y.Jinno, H.TsukagoshiStructural Properties of RC Walls Strengthened by Carbon Fiber Sheetsand CF-anchors, Summaries of Technical Papers of Annual Meeting -Architectural Institute of Japan,Structures IV, pp.67-68, Sep.1999, (in Japanese)[7] Japan Building Disaster Prevention AssociationRevised Edition, Standards for Evaluation ofSeismic Capacity and Comments for Existing Reinforced Concrete Buildings, 2001 (in Japanese)


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