Effectiveness of high performance ﬁber-reinforced cement...

Construction and Building Materials 68 (2014) 476–490

Contents lists available at ScienceDirect

Construction and Building Materials

journal homepage: www.elsevier .com/locate /conbui ldmat

Effectiveness of high performance fiber-reinforced cement compositesin slender coupling beams

http://dx.doi.org/10.1016/j.conbuildmat.2014.06.0890950-0618/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Address: School of Urban and Environmental Engineer-ing, Ulsan National Institute of Science and Technology (UNIST), 100 Banyeon-ri,Eonyang-eup, Ulju-gun, Ulsan, 689-798, Republic of Korea. Tel.: +82 52 217 2814.

E-mail address: [email protected] (M. Shin).

Myoungsu Shin a,⇑, Seong-Woo Gwon a, Kihak Lee b, Sang Whan Han c, Yeong Wook Jo d

a School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Koreab Department of Architectural Engineering, Sejong University, Seoul, Republic of Koreac Department of Architectural Engineering, Hanyang University, Seoul, Republic of Koread Residential Structural Team, Samsung C&T Corporation, Seoul, Republic of Korea

h i g h l i g h t s

� HPFRCC greatly contributed to reducing the cracking damage and shear distortion of coupling beams.� The HPFRCC specimens showed lower percentages of stiffness degradations than the normal concrete.� The conventionally reinforced specimen eventually suffered shear failure even with HPFRCC.� The diagonally reinforced specimens achieved much higher shear stresses than the code limit.

a r t i c l e i n f o

Article history:Received 19 December 2013Received in revised form 27 May 2014Accepted 30 June 2014Available online 24 July 2014

Keywords:High performance fiber-reinforced cementcompositeSlender coupling beamDiagonal reinforcementSeismic performance

a b s t r a c t

This study aims at exploring the use of high performance fiber-reinforced cement composites (HPFRCCs)as an innovative method of improving the seismic performance of slender coupling beams. Also, the effectof diagonal reinforcement in slender coupling beams is evaluated in comparison to conventional rein-forcement. Three 1/2-scale coupling beams having the length-to-depth ratio of 3.5 were tested under cyc-lic lateral loading up to about 10% drift. The key test variables were material type and reinforcementlayout. For the material type, normal concrete and HPFRCC using PVA discrete fibers of 2% volumetricratio were compared. The mix proportions of the HPFRCC were determined through detailed materialtests. Two types of reinforcement layout were tested: conventional and diagonal layout. Furthermore,the strength and stiffness characteristics of reinforced concrete or HPFRCC coupling beams are examinedby assembling a database of almost all coupling beam tests available in literature.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction and background

Reinforced concrete (RC) coupling beams in coupled wall sys-tems designed based on current codes [1–5] are expected toendure significant inelastic deformations, when subjected todesign-level earthquakes. Suitably devised coupling beams maybe able to not only survive over large displacement demands, butalso serve as a primary source for energy dissipation [6].

In high-rise residential buildings of which the seismic force-resisting system consists of structural walls combined with RCslab–column frames, the depth of coupling beams is typically lim-ited due to relatively small story heights [7]. Although this type of

construction has been popularly used for many decades, the seis-mic design of slender coupling beams has not been investigatedmuch. Most of the previous studies focused on deep couplingbeams to invent proper methods of ensuring satisfactory ductilityand relieving reinforcement congestion [8–11]. Some design codes(e.g. ACI 318-11 [2]) allow conventional reinforcement layout to beused for slender coupling beams having the length-to-depth ratiolarger than 2, even in high seismic zones. This appears based onthe presumption that diagonal reinforcement layout would neithermuch increase the shear strength nor improve the seismic perfor-mance. The possibility of sliding shear failure [6] that typicallyoccurs in conventionally reinforced coupling beams is neglectedin the case of slender coupling beams.

High performance fiber-reinforced cement composites(HPFRCCs) are characterized by strain-hardening response in direct(uniaxial) tension by developing numerous micro-cracks withassistance of engineered fibers [12–16]. HPFRCCs generally show

Nomenclature

Ag gross area of beam sectionAs area of longitudinal reinforcementAv area of transverse reinforcementAvd area of each group of diagonal reinforcementb beam widthd effective depth of beamEc modulus of elasticity of concretefcd design compressive strength of concretefcm measured compressive strength of concretefu measured ultimate strength of reinforcing steelfy measured yield strength of reinforcing steelfyl yield strength of longitudinal steelfyt yield strength of transverse steelGc shear modulus of concreteh beam depthIg gross moment-of-inertia of beam sectionK0,cal theoretical initial stiffnessK0,exp measured initial stiffness at the first loading cycleKy,exp measured yield stiffnessl beam lengthMn,0 nominal moment strength computed ignoring effects of

axial force

Mn,N nominal moment strength computed considering ef-fects of axial force

Np,max beam axial force imposed at the time of the maximumload Pmax

Pu ultimate beam shear assumed to be governed by nomi-nal moment strength

Pmax measured maximum lateral loadPn,0 lateral load corresponding to the nominal moment

strength Mn,0, Pn,0 = 2Mn,0/lPn,N lateral load corresponding to the nominal moment

strength Mn,N, Pn,N = 2Mn,N/ls spacing of transverse reinforcementVn nominal shear strengtha angle between diagonal reinforcement and the longitu-

dinal axis of beamDy yield displacementey measured yield strain of reinforcing steelU0 factor accounting for the relative importance of shear to

flexural deformationc shear distortion, (cL + cR)/2cL, cR angular changes in 90-degree angles at the side face of

coupling beam

M. Shin et al. / Construction and Building Materials 68 (2014) 476–490 477

much higher ductility under both tension and compression thannormal concrete [13,17–19]. Thus, confinement requirementsmay be relaxed in members of high reinforcement congestion byusing HPFRCCs [18]. When subjected to seismic forces, in particu-lar, HPFRCCs are deemed to improve energy dissipation throughfiber bridging over micro-cracks and by providing excellent bondbetween reinforcing steel and cement composites [13].

During the last decade, several leading research groups playedmajor roles in large-scale experimental investigations for the effec-tiveness of HPFRCCs in earthquake-resistant structures. Most ofthem tested shear-dominated building components such as deepcoupling beams, beam–column joints, slab–column connections,and infill panels [20–27]. From the previous studies, it has beenrevealed that HPFRCC materials were effective in improving seis-mic performance such as ductility, energy dissipation, and damagecontrol. However, the use of HPFRCCs in flexure-dominated mem-bers has not been investigated much.

Given the aforesaid concerns, this study explores the use ofHPFRCCs as an innovative method of improving the seismic capac-ity of slender coupling beams through an experimental program.Detailed material tests were conducted to determine the mix pro-portions of the HPFRCC used for the construction of the couplingbeam specimens. Also, the effectiveness of diagonal reinforcementlayout in slender coupling beams is investigated in comparisonwith conventional reinforcement layout. Furthermore, the strengthand stiffness characteristics of RC or HPFRCC coupling beams areexamined by assembling a database of almost all coupling beamtests available in literature.

2. Descriptions for coupling beam tests

In this study, three approximately 1/2-scale coupling beamspecimens were tested under cyclic lateral loading. Each specimenrepresented a slender coupling beam that is part of a coupled wallsystem combined with flat plates in a tall residential building. Thesignificance of this study is that (1) a HPFRCC and/or (2) diagonalreinforcement were applied in the tested slender coupling beamsfor the purpose of improving the seismic performance.

2.1. Specimen details and test variables

Fig. 1 illustrates dimensions and reinforcing details of the threespecimens: 1CF2Y, 1DF0Y, and 1DF2Y. In all specimens, the beamwidth (b) is 250 mm, the beam depth (h) is 300 mm, and the length(l) of the beam is 1050 mm, so that the length-to-depth ratio (l/h) is 3.5.

Table 1 summarizes design details and test variables of thethree specimens. The key test variables were (1) material typeand (2) reinforcement layout. For the material type, a single typeof HPFRCC using Polyvinyl Alcohol (PVA) fibers of 2% volumetricratio was compared with normal concrete. Specimens 1CF2Y and1DF2Y were made with the HPFRCC, while 1DF0Y was with normalconcrete.

Two types of reinforcement layout were tested: conventionaland diagonal layouts (Fig. 1). Specimen 1CF2Y was reinforced withthe conventional layout, while the other two specimens were withthe diagonal layout. In the conventional layout, longitudinal barswere arranged horizontally at the top and bottom of the beam,and transverse reinforcement was designed per ACI 318-11, §21.5.In the diagonal layout, four longitudinal bars were clustered as adiagonal group, and two mirror-opposite groups of diagonal barspassed through each other in the central region of the beam (seethe elevation views in Fig. 1 and the section views in Fig. 10), accord-ing to ACI 318-11, §21.9.7. Transverse reinforcement were providedfor the entire section of the beam as an alternative to enclosing eachgroup of diagonal bars, and intermediate horizontal bars used toanchor transverse ties had a short embedded length (i.e., 150 mm)into the stubs in order not to develop yielding.

The amount of longitudinal bars (Table 1), which are diagonal in1DF0Y and 1DF2Y or horizontal in 1CF2Y, was determined so thatthe ultimate shear stress (Pu/bh) expected in the beam is approxi-mately equal to 0:5

ffiffiffiffiffifcd

p(MPa) in all specimens, based on reaching

the nominal moment strength at the beam ends. (This designmethod [38,39] is deemed reasonable because the shear stresslevel is considered one of the key factors affecting the performanceof coupling beams.) Here, Pu is the ultimate beam shear assumed tobe governed by the nominal moment strength of the beam thatwas calculated using the design yield strength of reinforcing steelequal to 420 MPa. Also, fcd is the design compressive strength of

Fig. 1. Elevation views of test specimens and reinforcing details (units: mm).

Table 1Specimen details and test variables.

Specimen 1CF2Y 1DF0Y 1DF2Y

Beam width, b (mm) 250 250 250Beam depth, h (mm) 300 300 300Length-to-depth aspect ratio, l/h 3.5 3.5 3.5Material type HPFRCC (PVA 2%) Concrete HPFRCC (PVA 2%)Measured comp. strength (fcm) of concrete or HPFRCC (MPa) 49.2 29.2 49.2Reinforcement layout Conventional Diagonal DiagonalLongitudinal reinforcement 3 D25 @ top & bot. 4 D25 @ each diag.a 4 D25 @ each diag.a

Angle (a) of diagonal reinf. (�) – 8 8Transverse reinforcement, Av @ s 3 D10 @ 65 mm 2 D13 @ 120 mm 2 D13 @ 120 mm

a Area of each group of diagonal reinforcement, denoted by Avd.

478 M. Shin et al. / Construction and Building Materials 68 (2014) 476–490

concrete or HPFRCC equal to 45 MPa. In all specimens, longitudinalbars were anchored in the stubs with heads at the ends and theembedment length equal to 750 mm, which was more than twiceas large as the required development length for No. 25 headed bars(ldt) by ACI 318-11, §12.6. Also, the clear cover to transverse rein-forcement was 25 mm.

(a) Stub construction

Fig. 2. Construction o

Specimen 1DF0Y signifies a diagonally reinforced RC couplingbeam designed per §21.9.7 of ACI 318-11. Specimen 1DF2Y hasthe same design details with 1DF0Y except for using the HPFRCCinstead of normal concrete. Specimen 1CF2Y stands for a conven-tionally reinforced HPFRCC coupling beam that falls into theclassification of ‘‘special moment frame members’’ specified in ACI

(b) Shear key & dowel bars

f test specimens.

Table 2Properties of fibers included in HPFRCC.

Fiber type Density (g/m3) Tensile strength (MPa) Elastic modulus (GPa) Diameter (lm) Length (mm) Strain at fracture

PVA 1.3 1600 25 39 12 0.10

Table 3Properties of reinforcing steel.

Barsize

Yield strain,ey

Yield strength, fy

(MPa)Ultimate strength, fu

(MPa)

D10 0.286 538 632D13 0.310 540 657D25 0.253 478 635


318-11, §21.5. Hence, concrete contribution to the shear strengthwas taken zero in designing shear reinforcement of 1CF2Y. It isnoted that a smaller spacing of transverse reinforcement is requiredin the conventional layout (i.e., 65 mm) than in the diagonal layout(i.e., 110 mm).

2.2. Construction and materials

In each specimen, the coupling beam portion had been cast first(Fig. 2), and the top and bottom stubs that simulated the behaviorof coupled shear walls were cast about a week later. The ends ofthe beam were connected to the stubs with the help of tooth-shaped concrete shear keys and U-shaped dowel bars (Fig. 1), aswell as the dowel action of longitudinal or horizontal bars(Fig. 2); the feasibility of utilizing precast coupling beams was par-tially examined. For the two HPFRCC specimens, the HPFRCC was

Table 4Mix proportions for the detailed material tests.

Mixture Bindera (wt.%) Filler (wt.%)

Silica sand CaCO3

No. 1 72.3 25.0 –No. 2 67.4 30.0 –No. 3 67.1 10.0 20.0No. 4 64.2 13.0 20.0No. 5 57.8 – 40.0No. 6 56.2 – 41.0

a Binder: OPC (43%) + FA (40%) + OMEGA (9%) + SF (3%) + CSA (5%).b PCM: dry Premixed Cement Mortar (Binder + Filler + CA); OPC = Ordinary Portland Ce

Admixture (super-plasticizer, viscosity agent).

Fig. 3. An illustratio

used only for the beam portion, while the stubs were made withnormal concrete.

Table 1 summarizes the compressive strength (fcm) of theHPFRCC or normal concrete measured on the testing day. For thenormal concrete, the maximum aggregate size was 25 mm, whilethe HPFRCC contained neither coarse nor fine aggregates. Physicalproperties of the PVA fibers used are summarized in Table 2. Also,the measured properties of reinforcing steel are shown in Table 3.The mix proportions of the HPFRCC were determined from preli-minary material tests presented later; No. 6 mixture shown inTable 4 was used for the coupling beam specimens.

2.3. Test setup and loading history

Fig. 3 illustrates the test setup and the assumed distributions ofinternal resultant forces. The specimen was tested in a configura-tion that the coupling beam was vertically oriented. The bottomRC stub was anchored to the strong floor, and the top RC stubwas linked to the horizontal segment of the loading frame byanchor rods. Reversed cyclic loading was statically applied by ahydraulic actuator to the vertical segment of the loading frame,which was rigidly connected to the horizontal segment. The longi-tudinal axis of the actuator was arranged to pass through the mid-span of the coupling beam, in order to simulate zero moment at themidspan. Positive and negative loading directions are indicated inFig. 3.

CA (wt.%) Fiber (vol.%) W/PCMb (wt.%)

CW150

– 2.7 2.0 20.0– 2.6 2.0 20.0– 2.9 2.0 20.5– 2.8 2.0 20.50.5 1.7 2.1 22.01.0 1.8 2.1 22.0

ment, FA = Fly Ash; SF = Silica Fume, CSA = Calcium Sulfur Aluminate; CA = Chemical

n of test setup.

Fig. 5. Dog-bone specimen dimensions for direct tensile tests (units: mm).


Two vertical pin-ended supports (Fig. 3) were used to preventthe top of the coupling beam from rotating about an out-of-planeaxis, leading to the moment and shear distributions illustrated inFig. 3. The bottom of each support was anchored to the strong floor,and the top was to the horizontal segment of the loading frame.Also, the supports were to restrain the axial elongation of thebeam. In a coupled wall system, coupling beams attempt to elon-gate axially when earthquake loading causes severe concretecracking and inelastic residual strains in the longitudinal bars [6].However, in-plane stiffness of the adjacent walls restrains suchelongation, consequently imposing compression in the couplingbeams [28].

With respect to the instrumentation (Fig. 14) used in each test,twelve LVDTs (eight vertical, L1–L4 and L9–L12, and four diagonal,D1–D4) were installed on one side of the beam to estimate overallshear distortion in an average sense. Also, two wire potentiometers(L5 and L7 at bottom, or L6 and L8 at top) were installed at eachend of the beam, to evaluate the development of flexural hingingmechanism. Electrical strain gages were attached at multiple loca-tions on longitudinal bars, transverse hoops, and dowel reinforce-ment. Each of the two vertical supports was instrumented with aload cell to monitor the level of axial load that was imposed inthe coupling beam.

Reversed displacement cycles shown in Fig. 4 were staticallyapplied up to larger than 10% drift ratio. Three or two consecutivesame-drift cycles were tested to examine strength and stiffnessdegradations under repeated loading.

3. Preliminary material tests for HPFRCC

Preliminary material tests had been conducted to determine themix proportion of the high performance fiber-reinforced cementcomposite (HPFRCC) that was used to construct the coupling beamspecimens.

3.1. Material mixture types

A total of six HPFRCC mix proportions in Table 4 were examined,in which ‘‘CA’’ indicates chemical admixtures (e.g., super-plasticizer,viscosity agent), and ‘‘PCM’’ stands for dry premixed cement mortarconsisting of binder, fillers, and chemical admixtures. In all six types,the volumetric ratio of PVA fibers was approximately 2.0%, and thewater/PCM ratio (W/PCM) was kept roughly 20–22%. None of thesix HPFRCC mixtures contained coarse aggregate.

3.2. Material test methods

For each HPFRCC mixture type, at least two dog-bonespecimens shown in Fig. 5 were tested subjected to direct(uniaxial) tension. The design and fabrication of the dog-bone

Fig. 4. Loading history.

specimens were done according to JSCE recommendations [29].The specimens were taken out of the molds at 24 h after casting,and placed in a water tank for moisture curing. All the specimenswere tested in a dry condition at the age of 28 days includingone day for drying.

Fig. 5 shows the test setup used for the direct tensile tests. TwoLVDTs were mounted along the sides of the specimen in the load-ing direction, in which the gage length was equal to 80 mm. Thedirect tension tests were displacement-controlled, with an actua-tor travel velocity of roughly 0.5 mm/min based on JSCE recom-mendations [29].

3.3. Material test results

The direct tensile stress–strain responses of the six types ofHPFRCC specimens are compared in Fig. 6; for each mixture, twoor three similar results were acquired, and one of them is selectedfor this comparison. The average of the two LVDT measurements(Fig. 5) was used to estimate the tensile strain. All the HPFRCCdog-bone specimens showed strain-hardening behavior in tension.In general, the toughness increased when a larger amount of fillersuch as silica sand and/or calcium carbonate (CaCO3) was used as areplacement of binder. In particular, the use of calcium carbonate,compared with silica sand, generally resulted in the better ductilityand strength. The specimen made of No. 6 mixture presented thehighest ductility, developing numerous well-distributed micro-cracks (Fig. 7); the maximum tensile strain exceeded 5%, and thetensile strength was approximately 7 MPa. (In the dog-bone testof No. 6 mixture, the tensile stress suddenly dropped only afterthe major crack shown in Fig. 7 developed. This implies that the

Fig. 6. Direct tensile stress–strain responses of HPFRCC dog-bone specimens.

Fig. 7. Numerous micro-cracks in a dog-bone specimen of No. 6 mixture.

Fig. 8. Typical compressive stress–strain responses of HPFRCC and normal concrete(adopted from Shin et al. [37]).


tensile stress–strain curve up to about 5% strain in Fig. 6 was notaffected by the major crack.) Therefore, No. 6 mixture was chosento be used for the construction of the coupling beam specimens.

In Fig. 8, the compressive stress–strain response of No. 6HPFRCC mixture is compared with that of normal concrete havinga similar strength. It is clearly shown that the stress–strain rela-tionship of the HPFRCC is more ductile than that of normal con-crete; the maximum strain of the HPRCC in compression is muchlarger. This implies that the members made of the HPFRCC woulddemonstrate much better ductility.

4. Analysis of coupling beam test results

In this section, the cracking and failure mode, load–displace-ment response (e.g., ductility, energy dissipation), strength evalua-tion, and stiffness degradation of each specimen are discussed.Effects of the test variables on the aforesaid performance measuresare highlighted.

4.1. Cracking and failure mode

Fig. 9 illustrates cracking patterns observed in the three speci-mens at 10% drift ratio. Specimen 1DF2Y experienced no apparent

Side face Top face Side face(a) 1CF2Y (b) 1DF

Fig. 9. Cracking damage

failure by the end of testing, which showed the least damageamong the three specimens. In contrast, the normal concrete spec-imen (1DF0Y) suffered much more severe concrete cracking andspalling damage. A relatively small number of inclined crackswidely opened in 1DF0Y, while many hairline cracks occurred inthe HPFRCC specimens. Specimen 1DF0Y underwent flexural fail-ure in the end; concrete crushing in compression was observedat about 3.5% drift. Thus, it may be said that the use of the HPFRCCgreatly contributed to reducing the cracking damage of the slendercoupling beams.

Specimen 1CF2Y with conventional reinforcement layout even-tually underwent shear failure, accompanied by the yielding ofmost transverse reinforcement. However, 1CF2Y displayed onlyminor spalling damage, which was likely owing to the fiber bridg-ing effect of the HPFRCC across cracks. This failure mode is wellilluminated by the cracking patterns (Fig. 9); X-shape inclinedcracks occurred at the side faces of the beam, and large cracksoccurred along the longitudinal bars as well as the stirrups at thetop and bottom faces.

Fig. 10 reviews the drift cycles during which the onset of longi-tudinal bar yielding occurred at the beam–stub interfaces, whichwas judged based on the strain gage data. (In the figure, ‘‘N.A’’means the bar did not yield by the end of testing, and ‘‘N.D’’ meansthe strain measurement was ended in the middle of testing beforethe yield strain was reached.) In all tests, the maximum load (Pmax)was deemed to be mainly governed by the yielding of longitudinalbars. In specimen 1CF2Y, the initial yielding occurred during the 2%and �1.5% drift cycles in the positive and negative loadings respec-tively, and all longitudinal bars yielded by 2.5% drift. Thus, it maybe said that the conventionally reinforced specimen developed arelatively good flexural mechanism. However, many stirrups in1CF2Y yielded in sequence due to high shear demands as the driftincreased, with the first yielding detected at 2% drift. This signifiesthe shear failure of 1CF2Y.

In the diagonally reinforced specimens, a major number of longi-tudinal bars yielded between the 1.5% and 3% drift cycles, which wellagrees with overall load–drift responses in Fig. 11. However, thestrain gage data in 1DF0Y and 1DF2Y were not as reliable as thosein 1CF2Y. This might be in part because the strain gages were eitherinstalled at the bended parts of the bars or erroneously positionedaway from the critical sections. (Note that the ends of the diagonalbars were bended to be parallel to the longitudinal axis of the beam.)

4.2. Load–displacement response

Fig. 11 shows the cyclic lateral load–drift responses of the threespecimens, in which the lateral load is the force applied by theactuator, and the drift is defined as the lateral displacement at

Top face Side face Top face0Y (c) 1DF2Y

at 10% drift ratio.

(a) 1CF2Y

(b) 1DF0Y (c) 1DF2Y

Fig. 10. (%) Drift cycle at onset of longitudinal/diagonal bar yielding at beam–stub interfaces. (Note that cross ties are not shown. ‘‘N.A’’ means the bar did not yield by the endof testing, and ‘‘N.D’’ means the strain measurement was stopped in the midst of testing before the yield strain was reached.)


the top of the coupling beam divided by the beam length (l). Theenvelopes of the hysteretic load–drift curves are also plottedtogether in Fig. 11.

Specimen 1DF2Y exhibited the most stable load–displacementbehavior; the lateral load barely reduced by the end of testing,and almost no pinching was noticed in the hysteretic loops. Simi-larly, specimen 1DF0Y developed a stable load–drift responsethroughout the test, but it showed gradual strength degradationafter the 6% drift cycles. The better ductility of 1DF2Y was likelyattributed to the material properties: the HPFRCC was more ductilethan the normal concrete under both tension (Fig. 6) and compres-sion (Fig. 8).

In contrast, specimen 1CF2Y underwent relatively fast strengthdegradation after the 3% drift cycles, attaining the smallest dis-placement ductility equal to roughly 2.7, and it showed severepinching in the hysteretic load–drift curves. (The displacementductility is taken as the displacement at the point of a 20% strengthdrop from the peak load divided by the yield displacement (Dy inTable 6) that is determined based on Paulay and Priestley [6].)Therefore, it is concluded that the diagonal layout of longitudinalbars was much more effective than the conventional layout inthe slender coupling beams.

In Fig. 11, the calculated strength, Pn,0, is indicated for eachspecimen, which is the lateral load corresponding to the nominalmoment strength (Mn,0) of the coupling beam (i.e., Pn,0 = 2Mn,0/l),determined based on ACI 318-11 [2]: §10.2 for 1CF2Y with conven-tional reinforcement, and §21.9.7 for the specimens with diagonalreinforcement. Note that Mn,0 is estimated ignoring effects of the

axial force imposed in the coupling beam, as well as effects ofthe HPFRCC on the compressive and tensile stress–strainrelationships.

In all specimens, the measured maximum load (Pmax) wasapproximately 63–97% larger than the calculated strength Pn,0, asshown in Table 5. Thus, the maximum shear stress, Pmax/bh, wasroughly 0:93

ffiffiffiffiffiffifcm

pto 1:17

ffiffiffiffiffiffifcm

pin the specimens: 1DF0Y and

1DF2Y had about 41% and 22% higher stresses than the upper limitspecified in ACI 318-11, §21.9.7. Nevertheless, the diagonally rein-forced specimens showed no significant shear distress, while1CF2Y eventually failed in shear. Specimen 1DF2Y achieved thegreatest maximum load, about 13% higher than that of 1DF0Y inthe positive loading; this was likely attributed to combined effectsof the higher compressive strength and tensile strain hardening ofthe HPFRCC on the flexural strength of the beam. A detailed discus-sion for the large discrepancy between Pmax and Pn,0 is presented ina later section.

4.3. Energy dissipation

Energy dissipation capacity is considered as one of the key per-formance criteria of earthquake-resistant members. The amount ofenergy dissipated during a loading cycle is taken as the area enclosedby the corresponding load–displacement curve. Fig. 12 displays (a)the energy dissipated during the first cycle to each drift and (b)the cumulated amount of dissipated energy up to the indicated driftcycle (counting all cycles to each drift), in the three specimens. Also,the energy values shown in Fig. 12a and b are normalized by the

(a) 1CF2Y (b) 1DF2Y

(c) 1DF0Y (d) Envelope curves

Fig. 11. Hysteretic load–drift responses.

Table 5Measured and calculated strengths of the tested specimens.

Specimen 1CF2Y 1DF0Y 1DF2Y

Failure mode Flexure-shear Flexure No failureMeasured maximum load, Pmax (kN) +491/�466 +473/�426 +533/�441Max. shear stress, Pmax=bh (MPa) 0:93

ffiffiffiffiffiffiffifcm

p1:17


p1:01


pDrift ratio at Pmax 3% 2.5% 6%Beam axial force ignored Nominal moment strength, Mn,0 (kN m) 159 142 142

Calculated strength, Pn,0a (kN) 302 270 270

Pmax/Pn,0 +1.63/�1.54 +1.75/�1.58 +1.97/�1.63Nominal shear strength, Vn (kN) 446 270 270

Beam axial force at Pmax considered Np,max (kN) = beam axial force at Pmax 884 – 1009Nominal moment strength, Mn,N (kN m) 236 – 204Calculated strength, Pn,N

b (kN) 450 – 389Pmax/Pn,N +1.09/�1.04 – +1.37/�1.13

a Pn,0 = 2Mn,0/l.b Pn,N = 2Mn,N/l.

Table 6Yield and initial stiffnesses of the tested specimens.

Specimen Yield displ. Dy (mm) Ky,exp (kN/mm) K0,exp (kN/mm) K0,cal (kN/mm) Ky,exp/K0,exp Ky,exp/K0,cal

1CF2Y 20.2 24.3 52.0 154 0.47 0.161DF0Y 15.9 29.8 86.2 119 0.35 0.251DF2Y 28.1 19.0 51.7 154 0.37 0.12


measured maximum load (Pmax) in each test, and plotted in Fig. 12cand d, respectively.

Of the two specimens having diagonal reinforcement, 1DF0Ypresented slightly larger amounts of energy dissipation than1DF2Y during small drift cycles. This was mostly because speci-men 1DF0Y of normal concrete had higher stiffnesses up to 3%drift (see Fig. 13a). From about 4% drift cycles, 1DF2Y of the

HPFRCC dissipated larger amounts of energy, as 1DF0Y under-went gradual strength degradation. However, the effect of theHPFRCC was not eminent in the energy dissipation capacity ofthe diagonally reinforced coupling beams; the cumulated energiesin the two were very similar by 10% drift (Fig. 12b and d). Bothspecimens exhibited satisfactory energy dissipations throughoutthe tests.

(a) Energy dissipated in 1st cycle to each drift (b) Cumulated energy dissipation

(c) Energy values in (a) normalized by Pmax (d) Energy values in (b) normalized by PmaxFig. 12. Energy dissipation.

(a) Stiffness in 1st cycle to each drift

(b) Normalized stiffness

Fig. 13. Stiffness degradation.


In contrast, specimen 1CF2Y having conventional reinforcementshowed apparently smaller energy dissipations than the diagonallyreinforced specimens from about 6% drift, at which 1CF2Y sufferedsudden strength degradation. At the end of the 10% drift cycles, thecumulated energy in 1CF2Y was less than 50% of those in the otherspecimens. Therefore, it may be said that the use of diagonal rein-forcement layout was greatly effective in the energy dissipation ofthe slender coupling beams.

4.4. Stiffness degradation

The stiffness of the specimens gradually decreased due to con-crete (or HPFRCC) cracking and steel yielding. Fig. 13a plots thestiffness of each specimen in the first cycle to each drift; the stiff-ness is taken as the lateral load divided by the lateral displacementat the peak drift of the cycle. Comparing the two diagonally rein-forced specimens, 1DF2Y of the HPFRCC showed considerablysmaller stiffness than 1DF0Y of normal concrete at the beginning.This is likely attributed to the smaller stiffness of the HPFRCC itselfthat is observed in the uniaxial stress–strain curves (see Fig. 8).

Fig. 13b illustrates the stiffness of each specimen in the firstcycle to each drift, normalized by the initial stiffness measured atthe first cycle of the test (K0,exp in Table 6); the initial stiffnessK0,exp is taken as the slope of a secant line from the origin to thepoint at 0.1% drift, until which almost no cracking occurred. TheHPFRCC specimens generally showed lower percentages of stiff-ness degradations at a given drift than the normal concrete speci-men, although 1CF2Y had faster degradations from about 3% driftas it started to lose the overall strength.

4.5. Shear distortion

The degree of shear cracking damage in the specimen wasquantified by inspecting the increase of shear deformation with

Fig. 14. (a) Instrumentations for shear distortion and flexural rotation and (b)estimation of shear distortion.


respect to the applied drift. The shear distortion of the couplingbeam was assessed using the test data from the twelve LVDTsinstalled at one side face of the beam (L1–L4, L9–L12, D1–D4 inFig. 14). The shear distortion c was estimated in each of the fourregions shown in Fig. 14 as follows:

c ¼ cL þ cR

2ð1Þ

Here, cL and cR are the angular changes in the two 90-degreeangles shown in Fig. 14 (i.e., at points 2 and 3), computed consid-ering the deformed lengths of the two initially right triangles (hav-ing a common hypotenuse, i.e., between points 1 and 4) formed by

Fig. 15. Shear distortio

the LVDTs (see Reference [40] for detailed calculation procedures).It is assumed that there was no change in length along the trans-verse axis of the beam, i.e., no change in length between points 1and 2, and between points 3 and 4. In general, Regions-1 and -4showed similar shear distortions, and also Regions-2 and -3 did.

Fig. 15 presents the shear distortion behavior at Region-1 in thethree specimens, with respect to the lateral load. (LVDT measure-ments in 1DF0Y did not function after 3.5% drift.) Among the threespecimens, 1CF2Y showed the smallest shear distortions at givendrift ratios; for example, the maximum shear distortion duringthe 3.5% drift cycles was roughly 0.018, 0.026, and 0.024 in1CF2Y, 1DF0Y, and 1DF2Y, respectively. Noting that 1CF2Y sufferedsuccessive strength drops from about 3.5% drift due to shear dis-tress, it is likely that the HPFRCC was effective in bridging shearcracks to control the crack widths in 1CF2Y.

In Region-2, 1DF0Y of normal concrete exhibited much largershear distortions than the HPFRCC specimens, as shown inFig. 16. This was likely because specimen 1DF0Y experiencedsevere cracking damage with widely opened inclined cracks(Fig. 9).

4.6. Strength estimation

As shown in Fig. 11, the measured maximum load (Pmax) wasmuch larger than the calculated strength, Pn,0 = 2Mn,0/l, in all threespecimens. The higher measured strength seems to have resultedprimarily from the axial force (compression) imposed in the cou-pling beam by the loading frame system; the elongation of the cou-pling beam due to concrete cracking and inelastic residual strainsin the longitudinal bars was restrained, as in a real structure. Also,the strain hardening of the HPFRCC in tension may have slightlyincreased the flexural strength of the coupling beam (comparethe strengths of 1DF2Y and 1DF0Y).

n (c) at Region-1.

Fig. 16. Shear distortion (c) at Region-2.

Table 7Database of 19 conventionally reinforced coupling beam tests.

Specimen b (mm) h (mm) l/h Longitudinal steel fcm (MPa) Ky,exp

(kN/mm)K0,cal

(kN/mm)

Ky;expK0;cal

Pmax

(kN)Pn,0

(kN)

PmaxPn;0

Author Name As (mm2) fy (MPa)

Barney et al. (1980) [31] C2 102 169 2.50 128 516 21.0 17 95 0.18 46 57 0.80C5 102 169 2.50 128 457 21.7 14 96 0.15 42 51 0.82C7 102 169 5.00 128 459 25.6 5 17 0.29 23 25 0.93

Galano and Vignoli (2000) [10] P01 150 400 1.50 314 567 48.9 46 626 0.07 224 211 1.06P02 150 400 1.50 314 567 44.5 45 597 0.08 232 211 1.10

Bristowe (2006) [32] NR2 300 500 3.60 1530 433 41.0 20 157 0.13 321 306 1.05NR4 300 500 3.60 1530 433 41.0 22 157 0.14 321 306 1.05MR2 300 500 3.60 1530 433 79.8 20 219 0.09 328 318 1.03MR4 300 500 3.60 1530 433 79.8 20 219 0.09 328 318 1.03

Hong and Jang (2006) [33] 01MCB16-SMM 150 480 1.67 398 475 28.7 35 392 0.09 247 196 1.2602MCB13-SMM 150 600 1.33 398 475 28.7 47 593 0.08 344 253 1.3603MCB20-SMM 150 400 2.00 398 475 28.7 22 270 0.08 219 158 1.3807MCB16-SLM 150 480 1.67 398 475 28.7 31 392 0.08 260 196 1.3308MCB16-SHM 150 480 1.67 398 475 28.7 29 392 0.07 244 196 1.2510MCB16-SMN 150 480 1.67 398 475 28.7 32 392 0.08 213 196 1.09

Ihtiyar and Breña (2007) [34] CB-1 250 380 1.34 597 517 39.0 40 1139 0.04 480 492 0.98CB-3 250 380 1.34 597 517 31.0 47 1015 0.05 506 575 0.88CB-4 250 380 2.68 398 517 30.0 22 235 0.09 240 205 1.17

Yun et al. (2008) [11] CB-3a,b 200 600 1.00 402 474 57.0 108 1774 0.06 785 398 1.97Average 0.10 Average 1.13Standard dev. 0.06 Standard

dev.0.26

a Specimens with axial restraint.b HPFRCC specimens.


Tables 7 and 8 assemble 19 conventionally and 27 diagonallyreinforced coupling beam tests respectively, found in the literature[9–11,21,27,30–35]; in all the specimens, the maximum load wasgoverned by the flexural strength of the coupling beam. Only afew of the assembled tests were conducted in such a condition that

the elongation of the coupling beam was restrained, as indicated inthe tables. Fig. 17 shows the maximum load (Pmax) divided by thecalculated strength (Pn,0) determined assuming zero beam axialforce, for the specimens in Tables 7 and 8. The ratio of Pmax-to-Pn,0 is much greater in the tests in which the coupling beams were


restrained against axial elongation; it ranges between 1.33 and1.97. Also, HPFRCC specimens (denoted by ‘‘#’’ in the figure) gener-ally showed larger Pmax-to-Pn,0 values than normal concrete speci-mens. This tendency is in accordance with the test results acquiredin this study.

To more accurately estimate the strength of each specimen ofthis study, the axial forces imposed in the coupling beam are calcu-lated using the data measured by the load cells at the vertical sup-ports (see Fig. 3). Table 5 summarizes the beam axial force (Np,max)that is estimated to have been imposed at the time of the maxi-mum load (Pmax), and the nominal moment strength (Mn,N) of thebeam that is computed considering Np,max at the event of theextreme compression fiber reaching the maximum allowablestrain (taken as 0.003). The nominal moment strength Mn,N is sub-stantially larger than Mn,0 owing to moment-axial load interaction,so that the calculated strength, Pn,N = 2Mn,N/l, is much closer toPmax; the ratio of Pmax-to-Pn,N for an average of the positive and neg-ative maximum loads is 1.07 and 1.25 in 1DF2Y and 1CF2Y, respec-tively. (In the test of 1DF0Y, the load cells malfunctioned so that itwas not possible to estimate the beam axial forces.)

The above results imply that the coupling beams designedbased on the current codes could actually achieve much higherstrengths than those expected by the current codes (e.g., ACI318-11 [2], Eurocode 8 [3]). Therefore, it is proposed that thestrength of a coupling beam should be designed considering thelevel of beam axial force that would occur from design earth-quakes. Otherwise, severe plastic deformations may arise at thebases of the walls before the coupling beams develop appropriateplastic hinging.

Table 8Database of 27 diagonally reinforced coupling beam tests.

Specimen b (mm) h (mm) l/h Diagonal stee

Author Name Avd (mm2)

Paulay and Binney (1974) [30] 316 152 787 1.29 1548317 152 787 1.29 1548395 152 991 1.03 1548

Barney et al. (1980) [31] C6 102 169 2.50 142

Tassios et al. (1996) [9] CB-2A 130 500 1.00 314CB-2B 130 300 1.67 314

Galano and Vignoli (2000) [10] P05 150 400 1.50 314P06 150 400 1.50 314P07 150 400 1.50 314P08 150 400 1.50 314P10 150 400 1.50 314P11 150 400 1.50 314P12 150 400 1.50 314

Shimazaki (2004) [35] N1 200 400 2.50 804N2 200 400 2.50 804N3 200 400 2.50 804N4 200 400 2.50 804N5 200 400 2.50 804N6 200 400 2.50 804N7 200 400 2.50 1134N8 200 400 2.50 804

Canbolat et al. (2005) [21] Spec. 3b 150 600 1.00 398

Yun et al. (2008) [11] CB-1a 200 600 1.00 398CB-2a,b 200 600 1.00 398

Lequesne et al. (2011) [27] CB-1a,b 150 600 1.75 402CB-2a,b 150 600 1.75 402CB-3a,b 150 600 1.75 402

a Specimens with axial restraint.b HPFRCC specimens.

The measured maximum load (Pmax) is also compared with thenominal shear strength (Vn) of the coupling beam (Table 5) that iscomputed based on ACI 318-11 as follows, by using the measuredmaterial properties:

Vn¼Av fytd

sfor conventionally reinforced coupling beams ðACI 318

�11; x21:5:4:2Þð2Þ

Vn¼2Avdfylsina for diagonally reinforced coupling beams ðACI 318

�11; x21:9:7:4Þð3Þ

Here, Av and s are the area and spacing of transverse reinforce-ment, fyt is the yield strength of transverse steel, and d is the effec-tive depth of the beam. Also, Avd is the area of each group ofdiagonal reinforcement, fyl is the yield strength of longitudinal(diagonal) steel, and a is the angle between the diagonal reinforce-ment and the longitudinal axis of the beam. Note that concretecontribution to the shear strength is taken zero for both conven-tionally and diagonally reinforced coupling beams. Also, in diago-nally reinforced beams, the entire shear strength is to beprovided by the diagonal bars; the contribution of transverse rein-forcement is neglected.

In all three tests, the maximum load (Pmax) exceeded the nom-inal shear strength (Vn) by about 10%, 75%, and 97% in 1CF2Y,1DF0Y, and 1DF2Y, respectively. However, only 1CF2Y with theconventional layout ultimately underwent shear failure, while

l a (�) fcm (MPa) Ky,exp

(kN/mm)K0,cal

(kN/mm)

Ky;expK0;cal

Pmax

(kN)Pn,0

(kN)

PmaxPn;0

fy (MPa)

288 33.0 33.3 180 684 0.26 600 570 1.05280 33.0 50.7 160 844 0.19 600 525 1.14265 41.0 35.5 170 707 0.24 650 530 1.23

488 27.5 18.1 14 88 0.16 60 64 0.93

504 39.0 28.5 31 815 0.04 283 215 1.32504 23.0 26.3 14 783 0.02 170 147 1.16

567 28.5 39.9 49 565 0.09 239 199 1.20567 28.5 46.0 70 658 0.11 241 199 1.21567 28.5 54.0 91 654 0.14 238 199 1.20567 28.5 53.4 64 612 0.10 238 199 1.20567 28.5 46.8 48 565 0.08 241 199 1.21567 28.5 39.9 50 577 0.09 239 199 1.20567 28.5 41.6 49 565 0.09 240 199 1.21

476 17.5 54.0 60 299 0.20 351 365 0.96459 17.5 51.0 68 290 0.24 400 352 1.14476 17.5 54.0 58 299 0.20 351 365 0.96459 17.5 51.0 65 290 0.22 400 352 1.14459 17.5 51.0 67 290 0.23 393 352 1.12386 17.5 64.0 51 325 0.16 347 310 1.12380 17.5 48.0 58 282 0.21 380 387 0.98383 17.5 32.0 52 230 0.23 331 313 1.06

450 36.0 57.0 127 1365 0.09 800 582 1.37

474 30.0 44.0 184 1559 0.12 704 530 1.33474 30.0 57.0 178 1774 0.10 866 532 1.63

430 24.0 45.0 75 446 0.17 660 465 1.42430 24.0 32.0 61 376 0.16 655 400 1.64420 24.0 34.0 76 387 0.20 650 435 1.49

Average 0.15 Average 1.21Standard dev. 0.07 Standard

dev.0.18


1DF0Y and 1DF2Y exhibited no significant shear distress by the endof testing. This suggests that ACI 318-11 shear strength codes rel-atively well agreed with the conventionally reinforced couplingbeam (Pmax was only slightly larger than Vn in 1CF2Y). However,the ACI shear strength requirements were excessively conservativein the diagonally reinforced coupling beams. (Detailed investiga-tion on effects of both HPFRCC and beam axial force on the shearstrength of coupling beams is out of the scope of this study.)

4.7. Yield stiffness

In seismic analysis, the reduced stiffness of a coupling beam in theessentially elastic range is typically represented by the ‘‘yield stiff-ness’’ of the beam. In this study, the yield stiffness of a specimen Ky,-exp is taken equal to the slope of a secant line from the origin to thepoint of 0.75Pmax in the load–displacement envelope curve, as sug-gested in Paulay and Priestley [6]. The measured yield stiffness Ky,exp

was 24.3, 29.8, and 19.0 kN/mm in specimens 1CF2Y, 1DF0Y, and1DF2Y respectively, which is roughly 47%, 35%, and 37% of the mea-sured initial stiffness K0,exp in the same order, as shown in Table 6.

However, it is deemed that the measured initial stiffness K0,exp

was possibly affected by accidental rigid-body motions (e.g., slip,rocking) due to the incomplete tightness of the loading frame fix-tures [36] such as loose-fitting pins, bolts, and anchors. To accountfor the effect of such imperfections of the test setup in contrast tofixed boundary conditions in a real structure, the theoretical initialstiffness K0,cal of a coupling beam with a rectangular section isassessed by the following [41]:

K0;cal ¼12EcIg

ð1þU0Þl3 ; U0 ¼12EcIg

GcðAg=1:2Þl2 ð4Þ

Ec ¼ 4700ffiffiffiffif 0c

q; Gc ¼ 0:4Ec ð5Þ

(a) Conventionally reinforced beams

(b) Diagonally reinforced beams

Fig. 17. Measured maximum load vs. calculated strength (HPFRCC specimens areindicated by ‘‘#’’.).

Here, Ec is the modulus of elasticity of concrete in MPa, specifiedin ACI 318-11 [2], Ig is the gross moment-of-inertia of the beamsection, l is the length of the beam, and U0 is a factor accountingfor the relative importance of shear deformation to flexural defor-mation. Also, Gc is the shear modulus of concrete [2], and Ag is thegross area of the beam section. Eq. (4) stands for the stiffnessagainst the translation lateral to the axis of the coupling beam withno relative rotation permitted between the beam ends.

The Ky,exp-to-K0,cal ratio turns out to be about 0.25 in 1DF0Y ofnormal concrete, while the ratio is 0.16 and 0.12 in 1CF2Y and1DF2Y, respectively (see Table 6). The relatively large stiffnessreductions of the HPFRCC specimens, compared with the normalconcrete specimen, are mostly attributed to the fact that Eq. (5)overestimates the modulus of elasticity of the HPFRCC. (TheHPFRCC in compression had a smaller stiffness than the normalconcrete.) The levels of stiffness reduction in the tested specimensare larger than those expected by the current design codes [2,4,5].For example, ACI 318-11, §10.10.4.1 [2] specifies the reduced flex-ural rigidity of 0.35EIg for cracked beams for analysis under fac-tored lateral loads.

The tested slender specimens generally showed larger Ky,exp-to-K0,cal ratios than those observed in deep coupling beam tests [9–11,34,36]. To further explore the effect of beam slenderness on thestiffness reduction, both calculated initial stiffness (K0,cal) and mea-sured yield stiffness (Ky,exp) are determined for each of the assembledtests in Tables 7 and 8, except for the specimens that failed in shear.Fig. 18a and b plot the Ky,exp-to-K0,cal ratio for the specimens withconventional and diagonal reinforcement in Tables 7 and 8, respec-tively. While the ratio of Ky,exp-to-K0,cal widely varies (between 0.04and 0.29 in the conventionally reinforced specimens, or between0.02 and 0.26 in the diagonally reinforced specimens), the ratio isgenerally smaller when the length-to-depth (l/h) ratio is smaller.This points out that deep coupling beams suffered higher percent-ages of stiffness reductions. It is noted, however, that ACI 318-11

(a) Conventionally reinforced beams

(b) Diagonally reinforced beams

Fig. 18. Yield-to-initial stiffness (Ky,exp-to-K0,cal) ratio.


[2] takes no account of the effect of beam slenderness on the stiffnessdegradation of a coupling beam, while both CSA A23.3-04 [4] andNZS 3101:2006 [5] consider it in a similar way.

5. Conclusions

In this study, the effect of high performance fiber-reinforcedcement composites (HPFRCCs) on the seismic performance of slendercoupling beams was investigated, as well as the effect of diagonalreinforcement. In order to accomplish this, an experimental programwas conducted with three 1/2-scale slender coupling beams sub-jected to lateral cyclic loading. Detailed material tests were conductedto determine the mix proportions of the HPFRCC used in the couplingbeam specimens. Also, a test database was assembled includingalmost all coupling beam tests available in literature. Important find-ings and conclusions may be summarized as follows:

1. The use of the HPFRCC greatly contributed to reducing thecracking damage and shear distortion of the slender couplingbeams by better restraining the growth of shear cracks. Also,it enhanced the ductility of the diagonally reinforced couplingbeams. However, the effect of the HPFRCC was not apparentin the energy dissipation capacity of the diagonally reinforcedslender coupling beams.

2. The HPFRCC coupling beam specimens generally showed lowerpercentages of stiffness degradations than the normal concretespecimen.

3. The test results suggest that the seismic performance (i.e., duc-tility, energy dissipation) of a slender coupling beam is muchsuperior with diagonal reinforcement than with conventionalreinforcement. Therefore, it is proposed that diagonal reinforce-ment is used even in slender coupling beams for the purpose ofensuring satisfactory seismic performance, although diagonalreinforcement is less effective for increasing the shear strengthof a slender beam.

4. The diagonally reinforced specimens achieved considerablyhigher shear stresses than the upper limit specified in ACI318-11. Noting that no significant shear distress was observed,ACI 318-11 seems to be quite conservative on the maximumallowable shear stress in coupling beams.

5. The measured maximum load was much larger than the calcu-lated strength per current design codes in the tested specimens,which resulted primarily from the axial force imposed in thecoupling beam. It is proposed that the strength of a couplingbeam should be designed considering the level of beam axialforce that would occur from design earthquakes.

6. The yield stiffnesses of the tested specimens were smaller thanthose expected by current design codes. From the detailed anal-ysis of previous test results in literature, it is found that theyield-to-initial stiffness ratio strongly depended on the beamslenderness, and deeper coupling beams suffered higher per-centages of stiffness reductions.

Acknowledgements

This research was supported by Basic Science Research Programthrough the National Research Foundation of Korea (NRF) fundedby the Ministry of Education, Science and Technology (Grant No.2010-0022955).

References

[1] International Codes Council. 2012 International building code. ICC; 2012.[2] ACI Committee 318. Building code requirements for structural concrete (ACI

318-11) and commentary. Farmington Hills, Michigan, USA: AmericanConcrete Institute; 2011.

[3] Technical Committee CEN/TC 250. Eurocode 8: Design of structures forearthquake resistance: Part 1: General rules, seismic actions and rules forbuildings. Brussels, Belgium: European Committee for Standardization; 2004.

[4] Canadian Standards Association. CAN/CSA A23.3-04 Design of concretestructures. Mississauga, Ontario, Canada: Canadian Standards Association; 2010.

[5] New Zealand Standards Council. Concrete structures standard, Part 1 – Thedesign of concrete structures (NZS 3101: Part 1:2006). Wellington, NewZealand: Standards New Zealand; 2006.

[6] Paulay T, Priestley MJN. Seismic design of reinforced concrete and masonrybuildings. New York: John Wiley & Sons; 1992.

[7] Shin M, Kang T, Grossman JS. Practical modelling of high-rise dual systemswith reinforced concrete slab-column frames. Struct Des Tall Spec Build2010;19:728–49.

[8] Paulay T. Coupling beams of reinforced concrete shear walls. J Struct Divis1971;97(3):843–62.

[9] Tassios TP, Moretti M, Bezas A. On the behavior and ductility of reinforcedconcrete coupling beams of shear walls. ACI Struct J 1996;93(6):711–9.

[10] Galano L, Vignoli A. Seismic behavior of short coupling beams with differentreinforcement layouts. ACI Struct J 2000;97(6):876–85.

[11] Yun HD, Kim SW, Jeon E, Park WS, Lee YT. Effects of fibre-reinforced cementcomposites’ ductility on the seismic performance of short coupling beams.Mag Concr Res 2008;60(3):223–33.

[12] Kuder KG, Shah SP. Processing of high-performance fiber-reinforced cement-based composites. Constr Build Mater 2010;24(2):181–6.

[13] Li VC. On engineered cementitious composites. J Adv Concr Technol2003;1(3):215–30.

[14] Naaman AE. Engineered steel fibers with optimal properties for reinforcementof cement composites. J Adv Concr Technol 2003;1(3):241–52.

[15] Kim DJ, Naaman AE, El-Tawil S. High performance fiber reinforced cementcomposites with innovative slip hardening twisted steel fibers. Int J ConcrStruct Mater 2009;3(2):119–26.

[16] Yang EH, Li VC. Strain-hardening fiber cement optimization and componenttailoring by means of a micromechanical model. Constr Build Mater2010;24(2):130–9.

[17] Mechtcherine V. Novel cement-based composites for the strengthening andrepair of concrete structures. Constr Build Mater 2013;41:365–73.

[18] Parra-Montesinos GJ. High-performance fiber-reinforced cement composites:an alternative for seismic design of structures. ACI Struct J2005;102(5):668–75.

[19] Shin M, Choi Y, Kim I, Lee K. Effectiveness of low-cost fiber-reinforced cementcomposites in hollow columns under cyclic loading. Constr Build Mater2013;47:623–35.

[20] Naaman AE, Reinhardt HW. High performance fiber reinforced cementcomposites HPFRCC-4: international workshop Ann Arbor, Michigan, June16–18, 2003. Cem Concr Compos 2004;26(6):757–9.

[21] Canbolat BA, Parra-Montesinos GJ, Wight JK. Experimental study on seismicbehavior of high-performance fiber-reinforced cement composite couplingbeams. ACI Struct J 2005;102(1):159–66.

[22] Parra-Montesinos GJ, Peterfreund SW, Chao SH. Highly damage-tolerantbeam–column joints through use of high-performance fiber-reinforcedcement composites. ACI Struct J 2005;102(3):487–95.

[23] Maya LF, Zanuy C, Albajar L, Lopez C, Portabella J. Experimental assessment ofconnections for precast concrete frames using ultra high performance fibrereinforced concrete. Constr Build Mater 2013;48:173–86.

[24] Naaman AE, Likhitruangsilp V, Parra-Montesinos GJ. Punching shear responseof high-performance fiber-reinforced cementitious composite slabs. ACI StructJ 2007;104(2):170–9.

[25] Olsen EC, Billington SL. Cyclic response of precast high-performance fiber-reinforced concrete infill panels. ACI Struct J 2011;108(1):51–60.

[26] Park WS, Yun HD. Shear strength of pseudo strain hardening cementitiouscomposite coupling beam. Compos Part B: Eng 2011;42(3):429–43.

[27] Lequesne RD, Setkit M, Parra-Montesinos GJ, Wight JK. Seismic detailing andbehavior of coupling beams with high-performance fiber reinforced concrete.Four decades of progress in prestressed concrete, fiber reinforced concrete,and thin laminate composites (SP-272). Farmington Hills, Michigan, USA:American Concrete Institute; 2011. p. 205–22.

[28] Barbachyn SM, Kurama YC, Novak LC. Analytical evaluation of diagonallyreinforced concrete coupling beams under lateral loads. ACI Struct J2012;109(4):497–508.

[29] Japan Society of Civil Engineers. Recommendation for design and constructionof high performance fiber reinforced cement composites with multiple finecracks. Concr Eng Ser 2008;82.

[30] Paulay T, Binney JR. Diagonally reinforced coupling beams of shear walls. SP42-26, vol. 42. Detroit, Michigan, USA: American Concrete Institute; 1974. p.579–98.

[31] Barney GB, Shiu KN, Rabbit BG, Fiorato AE, Russell HG, Corley WG. Behavior ofcoupling beams under load reversals (RD068.01B). Skokie, Illinois,USA: Portland Cement Association; 1980.

[32] Bristowe S. Seismic response of normal and high strength concrete members.PhD Thesis 2006. McGill University, Montreal, Canada.

[33] Hong SG, Jang SK. The mechanism of load resistance and deformability ofreinforced concrete coupling beams. J Earthq Eng Soc Korea2006;10(3):113–23.

[34] Ihtiyar O, Breña SF. Assessment of FEMA 356 techniques for orthogonallyreinforced coupling beams through experimental testing. In: ASCE structurescongress: structural engineering research frontiers; 2007.


[35] Shimazaki K. De-bonded diagonally reinforced beam for good repairability. In:13th World conference on earthquake engineering, Vancouver (BC), Canada;2004.

[36] Wallace JW. Modelling issues for tall reinforced concrete core wall buildings.Struct Des Tall Spec Build 2007;16:615–32.

[37] Shin M, Gwon SW, Lee K, Han SW. Improved earthquake-resistant designmethods of slender coupling beams. In: The 2013 world congress on advancesin structural engineering and mechanics (ASEM13), Jeju, Korea; 2013.

[38] Harries KA, Fortney PJ, Shahrooz BM, Brienen PJ. Practical design of diagonallyreinforced concrete coupling beams-critical review of ACI 318 requirements.ACI Struct J 2005;102(6):876–82.

[39] Naish D, Fry A, Klemencic R, Wallace J. Reinforced concrete coupling beams –Part I: Testing. ACI Struct J 2013;110(6):1057–66.

[40] Shin M. Performance of reinforced concrete edge beam–column–slabconnections subjected to earthquake loading. PhD Thesis 2004. University ofIllinois, Urbana, Illinois, USA.

[41] Hughes TJR. The finite element method: linear static and dynamic finiteelement analysis. New Jersey, USA: Prentice Hall; Englewood Cliffs; 1987.

Effectiveness of high performance ﬁber-reinforced cement...

Documents

Transcript of Effectiveness of high performance ﬁber-reinforced cement...