Effects of Haunch on the Beam-Column Joint of Soft First-Story in RC Building

Transcription

1 Effets of Hauh o the Beam-olum Joit of Soft First-Story i R Buildig T. Ogawa, M. Teshigawara &. Nakamura Nagoya Uiversity, Nagoya, Japa S. Takahashi, G. Kotai, T. Kawai & T. Ihiose Nagoya Istitute of Tehology, Nagoya, Japa T. Kamiya, T. Taguhi, W. Kohira & T. Umeo Yahagi ostrutio o., Ltd., Nagoya, Japa H. Fukuyama Buildig Researh Istitue, Tsukua, Japa H. Suwada & T. Kaeyasawa Natioal Istitute for Lad ad Ifrastruture, Tsukua, Japa N. Haai Kyushu Sagyo Uiversity, Fukuoka, Japa SUMMRY There are may damage reports aout the soft-story ostrutio agaist earthquakes. Therefore, four speimes osistig of memers oly aroud the eam-olum joit of soft first-story are ostruted ad loaded to failure y statially yli load simulatig earthquake to otai fudametal data. I opeig diretio loadig, all the speimes showed flexural failure of first-story olum. I losig diretio loadig, the speimes i whih the first-story olum is exteded toward iside show flexural failure of first-story olum, whereas the speimes i whih the first-story olum is exteded toward outside showed joit failure. The stiffess ad the stregth of the speimes with hauhes are larger tha those of the speimes without hauhes. set of ew desig equatios to estimate the flexural ad joit stregth are proposed ased o the oserved failure modes, osiderig the effet of hauh ad positio of ritial setio. Keywords: soft first-story, Beam-olum joits, ahorage, hauh 1. INTRODUTION There are may damage reports aout the soft-story ostrutio agaist earthquakes. The first story i a multi-story apartmet uildig is expeted to use for parkig lot or ommerial spae. I these uildigs, shear walls with oudary olums are used as partitio wall i the upper stories whereas the first-story is sigle-ay momet resistig frame. Oe a earthquake would our, deformatio of the struture is oetrated to the soft first-story. Therefore, the uildig is i dager of ausig story ollapse. ahorage failure wall the seod-story olum eam the first-story olum modelig portio Figure 1.1. The typial eam-olum joit at the soft first-story

2 I order to preset from the soft first-story ollapse, the stiffess ad the stregth of the first-story are ireased y makig the depths of the first-story olums muh larger tha those of upper stories (See Fig 1.1). But it is hard to trasfer the momet of the top of the first-story olum to the eam ad the seod-story olum well due to the disotiuous of olum. I additio, uexpeted failure mode might ause, for example, shear failure o a eam-olum joit ad ahorage failure (G. Kotai., et al, 211). I this study, tests are oduted to lear the fore trasfer mehaism ad to avoid suh failures. 2. TEST SPEIMEN ND MTERIL Four speimes I-1t, I-ht, O-1t ad O-ht osistig of memers oly aroud the joit illustrated i Fig. 1.1 are tested. Sale of the speimes is oe half. The speimes are upside-dow for the oveiee of the loadig. The geeral shape ad re-ars arragemet of I-ht ad O-ht is show i Fig The test parameters are as follows: (1) extesio diretio of the first-story olum, outside (O-1t, O-ht) or iside (I-1t, I-ht), ad (2) with/ without hauh at the orer of the joit. axial fore axial fore losig opeig losig opeig eam wall 1st-story olum 2st-story olum B eam wall 1st-story olum 2st-story olum B (a) speime I-ht () speime O-ht Figure 2.1. The geeral shape ad re-ars arragemet of Test speimes, I-ht ad O-ht 2.1. Detail of I-1t, I-ht speimes The speimes I-1t ad I-ht are ostruted with the reiforig arragemet show i Figure 2.2 (a), (). The disotiuous first-story olum re-ars are ahored ito eam-olum joit with 18 degrees hook. The ahorage legth from the fae of the olum joit is satisfied with the IJ Guidelie [1]. The eam re-ars are ahored ito eam-olum joit with 9 degrees hook. The ahorage legth from the fae of the eam joit is also satisfied with the IJ Guidelie [1]. The speime I-ht is provided with hauh i whih five reiforemet (lue reiforemet i Fig. 2.2 ()) ilied 3 degrees are set at the orer of the joit. The ilied reiforemets are ahored ito olum with 18 degrees hook ad ito eam o straight ahorage Detail of O-1t, O-ht speimes The speime O-1t ad O-ht was ostruted with the reiforig arragemet show i Figure 2.2 (), (d). The disotiuous first-story olum re-ars are ahored ito eam-olum joit with 18 degrees hook. The ahorage legth from the fae of the olum joit is satisfied with the IJ

3 Guidelie [1]. The eam re-ars are ahored ito eam-olum joit with 9 degrees hook. The ahorage legth from the fae of the eam joit is also satisfied with the IJ Guidelie [1]. The ahorage legth of the top first layer reiforemet (gree reiforemet i Fig. 2.2 (), (d)) from the tail legth is also satisfied with the IJ Guidelie [1]. The speime O-ht is provided with hauh ad four reiforemets (lue reiforemet i Fig. 2.2 (d)) ilied 3 degrees at the orer of the joit. The ilied reiforemets are ahored ito olum with a 18 degree hook ad ito eam o straight ahorage. 11-D19 (2.53%) 2-D6@5 (.51%) D6@4 (.8%) 2-D19 (2.3%) D19 (2.53%) 2-D6@5 (.51%) story olum 1-story olum 2-story olum Ilied 1-story olum reiforemet 5-D D6@4 (.8%) 18-D19 (2.7%) hook ahorage 23d stirrups 6-D6@62.5 (1.54%) D19 (1.91%) 8-D19 (1.27%) eam Elevatio of joit eam Elevatio of joit (a) I-1t speime 2-D6@4 (.32%) stirrups 6-D6@62.5 (1.54%) D19 (1.91%) ahorage 35d () I-ht speime 2-D6@4 (.32%) 8-D19 (1.27%) D19 (2.53%) 2-D6@5 (.51%) D6@4 (.8%) 2-D19 (2.3%) D19 (2.7%) 2-D6@5 (.51%) D6@4 (.8%) 18-D19 (2.7%) story olum 1-story olum 2-story olum 1-story olum Ilied reiforemet 5-D hook ahorage 23d stirrups 6-D6@125 (.38%) D19 (2.21%) 12-D19 (2.21%) 5-D6@4 (.8%) eam Elevatio of joit eam Elevatio of joit () O-1t speime * d : diameter of the reiforemet stirrups 4-D6@125 (.38%) D19 (1.82%) ahorage 35d (d) O-ht speime 5-D6@4 (.8%) 1-D19 (1.82%) Figure 2.2. Test speime details of I-1t, I-ht, O-1t, O-ht

4 2.3. Material Normal Portlad emet orete is used. Mehaial properties of orete are show i Tale 2.1. Deformed ar (JIS G3112) is used for logitudial ars i olums, ad stirrups i the speime. The mehaial properties of deformed ars are listed i Tale 2.2. Tale 2.1. Mehaial properties of orete speime ompressive Stregth (MPa) Youg's modulus (GPa) Tesile Stregth (MPa) I-1t, O-1t I-ht, O-ht Tale 2.2. Mehaial properties of steel Setioal Reiforig rea Bars (mm 2 ) Yield Poit (MPa) Tesile Stregth (MPa) Youg's modulus (GPa) D * D *.2% offset stregth 3. TEST SETUP The loadig setup is show i Figure 3.1. The speimes are restraied the deformatio out-of-plae. Statially yli lateral load was applied at the top of the olum. The distae etwee the loadig poit ad the fae of the first-story olum is 7mm. tuator was used to apply the horizotal load. xial load was applied at the eter of the first-story olum y hydrauli lifter with apaity of -45kN to 2kN. The drift agle is defied to e divided the deformatio at the poit of the lateral load y the height from the fae of the first-story olum to the poit of the lateral load. Slider Restraiig jig xial Load Hydrauli lifter - + Pi oetio Reatio Wall 7mm 175mm Lateral Load tuator Strog Floor Figure 3.1. Test setup The horizotal loadig yles are show i Figure 3.2. Before the yles of.5% story drift, applied axial load was kn i ostat osiderig the sustaied load of the uildig. fter that, the axial fore is applied -45kN i pull yle ad 2kN i push yle osiderig the effets of overturig momet uder severe earthquake. Displaemets, loads, strais ad deformatios aroud eam-olum joit are measured.

5 6 Story drift agle, % opeig diretio loadig yle umaer losig diretio loadig Figure 3.2. Loadig history 4. TEST RESULTS Relatio of story drift ad story shear of eah speime is show i Fig Relatio of story drift ad story shear efore the story drift agle.5% are elarged ad also show i Fig The positio of the strai gauges ad the yield poits of re-ars are also show i Fig The rakig patter o the eam-olum joit of the eah speime at story drift of 4% is show i Fig 4.2. The solid lies show the rak of opeig diretio loadig, the dashed lies show the rak of losig diretio loadig ad the old lies show remarkale raks. The gray part shows the detahmet of orete I-1t speime I opeig diretio loadig, flexural rak of the first-story olum ad rak B of eam ourred durig the story drift of.2%. Shear rak of eam ad rak D of the first-olum ourred durig the story drift of.5%. Flexural rak exteded to 1.2mm i width ad maximum story shear fore 519kN was attaied at the story drift of 2%. rakig E exteded to 3.mm i width durig the story drift of 3%. Totally, the raks progressed with ars patter aroud a orer of eam-olum joit. Failure mode of I-1t is osidered to e flexural failure of the first-story olum judgig from the strais of the first-story olum ad rak appearae. I losig diretio loadig, flexural rak a of the first-story olum ourred durig the story drift of.2%. Flexural rak ad shear rak of the eam ourred durig the story drift of.5%. orete rushig d ourred at the orer of the joit durig the story drift of 1.5%. Flexural rak a exteded to 1.4mm i width ad maximum story shear fore 899kN was attaied at the story drift of 2%. Failure mode of I-1t is osidered to e flexural failure of the first-story olum at the fae of eam I-ht speime I oth opeig ad losig diretio loadig, the outlie of rak proess resemled I-1t. I opeig diretio loadig, flexural rak exteded to 3.mm i width ad maximum story shear fore 686kN was attaied at the story drift of 4%. Failure mode of I-ht is osidered to e flexural failure of the first-story olum. I losig diretio loadig, Flexural rak a exteded to 1.4mm i width ad maximum story shear fore 149kN was attaied at the story drift of 2.5%. Shear rak exteded to 4.mm i width durig the story drift of 4%. Failure mode of I-ht is osidered to e flexural failure of the first-story olum O-1t speime I opeig diretio loadig, flexural rak of the eam ad rak B of the first-story olum

6 ourred durig the story drift of.2%. Shear rak of eam ad diagoal rak i eam-olum joit ourred durig the story drift of.5%. orete rushig of the seod-story olum ase ourred durig the story drift of 3%. Flexural rak B exteded to 2.2mm i width ad maximum story shear fore 525kN was attaied at the story drift of 4%. Totally, the raks progressed with ars patter aroud a orer of eam-olum joit. Failure mode of O-1t is osidered to e flexural failure of the first-story olum. I losig diretio loadig, diagoal rak a i eam-olum joit, flexural rak of the first-story olum ad rak of the eam ourred durig the story drift of.2%. Shear rak of the first-story olum ad the eam ourred durig the story drift of.5%. orete rushig at the orer of the joit ourred durig the story drift of 1.5%. Flexural rak a exteded to.15mm i width ad maximum story shear fore 826kN was attaied at the story drift of 2.5%. Failure mode of O-1t is osidered to e flexural failure of joit failure O-ht speime I oth opeig ad losig diretio loadig, the outlie of rak proess resemled O-1t. I opeig diretio loadig, flexural rak at the hauh ourred durig the story drift of.2%. Flexural rak B exteded to 4.mm i width ad maximum story shear fore 686kN was attaied at the story drift of 4%. Failure mode of O-ht is osidered to e flexural failure of the first-story olum. I losig diretio loadig, orete rushig d of the hauh ourred ad diagoal rak a exteded to 1.4mm i width ad maximum story shear fore 99kN was attaied at the story drift of 2%. fter that, orete rushig d of the hauh progressed ad diagoal rak from aroud exteded joit ireased ad exteded. Failure mode of O-ht is osidered to e flexural failure of joit failure. Load (kn) Load (kn) 1-5% -4% -3% -2% -1% 1% 2% 3% 4% 5% 1-5% -4% -3% -2% -1% 1% 2% 3% 4% 5% Qmax Yield ar 5 W2 B3 B4 B5 3 1 W2 Qmax= +519kN W3 W kN 11 Q 4 W1 2 Qmax= +686kN 5 H4 2 H1 W3 B3 B4 B5 u H kN B4 H3 +61kN 1 4 H H1 6 u kN H2 5 H4 H2 Qmax S1 B9 H3 8 S1 B9 8 Yield ar H4 H4 H3 B8 7 B8 7 W1 W2 W3 -.5% -.2% 6.2%.5% W1 W2 W3 6-.5% -.2%.2%.5% kN kN kN u 7 5 S1 Qmax= -899kN -4 S1 1(ompressive) -6 Qmax= -149kN -6 W kN 8-8 Before R=1/2 u 8,12-8 Before R=1/2 11(ompressive) Deformatio (mm) Deformatio (mm) 1 (a) I-1t speime -5% -4% -3% -2% -1% 1% 2% 3% 4% 5% Qmax B4 Yield ar 1 Qmax= +525kN +539kN S1 5 H1 B4 H1 Q u +481kN Q u H3 8 B9 -.5% 4 () O-1t speime -.2%.2%.5% Load (kn) Load (kn) Figure 4.1. Relatio of story drift ad story shear () I-ht speime 1-5% -4% -3% -2% -1% 1% 2% 3% 4% 5% B5 1 Qmax= +651kN H1 2 1 B5 +674kN H2 Q u H1 +571kN B9 5 1 H2 Q u Qmax H3 Yield ar 8 B9 4-.5% B9 Q -864kN 3 5, S , H3 Qmax= -826kN Q u -926kN u -1 8 Q -2-1kN u -4 Qmax= -99kN Before R=1/2-121kN H3 B9 Q u Before R=1/ Deformatio (mm) Deformatio (mm) (d) O-ht speime -.2%.2%.5%

7 D B d a a B d E a B a (a) I-1t speime () I-ht speime () O-1t speime (d) O-ht speime 5. EQUTION OF ULTIMTE STRENGTH Figure 4.2. Oserved rak patter I opeig diretio loadig, failure mode of all speimes is osidered to e flexural failure of the first-story olum at the fae of eam judgig from the strais i the eam-olum joit ad rak appearae. I losig diretio loadig, failure mode of I-1t, I-ht is also osidered to e flexural failure of the first-story olum at the fae of eam. Failure mode of O-1t, O-ht is osidered to e joit failure ut the reiforemet of the first-story olum is yielded. Eah flexural stregths of the first-story olum Q u, whih is divided ultimate flexural momet M u alulated ased o Navier hypothesis y the height from ritial setio (I-1t, O-1t : at the fae of the first-story olum () i Fig 2.1, I-ht, O-ht : at the fae of hauh (B) i Fig 2.1) to the poit of the lateral load, is show i Fig 4.1. However, the test results do ot math with eah flexural stregth. To judge from the promiet flexural rak, the ritial setio is osidered to move ito the joit. Therefore the ritial setio is reset aordig to ritial setio of the first-story olum i opeig diretio loadig I opeig diretio loadig, the ompressive strut of the speimes is assumed as show i Fig 5.1. It is osidered that the first-story olum is yielded eause shear fore of first-story olum is pulled y tesile fore of reiforemet arraged at the ottom i the eam. Therefore the ritial setio of the flexural failure of the first-story olum is set to e at the eter of gravity positio of ottom reiforemet. The speime O-1t, O-ht is oserved to e promiet rak i Fig 4.2 (), (d). The effetive depth is smaller tha ormal depth due to that promiet rak. Therefore the effetive depth is realulated ased o the assumptio show elow. The equilirium oditio for effetive setio show i Fig. 5.1 () is give y Eq. (1). The ompressio out of the orete setio resisted y equilirium for out ad tesile of the joit Σa w σ wy show i the lue tie width ΔD i Fig 5.1 () is give y Eq. (2). The effetive depth D eff is give y Eq. (3). out d a D D w wy 1 2 (1) D F (2) out a d D l D l D (3) w wy eff 1 F D 1 D2

8 where, d : effetive depth of eam, D 1 : depth of first-story olum, D 2 : depth of seod-story olum, : width of first-story olum, F : ompressive stregth of orete, a w : ross setioal area of joit, σ wy : tesile yield poit of joit, l : the legth from the fae of the eam to the startig poit of the 9 degrees hooked show i Fig 5.1. D 1 the eter of the gravity lie T ritial lie l D eff T Σa w σ wy D out d a d out D 1 D 2 Σa w σ wy (a) I-1t, I-ht speime D 2 D 1 -D 2 () O-1t, O-ht speime () equilirium for out ad tesile of the joit Σa w σ wy Figure 5.1. ritial setio of the first-story olum i opeig diretio 5.2. ritial setio of the first-story olum i losig diretio loadig I losig diretio loadig, flexural failure of first-story olum is osidered as show i Fig 5.2. It is osidered that the first-story olum is yielded eause shear fore of first-story olum is resisted y ompressio rage x of the eam. The equilirium oditio for that ompressio rage x is give y Eq. (4). The average stress of orete is assumed as 85% of the ompressive stregth of the orete. Qu x =.85 F (4) where, : depth of eam, F : ompressive stregth of the orete Therefore, the ritial setio of the flexural failure of the first-story olum is set to e at the eter of ompressio rage of eam x /2. However the ritial setio of the flexural failure of the first-story olum of the speime I-ht, O-ht with hauh is reset to e the setio ased o the assumptio show elow. The failure plae of the orete y uofied ompressio is osidered to e plae ilied aroud 1:2 (arpiteri. et al., 21) show Fig 5.2 (). The orete lok show i Fig 5.2 (a) is also assumed to e failure plae of the orete ilied 1:2 with the legth 5 x. Besides, the speimes with hauh show i Fig 5.2 (), (d) are also assumed to e failure plae of the orete ilied 1:2 with the legth 5 x. The ompressio rage x h of the speimes with hauh is give y Eq. (5). Therefore the ritial setio of the flexural failure of the first-story olum is reset to e at the eter of ompressio rage of eam x h /2. x x (1 2 ta ) (5) h

9 F 2 F losig 5x 2x x () failure surfae i uofied ompressio 2x taθ θ 2 x 1 F h x h losig θ 5x 2x F h x x h (a) speime without hauh () failure surfae of hauh (d) speime with hauh Figure 5.2. ritial setio of the first-story olum i losig diretio loadig 5.3. Modellig of the joit failure i losig diretio loadig (O-1t, O-ht) I losig diretio loadig, the promiet rak a of the speime O-1t, O-ht show i Fig 4.2 (), (d) progress at aout 45 degrees. The failure mode of speimes O-1t ad O-ht is osidered to e joit failure mode show i Fig 5.3 (a). The poit at itersetio of failure lie of 45 degrees from outside of seod-story olum ad the ompressio rage x 2 of the seod-story olum is refleted to the eam. The ompressio rage x 2 ad ultimate flexural momet of the seod-story olum 2 M u is alulated y the way ased o Navier hypothesis. The rage from that poit to extreme ompressio fier is assumed to e the ompressio rage x of the eam. The joit failure stregth j Q u is osidered y the equilirium show i Fig 5.3 (). ll the tesile ad ompressio reiforemet of the eam are assumed to e yielded. Tesile fore ad ompressio fore represet T s ad s. The ompressio of the orete of the eam is give y Eq. (6). The eam momet is alulated at the eter of the eam. The ompressio is assumed to e ated at x /2. The momet M u of the eam is give y Eq. (7). The joit failure stregth j Q u is alulated y Eq. (8). The momet j M u of the ultimate joit stregth is alulated as a total of the momet 2 M u ad M u. The legth L is from the eter of the depth of the eam to the lateral load. jqu Ts s (6) D x Mu Ts gts s gs 2 (7) jm u 2 M u M ' u jq ' u L L (8) However, The joit failure stregth j Q u of the speime O-ht with hauh is osidered y the equilirium show i Fig 5.3 (). ompressio reiforemets of the eam are assumed to e ot yielded. Istead, ilied reiforemets are assumed to e yielded. The momet j M u of the ultimate joit stregth is alulated i the same way. The depth of the eam is iluded i the part of hauh. x x 2 45 x /2 g s g ts s (a) O-1t, O-ht speime () O-1t speime () O-ht speime T s 2 M u D j Q' u L x /2 g ts s g s T s 2 M u D j Q' u L Figure 5.3. Modellig of the joit failure i losig diretio loadig (O-1t, O-ht)

10 5.4. ompariso the alulated ad oserved story shear ompariso the alulated ad oserved story shear is show i Fig 5.4. The dashed lies show ±1% error lies. pproximately, i oth opeig ad losig diretio loadig, the stregth of the oserved failure mode is evaluated as show i Fig 5.4. O the other had, i losig diretio loadig, the oserved failure mode of the speimes O-1t, O-ht is osidered to e joit failure. However, Modified flexural stregths of the first-story olum Q u are lower tha joit failure stregths j Q u ad the oserved failure mode does ot orrespod to the alulated failure mode. story shear (test) 12 (kn) I-ht O-ht O-1t I-1t I-ht O-ht I-1t O-1t story shear (alulatio) (kn) Q' u Q' u j Q' u modified flexural failure of the first-story olum i opeig diretio loadig modified flexural failure of the first-story olum i losig diretio loadig joit failure i losig diretio loadig Figure 5.4. ompariso the alulated ad oserved story shear 6. ONLUSIONS The followigs are oluded: 1) I the opeig diretio loadig, all the speimes showed flexural failure of first-story olum. 2) I the losig diretio loadig, the speimes i whih the first-story olum are exteded toward iside show flexural failure of first-story olum, whereas the speimes i whih the first-story olum are exteded toward outside showed joit failure. 3) Hauh at the orer of the joit is effetive o improvig stregth ad stiffess. 4) The proposed equatios of the flexural stregth of the first-story olum ad the joit failure a estimate the stregth otaied y experimets. KNOWLEDGEMENT The authors akowledge the supports y the Grat-i-aid for researhes o the uildig odes improvemet y Miistry of Lad, Ifrastruture, Trasport ad Tourism, Japa. REFERENES rhitetural Istitute of Japa (IJ). ll Stadard for Strutural alulatio of Reifored orete Struture. Tokyo, Japa, 21. (i Japaese) Kotai, G., et al. (211). Experimetal Study o Joit Failure Mode of Soft-First-Story R Buildigs Part 1~3. rhitetural Istitute of Japa Tokai hapter rhitetural Researh Meetig 49:2, Kato, Y., et al. (212). Experimetal Study o Joit Failure Mode of Soft-First-Story R Buildigs Part 4~5. rhitetural Istitute of Japa Tokai hapter rhitetural Researh Meetig 5:2, , arpiteri,. et al, (21) Size-sale ad slederess ifluee o the ompressive strai-softeig ehavior of orete, Fatigue ad Frature of Egieerig Materials ad Strutures, Vol. 24,