CAPACITY OF STIFFENED STEEL SHEAR PANELS AS A STRUCTURAL CONTROL DAMPER

Transcription

1 CAPACITY OF STIFFENED STEEL SHEAR PANELS AS A STRUCTURAL CONTROL DAMPER H.B. Ge 1, K. Kaneko and T. Uami 3 1,3 Profeor, Department of Civil Engineering, Meijo Univerity, Nagoya , Japan Graduate Student, Department of Civil Engineering, Nagoya Univerity, Nagoya , Japan gehanbin@ccmf.meijo-u.ac.jp, kaneko@truct.civil.nagoya-u.ac.jp, uamit@ccmf.meijo-u.ac.jp ABSTRACT : Thi paper deal with the deformation capacity of hear panel damper (SPD), which i one type of acrificing member to be ued in damage control deign of tructure. The deformation capacity indexe of SPD conidered are the maximum deformation and cumulative inelatic deformation, and their target value are aumed to be 1% and 8%, repectively. To invetigate if the SPD i of thi capacity, an extenive numerical analyi i carried out. Validity of the analytical method i verified with experimental reult. It i found that the preent analyi can accurately predict the inelatic cyclic behavior of high performance SPD. KEYWORDS: Shear damper, Stiffened plate, Cyclic behavior, Deformation capacity 1. INTRODUCTION A hear-type hyteretic damper (tiffened or untiffened) i one type of variou hyteretic damper, whoe effective mechanim for diipation of energy input to a tructure from an earthquake i through inelatic deformation of the metal. When a hear panel i intalled into tructure acting a an energy aborber, it i important to pecify the range of hear deformation that the panel will utain capacity in the event of an earthquake, namely, the limiting range of hear deformation demand. For building tructure, maximum tory drift of 1% i uually pecified for Level II deign earthquake (Nakahima 1995). According to geometric configuration, the range of 3 5% i conequently taken a lower bound of hear deformation angle for a combined-type hear panel damper within building frame (Takahahi and Shinabe 1997). For bridge tructure, limiting value of 1 1% for ultimate hear deformation angle are pecified in the Guideline (RTRI ) and a previou paper by Uami (7). Extenive experimental and analytical reearche have been conducted on individual hear panel damper and building tructure incorporated with them (Nakahima et al. 1994; Tanaka and Saaki ; Nakahima 1995; Takahahi and Shinabe 1997; Tanaka et al. 1999). However, the reearche on bridge tructure remain infancy (RTRI ; McDaniel et al. 3; Chen et al. 5; Chen et al. 7). Recently, an experimental tudy on developing high-performance tiffened hear panel damper for poible ue in bridge tructure wa carried out by the author (koike et al. 8). It ha been confirmed that the tiffened SPD have high deformation capacity a large a 1% in train and 8% in cumulative inelatic train and high durability for low cycle fatigue by intalling the tiffener adequately. In thi paper, analytical reult of tiffened teel hear panel damper under cyclic hear loading are preented, and compared with the experiment (Koike et al., 8).. ANALYTICAL METHOD.1 Main Parameter The chematic of SPD i hown in Fig.1. The web lenderne parameter and the rigidity of tiffener are two important parameter in conidering hear deformation in web, becaue hear buckling i undeirable to diipate enough energy or in other word hyteretic loop hould be table. The web lenderne parameter R w i defined a

2 b f x Sub-panel Flange Stiffener a Web b Q Q σ y -.3σ y Web / Stiffener : b wc = 1 :.3 b t1 : b c : b t =.69: 1 :.17 y (a)web (b)tiffener Figure 1 SPD Figure FEM model Fig.3 Ditribution of reidual tree b wc b wc b wc / b t1 b c b t σ y -.3σ y 3σ y /17 Web Stiffener R ( ν ) b 1 1 τ w y = (.1) t k π E w w where b w and t w =width and thickne of web repectively, τ y =hear yield tre of web material (=σ y / 3 ), E=Young' modulu of elaticity, ν=poion' ratio, and k =elatic buckling coefficient of a imply-upported plate under hear, given by ( nl + 1) ( α ) α 1 k = (.) ( nl + 1) ( 5.35 α + 4) α 1 where n L =number of longitudinal tiffener, and α =apect ratio of ubpanel. A decribed in Eq.(.1), when b w (= height "a" in thi tudy) get large, there are two way to keep R w contant. One way i to ue a thicker plate, and another way i to add tiffener. In the former way, it i undeirable for the yield load of SPD to get larger becaue SPD hould yield earlier than main tructure to perform hyteretic damping. Thu, the latter way i effective and conidered in thi tudy. The rigidity of tiffener γ i defined a E I γ = (.3) bw Dw where I =moment of inertia of tiffener, taken at the interaction urface of tiffener and web, and D w =flexural rigiditie per unit width of web. In thi tudy, rigidity of tiffener i deigned with 3 time of optimum rigidity of tiffener γ *, defined a 3 nl.3 ( 1+ α ) γ = (.4) nL 3 nl nl n 1+ L α Analytical model deigned in thi tudy are hown in Table 1. The number after letter "SPD" in the model name are the web lenderne parameter and the number of tiffener, repectively. Stiffener locate both ide of web except for SPD-.-A. To make ure that hyteretic damper have enough performance in earthquake, the yield of SPD mut be prior to that of main tructure, a referred above. In thi tudy, low- yielding-point teel LY5, whoe yield point i controlled in a limited range, i ued for the web and SM49Y for tiffener and flange. Table how the material propertie.. Analytical Model The analyi i performed with general-purpoe finite element program ABAQUS (3). The web, tiffener nl 1

3 and flange are modeled by 3-dimenional reduced-integration hell element a hown in Fig.. The modified two urface model i employed a contitutive law in order to trace the material cyclic behavior accurately (Shen et al., 1995). Additionally, initial imperfection, reidual tre and initial deflection, are alo conidered. The ditribution of the reidual tre in the web and the tiffener i idealized in a rectangular pattern, a hown in Fig.3. On the other hand, initial out-of-plane deflection in web i aumed a a πx πy b + + w ( nl 1) πx ( nl 1) πy δ = + w in in in in (.5) 1 a bw 15( nl + 1) a bw Conidering that both end of the panel are welded on coniderably rigid plate in practice, the degree of freedom of the model at the plane x= and x=a (ee Fig.) are aumed fixed except for the diplacement in the x and y direction. Cyclic diplacement loading pattern i employed a the ame a in the experiment (Koike et al. 8). It i executed with an increment of % average hear train alternating with poitive and negative, a defined in Eq.(.6), until 1% and after reaching 1% contant amplitude loading i performed until cumulative platic deformation reache 8%. In thi tudy, pure hear i conidered without conidering the effect of vertical load. During the analyi, average hear tre, τ n, and average hear train, γ, are defined in Eq.(.6). Q δ τ n =, γ = (.6) bw tw a where Q=ummation of horizontal reaction force at the plane x=. Table 1 Structural parameter and dimenion of SPD R w Web Stiffener Flange Model a b w t w α α b w /t w R w n L n T b t γ /γ * b f t f (Deign value) mm mm mm mm mm mm mm 1SPD SPD SPD SPD SPD-.-A SPD-.-1/ SPD Table Material propertie Steel E (GPa) σ y (MPa) ε y ν E t (MPa) ε t σ u (MPa) ε u (%) SM49Y(9mm) SM49Y(11mm) SM49Y(14mm) SM49Y(19mm) SM49Y(mm) SM49Y(5mm) LY5(9mm) LY5(16mm)

4 th The 14 World Conference on Earthquake Engineering SPD SPD Analyi -5 5 Analyi -5 (a) 5 (b) SPD-.- SPD-.-A - Analyi -5 - Analyi (c) (d) SPD-.5- SPD Analyi -5 (e) 5 - Analyi -5 5 (f) Figure 4 Hyteretic hear tre-hear train curve 3. RESULTS AND COMMENTS Figure 4 how typical hyteretic curve of the normalized hear tre veru hear train of everal analytical model compared with correponding experimental curve. A can be een from Fig.4, hyteretic curve obtained from the analyi agree generally well with thoe from the experiment, although the gradient in hardening region i omewhat different between experiment and analyi in all the model. In the analyi, the trength deterioration occur at an average hear train of -6% or 8% in the cae of SPD-.5- (Fig.4(e)) and the pinching occur after reaching 1% in the cae of SPD-.3-1(Fig.4(f)). On the other hand, in the cae of SPD and Rw =. erie uch a SPD-.-1 and SPD-.- the analytical hyteretic curve agree with the experimental reult with a good accuracy, becaue hear trength deterioration wa not oberved in the analyi before the target capacity (1% of the maximum train and 8% of the cumulative train). It hould be noted that in final everal cycle of the analyi the hear trength deterioration

5 (a)overall view after tet (b)detail on left ide (c)detail on right ide Figure 5 Crack propagation in teted pecimen SPD-.- Energy/E y SPD-.5-1 experimet analyi half cycle Energy/E y 6 SPD experiment analyi half cycle Fig.6 Cumulative diipated energy Energy/E y 6 SPD experiment analyi half cycle occurred due to local buckling. In the experiment both the local buckling in ub-panel and crack propagation around edge of tiffener initiated by extremely low-cycle fatigue were oberved although the trength deterioration i hardly oberved in the pecimen with maller value of the width-thickne ratio, a hown in Fig.4. Figure 5 how crack around edge of tiffener in the cae of SPD-.- after tet. The crack firtly took place on boxing of tiffener, which tie fillet weld on both ide of the tiffener, and propagated in the thickne direction. In the preent analytical model, however, the crack initiation and propagation are not conidered. But the hear trength keep increaing for a while after crack initiation which happened before 8% of the cumulative inelatic deformation. Refer to the required capacity decribing above, all the model ued in thi tudy atified in both experiment and analyi except for analytical model of SPD-.3-1, whoe hyteretic loop eem untable a hown in Fig.4. It i alo found that the web lenderne parameter R w i a controlling parameter in determining the capacity. And in order to have deigned trength againt buckling, the tiffener need to work in good condition until the end of the loading. In thi tudy tiffener are deigned a 3 time of optimum rigidity of tiffener γ * a referred above, and uch a deign conideration i appropriate ince the buckling occurred at node of tiffener a hown in Fig.5. Comparion of SPD-.- with tiffener at one ide and SPD-.-A with tiffener at both ide how that there i no obviou difference either in the hyteretic loop or in deformation capacitie, although a little difference wa oberved in the experiment. Thi i becaue that in the cae of SPD-.- crack initiated on only one ide of the web and got delayed to go through in the thickne direction, compared with SPD-.-A. When SPD-.-1 with the ame value of R w but only one tiffener i compared with SPD-.-, the cumulative inelatic deformation in the cae of SPD-.-1 i almot the ame to that of SPD-.- The cumulative inelatic deformation of everal model are hown in Fig.6. In Fig.6, The vertical axi repreent the cumulative diipated energy which i normalized with E y (=Q y Δ y /) and horizontal axi repreent half cycle which count γ=+%, -%, +4% a 1,, 3 in the loading pattern. The prediction error at the final tage (i.e., the lat half cycle) between the experiment and analyi i larger than 1% in the cae of SPD-.5- and SPD-.3-1, where the buckling caued coniderable trength deterioration in analyi. On the other hand, in the analytical model with R w below., the prediction error i le than 5%.

6 Therefore, it can be concluded that the model with R w below. can be conidered to have high performance atified with the capacity limit. 4. CONCLUSIONS Thi paper preented reult of a numerical analyi on developing high-performance tiffened teel hear panel damper. It ha been hown that the cyclic behavior and capacity of the SPD with R w below. can be predicted uing the preent analytical model with good accuracy. Thi tudy i the firt tep for developing high-performance SPD with required capacity. To invetigate an appropriate capacity required for SPD, dynamic analyi of tructure intalled with SPD ha to be performed and repone of SPD induced by the earthquake ha to be invetigated with varying parameter. ACKNOWLEGEMENT: The tudy wa upported in part by grant from the Advanced Reearch Center for Seimic and Computation, Meijo Univerity. REFERENCES ABAQUS, Inc., ABAQUS/Analyi uer' manual-verion 6.5, Pawtucket, R.I., 3 Chen, Z.Y., Ge, H.B., and Uami, T. (6). Hyteretic model of tiffened hear panel damper. J. Struct. Eng., ASCE:13(3), Chen, Z.Y., Ge, H.B. and Uami T. (7). Study on eimic performance upgrading for teel bridge tructure by Introducing energy-diipation member, J. Struct. Eng., JSCE:Vol.53A, Koike Y., Yanaka T., Uami T., Ge H. B., Ohita S., Sagou D., Uno Y. (8). An experimental tudy on developing high-performance tiffened hear panel damper. J. Struct. Eng., JSCE :Vol.54A, McDaniel, C. C., Uang, C. M., and Seible, F. (3). Cyclic teting of built-up teel hear link for the new bay bridge. J. Struct. Eng., ASCE:19(6), Nakahima, M. (1995). Strain-hardening behavior of hear panel made of low-yield teel. I: Tet. J. Struct. Eng., ASCE:11(1), Nakahima, M., Iwai, S., Iwata, M., Takeuchi, T., Konomi, S., Akazawa, T., and Saburi, K. (1994). Energy diipation behavior of hear panel made of low yield teel. Earthq. Eng. Struct. Dyn.:3(1), RTRI. (). Guideline for deign of railway viaduct with damper and brace, Railway Technical Reearch Intitute, Tokyo, Japan (in Japanee). Shen, C., Mamaghani, I. H. P., Mizuno, E., and Uami, T. (1995). Cyclic behavior of tructure teel. Ⅱ: theory, J. Engng. Mech., ASCE:11(11), Takahahi, Y., and Shinabe, Y. (1997). al tudy on retoring force characteritic of hear yielding thin teel plate element. J. Struct. Contr. Eng., AIJ :494, (in Japanee). Tanaka, K., and Saaki, Y. (). Hyteretic performance of hear panel damper of ultra low-yield-trength teel for eimic repone control of building. 1WCEE (CD-Rom), Aucklan, NZ. Tanaka, K., Saaki, Y., and Yoneyama, S. (1999). An experimental tudy on hyteretic performance of hear panel damper uing different trength type of teel under tatic loading. J. Struct. Contr. Eng., AIJ:5, Uami T. (7). Developing high-performance damage control eimic damper, Proc. 1th Symp. On Ductility deign Method for Bridge, 11-.