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1 Journl of Civil & Environmentl Engineering IN: X Reserch Article Journl of Civil & Environmentl Engineering Ari et l., J Civil Environ Eng 16, :3 DOI: 1.417/ X.3-6 Open Access Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte Ryotro Ari*, Hnko toh, Kent Aoki, Tkumi Ito nd Chnghoon Choi Deprtment of Architecture, Tokyo University of cience, Jpn Abstrct A lot of steel structures hve experienced severe erthquke dissters in Jpn, nd its vrious kinds of filure mode hve been reported. Especilly on steel brced structure, the filure modes re generlly ctegorized into two modes; buckling nd frcture of brce member, nd yielding of joints nd fsteners. After lot of erthquke dissters, the technicl mnul hs been published to repir nd recover the dmged building structures in Jpn [1]. The mnul suggests the ctul repiring method for dmged steel brced structures; however, it is guessed tht few of these methods hve some difficulties relted to construction technique nd estimtion of recovery fter repir. In this pper, new repiring method for joints on dmged steel brce structure hs been proposed, nd its pplicbility nd fesibility re investigted experimentlly. Herein, the horizontlly loding test on digonl steel brce re performed with prmeters s follows; thickness of gusset plte, lyout of bolts, slenderness rtio of brce nd the method of joint. At first, the dmged stte of gusset plte is reproduced by horizontlly loding test. Next, the dmged gusset plte is repired. Finlly, the loding test is done to the repired specimen gin. From the test results, the strength is reinforced fter repir, nd the rigidity is lmost sme. The chnge of filure mode nd slenderness rtio is presented, nd which is relted to eccentric distnce nd torsionl prmeters. Furthermore, the evlution method of the filure mode nd buckling strength re proposed, nd this estimtion method shows good utility. Keywords: teel brced structure; Ultimte seismic stte; Repir method; Gusset plte; Evlution method Introduction Recently lot of buildings re dmged vriously fter huge erthquke dissters, nd it is necessry to decide whether they re rebuilt or reuse. The steel frme structures re clssified roughly into rhmen nd brced structure, nd serious dmges re reported to both of them. Receiving tht, the word resilience is focused on. From the viewpoint of reconstruction nd restortion of city function promptly, it is desirble to repir nd reuse the public buildings which become the bse of recover nd reconstruction in the stricken re. Also, these public buildings re minly brced structure. There re mny reports tht the vrious types of filure modes of steel brced structure, such s buckling, frcture of brce member, nd yielding of joints nd fsteners. In Jpn, the corresponding to these filure modes is discussed in the technicl guideline). The guideline suggests some ctul repir methods, however, it is not necessry the best method considering the stte of stricken re. In this study, in cse of the gusset plte is dmged, the new method which tkes plce the conventionl method is suggested nd the horizontlly loding tests re conducted on digonl steel brcing. And this pper ims to propose n evlution method of repired stte. Mterils nd Methods Repir methods of dmged steel brce joint This study focuses on the filure mode of joint which out of plne deformtion is occurred during ultimte seismic stte. It is premised tht the dmged brce nd fsteners re replced nd the gusset plte is repired. When the new brce is ttched on the dmged gusset plte, clernce occurs between gusset plte nd brce. And the tpered steel filler is inserted on this clernce. And to restrin the deformtion of gusset plte, the side stiffener is ttched. The outline of repir method is s follows: First, the tpered steel filler is welded on dmged gusset plte. Next, the side stiffener is welded on the side of gusset plte. The detils of proposed repir methods re shown in Figure 1. Inspection of repir effect by horizontlly loding test The outline of horizontlly loding test: In this loding test, the test specimen nd test setup re illustrted in Figure. The flow of the loding test is s follows: First, the test frme (Figure ) is horizontlly loded nd brce member nd gusset pltes re dmged (herein fter referred to s Initil loding ). econd, the gusset pltes which dmged by initil loding is repired. Finlly, the loding test is done to the repir specimen gin (herein fter referred to s econd loding ). Experimentl prmeters: Experimentl prmeters re s follows: the lyout of bolts on joint, the thickness of gusset plte, repir or not repir fter initil loding, the slenderness rtio of the brce nd the usge of tpered steel filler. The lyout of bolts is determined by the length of brce. The thickness of gusset plte is 4.5 mm, 6 mm, 16 mm. The slenderness rtio of the brce is 9, 1,15. And lso, the loding progrm is monotonic nd cyclic loding. On the monotonic loding, the brce member or the gusset plte become the ultimte sttes. During the cyclic loding, mximum story deformtion ngle is 1/3 rdin. Test specimens were instrumented with sensors for mesuring below items: horizontl displcement, in nd out of plne deformtion of brce, out of plne of the gusset plte. trin of brce is mesured t the mm, 4 mm, 6 mm, nd 8 mm from the end of brce. Mechnicl properties of mterils nd specimens list re summrized in Tbles 1 nd. Test results Initil loding test results During loding test, three kinds of filure mode were observed, nd it is summrized in Figure 3. Also, on the occsion of the buckling *Corresponding uthor: Ryotro Ari, Deprtment of Architecture, Tokyo University of cience, Jpn, Tel: +81() ; E-mil: @ed.tus.c.jp Received July 6, 16; Accepted August 17, 16; Published August 19, 16 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Copyright: 16 Ari R, et l. This is n open-ccess rticle distributed under the terms of the Cretive Commons Attribution License, which permits unrestricted use, distribution, nd reproduction in ny medium, provided the originl uthor nd source re credited.

2 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Pge of 7 occurred, two kinds of bending mode were observed s showed in Figure 4. L15 series: During the monotonic loding, it ws observed tht the brce remined within elstic when the buckling ws occurred. The gusset plte nd the brce members deformed to out of plne in one unit until the buckling is occurred. After buckling ws occurred, the plstic hinge ws formed t the middle of the brce nd the connection between brce nd gusset plte (herein fter referred to s filure mode C ). And lso, the out of plne of the brce ws remrkble. In cse of lrge slenderness rtio, the bending moment to the gusset plte does not become so lrge. Therefore, out of plne of gusset plte wsn t so lrge. Furthermore, the connection between brce nd gusset plte ws twisted. During the cyclic loding, the connection ws twisted nd the plstic hinge ws formed t the middle of brce nd connection. L1-6 series: From the results of strin during monotonic nd cyclic loding, the occurrence of intermedite of elstic nd plstic buckling ws considered. A plstic hinge ws generted on middle of the brce (herein fter referred to s filure mode A ) on the ll specimens. The out of plne deformtion is observed on gusset plte. L1-16 series: The occurrence of intermedite of elstic nd plstic buckling ws considered. The plstic hinge ws generted on middle nd both end of brce, becuse the gusset plte didn t deform. (herein fter referred to s filure mode B ). L9 series: In cse of smll slenderness rtio, xil lod ws lrger thn ny other series nd bending moment to gusset plte exerted enough. Therefore, the out of plne of gusset plte ws the lrgest. Also the filure mode A ws observed on ll specimens. The dmge sitution nd the repir method Exclude the L1-16 series; ll gusset pltes hve plstic deformtion. The result of residul deformtion ws summrized in Tble 3. In cse of the L15 series, the tpered steel filler wsn t New ide stiffener Dmged Gusset plte Tpered steel element Or Tpered steel element Bering-type connection ()Outline of repir method Friction-type connection Figure 1: Repir method. Tpered steel element (b)conception model Tpe mesure type displcement trnsducer Jck Rod displcement mesure Gusset plte (Right) trin gge Gusset plte (Left) Figure : Test set up. Gusset plte Rot oung s modulus (GP) ield strin (μ) ield strength (N/mm ) Tensile strength (N/mm ) b c d e b c d Tble 1: Mechnicl properties of steel mterils.

3 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Pge 3 of 7 pecimen nme lenderness rtio Thickness (mm) Bolt lyout (mm) Friction Repir Loding pttern L F-R-M1 L F-R-M 9 L F-R-C1 L F-R-C Repir L F-R-M1 L F-R-M 15 L F-R-C1 L F-R-C 4.5 Friction L F-N-M1 L F-N-M 9 L F-N-C1 L F-N-C L F-N-M1 L F-N-M 15 Non-repir L F-N-C1 L F-N-C L1-6--NF-N-M1 L1-6--NF-N-M L1-6--NF-N-C1 L1-6--NF-N-C Non- friction L1-6--NF-R-M1 L1-6--NF-R-M 6 L1-6--NF-R-C1 L1-6--NF-R-C Repir L1-6-4-F-R-M1 Friction 1 L1-6-4-NF-R-M 4 L1-6-4-NF-R-C1 Non- friction L1-6-4-NF-R-C L1-16--F-N-M1 Non- repir L1-16--F-N-C1 L1-16--F-R-M1 16 Friction L1-16--F-R-C1 Repir L F-R-M1 4 L F-R-C1 Tble : pecimens list. Lot Gusset plte d b e b b d c d c Plstic hinge ()Filure mode A Plstic hinge (b)filure mode B Plstic hinge (c)filure mode C Figure 3: Filure modes on ultimte stte.

4 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Pge 4 of 7 ide M compression ide V compression Figure 4: Compression side. pecimen side Residul deformtion L 13.9 L F-R-M R 13. L 1 L F-R-C R 17.8 L 5.1 L F-R-M R 8.8 L 5 L F-R-C R 1.9 L 3.1 L1-6--F-R-M R 4. L 8.1 L1-6--F-R-C R 3.7 L 38 L1-6-4-F-R-M R 37.8 L 1 L1-6-4-F-R-C R.5 Tble 3: Residul deformtion (mm). Nme of specimen Axil rigidity (kn/ mm ) Rtio of rigidity Buckling lod (kn) Rtio of buckling lod Buckling length (mm) Filure mode* Compression side L F-R-M B TB M L F-R-M TB V L F-R-C B TB M.7 1. L F-R-C TB V L F-R-M B TB M L F-R-M B V L F-R-C B TB M L F-R-C B V L F-N-M B M.8 L F-N-M B M L F-N-C B M.8 L F-N-C B M L F-N-M B TB M.9.9 L F-N-M TB V L F-N-C B TB M.8 1. L F-N-C TB V L1-6--NF-N-M B M.9 L1-6--NF-N-M B M L1-6--NF-N-C B M L1-6--NF-N-C B TB M L1-6--NF-R-M B M L1-6--NF-R-M B TB V

5 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Pge 5 of 7 L1-6--NF-R-C B M 1. L1-6--NF-R-C B V L1-6-4-F-R-M B M L1-6-4-NF-R-M B V L1-6-4-NF-R-C B M L1-6-4-NF-R-C B TB V L1-16--F-N-M B TB M L1-16--F-N-C B TB M L1-16--F-R-M B V L1-16--F-R-C B V L F-R-M B V L F-R-C B V *B = Bending, TB = Torsionl bending Tble 4: Comprison of test results. Test result of xil rigidity[kn/mm] 6 4 ttched. According to the Guidebook on Design nd Fbriction of High trength Bolted Connections []. When the clernce is less thn 1 mm, filler isn t necessry. The reson is tht the gusset plte wsn t repired by tpered steel filler. The detils of repir mterils re bellow. As mentioned in chpter, the tpered steel filler is welded on dmged gusset plte. Note tht the repir method of connection is one of the experimentl prmeters, the specimen by using friction joint is soked rust by medicine. And lso, when the brce is fstened with the gusset plte by the bolts normlly, nd then the sme shpe of tpered steel filler is dopted on both side of brce test specimen. The usge of tpered steel filler is shown in Figure 1. econd loding test results 4 6 Clculted vlue of xil rigidity[kn/mm] Figure 5: Comprison of xil. L15-N series: On the dmged stte, clernce between gusset plte nd brce were existing. And this clernce ws disppered little fter the bolts were fstened. From the test results, the elstic buckling ws occurred on ll specimens, nd side V is presented s the stte of compression. ince the initil deformtion exist on the brce, not enough bending moment exerted to the gusset plte. L1-N series: In similr mnner of L15 series, there ws clernce between the gusset plte nd the brce. From the test results, with comprison to the initil loding, the mximum lod (buckling lod) becomes lrger. Differ from the L15 series; bending moment exerted enough to return the gusset plte. Therefore, during second loding, the mximum lod becme lrger compred with initil loding. L9-N series: The clernce between gusset plte nd the brce ws the lrgest of ll series. In similr mnner of the L1 series, the mximum lod ws lrger thn initil loding. However, the bolts slipped frequently. L15-R series: Differ from the non-repir specimens, the clernce becme less thn 1 mm by welding the tpered steel filler on the gusset plte. And lso, the side V is presented s the stte of compression. L1-R series: ince the bolts weren t verticlly fstened on the gusset plte, they were stiffened s verticlly s possible. And lso ll specimens slipped frequently. o the criticl dmge ws confirmed round the bolt hole of tpered steel element nd the gusset plte. L9-R series: The tpered steel filler ws welded on gusset plte. ince the residul deformtion ws lrge, mesurement error nd processing precision ws not precisely. Therefore, clernce existed between brce nd tpered steel filler. This clernce ws disppered little fter the bolts stiffened. And lso, initil deformtion occurred on brce. A verifiction of repir To mke comprison between initil loding nd second loding is shown in Tble 4. Expect for L F-N-M, rtio of buckling lod is 1. or more. From tht, the effectiveness of this repir method is confirmed. tudy on the strength nd ductility Initil stiffness: Figure 5 compres the rigidity obtined from test nd theoreticl result. On ll specimens, test result underestimtes the rigidity. This is ssumed tht the frictionl force function not sufficiently becuse of slip. Buckling length: The buckling length of repired specimens become shorter thn before repir. Judging from tht, the bering sitution is enhnced nd come close to the fix support. Deformed stte: About the L1-16 nd repired specimens, deformtion of brce dvnces in plne, wheres other specimens (before repired specimens) dvnce out of plne. By this, in cse of the bering sitution come close to fix, direction of deformtion proceeds to in plne. In ddition, s showed in Tble 4, repired specimens (in brief, in the cse of bering sitution of joint is enhnced) tend to be compressed side V. Curvture distribution: As representtive exmple of specimens, the curvture description of L1-6--F-R-M is described in Figure 6. Focusing on 6 mm in Figure 5, s the ductility fctor rises, the curvture rises too. However, focusing on 6 mm in Figure 5b, there is no difference in curvture. By this, side stiffener restrins the deformtion not only gusset plte but brce.

6 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Pge 6 of 7 Curvture [ 1-6 /mm ] μ=.5 μ=.6 μ=.7 μ= μ=.9 μ= Distnce from the edge [mm] -4 Curvture [ 1-6 /mm ] μ=.5 μ=.6 μ=.7 μ= μ=.9 μ= Distnce from the edge [mm] -4 () Before repir Figure 6: Comprison of curvture distribution. (b) Loding bevel b G V X Loding bevel Tpered steel element G V X Gusset plte e x U Dmged Gusset plte e x U :hre center G:Center of grvity ()Before repir Figure 7: ection of joint. (b) M T M G M X X Proposl of evlution method of buckling lod Generl description of evlution method By foregoing chpter, in cse of the bering sitution is enhnced, torsionl buckling is likely to occur. And lso, the buckling lod reverted to originl stte by repiring. Therefore, the repiring method in this study is effective for dmged brcing structure. In this chpter, the evlution method of buckling lod for originl stte nd repired stte is discussed. Vrible of evlution method Z Figure 8: Definition of the vrible. Bering sitution: Considering the circumstnces of connection, X P e x G bering sitution is clculted. Furthermore, by ttching side stiffener, the rigidity of gusset plte is ten times s lrge s originl stte. o in this method, the rigidity of repired gusset plte clculted the sme wy. Eccentric distnce: A cross section of the repired gusset plte is shown in Figure 7. The eccentric distnce of originl stte is clculted by eqution (1), nd fter repired is clculted by eqution (). Note tht, the tsp1 nd the tsp is thickness of tpered steel element. tg t (b ) g e x = g+ tb t + t + t ex = g+ Evlution method g sp1 sp t b g + t (b ) t sp1 + t + sp The buckling stte is clssified into the bending buckling or the lterl torsionl buckling by using eqution of equilibrium s bending sitution nd eccentric distnce re vribles, nd buckling lod is evluted. Considering the test sitution, boundry conditions re s follows: Mx = Mt =, My = pex, P = P, y =. Eqution (3) shows the buckling lod in elstic region. The vribles of eqution (3) re shown in Figure 8. By these equtions, the buckling lod is clled by eccentric distnce nd bering sitution.

7 Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 Pge 7 of 7 Both end fixed lb=77 Before repir lb= Buckling lod [kn] Both end fixed lb=78 Befor repir lb= Buckling lod[kn] Both end foxed lb=78 Before repir lb= Buckling lod[kn] Both end fixed lb=78 Before repir lb= Buckling lod[kn] 5 Eccentric distnce [mm] Eccentric distnce [mm] Eccentric distnce[mm] -4-4 Eccentric distnce [mm] G :Initil loding :econd loding(repired) :econd loding(non-repired) G :Initil loding :econd loding(repired) :econd loding(non-repired) G :Initil loding :econd loding(repired) :econd loding(non-repired) G :Initil loding :econd loding(repired) :econd loding(non-repired) ()L15series (b)l1-6-series (c)l1-6-4series (d)l9series Figure 9: Comprison of test results nd evlution method. (P +αp ) (P α P ) + 4P P (x / ρ ) P = w EX w EX w EX { α (X / ρ) } ρ = (x + y ) da/ A { + } ex x(x y )da/ A α= 1 ρi y Inspection of evlution method L15 series: Reltion of eccentric distnce nd buckling lod is shown in Figure 9. tright line indictes bending buckling lod; curve indictes lterl torsionl buckling lod. In ll specimens, the test results exceed the evlution vlue. Especilly, initil loding test results gretly exceed the evlution vlue; it s ssumed tht the buckling is occurred round the strong xis. L1-6 series: Reltion of eccentric distnce nd buckling lod is shown in Figures 9b nd 9c. On the loding test, some specimen becme the plstic buckling. Therefore, the plstic buckling lod ws lso described in Figures 9b nd 9c. ome repired specimen, the buckling lod is less thn the evluting vlue. In this cse, xil rigidity becme round 6%. Therefore, compression stress is not trnsmitted enough to the brce. Except this specimen, the test results exceed the evlution vlue. L9 series: Reltion of eccentric distnce nd buckling lod is shown in Figure 9d. The plstic buckling lod is lso described in Figure 9d. Except some repired specimen, test results exceed the evluting (3) vlue. In repired specimens which re flling below the evluting vlue, they becme plstic lterl torsionl buckling. o this evlution method is not enough to such sitution. However, considering the oung s modules decline to round 65%, this evlution method cn pply to this series. Conclusion This pper focused on repir methods for dmged steel brce members. The min conclusions re shown below: 1. To investigte the mechnicl property, loding tests ws performed. From the test results, it is confirmed the buckling lod nd rigidity were lmost recovered to originl stte.. By using the eqution of equilibrium, the evlution method ws proposed nd comprison with test results. About specimens which becme elstic buckling, evluting vlue underestimte the buckling lod. However, for other specimens, this method gives good result. Acknowledgement This reserch ws supported by Grnts-in-Aid for cientific Reserch(C) (Hed: Tkumi Ito). References 1. The Jpn Building Disster Prevention Assocition (1) Technicl Mnul.. Architecturl Institute of Jpn (11) Guidebook on Design nd fbriction of high strength bolted connection. Cittion: Ari R, toh H, Aoki K, Ito T, Choi C (16) Repir Method of Dmged teel d tructure nd Restring Force Chrcteristics fter Repir tte. J Civil Environ Eng 3:6. doi: 1.417/ X.3-6 This rticle ws originlly published in specil issue, nd World Congress on Construction nd teel tructure hndled by Editor(s). D Michel T J Bry, Crdiff University, UK