OVERVIEW OF 2007 E-DEFENSE BLIND ANALYSIS CONTEST RESULTS

Transcription

1 The th World Conference on Earthquake Engneerng October -,, Beng, Chna OVERVIEW OF E-DEFENSE BLIND ANALYSIS CONTEST RESULTS Makoto Ohsak, Kazuhko Kasa, Tsuyosh Hkno and Yuch Matsuoka Assocate Professor, Dept. of Archtecture and Archtectural engneerng, Kyoto Unversty, Japan Professor, Structural Engneerng Research Center, Tokyo Insttute of Technology, Japan Natonal Research Insttute for Earth Scence and Dsaster Preventon (NIED), Japan Emal: ABSTRACT : A blnd analyss contest has been conducted n conuncton wth the full-scale total collapse test of a four-story moment frame n September at the E-Defense shake-table faclty. The purpose of the contest s to stmulate development of computatonal methods and effcent modelng technques for collapse analyss. In ths report, statstcal data are presented for the types and parameter values employed by the partcpants of the contest, and the key factors to accurate estmaton of collapse behavor are nvestgated. KEYWORDS: Blnd analyss contest, Collapse analyss, Sesmc response, Steel frame. OVERVIEW OF THE CONTEST A blnd analyss contest has been conducted n conuncton wth the collapse test of the full-scale four-story steel buldng frame n September at the E-Defense shake-table faclty. See Suta et al. () and Tada et al. () for the detals of the four-story buldng frame. The bref report of the test results can be found n Suta et al. (). The overvew of the seres of the tests of steel buldng frames s presented n Kasa et al. (). The contest has been carred out by two workng groups under the supervson of the executve commttee. The Analyss Method and Verfcaton WG dd tasks ncludng announcement, dstrbuton of data, answerng questons, and udgment. The Buldng Collapse Smulaton WG produced the expermental data for the collapse of the four-story buldng. The purpose of the blnd analyss contest s to stmulate development of computatonal methods and effcent modelng technques for steel frames for predcton of sesmc responses and collapse behavor. The fnal goal s to mprove sesmc performance of steel frames through numercal smulaton. The man dffcultes of the contest are summarzed as follows: The actual moton of the table s not known before the test due to the control error of the shake-table. The shake-table tests are conducted consecutvely wth ncreasng levels of sesmc moton, and the sesmc level of the subsequent test s decded accordng to the actual deformaton and damage observed n the current test. The property of the concrete materal s measured only a few days before the test. Therefore, the followng two-step process has been adopted for the contest:

2 The th World Conference on Earthquake Engneerng October -,, Beng, Chna The contest has two parts: pre-test analyss based on antcpated sesmc motons, and post-test analyss usng the actual table acceleraton. The buldng model and the analyss procedure for the post-test analyss must be dentcal to those for the pre-test analyss except the property of concrete materal and nput acceleratons. The contest s categorzed by the types of analyss methods and partcpants. Analyss methods are classfed to D-analyss and D-analyss. Each category has two wnners: one from researchers ncludng students, and another from practcng engneers. Therefore, a total of four wnners were expected to be selected; however, we had fve wnners, because the two best scores of the -D analyss by researchers were same. Although the purpose of the contest s the development of technques for collapse analyss, t s very dffcult to predct the total collapse behavor by the currently avalable smulaton technques. Furthermore, the total collapse s prevented n the test by placng the retanng walls so as to avod any damage to the shakng table. Hence, the responses to be predcted are determned as Analyss results should be submtted for the ncpent-collapse level, the sesmc level mmedately pror to the collapse level at whch collapse of the buldng occurs. The analyss should be performed contnuously from the sesmc level at whch the frst plastfcaton occurs up to the collapse level, by serally combnng the correspondng table motons. Only the tme at collapse s to be predcted for the collapse level.. METHOD OF JUDGMENT The data to be submtted for udgment are specfed as For ncpent-collapse level: Maxmum values of relatve dsplacement from base, absolute acceleraton and overturnng moment at each floor; maxmum values of story shear, story drft angle; maxmum engneerng stran at a specfed pont (center of the column n st story) n an elastc regon; and resdual story drft at each story (the story drft at the end of the specfed duraton of the sesmc moton). For collapse level:, measured from the begnnng of the collapse-level moton, at whch the drft angle of any story n X- or Y-drecton reaches. rad. The udgment process s summarzed as follows: (a) Compare the RMS errors for each response quantty, whch s computed from E = ( F F ) () *,, F, : analyss result of th response quantty at th floor/story. F : test result of th response quantty at th floor/story. *, E : RMS error of th response quantty * It s possble to normalze F, F, by F *, before summaton. However, n ths case the errors of the small responses are magnfed. Therefore, we dd not make normalzaton n ths

3 The th World Conference on Earthquake Engneerng October -,, Beng, Chna contest. (b) The basc pont b for th response quantty s for the mnmum error, for the second, for the thrd, and for the fourth. The total pont P s computed from n P = wb () = w : weght for th response quantty n: number of response quanttes The team/ndvdual wth maxmum total pont wll be the wnner for each category. The weght w was announced to be. for all response quanttes by the commttee before the submsson of pre-test analyss results. (c) The udgment s carred out completely anonymously. Judges wll only know the partcpant submsson name only va the ID-number. (d) In each category, up to and ncludng the thrd place wnners are announced and the names of all the partcpants are asked to dsclose ther names and afflatons.. RESULTS OF THE CONTEST The numbers of submsson are as follows: Total: (D:, D: ) Researchers: (D:, D: ) Practcng engneers: (D:, D: ) The numbers of types of softwares adopted n each category are shown n Table, where, commercal means any commercally avalable software package, research means free software that may possbly be used for commercal purpose, and personal means n-house program developed for own use. Table Numbers of types of softwares and analyss models adopted n each category. -dmensonal -dmensonal analyss analyss Researcher Engneer Researcher Engneer Types of softwares Model of beams and column Commercal Research Personal Unknown Lne Lne+hnge Lne+fber Lne+hnge+fber Shell Lumped mass Others Unknown 9 The numbers of methods of modelng of beams and columns are also lsted n Table. Lne ndcates the conventonal beam-column lne element. Lne+hnge+fber means that fber elements are used for beams, and plastc hnges are used for columns. Others nclude appled element

4 The th World Conference on Earthquake Engneerng October -,, Beng, Chna method and dscrete element method. Note that the plastc deformaton at each member end can be effectvely smulated wthout usng plastc hnge or fber element, f each member s dvded nto an approprate number of beam-column elements, e.g. elements, consderng plastc deformaton.. STATISTICAL INVESTIGATION OF RESULTS We next carry out statstcal nvestgaton of the RMS values defned by Eq. () for the responses n Y-drecton, for whch the responses are computed by both of D- and D-analyses. To prevent obvously wrong data from affectng the statstcal values of the results, the exceptonal data are extracted usng the standard technques of clusterng called K-means;.e., the RMS errors of all the partcpants are dvded to two clusters for each response quantty, and the data n the cluster wth larger errors are removed. In the followng, the data mnng tool called WEKA Ver... (Wtten and Frank, ) s used for clusterng and classfcaton of the data. The number of exceptonal data n each response s lsted n Table. After removng those data, the values of mean, maxmum, mnmum and standard devaton of each response are computed as shown n Table. Table Number of exceptonal data, and the values of mean, maxmum, mnmum and standard devaton of the RMS value of each response n Y-drecton (RD: relatve dsplacement, AA: absolute acceleraton, OM: overturnng moment, SS: story shear, IDA: nterstory drft angle, RIDA: resdual nterstory drft angle, CS: column stran, CT: collapse tme). Number of exceptonal data RD (mm) AA ( mm/s ) OM ( kn mm) SS ( kn) IDA ( - rad.) RIDA ( - rad.) CS ( - ) CT (sec.) 9 Mean Std. dev Max Mn Table Mean, maxmum, mnmum and standard devaton of the RMS errors of the maxmum nterstory drft angles and shear forces n Y-drecton by D- and D-analyses. D- analyss D-analyss Drft angle Shear force Drft angle Shear force Mean Maxmum Mnmum Std. Dev. ( - rad.)..9.. ( kn)..9.. ( - rad.)...9. ( kn)....9 Table shows the mean, maxmum, mnmum and standard devaton of the RMS errors of the maxmum nterstory drft angle and shear force n Y-drecton among the partcpants n D- and D-analyses. As s seen, D-analyss has better performance n shear force; however, D-analyss s better n drft angle. Note that the obvously wrong results have also been omtted n the same manner as Table. In order to compare the RMS errors of dfferent responses by D- and D-analyses n the same performance measure, the RMS errors are normalzed as NormRMS(,) = [RMS(,) Mean()] / StdDev()

5 The th World Conference on Earthquake Engneerng October -,, Beng, Chna where RMS(,) and NormRMS(,) are the orgnal and normalzed RMS errors of group for the th response, respectvely, and Mean() and StdDev() are the mean value and the standard devaton of the RMS error of th response. RMS(,) s then summed up over to obtan the total score of group, whch has smaller (negatve) value for a group wth better performance. Three exceptonal data have been extracted for the total score, and they are replaced by the maxmum value of the remanng data. The values of (mean, std. dev., max., mn.) are (.,.,.,.). For D-analyss, those values are (.,.,.,.), whle (.,.,.,.) for D-analyss. Among best groups n the total score, the ranks,,,,, and are D-analyss, and, 9 and are D-analyss. Therefore, a slght advantage of D-analyss s observed over D-analyss. CPU tme Table Values and selecton of key factors adopted n the groups n each category. D-analyss D-analyss Use of materal and member test results Consder composte beam. Rgd-floor assumpton Dampng type Less than mn. Between mn. and mn. Over mn. Use member test. Use materal test. Do not use. Yes. No. Yes. No. Raylegh Stffness-proportonal Other Dampng rato Less than.. Larger than. Consder geometrcal nonlnearty Method of ntegraton step Δt (sec.) for ntegraton Yes No Newmark-β Other Δt.. < Δt.. < Δt.. < Δt Researcher Engneer 9 Researcher Engneer The parameters for analyss and selecton of key factors that affect the analyss results of the groups n each category are summarzed n Table, where means that the detals are not avalable from

6 The th World Conference on Earthquake Engneerng October -,, Beng, Chna the submtted documents. Obvously, CPU tme for D-analyss s generally larger than that of D-analyss. However, the relaton between CPU tme and accuracy of the results cannot be dscussed, because the detals of the type of CPU, sze of memory, etc., were not avalable. To nvestgate the key factors on the accuracy of the results, the groups are classfed to four ranks based on the total score S, where the k-means method has been used. As a results, the ranks are defned as Rank : S ; Rank : < S Rank : < S ; Rank : < S where Rank s the best among the four ranks, and the numbers of groups n Ranks - are,, and, respectvely. Drft angle Drft angle Drft angle (a) (c) Drft angle Drft angle Drft angle of st story (b) -. (e) (f) Fgure hstores of nterstory-drft angles n Y-drecton of the st story; sold lne: numercal result, dotted lne: expermental result (d) -.

7 The th World Conference on Earthquake Engneerng October -,, Beng, Chna The method J n WEKA s used for fndng dependences of the accuracy of the results on the parameter values. Although the data mnng technques are generally used for dscoverng the rules or knowledge from the data of huge sze, we can use data mnng tools to fnd the hnts or clues of dependences. The followng relatons have been found:. Among 9 groups that used the materal/member test results, are classfed as Rank ; whle out of are classfed as Rank f test results are not used.. Among groups that used the materal/member test results, Raylegh dampng, and research-purpose program, 9 are classfed as Rank.. Among groups that assgned dampng rato larger than., are classfed as Rank.. Among groups that assgned dampng rato equal to., are classfed as Rank.. Among groups that assgned dampng rato less than., are classfed as Rank.. Among groups that consdered geometrcal nonlnearty, are classfed as Rank. Conversely, among groups n Rank, consdered geometrcal nonlnearty. Fgure shows the tme hstores of nterstory-drft angles n Y-drecton of the st story, where the sold lne s the numercal result and the dotted lne s the expermental result. The plots (a), (b), (c) and (d) are the hgh-rankng results that have moderately good accuracy, although the resdual drft angle seems to be very dffcult to predct. However, the numercal results are sgnfcantly dfferent from the expermental results for the low-rankng results n (e) and (f). Although t s very dffcult to pont out the maor cause of ths low accuracy, the result of member test has not been ncorporated n modelng of composte beam acton n (e) and (f). From the results above and addtonal nvestgaton of the results, the followng mportant ponts are observed from the contest results:. As ponted out above, t s mportant to use materal/member test results to obtan accurate results. However, n the usual desgn process, materal/member test s not carred out before the constructon of each frame; whch means that accurate responses cannot be obtaned n the desgn process usng the nomnal values of the materal propertes. Therefore, t s mportant to accurately ncorporate varablty of materal parameters n the desgn code.. Raylegh dampng leads to more accurate estmaton than the stffness-proportonal dampng. It s mportant that the dampng rato should be more than. to ncorporate the dampng effect by nonstructural components. However, an approprate value of the dampng rato s unknown.. Geometrcal nonlnearty should be consdered, n any form, for accurate predcton of collapse behavor.. Computatonal cost and accuracy are not correlated. It s amazng that one of the wnners of D-analyss used lumped-mass model for dynamc analyss, although the tr-lnear hysteress model s obtaned from statc pushover analyss of frame model.. Although t s mportant to consder the composte beam effect, the amplfcaton factor employed by each partcpant vares from. to., whch means that there s no establshed theoretcal bass for computng the amplfcaton factor. In order to prevent the process lke a random guess, more theoretcal, numercal and expermental studed are encouraged.. The response quanttes representng dsplacements (relatve dsplacement, nterstory drft angle) and forces (absolute acceleraton, overturnng moment, story shear), respectvely, are obvously correlated. Therefore, the number of response quanttes wth smlar propertes and preferably the weght coeffcents for the evaluaton of the total pont should be carefully

8 The th World Conference on Earthquake Engneerng October -,, Beng, Chna determned n the future event of blnd analyss contest.. CONCLUSIONS The framework of two-step submsson procedure of the blnd analyss contest has been presented, and the statstc nvestgaton has been carred out for the contest results. The key factors that have strong effect on the accuracy of the numercal results are explored wth the ad of a data mnng tool. It has been shown that no clear advantage of D-analyss over D-analyss, or vce versa, can be observed from the results of the partcpants of the contest. However, the use of materal and/or member test results and the approprate assgnment of dampng coeffcent may be very mportant for obtanng accurate results. ACKNOWLEDGEMENTS Ths study s a part of NEES/E-Defense collaboratve research program on steel structures, and was pursued by the Analyss Method and Verfcaton WG. The Japan team leader for the overall program s Kazuhko Kasa, Tokyo Insttute of Technology, and the WG leader s Motohde Tada, Osaka Unversty. The authors acknowledge the support by the members of Buldng Collapse Smulaton WG (leader: Kechro Suta, Kyoto Unversty), and the fnancal support provded by the Natonal Research Insttute for Earth Scence and Dsaster Preventon. Valuable corporaton from partcpants, especally submsson of addtonal data after the contest, s greatly acknowledged. The contest organzers also express grattude to Prof. Jose Restrepo, Unv. of Calforna, San Dego, for kndly nstructng the plan and excecuton of the past NEES blnd analyss contest. REFERENCES Kasa, K., Ook, Y., Motoyu, S., Takeuch, T. and Sato, E. (). E-Defense tests on full-scale steel buldngs: Part Experments usng dampers and solators, Proc. Structural Congress, ASCE, Long Beach,-. Suta, K., Yamada, S., Tada, M. Kasa, K. Matsuoka, Y. and Sato, E. (). E-Defense tests on full-scale steel buldngs: Part Collapse experments on moment frames, Proc. Structures Congress, ASCE, Long Beach,-. Suta, K., Yamada, S., Tada, M., Kasa, K., Matsuoka, Y. and Sato, E. (). Results of recent E-Defense tests on full-scale steel buldngs: Part Collapse experment on -story moment frame, Proc. Structures Congress, ASCE, Vancouver. Tada, M., Ohsak, M., Yamada, S., Motoyu, S. and Kasa, K. (). E-Defense tests on full-scale steel buldngs: Part Analytcal smulaton of collapse, Proc. Structures Congress, ASCE, Long Beach, -9. Wtten, I. H. and Frank, E. (). WEKA, Machne Learnng Algorthms n Java, Morgan Kaufmann Publshers.