別紙41(課程博士(英文))Date of submjssion (month day, yea"

July 8,2022

Depar〔ment ofArd〕ileC1Ⅲ'e andCiYⅡモngineel'iD冬

Sluden11D Kumber

D175510

Shoji Nakazawa
SupeTviSの'SへPplica111'S "amePhan viet Nhut

Tomoya Matsui
Yukihil'O Matsumoto

Abst"act (Doctor)
Title ofTI〕esis

Applications ofthin fib引'1'einf01、ced polymel'(FRP) malerials f01'the stl'el]othening ofS1ΠIctul'es in u〕e civil engineel'ing field

Civilinfl'ast札ICIUI'e plays a key faclor in lhe developmenl of the economy and hulnan Hfe. The
in命'ast川Ctul'es of constl'ucled facililies f01' 1he t】'ansp011a{ion an(H〕011Sinσ of l〕eople, goods, and S引、vices̲訊11ich
Wel'e lemal'1くably exl)anded in l'ecent yeal's al'e now l'eachjnσ a cl'itical aσe W11h 、videspl'ead sj01玲 of detel・iora{ionand inadequate functionalily. Designing eaiciel〕t me{hods f01'1'ehabilitaling l'ebuildiΠσ and mainlaininσ CiV11
infl、aS11'uctul'e is ve】'y essential to ensul'e the sustainable developlnel〕t of 小e economy and hea1小 inh・asil・uct111・esAtthe same time, fibel'・1'einf01'ced polymers (FRPS) composites have eme】'σed as exceⅡent conslruction malel・ials
for the l'ene、val of existing stnlctul'es.
TI〕is thesis is pl'esented as a compjlation of di仟erel]t invesligalions. pal't l of 小e thesis describeS 11]eSlrengtl〕ening e仟ecls of cal'bon nbel' 1'einf01'ced polymel'S (CFRPS) f01' the {hin、wa11ed steel S11・uct{11・es undel・Various loadh]g conditi01〕S: U ) axial coml)1'ession (chaplel' 3 al〕d 4),(2) bel](1inσ Sheal'10ad (chaptel・ 4), G) SI〕eal・10ad (chaptel' 5), an(1 (4) dynamic load (chal)1er 6). pal't 2 0ftl]e lhesis il〕vestiσates {1〕e stl'eng山ening e11'ects of
31ass flbel' SI]eels (GFSS) on the su'引]gtl〕 of pultnlded glass fibel'1'einf01'cemen( polymel・(PGFRP) sinσle b01{edConnec{jons.

The s{1'eng小ening eHecls of cil'cumfe↑ential cFRp laye】's on 11]e incl'easinσ 10ad、cal'1'yinσ Cal〕aciTies ofIhin‑wa11ed sleel cylindel'S (TSCS)瑚]del' con]1)ressive load lhl'OUσh nnile elemenl analysis (FEA) an〔1experimen{S 雛'e P↑esented in chapler 3. The l'esU11S SI〕0、 ed 小al cil、cumfel'enlial cFRp layel・s reveal their
Signincant e仟ecls on {he inc】'eased load・cal'rying capacily of TSCS.1n add11ion、 good c0Π・espondences 、¥el・efound beい、een expel'imenta1 田〕d FEA resU11S I'egal'dino def01'ma110n behavi01',10ad、can'yino capacily, and S11・alnand S11'ess l'elations.

In the nexl il]vesligation. the e11'ecls of carbon abel' 01'ien{ations f01' 11W Sれ'elN小eninσ of 丁Scs undel・Compl'esS八岻 and bel〕ding sheal'10ads al'e descl'ibed in chapler l.1n the fil、sl slaσe、 1he Yalidation of lhe accul・acbet、veen expe"menlal and FEA 、vas conducted for smaⅡ一scale TSCS. The FEA me11〕od was then used to ana17etl]e eザects of fibe】' OTientalion f01' 1he sl】'engtl〕ening of n1Ⅱ・scale TSCS. The ルSU11S 1Πdicated 小aT cil'cumfel・enlial

CFRp layel'S I'evealtheir siσniイicant effecls 01〕 the incl'eased load・can'yino capacily of Tscs undel・ axlal

Compl、esslon.1n addition, cil'cumfel'en{ial o゜ and o゜/90゜ CFRp layers pl'oved tl]e be廿e】' S11・englhening effec{s tl]an90゜ CFRp layel's for Tscs lmdel' beDdjnσ Shea】'10ads,The e行'ecls of cFRp stl'engthening on the sl]ear S11'eng11〕 oftl〕in・wa11ed slee11〕1ales (1SP) a】・e experimenlal

and numericalinvestigations in chapter 5. The results revealthat cFRp layers can be e丘ectively used to inm'easetl〕e ultin〕ate shear strength of tl〕e TSPS. The strengtl〕ening e丘ect 、刃as be廿er ifthe v.1idth・to・thickness ratio of theCFRp layer was low. M0鵜Ovel, equations usin8 tl〕e lalnination theoly of composite materials can be used toPredictthe critical and ultimate sl〕ear load for strengthened Tsps with high accuracy.
The effects of cFRp streng小ening for thin・wa11ed stm'age tanlくS (1ST) under dynamic loads are pl'esentedin chapter 6. A new expa'imental method using smaⅡ・diameter steel baⅡS to o'eate intemal pl'essule forthe TSTS

is applied.1n d〕e next steps, the stren部henin菖 effects oftwo types of extenlaⅡy bonded cFRP SI〕eets, including
the ch・culnfelential cFRp laya'(0゜) and two・dilectional cFRp layer (0゜/90゜), on the pel'fonnance ofTSTs und飢'dynamic loads wa'e investigated. The consequences show tl〕at cFRp layels can restrain both static and dynamic
hoop strains in TSTS, especia11y tl〕e o゜ CFRp layel'. The lestraint levels of static strains can be up t065ツ0 fm' tl]e0O CFRp layer and 62ツ0 f01'the o゜/90゜ CFRp layeTIn pa1120fd〕e u〕esls, a series ofexperiments W飢'e conducted to considerthe strengthening effects of GFSOn tl]e strenoth of pin、bealing pGFRp single bolted c01〕nectjons. h〕 addition, tl)e FEA n〕etl〕od was also used toConfirl〕〕 d〕e stren旦thening effects. ACCω、ding to a series of materialtests, a〕e equations wa'e proposed to w'edict
Cm1でCtly fai1山、e lnodes al〕d ultimate loads of GFS‑stTengtl)ened pin・bearing pGFRp single bolted connections
TI〕ree types of GFS、 which were molded by the vacU山n transfeT molding method, were used for theStrengthening:0゜/90゜ GFS,士45゜ GFS, and chopped strand mat (CSM) GFS. The researcl〕 results indicated tl〕at
aⅡ a11'ee types of GFSs could e丘ectively increase tl〕e maximum fai1山'e loads of a〕e pGFRp connections、 Thee丘ect of a11types ofGFss on tl〕e reinforcelnent was prop011ionalto the decrease in the ratios of end distances tobolt diamet引'(e/の, whereasthe e丘巳Ct ofuw ratios ofwidtl〕to bolt dialneter (W/の on d]e comlection stl'ength was
not siσnificant if tl〕e w/d Z 3.1n aln〕ost a11 Cases, CSM GFSS W'oved the best strengtlwning e丘ects con〕pared to士450 GFss and oo/90O GFSS. Relating the effects ofGFs tl〕ickness on the connection stren8th, the stlengthening

effects per GFs layer decreased when increasing the n磁nber ofstrengthening GFs layers. Fina11y, when ule sameInodes of failul・e W劔'e obtained for the specimens having tl〕e salne P引'alnet圃'S, the strengthening e丘ects wa'ehigher for the large・diameter bolts

Froln tl〕is overau resealch pl'0即'am, it cal〕 be concluded that tl〕in FRp matelials can be used e丘ectively to
StTengthen various structures in civi} engineering to in〕prove tl〕巳 10ad・car1ツing capacity and P引fon〕]ances、of steelStructures ol pGFRp connections. The rese砥'ch results and ploposed equations jn t}〕is study can help toencoul・age the p・actical applications ofadvanced lnaterial(FRP) in tl〕e civil engineering field