ABSTRACT

Date ofsubmission (1nonth day, year)
Depadme"tofDepar【ment of Archilectureand civil Engineerin旦
Pplicanl's na1れe也d引ltlD N山れberJuly,釦d,2023

D 209504
SupeτⅥSOTS

Yukihiro Matsumoto

Tran Quang DUC

Abstract (Doctor)
Iitle ofThesis

Str11CれⅡ'al design on S力'en即hening m111ti・bolted connections in pultnlded
glass flb引' reinforced polymer (PGFRP) using multi・djrectional flber sheets

Infrastructures that have been rapidly expanding in recent years are no、¥ reaching a
Critical age,、vith 、¥idespread signs of deterioration and inadequate functionality. Therefore,
designing effective methods for rehabilitating, rebuilding, and maintaining civilinfl'asu'uct山'e
is essential for sustainable development. Fortunately, glass fiber・reinf引'ced polyln引'(GFRP)
C0111Posites have em飢'ged as an exce11ent lnaterial for renewing existing structures.1n l'ecent
decades, n山ηerous research projects have been conducted to investigate the reinforcement
behavior for connections in GFRp str11Ctures. HO、Never, the main focus ofprevious studies has
been limited to strengthening based on the original material connections in GFRP. This
reseal'ch program aims to investigate a novel and promising method of strengthening bolted
ConnectionS 1Π GFRP, using multldirectional fiber sheets. The pl'imary advantage of thismethod is its simpli丘ed application, cost・effectiveness, and h電h e仟'ectiveness、Firsdy, abriefintroduction to pultruded GFRP (PGFRP) as a lnaterial and manufactul'ing
Process was presented、 The first experiment was conducted a series ofexpel'iments to consider
the effects of GFs on strengthening pGFRp multi bolted connections.1n this study, threeVarieties of lnulti・directional Glass Fiber sheets (GFS)、¥引'e employed for strengthening
Purposes, namely:0゜/90゜ GFS,士45゜ GFS, and chopped stral】d mat(CSM) GFS, a110fwhich

Were produced using the vacuum Transfer Molding technique.1he findings of thisinvestigation reveal that aⅡ tl〕ree types of GFs exl〕ibit a marked ability to e1小ance themaximum fa11Ure loads of pU1れ'uded GFRp connections. Fudhermore, the hnpact of aⅡ GFS.ー' 1、Va17iants on the reinforC引nent process was observed to be directly proportionalto increases inthe ratios of end distances to bolt diamet引'(ea/ or the nulnb引' of bolts (π).1n nearly a11
instances,0゜/90゜ GFss outperformed 士45゜ GFss and csM GFss in terms ofthe extent ofthe
reinforcement e仔ect achieved.

A subsequent experiment、刃as conducted to evaluate the bonding capability ofpultruded
GFRP.1his experiment was necessitated by the observationthatthe specjmel〕s with the highest
Connection stre】]gth in the previous experiment had experienced debonding failure.1n light ofa sequence of material tests, a set of equations were posited with the aim of accurately
Predicting the fai11Ⅱ'e modes and ultimate loads of multi・bolted pGFRp connections f01'ti行ed
With multi・directional GFS.

The thi↑d expel'ilnent investigates t11e inauence of bolt tightening force in connection
Strength. A silnilar series as non・tightening f引'ce wa'e designed and tested under apply a21N.m torque load. The outcomes ofthe connectiontesting evince thatthe employm引lt ofGFS
for strengthening P山'poses continues to be efflcacious, even when deployed under diverse
Conditions ofbolted pGFRp connection.、Nhile tl〕el'e 、Nas an increase in the maxim山n load foraⅡ Specilnen types in comparison to u〕e untigl]tened state, the effectiveness ofthe system, as
Ineasured by the ratio of the lnaximum loads before and a介er reinfⅨ'cement with GFSS,exhibited a S1地ht decrement.

The anal investigation involved detennining failure be1徐Vior and strengthening
effectiveness in bea1η一to・colulnn multi bolted connection. FU11 Scales experiments 、vere
implemented to investigate behavior and effectiveness ofbeam・to、column connection 、vith andWithout str引lgthened by GFS. The experimental findings did not a1電n W北h the expected
Outcomes, owing to unf01'eseen ch'cumstances in the design ofthe auxili引'y steel colnponents
in the beam. Although the adoption ofGFs served to enhance the reinforcement ofthe column,
it nevertl]e】ess suffered damage before the onset of failure observed in the beam's proale.
Consequently, a revision was put forward,、vhicl) entailed altering the connection ofthe cleats,
With 血e objective of aligning with the primary objective of the experiment, which 、¥as toinvestigate the behavior ofthe beam.
To summarize, the a11・encompassing research program deta11ed herein suggests that theUse of multi・directional GFs const北Utes an effective approach for enhancinσ the structuralH4愚゛

aptitude of civil engineel'ing constructions. speciacaⅡy, the inCⅨPoration of GFs sheets
enhancesthe load・bearing capacity a11d overaⅡ Perfbrmance ofpultnlded pGFRp connections、The findings a11d formulae proposed in tl]is study possess pl'acticaHmplicati0船 for promoting
the adoption of cutting・edge lnaterials such as FRPS 、¥迦lin the civil engineeling industry.
Nonetheless, ce11ain pe11inent issues ranain, which the autl]or has identified as prospective
areas for alture investigation.

iii