Externally bonded FRP systems have been used to
strengthen and retrofit existing concrete structures around the
world since the mid-1980s. The number of projects using FRP
systems worldwide has increased dramatically, from a few
20 years ago to several thousand today. Structural elements
strengthened with externally bonded FRP systems include
beams, slabs, columns, walls, joints/connections, chimneys
and smokestacks, vaults, domes, tunnels, silos, pipes, and
trusses. Externally bonded FRP systems have also been used
to strengthen masonry, timber, steel, and cast-iron structures.
The idea of strengthening concrete structures with externally
bonded reinforcement is not new. Externally bonded FRP
systems were developed as alternatives to traditional external
reinforcing techniques such as steel plate bonding and steel or
concrete column jacketing. The initial development of
externally bonded FRP systems for the retrofit of concrete
structures occurred in the 1980s in both Europe and Japan.
3.1—Historical development
In Europe, FRP systems were developed as alternates to
steel plate bonding. Bonding steel plates to the tension zones
of concrete members with adhesive resins were shown to be
viable techniques for increasing their flexural strengths
(Fleming and King 1967). This technique has been used to
strengthen many bridges and buildings around the world.
Because steel plates can corrode, leading to a deterioration of
the bond between the steel and concrete, and because they
are difficult to install, requiring the use of heavy equipment,
researchers have looked to FRP materials as an alternative to
steel. Experimental work using FRP materials for retrofitting
concrete structures was reported as early as 1978 in Germany
(Wolf and Miessler 1989). Research in Switzerland led to the
first applications of externally bonded FRP systems to
reinforced concrete bridges for flexural strengthening
(Meier 1987; Rostasy 1987).
FRP systems were first applied to reinforced concrete
columns for providing additional confinement in Japan in the
1980s (Fardis and Khalili 1981; Katsumata et al. 1987). A
sudden increase in the use of FRPs in Japan was observed
after the 1995 Hyogoken-Nanbu earthquake (Nanni 1995).
Researchers in the United States have had a long and
continuous interest in fiber-based reinforcement for concrete
structures since the 1930s. Development and research into
the use of these materials for retrofitting concrete structures,
however, started in the 1980s through the initiatives of the
National Science Foundation (NSF) and the Federal
Highway Administration (FHWA). The research activities
led to the construction of many field projects that encompassed
a wide variety of environmental conditions. Previous
research and field applications for FRP rehabilitation and
strengthening are described in ACI 440R and conference
proceedings (Neale 2000; Dolan et al. 1999; Sheheta et al.
1999; Saadatmanesh and Ehsani 1998; Benmokrane and
Rahman 1998; Neale and Labossière 1997; Hassan and
Rizkalla 2002; Shield et al. 2005).
The development of codes and standards for externally
bonded FRP systems is ongoing in Europe, Japan, Canada,
and the United States. Within the last 10 years, the Japan
Society of Civil Engineers (JSCE), the Japan Concrete Institute
(JCI), and the Railway Technical Research Institute (RTRI)
published several documents related to the use of FRP
materials in concrete structures.
In Europe, Task Group 9.3 of the International Federation
for Structural Concrete (FIB) published a bulletin on design
guidelines for externally bonded FRP reinforcement for
reinforced concrete structures (International Federation for
Structural Concrete 2001).
The Canadian Standards Association (CSA) and ISIS have
been active in developing guidelines for FRP systems.
Section 16, “Fiber Reinforced Structures,” of the Canadian
Highway Bridge Design Code was completed in 2006
(CAN/CSA-S6-06), and CSA approved CSA S806-00.
In the United States, criteria for evaluating FRP systems
are available to the construction industry (ICBO AC125;
CALTRANS Division of Structures 1996; Hawkins et al. 1998).
3.2—Commercially available externally bonded
FRP systems
FRP systems come in a variety of forms, including wet
layup systems and precured systems. FRP system forms can
be categorized based on how they are delivered to the site
and installed. The FRP system and its form should be
selected based on the acceptable transfer of structural loads
and the ease and simplicity of application. Common FRP
system forms suitable for the strengthening of structural
members are listed in Sections 3.2.1 through 3.2.4.
3.2.1 Wet layup systems—Wet layup FRP systems consist
of dry unidirectional or multidirectional fiber sheets or
fabrics impregnated with a saturating resin on site. The
saturating resin, along with the compatible primer and putty,
bonds the FRP sheets to the concrete surface. Wet layup
systems are saturated in place and cured in place and, in this
sense, are analogous to cast-in-place concrete. Three common
types of wet layup systems are listed as follows:
1. Dry unidirectional fiber sheets where the fibers run
predominantly in one planar direction;
2. Dry multidirectional fiber sheets or fabrics where the
fibers are oriented in at least two planar directions; and
DESIGN AND CONSTRUCTION OF EXTERNALLY BONDED FRP SYSTEMS 440.2R-11
3. Dry fiber tows that are wound or otherwise mechanically
applied to the concrete surface. The dry fiber tows are
impregnated with resin on site during the winding operation.
3.2.2 Prepreg systems—Prepreg FRP systems consist of
partially cured unidirectional or multidirectional fiber sheets
or fabrics that are preimpregnated with a saturating resin in
the manufacturer’s facility. Prepreg systems are bonded to
the concrete surface with or without an additional resin
application, depending on specific system requirements.
Prepreg systems are saturated off-site and, like wet layup
systems, cured in place. Prepreg systems usually require
additional heating for curing. Prepreg system manufacturers
should be consulted for storage and shelf-life recommendations
and curing procedures. Three common types of prepreg FRP
systems are:
1. Preimpregnated unidirectional fiber sheets where the
fibers run predominantly in one planar direction;
2. Preimpregnated multidirectional fiber sheets or fabrics
where the fibers are oriented in at least two planar directions;
and
3. Preimpregnated fiber tows that are wound or otherwise
mechanically applied to the concrete surface.
3.2.3 Precured systems—Precured FRP systems consist of a
wide variety of composite shapes manufactured off site.
Typically, an adhesive, along with the primer and putty, is
used to bond the precured shapes to the concrete surface. The
system manufacturer should be consulted for recommended
installation procedures. Precured systems are analogous to
precast concrete. Three common types of precured systems are:
1. Precured unidirectional laminate sheets, typically
delivered to the site in the form of large flat stock or as thin
ribbon strips coiled on a roll;
2. Precured multidirectional grids, typically delivered to
the site coiled on a roll; and
3. Precured shells, typically delivered to the site in the
form of shell segments cut longitudinally so they can be
opened and fitted around columns or other members;
multiple shell layers are bonded to the concrete and to each
other to provide seismic confinement.
3.2.4 Near-surface-mounted (NSM) systems—Surfaceembedded
(NSM) FRP systems consist of circular or rectangular
bars or plates installed and bonded into grooves made
on the concrete surface. A suitable adhesive is used to bond
the FRP bar into the groove, and is cured in-place. The NSM
system manufacturer should be consulted for recommended
adhesives. Two common FRP bar types used for NSM
applications are:
1. Round bars usually manufactured using pultrusion
processes, typically delivered to the site in the form of single
bars or in a roll depending on bar diameter; and
2. Rectangular bars and plates usually manufactured using
pultrusion processes, typically delivered to the site in a roll.
Externally bonded FRP systems have been used to
strengthen and retrofit existing concrete structures around the
world since the mid-1980s. The number of projects using FRP
systems worldwide has increased dramatically, from a few
20 years ago to several thousand today. Structural elements
strengthened with externally bonded FRP systems include
beams, slabs, columns, walls, joints/connections, chimneys
and smokestacks, vaults, domes, tunnels, silos, pipes, and
trusses. Externally bonded FRP systems have also been used
to strengthen masonry, timber, steel, and cast-iron structures.
The idea of strengthening concrete structures with externally
bonded reinforcement is not new. Externally bonded FRP
systems were developed as alternatives to traditional external
reinforcing techniques such as steel plate bonding and steel or
concrete column jacketing. The initial development of
externally bonded FRP systems for the retrofit of concrete
structures occurred in the 1980s in both Europe and Japan.
3.1—Historical development
In Europe, FRP systems were developed as alternates to
steel plate bonding. Bonding steel plates to the tension zones
of concrete members with adhesive resins were shown to be
viable techniques for increasing their flexural strengths
(Fleming and King 1967). This technique has been used to
strengthen many bridges and buildings around the world.
Because steel plates can corrode, leading to a deterioration of
the bond between the steel and concrete, and because they
are difficult to install, requiring the use of heavy equipment,
researchers have looked to FRP materials as an alternative to
steel. Experimental work using FRP materials for retrofitting
concrete structures was reported as early as 1978 in Germany
(Wolf and Miessler 1989). Research in Switzerland led to the
first applications of externally bonded FRP systems to
reinforced concrete bridges for flexural strengthening
(Meier 1987; Rostasy 1987).
FRP systems were first applied to reinforced concrete
columns for providing additional confinement in Japan in the
1980s (Fardis and Khalili 1981; Katsumata et al. 1987). A
sudden increase in the use of FRPs in Japan was observed
after the 1995 Hyogoken-Nanbu earthquake (Nanni 1995).
Researchers in the United States have had a long and
continuous interest in fiber-based reinforcement for concrete
structures since the 1930s. Development and research into
the use of these materials for retrofitting concrete structures,
however, started in the 1980s through the initiatives of the
National Science Foundation (NSF) and the Federal
Highway Administration (FHWA). The research activities
led to the construction of many field projects that encompassed
a wide variety of environmental conditions. Previous
research and field applications for FRP rehabilitation and
strengthening are described in ACI 440R and conference
proceedings (Neale 2000; Dolan et al. 1999; Sheheta et al.
1999; Saadatmanesh and Ehsani 1998; Benmokrane and
Rahman 1998; Neale and Labossière 1997; Hassan and
Rizkalla 2002; Shield et al. 2005).
The development of codes and standards for externally
bonded FRP systems is ongoing in Europe, Japan, Canada,
and the United States. Within the last 10 years, the Japan
Society of Civil Engineers (JSCE), the Japan Concrete Institute
(JCI), and the Railway Technical Research Institute (RTRI)
published several documents related to the use of FRP
materials in concrete structures.
In Europe, Task Group 9.3 of the International Federation
for Structural Concrete (FIB) published a bulletin on design
guidelines for externally bonded FRP reinforcement for
reinforced concrete structures (International Federation for
Structural Concrete 2001).
The Canadian Standards Association (CSA) and ISIS have
been active in developing guidelines for FRP systems.
Section 16, “Fiber Reinforced Structures,” of the Canadian
Highway Bridge Design Code was completed in 2006
(CAN/CSA-S6-06), and CSA approved CSA S806-00.
In the United States, criteria for evaluating FRP systems
are available to the construction industry (ICBO AC125;
CALTRANS Division of Structures 1996; Hawkins et al. 1998).
3.2—Commercially available externally bonded
FRP systems
FRP systems come in a variety of forms, including wet
layup systems and precured systems. FRP system forms can
be categorized based on how they are delivered to the site
and installed. The FRP system and its form should be
selected based on the acceptable transfer of structural loads
and the ease and simplicity of application. Common FRP
system forms suitable for the strengthening of structural
members are listed in Sections 3.2.1 through 3.2.4.
3.2.1 Wet layup systems—Wet layup FRP systems consist
of dry unidirectional or multidirectional fiber sheets or
fabrics impregnated with a saturating resin on site. The
saturating resin, along with the compatible primer and putty,
bonds the FRP sheets to the concrete surface. Wet layup
systems are saturated in place and cured in place and, in this
sense, are analogous to cast-in-place concrete. Three common
types of wet layup systems are listed as follows:
1. Dry unidirectional fiber sheets where the fibers run
predominantly in one planar direction;
2. Dry multidirectional fiber sheets or fabrics where the
fibers are oriented in at least two planar directions; and
DESIGN AND CONSTRUCTION OF EXTERNALLY BONDED FRP SYSTEMS 440.2R-11
3. Dry fiber tows that are wound or otherwise mechanically
applied to the concrete surface. The dry fiber tows are
impregnated with resin on site during the winding operation.
3.2.2 Prepreg systems—Prepreg FRP systems consist of
partially cured unidirectional or multidirectional fiber sheets
or fabrics that are preimpregnated with a saturating resin in
the manufacturer’s facility. Prepreg systems are bonded to
the concrete surface with or without an additional resin
application, depending on specific system requirements.
Prepreg systems are saturated off-site and, like wet layup
systems, cured in place. Prepreg systems usually require
additional heating for curing. Prepreg system manufacturers
should be consulted for storage and shelf-life recommendations
and curing procedures. Three common types of prepreg FRP
systems are:
1. Preimpregnated unidirectional fiber sheets where the
fibers run predominantly in one planar direction;
2. Preimpregnated multidirectional fiber sheets or fabrics
where the fibers are oriented in at least two planar directions;
and
3. Preimpregnated fiber tows that are wound or otherwise
mechanically applied to the concrete surface.
3.2.3 Precured systems—Precured FRP systems consist of a
wide variety of composite shapes manufactured off site.
Typically, an adhesive, along with the primer and putty, is
used to bond the precured shapes to the concrete surface. The
system manufacturer should be consulted for recommended
installation procedures. Precured systems are analogous to
precast concrete. Three common types of precured systems are:
1. Precured unidirectional laminate sheets, typically
delivered to the site in the form of large flat stock or as thin
ribbon strips coiled on a roll;
2. Precured multidirectional grids, typically delivered to
the site coiled on a roll; and
3. Precured shells, typically delivered to the site in the
form of shell segments cut longitudinally so they can be
opened and fitted around columns or other members;
multiple shell layers are bonded to the concrete and to each
other to provide seismic confinement.
3.2.4 Near-surface-mounted (NSM) systems—Surfaceembedded
(NSM) FRP systems consist of circular or rectangular
bars or plates installed and bonded into grooves made
on the concrete surface. A suitable adhesive is used to bond
the FRP bar into the groove, and is cured in-place. The NSM
system manufacturer should be consulted for recommended
adhesives. Two common FRP bar types used for NSM
applications are:
1. Round bars usually manufactured using pultrusion
processes, typically delivered to the site in the form of single
bars or in a roll depending on bar diameter; and
2. Rectangular bars and plates usually manufactured using
pultrusion processes, typically delivered to the site in a roll.
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ภายนอกผูกมัดระบบ FRP ได้ถูกใช้เพื่อเสริมสร้างและปรับปรุงโครงสร้างคอนกรีต
ที่มีอยู่รอบโลกตั้งแต่กลางทศวรรษ 1980 จำนวนของโครงการที่ใช้ระบบทั่วโลก FRP
ได้เพิ่มขึ้นอย่างรวดเร็วจากไม่กี่
เมื่อ 20 ปีก่อนหลายพันวันนี้ องค์ประกอบโครงสร้าง
ความเข้มแข็งภายนอกผูกมัดระบบ FRP รวม
คาน , แผ่นพื้น , เสา , ผนัง , ข้อต่อ / เชื่อมต่อและปล่อง
smokestacks , ห้องใต้ดิน , โดม , อุโมงค์ , ไซโล , ท่อ , และ
โครง . ภายนอกผูกมัดระบบ FRP ยังถูกใช้
เสริมสร้างปูน , ไม้ , เหล็ก และโครงสร้างเหล็ก .
ความคิดเสริมสร้างโครงสร้างคอนกรีตเสริมภายนอก
ผูกมัดนั้นไม่ใช่เรื่องใหม่ ภายนอกผูกมัดระบบ FRP
ถูกพัฒนาเพื่อเป็นทางเลือก
ภายนอกแบบดั้งเดิมเสริมเทคนิค เช่น เชื่อมแผ่นเหล็กและเหล็กหรือเสาคอนกรีต
แจ็คเก็ต . การพัฒนาเริ่มต้นของ
ภายนอกผูกมัดระบบ FRP เพื่อปรับปรุงโครงสร้างคอนกรีต
เกิดขึ้นในยุค 80 ทั้งในยุโรปและญี่ปุ่น .
พัฒนา 3.1-historical ในยุโรป ระบบ FRP ได้รับการพัฒนาเป็นทางเลือก
เชื่อมแผ่นเหล็ก เชื่อมแผ่นเหล็กแรงโซน
สมาชิกของคอนกรีตกับเม็ดกาวก็เป็นเทคนิคของการดัดได้
( จุดแข็งเฟลมมิ่งกษัตริย์ 1967 ) เทคนิคนี้ถูกใช้เพื่อสร้างสะพานและอาคารมากมาย
รอบโลก เพราะแผ่นเหล็ก สามารถกัดกร่อน ทำให้เกิดการเสื่อมสภาพของ
สายสัมพันธ์ระหว่างเหล็กและคอนกรีต และเพราะพวกเขา
ยากที่จะติดตั้งต้องใช้อุปกรณ์หนัก
นักวิจัยต้องดูวัสดุ FRP เป็นทางเลือก
เหล็ก งานทดลองที่ใช้วัสดุไฟเบอร์กลาสสำหรับโครงสร้างการเดิน
คอนกรีตมีรายงานก่อน 1978 ในเยอรมนี
( หมาป่า และ miessler 1989 ) งานวิจัยในประเทศสวิตเซอร์แลนด์ นำไปสู่การประยุกต์ใช้ภายนอกผูกมัดก่อน
ระบบ FRP เสริมสะพานคอนกรีตเสริม
ดัดโค้ง( rostasy ไมเออร์ 1987 1987 )
ระบบ FRP ก่อนใช้เสาคอนกรีตเสริมเหล็ก
ให้โอบรัดเพิ่มเติมในญี่ปุ่นในปี 1980 และปี fardis เ คาลิลี่ (
; คัทสึมาตะ และคณะ 1987 ) a
เพิ่มขึ้นอย่างฉับพลันในการใช้ frps ในญี่ปุ่นพบ
หลังจากที่ 1995 hyogoken นันแผ่นดินไหว ( Nanni 1995 ) .
นักวิจัยในสหรัฐอเมริกา ได้นานและ
ความสนใจอย่างต่อเนื่องในโครงสร้างคอนกรีตเสริมเส้นใยจาก
ตั้งแต่ปี 1930 . การพัฒนาและวิจัย
ใช้วัสดุเหล่านี้สำหรับโครงสร้าง การเดินคอนกรีต
แต่เริ่มต้นในปี 1980 โดยการริเริ่มของ
มูลนิธิวิทยาศาสตร์แห่งชาติ ( NSF ) และทางหลวงแห่งชาติการบริหาร (
fhwa ) กิจกรรมการวิจัย
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