Seismic Performance of Circular Concrete Bridge Piers

1. Introduction

Bridges are one of the most critical and important structures in the transportation systems that are constantly subjected to different

kinds of loadings. At times of natural disasters, transportation systems must withstand the calamities in order to sustain transport

connections and communication for better crisis management. One of the most commonly encountered and destructive natural calamities

is earthquake, thus, the seismic performance of the bridges should be strictly observed, especially the seismic performance of existing

bridges.

* 상명대학교 건설시스템공학과 석사과정 (Sangmyung University ․ [email protected])

** 종신회원 ․ 교신저자 ․ 상명대학교 건설시스템공학과 교수 (Corresponding Author ․ Sangmyung University ․ [email protected])

Received December 8, 2019/ revised January 29, 2020/ accepted February 6, 2020

Copyright ⓒ 2020 by the Korean Society of Civil Engineers

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0)

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Journal of the Korean Society of Civil Engineers ISSN 1015-6348 (Print)

Vol. 40, No. 2: 197-208/ April, 2020 ISSN 2287-934X (Online)

DOI: https://doi.org/10.12652/Ksce.2020.40.2.0197 www.kscejournal.or.kr

Seismic Performance of Circular Concrete Bridge Piers Externally

Strengthened by Carbon Fiber Reinforced Polymer

Catuira, Mabel*, Park, Jong Sup**

마벨*ㆍ박종섭**

탄소섬유강화 플라스틱(CFRP)로 보강된 원형콘크리트 교각의 지진성능 평가

ABSTRACT

This paper evaluated the optimum Carbon Fiber Reinforced Polymer (CFRP) using a circular concrete bridge pier subjected to dynamic

loading. A three-dimensional finite element model was simulated using finite element program, ABAQUS. Concrete Damage

Plasticity (CDP) option and plastic properties of the materials were incorporated to model the non-linearity of the structure. The

analyses parameters were changed in length-to-height ratio and width-to-span ratio where columns were subjected to dynamic loading.

Numerical analysis was conducted, and the seismic performance of the structures were evaluated by analyzing the ductility behavior

of the structure. Results showed that the use of CFRP enhances the structural performance of column and revealed that the increase

in length-to-height ratio plays vital role of improving the performance of the structure than the change in width-to-span ratio.

Key words : Concrete bridge pier, CFRP, Finite element analysis, Dynamic loading

초 록

본 연구에서는 콘크리트 원형 교각의 동적거동 특성을 향상시키기 위하여 최적의 탄소섬유강화 플라스틱 설치 방법에 대해서 해석적 기법을 적

용하여 평가하였다. 범용구조해석 프로그램인 ABAQUS가 해석연구에 사용되었으며, 소성 및 손상 콘크리트 재료특성을 적용하여 구조물의

비선형해석을 실시하였다. CFRP 적용에 따른 내진성능 향상도를 분석하고자 교각높이와 보강된 높이 비율, 교각 지름 대비 CFRP 보강 두께

를 해석변수로 고려하여 거동특성과 연성도를 비교 분석하였다. 해석결과를 토대로 보강에 따른 정량적인 성능향상을 확인할 수 있었으며, 보강

재료 두께 증가보다는 교각높이 대비 보강높이 비율이 보다 성능에 큰 영향을 미치는 것을 알 수 있었다.

검색어 : 콘크리트 교각, 탄소섬유 강화플라스틱, 유한요소해석, 동적하중

구조공학Structural Engineering

Seismic Performance of Circular Concrete Bridge Piers Externally Strengthened by Carbon Fiber Reinforced Polymer

Journal of the Korean Society of Civil Engineers198

The majority of existing bridges were built based on old

building codes and structural manuals. Old bridges constructed

from old structural standards assumed less service loads, which

made them vulnerable to structural damages resulting to possible

poor performance during an earthquake. In addition to that, most

of the existing bridges were made from reinforced concrete that

are constantly exposed to hostile physical and chemical conditions.

This aggressive environment contributes to the progressive damage

of reinforced concrete which made the structure susceptible to the

fatigue behavior of concrete, exposing the reinforcing steel to rust

and corrosion.

The minor damages in the concrete element such as cracks and

spalling in column of the bridges affects the confinement of

concrete to the structure, thus, leading to brittle failure of the

column that could result into serious failure or worse, total

collapse of the structure. The column of bridges is one of the main

structural members of the bridge that resist lateral seismic forces

and vertical forces, thus, the performance and reliability of the

column is vital regarding the performance of the entire structural

system. Therefore, in order to prevent the brittle failure, it is

essential to enhance the ductility of the columns, thus, increasing

the performance and reliability of existing bridges.

Ductility criteria of a concrete column member is a one of the

most important parameters in evaluating the seismic performance

of the structure. In order to increase this type of criteria, con-

finement or external strengthening of concrete column structures

could be provided in order to increase the ductility criteria.

Therefore, in this paper the seismic performance of the structure

was evaluated using the calculated ductility. The progressive

development of computer simulations was utilized using a finite

element software, ABAQUS (2013), to numerically evaluate and

observe the relationship of ductility of the structure with respect

to length-to-height ratio and width-to-span ratio of CFRP.

2. Background of Related Literatures

2.1 Research and Development of Bridge Rehabilitation

Techniques

Researchers and engineers have been interested in the continuous

development of bridge rehabilitation techniques since the mid

1980’s. According to the study of Saadatmanesh et al. (1996),

Özcan et al. (2008) Ye et al. (2003) and Rashid and Mansur (2005),

the problem with the columns constructed based on old codes

faces poor detailing of starter bars and inadequate lateral reinfor-

cement that leads to seismic performance deficiency. Forces

induced by seismic loads that result into shear forces are mainly

resisted by lateral reinforcement, if properly designed, buckling

of the longitudinal bars and sudden loss of bond could be

prevented. Therefore, existing columns with inadequate lateral

reinforcement must be provided by external confinement to

enhance the ductile behavior of the structure.

Many techniques have been implemented into the retrofit design

process mainly based on experimental testing of scaled-down

models of bridge structures. Previous researches, such as study

of Priestley et al. (1984), Chai et al. (1991), and Sun et al. (1992)

in University of California in San Diego have indicated that

strengthening of columns by using steel jackets significantly

improves the performance and ductility of a column. However,

rehabilitation techniques that utilize steel and concrete, such as

section enlargement of columns, confinement by concrete covers,

and attachment of steel jackets are time consuming and difficult

in execution of construction methodologies, therefore, considering

the disadvantages of existing materials, a study for new material

is necessary to develop new techniques.

Since then, researchers have conducted experimental tests to

find an effective and economical alternative material for bridge

rehabilitation. Priestley et al. (1992) presented the study of

column seismic retrofit using Fiberglass/Epoxy, Yamasaki et al.

(1993) investigated the use of Fiber Reinforced Polymers (FRP)

bars to retrofit concrete bridges, and Ehsani et al. (1993) analyzed

the use of glass fiber reinforced polymer (GFRP) bars by circum-

ferentially wrapping the columns around the plastic region. After

years of study using FRP bars and straps as retrofit materials,

Toutanji (1999) extended the study to FRP sheets and presented

a structural model for the behavior of GFRP and CFRP confined

concrete columns using large-scale samples in experiments. The

researches presented that the use of FRP as a material for retrofit

provided desirable results in increasing the performance of the

structure.

The desirable properties of FRP make it to be an appropriate

substitute material for rehabilitation techniques of existing

bridges. FRP is superior to resist corrosion, good adhesion to

concrete, has high strength-to-weight ratio, capability of vibration

absorption, and moisture resistance. In addition to that, Guide for

Catuira, MabelㆍPark, Jong Sup

Vol.40 No.2 April 2020 199

the Design and Construction of Externally Bonded FRP Systems

for Strengthening Concrete Structures (ACI, 2002), reported that

FRP has thermal expansion coefficient of close to concrete and

steel which made it to be a suitable material for externally

strengthening reinforced concrete. Although FRP laminates, bars

and straps are generally more expensive than concrete and steel,

research of Katsumata et al. (1988) and Teng et al. (2002) revealed

that the use of CFRP and GFRP is approximately 20 % less cost

than steel considering construction methodology.

In the recent years, development of computers and various

finite element software has progressed and provided accurate

results. Numerous researchers had corresponded to experimental

tests in the previous decades and conducted numerical experiments

through finite element simulations. In 1999, Tedesco et al. (1999)

assessed a FRP laminate-repaired bridge by finite element

method, Wang and Restrepo (2001) reported that good agreement

of results was observed between the numerical and analytical

results using a short-term assessment of axial load-deformation

of reinforced columns confined with GFRP and steel, Monti et

al. (2001) and Pantelides and Gergely (2002) presented formulae

for calculation of required FRP wrapping thicknesses and

provided design and analysis techniques for seismic retrofit of

concrete members by FRP.

Due to popularity and the increasing demand of research

matter, more and more researches with parametric studies have

been conducted to optimize the application of retrofit materials

to bridge columns. Experimental and analytical parametric

studies were made to establish relationship of column and retrofit

materials. In 2013, Taghia and Bakar (2013) studied parametric

studies and assessed the relationship of varying cross-section of

reinforced short column and varying CFRP layers based on finite

element analysis. Studies of varying reinforcing materials were

also made. Pateriya et al. (2015) presented a numerical analysis

of compressive strength of columns reinforced with varying

materials using steel, GFRP and CFRP and Han et al. (2016)

conducted experimental tests on reinforced concrete evaluating

the performance between CFRP, steel plate and fiber steel

composite plates (FSC). Varying shape of FRP reinforcement

were also studied such as the study of Zeng et al. (2018) which

investigated the behavior and three-dimensional finite element

modeling of circular concrete columns partially wrapped with

FRP strips.

2.2 Ductility Defined using Load-Displacement Curve

Ductility of a concrete bridge column is an important design

factor to consider in seismic performance of the structure. The

ductility of the structure is critical in aspect of dissipation of

seismic energy during earthquake, therefore, the reliability of

existing bridges is enhanced by improving ductility.

In 1994, Jeong (1994) developed energy based method using

load- displacement curve. This method defines the ductility of a

structure using concept of energy by the relating any two of

inelastic, elastic, and total energy as shown in the ductility indices

on Fig. 1. In order to determine the slope that distinguishes elastic

energy from inelastic energy, the slope, S, is calculated as:

(1)

where, slopes S1, S2, S3, were obtained through analytical

calculation and the loads, P1 and P2, were the intersection points

of extended slopes and P3 as the ultimate load. The inelastic,

elastic and total energies were calculated through numerical

integration and in this paper, the ratio of inelastic energy to total

energy is considered.

(2)

It is suggested by Grace et al. (1998) that the structure having

an energy ratio of greater than 75 % is classified to be ductile, and

semi-ductile behavior of energy ratio ranging from 70~74 %.

Fig. 1. Energy Index



3. Finite Element Modeling

Finite element program ABAQUS was chosen to simulate the

model. The software has wide variety of modelling capability and

has concrete damage plasticity (CDP) option that captures the real

behavior of concrete. Rodríguez et al. (2013) recommended that

the use of CDP model exhibits good behavior for concrete under

monotonic, cyclic and dynamic loading.

(a) Length-to-Height Ratio (b) Width-to-Span Ratio

Fig. 2. Nomenclature of Parametric Models

Table 1. Nomenclature of Length-to-Height Ratio Cases

Case Profile Analysis Designation Length (m) Height (m) Ratio Percentage (%)

Initial CFRP_0 0 1.65 0 0

Length-to-Height

CFRP_25 0.4 1.65 0.25 25

CFRP_50 0.825 1.65 0.50 50

CFRP_75 1.24 1.65 0.75 75

CFRP_100 1.65 1.65 1.0 100

Table 2. Nomenclature of Width-to-Span Ratio Cases

Case Profile Analysis Designation Width (m) Span (m) Ratio Percentage (%)

Initial CFRP_0 0 0.4 0 0

Width-to-Span

CFRP_1 mm 0.001 0.4 0.0025 0.25

CFRP_2 mm 0.002 0.4 0.0050 0.50

CFRP_3 mm 0.003 0.4 0.0075 0.75

(a) Mechanics of Hydraulic Actuator Test (b) Schematic Diagram of Numerical Model

Fig. 3. Model Configuration Setup


Vol.40 No.2 April 2020 201

The simulated structure was analyzed under three (3) model

cases, the initial case, the change in height of CFRP (length-

to-height ratio or wrapping height), and the change in thickness

of CFRP (width-to-span ratio or relative wrapping thickness). In

order to account for the effect of change in height of CFRP, the

cross-section of the circular concrete bridge pier was constant and

the thickness of the CFRP and set 2mm. In order to evaluate the

effect of change in thickness of CFRP, the cross-section of the

circular concrete bridge pier were to set to a fixed dimension and

the height of the CFRP were set to height of ¼ of the column. Fig.

2 demonstrates the finite element model cases and Tables 1 and

2 show the corresponding nomenclature of ratio with respect to

each case analysis.

The dimensions of the structure were taken from experimental

specimens subjected to real life hydraulic actuator as shown in

Fig. 3(a). In order to avoid creating unnecessary elements, the

foundation of the structure was not modelled and changed into

encased boundary condition to account for the footing. Fig. 3(b)

shows the schematic design of the numerical model. A three-

dimensional finite element was modelled as shown in the Fig. 4,

having C3D8R hexahedral elements for concrete structure as S4R

shell elements for CFRP.

In this study, numerical models were subjected to gravity

loading and dynamic loading were applied until failure of the

structure. Fig. 4 illustrates the direction and location of dynamic

loading which is positioned in the middle of the loading cap in

order to equally distribute the loads. Tie constraint option was

used in defining the interaction between CFRP and concrete

structure. CFRP was tied to concrete in order to force the nodes

to behave in the same translations. The assumed values of the

Table 4. Material Properties of Concrete

Density

(kg/m3)

Young’s

Modulus (GPa)Poisson’s Ratio

Dilation Angle

(°)Eccentricity fbo/fco Kc

Viscosity

Parameter

2400 28 0.2 36 0.1 1.16 0.667 0

Compressive Behavior Compressive Damage Tensile Behavior Tensile Damage

Yield Stress

(MPa)Inelastic Strain Damage Parameter Inelastic Strain Yield Stress (MPa) Cracking Strain Damage Parameter Cracking Strain

15 0 0 0 3 0 0 0

23 0.003 0.2 0.000333 2 0.0002 0.2 0.0002

29 0.00055 0.3 0.0007 1.5 0.0003 0.3 0.0003

33 0.00147 0.4 0.0013 1.2 0.0004 0.4 0.0004

25 0.0066 0.45 0.002 1 0.0005 0.5 0.0005

22 0.008 0.5 0.003 0.8 0.0008 0.6 0.0008

20 0.009 0.6 0.0043 0.5 0.001 0.8 0.001

10 0.01 0.8 0.007 0.4 0.002 0.7 0.002

0.9 0.01 0.2 0.003 0.9 0.003

0.1 0.005 0.99 0.005

Fig. 4. Boundary and Loading Conditions of Meshed Numerical Model

Table 3. Material Properties of CFRP

Density

(kg/m3)

Young’s Modulus

(MPa)

Poisson’s

Ratio

Yield Stress

(MPa)

Plastic

Strain

1500 2.35 0.3 344 0



mechanical properties of the materials were listed in Tables 3 and

4 while the dynamic loading is shown in Fig. 5.

The values of CFRP were taken from the experimental study

of Han et al. (2016) and the values of concrete properties were

taken from the study of Senturk and Pul (2017). Senturk and Pul

(2017) published a calibrated concrete damage plasticity parameter

by performing a standard cylinder test on ABAQUS using a f’c=30

MPa concrete. Table 4 listed the parameters of concrete material

where fb0/fc0 is the ratio of strength in biaxial state (fb0) to strength

in uniaxial state (fc0) and Kc, is the ratio of the distances between

the hydrostatic axis and respectively the compression meridian

and the tension meridian in the deviatoric cross section. Fig. 6

shows the graph of tensile and compressive stress-strain for the

numerical model of concrete.

4. Discussion of Results

The stress-strain and load-displacement hysteresis curve were

investigated through finite element results and the ductility of the

structure were obtained by numerical integration.

4.1 Finite Element Results

After performing finite element analysis, an element within the

plastic hinge section of the column was evaluated as shown in Fig.

7. The structure without CFRP reinforcement was compared to

CFRP with increasing thickness and wrapping ratio. Fig. 8 and

Table 5 show the effect of increasing the length-to-height ratio

of CFRP to stress-strain of the structure. It shows that the use of

Fig. 5. Applied Dynamic Loading

Fig. 6. Stress-Strain Curve of Simulated Concrete

Fig. 7. Evident Deformation at Plastic Hinge Region

(a) Stress-Strain Curve according to Length-to-Height Ratio

(b) Stress-Strain Curve according to Width-to-Span Ratio

Fig. 8. Comparison of Stress-Strain Curve without CFRP to Structurewith CFRP


Vol.40 No.2 April 2020 203

CFRP improves the performance of the structure in terms of

stress-stain. In addition to that, it was observed that the increase

of height in CFRP significantly enhanced the behavior of the

column than the increase of thickness of CFRP.

Load-displacement hysteresis curve was also analyzed and

compared with respect to length-to-height ratio. The follow

figures, Figs. 9, 10, and 11 shows the individual load-displacement

hysteresis curve and skeleton curve of the original structure, and

the cases of varying length-to-height ratio and width-to-span

ratio. Figs. 12 shows the comparison of hysteresis curve of

structure without CFRP to Fig. 12(a), structure with varying

wrapping ratio, and Fig. 12(b), structure with varying wrapping

relative thickness. Fig. 13 displays the combined skeleton curve.

Based from the finite element results, Fig. 13(a) illustrates that

the base shear of the structure and the displacement increases as

length-to-height ratio increases. In addition to that, it could be

observed from Fig. 13(b) that the combined skeleton curve with

respect to change in width-to-span ratio indicates that there is

insignificant change in the load-displacement of the structure as

the thickness of the CFRP is being increased. Tables 6 and 7

present the base shear and deformation as the length-to-height

Table 5. Comparison of Stress according to CFRP Ratio

Case RatioStress (kPa)

Yield Ultimate

Initial 0 1143.66 1980.51

Length-to-Height Ratio

0.25 2171.50 2303.76

0.50 2246.91 2507.11

0.75 2926.41 3049.41

1.00 2979.74 3211.01

Width-to-Span Ratio

0.0025 1651.31 2227.48

0.0050 2246.91 2507.11

0.0075 2280.45 2301.23

Fig. 9. Load-Deflection Curve of Concrete Column without CFRP

(a) Load-Deflection Hysteresis Curve and Skeleton Curve with L/H of 0.25

(b) Load-Deflection Hysteresis Curve and Skeleton Curve with L/H of 0.50

(c) Load-Deflection Hysteresis Curve and Skeleton Curve with L/H of 0.75

(d) Load-Deflection Hysteresis Curve and Skeleton Curve with L/H of 1.00

Fig. 10. Individual Load-Deflection Hysteresis Curve and Skeleton Curve with Varying Length-to-Height Ratio



ratio and width-to-span ratio varies. Based from the results, it was

observed that the increase of thickness in CFRP is capable of

slightly improving the performance of the structure but not as

significant as change in length-to-height ratio.

4.2 Seismic Performance Evaluation

The ductility of the structure was evaluated using numerical

analysis. The elastic, inelastic and total energy were obtained

through numerical integration. Table 8 lists the ductility of the

structure according to change in wrapping ratio and relative

thickness of the reinforcement. Based from the results, each of

the specimen confined by CFRP reduced the risk in brittle failure,

thus, improving the seismic performance of the structure. In

particular, the increase of length-to-height ratio of the reinforcement

significantly contributed to the enhancement of ductility of the

structure than the increase of width-to-span.

(a) Load-Deflection Curve of 1mm thick CFRP (b) Load-Deflection Curve of 2mm thick CFRP (c) Load-Deflection Curve of 3mm thick CFRP

Fig. 11. Individual Load-Deflection Hysteresis Curve and Skeleton Curve with Varying Width-to-Span Ratio

(a) Combined Load-Deflection Hysteresis Curve with Varying Length-to-Height Ratio

(b) Combined Load-Deflection Hysteresis Curve with Varying Width-to-Span Ratio

Fig. 12. Comparison of Load-Deflection Hysteresis Curve with and without CFRP

(a) Combined Load-Deflection Skeleton Curve according to Varying Length-to-Height Ratio

(b) Combined Load-Deflection Skeleton Curve according to Varying Width-to-Span Ratio

Fig. 13. Comparison of Load-Deflection Skeleton Curve with and without CFRP


Vol.40 No.2 April 2020 205

4.3 Summary of Results

The discussion in this section summarizes the relationship of

length-to-height ratio of the CFRP to the overall performance of

the structure. Fig. 14(a) to Fig. 14(d) show that the same increasing

trend was observed in general, the response of the circular

concrete column strengthened with CFRP improved as the height

of the reinforcement increased. The increasing trend indicates

that as the ratio of length-to-height increases, the capacity in

stress, load, deflection and ductility of the structure also increases.

Table 9 summarizes the performance of the structure under the

change in length-to-height ratio and it was found out that the full

Table 6. Comparison of Base Shear according to CFRP Ratio Table 8. Comparison of Ductility according to CFRP Ratio

Case RatioLoad (kN) Case Ratio Ductility (%)

Yield Ultimate Initial 0 77.921

Initial 0 30090.35 31785.50

Length-to-Height

Ratio

0.25 88.549

Length-to-Height

Ratio

0.25 38880.75 39965.20 0.50 90.149

0.50 53500.31 55626.30 0.75 91.812

0.75 86912.82 109029.60 1.00 91.917

1.00 113832.49 138392.00

Width-to-Span Ratio

0.0025 84.781

Width-to-Span

Ratio

0.0025 39369.27 39814.20 0.0050 88.549

0.0050 38880.75 39965.200.0075 89.186

0.0075 39466.61 40466.60

(a) Relationship of Stress and Length-to-Height Ratio (b) Relationship of Base Shear and Length-to-HeightRatio

(c) Relationship of Deformation and Length-to-HeightRatio (d) Relationship of Ductility and Length-to-Height Ratio

Fig. 14. Effect of Increasing Length-to-Height Ratio to the Performance of the Structure

Table 7. Comparison of Displacement according to CFRP Ratio

Case RatioDisplacement (mm)

Yield Ultimate

Initial 0 9.854 29.969

Length-to-Height Ratio

0.25 12.482 31.730

0.50 18.876 58.294

0.75 30.641 75.597

1.00 61.460 120.486

Width-to-Span Ratio

0.0025 9.785 31.312

0.0050 12.482 31.730

0.0075 9.609 32.821



confinement, length-to-height ratio of 1:1, exhibits significant

improvement in the seismic performance of the structure.

The relationship of increasing thickness of the reinforcement

and general behavior of the structure is discussed in this section.

Fig. 15(a) to 15(d) show that there is only slight improvement in

the performance of the circular concrete column as the thickness

of the CFRP increases. Based from the graphs of Fig. 15, there

is a seemingly flat slope trend observed as the width-to-span ratio

moves from 0.0025 to 0.0075. This gradual incline indicates that

there is only slight improvement in the performance of the

structure as the thickness of the CFRP is being increased. Table

10 summarizes the behavior of the structure with respect to change

in width-to-span ratio.

Table 9. Performance of the Structure according to Change in Length-to-Height Ratio

CASEStress (kPa) Load (kN) Displacement (mm) Energy Ratio

(%)Remarks

Yield Ultimate Yield Ultimate Yield Ultimate

0 1143.66 1980.51 30090.35 31785.20 9.854 29.969 77.921 Ductile

0.25 2171.50 2303.76 38880.75 39965.20 12.482 31.730 88.549 Ductile

0.50 2216.91 2477.11 53500.31 55626.30 18.876 58.294 90.149 Ductile

0.75 2926.41 3049.41 86912.82 109029.60 30.641 85.597 91.812 Ductile

1.00 2979.74 3211.01 113832.49 138392.00 61.460 120.486 91.917 Ductile

(a) Relationship of Stress Capacity to change in Width-to-Span Ratio (b) Relationship of Base Shear to change in Width-to-Span Ratio

(c) Relationship of Deformation and Width-to-SpanRatio (d) Relationship of Ductility and Width-to-SpanRatio

Fig. 15. Effect of Increasing Width-to-Span Ratio to the Performance of the Structure

Table 10. Performance of the Structure according to Change in Width-to-Span Ratio

CASEStress (kPa) Load (kN) Displacement (mm) Energy Ratio

(%)Remarks

Yield Ultimate Yield Ultimate Yield Ultimate

0 1143.66 1980.51 30090.35 31785.50 9.854 29.969 77.921 Ductile

0.0025 1651.31 2227.48 39369.27 39814.20 9.785 31.312 84.781 Ductile

0.0050 2171.50 2303.76 38880.75 39965.20 12.482 31.730 88.549 Ductile

0.0075 2280.45 2301.23 39466.61 40466.60 9.609 32.821 89.186 Ductile


Vol.40 No.2 April 2020 207

5. Conclusion

The following conclusions are drawn based by means of the

results of the conducted finite element analysis. The main aim of

this paper was to optimize the application of CFRP. The

performance of a circular concrete column was analyzed according

to the of change in length-to-height ratio and width-to-span ratio

of CFRP.

(1) For the change of length-to-height ratio, it was found out that

using CFRP as reinforcement with ratio of 0.25 to 1.0 could

increase the ductility of the circular concrete column from 78 %

ranging up to 89~92 %. In this regard, the continuous use of

CFRP throughout the length of circular concrete structure

showed significant improvement in the base shear, stress

capacity, lateral deformation and ductility. Furthermore, this

proves that the full confinement of the structure using CFRP

or the length-to-height ratio of 1.0 is the optimum wrapping

ratio of CFRP.

(2) The change of width-to-span ratio indicated that the increase

in the thickness of CFRP also increases the ductility of the

structure. It was found out that from the ductility of the

original structure, 78 %, it could be improved ranging from

85 % up to 89 % with a wrapping thickness ratio of 0.0025

to 0.0075. However, the effect of increasing the thickness of

CFRP to the overall performance structure tends to be

insignificant. It was observed that the increase of thickness

of the confining material could enhance the structure,

however, there is only slight improvement in the behavior of

the structure.

(3) For circular concrete columns, increasing the wrapping height

of external confinement developed significant improvement

than increasing the wrapping thickness of CFRP. The increase

in wrapping height provided more confinement to reduce the

brittle failure and to increase the ductility and earthquake

resistance of circular bridge pier columns.

Acknowledgement

This research is supported by the Ministry of Land, Trans-

portation and Maritime Affairs (19SCIP-B146946-02) and National

Research Foundation (NRF-No.2019R1F1A1060708), Republic

of Korean.

본 논문은 2019 CONVENTION 논문을 수정·보완하여 작성되

었습니다.

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Documents

Seismic Performance of Circular Concrete Bridge Piers