Effect of high-strength concrete on shear behavior of dry joints in precast concrete segmental bridges

Airong Liu,Haibo Jiang,Ying Chen,Tianlong Wang,Zhuangcheng Fang 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.5

The use of high-strength concrete (HSC) in precast concrete segmental bridges (PCSBs) can minimize the superstructure geometry and reduce beam weight, which can accelerate the construction speed. Dry joints between the segments in PCSBs introduce discontinuity and require special attention in design and construction. Cracks in dry joints initiate more easily than those in epoxy joints in construction period or in service. Due to the higher rupture strength of HSC, the higher cracking resistance can be achieved. In this study, shear behavior of dry joints in PCSBs was investigated by experiments, especially focusing on cracking resistance and shear strength of HSC dry joints. It can be concluded that the use of HSC can improve the cracking resistance, shear strength, and ductility of monolithic, single-keyed and three-keyed specimens. The experimental results obtained from tests were compared with the AASHTO 2003 design provisions. The AASHTO 2003 provision underestimates the shear capacity of single-keyed dry joint C50 and C70 HSC specimens, underestimates the shear strength of three-keyed dry joint C70 HSC specimens, and overestimates the shear capacity of three-keyed dry joint C50 HSC specimens.

Experimental study on reinforced high-strength concrete short columns confined with AFRP sheets

Han-Liang Wu,Yuan-Feng Wang 국제구조공학회 2010 Steel and Composite Structures, An International J Vol.10 No.6

This paper is aiming to study the performances of reinforced high-strength concrete (HSC) short columns confined with aramid fibre-reinforced polymer (AFRP) sheets. An experimental program, which involved 45 confined columns and nine unconfined columns, was carried out in this study. All the columns were circular in cross section and tested under axial compressive load. The considered parameters included the concrete strength, amount of AFRP layers, and ratio of hoop reinforcements. Based on the experimental results, a prediction model for the axial stress-strain curves of the confined columns was proposed. It was observed from the experiment that there was a great increment in the compressive strength of the columns when the amount of AFRP layers increases, similar as the ultimate strain. However, these increments were reduced as the concrete strength increasing. Comparisons with other existing prediction models present that the proposed model can provide more accurate predictions

Axial Compression Tests for Circular Concrete-Filled Steel Tube (CFST) Columns with Notch Imperfection

Mustafa Mohammed,Mustafa Fahmi Hasan,Hasan Fahmi Hasan,Alyaa Assad Mahdi,Sarwar Hasan Mohmmad,Mukhtar Hamid Abed 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.6

The study investigated how simulated notches within concrete-filled steel tube (CFST) columnsaffect their mechanical performance. It aimed to understand the impact of notch length, orientation, and location within the steel tubes on the behavior of these circular columns. Study conducted compressive tests on a total of 32 CFST specimens, varying in thickness (3 mm and 6 mm) and filled with High-Strength Concrete (HSC) or Normal-Strength Concrete (NSC). Four control specimens without notches served as reference points. Results indicated that CFST columns with notches exhibited reduced mechanical performance compared to those without notches. Notch parameters played a crucial role in this reduced performance. Notch length and orientation had a more significant influence than notch location. It also highlighted that the thickness of the steel tube was a paramount factor, surpassing the importance of concrete type. In summary, the study emphasized that presence of notches in CFST columns significantly impacted their load-bearing capacity, buckling behavior, and failure modes. Length and orientation of notches were identified as critical factors, with steel tube thickness being a dominant factor in determining overall mechanical performance of these columns. These findings provide valuable insights for structural engineers and designers working with CFST columns in various construction applications.

Reinforced high-strength concrete square columns confined by aramid FRP jackets. part I: experimental study

Yuan-feng Wang,Yi-Shuo Ma,Han-liang Wu 국제구조공학회 2011 Steel and Composite Structures, An International J Vol.11 No.6

Although retrofitting and strengthening reinforced concrete (RC) columns by wrapping fiber reinforced polymer (FRP) composites have become a popular technique in civil engineering, the study on reinforced high-strength concrete (HSC) columns is still not sufficient. The objective of these companion papers is to investigate the mechanical properties of reinforced HSC square columns confined by aramid FRP (AFRP) jackets under concentric compressive loading. In the part I of these companion papers, an experiment was conducted on 54 confined RC specimens and nine unconfined plain specimens, the considered parameters were the concrete strength, the thickness of AFRP jackets, and the form of AFRP wrapping. The experimental process and results are presented in detail. Subsequently, some discussions on the confinement effect, failure modes, strength, and ductility of the columns are carried out.

Behavior study of NC and HSC RCCs confined by GRP casing and CFRP wrapping

Fathollah Sajedi,Mahdi Shariati 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.5

This paper presents the results of axial compression testing and numerical modeling on reinforced concrete columns (RCC) with normal concrete (NC) and high-strength concrete (HSC), RCC confined by glass-fiber reinforced plastic pipes (GRP) casing as well as carbon fiber reinforced polymer (CFRP), The major parameters evaluated in the experiments were the effects of concrete type, GRP casing and CFRP wrapping, as well as the number of CFRP layers. 12 cylindrical RCC (150×600 mm) were prepared and divided into two groups, NC and HSC. Each group was divided into two parts; with and without GRP casing. In each part, one column was without CFRP strengthening layer, a column was wrapped with one CFRP layer and another column with two CFRP layers. All columns were tested under concentrated compression load. Numerical modeling was performed using ABAQUS software and the results of which were compared with experimental findings. A good agreement was found between the results. Results indicated that the utilization of CFRP wrapping and GRP casing improved compression capacity and ductility of RCC. The addition of one and two layer-FRP wrapping increased capacity in the NC group to an average of 18.5% and 26.5% and in the HSC group to an average of 10.2% and 24.8%. Meanwhile, the utilization of GRP casing increased the capacity of the columns by 3 times in the NC group and 2.38 times in the HSC group. The results indicated that although both CFRP wrapping and GRP casing increased confinement, the GRP casing gave more increase capacity and ductility of the RCC due to higher confinement. Furthermore, the confinement effect was higher on NC group.

Shear behavior of short square tubed steel reinforced concrete columns with high-strength concrete

Xiang Li,Xuhong Zhou,Jiepeng Liu,Xuanding Wang 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.3

Six shear-critical square tubed steel reinforced concrete (TSRC) columns using the high-strength concrete (fcu,150 = 86.6MPa) were tested under constant axial and lateral cyclic loads. The height-to-depth ratio of the short column specimens was specified as 2.6, and the axial load ratio and the number of shear studs on the steel shape were considered as two main parameters. The shear failure mode of short square TSRC columns was observed from the test. The steel tube with diagonal stiffener plates provided effective confinement to the concrete core, while welding shear studs on the steel section appeared not significantly enhancing the seismic behavior of short square TRSC columns. Specimens with higher axial load ratio showed higher lateral stiffness and shear strength but worse ductility. A modified ACI design method is proposed to calculate the nominal shear strength, which agrees well with the test database containing ten short square TSRC columns with shear failure mode from this study and other related literature.

Reinforced high-strength concrete square columnsconfined by aramid FRP jackets. part II: modeling

Han-liang Wu,Yuan-feng Wang,Yi-shuo Ma 국제구조공학회 2011 Steel and Composite Structures, An International J Vol.11 No.4

Based on the experimental data presented in part I of these companion papers, a semi-empirical model is proposed for axial stress-strain curves of reinforced high-strength concrete square columns confined by aramid fiber reinforced polymer (FRP) jackets. Additionally, a three-dimensional finite element model is developed to simulate the mechanical behaviors of the columns. In the finite element model, both material nonlinear and contact nonlinear are taken into account. Moreover, the influence of contact nonlinear (i.e., the end friction on the contact surface between test machines and specimens) is investigated deeply. Predictions from both the semi-empirical model and the finite element model agree with the experimental results, and it is also demonstrated that the friction coefficient of end friction notably affect the properties of columns when it ranges from 0.00 to 0.25.

Ductility and strength assessment of HSC beams with varying of tensile reinforcement ratios

Mohammadhassani, Mohammad,Suhatril, Meldi,Shariati, Mahdi,Ghanbari, Farhad Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.6

Nine rectangular-section of High Strength Concrete(HSC) beams were designed and casted based on the American Concrete Institute (ACI) code provisons with varying of tensile reinforcement ratio as (${\rho}_{min}$, $0.2_{{\rho}b}$, $0.3_{{\rho}b}$, $0.4_{{\rho}b}$, $0.5_{{\rho}b}$, $0.75_{{\rho}b}$, $0.85_{{\rho}b}$, $_{{\rho}b}$, $1.2_{{\rho}b}$). Steel and concrete strains and deflections were measured at different points of the beam's length for every incremental load up to failure. The ductility ratios were calculated and the moment-curvature and load-deflection curves were drawn. The results showed that the ductility ratio reduced to less than 2 when the tensile reinforcement ratio increased to $0.5_{{\rho}b}$. Comparison of the theoretical ductility coefficient from CSA94, NZS95 and ACI with the experimental ones shows that the three mentioned codes exhibit conservative values for low reinforced HSC beams. For over-reinforced HSC beams, only the CSA94 provision is more valid. ACI bending provision is 10 percent conservative for assessing of ultimate bending moment in low-reinforced HSC section while its results are valid for over-reinforced HSC sections. The ACI code provision is non-conservative for the modulus of rupture and needs to be reviewed.

Long-Term Performance of High Strength Concrete

강문명,최열 한국콘크리트학회 2004 콘크리트학회논문집 Vol.16 No.3

This paper describes an experimental investigation of how time-dependent deformations of high strength concretes are affected by maximum size of coarse aggregate, curing time, and relatively low sustained stress level. A set of high strength concrete mixes, mainly containing two different maximum sizes of coarse aggregate, have been used to investigate drying shrinkage and creep strain of high strength concrete for 7 and 28-day moist cured cylinder specimens. Based upon one-year experimental results, drying shrinkage of high strength concrete was significantly affected by the maximum size of coarse aggregate at early age, and become gradually decreased at late age. The larger the maximum size of coarse aggregate in high strength concrete shows the lower the creep strain. The prediction equations for drying shrinkage and creep coefficient were developed on the basis of the experimental results, and compared with existing prediction models.

Ductility and strength assessment of HSC beams with varying of tensile reinforcement ratios

Mohammad Mohammadhassani,Meldi Suhatril,Mahdi Shariati,Farhad Ghanbari 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.6

Nine rectangular-section of High Strength Concrete(HSC) beams were designed and casted based on the American Concrete Institute (ACI) code provisons with varying of tensile reinforcement ratio as (ρmin, 0.2ρb, 0.3ρb, 0.4ρb, 0.5ρb, 0.75ρb, 0.85ρb, ρb, 1.2ρb). Steel and concrete strains and deflections were measured at different points of the beam’s length for every incremental load up to failure. The ductility ratios were calculated and the moment-curvature and load-deflection curves were drawn. The results showed that the ductility ratio reduced to less than 2 when the tensile reinforcement ratio increased to 0.5ρb. Comparison of the theoretical ductility coefficient from CSA94, NZS95 and ACI with the experimental ones shows that the three mentioned codes exhibit conservative values for low reinforced HSC beams. For over-reinforced HSC beams, only the CSA94 provision is more valid. ACI bending provision is 10 percent conservative for assessing of ultimate bending moment in low-reinforced HSC section while its results are valid for overreinforced HSC sections. The ACI code provision is non-conservative for the modulus of rupture and needs to be reviewed.