scholarly journals Effect of Steel Fibers on the Hysteretic Performance of Concrete Beams with Steel Reinforcement—Tests and Analysis

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2923 ◽  
Author(s):  
Violetta K. Kytinou ◽  
Constantin E. Chalioris ◽  
Chris G. Karayannis ◽  
Anaxagoras Elenas
Keyword(s):  
Reinforced Concrete ◽  
Steel Reinforcement ◽  
Steel Fibers ◽  
Experimental Program ◽  
Engineering Practice ◽  
Cracking Behavior ◽  
Tension Softening ◽  
Proposed Model ◽  
Hysteretic Performance ◽  
Cracking Performance

The use of fibers as mass reinforcement to delay cracking and to improve the strength and the post-cracking performance of reinforced concrete (RC) beams has been well documented. However, issues of common engineering practice about the beneficial effect of steel fibers to the seismic resistance of RC structural members in active earthquake zones have not yet been fully clarified. This study presents an experimental and a numerical approach to the aforementioned question. The hysteretic response of slender and deep steel fiber-reinforced concrete (SFRC) beams reinforced with steel reinforcement is investigated through tests of eleven beams subjected to reversal cyclic loading and numerical analysis using 3D finite element (FE) modeling. The experimental program includes flexural and shear-critical SFRC beams with different ratios of steel reinforcing bars (0.55% and 1.0%), closed stirrups (from 0 to 0.5%), and fibers with content from 0.5 to 3% per volume. The developed nonlinear FE numerical simulation considers well-established relationships for the compression and tensional behavior of SFRC that are based on test results. Specifically, a smeared crack model is proposed for the post-cracking behavior of SFRC under tension, which employs the fracture characteristics of the composite material using stress versus crack width curves with tension softening. Axial tension tests of prismatic SFRC specimens are also included in this study to support the experimental project and to verify the proposed model. Comparing the numerical results with the experimental ones it is revealed that the proposed model is efficient and accurately captures the crucial aspects of the response, such as the SFRC tension softening effect, the load versus deformation cyclic envelope and the influence of the fibers on the overall hysteretic performance. The findings of this study also reveal that SFRC beams showed enhanced cyclic behavior in terms of residual stiffness, load-bearing capacity, deformation, energy dissipation ability and cracking performance, maintaining their integrity through the imposed reversal cyclic tests.

scholarly journals Experimental analysis of steel fiber reinforced concrete beams in shear

2022 ◽  
Vol 15 (3) ◽  
Author(s):  
Aaron Kadima Lukanu Lwa Nzambi ◽  
Dênio Ramam Carvalho de Oliveira ◽  
Marcus Vinicius dos Santos Monteiro ◽  
Luiz Felipe Albuquerque da Silva
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Concrete Beams ◽  
Reinforcement Ratio ◽  
Steel Fibers ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Longitudinal Reinforcement ◽  
Fiber Addition

Abstract Some normative recommendations are conservative in relation to the shear strength of reinforced concrete beams, not directly considering the longitudinal reinforcement rate. An experimental program containing 8 beams of (100 x 250) mm2 and a length of 1,200 mm was carried out. The concrete compression strength was 20 MPa with and without 1.00% of steel fiber addition, without stirrups and varying the longitudinal reinforcement ratio. Comparisons between experimental failure loads and main design codes estimates were assessed. The results showed that the increase of the longitudinal reinforcement ratio from 0.87% to 2.14% in beams without steel fiber led to an improvement of 59% in shear strength caused by the dowel effect, while the corresponding improvement was of only 22% in fibered concrete beams. A maximum gain of 109% in shear strength was observed with the addition of 1% of steel fibers comparing beams with the same longitudinal reinforcement ratio (1.2%). A significant amount of shear strength was provided by the inclusion of the steel fibers and allowed controlling the propagation of cracks by the effect of stress transfer bridges, transforming the brittle shear mechanism into a ductile flexural one. From this, it is clear the shear benefit of the steel fiber addition when associated to the longitudinal reinforcement and optimal values for this relationship would improve results.

BEHAVIOR OF CORRODED RC BEAMS WITHOUT STIRRUPS REPAIRED WITH CFRP SHEETS

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Abdullah Al-Saidy ◽  
Sherif El-Gamal ◽  
Khlaifa Al-Jabri ◽  
Bilal Waris
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Strength Loss ◽  
Steel Reinforcement ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Shear Reinforcement ◽  
Accelerated Corrosion ◽  
Cfrp Sheets ◽  
Externally Bonded

In reinforced concrete structures located in hot and humid areas, steel reinforcement is generally vulnerable to deterioration due to corrosion. Corrosion of reinforcement in many cases is considered the main cause of concrete structures deterioration, which in turn requires large budgets for repair and maintenance. This paper presents the experimental results of damaged/repaired reinforced concrete beams. The experimental program consisted of testing reinforced concrete rectangular beam specimen’s with/without shear reinforcement and exposed to accelerated corrosion of the longitudinal steel reinforcement on the tension side. Bonding external U-shaped CFRP sheets to restore the strength loss due to corrosion repaired corroded beams without shear reinforcement. The test results showed that corroded beams without stirrups failed in a brittle manner with drop in maximum deflection at failure of approximately 60% compared to the uncorroded beam. Corroded beams with stirrups lost some strength, but failed in ductile manner. Using externally bonded U-shaped CFRP sheets restored the ductility of corroded beams without stirrups and prevented bond failure at the steel concrete interface due to the absence of internal stirrups.

Cracking behavior and energy consumption of Steel Fiber Concrete Encased Steel beams

2021 ◽  
pp. 136943322110297
Author(s):  
Chao Xu ◽  
Kai Wu ◽  
Ping zhou Cao ◽  
Shi-qi Lin ◽  
Zhuo Chen
Keyword(s):  
Energy Consumption ◽  
Steel Fiber ◽  
Steel Reinforcement ◽  
Steel Fibers ◽  
Strengthening Effect ◽  
Fiber Volume ◽  
Volume Percentage ◽  
Cracking Behavior ◽  
Fiber Concrete ◽  
Steel Fiber Concrete

Steel Fiber Concrete Encased Steel (SFCES) beams were subjected to bending to investigate the effect of steel fibers on the behavior of Steel Reinforced Concrete beams with or without steel reinforcement. 18 SFCES beams reinforced with steel fibers, steel reinforcement, or both were cast. The parameters considered in the experiment were (a) the volume percentage of steel fiber (0%, 1%, and 2%), (b) the shear span to depth ratio( s/d = 2.5 and 3.5), (c) the stirrups spacing (180 mm and 360 mm), and (d) the presence or absence of longitudinal reinforcement (2Φ8+2Φ10).The cracking load, crack development, energy dissipation capacity, and ductility of the specimens were investigated. The results illustrate that the cracking load F c, the total energy consumption, and the energy ductility increase with increasing steel fiber volume, and the average improvement with a steel fiber volume increase of 1% can reach 36.5%, 21.2%, and 28.67%, respectively. However, this strengthening effect of steel fibers was weakened due to the addition of steel reinforcement. The influence of the steel fiber volume and reinforcement configuration on each stage of energy consumption was mainly concentrated in the elastic ( E 1) and failure stages ( E 3). Finally, mathematical equations were proposed to predict the cracking load and crack width of the SFCES specimens, which were verified by comparing the predictions with the experiment results.

scholarly journals Effect of fiber amount and stirrup ratio on shear resistance of steel fiber reinforced concrete deep beams

2021 ◽  
Vol 15 (2) ◽  
pp. 1-13
Author(s):  
Thang Do-Dai ◽  
Duong T. Tran ◽  
Long Nguyen-Minh
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Shear Crack ◽  
Shear Resistance ◽  
Shear Capacity ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Experimental Program ◽  
Deep Beam ◽  
Deep Beams

This paper deals with the effect of steel fiber amounts and the interaction between the fiber amount and stirrup ratio on the shear behavior and capacity of reinforced concrete (RC) deep beams with steel fibers. The experimental program was carried out on twelve deep beams with different fiber amounts (0, 30, 40, and 65 kg/m3) and stirrup ratios (0.1, 0.15, and 0.25%). The test results have shown that the use of steel fibers increased the shear resistance (up to 55%), reduced the shear crack width (up to 11 times) and deflection (up to 57%) of the tested deep beams. Also, it was found that using unsuitable steel fiber amount and stirrup ratio would reduce the efficiency of the fibers in a deep beam due to the interaction between the fibers and stirrups. Increasing the stirrup ratio in a deep beam with a high amount of steel fibers can reduce the efficacy of the fibers in enhancing the shear capacity of the beam. The most cost-effective steel fiber amount was found to be around 30 to 45 kg/m3. Keywords: steel fibers; deep beam; shear capacity; fiber amount; stirrup ratio.

scholarly journals Shear Performance of Steel Fibers in Reinforced Concrete Beams

2019 ◽  
Vol 9 (2) ◽  
pp. 345-350
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Resistance Mechanism ◽  
Shear Resistance ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Shear Reinforcement ◽  
Shear Span

Over the past few decades, a significant growth was observed on utilization of steel fibers in Reinforced Concrete (R.C) members. Past research studies on hybrid concrete endorsed optimum utilization of steel fibers (1.5% by volume) as it effectively contributed to improve flexural properties of reinforced concrete members such as R.C beams and slabs .But the contribution of fibers against shear resistance mechanism of R.C beams are not identified well in the previous research. In this context an experimental program was conducted to find Shear contribution and associated Parameters of fibers in the Steel Fiber Reinforced Concrete (SFRC) beams. A series of test programmes are conducted on three full scale reinforced concrete beams (NSF: No steel fibers, BSF1: Steel fibers in shear span, BSF2: Steel fibers in full span) with different configuration of shear reinforcement by using varied range of SFRC in the tested beam. The test results evaluated on the basis of strength and durability aspects at service loads and limit of failure conditions. The results concluded that the presence of steel fibers in reinforced concrete beam significantly contributed to induce shear resistance mechanism and ductile property of R.C beam. This improvement observed in BSF2, when the SFRC constituted in shear span region and the rest of R.C beam arranged with minimum conventional stirrups as shear reinforcement. Further the steel fibers possess good compatibility with concrete and steel reinforcement ,which enhance mechanical and serviceability conditions of R.C beam such as shear strength, ductility, stiffness with respect to strength and deflection, crack width during serviceability conditions of the beam.

Crack Resistance Analyses on RC Composite Floor Slab

2006 ◽  
Vol 302-303 ◽  
pp. 637-643 ◽  
Author(s):  
Peng Chang ◽  
Qian Feng Yao ◽  
A Ping Wang
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
Three Dimensional ◽  
Engineering Practice ◽  
Cracking Behavior ◽  
Floor Slab ◽  
Linear Elastic ◽  
Principal Tensile Stress ◽  
Concrete Layer ◽  
Linear Elastic Theory

Cracking behavior of reinforced concrete composite floor slab, which has a significant effect on durability of concrete structures, is studied. Crack resistance of one-way composite floor slab is analyzed during transfer stage, handling stage, construction stage and serviceability stage, and calculation formulas are presented. Precast prestressed plank and topping cast-in-situ concrete layer can be designed as composite floor slab. It is assumed that prestressed unit is in elastic stage under service loads and hence every stress subentry can be calculated on the base of linear elastic theory and can be added linearly. For two-way composite floor slab, principal tensile stress in concrete is deduced on the base of theory of three-dimensional stress state in material mechanics. In addition, two-way effect on stress and practical distribution pattern of moment and shear force are considered. A number of structure experiment and experiences from engineering practice show that cracking behavior of reinforced concrete composite floor slab is a necessary consideration in design and analysis method shown in this paper is convenient and effective.

Study of the residual axial capacities of shear-damaged reinforced concrete columns: Part 2—experimental verification of an evaluation model

2018 ◽  
Vol 22 (2) ◽  
pp. 459-472
Author(s):  
Yong Yang ◽  
Kazuto Matsukawa ◽  
Ho Choi ◽  
Yoshiaki Nakano
Keyword(s):  
Reinforced Concrete ◽  
Evaluation Model ◽  
Concrete Columns ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Concrete Core ◽  
Reinforced Concrete Columns ◽  
Damage Pattern ◽  
Axial Capacity ◽  
Proposed Model

This article presents an experimental program to further verify the arch resistance model, which was proposed for evaluating the residual axial capacities of shear-damaged reinforced concrete columns in part 1 of the companion papers. Three reinforced concrete columns with different transverse reinforcement ratios are designed and tested up to axial collapse under different axial force levels. Based on the experimental results, the transverse reinforcement within the shear-damaged region of the designed specimens is confirmed to be able to fully develop their strength at axial collapse. With regard to the evaluation of residual axial capacities, when the damage pattern of the concrete core is consistent with that described in the proposed model, the residual axial capacity of the column along with the included two contributions of the concrete core and longitudinal bars are estimated with a high level of accuracy. When the damage pattern of the concrete core is not completely consistent with that described in the proposed model, although the contribution of the concrete core is not accurately estimated, the contribution of the longitudinal bars is still accurately evaluated. Furthermore, because of the low percentage of the contribution of the concrete core, the damage pattern of the concrete core has little effect on the evaluation accuracy of the residual axial capacity of the column. Thus, using the proposed model, the residual axial capacities of the columns with slightly different damage patterns of the concrete core are still estimated with a high accuracy in this experimental program.

Post-earthquake assessment of moderately damaged reinforced concrete plastic hinges

2020 ◽  
Vol 36 (1) ◽  
pp. 299-321
Author(s):  
Kai Marder ◽  
Kenneth J. Elwood ◽  
Christopher J. Motter ◽  
G. Charles Clifton
Keyword(s):  
Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Plastic Hinges ◽  
Strong Earthquakes ◽  
Proposed Model ◽  
Residual Capacity ◽  
The Relationship ◽  
Crack Widths ◽  
Earthquake Assessment

Modern reinforced concrete buildings are often designed to dissipate energy during strong earthquakes by permitting the controlled formation of plastic hinges. Plastic hinges require assessment of residual capacity in post-earthquake situations. However, few past studies have investigated this topic, and results from experiments focused on undamaged structures are not always transferable to post-earthquake situations. Data from an experimental program, in which both cyclic and earthquake-type loadings were applied to nominally identical reinforced concrete beams, are used to investigate the relationship between residual crack widths and rotation demands. Assessment of the peak deformation demands incurred during a damaging earthquake is critical for post-earthquake assessments, but residual crack widths are shown to be dependent on several factors in addition to the peak rotation demand. Non-dimensional metrics capturing the distribution of cracking are proposed as a more informative alternative. The reduction in stiffness that occurs as a result of earthquake-induced plastic hinging damage was also investigated. A proposed model is shown to give a lower-bound estimate of the residual stiffness following arbitrary earthquake-type loadings.

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