scholarly journals Flexural Fatigue Performance of Steel Fiber Reinforced Expanded-Shales Lightweight Concrete Superposed Beams with Initial Static-Load Cracks

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3261
Author(s):  
Fulai Qu ◽  
Changyong Li ◽  
Chao Peng ◽  
Xinxin Ding ◽  
Xiaowu Hu ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Static Load ◽  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Stress Amplitude ◽  
Flexural Stiffness ◽  
Compression Zone ◽  
Fatigue Load ◽  
Upper Limit

Concerning the structural applications of steel fiber reinforced expanded-shales lightweight concrete (SFRELC), the present study focuses on the flexural fatigue performance of SFRELC superposed beams with initial static-load cracks. Nine SFRELC superposed beams were fabricated with the SFRELC depth varying from 50% to 70% of the whole sectional depth, and the volume fraction of steel fiber ranged from 0.8% to 1.6%. The fatigue load exerted on the beams was a constant amplitude sinusoid with a frequency of 10 Hz and a fatigue characteristic value of 0.10; the upper limit was taken as the load corresponded to the maximum crack width of 0.20 mm at the barycenter of the longitudinal rebars. The results showed that with the increase of SFRELC depth and the volume fraction of steel fiber, the fatigue life of the test beams was prolonged with three altered failure modes due to the crush of conventional concrete in the compression zone and/or the fracture of the tensile rebar; the failure pattern could be more ductile by the prevention of fatigue fracture by the longitudinal tensile rebar when the volume fraction of steel fiber was 1.6% and the reduction of crack growth and concrete strain in the compression zone; the fatigue life of test beams was sensitive to the upper-limit of the fatigue load, a short fatigue life appeared from the higher stress level and larger stress amplitude of the longitudinal rebar due to the higher upper-limit of the fatigue load. The methods for predicting the stress level, the stress amplitude of the longitudinal tensile rebar, and the degenerated flexural stiffness of SFRELC superposed beams with fatigue life are proposed. With the optimal composites of the SFRELC depth ratio and the volume fraction of steel fiber, the controllable failure of reinforced SFRELC superposed beams could be a good prospect with the trend curves of fatigue flexural stiffness.

Static and Fatigue Analysis on a Wing Spar Joint for a Light Jet Aircraft Structure Using 2024 T351 Material

2019 ◽  
Vol 895 ◽  
pp. 244-252
Author(s):  
G. Pavan ◽  
N. Kishore
Keyword(s):  
Fatigue Life ◽  
Static Load ◽  
Working Condition ◽  
Fatigue Loading ◽  
Fatigue Analysis ◽  
Fatigue Load ◽  
Aircraft Structure ◽  
Load Spectra ◽  
Loading Modes ◽  
Wing Spar

The main objective of this paper is to present prototype of wing spar joint using CATIA V5 software to study the behavior of wing spar joint as per actual working condition and to perform structural analysis of the wing spar joint based on condition of cyclic loading (fatigue loading). Determining the loading modes in the spar joint is subjected to static load and fatigue loads which should be taken into account in the evaluation of the strength and fatigue life. Initially, the components were modeled with CATIA V5 and imported to MSC PATRAN; MSC NASTRAN is used as a solver. From the obtained maximum tensile stresses, fatigue analysis was carried out to find fatigue life of the spar joint with different fatigue load spectra.

scholarly journals Development of Steel Fiber-Reinforced Expanded-Shale Lightweight Concrete with High Freeze-Thaw Resistance

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Mingshuang Zhao ◽  
Xiaoyan Zhang ◽  
Wenhui Song ◽  
Changyong Li ◽  
Shunbo Zhao
Keyword(s):  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Content Volume ◽  
Steel Fibers ◽  
Fine Aggregate ◽  
Test Results ◽  
Fiber Reinforced ◽  
Freeze Thaw ◽  
Expanded Shale

For the popularized structural application, steel fiber-reinforced expanded-shale lightweight concrete (SFRELC) with high freeze-thaw resistance was developed. The experimental study of this paper figured out the effects of air-entraining content, volume fraction of steel fibers, and fine aggregate type. Results showed that while the less change of mass loss rate was taken place for SFRELC after 300 freeze-thaw cycles, the relative dynamic modulus of elasticity and the relative flexural strength presented clear trends of freeze-thaw resistance of SFRELC. The compound effect of the air-entraining agent and the steel fibers was found to support the SFRELC with high freeze-thaw resistance, and the mechanisms were explored with the aid of the test results of water penetration of SFRELC. The beneficial effect was appeared from the replacement of lightweight sand with manufactured sand. Based on the test results, suggestions are given out for the optimal mix proportion of SFRELC to satisfy the durability requirement of freeze-thaw resistance.

scholarly journals Effect of Steel Fiber Content on Shear Behavior of Reinforced Expanded-Shale Lightweight Concrete Beams with Stirrups

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1107
Author(s):  
Changyong Li ◽  
Minglei Zhao ◽  
Xiaoyan Zhang ◽  
Jie Li ◽  
Xiaoke Li ◽  
...  
Keyword(s):  
Crack Width ◽  
Failure Modes ◽  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Shear Crack ◽  
Shear Capacity ◽  
Shear Cracks ◽  
Shear Cracking ◽  
Expanded Shale

To determine the validity of steel fiber reinforced expanded-shale lightweight concrete (SFRELC) applied in structures, the shear behavior of SFRELC structural components needs to be understood. In this paper, four-point bending tests were carried out on reinforced SFRELC beams with stirrups and a varying volume fraction of steel fiber from 0.4% to 1.6%. The shear cracking force, shear crack width and distribution pattern, mid-span deflection, and failure modes of test beams were recorded. Results indicate that the shear failure modes of reinforced SFRELC beams with stirrups were modified from brittle to ductile and could be transferred to the flexure mode with the increasing volume fraction of steel fiber. The coupling of steel fibers with stirrups contributed to the shear cracking force and the shear capacity provided by the SFRELC, and it improved the distribution of shear cracks. At the limit loading level of beams in building structures at serviceability, the maximum width of shear cracks could be controlled within 0.3 mm and 0.2 mm with the volume fraction of steel fiber increased from 0.4% to 0.8%. Finally, the formulas are proposed for the prediction of shear-cracking force, shear crack width, and shear capacity of reinforced SFRELC beams with stirrups.

scholarly journals Complete Stress–Strain Curves of Self-Compacting Steel Fiber Reinforced Expanded-Shale Lightweight Concrete under Uniaxial Compression

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2979 ◽  
Author(s):  
Zhao ◽  
Zhang ◽  
Shang ◽  
Fu ◽  
Zhang ◽  
...  
Keyword(s):  
Uniaxial Compression ◽  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Compressive Strain ◽  
Strain Curve ◽  
Lightweight Aggregate Concrete ◽  
Fiber Reinforced ◽  
Stress Strain ◽  
Expanded Shale

To expand the structural application of steel fiber reinforced expanded-shale lightweight concrete (SFRELC), a self-compacting SFRELC with high-workability was developed based on previous research. As part of the investigation, the present study focuses on the adaptability of formulas used for the complete stress–strain curves of steel fiber reinforced lightweight-aggregate concrete and conventional concrete under uniaxial compression. On the basis of mix proportion of SFRELC, self-compacting SFRELC was designed with the volume fraction of steel fiber as 0%, 0.4%, 0.8%, 1.2%, 1.6%, and 2.0%. Eighteen cylindrical specimens with dimensions of Φ150 mm × 300 mm were tested to measure the uniaxial compressive stress–strain curves of self-compacting SFRELC. Results indicated that, with the increasing volume fraction of steel fiber, the compressive strain at the peak-stress of the stress–strain curve increased, while the slope of the descending portion decreased. This increased the energy absorption of self-compacting SFRELC with a higher compression toughness. With a comparison of test results between four groups of calculation models, a group of formulas is selected to express the complete stress–strain curves of self-compacting SFRELC under uniaxial compression.

Bonding Strength of Expanded Polystyrene (EPS) Beads Enhanced with Steel Fiber in Reinforced Lightweight Concrete (LWC)

2014 ◽  
Vol 661 ◽  
pp. 100-105 ◽  
Author(s):  
Jamilah Abd. Rahim ◽  
Siti Hawa Hamzah ◽  
Mohd Saman Hamidah
Keyword(s):  
Aspect Ratio ◽  
Bonding Strength ◽  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Expanded Polystyrene ◽  
Normal Concrete ◽  
Pull Out ◽  
Concrete Mix ◽  
Reinforcement Bar

Lightweight concrete (LWC) is one of the favourable concrete to be used as it has low density with acceptable high strength, high durability, and toughness. In order to produce LWC, it is required special material such as expanded polystyrene (EPS) beads and steel fiber to be added into the design mix concrete. As known, EPS beads have zero strength. Meanwhile, the significant of steel fiber is to reduce micro and macro crack propagation. Therefore, pull out test were carried out to measure the bond strength between reinforcement bar and three series of concrete mix design which are normal concrete, EPS-LWC and EPS-LWC enhanced with steel fiber. Concrete adhesion and bearing deformation of reinforcing bar against the concrete are the two main mechanisms that influence the strength of bond in the steel reinforced concrete. Deformation will increase when the bonding stress increase. Normal concrete series shows the higher average bonding stress which is 531.22 kPa compared to others series concrete mix. Meanwhile, bonding stress of EPS-LWC mix is 174.54 kPa which is higher than EPS-LWC enhanced with steel fiber mix. Even though the present of the steel fibre can increase the strength of the LWC, but it effects to the bonding strength between reinforcement steel rod and concrete. There are two improtant factor in bonding determination which are volume fraction and aspect ratio of the steel fiber. Segregation will increase when the aspect ratio of steel fiber increased. Besides, the workability becomes low. This present study used types of hooked end steel fiber with 60 mm length and aspected ratio is 0.75. While the size of the cylindrical is 300 mm x 150 mm. The position of the steel fiber in the specimens is too compact and presenting the air voids. Consequently weaken the bonding strength between concrete and reinforcement bar.

scholarly journals Bond of Ribbed Steel Bar in High-Performance Steel Fiber Reinforced Expanded-Shale Lightweight Concrete

Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 582
Author(s):  
Mingshuang Zhao ◽  
Guirong Liu ◽  
Lingli Liu ◽  
Yanyan Zhang ◽  
Kang Shi ◽  
...  
Keyword(s):  
Bond Strength ◽  
High Performance ◽  
Steel Fiber ◽  
Lightweight Concrete ◽  
Volume Fraction ◽  
Bond Stress ◽  
Fiber Reinforced ◽  
Bond Slip ◽  
Steel Bar ◽  
Expanded Shale

For the structural application of high-performance Steel Fiber Reinforced Expanded-shale Lightweight Concrete (SFRELC), a reliable bond of ribbed steel bar should be ensured. In this paper, an experimental study was carried out on the bond properties of ribbed steel bar embedded in SFRELC by the direct pull-out test. The SFRELC was produced with a strength grade of 35 MPa and a volume fraction of steel fiber as 0%, 0.8%, 1.2%, 1.6% and 2.0%, respectively. Fifteen groups of specimens were made with a central placed steel bar with diameter of 14 mm, 20 mm and 28 mm, respectively. Complete bond stress-slip curves were determined for each group of specimens, and the characteristic values of bond-stress and slip at key points of the curves were ascertained. Results show that the bond strength, peak-slip and residual bond strength increased with the increase of the volume fraction of steel fiber. With the increase of steel bar diameter, bond strength decreased while the peak-slip increased, and the descending curves became sharp with a decreased residual bond strength. Formulas for calculating the bond strength and peak-slip were proposed. The relationships were determined for the splitting bond strength, residual bond strength with the bond strength, the splitting bond slip and residual bond slip with the peak-slip. Combined with rational fitting analyses of bond strength and slip, a constitutive model was selected for predicting the bond stress-slip of ribbed steel bar in SFRELC.

Fatigue Life Analysis of the Bolt

2011 ◽  
Vol 121-126 ◽  
pp. 259-262
Author(s):  
Zhong Chao Chen ◽  
Ji Min Zhang
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Shear Force ◽  
Static Load ◽  
Tensile Force ◽  
Fatigue Load ◽  
Safety Coefficient ◽  
Experiment Platform ◽  
Life Analysis ◽  
Fatigue Life Analysis

For the bolts on the experiment table, there are two main kinds of forces, namely, shear force and tensile force. This paper will test these two different forces that the bolts received, verifying their compliance with the service life. Finding out which situation is better by comparing the safety coefficient under the static load and the fatigue life under the fatigue load. And then put forward some reasonable measures for improving to make the bolts meet the fatigue life of the experiment platform.

Fatigue Life of the Human Teeth: A Continuum Damage Approach

2019 ◽  
Vol 43 ◽  
pp. 1-19
Author(s):  
Theddeus Tochukwu Akano
Keyword(s):  
Fatigue Life ◽  
Damage Mechanics ◽  
Stress Amplitude ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Elastoplastic Model ◽  
Human Teeth ◽  
Proposed Model ◽  
Number Of Cycles ◽  
Cycles To Failure

Normal oral food ingestion processes such as mastication would not have been possible without the teeth. The human teeth are subjected to many cyclic loadings per day. This, in turn, exerts forces on the teeth just like an engineering material undergoing the same cyclic loading. Over a period, there will be the creation of microcracks on the teeth that might not be visible ab initio. The constant formation of these microcracks weakens the teeth structure and foundation that result in its fracture. Therefore, the need to predict the fatigue life for human teeth is essential. In this paper, a continuum damage mechanics (CDM) based model is employed to evaluate the fatigue life of the human teeth. The material characteristic of the teeth is captured within the framework of the elastoplastic model. By applying the damage evolution equivalence, a mathematical formula is developed that describes the fatigue life in terms of the stress amplitude. Existing experimental data served as a guide as to the completeness of the proposed model. Results as a function of age and tubule orientation are presented. The outcomes produced by the current study have substantial agreement with the experimental results when plotted on the same axes. There is a notable difference in the number of cycles to failure as the tubule orientation increases. It is also revealed that the developed model could forecast for any tubule orientation and be adopted for both young and old teeth.

Uniaxial Ratcheting and Low-Cycle Fatigue Failure of U75V Rail Steel

2016 ◽  
Vol 853 ◽  
pp. 246-250 ◽  
Author(s):  
Tao Fang ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Rail Steel ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Cyclic Straining

Experiments on U75V rail steel were carried out to investigate the cyclic feature, ratcheting behavior and low-cycle fatigue under both strain- and stress-controlled loadings at room temperature. It was found that U75V rail steel shows strain amplitude dependent cyclic softening feature, i.e., the responded stress amplitude under strain-controlled decreases with the increasing number of cycles and reaches a stable value after about 20th cycle. Ratcheting strain increases with an increasing stress amplitude and mean stress, except for stress ratio, and the ratcheting strain in failure also increases with an increasing stress amplitude, mean stress and stress ratio. The low-cycle fatigue lives under cyclic straining decrease linearly with an increasing strain amplitude, the fatigue lives under cyclic stressing decrease with an increasing mean stress except for zero mean stress, and decrease with an increasing stress amplitude. Ratcheting behavior with a high mean stress reduces fatigue life of rail steel by comparing fatigue lives under stress cycling with those under strain cycling. Research findings are helpful to evaluate fatigue life of U75V rail steel in the railways with passenger and freight traffic.

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