Evaluation of strains at peak stresses in concrete: A three-phase composite model approach

Taşdemi̇r, Mehmet Ali; Taşdemir, Canan; Akyüz, S.; Jefferson, Tony; Lydon, F.D.; Barr, B.

doi:10.1016/s0958-9465(98)00012-2

Cited by 158 publications

(65 citation statements)

References 11 publications

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“…It is clear that the magnitude of the adhesion between the spatula and the surface depends not only on the scale of the contact area but also on the location of the annular zone. 49.38 (Wu et al 1994) Material of the surface Concrete 70 (Tasdemir et al 1998) 0.03 (Ay and Topcu 1995) 0.2 (Tasdemir et al 1998) 60 (Oliva et al 2002) SiO 2 72 (Petersen 1982) 5.9 (Petersen 1982) 0.19 (Sitti and Fearing 2003) 160 (Sitti and Fearing 2003) Glass 72 (Shackelford and Alexander 2001) 4.9 (Shackelford and Alexander 2001) 0.166 (Shackelford and Alexander 2001) 49.64 (Wu et al 1994) Wood (Pine) 12 (Panshin and DeZeeuw 1980) 0.029 (Panshin and DeZeeuw 1980) 0.3 (Panshin and DeZeeuw 1980) 58.5 (Mohammed-Ziegler et al 2004) hierarchies in achieving robust and releasable adhesion. At the lowest level of the hierarchical structure (the fi ber radius is 70 nm), the adhesion was found to be 308 nN.…”

Section: Resultsmentioning

confidence: 99%

The effect of contaminants on the adhesion of the spatulae of a gecko

Jeng

Mao

2010

J Biosci

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Many researchers have reported that the robust adhesion that enables geckos to move quickly and securely across a range of vertical and horizontal surfaces is provided by the hierarchical structure of their feet (i.e. lamellae, setae, spatulae, etc.). Maintaining this robust adhesion requires an intimate contact between the terminal tips of the spatulae and the surface. The aim of this study was to investigate the effect on the adhesive properties of the spatulae when a particle becomes trapped at the contact surface. Using the Johnson, Kendall and Roberts (JKR) theory, a model was constructed to assist in the analysis of the interactions between the spatula tip, the particle and the surface. The results showed that the keratin (the natural material of the spatula) provides a robust system for adhesion even when there is a particle in the contact area, and the effective contact area of spatulae will be 80%. When the particle is significantly harder than the surface, the adhesion properties of the contact surface influenced by the particle will be more obvious. The results also reveal that the generated adhesion is considerably higher when the spatula is in contact with a softer surface, such as wood or concrete, rather than a hard surface, such as glass or SiO2.

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Section: Resultsmentioning

confidence: 99%

The effect of contaminants on the adhesion of the spatulae of a gecko

Jeng

Mao

2010

J Biosci

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“…The cylinder strengths of unconfined concrete f' c at the day of testing are reported together with the corresponding axial strains ε co in Table 1 for each concrete batch. ε co values were not measured directly for all the control specimens but were calculated using the expression given by Tasdemir (1998). As can be seen in Table 1, the average test day cylinder strengths of these batches varied between 76.6 and 79.6 MPa.…”

Section: Experimental Program Test Specimens and Materialsmentioning

confidence: 99%

Axial Compressive Behavior of Square and Rectangular High-Strength Concrete-Filled FRP Tubes

Ozbakkaloglu

2013

J. Compos. Constr.

144

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This paper presents results of an experimental study on the behavior of square and rectangular high-strength concrete (HSC)-filled fiber reinforced polymer (FRP) tubes (HSCFFTs) under concentric compression. The effects of the tube thickness, sectional aspect ratio and corner radius on the axial compressive behavior of concrete-filled FRP tubes (CFFTs) were investigated experimentally through the tests of 24 CFFTs that were manufactured using unidirectional carbon fiber sheets and high-strength concrete (HSC) with 78 MPa average compressive strength. As the first experimental investigation on the axial compressive behavior of square and rectangular HSCFFTs, the results of the study reported herein allows a number of significant conclusions to be drawn. First and foremost, test results indicate that sufficiently confined square and rectangular HSCFFTs can exhibit highly ductile behavior. The results also indicate that confinement effectiveness of FRP tubes increases with an increase in corner radius and decreases with an increase in sectional aspect ratio. It is also observed and discussed that HSCFFTs having tubes of low confinement effectiveness may experience a significant strength loss at the point of transition on their stress-strain curves. Furthermore, it is found that the behavior of HSCFFTs at this region differ from that of normal-strength CFFTs and it is more sensitive to the effectiveness of confining tube. Examination of the test results have also lead to a number of important observations on the influence of the key confinement parameters on the development and distribution of the hoop strains on the tubes of CFFTs, which are presented and discussed in the paper.

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“…When the actual rupture strain of CFRP was not included in the test results, it was assumed to be 0.55 of the rupture strain from flat-coupon tests, as recommended by ACI 440.2R-08 (ACI 2008). In addition, when the axial strain at the peak stress of unconfined concrete (ε co ) was not specified, ε co was assumed to be equal to 0.002 or values estimated by using the equation of Tasdemir et al (1998). The performance of the proposed model was compared by using two different methods for estimating the values of ε co .…”

Section: Assumptionsmentioning

confidence: 99%

“…The performance of the proposed model was compared by using two different methods for estimating the values of ε co . In the first method, ε co was calculated using the equation proposed by Tasdemir et al (1998). In the second method, ε co was assumed to be 0.002.…”

Section: Assumptionsmentioning

confidence: 99%

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Strain Estimation of CFRP-Confined Concrete Columns Using Energy Approach

Pham

Hadi

2013

J. Compos. Constr.

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A new model is presented for calculating the axial strain of carbon fiber-reinforced polymer (CFRP)-confined concrete columns. An energy-balance approach is introduced to establish a relationship of the energy absorption between a confined concrete column and CFRP. The proposed model was verified using a large database collected from 167 CFRP-confined plain concrete specimens. This database contains 98 circular specimens with diameters ranging between 100 and 152 mm, and 69 square specimens having a side length ranging between 100 and 152 mm. The database covers unconfined concrete strengths from 20 to 50 MPa. The proposed model shows very good correlation with the experimental results. In addition, the proposed model also provides a comparative prediction of the strain of CFRP-confined concrete columns in two extreme cases, i.e., (1) insufficient confinement, and (2) heavy confinement, which are not usually well predicted by other models. Abstract: A new model is presented for calculating the axial strain of carbon fiber-reinforced polymer (CFRP)-confined concrete columns. An energy-balance approach is introduced to establish a relationship of the energy absorption between a confined concrete column and CFRP. The proposed model was verified using a large database collected from 167 CFRP-confined plain concrete specimens. This database contains 98 circular specimens with diameters ranging between 100 and 152 mm, and 69 square specimens having a side length ranging between 100 and 152 mm. The database covers unconfined concrete strengths from 20 to 50 MPa. The proposed model shows very good correlation with the experimental results. In addition, the proposed model also provides a comparative prediction of the strain of CFRP-confined concrete columns in two extreme cases, i.e., (1) insufficient confinement, and (2) heavy confinement, which are not usually well predicted by other models.

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Evaluation of strains at peak stresses in concrete: A three-phase composite model approach

Cited by 158 publications

References 11 publications

The effect of contaminants on the adhesion of the spatulae of a gecko

The effect of contaminants on the adhesion of the spatulae of a gecko

Axial Compressive Behavior of Square and Rectangular High-Strength Concrete-Filled FRP Tubes

Strain Estimation of CFRP-Confined Concrete Columns Using Energy Approach

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