Direct tension-dependent flexural behavior of ultra-high-performance fiber-reinforced concretes

2017 ◽  
Vol 52 (2) ◽  
pp. 121-134 ◽  
Author(s):  
Duy-Liem Nguyen ◽  
Duc-Kien Thai ◽  
Dong-Joo Kim

This research investigated the effects of direct tensile response on the flexural resistance of ultra-high-performance fiber-reinforced concretes by performing sectional analysis. The correlations between direct tensile and flexural response of ultra-high-performance fiber-reinforced concretes were investigated in detail for the development of a design code of ultra-high-performance fiber-reinforced concrete flexural members as follows: (1) the tensile resistance of ultra-high-performance fiber-reinforced concretes right after first-cracking in tension should be higher than one-third of the first-cracking strength to obtain the deflection-hardening if the ultra-high-performance fiber-reinforced concretes show tensile strain-softening response; (2) the equivalent bottom strain of flexural member at the modulus of rupture is always higher than the strain capacity of ultra-high-performance fiber-reinforced concretes in tension; (3) the softening part in the direct tensile response of ultra-high-performance fiber-reinforced concretes significantly affects their flexural resistance; and (4) the moment resistance of ultra-high-performance fiber-reinforced concrete girders is more significantly influenced by the post-cracking tensile strength rather than the tensile strain capacity. Moreover, the size and geometry effects should be carefully considered in predicting the moment capacity of ultra-high-performance fiber-reinforced concrete beams.

2021 ◽  
Vol 63 (3) ◽  
pp. 40-45
Author(s):  
Tri Thuong Ngo ◽  
◽  
Van Hai Hoang ◽  

In this study, the flexural resistance of ultra-high-performance fiber-reinforced concrete (UHPFRCs) containing different fiber volume content, under static and dynamic flexural loading was investigated. Thirty-six specimens of UHPFRCs, size 0.5x0.5x210 (mm), reinforced with 0.5%, and 1.5% volume of smooth steel fiber (d=0.2 mm, l=19 mm) were cast and tested by three-point bending test, under the static load (strain rate 1.67x10-5 s-1) and high acceleration load (strain rate up to 210 s-1). Experimental results show that the flexural strength of UHPFRCs increases significantly when the fiber reinforcement content increases. In addition, as the loading speed increases, the flexural resistance of the material also increases. The flexural strength of UHPFRC material reinforced with 0.5 and 1.5% of fiber volume content was 17.7 and 30.0 MPa at static loads, increased to 23.6 and 51.92 MPa at a loading rates of 110 s-1 and 28.86 and 61.04 MPa at loading rate of 210 s-1.


Author(s):  
Igor Chilin ◽  

Приведены результаты исследований и выполнена оценка влияния технологических факторов на реологические свойства самоуплотняющихся сталефибробетонных смесей, определены кратковременные и длительные физико-механические и деформативные характеристики сверхвысокопрочного сталефибробетона, включая определение его фактической морозостойкости.


Buildings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 63
Author(s):  
Anna L. Mina ◽  
Michael F. Petrou ◽  
Konstantinos G. Trezos

The scope of this paper is to investigate the performance of ultra-high performance fiber reinforced concrete (UHPFRC) concrete slabs, under projectile impact. Mixture performance under impact loading was examined using bullets with 7.62 mm diameter and initial velocity 800 m/s. The UHPFRC, used in this study, consists of a combination of steel fibers of two lengths: 6 mm and 13 mm with the same diameter of 0.16 mm. Six composition mixtures were tested, four UHPFRC, one ultra-high performance concrete (UHPC), without steel fibers, and high strength concrete (HSC). Slabs with thicknesses of 15, 30, 50, and 70 mm were produced and subjected to real shotgun fire in the field. Penetration depth, material volume loss, and crater diameter were measured and analyzed. The test results show that the mixture with a combination of 3% 6 mm and 3% of 13 mm length of steel fibers exhibited the best resistance to projectile impact and only the slabs with 15 mm thickness had perforation. Empirical models that predict the depth of penetration were compared with the experimental results. This material can be used as an overlay to buildings or to construct small precast structures.


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