scholarly journals Transverse Deformations and Structural Phenomenon as Indicators of Steel Fibred High-Strength Concrete Nonlinear Behavior

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Iakov Iskhakov ◽  
Yuri Ribakov
Keyword(s):  
High Strength Concrete ◽  
High Efficiency ◽  
Limit State ◽  
Nonlinear Behavior ◽  
High Strength ◽  
Steel Fibers ◽  
Ultimate Limit State ◽  
Strength Concrete ◽  
Brittle Behavior ◽  
Ductile Behavior

As known, high-strength compressed concrete elements have brittle behavior, and elastic-plastic deformations do not appear practically up to their ultimate limit state (ULS). This problem is solved in modern practice by adding fibers that allow development of nonlinear deformations in such elements. As a rule, are applied steel fibers that proved high efficiency and contribute ductile behavior of compressed high-strength concrete (HSC) elements as well as the desired effect at long-term loading (for other types of fibers, the second problem is still not enough investigated). However, accurate prediction of the ULS for abovementioned compression elements is still very important and current. With this aim, it is proposed to use transverse deformations in HSC to analyze compression elements' behavior at stages close to ultimate. It is shown that, until the appearance of nonlinear transverse deformations (cracks formation), these deformations are about 5-6 times lower than the longitudinal ones. When cracks appear, the tensile stress-strain relationship in the transverse direction becomes nonlinear. This fact enables to predict that the longitudinal deformations approach the ultimate value. Laboratory tests were carried out on 21 cylindrical HSC specimens with various steel fibers content (0, 20, 30, 40, and 60 kg/m3). As a result, dependences of transverse deformations on longitudinal ones were obtained. These dependences previously proposed by the authors’ concept of the structural phenomenon allow proper estimation of the compressed HSC state up to failure. Good agreement between experimental and theoretical results forms a basis for further development of modern steel fibered HSC theory and first of all nonlinear behavior of HSC.

scholarly journals Flexure Behaviour of Reinforced High Strength Concrete Elements Affected by Corrosion

2019 ◽  
Vol 289 ◽  
pp. 10009
Author(s):  
Camelia Negrutiu ◽  
Ioan Sosa ◽  
Bogdan Heghes
Keyword(s):  
High Strength Concrete ◽  
Limit State ◽  
High Strength ◽  
Concrete Cover ◽  
Ultimate Limit State ◽  
Accelerated Corrosion ◽  
Strength Concrete ◽  
Significant Strength ◽  
Bending Capacity ◽  
State Position

Corrosion of the reinforcement is a constant vulnerability for reinforced concrete structures exposed to aggressive environments. High strength concrete is known to prevent corrosion of the reinforcement, in a non-cracked state, when exposed to aggressive environments. The purpose of this study is to assess the opportunity of using high strength concrete in cracked elements exposed to corrosion and compare them with non-exposed elements. A series of simply supported reinforced high strength concrete beams with concrete cover of 25 and 50 mm were pre-cracked, up to a service life crack of 0.1 mm, further exposed to accelerated corrosion through a process of electrolysis and finally tested to failure. A series of non-exposed witness specimens were also tested to failure. All elements were designed with the same bending capacity. The flexure behaviour was assessed by plotting experimental and theoretical ultimate limit state position of the neutral axis at midspan and the results show no significant differences in the overall behaviour, despite the affected reinforcement, between the corroded and non-corroded elements. Moreover, the design bending moments were approximately 40% lower than the experimental ones, even for corroded beams, which can be a significant strength reserve of the beams, useful in aggressive environments.

CURVATURE DUCTILITY PREDICTION OF REINFORCED HIGH‐STRENGTH CONCRETE BEAM SECTIONS

2010 ◽  
Vol 16 (4) ◽  
pp. 462-470 ◽  
Author(s):  
Guray Arslan ◽  
Ercan Cihanli
Keyword(s):  
High Strength Concrete ◽  
Structural Parameters ◽  
Limit State ◽  
High Strength ◽  
Reinforced Concrete Beams ◽  
Ultimate Limit State ◽  
Factors Affecting ◽  
Strength Concrete ◽  
Curvature Ductility ◽  
Major Factors

The ductility of reinforced concrete beams is very important, since it is essential to avoid a brittle failure of the structure by ensuring adequate curvature at the ultimate limit state. One of the procedures used to quantify ductility is based on curvatures, namely, curvature ductility. It is necessary to know the curvature ductility of singly reinforced high‐strength concrete (HSC) sections for determining a maximum permissible tensile reinforcement ratio or a maximum depth of the concrete compression area in design codes. The requirements of several codes and methods of prediction of the curvature ductility are based on the experimental results of normal strength concrete (NSC). The rules derived for NSC sections may not be appropriate for HSC sections, and verifications and modifications may be required for the evaluation of curvature ductility of HSC sections. In this study, the major factors affecting the curvature ductility of a singly reinforced HSC beam section are investigated. Based on numerical analyses, a parametric study has been carried out to evaluate the effects of various structural parameters on the curvature ductility of reinforced HSC beam sections. Santrauka Gelžbetoniniu siju plastiškumas yra labai svarbi savybe, apsauganti konstrukcija nuo staigios irties. Tam užtikrinti reikalinga atitinkama kreive, esant tinkamumo ribiniam būviui. Plastiškumas ivertinamas naudojant kreivines diagramas – plastiškumo kreives. Norint nustatyti didžiausia tempiamos armatūros kieki arba didžiausia gniuždomosios zonos aukšti, remiantis normomis reikia žinoti armuoto stipriojo betono (HSC) plastiškumo kreive. Kai kurios normos ir metodai plas‐tiškumo kreive nustato pagal paprastojo betono (NSC) eksperimentinius duomenis. Taisykles, skirtos paprastojo betono skerspjūvio plastiškumo kreivei nustatyti, gali netikti stipriajam betonui, todel reikia atlikti papildomus tyrimus ir metodu pakeitimus. Šiame darbe tiriami pagrindiniai veiksniai, darantys itaka stipriojo betono plastiškumo kreivei. Atliekant skai‐tini modeliavima, buvo ivertinti ivairūs skerspjūvio konstrukciniai parametrai, darantys poveiki stipriojo betono plas‐tiškumo kreivei.

An Experimental Study on the Compressive Behavior of CFRP-Confined High- and Ultra High-Strength Concrete

2013 ◽  
Vol 671-674 ◽  
pp. 1860-1864 ◽  
Author(s):  
Thomas Vincent ◽  
Togay Ozbakkloglu
Keyword(s):  
Experimental Study ◽  
High Strength Concrete ◽  
Axial Stress ◽  
Concrete Strength ◽  
Experimental Studies ◽  
High Strength ◽  
Compressive Behavior ◽  
Stress Strain ◽  
Strength Concrete ◽  
Ductile Behavior

It is well established that external confinement of concrete with fiber reinforced polymer (FRP) sheets results in significant improvements on the axial compressive behavior of concrete. This understanding has led to a large number of experimental studies being conducted over the last two decades. However, the majority of these studies have focused on normal strength concretes (NSC) with compressive strengths lower than 55 MPa, and studies on higher strength concretes have been very limited. This paper presents the results of an experimental study on the compressive behavior of FRP confined high- and ultra high-strength concrete (HSC and UHSC) with average compressive strengths of 65 and 100 MPa. A total of 29 specimens were tested under axial compression to investigate the influence of key parameters such as concrete strength and method of confinement. All specimens were cylindrical, confined with carbon FRP and were 305 mm in height and 152 mm in diameter. Results obtained from the laboratory testing were graphically presented in the form of axial stress-strain relationships and key experimental outcomes are discussed. The results of this experimental study indicate that above a certain confinement threshold, FRP-confined HSC and UHSC exhibit highly ductile behavior. The results also indicate that FRP-wrapped specimens perform similar to concrete-filled FRP tube (CFFT) specimens at ultimate condition, however notable differences are evident at the transition region when comparing stress-strain curves.

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