Innovative strategies for enhancing fire performance of high-strength concrete structures

2018 ◽  
Vol 21 (11) ◽  
pp. 1723-1732 ◽  
Author(s):  
Venkatesh KR Kodur
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Published Data ◽  
Structural Members ◽  
Fire Performance ◽  
Normal Strength Concrete ◽  
Innovative Strategies ◽  
Strength Concrete ◽  
Normal Strength ◽  
Fire Conditions

High-strength concrete is being increasingly used in a number of building applications, where structural fire safety is one of the primary design considerations. Many research studies clearly indicate that the fire performance of high-strength concrete is different from that of normal-strength concrete and that high-strength concrete may not exhibit same level of performance as normal-strength concrete under fire conditions. This article outlines key characteristics that influence the performance of high-strength concrete structural members under fire conditions. Data generated in previous experimental and numerical studies are utilized to illustrate various factors that influence fire performance of high-strength concrete structural members. Based on the published data, observations and trends on the behavior of high-strength concrete members, innovative strategies for mitigating spalling and enhancing fire resistance of high-strength concrete structural members are proposed.

Is it reasonable to use high-strength concrete columns under fire conditions?

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Oliver Bahr
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Concrete Columns ◽  
Fire Performance ◽  
Normal Strength Concrete ◽  
Cross Sectional ◽  
Content Type ◽  
Strength Concrete ◽  
Normal Strength ◽  
High Strength Concrete Columns

PurposeThis paper aims to answer two questions. First, are there any differences in the fire performance of columns made of normal and of high-strength concrete? Second, under which circumstances does the fire design govern the cross-sectional dimensions of concrete columns? Is it feasible to replace columns out of normal strength concrete by more slender high-strength concrete columns?Design/methodology/approachThe author conducted numerical studies using the finite element code “Infocad” of the German company “Infograph”. The studies included the effect of different parameters on the fire performance of columns out of normal and high-strength concrete, i.e. the load ratio and eccentricity, boundary conditions and times of fire exposure.FindingsResults from the numerical investigations showed that high-strength concrete columns suffer much more from heating than normal strength concrete columns. This is the outcome of the unfavourable mechanical properties of high-strength concrete at elevated temperatures. Although the relative fire performance of columns out of high-strength concrete is worse than that of columns out of normal strength concrete, initial load reserves are beneficial to achieve even high fire ratings.Originality/valueMany researchers addressed in experimental and numerical studies the fire performance of columns out of normal and high-strength concrete. A special emphasis was often laid on the spalling of fire-exposed high-strength concrete. However, there are no systematic investigations when the fire design governs the cross-sectional dimensions of high-strength concrete columns. Based on a previous comparison of the relative fire performance of columns out of normal and high-strength concrete, this paper, hence, addresses the question whether there is a reasonable lower limit for the use of these columns. This is an important aspect for designers since there is a tendency to replace columns out of normal strength concrete by columns out of high-strength concrete. Higher concrete strengths allow for smaller cross sections of the columns, and designers may, hence, increase the usable space of buildings.

Bond Strength of Reinforcement in High-Strength Concrete

2000 ◽  
Vol 3 (3) ◽  
pp. 245-253 ◽  
Author(s):  
P. Mendis ◽  
C. French
Keyword(s):  
Bond Strength ◽  
High Strength Concrete ◽  
High Strength ◽  
Development Length ◽  
Normal Strength Concrete ◽  
Empirical Relationships ◽  
Strength Concrete ◽  
The World ◽  
Current Design ◽  
Normal Strength

The use of high-strength concrete is becoming popular around the world. The american code, ACI 318–95 is used in many countries to calculate the development length of deformed bars in tension. However, current design provisions of ACI 318–95 are based on empirical relationships developed from tests on normal strength concrete. The results of a series of tests on high-strength concrete, reported in the literature, from six research studies are used to review the existing recommendations in ACI 318–95 for design of splices and anchorage of reinforcement. It is shown that ACI 318–95 equations may be unconservative for some cases beyond 62 MPa (9 ksi).

Flexural Strength and Stiffness of High Strength Concrete Beams with Exposed Main Steel

2012 ◽  
Vol 446-449 ◽  
pp. 718-727
Author(s):  
Hamid Reza Azizipesteh Baglo ◽  
Mohammed Raoof
Keyword(s):  
High Strength Concrete ◽  
Large Scale ◽  
Structural Characteristics ◽  
High Strength ◽  
Design Parameters ◽  
Normal Strength Concrete ◽  
Strength Concrete ◽  
Beam Design ◽  
Wide Range ◽  
Normal Strength

In a number of previous publications, results were reported for a series of extensive and carefully conducted tests on large scale reinforced concrete (R.C.) beams with various extents of loss of concrete cover and exposure of main reinforcement along their spans, with such areas of simulated damage being located within their regions which are dominated by either shear or flexure. These tests on R.C. beams made with normal strength concrete have covered a wide range of first order beam design parameters, with their results used to verify the generality of various theoretical models. In the present paper, much attention will be devoted to various structural characteristics (such as ultimate strength, flexural stiffness, etc.) of similar damaged R.C. beams with the proviso that, instead of the previously used normal strength concrete, the beams are made with high strength concrete. No such results (for high strength R.C. beams) have previously been reported in the public domain.

Repairing of RC Structures by Steel Fibred High Strength Concrete

2016 ◽  
Author(s):  
Iakov Iskhakov ◽  
Yuri Ribakov
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Steel Fibers ◽  
Bending Moments ◽  
Normal Strength Concrete ◽  
Poisson Coefficient ◽  
Rc Structures ◽  
Strength Concrete ◽  
Dynamic Loadings ◽  
Normal Strength

<p>Steel fibered high strength concrete (SFHSC) is effective for repairing structures from normal strength concrete (NSC). Design of NSC structures that should be repaired is based on general concepts for design of two-layer beams, developed by the authors. Such beams are effective when their section carries large bending moments. Steel fibers increase the ultimate deformations of high strength concrete. The required ductility level of the repaired element is achieved by selecting appropriate fibers' content. This is important for design of structures to dynamic loadings. The paper is focused on interpreting the experimental data in order to find the optimal fibre content and correspondingly the highest Poisson coefficient and ductility of the repaired elements’ sections. The experimental results, obtained in the frame of this study, form a basis for provisions, related to repairing of NSC beams and slabs, using SFHSC.</p>

Nonlinear analysis of normal- and high-strength concrete slabs

1993 ◽  
Vol 20 (4) ◽  
pp. 696-707 ◽  
Author(s):  
H. Marzouk ◽  
Z. W. Chen
Keyword(s):  
Finite Element ◽  
Parametric Study ◽  
High Strength Concrete ◽  
High Strength ◽  
Nonlinear Finite Element ◽  
Concrete Slabs ◽  
Normal Strength Concrete ◽  
Tension Stiffening ◽  
Strength Concrete ◽  
Normal Strength

Concrete slabs supported on four edges and loaded axially and transversely are used in many civil engineering applications. High-strength concrete slabs are commonly used for marine structures and offshore platforms. The catastrophic nature of the failure exhibited by reinforced concrete slabs when subjected to concentrated loads has been a major concern for engineers over many years. Therefore, there is a great need to develop accurate numerical models suitable for normal-strength or high-strength concrete in order to reflect properly its structural behaviour.Proper simulation of the post-cracking behaviour of concrete has a significant effect on the nonlinear finite element response of such slabs. Cracking and post-cracking behaviour of concrete which includes aggregate interlock, dowel action, and tension-stiffening effects is especially crucial for any nonlinear concrete analysis. The post-cracking behaviour and the fracture energy properties of high-strength concrete are different from those of normal-strength concrete. This can be realized by comparing the experimental testing results of plain normal- and high-strength concrete. The experimental results of testing plain high-strength concrete in direct tension indicated that the total area under the stress - crack width curve in tension is different from that of normal-strength concrete.A suitable softening and tension-stiffening model is recommended for high-strength concrete; other existing models suitable for normal-strength concrete are discussed. The proposed post-cracking behaviour models are implemented in a nonlinear finite element program in order to check the validity of such models by comparing the actual experimental data with the finite element results. Finally, a parametric study was conducted to provide more insight into the behaviour of high-strength concrete slabs subjected to combined uniaxial in-plane loads and lateral loads. The effects of the magnitude of in-plane load and the sequence of loading on the structural behaviour of such slabs are examined. Key words: high-strength concrete, slabs, punching shear, fracture energy, tension-softening, tension-stiffening, parametric study.

Residual Strength of Super High Strength Concrete Used Stone-Chip after Exposure to High Temperatures

2011 ◽  
Vol 374-377 ◽  
pp. 2456-2460
Author(s):  
Guo Can Chen ◽  
Zhi Sheng Xu ◽  
Wei Hong Tang
Keyword(s):  
High Temperatures ◽  
High Strength Concrete ◽  
Elevated Temperatures ◽  
Experimental Studies ◽  
High Strength ◽  
Normal Strength Concrete ◽  
Strength Concrete ◽  
Fine Aggregates ◽  
Normal Strength ◽  
Peak Value

This paper presents the results of experimental studies on the residual compressive strength of concrete produced with stone-chip as fine aggregates with the compressive strengths of unheated specimen ranging from 45.8 to 129.5MPa after exposure to high temperatures and the experimental parameters being the temperature, admixtures, and PP fiber. Specimens were heated in an electric furnace for 4h to high temperatures ranging from 150 to 960°C. Experimental results showed that the compressive strengths of super high strength concrete used stone-chip (abbreviated to SHSCUS) and normal strength concrete used stone-chip (abbreviated to NSCUS) after exposure to elevated temperatures changed in the manners different from that of normal strength concrete, which reached their peak at about 400°C, and the presence of pp fibers in SHSCUS concrete could reduce the risk of spalling at the high temperatures and the peak value after fire.

Seismic behavior of normal-strength concrete-filled precast high-strength concrete centrifugal tube columns

2019 ◽  
Vol 23 (4) ◽  
pp. 614-629
Author(s):  
Shaohua Zhang ◽  
Xizhi Zhang ◽  
Shengbo Xu ◽  
Xingqian Li
Keyword(s):  
Axial Compression ◽  
High Strength Concrete ◽  
Seismic Behavior ◽  
Failure Modes ◽  
Concrete Strength ◽  
High Strength ◽  
Test Results ◽  
Normal Strength Concrete ◽  
Strength Concrete ◽  
Normal Strength

This study reports the cyclic loading test results of normal-strength concrete-filled precast high-strength concrete centrifugal tube columns. Seven half-scale column specimens were tested under cyclic loads and axial compression loads to investigate their seismic behavior. The major parameters considered in the test included axial compression ratio, filled concrete strength, and volumetric stirrup ratio. The structural behavior of each specimen was investigated in terms of failure modes, hysteresis behavior, bearing capacity, dissipated energy, ductility, stiffness degradation, drift capacity, and strain profiles. Test results revealed that the concrete-filled precast high-strength concrete centrifugal tube column exhibited good integral behavior, and the failure modes of all columns were ductile flexural failures. Lower axial compression ratio and higher volumetric stirrup ratio resulted in more satisfactory ductile performance. In contrast, the filled concrete strength has a limited influence on the structural behavior of concrete-filled precast high-strength concrete centrifugal tube columns. Based on the limit analysis method, the calculation formula for the bending capacity of the concrete-filled precast high-strength concrete centrifugal tube column was developed, and the results predicted from the formulas were in good agreement with the experiment results.

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