Fire Endurance of High-Strength Concrete Slabs

10.14359/2306 ◽  
1988 ◽  
Vol 85 (2) ◽  
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Concrete Slabs ◽  
Strength Concrete ◽  
Fire Endurance

Sensitivity of shear strength to fracture energy of high-strength concrete slabs

1998 ◽  
Vol 25 (1) ◽  
pp. 40-50 ◽  
Author(s):  
H Marzouk ◽  
M Emam ◽  
M S Hilal
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
High Strength Concrete ◽  
Shear Failure ◽  
High Strength ◽  
Tensile Fracture ◽  
Concrete Slabs ◽  
Square Root ◽  
Fracture Properties ◽  
Strength Concrete

The test results of an earlier experimental investigation conducted at Memorial University of Newfoundland on high-strength concrete slabs indicated that as the concrete slab strength increased from 35 to 75 MPa the shear strength increased by 7-20%, depending on the case of loading, i.e., concentric or eccentric loads. The increasing ratio of shear strength is less than half that prescribed in the Canadian code CSA-A23.3 (1994) or the ACI-318 code (1995). Hence, the significant difference between the experimental results and the predicted strength by existing North American codes tacitly means that the proportionality between the shear strength and the square root of the compressive strength is not accurate enough to predict the shear strength of high-strength concrete slabs. In the present investigation, a fracture mechanics model suitable for concrete was proposed. It was also suggested that this model might be an advantageous aid in the analysis of the shear failure of reinforced concrete slabs. In this research investigation the fracture mechanics approach utilizing finite element aided computer analysis of several reinforced slabs is briefly described, and calculated shear failure loads are given. The recommended model proves that it is necessary to consider not only the tensile strength of concrete, instead of the square root of the compressive strength, but also the tensile fracture properties of high-strength concrete. The tensile fracture properties of concrete are characterized by the parameter called characteristic length and the brittleness of concrete. The brittleness ratio of concrete slabs must be considered in any rational shear design expression to reflect the size effect factor and the aggregate type.Key words: fracture energy, uniaxial direct tension, shear strength, high-strength concrete, punching shear, slab, size effect, finite element analysis.

Fire Behavior of Thin CFRP Pretensioned High-Strength Concrete Slabs

2012 ◽  
Vol 16 (4) ◽  
pp. 381-394 ◽  
Author(s):  
Giovanni Pietro Terrasi ◽  
Luke Bisby ◽  
Michel Barbezat ◽  
Christian Affolter ◽  
Erich Hugi
Keyword(s):  
High Strength Concrete ◽  
Fire Behavior ◽  
High Strength ◽  
Concrete Slabs ◽  
Strength Concrete

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.

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