• Structural Engineering and Mechanics
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• 제65권1호
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• pp.1-7
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• 2018

This paper reviews the mechanical effects produced by reinforcement corrosion of prestressed concrete beams. Specifically, modifications in the bonding of the tendon to the concrete that reduce service life and load bearing capacity are studied. Experimental information gathered from previous works has been used for the theoretical analysis. Relationships between bond stress loss and reinforcement penetration in the concrete, and concrete external cracking were established. Also, it was analysed the influence that has the location of the area affected by corrosion on the loss magnitude of the initial prestress.

• Computers and Concrete
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• 제22권1호
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• pp.117-122
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• 2018

The use of nanotechnology materials and applications in the construction industry should be considered for enhancing material properties. However, in this paper, the technical and economical assessment of applying silica nanoparticles for construction of concrete structure is studied. In order to obtain the equivalent material properties of the structure, the Mori-Tanaka model is used considering agglomeration of nanoparticles. The effect of using these nanoparticles on mechanical properties of concrete, such as the modulus of elasticity, compressive strength, as well as its indirect effect on armature percentage is investigated. Finally, the price of silica nanoparticles and its effect on the price increase of concrete structure is investigated. The results show that increasing the volume percent of silica nanoparticles up to 10% improves elastic modulus 111% and reduces amateur percentage up to 72%.

• Structural Engineering and Mechanics
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• 제47권6호
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• pp.773-790
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• 2013

Bending behaviors of corroded reinforced concrete (RC) beams under repeated loading were investigated experimentally. A total of twenty test specimens, including four non-corrosion and sixteen corrosion reinforced concrete beams, were prepared and tested. A numerical model for flexural and cracking behaviors of the beam under repeated loading was also developed. Effects of steel corrosion on reinforced concrete beams regarding cracking, mid-span deflection, stiffness and bearing capacity of corroded beams were studied. The impact of corrosion on bond strength as the key factor was investigated to develop the computational model of flexural capacity. It was shown from the experimental results that the bond strength between reinforcement and concrete had increased for specimen of low corrosion levels, while this effect was changed when the corrosion level was higher. It was indicated that the bearing capacity of corrosion beam increased even at a corrosion level of about 5%.

• Computers and Concrete
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• 제12권1호
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• pp.19-36
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• 2013

In the finite element analysis of reinforced concrete structures, discrete representation of the steel reinforcing bars is considered advantageous over smeared representation because of the more realistic modelling of their bond-slip behaviour. However, there is up to now limited research on how to simulate the dowel action of discrete reinforcing bars, which is an important component of shear transfer in cracked concrete structures. Herein, a numerical model for the dowel action of discrete reinforcing bars is developed. It features derivation of the dowel stiffness based on the beam-on-elastic-foundation theory and direct assemblage of the dowel stiffness matrix into the stiffness matrices of adjoining concrete elements. The dowel action model is incorporated in a nonlinear finite element program based on secant stiffness formulation and application to deep beams tested by others demonstrates that the incorporation of dowel action can improve the accuracy of the finite element analysis.

• Computers and Concrete
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• 제5권3호
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• pp.195-216
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• 2008

This paper presents a new hypoelasticity model which was implemented in a nonlinear finite element formulation to analyze reinforced concrete (RC) structures. The model includes a new hypoelasticity constitutive relationship utilizing the rotation of material axis through successive iterations. The model can account for high nonlinearity of the stress-strain behavior of the concrete in the pre-peak regime, the softening behavior of the concrete in the post-peak regime and the irrecoverable volume dilatation at high levels of compressive load. This research introduces the modified version of the common application orthotropic stress-strain relation developed by Darwin and Pecknold. It is endeavored not to violate the principal of "simplicity" by improvement of the "capability" The results of analyses of experimental reinforced concrete walls are presented to confirm the abilities of the proposed relationships.

• Advances in concrete construction
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• 제1권4호
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• pp.305-318
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• 2013

Engineering properties such as compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity and Poisson's ratio of geopolymer concrete (GPC) and steel fibre reinforced geopolymer concrete (SFRGPC) have been obtained from standard tests and compared. A total of 15 specimens were tested for determining each property. The grade of concrete used was M 40. The percentages of steel fibres considered include 0.25%, 0.5%, 0.75% and 1%. In general, the addition of fibres improved the mechanical properties of both GPC and SFRGPC. However the increase was found to be nominal in the case of compressive strength (8.51%), significant in the case of splitting tensile strength (61.63%), modulus of rupture (24%), modulus of elasticity (64.92%) and Poisson's ratio (50%) at 1% volume fraction of fibres. An attempt was made to obtain the relation between the various engineering properties with the percentage of fibres added.

• Steel and Composite Structures
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• 제22권5호
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• pp.1141-1162
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• 2016

Concrete-filled double skin steel tube (CFDST) beam-columns are widely used in industrial plants, subways, high-rise buildings and arch bridges. The CFDST columns have the same advantages as traditional CFT members. Moreover, they have lighter weight, higher bending stiffness, better cyclic performance, and have higher fire resistance capacities than their CFT counterparts. The scope of this study is to develop finite element models that can predict accepted capacities of double skin concrete-filled tube columns under the combined effect of axial and bending actions. The analysis results were studied to determine the distribution of stresses among the different components and the effect of the concrete core on the outer and inner steel tube. The developed models are first verified against the available experimental data. Accordingly, an extensive parametric study was performed considering different key factors including load eccentricity, slenderness ratio, concrete compressive strength, and steel tube yield strength. The results of the performed parametric study are intended to supplement the experimental research and examine the accuracy of the available design formulas.

• Computers and Concrete
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• 제20권1호
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• pp.23-29
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• 2017

In this study engineered steel fibres used as reinforcement for concrete were characterized by number of key mechanical and spatial parameters, which are easy to measure and quantify. Such commonly used parameters as length, diameter, fibre intrinsic efficiency ratio (FIER), hook geometry, tensile strength and ductility were considered. Effective classification of various fibres was demonstrated using simple multivariate computations involving principal component analysis (PCA). Contrary to univariate data mining approach, the proposed analysis can be efficiently adapted for fast, robust and direct classification of engineered steel fibres. The results have revealed that in case of particular spatial/geometrical conditions of steel fibres investigated the FIER parameter can be efficiently replaced by a simple aspect ratio. There is also a need of finding new parameters describing properties of steel fibre more precisely.

• Structural Engineering and Mechanics
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• 제63권2호
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• pp.217-223
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• 2017

Glass fiber reinforced gypsum panels (GFRG) are hollow panels made from modified gypsum plaster and reinforced with chopped glass fibers. The hollow cores of panels can be filled with in-situ concrete/reinforced concrete or insulation material to increase the structural strength or the thermal insulation, respectively. GFRG panels are unfilled when used as partition walls. As load bearing walls, the panels are filled with M 20 grade concrete (reinforced concrete filling) in order to resist the gravity and lateral loads. The study was conducted in two stages: First stage involves formulation of the alternate light weight mix by conducting experimental investigations to obtain the optimum combination of phosphogypsum and shredded thermocol. In the second stage the alternate mixes are filled in GFRG panels and experimental investigations are conducted to compare the performance against panels filled with conventional M 20 mix.

• Computers and Concrete
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• 제20권1호
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• pp.1-10
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• 2017

This paper focuses on the mesh-size dependency in numerical simulations of reinforced concrete (RC) structures subjected to blast loading. A tensile failure criterion that can minimize the mesh-dependency of simulation results is introduced based on the fracture energy theory. In addition, conventional plasticity based damage models for concrete such as the CSC model and the HJC model, which are widely used for blast analyses of concrete structures, are compared with the orthotropic model that adopts the introduced tensile failure criterion in blast tests to verify the proposed criterion. The numerical predictions of the time-displacement relations at the mid-span of RC beams subjected to blast loading are compared with experimental results. The analytical results show that the numerical error according to the change in the finite element mesh size is substantially reduced and the accuracy of the numerical results is improved by applying a unique failure strain value determined by the proposed criterion.