scholarly journals THE ANALYSIS OF THE DISCRETE CRACKING MODEL OF REINFORCED CONCRETE TENSILE MEMBERS

2010 ◽  
Vol 2 (4) ◽  
pp. 146-156
Author(s):  
Donatas Salys ◽  
Gintaris Kaklauskas ◽  
Edgaras Timinskas ◽  
Viktor Gribniak ◽  
Darius Ulbinas ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Stress Transfer ◽  
Bond Stress ◽  
Experimental Program ◽  
Deformation Analysis ◽  
Tension Stiffening ◽  
Bond Slip ◽  
Secondary Cracks ◽  
Wide Range ◽  
Deformation Properties

Adequate modelling of reinforced concrete (RC) cracking, particularly post-cracking behaviour (tension stiffening), as one of the major sources of nonlinearity, is the most important and difficult task for deformation analysis. Deformationbehaviour of the cracked RC members is a complex process, including a wide range of effects such as differentstrength and deformation properties of steel and concrete, concrete cracking, tension-softening and tension-stiffening,bond slip between reinforcement and concrete etc. Even under low load, behaviour can be non-linear, which presents a challenge for calculating the deformations of RC members.When stress in concrete first reaches tensile strength at the weakest section,cracking occurs. After the formation of the first primary crack up to the final one, concrete contribution steadily decreases. At the final cracking point, the stable crack pattern has been reached. Increase in load will result in a further decrease of concrete contribution due to bond-slip causing cover-controlled cracks to develop between the primary cracks and a gradual breaking down of the bond. This process can be imagined as the formation of internal secondary cracks along the deformed bar due to bond stress transfer to sound concrete in between primary cracks. Total stresses in the cracked tensile reinforcement consisted of genuine stresses corresponding to the average strain of steel and additional stresses due to tension-stiffening. The internal forces that represent the latter stresses are called the residual and can be used for assessing the average bond behavior of RC members. This paper investigates tension-stiffening effect in RC members. The discrete cracking model of RC member is described in the paper. The discussed approach is based on bond-slip relationship that models the bond-action between concrete and reinforcement. This approach is realistically capable of modelling cracking and determining crack widths and deformations. However, the accuracy of calculation results depends on the assumed bond stress-slip relationship. A number of recent investigations aimed at developing and modifying such models were performed intending that discrete cracking modelling technique could become a powerful tool for the analysis of reinforced concrete members. The present study is dedicated to deformation analysis of reinforced members that are subjected to pure tension and is based on the results of the experimental program reported in literature. The average deformations of such members were calculated applying the discrete cracking method using different bond stress-slip relationships and compared with test results reported in literature. It was concluded that relationship recommended by CEB-FIP MC90 was unacceptable for the analysis performed.

scholarly journals Deformation of rockfill in bodies of rockfill dams

2019 ◽  
pp. 5-5
Author(s):  
Mikhail Sainov
Keyword(s):  
Reinforced Concrete ◽  
Deformation Modulus ◽  
Deformation Model ◽  
Observation Data ◽  
Linear Deformation ◽  
Laboratory Test Results ◽  
Wide Range ◽  
Deformation Properties ◽  
Non Linear ◽  
The Impact

Introduction. The main factor determining the stress-strain state (SSS) of rockfill dam with reinforced concrete faces is deformability of the dam body material, mostly rockfill. However, the deformation properties of rockfill have not been sufficiently studied yet for the time being due to technical complexity of the matter, Materials and methods. To determine the deformation parameters of rockfill, scientific and technical information on the results of rockfill laboratory tests in stabilometers were collected and analyzed, as well as field data on deformations in the existing rockfill dams. After that, the values of rockfill linear deformation modulus obtained in the laboratory and in the field were compared. The laboratory test results were processed and analyzed to determine the parameters of the non-linear rockfill deformation model. Results. Analyses of the field observation data demonstrates that the deformation of the rockfill in the existing dams varies in a wide range: its linear deformation modulus may vary from 30 to 500 МPа. It was found out that the results of the most rockfill tests conducted in the laboratory, as a rule, approximately correspond to the lower limit of the rockfill deformation modulus variation range in the bodies of the existing dams. This can be explained by the discrepancy in density and particle sizes of model and natural soils. Only recently, results of rockfill experimental tests were obtained which were comparable with the results of the field measurements. They demonstrate that depending on the stress state the rockfill linear deformation modulus may reach 700 МPа. The processing of the results of those experiments made it possible to determine the parameters on the non-linear model describing the deformation of rockfill in the dam body. Conclusions. The obtained data allows for enhancement of the validity of rockfill dams SSS analyses, as well as for studying of the impact of the non-linear character of the rockfill deformation on the SSS of reinforced concrete faces of rockfill dams.

Numerical Interpretation of Bond Between Steel and Concrete in Presence of Corrosion and Cyclic Action

2009 ◽  
Vol 417-418 ◽  
pp. 349-352 ◽  
Author(s):  
Luca Giordano ◽  
Giuseppe Mancini ◽  
Francesco Tondolo
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Stress Transfer ◽  
Experimental Tests ◽  
Radial Pressure ◽  
Mechanical Action ◽  
Concrete Cover ◽  
Reinforcing Bars ◽  
Cyclic Action ◽  
Bond Slip

Bond between steel and concrete in reinforced concrete structures plays a fundamental role. The stress transfer mechanism depends on the condition of the contact surface between the two materials, the mechanical characteristics of concrete near the rebar and on the available level of confinement. Corrosion of reinforcing bars in concrete structures modifies those three factors. Because of corrosion, on the rebar surface a granular oxide layer is present and with its expansion it generates a significant radial pressure; consequently tensile stresses grow till cracking of the concrete cover with a subsequent reduction of the confinement effect. Moreover the presence of a mechanical action modifies the resisting mechanism producing an increasing damage. In this study, a model is presented for the numerical simulation of experimental tests on r.c. ties subjected to mechanical action; furthermore some considerations on reinforced concrete ties subjected also to corrosion effect are reported. From those analyses it is possible to estimate a modified bond-slip law between the reinforcing bars and the concrete, in order to take into account the level of damage.

scholarly journals On the Numerical Modelling of Bond for the Failure Analysis of Reinforced Concrete

2017 ◽  
Author(s):  
Peter Grassl ◽  
Morgan Johansson ◽  
Joosef Leppänen
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Impact Test ◽  
Nonlinear Finite Element ◽  
Structural Performance ◽  
Finite Element Analyses ◽  
Tension Stiffening ◽  
Bond Slip ◽  
Element Size ◽  
Weight Impact

The structural performance of reinforced concrete relies heavily on the bond between reinforcement and concrete. In nonlinear finite element analyses, bond is either modelled by merged, also called perfect bond, or coincident with slip, also called bond-slip, approaches. Here, the performance of these two approaches for the modelling of failure of reinforced concrete was investigated using a damage-plasticity constitutive model in LS-DYNA. Firstly, the influence of element size on the response of tension-stiffening analyses with the two modelling approaches was investigated. Then, the results of the two approaches were compared for plain and fibre reinforced tension stiffening and a drop weight impact test. It was shown that only the coincident with slip approach provided mesh insensitive results. However, both approaches were capable of reproducing the overall response of the experiments in the form of load and displacements satisfactorily for the meshes used.

scholarly journals Increasing the Performance of a Fiber-Reinforced Concrete for Protective Facilities

Fibers ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 64
Author(s):  
Roman Fediuk ◽  
Mugahed Amran ◽  
Sergey Klyuev ◽  
Aleksandr Klyuev
Keyword(s):  
Reinforced Concrete ◽  
Impact Strength ◽  
Impact Energy ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Secondary Cracks ◽  
Wide Range ◽  
Long Time ◽  
The Impact ◽  
Hardening Coefficient

The use of fiber in cement materials is a promising and effective replacement for bar reinforcement. A wide range of fiber-reinforced concretes based on composite binders with increased impact strength characteristics have been developed. The synthesized composites included the composite binder made of Portland cement, silica, and carbonate additives. Basalt and steel were used as fibers. The nature of the influence of the composition and manufacturing technology of cement composites on the dynamic hardening coefficient has been established, while the growth of these indicators is achieved by creating a denser interfacial transition zone between the cement paste, aggregate, and fiber as a result of improving the homogeneity of the concrete mixture and controlling the consistency. Workability indicators (slump flow up to 730 mm; spreading time up to a diameter of 50 cm is up to 3 s) allow them to be classified as self-compacting concrete mixtures. An increase in the values of the impact strength coefficient by a factor of 5.5, the dynamic hardening coefficient by almost 70% as a result of interfacial interaction between fibers and binder matrix in the concrete composite, as well as absorption of impact energy by fiber, was revealed. The formula describing the effect of the loading rate on the coefficient of dynamic hardening of fiber-reinforced concrete has been refined. The fracture processes of the obtained materials have been established: after the initiation of primary cracks, the structure of the composite absorbs impact energy for a long time, while in the inelastic range (the onset of cracking and peak loads), a large number of secondary cracks appear.

scholarly journals A SHORT-TERM DEFORMATION ANALYSIS METHOD OF FLEXURAL REINFORCED CONCRETE MEMBERS

2011 ◽  
Vol 3 (3) ◽  
pp. 112-122
Author(s):  
Rokas Girdžius ◽  
Gintaris Kaklauskas ◽  
Renata Zamblauskaitė ◽  
Ronaldas Jakubovskis
Keyword(s):  
Reinforced Concrete ◽  
Reinforcement Ratio ◽  
Deformation Analysis ◽  
Analysis Method ◽  
Modulus Ratio ◽  
Short Term ◽  
Tension Stiffening ◽  
Eurocode 2 ◽  
Effective Depth ◽  
The Moment

The deformation analysis of cracked reinforced concrete (RC) members is not straightforward and often controversial. The main difficulties arise from the complex structure of concrete matrix, different mechanical properties of concrete and reinforcement, the creep and shrinkage of concrete and tension stiffening. The latter effect is related to intact concrete and reinforcement interaction between cracks. Tension stiffening effect has a significant influence on the results of a shortterm deformation analysis of RC members. The present research is aimed at deriving tension-stiffening relationship in accordance with the provisions of the Eurocode 2 technique. Using the inverse technique proposed by the second author, tension-stiffening constitutive laws were derived from the moment-curvature diagrams of RC beams calculated by Eurocode 2. The diagrams were calculated for a number of RC sections having a different amount of tensile reinforcement, the grade of concrete, effective depth and a modulus of steel elasticity. For the above model parameters, 450 moment-curvature diagrams were generated. For each of them, tension-stiffening relationships were obtained. The performed regression analysis led to analytical tension – stiffening relationship, which takes into account the reinforcement ratio, modulus ratio and concrete grade. A simplified short-term deformation analysis method of flexural RC members has been also proposed. This method is based on a bi-linear moment-curvature diagram: elastic and cracked parts. For the cracked part of the moment-curvature diagram, coefficient γ was introduced, which deals with the degradation of stiffness after cracking. An analytical expression was proposed for calculating coefficient γ, which takes into account the effective depth of the beam, reinforcement ratio and modulus ratio. A statistical verification of the proposed models has shown that a good agreement between calculated and experimental results was obtained at service loadings.

scholarly journals On the Numerical Modelling of Bond for the Failure Analysis of Reinforced Concrete

2017 ◽  
Author(s):  
Peter Grassl ◽  
Morgan Johansson ◽  
Joosef Leppänen
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Impact Test ◽  
Nonlinear Finite Element ◽  
Structural Performance ◽  
Finite Element Analyses ◽  
Tension Stiffening ◽  
Bond Slip ◽  
Element Size ◽  
Weight Impact

The structural performance of reinforced concrete relies heavily on the bond between reinforcement and concrete. In nonlinear finite element analyses, bond is either modelled by merged, also called perfect bond, or coincident with slip, also called bond-slip, approaches. Here, the performance of these two approaches for the modelling of failure of reinforced concrete was investigated using a damage-plasticity constitutive model in LS-DYNA. Firstly, the influence of element size on the response of tension-stiffening analyses with the two modelling approaches was investigated. Then, the results of the two approaches were compared for plain and fibre reinforced tension stiffening and a drop weight impact test. It was shown that only the coincident with slip approach provided mesh insensitive results. However, both approaches were capable of reproducing the overall response of the experiments in the form of load and displacements satisfactorily for the meshes used.

scholarly journals Numerical Deformation Analysis of Bridge Concrete Girders

2008 ◽  
Vol 3 (2) ◽  
pp. 51-56 ◽  
Author(s):  
Gintaris Kaklauskas ◽  
Rokas Girdzius ◽  
Darius Bacinskas ◽  
Aleksandr Sokolov
Keyword(s):  
Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Deformation Analysis ◽  
Tension Stiffening ◽  
Rc Structures ◽  
Reinforced Concrete Bridge ◽  
Finite Element Software ◽  
Concrete Girders ◽  
Bridge Girder ◽  
Good Agreement

Present research was aiming at deriving tension stiffening relationship based on EC2 provisions for deformation analysis of bending RC structures. According to the algorithm proposed by the first author, a tension stiffening relationships were derived from moment-curvature diagrams of reinforced concrete beams calculated according to EC2 technique. The obtained tension stiffening relationship was applied in the parametric study, using non-linear finite element software ATENA and layered model. Theoretical results were compared with experimental data of beams reported in the literature. The defined tension stiffening relationship was also applied for calculation of moment-curvature response of reinforced concrete bridge girder. The analyses have shown that the deformations calculated using the derived tension stiffening relationship and the EC2 technique were in good agreement.

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