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.

Long-Term Deformations of Strengthened Reinforced Concrete Linear Elements

2016 ◽  
Vol 691 ◽  
pp. 51-60 ◽  
Author(s):  
Martin Krizma ◽  
Lubomir Bolha
Keyword(s):  
Reinforced Concrete ◽  
Long Term Results ◽  
Short Term ◽  
Limit States ◽  
Linear Elements ◽  
Repeated Load ◽  
The Moment ◽  
Concrete Elements ◽  
Fiber Fabric

The issue of strengthening the damaged linear reinforced concrete elements have been engaged since 2008. We focused on the analysis of resistance and the characteristics of limit states of serviceability in the damaged and subsequently strengthened elements at a short-term loading. In the introduction phase, the strengthening of the elements was carried out with the following procedures – installation of an overlayer on the coupling board or a combination of the board and use of glass – fiber fabric (GFRP). The strengthening was also affected by the type of contact (reinforced/non-reinforced) – the deformed element/coupling board and its effect on resistance, type of deformation and serviceability. In the non-reinforced contact, we applied some of the types of adjustments to the surface of the strengthened element. At the moment, we are dealing with the effects of time and repeated load on the strengthened elements. The results correspond to the reinforced contact. The values are compared with the short-term results of the strengthened beams and with the long-term results of the beams prepared for strengthening.

scholarly journals Moment-Curvature Behaviors of Concrete Beams Singly Reinforced by Steel-FRP Composite Bars

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Zeyang Sun ◽  
Yang Yang ◽  
Wenlong Yan ◽  
Gang Wu ◽  
Xiaoyuan He
Keyword(s):  
Bearing Capacity ◽  
Concrete Beams ◽  
Reinforcement Ratio ◽  
Frp Composite ◽  
Steel Bar ◽  
Before And After ◽  
Frp Bar ◽  
Deformation Ability ◽  
Effective Depth ◽  
The Moment

A steel-fiber-reinforced polymer (FRP) composite bar (SFCB) is a kind of rebar with inner steel bar wrapped by FRP, which can achieve a better anticorrosion performance than that of ordinary steel bar. The high ultimate strength of FRP can also provide a significant increase in load bearing capacity. Based on the adequate simulation of the load-displacement behaviors of concrete beams reinforced by SFCBs, a parametric analysis of the moment-curvature behaviors of concrete beams that are singly reinforced by SFCB was conducted. The critical reinforcement ratio for differentiating the beam’s failure mode was presented, and the concept of the maximum possible peak curvature (MPPC) was proposed. After the ultimate curvature reached MPPC, it decreased with an increase in the postyield stiffness ratio (rsf), and the theoretical calculation method about the curvatures before and after the MPPC was derived. The influence of the reinforcement ratio, effective depth, and FRP ultimate strain on the ultimate point was studied by the dimensionless moment and curvature. By calculating the envelope area under the moment-curvature curve, the energy ductility index can obtain a balance between the bearing capacity and the deformation ability. This paper can provide a reference for the design of concrete beams that are reinforced by SFCB or hybrid steel bar/FRP bar.

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 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.

Size effect on shear strength of reinforced concrete beams with tension reinforcement ratio

2016 ◽  
Vol 20 (4) ◽  
pp. 582-594 ◽  
Author(s):  
Chan-Yu Jeong ◽  
Hyeong-Gook Kim ◽  
Sang-Woo Kim ◽  
Kang-Seok Lee ◽  
Kil-Hee Kim
Keyword(s):  
Shear Strength ◽  
Reinforced Concrete ◽  
Size Effect ◽  
Concrete Beams ◽  
Reinforcement Ratio ◽  
Reinforced Concrete Beams ◽  
Shear Tests ◽  
Effective Depth ◽  
Compressive Strength Of Concrete ◽  
Experimental Researches

It is well known that shear stress at peak of reinforced concrete beams decreases with increasing effective depth. Thus, several existing design codes and models have included various forms of formulas considering the size effect on shear strength of reinforced concrete beams; however, past experimental researches show that tension reinforcement ratio is also associated with the shear strength of reinforced concrete beams. To examine the effect of tension reinforcement ratio and effective depth on shear strength of reinforced concrete beams, this study has conducted experiments in which the effective depth (150, 300, 500, and 780 mm) and tension reinforcement ratio (1%, 2%, and 3%) are employed as variables. Besides, a formula for the shear strength considering both variables is proposed based on data samples collected from the present experiment and previous research. The proposed formula gives predictions comparable to the results of existing shear tests. Furthermore, rational predictions are made for effective depth of beams, compressive strength of concrete, shear span-to-depth ratio, and even tension reinforcement ratio exceeding 3%.

scholarly journals Cracking in Concrete near Joints in Steelconcrete Composite Slab / Zarysowanie Płyty Żelbetowej W Strefie Przywęzłowej Stropu Zespolonego

2015 ◽  
Vol 16 (1) ◽  
pp. 167-179
Author(s):  
Marcin Niedośpiał ◽  
Michał Knauff ◽  
Wioleta Barcewicz
Keyword(s):  
Reinforced Concrete ◽  
Experimental Tests ◽  
Crack Pattern ◽  
Full Scale ◽  
Steel Beam ◽  
Tension Stiffening ◽  
Factors Influencing ◽  
Eurocode 2 ◽  
Concrete Elements ◽  
Crack Widths

Abstract In this paper results of the experimental tests of four full-scale composite steel-concrete elements are reported. In the steel-concrete composite elements, a steel beam was connected with a slab cast on profiled sheeting, by shear studs. The end-plates were (the thickness of 8 mm, 10 mm and 12 mm) thinner than in ordinary design. Joints between the column and the beams have been designed as semi-rigid, i.e. the deformations of endplates affect the distribution of forces in the adjacent parts of the slab. The paper presents the theory of cracking in reinforced concrete and steel-concrete composite members (according to the codes), view of crack pattern on the surface of the slabs and a comparison of the tests results and the code calculations. It was observed, that some factors influencing on crack widths are not taken in Eurocode 4 (which is based on Eurocode 2 with taking into account the phenomenon called „tension stiffening”).

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