scholarly journals MODELLING DEFORMATION BEHAVIOUR OF RC BEAMS ATTRIBUTING TENSION-STIFFENING TO TENSILE REINFORCEMENT

2009 ◽  
Vol 1 (3) ◽  
pp. 141-147 ◽  
Author(s):  
Donatas Salys ◽  
Gintaris Kaklauskas ◽  
Viktor Gribniak
Keyword(s):  
Deformation Behaviour ◽  
Tensile Force ◽  
Material Model ◽  
Rc Beams ◽  
Tension Stiffening ◽  
Load Carrying ◽  
Reinforced Steel ◽  
Internal Forces ◽  
The Moment ◽  
Stiffening Effect

After cracking, the stiffness of the member along its length varies, which makes the calculation of deformations complicated. In a cracked member, stiffness is largest in the section within the uncracked region while remains smallest in the cracked section. This is because in the cracked section, tensile concrete does not contribute to the load carrying mechanism. However, at intermediate sections between adjacent cracks, concrete around reinforcement retains some tensile force due to the bond-action that effectively stiffens member response and reduces deflections. This effect is known as tension-stiffening. This paper discusses the tension-stiffening effect in reinforced concrete (RC) beams. Numerical modelling uses the approach based on tension-stiffening attributed to tensile reinforcement. A material model of reinforced steel has been developed by inverse analysis using the moment-curvature diagrams of RC beams. Total stresses in tensile reinforcement consist of actual stresses corresponding to the average strain of the steel and additional stresses due to tension-stiffening. The carried out analysis employed experimental data on RC beams tested by the authors. The beams had a constant cross section but a different amount of tensile reinforcement. It has been shown that additional (tension-stiffening) stresses in the steel depend on the area of reinforcement. However, the resulting internal forces are less dependent on the amount of reinforcement.

Tension Stiffening Analysis for Cyclically Loaded RC Beams

2014 ◽  
Vol 567 ◽  
pp. 517-521
Author(s):  
Ahmad Azim Bin Shukri ◽  
Mohd Zamin Jumaat
Keyword(s):  
Rc Beams ◽  
Interaction Theory ◽  
Tension Stiffening ◽  
Rc Structures ◽  
Friction Theory ◽  
Rc Structure ◽  
Partial Interaction ◽  
Interface Displacement ◽  
Displacement Based ◽  
The Moment

Ductility is an important aspect of cyclically loaded reinforced concrete (RC) structures. One of the method that can be used to measure the ductility of an RC structure is the moment-curvature approach. However, due to it being a strain-based approach it cannot be used to directly simulate behaviour associated with interface displacement that occur when an RC member is cracked. This leads to dependency on empirical values, which imposes limitations on how the moment-curvature approach can be used. In recent years a new displacement based method for measuring ductility has been developed, and can simulate the interface displacement behaviours through the use of partial-interaction theory and shear friction theory. This paper aims to extend the general tension stiffening analysis of the displacement-based approach to allow for cyclic loading. The tension-stiffening analysis was then validated against experimental results and the results were found to agree fairly.

Susceptibility of strain-hardening cementitious composite to curing conditions as a retrofitting material for RC beams

2021 ◽  
Vol 16 ◽  
pp. 155892502110203
Author(s):  
Mohammad Iqbal Khan ◽  
Galal Fares ◽  
Yassir Mohammed Abbas ◽  
Wasim Abbass ◽  
Sardar Umer Sial
Keyword(s):  
Strain Hardening ◽  
Environmental Conditions ◽  
Carrying Capacity ◽  
Flexural Behavior ◽  
Load Carrying Capacity ◽  
Rc Beams ◽  
Curing Conditions ◽  
Flexural Members ◽  
Load Carrying ◽  
Curing Regime

Strain-hardening cement-based composites (SHCC) have recently been developed as repair materials for the improvement of crack control and strength of flexural members. This work focuses on strengthening and flexural enhancement using SHCC layer in tensile regions of flexural members under three different curing conditions. The curing conditions simulate the effect of different environmental conditions prevailing in the central and coastal regions of the Arabian Peninsula on the properties of SHCC as a retrofitting material. In this investigation, beams with SHCC layer were compared to control beams. The beams with SHCC layer of 50-mm thickness were cast. The results revealed that the flexural behavior and the load-carrying capacity of the normal concrete beam specimens under hot and dry environmental conditions were significantly reduced, lowering the ductility of the section. However, compressive strength is comparatively unaffected. Similarly, the hot curing conditions have also led to a notable reduction in the loading capacity of the beam with SHCC layer with a slight effect on its stiffness. On the other hand, steam-curing conditions have shown improvement in load-carrying capacity and a reduction in section ductility of the beam with SHCC layer. It was found that the structural unit retrofitted with SHCC layer was a curing-regime dependent as the tensile and strain-hardening properties of SHCC are highly sensitive to the alteration in the cement hydration process. A normal curing regime was found effective and satisfying the practical, cost, and performance requirements. Accordingly, a normal curing regime could be implemented to retrofit reinforced concrete (RC) beams with SHCC layers as recommended in the study.

Anchorages of stirrups under transverse tension in concrete - development of a design model

2019 ◽  
Author(s):  
Mirhat Medziti ◽  
Daia Zwicky
Keyword(s):  
Crack Width ◽  
Concrete Beams ◽  
Tensile Force ◽  
Concrete Structures ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Design Model ◽  
Hook Effect ◽  
Internal Forces ◽  
Negative Bending

<p>According to Swiss code SIA 262 "Concrete structures", stirrups of reinforced concrete beams must "surround the tensile longitudinal reinforcement" and must "be anchored to mobilize the static height of internal forces". For existing concrete structures, Swiss code SIA 269/2 provides stirrup detailing requirements while limiting these directives for stirrup anchorage to the compression zone. In zones of negative bending, these requirements are often not satisfied for execution reasons. This question is addressed in a largely experimental Ra&amp;D project. Anchorage tests were performed and analyzed, with a total of 144 tests on 9 concrete beams. These underwent a longitudinal tensile force up to 1’000 kN to simulate transverse cracking at stirrup anchorages in negative flexure zones. The study parameters are crack width (0, 0.4 and 0.9 mm), stirrup diameter (10 and 14 mm), bar ribbing (smooth and ribbed) and hook angle (90°, 135°, 180° and straight bars). A design model based on the "tension chord model" (TCM) developed at ETH Zurich is proposed. This simple and practical design model has proved ist effectiveness to consider bond effects. Reduction factors for bar diameter (k<sub>Ø</sub>), relative bar ribbing (k<sub>fR</sub>), hook effect (k<sub>θ</sub>) and crack width (k<sub>w</sub>) were taken into account for calibration. Results of analytical calculations are coherent with experimental tests.</p>

Bending Behavior of Simply-Supported Sandwich Beams Subjected to Large Deflection

2018 ◽  
Vol 777 ◽  
pp. 569-574
Author(s):  
Zhong You Xie
Keyword(s):  
Energy Absorption ◽  
Large Deflection ◽  
Absorption Efficiency ◽  
Sandwich Beams ◽  
Element Simulation ◽  
Energy Absorption Efficiency ◽  
Load Carrying ◽  
Absorption Performance ◽  
Bending Behavior ◽  
The Moment

Due to thin skins and soft core, it is apt to local indentation inducing the concurrence of geometrical and material nonlinearity in sandwich structures. In the paper, finite element simulation is used to investigate the bending behavior of lightweight sandwich beams under large deflection. A modified formulation for the moment at mid-span section of sandwich beams under large deflection is presented, and energy absorption performance is assessed based on energy absorption efficiency. In addition, it is found that no local indentation arises initially, while later that increases gradually with loading displacement increasing. The height of the mid-span section as well as load-carrying capacity decreases significantly with local indentation depth increasing.

scholarly journals DETERMINATION OF DEFORMABILITY PARAMETERS OF CONCRETE SAMPLES BY THE FORMULAS OF FRACTURE MECHANICS

2020 ◽  
Vol 11 (2) ◽  
pp. 88-98
Author(s):  
B. A Bondarev ◽  
N. N Chernousov ◽  
V. A Sturova
Keyword(s):  
Fracture Mechanics ◽  
Lower Surface ◽  
Local Deformation ◽  
Concrete Sample ◽  
Test Scheme ◽  
Limit Value ◽  
Bending Load ◽  
Internal Forces ◽  
The Moment ◽  
External Forces

To determine the deformability parameters of concrete samples by the formulas of fracture mechanics, equilibrium tests were carried out at the stage of local deformation of the sample, which showed the correspondence of the change in external forces to the internal forces of the material resistance with the corresponding static development of the main crack. For the same purpose, the samples are tested for bending with an initial notch and the “load-deflection” diagram is recorded. In this work, we presented a test scheme for a specimen with a notch (crack) and constructed a diagram of the deformation of a specimen under bending “load-deflection”. Based on it, it is possible to predict the destruction of the material, that is, to determine the value of the load at which the limit value of deflection or the displacement of the outer edges of the notch (opening the throat of the crack on the lower surface of the specimen) can be taken as the moment of loss of the resource of the material. Also, we examined the deformation of a concrete sample during three-point bending and presented a diagram of the deformation of a concrete sample within the plastic zone. Dependencies were derived for determining the ultimate relative strains under tension and bending. Based on the results obtained, the state diagrams of the stretched concrete and the deformation scheme of the normal section of the concrete sample were constructed. As a result, the conclusion and convergence of the results.

scholarly journals Experimental and Numerical Study on Ultimate Shear Load Carrying Capacity of Corroded RC Beams

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhanzhan Tang ◽  
Zhixiang He ◽  
Zheng Chen ◽  
Lingkun Chen ◽  
Hanyang Xue ◽  
...  
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Cross Section ◽  
Loss Rate ◽  
Numerical Study ◽  
Rc Beams ◽  
Load Carrying ◽  
Shear Bearing Capacity ◽  
The Cross ◽  
The Impact

For an RC beam, the strength of steel rebar, the bonding strength between the concrete and reinforcement, and the bite action between the aggregates will deteriorate significantly due to corrosion. In the present study, 10 RC beams were designed to study the impact of corrosion on the shear bearing capacity. The mechanism of corrosion for stirrups and longitudinal bars and their effects were analyzed. Based on the existing experimental data, the correlation between the stirrup corrosion factor and the cross section loss rate was obtained. An effective prediction formula on the shear bearing capacity of the corroded RC beams was proposed and validated by the experimental results. Moreover, a numerical analysis approach based on the FE technique was proposed for the prediction of the shear strength. The results show that corrosion of the reinforcements could reduce the shear strength of the RC beams. The corrosion of stirrups can be numerically simulated by the reduction of the cross section. The formulae in the literature are conservative and the predictions are very dispersed, while the predictions by the proposed formula agree very well with the experiment results.

scholarly journals Flexural strengthening of Reinforced Concrete (RC) Beams Retrofitted with Corrugated Glass Fiber Reinforced Polymer (GFRP) Laminates

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
N. Aravind ◽  
Amiya K. Samanta ◽  
Dilip Kr. Singha Roy ◽  
Joseph V. Thanikal
Keyword(s):  
Reinforced Concrete ◽  
Carrying Capacity ◽  
Fiber Reinforced Polymer ◽  
Load Carrying Capacity ◽  
Rc Beams ◽  
Glass Fiber Reinforced Polymer ◽  
Flexural Strengthening ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Load Carrying

AbstractStrengthening the structural members of old buildings using advanced materials is a contemporary research in the field of repairs and rehabilitation. Many researchers used plain Glass Fiber Reinforced Polymer (GFRP) sheets for strengthening Reinforced Concrete (RC) beams. In this research work, rectangular corrugated GFRP laminates were used for strengthening RC beams to achieve higher flexural strength and load carrying capacity. Type and dimensions of corrugated profile were selected based on preliminary study using ANSYS software. A total of twenty one beams were tested to study the load carrying capacity of control specimens and beams strengthened with plain sheets and corrugated laminates using epoxy resin. This paper presents the experimental and theoretical study on flexural strengthening of Reinforced Concrete (RC) beams using corrugated GFRP laminates and the results are compared. Mathematical models were developed based on the experimental data and then the models were validated.

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