Figure 7 - uploaded by Said M. Allam
Content may be subject to copyright.
Source publication
![Figure 6 Tension softening curve suggested by Massicotte et al. [11].](profile/Said-Allam-2/publication/271580448/figure/fig19/AS:669588761100315@1536653809970/Tension-softening-curve-suggested-by-Massicotte-et-al-11_Q320.jpg)
Building codes consider the tension stiffening when calculating the crack width of the flexural members. A simple analytical procedure is proposed for the determination of forces, stresses and strains acting on a reinforced concrete section subjected to flexure considering the concrete contribution in tension up to tensile concrete strain correspon...
Context in source publication
Context 1
... [11] and is shown in Fig. 6. This relationship assumed that the strain softening after cracking reduces the stress to zero at a total strain of about 16 times the strain at first cracking. The curve, shown in Fig. 6, was soft- ened to permit a relatively gradual response behavior and consequently to decrease the convergence problems, as shown in Fig. 7. The input data includes: the concrete ten- sile strength; f ctmax , the strain at first crack; e cr and the strain softening curve. 3. Concrete in compression was modeled as elastic-plastic model. The input data includes: the concrete compressive strength; f cu, modulus of elasticity; E c , Poisson's ratio; t c (t c = 0.2), ...
Similar publications
This paper presents simple method to estimate the strength design of reinforced concrete beam sections based on structural safety and reliability. Irregular beam shaped sections are commonly used nowadays in the construction industry. This study reveals the simplified method to analyze and design the different irregular shaped beam sections. In thi...
The shear punching of the reinforced concrete slabs is a complex process occurring when considerable force is concentrated on the relatively small area of a column-slab connection. An incorrect assessment of load capacity of slab under the punching shear may lead to an accident. One of the most significant factors affecting the slab capacity is lon...
![Figure 1. Types of failure for reinforced concrete columns [1].](profile/Mohamed-Aboelhassan-2/publication/354871048/figure/fig1/AS:1072731487473664@1632770525986/Types-of-failure-for-reinforced-concrete-columns-1_Q320.jpg)
The main purpose of this paper is to study analytically the behavior of slender reinforced concrete columns existing in sway and non-sway structures. The studied variables were the stiffness of the beam connected to the slender columns, the stiffness of the bracing columns, and the number of bays and stories in the structure model. The stability of...
Concrete is strong in compression but weak in tension. Reinforced concrete, in which steel rods are provided to resist tensile stresses, however, does not meet the satisfactory structural demands. The concept of prestressing was introduced to generate compressive stresses in concrete prior to loading, by means of prestressing tendons inserted in th...
The use of near-surface mounted (NSM) Glass fiber reinforced polymer (GFRP) bars is one of the most popular and effective techniques for strengthening reinforced concrete (RC) beams. This paper presents an experimental research program to study the flexural strengthening of RC beams comparing two areas of bottom tensile reinforcing steel and three...
Citations
... Consequently, the section is cracked, and only hoop reinforcement resists the tensile forces. Assuming failure in the hoop direction occurs when the steel yields, the behavior in the hoop direction becomes elastic [19], which allows modeling the steel bars as equivalent concrete [20] with a tensile strength of , where is the reinforcement ratio in the ring direction, and fy is the steel yield stress. ...
... Consequently, the section is cracked, and only hoop reinforcement resists the tensile forces. Assuming failure in the hoop direction occurs when the steel yields, the behavior in the hoop direction becomes elastic [19], which allows modeling the steel bars as equivalent concrete [20] with a tensile strength of A s A c f y , where A s A c is the reinforcement ratio in the ring direction, and fy is the steel yield stress. ...
Fire is considered a common hazard for civil structures. Public and administrative buildings are commonly designed by considering the standard fire rating and, in many cases, contain large compartments with central domes, in which fire growth can be significant. Moreover, tanks and underground fortified structures may be constructed as domes to support the heavy soil above. This paper numerically addressed such a case. First, an axisymmetric finite element model was developed and validated to predict the dome's transient, thermal, structural, and thermal-structural behavior. Next, the model was used to conduct a parametric study to investigate the effects of the dome ring reinforcement, thickness, stiffness, central angle, base restraints, load type (external pressure or gravitational), and load ratio on the fire endurance of the dome. Design recommendations to increase the fire endurance of concrete domes were formulated based on the parametric study.
... Where ,ℎ is the Inelastic strain, is the damage parameter compression, and is the Young's modulus. (Hafezolghorani et al., 2017) Figure 5 -Model for confined and unconfined concrete (Kent & Park, 1971) Figure 7 shows the behavior the tension softening curve, and the following are the tensile stress-strain model equations which is applied to the (Massicotte et al., 1990) model using the modification of (Allam et al., 2013). ...
... Where the tensile strength of concrete is at 28 days, is the damage parameter, and Allam et al. (2013) The reinforcing steel properties employed by (Kurniawan et al., 2021) were used in this study. And the behavior of fiberglass was modelled using a type elastic linear by a lamina of 0.5 mm according to ABAQUS/CAE User's Manual (ABAQUS, Version 6.7, ABAQUS, Inc. DASSAULT Systems, USA, 2017). ...
This paper presents the results of finite element analysis (FE) to study the axial compression behavior of reinforced concrete columns wrapped with tapes and fiberglass cloths according to different techniques using ABAQUS software. In the beginning, columns are modeled as 3D solid elements with a concrete damage plasticity model (CDPM), as the columns in this study are considered to be low compressive strength reinforced concrete and the rebar as 3D mesh elements. And once assembled, the specimen is wrapped with tape and cloth in the form of three-dimensional shell elements. Then, in order to analyze the behavior of the ultimate loads, the deformation of the confinement material, and the distribution of deformations in the concrete, the controlled displacement method used to apply the uniaxial compression loads to the specimen. Finally, a new mixed confinement model between partial confinement and complete has been proposed using a database of the results of a numerical simulation for confined concrete by fiberglass tapes and cloths. And it was found that the confinement strategy proposed in this study is very effective for the behavior of the reinforced concrete column, as the stress decreases significantly with the expansion and widening of the confinement stiffness of concrete in the plastic phase which improves the axial stress resistance.
... The tri-linear approximation and the real trend are practically coincident and, thus reducing the number of tests required for the evolution of mechanical properties with age [11]. A modified tension softening curve by Allam et al. [30] was considered for tensile damage evaluation with modifications over the tension softening curve suggested by Massicotte et al. [31]. A global range of flow parameters (Drucker-Prager model), available for normal concrete were used (i.e., dilation angle ( ), eccentricity (e), biaxial to uniaxial strength ratio ( ∕ ), surface shape parameter ( ), viscosity parameter ( )) (see Table 4). ...
Managing the early-age thermal behavior of mass concrete structures like dams, dykes, bridge piers, thick raft foundations, etc., is the major concern during their construction. The heat of hydration (HOH) of the fresh concrete pour does not get easily dissipated to ambiance since concrete is predominantly a poor conductor of heat. Eventually, in the presence of external boundary conditions (thermal or mechanical), the slower rate of heat dissipation may at times induce a substantial thermal gradient within the mass concrete which further may induce thermal stresses leading to the formation of cracks. The article attempts to develop a thermo-mechanical numerical model based on the finite element (FE) methodology to mimic the early age behavior of mass concrete that accounts for time and temperature-dependent heat generation during the hydration process with the evolution of thermal and mechanical properties over time. A two-stage sequential thermo-mechanical model is developed consisting of a thermal model to assess the thermal history of a particular concrete mix which is experimentally validated by performing thermal monitoring of a fresh concrete pour for 10 days, and a mechanical model to assess the stress and the cracking states, the model utilizes the concrete damage plasticity (CDP) model based on the principle of continuum damage mechanics which is characterized by experimental results. Later on, the methodology so developed is employed over a practical scenario of the dam construction process considering the relevant boundary conditions to arrive at a suitable optimum lift height and pouring frequencies.
... where, ε t is the total tensile strain, the tensile elastic strain, the undamaged tensile elastic strain, is the tensile damage or cracking strain. The post-cracking tensile stress-strain (softening) behavior of the individual block and mortar units which make up the lightweight block masonry walls studied in this research were obtained using the relationship given by Allam et al. [23], which was modified based on the relationship suggested by Massicotte et al. [24]. ...
... Tensile stress-strain relationship curve suggested by Allam et al.[23]. ...
A damage plasticity macro-model for the static and cyclic in-plane loading analysis of hollow and solid (mortar-filled) lightweight concrete block masonry shear walls is proposed. The model is used to simulate typical wall configurations for both plane walls and walls strengthened or reinforced with mortar infill. As a macro-model, the new damage plasticity method is suitable for practice oriented predictions, and can give reasonably good results with less demand on computation power as compared to typical micro-modeling approaches. Calibration of model parameters and numerical simulation results for typical lightweight concrete block masonry wall configurations performed using the finite element software ABAQUS are presented in the companion paper.
... In the finite element (FE) modeling process, an evaluation of Fig. 6. The stress-strain curve for concrete in tension [33]. different mesh sizes was conducted to ensure accurate results. ...
This study investigates the impact of openings on the behavior of arched beams and the effectiveness of different strengthening materials in enhancing their performance. The study involves three stages. The first stage focuses on the effect of openings on the behavior of curved beams. The second stage examines the effect of different strengthening materials, including carbon fiber sheets, glass fiber sheets, and steel plates, on the deflection and failure load in the presence of openings. In the third stage, Finite Element models are used to simulate the tested beams with different strengthening materials, and the differences between beams with and without openings are analyzed. The results show that the presence of openings negatively affects the ultimate load, deflection, and ductility ratio of arched beams. Regarding strengthening, beams strengthened with steel plates demonstrate a higher ultimate load, approximately 5.6% and 21% higher than beams strengthened with carbon fiber and glass fiber sheets, respectively. Moreover, the deflection of beams strengthened with steel plates is 6.4% and 8.9% higher than beams strengthened with CFRP and GFRP. The presented work is introduced to offer a valuable solution to some developed systems for controlling, repairing, and supporting structures.
... En dónde es el esfuerzo a compresión, es el esfuerzo a compresión último, ´ es la deformación del hormigón en función del esfuerzo último a compresión y es la deformación del hormigón en función del esfuerzo aplicado en ese instante. Para la generación de la curva esfuerzo-deformación del material sometido a tracción se utilizará el modelo propuesto por (Allam et al., 2013), los cuales desarrollan una formulación aproximada para el comportamiento del concreto a tracción tomando en cuenta el agrietamiento. ...
... Figura 83: Modelo para la generación de la curva esfuerzo-deformación a compresión y tracción respectivamente (Allam et al., 2013;Kent & Park, 1971). ...
... Therefore, numerous methods were developed based on simplifications to estimate s at the location of a crack, denoted as ̂s [7] [8] [9]. The methods frequently assume a linear-elastic behaviour of concrete in compression and neglect the contribution of concrete in tension [10], leading to an overestimation of s , especially for the stage when the first cracks in the element are developing. This can lead to an overestimation of crack widths, which results in a higher reinforcement ratio , thus increasing costs. ...
An accurate calculation of steel stresses is essential for assessing reinforced concrete structures’ serviceability limit state, e.g., assessing crack widths. The steel stresses in elements loaded in bending are not known but are estimated by steel stress calculations. To get a more accurate crack width prediction, the calculated steel stress should approximately represent the actual steel stress at the location of the crack after the crack has been formed. Existing methods for calculating steel stresses are frequently based on numerous assumptions; e.g., the tensile stresses or tension softening effects in the cross-section are neglected, and a linear stress-strain distribution is assumed for the concrete in compression. This paper presents a method to calculate steel stresses based on existing constitutive theoretical relations that consider concrete's non-linear behaviour in compression and tension. They are compared with strain measurements of the reinforcement bars using distributed optical fiber sensors obtained from experiments described in the literature. Results showed that existing methods frequently overestimated the steel stress, especially when the first cracks were formed. Therefore, a method was developed for an improved calculation of steel stresses in elements loaded in bending with a rectangular cross-section. The paper demonstrated that the developed method could estimate steel stresses more accurately from the first to the final crack. The presented method applies to rectangular cross-sections with a single reinforcement layer but can be straightforwardly extended to other shapes in a similar procedure and can be used to assess the accuracy of crack width formulations based on experimental results.
... Figure 26 shows stress-strain curves of modelled specimens. Although the tensile strength of concrete is insignificant in comparison to reinforcement, various researchers have emphasized the significance of taking the tension-stiffening effect into account in the numerical modelling [21]- [23]. Tension stiffening describes the concrete post-cracking behavior after reaching its tensile strength. ...
Partially prestressing acts as an intermediate design alternative between fully prestressed and conventional reinforced concrete through relaxing the allowable concrete tensile stresses. Consequently, this results in lower prestressing forces, which subsequently reduces prestressing steel and the overall cost. The adoption of high-strength concrete (HSC) with partial prestressing improves both the economic and durability aspects. However, limited research has been conducted to investigate the effect of HSC on the serviceability requirements of partially prestressed girders. This paper presents a numerical investigation into the behavior of such girders under quasi-static loading. The presented numerical model was validated against experimental results in terms of deflection and cracking performance at different loading stages. Then it was conducted in a parametric study to assess the effect of concrete compressive strength, prestressing force, and non-prestressed reinforcement ratios on the behavior of the partial prestressed girders using full-scale sections. The proposed study presents different design optimization regimes for HSC partially prestressed girders.
... In order to specify both compressive as well as tensile material behavior of conrete, the suboption 'Concrete damaged plasticity' (CDP) was chosen. As only bilinear diagrams of concrete strength were obtained from material testing, the compressive and tensile diagrams were created based on Allam et al. 37 and Hafezolghorani et al. 38 , where the uniaxial compressive behavior was specfied by the Eqs. (2), (3) and (4), and the uniaxial tension behavior by Eqs. ...
The hunger for a better, more effective, more economic, easier for construction, and overall more sustainable bridge design is enormous nowadays. One of the solutions for the problems described is a steel-concrete composite structure with embedded continuous shear connectors. Such structure uses advantages of both materials (concrete in compression and steel in tension) while lowering the overall height of the structure and time of the construction. This paper presents a new design of the connector of twin dowel type, with clothoid dowel, where two dowel connectors are welded longitudinally by flanges to create one twin connector. Its geometrical attributes are closely described and the design origin is explained. The study of the proposed shear connector consists of experimental and numerical part. In experimental study, the experiments performed—four push-out tests—and their setup, instrumentation and material characteristics are described and their results in a form of load-slip curves are presented and analyzed. In numerical study the finite element model developed in ABAQUS software is presented with a detailed description of the modeling process. In results and discussions the results of the numerical study are compared with results from the experimental study and the resistance of the proposed shear connector is briefly compared to shear connectors from chosen studies.
... The tri-linear approximation and the real trend are practically coincident and, thus reducing the number of tests required for the evolution of mechanical properties with age [11]. A modified tension softening curve by Allam et al. [30] was considered for tensile damage evaluation with modifications over the tension softening curve suggested by Massicotte et al. [31]. A global range of flow parameters (Drucker-Prager model), available for normal concrete were used (i.e., dilation angle ( ), eccentricity (e), biaxial to uniaxial strength ratio ( ∕ ), surface shape parameter ( ), viscosity parameter ( )) (see Table 4). ...
