Software ATENA Research Articles

Numerical verification for concrete beams reinforced with CFRP subjected to pure torsion

Torsional behavior of concrete beams reinforced with longitudinal Fiber reinforced polymers (FRP) bars and FRP transverse stirrups has not been well-defined in various international codes and design guidelines as evidenced from the discrepancies in design equations. Such discrepancies are due to the complex behavior of beams subjected to torsional stresses and the limited research available in the literature; especially for FRP reinforced beams. A non-linear finite element (FE) analysis is conducted using ATENA software to generate a numerical model to predict and verify the failure loads and strains of beams of a compiled database from literature. This paper presents a comparison between the results of the experimental data and analytical models in order to verify the efficiency of the proposed numerical model for predicting failure load/strains in longitudinal FRP bars, FRP stirrups, and rotation angle of the tested beams. The comparison showed good agreement between experimental and analytical models in ultimate torque with difference of 6.5 % and the model is used in a parametric study to investigate the effect of concrete compressive strength, longitudinal reinforcement ratio, and beam depth under pure torsion in addition to the effect of concrete contribution to the torsional resistance. The numerically computed cracking and ultimate torques are compared with results from theory of elasticity, skew-bending theory and code equations such as: ACI-318 and CSA-S806-12. Based on this study, CSA-S806 gives acceptable prediction of ultimate torque, while ACI code is found to be more conservative. The increase of concrete compressive strength can enhance the cracking and ultimate torque. The increase of longitudinal reinforcement ratio has an insignificant effect on ultimate torque but increases the twist capacity of Reinforced concrete (RC) beams. The increase of longitudinal reinforcement can improve also the twist ductility.

Numerical study on shear strength of GFRP-RC T-Joints

This paper presents the numerical modeling and behavior of glass fiber-reinforced polymer (GFRP) reinforced concrete (RC) exterior beam-column joints (T-joints) under cyclic loading. The numerical modeling was implemented on four tested RC T-joints (two steel-RC and two GFRP-RC) in the finite element software ATENA. The numerical model was verified against the results of previous experimental studies. The validated numerical model was used to investigate the effects of the flexural reinforcement ratio of the beam, the compressive strength of concrete, axial load on the column, joint aspect ratio, joint confined area by lateral beams, and joint configurations on the shear strength and load–displacement envelope curves of the GFRP-RC T-joints. The numerical study results indicated that increasing the flexural reinforcement ratio of the beam by up to 1.77% increased the strength and stiffness of the GFRP-RC T-joints. The GFRP-RC T-joints were able to resist joint shear stress by up to 0.85fc′, and higher joint aspect ratios led to premature failure of the GFRP-RC T-joints. The GFRP-RC T-joint with 54% joint confined area by lateral beam attained 33% higher strength than the unconfined (no lateral beam) GFRP-RC T-joint.

Numerical analysis of reinforced concrete columns strengthened with sleeve wedge bolts and a self compacting concrete layer

With the development of technology in the field of structural analysis, it has now become possible to computationally model more complex structures, each with its own peculiarity, such as those with structural reinforcement. With regard to the non-linear analysis of structural elements in reinforced concrete, the Finite Element Method is ideal, since it is only possible with the use of computational resources. For columns subjected to flexion compression, elements that are highly susceptible to second-order effects and which have as an important function the global stability of buildings, software for numerical analysis, such as ATENA, become especially applicable for the study of behavior structural of these elements. Marques et al. (2015) carried out a study on the performance of columns reinforced through casing with self-compacting concrete and wedge bolts applied to prevent slipping between these materials. Based on this study, then, in this work, 5 numerical models were developed in the ATENA software: PO, PR, P150-18, P150-26 and P75-50. The first two are references (original column and reference column, respectively), while the others are reinforced, whose nomenclature distinguishes them in terms of the quantity and disposition of wedge bolts on the compressed face of the element. The relationships and parameters that allowed the analysis of the models were: rupture load versus displacement, specific strains in longitudinal reinforcement, cracking and stresses in wedge bolts at failure. Good results were obtained, both with regard to the variation between the experimental results and those obtained numerically, and for the performance of the structural reinforcement technique, which represents the reliability of the computational modeling and the adopted methodology. The variation between such results respected the 15% limit established by the comments of the ACI 318 (2011) standard, with the exception of the PO, and the reinforcement technique, in turn, resulted in the growth of the initial strength of the column in its original condition (PO). The present study allows, therefore, to guarantee and disseminate the application of numerical simulation for the analysis and design of reinforced concrete elements.

Bond Behavior of FRP Bars in Lightweight SCC under Direct Pull-Out Conditions: Experimental and Numerical Investigation.

In recent decades, lightweight aggregate concrete (LWC) became a popular building material due to its desired properties. However, various attributes of LWC, such as bond behavior of used reinforcing, have not been described thoroughly. In this regard, LWC produced with 0%, 50%, and 100% expanded clay aggregate was designed, and the physical–mechanical properties were assessed for material characterization. Subsequently, the bond behaviors of LWC reinforced with steel, glass fiber reinforced polymer (GFRP), and basalt fiber reinforced polymer (BFRP) bars were evaluated by pull-out tests. The results of the experimental program allowed the effects of expanded clay aggregate incorporation on LWC properties to be quantified. The bond strength of BFRP bars was not affected by the replacement of coarse aggregate by expanded clay aggregate, whilst the GFRP bars showed lower bond strength values of LWC specimens. Contrarily, in the case of steel bars, both the bond strength and bond stiffness were higher for LWC specimens than for those of normal concrete. Finite element software ATENA 3D was used for simulation of the bond behavior of LWC, and the model validated by the experimental results referred to reasonably corresponding outputs.

Numerical analysis of composite slim-floor beams

Abstract In this research work existing laboratory tests of slim floor beams with solid monolithic concrete slab were modeled and analyzed using GID and Atena software. After validating the advanced finite element model with the test results of the international literature, structural parameters were analyzed with the aim to study their influence on the load bearing and deformation capacity of the beams. The parameters were related to the geometric of the beam: size of web openings and top concrete cover. With these results conclusion can be noticed that focusing on the optimal arrangement of the geometrical parameters of the composite beam could lead to better structural behavior with more economical solutions.

Application of high performance concrete for reconstruction

One of the sustainability aspects of the construction is a sufficient durability. In objectively justified cases, the durability is enhanced by reconstruction. To ensure economic design of the reconstruction, non-liner approaches are often applied. This paper deals with aănonlinear numerical simulation of disassembled reinforced concrete (RC) panels strengthened by an ultra-high performance concrete (UHPC) layer. Based on the prior experimental programme, simulations of four-point bending tests of the original and strengthened panels are created using software ATENA Science. Calibration of the material parameters is based on the destructive and non-destructive investigations performed in the experimental programme. The comparison of the experimental and numerical model loading curves indicates that additional mechanical testing will be needed in order to achieve an accurate numerical simulation. Although the bending test of the RC panel and the crack mouth opening displacement (CMOD) test performed on the applied UHPC beam were calibrated, the final model of the UHPC strengthened panel does not correspond completely with the experimental measurements. In this paper the possible reasons for this result are discussed.

Experimental and analytical investigation of UHPC confined concrete behavior

Ultra-High Performance Concrete (UHPC) is a self-levelling cementitious material with enhanced mechanical and durability properties when compared to normal strength concrete. Accelerated construction of concrete columns can be realized using a precast hollow UHPC shell as permanent formwork. Also, as a retrofit solution, UHPC can be placed around existing concrete columns with deficient confinement details. The continuous confinement provided by UHPC shell to both the concrete core and longitudinal reinforcement could be used to improve the seismic behavior of columns or reduce the amount of confining hoop reinforcement required in traditional column designs. An experimental and analytical study is performed with a main objective of quantifying the confinement effect provided by plain UHPC shell. The experimental investigation compressed of axial testing of 228 mm (9 in.) and 280 mm (11 in.) dia circular columns, 203 mm (8 in.) and 305 mm (12 in.) square columns confined with UHPC shell. Experimental investigation included a total of two normal strength concrete column specimens as control specimens and 11 column specimens confined with 1 in. and 2 in. thick UHPC shell. All the specimens were tested to failure under axial compression and were extensively instrumented. The confinement provided by the unreinforced UHPC shell improved the peak compressive stress and the crushing strain values of the core concrete by 15%–30% and 26%–46% respectively. The effectiveness of plain UHPC shell to provide confinement was found to considerable in circular columns compared square columns. A detailed 3D FEA models were developed in ATENA software and were validated using the experimental data. The FEA models captured observed responses accurately and provided insight into the observed experimental behavior. Based on the experimental and analytical study, it is recommended to include some transverse reinforcement in UHPC shells, especially for non-circular cross-section for improved confinement effect.

Numerical Deformation Analysis of Reinforced Lightweight Aggregate Concrete Flexural Members.

In the modern construction industry, lightweight aggregate concrete (LWAC) is often used to produce load-bearing structural members. LWAC can be up to 40% lighter by volume than normal strength concrete. However, the lack of adequate numerical models often limits the practical application of innovative building materials such as lightweight concrete in real projects. The present study conducted a comparative numerical deformation analysis of a full-scale bridge deck slab and girder. Using the physical model proposed by the authors and the finite element software ATENA, the deformations of full-scale lightweight and traditional reinforced concrete elements under the short-term effects of permanent and variable loads were compared. Depending on the safety and serviceability limit requirements, it was found that the amount of longitudinal reinforcement in lightweight reinforced concrete elements could be reduced compared with that in standard reinforced concrete elements with the same parameters. The results of the numerical analysis showed that the deformation analysis model proposed by the authors could serve as an alternative tool for the design of lightweight concrete flexural members with the selection of optimum geometric and reinforcement parameters limited by the stiffness condition.

Numerical study on the bond behaviour of plain and ribbed bars in self-compacting concrete

The bond between steel and concrete is an important phenomenon for the composite behaviour of Reinforced Concrete (RCC). This bond is affected by different parameters like type of bar, diameter of bar and grade of concrete etc. In the present study, these parameters were considered and investigated for their effect on the bond behaviour in self-compacting concrete. The self-compacting concrete possess advantages compared to conventional vibrated concrete like better compactability thereby the enhanced strength and durability. In the present study the various parameters that influence the bond in concrete are considered., type of bar (plain and ribbed), diameter of bar (10, 12 & 16 mm) and the grade of concrete (Mix-I (20 MPa), Mix-II (40 MPa) and Mix-III (60 MPa)) were considered. The numerical modelling is performed using the software ATENA. The parameters determined include the bond stress and slip. The results obtained from the numerical model were validated using the pull-out experiments. From the results obtained, it can be concluded that the ribbed bar has shown much higher bond stress compared to plain bars and the bond stress increases with increase in concrete strength.

Crack Pattern Analysis of Plain Concrete Pavement due to Swelling Pressure on Expansive Soil

This research was conducted on the Surakarta-Gemolong-Geyer provincial road which is suspected to be built on expansive soil using the ATENA V5 3D software program. ATENA program can be used to simulate crack propagation in concrete and reinforced concrete structures. This study uses quantitative analysis methods, to the analysis of fracture patterns of rigid pavements with transverse reinforcement on expansive soils. Rigid pavement is modeled into 2 types, namely rigid transverse reinforced pavement models due to swelling pressure forces on expansive soils and transverse reinforced rigid pavements without swelling pressure forces on expansive soils. The swelling test on the soil carried out in the laboratory was 37 kPa. The rigid pavement model is subjected to load testing. The load used is the standard load of a medium-sized truck. The repetition of loading used is 30 times. The loading is divided into 3 types, namely: edge, center, and corner loading. The results of the analysis of rigid pavements were compared between rigid pavements due to swelling pressure forces on expansive soils with rigid pavements without swelling pressure forces. The results of the analysis from the ATENA software program show that every loading test on rigid pavement due to swelling pressure forces cracks greater than loading without swelling pressure forces. Edge loading shows that cracks due to swelling pressure are 3.5% higher than those without swelling pressure. Middle loading shows cracks due to swelling pressure which is 8.33% greater. Middle loading shows that cracks due to swelling pressure are 3.56% higher than without swelling pressure. This research can be used as a reference and prediction in identifying cracks that occur so that the government can carry out appropriate design planning and maintenance and rehabilitation of rigid pavements on expansive soils.

Strengthening flat slabs without shear reinforcement against punching shear by concrete overlay

Research in this paper presents a theoretical study of increasing in punching shear capacity of the strengthened flat slab by concrete overlay. The parametric study is based on comparison of three different relevant standards design models and presents results how Eurocode 2 (EN 1992-1-1), Model Code 2010 and draft of second generation of Eurocode 2 (prEN 1992-1-1) take into account strengthening by concrete overlay. A reference specimen is represented by a fragment of a flat slab supported by circular column. Influence of concrete toppings depends on thickness and also on reinforcement ratio. In Eurocode 2 and new generation of Eurocode 2 the increase of punching shear resistance of the slab with concrete topping can be taken into account only by reinforcement ratio and thickness of the slab considering the perfect connection and bond between the original slab and new layer of concrete overlay. Model Code 2010 is based on Critical shear crack theory and the reinforcement ratio in concrete topping was considered in equation of moment of resistance and punching shear resistance is calculated by considering the rotation and deformation of the slab. Estimation of results by parametric study are compared by non-linear model from Atena software.

Ecological Efficiency of Life Cycle of Concrete Fabricated Composite Slab in Earthquake Area

With the development of prefabricated buildings, the construction mode of buildings has changed greatly. Infilled wall is an important part of architecture. The traditional manual masonry method is not suitable for the construction of prefabricated buildings. Precast concrete infilled wall, as a form of infilled wall suitable for the construction of prefabricated buildings, came into being. Infilled wall has a great influence on the performance of frame structure. Compared with the traditional masonry infilled wall, the concrete infilled wall has greater stiffness, better integrity and stronger bearing capacity. Based on the existing research, this paper analyzes the influence of the height width ratio of the concrete infilled wall, the wall thickness, and the tie mode with the frame on the structural performance through the finite element software Atena. Combined with the results of practical engineering modal analysis, this paper evaluates the value method of natural vibration period of concrete frame infilled wall structure, and puts forward some suggestions for Chinese codes.

Effects of Web Height Reduction and Skew Angle Variation on Behavior of RC Inverted T-Beams

The use of precast inverted T-beams has been frequently used to minimize construction activities and installation time. However, shipping and placement of large invert T-beams can become challenging tasks due to their weight. Decreasing the web height of the beam can be effective in reducing the beam weight. This paper considers inverted T-beams with two overhangs, negative moment regions, and one span, a positive moment region. The examined parameters were the web height and skew angle of the inverted T-beams. To avoid high costs of testing beams and to save time, the application of numerical modeling is, hence, inevitable. A calibrated 3D nonlinear numerical model, using ATENA software, was further used to numerically investigate the effects of reducing the weight, by decreasing the web height and varying the skew angle of inverted T-beams on their structural performance. The outcomes of this study indicated that reducing the web height of the beam was an effective tool to reduce the weight without jeopardizing the strength of the beams. Increasing the skew angle of the inverted T-beam also decreased their ductility.

Fire response model of the steel fibre reinforced concrete filled tubular column

This study focuses on numerical finite element modelling of the global mechanical behaviour of circular hollow section columns with steel fibre-reinforced concrete infill at elevated temperatures. The three-dimensional numerical model was designed using ATENA software. The fracture-plastic material model was used to simulate the exact behaviour of the steel fibre-reinforced concrete (SFRC) in compression and tension. Work includes data from experimental studies in the vertical furnace, development of the SFRC material model, description of the global thermal and mechanical model, validation of the model, and a sensitivity study of the main parameters. The sensitivity study shows definite improvements in columns fire resistance by implementing the SFRC unique properties. The model is recommended to be used for the further parametric study and preparation of an analytical model for columns with steel fibre-reinforced concrete infill as per the European standard for composite member design in the fire in prEN1994-1-2:2020.

Behavior of the Experimental Flat Slab Specimen Supported by an Elongated Column

The paper deals with the results of a loading an isolated fragment of flat slab specimen with two openings located close to the column. Slab specimen was supported by an elongated column and was without shear reinforcement. The accuracy of the relevant design models for prediction punching resistance was tested with obtained test results. All design models provided punching capacity on the safe side. The best accuracy has been achieved by non-linear analysis that was carried out with Atena software.

Experimental and theoretical study of the strength of plates for pressure

Introduction. The issues of strength and deformability of reinforced concrete floors during punching remain insufficiently studied at present, despite the numerous publications in the technical literature. This article presents the results of experimental studies of the punching shear strength of fragments of conjugation of flat reinforced concrete monolithic slabs with a column under static loading. The purpose of these studies was to obtain experimental data on the stress-strain state of a fragment of a monolithic floor during static punching and to develop a spatial model based on the finite element method with subsequent numerical studies. Materials and methods. Experimental studies were carried out on a test bench. The characteristics of prototypes are given: dimensions, reinforcement, class of concrete and reinforcement. A test setup is described. For the numerical simulation of the slab-column interface, the ATENA software package was used, which allows for physically and geometrically nonlinear calculations of reinforced concrete structures, taking into account the real work of the materials used to create experimental models. Results. Comparison of the results for the breaking load, obtained during the experiment, with the results of numerical modeling by the finite element method and with the results of calculations using the methods of SP 63.13330.2018 and Eurocode 2. The diagrams of the distribution of deformations in reinforcement and concrete, breaking loads and patterns of distribution of cracks in the samples are obtained. Conclusions. The analysis of experimental and numerical studies made it possible to formulate the conditions for the pun­ching shear strength of flat slabs with longitudinal reinforcement and to give recommendations on the strength calculation under central loading.

Strengthening of Non-Engineered Building with Steel Plate to Increase Seismic Performance

Residential buildings are included in the category of non-engineered buildings that suffered the most damage during an earthquake. This is because most of the building materials used and the working techniques, especially the reinforcement, do not meet the requirements. This research will be reviewed numerically using ATENA software on three types of numerical models, each of which represents non-engineered buildings, engineered buildings and reinforcement models with steel plates. The results showed that the non-engineered building model would experience the largest deflection and the smallest load bearing capacity, while the other 2 models experienced a smaller displacement with a greater load capacity. The best performance is shown in models with steel plate reinforcement, so that the reinforcement of steel plates in non-technical buildings will effectively increase the performance of non-engineered buildings.

Seismic response of 1/2 scaled two storey reinforced concrete moment resisting frame system using nonlinear static analysis

Reinforced concrete (RC) frame systems represent one of the structural solutions used in seismic zones by engineers. For this reason, the importance of knowing the real seismic response for these types of structures is essential and presents the research problem studied in this article. Thus, the seismic response for two storey axial RC frame (one bay-one span) system was studied using nonlinear static analysis in ATENA software. The structural degradation of the two storey RC frame system was investigated for several steel reinforcement possibilities and three distinct RC beams cross sections. Particular attention was paid to RC beam-column joints degradation areas and to seismic energy dissipation mechanism in the marginal regions of the RC columns. Thus, it was observed a nonlinear inelastic response in the potential degradation zones with contrary effects with respect to the specified conclusions in the current seismic design norms. Also, it was studied the RC slab bending stiffness influence to horizontal structural elements (RC beams) and to vertical structural elements (RC columns) alongside the cracking mode for horizontal static actions and RC slab local degradation beside RC beam-column joint area. In these conditions, conclusions regarding the seismic response of the moment resisting (MR) RC frame system with low height regime designed according to the current seismic code were specified and an unsatisfactory seismic response was proved.

Carbon fiber reinforced polymer strengthened reinforced concrete square columns under pre-existing eccentric loads

Numerous experimental studies have been conducted on the behavior of strengthened columns, mostly with glued layers of FRP before load application, and rarely under the pre-existing load. Results confirm a good efficiency of strengthening in the compression-controlled region of the columns, as mentioned in design codes and guides such as ACI 440.2R-17. However, their behavior in the tension-controlled region is still a challenging subject. Moreover, when the eccentricity is large enough, the efficiency of the strengthening method needs more attention. This study aimed at strengthening six RC columns in the tension-controlled region under the pre-existing load condition. Furthermore, tested specimens were verified using a nonlinear finite element analysis performed in ATENA software. Moreover, some identical strengthened specimens, which were not subjected to pre-existing load during strengthening, were modeled to capture the effect of pre-existing loads. The results of the analyses were in good agreement with experimental data. Comparison of numerical results obtained for columns strengthened without pre-existing load, and under pre-existing load showed that pre-existing loading significantly reduced the efficiency of FRP jacketing. Also, assuming a linear variation of confinement pressure in the tension-controlled region of the interaction diagram results in good agreement with attained results.

Experimental investigation and analysis of pure bending plastic hinge zone in hybrid beams reinforced with high reinforcement ratio under static loads

This article investigates the formation of plastic region length and parameters affecting the region length in hybrid glass fibre reinforced polymer (GFRP)/steel reinforced concrete (RC) beams by using finite element method based on the ATENA software. Totally nine concrete beams with dimension of 150 × 250 × 2700 mm reinforced with hybrid GFRP/steel reinforcement were tested in four-point bending. Tested beams reinforced with an effective reinforcement ratio between 0.57% and 1.18%. The tested outcomes along with the experimental data on behaviour of GFRP/steel RC beams available in the literature were collected for validating the 2D FE model. The comparison results confirm a good agreement between the experimental and numerical data. The experimental results of this study show that the effect of the ratio of steel to GFRP bars and the amount of longitudinal reinforcement are the main factors controlling the strength and failure modes of beams. The parametric study using FE model is conducted to evaluate the effect of effective reinforcement ratio, yield strength of steel, concrete compressive strength, ratio of elastic modulus of GFRP and steel bars, and ratio of shear span to effective height of section on spread of the length of plastic hinge region of GFRP/steel RC beams.