Behavior Of Concrete Material Research Articles

Time-varying damage evolution of concrete under cyclic disturbance loading- an experimental observation utilizing AE and DIC

Cyclic disturbance loading affects the continuous operation of concrete structures. This study aims to better understand the failure behavior of concrete structures under cyclic disturbance loading. This study combined acoustic emission (AE) and digital image correlation (DIC) technologies to study mechanical failure behavior and damage evolution of concrete materials under cyclic disturbance loading and unloading. The AE event time-frequency characteristics, surface principal strain program, and damage parameters of samples with different cyclic disturbance amplitudes were obtained by theoretical calculation. The results reveal that when minor disturbance amplitudes are applied, the elastic modulus of concrete specimens tends to increase. When the disturbance amplitude is too large, the elastic modulus of the specimens drops, leading to faster specimen failure. The AE characteristic parameters exhibit a Felicity effect after the sample is subjected to a cyclic disturbance loading. Moreover, the larger the amplitude of the disturbance load, the more frequent the low-frequency and high-amplitude events generated during the final rupture, the higher the concentration of the principal strain on the sample's surface, and the wider the crack band distribution. AE energy and Effective crack are consistent in characterizing damage, and the changing trend of these two damage parameters can better reflect the deterioration process of concrete. The research results will provide practical and theoretical insights for safely operating and maintaining concrete structures.

Research on rheological behavior of fresh concrete single-cylinder pumping based on SPH-DEM

In contrast to traditional approaches to simulating fresh concrete, the model applied here allows issues such as liquid phase and the motion of sub-scale particles to be considered. The rheological behavior of fresh concrete materials was investigated, and the slump test and pumping process of fresh concrete were simulated by combining the smooth particle hydrodynamics coupled with discrete element method. Based on Bi-viscosity model and Bingham model, linear and nonlinear fitting of rheometer data and the derivation equations were educing. Bi-viscosity model and the Bingham model were compared in slump test. The results show that the Bi-viscosity model is more accurate in simulation, and the error percentage is less than 10%. The Bi-viscosity model was used to simulate and predict the results of slump experiment, and the influence of rheological parameters on the slump velocity and shape was obtained. The simulation analysis model of concrete single-cylinder pumping is established, and the experimental and simulation analysis models are compared. The results show that the SPH-DEM pumping pressure prediction is very close to the experimental results.

Mechanical and Fracture Behavior of Concrete Material Derived from CDA, Crumb Rubber Particles and Inclusion of Basalt Fiber

Mechanical and Fracture Behavior of Concrete Material Derived from CDA, Crumb Rubber Particles and Inclusion of Basalt Fiber

Meso-scale analysis on the effect of coarse aggregate properties on the creep behaviors of concrete based on the 3D particle-based method

Coarse aggregate, as the main component of concrete, has a significant influence on its behaviors. In this work, a 3D particle-based method was utilized to investigate the effect of coarse aggregate properties on the creep behaviors of concrete at a meso-scale level, in which concrete was composed of mortar, coarse aggregate, and interfacial transition zone (ITZ). Firstly, cluster-based modules for aggregate were generated based on the real aggregate geometry obtained by 3D scanning, and then, the developed aggregates were randomly distributed in the model according to the specified aggregate gradation and content. Then, the Burger model, a linear viscoelastic-plastic model, was employed to define the contact mechanical characteristics of mortar and ITZ. Meanwhile, the linear parallel bond model, a linear elastic bonding interface with dimensions that can transmit forces and moments, was utilized to describe the contact bonds between balls in the aggregate. On this basis, the effects of coarse aggregate properties (i.e., surface topography, shape, gradation, content, and elastic modulus) on the concrete creep were studied quantitatively. The results show that the coarser the surface topography of aggregate, the smaller creep. Also, with the increase in the content or elastic modulus of coarse aggregate, concrete creep showed a decreasing trend. In addition, the constraint action of the aggregate can be illustrated by the displacement fields. Overall, the 3D particle-based proposed in this work can provide an effective tool to explain the creep behavior of concrete materials from the meso-scale.

Two-Dimensional Mesoscale Finite Element Modeling of Concrete Damage and Failure

Methodologies are developed for analyzing failure initiation and crack propagation in highly heterogeneous concrete mesostructures. Efficient algorithms are proposed in Python to generate and pack geometric features into a continuous phase. The continuous phase represents the mortar matrix, while the aggregates and voids of different sizes represent the geometric features randomly distributed within the matrix. The cohesive zone model (CZM) is utilized to investigate failure initiation and crack propagation in mesoscale concrete specimens. Two-dimensional zero-thickness cohesive interface elements (CIEs) are generated at different phases of the concrete mesostructure: within the mortar matrix, aggregates, and at the interfacial transition zone (ITZ). Different traction–separation laws (TSL) are assigned to different phases to simulate potential crack paths in different regions of the mesoscale concrete specimen. The mesoscale finite element simulations are verified using experimental results from the literature, with a focus on implementing mixed-mode fracture and calibrating its corresponding parameters with respect to the experimental data. In addition, the current study addresses the limited exploration of void effects in mesoscale concrete simulations. By investigating voids of diverse sizes and volume fractions, this research sheds light on their influence on the mechanical behavior of concrete materials. The algorithms for generating cohesive interface elements and concrete microstructures are described in detail and can be easily extended to more complex states. This methodology provides an effective tool for the mesostructural optimization of concrete materials, considering specific strength and toughness requirements.

Characterizing fatigue damage behaviors of concrete beam specimens in varying amplitude load

In this paper, the random and nonlinear mechanical characteristics of the composition distribution of concrete in each phase are investigated to solve the difficulty of fatigue damage test of concrete beam specimens under variable amplitude loading. A three-dimensional (3D) concrete composite random aggregate meso-model of concrete beam specimens is built with Digimat as a composite modeling tool. Subsequently, the bending-tensile strength and fatigue life of the model under four-point bending loading is analyzed and calculated using Abaqus finite element analysis model based on the concrete elastic-plastic damage criterion. The mechanical behaviors of concrete materials under static load failure, multistage fatigue loading, and random fatigue loading are studied. Finally, compared with the test results, the following conclusions are obtained. The random aggregate model and elastoplastic damage mechanics model of concrete composite constructed by concrete in Abaqus and Digimat can better describe the geometric and distribution characteristics of composite structure and aggregate in concrete beams and the mechanical behavior of fatigue and static load failure. The difference is 4.08 % with the experimental results, which verifies the validity and reliability of the numerical simulation model, and the fatigue life of concrete beams under random loading Sra and Srb is 1622 and 164 times, respectively. The research results have certain guiding significance and reference value for accurate calculation of bending and tensile strength of concrete beams under specified raw material and mix ratio and prediction of fatigue damage cracking in airport cement concrete pavement structure.

Experimental study on the size effect on the equation of state of concretes under shock loading

Adopting the classical theory of hydrocodes, the constitutive relations of concretes are separated into an equation of state (EoS) which describes the volumetric behavior of concrete material and a strength model which depicts the shear properties of concrete. The experiments on the EoS of concrete is always challenging due to the technical difficulties and equipment limitations, especially for the specimen size effect on the EoS. Although some researchers investigate the shock properties of concretes by fly-plate impact tests, the specimens used in their tests are usually in one size. In this paper, the fly-plate impact tests on concrete specimens with different sizes are performed to investigate the size effect on the shock properties of concrete materials. The mechanical background of the size effect on the shock properties are revealed, which is related to the lateral rarefaction effect and the deviatoric stress produced in the specimen. According to the tests results, the modified EoS considering the size effect on the shock properties of concrete are proposed, which the bulk modulus of concrete is unpredicted by up to 20% if size effects are not accounted for.

Development of Mesoscale Simulation Approach of Concrete Material and Structural Behavior with Physical Damages with RBSM

Development of Mesoscale Simulation Approach of Concrete Material and Structural Behavior with Physical Damages with RBSM

Modeling and Simulation of the Hysteretic Behavior of Concrete under Cyclic Tension-Compression Using the Smeared Crack Approach.

Concrete structures under wind and earthquake loads will experience tensile and compressive stress reversals. It is very important to accurately reproduce the hysteretic behavior and energy dissipation of concrete materials under cyclic tension-compression for the safety evaluation of concrete structures. A hysteretic model for concrete under cyclic tension-compression is proposed in the framework of smeared crack theory. Based on the crack surface opening-closing mechanism, the relationship between crack surface stress and cracking strain is constructed in a local coordinate system. Linear loading-unloading paths are used and the partial unloading-reloading condition is considered. The hysteretic curves in the model are controlled by two parameters: the initial closing stress and the complete closing stress, which can be determined by the test results. Comparison with several experimental results shows that the model is capable of simulating the cracking process and hysteretic behavior of concrete. In addition, the model is proven to be able to reproduce the damage evolution, energy dissipation, and stiffness recovery caused by crack closure during the cyclic tension-compression. The proposed model can be applied to the nonlinear analysis of real concrete structures under complex cyclic loads.

Strain Rate Influences on Concrete and Steel Material Behavior, State-of-the-Art Review

Strain Rate Influences on Concrete and Steel Material Behavior, State-of-the-Art Review

Mechanical performance of Bio-Inspired Gyroid and Primitive concrete structures under combined compression and torsion Loads: A discrete element method study

Bioinspired lightweight Primitive and Gyroid structures are two well-known TPMS (triply periodic minimal surface) cellular structures. These structures have been shown to possess high specific strength and energy absorption capacity, and thus hold great promise for a range of prefabricated civil engineering applications. As a result, concrete cellular TPMS structures have garnered the attention of researchers. However, prior to this study, no investigation has been carried out on the mechanical properties and failure patterns of concrete Primitive and Gyroid structures under coupled compressive and torsional loads. This lack of knowledge on the behaviour of these structures can lead to safety concerns in construction projects. To better understand the mechanical behaviour of Primitive and Gyroid structures under combined compression and torsion, the discrete element method (DEM) is adopted to simulate the TPMS structures. Both linear contact and nonlinear softbond contact models are utilized to simulate the brittle mechanical behaviour of concrete material. After validating the DEM parameters using published experimental data, the DEM models are subjected to coupled compressive and torsional loads to study their compressive and torsional bearing capacity and cracking patterns. The results indicate that the Primitive based structures outperform the Gyroid based structures in terms of both compressive and torsional resistance. The study is the world's first to reveal that a compressive load enhances the ultimate torsional bearing capacity of TPMS structures, but a torsional load reduces their compressive bearing capacity. Additionally, the loading conditions have little impact on the cracking patterns of the four TPMS structures.

A novel approach in forecasting compressive strength of concrete with carbon nanotubes as nanomaterials

The evolution of nanotechnology in cementitious concrete can be used to enhance the mechanical behavior of concrete and other materials. Thus, the utilization of carbon nanotubes (CNTs) in the concrete cementitious industry will deliver important remedial measures for generating an eco-friendly environment with multifunctional properties. In addition, planning and conducting experimental tests for different samples and testing at varying ages is laborious, time taking and expensive. Consequently, the prediction model looks necessary. Because of the complex nature of contemporary construction materials, empirical and statistical approaches do not work well for such materials; thus, machine learning approaches were utilized for this study. Thus, the process of forecasting concrete strength (CS) can be accelerated by employing soft machine learning (ML) techniques. Moreover, the ensemble of the models is also done for an accurate estimation of the CS with the Python Jupyter Notebook. Decision tree (DT), multilayer perceptron neuron network (MLPNN), and support vector machine (SVM) were utilized as individual approaches. These individual ML models then ensemble with two approaches namely bagging and boosting with twenty sub models. The outcome of the model depicts a robust performance by showing significant correlations (R2) as compared to individual ML. Data points with 282 having contribution factors (e.g., curing (days), cement (kg/m3), water to binder (w/b), fine aggregate (kg/m3), nanomaterial as carbon nanotubes (%), coarse aggregate (kg/m3), and CS were used as input parameters for ML modeling. To ensure that each model is as accurate as possible, cross-validation (CV) with K-folding and statistical error analysis (i.e., MAE, MAE, and RMSE) was utilized. The result reveals that the ensemble algorithm with bagging and boosting give robust correlation R2 ranging from 0.9 to 0.95. Moreover, DT with Ada-boost yields a strong R2 of about 0.93. Similarly, ensemble model of SVM and MLPNN with boosting depicts R2 = 0.93 and 0.94 respectively. K-fold cross-validation confirms the model’s accuracy with minimal statistical error. Also, statistical checks reveal that the ensemble model provides an increase in the overall performance by showing minimal error as compared to standalone method.

Finite element modeling of precast reinforced concrete wall with dual boundary elements under lateral load

This study aimed to stimulate the structural behaviour of the precast wall PC with dual boundary elements under constant axial load and incremental lateral load in terms of displacement control and assess its response based on the load–displacement response, stiffness degradation and modes of failure using Abaqus Software and validate the result of the tested specimen. Two approaches were used for defining the interaction between the steel reinforcement and the surrounding concrete where the high-stress regions are. Friction and cohesive behaviour using traction separation law were employed to define the interaction between the interfaces of the PC wall and post-cast concrete boundary elements. Furthermore, this study primarily focused on the nonlinear behaviour of concrete and steel materials, the bond-slip behaviour between concrete-to-steel interface, the interaction between precast and post-cast concrete interfaces, and load and boundary conditions. The concrete damage plasticity model was adopted to simulate the concrete behaviour and the cohesive and frictional behaviour to model the interaction between precast and post-cast concrete interfaces. The findings show that the initial response of both FE models agreed well with test rested specimen. However, Model I exhibited a stiffer response up to the yielding point. Furthermore, both FE models continued to exhibit ductile response, showing that the right-hand side post-cast cornet boundary element didn’t experience total crushing at the bottom right concrete.

Numerical Modeling of Interface Bond Behavior Between Hybrid Steel-PVA Fiber-Reinforced Engineered Cementitious Composite and Concrete

This paper presents a numerical study on interfacial behavior between hybrid steel and polyvinyl-alcohol fiber-reinforced engineered cementitious composite (HSP-ECC) and concrete. Concrete damage plasticity (CDP) model was used to define the mechanical behavior of HSP-ECC and concrete materials. Interfacial behavior was simulated for as-cast and sandblasted surfaces by adopting traction-separation constitutive model. Key interface parameters were determined by calibration of finite element (FE) modeling results with experimental results. The FE modeling results illustrated the reliability and efficiency of the proposed numerical approach in the prediction of interface bond behaviors between HSP-ECC and concrete for different degrees of surface roughness.

Polymorphic Uncertain Structural Analysis: Challenges in Data‐Driven Inelasticity

AbstractThis contribution addresses polymorphic uncertainty quantification within structural analysis of reinforced concrete structures composed of heterogeneous concrete and reinforcement (e.g. steel bars or carbon fibres). The macroscopic material behaviour of concrete is strongly dependent on the mesoscopic heterogeneities, which are considered by multiscale modelling. The heterogeneous mesoscopic material behaviour is characterized by representative volume elements (RVE) and the transition of scales is carried out by utilizing numerical homogenization methods.The concept of data‐driven computational mechanics enables material model free finite element analyses directly based on material data sets, overcoming the necessity of assumptions in material modelling. This approach mainly consists in assigning a stress‐strain state, which leads to a minimum of an objective function and fulfils equilibrium as well as compatibility constraints of every integration point. Inelastic material behaviour is taken into account through the definition of local data sets containing only data set states which are consistent with respect to the past local history . The realistic modelling of structures requires the consideration of data uncertainty. Generalized polymorphic uncertainty models are utilized in order to take variability, imprecision, inaccuracy and incompleteness of material data into account by combining aleatoric and epistemic uncertainty models.In this contribution, a computationally efficient approach for the consideration of data sets containing uncertain stress‐strain states within data‐driven analysis based on information reduction measurements is presented. Due to generalization, the approach is applicable to various aleatoric, epistemic and polymorphic uncertainty models. The identification of admissible local data sets for taking inelastic material behaviour into account within data‐driven analysis is realized by an energy based history parametrization which is extended to uncertain data. An approach for the efficient selection of these local data sets is presented and challenges in data‐driven inelasticity, particularly in the use case of polymorphic uncertain analyses of concrete structures, are pointed out.

The Effect of Elevated Temperatures on the Behavior of Concrete Material

Abstract: The purpose of this study was to provide an overview of the effect of elevated temperature on the behavior of concrete materials. The effects of elevated temperatures on the properties of common portland cement concretes and manufacturing materials are summarized. The effect of elevated temperature on conventional concrete, GGBS concrete and BFS concrete is considered and the performance is compared with the strength of conventional concrete. Concrete in case of an unexpected fire, the properties of the concrete will change after the fire. The building must be designed to withstand high temperatures and also mainly fire. When exposed to high temperatures, such as during a fire, the mechanical properties of concrete such as strength, modulus of elasticity and volume stability are significantly reduced. Concrete structure is exposed to high temperatures, it degrades in many different ways, such as color, compressive strength, elasticity, and high temperature affects concrete density and surface appearance

Identification of optimum reinforcement detailing using tuned CDP parameters in RC beam under drop-weight impact

A numerical investigation has been carried out in this study to investigate the dynamic response of RC beam subjected to low velocity impact. Concrete damage plasticity (CDP) model including the strain rate effects is used in this study to simulate material behavior of concrete. Sensitivity analysis is performed to understand the influence of crucial CDP parameters and to obtain tuned CDP parameters of concrete for accurate prediction. Then an attempt has been made to identify and benchmark effects of reinforcement detailing parameters in effective impact resistance of reinforced concrete beams for inclusion in design requirement as per specific performance level sought. The results obtained from the present model have been coherently validated with the established experimental results. Energy distribution in major dissipating mechanisms like plastic flow (plastic dissipation energy, PD), crack surface nucleation (damage dissipation energy, DMD) and global failure modes are investigated to quantify the exclusive effects of both flexure and shear reinforcement details. It is observed that tensile reinforcement helps to reduce the permanent plastic displacement and flexure cracks. But it is not that much effective for overall damage prevention and specifically the shear cracks. Stirrups spacing in stead of diameter is found to be the controlling details for reducing DMD. Hence the use of optimum tensile reinforcement along with closely spaced stirrups is found to be the most effective way to improve structural behavior under impact loading and present framework can effectively quantify the effects of such detailing.

Numerical Modeling Technique of Damage Behavior of MaSonry-Infilled RC Frames

The damage pattern of masonry-infilled reinforced concrete (RC) frame structures in earthquake events is complicated, and understanding the detailed failure behavior of these structures and modeling it accurately has been a challenging task. In this paper, the extended finite element method (XFEM) is introduced to reproduce arbitrary cracks initiating and propagating in concrete frame and masonry units, combined with interface elements to model various behaviors of masonry-infilled RC frames. Within the finite element analysis program FEAP, a user element subroutine is adopted for the incorporation of XFEM and two types of extended finite elements with and without crack tip enrichments are built to simulate the behavior of concrete material for frame members and masonry blocks for the infill panel, respectively. In addition, a macro command is created to check the crack-propagation criterion and update crack and enrichment information. Furthermore, numerical examples are performed with existing test data, which reveal the efficiency of the implementation procedure. A comparison of the analytical and experimental results show that the proposed modeling can be used to predict the crack and failure process and the load-bearing capacity curves of the structures and reflect accurately the interaction of masonry infill and RC frames.

Experimental and numerical study on nonlinear basic and drying creep of normal strength concrete under uniaxial compression

The material behavior of concrete is highly nonlinear and time-dependent. In particular, the evolution of deformation due to creep is crucially dependent on the acting stress and the environmental conditions. Numerous experimental campaigns for determining the complex material behavior of concrete in various loading conditions and environmental conditions can be found in the literature. However, the experimental investigation of the time-dependent deformation due to high sustained loading, i.e., nonlinear creep, has received less attention. Especially, the evaluation of the impact of different environmental conditions on nonlinear creep is still pending. In this contribution an experimental study on basic and drying creep under moderate and high uniaxial compression is presented. The experimental results indicate that the nonlinearity of the deformation due to creep in high uniaxial compression is dependent on the environmental conditions. Additionally, the capability of selected constitutive models for representing nonlinear creep is assessed in a numerical study based on the novel experimental results.

Numerical investigations on the viscoelastic-damage behaviors of RIVE-induced concrete

Due to the remarkable influence of aggregate characteristics on the mechanical behaviors of concrete materials, and in particular the microcracking development, complex aggregates shapes instead of widely used spherical-shape need to be considered in advanced numerical approaches. Apart from that, in numerical simulations, an extra consideration of the influences of concrete’s heterogeneity on its softening behaviors is strongly recommended by the scientific community. In this context, the softening behaviors of concrete materials undergoing heterogeneous expansion in the aggregates due to fast neutron radiation were investigated in the present paper, and the influences of both aggregate shape and the heterogeneity of aggregate expansion were considered. According to the real shapes of aggregates, polygon-shaped aggregates with random orientation were placed into a 3D numerical concrete specimen, and a two-stage finite element (FE) approach allowing a coupled thermal–mechanical analysis was proposed. In the first stage, the temperature field evolves in time and the 3D concrete specimen was estimated. In the second stage, the temperature- and neutron fluence-dependent heterogeneous expansion in the aggregates was calculated and introduced into the 3D mesoscopic model, and the development of microcracks in the concrete, the resulting mechanical responses, the loss in mechanical properties of the radiation-induced concrete was evaluated. Surmounting the limitations due to the spherical-shape of aggregate and the homogeneous assumption of the aggregate expansion in the concrete, the present paper developed a new methodology in which the combined effects of aggregate’s shape and the heterogeneous distribution of aggregate expansion on the mechanical properties of radiation-induced concrete were considered, permitting evaluating the changes in the dimensional and mechanical properties of radiation-induced concrete. The proposed model provides a reference to assess the long-term durability and the structural integrity of nuclear power plants.