Behavior Of Concrete Research Articles

Mechanical Behavior Analysis of Lightweight Concrete Reinforced by Metalized Plastic Waste Fibers

This study evaluates the impact of adding metalized plastic waste (MPW) fibers to lightweight concrete that is used as a filler material in building slopes and bridge ramps. The goal is to open up new opportunities for recycling plastic waste and promote a more sustainable and productive construction industry. This study examined the mechanical behavior of lightweight concrete (LC) at 3, 28, and 90 days, both with and without MPW fiber (1%, 2%, and 3%). Compression tests, 3-point bending tests, and pull-out tests were used to measure the fibers' compressive strength, flexural strength, and maximum load-bearing capacity, respectively. According to the results, the compressive strength (CS) and elasticity modulus (MOE) decreased with increasing fiber content when MPW fiber was added. In the long term, the CS and MOE decrease for the LC containing 3% MPW fiber was 8% and 7%, respectively, lower than for the control concrete. At 90 days, the flexural strength of the LC with 1% MPW fiber was marginally higher than that of the control concrete, rising by 2.40%. After this initial rise, however, the flexural strength declined as the fiber concentration increased, eventually reaching an 8% reduction for LC with 3% MPW fiber.The optimum method for determining maximal load-bearing and comprehending the deformation mechanism is hence the fiber pull-out test. The microstructure study of the LC examined how the pull-out test affected the quality of bonding at fiber-matrix interfaces. The tensile and flexural strength of lightweight concrete are enhanced by MPW fiber's ability to bear significant pulling stress.

CRACKING PATTERN ANALYSIS OF THE TURNING BAND METHOD (TBM) APPLICATION ON A SINGLE-REINFORCEMENT BAR CONCRETE BEAM MODELLING USING THE MAZARS DAMAGE

The development of crack patterns in reinforced concrete structures is a randomly stochastic process influenced by the heterogeneous nature of concrete materials, which impacts the sensitivity to damage and variability in mechanical properties. The numerical simulation of damage pattern appearance on the reinforced concrete for special building structures needs a realistic result, especially in terms of crack distribution. The Turning Band Method (TBM) serves as a tool for assessing the variability of concrete heterogeneity, functioning as an operator to generate a random variable for each specific field. In this study, the investigation of crack patterns in reinforced concrete structures involves using a simple concrete beam sample, measuring 10x10x50 cm3, with a single longitudinal reinforcement cast in the centre. This beam is subjected to an axial tensile loading, while the Mazar Damage Model is employed as the concrete behaviour law. Through the implementation of The Turning Band Method (TBM) and the variation of the random field parameters, distinct crack patterns are observed, not only the number but also the locations of cracks. The use of a smaller correlation length showed 2 cracks while the larger size had around 1 to 3 cracks, with the first crack localizations of each sample generally occurring in the middle surface, in which a noticeable contrast to non-TBM modelling just displays 1 crack. Furthermore, the resulting probability of cracks for ten random draws demonstrates similarity to experimental tests and numerical simulation of the previous study, both at global and local levels.

A path-dependent stress-strain model of FRP-confined circular concrete columns derived from an energy balance approach

It is generally believed that the use of fibre-reinforced polymer (FRP) confinement can effectively improve the strength and ductility of concrete. Passive confinement is one of the key features of the behavior of FRP-confined concrete. Analysis-oriented models for passively confined concrete have been established on the base of the active confinement model by many researchers. Among them, a stress path-independent assumption was made for those passively confined concrete. However, in recent years, numerous researchers have found that the influence of stress path on the stress-strain relationship of confined concrete cannot be neglected. Therefore, in order to further understand and simulate the uniaxial behavior of FRP-confined concrete, this paper presents a stress path-dependent model of FRP-confined concrete based on an energy balance approach in which the extra work done by the active confining pressure in the stress path-independent model is considered. Firstly, experimental data comprising 341 sets of FRP jacket confined concrete tests and 28 sets of concrete-filled FRP tube (CFFT) tests were collected. Subsequently, the stress paths of the two types of specimens were identified based on the properties of FRP materials, and then the energy balance assumption was introduced, and finally a new stress path-dependent model was established using the energy balance approach. By comparing the predictions of the proposed model with collected experimental data and those of several existing models, it was observed that the proposed model can more accurately predict the ultimate stress of FRP-confined concrete and exhibit good agreement with the experimental stress-strain curves.

Verification, validation, and uncertainty quantification (VVUQ) in structural analysis of concrete dams

Over the past three decades, advancements in computational power and numerical methods have significantly enhanced the role of structural analyses in the design and safety assessment of dams. Simulating concrete dam behavior, particularly in interactions with reservoir water and rock foundations, poses formidable computational challenges. Additionally, the need to define uncertainties related to material parameters, loading conditions, and modeling strategy adds complexity to the modeling process, therefore, quantifying sources of uncertainty is crucial for maintaining credibility and confidence in analysis results. This paper provides a synthesis and an overview of existing research and presents a generic framework for evaluating the credibility of advanced structural analysis methods for concrete dams, with a focus on their limitations and associated uncertainties. The methodology includes a comprehensive process for structural analysis, verification, validation, and uncertainty quantification, aiming to facilitate condition assessments of concrete dams.

Pre-and post-heating bar-concrete bond behavior of CFRP-wrapped concrete containing polymeric aggregates and steel fibers: Experimental and theoretical study

The present research attempted to explore the impact of steel fibers and carbon fiber-reinforced polymer (CFRP) sheets on the pre-and post-heating bond behavior of steel bars in high-strength concrete incorporating waste polyethylene terephthalate (WPET) by conducting the pullout and beam tests and in both pullout and splitting failure modes. To achieve this aim, one hundred and forty-four cubes and forty-eight prisms were cast for the pullout and beam tests, respectively. The variable parameters included the replacement ratio of the fine aggregates with waste polyethylene terephthalate (WPET) particles (0 % and 10 % by volume), steel-fiber content (0 % and 1 % by volume), bar diameter (12-and 16-mm), target temperature (25, 200, and 600 °C), and confinement level (no confinement or CFRP wrapping applied after the thermal regime). Bond strength, bond stress-slip behavior between rebar and concrete, failure mode, and rebar debonding energy were among the parameters investigated after cooling. The results showed that in contrast with the positive effect of CFRP sheets on debonding energy, steel fibers have a positive effect on debonding energy only at 600 °C. Steel fibers did not offset the negative effect of polymeric aggregate, negatively changed the pullout mode to a mixed pullout/splitting failure at 200 °C, and tended to favor splitting failure mode to mixed mode at 600 °C. Moreover, steel fibers negatively affected the bond strength of pullout specimens in both confined and unconfined conditions, especially at 25 and 200 °C, and were less effective than CFRP sheets in avoiding splitting. Small-diameter bars reduced the negative effect of steel fibers on the bond, while polymeric aggregate tended to enhance the bond strength differences between large- and small-diameter bars. The effect of increasing the bar diameter on the effectiveness of CFRP sheets on the bond strength was not clear, but as a general trend, the effectiveness increased with the increase of the bar diameter. A predictive model based on the experimental results of this study and other studies was proposed as well to introduce the positive effect of the CFRP confinement and the dubious effect of steel fibers and polymeric aggregate on bond strength.

Mechanical characteristics and structural performance of rubberized concrete: Experimental and analytical analysis

Rubberized concrete is referred to as "green concrete" by replacing fine aggregate with used tire rubber. However, although significantly increasing ductility, rubber particles lowered compressive strength. The study aimed to find the optimum ratio of crumb rubber (C-Ru) to employ in large scale elements. Firstly, the effect of C-Ru treatment and content on concrete mechanical behavior is examined. The experimental program contains 96 cubes and 78 cylinders using different percentages of untreated/treated C-Ru with portions from 5 % to 30 % replacing the sand. Then, four beams were produced with 5, 10, and 15 % sand volume substitution by C-Ru to investigate the effects of rubber content on structural performance and compared with conventional beam. It is found that C-Ru treatment has less enhancement for concrete fresh properties (workability) for using small ratios of rubber and this enhancement increases to reach 20 % for higher rubber content ratio while the comparable enhancement for hardened properties (compressive strength). In addition, well washing of the C-Ru after treatment did not affect the fresh RuC properties, while the improved the hardened properties of RuC (compressive and tensile strengths). Increasing the C-Ru content ratio decreased concrete fresh and hardened properties. Untreated C-Ru not more than 15 % as a replacement of fine aggregates is preferred to avoid large strength reductions while benefiting workability, economy, and safety. While the addition of C-Ru to the concrete mix increased the ductility, toughness, and self-weight of the beams, it also decreased their flexural capacity. Finally, the finite element analysis using ANSYS is used to compare with experimental results and thus it could accurately model behavior of rubberized concrete as a complex material that recommended for further studies.

Influence of Printing Interval on the Imbibition Behavior of 3D-Printed Foam Concrete for Sustainable and Green Building Applications

Foam concrete is highly valued as a sustainable cement-based material, but the development of 3D-printed foam concrete (3DPFC) has remained constrained. This study investigated the influence of printing interval on the microstructure and imbibition behavior of 3DPFC. The results revealed that horizontal interlayers are broader compared to vertical interlayers, leading to more significant imbibition. For X-oriented 3DPFC, the vertical interlayer was rapidly occupied by water after imbibition, forming an elliptical moisture profile. For Y-oriented 3DPFC, the moisture profile appeared more convoluted, mainly surrounding the horizontal interlayers but shifting at intersections with the vertical interlayers. In Z-oriented 3DPFC, where only tight horizontal interlayers were present, interlayer imbibition was almost negligible. Additionally, when the printing interval was less than 15 min, imbibition was primarily restricted to the top filament since the bottom filament was compacted by the filament above. Conversely, with a printing interval longer than 15 min, the bottom filament hardened before the setting of the top filament. This allowed the surface of the bottom filament to be compacted by the top filament, resulting in a dense interlayer that offers better resistance against imbibition compared to the matrix of 3DPFC. This work contributes to the advancement of green building technologies by providing insights into optimizing the 3D printing process for foam concrete, thereby enhancing its structural performance without compromising the designated air content and consistency of the foam concrete, facilitating a more efficient utilization of materials and a reduction in overall material consumption.

Effects of mineral additions on the rheology of self-compacting concrete: a review

The rheological study of concrete is crucial for the construction sector because of its influences on the casting process and hardened properties. This is even more important when designing and producing self-compacting concrete (SCC). By controlling yield stress and plastic viscosity, it is possible to predict and optimise the flowability of SCC. Understanding the rheological behaviour of SCC is a major step in achieving adequate flow behaviour to fill the formwork without any sign of segregation or blockage and hence yielding satisfactory performance of hardened concrete. This paper provides a critical and detailed review on rheological properties of SCC based on studies published in recent years. The rheological models for characterising the flow behaviour of fresh concrete are briefly assessed. The influence of water to cementitious materials ratio on SCC properties is also discussed. A comprehensive review on the influence of fine additions (i.e. fly ash, ground blast furnace slag, silica fume, metakaolin and limestone powder) on SCC rheology has also been presented in this review.

When identification with your group matters: leader consultation in response to constructive follower voice

ABSTRACT Integrating social exchange and social identity theory, the present research investigates to what extend and why follower social identification matters for the relationship between constructive follower voice and leader consultation. We argue that when the voicing follower is strongly identified with the joint workgroup, leaders will positively reciprocate constructive voice with consultation, as a concrete participatory leader behaviour, because they perceive this follower’s voice as more constructive. We conducted a multi-wave field study (N = 177) and two pre-registered experiments (N = 199 and N = 528). Overall, we found that leaders consulted constructive voicers more when they were strongly rather than weakly identified with the joint workgroup, because they perceived their voice as a more constructive contribution. Comparison with a neutral control condition further showed that this effect was mainly due to leaders refraining from consultation when voicing followers were weakly identified. Additionally comparing constructive voice to two other types of proactive expressions (i.e. destructive voice, supportive voice) in Study 3 showed that followers’ weak social identification attenuated the positive effect of voice on leaders’ perceived voice constructiveness only for constructive voice (i.e. challenging and promotive) but not for non-challenging (i.e. supportive) or non-promotive (i.e. destructive) follower expressions.

A modified bond-based peridynamic approach for rigid projectile perforation on concrete slabs

Peridynamic (PD) has a unique advantage in describing the crack growth and fragmentation of brittle materials. Concerning the dynamic behaviors and failure patterns of concrete slabs under projectile perforations, a modified bond-based PD approach maintaining both the easy implementation and computational stability characteristics was firstly developed from the following three aspects, (i) a rate-dependent PD constitutive model was proposed for describing the dynamic behaviors of concrete; (ii) a progressive damage criterion considering the tension-compression anisotropy, softening behavior, and strain rate effect of concrete was incorporated to more accurately reproduce the damage and failure of concrete; (iii) an improved micro-modulus function related to bond length was introduced to reveal the internal length effect of bond force. Then, numerical simulations of projectile perforation on concrete slabs by utilizing the developed modified bond-based PD approach, as well as the corresponding sensitivity analyses of discretization parameters including horizon size and particle spacing were performed. Based on the recommended horizon size and particle spacing, the predicted residual velocity of projectile and failure patterns of concrete slabs exhibited an excellent agreement with the test data. Furthermore, by comparisons of the traditional bond-based PD and classical finite element methods, the superiority of developed approach in describing the perforation damage of concrete targets against projectile impact was demonstrated. Finally, the modified bond-based PD approach was employed to blind simulate the projectile normal and oblique perforating multi-layered spaced concrete target plates. It was found that the modified PD model reasonably predicted the terminal ballistic trajectory, deflection angle, and residual velocity of projectile, as well as the failure patterns of target plates. The present work provides a new way to predict the terminal ballistic effect of projectile and dynamic behaviors of concrete slabs.

Thermomechanical behavior of concretes with addition of non-functionalized and functionalized carbon nanotubes

The development of more durable materials is crucial for ensuring user safety in construction, particularly under adverse conditions. Carbon nanotubes are currently being studied as components in civil engineering composites due to their high tensile strength, high modulus of elasticity, high failure temperature, and satisfactory electrical and thermal conductivity. These nanotubes can be either non-functionalized (CNT), the more conventional type, or functionalized (CNT-F).This study aims to evaluate and compare the thermomechanical properties of concrete with the addition of CNT and CNT-F, analysis that still has not been extensively covered in the literature. The results show that the addition of nanomaterials did not significantly impact the mechanical properties of the concrete, although CNT-F exhibited slightly better performance. At 300 °C, CNT-F concrete experienced a 26 % reduction in strength, compared to a 34 % reduction in the control concrete and a 57 % reduction in concrete with CNT. At 900 °C, all types of mixtures were degraded, showing no significant difference in performance. This behavior was expected, as carbon nanotubes deteriorate at around 600 °C and are no longer effective at higher temperatures. Additionally, this trend was observed in other mechanical properties, such as tensile strength. It was also found that dispersing the nanotubes uniformly within the concrete mixture remains a challenge, as they can concentrate in specific regions of the composite. Finally, it's important to note that incorporating nanotubes into concrete helps store carbon within the material, preventing its release into the atmosphere and thereby reducing environmental damage.

Intrinsic self-sensing piezoresistive behaviors of ultra-high strength alkali-activated concrete

In this work, the self-sensing piezoresistive behaviors of carbon fiber (CF)-reinforced ultra-high strength concrete (UHSC) are investigated using alternating current impedance spectroscopy (ACIS) technique. The effects of different fiber contents, fiber lengths, and curing ages are considered. The electrical behaviors of alkali-activated slag (AAS)-based UHSC (AAS-UHSC) and ordinary Portland cement (OPC)-based UHSC (OPC-UHSC) at similar strength from 80 to 110 MPa are compared. The findings reveal that the intrinsic electrical resistivity of AAS-UHSC is significantly lower than that of OPC-UHSC, approximately 1/30 of the latter. The addition of CF results in a substantial reduction in electrical resistivity for both UHSC types, with reductions of up to 96 %, and shows better compatibility with the AAS-UHSC matrix. The piezoresistive properties of CF-reinforced UHSC are investigated using ACIS at a fixed frequency and further evaluated by parameters including sensitivity, linearity, repeatability, and hysteresis. The results indicate that plain OPC-UHSC does not exhibit piezoresistivity, whereas the addition of CF enhances both the sensitivity and linearity of piezoresistivity. In contrast, AAS-UHSC demonstrates inherent piezoresistive behaviors even without CF. The introduction of 0.5 wt% CF improves the sensitivity (by up to 50 %) and linearity (R2 increased from 0.76 to above 0.90) of piezoresistivity in AAS-UHSC. However, increasing the CF content to 1.0 wt% diminishes the sensitivity (by up to 62.5 %) due to decreased fiber dispersion uniformity. Moreover, the addition of 1.0 wt% 8-mm CF reduces the hysteresis of UHSC regardless of the binder type, with the maximum reduction reaching 62.2 %.

Behavior of Beam-Column Joint Self-Compacting Concrete (SCC) Using Steel Fiber 5D under Lateral Cyclic Loading

Behavior of Beam-Column Joint Self-Compacting Concrete (SCC) Using Steel Fiber 5D under Lateral Cyclic Loading

Fracture evolution characteristics of asphalt concrete using digital image correlation and acoustic emission techniques

The cracking damage of asphalt concrete significantly affects the service life of pavement. The objective of this research is to investigate fracture mechanisms of asphalt concrete by employing a synergistic approach combining digital image correlation (DIC) and acoustic emission (AE) techniques under three-point bending tests. Firstly, the crack tip opening displacement (CTOD) and the fracture process zone (FPZ) derived from DIC were utilized to classify fracture stages and describe the entire crack propagation process. Meanwhile, AE-related parameters were applied to detect the internal damage and fracture characteristics. Subsequently, the results from DIC and AE were utilized for comparative analysis to evaluate the cracking resistance of different materials. Finally, the fractal dimension and AE b-value were used to distinguish the characteristics of the critical damage conditions. The results indicated that both techniques are effective in classifying the fracture stage of asphalt concrete. DIC can visualize and analyze crack propagation processes and paths on concrete surfaces, especially at the stage of macrocrack initiation and propagation. AE allows for continuous monitoring and highly sensitive detection of early-stage damage inside concrete. The distinct advantages of DIC and AE result in different fracture stage identification results at the early stage, but consistent after the appearance of macrocracks. Based on the relationship between CTOD and AE cumulative count, a simple approach is proposed to directly evaluate the cracking resistance of different asphalt concretes. The formation of macrocracks in asphalt concrete can be reflected by a shift where the correlation dimension drops steeply to the minimum value, and a minimum inflection point in the AE b-value curve acts as a precursor of complete fracture. The research offers an in-depth insight of both surface deformation and internal damage, thus enhancing the understanding of crack growth behavior and fracture process in asphalt concrete.

Shrinkage evolution and mechanism of self-curing concrete cooperatively cured with superabsorbent polymers and waterborne epoxy coatings

Shrinkage-induced cracking is a common phenomenon in concrete structures. To reduce concrete shrinkage, herein, a novel curing approach involving the concurrent application of internal superabsorbent polymers (SAPs) and external waterborne epoxy coatings (WECs) was adopted. Subsequently, the combined effects of the SAPs and WECs on the internal temperature, water retention behavior, relative humidity, and shrinkage performance of concrete were investigated. Furthermore, their underlying shrinkage-mitigation mechanisms were clarified and verified through mercury intrusion porosimetry tests. Results revealed that increasing the WEC application rates and number of spraying turns increased the relative humidities and reduced the shrinkage strains of the concrete specimens. The combined use of SAPs and WECs led to considerable reductions in the specimens’ humidity drop, water loss, and shrinkage values. The water losses of the concrete specimens exerted more considerable impacts on their relative humidity and shrinkage compared to their cumulative temperatures. Furthermore, the combination effects of the SAPs and WECs reduced the median pore diameters and increased the fractal dimensions of gel pores, thus triggered a reduce in capillary tension, and further mitigated the development of shrinkage strains. Overall, this study underscores the critical roles of evaporation, temperature, relative humidity, and pore-structure parameters on the shrinkage behavior of concrete. Additionally, it highlights the effectiveness of the combined application of SAP-based internal curing and WEC-based external curing, offering a feasible approach and technical support for reducing shrinkage in concrete structures.

Experimental study on compressive behavior of compressive stress-loaded concrete at different strain rates under simulated acid rain environment

Concrete is typically under stress when exposed to acid rain corrosion. This study aimed to assess the physical and compressive behavior of compressive stress-loaded concrete (CSLC) under a simulated acid rain environment. The compressive stress states (0 %, 15 %, 20 %, 25 %, and 30 % of its compressive strength) and a simulated acid rain environment (pH = 2) were replicated in the laboratory. A compression tester was used to control loading at different strain rates (0.5 × 10−3/s, 10−3/s, 10−2/s, and 10−1/s). The results elucidate a three-stage pattern in the mass degradation of CSLC, accompanied by shallower corrosion depth compared to unstressed concrete. During the initial phases of the corrosion, compressive stresses at levels of 15 %, 20 %, and 25 % enhance the concrete's compressive strength by 2.8 %–10.1 %. However, this initial enhancement transitions to deterioration as external stress levels and corrosion time increase. SEM images validate these findings, showcasing initially denser internal structures in CSLC (15 %–25 %) compared to unstressed concrete (0 %), but severe deterioration at a 30 % stress level. Additionally, the strain-rate effect is more pronounced in unstressed concrete initially, with enhancement ranging from 12 % to 15 %, but gradually diminishes with increasing stress levels and corrosion time. It can be concluded that service stress significantly accelerates the long-term deterioration of concrete exposed to acid rain and should not be ignored in practical analysis.

A missing data processing method for dam deformation monitoring data using spatiotemporal clustering and support vector machine model

Deformation monitoring is a critical measure for intuitively reflecting the operational behavior of a dam. However, the deformation monitoring data are often incomplete due to environmental changes, monitoring instrument faults, and human operational errors, thereby often hindering the accurate assessment of actual deformation patterns. This study proposed a method for quantifying deformation similarity between measurement points by recognizing the spatiotemporal characteristics of concrete dam deformation monitoring data. It introduces a spatiotemporal clustering analysis of the concrete dam deformation behavior and employs the support vector machine model to address the missing data in concrete dam deformation monitoring. The proposed method was validated in a concrete dam project, with the model error maintaining within 5%, demonstrating its effectiveness in processing missing deformation data. This approach enhances the capability of early-warning systems and contributes to enhanced dam safety management.

Predicting the compressive strength of self-compacting concrete by developed African vulture optimization algorithm-Elman neural networks

The compressive strength of concrete depends on various factors. Since these parameters can be in a relatively wide range, it is difficult for predicting the behavior of concrete. Therefore, to solve this problem, an advanced modeling is needed. The aim of the literature is to achieve an ideal and flexible solution for predicting the behavior of concrete. Therefore, it is necessary to develop new approaches. Artificial Neural Networks (ANNs) have evolved from a theoretical method to a widely utilized technology by successful applications for a variety of issues. Actually, ANNs are a strong computing tool that provides the right solutions to problems that are difficult to use conventional methods. Inspired by the biological neural system, these networks are now widely used for solving a wide range of complicated problems in civil engineering. This study’’s target is evaluating the performance of developed African vulture optimization algorithm (DAVOA)-Elman neural networks (ENNs) by considering different input parameters in predicting the self-compacting concrete compressive strength. Hence, once 8 parameters and again to get as close as possible to the prediction conditions in the laboratory, 140 parameters entered to the improved version of Elman Neural Networks as input. According to the results, the element network has the lowest mean squares of the test error in predicting the compressive strength of 7 and 28 days in 100 repetitions. Further, in predicting both compressive strengths, the element grid with the Logsig-Purelin interlayer transfer function has the lowest test error, which determines the optimal transfer function. Moreover, the results showed that DAVOA as a reliable tool with time and cost savings have high power in predicting the desired characteristics. Also, in predicting both 7-day and 28-day compressive strength, networks built with 140 parameters have a 74.54 and 70.44% improvement in test error over 8-parameter networks, respectively, which directly affects this effect. Further parameters are considered as input to the network error rate in predicting the desired properties.

Tensile behavior of rubberized high strength-high ductile concrete under elevated temperature

High Ductility Concrete (HDC) exhibits unique mechanical properties at ambient temperatures, but its behavior at elevated temperatures is less understood. This study examines the mechanical behavior of Rubber-modified High-Strength High-Ductility Concrete (R-HSHDC) across various temperatures (25, 75, 100, and 150°C) and rubber replacement ratios. The study explores R-HSHDC’s microstructure, failure modes, strength, and deformability, focusing on its pseudo-strain hardening behavior. Results indicate that below 100°C, R-HSHDC displays typical HDC characteristics, including multiple cracking and high tensile deformation. As temperature increases, both initial cracking strength and tensile strength decrease, while crack control and energy absorption are maintained. Moderate rubber powder reduces initial cracking strength and enhances tensile deformability. When using R-HSHDC as a structural material, temperature effects must be considered. At higher temperatures, R-HSHDC is more suitable for crack control and energy dissipation. This research improves understanding of R-HSHDC's behavior at different temperatures, aiding in structural and functional design for high-temperature environments.

Numerical prediction of beam capacity using the new constitutive model based on concrete biaxial behavior

The biaxial strength of concrete exhibits intriguing nonlinearity and scattering, posing challenges to the assessment of building structural safety. Experiments have confirmed that biaxial strength envelopes can manifest concave, quasi-linear, and convex shapes. Despite various empirical formulas being proposed to describe this behavior, they cannot be applied to finite element simulations due to the absence of a constitutive perspective. To study the mechanisms forming the shape of strength envelopes, a novel three-invariant model constitutive model is proposed, which reveals the characteristics of the envelopes resulting from the coupling effect of hydrostatic pressure and Lode angle. By adjusting the model parameters, it effectively describes concave, quasi-linear, and convex envelopes. The model's accuracy and compatibility were validated against experimental data spanning various concrete types, with compression strengths ranging from 19.29 to 96.5 MPa and tension-compression ratios form 0.056 to 0.095. To investigate how biaxial strength impacts the capacity of beams, numerical experiments were conducted on notched and intact beams based on the proposed model. The results underscored that beams prepared using concrete with convex envelopes exhibited higher capacity compared to those with quasi-linear envelopes. Therefore, conducting biaxial tension-compression experiments is recommended to accurately evaluate beam bearing capacity. The proposed model is expected to have further applications in the safety evaluation of building structures.