Concrete Damaged Plasticity Research Articles

Statistical approach of performance-based uncertainty quantification of prestressed concrete containment structures for internal pressure capacity

With several experiences on economic losses and environmental impacts caused by serious accidents, the ultimate internal pressure and failure modes of Prestressed Concrete Containment Structures (PCCSs) during severe accidents have gained greater attention. Regulatory Guide allows the use of a 3D Finite Element (FE) model to determine the containment internal pressure capacity, because the experiments of PCCSs are a very cost and time-consuming process. In this study, an FE model of PCCS tested at Sandia National Laboratories is developed to identify an effect of parameters in the Concrete Damage Plasticity (CDP) model on the response of the PCCS and is validated from the experimental data. In addition, a closed-form equation is developed to predict the responses of the PCCS through a regression analysis in conjunction with the validated FE model and performance-based uncertainty quantification of the PCCS is estimated by numerical analysis and the closed-form equation. The developed closed-form equation achieves high accuracy of 98% and the probabilistic characteristic of the PCCS obtained from the equation well represents the one obtained from the validated FE model. The closed-form equation rarely requires computational cost to investigate the probabilistic responses of the PCCS.

Numerical Simulation of Explosive Storage Underground Structure Subjected to Blast

In this study, finite element (FE) analysis of underground structure is carried out, which is subjected to the internal blast loading and the structure is surrounded with soil media. Three different methods to analyze the effect of blast loading on structure, i.e. ConWep, smooth particle hydrodynamics (SPH), and couple Eulerian-Lagrangian (CEL) are used for the simulation of blast loading using ABAQUS/ExplicitⓇ. Concrete damage plasticity (CDP), Mohr–Coulomb, Johnson–Cook (JC) plasticity model, Jones–Wilkins–Lee (JWL) equation of state and ideal gas are utilized for defining behavior of concrete, soil, steel, explosive and air, respectively. FE analysis is performed to compare the behavior of structure under different blast modelling methods. The effect of different explosive weights is considered to see the impact of the blast load on the structure. For parametric analysis, three explosive weights, 3[Formula: see text]kg, 5[Formula: see text]kg, and 10[Formula: see text]kg of TNT (trinitro toluene), and three concrete grades, M30, M35, and M40 are considered to see the stability of the structure. The effect of varied explosive weights and varied concrete grades is compared in terms of stress, pressure, and displacement at critical locations of the structure. The outcome of this shows that the change in explosive weight and concrete grade considerably affects the stability of the structure. As the explosive weight increases, damage to the structure increases, and with the increase in the concrete grade, the blast load resistance capacity of the structure increases. It is observed that buried part of the structure is more resistant to blast load compared to the structure visible above ground.

Auxetic cementitious cellular composite (ACCC) PVDF-based energy harvester

The high deformation capacity of auxetic cementitious cellular composites (ACCCs) makes them promising for strain-based energy harvesting applications in infrastructure. In this study, a novel piezoelectric energy harvester (PEH) with ACCCs and surface-mounted PVDF film based on strain-induced piezoelectric mechanisms has been designed, fabricated, and experimentally tested. Furthermore, a numerical model for simulating the energy harvesting of ACCC-PVDF system undergoing repeated mechanical loading has been established and validated against the experimental data. The mechanical behavior of ACCCs was simulated by the concrete damage plasticity model during the preloading stage, which was converted to the second-elasticity model during cyclic loading stage. Based on the mechanical responses, analytical formulas for piezoelectric effects were developed to calculate the output voltage of the PVDF film. The output voltages of the ACCCs-PVDF system under different loading amplitudes and loading frequencies were assessed. The experimental results and models of the ACCCs-PVDF energy harvester lay a solid foundation for utilizing architected cementitious composites in energy harvesting applications to supply self-power electronics in infrastructure.

Damage performance and failure analysis of reinforced concrete doubly curved shells under seismic excitations considering curvature and thickness variation

Most of the past investigations on the structural response of the doubly curved shell (DCS) roofs under seismic excitation were limited to linear dynamic analysis, whereas nonlinear dynamic analysis was rarely introduced, making it difficult to understand their dynamic behavior and draw general conclusions. Therefore, in the current study, linear dynamic analysis (LDA) and nonlinear dynamic analysis (NLDA) are conducted in tandem to fill the gap in the literature and give a complete perception of how these roofs respond to earthquakes. To this end, an innovative automatic finite element-based design algorithm is developed to obtain the steel reinforcement in preparation for the NLDA. Accordingly, the current study exploits the multi-layered shell element incorporated with the multi-axial concrete damage plasticity model (implemented via VUMAT subroutine) and the developed design algorithm (via Python script) to perform the NLDA and accurately capture the structural response and damage performance of these roofs. Unlike most common structures, the results demonstrated that DCS is highly affected by the vertical component of the earthquake rather than the horizontal component. The NLDA revealed that the shell exhibits severe damage and a high displacement response under strong seismic excitations, which could not be captured via the LDA. Additionally, the failure analysis is performed for the studied roof, considering the variation in shell curvature and thickness. This analysis shows a notable decrease in the demand-capacity ratio and steel rebar’s stress with increasing the shell curvature. Consequently, according to the proposed performance levels, the shell’s state changed from the initial failure to the elastic state. In contrast, slight changes in the overall behavior are observed due to the variation in the shell thickness. Finally, a new formula is proposed to predict the damage induced in the DCS under seismic excitations.

From ductile damage to unilateral contact via a point-wise implicit discontinuity

Ductile damage models and cohesive laws incorporate the material plasticity entailing the growth of irrecoverable deformations even after complete failure. This unrealistic growth remains concealed until the unilateral effects arising from the crack closure emerge. We address this issue by proposing a new strategy to cope with the entire process of failure, from the very inception in the form of diffuse damage to the final stage, i.e. the emergence of sharp cracks. To this end, we introduce a new strain field, termed discontinuity strain, to the conventional additive strain decomposition to account for discontinuities in a continuous sense so that the standard principle of virtual work applies. We treat this strain field similar to a strong discontinuity, yet without introducing new kinematic variables and nonlinear boundary conditions. In this paper, we demonstrate the effectiveness of this new strategy at a simple ductile damage constitutive model. The model uses a scalar damage index to control the degradation process. The discontinuity strain field is injected into the strain decomposition if this damage index exceeds a certain threshold. The threshold corresponds to the limit at which the induced imperfections merge and form a discrete crack. With three-point bending tests under pure mode I and mixed-mode conditions, we demonstrate that this augmentation does not show the early crack closure artifact which is wrongly predicted by plastic damage formulations at load reversal. We also use the concrete damaged plasticity model provided in Abaqus commercial finite element program for our comparison. Lastly, a high-intensity low-cycle fatigue test demonstrates the unilateral effects resulting from the complete closure of the induced crack.

Finite element analysis of RC moment-resisting frames to assess effective slab width; a parametric study

In reinforced concrete (RC) moment-resisting frames (MRFs) with cast-in-situ slabs, the slab action as tension flange during lateral loading enhances the flexural capacity of beams in negative moments. This enhancement may lead to strong beam-weak column unfavorable failure mode in these structures. Field observations of RC MRFs during strong ground motion indicated that the effective slab width values considered by the seismic provisions of the design codes are not adequate to guarantee the achievement of the design method of weak beam-strong column. An accurate estimation of effective slab width needs to assess factors such as geometrical characteristics of connection, continuity of models, and imposed story drift level. A 3D spatial two-story RC MRF was developed using finite element analysis (FEA) to explore the effect of mentioned factors on effective slab width. For finite element (FE) modeling of RC MRF, the concrete damaged plasticity (CDP) model is applied. The CDP model parameters are defined using a mesh-independent methodology introduced in the literature. Comparing the FEA results and results obtained from three half-scale RC MRFs, tested under reversed cyclic loading conditions showed an excellent correlation. The results predicted by the FE model in terms of lateral load–displacement response, reinforcement yielding sequence, crack patterns, and failure modes had a considerable agreement with test observations. The validated FE model was used to develop the other models to conduct a parametric study in the next step. Geometric parameters studied in this paper through numerical modeling were longitudinal and transverse beam length and height, and cross-sectional column dimension. Results of the parametric study showed that the effect of the ratio of transverse beam length to height is significantly more than the ratio of longitudinal beam length to height. The trend of effective slab width versus story drift depends on connection geometry, especially the ratio of transverse beam length to transverse beam height. Finally, an equation was driven to predict the effective slab width using linear regression analysis.

Numerical analysis on the mechanical response of grouted connection for pile-bucket foundation

As a new foundation type for offshore wind turbine (OWT), pile-bucket foundation, which consists of a monopile and a bucket foundation, has good prospect in engineering application and has received wide attention. However, most of the current research ignored the function of grouted connection (GC) and assumed that the pile and bucket were rigidly connected, which may lead to unrealistic estimation of the loading response of pile-bucket foundation. In this study, Finite Element Analysis (FEA) is conducted to study the influence of grout connection on the bearing characteristics of pile-bucket foundation, with a special focus on the mechanical response of the grout connection itself. The concrete damage plasticity (CDP) model is used to simulate the mechanical response of the grout material. After validation of the numerical model, twelve simulations are conducted by changing the grout thickness, grout length and stiffener arrangements. Though the variance of grout thickness and grout length has little impact on the load-displacement curves of the pile-bucket foundation, the optimal grout thickness and grout length could be determined according to the development of contact pressure, stress and damage of the grout connection. On the other hand, the employment of stiffener leads to notable stress concentration and fluctuation, however, it also improves the overall capacity of the pile-bucket foundation and effectively controls the damage of the grouted connection. The numerical result is expected to provide some reference value for the structural design of grouted connection for pile-bucket foundation.

Effects of Jack Thrust on the Damage of Segment Lining Structure during Shield Machine Tunnelling

Constructing a tunnel with a large longitudinal slope and a small-radius sharp curve is challenging. During the construction process, it necessitates a series of intricate operations, including adjusting the horizontal and vertical posture of the shield machine, controlling the tunnelling thrust, and consistently ensuring the appropriate over-excavation amount inside and outside of the turn. Improper operations can easily induce undue stress on the segments. This study establishes a finite element numerical model of lining segments subjected to jacking force under various construction conditions. The concrete damage plasticity (CDP) constitutive model was used to characterize the mechanical behavior of concrete under load. The mechanical characteristics and damage behavior of segments under construction conditions, such as significant thrust escape, vertical attitude adjustment of the shield machine, excavation in soft and hard interbedded strata, line turning, sudden failure of the propulsion system, and eccentricity of brace boots, were analyzed. The results revealed that, when advancing according to the maximum thrust design value (50 MPa), cracks in the tensile plastic damage zone near the brace boot plate and the edges of the segment can develop. This can lead to localized corner failure of the concrete at the lining’s edge. Therefore, it is recommended that the jack’s thrust value should not surpass 30 MPa. Maintaining the usual uneven jack thrust state of shield tunnelling along the design axis is unlikely to result in segment concrete cracking. Damage to the segment caused by the eccentricity of the brace boot plate is the most severe; hence, avoiding the eccentricity of the brace boot plate during construction is crucial. The findings of this research can guide the control of jack thrust during shield tunnelling construction and offer insights into the design of segment parameters.

Numerical seismic analysis of high-piled wharf strengthened with CFRP

High-piled wharves are widely employed in coastal areas, but their vulnerability to earthquake damage necessitates effective strengthening measures. This research focuses on investigating the effectiveness of carbon fiber reinforced polymer (CFRP) laminates in enhancing the seismic resistance of high-piled wharves. Full-scale 3D numerical high-piled wharves, divided into As-built groups and Retrofit groups, were established herein. During modeling, the concrete damage plasticity model (CDP) and the finite-infinite coupling element were contemplated. Two representative ground motions, i.e., the EI Centro wave and the Northridge wave, with peak accelerations of 0.2g and 0.4g, respectively, were utilized to simulate different earthquake scenarios. The responses of the resulting earthquake-induced deck displacement, pile distortion, and pile bending moment profile were explored. The computational analysis revealed significant improvements in the seismic performance of the retrofitted wharves compared to the as-built structures, proving that the externally bonded CFRP method was of great significance in improving overall structural seismic performance. Notably, the retrofitted wharf exhibited reduced deck displacement and remarkable decreases in pile deformation and bending moment. The modeling and analysis techniques can be applied to general wharves or other buildings strengthened with CFRP.

Numerical Modelling of Impact Loads on RC Beams Utilizing Spent Garnet as a Replacement for Fine Aggregate

Spent Garnet (SG) is one of the waste materials that attracts the interest of researchers to use it as a replacement for fine aggregate in concrete materials. As experimental investigation was carried out to assess the performance of a reinforced concrete (RC) beam incorporating SG as a substitute for fine aggregate. The study involved subjecting the beam to low-velocity impact loads within a controlled testing configuration. The primary objective of this study was to determine the optimal proportion of spent garnet (SG) to replace fine aggregates in reinforced concrete (RC) beams subjected to impact loads with a 100 kg impact weight dropped from a height of 1.5m, equivalent to a velocity of 5.4 m/s. To evaluate the effectiveness of SG as a replacement for fine aggregates, RC beams with varying percentages of SG (0%, 10%, 20%, 30%, and 40%) were numerically modelled using the Finite Element Method (FEM) incorporating the Concrete Damage Plasticity (CDP) constitutive model to simulate their behaviour under low-velocity impact loads. The study aimed to comprehensively examine the failure mode of the RC beams. The findings through FEM showed that the inclusion of SG in the concrete mix enhanced the material's behaviour and decreased the failure and damage of the beams as the percentage of SG in the mix increased, indicating its effectiveness as a replacement for fine aggregates, which is consistent with the experimental results.

Comparative performance evaluation of microarchitected lattices processed via SLS, MJ, and DLP 3D printing methods: Experimental investigation and modelling

Additively manufactured mechanical metamaterials are gaining prominence in lightweight energy-absorption applications due to their exceptional mass-specific properties. Herein, we examine the energy absorption characteristics of micro-architected truss-, shell- and plate-lattice structures, namely, Octet, Kelvin, Gyroid, SC, BCC and FCC over a range of relative densities under quasi-static compression via both experiments and finite element analysis (FEA). Employing different 3D printing methods, namely, Digital Light Processing, Selective Laser Sintering and Material Jetting, the lattices were fabricated using PlasGray™ (photo-resin based plastic), PA12 (Nylon) and VeroWhite (photo-resin based rigid plastic) respectively. Our results indicate that the SC lattice structure outperforms in terms of stiffness and strength, while the Gyroid lattice outperforms in terms of energy absorption efficiency (η). At lower relative densities (<0.3), η reaches up to 61% for the Gyroid lattices made of PlasGray, while only at high relative densities the Octet truss lattices compete with the Gyroid lattices. For Gyroid lattices made of PA12 with a relative density of 0.23, an energy absorption efficiency of 68% was observed. Design maps are presented for all lattice structures processed and tested herein, to demonstrate their relative merits. Moreover, a two-step FEA was executed on a chosen array of lattices to thoroughly investigate the extensive design possibilities, utilising the elastic-plastic, Drucker-Prager, and concrete damage plasticity material models for PlasGray, PA12, and VeroWhite, respectively, with calibration based on experimental results. The results highlight that the tailored design of Gyroid lattices enabled by AM positions them as promising candidates for lightweight energy-absorbing applications.

Tensile Behavior of Anchored Stainless Steel T‐Head Blind Bolts within Concrete‐Filled Steel Square Tubes

AbstractBased on a recent review on blind bolted connections to concrete‐filled steel tubes, there is a need to improve the performance of anchored blind bolts in such composite connections. This paper presents a study on the pull‐out behavior of anchored blind bolts under applied tensile load in terms of stiffness, yield strength, ultimate strength and load‐displacement response. A finite element (FE) model with concrete damage plasticity model was developed for parametric study. Effects of key parameters, such as concrete strength, bolt grade, embedment length, tube thickness and tube grade, on the tensile behavior of the connection were studied to identify the key parameters influencing the behavior. Finally, a predictive model based on component method was proposed to estimate the structural behavior of the blind‐bolted connections.

Damage of CRTS III type ballastless track-32 m simply supported girder structural system under long-term deformation effects

Until now, the CRTS (China’s Railway Track System) III type ballastless track-girder system has been gradually used in high-speed railway engineering. However, the effect of long-term deformation of prestressed box girders on the upper track structure is often overlooked. Given the strict requirements for track smoothness in high-speed railways, an in-depth study of the long-term deformation of the CRTS III type ballastless track-32 m simply supported girder system (girder-track system) is particularly important. In this study, a refined finite element model was established for a three-span CRTS III type ballastless track- simply supported box girder system. Based on the aid of the CEB-FIP 90 creep model and the UMAT (User-Material) subroutine, the long-term deformation calculations were investigated. Furthermore, an in-depth analysis of stress and damage of the CRTS III type ballastless track under the long-term deformation of the box girder was conducted by combining concrete damaged plasticity (CDP) and cohesive zone model (CZM) constitutive models. The numerical simulated results indicated that after four years of operation, the creep camber of the box girder in the girder-track system would reach to 3.41 mm. The maximum tensile and compressive longitudinal stresses of the base plate would reach to 0.537 MPa and 11.983 MPa, respectively. Meanwhile, the maximum tensile and compressive longitudinal stresses of the self-compacting concrete layer would reach to 0.958 MPa and 2.701 MPa, respectively. In the box girder mid-span, significant damage could be observed in the edge of the two base plates near the mid-span, with a maximum compressive damage rate of 0.164 and the maximum tensile damage rate of 0.304. The research of this study has achieved the prediction of long-term deformation in the girder-track system, providing an important basis for the reliability assessment and life prediction of the girder-track system.

A quantitative investigation on the fragmentation performance of SCDA in cracking steel fiber reinforced concrete

A better application of Soundless Chemical Demolition Agents (SCDAs) in fragmentation is based on our knowledge on their expansive characteristics. In this study, an integration of experimental and modeling approaches was developed to investigate SCDA expansion and corresponding cracking processes of Steel Fiber Reinforced Concrete (SFRC). The expansive properties of the selected SCDA were first estimated by free volume expansion (FVE) tests and expansion pressure (EP) tests. Then, cracking experiments were performed on 150 mm cubic SFRC blocks with a predrilled hole, and the cracking process was monitored by using Acoustic Emission (AE) and Digital Image Correlation (DIC) techniques. Generally, the cracking process can be divided into three phases, termed micro-cracking phase, macro-cracking phase, and failure phase. It was observed the hole diameter and fiber content exert significant influences on the cracking process. The crack initiation time was shortened as the hole diameter increases, while it was prolonged with increasing fiber content. The cracked area ratio was further proposed and measured to assess the cracking performance of SCDA. The ratio increases from 2.73% to 8.293% as the hole diameter increases from 16 mm to 26 mm, while it decays from 9.75% to 1.823% as the fiber content increases from 0 to 2.4%. After verified with the experimental data, a modified Concrete Damaged Plasticity (CDP) model was adopted to extend the fragmentation of SFRC from the centimeter scale to the meter scale. The simulations were conducted on SFRC models with various hole diameters, spacings, and fiber contents. The simulated results show the fragmentation performance is related to both hole parameters (e.g., hole diameter, spacing, etc.) and SFRC properties (including elastic modulus, fiber content, etc.). In particular, the cracked area (DamageT > 0.9) varies directly with hole spacing, diameter, and fiber content. Built on the simulated results, an empirical equation was formulated to quantitatively evaluate the fragmentation ability of individual holes. In addition, extra simulations were conducted to assess the efficiency of SCDA in cracking PC/SFRC beams of various sizes. The obtained cracked area tends to decrease first and then approach a constant value with increasing beam sizes, indicating the existence of a size effect, which is primarily due to variations in concrete restraints provided by beams of different sizes. This work quantitatively evaluates expansive properties of SCDA and SCDA-induced cracks, and thus provides a reference for optimizing the field application parameters.

Application of bridge information modelling using laser scanning for static and dynamic analysis with concrete damage plasticity

A new proposal has been applied using Bridge Information Modeling associated to Terrestrial Laser Scanning TLS and photogrammetry to obtain the digital model of an existing bridge. For the laser scanning process. Thus, it was also possible to identify the pathologies and damages in the concrete of the bridge. Furthermore, it was shown how geo-information with remote sensing using the station Trimble SX 10 can be applied in area of bridge projects with less time and lower cost, in relationship to a conventional survey Asbuilt with manual survey in field. One of the innovations of this paper was to obtain the digital model of the bridge by integration of TLS and photogrammetry to obtain the 3D digital model. The new methodology consisted of acquisition of the bridge scenes through points previously implanted, making the polygonal contour of the entire bridge. Furthermore, the execution of the field survey from georeferenced points to capture the scenes during the sweep with TLS facilitated the refinement and, consequently, it was possible to obtain the digital model with the concrete damage. It was also possible to perform a complex nonlinear analysis with Finite Element with the digital model of the bridge. Therefore, it was applied a reverse analysis of the strength of the structure using the Concrete Damage Plasticity Model using ABAQUS software. Two numerical analyses were performed on the bridge; one considering only the static behavior of the bridge and another considering the dynamic behavior. In the static analysis, the behavior of the dapped-end beam of the bridge, was investigated. On the other hand, in the dynamic evaluation, the natural frequency and damping ratio for bridges with Dapped-end beams was obtained in ABAQUS through Rayleigh damping and compared with the technical literature, which presented satisfactory results.

Non-linear finite element modeling of damages in bridge piers subjected to lateral monotonic loading

Bridges are among the most vulnerable structures to earthquake damage. Most bridges are seismically inadequate due to outdated bridge design codes and poor construction methods in developing countries. Although expensive, experimental studies are useful in evaluating bridge piers. As an alternative, numerical tools are used to evaluate bridge piers, and many numerical techniques can be applied in this context. This study employs Abaqus/Explicit, a finite element program, to model bridge piers nonlinearly and validate the proposed computational method using experimental data. In the finite element program, a single bridge pier having a circular geometry that is being subjected to a monotonic lateral load is simulated. In order to depict damages, Concrete Damage Plasticity (CDP), a damage model based on plasticity, is adopted. Concrete crushing and tensile cracking are the primary failure mechanisms as per CDP. The CDP parameters are determined by employing modified Kent and Park model for concrete compressive behavior and an exponential relation for tension stiffening. The performance of the bridge pier is investigated using an existing evaluation criterion. The influence of the stress–strain relation, the compressive strength of concrete, and geometric configuration are taken into consideration during the parametric analysis. It has been observed that the stress–strain relation, concrete strength, and configuration all have a significant impact on the column response.

Thin corrugated-edge shells inspired by Nervi’s dome: Numerical insight about their mechanical behaviour

During the last decades, the constant evolution of the construction systems has led to the possibility of carrying out increasingly complex architectural project. Among the wide range of construction systems, thin concrete shells with corrugated-edge stand out for their relevance.In this paper, the mechanical behaviour of thin concrete corrugated-edge shell inspired by Nervi’s Flaminio dome has been analysed in detail, considering different load configurations (self-weight, uniform normal pressure and antisymmetric vertical load) and constraints (pure membrane vs. displacements restrained boundary conditions).Non-linear static analysis has been performed to assess the vertical load-bearing capacity of the corrugated-edge shell considering a Concrete Damaged Plasticity (CDP) constitutive model and linear and non-linear buckling analyses have been carried out to evaluate the effects of the corrugation on buckling behaviour.The results obtained from linear and non-linear analyses have been compared with those obtained for a concrete thin smooth-edge shell having the same geometric global characteristics. The comparison highlighted improvements provided by corrugated-edge in terms of structural behaviour.

Failure prediction of syntactic foam core L-shaped sandwich structures

L-shaped laminates with a syntactic foam core were manufactured to investigate the bending behavior of the sandwich structures including sharp corners. The bending behavior, initial, and progressive failure modes of the sandwich structure were analyzed by four-point bending tests and the finite element method. The cohesive zone model and Hashin’s failure criteria were used for inter-laminar and intra-laminar failure of the laminates, respectively. The concrete damage plasticity model was proposed to model the foam material with considering different material properties in tension and compression. Mode-I and Mode-II fracture toughness of the foam was obtained to characterize the foam/laminate interface. Load-displacement curves predicted under bending simulation were quite well compliant with experimental results. The difference between numerical and experimental failure loads was 10.6 %, 1.2 %, and 1.9 % for the foam with facesheet stacking sequence of [0/90]2s, [0/90]3s, and [0/45/-45/90]2s, respectively. Predicted radial and hoop direction strain fields in the foam section were also compared to the measured one using a digital image correlation technique. Strain fields and failed regions and their mechanisms were captured well using the model. The initial failure mechanism was delamination at the interface between the foam and facesheet followed by foam tensile fracture.

Numerical Modeling of Single-Lap Shear Bond Tests for Composite-Reinforced Mortar Systems

The large demand of reinforcement systems for the rehabilitation of existing concrete and masonry structures, has recently increased the development of innovative methods and advanced systems where the structural mass and weight are reduced, possibly avoiding steel reinforcements, while using non-invasive and reversible reinforcements made of pre-impregnated fiber nets and mortars in the absence of cement, commonly known as composite-reinforced mortars (CRMs). To date, for such composite materials, few experimental studies have been performed. Their characterization typically follows the guidelines published by the Supreme Council of Public Works. In such a context, the present work aims at studying numerically the fracturing behavior of CRM single-lap shear tests by implementing a cohesive zone model and concrete damage plasticity, in a finite element setting. These specimens are characterized by the presence of a mortar whose mechanical behavior has been defined by means of an analytical approximation based on exponential or polynomial functions. Different fracturing modes are studied numerically within the CRM specimen, involving the matrix and reinforcement phases, as well as the substrate-to-CRM interface. Based on a systematic investigation, the proposed numerical modeling is verified to be a useful tool to predict the response of the entire reinforcement system, in lieu of more costly experimental tests, whose results could be useful for design purposes and could serve as reference numerical solutions for further analytical/experimental investigations on the topic.

Basalt fibre reinforced polymer bars as main reinforcement of axially compressed concrete column – experimental and numerical considerations of fire resistance

The study aimed to highlight the possibility of achieving satisfactory level of fire resistance in concrete column reinforced with Basalt Fibre Reinforced Polymer (BFRP) bars as a main reinforcement.The literature data [1] of steel reinforced columns was used for preliminary validation of the numerical model. Full scale BFRP-reinforced column was analyzed experimentally and numerically along with experimental evaluation of thermo-mechanical parameters of the BFRP bars and concrete.Fire resistance of the element was calculated by means of numerical simulation, as the time when further sustaining of the mechanical load was no longer possible. The Concrete Damaged Plasticity (CDP) model for concrete was used.The model appeared to be effective in predicting fire resistance of concrete columns with steel reinforcement with various spacings of stirrups (differences up to 12%). In terms of element reinforced with BFPR, the fire resistance of the column tested was about 30% higher than the numerically determined value. Also, the calculated temperatures were compared to values measured by means of thermocouples. Finally, the possibility of achieving over 3 h of fire resistance for columns with BFRP main reinforcement has been proven in both – numerical and experimental investigations.