Blast loading and seismic excitations are widely recognized as the most detrimental occurrences that a building structure may encounter throughout its lifespan. Therefore, this study investigated the ...retrofitting capacity of external devices (ENTA damper systems) for reinforced concrete (RC) frames in term of enhancing their resistance under the combined effects of blast and seismic loads. This study presents the establishment of finite element (FE) models for retrofitted RC frames with ENTA damper systems through the utilization of the dynamic analysis software LS-DYNA. The investigation involved the validation for blast performance of RC column in order to identify the most effective method for modeling blasts. Additionally, the study aimed to validate the performance of RC frame models through effects of ENTA damper systems under seismic loading. Subsequently, a performance evaluation of RC frame structures was carried out to examine the impact of the ENTA damper systems when subjected to blast loading. The findings of the study indicate that the use of external ENTA damper systems effectively enhanced the rigidity and structural integrity of RC frames, while maintaining their ability to resist deformation. Finally, the damage assessment of blast and seismic performance is investigated based on various parameters such as ductility, drift and energy-based damage limits.
•Finding the suitable model blasts based on the blast performance of RC column.•Validating performance of the RC frame models under seismic loading.•Investigating the blast performance of RC frame and retrofitted RC frame.•Considering the damage performance of RC frames under blast and seismic loadings.
Epoxy asphalt has excellent fatigue resistance, making it a valuable addition to recycled asphalt mixtures. However, the lack of sufficient understanding of the cracking mechanism in epoxy-modified ...recycled asphalt mixtures (EMRAM) hinders its widespread application. The purpose of this paper was to investigate the damage and crack characteristics of EMRAM based on a three-dimensional meso-heterogeneous model. The coarse aggregates were first randomly generated using the secondary Delaunay algorithm. Meanwhile, the fracture parameters of each component material and asphalt-aggregate interface in EMRAM were tested through three-point bending tests and direct shear tests, respectively. Cohesive zone model elements were then inserted at the aggregates, asphalt mastic, and interfaces between different materials to establish a three-dimensional meso-heterogeneous model of EMRAM. Finally, based on the established model, the damage degree of each composition material in EMRAM was quantitatively analyzed to identify the vulnerable aspects of EMRAM during the crack propagation stage. Optimization strategies were proposed accordingly. The results demonstrated that the model established in this study can accurately represent the meso-heterogeneous of EMRAM and effectively simulate its cracking behavior. EMRAM was more susceptible to developing internal damage within the aggregates, followed by relatively noticeable damage at the interface and the internal regions epoxy-modified fine aggregate mastic. The cracking resistance of EMRAM showed a trend of initially increasing and then decreasing with an increase in the volume fraction of coarse aggregates with a size above 4.75 mm. The optimal range for the volume fraction of coarse aggregates in EMRAM was within 35–44 %. The fracture energy of EMRAM was improved by more than 30 % after gradation optimization compared to EMRAM with gradation at the median value of AC20. Within the designed service life, EMRAM durable pavement can save at least 30 % more in economic costs compared to ordinary asphalt concrete pavement.
•The order of material damage proportion from high to low is BA > EFAM-BA > EAFAM-BA > EFAM.•The optimal range for the volume fraction of coarse aggregates in EMRAM was within 35–44 %.•The fracture energy of EMRAM was improved by more than 30 % after gradation optimization compared to EMRAM with gradation at the median value of AC20.•EMRAM durable pavement saves at least 30 % more in economic costs compared to ordinary asphalt concrete pavement.
The designed service life of slab tracks of high speed railways can be 60 years. To achieve this goal, maintenance measures must be used properly to maintain tracks’ damage resistance and durability ...over the long run. The dual application of interface adhesives and solar reflective coatings is expected to improve the long-term serviceability of the longitudinally continuous slab tracks. This paper is therefore motivated to investigate effects of the combined use of interface adhesives and solar reflective coatings on damage of longitudinally continuous slab tracks subjected to nonlinear temperature load. Firstly, the effect of adhesives on interface bond properties and the influence of coatings on track temperature field were investigated. Secondly, a novel finite element model of the longitudinally continuous slab track considering the nonlinear mechanical properties of structural interfaces and concrete materials was established and verified. Then the nonlinear temperature field was applied to the nonlinear finite element model to investigate the damage development pattern of the track using the two measures. Lastly, the equivalent adhesive-use size to the coating on damage mitigating was identified base on finite element analysis. The following novel insights are drawn: (1) The dual application of the adhesive and the coating can improve the yield temperature of interfacial failure by 10.6 °C, indicating the significant effects of the maintenance method on mitigating interfacial debonding and gapping of the tracks. (2) The adhesive, the coating and the dual application of both measures in a typical scenario can reduce the maximum vertical displacement of track slabs by 21 %-35 %, 52 %-63 % and 66 %- 72 % respectively. (3) The effect of the coating on mitigating compressive damage of concrete of T-shaped joints outweighs the interface adhesive, and approaches the combined use of both measures. (4) If the width of the adhesive use area is 0.4 m, there should be at least 3 slabs using the adhesive in order to have the same effect on mitigating the vertical displacement as the coating.
•Effects of dual application of adhesives and coatings were evaluated.•Influence of maintenance measures on track interface damage was analyzed.•Evolution of deformation of restored tracks was studied.•Equivalent adhesive-use size to the coating on damage mitigating was determined.
To study the removal mechanism and damage behavior during the machining of ceramic particle-reinforced metal matrix composites, a finite element model (FEM) comprehensively considering the ...distribution and shape of the particles and the damage behavior of ceramic particles is established. Corresponding experiments are conducted to demonstrate the reliability of FEM. The results demonstrate that chips are easy to separate where the particles gather. The stress concentration is serious at the edges and corners of the particles. The cutting and thrust force, subsurface damage, surface roughness and maximum profile peak-valley height increase with the increase of depth of cut. Voids, particle fracture, particle peeling off, matrix tearing and interface failure are the main surface defects. Moreover, according to the failure mode and mechanism of ceramic particles, the positional relationships between the ceramic particles and the tool are divided into three categories: the particle is below, on and above the cutting path.
The effect of shot peening (SP) on the fatigue life of S42200 steel at room and elevated temperature is investigated. The fatigue test is carried out on a high temperature rotating bending tester. ...Surface integrity characterization is used to study the effect of SP on surface properties. Furthermore, Finite Element Method (FEM) combined with a fatigue damage model, namely Zheng Equation, is proposed to predict the fatigue life. The results show that SP effectively improves the fatigue life of S42200 steel under all temperatures. However, at lower temperature, higher strength SP leads to higher fatigue resistance, while at higher temperature, lower strength SP leads to higher fatigue resistance. This can be explained by the competitive effect of surface roughness and compressive residual stress (CRS) relaxation on the local stress concentration. This research can be a good guide to the application of SP at different temperatures.
•A new PVA-ECC with reduced cost and strain capability matching that of steel rebar.•Extensive tests on the mechanical behaviour including large number of tensile test.•A statistical analysis for the ...study of the probability distribution.•A new finite element model for modelling of flexural behaviour of PVA-ECC beams.•Development of a relationship on tensile strength between 2D and 3D specimen.
A polyvinyl alcohol fibre reinforced engineered cementitious composite (PVA-ECC) using local ingredients is developed, aiming for a reduced cost and a tensile strain capacity matching that of steel reinforcement for commonly used reinforced concrete structures. Experiments are conducted to determine mechanical behaviour of the composite. In addition, a finite element model is developed to simulate the flexural behaviour of PVA-ECC beams, and experimental results are used to calibrate the model. The material models of the PVA-ECC under compression and tension are calibrated using experimental results of uniaxial compression and tension tests. Furthermore, a theoretical relationship on the tensile strength between specimens with two-dimensional and three-dimensional fibre distribution is derived, and accuracy of the simulation is improved by using the theoretical ratio. Agreement between the computed results and the experimental data demonstrates the effectiveness of the finite element model.
With high strength, excellent durability, and cracking resistance, ultra-high-performance concrete (UHPC) has gradually become popular. In this study, a novel hybrid beam was designed to fully ...harness the cracking resistance and tensile strength of UHPC. A series of experiments were conducted to investigate the influence of UHPC layer depth and steel bar diameter on the flexural performance of UHPC-RC hybrid beams. The experimental results indicated that the use of UHPC in the tensile zone of UHPC-RC hybrid beams can significantly improve the bearing capacity, crack resistance, and ductility of the structure. Based on the application of cohesive zone model (CZM), a finite-element (FE) model was proposed to simulate the mechanical behavior of the UHPC-RC hybrid beams, and the cohesive elements were used to represent the potential fracture surfaces of UHPC (concrete) and the rebar-concrete interface. A constitutive model for potential fracture of UHPC, taking into account the bridging effect of fibers, has been proposed. This FE model can reflect the fracture behavior of UHPC-RC hybrid beams. The simulation results demonstrate that the proposed model can accurately simulates the mechanical response and fracture behavior during the whole fracture process. Based on the results obtained from the experiment and simulation, a theoretical method for predicting the bearing capacity of UHPC-RC hybrid beams was developed, which can provide the reference for the design of similar structures.
•Increasing UHPC thickness and reinforcement ratios enhances stiffness, load capacity, and crack control but reduces ductility.•Higher reinforcement in UHPC-NC composite beams increases strength but decreases flexibility.•A new finite-element model accurately simulates the behavior of UHPC-NC beams.•A simplified method reliably predicts the flexural capacity of UHPC-NC beams.•Experimental results validate the accuracy of the proposed finite-element model and prediction method.
Glass Fiber-Reinforced Polymer (GFRP) bars can enhance the flexural bearing capacity and durability of concrete beam members under sustained loading and alkaline environment over an extended period. ...However, addressing the challenges related to durability and deformation resistance remains crucial for long-term service. In this paper, the flexural performance of GFRP-reinforced concrete beams with different glass fiber contents under the coupling action of the alkaline environment and continuous load is studied, and the mechanism of improving the flexural performance of GFRP-reinforced concrete beams by dispersed fibers is analyzed from a microscopic point of view by scanning electron microscope (SEM) test. In addition, the finite element analysis software was used to simulate and verify the improvement effect of singly dispersed fiber on the bending of GFRP-reinforced concrete beams. The results demonstrate that GFRP-RC beams containing 0.5%, 1.0%, or 1.5% glass fiber exhibit a reduction in deflection ranging from 11% to 23% compared GFRP-RC beams without glass fiber, thereby improving their deformation resistance. The optimal glass fiber content is 1.5%. Simulation analysis demonstrates that the model exhibits enhanced resistance to deformation when the glass fibers are randomly dispersed. Specifically, increasing the random scattering of fibers at the bottom of the beam by two to three times results in a reduction of 7%-12% in mid-span displacement of the model. Additionally, within the cracked area, the fibers bear greater tensile stress compared to those in other uncracked regions, effectively preventing further cracking of GFRP-RC beams. This study offers valuable design guidance for enhancing performance of GFRP-RC members during long-term service.
•This paper studied glass fiber GFRP-RC beams.•The working condition is the coupling of sustained loading and alkaline environment.•The influence of fiber on the flexural property of beam was investigated by finite element method.•The corrosion age of alkaline environment is 450 d.
Accurate muscle geometry is essential to estimate moment arms in musculoskeletal models. Given the complex interactions between shoulder structures, we hypothesized that finite element (FE) modelling ...is suitable to obtain physiological muscle trajectory. A FE glenohumeral joint model was developed based on medical imaging. Moment arms were computed and compared to literature and MRI-based estimation. Our FE model produces moment arms consistent with the literature and with MRI data (max 17 mm differences). The inferior and superior fibres of a same muscle can have opposite action; predictions of moment arms are sensitive to muscle insertion (up to 20 mm variation).
This paper presents a framework for structural health monitoring (SHM) and damage identification of civil structures. This framework integrates advanced mechanics-based nonlinear finite element (FE) ...modeling and analysis techniques with a batch Bayesian estimation approach to estimate time-invariant model parameters used in the FE model of the structure of interest. The framework uses input excitation and dynamic response of the structure and updates a nonlinear FE model of the structure to minimize the discrepancies between predicted and measured response time histories. The updated FE model can then be interrogated to detect, localize, classify, and quantify the state of damage and predict the remaining useful life of the structure. As opposed to recursive estimation methods, in the batch Bayesian estimation approach, the entire time history of the input excitation and output response of the structure are used as a batch of data to estimate the FE model parameters through a number of iterations. In the case of non-informative prior, the batch Bayesian method leads to an extended maximum likelihood (ML) estimation method to estimate jointly time-invariant model parameters and the measurement noise amplitude. The extended ML estimation problem is solved efficiently using a gradient-based interior-point optimization algorithm. Gradient-based optimization algorithms require the FE response sensitivities with respect to the model parameters to be identified. The FE response sensitivities are computed accurately and efficiently using the direct differentiation method (DDM). The estimation uncertainties are evaluated based on the Cramer–Rao lower bound (CRLB) theorem by computing the exact Fisher Information matrix using the FE response sensitivities with respect to the model parameters. The accuracy of the proposed uncertainty quantification approach is verified using a sampling approach based on the unscented transformation. Two validation studies, based on realistic structural FE models of a bridge pier and a moment resisting steel frame, are performed to validate the performance and accuracy of the presented nonlinear FE model updating approach and demonstrate its application to SHM. These validation studies show the excellent performance of the proposed framework for SHM and damage identification even in the presence of high measurement noise and/or way-out initial estimates of the model parameters. Furthermore, the detrimental effects of the input measurement noise on the performance of the proposed framework are illustrated and quantified through one of the validation studies.
•A new framework is proposed for structural health monitoring based on nonlinear FE model updating using a batch Bayesian estimation approach.•The batch Bayesian approach leads to an extended ML estimation method to jointly identify the FE model parameters and measurement noise.•The parameter estimation uncertainties are quantified using the Cramer–Rao lower bound theorem by computing the Fisher Information matrix.•Two validation studies using numerically simulated data are provided to investigate the performance of the proposed framework.
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