Deflection Time Histories Research Articles

Blast resistance of 3D-printed Bouligand concrete panels reinforced with steel fibers: Numerical investigations

3D-printed concrete structures inspired by Bouligand architecture with helically twisted sequences exhibit excellent mechanical performance owing to its aligned fiber orientation. In this study, 3D-printed concrete panels with different numbers of layers (five, ten, and 15 layers) and spiral angles (0°, 15°, 30°, and 45°) are designed for numerical investigations of their blast-resistant capacity. A multi-scale model is developed to capture the isotropic and anisotropic properties of the fiber-concrete composite. The adequacy and accuracy of the model are evaluated and validated by experimental data in the literature. Blast resistance of different types of panels in terms of time histories of central-point deflection, contact explosion-induced plastic dissipation energy, stress propagation, and principal stress distribution is examined. It is found that extrusion-based concrete panels with aligned fiber orientation substantially enhance the blast resistance compared to traditional cast concrete panels with random fiber orientation. Furthermore, more layers of printed concrete panels prove to be more efficient in filtering blast waves. In particular, shifting a pitch angle of 30° after printing each layer plays an important role in reducing the maximum deflection. Meanwhile, 3D-printed concrete panels with a pitch angle of 0° can better mitigate blast-induced damage. Through parametric studies, the intrinsic mechanism of steel fibers aligned in 3D-printed panels is numerically analyzed to support the conclusions.

Experimental and numerical investigations of the impact resistance of socket and pocket connections for precast bridge columns

This study investigates the dynamic performance of precast bridge columns under pendulum impact testing, including socket connection, pocket connection, and cast-in-place (CIP) columns. The study focuses on comparing the impact behavior of CIP and precast columns regarding failure modes, impact force-time, and deflection-time histories. Furthermore, the mechanism by which the socket or pocket connection configurations affect the impact resistance of the precast columns is discussed. The results indicate that the development of cracks in the precast and CIP columns is consistent under the same impact conditions. Notably, the shear resistance mechanisms and failure modes vary significantly at the bottom of the two columns. For the precast specimens, substantial local damage occurs at the connections with consecutive impacts. Specifically, punching shear failure is observed at the pocket connections, whereas the connection sections of the socket columns may pull out from the grooves. Local damage to the column-footing connections reduces the global stiffness of precast columns, leading to higher deformation, greater residual displacements, and lower impact forces than those of CIP columns. A simplified finite element modelling method is proposed to simulate the characteristics of precast column connections, and its accuracy is verified using the test results. The numerical findings show that increasing the friction coefficient at the connection interface promotes the formation of diagonal compression struts within the connection, effectively resisting impact loads and preventing excessive shear stress produced by sliding at the interface. Furthermore, amplifying the minimum embedment depth of the socket-connected precast column to 1.0 D is recommended to ensure safe performance under impact loading.

Dynamic response of sandwich beam with porous core excited by two harmonic loads travelling in opposite directions

This paper presents the time history response of a sandwich beam with a porous core subjected to two moving harmonic loads with opposite directions. In the modelling, the beam is combined of two isotropic face sheets and a porous core with symmetric porosity distribution. The quasi-3D shear deformation beam theory in conjunction with Hamilton's variational principle is utilized to set up the governing equations of motion. The Navier solution is used to obtain the displacement field. The accuracy of the study is validated by comparing with existing results in the literature for specific cases. Effects of the velocity and excitation frequency of the moving loads on the deflection-time history are investigated and discussed. Numerical results reveal that in the case of the double-moving harmonic loads in the antiphase, the resonance phenomenon cannot occur when the excitation frequency approaches the natural frequency of the beam.

Static and dynamic behaviour of sandwich beams with porous core: Experiment and moving least squares mesh-free analysis

In this paper, the static and dynamic behaviour of sandwich beams with porous core are numerically analyzedand validated by experimental tests. The beam consists of a thick porous core with a uniform porosity distribution over its domain and two outer face layers. For the theoretical study, the virtual work principle is employed to derive the governing equation. A one-dimensional (1D) mesh-free approach, associated with the moving least squares Hermite interpolation, is developed to approximate the primary variable fields and discretize the governing equation. Additionally, a simple transformation method is applied to create Kronecker delta property of constructed shape functions, straightforwardly facilitating the imposition of the boundary condition, similar to the finite element method without additional techniques. The accuracy of the computational method is subsequently verified against previous literature. For the experimental tests, various mechanical responses, such as the natural frequency, static deflection, and deflection-time history of a cantilever porous sandwich beam consisting of cemboard faces and a concrete core with Expanded Polystyrene are measured and compared with the theoretical prediction. The outcomes of this study can be valuable for the design of sandwich beams with porous core.

Wave propagation in beams with functionally graded porosity distribution under highly transient axial and transverse impacts

Recent advances in the manufacturing process provide a possibility of fabricating a new generation of porous materials denoted by functionally graded porous materials (FGPM). This paper aims to present a time domain analysis of wave propagation through the porous structures with functionally graded porosity distribution, which has not been completely studied before. For this purpose, the beams with different functionally graded porosity distributions subjected to both axial and transverse tip impact loads with a high-frequency content are investigated. The shear deformable cantilevered functionally graded porous beams with various porosity distributions through the beam thickness are studied. The governing differential equations are derived using the Hamiltonian principle based on the Timoshenko beam theory. A locking-free first-order shear deformable beam element is used to derive the finite element formulation of the equations. The Newmark time integration method is used to perform a time domain analysis of the equations of motion and to investigate the transient response of the beams. The axial and transverse wave propagation characteristics through functionally graded (FG) porous beams are found using time domain analysis of the results. Deflection and velocity time histories of the tip and each point of the beam, reflection time, and variation of support reactions are obtained. The influences of the porosity magnitude and porosity distribution on the wave propagation characteristics and overall time responses are investigated. The results reveal that porosity distribution has a significant effect on the wave amplitude, wave speed, and reflection from the boundary. Also, this study can help in a better understanding of porous structures' behavior subjected to high-transient impact loads in different engineering applications.

Dynamic behaviors of RC caisson subjected to underwater explosions

Due to the vulnerability of wharves against accidental attacks, the reinforced concrete (RC) caisson quay wall, as a widely adopted wharf form, is faced with the potential threat of underwater explosions. The present work aims to study the dynamic responses and damage modes of caisson against underwater explosions through the underwater explosion test and numerical simulations. Firstly, four shots of underwater explosion test were conducted, including two cases for different focuses, i.e., two shots of the free field underwater explosion with a charge weight of 0.2 and 1 kg respectively, and another two shots of a 1/5 reduced scale caisson specimen subjected to the underwater explosion with a charge weight of 0.2 and 1 kg successively. The underwater explosion overpressure-time histories and periods of bubble pulsation, as well as the deflection-time histories and damage modes of caisson specimen were experimentally obtained. Then, the refined finite element (FE) models were established, including the 1D model for explosion loading and the 3D model for predicting the dynamic behaviors of caisson with adopting the Coupled-Eulerian-Lagrangian algorithms and remapping technology, which were validated by comparing with the test data. Finally, the influences of explosion conditions, such as explosion standoff, depth of burst, and charge weight on the dynamic behaviors of caisson specimens were numerically discussed. It derives that, the existing calculation formulas of overpressure and period of bubble obtained from the spherical charge are also applicable to the group charge; the reflection coefficient of hydraulic RC structure is around 1.7; the bubble pulsation induced by the underwater explosion could further deteriorate the damage level of RC caisson when the blast wave has already led to an inelastic structural response. The present work could provide beneficial references for the blast-resistance evaluation and design of hydraulic RC structures against underwater explosions.

An experimental study of the effects of degrees of confinement on the response of thermoplastic fibre–metal laminates subjected to blast loading

A series of tests on the dynamic response of thermoplastic fibre–metal laminates (TFMLs) subjected to blast loading with three different degrees of confinement (unconfined, vented and fully confined) were performed. The deflection time histories, the residual deformation, the internal delamination and damage mode of the TFMLs were recorded or observed by employing the digital image correlation, the 3D scanning and X-ray computed tomography techniques. Based on equivalent material properties combined with dimensionless damage numbers φq, the deformation of fibre–metal hybrid structures of different configurations can be effectively predicted and verified by experimental data. In addition, the effective load applied to the hybrid structure within the saturation response time is a key factor in determining the blast performance at different degrees of confinement. Vented explosions can result in the same dynamic response as fully confined explosions with even more severe internal delamination. The presence of quasi-static pressure in fully confined explosions can contribute more than 20% to the final deformation. The results can provide a basis for further understanding of the dynamic response and failure behaviour of fibre–metal hybrid structures subjected to blast loading with different degrees of confinement.

Falling weight deflectometer dispersion curve method for pavement modulus calculation.

The falling weight deflectometer (FWD) test is a common non-destructive testing method for evaluating the structural capacity of pavements. At present, data processing of the FWD test mainly focuses on the deflection data, while paying less attention to the deflection-time history. Because a FWD is equipped with impulse loads and geophones, which allow for the generation and capture of surface wave signal propagation, it is hypothesized that Rayleigh wave dispersion theory can be applied to calculate the modulus profile along the pavement depth by analysing the dispersive properties of the deflection signal measured during FWD tests. To test this hypothesis, we develop a new methodology for the FWD test and data analysis, referred to as the FWD dispersion curve method. We first introduce the concept of the new method, followed by an illustration of the procedure and the experimental set-up. Case studies on three concrete pavement segments are then presented to evaluate the effectiveness of the FWD dispersion curve method. Modifications to the existing FWD device are further recommended for the impact loading sources and signal collection process so that the modulus of a much shallower layer, such as the concrete slab and upper asphalt layers, can be obtained. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'.

Finite Element Analysis of Reinforced Concrete T-Beams with Multiple Web Openings under Impact Loading

In this study, a three-dimensional finite element analysis using ANSYS 12.1 program had been employed to simulate simply supported reinforced concrete (RC) T-beams with multiple web circular openings subjected to an impact loading. Three design parameters were considered, including size, location and number of the web openings. Twelve models of simply supported RC T-beams were subjected to one point of transient (impact) loading at mid span. Beams were simulated and analysis results were obtained in terms of mid span deflection-time histories and compared with the results of the solid reference one. The maximum mid span deflection is an important index for evaluating damage levels of the RC beams subjected to impact loading. Three experimental T-beams were considered in this study for calibration of the program. All models had an identical cross-section and span similar to those of the experimental beams. The diameter of the openings of the experimental beams was 110 mm. Three other diameters were varied (50, 80 and 130) mm. The location of the face of the opening with respect to the location of impact loading was investigated (the face of the opening at distance varied 0d, 0.5d, 1d and 1.5d from the location of loading, where d is the effective depth) and the number of web openings was varied (2,4 and 6) openings. All modeled beams subjected to dropping mass of 24.5 kg with height of drop of 250 mm (as for the experimental beams). Results obtained from this study showed that the behavior of beams with circular openings of diameter equal to 22% the web depth has a small effect on the response of the RC T-beams. On the other hand, introducing circular openings with a diameter equal to 35% and 57% of the web depth (80 and 130 mm) increases the maximum mid span deflection by 23% and 43% respectively. Results also showed that, openings with a distance greater than or equal to 1.5 d from the location of impact loading have no effect on the deflection of the RC beams.

Dynamic response and failure behaviour of thermoplastic fibre–metal​ laminates subjected to confined blast load

Due to the confinement effect, the blast load from a confined space explosion tends to cause more severe damage to structures. When subjected to this type of confined explosion, thermoplastic fibre–metal laminate (TFML) panels would experience repeated shock waves and relatively longer durations of quasi-static pressure. A better understanding of the dynamic response and damage mechanism of TFMLs under confined blast loading can greatly benefit the design of composite structures with improved blast resistance. In the present work, TFMLs with seven different configurations were designed and fabricated. Confined-blast experiments with various masses of trinitrotoluene (TNT) were performed on these TFMLs. The experimental results, including deflection time histories and X-ray computed tomography (CT) images, have been applied to the development of a method for predicting the dynamic response of laminates under confined blast loads. The findings of this work will assist in the rapid assessment of the deformation of fibre–metal laminates and assist in the pre-design of laminate structures in confined explosions.

Biofidelity Assessment of the WIAMan Thorax by a Comparative Study With Hybrid III, THOR, and PMHS in Frontal Sled Testing.

The Warrior Injury Assessment Manikin (WIAMan) anthropomorphic test device (ATD) has been originally developed to predict and prevent injuries for occupants in military vehicles, in an underbody blast environment. However, its crash performance and biofidelity of the thoracic region have not been explored. The aim of this study was to determine and evaluate the WIAMan thoracic responses in a typical frontal sled test. The 40 kph frontal sled tests were conducted to quantify the WIAMan thoracic kinematics, chest deflection, and belt loads. Comparative biofidelities of the WIAMan thorax and other surrogates, including postmortem human surrogates (PMHSs), Hybrid III, and test device for human occupant restraint (THOR) ATDs, were assessed under comparable testing conditions. The similarities and differences between WIAMan and the other surrogates were compared and analyzed, including the motion of bilateral shoulders and T1, time histories of chest deflections, and belt loads. The CORrelation and Analysis (CORA) ratings were used to evaluate the correlations of thoracic responses between the ATDs and PMHS. Compared to the PMHS and THOR, the WIAMan experienced a similar level of left shoulder forward excursions. Larger chest deflection was exhibited in WIAMan throughout the whole duration of belt compression. Differences were found in belt loads between subject types. Overall, WIAMan had slightly lower CORA scores but showed comparable overall performance. The overall thoracic responses of WIAMan under the frontal sled test were more compliant than HIII, but still reasonable compared with PMHS and THOR. Comprehensive systematic studies on comparative biofidelity of WIAMan and other surrogates under different impact conditions are expected in future research.

Influence of bedrock on viscoelastic responses and parametric back-calculation results for asphalt pavements and prediction of bedrock depth under FWD tests

Structural evaluation with a falling weight deflectometer (FWD) plays an essential role in the maintenance and rehabilitation of highways. Research on the influence of bedrock on the results of FWD tests and dynamic back-calculations for asphalt pavements has been a hot topic. In this study, the viscoelastic characteristics of the asphalt surface layer were described by the modified Havriliak-Negami (MHN) model rather than the layered elastic theory computing framework. The effects of bedrock on the deflection time history curves of viscoelastic asphalt pavement under the FWD test were investigated and analyzed by the spectral element method with fixed-end boundary conditions (B-SEM). The effects of bedrock on parametric back-calculation results for the viscoelastic asphalt surface layer and other elastic layers were explored by dynamic back-calculations. To exclude the impact of bedrock and improve the back-calculation accuracy, support vector regression optimized by the gravitational search algorithm (GSA-SVR) was adopted to predict bedrock depth. The viscoelastic responses and dynamic parametric back-calculation results were significantly influenced by bedrock beneath asphalt pavements, and the influence decreased (but was not eliminated) with increasing depth of bedrock. The GSA-SVR model provided excellent predictions of bedrock depth, and it can be applied for pavement performance assessment in road projects.

TDOF model for UHPC members under lateral low-velocity impact

The dynamic behaviors of ultra-high performance concrete (UHPC) members under lateral low-velocity impact loading have been intensively studied by experiment and numerical simulation, while the corresponding structural design approach is still limited and mainly concerned in this study. Firstly, through comprehensively considering the compression arch action, strain rate effect, and unloading stiffness, the dynamic resistance function of UHPC members, e.g., reinforced UHPC (R-UHPC) and UHPC-filled steel tube (UHPC-FST) beams/columns, are built and verified. Then, a two degrees of freedom (TDOF) model of the drop hammer test on UHPC members is improved by considering the P-δ effect and stress wave propagation effect. Furthermore, the impact force- and mid-span deflection-time histories of the existing five series of drop hammer tests on UHPC members are applied to verify the validity and applicability of the established TDOF model. The influence of considering the stress wave propagation effect, strain rate effect, and steel fibers in UHPC for predictions of the TDOF model are discussed by parametric analyses. Finally, based on the energy balance, the explicit formulae are proposed to predict the maximum and residual mid-span deflections of the flexural critical UHPC members under the lateral low-velocity impact, which can be helpful for the design of UHPC structures under lateral impact loadings.

Failure mechanism and static bearing capacity on circular RC members under asymmetrical lateral impact train collision

This paper aims to validate circular reinforcement concrete (RC) members' responses to the effect of an asymmetrical lateral impact span train collision. It was determined that the RC members' failure mechanism and dynamic response characteristics were important. Numerical analyses were conducted on four specimens. The specimen's crack development pattern, failure mode, impact force, and deflection time history curves are verified. Due to the difference in impact velocity, longitudinal reinforcement, and stirrups ratios, shear cracks indicate two types. A finite element (FE) modeling method has been proposed and successfully demonstrated. Using the control variables to study the failure process and mode, which were affected by reinforcement ratio, impact velocity, and slenderness ratio, by analyzing impact response characteristics. It is found that parameters greatly influence shear cracks' type and development range. Simultaneously, the changes in impact velocity and slenderness ratio affect the failure mode of the members. RC members' mechanical properties and failure mechanisms are studied using test and FE analysis. Members' failure modes, bending moment distribution and development, shear forces, reinforcement strain, and energy consumption are also investigated. The development of type I and type II shear cracks is discussed. A method to determine the shear cracks was proposed through regression analysis by supplementing other scholars' test data and combining it with the study test data.

Low Velocity Impact Response of Reinforced Concrete Flat Slabs

Background Dimensions of the reference concrete slab are 1950x1950x100 mm subjected to drop-weight impact loading. Objective A comprehensive parametric study was performed to examine the influence of many parameters on the RC slabs. Method From the viewpoint of cost and time savings, a three-dimensional finite element is a very good tool to predict the real behavior of the structural elements. Result and Discussion Results showed that the use of CFRP strips enhance the impact behavior of the slab. Contrarily, the existence of opening led to a dramatic decrease in the dynamic capacity of RC slabs with stress concentration around the openings. Furthermore, changing the shape of the impactor showed a significant effect on the peak impact load as well as the ultimate deflection at impact instant. Conclusion In the scope of this paper, the response of RC slab with top and bottom reinforcements exposed to drop-weight impact loading was inspected. Time histories of impact loads and deflections were presented in detail based on ABAQUS/ Explicit analysis. The findings presented in this paper can be presented as follows: 1. The FE models show a good correlation with the experimental data. Consequently, the proposed finite element models are efficient and economical tool to explorer the effect of many parameters on the performance of RC slabs subjected to drop-weight impact load. 2. The numerical simulation confirmed that using externally bonded CFRP strips has more influence on the peak deflection of the reinforced concrete slab than the recorded impact force. 3. Comparing to the flat shape of the impactor, the hemispherical and curved shape impactor can produce large penetration depth at the impact zone with higher plastic deformations in the concrete slab. However, the flat impactor produced higher deflection at the impact instant. 4. As the radius of the impactor increases, both the duration time and the peak impact force are increased. This is because of the higher contact area was obtained when the flat impactor (infinity radius of curvature) was used as compared to other impactors. 5. Due to decreases in RC slab stiffness, the presence of openings (regardless of their shape) has considerably increased deformations in concrete especially around perimeter of the openings extended to the nearby support. 6. It has been found that the eccentric impact loading causes higher plastic deformations than the concentric one.

Novel constitutive model of UHPC under impact and blast loadings considering compaction of shear dilation

Based on the framework of elastic-plastic-hydrocode concrete model, this study established a novel constitutive model of ultra-high performance concrete (UHPC) for impact and blast loadings considering the compaction of shear dilation. First, the established UHPC model is introduced, including five parts: (i) the dynamic failure strength surface, which is divided into tensile, compressive, and tensile-to-compressive regions and considers the Lode-dependence and strain rate effect; (ii) equation of state (EOS) that accounts for the nonlinear volumetric compaction; (iii) damage of strength, which contains independently described tensile and compressive strength hardening or softening formulae; (iv) damage of stiffness for depicting the compaction of shear dilation; (v) plastic flow rule, where the radial return algorithm is adopted for updating stress and an independent plastic potential function is employed to model the shear dilation. Then, parameters of the established UHPC model are systematically calibrated according to tests and empirical suggestions, and are further validated by conducting single element tests under varying loading paths. Through simulating the tests of reinforced UHPC beams/columns and UHPC filled steel tubes under drop hammer impact and reinforced UHPC panels under field explosion, it demonstrates that both the damage patterns and deflection-time histories of UHPC members are precisely reproduced by the established UHPC model. Furthermore, based on comparative simulations, it shows the compaction of shear dilation is critical for predicting the structural residual deflection of reinforced UHPC members. This study discloses a possibility to establish a constitutive model of concrete suitable for impact and blast scenarios with a wide range of strain rate and hydrostatic pressure.

Influence of water level on RC caisson subjected to underwater explosions

With the increasing significance of marine safety issues, the studies on the underwater blast-resistant performance of wharves, e.g., reinforced concrete (RC) caissons, has become an urgent demand. At present, the influence of water level on caisson subjected to underwater explosions was studied experimentally and numerically, e.g., underwater explosion loading characteristics and dynamic behaviors of caisson. Firstly, four shots of underwater explosion test were carried out both in free field and on a partially submerged caisson specimen, and the overpressure- and deflection-time histories, as well as the structural damage pattern were recorded. Then, the underwater explosion loading characteristics including the preceding blast wave and the succeeding bubble oscillations, the cut-off effect of the water surface, as well as the dynamic behaviors of caisson are comprehensively discussed. Furthermore, both the 1D and 3D finite element (FE) models were established, and by adopting Coupled Eulerian-Lagrangian method and remapping technology, the reliability of the FE models and analysis approach were validated by comparing with the test results. Finally, the influence of water level on the dynamic behaviors of caisson against underwater explosions were numerically examined. It derives that, the empirical formula derived based on spherical charge for underwater explosion peak overpressure is applicable to group charge, while the formula for impulse provides higher prediction on group charge; bubble oscillation has great influence on the impulse of underwater explosions; the unsubmerged part of hydraulic structures suffers slighter damage during underwater explosions than submerged part; the upper part of caisson is more sensitive to the change of water level; the partially submerged caisson shows better blast-resistant performance than fully submerged caisson. The present work could provide helpful reference for the studies on the underwater explosion loadings, as well as the blast-resistant assessment and design of hydraulic structures.

In-Situ Modulus Determination Using Dispersion Curves Developed From the Deflection-Time History Data

The advanced non-destructive tests (NDT) have become increasingly popular in the structural performance evaluation of transportation infrastructures including pavements. Among them, Falling Weight Deflectometer (FWD) and Spectral Analysis of Surface Waves (SASW) are the two most widely used methods in modulus measurement. Although popularly used, FWD methods base the analysis purely on the deflection characteristics of the pavement and the back-calculated modulus values are usually not unique for different data processing methods. SASW is based on fundamental spectral analysis of the Rayleigh waves but is practically limited in field operation due to its efficiency concern. On the other hand, the impact loading applied by the FWD will generate the Rayleigh wave, and the geophones used in FWD can capture Rayleigh wave fluctuation and measure the particle motion for phase velocity calculations. It is theoretically possible to use the deflection-time history collected by FWD to perform dispersion analysis based on the Rayleigh wave propagation theory, as used in the SASW method. Inspired from that, the main objective of this paper is to propose a new approach of using the deflection-time history collected by FWD to develop the dispersion curves and thus obtain the in-situ modulus of the layered asphalt pavement. This approach is referred as the FWD dispersion curve method. Two in-service semirigid base asphalt pavement segments were used as case studies to explain the new methodology. The results of layered modulus from the FWD dispersion curve method were compared with the traditional FWD and SASW method, as well as the laboratory Indirect Tensile (IDT) testing results using field cores. Findings demonstrated the feasibility of the FWD dispersion curve method in accurately capturing the layered modulus profile of the asphalt pavements.

A comparative analysis of thermos-mechanical behavior of CNT-reinforced composite plates: Capturing the effects of thermal shrinkage

In this study, an analytical model based on the classical laminate theory (CLT) is developed for the prediction of the effective thermal expansion coefficients (ETECs) of general angle-ply laminates (symmetrical and asymmetrical). The applications of the derived model are shown by solved examples for the prediction of ETEC of carbon nanotube-reinforced (CNTRC) angle ply laminates for various ply angles. CNTRC laminates with a negative thermal coefficient (NTC) are obtained and considered as a special case. For an extreme case, a laying angle of (35/-35)3T and (55/-55)3T, along with an NTC of −0.79 × 10−5/K is achieved. Meanwhile, the Reddy shear plate model is extended to the framework of Von Kármán nonlinearity. The corresponding dynamic equations are analytically established. With the help of the two-perturbation approach, the deflection time history curves of the forced vibration are obtained. Numerical results show that the thermal-vibration behaviors may be adjusted and controlled by changing the TEC and functionally graded pattern. The presented analytical results not only are theoretically fundamental for understanding the thermal-vibration behavior of FG-CNTRC but also serve as guidelines for NTC design of composited laminated structures.

Numerical study on existing RC circular section members under unequal impact collision

Traffic accidents and derailed train-related incidents have occurred more often than ever in recent years, resulting in some economic damage and casualties. Reinforced concrete (RC) constructions often involve derailed train and vehicle accidents. Rarely are such side collisions studied in previous studies. To do this, high-fidelity simulation-based finite-element (FE) models are created in this paper to accurately simulate the collision of circular RC members with a derailed train. The reinforced concrete member structure is common in high-speed railway stations. The impact energy of the impact body is significant, causing structural member failure. It analyses the dynamic behavior of reinforced concrete members under unequal span impact loads. Numerical implementations of impact issues are discussed from the perspective of geometric, contact, and material properties. The reliability and precision of the ABAQUS code to solve impact issues are verified by comparing failure modes, impact, and deflection time history experimental outputs. By analysing the impact response characteristics, used the control variables to study the failure process and mode (including the characteristics of impact and reaction forces, deflection time history curve, impact force–deflection curve, and bearing reaction force–deflection curve). The reinforcement ratio, impact velocity, concrete strength, and slenderness ratio significantly affect shear crack pattern and development. Changes in impact velocity and slenderness ratio also affect member failure modes.