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Biochar has shown great promise in producing low-cost low-carbon concrete for civil infrastructure applications. However, there is limited research comparing the use of pristine and contaminated biochar in concrete. This paper presents comprehensive laboratory experiments and three-dimensional nonlinear finite element analysis on the mechanical, economical, and environmental performance of reinforced concrete beams made using concrete blended with biochar generated from vetiver grass roots after the roots were used in an oil extraction process. Both pristine biochar and biochar that were used to treat wastewater through adsorbing heavy metals (100 mg/L of Pb, Cu, Cd, and Zn) were investigated. The biochar was used to replace up to 6% Portland cement in concrete. Laboratory experiments were conducted to characterize the workability, mechanical properties, shrinkage, and leaching potential of the concrete blended with biochar. The results showed that using biochar could increase the compressive strengths and reduce the shrinkage of concrete without causing a leaching problem. The results from finite element analysis of the reinforced concrete beams showed that the use of biochar was able to increase the flexural performance of the beams as well as their economic and environmental performance. This research will promote the development and structural applications of low-cost low-carbon concrete. [ABSTRACT FROM AUTHOR]

• A numerical method is proposed for the fatigue analysis of steel-UHPC composite decks. • Fatigue degradation of stud connectors is considered in the numerical method. • Effects of stud degradation and stud arrangement on the fatigue performance of steel-UHPC composite decks are evaluated. The fatigue degradation of stud connectors is generally neglected in the fatigue analysis of steel-UHPC composite decks, which may lead to inaccurate results. This paper studies the effects of stud degradation and stud arrangement on the fatigue behavior of steel-UHPC composite decks via finite element analysis. A numerical method for the fatigue analysis of composite decks is proposed considering the fatigue degradation of studs. The numerical method is experimentally validated and applied to evaluate the fatigue performance of composite decks. The effect of stud arrangement on the fatigue response of composite decks is studied by parametric analysis. The results indicated the fatigue degradation of studs and the decrease in stud spacing caused more uniform distribution of shear forces at steel-UHPC interfaces. The fatigue degradation of stud connectors reduced the structural stiffness, while reducing the stud spacing enhanced the local stiffness but increased the stress ranges of some fatigue-critical details. Neglecting the stud degradation could lead to an underestimation of the fatigue life of stud connectors. This study advances the understanding of the fatigue behavior and the ability to analyze the fatigue behavior of steel-UHPC composite decks. [ABSTRACT FROM AUTHOR]

In this study, the dynamic behavior of a concrete-filled steel tube (CFST) hybrid framed arch railway bridge under moving trains are investigated through an in-site dynamic test. The bridge was tested under train loadings in different scenarios and at different speeds of the trains. The free vibration characteristics, strain, displacement, and acceleration of the bridge structure were measured to evaluate the dynamic responses of the train-bridge coupling system. A three-dimensional finite element model, which took into account the train-bridge coupling and track irregularities, was established to analyze the behaviors of the train-bridge system. The model was validated against the in situ test results. The impact effect on the girder was greater than that of the arch frame. The acceleration responses of the trains on the bridge increased with the train's speed. The riding comfort of the trains was evaluated based on the measured dynamic responses of trains. [ABSTRACT FROM AUTHOR]

Ship collision is rare, yet it leads to serious consequences once it occurs, in particular for long-span bridges. This study investigates dynamic responses of a long-span, rail-cum-road cable-stayed bridge under ship collision through finite element analysis. Three ship tonnages were investigated, which are 3000, 5000, and 8000 t, respectively. The displacement, velocity, and acceleration of the bridge under ship collision are analyzed. The collision process is simulated in two explicit steps to improve the computational efficiency. First, the collision force is determined through a collision simulation of the ship to a rigid body that simulates the massive bridge pier. The collision force is then applied to the bridge to analyze the dynamic responses of the bridge. The simulation results of the collision force are compared with four different design codes. Analysis results from different codes show significant discrepancies, demonstrating lack of reliability of the formula recommended by the codes. The results indicate that the maximum displacement and acceleration occur at the top of the bridge pylon. The bridge's responses under ship collision decrease as the collision angle increases from 0° to 20°. [ABSTRACT FROM AUTHOR]

Pouring position as the input heat source has great influence on the temperature field evolution. In this study, the Flow3D simulation software was applied to investigate the influence of pouring methods (with fixed or moving pouring channel) on AZ91 Mg alloy horizontal centrifugal casting (HCC) process. The simulation results show that the moving pouring channel method can effectively increase the cooling rate and formability of casting pipe. The casting experiment shows that an AZ91 Mg alloy casting pipe with homogeneous microstructure and clear contour was obtained by the moving pouring channel method, and the grain size of the casting pipe is significantly decreased. Meanwhile, serious macro-segregation appeared in the AZ91 casting pipe by the fixed pouring channel HCC process. Compared with the fixed pouring channel, the moving pouring channel can remarkably improve the ultimate tensile strength and elongation of the AZ91 HCC pipe from 142.2 MPa to 201.5 MPa and 6.2% to 6.7%, respectively . [ABSTRACT FROM AUTHOR]

Purpose A simple shape-free high-order hybrid displacement function element method is presented for precise bending analyses of Mindlin–Reissner plates. Three distortion-resistant and locking-free eight-node plate elements are proposed by utilizing this method.Design/methodology/approach This method is based on the principle of minimum complementary energy, in which the trial functions for resultant fields are derived from two displacement functions, F and f, and satisfy all governing equations. Meanwhile, the element boundary displacements are determined by the locking-free arbitrary order Timoshenko’s beam functions. Then, three locking-free eight-node, 24-DOF quadrilateral plate-bending elements are formulated: HDF-P8-23β for general cases, HDF-P8-SS1 for edge effects along soft simply supported (SS1) boundary and HDF-P8-FREE for edge effects along free boundary.Findings The proposed elements can pass all patch tests, exhibit excellent convergence and possess superior precision when compared to all other existing eight-node models, and can still provide good and stable results even when extremely coarse and distorted meshes are used. They can also effectively solve the edge effect by accurately capturing the peak value and the dramatical variations of resultants near the SS1 and free boundaries. The proposed eight-node models possess potential in engineering applications and can be easily integrated into commercial software.Originality/value This work presents a new scheme, which can take the advantages of both analytical and discrete methods, to develop high-order mesh distortion-resistant Mindlin–Reissner plate-bending elements. [ABSTRACT FROM AUTHOR]

• Shear behaviors of studs embedded in ECC are studied. • Effects of stud height-to-diameter ratio on the shear behaviors of the studs are evaluated. • Formulas are provided to predict the shear capacity of studs embedded in ECC. Engineered Cementitious Composite (ECC) exhibits superior mechanical properties such as high tensile strength, ductility, and toughness, which enable using thinner sections in steel-ECC composite structures. Existing design equations for the shear capacity of stud connectors were derived by regression analysis of test data from push-out specimens using normal concrete, which often have stud height-to-diameter ratios above 4. This research investigates the shear behaviors of stud connectors, with different height-to-diameter ratios from 2.73 to 4.62, embedded in ECC. Push-out tests showed that the height-to-diameter ratio is important for the shear capacity of studs. Finite element analysis was performed to evaluate the effects of the diameter, height-to-diameter ratio, and tensile strength of studs as well as the compressive properties of ECC on the shear behaviors. Regression analysis was performed using the analysis data to modify the equations for predicting the shear capacity of studs embedded in ECC for steel-ECC composite structures. [ABSTRACT FROM AUTHOR]

Abstract: Thermal residual stress analysis and failure simulation of particle-reinforced composites are performed based on thermomechanics and the finite element method (FEM) to investigate the effects of particles on strength and toughness. It is discovered that the residual stresses in matrix are controlled mainly by adjacent particles via stress superposition, and an expression for the residual stress is derived. The size of the residual stress zone in the matrix is found to increase with the particle size. The FEM failure simulation in uniaxial tension reveals two features: (i) the residual stress caused by the second phase particles in ceramic matrix would lead to strength degradation due to the weakest link theory; (ii) the second phase particles in the composite may enhance the fracture toughness because of the crack arrest and crack-deflection caused by residual compressive stress. These features have been confirmed by experimental results of TiN/Si3N4 composite. [Copyright &y& Elsevier]

Abstract: In this paper, a new shape-free multi-node singular hybrid stress-function (HSF) element and a shape-free 8-node plane HSF element proposed recently are employed to simulate the quasi-static 2D crack propagation problem. Compared with other well-known methods, such new scheme exhibits four advantages: (i) for the singular element, the shape and the number of nodes can be flexibly adjusted as required; (ii) high precision for stress intensity factors (SIF) can be obtained due to the advantages of the HSF method; (iii) only simple remeshing with a very coarse mesh is needed for each simulation step; (iv) unstructured mesh containing extremely distorted elements can be used without losing precision. It demonstrates that the proposed scheme is an effective technique for dealing with crack propagation problems. [Copyright &y& Elsevier]

This paper presents an approach to investigate the effect of temperature on the transmission and distribution of vibration energy for train-track-bridge coupled systems. The vibration of the coupled system can be simulated by integrating the multi-body dynamics model of the train with the finite element models of the track and bridge. The transmission and distribution of vibration energy can be evaluated using a structural intensity method. This approach was implemented to investigate the vibration characteristics of a coupled system under extreme temperature conditions. The system consisted of a CRH2 high-speed train, a CRTS I double-block ballastless track, and an arch bridge. The results show that extreme temperature not only impacts the characteristics of vibration energy transmission in the coupled system but also affects vibration energy distribution. This research provides new insights into vibration control and optimization design for bridges in regions with significant temperature variations. • A vibration energy quantification and visualization method for train-track-bridge coupled systems is proposed. • Hybrid modelling integrating multi-body dynamics and finite element models is performed. • Thermal effect as well as track irregularity are considered. • Vibration energy transmission characteristics of each substructure of the coupled system are analyzed. • The distribution law of vibration energy under various thermal conditions is analyzed for a high-speed railway arch bridge. [ABSTRACT FROM AUTHOR]

• Flexural behavior of corrugated steel-(ultra-high-performance concrete) UHPC composite bridge decks were tested. • Finite element analysis of the corrugated steel-UHPC composite bridge decks was conducted. • Parametric studies on main influencing parameters on flexural behaviors were performed. • A theoretical model was developed to predict load capacity of the proposed composite bridge decks. This paper investigates flexural behavior of composite bridge decks composed of corrugated steel deck and ultra-high-performance concrete (UHPC) slab connected via modified clothoid-shaped (MCL-shaped) dowels. Six composite bridge deck specimens were fabricated and tested under different shear span lengths. A finite element model was established and validated against the experimental results, and used for parametric studies to evaluate the effects of the depth of corrugated steel deck, thickness of UHPC slab, and shear span length on the flexural behavior. The results indicated that the MCL-shaped dowels provided adequate longitudinal and transverse shear strengths. The composite bridge decks demonstrated flexural failure mode regardless of shear span length, and showed sufficient ductility. The depth of corrugated steel deck showed the highest impact, followed by the thickness of UHPC slab. Finally, a theoretical model was developed to predict the load-bearing capacity of the composite bridge deck. The maximum discrepancy of the theoretical results was −5.9% by validating against the experimental and numerical results within the investigated ranges of parameters. [ABSTRACT FROM AUTHOR]

• Vibration energy transmission of high-speed train-track-bridge systems is characterized. • Hybrid modelling integrating multi-body dynamics and finite element models is performed. • Interactions between the train, track, and bridge as well as track irregularity are considered. • A power flow method is utilized to characterize vibration energy transmission. • Effects of key variables of ballastless track and bridge on energy transmission are evaluated. This paper investigates the vibration energy transmission characteristics of high-speed train-track-bridge coupled systems based on a high-speed railway in China. A coupled system composed of a CRH380A high-speed train, CRTS II slab ballastless track, and standard 32-meter girder bridge was analyzed through hybrid simulations that integrated multi-body dynamics and finite element analysis. The hybrid model included the interactions between the train, track, and bridge of the coupled system as well as track irregularity. The vibration energy of the coupled system was quantitatively investigated under various train velocities. The effects of key variables of ballastless track and bridge on energy transmission characteristics were evaluated. The studied variables included fastener stiffness, fastener damping, mortar layer stiffness, bridge cross section, and bridge damages. The results show that these variables have significant effects on vibration energy transmission, suggesting that it is important to consider these variables in the design and operation of high-speed railways. [ABSTRACT FROM AUTHOR]

• The effects of the geometrical parameters on the weld root NSIFs of the rib-to-deck welded joints is investigated. • Multi-parameter analysis is carried out to propose the formulae of predicting the weld root NSIFs. • The proposed NSIFs formulae are applied to evaluate the stress distributions and averaged SED of the fatigue test specimens. • The predicted averaged SED is used to link the fatigue test data to the W-N curves. Orthotropic steel deck (OSD) has been widely employed in the bridge engineering owing to its superiorities of light-weight and high strength. However, the fatigue damage of rib-to-deck welded joint in OSD is one of the most challenging issues. The notch stress intensity factors (NSIFs) that characterize the local mechanical properties of notch tips are major parameters for fatigue evaluation of rib-to-deck welded joint. This paper proposes formulae of the NSIFs of weld root for rib-to-deck welded joint under deck loading modes. First, parametric studies are conducted using a finite element model to establish a holistic understanding of the effects of the geometrical parameters on the NSIFs. The investigated parameters include the weld penetration rate, relative weld height, deck toe flank angle, and plate thickness ratio. Then, multi-parameter analysis is carried out based on the data generated from the parametric study. Finally, the proposed formulae of the NSIFs are evaluated and applied to evaluate the stress distribution and the averaged strain energy density of single-weld specimens for rib-to-deck welded joints. The maximum error of 9.5% indicates that the NSIFs predicted using the proposed formulae are in good agreement with the finite element analysis results. The proposed formulae provide useful tools for determining the stress distributions and the averaged strain energy density of single-weld rib-to-deck welded joint specimens. [ABSTRACT FROM AUTHOR]

• A unified fatigue resistance evaluation method of riveted joints is developed using structural stress approach. • Master S - N curves of riveted joints are proposed and the single fatigue category was recommended for the different types and sizes of riveted structures. • The unified fatigue resistance evaluation method appears insensitive to the mesh size and element type in finite element analysis. Many riveted steel bridges were constructed worldwide between 1850 and 1950. A number of them are still in operation, and their fatigue damage is a major burden in maintenance. This paper presents a unified structural stress approach to evaluate the fatigue resistance of riveted joints for steel bridges. The presented approach was utilized to establish and calibrate S - N curves for riveted joints based on fatigue data from 114 tested specimens, and the curves were validated by fatigue test data from large-scale riveted structures. A single fatigue category was obtained to evaluate different types and sizes of riveted structures. The investigation results showed that the presented approach is capable of evaluating different types of riveted joints and structural stresses. The structural stress approach is insensitive to the mesh size and the element type in finite element analysis. The presented method is convenient for practical engineers to evaluate the fatigue resistance and fatigue life of riveted steel bridges. [ABSTRACT FROM AUTHOR]

• An innovative steel–concrete joint is proposed for railway hybrid girder cable-stayed bridges. • The proposed design utilizes double bearing plates and concrete filled steel cells. • The proposed design is investigated through large-scale model test and finite element analysis. • The stress distributions and load transfer pathway are investigated to promote the design. • The proposed design delivers desired force transfer performance with a high uniformity. This research proposes an innovative steel–concrete joint, which utilizes front and rear bearing plates and concrete filled steel cells, for long-span railway hybrid box girder cable-stayed bridges. This study investigates the mechanical behavior of the steel–concrete joint through a model test and finite element analysis, aiming to understand the stress distributions, shear lag effects, deformations, and force transfer pathway of the joint under axial and shear loads. A large-scale model (scale: 1/5) was designed following the similarity theory. The model was fabricated and tested under representative load cases. Based on the model test, a three-dimensional finite element model was established and validated using the model test results. Then, the finite element model was utilized to perform a parametric study on the effects of the length of the joint, the thickness of the bearing plates, the height of steel cells, and the stiffness of shear connectors. The results show that the proposed steel–concrete joint provides desired stress distribution and force transfer behavior, in terms of the force transfer rate and uniformity. In the composite section of the joint, the rear bearing plate transfers 57% the total axial force. This study is expected to promote the design and applications of hybrid girders. [ABSTRACT FROM AUTHOR]