Journal of Engineering Mechanics

The damage to pipelines from submarine landslides or debris flows has been vastly reported. In this paper, the behavior of pipelines is investigated through analytical and numerical analyses. A refined analytical method is first brought forward by improving the tension assumption. The pipeline is divided into different segments based on loading conditions, and the continuity of displacement, inclination angle, bending moment, and shear are all preserved. Then numerical analysis by vector-form intrinsic FEM is carried out by further considering the axial soil resistance at the sliding zone. The numerical analysis demonstrates that the initial negative pipeline displacement is a threat to pipeline safety because of the large increase in bending moment. The axial tension is closely related to the location of the landslide impact and the initial pipeline configuration. The variations in displacement and tension with time are also investigated in the parametric analysis.

A coupled finite-element squared (${\text{FE}}^2$)-framework is formulated and employed for simulation of a transient and coupled moisture-chloride ion diffusion problem in concrete. Simulations are carried out on the macroscale, where the material response is obtained concurrently in the computations by introducing a representative volume element (RVE) in the macroscale quadrature points. The RVE, in turn, contains the mesoscale heterogeneities of concrete in terms of cement paste, aggregates, and interfacial transition zone (ITZ). In this fashion, the RVE comes to serve as a constitutive model for the macroscale. A numerical example is given to show how the transient macroscale diffusion is influenced by the composition of the mesoscale constituents. Parametric studies were carried out with respect to the aggregate content within the RVE, both including and excluding the ITZ, and the coupling parameters of moisture and chloride ions.

This paper focuses on the problem of static reanalysis with modifications of supports. An efficient approximate reanalysis method is proposed. The definition of an augmented stiffness matrix is first introduced, and the preconditioned conjugate gradient method is then used. A preconditioner is constructed by fully using the Cholesky factorization of the initial stiffness matrix. The method preserves the ease of implementation, and the accuracy of the approximate solutions can be adaptively monitored. Numerical examples show that high-quality results can be provided by the proposed method and that the convergence is fast.

The dynamic response of concrete-filled fiber-reinforced polymer (FRP) steel tubes under impact loading was investigated in this study. Eleven column specimens with the same cross-sectional area but different lengths were tested on a drop-weight system. These specimens included eight concrete-filled carbon-FRP steel tubes, two concrete-filled glass-FRP steel tubes, and one concrete-filled steel tube as a baseline material. The time-history curves of impact force, acceleration, deflection, and strain were recorded. Experimental results showed that the improvement of FRP on the impact resistance of concrete-filled steel tubes is remarkable, especially for glass-FRP steel tubes.

The piezoelectric transduction mechanism is widely used in passive sensing, health monitoring, and energy harvesting. Plate-type energy harvesters are usually discouraged; however, piezoelectric layers on a substrate in a certain pattern were found to be suitable for harvesting energy from a wider band of frequencies. However, to understand the theoretical behavior of the harvesters with any arbitrarily shaped piezo patch, a detailed mathematical model is lacking. This paper proposes a comprehensive analytical model to calculate the frequency response function (FRF) from simply patterned piezoelectric layers. A generalized mathematical form is presented for an arbitrary rectangular piezoelectric patch placed on a host plate. The strain-rate damping mechanism is incorporated for better and more accurate results. First, a comparative study on the strain-rate damping effect is presented by placing the piezoelectric layer on the entire plate. Without strain-rate damping, the model incorrectly estimates voltage output. Further, a methodology through a genetic algorithm optimization process is proposed to generate the required pattern of piezoelectric layers tailored to a desired requirement. With the proposed generalized mathematical model, the voltage output from the harvester with any particular shape and size of piezoelectric layers can be calculated predictively.

Crack initiation is the premise of fracture. Various analytical models are available to elucidate its mechanisms, but some require many details that may not be suitable for engineering practice or some specify a single crack that is not applicable for a large number of distributed cracks. To fill this research gap, this paper aims to develop an energy-based crack initiation criterion for viscoelastoplastic materials with a distributed crack system using the energy that can be measured from the test. The composition and formulation of the criterion are determined by studying fracture behaviors and local energy redistribution around cracks in asphalt mixtures as typical viscoelastoplastic materials. The energy in the local nonlinear zone, the energy in the local energy release zones, and the surface energy of the material are identified to constitute the energy-based crack initiation criterion. The energy in the local nonlinear zone and local energy release zones are measured by designing repeated load tests to determine the critical condition for crack initiation, called the endurance limit. The surface energy of an asphalt mixture is composed of the surface energy of cohesion and surface energy of adhesion, which are measured from surface energy tests. Then the criterion is validated using the measured energy components. Statistical analysis is conducted on eight different types of asphalt mixtures and proves that the criterion is balanced at the point of crack initiation. The energy-based crack initiation criterion, along with repeated load tests, can act as a substitute for surface energy tests. Depending on the cracking pattern in the material, the surface energy solved from the criterion is the surface energy of cohesion, the surface energy of adhesion, or the combined product of both. When there is both cohesive and adhesive cracking, the calculated surface energy from the criterion can be used to separate cohesive cracking and adhesive cracking in the same material.

This work presents a novel approach to circumventing the difficulties associated with using digital image correlation (DIC) for problems that involve discontinuities like fracture and fragmentation. The proposed method provides a simple means to combine traditional DIC approaches with peridynamics to achieve full-field displacements, even in the vicinity of cracks. In regions where DIC is accurate and effective, the displacement field is determined using a traditional approach. In discontinuous regions, the displacement field is solved for using peridynamics. This study shows that this method can be used successfully for investigating damage in materials such as nuclear graphite and fiber-RC (FRC). It also shows that the proposed method alleviates nonphysical strains in the vicinity of cracks, common to alternative approaches, which detrimentally degrade the quality of postprocessed quantities of interest such as fracture toughness.

Many researchers have asserted the importance of considering the nonlinearity of the mechanical behavior of asphalt binders for accurately estimating their performance under field conditions, and for comparing and ranking them accordingly. To do so, it is necessary to have a robust and reliable nonlinear viscoelastic theory and a model derived under its purview that can describe the mechanical response of asphalt binders reasonably well. The objective of this study is to develop such a model. A new Gibbs-potential–based thermodynamic framework is used for this purpose. The model developed in this paper is a generalization of the Oldroyd-B model. It is used successfully to describe results of several experiments from the literature concerning the nonlinear response of asphalt binders, including nonlinear creep-recovery and stress-relaxation behavior, thinning behavior, and the appearance of normal forces perpendicular to the plane of shear in simple shear tests.

For the nonlocal theory of structures, Eringen’s small length-scale coefficient $e_0$ may be identified from atomistic modeling or experimental tests. In this study, Eringen’s small length-scale coefficients are presented for the vibration and buckling of nonlocal rectangular plates with simply supported edges. The coefficients are calibrated by comparing the vibration frequency and buckling loads obtained from a nonlocal plate and a microstructured beam-grid model with the same characteristic length. The beam-grid model is composed of rigid beams connected by rotational and torsional springs. It is found that the small length-scale coefficient $e_0$ varies with respect to the initial stress, rotary inertia, mode shape, and aspect ratio of the rectangular plate.

The complex variable FEM (ZFEM) has been enhanced in this research to compute derivatives with respect to shape, material properties (elastic modulus, yield stress, plastic modulus, hardening parameters), and loads for a nonlinear solid mechanics model undergoing plastic deformation. This method presents a new and novel approach that uses complex variables to estimate derivatives within an incremental-iterative procedure for the solution of nonlinear finite-element equations. ZFEM offers significant advantages over real-valued finite-element analysis in that highly accurate derivative information may be obtained from a single analysis. The method has been implemented within a commercial finite-element software package using the user element and user material options. A strategy was developed to allow the software’s solver algorithm to handle complex variable operations needed by ZFEM to perform sensitivity analysis. Numerical results confirm the high accuracy of the method through the analysis of a thick-walled cylinder case using perfectly plastic, bilinear hardening, and Ramberg-Osgood plasticity models.

Benchmark flexure solutions for rectangular thick plates with combinations of clamped and simply supported edges, as well as for cantilever rectangular thick plates, are obtained by using an up-to-date symplectic superposition method in the Hamiltonian system. The method developed offers a rational way to obtain sufficiently accurate solutions to thick-plate problems, which can yield more benchmark solutions to similar problems. Comprehensive numerical results are presented for the future validation of various approximate/numerical methods.

A novel continuum damage mechanics-based framework is proposed to model the detrimental effect of moisture on the response of particulate composite materials. This framework extends the well-known Kachanov’s effective (undamaged) configuration and the concept of effective stress space to moisture-susceptible materials by introducing wet-undamaged and wet-damaged natural configurations. Physically based moisture-induced damage internal variables are introduced within the proposed framework to consider the moisture aggravation effect and to couple moisture-induced damage with mechanical responses. Constitutive relationships are proposed for the time-dependent evolution of adhesive and cohesive moisture-induced damage to explicate the fundamental processes associated with the moisture-induced damage phenomena. The material properties associated with the moisture-induced damage constitutive relationship are determined based on the available experimental data from asphalt concrete materials. Comparison of the model predictions with independent experimental measurements illustrates the capabilities of the model in capturing the coupled moisture-mechanical response of asphalt concrete.

This study formulates a simple tetrahedral finite element equipped with rotational degrees of freedom that can be used effectively to solve problems for both Cosserat and Cauchy continua. The formulation makes no assumption regarding the symmetry of the stress tensor, and such symmetry is achieved at convergence for the Cauchy problems. The numerical implementation of the new element is straightforward, and numerical tests demonstrate second-order accuracy in the case of both Cosserat and Cauchy elasticity.

Modeling natural roll waves in unstable open channel flows where Froude number $\mathsf{F}>2$ has not been well understood. In this investigation, some evolution properties of natural roll waves are numerically disclosed, with the intention to advance the development of modeling unstable open channel flows. To simulate natural roll waves, the diffusive Saint-Venant equations are solved using a high-resolution scheme based on the finite-volume formulation. The numerical solutions of detailed wave–wave interaction processes, including wave overtaking, absorption, and spawning, are displayed. Wave overtaking and absorption result in the coalescence of multiple waves; wave spawning results in the birth of new waves. The spatial evolution of roll waves always undergoes initial, transition, and final phases. The three phases constitute a generality for roll-wave evolutions. Finally, the spectral analysis along channel reveals that both the wave period and nonperiodicity increase from upstream to downstream channel locations.

A new concept for designing a dome is introduced. The dome is inverted from a basket made of catenary strips, thereby maintaining the optimal properties of the catenary. Four kinds of domes are considered: the polygonal catenary dome, the catenary dome of uniform thickness, the catenary dome of uniform stress, and a dome supporting a uniform platform. Given the height and width of the dome, the solutions are in closed form and are unique.

The vibration method is a very important technique used to estimate cable force. However, the measured in-plane frequency may include a contribution from the cable-deck interaction. In this study, the equations of motion of a cable-stayed beam are obtained to consider the effects of the interaction, and its eigenvalue problems are investigated. The closed-form eigenvalue solution and numerical results are applied to discuss the measured frequency for the estimation of the cable force. It is shown that the cable-deck interaction does not affect the low-order out-of-plane frequencies of the cable-stayed beam, and the fundamental frequency can be used to estimate the cable force. Finally, a practical treatment of the measured frequency is proposed.