The reliable prediction of the seismic response of reinforced concrete (RC) structures hinges on accurate modeling of the cyclic behavior of their constituent elements. The load–deflection curve in RC beams exhibits a pinched hysteresis pattern corresponding to energy dissipations. This pinching effect, often observed under seismic loading conditions, reflects a reduction in stiffness and energy dissipation capacity at certain loading stages. Despite its significance, the detailed mechanisms underlying this phenomenon remain underexplored in existing literature. This paper aims to address this gap by presenting simplified models that directly represents the pinching effect at the crack scale. The model is grounded in a comprehensive analysis of shear stress interactions and crack closure dynamics, hypothesized as primary contributors to the pinching phenomenon. Our approach involves a meticulous examination of the hysteresis loops’ area and shape, facilitating the estimation of an equivalent viscous damping ratio to represent energy dissipation in seismic simulations, irrespective of changes in the structure’s damage or ductility levels. The paper unfolds in three key sections: The first section underscores the significance of a nuanced understanding of the pinching effect in seismic analysis. The second section presents an extensive literature review, consolidating crucial insights into the nature of the pinching phenomenon. The third section details the development and application of the proposed mesoscopic model, highlighting the impact of various geometrical and material parameters on the pinching effect.

The paper deals with the current state of the art arising in the design of the structures, operating under traditional mechanical loading in the aggressive environment causing their corrosion. The express goal in this case is establishing the corrosion rate dependence on the stress state of the structure and considering its durability. Thus, the use of basic mathematical models that describe the effect of corrosion rate depending on the stress state of the structure is considered. The main objective of this paper is to provide a review of useful approximations that have been suggested to deal with interaction of stress and corrosion fields. The first model that considers such a relationship is the Dolinsky model, which uses a linear dependence of the stress effect on the corrosion rate. Additionally, the Gutman model, in which the dependence of the corrosion rate on stress is expressed by an exponential law, is considered. When constructing mathematical models of structures’ corrosion wear, it is also necessary to take into account the protective coatings operation and determine the incubation period duration, which is the durability of the applied protective coatings. In this regard, the use of one of these models, which takes into account the decrease in the polymer coatings’ protective properties and a combined approach to accounting for corrosion and the anti-corrosion coatings’ protective properties are presented. Determining their reliability is an equally important aspect in the design of structures subject to corrosion. Therefore, the main theories of reliability and their practical application were considered on specific examples. A characteristic feature of the work is the coverage of issues related to the optimal design of structures operating in corrosion conditions. Two classes of problems were studied. First, determining the optimal form of structures under various types of mechanical loading and the use of the above corrosion models is considered. In the second class, the use of promising optimization models related to the solution of multi-criteria problems (using the fuzzy sets theory), as well as models with a pronounced economic bias, which allow making a cost estimate of structures failure-free operation during their lifetime, is considered. This article's novelty consists of preparing a comprehensive review of the interaction of stress and corrosion conditions. Researchers are deemed to greatly benefit from knowing the existing literature along with their strengths and weaknesses.

This paper studies the flow over a solid inclusion embedded in a porous medium of low permeability. We study Rankine bodies which represent circular cylinders and spheres when the aspect ratio is one, and thin plates and almost uniform rods when the aspect ratio is small. Using boundary layer theory, the flow field and pressure distribution are determined. It is found that the pressure drag dominates the shear drag except for small aspect ratios. Thus, geometry plays a decisive role in the choice of using the Darcy equation or the Darcy-Brinkman equation. The results are important for the determination of flow resistance of a non-homogeneous porous medium which has solid inclusions.

To improve the accuracy of predicting multiaxial fatigue life, an enhanced multiaxial low-cycle fatigue life model is proposed based on the FS model. This model introduces a correction parameter for the stress-related term to consider the influence of normal stress and shear stress on the critical plane. The feasibility of the model is investigated, and it is validated using fatigue test data from eight different materials. The results indicate that the proposed model is applicable for both symmetric and asymmetric loading conditions under constant amplitude loading, with highly accurate fatigue life prediction results.

For tensegrity structures, there are many groups of cables and bars with symmetrical structures or similar internal forces. In this paper, an application of a fuzzy clustering algorithm in the context of form-finding processes for symmetric tensegrity structures is proposed. This algorithm aims to automate grouping, optimize form-finding strategies, and expedite convergence. Point sets are generated through the segmentation of structural components, and Hausdorff distance is used to extract spatial features. Following this, fuzzy clustering automatically groups components with geometric symmetry. The resultant clustering matrix facilitates the refinement of form-finding processes, thus reducing the computational load associated with solving the equilibrium matrix for internal forces within tensegrity structures. By clustering components with analogous internal forces, computational efficiency is enhanced. Additionally, this methodology refines numerical form-finding outcomes based on symmetrical attributes, improving form-finding precision.

This paper established the exact formulas for mode shapes of cracked nonuniform axially functionally graded (AFG) beams. The formula of the mode shape of cracked nonuniform AFG beam is derived in the form of a power presented as a recurrent relation. The power series solution of cracked beam is the same with the intact beam where the effect of cracks contributes to only the first four coefficients of the power series. The derivation of the formula of mode shapes is presented in details. Numerical simulations show that these effects on the natural frequency and mode shape are quite significant. The natural frequency and mode shape are more sensitive to cracks located at positions with low elastic modulus, small cross section and high mass density. For the case of tapered AFG cantilever beam, it is important to consider not only cracks located close to the fixed end but also cracks located close to the free end, especially when the free end has lower elastic modulus and higher mass density.

This paper applies wave equations and boundary conditions to a periodic electro-elastic microbeam, which incorporates transverse shear, microstructure and flexoelectric effects to anticipate the occurrence of band gaps in elastic waves. The new model has been simplified as the flexoelectric model and classical elastic model, as special cases. Meanwhile, compared to Bernoulli-Euler beam model, it is found that transverse shear effect has a significant effect on the band gap predictions of thick beams, but this effect is negligible for slender beams, indicating that this new model can be used to predict band gaps of both thick and slender beams in the high-frequency range. Furthermore, the impacts of microstructure and flexoelectric effects as well as material and microstructural parameters on band gaps are studied. The numerical results show that the influence of flexoelectricity on band gaps is the primary in the submicron beams, while the microstructure effect is the main in the micron beams. Additionally, the band gap frequencies and sizes (bandwidth) are significantly affected by the beam thickness, unit cell length and volume fraction. Thus, these discoveries demonstrate the feasibility of tailoring the band gap frequencies and sizes through the adjustment of material and microstructural parameters.

Temperature increases and creep in saline rocks can cause annular pressure buildup (APB), presenting a significant challenge in oil well operations, particularly in deep and ultra-deep pre-salt fields. This paper proposes a one-dimensional axisymmetric multilayer thermomechanical model that accounts for the influence of evaporite layers and thermomechanical effects on APB. We developed a finite element model that integrates heat transfer and thermomechanical interactions, utilizing a double deformation mechanism as a constitutive model to represent the viscous behavior of the rock formation. Additionally, this model enables the iterative calculation of fluid properties based on temperature and pressure conditions. To validate the model, we conducted case studies using widely adopted commercial finite element software. Its consistent results provide a deeper understanding of the pressure increases caused by the influence of saline rock and thermal effects, offering valuable insights into the safe and efficient operation of oil wells using a model with reduced computational complexity.

Bone remodelling is regulated by specific cellular activities. In particular, the osteocytes are able to transform a mechanical signal into a chemical one and transmit it to the osteoclasts and osteoblasts cells. Additionally, osteocytes are more sensitive to fluid shear than pressure stress. Thus, the mechanical environment, especially the type of external loads applied to the bone structure, may highly influence its evolution over time. In this paper we propose a strain energy based model in which we distinguish between the deviatoric and hydrostatic energy contributions. We study here simple loads and geometries for which the strain energy distribution is homogeneous. From these two cases, we are able to show that when considering more complex structures such as the bone microstructure where the energy distribution is heterogeneous, it is necessary to discriminate between the deviatoric and hydrostatic energy parts.

The nonlinear strain solitary waves in a metamaterial mass-in-mass lattice model with a di-atomic symmetry is studied when attached masses tare located through one element of main chain are studied in the continuum limit. The reasonable variables are introduced to account for strains. An asymptotic procedure is developed to reduce coupled continuum equations to a single equation for longitudinal strains. A correspondence with the classic model with a di-atomic symmetry is established. An improvement of the model is suggested to account for a switch-on/off of the parts of the metamaterial model arising due to the studied kind of symmetry. It allows us to change the behavior of the localized nonlinear strain waves. This improvement is important for description of a durability of the metamaterial. Also it helps to understand new heat processes, like thermal diode, in complex symmetric lattices.