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Abstract In designing control systems, it is known that fractional-order proportional integral derivative (FOPID) controllers often provide greater flexibility than conventional proportional integral derivative (PID) controllers. This higher level of flexibility has proven to be extremely valuable for various applications such as vibration suppression in structural engineering. In this paper, we study the optimization of FOPID controllers using twelve well-established algorithms to minimize structural responses under seismic excitations. The algorithms include crystal structure algorithm (CryStAl), stochastic paint optimizer, particle swarm optimization, krill herd, harmony search, ant colony optimization, genetic algorithm, grey wolf optimizer, Harris hawks optimization, sparrow search algorithm, hippopotamus optimization algorithm, and duck swarm algorithm. In addition to highlighting the benefits of fractional calculus in structural control, this study provides a detailed analysis of FOPID controllers as well as a brief description of the algorithms used to optimize them. To evaluate the efficiency of the proposed techniques, two building models with different numbers of stories are examined. FOPID controllers are designed based on oustaloup’s approximation and the El Centro earthquake data. Using five well-known metrics, the performances of the developed methods are evaluated against five earthquake scenarios, including the recent earthquake in Turkey. A non-parametric (Friedman) test is also employed to compare the algorithms based on their corresponding vibration reduction. The findings of this analysis show that CryStAl consistently performs better than the other algorithms for both building models, thus resulting in superior vibration suppression.

In recent years, the design and development of negative-stiffness metamaterials and metastructures have been considered a research field with great potential for applications such as energy absorption and vibration isolation. As a particular example, it is known that the reaction force of a typical negative-stiffness honeycomb (NSH) metastructure under compression will not monotonically increase with displacement, but manifests successive local extremums. This makes it an attractive choice as a concept for energy-absorbing applications, especially for recurrent low-velocity collision scenarios. Here, we analytically derive the equations of the piecewise-defined force–displacement functions for the general case of an NSH two-dimensional lattice metastructure followed by finding the optimal geometric design parameters. Using analytical methods, we demonstrate that there is a fundamental upper limit of 5/6 to the energy absorption efficiency of such metastructures. The obtained theoretical results are validated by finite-element numerical simulations and experimental compression tests. The findings of this study enable designers to identify optimal geometries of NSH metastructures for different practical applications with particular requirements on maximum reaction force and displacement.

The ribbon kirigami pattern has garnered significant attention over the past decade because of its interesting geometric and mechanical properties such as extreme elongation and high ductility, making it a viable choice for various applications such as developing medical devices and flexible electronics. Despite the promising prospects of this type of morphing structure, its deformation mechanism and sensitivity to materials properties and geometric parameters have remained largely unexplored. Here we take a computational approach to studying the deformation process and ductility of a typical ribbon kirigami metastructure. To this end, the deformation process is divided into various stages. We demonstrate the existence of a certain threshold of the process at which the deformation behavior starts to be dominated by the properties of the constituent material, after the initial geometric-design-dominated stages. This turning point, called the design–material transition (DMT) threshold, determines a key limit in the deformation capacity of such metastructures for practical applications. Based on the introduced deformation mechanism, an elongation prediction model is derived for the metastructure, followed by conducting experiments to validate the accuracy of the model. Furthermore, a genetic algorithm and an interior-point method are utilized to develop an efficient algorithm for the optimization of the geometric parameters of the kirigami pattern. We anticipate that the findings of this study open a path to engineering functional kirigami patterns for the design and fabrication of highly ductile shape-shifting structures.

Conical origami structures are characterized by their substantial out-of-plane stiffness and energy-absorption capacity. Previous investigations have commonly focused on the static characteristics of these lightweight structures. However, the efficient analysis of the natural vibrations of these structures is pivotal for designing conical origami structures with programmable stiffness and mass. In this paper, we propose a novel method to analyze the natural vibrations of such structures by combining a symmetric substructuring method (SSM) and a generalized eigenvalue analysis. SSM exploits the inherent symmetry of the structure to decompose it into a finite set of repetitive substructures. In doing so, we reduce the dimensions of matrices and improve computational efficiency by adopting the stiffness and mass matrices of the substructures in the generalized eigenvalue analysis. Finite element simulations of pin-jointed models are used to validate the computational results of the proposed approach. Moreover, the parametric analysis of the structures demonstrates the influences of the number of segments along the circumference and the radius of the cone on the structural mass and natural frequencies of the structures. Furthermore, we present a comparison between six-fold and four-fold conical origami structures and discuss the influence of various geometric parameters on their natural frequencies. This study provides a strategy for efficiently analyzing the natural vibration of symmetric origami structures and has the potential to contribute to the efficient design and customization of origami metastructures with programmable stiffness.

Windows and their control elements, including shading systems, are among the most critical building components affecting both energy consumption and occupant comfort. With the increasing demand for full-glazed facades, designers and researchers are actively devising advanced control strategies to address the challenges posed by excessive sunlight penetration and heat transfer. These strategies aim to harmonize the benefits of natural light with the need for comfortable indoor environments and energy consumption reduction. This study investigates the impact of external shading configurations for an office room in Tehran, categorized as group B in the Köppen climate classification, to reduce total building energy consumption and improve occupant thermal and visual comforts. The shading parameters include shading angle, shading depth, and the number of shading slats. More specifically, this study analyzes and compares two design configurations for the considered office room. The first configuration consists of a single southern window with horizontal shading, whereas the second configuration consists of two windows on the south and west, one being horizontal shading on the southern side and the other being vertical shading on the western side. There are a total of 1330 models investigated from which 20 models are selected as the most suitable solutions. Finally, this paper examines the effect of each design parameter on the overall performance of each configuration in terms of energy efficiency and visual-thermal comfort.

Global energy consumption has increased significantly in recent decades due to changes in the industrial and economic sectors. Accurate demand estimates are critical for decision-makers to save operation and maintenance costs, improve energy reliability, and make informed decisions for future development. This study evaluates a newly proposed soft technique called Variational Mode Decomposition (VMD) to improve the accuracy of power consumption forecasts. To validate the experimental results, we compared the predicted energy consumption values with measured values from five geographically diverse countries, including developed and developing countries. The study examined different time horizons and performed seasonal evaluations. The VMD-BiGRU and VMD-LSTM models show consistent and superior prediction accuracy, outperforming other models by 20% to 50% on all evaluation measures. In addition, we evaluated the efficiency of VMD-based models over different forecast horizons and find that they are most effective for short- to medium-term forecasts (1 to 12 months). For longer-term forecasts, we recommend combining VMD with specialized techniques. Overall, this study recommends using VMD to forecast electricity consumption in different regions, emphasizing carefully considering forecast horizons for optimal results.

Abstract The energy performance of a building has a significant impact on the environment as well as the comfort of its occupants. Given that window systems and control elements such as shading devices play a critical role in a building's energy consumption and comfort, this article presents an investigation into the optimization of windows in four different orientations, along the four cardinal directions, for a typical office room in Tehran. The objective is to reduce cooling, heating, and lighting energy consumption while improving occupant comfort simultaneously, using the NSGA‐II algorithm as a multi‐objective optimization method. To this end, first, an investigation into the effects of various parameters on total building energy consumption and occupant comfort is conducted. Subsequently, each parameter is evaluated in detail concerning its impact on each façade. As the final step, for each façade, the optimal solutions and the most undesirable scenarios are determined. The results, in which the possibility of glare is also considered, can be used by architects and designers for making informed design decisions. The results show that, in all orientations, the number of slats and their distance from the wall are the most effective parameters of shading configurations. Although the eastern and western windows are larger in this study, visual discomfort can be controlled using suitable shadings to achieve acceptable levels of visual comfort. Furthermore, north façades provide the least amount of thermal comfort and consume the least amount of energy while experiencing glare for longer periods.

Pivotally interconnected polygons are capable of auxetic behavior, but have not been fully explored. Here, a design method is demonstrated based on the selective removal of rotational hinges in pivotally interconnected polygons with even-numbered modules, leading to fully-deployable structures.

Abstract Tunnels, as highly cost-demanding infrastructures which facilitate the transportation of people and goods, have been a target of terrorist attacks within the past few decades. The significance of the destructive impact of explosives on these structures has resulted in research on the development of blast-resistant design approaches. In this paper, water curtains are proposed as a blast-resistant system due to the established performance of water against explosives in free fields in previous studies as well as its capability to mitigate the potential incoming fire after an explosion. A parametric study was conducted for this purpose, considering the effects of curtain thickness, the distance of the curtain from the tunnel opening, and the amount of TNT charge. Accordingly, fifty-two finite element (FE) models were created in the FE package ABAQUS to investigate the performance of a water wall in a typical tunnel through the Eulerian approach to simulation. The water curtains had four different thicknesses and were located at three different distances from the reference point. TNT explosive charges were placed at the tunnel opening with four different masses. The thicker walls nearer to the tunnel opening were found to be more effective. However, the peak pressure reduction in all charges was in a desirable range of 53 to 80%. The parametric study also illustrated that the peak pressures were more sensitive to wall thickness rather than TNT charges mass and the wall distance from the explosives. We anticipate this preliminary study to be a starting point for the further development of the concept of water curtains for blast mitigation.

Abstract Various methods have been proposed to ensure the serviceability of buried structures such as road tunnels, urban utility tunnels, water conduits, underground shelters, and deposition chambers against extreme loads, the most common of which are experimental and computational methods. An external explosion in the vicinity of such structures is one of these extreme loads. In general, different types of external blasting for buried structures can be classified as surface blasting, coupled or uncoupled buried explosions, excavation by drilling and blasting near the structure, and the accidental detonation of explosive depositions. Laboratory or field tests for explosions are usually limited by financial and safety constraints; therefore, numerical simulations are often regarded as a vital tool in the study of such problems. Though computer software and hardware have improved rapidly in recent decades, and various numerical solvers have been developed, there is no universal method for solving all external explosion problems. Each numerical method can produce sensible results under certain conditions and assumptions, along with its limitations in computational cost. Consequently, these problems have been particularly difficult to investigate, and even in some cases, the results of different studies seem to be inconsistent. Besides providing an extensive review of the available literature in the field of numerical simulation of external explosions near buried structures and a discussion of the damage criteria associated with such explosions, this study also highlights some inconsistencies that may need further investigation.

Abstract Fusion–Fission Optimization (FuFiO) is proposed as a new metaheuristic algorithm that simulates the tendency of nuclei to increase their binding energy and achieve higher levels of stability. In this algorithm, nuclei are divided into two groups, namely stable and unstable. Each nucleus can interact with other nuclei using three different types of nuclear reactions, including fusion, fission, and β-decay. These reactions establish the stabilization process of unstable nuclei through which they gradually turn into stable nuclei. A set of 120 mathematical benchmark test functions are selected to evaluate the performance of the proposed algorithm. The results of the FuFiO algorithm and its related non-parametric statistical tests are compared with those of other metaheuristic algorithms to make a valid judgment. Furthermore, as some highly-complicated problems, the test functions of two recent Competitions on Evolutionary Computation, namely CEC-2017 and CEC-2019, are solved and analyzed. The obtained results show that the FuFiO algorithm is superior to the other metaheuristic algorithms in most of the examined cases.

In the real world, many optimization problems have such levels of uncertainty and complexity that a single objective function cannot represent all the characteristics of the considered system. Hence, multi-objective optimization algorithms are needed to account for multiple aspects of the problem, represented by multiple objective functions, to achieve reasonable and useful results through the optimization procedure. In this paper, we introduce the multi-objective version of a recently-developed single-objective metaheuristic algorithm known as Atomic Orbital Search (AOS), which will be called Multi-Objective Atomic Orbital Search (MOAOS). To this end, the general aspects and main searching loop of the AOS algorithm are modified to make it capable of dealing with problems with multiple objectives. For the performance evaluation of this algorithm, the mathematical benchmark problems ZDT and DTLZ, alongside several real-world engineering design problems and the CEC- 2020 MMO test problems, are utilized. Based on the results obtained in this study, we can conclude that MOAOS is capable of producing either superior or closely comparable results when evaluated in competition with alternative state-of-the-art metaheuristic methods.

Metaheuristics are computational procedures that intelligently lead the search process through the efficient exploration of the search space associated with an optimization problem. With the progressive outburst of problems with large data sets in various fields, there is an ongoing quest for enhancing existing metaheuristic algorithms as well as developing new ones with greater accuracy and efficiency. In general, a powerful and efficient metaheuristic algorithm is based on a rich inspiration source, implemented effectively through a precise mathematical model. Aiming to develop a highly efficient, nature-inspired optimization algorithm, here we propose a novel metaheuristic called Crystal Structure Algorithm (CryStAl). This method is chiefly inspired by the principles underlying the formation of crystal structures from the addition of the basis to the lattice points, which is a natural phenomenon that can be seen in the symmetric arrangement of constituents (i.e. atoms, molecules, or ions) in crystalline minerals such as quartz. A total number of 239 mathematical functions which are categorized into four different groups are utilized to evaluate the overall performance of the proposed method. To validate the results of this novel algorithm, 12 different classical and modern metaheuristic algorithms are selected from the literature. The minimum, mean, and standard deviation values alongside the number of function evaluations for CryStAl and the other metaheuristics for a specific tolerance are calculated and presented accordingly. The obtained results, further supported by a complete statistical analysis, demonstrated that the proposed algorithm is capable of providing very competitive results, outperforming the other metaheuristics in most cases.

In many optimization problems, the main goal is to improve a single performance index in which a minimum or maximum value of this index fully reflects the quality of the response obtained from a system. However, in some cases, it is impossible to rely solely on a single index, so a multi-objective optimization problem with multiple performance indicators is considered where the values of all of them should be optimized simultaneously. The mentioned process requires a multi-objective optimization algorithm that can deal with the complexity of problems with simultaneous indexes. This paper presents the multi-objective version of a recently proposed metaheuristic algorithm called Crystal Structure Algorithm (CryStAl) which was inspired by the principles underlying the formation crystal structures. For the performance evaluation of this algorithm which is called MOCryStAl, the benchmark problems of the Completions on Evolutionary Computation (CEC) on multi-objective optimization, called CEC-09, are utilized. Some real-world engineering design problems are used to evaluate the efficiency of the proposed approach. The results demonstrate that the proposed methods can provide excellent results in dealing with the considered multi-objective problems.

Introducing multi-resonator microstructure into phononic metamaterials provides more flexibility in bandgap manipulation. In this work, 3D-acoustic metamaterials of the body- and face-centered cubic lattice systems encompassing nodal isotropic multivibrators are investigated. Our main results are: (1) the number of bandgaps equals the number, n, of internal masses as each bandgap is a result of the classical analog of the quantum level-repulsion mechanism between internal and external oscillations, and (2) the upper boundary frequencies, ωupper2i, i = 1, 2, ⋯, n, of the gaps formed coincide with eigen-frequencies, ωint;i2 ≠ 0, of the isolated multivibrator, ωupper2;i = ωint; i2, and the lower boundary frequencies, ωlower2,i2, are in good agreement with estimations as ωlower,i2≈ω^int;i2 (ωlower,i2

Engineered Wood Products (EWPs) are increasingly being used as construction and building materials. However, the predominant use of petroleum-based adhesives in EWPs contributes to the release of toxic gases (e.g. Volatile Organic Compounds (VOCs) and formaldehyde) which are harmful to the environment. Also, the use of adhesives in EWPs affects their end-of-life disposal, reusability and recyclability. This paper focusses on dowel laminated timber members and densified wood materials, which are adhesive free and sustainable alternatives to commonly used EWPs (e.g. glulam and CLT). The improved mechanical properties and tight fitting due to spring-back of densified wood support their use as sustainable alternatives to hardwood fasteners to overcome their disadvantages such as loss of stiffness over time and dimensional instability. This approach would also contribute to the uptake of dowel laminated timber members and densified wood materials for more diverse and advanced structural applications and subsequently yield both environmental and economic benefits.

Flat-foldable origami tessellations are a rich source of inspiration in the design of transformable structures and mechanical metamaterials. Among all such tessellations, the developable double corrugation (DDC) surface, popularly known as the Miura-ori, is perhaps the most ubiquitous origami pattern in science, engineering, and architectural design. Origami artists, designers, and researchers in various fields of science and engineering have proposed a range of symmetric variations for this pattern. While designing many such derivatives is straightforward, some of them present considerable geometric or crystallographic challenges. In general, the problem of finding flat-foldable derivatives for a given origami tessellation is more challenging for less symmetric descendants. This paper studies the existence and design of the least symmetric derivative of the Miura fold pattern with minimal unit cell enlargement in the longitudinal direction. The course of this study raises a fundamental problem in the flat-foldability of quadrilateral-shaped flat sheets on fold lines through their vertices. An analytical solution to this general problem is presented along with solutions for the special cases of convex quadrilaterals. Keywords: Origami design and engineering, Symmetry, Tessellations, Flat-foldability, Conics, Cubics

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