Design Of Engineering Structures Research Articles

Structural design against brittle fracture: Optimizing energy release rate and experiment

Despite substantial advancements in optimizing structural designs for stiffness, the field of design against fracture is still in its early stages. This paper introduces a fundamental and standardized paradigm for structural design against brittle fracture, achieved through the minimization of the energy release rate G within the framework of linear elastic fracture mechanics (LEFM). By leveraging the Griffith criterion expression and the total potential energy in LEFM, we propose an efficient approach for structural optimization that enhances the toughness of architected materials. The energy release rate G is evaluated a synergistic application of finite element analysis and finite difference methods, yielding a precision of 0.6% compared to benchmarks in published handbooks. We demonstrate significantly reduced G values compared to standard stiffness and stress-oriented topology optimization, which directly contributes to increased toughness. To comprehensively analyze the fracture process encompassing damage, crack initiation, propagation, and failure, we employ post-processing phase field fracture modeling on the optimally designed architected materials. By performing multi-objective optimization of the stiffness and energy release rate G, the toughness and extreme load-bearing capacity can be simultaneously improved. The resulting perforated architecture effectively outperforms homogeneous structures in both toughness and peak load. Additionally, we extend our analysis to various configurations, such as non-center cracks, pure shear loading, and adherence to the standard 3D compact tension ASTM E-399-72. The designed structures are additively manufactured and experimentally validated, demonstrating a toughness increase of over 10 times compared to stress-based design. These contributions offer promising prospects for advancing the design of future engineering structures and materials with a favorable balance of critical fracture resistance characteristics.

Rod-like Ni-CoS2@NC@C: Structural design, heteroatom doping and carbon confinement engineering to synergistically boost sodium storage performance

Currently, conversion-type transition metal sulfides have been extensively favored as the anodes for sodium-ion batteries due to their excellent redox reversibility and high theoretical capacity; however, they generally suffer from large volume expansion and structural instability during repeatedly Na+ de/intercalation. Herein, spatially dual-confined Ni-doped CoS2@NC@C microrods (Ni-CoS2@NC@C) are developed via structural design, heteroatom doping and carbon confinement to boost sodium storage performance of the material. The morphology of one-dimensional-structured microrods effectively enlarges the electrode/electrolyte contact area, while the confinement of dual-carbon layers greatly alleviates the volume change-induced stress, pulverization, agglomeration of the material during charging and discharging. Moreover, the introduction of Ni improves the electrical conductivity of the material by modulating the electronic structure and enlarges the interlayer distance to accelerate Na+ diffusion. Accordingly, the as-prepared Ni-CoS2@NC@C exhibits superb electrochemical properties, delivering the satisfactory cycling performance of 526.6 mA h g−1 after 250 cycles at 1 A g−1, excellent rate performance of 410.9 mA h g−1 at 5 A g−1 and superior long cycling life of 502.5 mA h g−1 after 1,500 cycles at 5 A g−1. This study provides an innovative idea to improve sodium storage performance of conversion-type transition metal sulfides through the comprehensive strategy of structural design, heteroatom doping and carbon confinement.

Working mechanism evaluations of full-scale joints with bolted-cover plate connection for modular steel buildings

The force-reliability of the modular structural joints is crucial for ensuring the structural integrity of modular steel buildings. However, the welds connecting the beam and column within the module are susceptible to tear during seismic events. This mode of failure greatly undermines the ability of these joints to withstand seismic forces. Four full-scale modular structural joints with bolted-cover plate connection were designed and conducted for seismic performance testing, emphasizing the significance of methods such as reinforcing diagonal braces and strengthening flanges on the protective effect of beam–column welds in the module. The simplified modular structural joint and frame finite element model were proposed based on experimental data, refined finite element modeling, and theoretical analysis. The findings suggest that the seismic behavior of the modular structural joint remains unaffected by variations in axial compression ratio within the designed range of parameters. The beam–column weld of the module in the reinforced joint exhibits almost no weld tearing, and both strengthening methods demonstrate exceptional capacity for energy dissipation. The proposed simplified modeling method facilitates the efficient determination of the modular structural joint bearing capacity and the lateral stiffness of the modular frame. The research findings presented in this paper can serve as a valuable reference point for the engineering design of modular steel structures.

Numerical Simulation of Pipeline Scour and Sedimentation around Submerged Pipelines with an Open-Source Multiphase-CFD Model

This paper presents a comprehensive study on pipeline scour and sedimentation phenomena using an open-source multiphase Computational Fluid Dynamics (CFD) model. The research focuses on understanding the complex interactions between fluid flow, sediment transport, and scour formation around submerged pipelines. The proposed analysis aims to enhance the understanding of scour development and sedimentation deposition, which is crucial for the design, operation, and maintenance of various engineering structures, including offshore pipelines and underwater infrastructure. The results show that the model exhibits the ability to compute sediment transport without depending on traditional assumptions related to bed-load and suspended-load layers. The simulation results affirm the model's proficiency in replicating the underlying mechanisms accountable for the onset of these processes, notably seepage flow and piping. Furthermore, this model can successfully depict the vortex phenomenon, which promotes the accumulation of sediment around the pipe. This phenomenon arises from the contrast in pressure between the centre of the vortex and the pressure exerted on the sediment beneath it.

Study on the dynamic response of aluminum‐based curved panels coated with polyurea under impact loads

AbstractMetal curved panels are commonly used in engineering structures, but they may be more susceptible to damage under impact loads compared to flat panels. Polyurea coating has been proposed as a solution to improve impact resistance. Therefore, this study investigates the impact resistance performance of curved composite panels by applying polyurea coating to aluminum‐based panels with different curvatures. First, a numerical model of polyurea‐coated aluminum composite panels was established using the finite element software LS‐DYNA, and the sensitivity of model mesh and the numerical model validity were carried out. Then, the impact resistance performance of polyurea‐coated aluminum‐based flat panels was studied from the aspects such as deformation modes and energy dissipation, and the influence of polyurea layer thickness and coating position on the impact resistance performance of polyurea‐coated aluminum composite panels was analyzed. Based on the above results, numerical models of polyurea‐coated aluminum‐based curved panels under different curvatures are further established, and the impact resistance performance of composite curved panels and the structural forms for effective protection against impact loads are comprehensively analyzed. The research results indicate that double‐sided polyurea coating is the optimal coating method for both aluminum flat panels and aluminum curved panels. After the coating thickness reaches 4 mm, there is no significant improvement in the structural impact resistance performance. The impact deformation of curved panels can be divided into four stages: dynamic buckling, plastic indentation, rebound deformation, and vibration. The concave surface has strong impact and deformation resistance, and the convex surface has strong impact resistance. The research results have important theoretical implications for the safe engineering design of protective structures using metal curved panels.

Collège Amadou Hampaté Bâ, Niamey, Niger: structural design in an international development context

Collège Amadou Hampaté Bâ, a school in Niamey, Niger, was MHA Structural Design's winning entry to the Structural Awards 2023. The project won an award for its use of sustainable local materials and for enabling positive social impact. For this article, the IStructE's Humanitarian and International Development Panel spoke to the firm's structural engineering design lead for the project, Marco Conti. The case study explores key considerations and appropriate technological approaches to structural design in humanitarian and international development contexts.

A two-direction cross-iteration solution for in-plane vibrations of thin-walled composite plates with a simplified explicit vibration mechanical model

For the fine and high reliability design of advanced precision engineering structures, this work presents an analytically cross-iteration method for in-plane vibrations analysis of thin-walled composite plates, the single-layer and laminated structures both involved. The governing equations and corresponding boundary conditions are derived adopting Rayleigh’s principle, in which the governing partial differential equations are transferred into ordinary differential equations. The most important advantage of this method lies in the fact that the explicit eigenvalue equations and mode functions are obtained with only a series of four-by-four matrices by simplifying boundary conditions in the two-direction cross-iteration procedures. Accuracy of the present method is verified by comparison with the previous studies and the finite element method in natural characteristics solutions, and convergence analysis on the single-layer orthotropic plates and composite laminates reveals the high efficiency and stability. Finally, the effects of boundary conditions, ply orientation angles, stacking sequences, aspect ratios and stiffness ratios on the in-plane natural characteristics are investigated. The extensive results presented in this work for the first time can be taken as the benchmarks data compared with other methods.

Coupling of bond-based peridynamics and continuous density-based topology optimization methods for effective design of three-dimensional structures with discontinuities

AbstractThis study proposes continuous density-based three-dimensional topology optimization (TO) approaches developed by coupling the peridynamic theory (PD) with optimality criteria (OC) and proportional approach (PROP). These frameworks, abbreviated as PD-OC-TO and PD-PROP-TO, can be practically utilized to enhance the fracture toughness of the structures during the optimization process by taking critical regions into account as pre-defined cracks. Breaking the non-local interactions (bonds) between relevant PD particles enables us to readily model cracks. Utilizing this advantage, we solve several benchmark optimization problems including different numbers, positions, and alignments of the cracks. The major differences between the proposed methods are examined by comparing optimum topologies for various cracked scenarios. Moreover, the mechanical behaviour of the optimized structures is investigated under dynamic loads to prove the significant improvements achieved by the present approach in the final designs. The results of dynamic analyses reveal the viability of both PD-TO methods for increasing the fracture toughness of the structure in the optimization stage. Overall, the proposed approach is confirmed as a superior design and optimization tool for future engineering structures. Graphical abstract

Processing of earth-based materials: current situation and challenges ahead

With the overall aim of supporting the development of new construction techniques and materials that are more economical and less carbon intensive, RILEM has decided to launch three new technical committees on earth construction in 2022. One of these committees will focus on the manufacturing processes used in earth construction (TC PEM). The aim of this committee is to bring together experts from several disciplines (materials science, earth construction, rheology, geotechnics, cement chemistry, etc.) to advance earth construction techniques by sharing and promoting good practice. The processing of earth is today based on solid empirical knowledge which fails to convince structural design engineers. As a result, earth construction is still limited to small buildings. To upscale the use of earthen material in construction, it is required to provide a solid scientific background that can be used for the writing of standards and recommendations to guarantee minimal performances in service. Areas of work include improving understanding of the mechanical behaviour of the material in the fresh state, developing characterization methods, monitoring the material during curing, and studying new construction techniques, particularly digital ones. The work of the technical committee PEM “Processing of earth-based materials” is expected to gather the scientific knowledge that can be further used for the writing of construction and design codes for earthen materials.

On crashworthiness and energy-absorbing mechanisms of hygrothermal-aged CFRP structures subjected to quasi-static loads

Understanding the gradual performance degradation of carbon fiber reinforced polymers (CFRP) is critical for the design of engineering structures that are expected to be affected by hygrothermal environments. This study aims to investigate the effects of hygrothermal aging on the degradation mechanisms of the mechanical properties and energy absorption of CFRP structures. An experimental database comprising tensile, compressive, and shear tests for CFRP composite laminates (in this study) and axial crushing tests for energy-absorbing structures (from the literature) was constructed, in which all CFRP samples were immersed in deionized water to achieve a saturated water-absorption state. A material constitutive model considering the effects of water absorption and temperature was developed and implemented via the user subroutine VUMAT of the ABAQUS software. The simulated results correlated well with the experimental measurements. Simulation results of axial crushing indicated that the degradation of the inter-layer properties tends to worsen the mismatch between the intra-layer and inter-layer properties, thus significantly degrading the load-carrying capability. Owing to degradation in compressive fracture toughness, the simulated results showed reduced post-crushing integrity, thus indicating a favorable effect on the load-carrying capability.

A novel porous layered K2Ti8O17 for capturing MB and Cu(Ⅱ) in wastewater

Appropriate structural design engineering is an effective method to achieve high adsorption performance, and optimizing the architecture to meet the desired properties remains challenging for adsorbents. Herein, a novel porous layered K2Ti8O17 (PLKTO) formed by interweaved nanowires has been successfully synthesized using MAX phase Ti2AlN and g-C3N4 as the precursors. The K2Ti8O17 nanowires consisted of numerous interconnected pores in a network-like distribution configuration, with a diameter of approximately 20 nm and a length exceeding one μm. Attractively, the PLKTO exhibited fast kinetics, large adsorption capacity, and excellent reusability toward methylene blue (MB) and Cu2+ adsorption. The maximum equilibrium adsorption capacity of MB and Cu2+ was 95.00 mg/g and 330.75 mg/g, with equilibrium times of ∼18 min and ∼25 min, respectively. The adsorption mechanism unveiled that the elimination of MB and Cu2+ was dominated by the pore-filling effect, electrostatic interaction, hydrogen bond, and surface complexation. Additionally, the PLKTO enjoyed highly selective for Cu2+ while investigating competitive adsorption behaviors in binary systems and real-world applications in various water matrices. These results indicated that the PLKTO revealed appealing application prospects for treating wastewater and pollutants and provided methodological guidance for design engineering in fabricating porous and layered structures.

A numerical study on load effects of low-rise buildings in a wind-blown sand environment

The transportation process of wind-blown sand, represented by sandstorms, occurs frequently in arid and semi-arid regions. The combined action of wind and sand impact load in a wind-sand environment poses a serious threat to the safety of construction, transportation and other engineering structures. However, most of the current structural designs only considers the effect of wind, and there is little detailed research on the surface load distribution of structures caused by sand impact, which leads to uncertainty in the safety assessment of engineering structures in wind-sand areas. In this paper, low-rise buildings which are easily damaged in strong wind-sand environments are taken as the research object. A numerical model of coupling turbulent wind field and particle motion was then established, and the reliability of the numerical simulation results was verified through wind tunnel experiments. Finally, the wind-sand movement around the low-rise building model and the load distribution characteristics on the building surface are simulated under different wind speed and sand concentration conditions. The results show that the edges and corners of engineering structures are subject to more severe particle erosion-abrasion. As the sand concentration increases in the flow field, the wind speed and the wind load acting on the structures weakens. Whereas the sand impact load increases with the increment of wind speed and sand concentration. The increased effect of sand particles on the total load can be considered by amplifying the wind load shape coefficient on the windward side. This study is helpful to understand the mechanism of sand wind-induced damage on low-rise buildings, and provides basic tools and a theoretical basis for the wind and wind-blown sand resistance design and performance optimization of engineering structures.

Additive manufacturing of ULTEM 9085: Weak interface-enriched multi-toughening mechanisms and fracture resistance optimization

Modulating the fracture toughness can be used to tailor or enhance the mechanical performances in the design of specific additively-manufactured engineering structures. In this research, we explored the fracture behavior of ULTEM 9085 materials fabricated by material extrusion (MEX) 3D printing technique, with a particular emphasis on the effect of weak interfaces between deposited beads. Under quasi-static bending condition, the MEX-fabricated ULTEM 9085 exhibits brittle and quasi-brittle fracture behaviors by adjusting the print orientations and raster angles. Several intrinsic toughening mechanisms are identified, including crack deflection and twisting, fibril bridging, constrained microcracking and delamination of the weak interface. Notably, the samples that experienced delamination along the weak interface displayed the highest performance in terms of the fracture toughness. To achieve high fracture toughness, we employed an analytical model based on linear elastic multilayers fracture mechanics to understand the crack onset and predict the crack propagate orientation. Based on the insight gained from this model, we proposed an intuitive optimal strategy to enhance the fracture resistance by fine turning the bonding strength and layer height to trigger the crack deflecting towards and propagating at the weak interface consistently. By implanting this approach, we achieved an increase of over 35% in fracture resistance while effectively preventing the catastrophic failure, demonstrating exceptional fracture-resistant performance. Overall, our study elucidates the impact of layer-by-layer MEX-induced weak interfaces on the fracture resistance of MEX-fabricated high temperature engineering materials. The findings of this research hold potential for engineering applications, particularly in optimizing the design of additive manufactured products aiming at high fracture resistant.

Mechanical behavior of a novel lattice structure with two-step deformation

Lattice structures are increasingly attracting attention due to their excellent mechanical properties and broad application prospects. However, most developed lattices feature single-step deformation or single plateau stress, which confine its multi-task applications. Herein, a novel body-centered cubic (NBCC) with two-step deformation based on body-centered cubic (BCC) and bionic fractal design is introduced. NBCC exhibits bi-plateau stress in the stress–strain curves. The underlying mechanism is caused by the bending and buckling deformation of the struts. The mechanical behaviors of NBCC are investigated by finite element simulation which verified by experiment. Compared with traditional BCC, NBCC has improved modulus of elasticity by 88 %, yield strength by 21.2 %, and specific energy absorption by 108 % when ρ′ and α are 0.07 and 0.5, respectively. Moreover, the elastic modulus as well as yield strength increase with geometrical ratio α. The specific energy absorption tends to maximum at the geometric ratio α = 0.6 ∼ 0.7. From the Ashby map, the proposed NBCC lattice possesses high energy absorption, exceeding most of the existing architected materials at the same density. Furthermore, the results show that NBCC has better isotropy of elastic modulus and tends to be more isotropic material compared to BCC. Finally, theoretical model of two-step plateau stress is established based on hinge dissipation principle. This work opens up new insights into the use of element replacement design to create multi-step pathways that can be applied to design engineering structures with multiple tasks and application for impact protection.

Contribution of hydraulic modeling and hydrology to flood prevention and design of engineering structures: Case study of a bridge over the Oued Ourika – Morocco

Located downstream of the Ourika watershed near the commune of Chouiter, the bridge studied is built over the Oued Ourika at the level of the N9 (national road linking Marrakech to Ouarzazat). The flood event of November 2014, reaching a peak flow of 347 m3/s, destabilized the bridge’s overall structure. Hence, the need to rebuild a new bridge, taking into account the magnitude of these extreme events. Hydraulic modeling involves creating mathematical and computer-based representations of hydraulic systems. Its purpose is to simulate water flow behavior and map flood-prone areas. Before initiating any hydraulic simulation, it is imperative to conduct a hydrological study to provide the input data for the hydraulic model. Precipitation records, evaporation rates, soil permeability, historical peak flow data, and site topography constitute, on the one hand, the product of the hydrological study and, on the other, the inputs for the hydraulic model. The hydraulic model is based on Saint-Vant equations to solve the conservation of mass and momentum equations. The aim of this work is to determine the critical water level at the bridge for a 100-year flood in order to optimize the height of the new bridge.

Special IASS 2024_A Novel Flexible Joint for Bamboo Structures

Joints are one of the main problems concerning the design of bamboo structures. This paper proposes a classification of the main joints applied in full-culm bamboo structures according to their constructive behavior, subdivided into semi-rigid and flexible joints. A novel flexible joint called the Hinged Flexible Connection (HFC) for lightweight bamboo structures is developed and analytically described, allowing for a deployable motion in the center of the joint and mobile assembly procedures. The joining system utilizes lashed polyester ropes and bio-composite rings coupled in the bamboo culms working as geometric and mechanical constraints. The HFC has the potential to substitute bolted joints for the engineering design of bamboo structures.

Structural engineering of rare earth metal-organic frameworks derivatives with high anisotropy for high-efficiency electromagnetic wave absorption

Structural engineering and component design are crucial for conceiving outstanding metal-organic frameworks (MOFs)-based electromagnetic wave (EMW) absorption materials. However, an efficient and direct clarification of the structural influences on the EMW absorption performance of MOF-based absorption materials remains highly challenging and still awaits exploration. To this end, we synthesized a new type of rare earth (RE) MOFs with hexagonal-bipyramidal, snowflake-like, and dendritic structures through facilely controlling the solvent ratios in a scalable coprecipitation approach. The MOF-derived CeO2/Co/C hybrids with the same component content inheriting the morphological structures showcased tunable dielectric property and EMW absorption performance. The dendritic MOF derivatives with the highest anisotropy achieved a superior EMW absorption performance, manifesting a minimum reflection loss value of −71.5 dB at 1.7 mm and an effective absorption bandwidth of 5.2 GHz at 1.6 mm thickness, comparable to those of the best EMW absorbers. This work not only confirmed the high potential of RE MOF derivatives for EMW absorption, but also directly and efficiently unveiled the mechanism of morphological structure on the dielectric property and EMW absorption performance for the MOF-based EMW absorption material.

Experimental studies of the stability of wave-damping slopes to protect bridge supports from wave action

This article presents the results of experimental studies of the stability of wave-damping slopes to protect bridge supports from wave action. The object of the study is the construction of protective wave-damping slopes constructed to protect the supports of bridges designed and operated under wave action conditions (such as the bridge to Russian Island in Vladivostok, etc.) on the shores of the seas. The purpose of the work is to select the optimal design solutions for protective slopes that ensure reliable and safe operation of the bridge crossing during sea storms of rare frequency. The research was carried out by the method of physical modeling in a wave pool. Various variants of structural solutions of protective slopes are considered: from a stone outline and from gabions, as well as combined structures. According to the results of research on a physical model in the wave basin, the structures of the protective slopes of bridge supports that are most resistant to the effects of sea storm waves of rare frequency have been obtained. The results of the research are intended to select optimal design solutions for protecting bridge supports from wave action and can also be used to protect other transport structures, for example, the roadbed of railways designed on sea coasts. These results were used by the author in the development of the regulatory framework for the design and monitoring of engineering structures for the protection of transport structures from wave action.

Active Materials for Functional Origami.

In recent decades, origami has been explored to aid in the design of engineering structures. These structures span multiple scales and have been demonstrated to be used toward various areas such as aerospace, metamaterial, biomedical, robotics, and architectural applications. Conventionally, origami or deployable structures have been actuated by hands, motors, or pneumatic actuators, which can result in heavy or bulky structures. On the other hand, active materials, which reconfigure in response to external stimulus, eliminate the need for external mechanical loads and bulky actuation systems. Thus, in recent years, active materials incorporated with deployable structures have shown promise for remote actuation of light weight, programmable origami. In this review, active materials such as shape memory polymers (SMPs) and alloys (SMAs), hydrogels, liquid crystal elastomers (LCEs), magnetic soft materials (MSMs), and covalent adaptable network (CAN) polymers, their actuation mechanisms, as well as how they have been utilized for active origami and where these structures are applicable is discussed. Additionally, the state-of-the-art fabrication methods to construct active origami are highlighted. The existing structural modeling strategies for origami, the constitutive models used to describe active materials, and the largest challenges and future directions for active origami research are summarized.

Generative adversarial surrogate modeling framework for aerospace engineering structural system reliability design

To effectively realize the reliability design of engineering structural system, a generative adversarial surrogate modeling (GASM) concept is proposed by innovating generative adversarial theory into surrogate modeling methods, which realize the aerospace engineering structural system reliability design adversarial modeling. In this concept, the surrogate model is adopted as a basis function to describe the functional relationship between input variables and output response; the generative adversarial theory is employed to obtain hyper-parameters of basis functions by continuous confrontation and evolution between the generation model and discrimination model. Under the GASM concept, the generative adversarial polynomial chaos expansion (GAPCE) method is developed to achieve aerospace engineering structural system reliability design. The effectiveness of presented GAPCE is verified by three examples including the nonlinear functions approximation, reliability design of flap deflection angle, and reliability estimation for turbine blisk radial deformation. The reliability level of flap deflection angle and turbine blisk radial deformation are 0.9998 and 0.9984, when the allowable values are 9° and 1.9222 × 10−3 m. Besides, the introduced approach possesses advantages of modeling performance (i.e., modeling accuracy and efficiency) and simulation properties (i.e., simulation precision and efficiency) by comparing with various methods. The efforts of this paper can provide a valuable reference for the operational safety of flap systems and engine structures and the development of reliability design theory.