Engineering Structures Research Articles

Minimum magnitude boundaries in probabilistic seismic hazard analysis: an insight from structural engineering

AbstractIn order to systematically advance our understanding of the minimum magnitude limit (Mmin) in the probabilistic seismic hazard analysis (PSHA) calculations, a novel and useful approach utilising a broad range of Single-Degree-of-Freedom oscillators and hazard conditions is being developed and tested. We have determined the most reasonable Mmin value for a variety of structures by examining the impact of Mmin on the mean annual frequency (MAF) of various limit states (LSs) (including the collapse capacity). The originality of the suggested methodology in the current work, known as the MAF saturation strategy, is the recommended Mmin, which is the cut-off value at which lesser magnitude events do add to the hazard but do not significantly change the MAF. The current work is the first to offer the MAF saturation strategy methodology, which searches for the cut-off magnitude at which the MAF value essentially remains constant even when smaller values of this cut-off are utilised as Mmin for hazard assessments. Therefore, given a series of carefully chosen ground motions in each oscillator instance, an incremental dynamic analysis is carried out (by applying the Hunt and Fill algorithm), and the appropriate LS (including the collapse capacity defined as global instability) points are calculated. Thus, the relationship between the distribution of LSs and the Engineering Demand Parameter and intensity measure is found. A simple point source hazard curve is convoluted with this distribution, yielding the structure-specific MAF. In order to find the cut-off lower magnitude (Mmin), this convolution is repeated for several Mmin values. This cut-off is defined as the point at which, when lower values are utilised as Mmin in the PSHA computation, the MAF’s values do not change considerably (with a five per cent threshold). The acquired data were thoroughly discussed in relation to various structural features and seismic input factors. The primary findings showed that each of the structures under consideration requires a Mmin value in the range of 4–4.3. Put otherwise, the suggestions seen in technical literature, which range from 4.5 to 5, are not cautious, at least not when it comes to probabilistic structural limit state frequency. The derived Mmin value is mostly controlled by the natural period of the structure and is largely unaffected by other structural characteristics like ductility, damping ratio and overstrength factor.

Investigating the synergistic performance of masonry buildings with steel slabs in structural Design: A case of historical Mahmut Nedim Kurkcuoglu mansion in Turkey

The main aim of this study is to explore the collaborative performance of masonry structures incorporating steel slabs in their structural design. The focal point of the investigation is the historically significant Mahmut Nedim Kurkcuoglu Mansion located in Urfa, Turkey, renowned for its cultural heritage. The research methodology encompasses a comprehensive analysis of the mansion’s structural design, utilizing both numerical modeling and experimental testing. The findings of the study reveal that integrating steel beams into slabs within the structural design of masonry buildings can exert a significant influence on overall structural performance. This integration contributes to the heightened safety and durability of the structure. The results underscore the importance of accounting for the historical and cultural value of heritage buildings when implementing structural modifications. In terms of methodology, the research adds value to the field of structural engineering by offering insights into the incorporation of steel beams in the design of masonry structures. Moreover, it emphasizes the significance of preserving cultural heritage sites through sustainable and innovative engineering solutions. The study not only enriches the understanding of structural engineering but also holds practical implications for professionals such as architects, engineers, and preservationists engaged in the design and maintenance of heritage buildings. In conclusion, this research significantly contributes to the realms of both structural engineering and heritage preservation. Its implications extend to practical applications and can serve as a foundational platform for further exploration and investigation in this interdisciplinary domain.

Design of Structures Subjected to Blast Loads: Analysis and Design Review

When designing structures to withstand explosions, the main goals are to minimize the number and extent of occupant injuries and to reduce the chance of catastrophic damage to structures. Although there is uncertainty in the source, extent, and location of explosions, the assessment of blast loading and structural performance is important when designing blast-resistant structures. This study is a review of the literature on the prediction of blast loads, structural modeling and analysis, and design criteria for structures to resist explosions. The paper provides in one concise document the general guidelines, references, and tools that structural engineers and researchers need to analyze and design structures subjected to blast loading. References on the topics discussed in this work are provided for more detail.

Influence of Nonstationary Processes in Drill Rigs on the Durability of Structural Elements

Assessing the effects that nonstationary dynamic processes have on the durability of structural elements belongs to an important trend in modern dynamics and technical diagnostics of machines. Normally, fatigue strength calculations are performed taking into account only periodically variable stresses, as steady operating modes of machines are much longer in comparison with transient modes. However, a significant role in fatigue failure in machines and engineering structures is also played by nonstationary loads. This is explained by emerging intensive oscillations in the mechanical system during accelerating, braking, or changing the operation mode of a machine unit, which often lead to the accumulation of fatigue damages in the materials of parts in heavy loaded assemblies. The combination of stationary and nonstationary dynamic loads manifests itself, particularly in drilling rigs, where technological cycles include steady motion modes, starts, and stops. This paper represents a generalized mathematical model describing nonstationary processes in the lift system of a drill rig, which considers the relationship between electromagnetic processes in asynchronous motors and mechanical oscillatory phenomena, with the purpose of determining dynamic loads and stresses in structural elements of the rigs. Nonlinear physical systems include mechanical members with both concentrated and clearly expressed distributed parameters. The durability of structural elements is evaluated by means of a computer algorithm for analysis of crack growth rates using the NASGRO equation obtained with the presence of plastic deformation zones. An example of the crown block axis illustrates the influence of nonstationary dynamic processes in drill rigs on the durability of structural elements.

Seismic mitigation performance of a periodic foundation for nuclear power structures considering soil-structure interactions

Periodic structures may be designed as periodic foundations to reduce the seismic response of engineering structures. The periodic foundation is more suitable for the seismic mitigation of nuclear power structures because of its wide attenuation domain. Based on the dispersion relationship of infinite periodic structures, this research constructs a one-dimensional layered periodic foundation using rubber and concrete materials, determines the attenuation domain frequency band gap that meets the seismic design requirements of nuclear power structures, and optimizes the raft design of nuclear power structures. At the same time, with the scarcity of bedrock sites, the site selection of nuclear power structures is inevitably shifted to soft rock sites. Therefore, this paper also considers the influence of the soil-structure interaction (SSI) on the seismic response of nuclear power structures. A three-dimensional finite element model of the nuclear power structure-periodic foundation-site system was established, and a detailed parameter analysis of the seismic performance of the periodic foundation of nuclear power structures considering the SSI effect was carried out. The results show that the seismic response of nuclear power structures can be significantly reduced by designing the attenuation domain of the periodic foundation.

Advancements in Rechargeable Zn-Air Batteries with Transition-Metal Dichalcogenides as Bifunctional Electrocatalyst.

Zinc-air batteries are promising energy storage devices owing to their high energy density, low cost, and environmental friendliness. However, the development of durable and efficient bifunctional electrocatalysts is a major concern for Zn-air batteries. In this review, we summarize the recent progress on transition metal dichalcogenides (TMDs) as bifunctional electrocatalysts for Zn-air batteries. We discuss the advantages of TMDs, such as high activity, good stability, and tunable electronic structure, as well as the challenges, such as low conductivity, poor durability, and limited active sites. We also highlight the strategies for fine-tuning the properties of TMDs, such as defect engineering, doping, hybridization, and structural engineering, to enhance their catalytic performance and stability. We provide a comprehensive and in-depth analysis of the applications of TMDs in Zn-air batteries, demonstrating their potential as low-cost, abundant, and environmentally friendly alternatives to noble metal catalysts. We also suggest future directions like exploring new TMDs materials and compositions, developing novel synthesis and modification techniques, investigating the interfacial interactions and charge transfer processes, and integrating TMDs with other functional materials. This review aims to illuminate the path forward for the development of efficient and durable Zn-air batteries, aligning with the broader objectives of sustainable energy solutions.

Application of a folded nanostructure reinforcement for the pole vault curved shell

Foldability capacity is now introduced as a novel nanofiller reinforcement production procedure using some operation to control the mechanical, thermal and electrical properties in the sport equipment. Application of this type of nanofillers in the curved structures like pole vault shell leads to a novel engineering and sport shell shape structures. This article is organized to suggest a vibration-based formulation for analysis of folded reinforced curved shell sport structure subjected to thermal and mechanical loading. Using computation of kinetic, strain and external energies, one can arrive the motion’s equations using the minimization of total energy and Hamilton’s principle. Using solution of the motion’s equations through an analytical approach, the parametric analysis is presented. The verified test is presented for confirmation of the solution and trend of results.

Advances in Marine Mechanical and Structural Engineering

In the design of modern ship and offshore structures, one of the key issues is the accurate prediction of strength with regard to various new materials and structures used in the structural design stage and under extreme sea environment and accidental states [...]

Structural engineering on indole derivative for rechargeable organic lithium-ion battery

Structural engineering on indole derivative for rechargeable organic lithium-ion battery

Structural Damage Identification Using Autoencoders: A Comparative Study

Structural health monitoring (SHM) ensures the safety and reliability of civil infrastructure. Autoencoders, as unsupervised learning models, offer promise for SHM by learning data features and reducing dimensionality. However, comprehensive studies comparing autoencoder models in SHM are scarce. This study investigates the effectiveness of four autoencoder-based methodologies, combined with Hotelling’s T2 statistical tool, to detect and quantify structural changes in three civil engineering structures. The methodologies are evaluated based on computational costs and their abilities to identify structural anomalies accurately. Signals from the structures, collected by accelerometers, feed the autoencoders for unsupervised classification. The latent layer values of the autoencoders are used as parameters in Hotelling’s T2, and results are compared between classes to assess structural changes. Average execution times of each model were calculated for computational efficiency. Despite variations, computational cost did not hinder any methodology. The study demonstrates that the best fitting model, VAE-T2, outperforms its counterparts in identifying and quantifying structural changes. While the AE, SAE, and CAE models showed limitations in quantifying changes, they remain relevant for detecting anomalies. Continuous application and development of these techniques contribute to SHM advancements, enabling the increased safety, cost-effectiveness, and long-term durability of civil engineering structures.

Improved Bayesian Model Updating Method for Frequency Response Function with Metrics Utilizing NHBFT-PCA

To establish a high-fidelity model of engineering structures, this paper introduces an improved Bayesian model updating method for stochastic dynamic models based on frequency response functions (FRFs). A novel validation metric is proposed first within the Bayesian theory by using the normalized half-power bandwidth frequency transformation (NHBFT) and the principal component analysis (PCA) method to process the analytical and experimental frequency response functions. Subsequently, traditional Bayesian and approximate Bayesian computation (ABC) are improved by integrating NHBFT-PCA metrics for different application scenarios. The efficacy of the improved Bayesian model updating method is demonstrated through a numerical case involving a three-degrees-of-freedom system and the experimental case of a bolted joint lap plate structure. Comparative analysis shows that the improved method outperforms conventional methods. The efforts of this study provide an effective and efficient updating method for dynamic model updating based on the FRFs, addressing some of the existing challenges associated with FRF-based model updating.

Kenneth Severn Award 2024: Structural engineering satnav: destination set, journey begins – wait, did you pack the snacks?

This winning entry to the Institution's Kenneth Severn Award 2024 – an annual essay competition for young engineers – responds to a question set by President Tanya de Hoog which asked: What does success look like for the future of the structural engineering profession? What qualities and competencies do we need as individuals, and as an engineering community, in order to play a pivotal role in addressing climate change and ensuring public safety through our work? In her thought-provoking answer, Romilly Bobby asks three questions of the structural engineering profession: where are we going? How will we get there? And what should we bring?

Hollow Co9S8-carbon fiber hierarchical heterojunction with Schottky contacts for tunable microwave absorption

Heterogeneous interface engineering of hollow hierarchical structures with Schottky contacts is an attractive approach for designing light weight and efficient microwave absorption (MA) materials. Herein, hollow Co9S8-carbon fiber (CF) composites were prepared by solvothermal, electrostatic spinning, and pyrolysis methods. CF was used as the main chain and hollow Co9S8 derived from metal-organic frameworks (MOFs) was homogeneously embedded in it, which overcame the difficulties of the traditional template method and effectively avoided the particle agglomeration problem. The interface polarization relaxation process is improved by the construction of Co9S8-CF heterojunction with Schottky contacts, which effectively modulates the dielectric loss. The internal hollow macroporous cavity and CF with lightweight properties enhance the reflection attenuation of the internal cavity. In addition, the electromagnetic characteristics can be flexibly adjusted to achieve the tunable MA performance by varying the reaction parameters. As a result, the Co9S8-CF-3–700 exhibits optimum MA performance, with a reflection loss (RL) of −60.83 dB at 10.85 GHz and a thickness of 2.76 mm. The effective absorption bandwidth (EAB) extends to 5.6 GHz at a thickness of 2.19 mm. This research provides a promising approach to creating light weight and efficient MA materials with potential applications in radar and communication systems.

Mitigating chain degradation of lithium-rich manganese-based cathode material by surface engineering

Due to offering joint cationic and anionic redox, lithium-rich manganese-based layered oxides (LMLOs) allow high energy density in lithium-ion batteries. However, the oxygen loss, electrode-electrolyte interface side reactions and the structural degradation have resulted in continuous performance decay, hindering the scale-up application of LMLOs. Here, Li1.3V0.94(BO3)2 (LVB) is uniformly coated on the Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) surface by using a sol-gel method combined with a high-temperature calcination. By applying multiple characterizations including in-situ XRD, DEMS, HRTEM, AFM and electrochemical test, we prove that the LVB layer provides a physical barrier, which effectively inhibits the surface reactivity and blocks the chain degradation from the source, improves the reversibility of O2- redox and prevents the phase transition and structural degradation propagating from the surface to the bulk. Moreover, the kinetic investigations and calculations reveal that the LVB modification not only improves the electron conductivity by the strong bond of V-O and B-O to decrease the surface work function and increase the electron density near the Fermi energy level, but also provides expanded pathways with lower impedance to facilitate the Li+ transfer and diffusion. Impressively, the modified cathode exhibits the higher rate performance (151 mAh g-1 at 5C) and improved cycle stability under high cutoff voltage (217.7 mAh g-1 after 200 cycles at 0.2C in 2.0–4.8 V, 92.5% capacity retention; even in 2.0–5 V, 93.9% after 100 cycles). This work systematically investigates the inhibiting degradation mechanism and establishes the correlation between the intrinsic structure and surface engineering, and offers valuable insight into the development of high-performance LMLOs.

Mitigating chain degradation of lithium-rich manganese-based cathode material by surface engineering

Due to offering joint cationic and anionic redox, lithium-rich manganese-based layered oxides (LMLOs) allow high energy density in lithium-ion batteries. However, the oxygen loss, electrode-electrolyte interface side reactions and the structural degradation have resulted in continuous performance decay, hindering the scale-up application of LMLOs. Here, Li1.3V0.94(BO3)2 (LVB) is uniformly coated on the Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) surface by using a sol-gel method combined with a high-temperature calcination. By applying multiple characterizations including in-situ XRD, DEMS, HRTEM, AFM and electrochemical test, we prove that the LVB layer provides a physical barrier, which effectively inhibits the surface reactivity and blocks the chain degradation from the source, improves the reversibility of O2- redox and prevents the phase transition and structural degradation propagating from the surface to the bulk. Moreover, the kinetic investigations and calculations reveal that the LVB modification not only improves the electron conductivity by the strong bond of V-O and B-O to decrease the surface work function and increase the electron density near the Fermi energy level, but also provides expanded pathways with lower impedance to facilitate the Li+ transfer and diffusion. Impressively, the modified cathode exhibits the higher rate performance (151 mAh g-1 at 5C) and improved cycle stability under high cutoff voltage (217.7 mAh g-1 after 200 cycles at 0.2C in 2.0–4.8 V, 92.5% capacity retention; even in 2.0–5 V, 93.9% after 100 cycles). This work systematically investigates the inhibiting degradation mechanism and establishes the correlation between the intrinsic structure and surface engineering, and offers valuable insight into the development of high-performance LMLOs.

An introduction to the Association of Geotechnical and Geoenvironmental Specialists

Vivien Dent and Alex Dent introduce the AGS and explain how its members' work can support that of structural engineers.

Engineering high-performance oxide anodes for lithium storage: SnO2/TiO2 heterojunction nanofibers with core–shell structures

Oxide anodes require a robust structure to enhance cyclability during lithium storage processes, and structural engineering plays a crucial role in achieving this goal. In this work, the SnO2/TiO2 heterojunction nanofibers with core–shell structures is carefully engineered by electrospinning and following annealing processes. These nanofibers exhibit exceptional cyclability and rate performance at a condition of Sn/Ti molar ratio of 1:2, with a reasonable reversible capacity of 650 mAh g−1 at 0.2 A g−1, a notable rate capacity of 326 mAh g−1 at 2 A g−1 and enhanced cyclability of 303 mAh g−1 (2 A g−1) over 2000 cycles. The performance enhancement can be attributed to the distinctive core–shell structure, which provides effective volume buffering, and the heterojunction introduces internal electric fields, enhancing charge transfer kinetics and reducing electric resistance. The study reveals that systematically designed SnO2/TiO2 nanocomposites exhibit enhanced electrochemical performance, showing promise for lithium storage applications.

External manipulation of the spin-orbit torque and magnetization switching in gradient CoPd single layer via hydrogen

Recent findings regarding spin-orbit torques (SOTs) and current-induced magnetization switching in ferromagnetic (FM) single layers have attracted substantial attention due to the advantage of not necessitating the use of heavy-metal layers. Nevertheless, despite prior studies on the interior structural engineering of the SOT, the external techniques for manipulating the SOT in the FM single layer remains elusive, which is indispensable for the practical application of the single layer SOT devices. Here, we demonstrate external manipulation of SOT generation in CoPd single layer through the fabrication of CoPd film with a composition gradient, utilizing the H2-absorption property of Pd. It is found that the H-induced strain within the CoPd film plays a pivotal role in generating SOT. Meanwhile, we demonstrate that the critical current density required for the current-induced magnetization switching is markedly diminished with the application of H2 due to the enhanced SOT generation and reduced perpendicular magnetic anisotropy energy. Our findings offer a straightforward method for external manipulation of single layer SOT devices, and hold the potential for applications of the spintronic devices.

Machine Learning and Traditional Approaches in Shear Reliability of Steel Fiber Reinforced Concrete Beams

In the field of structural engineering, the exploration of steel fibre reinforced concrete (SFRC) beams has recently intensified, particularly due to their improved tension and shear performance of structure. This study pioneers a novel reliability analysis of shear capacity predictions for SFRC beams, distinctively classifying the datasets into high-strength (HSFRC) and normal-strength (NSFRC) categories. A comprehensive database of 142 HSFRC and 265 NSFRC beams serves as the foundation for this analysis, which critically examines the standard Gaussian distribution in shear design models and proposes the Lognormal and Weibull distributions as more precise alternatives. Employing advanced First-order (FORM) and Second-order Reliability Methods (SORM), the study covers a broad spectrum of load conditions, including dead, live, snow, wind, and seismic loads, to evaluate various empirical, semi-empirical and machine learning proposed shear capacity prediction formulas. One of the key innovations of this research is the development of differentiated resistance coefficients for various risk levels in the reliability analysis, allowing future structural designers to tailor their designs according to specific risk profiles. This approach significantly enhances the balance between economic efficiency and structural safety based on the evolution of different target reliability indexes. The study reveals that existing design equations for SFRC beams generally lean towards conservatism. This study found that formulas derived from machine learning exhibited superior prediction ability compared to traditional theoretically derived regression formulas. When compared the proposed machine learning formulas, the Tarawneh's formula demonstrated better prediction ability than the Kara's formula when applied to larger datasets. However, high predictive power does not necessarily equate to high reliability. Machine learning formulas prioritize predictive accuracy, often at the expense of insufficient redundancy for ensuring safety. Overall, it introduces Kara's formula for NSFRC beams, which stands out with its superior predictive performance, offering an optimal balance of safety and cost-efficiency. Ashour's formula is also identified as a more effective and safer option for HSFRC beams. Complementing these findings, the extensive sensitivity analysis of the collected data not only confirms the robustness of the conclusions but also prepares for the integration of broader datasets in the future.

Structural forming of soil composites using as a pavement subgrade strengthening

The article substantiates the possibility of obtaining composite materials with improved functional properties to strengthen the subgrade, containing technogenic soil stabilized by an additive based on a gelling polymer. The introduction of technogenic soils into composites will not only reduce the consumption of expensive materials, but also solve a complex of acute environmental problems. Composite materials can be used in the construction of structural layers of road pavements, foundations of buildings and structures, sites for various purposes, for the prevention and elimination of defects in the foundations of engineering structures during their construction, reconstruction and repair, including in permafrost areas. Stabilized technogenic soils are more durable, frost-resistant and waterproof, which makes them applicable for creating impervious curtains in hydraulic structures and sealing storage facilities for hazardous substances. The cryogenic effect on a composite material allows one to vary its properties within a wide range and modify its macroporous structure. Studying the process of structure formation of the resulting organic-inorganic materials, consisting of macromolecules of high-molecular substances and inorganic inclusions that have undergone cryogenic treatment, will make it possible to specifically regulate their performance characteristics. The best values of strength characteristics were obtained for samples with a stabilizing additive concentration of 100g/l. The resulting composite materials are hydrophobic, frost-resistant, characterized by a compressive strength of 2.3-6.5MPa and a thermal conductivity of 0.19-0.20W/(m·K). Data from differential scanning calorimetry and thermogravimetry and IR spectroscopy revealed that the binding of mineral particles by a stabilizing additive occurs due to the formation of organomineral complexes with the participation of clay minerals and the restructuring of hydration shells. SEM data indicate that crystallinity zones formed due to hydrogen bonds of hydroxyl groups of neighboring polymer chains can participate in the formation of the composite structure. An increase in the number of cryogenic treatment cycles promotes additional structuring and strengthening of the polymer phase due to the formation of additional nodes of the supramolecular network, ordering of crystallinity zones and the appearance of compacted areas in the structure. Computed X-ray tomography revealed an increase in the density of the composite upon drying, which helps to increase its strength characteristics. The structure of the sample is characterized by heterogeneity of the pore space, which is characterized by the presence of both fine-porous and large-porous regions, which determines its thermophysical properties.