Structural Design Requirements Research Articles

A comparative study between ultra-high-performance concrete structures and normal strength concrete structures exposed to fire

The use of ultra-high-performance concrete (UHPC) in civil infrastructure is increasing due to its numerous advantages compared to normal strength concrete (NSC). In this research, thermal analysis of NSC and UHPC beams and columns was developed to understand and compare the fire performance of these structures. A numerical analysis was performed using finite element (FE) modeling with ABAQUS software. Compared to NSC, UHPC structures in some cases have lower fire resistance due to their slender cross-sections and unfavorable thermal properties and mechanical capacity degradation due to temperature effect. The results show that UHPC structures experience significantly higher cross-sectional temperatures when exposed to fire compared to NSC. The results are particularly relevant for high-rise buildings, where fire safety requirements are more stringent and the use of UHPC is attractive, leading to an unprecedented contradiction. Alternative strategies for the application of UHPC, such as the contradictory increases in cross-section or the use of fire protection coatings, must be considered. In some cases, NSC may be more attractive as a structural material than UHPC if structural fire design requirements are taken into account.

Design and Conformation of Separators for High-performance Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are considered promising candidates for large-scale energy storage due to their high safety, low cost, and environmental friendliness. As a core component, separator plays a unique yet oftentimes overlooked role in providing electrochemical stability in AZIBs. This concept focuses on the exquisite structure-property relationship of separators, highlighting three forms of these components and their structural design requirements, i.e., traditional membranes, solid-stateelectrolytes, and electrode coatings. The mechanism by which separators influence the zinc anode and the cathode is discussed. The article also identifies the challenges and potential future directions for functional separators in the development of high-performance AZIBs.

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.

Heat exchange performance of an energy-pile group in a hybrid GSHP system and effects of pile spacing

In long-term operations, seasonal imbalance in the thermal load may adversely affect the heat transfer performance of the energy piles, potentially resulting in thermal accumulation within the ground and eventual system failure. The heat transfer performance of energy pile systems during long-term operation under unbalanced thermal loads must be investigated. Moreover, the design parameters of energy piles are usually constrained by the requirements of foundation structural design, resulting in energy piles being densely arranged. Hence, the influence of pile spacing on the heat exchange performence of energy piles must be comprehensively understood. In this study, two- and three-dimensional energy-pile heat transfer models were established and innovatively coupled based on an engineering project currently under design. Numerical simulations were performed to investigate the heat transfer behavior of energy-pile groups subjected to unbalanced thermal loads and the effect of pile spacing on their heat exchange performance. Furthermore, design recommendations regarding the determination of the proportion of thermal loads to be borne by the energy piles in a hybrid GSHP system were provided. The results indicate that the proposed 2D-3D coupled modeling approach is able to simulate the heat exchange performance of large-scale energy pile groups. Pile spacing considerably affects the long-term thermal performance of energy-pile groups, especially in cases with small pile spacings. The influence of pile spacing on the heat exchange capacity of energy piles can be considered in the design phase by incorporating a group effect coefficient η, which are calculated to be 0.165, 0.470, 0.732, and 1 for pile spacings of 2 m, 4 m, 6 m, and 10 m, respectively.

STUDY ON CONSTRUCTION MONITORING AND CONTROL OF MULTI-SPAN PRESTRESSED CONCRETE CONTINUOUS BEAM BRIDGE

This article focuses on the construction monitoring and control of a pre-stressed concrete continuous beam bridge, consisting of 13 spans. The goal is to ensure that the bridge structure meets the design requirements throughout the entire construction process. By comparing the theoretical and measured values of the bridge’s alignment and stress during the cantilever construction, closure, and completion phases, it can be observed that the deflection deformation of the bridge is generally in agreement with the theoretical calculations. After the completion of the entire bridge, the measured elevations of each section have an error range of -18mm to 20mm compared to the design elevations, which satisfies the specifications. A comparison analysis of the measured and theoretical stress values at the root and mid-span of the cantilever indicates that the stress difference at the root is within the range of -0.2MPa to 0.2MPa, and the stress differences at the mid-span after completion are 0.03MPa (upper) and 0.09MPa (lower), all of which meet the structural design and code requirements. By establishing a gray GM (1,1) model and using gray system theory, the deflection error during the construction process is predicted and controlled. The prediction accuracy of different methods is compared to determine a reasonable prediction method suitable for long-span pre-stressed continuous beam bridges, providing reference for similar engineering projects.

Static test of T800 carbon fiber reinforced polymer (CFRP) wing-box

This paper studies static test methods and test loads of Carbon Fiber Reinforced Polymer (CFRP) wing-box, analyzes the test results, and compares the test results of T800 CFRP wing-box from HENGSHEN Co., LTD and TORAY. It comes out that the stiffness of the T800 CFRP wing-box from HENGSHEN is equivalent with that of TORAY, while the strength meets the structural design requirements, which can be applied on the scheduled aircraft structure for further verification.

Microstructure and Mechanical Properties of Powder Metallurgy Superalloy Joints Welded by Inertia Friction Welding.

In recent years, for the structural characteristics and design requirements of the integral rotor and disc shaft of the integrated engine, the welding quality and mechanical properties of superalloy weldments have received increasing attention. In this paper, inertia friction welding (IFW) of FGH96 alloy was carried out using different welding parameters, and the homogeneous connection of FGH96 alloy hollow bars was successfully realized. The microstructure evolution, mechanical properties and fracture failure of the welded joints at room and high temperatures were investigated. The FGH96 alloy IFW joints were divided into the weld nugget zone (WNZ), the thermo-mechanically affected zone (TMAZ), the heat-affected zone (HAZ) and the base metal (BM), and there were significant differences in grain structure and distribution of the γ' phase in each of the characteristic zones. The microhardness and tensile properties of the IFW joints were investigated, and the results showed an "M"-shaped curve in the microhardness distribution, with the lowest point of hardness observed in the HAZ. The tensile test results indicated that the fracture position moved from the BM to the WNZ with the increase in temperature, the microstructure at the fracture changed significantly and the tensile strength decreased from 1512.0 MPa at room temperature to 1201.3 MPa at 750 °C. The difference in the mechanical properties of the joints was mainly attributed to the changes in the dissolution and precipitation of the γ' phase.

Different Design Aspects of L-Shaped Earth Retaining Structures

The L-shaped retaining walls (L-SRWs) are considered one of the important earth retaining structures (ERSs). The investigation of L-SRWs mainly depends on factors directly related to the design process. Reviewing these factors represents the key matter in the design of ERSs, and this is the main purpose of this paper. This review showed that, in the design of L-SRWs, there are important issues to be considered. Some of them are related to the backfill and foundation soils e.g. the dependency of soil stiffness on the state of stresses, information related to soil behavior, inclination and quality of backfill, and settlement of foundation soil. Other issues are related to the wall itself such as the wall dimensions, failure mechanism, and flexural failure mode. In the design processes of L-SRWs, structural and geotechnical design requirements should be considered. L-SRWs should be designed to be proportional in their dimensions, the width of the wall base and its height should be designed to meet a specific ratio. Considerations related to the "conjugate rupture planes", the displacement pattern, and flexural failure mode should be included in the design process of L-SRWs.

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Optimal structural design for a certain near-space composite propeller of airship using adaptive region division blending model

Near-space airship is a frontier and hotspot in current military research and development, and the near-space composite propeller is the key technology for its development. In order to obtain higher aerodynamic efficiency at an altitude of 22 km, a certain near-space composite propeller is designed as a long and slender aerodynamic shape with a 10 m diameter, which brings many challenges to the composite structure design. The initial design is obtained by the composite structure variable stiffness design method using based on fixed region division blending model. However, it weighs 23.142 kg, exceeding the required 20 kg. In order to meet the structural design requirements of the propeller, a variable stiffness design method using the adaptive region division blending model is proposed in this paper. Compared with the methods using the fixed region division blending model, this method optimizes region division, stacking thickness and stacking sequence in a single level, considering the coupling effect among them. Through a more refined region division, this method can provide a more optimal design for composite tapered structures. Additionally, to improve the efficiency of optimization subjected to manufacturing constraints, a hierarchical penalty function is proposed to quickly filter out the solutions that do not meet manufacturing constraints. The above methods combined with a Genetic Algorithm (GA) using specific encoding are adopted to optimize the near-space composite propeller. The optimal design of the structure weighs 18.831 kg, with all manufacturing constraints and all structural response constraints being satisfied. Compared with the initial design, the optimal design has a more refined region division, and achieves a weight reduction of 18.6%. This demonstrates that a refined region division can significantly improve the mechanical performance of the composite tapered structure.

Blended structural optimization of steel joints for Wire-and-Arc Additive Manufacturing

Metal Additive Manufacturing, and in particular Wire-and-Arc Additive Manufacturing (WAAM) has proved to be a great and efficient alternative to the common subtractive manufacturing processes to realize complex-shape members and connections for construction. With reference to complex spatial structures such as gridshells, the connections play a crucial role both in the design and the construction processes. Novel computational design tools allow designers to conceive optimized joint solutions while minimizing the material use, resulting in difficult geometries to be fabricated with conventional methods. The present work aims at providing an innovative integrated design and fabrication framework to efficiently apply topology optimization algorithms to improve the efficiency of steel joints in complex spatial structures. The framework is based on the so-called “blended” structural optimization approach aimed at incorporating manufacturing constraints, basic principles of conceptual structural design and structural requirements into topology optimization to design ready-to-fabricate complex steel joints. The designs are suitable for fabrication with the WAAM process. The approach is applied to a case study to re-design the joint connections of the world’s renowned British Museum gridshell rooftop structure. From a catalogue of various designs for each unique joint, one selected design is optimized and then checked for structural requirements in terms of strengths and stiffness. Then the optimized joint is validated for fabrication with WAAM process.

Characterization and evaluation of stress resistance in the structural bonding of electric cooktops

This work presents the definition and validation of a methodology for assuring proof of conformity of electrical appliances structural bonded joints. Stress and stress resistance calculation for assessing the adhesive bonding is performed. This includes analytical and simulation studies with Finite Element Analysis (FEA), contact substrate area calculation and real components experimental testing under ageing conditions such as high temperature, low temperature and humidity. To achieve this, standard DIN 2304-1:2020-04 was used as a reference for the definition of the methodology and to prove the fulfilment of the bonding requirements for the high quality structural joint design, covering all steps of the adhesive bonding process specially focusing on the joint design. The validation of this methodology was done with an electrical appliance, where metallic profiles are assembled with a ceramic glass by means of an adhesive structural bond. The results of the work prove that the evaluated bonding joint successfully meets the required criteria assuring that the stress is lower than stress resistance value.

Physical Modelling in Development of the Regulatory Framework for Transport Construction

Application of the physical modelling method to justify regulatory requirements for design of structures for engineering protection of transport facilities from wave action is considered using the example of three completed research and development works. The described experimental studies of interaction of waves with structures were carried out in wave basins and tanks.The objective of the research is to scientifically substantiate the requirements of regulatory documents for design of shore protection to ensure safe operation of the roadbed of railways and roads, bridge supports, and other transport structures operated under conditions of wave action on the shores of seas and lakes. In this case, the normalised parameters, depending on the hydrological (wind-wave and sea-level regimes of the water area and current), geological-morphological and lithodynamic (coastal zone dynamics) conditions are the types of protective structures used, planned and design solutions for protective hydraulic structures (location, elevations, dimensions), as well as the materials and products used for construction (including quality requirements).The experimental design part of the described studies was carried out by the method of physical (hydraulic) modelling in wave basins and tanks. Physical modelling was carried out in accordance with the theory of similarity. At the same time, a «flat problem» is solved in wave tanks, and a «spatial problem» is solved in wave basins.

Nonlinear analysis model and seismic resilience assessment of LEM-filled CFS residence

Lightweight EPS materials (LEM)-filled cold-formed steel (CFS) shear wall structure is a new type of green, low-carbon and prefabricated rural residence, which has drawn in expanding consideration due to the promotion of the rural revitalization strategy. However, most of the existing research on this type of residence has focused on its behaviours of components, with little attention was paid to its overall response to resist earthquake disasters. During the past two decades, significant advancements have been made in effectively mitigating building collapses and reducing casualties resulting from earthquakes. Thus, the concept of seismic resilience is proposed, and the seismic performance requirements of structural design have been elevated from “safety” to “resilience”. To analyze the seismic resilience of LEM-filled CFS residence, this paper proposed a strut and tie- equivalent spring model to establish the simplified analysis model of a single composite wall, and the precision of the model was confirmed by test results, in which the nonlinear characteristic and the supporting effect of fillers was considered. Subsequently, three LEM-filled CFS residences are designed using the direct displacement-based design method. Then the three-D models are established for nonlinear analysis, and the inter-drift ratio (IDR) and residual inter-drift ratio (RIDR) are adopted to estimate the seismic response of the three archetypes. The seismic resilience of the three archetypes are assessed based on FEMA P58. This paper would provide a guidance for the nonlinear analysis and seismic resilience assessment of this type of residences, and promote the application and popularization of this kind of residence.

Exploratory Thermo-Mechanical Assessment of the Bottom Cap Region of the EU DEMO Water-Cooled Lead Lithium Central Outboard Blanket Segment

The Water-Cooled Lead Lithium (WCLL) Breeding Blanket (BB) is one of the two BB concept candidates to be selected as the driver blanket for the EU DEMO fusion reactor. In this regard, the development of a sound architecture of the WCLL Central Outboard Blanket (COB) Segment, ensuring the fulfilment of the thermal and structural design requirements, is one of the main goals of the EUROfusion consortium. To this purpose, an exploratory research campaign has been launched to preliminarily investigate the thermo-mechanical performances of the Bottom Cap (BC) region of the WCLL COB segment because of its peculiarities making its design different from the other regions. The assessment has been carried out considering the nominal BB operating conditions, the Normal Operation (NO) scenario, as well as a steady-state scenario derived from the in-box LOCA accident, the Over-Pressurization (OP) scenario. Starting from the reference geometric layout of the WCLL COB BC region, a first set of analyses has been launched in order to evaluate its structural performances under a previously calculated thermal field and to select potential geometric improvements. Then, the analysis of a complete BC region was conducted from both the thermal and structural standpoints, evaluating its structural behaviour in compliance with the RCC-MRx code. Finally, after some iterations and geometric updates, a promising geometric layout of the BC region has been obtained even though some criticalities still persist in the internal Stiffening Plates and First Wall. However, the obtained results clearly showed that the proposed layout is worthy to be further assessed to achieve a robust enough configuration. The work has been performed following a theoretical-numerical approach based on the Finite Element Method (FEM) and adopting the quoted Ansys commercial FEM code.

Structural Design and Simulation of a Multi-Channel and Dual Working Condition Wafer Defect Inspection Prototype.

Detecting and classifying defects on unpatterned wafers is a key part of wafer front-end inspection. Defect inspection schemes vary depending on the type and location of the defects. In this paper, the structure of the prototype is designed to meet the requirements of wafer surface and edge defect inspection. This prototype has four inspection channels: scattering, reflection, phase, and contour, with two working conditions: surface and edge inspection. The key structure of the prototype was simulated using Ansys. The simulation results show that the maximum deformation of the optical detection subsystem is 19.5 μm and the fundamental frequency of the prototype is 96.9 Hz; thus, these results meet the requirements of optical performance stability and structural design. The experimental results show that the prototype meets the requirements of the inspection sensitivity better than 200 nm equivalent PSL spherical defects.

Fatigue life estimation of aircraft structural component using FE approach and validation through analytical and experimental methods

Aircraft structural design requirements encompass safe-life and damage-tolerant design, analysis, and verification through testing to arrive at the overall service life. The fatigue phenomenon is most critical and local; hence fatigue studies are necessary to conduct first at the coupon level before attempting at the component or full-scale level. The present work demonstrates the development of fatigue life estimation procedures such as high cycle fatigue (HCF) life and fatigue crack growth (FCG) life on specimens as per ASTM standards.The HCF life is predicted for the Aluminum (Al) 2024-T3 ASTM E466 specimen subjected to constant amplitude loading with a stress ratio (R) of 0.1 based on Basquin's method. The computational 2D finite element (FE) model is developed to predict HCF life using a safe-life approach through Nastran Embedded Fatigue (NEF). The effect of fatigue strength modifying factors affecting fatigue life is also explored. Similarly, the FCG life is predicted for the Al 2024-T3 ASTM E647 specimen subjected to constant amplitude loading with a stress ratio of 0.1 using Walker's equation. The computational 3D FE models with a single edge crack in each are developed to predict FCG life using FRANC3D. The FE-based HCF and FCG life prediction procedures demonstrated in this work are verified by comparing FE results with analytical and experimental ones. Therefore, these FE-based methodologies for HCF and FCG life prediction can be adopted at the feature and structural component levels. The developed computational methods reduce the experimental effort, cost, and time involved in the overall fatigue design of the aircraft structures.

Design and Development of Cfrp Tubular Structure For Soft X-Ray Telescope Payload of Astrosat

India has launched an astronomical space based observatory ASTROSAT in the year 2015 for unravelling the some of the secrets of our universe. Soft X-ray Telescope (SXT) was one among the payloads onboard for studying the sources of Soft X-rays in deep space. A composite structure was required for this purpose. It had to support the payload elements and maintain their relative locations precisely during launch as well as during its operation, in-orbit. The interface with the spacecraft was at the middle of the SXT structure with one part is inside and remaining part is outside of the spacecraft deck. The structural design was carried out to meet all the structural design requirements such as stability, stiffness and strength with minimum mass under the constraints of spacecraft interface and envelope. This paper presents the details of the structural design, development and qualification of a CFRP tubular SXT structure, which has been functioning satisfactorily in-orbit.

Plastic redistribution capacity of stainless steel frames in fire

Stainless steel frames with compact cross-sections are capable of redistributing internal forces at room temperature and forming plastic failure mechanisms, which is reflected in the new generation of structural codes for stainless steel by allowing to carry out global plastic analyses on certain types of stainless steel if the joints conforming the structure are classified as full-strength joints. Nevertheless, the requirements for the fire design of stainless steel structures in current standards is still primarily based on the resistance of individual members, disregarding strain hardening effects and the redistribution of internal forces, mainly because the influence of the performance of stainless steel joints on the response of the frames under fire situation is yet unknown. On this basis, this paper presents a numerical study focused on stainless steel frames with compact rectangular hollow sections, both at room temperature and at elevated temperatures, to analyse the influence of full-strength joints on the frame's response by means of two joint modelling techniques, and to assess the plastic redistribution capacity of stainless steel frames, especially under fire situation. In addition, an exhaustive revision of the failure criteria for stainless steel frames under fire situation is carried out and a new failure criterion is proposed based on the results derived from the parametric study. The results demonstrate that stainless steel frames are also capable of redistributing internal forces and forming plastic collapse mechanisms under fire situations, suggesting a new procedure to predict the response of these structures under fire situation more accurately.

Structural efficiency evaluation of innovative reusable launch vehicles

This work is focused on evaluating the structural design of the innovative reusable micro launcher MESO, originated from the RRTB, a funded project by EU. The structural efficiency of MESO is evaluated in association with its mass budget, which is based on project’s early adopted requirements. In this particular design loop, the reusability concept is intergraded by implementing the fail-safe design approach, considering the exclusive use of high TRL aluminum alloys. The main objective of this work is achieved by developing a global Finite Element Model (FEM), comprising a set of sub-models, which represent the primary structure, the secondary structures, the equipment and their interfaces as well.The paper proceeds with the description of the modelling approach regarding mesh development and the connections created between the sub-models for assembling the integrated Global FEM of the launcher. The first iteration of the load analysis loop resulted in the extraction of the Design Limit Loads (DLL). The DLL investigated in both ground and flight cases, which comprise the most severe combination of quasi-static loads. The FEM is verified and subjected to various types of preliminary structural analysis, taking into consideration the required ECSS design and safety factors for static strength and stability assessment.The analyses results indicated the order of magnitude and the location of all weak areas of the launcher. Subsequently a preliminary sizing procedure is performed in order to prevent all failure modes according to the structural design requirements. The conclusions derived from the structural analysis of the first design loop influence the design modifications to be considered for the next design loop, where the same steps are going to be followed until the structural design requirements are satisfied once again.