Design Of Structural Components Research Articles

Green Concretes : Principle Design Approaches for Materials and Components

This article deals with the evaluation and design of eco-concretes (green concretes) and structural components made from them. Such concretes are characterized by a pronouncedly reduced CO2 footprint compared to conventional structural concretes made with Portland cement clinker. After an introduction to the sustainability problems of today’s structural concretes, the basic approaches to the development of sustainable concretes are presented. The specific parameter Concrete Sustainability Potential is introduced, which combines the main effecting parameters environmental impact, service life (durability) and performance (strength). An overview in possibilities available today for producing green concrete mixtures is given. Certain emphasis is placed on eco-concretes, in which a large proportion of the cement is replaced by rock powders. Further, a new and innovative relationship for sustainability design is introduced. This concept is equally applicable to concrete as a material and to components made from it. The article concludes with considerations on the implementation of this new concept in practice.

Influence of geometric constraints on aircraft design

The paper considers the requirements to helicopter operating conditions, forming geometrical constraints at the design stages and their influence on the geometrical appearance of the helicopter as a whole, structural design and layout of individual components and assemblies of helicopters. The methodology of forming the system of geometrical constraints is based on the generalised requirements to ensure the operational and technical characteristics of the helicopter: ensuring the basing and production of take-off and landing operations on marine vessels, ensuring transportability, ease of access to the cockpit, ease of access to the units during maintenance, reducing the labour intensity of individual helicopter maintenance operations.

Development of a reliability model for crack growth occurrence for a secondary hull component

Ship hull vibration is a major contributor to fatigue crack growth and main engine excitation is identified as an important vibration source. A general method to solve any vibration problem arising onboard a ship does not exist, which encourages the use of a reliability-based framework for assessing ship vibration and its consequences. A stochastic model of vibration response is developed for the probabilistic formulation of the failure probability of the occurrence of crack propagation of a secondary structural hull component. The secondary structural component considered is a pipe stack support. The pipe stack support connects a cargo pump pipe stack to the wall inside the cargo tank, and the support is welded directly onto this wall. First, a generic cargo hold model is analysed with engine speed and the relative distance between the engine and the structural component under consideration as stochastic variables. Then, submodels are used to investigate the local vibration of the support and the stress response is evaluated for a combination of different engine speeds and relative distances. A surface is fitted to the vibration response and used for probabilistic analysis by Monte Carlo (MC/DSPS) and FORM/SORM reliability methods. The limit state is formulated as the possibility of fatigue crack growth based on a threshold stress intensity factor. This threshold factor depends on the initial crack size and different initial sizes are investigated. The adequacy of the functional representation for the stochastic model, which is fitted to discrete data points, is also assessed. It is seen that a functional representation using a sum of sine terms give an adequate fit for describing the stress response induced by engine speed, while a polynomial representation was adequate for the relative distance variable. The failure probability estimated by Monte Carlo simulations and SORM indicates that the pipe stack support is not critical for the occurrence of fatigue crack growth. A main observation from the analysis is that the reliability-based design of secondary structural components, also looking at the interaction with the global structure, may help to improve the vibration-induced stresses in local hull details by application of proper design measures.

Stochastic analysis of small-scale beams with internal and external damping

Random flexural vibrations of small-scale Bernoulli–Euler beams with internal and external damping are investigated in the paper. Such a kind of problem occurs in design and optimization of structural components of smart miniaturized electromechanical systems. Internal damping is related to the viscoelastic stress–strain law describing the beam time-dependent behavior while the external damping represents the interaction between the structure and the surrounding viscous environment. In the proposed formulation, Boltzmann superposition integral and fractional-order viscoelasticity are exploited to capture the above mentioned non-conventional phenomena. Size effects caused by long range interactions arising at small-scale are also taken into account and modeled by means of an integral nonlocal formulation based on the stress-driven approach. Moreover, in order to reproduce stochastic vibrations of small-size devices, such as resonators and sensors, the external loading are modeled by taking into account their random nature. The relevant dynamic problem is thus described by a fractional-order stochastic partial differential equation in space and time equipped with standard and non-classical boundary conditions. A proper differential eigenanalysis for the nonlocal viscoelastic bending problem is performed to find the modal shapes and closed-form expressions of power spectral density and stationary variance of displacements are provided. The proposed methodology, accounting for size-effects, hereditariness behaviors, viscous properties of surrounding environment and randomness of external loadings, is suitable to model and capture the effective behavior of miniaturized devices. The presented theoretical findings and numerical outcomes show the influence of size-effects and viscoelastic parameters on the structural response.

Prediction of ultimate conditions and stress–strain behaviour of steel-confined ultra-high-performance concrete using sequential deep feed-forward neural network modelling strategy

Recognising that ultra-high-performance concrete (UHPC) is gaining momentum in structural applications, providing an accurate confinement model is essential to developing a reliable design of UHPC structural members. However, very limited number of models are currently available and these models were empirically formulated and calibrated upon limited test data obtained by the originators of the models. The significant cost associated with comprehensive experimental testing motivates the exploration of cheaper and more efficient data-driven based machine learning approach. This study proposes a sequential artificial neural network (ANN) framework to develop such a data-driven confinement model, incorporating a comprehensive database of 228 axially loaded UHPC columns compiled from available literature. Three deep feed-forward neural network models were established to predict the ultimate stress, ultimate strain and stress–strain behaviour of confined UHPC. The results show that the proposed ANN-based ultimate condition models provide a more robust prediction results compared to the existing design-oriented models for confined UHPC. The stress–strain behaviour, predicted using the proposed ANN model, shows high accuracy levels in capturing different types of stress–strain curves as well as reasonably matching results with those experimentally measured responses. The encouraging outcomes in this study suggest that the proposed models are capable of providing rapid prediction tools that will help to facilitate the on-demand design of UHPC structural components and systems.

Design of Structural Steel Components According to Manufacturing Possibilities of the Robot-Guided DED-Arc Process

Additive manufacturing with the DED-arc process offers limited freedom in terms of the geometric shape of work pieces. The process and fabrication systems restrict the part geometry producible, which must be taken into account during design already. For this reason, a design process was investigated in which geometry generation is based on a self-organizing system. The aim of using a self-organizing system is the possibility to directly control the geometry-defining points. Next to load cases, the design method considers geometric boundary conditions from the production process when generating the geometry. In order to identify these geometrical constraints from production experimentally, a concept of Case Study Demonstrators was applied. This was used to investigate how path planning and production can be carried out for specific geometrical features and to identify restraints of the process and the manufacturing system, e.g., smallest producible wall thickness and overhangs. Subsequently, the obtained restraints were considered as boundary conditions for the design process and were included in the modification of an example geometry. By applying the presented design method, it was possible to maintain a minimum wall thickness throughout the structure while generating a topologically optimized geometry. In contrast to compliance with the minimum wall thickness, no satisfactory behavioral rule could be found for limiting the overhang.

Out‐of‐plane Stability Design by GMNIA – Equivalent Imperfections and Strain Limits

AbstractAn accurate and consistent approach to the out‐of‐plane stability design of steel beams and structures utilising geometrically and materially nonlinear analysis with imperfections (GMNIA) and strain limits is proposed. The method is implemented using computationally efficient beam elements, with the ultimate structural resistance defined either by (i) the ultimate load factor or (ii) the load factor at which a strain limit, determined on the basis of the continuous strength method (CSM), is attained, whichever occurs first. In the present paper, the scope of this method is extended from the in‐plane design of steel structures and structural components to scenarios in which out‐of‐plane stability effects, with a focus on lateral‐torsional buckling (LTB), govern. First, two shapes and corresponding amplitudes of equivalent imperfections, which consider the combined influence of both geometric imperfections and residual stresses, for the out‐of‐stability design of steel and stainless steel members by GMNIA are established. The existing CSM strain limits for in‐plane design are then extended to allow for the influence of shear, torsion and warping, to enable their general applicability to three‐dimensional buckling problems. It is shown that employing the proposed design method together with the proposed equivalent imperfections generally provides more accurate and consistent ultimate strength predictions than traditional Eurocode design calculations and also streamlines the design process by eliminating the need for cross‐section classification and individual member design checks.

Building height-related creep properties of Inconel 718 superalloy fabricated by laser powder bed fusion

The building height-dependent creep properties and microstructures of laser powder bed fusion-fabricated Inconel 718 superalloy were investigated. Creep specimens taken from the as-fabricated plate component at different building heights were tested along the building direction at 650 °C. The results show that under the same heat treatment condition, the recrystallization degree of the specimens taken from the bottom, middle and top of the Inconel 718 plate component differs widely due to the differences in the dislocation density and the texture intensity along the building direction. The bottom specimen exhibited a high recrystallization degree and thus had the longest creep life. Such excellent creep properties of the bottom specimen are mainly attributed to the lower dislocation density and the higher Taylor factor, which cause the lower creep rate, and the lower grain boundary volume fraction, thus reducing the void nucleation sites. The present findings reveal that the impact of the building height-dependent creep performance on the overall service reliability should be considered comprehensively in the subsequent geometrical design of the laser powder bed fusion-fabricated complex structural components.

Virtual testing of multifunctional moveable actuation systems

This work presents the current state of the virtual testing activities performed within the Virtual Product House (VPH) start-up project. In this project a multidisciplinary, collaborative end-to-end process for virtual product design is developed. On the basis of preliminary design and concept studies on aircraft level, the process focusses on design, manufacturing and testing of aircraft systems and structural components with special attention to certification aspects. The initial use case considers the trailing edge flap of a long-range aircraft and its actuation system. Design and analysis tools are integrated in a remote workflow execution environment to automatically generate designs and evaluate them by virtual test means. Virtual tests facilitate knowledge on properties and behavior of the virtual product in early development phases and allow to optimize design flaws in consecutive design iterations to hence reduce the risk of costly corrections later in the development process. The testing is setup in multiple stages. Currently, domain-specific tests are carried out for the moveable structure and its actuation system, with the latter being in focus for the current text. These tests address the functional verification of the actuation system in nominal and failure cases. A SysML model comprising system requirements and architecture is used to model test cases and trace test results. On the basis of these test cases, simulation configurations for virtual tests are automatically built, executed and evaluated. With this method, a continuous evaluation of designs in terms of functional verification of the moveable actuation system is possible. Moreover, the automated execution of all steps allows to determine the effects of design changes quickly without a large amount of labor-intensive and error-prone work.

Progressive optimization on structural design and weight reduction of CFRP key components

In recent years, carbon fiber reinforced plastics (CFRP) have attracted widespread attention in many industrial fields such as aerospace, automobiles, and high-speed railways. It has become a trend to replace traditional aluminum alloys and steels with CFRP in certain key components in order to achieve a better lightweight effect. However, due to the huge difference in the performance of metal materials and CFRP, problems such as unreasonable structural design and insufficient weight reduction may occur during the material replacement process. In order to solve the above problems, a progressive optimization method was proposed by this article. This progressive optimization method includes the conceptual design stage and the detailed design stage. The conceptual design stage includes modal analysis and topography optimization. The detailed design stage involves the weight reduction analysis of components, including the optimization of fiber layup angle, stacking sequence, and thickness. This article takes a CFRP key component as an example to verify the feasibility of the optimization method. Compared with the traditional method, using the optimization method, the structural stability of key components is improved. The weight reduction ratio of key components reaches 61.1%. Finally, a test sample was manufactured according to the optimized results by molding and RTM molding process, the actual weight reduction ratio is 57%, and the sample successfully passed the tests required by the relevant standards. These results indicate that the proposed progressive optimization method has great application potential in the design of CFRP lightweight structures in the aerospace field.

"Comparative Study of RC Frame Building with NBC 105:2020 and IS Code 1893:2002"

Construction is a vital part of every developing country in this era. Every country has specific building design codes which provide the standards to engineers for the design of various structural components like beam, column and slab. RC building design of every country is based on their geographical location. In today world of globalization, an engineer must be efficient to understand and handle codes of various countries. Considering this the main focus of this research work is to bring out differences and similarities between different RC design codes and to use it to develop a common platform. In this research RC design code of NEPAL, INDIA are considered. The main focus is the relative gains and shortcomings of various buildings design codes under certain criteria like loading analysis, design analysis, ease of use and economical point of view. Several parameters for different cross-section and different building material on basis of strength are considered. Comparison work has worked out on the basis of loading comparison like live load, dead load, wind load and different parameters for various elements of the building such as beam, column and slab. Load factor and load combination are also compared. This comparison investigates the design capacities for various building design codes.In present study RCC building models having G+8 stories with regular plan is considered for analysis. The analysis of model is done using equivalent static method in ETABS software.

An experimental assessment of fracture toughness in novel crimp‐free‐based composite materials for aerospace applications

AbstractIn the design of structural composite components for aerospace applications, durability and reliability play a very significant role. To assess the reliability of these material it is essential to carry out robust experimental tests on several specimens and under different loading conditions to allow the determination of fundamental fracture parameters. Fracture toughness, in particular, allows the quantification of the material strength to fracture. This work proposes a study on non‐crimp fabric (NCF) together with a two‐component epoxy resin. The selected system has been selected based on its suitability to produce aerospace‐approved components using resin transfer molding (RTM) process. The fabric adopted is a SAERTEX NCF with very high modulus and strength, whereas the resin is BDP 4294. This work shows the methods, equipment, and results of an experimental campaign carried out to determine the fracture toughness of the manufactured NCF composite material. Finally, to quantify the fracture toughness of the NCF composite material, Mode I, II, Mixed Mode I–II, and translaminar fracture tests were also considered.

A New Approach to Estimate the Fatigue Limit of Steels Based on Conventional and Cyclic Indentation Testing

For a reliable design of structural components, valid information about the fatigue strength of the material used is a prerequisite. As the determination of the fatigue properties, and especially the fatigue limit σw, requires a high experimental effort, efficient approaches to estimate the fatigue strength are of great interest. Available estimation approaches using monotonic properties, e.g., Vickers hardness (HV), and in some cases the cyclic yield strength, only allow a rough estimation of σw. The approaches solely based on monotonic properties lead to substantial deviations of the estimated σw in relation to the experimentally determined fatigue limit as they do not consider the cyclic deformation behavior. In this work, an estimation approach was developed, which is based on a correlation analysis of the fatigue limit σw, HV, and the cyclic hardening potential obtained in instrumented cyclic indentation tests (CIT). For this, eleven conditions from five different low-alloy steels were investigated. The CIT enable an efficient and quantitative determination of the cyclic hardening potential, i.e., the cyclic hardening exponentCHT eII, and thus, the consideration of the cyclic deformation behavior in an estimation approach. In this work, a strong correlation of σw with the product of HV and |eII| was observed. In relation to an existing estimation approach based solely on HV, considering the combination of HV and |eII| enables the estimation of σw with an enormously increased precision.

Strength prediction and progressive damage analysis of carbon fiber reinforced polymer-laminate with circular holes by an efficient Artificial Neural Network

The composite laminates with circular holes find numerous applications in aerospace, automobile manufacturing and other fields due to the design and assembly of structural components. The failure analysis of composite laminates with notches or holes is of great importance in structural applications. In this work, a finite element method (FEM) based artificial neural network (ANN) model is presented to predict the strength and progressive damage behavior of carbon fiber reinforced polymer (CFRP) laminates with holes subjected to the external loads. The activation functions in the model design are reasonably chosen. The ANN prediction results are found to be in good agreement with the simulation results, thereby confirming the accuracy of ANN model. The developed ANN model is suitable for the rapid prediction of progressive damage failure behavior of the open-hole composite laminates. The elastic deformation and the progressive damage behavior of the CFRP laminates with circular holes are predicted by the proposed ANN model, which provides a good machine learning platform with high efficiency and finds potential applications in other fields.

Damage Mechanisms and Anisotropy of an AA7010-T7452 Open-Die Forged Alloy: Fatigue Crack Propagation.

The process–microstructure–property relationship of high-strength 7000 series aluminum alloys during fatigue crack propagation (FCP) is highly relevant for safety during the design and service of aircraft structural components. It is scientifically evident that many metallurgical factors affect FCP properties, but partly contradictory or inconclusive results show that the quantitative description of the relationships is still a major challenge among researchers and engineers. Most research focuses on sheet or plate products and investigations lack quantitative information on the process–property relationship between open-die forged thick products and FCP. The present study contributes to this field by investigating the fatigue crack growth behavior of an open-die forged AA7010-T7452 aluminum alloy. Four different forging conditions comprising different characteristic microstructures are comparatively analyzed. The influence of grain size, grain shape, specimen orientation, crystallographic texture, and primary phase particles is investigated. Fractographic analysis reveals different active damage mechanisms during fatigue crack growth. Based on that, the microstructure features relevant to fatigue damage areidentified in each regime of crack growth.

Manta ray foraging optimization algorithm and hybrid Taguchi salp swarm-Nelder–Mead algorithm for the structural design of engineering components

Abstract The adaptability of metaheuristics is proliferating rapidly for optimizing engineering designs and structures. The imperative need for the fuel-efficient design of vehicles with lightweight structures is also a soaring demand raised by the different industries. This research contributes to both areas by using both the hybrid Taguchi salp swarm algorithm-Nelder–Mead (HTSSA-NM) and the manta ray foraging optimization (MRFO) algorithm to optimize the structure and shape of the automobile brake pedal. The results of HTSSA-NM and MRFO are compared with some well-established metaheuristics such as horse herd optimization algorithm, black widow optimization algorithm, squirrel search algorithm, and Harris Hawks optimization algorithm to verify its performance. It is observed that HTSSA-NM is robust and superior in terms of optimizing shape with the least mass of the engineering structures. Also, HTSSA-NM realize the best value for the present problem compared to the rest of the optimizer.

Post-failure behavior of 2-ply laminated glass plates with different interlayers

Modern design codes, such as the new Eurocode on the design of structural glass components, consider the prediction of the post-failure behavior of these elements of paramount importance for a proper and safe design. In this view, an experimental investigation is presented in the paper, on the mechanical response of undamaged and damaged 2-ply Laminated Glass (LG) under quasi-static loads, with different interlayers, namely polyvinyl butyral (PVB), SentryGlas (SG) and a plasticized version of PVB, Saflex DG41 (DG41). Firstly, undamaged specimens (UDLG) were tested in simply supported configuration (configuration 0) with a vertical load in the middle increased up to the failure of the bottom glass ply. damaged LG specimens (PDLG) were then tested into two different configurations: configuration I, with broken ply below (bottom ply) and configuration II, with broken ply above (top ply). All the presented tests were performed under displacement control. For both configurations, the interlayers influence on the post-breakage behavior was discussed. It is underlined that the global response of the two configurations was completely different: configuration II, which was characterized by a deformed shape opposite to the load direction, showed a good residual stiffness and reached high failure loads. On the contrary, in configuration I, the response was characterized by a low stiffness and load carrying capacity. In addition, also the influence of different glass types was discussed, focusing attention on tempered and toughened glass. The results showed that the contribution of the fractured layer cannot be disregarded in the evaluation of the global stiffness of a PDLG and its contribution is strictly related to the interlayer and glass typologies.

Modeling nonlinear viscoelastic responses of flexible composites for soft robotics applications

This study examines the deformation of soft composites comprising stiff elastic unidirectional fibers and soft matrix, such as silicone elastomer, rubber and PDMS (Sylgard 184) with potential applications for soft robots. In some soft robotic applications, precise controls of shape reconfigurations are necessary. To design soft robots with high precision motions, it requires a detailed understanding of material responses. In this study, we formulate a constitutive model for the nonlinear viscoelastic response for soft isotropic materials, which is used for the soft matrix in the composites. We examine mechanical deformations of soft composite laminas with two different matrices i.e., Ecoflex 00-30 and PDMS (Sylgard 184), which differ significantly in their extensibility, and different fiber orientations. The initial fiber orientation and matrix extensibility govern the shape reconfigurations of the laminas. The viscoelastic response of the soft matrix causes continuous shape reconfigurations associated with the creep behaviors, which influence the final shapes of the lamina. We also present the design and analyses of soft composite structural components, incorporating the nonlinear viscoelastic responses of the matrix.

Natural disaster mitigation using advanced ferrocement – Future research directions for improved building resilience

Natural disaster mitigation encompasses a wide range of activities which are required to avert the occurrence of natural disasters and is a major goal of the Sendai Framework applicable to all exposed territories worldwide. With respect to earthquakes and hurricanes, the structural retrofitting of buildings which were designed before the availability of seismic codes of practice, or the enforcement of existing codes, can be an effective form of mitigation. Advanced Ferrocement (AF), which is ferrocement based on Lamination Theory (LT), encompasses the use of mesh angle, layer-by-layer mesh layup, possibly with non-metallic mesh, and/or non-standard mortars, for the design and construction of structural components. As a pilot study, a set of core research questions and nine research directions or study areas are presented for investigating the use of AF for retrofitting existing buildings, in the context of earthquake and hurricane resilience. This is also useful for deriving new structural components for new buildings,. The experimental results of the pilot study are that when ferrocement overlays were applied to the faces of concrete masonry-infilled walls of steel frames, the lateral yield strength and displacement at yield increased by factors of 1.50 and 2.30, respectively. For the tested ferrocement shear panels of channel-shaped cross-section, the lateral maximum strength-to-weight ratio was 3.37 times higher than that for an alternative reinforced concrete masonry minimum cost solution. For the tested AF one-way spanning roof panel, the wind load capacity had a strength-to-weight ratio 10.78 times higher compared with the present minimum cost metal sheet-and-purlins solution. LT suggests that the performance of the infilled-frame retrofit, and the ferrocement wall panel, can be increased by aligning the mesh in the principal stress directions, etc. The research directions and preliminary findings presented can serve as the basis for an extensive research effort regarding AF as the application of LT to mesh-reinforced cementitious composite structural building components.

Machine-learning-accelerated design of functional structural components in deep-sea soft robots

To explore the deepest regions of the ocean with high flexibility and environmental adaptability, deep-sea soft robots have been developed recently. One prominent example is the self-powered soft robot that successfully operated in the Mariana Trench at a depth of 11,000 meters. Notably, many functional electronic components such as resistive elements, capacitors, and crystal oscillators may fail under extreme hydrostatic pressure, posing significant challenges for the practical massive deployment of deep-sea soft robots. Consequently, designing miniature pressure vessels on the printed circuit board to protect these vulnerable electronic components is vital for enhancing the reliability of deep-sea soft robots. However, traditional structure design methods – which often rely on theoretical analysis, experimental testing and numerical simulations – are often costly and time-consuming, especially for design problems in high-dimensional design spaces. Herein, we demonstrate a machine-learning-accelerated design method for devising miniature pressure vessels for vulnerable electronic components in deep-sea soft robots. Machine learning algorithms including decision trees and neural network models are employed and compared. The resulting design algorithm can predict whether a specific design can survive the deep-sea hydrostatic pressure with high accuracy in ∼0.35 ms, roughly seven orders of magnitude faster than traditional design methods.