Structural Design Approach Research Articles

Design of Steel Columns in Fire using Second‐order Inelastic Analysis with Strain Limits

AbstractIn this paper, a structural steel fire design approach using second‐order inelastic analysis with strain limits is proposed and applied to the design of steel columns in fire. The proposed design approach employs beam finite elements to conduct a second‐order inelastic analysis. Within the proposed method, strain limits are used to account for the effects of local buckling; while global instability, the loss of strength and stiffness and thermal effects are fully considered through second‐order inelastic analysis carried out using beam finite elements. The proposed method is assessed against validated shell FE results. It is observed that the proposed design approach provides consistently accurate and safe capacity predictions for steel columns in fire.

Reliability-based optimal control design for seismic-excited structures: A hybrid IS-MTLBO pseudo-double loop method

This study addressed a reliability-based optimal control design (RBOCD) approach for seismic-excited structures. For this aim, a hybrid importance sampling-modified teaching-learning based optimization (IS-MTLBO) pseudo-double loop method is developed. Uncertainty sources such as structural model, stochastic model of the ground acceleration, structural response measurements in sensors, and designed/applied forces in actuators are considered in this study. Numerical studies are carried out on a 10-story building subjected to earthquake excited. A deterministic optimal control design (DOCD) approach based on the MTLBO algorithm is firstly conducted for the structure. Then, a sensitivity analysis using the Borgonovo sensitivity method is carried out to identify and measure the effectiveness of the mentioned uncertainty sources on the seismic responses. Finally, the IS-MTLBO pseudo-double loop approach as an RBOCD approach is implemented for the studied structure. The average reductions of the seismic responses in terms of maximum displacement, acceleration, and drift of floors are obtained as 18.95%, 27.7%, and 24.65% for the RBOCD approach, while, the corresponding reduction are 7.30%, 19.45%, and 14.05% for the DOCD approach. It is shown that although the designed controller based on the DOCD approach satisfies the limitation considered for the maximum floor drift in the nominal model, it is not able to satisfy it in the presence of uncertainties. In other words, the RBOCD approach represents a robust control design against uncertainties, while the DOCD approach gives an uncertainty-sensitive control scheme. Considering four well-known earthquakes, the failure probabilities of the structure controlled by both DOCD and RBOCD approaches are compared. The results indicate the failure probability of the structure controlled by the RBOCD approach is much less than those given using the DOCD approach.

A defect-based physics-informed machine learning framework for fatigue finite life prediction in additive manufacturing

Defects in additively manufactured materials are one of the leading sources of uncertainty in mechanical fatigue. Fracture mechanics concepts are useful to evaluate their influence, nevertheless, these approaches cannot account for the real morphology of defects. Preliminary attempts to exploit a more comprehensive description of defects can be found in the literature, by using Machine Learning. These approaches are notoriously data-hungry and neither physics laws nor phenomenological rules are introduced to assess the soundness of the outcome. Hereby, to overcome this limitation, an approach to predicting fatigue finite life of defective materials, based on a Physics-Informed Neural Network framework, is presented for the first time. The training process of a Neural Network is reinforced by introducing novel Fracture Mechanics constraints. Experimental results obtained from the literature, including detailed defect analysis from computer tomography and fractography, were used to check its accuracy. The proposed predictive tool fully exploits the advanced capabilities of machine learning to account for morphological aspects of defects that could not be accounted for otherwise, while at the same time obeying fracture mechanics laws and requiring a smaller experimental dataset . The approach paves the way for new structural design approaches with an unprecedented degree of accuracy.

The design of continuous carbon fiber composite honeycombs and study on its properties

A lot of researches on continuous carbon-fiber composite laminates have been conducted, but no scrutiny has been devoted to continuous carbon-fiber composite honeycomb sandwiches. This paper is aimed to assess the design and properties aspects of honeycomb sandwiches made of continuous carbon-fiber composite laminates. The applicability of the existing theoretical formulas for the mechanical properties of isotropic material honeycomb sandwich on continuous carbon-fiber composite honeycomb is examined by comparing the obtained results from the finite-element modeling and experimental results. The results reveal that the theoretical formulas of isotropic material honeycomb sandwich in density and out-of-plane compressive elastic modulus are suitable for continuous carbon-fiber composite honeycomb, while other performances cannot be achieved by theoretical formulas of isotropic material honeycomb sandwiches. The out-of-plane compression and shear properties of continuous carbon-fiber composite honeycomb can be evaluated by finite-element modeling. The effects of cell side length, wall thickness, and 45° ply content on the honeycomb density, out-of-plane compression properties and out-of-plane shear strength are researched. Subsequently, the out-of-plane compression experiments of honeycomb are carried out to show the accuracy of the finite-element modeling. Finally, a design approach for continuous carbon-fiber composites honeycomb structures is proposed. This methodology results in the design of honeycomb sandwiches with better performances. The chief innovation of this paper is to develop the concept of continuous carbon-fiber composite honeycomb sandwich structures. To this end, a honeycomb structure finite-element model of continuous carbon-fiber composite is established, and the mechanical properties of continuous carbon-fiber composite honeycomb sandwiches are explored. A methodology for the rapid design of honeycomb size parameters of continuous carbon fiber composite honeycomb sandwich is also proposed.

Design-related reassessment of structures integrating Bayesian updating of model safety factors

In the semi-probabilistic approach of structural design, the partial safety factors are defined by considering some degree of uncertainties to actions and resistance, associated with the parameters’ stochastic nature. However, uncertainties for individual structures can be better examined by incorporating measurement data provided by sensors from an installed health monitoring scheme. In this context, the current study proposes an approach to revise the partial safety factor for existing structures on the action side, γE by integrating Bayesian model updating. A simple numerical example of a beam-like structure with artificially generated measurement data is used such that the influence of different sensor setups and data uncertainties on revising the safety factors can be investigated. It is revealed that the health monitoring system can reassess the current capacity reserve of the structure by updating the design safety factors, resulting in a better life cycle assessment of structures. The outcome is furthermore verified by analysing a real life small railway steel bridge ensuring the applicability of the proposed method to practical applications.

Architectural And Structural System Design of Precast Concrete Structures In Earthquake Zones

Precast concrete systems, which are the result of industrialization in the field of construction, are faced with the prejudice of insufficient earthquake resistance despite their many advantages and their use is limited in Turkey. These systems, which have proven earthquake resistance if they are designed properly, can be used safely in low-rise or multi-storey buildings with different functions in earthquake zones. The aim of this study is to determine the architectural design requirements of earthquake-resistant precast concrete structures and to reveal the structural system design approaches. In accordance with this aim, the earthquake effect on the structures was summarized and architectural design principles that would contribute to the earthquake resistance of precast concrete structures were determined firstly. Then, earthquake-resistant structural system design approaches of frame, panel, and cell construction were evaluated separately.

3D Printed Ultra-thin Acoustic Metamaterials with Adaptable Low-frequency Absorption Performance

The inherent absorption frequency of traditional sound absorbers makes it difficult to solve the problem of acoustic wave removal in a changeable acoustic environment. In this study, acoustic absorption metamaterials (AAMs) with adaptable sound absorption performance were innovatively designed using the structural combination concept and fabricated via 3D printing. Accordingly, two coiled-up channels were combined in a single cell, which could effectively broaden the absorption bandwidth in a limited space. The longitudinal movement of the coiled-up channels endowed the tunable entire depth and internal cavity of the AAMs; thus, the sound absorption performance could be tailored accordingly. Through computational analysis and experimental verification, it was demonstrated that the depth of the AAM could be adjusted from 10 mm to 20 mm, and the corresponding absorption frequencies of the two channels ranged from 206 Hz to 179 Hz and 379 Hz to 298 Hz, respectively. In addition, the finite element results also indicate that the sound absorption bandwidth of AAMs could be further improved by the periodic arrangement of the units. This work opens a promising structural design approach for presenting a route toward acoustic devices with adaptable absorption performances.

Behavior of Post-Tensioned Concrete Girders Subject to Partially Strand Damage and Strengthened by NSM-CFRP Composites

Studies on the flexural behavior of post-tensioned beams subjected to strand damage and strengthened with near-surface mounted (NSM) technique using carbon fiber-reinforced polymer (CFRP) are limited and fail to examine the effect of CFRP laminates on strand strain and strengthening efficiency systematically. Furthermore, a design approach for UPC structures in existing design guidelines for FRP strengthening techniques is lacking. Hence, the behavior of post-tensioned beams strengthened with NSM-CFRP laminates after partial strand damage is investigated in this study. The testing program consists of seven post-tensioned beams strengthened by NSM-CFRP laminates with three partial strand damage ratios (14.3% symmetrical damage, 14.3% asymmetric damage, and 28.6% symmetrical damage). The experimental results showed that the use of CFRP laminates significantly increases the flexural capacity by up to 17.4 to 20.4%, corresponding to a strand damage ratio of 14.3 and 28.6%, respectively, enhances the stiffness, and reduces strand strain by up to 15.8 to 22.2%. However, the flexural stiffness of strengthened beams during serviceability phases is critical as strand damage ratios increase. Additionally, semi-empirical equations were proposed to predict the actual strain of unbonded strands whilst considering the effects of CFRP laminates. The suggested equations provide accurate predictions with little variance. Doi: 10.28991/CEJ-2022-08-07-013 Full Text: PDF

Adjusting unit cell three-dimensional posture and mirror array: A novel lattice structure design approach

Lattice structures’ performance is directly determined by the topological structure and arrangement of cells. Here, we propose a lattice structure design approach that generates predictable mechanical properties by adjusting the three-dimensional posture and mirror arrays of cells. Specifically, the Euler angle (α β γ) is introduced to accurately control the three rotational degrees of freedom of the orthogonal unit cell. Then, a new unit cell with symmetric characteristics composed of multiple primitive rotation units is constructed by mirror operation, which is called super variable pose Octahedral Structures (SVPOS). The mathematical model of SVPOS topological structure is established, the mapping relationship between Euler Angle and relative density is deduced, and the mechanical response of structures with different Euler angles is studied. The results show that Structure of α = β = γ = 30˚ obtained the best performance, and the elastic modulus, compressive strength, and energy absorption at 50% strain of it are 553.1%, 471.9% and 529% of that of the octahedral, respectively. The new lattice structure can be obtained by adjusting the Euler Angle, its relative density and performance can be better predicted, which can provide experimental and theoretical basis for the design of lattice structures that meet different requirements.

Efficient design of a prefabricated steel structure integrating design for manufacture and assembly concepts

ABSTRACT Volumetric steel structures are commonly used in the construction of modular buildings to overcome environmental hazards, control wastage, minimise construction safety issues, improve productivity and cost-effectiveness, reduce labour, and execute quick project completion. An adequate structural design and effective manufacturing are both integral processes to produce efficient and durable volumetric steel structures. Design for Manufacture and Assembly (DfMA) principles known for efficient design in the automobile industry can significantly improve the design of volumetric steel structures in terms of overall cost, safety, sustainability, productivity and time. The current research presents a case study of a volumetric steel structure in which structural design and DfMA approaches were integrated, and 3D visualisation was achieved by Building Information Model (BIM) and Solidworks that has limited previous research. The findings of this research reveal sustainable, material and cost optimised design for the prefabricated 3D steel structures. Furthermore, the novelty of the current research is enhanced by proposing a model for the automated efficient design and production of volumetric steel structures.

Two-level performance-based seismic design approach for steel frames with novel self-centring seismic base isolators

A two-level performance-based seismic design (PBSD) approach for frame structures isolated by self-centring isolators (SCIs) is proposed in this study. Unlike the traditional PBSD process that generally designs a structure for a specific seismic intensity level first and then checks structural performance for other levels, the proposed PBSD approach considers both the design basis earthquakes (DBE) and maximum considered earthquakes (MCE) by analysing two different nonlinear equivalent structural models, thereby enabling the accurate control of structural performance objectives at two different seismic intensity levels during the design process. The design method combines the fundamental displacement-based design process and the widely-accepted nonlinear response spectra. A four-storey frame structure, equipped with novel SCIs consisting of rubber bearing, steel U-shaped dampers, and shape memory alloy U-shaped dampers, is designed as an example. Seismic analysis results demonstrate that the two-level PBSD approach can satisfactorily achieve the predefined performance objectives at both DBE and MCE levels. Although the design process is applied to SCI-isolated structures in this study, the design framework can be easily extended to other types of isolated structures to enable the advanced design that can achieve the target performances at DBE and MCE levels simultaneously.

Design and Simulation of Oil Palm FFB Loading Machine

The process of loading the fresh fruit bunches of oil palm to the truck requires a lot of manpower if it is done manually. In fact, either the palm oil plantation or the smallholder palm oil farmer still performs this task manually, so that it can lead to fatigue and can result in injuries for the worker due to heavy workload. The purpose of this research is to design and simulate a machine for lifting the fresh fruit bunches to the truck, so that the activities of lifting the fresh fruit bunches to the truck become easier and can have a bigger working capacity. This research was conducted using a functional and structural design approach consisting of several stages, including: problem identification, design concept formulation, engineering analysis, engineering drawings, material strength analysis, kinematics simulation, power consumption simulation, and digital scale simulation. A simple structure of electric motor-driven bucket elevator was designed to load the fresh fruit bunches on to the truck tailgate. Based on the simulation results, the fresh fruit bunches can be lifted up satisfactorily from the bottom to the top with an elevator mechanism. This elevator is designed with lightweight for easy installation and kept at the tailgate of the truck. The maximum electric power consumption for lifting the fresh fruit bunches was found to be 1466.24 watts with designed loading capacity 23 ton/hour.

Analyzing the Explanatory Power of Bionic Systems With the Minimal Cognitive Grid.

In this article, I argue that the artificial components of hybrid bionic systems do not play a direct explanatory role, i.e., in simulative terms, in the overall context of the systems in which they are embedded in. More precisely, I claim that the internal procedures determining the output of such artificial devices, replacing biological tissues and connected to other biological tissues, cannot be used to directly explain the corresponding mechanisms of the biological component(s) they substitute (and therefore cannot be used to explain the local mechanisms determining an overall biological or cognitive function replicated by such bionic models). I ground this analysis on the use of the Minimal Cognitive Grid (MCG), a novel framework proposed in Lieto (Cognitive design for artificial minds, 2021) to rank the epistemological and explanatory status of biologically and cognitively inspred artificial systems. Despite the lack of such a direct mechanistic explanation from the artificial component, however, I also argue that the hybrid bionic systems can have an indirect explanatory role similar to the one played by some AI systems built by using an overall structural design approach (but including the partial adoption of functional components). In particular, the artificial replacement of part(s) of a biological system can provide i) a local functional account of that part(s) in the context of the overall functioning of the hybrid biological–artificial system and ii) global insights about the structural mechanisms of the biological elements connected to such artificial devices.

Doublet Open‐Shell Graphene Fragments

Recent advances in neutral delocalized radical species based on polycyclic aromatic hydrocarbons with fused hexagonal rings, herein defined as doublet open-shell graphene fragments, are summarized in this review. A few simple yet useful theoretical approaches for structural analysis and molecular design were introduced at first. Then, based on the number of fused hexagonal rings, molecular systems with different size, symmetry and edge structure were discussed with emphasis on those isolated in the crystalline form. Their unique self-association behavior, chemical reactivity and physical properties were summarized and discussed, and insights on their functions and potential applications were provided.

Dengue Early Warning System as Outbreak Prediction Tool: A Systematic Review.

Early warning system (EWS) for vector-borne diseases is incredibly complex due to numerous factors originating from human, environmental, vector and the disease itself. Dengue EWS aims to collect data that leads to prompt decision-making processes that trigger disease intervention strategies to minimize the impact on a specific population. Dengue EWS may have a similar structural design, functions, and analytical approaches but different performance and ability to predict outbreaks. Hence, this review aims to summarise and discuss the evidence of different EWSs, their performance, and their ability to predict dengue outbreaks. A systematic literature search was performed of four primary databases: Scopus, Web of Science, Ovid MEDLINE, and EBSCOhost. Eligible articles were evaluated using a checklist for assessing the quality of the studies. A total of 17 studies were included in this systematic review. All EWS models demonstrated reasonably good predictive abilities to predict dengue outbreaks. However, the accuracy of their predictions varied greatly depending on the model used and the data quality. The reported sensitivity ranged from 50 to 100%, while specificity was 74 to 94.7%. A range between 70 to 96.3% was reported for prediction model accuracy and 43 to 86% for PPV. Overall, meteorological alarm indicators (temperatures and rainfall) were the most frequently used and displayed the best performing indicator. Other potential alarm indicators are entomology (female mosquito infection rate), epidemiology, population and socioeconomic factors. EWS is an essential tool to support district health managers and national health planners to mitigate or prevent disease outbreaks. This systematic review highlights the benefits of integrating several epidemiological tools focusing on incorporating climatic, environmental, epidemiological and socioeconomic factors to create an early warning system. The early warning system relies heavily on the country surveillance system. The lack of timely and high-quality data is critical for developing an effective EWS.

Rapid approach for structural design of the tower and monopile for a series of 25 MW offshore turbines

The goal of further reducing the Levelized Cost of Energy (LCOE) has driven the investigation of large-scale wind turbines. This work presents a simple, rapid and detailed approach for the structural design of the tower and monopile without a controller, but with frequency and high fidelity structural verification. The approach uses an optimization to reduce the mass of the structures while meeting strength, buckling and geometric constraints by using analytical equations. A verification of frequency constraints is performed with BModes, and ANSYS Mechanical APDL is used for high fidelity verification of stress and buckling. The approach is applied to study the design space of three 25 MW offshore wind turbines with different rotor diameters and cone angles, and to evaluate the nacelle center of mass fore-aft location effect. Results obtained show that the tower and monopile are more susceptible to changes in the rotor thrust than the overturning moment even for designs with high pre-cone angle and large distance of the nacelle center of mass from the tower axis. But it is possible to obtain structurally feasible tower and monopile designs for the three 25 MW turbines studied while not exceeding diameter and wall thickness limits. However, mass penalties can be decreased by 0.8-14%, to further reduce the cost of energy, by increasing the diameter limit which may require manufacturing technology development. The approach applied and studies serve to understand the design space of the tower and monopile for a 25 MW turbine, and provide baseline designs that can be used in the development of a controller and evaluation of a full suite of design load cases.

Mixed Ionic-Electronic Conduction, a Multifunctional Property in Organic Conductors.

Organic mixed ionic-electronic conductors (OMIECs) have gained recent interest and rapid development due to their versatility in diverse applications ranging from sensing, actuation and computation to energy harvesting/storage, and information transfer. Their multifunctional properties arise from their ability to simultaneously participate in redox reactions as well as modulation of ionic and electronic charge density throughout the bulk of the material. Most importantly, the ability to access charge states with deep modulation through a large extent of its density of states and physical volume of the material enables OMIEC-based devices to display exciting new characteristics and opens up new degrees of freedom in device design. Leveraging the infinite possibilities of the organic synthetic toolbox, this perspective highlights several chemical and structural design approaches to modify OMIECs' properties important in device applications such as electronic and ionic conductivity, color, modulus, etc. Additionally, the ability for OMIECs to respond to external stimuli and transduce signals to myriad types of outputs has accelerated their development in smart systems. This perspective further illustrates how various stimuli such as electrical, chemical, and optical inputs fundamentally change OMIECs' properties dynamically and how these changes can be utilized in device applications.

Evaluation of anticipated post-fire repair cost for resilient design of composite slab panels

The design limit states form the basis of current structural fire design approaches. These design practices overlook the post-fire resilience and repairability of the structure. Consequently, a minor fire might lead to an irreparable structure and a need of demolishing it. We propose a framework to evaluate during the design phase the anticipated repair cost for a structure in case of a fire event, in order to enable consideration of post-fire resilience in design decisions. We apply the framework to evaluate the repair cost for a composite slab panel comprising a concrete slab, two girder and two boundary beams at opposite edges, and two central beams at the center. Two fire designs for the composite slab panel satisfying the nominal fire design requirement are considered: a prescriptive design and a performance-based design which harnesses tensile membrane action and omits insulation on central beams. The repair costs are evaluated and compared for both designs for a range of natural fire exposures, demonstrating that the performance-based design achieves its target of stability during fire, but also results in higher anticipated post-fire damages. This concept of pre-evaluation of repair cost can further be implemented in life-cycle cost optimization procedures to allow an optimized structural design.

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

A structural design approach for a droop nose morphing demonstrator with shape memory alloy patches

An innovative concept has been devised for assisting an actuator to morph a Droop Nose (DN) structure, which is comprised from the skin and three longitudinal omega stringers. The concept is based on the development of a suitable composite patch, with embedded shape memory alloy (SMA) wires, and the appropriate design of a DN configuration for morphing purposes. The integration of composite patches, to the DN structure, has a dual innovative role: (a) it can either provide/extend the morphing capabilities of the structure, in terms of displacement or (b) it can reduce the required actuation forces for obtaining morphing of the DN structure. For determining the most suitable DN configuration, for the application, a sensitivity analysis, with the aid of ANSYS finite element (FE) software and a design of experiments (DoE) approach, has been carried out. The investigated parameters (geometrical and lamination characteristics) are selected to vary the stiffness of the DN structure. Additionally, a numerical parametric FE model, of the SMA patch and its configuration, is developed and analysed. The developed FE models simulated the shape memory effect of SMA wires considering their activation temperature and hence their thermo-mechanical behaviour. Eventually, a possible integration of the SMA patches to the DN structure is proposed and the respective remarks are highlighted.