Alternative Design Method Research Articles

Analysis of floating city design solutions in the context of carbon neutrality-focus on Busan Oceanix City

Excessive carbon emissions are causing global climate change, leading to higher temperatures and continued sea level rise, affecting all the world’s seaside cities. Concentrated population migration to large cities, flooding and rising sea levels are limiting the spatial growth potential of coastal urban water bodies. In response to climate change, the city of Busan, where sea levels are set to rise by 70.6 cm by 2100, is actively promoting the development of marine cities, and the development of marine space has become a hotspot. In response, the United Nations has proposed the world’s first floating city design scheme, Oceanix City. The aim of this thesis is to build a new type of carbon neutral floating city, by reviewing existing research papers on floating cities and carbon neutrality, analyzing in depth the carbon neutral design elements of the scheme, exploring the possibility of creating a zero carbon zone in the ocean and finally proposing alternative energy sources and design methods for marine cities. Using a case study approach, this thesis analyses carbon sequestration and carbon emissions, providing a theoretical basis for the design of future carbon-neutral floating cities with positive implications for achieving carbon neutrality. The study also proposes macro design criteria for a carbon neutral vision for floating cities, providing a theoretical basis and reference for the development of future floating cities.

A finite difference-based approach for strain demand prediction of inelastic pipes subjected to permanent ground displacements

Permanent ground displacement triggered by geohazards constitutes a major threat to the integrity of long-distance pipelines. In this study, a novel and simple method is proposed to evaluate inelastic pipes’ behavior under ground movements considering soil-pipe interaction based on the finite difference method. The existing finite difference-based method previously proposed by the authors for strain analysis of buried pipelines subjected to ground movements excludes material nonlinearity in pipes, which limits its applicability in engineering practice. To remedy this situation, the method presented herein maintains the well-established concepts of the existing finite-difference-based method but also introduces the scheme to consider the inelastic material behavior of steel pipes. More specifically, the expressions of internal axial force and bending moment, required in the finite difference equations, are explicitly derived based on the actual stress distribution on the pipe cross-section. The proposed method is validated against the finite element method (one-dimensional beam model) in terms of the strain and deformation demands using two indicative case studies, referred to as symmetric and non-symmetric soil resistance conditions, respectively. The comparison between finite element analysis and the proposed method indicates good agreement. Additionally, the proposed method is compared with four existing analytical methods for pipes subjected to strike-slip fault displacement. The proposed method is a simple but general technique to analyze pipes’ response under a wide range of geohazards, and thus can be potentially used as an alternative method for preliminary design, safety prescreening, and reliability-based assessment of pipes against geohazards.

DSM design of LSF walls subject to distortional buckling

With the new advancements in constructions technologies, the use of cold-formed steel (CFS) construction is becoming popular due to its inherent advantages over conventional construction materials. These high performing CFS sections, such as the web stiffened lipped channel studs, are more likely to be subjected to distortional buckling under compression load. Although many numerical and experimental studies have been undertaken on unsheathed CFS columns subjected to distortional buckling, there is limited research on light gauge steel framed (LSF) walls subject to distortional buckling. The behaviour of sheathed wall studs is significantly different to that of columns due to the complicated boundary conditions provided by the stud-to-sheathing contact interactions and screw connections. Although CFS design standards recognize the sheathing boards as a means of providing lateral and rotational restraints, they do not provide any information on their effects on studs subject to distortional buckling. In this study, the suitability of currently available numerical modelling techniques on predicting the distortional buckling behaviour of LSF walls was investigated. It was identified that the distortional buckling capacity is highly sensitive to the in-plane restraints provided by screw connections. The effects of stud geometry, stiffness of screw connections and stud length on the distortional buckling capacity were investigated in a detailed numerical parametric study involving more than 3500 finite element analyses. Finally, the accuracy of the current direct strength method was investigated and suitable modifications are proposed. Moreover, alternative simplified design methods and their accuracy are also discussed.

Investigating the evolution process of lung adenocarcinoma via random walk and dynamic network analysis.

Lung adenocarcinoma (LUAD) is a typical disease regarded as having multi-stage progression. However, many existing methods often ignore the critical differences among these stages, thereby limiting their effectiveness for discovering key biological molecules and biological functions as signals at each stage. In this study, we propose a method to discover the evolution between biological molecules and biological functions by investigating the multi-stage biological molecules of LUAD. The method is based on the random walk algorithm and the Monte Carlo method to generate clusters as the modules, which were used as subgraphs of the differentiated biological molecules network in each stage. The connection between modules of adjacent stages is based on the measurement of the Jaccard coefficient. The online gene set enrichment analysis tool (DAVID) was used to obtain biological functions corresponding to the individual important modules. The core evolution network was constructed by combining the aforementioned two networks. Since the networks here are all dynamic, we also propose a strategy to visualize the dynamic information together in one network. Eventually, 12 core modules and 11 core biological functions were found through such evolutionary analyses. Among the core biological functions that we obtained, six functions are related to the disease, the biological function of neutrophil chemotaxis is not directly associated with LUAD but can serve as a predictor, two functions may serve as a predictive signal, and two functions need to be verified through more biological evidence. Compared with two alternative design methods, the method proposed in this study performed more efficiently.

Direct Design of Stainless Steel Frames: Recommendations and Case Studies

AbstractAcknowledging the potential of system‐based design approaches, most international design standards for steel structures include preliminary versions of such alternative design methods. The Direct Design Method (DDM) is one of these approaches, which allows designing steel structures directly using advanced numerical analyses without requiring further member checks. This paper presents the DDM design (and verification) procedure and summarizes the key aspects of the advanced finite element model necessary for the determination of the system strength, with an emphasis on cold‐formed stainless steel portal frames. Through the design of two frames, the DDM design procedure is illustrated and the resulting cross‐sections are compared with those derived using the traditional two‐step design approach in the Eurocode and ASCE design frameworks. The results demonstrate that the DDM verification process is simpler and more direct, and that lighter structures are obtained when designing using the DDM for strength considerations. Finally, this paper also highlights that allowing larger deformations in the ultimate limit state design for the DDM does not have additional negative effects on the serviceability requirements if compared to the traditional two‐step design approach.

Synthesis of Heterogeneous Catalysts in Catalyst Informatics to Bridge Experiment and High-Throughput Calculation.

The coupling of high-throughput calculations with catalyst informatics is proposed as an alternative way to design heterogeneous catalysts. High-throughput first-principles calculations for the oxidative coupling of methane (OCM) reaction are designed and performed where 1972 catalyst surface planes for the CH4 to CH3 reaction are calculated. Several catalysts for the OCM reaction are designed based on key elements that are unveiled via data visualization and network analysis. Among the designed catalysts, several active catalysts such as CoAg/TiO2, Mg/BaO, and Ti/BaO are found to result in high C2 yield. Results illustrate that designing catalysts using high-throughput calculations is achievable in principle if appropriate trends and patterns within the data generated via high-throughput calculations are identified. Thus, high-throughput calculations in combination with catalyst informatics offer a potential alternative method for catalyst design.

Modelling underground excavations in rock masses with anisotropic time-dependent behaviour

When modelling rock masses that behave anisotropically and in addition present a time dependent behaviour, it is relevant to select a constitutive model able to represent their actual behaviour realistically. This article presents an alternative anisotropic time-dependent constitutive model able to predict the coupling between anisotropic behaviour and time-dependent (or viscous) behaviour. The viscous behaviour is simulated with the Burgers model and all elastic springs and viscous dashpots are considered to exhibit transversely isotropic properties. The proposed constitutive model has been implemented in the finite element method software CODE_BRIGHT. To verify the basic anisotropic elastic solution, it has been compared with that of PLAXIS results. And to verify the isotropic viscoelastic solution, it has been compared with analytical solutions. Furthermore, the proposed constitutive model has been used to predict the behaviour of samples from laboratory tests. Finally, parametric analyses have been carried out to investigate the influence of different factors on tunnelling responses, including the selection of different constitutive models, anisotropy of initial stresses and anisotropy of material properties. The proposed model provides an alternative method for the preliminary design of geotechnical engineering works involving geomaterials that exhibit anisotropic time-dependent behaviour.Article highlights• An anisotropic time-dependent model has been implemented in CODE_BRIGHT and validated.• The model can predict the coupled anisotropic time-dependent behaviour of geomaterials.• Parametric analyses have been performed to study the influence of different factors in ground response.

Design of an objective for a hyper-numerical-aperture immersion lithography tool with a multi-step alternative grouping design method.

An adequate initial structure plays an important role in achieving a high-quality hyper-numerical-aperture (NA) catadioptric objective for an immersion lithography tool. A multi-step alternative grouping design method is innovated to achieve a feasible aspherical initial structure of the hyper-NA objective. The objective is first divided into three groups: the object-side group (G1), the middle group (G2), and the image-side group (G3), and then each group is designed separately. To guarantee the effective connection of these separate groups, G1 and G2 or G2 and G3 are connected as G12 or G32 on the object or image side with an aspherical structure. Then, through ray tracing in the forward path and the reverse path, G2 will be recalculated to a new aspherical structure, and the hybrid iterating process will be adopted to get a better G2 and to better connect the whole system. Finally, G1 and the new G2 and G3 are connected as a feasible aspherical initial structure of the hyper-NA catadioptric objective, which can be considered a good starting point for further optimization. A high-performance catadioptric objective with a hyper-NA of 1.35 was designed by the proposed method.

On the design of shell-and-tube heat exchangers under uncertain operating conditions

This paper addresses the problem of designing shell and tube heat exchangers operating under uncertain conditions. Traditional design methods assume constant process conditions and known value of thermal design factors. Thus may fail to meet specifications when operational conditions change. Use of safety factors or worst-case design often leads to conservative design and equipment oversizing. No guideline is available in the literature for choosing a design approach. In order to provide designers better awareness on this issue, we investigate when uncertainty should be taken into account, what are the advantages and drawbacks of available approaches for design under uncertainty, and which is the preferred method to be applied in specific problem instances. To answer the above research questions, comparative sizing of equipment is carried out under consistent assumptions adopting five alternative design methods; namely design for nominal reference condition with verification of off-design performances, worst case design, use of safety margins, design to optimize a prescribed objective function, and robust design. Either random uncertainty in external process conditions, and epistemic uncertainty in heat transfer coefficients and fouling resistances are considered. Different types of specifications (more/less is better or nominal is better) are accounted for. Probability of meeting specifications and resulting geometrical characteristics are compared. It is the first time that a similar comparison is carried out, and results discussion allows to identify merits and limitations of the considered approaches. It is found that no single approach is superior, as any method can be suited to a design situation but perform poorly in other cases. Justification for explaining the observed behaviour is used in order to provide guidance to designers in choosing the preferable design method for a specific instance resulting in more cost-effective equipment configuration with higher probability of meeting specifications.

Design of aluminium alloy channel sections under minor axis bending

In recent years, numerous research works have been reported on the flexural response of aluminium alloy tubular cross-sections. However, studies on monosymmetric cross-sections and particularly channel (C-) sections are limited, albeit their increased usage in structural applications. This paper aims to address this knowledge gap providing an improved understanding about the minor axis bending behaviour of C-sections through an experimental and numerical investigation. In total 14 specimens made from 6082-T6 heat-treated aluminium alloy were subjected to four-point bending. Tensile coupon tests were also performed to determine the mechanical properties of the examined aluminium alloy. The obtained experimental results are analysed and discussed. A series of geometrically and materially nonlinear analyses were also carried out to study the flexural performance of C-sections in two aluminium alloys and two bending orientations over a range of cross-sectional aspect ratios and slendernesses. The experimental and numerical results are utilised to assess the European design standards. The applicability of the Continuous Strength Method and the Direct Strength Method is also evaluated. An alternative design method based on the plastic effective width concept is proposed for slender C-sections subjected to minor axis bending. This method accounts for the inelastic reserve capacity which is in accordance with the experimental and numerical observations.

Structural flexural strengthening through material bonded to the concrete substrate

This article proposes an alternative method for the structural design of reinforced concrete elements strengthened in bending by metallic plates or fiber-reinforced polymer (FRP) bonded to the concrete substrate. It is proposed a new calculation procedure for the strengthening using thin adhered material bonded to the element surface that dispenses the iterative process generally used in the design. The proposed routine is validated by comparison with other methods. A practical example is also presented, applying the procedure to an element of a building where a load change was foreseen. As result, it was verified that the proposed procedure provides values similar to the trial-and-error method used in the FRP strengthening design. Results are also coherent with other methods available in the literature for metallic plates. Therefore, since this routine obtains similar values without using an iterative method, its applicability in the design becomes advantageous.

A convex approach to optimum design of experiments with correlated observations

Optimal design of experiments for correlated processes is an increasingly relevant and active research topic. Present methods have restricted possibilities to judge their quality. To fill this gap, we complement the virtual noise approach by a convex formulation leading to an equivalence theorem comparable to the uncorrelated case and to an algorithm giving an upper performance bound against which alternative design methods can be judged. Moreover, a method for generating exact designs follows naturally. We exclusively consider estimation problems on a finite design space with a fixed number of elements. A comparison on some classical examples from the literature as well as a real application is provided.

Study Designs to Assess Real-World Interventions to Prevent COVID-19.

Background: In the face of the novel virus SARS-CoV-2, scientists and the public are eager for evidence about what measures are effective at slowing its spread and preventing morbidity and mortality. Other than mathematical modeling, studies thus far evaluating public health and behavioral interventions at scale have largely been observational and ecologic, focusing on aggregate summaries. Conclusions from these studies are susceptible to bias from threats to validity such as unmeasured confounding, concurrent policy changes, and trends over time. We offer recommendations on how to strengthen frequently applied study designs which have been used to understand the impact of interventions to reduce the spread of COVID-19, and suggest implementation-focused, pragmatic designs that, moving forward, could be used to build a robust evidence base for public health practice.Methods: We conducted a literature search of studies that evaluated the effectiveness of non-pharmaceutical interventions and policies to reduce spread, morbidity, and mortality of COVID-19. Our targeted review of the literature aimed to explore strengths and weaknesses of implemented studies, provide recommendations for improvement, and explore alternative real-world study design methods to enhance evidence-based decision-making.Results:Study designs such as pre/post, interrupted time series, and difference-in-differences have been used to evaluate policy effects at the state or country level of a range of interventions, such as shelter-in-place, face mask mandates, and school closures. Key challenges with these designs include the difficulty of disentangling the effects of contemporaneous changes in policy and correctly modeling infectious disease dynamics. Pragmatic study designs such as the SMART (Sequential, Multiple-Assignment Randomized Trial), stepped wedge, and preference designs could be used to evaluate community re-openings such as schools, and other policy changes.Conclusions: As the epidemic progresses, we need to move from post-hoc analyses of available data (appropriate for the beginning of the pandemic) to proactive evaluation to ensure the most rigorous approaches possible to evaluate the impact of COVID-19 prevention interventions. Pragmatic study designs, while requiring initial planning and community buy-in, could offer more robust evidence on what is effective and for whom to combat the global pandemic we face and future policy decisions.

Extended state observer-based composite-system control for trajectory tracking of underactuated AUVs

In this paper, an alternative design method is presented for the horizontal trajectory tracking of underactuated autonomous underwater vehicles (AUVs) subject to unknown internal and external disturbances. In the guidance loop, a kinematic control law of the desired surge speed and trajectory angle is derived. To meet the previous convergence requirement, a kinetic control law is developed. It consists of two terms: the disturbance rejection and the stabilizing controller. The former is given by using an extended state observer (ESO) based on the high gain technique. In this process, the singular perturbation theory is applied to analyze the extended state system via order reduction. Then the latter is designed in the reduced model independently, in term of the backstepping technique and a composite-system method. Moreover, this paper also proves that the proposed controller makes the closed-loop system asymptotically stable. Finally, simulation results are presented to illustrate the control performance.

Behaviour of cold-formed steel channels bent about the minor axis

The Direct Strength Method (DSM) in AISI S100 and AS/NZS 4600 is a newly developed alternative design method to the Effective Width Method in calculating the design moment capacity of cold-formed steel channels. The DSM uses elastic buckling stresses with an appropriate strength curve to calculate the design moment capacity. However, the current DSM design equation has been calibrated for channels bent about the major axis and is known to be conservative for channels bent about the minor axis with the web in compression. In order to extend the DSM for channels bent about the minor axis, it is necessary to prescribe and calibrate a DSM design equation for minor axis bending. This paper aims at deriving a new DSM design equation for cold-formed steel channels bent about the minor axis with the web in compression. For this purpose, the behaviour of 33 cold-formed steel channels bent about the minor axis inducing local buckling in the web are investigated using elastic finite strip buckling analysis and nonlinear finite element analysis. The cross-sectional dimensions such as thickness, web and flange widths are varied to cover a wide range of section slenderness. Deformed shapes and stress distributions at ultimate moment for various channels of different slenderness are described. Due to the considerable conservatism the current DSM design equation exhibited in comparison to the nonlinear finite element analysis results, a new DSM design equation for cold-formed steel channels bent about the minor axis is proposed.

Design of chord sidewall failure in RHS joints using steel grades up to S960

It is well known that the current design rules adopted by international design codes such as ISO 14346 and design guides, e.g., the CIDECT design guide No. 3, for chord sidewall failure in mild steel rectangular hollow section (RHS) joints under brace axial compression are considerably conservative, if the RHS joints are adequately supported out-of-plane. This paper presents an investigation into chord sidewall failure in RHS joints using steel grades up to S960. Representative existing design methods for chord sidewall failure in RHS joints are reviewed, and two alternative design methods, i.e., the modified bearing–buckling method and the Lan–Kuhn​ method, are proposed. Up-to-date test and numerical results reported in the literature are compiled. A wide range of geometric parameters, steel grades up to S960 and loading cases of brace axial loading, brace in-plane bending and brace out-of-plane bending are covered. The existing and proposed design methods are assessed against the collated results. The effects of brace-to-chord height ratio, brace angle, steel grade and chord stress ratio are evaluated. It is shown that the proposed design methods can provide more consistent resistance predictions for chord sidewall failure in mild steel and high-strength steel RHS joints under brace axial compression. Corresponding user-friendly design rules are suggested. The design of chord sidewall failure in RHS joints under brace axial tension, brace in-plane bending and brace out-of-plane bending is discussed. Further required research on, in particular, high-strength steel RHS joints is highlighted.

Superpave Gyratory Compactor as an Alternative Design Method for Roller Compacted Concrete in the Laboratory

AbstractThe introduction of the Superpave gyratory compactor (SGC) to pavement laboratories was a large step for the design process of hot mix asphalt (HMA). Considering the similarities between HM...

Beam theory – a proposed alternative basis for RC design

It has recently been shown that the ever-increasing complexity and inability of methods used for the design of reinforced concrete (RC) structures to consistently safeguard against brittle types of failure is the outcome of the conflict between the assumptions of the underlying theory and the fundamental concrete material characteristics. This paper demonstrates that these drawbacks can be eliminated through a coherent alternative theory developed on the basis of simplified beam theory modified to account for true concrete behaviour. Through the use of experimental information obtained from the literature, the proposed theory shows that, in contrast with widely held views, a structural member's load-carrying capacity depends solely on the strength of the compressive zone, which was found to be significantly larger than what it is widely considered to be. Moreover, load transfer is accomplished by the bending action of the concrete cantilevers formed between consecutive inclined or flexural cracks in the tensile zone. The above findings essentially underline the development of an alternative design method – the compressive force path method – and this is an indication of the suitability of the proposed theory to open up new possibilities for improving RC design.

Improved Stability and Damping Characteristics of LCL-Filter Based Distributed Generation System

The voltage source inverter is a key component in the distributed power generation systems where the LCL-filter is a popular choice for interfacing with the grid. However, the well-known resonance issue associated with the LCL-filter deteriorates the control performance and risk the inverter system stability. The inverter control design plays a significant role to ensure the quality of the injected grid current and stable operation according to the requirements of grid interconnection standards. This paper deals with an alternative control design method that modifies the internal damping loop design to improve the stability and damping characteristics. The proposed design employs a compensator across the filter and feedbacks the output of the augmented plant at the reference voltage point, and named as parallel feedforward compensation method. The filter capacitor current measured for damping loop implementation, and a high-pass filter compensator adopted in the proposed configuration. The proportional capacitor current feedback compensation method is considered for comparative studies. The current loop stability and control performance characteristics are investigated in detail under the resonance frequency and filter parameters variation condition. The significant outcomes of the proposed scheme are faster dynamic response, higher delay compensation capability, relatively improved resonance suppression, and potential for better tracking performance. An experimental prototype is developed to validate the efficacy of the proposed method.

Seismic response of multi-span continuous irregular bridges using displacement-based and conventional force-based methods

In the recent years, the displacement-based seismic design (DBD) method of structures has been recognized as the alternative design method to the conventional force-based seismic design (FBD) method. The problems inherited in the FBD method are mostly overcome by the DBD method as it better correlates the structural damage with displacement-based quantities. In this study, the seismic response of multi-span bridges with varying number of spans and unequal pier heights was evaluated using the DBD method and compared with the conventional FBD method. Two approaches were employed in the DBD method, such as the traditional direct displacement-based seismic design (DDBD) approach and the proposed approach in this study entitled as alternative-to-direct displacement-based seismic design (ADBD). For seismic evaluation of the bridge structures with the FBD method, acceleration response spectra as suggested in the Bangladesh National Building Code were used; while in the DBD method, displacement response spectra for different damping ratios were developed keeping consistency with the above-mentioned design acceleration spectra. Five bridge models were used in the analysis to compare the seismic response in both the longitudinal and transverse directions taking into account the number of spans and height irregularity in the bridge models. Numerical analysis showed very obvious results that the base shear calculated by both approaches of the DBD method is found to be smaller than the FBD method indicating that an economic member section be attained for meeting the same design objective. More specifically, the ADBD approach provides the design professionals a more conservative design approach in compared with the DDBD approach keeping an economic design approach comparing with the FBD method.