Numerical Design Method Research Articles

Development and Design Validation of an Inflow-Settling Chamber for Turbomachinery Test-Benches

At Leibniz University of Hannover, Germany, a new turbomachinery test facility has been built over the last few years. A major part of this facility is a new 6 MW compressor station, which is connected to a large piping system, both designed and built by AERZEN. This system provides air supply to several wind tunnel and turbomachinery test rigs, e.g., axial turbines and axial compressors. These test rigs are designed to conduct high-quality aerodynamic, aeroelastic, and aeroacoustic measurements to increase physical understanding of steady and unsteady effects in turbomachines. One primary purpose of these investigations is the validation of aerodynamic and aeroacoustic numerical methods. To provide precise boundary conditions for the validation process, extremely high homogeneity of the inflow to the investigated experimental setup is imminent. Thus, customized settling chambers have been developed using analytical and numerical design methods. The authors have chosen to follow basic aerodynamic design steps, using analytical assumptions for the inlet section, the “mixing” area of a settling chamber, and the outlet nozzle in combination with state-of-the-art numerical investigations. In early 2020, the first settling chamber was brought into operation for the acceptance tests. In order to collect high-resolution flow field data during the tests, Leibniz University and AERZEN have designed a unique measurement device for robust and fast in-line flow field measurements. For this measurement device, total pressure and total-temperature rake probes, as well as traversing multi-hole probes, have been used in combination to receive high-resolution flow field data at the outlet section of the settling chamber. The paper provides information about the design process of the settling chamber, the developed measurement device, and measurement data gained from the acceptance tests.

Numerical methods for shape optimal design of fluid–structure interaction problems

We consider the method of mappings for performing shape optimization for unsteady fluid–structure interaction (FSI) problems. In this work, we focus on the numerical implementation. We model the optimization problem such that it takes several theoretical results into account, such as regularity requirements on the transformations and a differential geometrical point of view on the manifold of shapes. Moreover, we discretize the problem such that we can compute exact discrete gradients. This allows for the use of general purpose optimization solvers. We focus on problems derived from an FSI benchmark to validate our numerical implementation. The method is used to optimize parts of the outer boundary and the interface. The numerical simulations build on FEniCS, dolfin-adjoint and IPOPT. Moreover, as an additional theoretical result, we show that for a linear special case the adjoint attains the same structure as the forward problem but reverses the temporal flow of information.

Numerical analysis and design method of Y-shaped connectors encased in UHPC for prefabricated composite bridges

In this paper, the shear mechanism of the novel Y-shaped (Y-S) connector encased in ultra-high-performance concrete (UHPC) was analyzed to reveal the steel-concrete interface separation mechanism and the interaction mechanism between the connector and UHPC. Subsequently, a validated finite element (FE) model was established for parametric analysis to investigate the effects of strength parameters and structural parameters on the shear performance of the Y-S connector, including the yield strength of the steel plate and penetrating rebar, the compressive strength of the concrete and UHPC, the diameter of the penetrating rebar, the effective width and thickness of the steel plate, and the dimensions of the UHPC shear pocket. The design method for the Y-S connector was finally developed and validated, including the improved shear capacity model, the shear stiffness model, the peak slip model, and the method for calculating the load-slip curves. The results indicate that the UHPC dowel in the holes experiences triaxial compressive stress, and the penetrating rebar undergoes deformation under the force from the top and bottom UHPC. The yield strength of the steel plate, as well as the effective width and thickness of the steel plate, have remarkable effects on the shear performance of the Y-S connector compared with other parameters. These analytical models can well predict the shear performance of the Y-S connector in the required precision range.

Numerical Study and Design Method for Lateral Torsional Buckling of High-Strength Steel Beams

Given the increasing use of high-strength steels in building constructions, the stability design of high-strength steel beams has become a crucial consideration. However, the current standards of various countries are based on analyses and fittings derived from conventional steel, rendering them unsuitable for high-strength steel. Moreover, existing research indicates that these standards underestimate the ultimate load-bearing capacity of high-strength steel beams. A finite element model was established to investigate lateral torsional buckling in high-strength steel beams. The obtained results were then compared with test results from experiments conducted on Q460GJ and Q690 steel beams. The reliability and accuracy of the established finite element model were validated. Through parametric studies, the impact of depth-to-width ratio, boundary condition, and steel grade on the stability coefficient was evaluated. It was observed that at the same non-dimensional slenderness, an increase in the depth-to-width ratio or a reduction in support constraints led to a decrease in the stability coefficient. It should be noted that the steel grade had little effect on the stability coefficient. Comparisons with the current steel structure design codes, such as EN1993-1-1, GB50017-2017, JGJ/T483-2020, and ANSI/AISC360-22 revealed an underestimation of the stability coefficient for clamped high-strength steel beams under uniformly distributed loads. Based on finite element simulations, stability coefficients for high-strength Q460, Q690, and Q960 clamped beams were determined. Similar to the stability coefficient proposed in GB50017-2017 for the lateral buckling stability design of steel beams, a lateral buckling stability coefficient for high-strength steel clamped beams subjected to uniformly distributed loads was proposed.

Numerical investigation and design methods of the local buckling of WAAM stainless steel circular hollow section stub columns

3D printing is an advanced technology that has been used in biomedical and automotive engineering, and has raised a significant response in civil engineering. Wire and arc additive manufacturing (WAAM), a metal 3D printing technology, has prospective applications in steel construction because it can fabricate large-scale structural members at an acceptable cost and manufacturing efficiency. Fundamental studies are still urgently needed to realize its engineering application. However, due to the irregular geometric features, limited studies on the structural performance of WAAM components, particularly the numerical studies, have been carried out. To this end, a numerical investigation on the local buckling of WAAM stainless steel circular hollow section (CHS) stub columns under axial compression has been conducted and presented herein. The finite element (FE) models were established and validated against the existing experimental research. Parametric studies were subsequently carried out to broaden the cross-sectional resistance data pool using the developed FE models. The applicability of the cross-section design provisions specified in EN 1993-1-4:2006 + A2:2020, ANSI/AISC 370-21 and the continuous strength method (CSM) for the design of WAAM CHS was evaluated according to the experimental and FE results. Furthermore, a modified design method with improved accuracy was suggested.

Experimental and Numerical Investigation Integrated with Machine Learning (ML) for the Prediction Strategy of DP590/CFRP Composite Laminates.

This study unveils a machine learning (ML)-assisted framework designed to optimize the stacking sequence and orientation of carbon fiber-reinforced polymer (CFRP)/metal composite laminates, aiming to enhance their mechanical properties under quasi-static loading conditions. This work pioneers the expansion of initial datasets for ML analysis in the field by uniquely integrating the experimental results with finite element simulations. Nine ML models, including XGBoost and gradient boosting, were assessed for their precision in predicting tensile and bending strengths. The findings reveal that the XGBoost and gradient boosting models excel in tensile strength prediction due to their low error rates and high interpretability. In contrast, the decision trees, K-nearest neighbors (KNN), and random forest models show the highest accuracy in bending strength predictions. Tree-based models demonstrated exceptional performance across various metrics, notably for CFRP/DP590 laminates. Additionally, this study investigates the impact of layup sequences on mechanical properties, employing an innovative combination of ML, numerical, and experimental approaches. The novelty of this study lies in the first-time application of these ML models to the performance optimization of CFRP/metal composites and in providing a novel perspective through the comprehensive integration of experimental, numerical, and ML methods for composite material design and performance prediction.

Advancements in numerical modeling of ideal multicomponent isotope separation Cascades: A comparative study

The complexity of operational conditions in stable isotope separation cascades necessitates the utilization of numerical methods for cascade design and performance analysis. This study focuses on solving a system of nonlinear algebraic equations derived from the mass and energy balance equations, which is a fundamental challenge in analyzing and designing cascades and developing numerical methods. Two existing numerical algorithms were selected from the literature and modified for quasi-ideal cascade systems. The performance of these algorithms was examined and compared, with a particular emphasis on influential parameters such as the number of stages, the number of isotopes, and the separation factor. The first algorithm solves the concentration and flow equations separately, while the second algorithm solves all equations simultaneously. The results indicate that the first algorithm exhibits significant superiority over the second algorithm. In most cases, the second algorithm either fails to converge or exhibits a slower convergence speed. Additionally, the results demonstrate that increasing the number of stages impacts the convergence time, while an increase in the separation factor leads to greater convergence complexity.

Numerical simulation and design method of dowel-type timber joints connecting laminated veneer lumber

Dowel laminated timber (DLT) is a structural engineering wood product composed of laminates connected by wood dowels. It has the characteristics of green, low-carbon, and a high degree of prefabrication. Wood dowel connection is the forming method of DLT, and its joint design is the key to DLT. The properties of laminates affect the mechanical properties of both DLT and dowel-type timber joints. Laminated Veneer Lumber (LVL) is an engineering wood product made by gluing veneers along a fixed grain direction, with excellent physical and mechanical properties. Utilizing small-thickness LVL as the laminates of DLT, a design method of dowel-type timber joints connecting LVL was explored through numerical simulation and theoretical calculation. A three-dimensional finite element model of dowel-type timber joints connecting LVL was presented, and experimental calibration were carried out. The parametric study was adopted to explore the influence of main variables on the shear performance of joints. The calculation formula for the shear capacity of joints was proposed and optimized, and the design method of joints was summarized. The results indicated that the failure mode and shear capacity of joints were dramatically influenced by two variables: the ratio of side laminate thickness to dowel diameter (n) and the thickness ratio of middle-to-side laminate (m). The two variables affected the shear capacity of joints by affecting the failure mode of joints. When the ratio of side laminate thickness to dowel diameter was 1 < n ≤ 3.75, the optimized Johansen theoretical formula could effectively predict the shear capacity of dowel-type timber joints connecting LVL.

Numerical analysis and design methods of grout-filled GFRP tube repaired corroded CHS T-joints

This study explores the compressive behavior of Grout-Filled GFRP Tube (GFGT) repaired corroded circular hollow section (CHS) T-joints. Finite element models of GFGT repaired corroded joints were developed, validated, and utilized to examine the influence of the joint geometric, material, and chord end stress parameters on the compressive strength and repairing efficiency of the joints. The findings reveal that the ultimate strength of the GFGT repaired joint increases with a thicker GFRP tube, a lower repaired chord section hollow ratio, a higher grout strength, and a longer repaired range. By optimizing the repairing parameters of the grout-filled GFRP tube, the compressive strength of GFGT repaired corroded joints with 16% and 32% corrosion rates can be up to increase to 164% and 147% of the uncorroded counterparts, respectively. The chord end stress exerts a similar but weaker effect on the repaired joints than on the unrepaired joints. A series of suggestions were proposed for repairing joints with different corrosion degrees to achieve a 20% ultimate strength enhancement compared to uncorroded joints. The compressive strength degradation rate of corroded joints was accurately predicted by the design method in the CIDECT and prEN guidelines. The feasibility of the guideline formulae to evaluate the strength reduction rate caused by the chord end preload was verified. A design method to predict the compressive strength of GFGT repaired corroded joints was proposed.

Numerical FE Modeling and Design Methods of CCES Columns with Normal-Weight Crushed Dolomite Coarse Aggregate Fully Embedded IPE Steel-Section

The composite concrete-encased steel (CCES) column member is made by the steel section embedded and covered in concrete from all sides. Due to the ability of the composite sections to bear heavy loads while using smaller sections, CCES columns have been widely used. Analytical studies on the CCES columns’ behavior using crushed dolomite coarse aggregate (CDCA) with different shear connectors (SCs) types/shapes and sizes under axial loads are described here. This study also aims to evaluate the current design methods to determine the ultimate capacity of the CCES with CDCA concrete columns using nine available codes. The results show that the finite element (FE) analysis could accurately predict the ultimate capacity of the CCES columns; the column’s capacity improved by about 41.75% as fcu increased by 60%. Increasing the IPE-shaped steel strength (fss) strategy is not very effective and gives brittle behavior even though enhancing the fss improves the capacity. The column's capacity increased as the tie stirrups and steel bars ratios increased. The column’s capacity increased by about 17.63%, as steel bars ratios increased by 155.49%. The efficiency factors increased slightly as tie stirrups were raised but slightly decreased as steel bar ratios increased. Using the SCs system increases the columns’ capacity by an average value of about 4.9% of the specimen without SCs. The computed capacities using the nine available codes are conservative and safe. The closest estimates made by the YB9082-06 code are 26% less on average than the test results; in contrast, the safest predictions made by the ECP-LRFD code are 68% less, on average, than test results.Graphical

Consensus control of multi-agent systems with delays

&lt;p&gt;This paper concerns the consensus problem of linear time-invariant multi-agent systems (MASs) with multiple state delays and communicate delays. Consensus control is widely applied in spacecraft formation, sensor networks, robotic manipulators, autonomous vehicles, and others. By introducing a linear transformation, the consensus problem of the delayed MAS under an undirected network was converted into a robust asymptotic stability problem associated with the eigenvalues of the normalized Laplacian matrix of the network. By means of the argument principle and optimization technologies, a numerical controller design method was presented for the delayed MAS to reach consensus. The effectiveness of the proposed approach was illustrated by some numerical examples. The proposed approach may be applied to multi-agent systems with distributed delays.&lt;/p&gt;

The importance of experimental airframe noise research

Numerical methods progress rapidly in terms of capabilities and efficiency. Accordingly, one could conclude that experimental activities will sooner or later disappear. In this context the paper will exemplify the use of numerical methods for the proper design and conduct of wind tunnel experiments. Examples will cover the research topics on high lift system's aero-acoustic and landing gear noise. Finally, the paper will describe the development of selected noise reduction concepts from their first experimental assessment in wind tunnels up to being flight tested.

Lateral impact behaviour of CCFT columns with spherical-cap gap imperfection: Numerical modelling and design method

To clarify the influence of gap imperfection on the impact behaviour of the concrete-filled steel tube (CFT) column, this paper performs numerical modelling on the mechanical responses of the circular CFT columns holding spherical-cap gaps (CCFT-SG) under lateral impact load. The effects of gap ratio, axial compression ratio, impact position, diameter/thickness ratio, boundary condition and material strength on the energy dissipation (Ea), the maximum (Fm) and equivalent impact forces (Feq), the peak (δm) and residual lateral deflections (δr) are analyzed after establishing and validating the finite element (FE) model. The typical failure pattern, time-history curve and contact response between the tube and concrete of the laterally impacted CCFT-SG column are revealed as well. The result declares that the overall failure morphology of the CCFT-SG column imposed with lateral impact showing as overall bending, is similar to that of the common CFT column, but distinct local depression is obtained because of the existence of spherical-cap gaps. With the gap ratio increasing, the Feq, Fm and Ea decrease gradually, while the δm and δr rise slowly. The calculation formulae for predicting the dynamic impact force and resistance of the CCFT-SG column are presented and validated against the existing test and numerical results.

Design and analysis of timber-concrete-based civil structures and its applications: A brief review

Abstract Builders, designers, and the research community are becoming interested in incorporating timber and concrete based composite structures because they effectively integrate the structural qualities of timber and concrete. The structure’s stiffness, ductility, and load capacity are all affected by the quality of the timber connections used in construction. However, timber-concrete-based structures are limited due to a lack of design knowledge and the brittle failure behaviour of timber under shear or tensile loading. Experimental, numerical, and analytical methods have been proposed in the literature, and the key parameters influencing the performance of timber-concrete structures have been discussed. This study addresses the current challenges in designing timber-concrete connections and their failure modes and suggests simple performance-based analytical models that determine the failure mode. It looks at some of the best numerical design methods used in the past and tries to determine the best way to use timber as a possible way to use safe design principles for timber–concrete composite structures in the future.

Generalized Global Self-Optimizing Control for Chemical Processes Part I. The Existence of Perfect Controlled Variables and Numerical Design Methods

Generalized Global Self-Optimizing Control for Chemical Processes Part I. The Existence of Perfect Controlled Variables and Numerical Design Methods

Numerical investigation and design method of cold-formed sorbite stainless steel circular tubes under uniaxial compression

The recently developed novel high-strength sorbite stainless steel (S600E) combines the advantages of exceptional mechanical properties, high corrosion resistance, effortless weldability, and cost-effectiveness, granting remarkable competitiveness in stainless steel structures. The authors have conducted and published experiment results on S600E circular hollow section (CHS) columns under uniaxial compression, which serve as a foundation for the subsequent numerical analysis presented in this study. An extensive parametric study encompassed key variable parameters such as slenderness ratio, section size, and diameter-to-thickness ratio, culminating in 748 numerical models. Meanwhile, the ultimate strength obtained through finite element analysis (FEA) was utilized to evaluate the calculation methods prescribed by current European, Australian/New Zealand, and Chinese stainless steel structural design standards and the direct strength method (DSM) available in the literature. The result shows that the DSM can accurately predict the ultimate strength of CHS columns with an average error of 0.2%, while other specifications are slightly conservative. Then, the effective area calculation method was proposed in this paper, whose rationality was verified by meso finite element analysis. Moreover, a revised equation in Chinese code was proposed, which can improve the prediction accuracy by 9.2%. Finally, a reliability analysis was conducted to assess the safety levels of the design standards and DSM. The findings of this study can not only benefit the adoption of the high-strength stainless steel in the construction industry and therefore potentially mitigate carbon-emission-related environmental issues.

Analysis and design of RC unbonded PT shear walls in isolation and integrated into buildings: A state-of-the-art review

Shear walls play crucial roles in buildings located in the seismically active regions by efficiently mitigating the impact of seismic forces. However, they have drawbacks regarding their non-recoverable deformation and, thus, lack of reusability once damaged during an earthquake. One potential solution to this problem is the use of post-tensioned (PT) shear walls. These walls rock over the base during seismic events and regain their original position after the event, showing self-centering behaviour. The self-centering behaviour makes these walls reusable and reduces the downtime of the structure, thus making them a sustainable solution over conventional shear walls. Often, they are fitted with either internal or external energy dissipators to enhance the energy dissipation capacity. The present study aims at reviewing past analytical and numerical works, design methods, and international codes on reinforced concrete (RC) PT shear walls. The study also focuses on the models used in the past to investigate the behaviour of these walls. The parameters that affect the performance of RC PT shear walls are presented. Also, the global behaviour and the system interaction of RC PT shear walls integrated into buildings have been discussed. Finally, this paper presents the summary and critical observations, along with future recommendations on RC PT shear walls.

Patch-loading resistance performance of stainless-clad bimetallic steel plate girders: Numerical investigations and design methods

Compared with stainless steel, stainless-clad bimetallic steel (SCBS), which comprises a stainless steel cladding layer and a carbon steel base layer, requires a lower project cost and can maintain the same corrosion resistance, thus allowing the corrosion weakening of steel structures to be solved effectively. Investigations regarding SCBS plate girders, which can be widely used in bridge and industrial structure servicing in corrosive environments, are few. In this study, the patch-loading resistance performance of SCBS plate girders is investigated systematically, and the effects of cladding ratios are considered. A finite element modelling method is proposed to predict the patch-loading resistance performance of SCBS plate girders, which is validated using 33 experimental results regarding conventional structural steel and bimetallic steel plate girders. A comparison of the ultimate strength, load–deflection curve, and failure mode shows that the proposed finite element modelling method can be used to effectively clarify the patch-loading resistance performance of SCBS plate girders. A comprehensive parameter study involving 288 numerical models is conducted. Based on numerical results, the basis for design recommendations is presented. The relationship among the ultimate strength of the plate girders corresponding to SCBS, stainless steel (cladding layer), and HSS (base layer) is determined, and a linear equation is proposed. The applicability of Chinese, American, and European codes in determining the ultimate strength of SCBS plate girders is verified. The verification results show that the existing codes cannot be directly used to determine the ultimate strength of SCBS plate girders. Therefore, two strength reduction functions are proposed to modify the design equations in European codes. The undetermined constants in the proposed strength reduction functions for SCBS plate girders with different cladding ratios are statistically calibrated. Additionally, a predictive equation for determining the undetermined constants in function-I is proposed. When these proposed strength reduction functions are employed, the calculation accuracy of the European codes is significantly improved. The basis for design recommendations presented in this study is valid for the SCBS plate girders with specific geometric dimensions and material properties included in the parametric study.

Numerical Modeling and Design Method for Reinforced Polyvinyl-Alcohol-Engineered Cementitious Composite Beams in Bending

The polyvinyl-alcohol-engineered cementitious composite (PVA-ECC) is a superior cementitious material when used for tension and flexural loading. The utilization of PVA-ECC in the tension zone can prevent the development of wide cracks and increase the flexural resistance of reinforced PVA-ECC members. In this paper, a nonlinear finite element model is established to simulate the behavior of PVA-ECC beams in bending. In the model, the constitutive models for PVA-ECC in compression and tension are employed by simplifying them as piece-wise linear models, and the bond between the reinforcing bar and PVA-ECC is also considered. The load–deflection curve and failure mode of beams can be obtained from the finite element model. Comparisons between numerical and experimental results show that the developed numerical model can estimate the ultimate load and failure mode of beams with reasonably good accuracy. After evaluating the accuracy of the finite element model, parameter analysis is conducted to investigate the effects of the reinforcement ratio, steel strength grade, and mechanical properties of PVA-ECC on the flexural behavior of reinforced PVA-ECC beams. The numerical results conclude that the effects of reinforcement ratio on the peak load, stiffness, and deflection are obvious while the influence of steel grade is mainly on the peak load. The tensile localization strain of PVA-ECC mainly affects the ductility of the beam. Furthermore, a design method is proposed based on the plane-section assumption to calculate the ultimate load of reinforced PVA-ECC beams, in which the contribution of PVA-ECC to the moment resistance of beam sections is considered. Comparisons between existing design methods and the proposed method indicate that the ultimate load of beams can be predicted more accurately by considering the tensile strength of PVA-ECC in the tension zone.

Numerical simulation and design method of the interface of UHPFRC-strengthened RC structures using post-installed rebars

The interface using post-installed rebar (PR) connections has been proven to possess robust mechanical properties for strengthening reinforced concrete (RC) structures with ultra-high performance fiber reinforced concrete (UHPFRC). However, current studies have not yet clarified the design method for this type of interface, which significantly hinders its widespread application. To this end, this study is devoted to developing a design method for the interface of UHPFRC-strengthened RC structures using PR connections. Detailed finite element (FE) models were established to capture the interfacial performance, and their accuracy was verified using the experimental data. An extensive parametric study was performed to identify the essential factors for interfacial performance. The FE results revealed that the concrete between the rebars failed before the rebars when the post-installed rebar spacing was three times the diameter of the rebar. Moreover, it was found that the thickness of the UHPFRC layer had a negligible influence on interfacial shear strength. The detailing requirements for the interfacial design using post-installed rebars were given. Combining the experimental and numerical findings, a design method was proposed for the interface of UHPFRC-strengthened RC structures using PR connections. An existing experimental study on RC beams strengthened by UHPFRC was chosen to examine the applicability of the proposed design method. It was found that the well-designed beam exhibited good ductility and energy dissipation capacity. The perfect bond was proved to be acceptable for analysis simplification when the UHPFRC-strengthened RC structures were well-designed by the proposed method.