Design Values Research Articles

Hybrid joints consisting of pre-tensioned bolts and a bonded connection—The influence of adhesives on the load-bearing capacity

This study explores the intricate mechanics of hybrid joints, which combine prestressed bolts and adhesive bonding, with a focus on increasing the joint capacity of steel structures. Despite their potential, the fundamental behaviour of these joints is not fully understood. The research focuses on unravelling the load-bearing capacity of these hybrid joints, emphasising the influence of the adhesive properties. The unique manufacturing process, involving the pre-tensioning of bolts while the adhesive is uncured, introduces additional dependencies not present in conventional adhesive joints. Analysis of the mechanical and physical properties of five adhesives provides key insights into the mechanics of load transfer and failure modes in hybrid joints, providing a comprehensive understanding. The study shows that load transfer occurs through micron-thin adhesive layers, highlighting the significant influence of adhesive properties on joint performance. Epoxies emerge as the top performers, with 2.5 times the average friction joint and more than five times the average bonded joint capacity, indicating their superiority in hybrid joint applications. Hybrid joints show significantly less variation than adhesive and friction joints, underlining their consistency and reliability in structural applications. When comparing hybrid and bonded joints with the same adhesive (SW7240), the variance was suppressed to one seventh by the application of preloaded bolts, with practical implications for design values based on quantiles. The study establishes correlations between joint strength and adhesive properties, emphasising the critical role of Young's modulus and tensile strength. It also finds that the elongation of hybrid joints at break is almost entirely dependent on load capacity, with viscosity having a lesser effect. Fracture surface investigations provide insight into the failure modes of hybrid joints, highlighting differences from those observed in frictional or purely bonded joints. This comprehensive study, combining experimental campaigns and in-depth analysis, provides valuable insights into the intricate relationships between joint capacity and adhesive properties in hybrid joints. The findings guide the selection of appropriate adhesives and provide the basis for the development of accurate load prediction methods, unlocking the full potential of hybrid joints and overcoming the limitations of conventional joining techniques in steel structures. Further research is encouraged to investigate the influence of adhesive class, post-tensioning stability and the nuanced mechanics of load transfer in these innovative joints.

Optimizing Lumber Densification for Mitigating Rolling Shear Failure in Cross-Laminated Timber (CLT)

Rolling shear in cross-laminated timber (CLT) has been identified as the governing factor influencing design value. Likewise, densification has been found to be an effective method of enhancing the rolling shear strength of lumber and in turn, CLT. In this study, utilizing knowledge of material properties, optimization of the compression ratio for densification has been presented. Three-layered CLT beams made from non-densified lumber, grade #1 loblolly pine (Pinus taeda L.), were subjected to a bending load at a span-to-depth ratio of eight and had a rolling shear failure at the mid-layer with a shear strength of 3 MPa. Assuming the same modulus of rupture (MOR) for both lumber and CLT made from the same species and grade, the MOR of lumber was used to calculate the minimum required shear strength (MRSS) of the transverse mid-layer to change the failure mode of the CLT beam from rolling shear to tensile failure. Using the relationship between the compression ratio and the increase in rolling shear strength, the optimized compression ratio for densification was calculated. This procedure resulted in a compression ratio of 16.67% for densification of the mid-layer to avoid rolling shear in the case of CLT beams with a span-to-depth ratio of eight. To verify this process, CLT beams with mid-layers densified at 16.67% were fabricated and submitted to a bending test. Rolling shear failure was mitigated and densified CLT beams failed in tension with a MOR similar to that of lumber, 47.45 MPa. Likewise, rolling shear strength was observed to increase by 48% for CLT that had a densified mid-layer at 16.67%.

Film cooling effect of upstream jump coolant on turbine endwall with combustor-turbine interface misalignment

The investigation of jump cooling performance on turbine endwall independently causes its actual cooling effectiveness to deviate from the design values. In this paper, the endwall jump cooling structure with combustor-turbine interface cavity and combustor liners is modeled. Taking the realistic combustor-turbine interface features into account, the effect of jump coolant on turbine endwall film cooling and heat transfer characteristics is numerically studied. Under different endwall misalignment modes, the aerodynamic interaction mechanisms of realistic combustor outflow profile, jump coolant jet and cascade secondary flows at turbine endwall region are revealed. The modification effects of combustor-turbine interface features on jump cooling of the endwall are investigated. The results show that the combustor outflow severely ingests into the combustor-turbine interface cavity after flowing across several steps. Two branches of cavity vortex are subsequently generated in the middle-pitch region of cascade to affect the jump coolant jet. At low coolant blowing ratio, the attachment and separation sides of cavity vortex individually result in high and low cooling regions, while the horseshoe vortex leads to a large wedge-shaped cooling region. At z/Cax < 0, the backward step leads to a higher cooling effectiveness than forward step by 0.2. The jump coolant only leads to phantom cooling effect on downstream part of the vane suction side surface. The net heat flux reduction (NHFR) between two cavity vortexes and at pressure side junction are individually 0<NHFR<0.2 and −0.2<NHFR < −0.1. At high blowing ratio, the jump coolant can cover the pressure side junction with the highest cooling effectiveness of 0.5. The jump coolant can flow across the horseshoe vortex and directly upwash the vane surface. The weak protection regions between two cavity vortexes and near the attachment line of the pressure side horseshoe vortex enlarges. Compared with the forward step, the backward step achieves a lower NHFR by up to 0.1 and a higher Nusselt number. This paper provides an in-depth analysis of the aero-thermal physics of endwall jump cooling concerning realistic combustor-turbine interface conditions.

An Integrated Approach to Geomechanical Modeling of the Urikhtau Oil and Gas Condensate Field to Optimize Well Design

Background: The rock and geological section of the Urikhtau oil and gas condensate field is a complex geological system, including a variety of rocks of different densities and angles of occurrence, as well as disjunctive faults, which in turn complicates the process of designing and constructing wells. This article discusses the experience of geological and geomechanical modeling at this field.&#x0D; Aim: The purpose of this work is to consider geological and geomechanical modeling at the Urikhtau oil and gas condensate field as a method for further application in the design of well construction, taking into account the complexity of the geological structure of the field.&#x0D; Materials and methods: To build a 3D model, data from seismic and geophysical surveys were used, as well as historical data to correlate calculations.&#x0D; Results: The result of the modeling is the development of recommendations for the well profile, its design and optimal values of drilling fluid density, which will create a safe “drillability window” for well construction.&#x0D; Conclusion: Geological and geomechanical modeling allowed us to develop key recommendations for well design, including optimizing drilling fluid density and ensuring wellbore stability.

Assessment of Design Values in Designing Product Standards: A Design Study on a Sport PPE

Participation in sports requires using Personal Protective Equipment (PPE) to preserve athletes’ well-being. Although equipment may negatively impact performance, governing bodies often impose standards on participants subject to their jurisdiction. Although the vast majority of new products are incremental innovations, radical innovation still attracts design researchers&amp;apos; and professionals&amp;apos; attention. The design of complex systems needs the expertise of various kinds: designers are fundamental in conceiving innovations in response to developing ways of product use and customer needs, despite they must face product standards, which often act against product innovation. Despite product innovations benefiting consumers in many markets, they do not necessarily benefit consumers in sports PPE markets. In this paper, the author reflects on an ethnographic case study and the importance of the involvement of end and co-dependent users in the design of sports PPE. For this study, the design of the Australian safety vests for jockeys, frequently overlooked, was examined for incremental innovation and its relationship with its standards. This was inspiring to consider an assessment of design values in designing product standards in the sports field. As co-design is increasingly applied across multiple sectors, there is a huge need for practical design guides to support product development and co-designing with users. Further research in this field is highly recommended.

Tune optimization for alleviating space charge effects and suppressing beam instability at the RCS of CSNS

The design betatron tune of the Rapid Cycling Synchrotron (RCS) of China Spallation Neutron Source (CSNS) is (4.86, 4.80), which allows for incoherent tune shifts to avoid serious systematic betatron resonances. When the operational bare tune was set at the design value, serious beam instability in the horizontal plane and beam loss induced by half-integer resonance in the vertical plane under space charge detuning were observed. Simulations and experiments have shown that space charge-induced beam loss reduces as the tunes move up and away from half-integer resonance lines. However, experimental observations have shown that instability growth rates increase rapidly as the tune approaches integer from below. The tune requirements for reducing the beam loss caused by space charge effects and suppressing beam instability are different at the RCS of CSNS. The tunes over the whole acceleration process are optimized based on space charge effects and beam instability. The optimized tune pattern was able to well control the beam loss induced by space charge and beam instability. The beam power of CSNS achieved the design value of 100 kW with small beam loss.

Utilization of Fly Ash and Bottom Ash Waste of PLTU Jeranjang on Geopolymer Paving

Waste is produced as fly ash and bottom ash from coal-fired power stations. PLTU in West Nusa Tenggara uses 13,000 tons of coal in one month, so it can be estimated that Fly Ash waste will be produced around 1,950-2,210 tons. Geopolymer concrete utilizes fly ash as an adhesive to replace Portland cement. Fly ash is used to make geopolymer concrete, which is created by polymerization reactions caused by alkali-aluminosilicate reactions that result in materials with strong structures. In this study, the ratio of the composition of the weight ratio of paste (fly ash and alkaline solution) with aggregate was 35:65. The aggregates used are sand and bottom ash. The test object is a prototype paving block with a specific dimension of 10cm x 21cm x 6cm. Mechanical testing using compressive strength and water absorption testing with a specimen life of 7, 14, 21, and 28 days. Testing of bottom ash and fly ash characteristics in the form of XRF testing. The XRF test results found that the bottom ash and fly ash of PLTU Jeranjang belonged to class F. The average test result of compressive strength at the age of 28 days for mix designs A, B, and C was 8.54 MPa, respectively; 10.29 MPa; and 16.10 MPa. Quality geopolymer paving can be applied to gardens and other interiors used. Another result of the absorption value of Mix design C of 8% shows the addition of fly ash can be utilized in place of some of the used cement in paving blocks that satisfy SNI 03-0691-1996 Quality C criteria.

Manufacturability and mechanical properties of Ti-35Nb-7Zr-5Ta porous titanium alloys produced by laser powder-bed fusion

Porous titanium alloys with low modulus are in high demand for medical implants. In this study, laser powder-bed fusion (LPBF) was used to create biomedical Ti-35 Nb-7Zr-5Ta (wt%; TNZT) porous titanium alloys. The relationships between the processing parameters, forming quality, and performance were established. The results revealed that increasing the scanning speed or decreasing the laser power allowed the manufacturing deviation of the porous titanium alloys to be reduced and become closer to the design value. However, excessively high or low laser energy can cause internal defects. The optimal processing parameters for eliminating defect porosity in porous titanium alloys required an energy density lower than that required for the LPBF of fully dense materials. Additionally, high scanning speeds weakened texture and refined grains, which in turn decreased the yield strength and hardness, owing to the formation of the β’ phase with large lattice distortion. Porous titanium alloys prepared with optimal processing parameters exhibited a low modulus and exceptional energy absorption capabilities, prominently positioning in the modulus-energy absorption spectrum compared with reported lattice structures. This study offers valuable guidelines for the development of novel biomedical titanium alloys and the engineering applications of porous TNZT alloys.

Nonlinear analysis and design of high-strength concrete filled steel tubular columns under nonuniform fires

The main objective of this study is to investigate the behaviour of concrete-filled steel tubular (CFST) columns with ultra-high strength concrete (UHSC) and high strength steel (HSS) under fires through finite element method (FEM). High-strength materials can be used in CFST columns to reduce member dimensions, lowering material consumption and foundation loads. However, their fire behaviour has been insufficiently examined, especially under nonuniform fire exposure. In this study, thermal-structural models of the composite columns are developed using the SAFIR software. The numerical results are compared with published test data on temperature distribution, axial displacement, lateral displacement, failure modes and failure time. Then, parametric analyses are conducted to investigate the influence of various factors such as concrete strength, steel strength, different fire exposures, column length and load ratio on the fire performance of the CFST columns. In addition, the tabular design approach in European code EN1994–1-2 and Australian/New Zealand code AS/NZS 2327:2017 for designing uniformly exposed CFST columns is evaluated. It is observed that the prescribed design values in the table for R30 and R60 fire ratings under load ratio lower than 0.47 appear insufficient for the allowable slenderer columns. The applicability of the tabulated data for a load ratio up to 0.47 is further checked for the columns with UHSC of 120 MPa and HSS of 690 MPa, which is the strength limits recommended in AS/NZS 2327:2017.

Insights into thermodynamic performance of a hypersonic precooled air-breathing engine with a complicated multi-branch closed cycle

An advanced precooled airbreathing engine with a closed Brayton cycle is a promising solution for high-speed propulsion, of which the Synergetic Air Breathing Rocket Engine (SABRE) is a representative configuration. The performance of the latest SABRE-4 cycle was analyzed in this paper. Firstly, a relatively complete engine performance model that considers the characteristics of turbomachinery and heat exchangers was developed. Then, Sobol’ global sensitivity analysis of key performance parameters was carried out to identify the most influential design variables. Optimal specific impulses under different target specific thrusts were obtained by particle swarm optimization, of which the thermodynamic parameters corresponding to a specific thrust of 1.12 kN·s·kg−1 and a specific impulse of 3163 s were chosen as the design values. Four different control laws were analyzed in contrast, and the charge control method had the strongest ability of thrust regulation as well as maintaining a favorable specific impulse performance. Finally, working characteristics under the charge control and over a typical flight envelope were calculated, in which the average value of the maximum specific impulse was as high as 5315 s. This study would help to deepen the understanding of SABRE-4 thermodynamic characteristics and other precooled airbreathing engine cycles with similar layouts.

The effect of pipeline root weld microstructure on crack growth behaviour

The girth weld is the weak link of high-pressure pipeline, which is easy to crack under the combined action of internal and external loads, defect and stress concentration. At present, the safety hazards of high-strength pipeline girth welds are prominent, and it is of great significance to study the failure law of girth welds to ensure the safe operation of pipelines. In this paper, the failure analysis of 6 welded joints with crack defects excavated on site in a gas transmission company was carried out. Through metallographic analysis, scanning electron microscope (SEM) observation and electron backscatter diffraction (EBSD) analysis, the relationship between root welding, weld microstructure and crack generation was analyzed in detail. The influence of grain boundary distribution behavior of weld microstructure on crack propagation path was studied, and the mechanism of welding inclusions on crack propagation and aggregation nucleation was revealed. The results show that the cracks in root welding, hot welding, filling welding and heat affected zone are all transgranular propagation types, and the deflection of crack propagation path may be related to the complex stress state at the welded joint. Local strain concentration often exists in the near crack surface, secondary crack and crack deflection position on the crack propagation path, which indicates that the formation and propagation of root cracks are likely to be related to the deterioration of weld metal properties caused by local strain concentration at the root. The research conclusions have certain reference value for the intrinsic safety design, construction, and integrity operation and maintenance of pipeline girth welds.

Numerical Simulation Study of Midas-Based Tunnel Section Structural Forces and Deformations

The burial depth significantly influences the structural forces and deformations of tunnel sections, playing a crucial role in the safe operation of tunnels. This study focuses on the structural design and deformation analysis in underground tunnel engineering. Utilizing Midas modeling techniques, tunnel models were designed for experimentation to comprehensively explore the impact of tunnel burial depth and key design parameters on structural deformations and safety.(1) The research reveals that design parameters such as tunnel diameter are the dominant factors affecting deformation, lining pressure, and structural displacement.(2) With an increase in tunnel diameter, substantial deformation occurs, and the lining pressure distribution evolves from a "fan-shaped" pattern to a "peach-shaped" pattern. The bottom structure transitions from uplift to slight settlement. (3) The study results provide a rational range of parameter values for tunnel design. Simulation outcomes highlight areas with higher deformation, offering insights for proposing corresponding remedial measures.

Molecular dynamics simulation and performance verification of γ-polyglutamic acid/cold water-soluble starch film formation and permeability

Six types of γ-polyglutamic acid (γ-PGA)/cold water-soluble starch (St) composite film models were constructed using molecular dynamics simulation, and their properties were investigated and compared with the corresponding experimental values. The compatibility between the composite film components was analyzed using the radial distribution function and mean square displacement (MSD). The hydrogen-bond number and bond energy were used to track the film-formation process. The mechanical property data of the films were extracted, and MSD was used to analyze the permeability of the film to carbon dioxide, oxygen, water vapor, and carbon-16 saturated fatty acids. Finally, the simulated values of mechanical properties and permeability were compared with the experimental values. The results demonstrated that γ-PGA is well compatible with St. The intramolecular and intermolecular hydrogen bonds of γ-PGA and St did not change considerably during the film-formation process. The simulated values of the mechanical properties exhibited a similar trend as the experimental values; however, in terms of permeability, a difference was observed between the initial values of the simulated design and actual material parameters, as well as the complexity of the experiment.

Exploring epistemic aspects of engineering for K–12 science and engineering education

AbstractBackgroundSince the advent of the Next Generation Science Standards (NGSS), there has been an increasing focus on engineering in K–12 education. As educators and researchers have gained a better understanding of the nature of engineering in the decade following the release of the NGSS, there are new opportunities for growth and complexity.PurposeThis study used an epistemological approach to seek insights from experts in the science and engineering communities about the prominent aspects of engineering for K–12 education.Design/MethodThis mixed‐methods study employed a three‐round Delphi study and a focus group meeting to elicit experts' opinions on the epistemic aspects of engineering that could shed light on the nature of engineering knowledge and practices. Constructivist grounded theory methodology was used to identify preliminary themes concerning the epistemic aspects of engineering and then to develop main themes by combining relevant themes together.ResultsThe analysis process yielded 21 preliminary themes that reflect key ideas about the engineering knowledge base, engineering design activities, and values and norms of the engineering community. Additionally, the current study identified eight main themes that captured the broader patterns in the data.ConclusionsThe outcome of this study, including the preliminary themes and main themes concerning the epistemic aspects of engineering, could serve as a conceptual tool for establishing and improving students' conceptions of engineering and as a guide for designing and implementing engineering design activities in K–12 education settings.

A reliability analysis and optimization method for a turbine shaft under combined high and low cycle fatigue loading

AbstractThe combined high and low cycle fatigue (CCF) loading condition and random uncertainty exert a considerable impact on the design of turbine shafts. To enhance the fatigue life and reliability, this research proposes a CCF reliability analysis and optimization method for turbine shafts. A CCF fatigue reliability analysis framework is established, which focuses on the quantification of CCF loading characteristics and random uncertainty. The consideration of CCF loading characteristics contain the loading frequency ratio of high cycle fatigue (HCF) to low cycle fatigue (LCF), the stress amplitude ratio of HCF to LCF, as well as their interaction. The consideration of random uncertainty contains material, geometry and load, and a surrogate model‐based method is introduced to improve the quantification efficiency. Through the validation by comparing with experimental data and traditional methods, the proposed method is with higher accuracy and efficiency. By integrating the proposed fatigue reliability analysis method with design optimization, optimal design values for the turbine shaft were identified. This method theoretically extends the shaft's CCF life and provides practical engineering guidance for its reliability analysis and design.

Impact of hospital design on the psychological well-being of geriatric patients

PurposeThe study investigates the relationship between hospital environmental factors and the well-being of geriatric in-patients. It aims to identify the impact of architectural design on comfort, safety, privacy and stress levels experienced by elderly patients during their hospital stays.Design/methodology/approachEmploying a mixed-methods approach, the research assesses the experiences of 100 geriatric in-patients across various hospital types through surveys, observational checklists and state anxiety measurements. The methodology involves examining architectural features, patient perceptions and correlations among environmental variables and patient experiences. Statistical analyses, including correlations and chi-square tests, were employed to discern associations between environmental variables and patient experiences.FindingsThe research identified key architectural features significantly impacting geriatric patients' experiences. Factors such as sturdy beds, furniture quantity, lighting conditions, proximity to facilities and ward occupancy levels were found to influence spatial, sensory and social comfort. Notably, proximity to facilities and control over the immediate environment were crucial for self-control and safety perceptions. Privacy, highly valued by patients, correlated with the presence of curtains and ward occupancy. Moreover, patient stress levels exhibited correlations with autonomy, privacy and ward occupancy.Originality/valueThis research offers significant insights into the criticality of specific architectural elements in enhancing comfort and reducing stress for geriatric in-patients. These findings hold substantial value for healthcare facility design, emphasizing the need to prioritize certain design aspects to promote the well-being of elderly patients during hospitalization.

Serpentine spring design technique for high sensitivity MEMS capacitive accelerometer fabricated by gold multi-layer metal technology

This paper describes a design technique for serpentine spring with the edge span beam L/2. In order to improve design accuracy, we investigate the key structure parameters influenced by the fabrication process for MEMS device, comparing finite element analysis (FEA) and analytical models. It is found that the Fedder model as the analytical model is suitable for the spring constant characteristics of FEA with the edge span beam L/2. Further, the thickness and width are found to be the key structure parameters and the dominant factor of variation regarding the serpentine spring. Based on the analysis, we propose a spring design technique. The experimental results show that the variation between the measured data of 4.46 N m−1 and the design value of 4.15 N m−1 was 7.5%, satisfying the target of ±10%. It is confirmed that the proposed technique can establish the serpentine spring for high sensitivity gold proof-mass MEMS accelerometers.

Multidimensional analysis for the techno-economic study of the CSP plant

The profitability of a concentrated solar plant depends on the type of storage system and its daily operation. In addition, this profitability can be evaluated using different economical criteria such as the minimum time to recover the initial investment, the total profit at the end of the project and others. Given a solar field and a power block, the objective in this work is to determine an optimal design of the storage system for the concentrated solar plant. Two types of storage technology are considered, namely Thermochemical reactor or Two-tank molten salt system, two different production strategies, four different economical criteria and three price scenarios for the electricity market. And for each such combination (called profile), the model determines the optimal design of the concentrated solar plant. But, contrary to classical economical evaluation in literature, in this approach an optimal design consists of the optimal values of the physical design of the storage system but also the optimal operations of the plant (Production, Storage, Discharge). Thanks to this model and the results obtained, conditions can be exhibited under which thermochemical storage is economically more pertinent than Two-tank storage and also situations ensuring an economical equilibrium of the concentrated solar plant without subsidy.

Review of Using Shear Walls and Bracings for Seismic Strengthening of High-Rise RC Structures

This review explores the seismic resistance of high-rise buildings through the implementation of shear wall and steel bracing systems. The use of reinforced concrete (RC) buildings with shear wall systems and steel structures with concentrated steel bracing systems has become increasingly common to mitigate seismic effects. However, the response of these systems to seismic loads varies due to differences in structural design and response factor values. Additionally, the presence of asymmetrical building designs poses a potential risk during earthquakes, necessitating a thorough examination of both new and old structures. By analyzing the dynamic properties and influencing factors of irregular RCC buildings with shear walls, this research aims to assess the impact of shear walls on factors such as base shear, torsion, story displacement, and drift. Furthermore, the study investigates the effectiveness of steel bracing systems in enhancing the performance of high-rise buildings under wind and seismic loading conditions. Different bracing configurations are evaluated to determine their ability to reduce lateral displacements and improve structural strength and stiffness. The findings will provide valuable insights into optimizing the location and design of bracing systems for enhanced structural resilience against seismic and wind forces while considering both economic and effectiveness factors.

A simple direct current model for residual bond strength assessment of embedded rebars in thermally damaged concrete

Fire events are highly fatal to human lives and properties, and should be considered at structural design phases. Concrete structures are essentially fire resistant up to certain level, beyond that structural components would degrade away from their design values. Residual capacities of fire exposed structures should be properly assessed before strengthening tasks can be carried out. Among those, the residual bond strengths between reinforcing bars and concrete are of particular importance because they determine the mechanical performance of all reinforced concrete components. This study focused on proposing novel nondestructive approaches to assess the residual bond strengths after thermal exposures. Specifically, a simple direct current (DC) model was implemented to yield electrical resistivity indices that can closely reflect the bond strength degradations up to 400 ℃. DC polarization measurements were split into three phases through which each index induced the degradations differently. Capability and efficiency of the DC indices to assess residual bond strengths of thermally damaged concrete were analyzed and discussed. Results presented have suggested that the proposed DC approach performed better than using residual compressive strengths to assess residual bond strengths, and was more advantageous for its nondestructive features.