Conservative Predictions Research Articles

Study on Prediction of Energy Conservation and Carbon Reduction in Universities Based on Exponential Smoothing

With the continuous development of China’s economy, the phenomenon of energy scarcity has become more and more prominent, for which China has put forward the strategic goal of carbon peak and carbon neutrality (double carbon target). As densely populated areas, the demand for energy is especially tight in universities. In combination with the work of “conservation-oriented colleges” carried out by the Ministry of Education, the accurate monthly electrical and water energy consumption of Kunming University of Science and Technology from 2018–2021 was counted, and the data were plotted into an energy consumption analysis chart to determine its compliance with the prediction range of the smoothing index prediction model. The corresponding smoothing indices were calculated by writing smoothing formulas through Excel, and, finally, the overall energy consumption indexes for 2022 and 2023 were successfully predicted using the exponential smoothing method. The errors between the real and forecasted values of electricity and water consumption in 2021 are reduced to 2.61% and 2.44%. The smoothing index predicts that the baseline discounted electricity energy consumption in 2022 is 5,423,658.235 kgce and in 2023 is 5,758,865.224 kgce; on the other hand, the baseline discounted water energy consumption in 2022 is predicted to be 632,654.321 kgce, while in 2023 it is predicted to be 652,321.238 kgce. The projected values can be used as an early warning line for the energy consumption index, and long-term management approaches and data support for energy conservation and carbon emission reduction can be effectively provided. The mentioned research provides an important reference for the proposal and implementation of efficient management measures, and provides strong theoretical technical support for the implementation of the carbon peak and neutrality in universities.

Bayesian characterization of circumbinary sub-stellar objects with LISA

ABSTRACT The Laser Interferometer Space Antenna (LISA) will detect and characterize ∼104 Galactic Binaries, consisting predominantly of two white dwarfs (WDs). An interesting prospect within this population is a third object – another WD star, a circumbinary exoplanet (CBP), or a brown dwarf (BD) – in orbit about the inner WD pair. We present the first fully Bayesian detection and posterior analysis of substellar objects with LISA, focusing on the characterization of CBPs. We used an optimistic astrophysically motivated catalogue of these CBP third-body sources, including their orbital eccentricity around the inner binary for the first time. We examined Bayesian evidence computations for detectability, as well as the effects on the posterior distributions for both the inner binary parameters and the third-body parameters. We find that the posterior behaviour bifurcates based on whether the third-body period is above or below half the observation time. Additionally, we find that undetectable third-body sources can bias the inner binary parameters whether or not the correct template is used. We used the information retrieved from the study of the CBP population to make an initial conservative prediction for the number of detectable BD systems in the original catalogue. We end with commentary on the predicted qualitative effects on LISA global fitting and Galactic Binary population analysis. The procedure used in this work is generic and can be directly applied to other astrophysical effects expected within the Galactic Binary population.

Innovative compressive design resistance and behaviour of concrete-filled short columns with stiffened square steel sections

The concrete-filled tubular steel columns with stiffened steel sections, abbreviated as CFSST, have lower sensitivity to local buckling and higher confinement of the concrete core than standard concrete-filled tubes. Herein, available test results for CFSST short columns with a single stiffener or multiple stiffeners are collected from the literature. They are analysed and then a new power law formula for the lateral confining pressure (frp) is proposed. After that, the results provided by the formula are verified by simulating the behaviour of the available test specimens using ABAQUS finite element (FE) software. The results of the test and FE analyses reveal that the proposed frp formula performs well and it is used further in the parametric studies on the strength and behaviour of CFSST columns, namely the effect of (i) the plate slenderness ratio, (ii) the steel yield strength, (iii) the concrete cylindrical strength and (iv) the number of stiffeners and their depth. Increasing the concrete cylindrical strength is found to provide the largest increase in the strength of the columns compared to other parameters, although it reduces the ductility of the columns. In addition, the resistance values for the CFSST columns are calculated on the basis of Japanese, British, European and Chinese structural standards for comparison with the values obtained numerically. Because these standards provide conservative predictions, an innovative design formula is suggested for CFSST columns based on the analytical expression developed for the lateral confining pressure. The new design formula yields much better predictions than the formulae in the existing structural standards.

Integrating operating conditions to develop a neural network for predicting organics removal and power density in an earthen microbial fuel cell treating leachate

Nowadays, the acceptability of artificial neural networks (ANNs) to develop models for biological treatment systems has been broadened instead of the complex mechanistic mathematical model. The present study attempts to train neural networks to predict organics removal and power output from an earthen microbial fuel cell treating acidogenic leachate obtained from kitchen waste. To model the effluent chemical oxygen demand (COD) and volatile fatty acid (VFA) values and power density, the study used four input parameters: influent COD, and VFA, hydraulic retention time, and anode electrode surface area. Among the multiple algorithms employed, the Bayesian inference proved to deliver a winning model to forecast the response variable with an overall high coefficient of determination of 0.9890. This high correlation for a biological system employing a real substrate, i.e. leachate, ensures the model’s reproducibility and adequacy. Additionally, the statistical error criteria for model efficacy showed acceptable values. Besides, the study performs validation runs with an error of approx. 11% with conservative predictions. Ultimately, the ANN model fared well in predicting the response for effluent COD and power output when compared with kinetic study (Han-Levenspiel) and statistical equation (from ANOVA) to the experimental values.

Strength of Partially Encased Steel-Concrete Composite Column for Modular Building Structures.

Modular structural systems have been used increasingly for low- and mid-rise structures such as schools and apartment buildings, and applications are extending to high-rise buildings. To provide sufficient resistance and economical construction of the high-rise modular structural system, the steel-concrete composite unit modular structure was proposed. The proposed composite unit modular system consists of the composite beam and the partially encased nonsymmetrical composite column. The outside steel member of the composite column has an open section, and is manufactured using a pressed forming procedure so that easy joining connecting work and manufacturing cost reductions are possible. However, the design methods are complicated due to the inherent nonsymmetrical properties of the section. Therefore, in this study, the focus was made on the strength evaluation and development of design methods for the partially encased nonsymmetrical steel-concrete composite column. Four full-scale specimens were constructed and tested. The experimental study focused on the effect of the slenderness ratio of the column, eccentricity, and the through bars on the strength of such columns. Additionally, the P–M interaction curve to estimate the strength of the proposed composite column under general combined loading was developed based on the plastic stress distribution method. The results indicate that the through bars are needed to delay the local buckling and distribute the loading uniformly throughout the composite column. Finally, the proposed design methods provide a conservative strength prediction of the proposed composite column.

PARAMETRIC STUDY IN SHEAR BUCKLING CAPACITY OF SINUSOIDAL CORRUGATED STEEL WEB

Sinusoidal corrugated steel web has gradually gained attention over trapezoidal corrugated steel web. The design of shear buckling capacity for the trapezoidal corrugated web is governed by interactive buckling which normally has the lowest value among global, local and interactive failures. It was discovered in some studies that the shear buckling in a sinusoidal section is found to be governed by either local or global failures, where there is a lack of study in this area. The purpose of this study is to determine the effect of web thickness, web height, and sinusoidal radius on the shear buckling capacity and buckling mode in the sinusoidal corrugated steel web. Finite element analysis was conducted on 150 specimens with different radius of sinusoidal corrugated web, web height and web thickness to investigate their influence to the shear buckling capacity of the sections. The result shows that the increase in web thickness has been shown to increase the shear buckling capacity linearly. The increase in web height and radius of corrugated web reduce the shear buckling capacity of the beam exponentially. The results from finite element analysis are compared with an analytical equation from existing literature. It is found that the equation gives a conservative prediction of the shear capacity, however, could be used for a radius greater than 150 mm

Experimental and numerical studies on post-fire behaviour of S700 high strength steel circular hollow sections under combined compression and bending

The present paper reports experimental and numerical investigations into the post-fire local buckling behaviour and residual resistances of S700 high strength steel circular hollow sections (CHS) under combined compression and bending. A testing programme was firstly conducted and included heating and cooling of specimens as well as post-fire material tensile coupon tests and eccentrically loaded stub column tests. Following the testing programme, a numerical modelling programme was carried out, where finite element models were developed to replicate the test results and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and loading combinations. Due to the absence of design standards for high strength steel structures after exposure to fire, the codified ambient temperature design interaction curves for high strength steel CHS under combined compression and bending were assessed, using post-fire material properties, for their applicability to post-fire S700 high strength steel CHS. The assessment results revealed that the design interaction curves in the European code and American specification yield a satisfactory level of accuracy and consistency when used for post-fire S700 high strength steel CHS, while the design interaction curves in the Australian standard provide slightly conservative residual resistance predictions.

Experimental and numerical investigations of S960 ultra-high strength steel slender welded I-section columns failing by local–flexural interactive buckling

The present paper reports experimental and numerical investigations into the local–flexural interactive buckling behaviour and resistance of S960 ultra-high strength steel slender welded I-section columns. A testing programme was firstly conducted and included initial geometric imperfection measurements and ten pin-ended column tests. The pin-ended column test setup, procedures and results were fully reported and analysed. The progression of local buckling and flexural buckling was discussed. Following the testing programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test structural responses and then employed to perform parametric studies to generate further numerical data. It is worth noting that the current European code and American specification are only applicable to steel structures with material yield strengths up to 700 MPa (or 690 MPa). Regarding the design of slender welded I-section columns failing by local–flexural interactive buckling, both codes adopt the same concept — combined use of effective width method to account for local buckling and buckling curve to account for flexural buckling. The obtained test and numerical data were employed to assess the applicability of the codified design rules to S960 ultra-high strength steel slender welded I-section columns. The assessment results revealed that the European code leads to conservative interactive buckling resistance predictions, mainly due to the use of conservative buckling curve, while the American specification yields a good level of design accuracy and consistency. Finally, a revised Eurocode design approach was proposed and shown to result in more accurate and consistent interactive buckling resistance predictions for S960 ultra-high strength steel slender welded I-section columns.

Cold-formed ferritic stainless steel SHS and RHS beams: Testing, modeling and design

Ferritic stainless steel is characterized by its low or even no nickel content and has relatively lower material cost than austenitic and duplex stainless steel. It may offer a viable alternative in structural applications. In this study, a series of four-point bending tests was firstly carried out on cold-formed ferritic stainless steel (CFFSS) square and rectangular hollow sections (SHS and RHS) to investigate the flexural performance of the tubular section beams. A finite element model was then developed for CFFSS tubular beams. The model was shown capable of predicting the flexural behavior of the beams and therefore an extensive parametric study was undertaken to generate more data over larger ranges of key parameters of the CFFSS sections. The experimental and numerical results as well as the available data on CFFSS SHS and RHS beams were employed to assess the slenderness limits as well as to evaluate the moment capacities predicted by various design provisions such as the American Specification, Australian/New Zealand Standard, European Code, direct strength method and continuous strength method for cold-formed stainless steel beams. It is shown that the current design methods provided quite conservative predictions on the moment capacities of the CFFSS flexural members. Reliability analyses were undertaken and appropriate design rules for CFFSS SHS and RHS beams were suggested in this study.

Behaviour and design of cold-formed normal- and high-strength steel SHS and RHS columns at elevated temperatures

The behaviour of cold-formed normal- and high-strength steel columns with square and rectangular hollow sections (SHSs and RHSs) at elevated temperatures was investigated numerically in this paper. A finite element model was developed and validated against experimental results for the cold-formed steel SHS and RHS stub and long columns tested at ambient and elevated temperatures. Parametric studies were subsequently conduced on cold-formed normal- and high-strength steel SHS and RHS columns with various cross-section slenderness and member slenderness at elevated temperatures ranging from ambient to 800 °C. Based on the numerical results and experimental results reported in literature, the applicability of existing design approaches in European and North American standards to the columns at elevated temperatures was evaluated. The evaluation shows that the approaches in standards provide quite conservative strength predictions for the cold-formed normal- and high-strength steel SHS and RHS columns at elevated temperatures except for the overestimation of cross-sectional resistance obtained based on the North American standard. Modified design approaches were proposed to improve the accuracy of strength predictions and can be safely applied to generate designs for the columns under various elevated temperatures.

Numerical and simplified analytical investigation on RC frame behaviours under progressive collapse scenarios

Although progressive collapse research has been extensively carried out for more than two decades after from the tragic events of 9/11, not many actual dynamic experiments have been conducted due to the constraint in laboratory facilities and expense. Instead, numerical and simplified analytical studies were preferred to achieve a comprehensive understanding of the structural behaviour against these rare dynamic events. In this research, a numerical and analytical investigation programme is carried out to study the mobilisation of alternate-load-path mechanisms, such as compressive arch or catenary action, in RC beam-column substructures undergoing missing column scenarios. First, a physics-based finite element modelling is developed and validated with two published test series conducted under quasi-static and free-fall dynamic conditions. These tests concentrated on 2D reinforced concrete sub-frame structures, investigating two column-loss scenarios, i.e. internal and penultimate columns. After being validated, the model is then employed to further investigate important parameters which can significantly affect the behaviour of a 2D frame structure under both static and dynamic environments, such as concrete grade, release time, column pre-loaded force, etc. Thereafter, a simplified analysis using an equivalent SDOF system is developed to provide a convenient tool for assessing dynamic capacities of RC frame structures. The simplified method produces conservative predictions compared to actual tests and detailed numerical analyses, however it requires very little computing time.

Study of local buckling performance of 7075-T6 high-strength aluminium alloy H-section stub columns

The local buckling performance of 7075-T6 high-strength aluminium alloy extruded H-section stub columns are investigated in this paper. Seven H-section stub column tests were carried out, in which the material properties, initial geometric imperfections, failure modes, critical local buckling strengths and load carrying capacities of specimens are all reported. Then the finite element (FE) models were developed and validated against the test results. Upon validation, a thorough parametric study was conducted to obtain further data over a large range of cross-sections. Afterwards, on the basis of test results and FE data, provisions in the current design standards, GB 50429 (Chinese), EN 1999-1-1:2007 (European) and AADM 2015 (American) were evaluated. The design codes showed conservative strength predictions, especially for stub columns with large cross-section slenderness. A modified DSM design approach was proposed for 7075-T6 H-section stub columns, and the reliability analysis was performed to confirm the applicability of the proposed modified DSM approach.

Experimental Study on the Seismic Behavior of Squat SRC Shear Walls with High Axial Load Ratio

This paper aims to study the seismic behavior of squat steel-reinforced concrete (SRC) shear walls with a high axial load ratio. Nine squat SRC shear walls with varying axial load ratios, steel ratios, and horizontal distributed reinforcement ratios were tested under lateral cyclic reversed loading and an axial load. The failure process, load-deformation hysteretic response, shear strength, ductility, and the strain of the specimens are reported. The results show that all the specimens failed in shear with the crushing of the web concrete. No axial failure occurred after the web concrete was crushed since the boundary elements encased with structural steel sections maintained the axial load. Larger steel ratios reduced the buckling degree of the structural steel. A larger horizontal distributed reinforcement ratio was clearly beneficial for the ductility and energy dissipation capacity of the specimen, while it had a negligible effect on the shear strength. The Chinese code provided an extremely conservative prediction of the shear strength of the tested squat SRC shear walls with a mean calculated-experimental strength ratio of 0.42. An improved formula was established mainly by the modification of the shear resistance contributed by the concrete and the structural steel, leading to a mean calculated-experimental strength ratio of 0.74. More experimental data are still needed to establish more accurate deformation acceptance criteria for SRC shear walls and to promote the performance-based seismic evaluation of SRC structures.

Compression behaviours of aluminium alloy I-column at low temperatures

Aluminium alloys have been used in cold-region engineering constructions. To make more comprehensive understandings of aluminium material properties and structural behaviours at cold-region low temperatures (T), mechanical properties of aluminium alloy 6061-T6 at different T of −80 – 20 °C were investigated through tensile coupon tests. Then, seven aluminium alloy 6061-T6 I-columns were tested under axial compression and different T of 20, −30, −60, and −80 °C. The failure modes, load-shortening/strain behaviours of aluminium I-columns under low-temperature compression were detailed studied. These tests showed that the decreasing T increased the yield/ultimate strength of aluminium alloy 6061-T6 by 10%, and also increased the axial ultimate compression resistance (Pu) of I-column by 7% without reductions in their ductility. Finite element models (FEMs) were also developed by ABAQUS for simulating structural behaviours of aluminium I-columns using the obtained low-temperature material properties. Validations of FEM simulations showed its reasonable simulations on compression behaviours of aluminium I-columns. The code equations in Chinese code GB 50429 and Eurocode 9 were also checked to estimate Pu of aluminium I-columns at low temperatures. It shows that both codes provided conservative predictions on Pu of aluminium I-columns at low temperatures.

Redshift factor and the small mass-ratio limit in binary black hole simulations

We present a calculation of the Detweiler redshift factor in binary black hole simulations based on its relation to the surface gravity. The redshift factor has far-reaching applications in analytic approximations, gravitational self-force calculations, and conservative two-body dynamics. By specializing to nonspinning, quasicircular binaries with mass ratios ranging from ${m}_{A}/{m}_{B}=1$ to ${m}_{A}/{m}_{B}=9.5$ we are able to recover the leading small-mass-ratio (SMR) prediction with relative differences of order ${10}^{\ensuremath{-}5}$ from simulations alone. The next-to-leading order term that we extract agrees with the SMR prediction arising from self-force calculations, with differences of a few percent. These deviations from the first-order conservative prediction are consistent with nonadiabatic effects that can be accommodated in an SMR expansion. This fact is also supported by a comparison to the conservative post-Newtonian prediction of the redshifts. For the individual redshifts, a reexpansion in terms of the symmetric mass ratio $\ensuremath{\nu}$ does not improve the convergence of the series. However we find that when looking at the sum of the redshift factors of both back holes, ${z}_{A}+{z}_{B}$, which is symmetric under the exchange of the masses, a reexpansion in $\ensuremath{\nu}$ accelerates its convergence. Our work provides further evidence of the surprising effectiveness of SMR approximations in modeling even comparable mass binary black holes.

Experimental and Numerical Study of Press-Braked S690 High-Strength Steel Channel–Section Columns Failing by Minor-Axis Flexural Buckling

This paper reports an experimental and numerical investigation into the minor-axis flexural buckling behavior and capacity of press-braked S690 high-strength steel channel–section columns. The experimental investigation comprised initial geometric imperfection measurements and 10 pin-ended column tests. This was accompanied by a numerical modeling program, in which finite-element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. The obtained test and numerical data were adopted to assess the accuracy of the buckling curves, as given in the Eurocode, North American specification, and Australian/New Zealand standard, for press-braked S690 high-strength steel channel–section columns prone to minor-axis flexural buckling. Overall, it was found that the Eurocode buckling curve yields many conservative capacity predictions, whereas the buckling curves in the North American specification and the Australian/New Zealand standard lead to an overall good degree of design accuracy. A revised Eurocode buckling curve is proposed, and was shown to offer accurate capacity predictions for press-braked S690 high-strength steel channel–section columns prone to minor-axis flexural buckling.

Influence of mechanical characterization on the prediction of necking issues during sheet flow forming process

Flow forming is an incremental sheet forming (ISF) process during which a sheet metal is compressed and stretched multiple times by means of one or multiple rotating roller tools. The local tool-workpiece contact zone evolves during the entire process. The necking phenomenon, which corresponds to an uncontrolled thinning of the part wall, is introduced. This phenomenon represents a major issue for ISF processes. A review of the state-of-the-art about ISF processes shows that most studies do not consider the loading path complexity when choosing the mechanical characterization test and its associated constitutive model. Besides, the prediction of necking occurring during sheet flow forming is poorly studied in the literature. In this paper, a finite element analysis (FEA) using the FORGE® software enables a detailed understanding of the loading path (strain and stress states) prevailing during the flow forming operation. Based on the peculiarities of this loading path, different mechanical tests associated with adequate constitutive models are chosen to characterize the material behavior. The ability of each constitutive model used within the FE approach to predict necking is then assessed. Results show that the best prediction of a geometry exhibiting necking issues is obtained with the cyclic in-plane torsion test (ITT) associated with its calibrated isotropic – kinematic hardening model. These results suggest that the behavior characterization under cyclic shear loadings is relevant. Using a simple tensile test with associated power-law provides a faster and conservative necking prediction.

How Is Professional Identity Associated with Teacher Career Satisfaction? A Cross-Sectional Design to Test the Multiple Mediating Roles of Psychological Empowerment and Work Engagement.

(1) Purpose: Previous studies investigated the positive relationship between professional identity and career satisfaction in teachers, but the underlying reasons were not explored. Therefore, the present study explores the mediating effects of two variables, namely, psychological empowerment and work engagement on the relationship between professional identity and career satisfaction. (2) Method: The present study used the professional identity scale, psychological empowerment scale, Utrecht Work Engagement scale and career satisfaction scale to investigate 2104 teachers (Mage = 39.50 years, SD = 8.74) in a province in China. The demographic variables (e.g., gender, age, teaching age) were controlled as covariates to conduct conservative predictions. (3) Result: (a) professional identity is positively related to career satisfaction; (b) psychological empowerment and career satisfaction play parallel mediator roles between professional identity and career satisfaction; (c) psychological empowerment and career satisfaction play serial mediator roles between professional identity and career satisfaction. (4) Limitations: Data were collected by participant self-report. This method may lead to recall bias. Further, we adopted a cross-sectional rather than experimental or longitudinal design, thus precluding causal conclusions. Lastly, it would be useful to validate our findings with a national sample. (5) Conclusions: The present study indicates that the relationship between professional identity is positively associated with teacher career satisfaction. More importantly, professional identity can indirectly make an impact on teacher career satisfaction through the single mediating effects of psychological empowerment and work engagement, and the chain mediating effect, by improving the level of psychological empowerment, and thereby increasing work engagement.

Derivation of a normalised failure surface for square CECFST columns embedded with circular steel tube: A unified approach

Concrete-Encased Concrete-Filled Steel Tube (CECFST) columns are a new type of composite columns that possess great strength, stiffness, ductility, corrosion and fire resistance. To fully realise their benefits, an accurate design approach of calculating the strength of these members is necessary. In this paper, the plastic stress distribution (PSD) and load contour (LC) methods in the design code of predicting the cross-section strength of CECFST columns is first evaluated through numerical and published experimental data. Considering the shortcomings of conventional design methods, a unified design approach is then developed. Compared to the conventional PSD method, the developed method can yield conservative resistance predictions for uniaxial eccentric loaded (UEL) CECFST columns. In addition, instead of using linear moment interaction curves to predict the strength of biaxial eccentric loaded (BEL) CECFST columns, elliptical moment interaction curves are adopted in the proposed design approach. Most importantly, a normalised 3D axial-load–biaxial-moment (n–my–mz) interaction surface can be generated through the proposed method, which only requires determining 6 critical points on the interaction surface. Unlike the conventional design approach, in which the UEL and BEL composite columns need to be respectively designed through PSD and LC methods, a unified design procedure can be achieved through the proposed approach. Besides, the confinement effect from both the steel tube and the stirrups can also be considered in the proposed approach and much higher accuracy and consistency can be achieved in predicting the cross-section strength of CECFST columns.

Flexural buckling of extruded high-strength aluminium alloy SHS columns

The structural performance and design of extruded high-strength aluminium alloy square hollow section (SHS) columns were presented in this paper. A total of 12 extruded 7A04-T6 aluminium alloy SHS column specimens were tested under axial compression, together with tensile coupon tests and initial global geometric imperfection measurements. The flexural buckling failure mode and axial load versus end shortening and mid-height lateral deflection curves were reported. Based on validated finite element (FE) models, 480 numerical results were generated by means of parametric studies over a broad range of cross-section dimensions, member lengths, proof strengths and strain hardening exponents of the aluminium alloy material. The applicability of current design rules used for normal-strength aluminium alloy columns in European, Chinese and American standards to extruded 7A04-T6 high-strength aluminium alloy SHS columns was evaluated through comparisons with the test and FE results. The analysis results showed that the three standards consistently yielded conservative axial compression resistance predictions by about 9% for extruded 7A04-T6 high-strength aluminium alloy SHS columns. New flexural buckling curves with linear and nonlinear imperfection terms for the Chinese code, as well as modifications to the American specification, were separately proposed, resulting in improved accuracy with significantly reduced scatter. Additionally, the continuous strength method (CSM) was further extended for the flexural buckling design of extruded 7A04-T6 high-strength aluminium alloy SHS columns, and was shown to provide accurate and consistent resistance predictions. Reliability analyses of the codified and the proposed design methods were performed, confirming that the design proposals meet the target reliability indices except the Eurocode approach.