Simple Model Calculations Research Articles

Seismic mitigation performance evaluation of linked buildings with a vibration-suppression layer

Linked buildings (LBs) have been widely used in urban areas because of their aesthetic quality and versatility. As LBs are vulnerable to damage under earthquake excitation, undesired vibrations should be suppressed. The use of weak connections is an effective approach to improve the seismic performance of LBs; however, they are inapplicable to LBs with inherently strong connections. In this study, a novel control system—a LB with a vibration-suppression layer (LBVSL)—is proposed to reduce the seismic responses of the LBs with strong connections. The LBVSL system is implemented by introducing a vibration-suppression system into one of the buildings. To extensively investigate the seismic mitigation performance of the LBVSL, a parametric study is conducted to evaluate the trends of its mean vibration energy with the control and structural parameters based on a simplified calculation model. The control parameters include the equivalent stiffness and damping of the vibration-suppression system, and the structural parameters include the stiffness and mass of the LBs. To understand the damping effect of the LBVSL, several numerical examples are studied. The analytical results suggest that the LBVSL has substantially reduced vibration energy and responses compared to the plain LBs. For instance, the LBVSL with the optimal parameters achieves a vibration energy reduction of 69% and a stochastic seismic response decrease of 30–50% relative to those of plain LBs. Additionally, the LBVSL achieves better damping performance and robustness when the vibration-suppression layer is placed on a lower floor. Furthermore, the simplified model provides an alternative for effectively optimizing critical parameters in the preliminary design stage.

A study on optimal rotor speed control method for helicopter power system considering the influence of infrared suppressors

Abstract In order to realize the most economical operation of helicopter power system, the optimal rotor speed control method is proposed and designed. Firstly, the simplified performance calculation model of helicopter required power and turboshaft engine are established, which constitute the performance calculation model of helicopter power system together. Then, according to the above model, through applying blade loading constraint and selecting the minimum engine fuel flow as the optimization objective, an integrated optimization method of optimal rotor speed based on golden section method is proposed, which reveals the variation law of optimal rotor speed under different operation conditions. Finally, the numerical simulation and hardware-in-loop (HIL) simulation are conducted separately to validate the optimal rotor speed control method. The results indicate that compared with constant rotor speed operation, optimal rotor speed control method can decrease engine fuel flow by more than 21 %, which proves the significant effectiveness and satisfactory feasibility. The optimal rotor speed control method ensures that the helicopter power system operates at the optimal rotor speed, and is beneficial to reach the most economical cruise target.

Simplified Calculation Model and Experimental Validation of the Force Transfer Ratio of Steel-Concrete Joint of Hybrid Box Girder.

The axial force transfer ratio of steel-concrete joints in hybrid box girder bridges is crucial for bridge design. However, the current standard oversimplifies the transfer ratio distribution coefficients, and both model tests and finite element analysis are time- and labor-intensive. This article proposes a simplified calculation model based on the deformation coordination theory to estimate the transfer ratio of the axial force between the bearing plate and shear connectors of the steel-concrete joint under compression bending conditions. Additionally, a large-scale model (1/5 scale) is established, and the mechanical properties of the steel-concrete joint section under compression-bending conditions are experimentally tested. A three-dimensional finite element model is developed and verified using the obtained test data. Results confirm the favorable mechanical properties and ample safety reserve of the SCJ, with all components remaining within the elastic stage under 1.6 times design conditions. By comparing the axial force transfer ratios obtained from the simplified calculation model and the finite element model, a small difference is observed, validating the reliability of the simplified calculation model. This paper provides a straightforward and efficient method for the design and evaluation of steel-concrete joints in hybrid box girder bridges.

Determining the optimum span of a solar greenhouse

The span of a solar greenhouse is a crucial parameter determining its architectural space form characteristics, which in turn directly influences the passive solar energy utilization and light-heat environment within the greenhouse. As a result, building on prior research concerning the optimal orientation and height-span ratio of solar greenhouses, this study delves into the key factors affecting the optimal span and its evaluation indices. Global solar radiation is broken down into direct radiation and diffuse radiation, both of which serve as input parameters for Energy Plus weather files. Additionally, the soil temperature calculation model within a solar greenhouse is employed as the input condition for “Ground temperature” boundary conditions in Energy Plus. The field test demonstrates the efficacy of the Energy Plus model. Taking the calculation results into account, this research provides a comprehensive analysis of the impact of outdoor air temperature, solar radiation, north wall height, heat storage capacity, and soil temperature inside the greenhouse on the thermal environment when the span is altered. A simplified calculation model for determining the optimal span of solar greenhouses across various latitudes in China is proposed based on the optimal span evaluation index. Field tests confirm the effectiveness of this calculation model. This study enhances the design and calculation methods for optimal space form characteristic parameters of solar greenhouses. Furthermore, it offers an analytical method reference for the optimal design of solar greenhouses, efficient construction of thermal environments, and intelligent management and control.

Modified Fermi's golden rule rate expressions.

Fermi's golden rule (FGR) serves as the basis for many expressions of spectroscopic observables and quantum transition rates. The utility of FGR has been demonstrated through decades of experimental confirmation. However, there still remain important cases where the evaluation of a FGR rate is ambiguous or ill-defined. Examples are cases where the rate has divergent terms due to the sparsity in the density of final states or time dependent fluctuations of system Hamiltonians. Strictly speaking, assumptions of FGR are no longer valid for such cases. However, it is still possible to define modified FGR rate expressions that are useful as effective rates. The resulting modified FGR rate expressions resolve a long standing ambiguity often encountered in using FGR and offer more reliable ways to model general rate processes. Simple model calculations illustrate the utility and implications of new rate expressions.

Investigation into the operation of an autothermal two-section subbituminous coal fluidized bed gasifier

Using a newly developed experimental setup, the features and advantages of an autothermal single-casing atmospheric subbituminous coal fluidized bed air-blown gasifier, combining a combustion and gasification section, and mixing the dispersed phase (inert material, char) and heat exchange between them through an annular transfer device, have been revealed. To increase the efficiency of the gasifier, an experimental-computational method was developed find the conditions for optimal operation, combining changing the annular flow’s geometry and regulating the primary air for gasification. A simple and reliable multizone thermodynamic calculation model makes it possible to predict the composition of char and syngas in the gasification section with acceptable accuracy. This method confirmed that a two-section fluidized bed gasifier can provide efficient gasification of solid fuels and is suitable for use in small-scale cogeneration plants. Syngas with a heating value of 3.6–4.5 MJ/m3 and CGE of 38.2%–42.3% was obtained in the experimental setup without optimizing the primary air flow rate. With optimization, the indicators increased to the heating value of syngas of 5.20–5.34 MJ/m3 and CGE of 42.5%–50.0%. With heat regeneration of 0.8, CGE increases to 70%.

Analysis of the impact of groundwater-level decrease caused by drainage on tunnel water inflow

Affected by excavation, the phenomenon of groundwater-level drop around mountain tunnels is widespread, resulting in poor accuracy of the existing water-inflow calculation formula derived when the groundwater level is fixed. Based on this, a simplified calculation model of tunnel water inflow is constructed that considers drainage; and the tunnel water inflow is calculated according to the Dupuit assumption and conformal transformation. The law of conservation of fluid mass is used to solve the equivalent water head around the tunnel after drainage and the Taylor formula is used for degradation analysis, and the rationality of the model construction and the correctness of the formula derivation are verified through the tunnel under construction and numerical simulation. Finally, the sensitivity of the characteristic parameters is studied, the evolution law of the equivalent head is revealed and the influence mechanism is discussed. The research shows that the error between the calculated value of tunnel water inflow and the field measured value can be reduced from 16.1 to 8.9%, which improves the prediction accuracy of tunnel water inflow to a certain extent.

Parameter optimization strategy of LLC converter soft start-up process based on a simplified numerical calculation model

High-frequency start-up strategy is usually used to limit the current overshoot in the resonant tank of LLC converter. However, the strong coupling among start-up frequency, initial duty cycle, and current limit increases the design complexity of parameters. This paper proposes a parameter optimization strategy of the LLC converter soft start-up process based on the numerical calculation method. With this strategy, the initial switching frequency and duty cycle are determined adaptively according to the given maximum current requirements during the start-up process. The current overshoot is suppressed and soft switching is achieved in the whole process. After the second switching period, 50% duty cycle operation occurs without oscillation. Furthermore, exponential frequency reduction is used in the process, and the current overshoot limiting condition in the initial period is discussed. Finally, a 240 W LLC converter prototype is built to verify the correctness of the theoretical analysis in this paper. In terms of current limiting, soft switching, and initial switching frequency, the comprehensive performance of the soft start-up control strategy proposed in this paper is better. Compared to the traditional control strategy, the current overshoot is reduced by 45.6%. The theoretical calculation, simulation, and experimental results are consistent.

A method for power flow calculation and optimal dispatch of gas–thermal–electricity multi energy system considering unit commitment

The optimal scheduling of integrated energy system considering unit commitment is a mixed integer nonlinear programming (MINLP) problem with 0-1 binary variables, and the efficient solution of MINLP has always been a research hotspot. In this paper, a power flow calculation method of gas thermal power multi energy coupling system is proposed. Considering the output of coal-fired, gas-fired and new energy units, a simplified unit commitment calculation model is established, which can greatly reduce the number of binary variables and constraints. At the same time, an optimal scheduling model with minimum economic cost and minimum carbon emission is established. For the nonlinear and non convex problem of air pressure equations, the incremental piecewise linearization method based on the idea of feasible region segmentation is used to transform it into MILP model, and the effective optimal solution is obtained. Finally, an example is given to verify the effectiveness and accuracy of the proposed algorithm.

Reduction of the Longitudinal Seismic Response of High-Speed Railway Multi-Span Simply-Supported Bridges by the Track Constraint

ABSTRACT The longitudinal seismic response reduction in railway bridges is worthy of attention because it relates to the engineering cost. It is difficult to further explore the reduction effect because the complexity of traditional analysis model leads to the low efficiency in parametric analysis. In this paper, the track structure was simplified, and a simplified calculation model was established. The parametric analysis considering the span number and pier height on the simplified model seismic responses was carried out. The results showed that the reduction effect was extensive and there was a great internal force transferred to the subgrade-track structure.

Steel fiber reinforced concrete beams with predetermined failure surface and no stirrups

This paper treats an experimental study of shear problems in steel fiber reinforced concrete beams without shear reinforcement, where a specific groove in the shear span is used to specify the location of diagonal cracks, aiming to reduce the arch effect, controlling the critical crack inclination at 30°, and evaluating the assertiveness of the normative shear strength predictions. The experimental program includes four (4) beams, varying the steel fiber ratio. The results showed that the mechanism was satisfactorily induced shear failure, as expected. Also, it was observed that the ratio av/d did not influence the proposed model significantly, such behavior was expected because the shear cracks observed in the beams were more pronounced after distance av/4, making the arching action and dowel action less effective in the ultimate shear strength value. The proposed model excelled in the accuracy of the normative predictions, with a coefficient of variability between 4 and 8 %, probably to eliminate any arch effect for the ratio av/d = 1.86. However, a simplified calculation model based on the fiber residual stress distribution along the considered inclined section was proposed, and it was noted that the proposal presented better results, with an average value of 1.0 and a coefficient of variation (CoV) of only 3 %. It also showed a mean of 1.02 and a CoV of 8 % compared to the experimental results from the literature. Thus, the proposed predetermined shear failure surface and the calculation model are viable alternatives to evaluate estimates for shear resistance even with shear reinforcement or steel fibers.

Substructure Pseudo-Dynamic Test Study for a Structure Including Soil–Pile–Structure Dynamic Interaction

An improved Penzien model is proposed in this paper as a simplified model of soil–pile–structure interaction. The dynamic nonlinearity of soil under earthquake excitation is simulated by ANSYS in a free-field model and added to the original Penzien model. The improved Penzien model uses the finite element software ANSYS 2021 to simulate the dynamic nonlinearity of soil. The improved Penzien model is then used as a simplified calculation model of the numerical substructure. A substructure pseudo-dynamic test based on the improved Penzien model is carried out. The realization of the substructure pseudo-dynamic test verifies the feasibility and effectiveness of this method, which provides a convenient test method for the study of soil–pile–structure interaction in general laboratories. Soil and structure interaction reduces the acceleration of the structure, and the response exhibited a hysteresis phenomenon because of the nonlinear characteristics of the soil. The influences of soil–pile–structure interaction on velocity and displacement are very complex. The conclusions are reasonable, which proves that the substructure pseudo-dynamic test method of soil–pile–structure dynamic interaction using the improved Penzien model is feasible.

Simulation Study on Stability of Half-Through Steel Truss Girder

In order to discuss and analyze the simplified calculation model and influence factors of external stability of half-through steel truss girder. 56 m half-through railway steel truss girder was set as a study object. Its 3-D whole model was build with finite element software ANSYS. The linear stability coefficient and the buckling mode under different load conditions were analyzed. The results show: The buckling curves under all conditions present as that external buckling of upper chord. According to the structural features and buckling features of half-through steel truss girder, the whole model was simplified as plane model. It was composed of semi-frame and upper chord with lateral elastic bearings, and the calculating steps in external stability analysis are given. On the basis of simple plane model, the parameter effect analysis of external stability of half-through steel truss girder was conducted with finite element method. The influence law of the high, the width of main truss and area of wind brace on lateral displacement of semi-frame, lateral stiffness of upper chord and overall structural stability coefficient. The results show: increasing the high of main truss, decreasing the width of main truss and installing wind brace all can effectively improved stability.

A methodology for data-driven modeling and prediction of the drag losses of wet clutches

AbstractIn wet clutches, load-independent drag losses occur in the disengaged state and under differential speed due to fluid shearing. The drag torque of a wet clutch can be determined accurately and reliably by means of costly and time-consuming measurements. As an alternative, the drag losses can already be precisely calculated in the early development phase using computing-intensive CFD models. In contrast, simple analytical calculation models allow a rough but non-time-consuming estimation. Therefore, the aim of this study was to develop a methodology that can be used to build a data-driven model for the prediction of the drag losses of wet clutches with low computational effort and, at the same time, sufficient accuracy under consideration of a high number of influencing parameters. For building the model, we use supervised machine learning algorithms. The methodology covers all relevant steps, from data generation to the validated prediction model as well as its usage. The methodology comprises six main steps. In Step 1, the data is generated on a suitable test rig. In Step 2, characteristic values of each measurement are evaluated to quantify the drag loss behavior. The characteristic values serve as target values to train the model. In Step 3, the structure and quality of the dataset are analyzed and, subsequently, the model input parameters are defined. In Step 4, the relationships between the investigated influencing parameters (model input) and the characteristic values (model output) are determined. Symbolic regression and Gaussian process regression have both been proven to be suitable for this task. Lastly, the model is used in Step 5 to predict the characteristic values. Based on the predictions, the drag torque can be predicted as a function of differential speed in Step 6, using an approximation function. The model allows a user-oriented prediction of the drag torque even for a high number of parameters with low computational effort and sufficient accuracy at the same time.

Design of multi-cell T-shaped concrete-filled steel tubular columns under compression and bending

To date, a number of studies have been done on the calculation methods for predicting bearing capacities of multi-cell special-shaped concrete-filled steel tubular (MS-CFST) columns under axial, pure bending, and eccentric load. However, most of the existing methods only apply to a specific combination form of cross-section and have not been established in a unified formulation. In this study, finite element (FE) models were established to predict the performances of the four common combination forms of multi-cell T-shaped concrete-filled steel tubular (MT-CFST) sections subjected to axial, eccentric, and pure bending loads, and verified with the available test data. The parametric analyses were conducted to investigate the effects of steel thickness t, concrete strength fck, steel yield strength fy, aspect ratio of the web c/b, and slenderness ratio λ on the flexural and eccentric compressive performance based on the FE models. The study results demonstrated that the four common combination forms of MT-CFST sections showed the same changing trends of flexural capacity with different parameters, and the flexural capacity rose almost linearly with the increase of the parameters. The parameters (t, fy, fck, c/b, and λ) had a definite effect on the N/Nu-M/Mu correlation curve, especially c/b and λ. Furthermore, by analyzing the stress distribution of mid-span cross-section at ultimate state, the simplified calculation model for asymmetric flexural capacity applicable to different combination forms of MT-CFST section was put forward. The reduction factor of 0.9 for positive flexural capacity (WC) and the restricted width-to-thickness ratio 60235/fy are recommended. Based on the study of the constraint stress of steel tube to core concrete and the concrete constraint region distribution for the columns subjected to compression, the calculation method for predicting the axial bearing capacity applicable to different combination forms of MT-CFST section was proposed. According to the parametric analysis and shape of N/Nu-M/Mu correlation curve, the simplified method for N/Nu-M/Mu correlation curves applicable to different combination forms of MT-CFST sections was developed, which simultaneously took the influence of slenderness ratio into consideration. Besides, the calculation methods for MT-CFST members proposed in this paper have been verified with available test results and FE ones.

Addressing dairy industry's scope 3 greenhouse gas emissions by efficiently managing farm carbon footprints

Corporate climate action is increasingly considered important in driving the transition towards a low-carbon economy. Especially in the food processing industry indirect greenhouse gas (GHG) emissions upstream in a producer's value chain (scope 3 emissions) often represent the largest portion of the GHG inventory. In order to manage those GHG emissions efficiently there is a need for simple GHG calculation models ready for large scale application on supplying farms. The aim of this study is to describe a procedure for the development of a simplified GHG calculation model specific for dairy farms based on detailed GHG emission calculations. The results presented are obtained from a case study of supplying farms of a Bavarian organic dairy. The simplified model shall reduce the number of input parameters significantly while representing the variations in GHG emissions across farms and allowing the quantification of GHG mitigation measures. The median farm carbon footprint (CCF) of the case study farms calculated with the detailed calculation model is 441.7 t CO2e/a (mean number of dairy cows per farm is 57). The total GHG mitigation potential per farm ranges from 6.51 t CO2e/a to 112.29 t CO2e/a. The simplification of the calculation model results in a less complex and time consuming questionnaire covering 57 parameters instead of up to 467 in the detailed model. The total CCF results of the simplified model give highly comparable results to the detailed calculation model (R2 = 99.7% , standard error = 2.3% of the mean CCF). The correlation between the total mitigation potential calculated per farm by the simplified and detailed calculation model is also high (R2 = 98.92%, standard error = 7.0% of the mean total mitigation potential per case study farm). For the quantification of some mitigation measures with the simplified model, attention must be paid to the question whether calculated GHG emission reductions are significantly higher than the standard error of GHG emissions calculated for the relevant life cycle stage. Summarizing the procedure for the development of a simplified GHG calculation model proposed in this paper, leads to a model that meets the defined requirements.

The effects of steel fibers and boundary elements on the seismic behavior of high-strength concrete shear walls

Six shear walls using high-strength concrete and high-strength steels were studied by conducting cyclic load tests, including two reinforced concrete shear walls, and four composite walls reinforced by concrete-filled steel tubes (CFSTs). The effects of steel fibers and boundary element forms on the cyclic behavior of the walls were investigated. Research founds that the steel fiber reinforced specimens showed lighter damage degree, lower deformation capacity, and lower proportion of shear deformation than the non-fiber reinforced specimens. Among the three types of specimens with different boundary elements, steel fibers had the greatest influence on the composite walls with concrete-encased CFST columns in boundary zone. Compared the two types of composite walls reinforced by CFSTs which were designed by the principle of “equal vertical bearing capacity of the boundary elements”, the walls with outer CFST columns showed better energy dissipation capacity than the walls with concrete-encased CFST columns. Finally, considering the stress characteristics and the constraint effect of boundary elements of different kinds of shear walls, the simplified calculation model of load-carrying capacity and the finite element analysis model were established and verified.

Simplified calculation model for offshore wind tower founded on monopile member

The objective of the study, concerning the soil-structure interaction of monopile foundations of wind towers consituted by steel tube with hollow cross-sections, was to determine the structural response of wind tower considering the interaction with the foundation. The study was based on elastic and plastic analyses of monopile foundation. The moment-rotation curves of the soil-foundation complex were determined, to be used in verification of the ultimate and operating limit states. The influence of foundation characteristics and type of soil was considered in the calculus of first frequency and critical length. Finally, an experimental validation of the proposed model was made with the data available from the literature in terms of both first frequency and moment rotation response.

Event-by-event antideuteron multiplicity fluctuation in Pb+Pb collisions at [formula omitted] TeV

Using the nucleon coalescence model based on kinetic freeze-out nucleons from the hybrid model of MUSIC hydrodynamics and UrQMD hadronic transport model, we study the production of antideuteron and its event-by-event fluctuation in Pb+Pb collisions at sNN=5.02 TeV. We find a clear suppression of the antideuteron to antiproton yield ratio in peripheral collisions, which is in accordance with the measurements from the ALICE Collaboration. Also found is a Poissonian event-by-event fluctuation of the antideuteron multiplicity in all collision centralities, which is different from the prediction of a simple coalescence model calculation which assumes that all antiproton and antineutron pairs have the same probability to form an antideuteron. However, due to the lack of baryon number conservation at the particlization when the viscous fluid in the hydrodynamic stage of MUSIC is converted to a hadronic matter, our model fails to describe the net-proton number fluctuation and the negative correlation between the antiproton and antideuteron multiplicities at large pseudorapidity acceptance observed in ALICE experiments. Both can nevertheless be well reproduced after selecting a suitable subset of events to fit the measured net-proton number fluctuation.

Calculation Model of Compaction Coefficient of Soil among SP−PSC Pile Group on Collapsible Loess Foundation

Collapsible loess is a kind of soil with special properties, and is widely distributed in China. When it is not wetted by water, its strength is generally high and its compressibility is low. However, when collapsible loess is wetted by water under a certain pressure, the soil structure will be rapidly destroyed, resulting in large additional subsidence. Therefore, when engineering constructions on collapsible loess sites are carried out, appropriate foundation treatment measures must be taken to eliminate foundation collapsibility. Because of their advantages, static pressure plain soil compaction (SP−PSC) piles are widely used for collapsible loess foundation treatments in China. However, at present, there is still a lack of accurate understanding of the distribution of compaction coefficient of soil among SP−PSC pile groups on collapsible loess foundations. The present study systematically investigated the distribution of the soil compaction coefficient among SP−PSC pile groups based on SP−PSC pile group tests and finite element analyses. The effect of different factors on soil compaction coefficient was analyzed and explored, including the pile diameter and length of SP−PSC piles, the soil moisture content, the pile spacing within the SP−PSC pile group, and the depth to ground. Finally, the simplified calculation models of the compaction coefficient of the soil at the center of pile group and at the midpoints of adjacent piles were analytically formulated. These models established a theoretical basis for the design and construction of SP−PSC pile groups on collapsible loess foundations.