Simplified Load Model Research Articles

A simple load model based on hybrid mechanism and data-driven approach for district heating in building complex

Accurate prediction of heating loads in district heating systems is essential for the implementation of demand-driven heating. This work presents a novel heating load prediction model that is particularly suitable for complex multi-user buildings. The input characteristics of the model are established through the heat transfer mechanism, considering factors such as the cumulative impact of outdoor temperature and user demand (indoor temperature). The specific form of the heating load function is determined using the MLR-PSO (Multiple Linear Regression-Particle Swarm Optimization) method. Only the indoor and outdoor temperatures need to be provided for the model to calculate future heating loads. Practical engineering tests demonstrated that the model achieved normalized mean bias errors of daily loads between 4.98 % and 5.54 % across different heating seasons, with a minimum annual relative deviation of 0.75 % for annual loads. Additionally, the model helps guide the operation of heating systems. For example, during the 2021–2022 heating season, setting the target indoor temperature at 18 °C reduced weekly energy consumption by 15.3 % compared to the previous season. This approach may be employed to construct a simple load model for existing heating systems to accurately predict both short-term and long-term loads, providing valuable insights into the management and control of heating systems.

Assessment of implant internal stresses under physiological femoral loading: Translation to a simplified bending load model

The success of surgical treatment for fractures hinges on various factors, notably accurate surgical indication. The process of developing and certifying a new osteosynthesis device is a lengthy and costly process that requires multiple cycles of review and validation. Current methods, however, often rely on predecessor standards rather than physiological loads in specific anatomical locations. This study aimed to determine actual loads experienced by an osteosynthesis plate, exemplified by a standard locking plate for the femoral shaft, utilizing finite elements analysis (FEA) and to obtain the bending moments for implant development standard tests. A protocol was developed, involving the creation and validation of a fractured femur model fixed with a locking plate, mechanical testing, and FEA. The model’s validation demonstrated exceptional accuracy in predicting deformations, and the FEA revealed peak stresses in the fracture bridging zone. Results of a parametric analysis indicate that larger fracture gaps significantly impact implant mechanical behavior, potentially compromising stability. This study underscores the critical need for realistic physiological conditions in implant evaluations, providing an innovative translational approach to identify internal loads and optimize implant designs. In conclusion, this research contributes to enhancing the understanding of implant performance under physiological conditions, promoting improved designs and evaluations in fracture treatments.

Ambient Signals based Load Modeling with Two Three-phase Induction Motors

Abstract The traditional electric power system simulation and calculation are based on the simple load model including one motor and one static load. On the one hand, the power system load is getting more and more complex. On the other hand, it’s proved that two kinds of three-phase induction motors will show a little difference. As a result, in this paper, a new model load with two three-phase induction motors is proposed. Besides, the dynamic of the power system load is taken into account. The torque of those two three-phase motors will show different characteristics, that one is constant and the other is variable. Formerly, the dynamic of the load is regarded as the result of an induction motor. However, the single-phase motor and electronic load both lead to the complexity of the load. To get a more accurate calculation, we need a more proper load model. One of the ways to improve the load model is to pay more attention to the ingredients ignored. The single-phase motor and power electronic load make a great difference. Besides, it’s proved that the composited load model with two three-phase motors will be better in the calculation.

A Review of Evaluation Methods of Standards for Structural Vibration Serviceability under Crowd Walking

Structures such as long-span footbridges, floors, and long cantilevers are vulnerable to vibration serviceability problems under crowd walking, which should be taken into consideration during the structural design, operation, and maintenance stages. Standards have been developed to enable designers to assess the vibration serviceability of structures using simplified load models that simulate crowd-induced loading. To facilitate engineers in quickly selecting appropriate standards for vibration serviceability design, ten current standards were collected which deal with the assessment of structural vibration serviceability under walking loads, including the French “Assessment of vibrational behavior of footbridges under pedestrian loading” (2006), the German “Design of footbridges guideline” (2007), the Chinese “Technical standard for human comfort of the floor vibration” (2019), etc. The ten standards were reviewed and evaluated from three aspects including the crowd loading model, structural response calculation method, and vibration serviceability evaluation standard in this paper. Through summary and comparison between standards, three directions for future improvement and perfection of the standards were proposed: the challenges of the improvement of the standards focus on the establishment of the refined stochastic load model, the analysis of the crowd–structure coupling system, and the modelling of multifactor coupling serviceability evaluation indexes.

Design and Simulation of Advanced Solar power Electric Vehicle Charging Station

the main aim of this thesis is to design such a charging station coupled with solar energy for urban cities. Simplified EV load models are developed by considering most popular commercial EV in the market. The designed solar powered charging station is tested with the developed EV load models and, would be located in selected urban cities. In this paper, battery of electric vehicle is charge through two source, solar and electricity board. Solar is primary source, if any case solar isn’t working (in winter season or rainy season), EV draws power from electricity board.

Field test and theoretical analysis of a large underground arch structure subjected to buried explosion

Underground arch structures play a crucial role in protective engineering. However, with the advancement of military technology, buried explosions caused by earth penetrators have emerged as a significant threat to these structures. To investigate the dynamic response of underground arch structures subjected to buried explosions, a large arch structure was designed and constructed in a weathered basalt mountain, followed by field explosion tests. During these tests, various parameters such as pressure, velocity, acceleration, and displacement of the structure were recorded and analyzed. The test results demonstrate that conducting field explosion tests on a large arch structure facilitates the acquisition of detailed and comprehensive insights into the dynamic response of underground arch structures. When subjected to overhead explosions, the structure exhibited an overall response, with a noticeable local effect. The dynamic response of the arch was found to be significantly larger than that of the floor slab. Additionally, as TNT mass increased, the response of the structure became more intense, while its rebound ability weakened. The acceleration frequencies of the structure were primarily concentrated in the low-frequency ranges. Furthermore, the dynamic response of the structure was analyzed using a simplified load model and modified governing equations. The proposed theoretical analysis model effectively predicted the peak displacement of the arch. These research findings can serve as a valuable reference for the design of anti-explosion in large underground protective structures.

Wave-in-deck loads: an assessment of present design practice given recent improvements in the description of extreme waves and the nature of the applied loads

This paper contributes to the on-going discussion of how best to calculate the reliability of a fixed offshores structure. This discussion has been driven, in large part, by improved physical understanding of waves arising in realistic design sea-states, with a growing appreciation that many ‘design wave events’ will be breaking, irrespective of water depth. As such, it is increasingly acknowledged that some aspects of present design practice are non-conservative. In re-assessing older structures, the accurate calculation of horizontal wave-in-deck (WID) loads is often the most important and least tractable part. This paper explains the underlying reason, highlights the wider implications for identifying an appropriate design point, and raises fundamental questions in the assumptions underpinning present practice. Specifically, a large laboratory data base of WID events is used to assess the success of available models. These comparisons confirm that recommended practice, including recent updates, consistently under-predict the maximum WID loads on which reliability calculations should be based. In contrast the recently developed Lagrangian Momentum Absorption (LMA) model (Ma and Swan, 2020b), a simple but complete load model that combines fully-nonlinear wave inputs and the openness/porosity of a structure, provides highly accurate predictions. This is achieved without empirical coefficients/calibrations and therefore ideally suited to design/re-assessment applications.

Long-term analysis of wave-induced loads using High Order Spectral Method and direct sampling of extreme wave events

An approach for running long-term analysis of the wave environment and associated wave-induced structural loads, which includes effects of nonlinearity, irregularity and short crestedness of ocean waves is presented. The suggested approach combines a novel event-sampling technique with the efficient nonlinear wave solver High Order Spectral Method (HOSM) to represent the long-term wave environment by a large, yet computationally feasible, number of short-crested wave events which are simulated in HOSM. For the present study, HOSM is enhanced with a wave-breaking model, which improves the description of steep sea states in which wave breaking plays a role.Extensive validation of HOSM and the implemented wave-breaking model is carried out through comparison with model-test results for wave-crest statistics in long- and short-crested sea states and through direct comparison with CFD simulations.The proposed methodology is demonstrated on a case study considering a 106 years long-term analysis of wave crests and wave-in-deck loads, using a simplified load model to estimate drag loads on a deck structure.

Vibration Analysis of Low Height-to-Span Ratio Pedestrian Bridge under Human-Induced Excitation

Driven by the aesthetic pursuit of the urban landscape, pedestrian bridges become longer, lighter, and slender, which may be susceptible to unacceptable vibrations induced by human activities. This paper presented on-site vibration tests of a pedestrian bridge with a very low height-to-span ratio (1/60). The vibration characteristics and dynamic responses were analyzed using environmental, heel-drop, and walking tests. Then, a verified finite model was established to investigate the effect of the height-to-span ratio and the concrete filling ranges of tree-like steel piers on the vibration characteristics and acceleration responses of this kind of pedestrian bridges. Moreover, the relationship between different peak accelerations under heel-drop and walking at various frequencies by the same person was detailed and studied experimentally and by computer simulation, after which the ratios of the peak acceleration during walking and the one under heel-drop were recommended. Finally, a method that demonstrates the feasibility of predicting the peak acceleration of pedestrian bridges of a small height-to-span ratio across a range of walking frequencies was proposed based on a simplified heel-drop load model developed according to 60 time-history records.

An investigation of the Steady-State and Fatigue Problems of a Small Wind Turbine Blade Based on the Interactive Design Approach

A wind turbine blade is an essential system of wind energy production. During the operation of the blade, it is subjected to loads resulting from the impact of the wind on the surface of the blade. This leads to appear large deflections and high fatigue stresses in the structure of blades. In this paper, a 5 kW horizontal axis wind turbine blade model is designed and optimized using a new MATLAB code based on blade element momentum (BEM) theory.The aerodynamic shape of the blade has been improved compared with the initial design, the wind turbine power has been increased by 7% and the power coefficient has been increased by 8%. The finite Element Method was used to calculate the loads applied to the blade based on Computational Fluid Dynamics (CFD) and BEM theory.High agreements were obtained between the results of both approaches (CFD and BEM).The ANSYS software was also used to simulate and optimize the structure of the blade by applying variable static loads 3.3, 6, and 8.3 kg and compared the results with the experimental results. It was reduced the maximum deflectionswith 37%, 42.85%, and 42.61% when using CFRP material and 4.5%, 15.45%, and 16.19% for GFRP material that corresponds to the applied forces. Based on the results, the mass of the optimized model decreased by 47.86% for GFRP and 71.24% for CFRP. IEC 61400.2 standard was used to estimate thefatigue loads, damage, blade life prediction, and verify blade safety usinga Simplified Load Model(SLM) and FAST software. It was found that the blade will be safe under extreme wind loads, and the lifetime of the wind blade (GFRP) is 5.5 years and 10.25 years,according to SLM and FAST software, respectively. At the same time, the lifetime of the wind blade (CFRP)is more than 20 years, according to the two applied methods.

Wave loads on ocean infrastructure increase as a result of waves passing over abrupt depth transitions

Abrupt changes in water depth are known to lead to abnormal free-surface wave statistics. The present study considers whether this translates into abnormal loads on offshore infrastructure. A fully non-linear numerical model is used which is carefully validated against experiments. The wave kinematics from the numerical model are used as input to a simple wave loading model. We find enhanced overturning moments, an increase of approximately 20%, occur over a distance of a few wavelengths after an abrupt depth transition. We observe similar results for 1:1 and 1:3 slopes. This increase does not occur in linear simulations.

Comparison of different approaches for considering vehicle-bridge-interaction in dynamic calculations of high-speed railway bridges

The consideration of vehicle-bridge-interaction effects can be crucial in the computational determination of realistic dynamic bridge vibrations during train crossing. In order to implement these effects into calculations with the simplified Moving Load Model, the concept of additional mass or additional damping of the bridge structure was developed. Besides normative specifications, further numerically and analytically derived approaches are now available to determine the bridge structure's additional damping value. In this numerical study, one approach for determining an additional mass and four different approaches to determine additional damping are applied to dynamic calculations of 65 railway bridges. The calculation results are compared with those obtained by applying a more sophisticated multi-body model of the train, yielding results closer to reality. All calculations are performed for two train types, a conventional locomotive-hauled Railjet and the ICE 4 with partly powered passenger cars. The comparison of results indicates that applying one of the redesigned approaches can reflect the influence of vehicle-bridge-interaction for the investigated trains significantly better than the approach according to current calculation standards. However, several application limitations due to structural and train properties were observed.

Vibration Serviceability Assessment of a Historic Suspension Footbridge

Experimental and numerical studies for the structural and vibration serviceability assessment of a historic suspension footbridge adopting non-invasive surveys and low-cost equipment are presented. Field surveys have been carried out to determine geometric properties, ambient vibration tests have been performed to estimate the dynamic properties, and the dynamic response of the footbridge under the action of a single crossing pedestrian has been recorded. Based on field surveys, a 3D Finite Element model was built and was then calibrated against ambient vibration test results. The experimentally-measured maximum acceleration under the action of one crossing pedestrian is compared with the ones obtained numerically and analytically. Furthermore, vibration serviceability assessment under multi-pedestrian loading is carried out, adopting the simplified procedure recommended by a recent guideline. Results show that low-cost non-invasive dynamic testing is suitable to correctly identify the footbridge vertical natural frequencies and mode shapes, including higher-order ones, and to draw considerations about the state of degradation of the structure. Moreover, the level of vibration under the action of a single pedestrian can be estimated with sufficient accuracy using a simplified loading model, provided that the modal damping ratio is properly tuned.

Online Parameter Identification of a Simplified Composite Load Model by Voltage Sag Events

Online Parameter Identification of a Simplified Composite Load Model by Voltage Sag Events

Finite element analysis of train speed effect on dynamic response of steel bridge

AbstractThe development of materials engineering has facilitated the design of slender, light bridges replacing standard construction materials with others, which fulfil their purpose both in terms of structural behaviour and safety. This article focuses on the presentation of the problems related to the modelling of bridges and their loads modelling train passages, as well as an analysis of the influence of load parameters on the dynamic response of a structure. The problem has become essential with the development of materials engineering which enabled the design of slender and light bridges according to the assumptions of sustainable development. The article contains a number of numerical analyses which allowed the verification of the developed finite element bridge model (frame and plate-frame types) in terms of the possibility of using them at the design stage. The load was modelled as a system of concentrated forces, the so-called moving load (ML) model. The results obtained from theoretical analyses were compared within situmeasurements of the existing bridge subjected to the load variable in time (set of locomotives ST43 and ST45 and locomotive EP09). It has been found that in dynamic analysis, modelling of the load is essential. A simplified load model such as ML can be used when displacement values are the only results analysed in detail. ML and finite element plate and frame models give high accordance of the displacement results.

A Statistical Approach for Modeling Individual Vertical Walking Forces

This paper proposes a statistical approach for modeling vertical walking forces induced by single pedestrians. To account for the random nature of human walking, the individual vertical walking force is modeled as a series of steps and the gait parameters are assumed to vary at each step. Walking parameters are statistically calibrated with respect to the results of experimental tests performed with a force plate system. Results showed that the walking parameters change during walking and are correlated with each other. The force model proposed in this paper is a step-by-step model based on the description of the multivariate distribution of the walking features through a Gaussian Mixture model. The performance of the proposed model is compared to that of a simplified load model and of two force models proposed in the literature in a numerical case study. Results demonstrate the importance of an accurate modeling of both the single step force and the variability of the individual walking force.

Effect of postural alignment alteration with age on vertebral strength.

The purpose of this study was to analyze the impact of postural alignment changes with age on vertebral strength using finite element analysis and barycentremetry. A total of 117 subjects from 20 to 83years were divided in three age groups: young (20 to 40years, 62 subjects), intermediate (40 to 60years, 26 subjects), and elderly (60years and over, 29 subjects). EOS biplane radiographs were acquired, allowing 3D reconstruction of the spine and body envelope as well as spinal, pelvic, and sagittal alignment parameter measurements. A barycentremetry method allowed the estimation of the mass and center of mass (CoM) position of the upper body above L1, relatively to the center of the L1 vertebra (lever arm). To investigate the effect of this lever arm, vertebral strength of a generic finite element model (with constant geometry and mechanical properties for all subjects) was successively computed applying the personalized lever arm of each subject. A combination of an increase in thoracic kyphosis, cervical lordosis, and pelvic tilt with a loss of lumbar lordosis was observed between the young and the older groups. Sagittal alignment parameters indicated a more forward position as age increased. The lever arm of the CoM above L1 varied from an average of 1mm backward for the young group, to averages of 10 and 24mm forward, respectively, for the intermediate and elderly group. As a result, vertebral strength decreased from 2527N for the young group to 1820N for the elderly group. The global sagittal alignment modifications observed with age were consistent with the literature. Posture alteration with age reduced vertebral strength significantly in this simplified loading model. Postural alignment seems essential to be considered in the evaluation of osteoporotic patients.

Definition of scaled distance of close-in explosion and blast load calculation model

How to accurately define “close-in explosion” has always been a hotspot in the field of protection engineering research. In this paper, based on the fully validated 2D axisymmetric fine finite element model, the characteristics and laws of the propagation of air shock waves and high-speed expansion of detonation products generated by TNT spherical charge were studied. It is found that there is a significant influence of the detonation products on the blast load on rigid wall when the range of the scaled distance less than 0.8 m/kg1/3. It is recommended to use the scaled distance range from 0.30 m/kg1/3 to 0.80 m/kg1/3 as the definition criterion of close-in explosion for spherical TNT charge explosion. It was found that: due to the inhomogeneity and randomness of the detonation product rapid expansion, the peak value of the rigid-wall reflected overpressure experienced a sharp drop within a range of incident angle of 0°～5° in the case of close-in explosion defined in the paper. In addition, there were two peaks on the reflected overpressure curve in close-in explosion cases, and the first peak overpressure was caused by the interaction between the shock wave and rigid wall while the second peak overpressure was generated by the interaction between the detonation products and rigid wall. Based on curve fitting, the formulas for calculating the two peak values were proposed, respectively, and a simplified load model suitable for calculation of engineering structure response was put forward; The distribution law of the reflected overpressure on the rigid wall under close-in explosion was revealed.

Research on Bridge Structure Reliability Evaluation due to Vessels Collison Based on a Statistical Moment Method

Damage to bridge structures caused by vessel collision is a risk for bridges crossing water traffic routes. Therefore, safety around vessel collision of existing and planned bridges is one of the key technical problems that must be solved by engineering technicians and bridge managers. In the evaluation of the reliability of the bridge structure, the two aspects of vessel‐bridge collision force and structural resistance need to be considered. As there are many influencing parameters, the performance function is difficult to express by explicit function. This paper combines the moment method theory of structural reliability with finite element analysis and proposes a statistical moment method based on finite element analysis for the calculation of vessel‐bridge collision reliability, which solves the structural reliability problem with a nonlinear implicit performance function. According to the probability model based on current velocity, vessel velocity, and vessel collision tonnage, the estimate points in the standard normal space are converted into estimate points in the original state space through the Rosenblatt reverse transform. According to the estimate points in the original state space and the simplified dynamic load model of vessel‐bridge collision, the sample time‐history curve of random vessel‐bridge collision force is generated, the dynamic response of the bridge structure and the structural resistance of the bridge are calculated by establishing a finite element model, and the failure probability and reliability index of the bridge structure is calculated according to the fourth‐moment method. The statistical moment based on the finite element analysis is based on the finite element analysis and the moment method theory of structural reliability. The statistical moment of the limited performance function is calculated through a quite small amount of confirmatory finite element analysis, and the structural reliability index and failure probability are obtained. The method can be widely used in existing finite element analysis programs, greatly reducing the number of finite element analyses needed and improving the efficiency of structural reliability analysis.

The heat load modelling for an air-conditioned room using Buckingham-Pi theorem

The objective of this study is to develop and compare two simplified heat load models for air-conditioned rooms. The heat load models are intended for use in a demand response (DR) program in future work, to solve critical electricity peaks from air-conditioners used. Buckingham-Pi theorem was applied to develop the heat load model in this study. Moreover, another heat load model using sensitivity analysis and multiple linear regression was developed in this study. Then, the result of the heat load model using Buckingham-Pi theorem was compared to the heat load model using sensitivity analysis and multiple linear regression to identify the advantage of both heat load models. In this study, heat load model using the Buckingham-Pi theorem was successfully developed. A heat load model with three independent variables was recommended for heat load prediction. The results showed that the heat load model gave a good prediction of the heat load with an RMSE of 4.82%. However, the RMSE of predicting the heat load model using sensitivity analysis and multiple linear regression is 0.55% using a model with ten independent variables. The comparison shows that the heat load model using Buckingham-Pi theorem has a good agreement and simplifies the model better than using sensitivity analysis and multiple linear regression.