Realistic Load Models Research Articles

An approach for fatigue life assessment of a road bridge based on measured corrosion and actual traffic loading

Fatigue and corrosion play a significant role in the aging of steel bridges, especially in a marine environment. An absence of fatigue strength curves for details which are exposed to corrosive environments, realistic traffic load models and accurate damage accumulation models increase the susceptibility of fatigue damage of steel bridges. In this paper, remaining fatigue life of a road bridge is assessed based on the measured corrosion wastage and more realis-tic traffic loads. Corrosion fatigue is also studied as it is one of the main factors that reduce the fatigue life and recently proposed fatigue strength curve for structural details exposed to corrosive environments is utilized for this study. A non-linear fatigue damage accumulation model is used for life assessment apart to the conventional damage model, Miner’s rule. The calculated fatigue lives are compared and discussed in quantitative manner to identify the most conservative remaining life and corresponding methods.

An Efficient Hybrid Approach for Optimal Integration of Capacitors in Radial Distribution Networks with Realistic Load Models Using Giant Trevally Optimizer and Voltage Stability Index

An Efficient Hybrid Approach for Optimal Integration of Capacitors in Radial Distribution Networks with Realistic Load Models Using Giant Trevally Optimizer and Voltage Stability Index

Enhancement of performance indices on realistic load models with distributed generators in radial distribution network

Enhancement of performance indices on realistic load models with distributed generators in radial distribution network

Possibilistic uncertainty assessment in the presence of optimally integrated solar PV-DG and probabilistic load model in distribution network

To integrate network load and line uncertainties in the radial distribution network (RDN), the probabilistic and possibilistic method has been applied. The load uncertainty is considered to vary as Gaussian distribution function whereas line uncertainty is varied at a fixed proportion. A voltage stability index is proposed to assign solar PV-DG optimally followed by application of PSO technique to determine the optimal power rating of DG. Standard IEEE 33- and 69-bus RDN are considered for the analysis. The impact of various uncertainties in the presence of optimally integrated solar PV-DG has been carried out on 69-bus network. The results obtained are superior to fuzzy-arithmetic algorithm. Faster convergence characteristic is obtained and analyzed at different degree of belongingness and realistic load models. The narrower interval width indicates that the observed results are numerically stable. To improve network performance, the technique takes into account long-term changes in the load profile during the planning stage. The significant drop in network power losses, upgraded bus voltage profile and noteworthy energy loss savings are observed due to the introduction of renewable DG. The results are also statistically verified.

Voltage-Led Load Management in Whole Distribution Networks

The ability to manage loads can play a significant role in the future operation and planning of electricity networks. One way of unlocking this source of flexibility without directly involving thousands or millions of customers is to exploit the positive correlation between supplied voltage and demand, i.e., voltage-led load management. Distribution network operators, in particular, could achieve this by adequately controlling voltage regulation devices. Nonetheless, to quantify this it is key to understand the extent to which voltages can be changed (reduced) while considering the dependencies across different voltage levels. A methodology is proposed here to quantify the aggregated demand reduction unlocked by controlling primary substations considering the voltage interactions and constraints throughout the whole distribution network. Given the complexity and dimensions, the influence of the upstream network on primary substations and the effects on low voltage customers are analyzed separately whilst maintaining their dependencies. The methodology, developed within the largest UK load management trial, is applied to real 132 to 0.4 kV distribution networks adopting realistic load models. Results demonstrate not only the significance of the scheme as a source of flexibility but, crucially, that the interactions and constraints across voltage levels are key in its adequate time-varying quantification.

Finite Element Analysis of the Dynamic Response of Composite Floors Subjected to Walking Induced Vibrations

The applications of composite materials have been widely practiced in modern construction. Structural engineers are often urged to consider aesthetic values as well as the financial aspects in their work, which results in structures that have long span, lightweight and low natural frequencies. These structures exhibit excessive vibrations that cause major discomforts to the occupants. The purpose of this study is to establish a methodology using finite element analysis for assessing the dynamic responses of composite floors and determining the corresponding level of comfort. Linear elastic finite element analysis was conducted using more realistic load models with respect to the application of different geometries of concrete slab and fiber reinforced polymer materials. The composite floor investigated included FRP deck, FRP beams, and concrete slabs of various thicknesses. The resulting maximum peak accelerations indicated the need for more realistic load models to generate a time function including space, time and heel impact descriptions. The FRP deck or beam was satisfactory in terms of serviceability and comfort level. There were no significant differences between the results when fiber reinforced polymer materials or common concrete-steel composite floors were used.

Learning HMM-based cognitive load models for supporting human-agent teamwork

Cognitive studies indicate that members of a high performing team often develop shared mental models to predict others’ needs and coordinate their behaviors. The concept of shared mental models is especially useful in the study of human-centered collaborative systems that require humans to team with autonomous agents in complex activities. We take the position that in a mixed human-agent team, agents empowered with cognitive load models of human team members can help humans develop better shared mental models to enhance team performance. Inspired by human information processing system, we here propose a HMM-based load model for members of human-agent teams, and investigate the development of realistic cognitive load models. A cognitive experiment was conducted in team contexts to collect data about the observable secondary task performance of human participants. The data were used to train hidden Markov models (HMM) with varied numbers of hypothetical hidden states. The result indicates that the model spaces have a three-layer structure. Statistical analysis also reveals some characteristics of the models at the top-layer. This study can be used in guiding the selection of HMM-based cognitive load models for agents in human-centered multi-agent systems.

Combination of global still-water and wave load effects for reliability-based design of floating production, storage and offloading (FPSO) vessels

The purpose of this paper is to establish probabilistic models for still-water loads, based on design data, and the combined still-water and wave load effects for semi-probabilistic and probabilistic design of floating production, storage and offloading vessels (FPSO). A new still-water load model for FPSOs is proposed, based on a Poisson square-wave model, with a modified Weibull distribution for load intensity, which accounts for load control during operation. The long-term variation of wave-induced load effects is modelled by a Poisson square-wave process. A new solution for the combined effect is derived. A procedure for determining characteristic extreme values for individual and combined load effects, and load combination factors, is established. The methodology is used to illustrate load combination factors suitable for typical FPSOs. This approach is also shown to be useful in obtaining realistic load models, in terms of random variables, for use in reliability formulations.

Load Behavior Observed in LILCO and RG&E Systems

Realistic load models are required to improve the quality of bulk power system studies. For a better understanding of the basic nature of the load behavior under abnormal conditions, an extensive series of tests were conducted during different seasons at three test sites of two utility systems in New York State.

On Combinations of Random Loads

Structures are subject to changing loads from various sources. In many instances these loads fluctuate in time in an apparently random fashion. Certain loads vary rather slowly (called constant loads); other loads occur more nearly as impulses (shock loads). Suppose that the stress put on the structure by various loads acting simultaneously can be expressed as a linear combination of the load magnitudes. In this paper certain simple but somewhat realistic probabilistic load models are given and the resulting probabilistic model of the total stress on the structure caused by the loads is considered. The distribution of the first time until the stress on the structure exceeds a given level x, and the distribution of the maximum stress put on the structure during the time interval $( 0,t]$ are studied. Asymptotic properties are also given. It is shown that the asymptotic properties of the maximum stress are related to those of the maxima of a sequence of dependent random variables. Classical extreme value ty...

System Load Dynamics-Simulation Effects and Determination of Load Constants

Justification for using more realistic load models in stability studies than has been the practice heretofore is presented below. Examples are given which show that stability tests may be dramatically affected by load-voltage characteristics, or that more sophisticated models are necessary under conditions which preclude the usual composite load assumptions. In conclusion the paper states that system measurements are the most practical means of obtaining realistic load-voltage data for use in computer stability programs.