The Time-Varying Characteristics of Overhead Electric Transmission Lines Considering the Induced-Ice-Shedding Effect

More ice deposits accreted on conductors or ground wires may be shed off when an overhead electric transmission line is responding to shocks initiated by natural ice shedding. Ice shedding causes the global mass, stiffness, and damping of the tower-line system to vary with time, and the successive shedding effect beyond a trigger event has not been taken into account in previous studies due to the lack of an adequate ice detachment model. In this paper, the ice shedding effect induced by initial shocks was considered in finite element (FE) analysis. An ice detachment criterion, in the way of user-defined element rupture subroutine, was implemented into the main commercial nonlinear FE program ADINA, making it possible to consider the induced-ice-shedding effect numerically. The incremental FE form of the system's governing equations of motion is presented where the variations in the mass and stiffness matrices of the system are taken into consideration. Taking a transmission line section following natural ice shedding as a case study, the results indicate that neglecting successive ice shedding underestimates the adverse influence of natural ice shedding. The proposed method can help to improve the design and evaluation of transmission lines in cold regions and to ensure their mechanical security

Analyse dynamique des structures avec câbles : revue bibliographique

Caractéristiques structurales des câbles -- Comportement statique des câbles suspendus -- Charges dynamiques sur les structures avec câbles -- Notes historiques sur la dynamique des câbles -- Dynamique linéaire des câbles avant 1974 -- Dynamique non linéaire des câbles avant 1974 -- Cas spéciaux -- Analyse dynamique des structures avec câbles -- Modélisation des câbles sous charges dynamiques -- Méthodes d'analyse et techniques numériques -- Comportement dynamique des lignes de transport aériennes sous charges exceptionnelles -- Comportement des lignes sous charges exceptionnelles -- Outils d'analyse -- Critères de conception des lignes de transport aériennes sous charges exceptionnelles -- Évolution des critères pour les charges longitudinales -- Critères de conception pour la prévention des cascades

Analyse dynamique de la salle des turbines (unité #1) et de la baie auxiliaire (unité #2) de la centrale thermique de Suralaya (République d'Indonésie)

Modèle simplifié -- Modèle B et C : modèles détaillés e la baie auxiliaire et de la salle des turbines -- Modèles B et C : modèle détaillées de la salle des turbines et de la baie auxilliaire -- Comparaison des résultats du modèle C avec ceux du modèle traité par stardyne -- Chargements séismiques étudiés et méthode de combinaison des résultats

Direct generation of floor design spectra (FDS) from uniform hazard spectra (UHS) — Part II: extension and application of the method

This paper extends the methodology presented in the companion paper to study the effects of non-structural components’ (NSCs) damping ratio and their location in the building on the pseudo-acceleration floor response spectra (PA-FRS) of reinforced concrete buildings, and propose equations to derive floor acceleration design spectra (FDS) directly from the uniform hazard design spectra (UHS) for Montréal, Canada. The buildings used in the study are 27 existing reinforced concrete structures with braced frames and shear walls as their lateral load resisting systems: 12 are low-rise (up to 3 stories above ground), 10 are medium-rise (4 to 7 stories), and 5 are high-rise (10 to 18 stories). Based on statistical and regression analysis of floor acceleration spectra generated from linear dynamic analysis of coupled building–NSC systems, two sets of modification factors are proposed to account for floor elevation and NSC damping, applicable to the experimentally-derived FDS for roof level and 5% NSC damping. Modification factor equations could be derived only for the low-rise and medium-rise building categories, as insufficient correlation in trends could be obtained for high-rises given their low number. The approach is illustrated in detail for two typical buildings of the database, one low-rise (Building #4) and one medium-rise (Building #18), where the proposed FDS/UHS results show agreement with those obtained from detailed dynamic analysis. The work is presented in the context of a more general methodology to show its potential general applicability to other building types and locations.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Direct generation of floor design spectra (FDS) from uniform hazard spectra (UHS) — Part I: formulation of the method

In most current building codes, seismic design of non-structural components (NSCs) is addressed through empirical equations that do not capture NSC response amplification due to tuning effects with higher and torsional modes of buildings and that neglect NSC damping. This work addresses these shortcomings and proposes a practical approach to generate acceleration NSC floor design spectra (FDS) in buildings directly from their corresponding uniform hazard spectra (UHS). The study is based on the linear seismic analysis of 27 reinforced concrete buildings located in Montréal, Canada, for which ambient vibration measurements (AVM) are used to determine their in situ three-dimensional dynamic characteristics. Pseudo acceleration floor response spectra (PA-FRS) are derived at every building floor for four different NSCs damping ratios. The calculated roof FRS are compared with the 5% damped UHS and a formulation is proposed to generate roof FDS for NSCs with 5% damping directly from the UHS.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Dynamic Characteristics of Light-Frame Wood Buildings

This paper deals with dynamic field testing of light-frame wood buildings with wood based shear walls. The primary objective of the investigation is to provide an estimate of the fundamental period of such buildings, through field testing and numerical modelling. An experimental program is established to perform ambient vibration testing on forty-one light-frame wood buildings of both regular and irregular layouts, located in moderate to high seismic zones in different regions in Canada. The research objective is to develop a reliable method of estimating the building period of light-frame wood buildings and develop an accurate expression for building period estimate based on field testing and numerical modeling. The study found that significant scatter is observed in the measured data when plotted as a function of building height. Finite element models were developed and compared with the natural periods of the buildings with reasonable accuracy. Using the validated FE models to examine different commonly used stiffness models showed that in general current analysis approaches overestimate the building periodThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Effect of nonstructural components on the dynamic characteristics of light-frame wood buildings

This research deals with ambient vibration measurements (AVM) in 16 multi-storey light-frame wood buildings with wood-based shear walls as the main lateral load resisting system. Its primary objective is to evaluate the effect of nonstructural sheathing panels and the connectivity between firewall-separated buildings, on the modal properties of the tested buildings. Lower natural frequencies, corresponding mode shapes and equivalent structural damping were extracted from the AVM records. The study confirmed that the increase in stiffness of the finished buildings was dominant over their increase in mass when sway mode periods of finished buildings and bare structural frameworks are compared. The stiffening effect of gypsum wallboard was deemed significant and should be accounted for in seismic design. The study also indicates that even when the building section were only nominally connected to the firewall, composite action in the lateral response was taking place.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Establishing the Fundamental Period of Light-Frame Wood Buildings on the Basis of Ambient Vibration Tests

This research project deals with dynamic field testing of light-frame wood buildings with wood- based shear walls. The primary objective of the investigation is to evaluate the building code formula for estimating light- frame wood buildingâ s fundamental period for seismic analysis, through intensive field testing and numerical modelling. The project also aims to propose an alternative simplified rational approach to seismic analysis of these structures. The paper presents ambient vibration (AV) testing results of light-frame wood buildings in Canada. The dynamic characteristics of the measured buildings, such as natural frequency, mode shapes and equivalent structural damping were obtained from Frequency Domain (FD) analysis of ambient motion records. Using a simplified method of period estimation based on the Rayleigh approximation while using the building mass and replacing the stiffness of shear walls by their length showed reasonable fit when compared with the FE model results and AVT measured periods. A formula was developed based regression analysis of tested buildings. The expression is a function of building height, floor area and shear wall length and it was shown to provide a reasonably good fit with the measured resultsThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author