Evaluation of design requirements for footbridges excited by vertical forces from walking

2001 ◽  
Vol 28 (5) ◽  
pp. 769-777 ◽  
Author(s):  
R L Pimentel ◽  
A Pavic ◽  
P Waldron
Keyword(s):  
Dynamic Loading ◽  
Vertical Direction ◽  
Design Guidelines ◽  
Scientific Data ◽  
Codes Of Practice ◽  
Safety Margins ◽  
Vibration Serviceability ◽  
Factor Evaluation ◽  
Definition Of ◽  
Proper Consideration

The continuing trend towards the design of more slender, lighter, and livelier footbridges has created new challenges that are not properly addressed in a number of widely used codes of practice in Europe and Canada. Recent research into vibration serviceability of slender structures under human-induced dynamic loading suggests that improvements to the existing footbridge design guidelines are possible in the area of modelling human-induced excitation in the vertical direction. This paper evaluates the performance of currently used codes of practice regarding vibration serviceability of footbridges under human-induced loads due to walking. The evaluation is supported by experimental evidence from tests carried out by the authors on potentially lively footbridges. A description of recent research advances is included, together with a comparative analysis of the approaches of some pertinent guidelines used internationally to tackle this design problem. In addition, suggestions are made for re-addressing the problem of vibration serviceability of footbridges by focusing attention on a more realistic definition of vertical pedestrian loading and the corresponding frequency ranges of interest. It was found that the codes are either conservative or lack appropriate safety margins, depending on the frequency range excited by moving pedestrians. This is principally due to the lack of proper consideration for the frequency content of the pedestrian load, which would take into account developments since the 1970s when the scientific data used in the majority of the current codes of practice were produced.Key words: vibration, serviceability, walking, footbridges, design, codes, dynamic loading factor, evaluation.

scholarly journals Quantification of Dynamic Excitation Potential of Pedestrian Population Crossing Footbridges

2011 ◽  
Vol 18 (4) ◽  
pp. 563-577 ◽  
Author(s):  
Stana Žcaronivanović ◽  
Aleksandar Pavić
Keyword(s):  
Real Life ◽  
Vertical Direction ◽  
Design Guidelines ◽  
Vibration Response ◽  
Step Frequency ◽  
Response Level ◽  
Dynamic Excitation ◽  
Excitation Potential ◽  
Vibration Serviceability ◽  
Single Response

Due to their slenderness, many modern footbridges may vibrate significantly under pedestrian traffic. Consequently, the vibration serviceability of these structures under human-induced dynamic loading is becoming their governing design criterion. Many current vibration serviceability design guidelines, concerned with prediction of the vibration in the vertical direction, estimate a single response level that corresponds to an "average" person crossing the bridge with the step frequency that matches a footbridge natural frequency. However, different pedestrians have different dynamic excitation potential, and therefore could generate significantly different vibration response of the bridge structure. This paper aims to quantify this potential by estimating the range of structural vibrations (in the vertical direction) that could be induced by different individuals and the probability of occurrence of any particular vibration level. This is done by introducing the inter- and intra-subject variability in the walking force modelling. The former term refers to inability of a pedestrian to induce an exactly the same force with each step while the latter refers to different forces (in terms of their magnitude, frequency and crossing speed) induced by different people. Both types of variability are modelled using the appropriate probability density functions. The probability distributions were then implemented into a framework procedure for vibration response prediction under a single person excitation. Instead of a single response value obtained using currently available design guidelines, this new framework yields a range of possible acceleration responses induced by different people and a distribution function for these responses. The acceleration ranges estimated are then compared with experimental data from two real-life footbridges. The substantial differences in the dynamic response induced by different people are obtained in both the numerical and the experimental results presented. These results therefore confirm huge variability in different people's dynamic potential to excite the structure. The proposed approach for quantifying this variability could be used as a sound basis for development of new probability-based vibration serviceability assessment procedures for pedestrian bridges.

SIDS and Sleeping Position

PEDIATRICS ◽  
1993 ◽  
Vol 91 (2) ◽  
pp. 511-512
Author(s):  
DANIEL C. SHANNON ◽  
CARL E. HUNT
Keyword(s):  
Clinical History ◽  
Scientific Data ◽  
Statistical Association ◽  
Review Of The Literature ◽  
Sleeping Position ◽  
Death Scene ◽  
Death Scene Investigation ◽  
Prone Sleeping ◽  
Scene Investigation ◽  
Definition Of

In Reply.— Guntheroth and Spiers,1 displeased with our commentary in Pediatrics,2 have raised many issues. However, the key question is whether the scientific data incriminating the prone position as a contributor to SIDS warrant a recommendation to change sleeping position at this time. Based on our critical review of the literature, we conclude that this recommendation was premature and unwarranted. Accepting the current definition of SIDS as the sudden death of an infant that remains unexplained even after a thorough postmortem examination, death scene investigation, and review of the clinical history, one can decide which of the 15 published studies in which a statistical association is described between prone sleeping and SIDS is acceptable.

The Constitution: Its Theory and Interpretation

2004 ◽  
Author(s):  
Geoffrey Marshall
Keyword(s):  
General Acceptance ◽  
Codes Of Practice ◽  
Definition Of

This chapter examines the theory of the British constitution, providing a definition of constitution and describing what theories about the constitution have been held in Britain. It explains that one interpretation of the constitution in Britain is the judicial one, of the large and indeterminate number of statutes and secondary legislation that make up the legal elements in the constitution. The chapter suggests that, in some respects, the conventional rules which regulate certain areas of governmental behaviour have become more crystallised and less debatable in recent years with the promulgation and general acceptance of codes of practice.

Context-Awareness and Mobile Devices

2008 ◽  
pp. 205-217 ◽  
Author(s):  
Anind K. Dey ◽  
Jonna Häkkilä
Keyword(s):  
Human Computer Interaction ◽  
Mobile Computing ◽  
Ubiquitous Computing ◽  
Mobile Devices ◽  
Context Awareness ◽  
Design Guidelines ◽  
Context Aware ◽  
Definition Of ◽  
Mobile Context ◽  
Computer Interaction

Context-awareness is a maturing area within the field of ubiquitous computing. It is particularly relevant to the growing sub-field of mobile computing as a user’s context changes more rapidly when a user is mobile, and interacts with more devices and people in a greater number of locations. In this chapter, we present a definition of context and context-awareness and describe its importance to human-computer interaction and mobile computing. We describe some of the difficulties in building context-aware applications and the solutions that have arisen to address these. Despite these solutions, users have difficulties in using and adopting mobile context-aware applications. We discuss these difficulties and present a set of eight design guidelines that can aid application designers in producing more usable and useful mobile context-aware applications.

Context-Awareness and Mobile Devices

2009 ◽  
pp. 3222-3235 ◽  
Author(s):  
Anind K. Dey ◽  
Jonna Häkkilä
Keyword(s):  
Human Computer Interaction ◽  
Mobile Computing ◽  
Ubiquitous Computing ◽  
Mobile Devices ◽  
Context Awareness ◽  
Design Guidelines ◽  
Context Aware ◽  
Definition Of ◽  
Mobile Context ◽  
Computer Interaction

Context-awareness is a maturing area within the field of ubiquitous computing. It is particularly relevant to the growing sub-field of mobile computing as a user’s context changes more rapidly when a user is mobile, and interacts with more devices and people in a greater number of locations. In this chapter, we present a definition of context and context-awareness and describe its importance to human-computer interaction and mobile computing. We describe some of the dif- ficulties in building context-aware applications and the solutions that have arisen to address these. Despite these solutions, users have difficulties in using and adopting mobile context-aware applications. We discuss these difficulties and present a set of eight design guidelines that can aid application designers in producing more usable and useful mobile context-aware applications.

Phylogenetic pattern and the quantification of organismal biodiversity

1994 ◽  
Vol 345 (1311) ◽  
pp. 45-58 ◽  
Keyword(s):  
General Framework ◽  
Phylogenetic Diversity ◽  
Species Level ◽  
Option Value ◽  
Alternative Definition ◽  
Phylogenetic Pattern ◽  
Alternative Approaches ◽  
Definition Of ◽  
Different Levels ◽  
Proper Consideration

Biodiversity can be explored at a number of different levels and in principle may be separately quantified at each. Phylogenetic pattern has the potential to quantify and estimate biodiversity at the finest scale, that is, variation among species in features or attributes. This scale is an important one for conservation, as it should form the basis for prioritizing conservation efforts at the species level. Further, recent published objections to differentially weighting species are answered by defining option value at this feature-level. Unfortunately, there has been no consensus on exactly how phylogeny can be used to value species, possibly because proper consideration of the link between pattern and underlying features generally has been unresolved. ‘Phylogenetic diversity’ (PD) represents just one of several approaches that do consider diversity at the feature-level explicitly. These alternative approaches are discussed in the context of a general framework for using pattern to quantify diversity at a level below that of the original objects. The pattern framework highlights that estimation of biodiversity at a lower level using pattern will require decisions about the nature of the units of diversity, the kind of pattern to be used, the model relating unit items to pattern, and finally how this implies a pattern-based measure reflecting biodiversity. An alternative published model for relating features to a particular form of phylogenetic pattern is considered, and shown to make unwarranted assumptions. A possible alternative definition of the underlying units of diversity is examined, which may represent a different form of option value, also quantifiable using phylogeny. A possible alternative pattern to a phylogenetic tree for the prediction of feature diversity is also discussed. The appeal of these alternative approaches depends on the goals of conservation; in addition, justification for prioritizing or weighting requires that any practical approach avoid arbitrary, unwarranted, assumptions.

scholarly journals Assessment of the Lateral Vibration Serviceability Limit State of Slender Footbridges Including the Postlock-in Behaviour

2020 ◽  
Vol 10 (3) ◽  
pp. 967 ◽  
Author(s):  
Rocío G. Cuevas ◽  
Javier F. Jiménez-Alonso ◽  
Francisco Martínez ◽  
Iván M. Díaz
Keyword(s):  
Limit State ◽  
Sudden Onset ◽  
Design Guidelines ◽  
Comfort Level ◽  
Lateral Vibration ◽  
Vibration Serviceability ◽  
Current Design ◽  
Common Criterion ◽  
Lock In Effect ◽  
Lock In

The lateral vibration serviceability of slender footbridges has been the subject of many studies over the last few decades. However, in spite of the large amount of research, a common criterion has not been set yet. Although the human–structure interaction phenomenon is widely accepted as the main cause of the sudden onset of high amplitudes of vibration, the current design recommendations do not include an expression for the auto-induced component of the pedestrian action and, as a consequence, it is not possible to evaluate the footbridge comfort once the lock-in effect has developed. Hence, the purpose of this paper is to propose a general formulation, which allows the analysis of the different load scenarios that the footbridge will experience during its overall life cycle. An important advantage over most current design guidelines is that the procedure permits the evaluation of the comfort level of the footbridge, even with crowd densities above the “critical number”, and thus takes informed decisions about the possible use of external devices to control the vibration response, depending on the probability of occurrence of the problem. The performance of the proposed method is successfully evaluated through numerical response simulations of two real footbridges, showing a good agreement with the experimental data.

scholarly journals Impact of COVID-19 on the Level of Energy Poverty in Poland

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4977
Author(s):  
Rafal Nagaj ◽  
Jaroslaw Korpysa
Keyword(s):  
Negative Impact ◽  
Scientific Data ◽  
Disposable Income ◽  
Energy Poverty ◽  
Household Energy ◽  
Energy Carriers ◽  
Financial Difficulties ◽  
Polish Economy ◽  
Definition Of ◽  
The Impact

The main objective of the paper is to determine the impact of the COVID-19 pandemic on the level of energy poverty in Poland. In order to achieve such a goal, the first part of the article presents the definition of energy poverty and the nature of its measures, as well as the determinants and policies of the state addressing the issue of energy poverty mitigation. In the second part of the paper, the results of research into the level of energy poverty are analyzed and the variables affecting energy poverty in Poland during the pandemic are determined. It was established on the basis of these results that the present pandemic contributed to the aggravation of financial difficulties in Polish households with regard to financing expenditure on energy carriers. It was found that COVID-19 had a negative impact on the average disposable income of Polish households, which, with the increase in prices and expenditure on energy carriers, led to an increase in the proportion of disposable income spent on energy carriers. The most affected have been the poorest households. Moreover, the long downward trend in the level of energy poverty in Poland has reversed. Thus, it has been proved that COVID-19 has contributed to the intensification of energy poverty in Poland. The theoretical and empirical considerations contained in this paper may be a valuable source of scientific data on the impact of the pandemic on household energy poverty, while public institutions may find them a source of useful information, helping to create effective instruments to mitigate energy poverty in the Polish economy.

scholarly journals The shrimp superfamily Sergestoidea: a global phylogeny with definition of new families and an assessment of the pathways into principal biotopes

2017 ◽  
Vol 4 (9) ◽  
pp. 170221 ◽  
Author(s):  
A. L. Vereshchaka
Keyword(s):  
Phylogenetic Analysis ◽  
Vertical Direction ◽  
Evolutionary Model ◽  
Copulatory Organ ◽  
Morphological Characters ◽  
Valid Species ◽  
Genus Level ◽  
Family Level ◽  
Medium Level ◽  
Definition Of

The phylogenetic analysis of Sergestoidea based on 253 morphological characters and encompassing all 99 valid species confirmed all previously recognized genus-level clades. Analysis retrieved five major robust clades that correspond to families Luciferidae, Sergestidae, Acetidae fam.n., Sicyonellidae fam.n. and Petalidiumidae fam.n. Synonymy, emended diagnoses and composition of revealed family-level clades are provided. Three types of morphological characters were important in the phylogeny of the Sergestoidea: general external characters, copulatory organs, and photophores. Novel metrics to quantify the contribution of these character types were tested. General external characters were significant in supporting the major clades (80% of the families and nearly half of the genera). Copulatory organ characters and photophores greatly supported the medium-level clades: Lucifer, Belzebub , Petalidium, Neosergestes, Challengerosergia (copulatory organ characters) and Lucensosergia , Challengerosergia, Gardinerosergia , Phorcosergia (photophores). An evolutionary model of the Sergestoidea showing their pathways into their principal biotopes is proposed: the major clades evolved in a vertical direction (from epi- to bathypelagic); further divergence at the genus level occurred within vertical zones in a horizontal direction, with the invasion of the benthopelagic and neritic (shelf and estuarine) habitats and speciation within these domains.

scholarly journals SUDDEN CARDIAC DEATH IN PATIENTS WITH DILATED CARDIOMYOPATHY

2014 ◽  
Vol 5 (4) ◽  
pp. 41-48
Author(s):  
D V Duplyakov ◽  
I V Kondratyeva ◽  
S V Garkina
Keyword(s):  
High Risk ◽  
Sudden Cardiac Death ◽  
Risk Stratification ◽  
Dilated Cardiomyopathy ◽  
Cardiac Death ◽  
Clinical Manifestations ◽  
Scientific Data ◽  
National Guidelines ◽  
Causative Factors ◽  
Definition Of

The review discusses accumulated to date scientific data on dilated cardiomyopathy: causative factors, clinical manifestations, sudden cardiac death in patients with the disease and its risk-stratification in the light of National guidelines on the definition of risk and prevention of sudden cardiac death (2012). A case of a patient with dilated cardiomyopathy and high-risk of sudden cardiac death is presented.

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