scholarly journals Wind-Induced Fatigue and Asymmetric Damage in a Timber Bridge

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3867 ◽  
Author(s):  
Olga Thalla ◽  
Stathis C. Stiros
Keyword(s):  
High Amplitude ◽  
Lateral Stiffness ◽  
Lateral Bending ◽  
Northerly Wind ◽  
Vertical Stiffness ◽  
Longitudinal Splitting ◽  
Multi Stage ◽  
Strong Winds ◽  
Wind Events ◽  
Lateral Deflections

The transformation of a 30 m long timber pedestrian bridge into a wobbly (laterally swaying) bridge with a dramatically reduced first lateral modal frequency has been monitored by seven annual, multi-sensor surveys. This evidence, in combination with analysis of the wind record, observations of local damage and evidence of wind-induced excitations from other bridges, is used to present a multi-stage scenario of the extraordinary structural weakening of our study bridge in only a few years. Our analysis is constrained by observations of asymmetric damage (longitudinal splitting cracks around metallic connections along the south side of the deck, not explained by ordinary, essentially symmetric lateral oscillations) and over-threshold analysis of strong northerly wind events, including gusts. The proposed scenario is that an unexpected for the area icing event took advantage of construction vicissitudes and produced damage that reduced the lateral stiffness of the bridge, especially of the arch superstructure. In addition, strong winds sharing common direction with gusts produced a combination of semi-static lateral bending and of dynamic oscillations, leading to numerous cycles of asymmetric high amplitude lateral deflections producing tensile stress normal to grain, cracks localized in connections, and fatigue. The vertical stiffness of the bridge was only slightly affected.

scholarly journals A methodology to conduct wind damage field surveys for high-impact weather events of convective origin

2020 ◽  
Vol 20 (5) ◽  
pp. 1513-1531 ◽  
Author(s):  
Oriol Rodríguez ◽  
Joan Bech ◽  
Juan de Dios Soriano ◽  
Delia Gutiérrez ◽  
Salvador Castán
Keyword(s):  
Field Studies ◽  
High Impact ◽  
Strong Wind ◽  
Field Surveys ◽  
Weather Events ◽  
Straight Line ◽  
High Impact Weather ◽  
Strong Winds ◽  
Wind Events ◽  
The One

Abstract. Post-event damage assessments are of paramount importance to document the effects of high-impact weather-related events such as floods or strong wind events. Moreover, evaluating the damage and characterizing its extent and intensity can be essential for further analysis such as completing a diagnostic meteorological case study. This paper presents a methodology to perform field surveys of damage caused by strong winds of convective origin (i.e. tornado, downburst and straight-line winds). It is based on previous studies and also on 136 field studies performed by the authors in Spain between 2004 and 2018. The methodology includes the collection of pictures and records of damage to human-made structures and on vegetation during the in situ visit to the affected area, as well as of available automatic weather station data, witness reports and images of the phenomenon, such as funnel cloud pictures, taken by casual observers. To synthesize the gathered data, three final deliverables are proposed: (i) a standardized text report of the analysed event, (ii) a table consisting of detailed geolocated information about each damage point and other relevant data and (iii) a map or a KML (Keyhole Markup Language) file containing the previous information ready for graphical display and further analysis. This methodology has been applied by the authors in the past, sometimes only a few hours after the event occurrence and, on many occasions, when the type of convective phenomenon was uncertain. In those uncertain cases, the information resulting from this methodology contributed effectively to discern the phenomenon type thanks to the damage pattern analysis, particularly if no witness reports were available. The application of methodologies such as the one presented here is necessary in order to build homogeneous and robust databases of severe weather cases and high-impact weather events.

The Dynamic Characteristics of Rigid Frame Single-Rib Arch Bridge

2013 ◽  
Vol 368-370 ◽  
pp. 1426-1430
Author(s):  
Li Xiong Gu ◽  
Rong Hui Wang
Keyword(s):  
Dynamic Characteristics ◽  
Bending Strength ◽  
Dynamic Properties ◽  
Structural Parameters ◽  
Bending Stiffness ◽  
Torsional Stiffness ◽  
Lateral Stiffness ◽  
Arch Bridge ◽  
Vertical Stiffness ◽  
Rigid Frame

In this paper, by establishing the finite element model to study the dynamic characteristics of rigid frame single-rib arch bridge. By respectively changing structural parameters of the span ratios, and the compressive stiffness of arch, and the bending stiffness of arch, and the bending stiffness of bridge girder, and the layout of boom to find out the regularity of the structure on lateral stiffness, and vertical stiffness, and torsional stiffness as well as dynamic properties, it come out the results of that lateral stiffness of the structure is weaker, and increasing the span ratios and the compressive strength of arch are conducive to the improvement of the overall stiffness, and improving the bending strength of arch and layout of boom are less effect on the overall stiffness and mode shape.

scholarly journals Performance research and safety verification of compound structure air spring

2020 ◽  
Vol 12 (12) ◽  
pp. 168781402097479
Author(s):  
Lihang Yin ◽  
Wei Xu ◽  
Zechao Hu ◽  
Yuanchao Zhang ◽  
Chuang Li
Keyword(s):  
Natural Frequency ◽  
Dynamic Stiffness ◽  
Lateral Stiffness ◽  
Test Results ◽  
Air Spring ◽  
Compound Structure ◽  
Static And Dynamic Characteristics ◽  
Vertical Stiffness ◽  
Safety And Reliability ◽  
Performance Research

To further reduce the vertical stiffness of the air spring, appropriately reduce its lateral stiffness to attenuate the transmission of vibration along the lateral and longitudinal directions, a compound structure air spring (CSAS) was designed. It is a laminated structure with a hard elastic layer at the lower end of the original air spring. Prototypes of the air spring and the CSAS were produced, then related static and dynamic characteristics tests were conducted. Compared with the test results of the air spring, it can be found that under the same air pressure, the bearing capacity of the CSAS is decreased slightly; under rated load, the vertical static/dynamic stiffness and natural frequency is decreased slightly, and the lateral static/dynamic stiffness is decrease significantly. Furthermore, the CSAS was subjected to the safety and reliability tests, and its performance was stable without damage. This article expands the stiffness range of the air spring, and provides a new idea for the design of the air spring with low lateral to vertical stiffness ratio and low natural frequency.

Statistical Summary and Case Studies of Strong Wind Damage in China

2013 ◽  
Vol 8 (6) ◽  
pp. 1096-1102 ◽  
Author(s):  
Shuyang Cao ◽  
◽  
Jin Wang ◽  
Keyword(s):  
Case Studies ◽  
Low Cost ◽  
Wind Damage ◽  
Strong Wind ◽  
Severe Damage ◽  
Engineering Measures ◽  
Strong Winds ◽  
Wind Events ◽  
Forestry Products ◽  
Statistical Summary

Strong wind events, such as typhoons and tornados, have caused severe damage to buildings and other structures as well as agricultural and forestry products in China. This paper analyzes statistical data on typhoons and tornados in China, and it reports case studies on strong wind damage. Lessons from past damage from strong winds, as well as engineering measures against potential wind damage to low-cost houses, are presented for the purpose of wind-related disaster risk reduction.

Diverse anguilliform swimming kinematics in Pacific hagfish (Eptatretus stoutii) and Atlantic hagfish (Myxine glutinosa)

2015 ◽  
Vol 93 (3) ◽  
pp. 213-223 ◽  
Author(s):  
J.L. Lim ◽  
T.M. Winegard
Keyword(s):  
High Speed ◽  
Wave Speed ◽  
High Amplitude ◽  
The Body ◽  
Whole Body ◽  
Lateral Bending ◽  
Myxine Glutinosa ◽  
Eptatretus Stoutii ◽  
Swimming Kinematics ◽  
Broad Classification

Anguilliform mode swimmers pass waves of lateral bending down their elongate bodies to propel forward. Hagfishes (Myxinidae) are classified as anguilliform swimmers, but their unique habits and reduced morphology—including a flexible body lacking a vertebral column—have the potential to translate into unique swimming behaviour within this broad classification. Their roles as active scavengers and hunters can require considerable bouts of swimming, yet quantitative data on hagfish locomotion are limited. Here, we aim to provide a more complete mechanistic understanding of hagfish swimming by quantifying whole-body kinematics of steady swimming in Pacific hagfish (Eptatretus stoutii (Lockington, 1878)) and Atlantic hagfish (Myxine glutinosa L., 1758), species from the two main lineages of Myxinidae. We analyzed high-speed video of hagfishes swimming at voluntary swim speeds and found that both species swim using high-amplitude undulatory waves. Swim speed is generally frequency-modulated, but patterns in wave speed, wavelength, and amplitude along the body and across swim speeds are variable, implying versatile mechanisms for the control of swim speed in these highly flexible fishes. We propose mechanistic explanations for this kinematic variability and compare hagfish with other elongate swimmers, demonstrating that the hagfish’s rich locomotory repertoire adds variety to the already diverse set of locomotory kinematics found in anguilliform swimmers.

Review of Techniques for Predicting the Fundamental Period of Multi-Storey Buildings: Effects of Nonstructural Components

2015 ◽  
Vol 15 (02) ◽  
pp. 1450039 ◽  
Author(s):  
Massoud Sofi ◽  
Graham Leighton Hutchinson ◽  
Colin Duffield
Keyword(s):  
Tall Buildings ◽  
Lateral Load ◽  
Wind Load ◽  
Lateral Stiffness ◽  
Limit States ◽  
Nonstructural Components ◽  
Lateral Deflection ◽  
Moderate Seismicity ◽  
Drift Limit ◽  
Lateral Deflections

The design of lateral load resisting elements of tall buildings in regions of low to moderate seismicity is normally governed by the requirements to meet inter-storey drift limit under wind load. The key objective of the design of tall buildings is to provide adequate lateral stiffness to the buildings to limit their lateral deflections and inter-storey drifts under the lateral load. The current design practice assumes that only the structural skeleton provides lateral resistance against wind load. Although the effects of nonstructural elements on the lateral stiffness are widely acknowledged, the effects are often ignored in the analysis of the buildings. This paper presents a state-of-the-art of review on the effects of nonstructural elements on the lateral deflections and inter-storey drifts of buildings at serviceability limit states. It was found that ignoring the nonstructural elements could significantly underestimate the lateral deflection for certain types of buildings. However, the shape and form of the lateral deflection in the overall building is not significantly affected by the nonstructural elements.

Climatology of High Wind Events in the Owens Valley, California

2008 ◽  
Vol 136 (9) ◽  
pp. 3536-3552 ◽  
Author(s):  
Shiyuan Zhong ◽  
Ju Li ◽  
C. David Whiteman ◽  
Xindi Bian ◽  
Wenqing Yao
Keyword(s):  
Sierra Nevada ◽  
Blow Up ◽  
Common Belief ◽  
Strong Wind ◽  
High Wind ◽  
Owens Valley ◽  
Reanalysis Dataset ◽  
Strong Winds ◽  
Wind Events ◽  
Upper Level

Abstract The climatology of high wind events in the Owens Valley, California, a deep valley located just east of the southern Sierra Nevada, is described using data from six automated weather stations distributed along the valley axis in combination with the North American Regional Reanalysis dataset. Potential mechanisms for the development of strong winds in the valley are examined. Contrary to the common belief that strong winds in the Owens Valley are westerly downslope windstorms that develop on the eastern slope of the Sierra Nevada, strong westerly winds are rare in the valley. Instead, strong winds are highly bidirectional, blowing either up (northward) or down (southward) the valley axis. High wind events are most frequent in spring and early fall and they occur more often during daytime than during nighttime, with a peak frequency in the afternoon. Unlike thermally driven valley winds that blow up valley during daytime and down valley during nighttime, strong winds may blow in either direction regardless of the time of the day. The southerly up-valley winds appear most often in the afternoon, a time when there is a weak minimum of northerly down-valley winds, indicating that strong wind events are modulated by local along-valley thermal forcing. Several mechanisms, including downward momentum transfer, forced channeling, and pressure-driven channeling all play a role in the development of southerly high wind events. These events are typically accompanied by strong south-southwesterly synoptic winds ahead of an upper-level trough off the California coast. The northerly high wind events, which typically occur when winds aloft are from the northwest ahead of an approaching upper-level ridge, are predominantly caused by the passage of a cold front when fast-moving cold air behind the surface front undercuts and displaces the warmer air in the valley. Forced channeling by the sidewalls of the relatively narrow valley aligns the wind direction with the valley axis and enhances the wind speeds.

scholarly journals Climatology of Westerly Wind Events in the Lee of the Sierra Nevada

2017 ◽  
Vol 56 (4) ◽  
pp. 1003-1023 ◽  
Author(s):  
Stefano Serafin ◽  
Lukas Strauss ◽  
Vanda Grubišić
Keyword(s):  
Sierra Nevada ◽  
Westerly Wind ◽  
Owens Valley ◽  
Mountain Waves ◽  
Wind Variability ◽  
Westerly Winds ◽  
Thermally Driven ◽  
Strong Winds ◽  
Wind Events ◽  
Westerly Wind Events

AbstractA 5-yr climatology of westerly wind events in Owens Valley, California, is derived from data measured by a mesoscale network of 16 automatic weather stations. Thermally driven up- and down-valley flows are found to account for a large part of the diurnal wind variability in this approximately north–south-oriented deep U-shaped valley. High–wind speed events at the western side of the valley deviate from this basic pattern by showing a higher percentage of westerly winds. In general, strong westerly winds in Owens Valley tend to be more persistent and to display higher sustained speeds than strong winds from other quadrants. The highest frequency of strong winds at the valley floor is found in the afternoon hours from April to September, pointing to thermal forcing as a plausible controlling mechanism. However, the most intense westerly wind events (westerly windstorms) can happen at any time of the day throughout the year. The temperature and humidity variations caused by westerly windstorms depend on the properties of the approaching air masses. In some cases, the windstorms lead to overall warming and drying of the valley atmosphere, similar to foehn or chinook intrusions. The key dynamical driver of westerly windstorms in Owens Valley is conjectured to be the downward penetration of momentum associated with mountain waves produced by the Sierra Nevada ridgeline to the west of the valley.

scholarly journals Gaia Data Release 2

2019 ◽  
Vol 625 ◽  
pp. A97 ◽  
Author(s):  
L. Rimoldini ◽  
B. Holl ◽  
M. Audard ◽  
N. Mowlavi ◽  
K. Nienartowicz ◽  
...  
Keyword(s):  
Time Series ◽  
High Amplitude ◽  
Rr Lyrae Stars ◽  
Long Period ◽  
Rr Lyrae ◽  
Multi Stage ◽  
Long Period Variables ◽  
Data Release ◽  
Lyrae Stars

Context. More than half a million of the 1.69 billion sources in Gaia Data Release 2 (DR2) are published with photometric time series that exhibit light variations during the 22 months of observation. Aims. An all-sky classification of common high-amplitude pulsators (Cepheids, long-period variables, δ Scuti/SX Phoenicis, and RR Lyrae stars) is provided for stars with brightness variations greater than 0.1 mag in G band. Methods. A semi-supervised classification approach was employed, firstly training multi-stage random forest classifiers with sources of known types in the literature, followed by a preliminary classification of the Gaia data and a second training phase that included a selection of the first classification results to improve the representation of some classes, before the improved classifiers were applied to the Gaia data. Dedicated validation classifiers were used to reduce the level of contamination in the published results. A relevant fraction of objects were not yet sufficiently sampled for reliable Fourier series decomposition, consequently classifiers were based on features derived from statistics of photometric time series in the G, GBP, and GRP bands, as well as from some astrometric parameters. Results. The published classification results include 195 780 RR Lyrae stars, 150 757 long-period variables, 8550 Cepheids, and 8882 δ Scuti/SX Phoenicis stars. All of these results represent candidates whose completeness and contamination are described as a function of variability type and classification reliability. Results are expressed in terms of class labels and classification scores, which are available in the vari_classifier_result table of the Gaia archive.

Sensitivity Analysis of the Elastic Properties of Rail Vehicle Suspensions on Vibration Based on the HXN5 Locomotive Model

2014 ◽  
Vol 635-637 ◽  
pp. 201-207 ◽  
Author(s):  
Hao Zhou ◽  
Bin Xu ◽  
Jian Wu Zhang
Keyword(s):  
Sensitivity Analysis ◽  
Ride Comfort ◽  
Dynamic Performance ◽  
Lateral Stiffness ◽  
Dynamic Simulations ◽  
Direct Role ◽  
Vertical Stiffness ◽  
Vehicle Suspensions ◽  
Longitudinal Stiffness ◽  
Secondary Suspension

The dynamic performance of suspensions plays direct role in vibration control of railway vehicles and also has great impact on the ride comfort and operation stability. For assessment of the influence, a method of sensitivity analysis was performed, in which a Multi-Body System (MBS) dynamic model for the HXN5 locomotive counting for significant DOFs and nonlinearities was developed in SIMPACK platform and validated by real tests. More than tens of dynamic simulations were performed by a variety of damping and stiffness coefficients of the primary and secondary suspensions. By simulation, it is found that the vertical stiffness and damping of the primary suspension have the most sensitive influence. The lateral stiffness of the primary suspension, the longitudinal and lateral stiffness as well as the longitudinal and vertical damper of the secondary suspension possess the least effect on the railway locomotive vibration characteristics. It is also shown parameters of the longitudinal stiffness of the primary suspension, the vertical stiffness and lateral damper of secondary suspensions are of intermediate influence.

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