scholarly journals Effect of different wind loading frequencies on tree deflection and uprooting

2021 ◽  
Author(s):  
Mehdi Zadehmohamad
Keyword(s):  
Loading Condition ◽  
Numerical Models ◽  
Wind Loading ◽  
Loading Frequency ◽  
Common Occurrence ◽  
Root Parameters ◽  
Tree Resistance ◽  
Tree Uprooting

Tree uprooting is the most common occurrence in hurricanes and storms; however themechanism is not well known. Numerous attempts have been made to model the damage causedto the trees by the storm. Less is known about the loading condition, which is important forpredicting the occurrence of uprooting. In this analysis, numerical models were used to investigatethe effect of loading frequency on tree resistance using theoretical soil and root parameters. Resultsshow that tree deflection under wind loading is highly dependent on loading frequency and lowfrequencyloading is highly probable.

Numerical Study of Corrugated Metal Panels Subjected to Windborne Debris Impacts

2014 ◽  
Vol 626 ◽  
pp. 109-114
Author(s):  
Wen Su Chen ◽  
Hong Hao ◽  
Hao Du
Keyword(s):  
Extreme Event ◽  
Numerical Study ◽  
Numerical Models ◽  
Economic Loss ◽  
Wind Loading ◽  
Windborne Debris ◽  
Study Laboratory ◽  
The Impact ◽  
Metal Panels ◽  
Corrugated Metal

Hurricane, typhoon and cyclone take place more and more often around the world with changing climate. Such nature disasters cause tremendous economic loss and casualty. Various kinds of windborne debris such as compact-like, plate-like and rod-like objects driven by hurricane usually imposes localized impact loading on the structure envelopes such as cladding, wall or roof, etc. The dominant opening in the envelope might cause serious damage to the structures, even collapse. To withstand the impact of such extreme event, the requirements on panel capacity to resist windborne debris impact has been presented in the Australian Wind Loading Code (2011) [1]. Corrugated metal panels are widely used as building envelop. In a previous study, laboratory tests have been carried out to investigate the performance of corrugated metal panels subjected to a 4kg wooden projectile by considering various impact locations, impact velocities and boundary conditions. In this study, numerical models were developed to simulate the responses of the corrugated metal panels subjected to wooden debris impacts by using commercial software LS-DYNA. The predicted data from the numerical simulations were compared with the experimental results. The validated numerical model can be used to conduct intensive numerical simulation to study the failure probabilities of corrugated structural panels subjected to windborne debris impacts.

Probabilistic characterization of roof panel uplift capacity under wind loading

2012 ◽  
Vol 39 (12) ◽  
pp. 1285-1296 ◽  
Author(s):  
W.X. He ◽  
H.P. Hong
Keyword(s):  
Numerical Models ◽  
Probability Model ◽  
Experimental Tests ◽  
Wind Pressure ◽  
Statistical Characteristics ◽  
Wind Loading ◽  
Experimental Investigations ◽  
Nonlinear Behaviour ◽  
Uplift Capacity ◽  
Roof Panel

The integrity of the roof system is important to the safety of inhabitants and prevents excessive damage to light-frame wood structures. The uplift capacity of fastened roof panels has been investigated using experimental tests and numerical models. Monotonically increasing uniform static pressure is often employed in experimental investigations and numerical modeling is carried out by assuming that the tributary area method is adequate and the fasteners can be modeled as linear elastic springs, even though the force–deformation relationship for nail withdrawal is nonlinear and uncertain. This study is aimed at assessing the statistical characteristics and modeling the uplift capacity for the roof panel under stochastic wind pressure by incorporating the uncertainty in nail withdrawal behaviour. The results show that the nonlinear behaviour of nail withdrawal needs to be considered to improve the accuracy of the estimated uplift capacity; the statistics and the probability model of the uplift capacity are affected by the degree of correlation of the fastener behaviour within the panel; and that nail spacing and missing nails influence the uplift capacity significantly.

Health monitoring of long span bridges and design verification with typhoon data

2019 ◽  
Author(s):  
Matt Carter ◽  
Naeem Hussain ◽  
Ngai Yeung ◽  
Steve Kite ◽  
K. W. Y. Chan ◽  
...  
Keyword(s):  
Hong Kong ◽  
Monitoring System ◽  
Health Monitoring ◽  
Loading Condition ◽  
Measurement Data ◽  
Wind Loading ◽  
Health Monitoring System ◽  
Long Span Bridges ◽  
Long Span ◽  
Bridge Responses

<p>Stonecutters Bridge is 1,018m main span cable stayed bridge in Hong Kong. The bridge incorporates a Wind and Structural Health Monitoring System (WASHMS) for monitoring the environmental loading condition such as traffic, temperature, wind and earthquake as well as the structural responses of the bridge including deflections, strains and long-term change of the bridge. A very powerful typhoon called Mangkhut, with 1- minute sustained wind speed up to 285km/h (180mph), struck Hong Kong on September 16, 2018. The response of Stonecutters Bridge under the action of this typhoon and the site-specific typhoon data have been recorded by the WASHMS. This paper analyses the measurement data of the typhoon loading and the bridge responses to demonstrate the use of health monitoring system for long span bridges and to verify the design of the bridge by comparison of the wind loading condition and stress conditions in major structural components.</p>

scholarly journals Drifting Dynamics of the Bluebottle

2021 ◽  
Author(s):  
Daniel Lee ◽  
Amandine Schaeffer ◽  
Sjoerd Groeskamp
Keyword(s):  
Linear Combination ◽  
Wind Velocity ◽  
Current Velocity ◽  
Equilibrium Condition ◽  
Shape Parameter ◽  
Numerical Models ◽  
Angle Of Attack ◽  
Ocean Current ◽  
Common Occurrence ◽  
Aerodynamic Forces

Abstract. Physalia physalis, also called the Bluebottle in Australia, is a colonial animal resembling a jellyfish that is well known to beachgoers for the painful stings delivered by their tentacles. Despite being a common occurrence, the origin of the Bluebottle before reaching the coastline is not well understood, and neither is the way it drifts at the surface of the ocean. Previous studies used numerical models in combination with simple assumptions to calculate the drift of this species, excluding complex drifting dynamics. In this study, we provide a new parametrization for Lagrangian modelling of the Bluebottle by considering the similarities between the Bluebottle and a sailboat. This allows us to compute the hydrodynamic and aerodynamic forces acting on the Bluebottle and use an equilibrium condition to create a generalised model for calculating the drifting speed and course of the Bluebottle under any wind and ocean current conditions. The generalised model shows that the velocity of the Bluebottle is a linear combination of the ocean current velocity and the wind velocity scaled by a coefficient ('shape parameter') and multiplied by a rotation matrix. Adding assumptions to this generalised model allows us to retrieve models used in previous literature. We discuss the sensitivity of the model to different parameters (shape, angle of attack and sail camber) and explore different cases of wind and current conditions to provide new insights into the drifting dynamics of the Bluebottle.

scholarly journals Drifting dynamics of the bluebottle (<i>Physalia physalis</i>)

Ocean Science ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1341-1351
Author(s):  
Daniel Lee ◽  
Amandine Schaeffer ◽  
Sjoerd Groeskamp
Keyword(s):  
Linear Combination ◽  
Current Velocity ◽  
Equilibrium Condition ◽  
Shape Parameter ◽  
Numerical Models ◽  
Ocean Current ◽  
Common Occurrence ◽  
Aerodynamic Forces ◽  
Generalized Model ◽  
Physalia Physalis

Abstract. Physalia physalis, also called the bluebottle in Australia, is a colonial animal resembling a jellyfish that is well known to beachgoers for the painful stings delivered by its tentacles. Despite being a common occurrence, the origin of the bluebottle before reaching the coastline is not well understood, and neither is the way it drifts at the surface of the ocean. Previous studies used numerical models in combination with simple assumptions to calculate the drift of this species, excluding complex drifting dynamics. In this study, we provide a new parameterization for Lagrangian modelling of the bluebottle by considering the similarities between the bluebottle and a sailboat. This allows us to compute the hydrodynamic and aerodynamic forces acting on the bluebottle and use an equilibrium condition to create a generalized model for calculating the drifting speed and course of the bluebottle under any wind and ocean current conditions. The generalized model shows that the velocity of the bluebottle is a linear combination of the ocean current velocity and the wind velocity scaled by a coefficient (“shape parameter”) and multiplied by a rotation matrix. Adding assumptions to this generalized model allows us to retrieve models used in previous literature. We discuss the sensitivity of the model to different parameters (shape, angle of attack and sail camber) and explore different cases of wind and current conditions to provide new insights into the drifting dynamics of the bluebottle.

Mitochondrial Changes in Cholestasis

1972 ◽  
Vol 30 ◽  
pp. 258-259
Author(s):  
F. G. Zaki
Keyword(s):  
Biliary Obstruction ◽  
Alcoholic Cirrhosis ◽  
Ultrastructural Changes ◽  
List Type ◽  
Common Occurrence ◽  
Extrahepatic Cholestasis ◽  
Mitochondrial Alteration ◽  
Extrahepatic Biliary Obstruction ◽  
Liver Biopsies ◽  
Mitochondrial Anomalies

Alterations of liver cell mitochondria represent pathologic phenomenon of a fundamental nature. Mitochondrial anomalies have been often described in association with cholestasis. In attempt to determine whether a given pattern of mitochondrial alteration has any correlation with the cause of cholestasis, liver biopsies were examined from 38 patients showing :a. extrahepatic cholestasis due to complete or partial extrahepatic biliary obstruction (8 cases proven at operation)b. intrahepatic cholestasis due to drugs (9 cases), viral hepatitis (6 cases) and alcoholic cirrhosis (15 cases).Mitochondria exhibiting ultrastructural changes due to aging or to the ‘wear and teart’ processes were not considered. In this study, the only profound and most prominent mitochondrial deformation was reported on basis of their common occurrence in randomly examined sections.

Stochastic simulation of the spatio-temporal field of the average daily heat index in Southern Russia

2020 ◽  
Vol 82 ◽  
pp. 149-160
Author(s):  
N Kargapolova
Keyword(s):  
Heat Waves ◽  
Numerical Models ◽  
Heat Index ◽  
Real Field ◽  
Gaussian Field ◽  
The Real ◽  
Southern Russia ◽  
Weather Stations ◽  
Spatio Temporal ◽  
Temporal Field

Numerical models of the heat index time series and spatio-temporal fields can be used for a variety of purposes, from the study of the dynamics of heat waves to projections of the influence of future climate on humans. To conduct these studies one must have efficient numerical models that successfully reproduce key features of the real weather processes. In this study, 2 numerical stochastic models of the spatio-temporal non-Gaussian field of the average daily heat index (ADHI) are considered. The field is simulated on an irregular grid determined by the location of weather stations. The first model is based on the method of the inverse distribution function. The second model is constructed using the normalization method. Real data collected at weather stations located in southern Russia are used to both determine the input parameters and to verify the proposed models. It is shown that the first model reproduces the properties of the real field of the ADHI more precisely compared to the second one, but the numerical implementation of the first model is significantly more time consuming. In the future, it is intended to transform the models presented to a numerical model of the conditional spatio-temporal field of the ADHI defined on a dense spatio-temporal grid and to use the model constructed for the stochastic forecasting of the heat index.

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