scholarly journals Probabilistic Assessment of Roof Snow Load and the Calibration of Shape Coefficients in the Eurocodes

2021 ◽  
Vol 11 (7) ◽  
pp. 2984
Author(s):  
Pietro Croce ◽  
Paolo Formichi ◽  
Filippo Landi
Keyword(s):  
Conversion Factor ◽  
Reference Value ◽  
Construction Site ◽  
Probability Of Exceedance ◽  
Snow Load ◽  
Shape Coefficient ◽  
Annual Probability ◽  
Wind Exposure ◽  
Design Values ◽  
One Year

In modern structural codes, the reference value of the snow load on roofs is commonly given as the product of the characteristic value of the ground snow load at the construction site multiplied by the shape coefficient. The shape coefficient is a conversion factor which depends on the roof geometry, its wind exposure, and its thermal properties. In the Eurocodes, the characteristic roof snow load is either defined as the value corresponding to an annual probability of exceedance of 0.02 or as a nominal value. In this paper, an improved methodology to evaluate the roof snow load characterized by a given probability of exceedance (e.g., p=0.02 in one year) is presented based on appropriate probability density functions for ground snow loads and shape coefficients, duly taking into account the influence of the roof’s geometry and its exposure to wind. In that context, the curves for the design values of the shape coefficients are provided as a function of the coefficient of variation (COVg) of the yearly maxima of the snow load on the ground expected at a given site, considering three relevant wind exposure conditions: sheltered or non-exposed, semi-sheltered or normal, and windswept or exposed. The design shape coefficients for flat and pitched roofs, obtained considering roof snow load measurements collected in Europe during the European Snow Load Research Project (ESLRP) and in Norway, are finally compared with the roof snow load provisions given in the relevant existing Eurocode EN1991-1-3:2003 and in the new version being developed (prEN1991-1-3:2020) for the “second generation” of the Eurocodes.

scholarly journals Treatment and benefit analysis of wastewater from construction of hydropower project

2019 ◽  
Vol 136 ◽  
pp. 06024
Author(s):  
Haitao Ling ◽  
Cong Su ◽  
Haotian Xia ◽  
Fei Suo ◽  
Mengjie Xiao ◽  
...  
Keyword(s):  
Surface Water ◽  
Reference Value ◽  
Environmental Benefits ◽  
Construction Site ◽  
Construction Process ◽  
Hydropower Project ◽  
Benefit Analysis

In order to treat oil and other pollutants in downstream surface water causing by the construction process of a hydropower project, many methods were used. Besides that, a set of flocculation and precipitation facilities was designed as an emergency device for entire construction site. Good results were achieved in the treatment of construction wastewater, which has obvious economic and environmental benefits and has reference value for similar projects.

A Probabilistic Approach to the Prediction of Snow Loads

1974 ◽  
Vol 1 (1) ◽  
pp. 28-49 ◽  
Author(s):  
N. Isyumov ◽  
A. G. Davenport
Keyword(s):  
Formation Process ◽  
Extreme Values ◽  
Meteorological Data ◽  
Digital Simulation ◽  
Probabilistic Approach ◽  
Snow Accumulation ◽  
Meteorological Variables ◽  
Snow Load ◽  
Design Values ◽  
Snow Loads

The magnitudes of loads imposed by snow depend upon a number of climatological and meteorological variables and as a result exhibit marked variations geographically, due to local effects within a particular region, and with time. The snowload formation process, which depends both on the macro- and microclimates of such meteorological variables as the depth of the snowfall, the snowfall density, wind speed, air temperature etc., as well as, the size and geometry of particular roofs and the influence of their immediate environment, is discussed.A model of the snow load formation process based on a mass balance approach, which takes into account the deposition of snow by individual snowfalls and the depletion of the snow load by wind action and thermal effects, is introduced. The use of this approach requires the establishment of statistical descriptions of the various meteorological variables, as well as a knowledge of the physical process of snow accumulation and depletion for a particular roof. The statistical properties of some of the more important meteorological variables are discussed. Also presented are some model derived data of snow accumulation and depletion for particular roofs located in different terrain.It is shown that even relatively simple statistical descriptions of the relevant meteorological data and snow accumulation and depletion mechanisms can lead to realistic predictions of roof snow loads. Snow loads on a flat roof are generated by a digital simulation technique and compared with full scale observations. Annual extreme values of the simulated snow load process are presented and compared with currently specified design values. Comments are made regarding the practicability of this approach.

scholarly journals THE RELEVANCE OF CHANGING THE DESIGN SOLUTION COVERAGE WITHOUT STRENGTHENING EXISTING FOUNDATIONS

2019 ◽  
Vol 7 (2) ◽  
pp. 42-49
Author(s):  
Ольга Хрянина ◽  
Ol'ga Hryanina ◽  
Мария Колесникова ◽  
Maria Kolesnikova
Keyword(s):  
Raw Materials ◽  
Technical Condition ◽  
Operating Conditions ◽  
Design Solution ◽  
Building Structures ◽  
Construction Site ◽  
Satisfactory Condition ◽  
Geological Conditions ◽  
Design Values ◽  
Instrumental Methods

The authors carried out the study of raw materials and their analysis, which allowed to identify the engineering-geological conditions of the construction site and outline the program of scientific and survey works. Full-scale and instrumental examination of the technical condition of the bearing and enclosing structures of the building. It is established that the building structures during operation have not received deformations that prevent normal operating conditions and are currently in satisfactory condition. The strength of concrete Foundation organoleptic and instrumental methods, which showed compliance with the design values. Analysis of verification calculations of the base, a satisfactory condition of the building structures showed that the structural solution of the coating can be changed and performed in kind without strengthening the existing foundations.

scholarly journals WATER VAPOR CONVERSION FACTOR OVER QINGHAI-TIBET PLATEAU REGION CONSIDERING ELEVATION, LATITUDE AND FINE SEASONAL VARIATION IS CONSTRUCTED

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 271-277
Author(s):  
H. Peng ◽  
L. K. Huang ◽  
C. Li ◽  
L. L. Liu ◽  
S. Wang ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Precision ◽  
Conversion Factor ◽  
Conversion Coefficient ◽  
Reference Value ◽  
Radiosonde Data ◽  
Tibet Plateau ◽  
Grid Data ◽  
Plateau Region ◽  
Qinghai Tibet Plateau

Abstract. In this paper, the conversion factor K model of Qinghai-Tibet plateau region was established based on the QTm model which is established using high-precision the Global Geodetic Observing System (GGOS) Atmosphere grid data from 2007 to 2014. The model took into account the influence of elevation fluctuation and latitude change on the model, and analyzed the relevant characteristics with seasonal changes. The 2015 GGOS grid data and radiosonde data were used as the reference value for accuracy assess. The established QTm model was compared with GPT2w model in bias and RMS. Compared with GGOS grid data, the average annual bias and RMS of QTm model were -0.28K and 2.70k respectively. The RMS of GPT2w-5 and GPT2w-1 were 58.16% and 28.84% higher, respectively. Compared with radiosonde data, QTm model has 1.13k average annual bias and the RMS error of 2.92k. Compared with GPT2w-5 and GPT2w-1, the RMS value of QTm model was improved by 25.08% and 29.43%, respectively. The value of atmospheric water vapor conversion coefficient was calculated by the integral method calculated by radio sounding data in the Qinghai-Tibet region in 2015 was used as the reference value for assess the performance of conversion factor K, and compared and analyzed the conversion coefficient K which provided by QTm and GPT2w. The results show that the value of Tm provided by QTm model has the highest accuracy, which is 25.07% higher than that of GPT2w-5 and 29.42% higher than that of GPT2w-1. QTm models can achieve GPS-PWV retrieval precision of better than 2 mm. Which has potential application for high-precision real-time GNSS-PWV retrieving in Qinghai-Tibet region.

Long-Term Analysis of Extreme Global Restoring Loads on a FPSO Turret Structure Using a Coupled Model

2018 ◽  
Author(s):  
Isabel Jimenez Puente ◽  
Kjell Larsen
Keyword(s):  
Coupled Model ◽  
Element Model ◽  
Contour Line ◽  
Structural Element ◽  
Mooring Lines ◽  
Probability Of Exceedance ◽  
Extreme Loads ◽  
Annual Probability ◽  
Term Analysis

A turret structure can be a major design driver for FPSO systems. Therefore, careful attention needs to be given to the estimation of extreme loads on this structural element. This paper presents an all seas long-term analysis of the extreme global restoring forces acting on a FPSO turret structure, and a comparison with the results obtained through the contour line approach. The analysis is performed in the time domain using a coupled model, where the floater is modelled in the software SIMO, and the risers and mooring lines are represented by a Finite Element Model in RIFLEX. The characteristic responses of the turret structure with q-annual probability of exceedance are estimated from a full long-term analysis where both the short and long-term variability are considered. These results are compared to those obtained through the long-term estimate from the contour line approach when assuming 90th percentile for the worst sea state with q-annual probability of exceedance. The results from the full long-term analysis will allow us to verify the adequate percentile level to be used with a contour line approach when estimating extreme turret structure loads.

Ambient dose during intraoral radiography with current techniques: part 3: effect of tube voltage

2020 ◽  
pp. 20190362
Author(s):  
Reinier Cornelis Hoogeveen ◽  
Dirk van Beest ◽  
Erwin Berkhout
Keyword(s):  
Scattered Radiation ◽  
Conversion Factor ◽  
Reference Value ◽  
Radiation Doses ◽  
Intraoral Radiography ◽  
Tube Voltage ◽  
Mathematical Equations ◽  
Beam Transmission ◽  
The Impact ◽  
Ambient Dose

Objectives: This study was conducted to assess the impact of tube voltage on ambient dose during intraoral radiography, specifically remnant-beam transmission and scattered radiation. Methods and materials: Remnant-beam and scattered radiation doses were recorded using a phantom at tube voltages of 60, 63, 66, and 70 kV. Mathematical equations depicting their relations were then formulated, and reference values were calculated at the various voltages tested. Total ambient doses per exposure at 60 kV and at 70 kV were compared. Results: Both remnant-beam transmission and scattered radiation increased ~40% by increasing tube voltage from 60 kV to 70 kV, and the relation was linear. A remnant beam transmission reference value of 7.5% was established at 70 kV, as well as a conversion factor of 0.035µSv/mAs at one meter for scattered radiation at 60 kV. Given longer exposure times at 60 kV, total ambient dose proved higher at 60 kV than at 70 kV. Conclusion: Higher tube voltage results in higher remnant-beam transmission and more scattered radiation per workload. The relation is linear in the range between 60kV and 70 kV. Remnant-beam transmission at 70 kV is safely assessed at 7.5%. A conversion factor at 60 kV of 0.035 µSv/mAs at one meter for the scattered radiation dose can be proposed. Total ambient dose per exposure was higher at 60kV than at 70 kV.

Long Term Analysis of TLP Extreme Tendon Tensions Using a Coupled Model and Comparison With the Contour Line Approach

2017 ◽  
Author(s):  
Isabel Jimenez Puente ◽  
Gunnar Lian
Keyword(s):  
Coupled Model ◽  
Element Model ◽  
Contour Line ◽  
Probability Of Exceedance ◽  
Tension Response ◽  
Annual Probability ◽  
Short And Long Term ◽  
The Time Domain ◽  
Term Analysis

This paper presents a full long term analysis of a TLP extreme tendon tensions using the all seas approach, and its comparison to the results estimated by the contour line approach. The analysis of the TLP tendon tension response is performed in the time domain using a coupled model where the floater is modelled in the software SIMO, while the tendon system is represented by a Finite Element Model in RIFLEX, including therefore the effects of non-linear restoring from the tendon system and bending and deformations of the tendons. The characteristic tendon tensions with q-annual probability of exceedance are estimated from a full long term analysis where both the short and long term variability are considered. These results are then compared to those obtained through the long term estimate from the contour line approach when assuming the 90th percentile for the worst sea state with q-annual probability of exceedance. The results from the full long term analysis will allow us to verify the adequate percentile level to be used with a contour line approach when estimating extreme TLP tendon tensions.

scholarly journals Storm surge and ponding explain mangrove dieback in southwest Florida following Hurricane Irma

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David Lagomasino ◽  
Temilola Fatoyinbo ◽  
Edward Castañeda-Moya ◽  
Bruce D. Cook ◽  
Paul M. Montesano ◽  
...  
Keyword(s):  
Storm Surge ◽  
Ground Surface ◽  
Tree Height ◽  
Water Levels ◽  
Airborne Lidar ◽  
Southwest Florida ◽  
Before And After ◽  
Wind Exposure ◽  
One Year ◽  
Hurricane Irma

AbstractMangroves buffer inland ecosystems from hurricane winds and storm surge. However, their ability to withstand harsh cyclone conditions depends on plant resilience traits and geomorphology. Using airborne lidar and satellite imagery collected before and after Hurricane Irma, we estimated that 62% of mangroves in southwest Florida suffered canopy damage, with largest impacts in tall forests (>10 m). Mangroves on well-drained sites (83%) resprouted new leaves within one year after the storm. By contrast, in poorly-drained inland sites, we detected one of the largest mangrove diebacks on record (10,760 ha), triggered by Irma. We found evidence that the combination of low elevation (median = 9.4 cm asl), storm surge water levels (>1.4 m above the ground surface), and hydrologic isolation drove coastal forest vulnerability and were independent of tree height or wind exposure. Our results indicated that storm surge and ponding caused dieback, not wind. Tidal restoration and hydrologic management in these vulnerable, low-lying coastal areas can reduce mangrove mortality and improve resilience to future cyclones.

scholarly journals Effect of Folic Acid Supplementation on Serum Homocystene and Lipid Profile in Acute Myocardial Infarction

1970 ◽  
Vol 5 (2) ◽  
pp. 21-23
Author(s):  
MA Wahab ◽  
F Zafreen ◽  
MA Siddique ◽  
Y Akter ◽  
Z Parveen ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Folic Acid ◽  
Lipid Profile ◽  
Reference Value ◽  
Folic Acid Supplementation ◽  
Double Blind ◽  
Acid Supplementation ◽  
One Year ◽  
Medical University

This double blind randomized placebo controlled experimental study was carried out at the department of Biochemistry and Cardiology, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh over a period of one year. A total number of sixty (60) hospitalized acute myocardial infarction (AMI) patients of both sexes, age ranging 35 to 65 years, agreed after informed written consent, were included in the study. Cases were selected purposively on the basis of specified inclusion and exclusion criteria from hospitalized diagnosed patients of AMI. After detail history, clinical examination, physical and anthropometrics measurements study subjects were randomized into two groups and treated with 5 mg folic acid or placebo for 4 weeks. Fasting serum homocysteine (Hcy) and lipid profile of all the study subjects were estimated both before starting the drug and after completion of treatment, Hcy concentration was estimated by fluorescence polarization immunoassay (FPIA) method in 'AxSYM system' (Abbott, USA). Statistical analyses were done by using 'SPSS 12.0, continuous data were expressed as mean ± SEM and categorical data in percentage (%) and frequency. AMI patients Hcy concentration was higher than normal reference value (5 - 15 mmol/L). Folic acid supplementation decreased serum Hcy concentration very significantly (p<0.001) in drug group (from 25.92 ± 2.47 to 15.38 ± 0.68 mmol/L) but effect in placebo group was found no significant (p>0.05). In this study folic acid supplementation at a dose of 5 mg/day decreased Hcy concentration almost by 27%. Folic acid supplementation significantly (p<0.05) increased HDL concentration but shown no significant effect on other parameter of lipid profiles. Key words: Acute myocardial infarction (AMI), homocystein (Hcy), folic acid (Folate). DOI: 10.3329/jafmc.v5i2.4578 JAFMC Bangladesh Vol.5(2) (December) 2009, pp.21-23

scholarly journals Chemical Composition of Bulk Precipitation and Its Toxicity Potential Index in the Metropolitan Area of Monterrey, Northeastern Mexico

Environments ◽  
2020 ◽  
Vol 7 (12) ◽  
pp. 106
Author(s):  
Darithsa Loya-González ◽  
Daniel López-Serna ◽  
Juan Manuel Alfaro-Barbosa ◽  
Antonio López-Reyes ◽  
Humberto González-Rodríguez ◽  
...  
Keyword(s):  
Metropolitan Area ◽  
Environmental Protection Agency ◽  
Reference Value ◽  
Metallurgical Industry ◽  
Environmental Variable ◽  
Average Concentration ◽  
Potential Index ◽  
Toxicity Potential ◽  
One Year ◽  
The University

The rainwater chemistry within the Metropolitan Area of Monterrey (MAM) was studied during a one-year period (January 2019–January 2020) in seven sampling sites. The metal concentration of Zn, Fe, Cd, Cu, Ni, and Mn was analyzed in bulk samples and the toxicity potential (TP) was calculated for each metal. A canonical correspondence analysis (CCA) was applied to identify the relationship between environmental variables and metals concentrations. An average of 26.6 ± 10 mm of rainfall was obtained. A mean pH of 7.2 ± 0.3 and a mean electrical conductivity of 177.8 ± 8.7 µS cm−1 were observed. The average concentration of metals in all sites follows a descending order of Fe> Zn > Mn > Cu > Ni > Cd. The university site shows the highest averages of Fe, Zn, Cu, and Mn, which is attributed to its proximity to the metallurgical industry. The TP value of Cd reflects a risk in all sites and Fe only for the Universidad, Obispado, Pastora, and Santa Catarina sites, using as a reference value the Environmental Protection Agency (EPA) Drinking Water Regulations and Mexican norm NOM-127-SSA1-1994. The CCA analysis showed that only Ni and Cd had a strong correlation with the environmental variable of relative humidity of air.

Sign in / Sign up

Export Citation Format

Share Document