scholarly journals Spatial Variability of Ozigo Wood Beams under Long-Term Loadings in Various Environmental Exposures

2021 ◽  
Vol 13 (10) ◽  
pp. 5356
Author(s):  
Valérie Nsouami ◽  
Nicaise Manfoumbi ◽  
Rostand Moutou Moutou Pitti ◽  
Emilio Bastidas-Arteaga
Keyword(s):  
Spatial Variability ◽  
Statistical Tests ◽  
Sustainable Construction ◽  
Bending Tests ◽  
Three Point Bending ◽  
Wood Beams ◽  
Renewable Material ◽  
Support Conditions ◽  
Term Creep

Timber is a renewable material that should be more used for sustainable construction. While the mechanical behavior and durability of some species have been widely studied in the past, few studies are available for the Ozigo (Dacryodes buettneri) specie. This paper deals with the spatial variability of Ozigo beams subjected to long-term loadings and different environmental conditions. These beams were previously subjected to long-term creep in three environments (air-conditioned, unsheltered, and sheltered) at Masuku in the south-east of Gabon. Various specimens were extracted from these beams to determine its moisture content and subjected to three-point bending tests to obtain the modulus of elasticity and failure stress at various points in the space. The results obtained showed that, after long-term loadings, environmental exposure combined with mechanical loading, play a key role in the mechanical properties of the timber beams. A reduction of strength was found for the specimens extracted from the unsheltered and sheltered outdoor exposures in comparison with those extracted from the air-conditioned exposure. Concerning the spatial variability, statistical tests confirm that there is significant spatial correlation. It was also found that the spatial variation of properties in the beam is not stationary because it was affected by loading and support conditions.

scholarly journals The usability of Burger body model on determination of oriented strand boards’ creep behavior

2020 ◽  
Vol 29 ◽  
pp. 2633366X2093589
Author(s):  
Nadir Yildirim ◽  
Stephen Shaler ◽  
William West ◽  
Ema Gajic ◽  
Russel Edgar
Keyword(s):  
Creep Behavior ◽  
Short Term ◽  
Bending Tests ◽  
Body Model ◽  
Bending Strain ◽  
Strain Data ◽  
Measured Strain ◽  
Group 2 ◽  
Term Creep

In this work, the usability of the Burger body model (BBM) for determining the behavior of oriented strand boards (OSBs) under long-term loads was evaluated. The actual bending strain data and predicted strain data as a function of different stress levels and load durations under constant environmental conditions (25 ± 2°C and 50% relative humidity) were compared. Two test groups, short-term bending tests and long-term creep-rupture bending tests, were performed according to relevant ASTM standards. Specimens were randomly assigned to three groups and loaded at 47% (132.2 kg), 51% (137.4 kg), or 55% (154.9 kg) of the mean static short-term flexural strength. Specimen creep was monitored for 10,000 h using an automated measurement system. The four-parameter BBM parameters were obtained for all specimens at 2000-h time intervals, providing five different estimates. Measured strain values were compared with strain predictions from the BBM and with the goal of evaluating length of experiment on prediction accuracy. Each stress level provided statistical differences based on the error between the actual strain and predicted strain values. Group 3 provided minimum error compared to group 1 and group 2. The 10,000 and 8000 h loading provided the most accurate predictions compared to 6000, 4000, and 2000 h of data. Overall, the longer the actual data is collected the more accurate predictions were obtained. As a result, the BBM was found useful tool for predicting the creep behavior of OSBs under different loads and load durations. It was also shown that the increased duration of practical loading minimizes the error between the prediction. Therefore, the BBM is suggested for use predicting the creep behavior of OSBs over 8000 h load durations.

Investigation of the Deformation Twins on the Bending Cross Section of TA2 Titanium Sheet

2020 ◽  
Vol 837 ◽  
pp. 41-45
Author(s):  
Shuai Sun ◽  
Kai Hua Liu
Keyword(s):  
Electron Backscatter Diffraction ◽  
Testing Machine ◽  
Pure Titanium ◽  
Titanium Sheet ◽  
Bending Tests ◽  
Three Point Bending ◽  
Deformation Twins ◽  
Ebsd Technique ◽  
Backscatter Diffraction ◽  
Deformation Area

In order to determine the evolution features of deformation twins for TA2 commercial pure titanium (cp-TA2), the TA2 samples were bent under different bending angles in three-point bending tests via a universal testing machine. The electron backscatter diffraction (EBSD) technique was applied to identify the grain boundaries (GBs) and twin boundaries (TBs) in the bending areas. The results reveal that the type of deformation area would effect the evolution of different deformation twins. It is inferred that the state of stress would promote the multiplication of the same type of deformation twins.

Statistical reinterpretation of the long term creep behaviour of the Ismetpasa segment of North Anatolian Fault, Turkey

2021 ◽  
pp. 228947
Author(s):  
Gokhan Gurbuz ◽  
Caglar Bayik ◽  
Saygin Abdikan ◽  
Kurtulus Sedar Gormus ◽  
Senol Hakan Kutoglu
Keyword(s):  
Creep Behaviour ◽  
North Anatolian Fault ◽  
Term Creep

scholarly journals A Study of the Flexural Behavior of Fiber-Reinforced Concretes Exposed to Moderate Temperatures

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3522
Author(s):  
Marta Caballero-Jorna ◽  
Marta Roig-Flores ◽  
Pedro Serna
Keyword(s):  
Steel Fiber ◽  
Flexural Behavior ◽  
Polypropylene Fibers ◽  
Fiber Reinforced ◽  
Insulation System ◽  
Bending Tests ◽  
Synthetic Fibers ◽  
Three Point Bending ◽  
Lower Performance ◽  
Cracked Specimens

The use of synthetic fibers in fiber-reinforced concretes (FRCs) is often avoided due to the mistrust of lower performance at changing temperatures. This work examines the effect of moderate temperatures on the flexural strengths of FRCs. Two types of polypropylene fibers were tested, and one steel fiber was employed as a reference. Three-point bending tests were carried out following an adapted methodology based on the standard EN 14651. This adapted procedure included an insulation system that allowed the assessment of FRC flexural behavior after being exposed for two months at temperatures of 5, 20, 35 and 50 °C. In addition, the interaction of temperature with a pre-cracked state was also analyzed. To do this, several specimens were pre-cracked to 0.5 mm after 28 days and conditioned in their respective temperature until testing. The findings suggest that this range of moderate temperatures did not degrade the behavior of FRCs to a great extent since the analysis of variances showed that temperature is not always a significant factor; however, it did have an influence on the pre-cracked specimens at 35 and 50 °C.

scholarly journals Statistically rigorous calculations do not support common input and long-term synchronization of motor-unit firings

2014 ◽  
Vol 112 (11) ◽  
pp. 2729-2744 ◽  
Author(s):  
Carlo J. De Luca ◽  
Joshua C. Kline
Keyword(s):  
Motor Unit ◽  
Statistical Tests ◽  
Vastus Lateralis ◽  
Common Input ◽  
Data Set ◽  
Order Of Magnitude ◽  
Score Method ◽  
Surface Electromyographic Signal ◽  
Measure Synchronization

Over the past four decades, various methods have been implemented to measure synchronization of motor-unit firings. In this work, we provide evidence that prior reports of the existence of universal common inputs to all motoneurons and the presence of long-term synchronization are misleading, because they did not use sufficiently rigorous statistical tests to detect synchronization. We developed a statistically based method (SigMax) for computing synchronization and tested it with data from 17,736 motor-unit pairs containing 1,035,225 firing instances from the first dorsal interosseous and vastus lateralis muscles—a data set one order of magnitude greater than that reported in previous studies. Only firing data, obtained from surface electromyographic signal decomposition with >95% accuracy, were used in the study. The data were not subjectively selected in any manner. Because of the size of our data set and the statistical rigor inherent to SigMax, we have confidence that the synchronization values that we calculated provide an improved estimate of physiologically driven synchronization. Compared with three other commonly used techniques, ours revealed three types of discrepancies that result from failing to use sufficient statistical tests necessary to detect synchronization. 1) On average, the z-score method falsely detected synchronization at 16 separate latencies in each motor-unit pair. 2) The cumulative sum method missed one out of every four synchronization identifications found by SigMax. 3) The common input assumption method identified synchronization from 100% of motor-unit pairs studied. SigMax revealed that only 50% of motor-unit pairs actually manifested synchronization.

Utilization of Dacite as Alternative Aggregate in Asphalt Mixture

2012 ◽  
Vol 509 ◽  
pp. 209-214
Author(s):  
Shao Peng Wu ◽  
Pan Pan ◽  
Ming Yu Chen
Keyword(s):  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Major Objective ◽  
Widespread Application ◽  
Bending Tests ◽  
Three Point Bending ◽  
Large Numbers ◽  
Asphalt Content ◽  
The Cost ◽  
Cost Of Construction

With the widespread application of asphalt mixture, current demand from transportation managers for construction and maintenance of their pavement network consumes large numbers of aggregates. If agencies excessively favor to some certain kinds of excellent aggregates, the cost of construction could be considerably expensive. The major objective of this study is to determine the feasibility of utilizing dacite in asphalt mixtures. By means of Marshall, freeze-thaw, rutting and three-point bending tests, the performances of dacite and basalt asphalt mixture are compared. The results of the testing illustrate that dacite asphalt mixture is more susceptible to gradation and asphalt content than basalt asphalt mixture. Meanwhile it is showed that the performances of dacite asphalt mixture can be improved greatly with the involvement of additives including active mineral powder and cement. Furthermore, it is validated that dacite can be used as alternative aggregate in asphalt mixture.

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