Mechanosorptive Creep of Hemlock under Conventional Drying: I. The Determination of Free Shrinkage Strain

2011 ◽  
Vol 29 (7) ◽  
pp. 789-796 ◽  
Author(s):  
Jian-Feng Zhan ◽  
Stavros Avramidis
Keyword(s):  
Shrinkage Strain ◽  
Free Shrinkage ◽  
Conventional Drying

scholarly journals Laws Governing Free and Actual Drying Shrinkage of 50 mm Thick Mongolian Scotch Pine Timber

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1500
Author(s):  
Xiaodong Zhu ◽  
Jingyao Zhao ◽  
Wanhui Gao ◽  
Cheng Qian ◽  
Yunjia Duan ◽  
...  
Keyword(s):  
Early Stage ◽  
Drying Shrinkage ◽  
Shrinkage Strain ◽  
Scotch Pine ◽  
Free Shrinkage ◽  
Different Temperatures ◽  
Conventional Drying ◽  
Sawn Timber ◽  
The Difference ◽  
Shrinkage Coefficient

The relationships between free shrinkage and actual shrinkage of different layers in Mongolian Scotch pine (Pinus sylvestris var. mongolica Litv.) were explored to provide basic data for the further study of drying shrinkage properties. The free shrinkage coefficients at different temperatures and the actual shrinkage strain of each layer were examined under conventional drying. The results showed high precision of free drying shrinkage of corresponding layers of thin small test strips in each layer of sawn timber. The free shrinkage increased linearly as moisture content declined. At the same temperature, the free shrinkage coefficient reached the largest values for the first layer (above 0.267), while the smallest values were recorded for the ninth layer (below 0.249). Except for the ninth layer, the free shrinkage coefficients in width directions of other representative layers decreased as temperature increased. At constant temperature, the difference in free shrinkage coefficient of test materials in the length direction of sawn timber was small for the first layer, but slightly larger and changed irregularly in the fifth and ninth layer direction. At the end of conventional drying, the plastic deformation of each layer in the early stage of drying showed a reducing trend or even reversal due to the effects of reverse stress and later damp heat. In sum, these findings look promising for future optimization of wood drying process.

scholarly journals Determination of Cure Shrinkage in Sl Layer Built Plates using Lamination Theory

2001 ◽  
Vol 10 (1) ◽  
pp. 096369350101000 ◽  
Author(s):  
A. Aggelopoulos ◽  
D. Karalekas
Keyword(s):  
Experimental Investigation ◽  
Solidification Process ◽  
Shrinkage Strain ◽  
Uv Exposure ◽  
Chemical Shrinkage ◽  
Resin Layer ◽  
Lamination Theory ◽  
Cure Shrinkage

This paper reports on a combined analytical and experimental investigation undertaken for the determination of polymerisation shrinkage strains resulted in photopolymer resin plates during the laser solidification process. A resin layer is laser cured on an identical layer of the same material that already has been cured and post cured under ultraviolet (UV) exposure. The assembled laminate is then UV cured, and the resulting warpage is recorded by means of the shadow moirtι method. The resulting warpage, consisting of elliptical equal deflection contours, is related to the polymerisation effective chemical shrinkage strain using the elastic lamination theory.

Thermo-Hygral Model for of Shrinkage Induced Stresses in Concrete Structures

2008 ◽  
Vol 400-402 ◽  
pp. 929-934 ◽  
Author(s):  
M.H. Baluch ◽  
Isam A. Mahmoud ◽  
M. Kalimur Rahman
Keyword(s):  
Finite Element ◽  
Thermal Stresses ◽  
Concrete Structures ◽  
Moisture Diffusion ◽  
Shrinkage Strain ◽  
Moisture Loss ◽  
Finite Element Software ◽  
Shrinkage Cracks ◽  
Rapid Moisture

Rapid moisture loss in concrete and the coupled shrinkage strain in concrete elements cause distress in structural members at early ages. The shrinkage stresses and the associated cracks can be reduced by controlling the rate of the moisture loss. However, under some circumstances, controlling the rate of the moisture rate is not practically possible which may add additional cost to the concrete construction. A finite element based technique is suggested in this paper to predict the shrinkage stresses and consequently predict the possibility of having shrinkage cracks. The technique utilizes the analog between the heat transfer and moisture diffusion, thermal stresses and shrinkage stresses. The analysis was performed using thermal and structural modules in the commercial finite element software ANSYS. The process described in this work makes the determination of restrained shrinkage stresses in problems of concrete structures readily accessible to design, repair and construction engineers.

Restrained concrete shrinkage in composite trusses

2012 ◽  
Vol 39 (7) ◽  
pp. 779-788
Author(s):  
Luis Orta ◽  
F. Michael Bartlett
Keyword(s):  
Shrinkage Strain ◽  
Mean Value ◽  
Tensile Creep ◽  
Restrained Shrinkage ◽  
Free Shrinkage ◽  
Concrete Shrinkage ◽  
Large Gradient ◽  
Independent Analysis ◽  
Steel Truss ◽  
Concrete Deck

An analytical approach to compute restrained shrinkage effects on composite concrete deck – steel truss members is presented and validated using strains and deflections obtained by Brattland and Kennedy, who in 1986 tested two full-scale (11.8 m × 2.35 m in plan) composite trusses and companion drying specimens for approximately 90 d. The test-to-predicted ratios for these quantities are excellent, with a mean value of 0.89 and a coefficient of variation of 0.11. It is also demonstrated that (1) single test specimens with a single drying face exhibit a large gradient of free shrinkage strain across the depth of the specimen that must be properly considered in the analysis; (2) shrinkage parameters estimated using generic rules based on the concrete mixture composition are not realistic for the particular mix used by Brattland and Kennedy; and (3) history-independent analysis methods, as described in Annex H of CSA S16-09, do not accurately predict the slab strains and truss deflections observed by Brattland and Kennedy unless the variation of the free shrinkage strain with slab depth, tensile creep, and concrete modulus of elasticity are properly accounted for.

Combined Influence of Expansive and Shrinkage Reducing Admixtures on the Shrinkage Behavior of Ultra-High Performance Concrete

2011 ◽  
Vol 488-489 ◽  
pp. 242-245 ◽  
Author(s):  
Jung Jun Park ◽  
Doo Youl Yoo ◽  
Sung Wook Kim ◽  
Young Soo Yoon
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Shrinkage Strain ◽  
Reducing Agents ◽  
Reinforcing Bars ◽  
Ultra High Performance Concrete ◽  
Free Shrinkage ◽  
Shrinkage Cracks ◽  
Binder Ratio ◽  
Shrinkage Reducing Admixtures

Since ultra-high performance cementitious composite (UHPCC) exhibits remarkable compressive strength and ductility, its application for structural member provides significant reduction of the section. The use of low water-to-binder ratio and admixtures with high fineness induce large shrinkage strain, leading to the possibility of large occurrence of shrinkage cracks due to the restraints of the form and reinforcing bars. Therefore, this study admixes a combination of expansive and shrinkage reducing agents as a solution to reduce the shrinkage of UHPCC. The eventual appropriateness is computed to evaluate the free shrinkage and restrained shrinkage behaviors. From the test results, the admixing of a combination of expansive and shrinkage reducing agents is seen to achieve a reduction of the free shrinkage by 30% to 50% at 28 days and a reduction of the strain of the external steel by about 19%.

scholarly journals Experimental Determination of the Global Mass Transfer Coefficients of the Tropical Woods in order to Deduce the Drying Curves at the Lower Temperature

2015 ◽  
Vol 12 (1) ◽  
Keyword(s):  
Mass Transfer ◽  
Drying Kinetics ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Solar Dryer ◽  
Conventional Drying ◽  
Drying Curves ◽  
Lower Temperature ◽  
Tropical Woods

We determine the global mass transfer coefficients of five tropical woods (obeche, iroko, lotofa, sapele and frake) coming from Cameroon. In this effect, drying kinetics using a solar dryer and a conventional dryer are utilized. In addition, comparison is doing between the values obtained and these coming from Chileans tropical woods and temperate. Thus, when the drying kinetics are between 0.25 to 1.5m/s, dry temperature equal to 33.5°C and wet temperature equal to 25°C, global mass transfer coefficients are between 2x10-5 and 4x10-5 kg/(m2 .s), for the conventional dryer. These values are conform to these obtained on the Chilean tropical woods and less than these obtained on the temperate woods. In the case of an indirect solar dryer functioning between October and November 2004 at Yaoundé, this coefficient is lower because the wood thickness is almost 24mm in the case of conventional drying and 50mm in the case of solar drying. It is coherent to use the correlation established with the temperate wood and given below where the parameters ao, bo, co and p should be specific on the tropical woods:

Analysis of Concrete Early-Age Shrinkage Based on the Theory of Humidity Diffusion

2011 ◽  
Vol 462-463 ◽  
pp. 183-187 ◽  
Author(s):  
Yun Feng Li ◽  
Rong Qiang Du ◽  
Fan Ying Kong
Keyword(s):  
Cement Content ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Analytical Models ◽  
Early Age ◽  
Free Shrinkage ◽  
Shrinkage Cracking ◽  
Binder Ratio ◽  
Water Binder Ratio

The early-age shrinkage cracking of concrete plays an important role to the accelerated deterioration and shortening the service life of concrete structures. Modern concretes are more sensitive to cracking immediately after setting, which is due to material characteristics (lower water/binder ratio and higher cement content) and external environmental fluctuations (humidity and temperature change). Determination of concrete free shrinkage is the basis of shrinkage cracking research. Analytical models of the autogenous shrinkage and drying shrinkage are established in this paper. The calculated results agree well with the experimental results.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

International determination of the total motion of the pole

1961 ◽  
Vol 13 ◽  
pp. 29-41
Author(s):  
Wm. Markowitz
Keyword(s):  
Secular Motion ◽  
The Future

A symposium on the future of the International Latitude Service (I. L. S.) is to be held in Helsinki in July 1960. My report for the symposium consists of two parts. Part I, denoded (Mk I) was published [1] earlier in 1960 under the title “Latitude and Longitude, and the Secular Motion of the Pole”. Part II is the present paper, denoded (Mk II).

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