scholarly journals Strength without Size Effect and Formula of Strength for Concrete and Natural Marble

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2685
Author(s):  
Guangchun Zhou ◽  
Jun Shi ◽  
Maohong Yu ◽  
Yu Zhang ◽  
Xiaochun Li ◽  
...  
Keyword(s):  
Size Effect ◽  
State Theory ◽  
Material Strength ◽  
Specific Load ◽  
Strength Theory ◽  
Principal Stresses ◽  
Unified Strength Theory ◽  
Uniaxial Load ◽  
Practical Engineering ◽  
History Of

Throughout the several-hundred-year-long history of the concept of strength, inaccurate material strength as a result of the size effect and the inconsistency of strength theories have been two continuous and challenging issues, and have even been taken to be inherent attributes of material strength. Applying the structural stressing state theory and method, this study experimentally investigates the uniaxial load-bearing process of concrete specimens and reveals their stressing state mutation features at specific load levels. Exploration of this general feature resulted in the discovery of essential strength, which is basically without size effect. Then, biaxial and triaxial experiments with concrete specimens were conducted in order to obtain the results for various combinations of principal stresses on essential strength. Consequently, according to Yu’s unified strength theory, the formula for strength of concrete was determined by fitting the relation between the combined principal stresses and the essential strength, which was verified by experiments carried out using natural marble specimens. Essential strength could promote the accuracy of strength indices, and the formula for strength might replace the existing strength theories for brittle materials. The initial solution of these two classic issues could make a new contribution to Yu’s unified strength theory and its final goal, promoting related research on material strength and leading to a more rational use of material strength in practical engineering.

Ultimate Bearing Capacity Analysis of Axially Compressive Circular Steel Tube Columns Filled with Bar-Reinforced Concrete

2011 ◽  
Vol 94-96 ◽  
pp. 1205-1210
Author(s):  
Zhao Liu ◽  
Jun Hai Zhao
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Steel Tube ◽  
Ultimate Bearing Capacity ◽  
Strength Theory ◽  
Principal Stresses ◽  
Unified Strength Theory ◽  
Short Columns ◽  
Circular Steel Tube ◽  
Circular Bar

The mechanical behavior and ultimate bearing capacity of the circular bar-reinforced concrete filled steel tube (BRCFST) short columns under axial compression are analyzed in this paper based on the unified strength theory. Considering the restriction effect of steel tube and hoop bar on concrete, the calculation formula of bearing capacity of the column is deduced. Parametric studies are carried out to evaluate the effects of intermediate principal stresses, diameter-thickness ratio of steel tube and the stirrup ratio on the bearing capacity of the column. A good agreement is reached by comparing the results calculated by the formula with the test results. It is concluded that the unified strength theory is applicable in the theoretical analyses of the BRCFST columns.

Application of the Unified Strength Theory in Analyzing Fracture Strength

2004 ◽  
Vol 261-263 ◽  
pp. 111-116 ◽  
Author(s):  
M.H. Yu ◽  
W. Fan ◽  
A.L. Che ◽  
M. Yoshimine ◽  
Takahiro Iwatate
Keyword(s):  
Fracture Mechanics ◽  
Mixed Mode ◽  
Fracture Criterion ◽  
Complex Stress ◽  
Strength Theory ◽  
Principal Stresses ◽  
Unified Strength Theory ◽  
Fracture Function ◽  
The Difference ◽  
Stress States

In practical engineering, the cracks are always mixed mode. The research on the mixed fracture criterion has an important significance in fracture mechanics and engineering. Stress state of the mixed mode cracks is complicated. A new unified strength theory considering the effects of all the three principal stresses is generalized into the fracture mechanics in this paper. The complex stress states are common characteristics between the mixed mode cracks and the unified strength theory. A unified fracture function criterion is established by using the unified strength theory in this paper. In the unified fracture function, the difference between tension and pressure and the effect of the intermediate principal stress σ2are considered. With the variation of α = σt/ σcand failure parameter b , a series of mixed mode crack criteria are formed, and can be applied for many materials. The J-integral is calculated through FEM. According to the relation between the result and the stress intensity factor, Klccan be obtained. Then it is used in the unified fracture function. The unified fracture criterion is compared with those of other mixed mode criterions.

Rentier Islamism

2018 ◽  
Author(s):  
Courtney Freer
Keyword(s):  
United Arab Emirates ◽  
Muslim Brotherhood ◽  
State Theory ◽  
Government Policies ◽  
The Political ◽  
Contemporary History ◽  
Rentier State ◽  
Oil Rents ◽  
History Of ◽  
Islamist Movements

This book, using contemporary history and original empirical research, updates traditional rentier state theory, which largely fails to account for the existence of Islamist movements, by demonstrating the political capital held by Muslim Brotherhood affiliates in Kuwait, Qatar, and the United Arab Emirates (UAE). While rentier state theory predicts that citizens of such states will form opposition blocs only when their stake in rent income is threatened, this book demonstrates that ideology, rather than rent, has motivated the formation of independent Islamist movements in the wealthiest states of the region. It argues for this thesis by chronicling the history of the Brotherhood in Kuwait, Qatar, and the UAE, and showing how the organization adapted to the changing (and often adverse) political environs of those respective countries to remain a popular and influential force for social, educational, and political change in the region. The presence of oil rents, then, far from rendering Islamist complaint politically irrelevant, shapes the ways in which Islamist movements seek to influence government policies.

scholarly journals Through-wall yield collapse pressure of casing based on unified strength theory

2016 ◽  
Vol 43 (3) ◽  
pp. 506-513 ◽  
Author(s):  
Yuanhua LIN ◽  
Kuanhai DENG ◽  
Yongxing SUN ◽  
Dezhi ZENG ◽  
Tianguo XIA
Keyword(s):  
Strength Theory ◽  
Unified Strength Theory ◽  
Collapse Pressure

scholarly journals Size Effect in Fracture of Sandwich Structure Components: Foam and Laminate

2001 ◽  
Author(s):  
Zdeněk P. Bažant ◽  
Yong Zhou ◽  
Drahomír Novák ◽  
Isaac M. Daniel
Keyword(s):  
Size Effect ◽  
Size Effects ◽  
Sandwich Structure ◽  
Maximum Load ◽  
Material Strength ◽  
Large Structures ◽  
Nominal Strength ◽  
Sandwich Plates And Shells ◽  
Extensive Test ◽  
Plates And Shells

Abstract In the design of sandwich plates and shells for very large structures, such as ships in the range of 100 m length, it is very important to take the size effect on the nominal strength into account, and do so in a realistic, physically justified, manner. Before the size effect is addressed for a sandwich structure, it must be understood for its components — the foam core and the laminate skins. In the current practice, the size effects are automatically attributed to the randomness of material strength, as described by the Weibull theory. The purpose of this paper is to show that in both the foam and the laminate there are deterministic size effects, which are generally more pronounced. They are caused by stress redistribution and energy release due to the growth of large fractures or large cracking zones prior to attaining the maximum load. This deterministic size effect is verified and calibrated by new tests of notched specimens of rigid close-cell vinyl foam. A combined deterministic-probabilistic theory of size effect of the laminates is proposed and verified by extensive test data.

Application of Numerical and Block Geomechanical Modelling to Determine Parameters of Large-Section Chambers

2021 ◽  
pp. 127-131
Author(s):  
M.A. Sonnov ◽  
A.V. Trofimov ◽  
A.E. Rumyantsev ◽  
S.V. Shpilev
Keyword(s):  
Rock Mass ◽  
Strain State ◽  
Stress And Strain ◽  
Underground Structures ◽  
Geomechanical Model ◽  
Principal Stresses ◽  
Mine Support ◽  
History Of ◽  
Crushing Plant ◽  
Ore Pass

The study is exemplified by complex workings of a main ore pass that include a variety of underground structures, usually with unique dimensions which depend on the function and size of the equipment placed. The technical solutions for the underground crushing plant and associated structures envisage construction of chambers with the height of up to 35 m and the width of up to 20 m at the depths exceeding 800-1000 m. Such conditions call for a closer attention to be paid to the mine support parameters, especially the bolting depth. A block geomechanical model was designed in the Micromine Mining Software for the rock mass of the new main ore pass. Geotechnical boreholes logs and results of physical and mechanical rock tests were used as the input data for the model. Four domains were identified in the block geomechanical model for subsequent numerical modelling. A 3D model of the stress-and-strain state of the rock mass was made using the CAE Fidesys software based on the Micromine wire-frame model of the main ore pass. The history of the rock mass incremental loading was reconstructed for correct simulation of its stress-and-strain state. Prior to the excavation, the rock mass is pre-stressed by the weight of the rock strata. The excavation phase was then simulated in the stepwise manner. An array of points with the values of maximum principal stresses was downloaded from the numerical model post-processing program and interpolated into the block geomechanical model to refine the SRF parameter of the Barton's Q rating. Based on the obtained Q values, the mine support parameters for chambers were determined using the Barton, Hutchinson and Potvin empirical methods.

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