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Study on the Energy Dissipation of Structurally Dissipating Rock-sheds by LS-DYNA

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Tutor: LiZhenHuan
School: Huazhong University of Science and Technology
Course: Solid Mechanics
Keywords: rock-fall impact,rock-shed,cylindrical shell buckling,energy dissipating
CLC: U417.1
Type: Master's thesis
Year:  2011
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Geological disasters are common in western mountainous areas of our country where mountain collapse and rock-falls are always induced by earthquakes, landslides, debris flow and other geological disasters. The cost of destruction of highways and bridges caused by geological disasters is increasing rapidly these years. Therefore it is of great significance to study the rock-falls protective structures.As a low-cost, simple and effective protective structure against rock fall, rock-sheds have been used more and more widely used nowadays. A new concept of rock-shed protection was proposed by TonelloI.C.Office in 2001. It consists of a reinforced concrete slab (not covered by any cushion) and cylindrical shell supports designed to dissipate the energy of rocks hitting on the edge of the slab.Light thin-walled metal structures were widely used in high-speed impact as energy absorbers because of its low cost, good energy absorption capacity and reliability. With the development and maturity of the circular tube study, scholars have proposed other section tubes, such as square cross section and, crisscross section and a variety of thin-walled composite structures, such as including the double cylindrical shell, and foam-filled structures.Based on the theory of dynamic explicit Finite Element Method (FEM) and LS-DYNA program, relationship between deformation modes and energy absorption of the tube under axial crushing was well studied. On that basis, three-dimensioned parametric studies on the new rock-sheds in multiple load cases were conducted.The numerical results show that:1¡¢With the same length and same thickness, crushing force peak of cross tubes and square tubes with the same perimeter was larger than square-containing circular tubes; Average crushing force of cross tubes and square tubes was smaller than square-containing circular tubes. The latter had better energy absorption capacity2¡¢Energy absorption capacity of the tube depended on the deformation mode, the length-diameter ratio and diameter- thickness ratio had significant influence in deformation mode. Besides, energy absorption capacity was in proportion with the material yield stress 3¡¢When cylindrical shells energy absorber sets increased from four to five, the shed¡¯s dissipation energy and damage decreased under both vertical impact and slant impact.4¡¢Increasing the thickness of the shell could enhance the energy absorption capacity, when the thickness was increased lager than 8mm and 7mm for four and five columns cases respectively, the enhancement of energy absorbing capacity was not significant anymore.5¡¢The double-layered cylinder shell structure could absorb more energy than single-layer shell, while the fill of aluminum foam filler in metal cylinder shell did not have significant influence in SDR structure.
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