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Technique of Element Growing and Its Application in Simulating Reality of Roller Compacted Concrete

Author: PengWenMing
Tutor: DuanYunLing
School: Tsinghua University
Course: Hydraulic Engineering
Keywords: Roller Compacted Concrete(RCC) Laminated Element Growing Element Finite element method Shape Function
CLC: TV544
Type: Master's thesis
Year: 2005
Downloads: 75
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Abstract

Transient analysis on thermal effect in Roller Compacted Concrete(RCC)during construction is very important for quality control. RCC is of thin layerswith fast rising and each layer’s material properties are different for variousages. Laminated element including multi-layer materials can efficientlyreduces calculating scale. But there are some problems when using laminatedelement, for example its integration is too complicated, its shape function cannot reflect the difference of material properties when describing deformation,it can not simulate construction of RCC.Laminated integration is thought out for multi-layer materials. In thismethod integration points lie in middle of each layer and the weightcoefficient is relative thickness. Laminated element is taken as the naturalcoordinates of the quadrilateral when calculating the integral of each layer,which avoids the complexity brought on by Gaussian integration that musttake each material layer as the natural coordinates.According to the character of mechanical properties and deformation,modified shape function of laminated element is put forward in this thesis.The modified shape function is continuous or step function, and both candescribe zigzag deformation. Standard laminated element adopts bilinearshape function, which can not describe the true deformation in element whichis zigzag along the direction of layer height, so certain error exists in finiteelement analysis. And the error is magnified when material mechanicalproperties of each layer are different. Modified shape function can alsocontrol the error efficiently even if huge difference exists. Examples showthat shape function improves precision after modified.Based on laminated element, growing-joint model made up of jointelement, joint-laminated element and growing element, which can simulateconstruction of RCC is put out. Growing element include multi-layermaterials, which reduces the number of elements and nodes and avoidselement combination when simulating reality of RCC. Joint element andjoint-laminated element can deal with problems induced by connection ofelements between new casting concrete and rock or casted concrete, whichprovides gradual transition between fine and coarse meshes. Auto-searchreplacement and increment technique for boundary conditions is applied ingrowing-joint model. Numerical simulation reality shows that growing-jointmodel not only improves efficiency but also retains precision, whichpossesses important application value.Some interesting phenomena are revealed when applying the model andnumerical method in thermal effect transient analysis of right part of LongtanDam during construction. 1. Too low cast tempareture of concrete is notsuitable in hot weather, 2. Stress in inner foundation concrete is beyond ofallowable value, 3. Stress convergence is some severe in impervious layer ofupriver dam. The last two will bring on serious cracks, so correspondingmeasures which are introduced in this thesis should be carried out. Thecalculation results provides reference for temperature control and crackprevention in simulation reality of Longtan Dam and other similar projects.

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