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- 저자 : Wenya Shu (검색결과 2 건)
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Constitutive Model of Q345 Steel at Different Intermediate Strain Rates
Junling Chen,Wenya Shu,Jinwei Li 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.1
Structural elements of steel frame experience very high strain rates in the progressive collapse, and hence their constitutive properties do not remain constant but change significantly with time. Quasi-static and dynamic tensile tests of Q345 steel were performed to study the dynamic tensile behavior within the range of 0.001 to 330/s strain rates by INSTRON and Zwick/Roell HTM5020 testing machine. A three dimensional finite element model is developed using LS-DYNA to extrapolate the true stress-strain relationship after necking of Q345 steel. The hardening behavior of Q345 steel after the onset of necking is predicted with the Ludwik constitutive equation at quasi-static strain rates and with the Voce constitutive equation at higher strain rates, in which the strain hardening parameters are obtained by trial and error until the numerical results agree well with the experimental results. The linear combination of Hollomon and Voce (H/V-R) model is proved to be capable of predicting the transition of hardening rate with the increasing strain rate for Q345 steel although there is a little deviation between the experimental and fitting results. In this study, an empirical constitutive model is developed by introducing the Wagoner rate law into the H/V-R model to improve its precision in predicting the dynamic behavior of Q345 steel.
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An Improved Solution for Beam on Elastic Foundation using Quintic Displacement Functions
Tongji Univ,Youquan Feng,Wenya Shu 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2
The theory of beam on elastic foundation is a simple and popular analytic approach for computing the response of laterally loaded piles. For a laterally loaded pile with constant subgrade reaction coefficient, an analytical solution can be easily deduced based on the theory of beam on elastic foundation when the load distribution and boundary condition are simple. However, when the subgrade reaction coefficient increases linearly with the depth or when the constraint condition is complex, an approximate solution can only be obtained by numerical method. At present, the node-spring simulation method and the modifying stiffness matrix method are two main solution methods for beam on elastic foundation with a nonuniform distribution of subgrade reaction coefficient, but a large number of elements are necessary for obtaining a sufficient calculation accuracy. Based on the Winkler elastic foundation model, an improved Finite Element (FE) method for the laterally loaded pile on an elastic foundation with a linearly distributed modulus of the subgrade reaction is proposed. A quintic displacement function is proposed as an approximate solution, and the weighted residual method is used for solving differential equations. The corresponding element stiffness matrix and nodal force vector are derived, and a more accurate nodal displacement, element internal force and displacement distribution can then be obtained by employing fewer elements. Three beams on elastic foundations under different boundaries and loading conditions are taken as typical examples to compare the difference of the calculation accuracy between the improved method and the node-spring simulation method. A laterally loaded pile is analyzed by the improved method, and the numerical results show that two elements for one soil layer can provide a sufficient calculation accuracy.
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