scholarly journals Adaptive Powell’s Identification of Elastic Constants of Composite Glass Girder with Layered Shell Element Theory

Mechanika ◽  
2020 ◽  
Vol 26 (5) ◽  
pp. 390-397
Author(s):  
Jian ZHANG ◽  
Yanlong JIANG ◽  
Wei SUN ◽  
Hua LIU ◽  
Guodong LI ◽  
...  
Keyword(s):  
Objective Function ◽  
Elastic Constants ◽  
Optimization Theory ◽  
Shell Element ◽  
Layered Shell ◽  
Box Girder ◽  
Computation Efficiency ◽  
Interpolation Search ◽  
Composite Glass ◽  
Element Theory

For the composite glass box girder, the generalized Bayesian objective function of elastic constants of the structure was derived based on layered shell element theory. Mechanical performances of the composite glass box girder were solved by layered shell element method. Combined with quadratic parabolic interpolation search scheme of optimized step length, the adaptive Powell’s optimization theory was taken to complete the stochastic identification of elastic constants of composite glass box girder. Then the adaptive Powell’s identification steps of elastic constants of the structure were presented in detail and the adaptive Powell’s identification procedure was accomplished. From some classic examples, it is finally achieved that the adaptive Powell’s identification of elastic constants of composite glass box girder has perfect convergence and numerical stability, which testifies that the adaptive Powell’s identification theory of elastic constants of composite glass box girder is correct and reliable. The stochastic characteristics of systematic responses and elastic constants are well deliberated in generalized Bayesian objective function. And in iterative processes, the adaptive Powell’s identification is irrelevant with the complicated partial differentiation of the systematic responses from the layered shell element model to the elastic constants, which proves high computation efficiency.

scholarly journals Updated Bayes identification of displacement constants of curve indeterminate box girder with variable scale theory

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881763
Author(s):  
Cheng Xi ◽  
Zhang Jian ◽  
Jia Chao ◽  
Tian Jiawei
Keyword(s):  
Objective Function ◽  
Optimization Theory ◽  
Optimization Method ◽  
Step Length ◽  
Mechanical Analysis ◽  
Box Girder ◽  
Scale Theory ◽  
Automatic Search ◽  
Scale Optimization ◽  
Identification Model

For curve indeterminate box girder, updated Bayes identification model of displacement constants was derived and studied with the variable-scale optimization theory. First, the updated Bayes objective function of displacement constants of the structure was founded. The gradient matrix of the objective function to displacement constants and the calculative covariance matrix were both deduced. Then, with finite curve strip element method, mechanical analysis of curve indeterminate box girder was completed. With automatic search scheme of quadratic parabola interpolation for optimal step length, the variable scale theory was utilized to optimize the updated Bayes objective function. Then, the identification steps were expounded, and the identification procedure was developed. Through typical examples, it is achieved that the updated Bayes identification model of displacement constants has numerical stability and perfect convergence. The stochastic performances of systematic parameters and systematic responses are simultaneously deliberated in updated Bayes objective function, which can synchronously take the actual measured information at different times into account. The variable-scale optimization method continually changes the spatial matrix scale to generate renewed search directions during the iterations, which certainly accelerates the identification of the displacement constants.

Inversion of induced polarization data

Geophysics ◽  
1994 ◽  
Vol 59 (9) ◽  
pp. 1327-1341 ◽  
Author(s):  
Douglas W. Oldenburg ◽  
Yaoguo Li
Keyword(s):  
Inverse Problem ◽  
Objective Function ◽  
Effective Conductivity ◽  
Optimization Theory ◽  
Induced Polarization ◽  
Dc Resistivity ◽  
Earth Structure ◽  
Nonlinear Inverse Problem ◽  
Polarization Data ◽  
The Earth

We develop three methods to invert induced polarization (IP) data. The foundation for our algorithms is an assumption that the ultimate effect of chargeability is to alter the effective conductivity when current is applied. This assumption, which was first put forth by Siegel and has been routinely adopted in the literature, permits the IP responses to be numerically modeled by carrying out two forward modelings using a DC resistivity algorithm. The intimate connection between DC and IP data means that inversion of IP data is a two‐step process. First, the DC potentials are inverted to recover a background conductivity. The distribution of chargeability can then be found by using any one of the three following techniques: (1) linearizing the IP data equation and solving a linear inverse problem, (2) manipulating the conductivities obtained after performing two DC resistivity inversions, and (3) solving a nonlinear inverse problem. Our procedure for performing the inversion is to divide the earth into rectangular prisms and to assume that the conductivity σ and chargeability η are constant in each cell. To emulate complicated earth structure we allow many cells, usually far more than there are data. The inverse problem, which has many solutions, is then solved as a problem in optimization theory. A model objective function is designed, and a “model” (either the distribution of σ or η)is sought that minimizes the objective function subject to adequately fitting the data. Generalized subspace methodologies are used to solve both inverse problems, and positivity constraints are included. The IP inversion procedures we design are generic and can be applied to 1-D, 2-D, or 3-D earth models and with any configuration of current and potential electrodes. We illustrate our methods by inverting synthetic DC/IP data taken over a 2-D earth structure and by inverting dipole‐dipole data taken in Quebec.

Study of a curved continuous composite box girder bridge

1993 ◽  
Vol 20 (1) ◽  
pp. 107-119 ◽  
Author(s):  
S. F. Ng ◽  
M. S. Cheung ◽  
H. M. Hachem
Keyword(s):  
Finite Element ◽  
Structural Response ◽  
Shell Element ◽  
Elastic Response ◽  
Box Girder ◽  
Girder Bridges ◽  
Bridge Model ◽  
Box Girder Bridge ◽  
Girder Bridge ◽  
Critical Sections

To better understand the behaviour of curved box girder bridges in resisting eccentric design truck loads, and the influence of plan curvature on the structural response, a model study was conducted at the University of Ottawa. In this study, the elastic response of a curved composite box girder bridge model was evaluated experimentally and confirmed analytically using the finite element method. Analytical predictions of both vertical displacements and normal stresses at critical sections compared fairly well with those evaluated experimentally. The isoparametric thin shell element employed in the analysis proved to be versatile and provided an accurate representation of the various structural components of a curved box girder bridge. Despite the eccentric nature of the applied OHBDC design truck loads and the bridge plan curvature, it was evident that in resisting the applied live loads, the girders at critical sections share equal proportions of the applied bending moments. Key words: bridge, curved, cellular, composite, eccentric loads, static, linear, experimental, finite element.

scholarly journals On finding a point in the relative interior of a polyhedral set and degeneracy in geometric programming

1978 ◽  
Vol 20 (4) ◽  
pp. 487-494 ◽  
Author(s):  
T. R. Jefferson ◽  
C. H. Scott
Keyword(s):  
Objective Function ◽  
Geometric Programming ◽  
Dual Problem ◽  
Optimization Theory ◽  
Inequality Constraints ◽  
Linear Constraints ◽  
Relative Interior ◽  
Nonlinear Inequality ◽  
Nonlinear Inequality Constraints ◽  
Nonlinear Objective Function

AbstractGeometric programming is now a well-established branch of optimization theory which has its origin in the analysis of posynomial programs. Geometric programming transforms a mathematical program with nonlinear objective function and nonlinear inequality constraints into a dual problem with nonlinear objective function and linear constraints. Although the dual problem is potentially simpler to solve, there are certain computational difficulties to be overcome. The gradient of the dual objective function is not defined for components whose values are zero. Moreover, certain dual variables may be constrained to be zero (geometric programming degeneracy).To resolve these problems, a means to find a solution in the relative interior of a set of linear equalities and inequalities is developed. It is then applied to the analysis of dual geometric programs.

Layered-Shell Element Method of Calculating the Multi-Ribbed Composite Slab’s Elastic Lateral Stiffness

2011 ◽  
Vol 243-249 ◽  
pp. 1346-1350
Author(s):  
Peng Chang ◽  
Yao Luo
Keyword(s):  
Elastic Modulus ◽  
Influence Factor ◽  
Shell Element ◽  
Lateral Stiffness ◽  
Layered Shell ◽  
Element Analysis ◽  
Factors Affecting ◽  
Modeling Process ◽  
The Finite Element Analysis ◽  
Element Method

A new method for calculating the elastic lateral stiffness of the multi-ribbed composite slab by ANSYS—the layered-shell element method is introduced in this paper. In the modeling process, there are two ways for establishing the model using element SOLID46: the first refers to regarding the slab as a whole to make arranged layers. While the second type suggests that making arranged layers in each part already separated according to the materials. Especially when there are reasonable hypothesis, the analysis results can guarantee certain precision. By comparison among the two models and the experimental results, no errors with each other have exceeded 5%. The whole model is used for the numerical simulation in view of its briefness. Several factors affecting elastic lateral stiffness are considered, mainly including elastic modulus of the concrete, elastic modulus of the brick, and number of the ribbed-column. From the calculating results, conclusion can be deduced that all of these factors affecting the slab’s stiffness significantly. Along with the factors’ rising, the elastic lateral stiffness of the wall grows up. Basically, the influence factor and the elastic lateral stiffness of the slab present to be linear relationship. It is also meaningful to see that the elastic modulus of the brick plays a very important part in the elastic lateral stiffness of the wall. When compared to the SOLID65 and LINK8 used for the slab’s modeling before, the layered-shell element method is simple in principle, and distinct in conception. Above all, because only one type of element in the finite element analysis is used, it will cost less time when used on building a model of integrated architectural construction.

Stochastic Filtering Back Analysis of Elastic Modulus of Box Shaped Beam

2015 ◽  
Vol 1096 ◽  
pp. 557-561
Author(s):  
Bo Yu ◽  
Tao Hong ◽  
Jian Zhang
Keyword(s):  
Elastic Modulus ◽  
Analytical Procedure ◽  
Back Analysis ◽  
Shell Element ◽  
Mechanical Analysis ◽  
Displacement Function ◽  
Shaped Beam ◽  
Stochastic Filtering ◽  
Practical Engineering ◽  
Element Theory

With the development of civil engineering, the box shaped beam has been widely applied in practical engineering. In general, it is composed of concrete and steel and compared with mechanical analysis, little research has been carried on the back analysis of elastic modulus of box shaped beam. With degraded solid element theory, the shell element is deduced and the displacement function is obtained. The necessary observation revision equation and Kalman regenerative matrix are derived. The stochastic filtering back analysis steps of elastic modulus of the box shaped beam are presented and the analytical procedure is compiled. Through analysis of a classic example, some important conclusions about stochastic filtering back analysis of elastic modulus of box shaped beam are obtained.

Research on Skew Coefficient for Stresses of Skewly Supported Three-Span Continuous Box Girders

2014 ◽  
Vol 587-589 ◽  
pp. 1483-1487
Author(s):  
Liang Liu
Keyword(s):  
Cross Section ◽  
Shell Element ◽  
Skew Angle ◽  
Box Girders ◽  
Concentrated Load ◽  
Box Girder ◽  
Lag Effect ◽  
The Cross ◽  
Skew Angles ◽  
Bottom Slab

Skewly supported continuous box girders have special mechanical properties compared with common continuous box girders. Skew coefficient for stress of skewly supported three-span continuous box girder is introduced to reflect the decrease degree of the normal stresses at the cross section of the middle span of the box girder. The finite element models of the skewly supported three-span continuous box girders with different skew angles are established by applying the SHELL63 shell element in software ANSYS. The variation of the skew coefficient for stress at different calculation points of middle span cross section under concentrated load is analyzed and the corresponding influence law is revealed. Research results show that the skew coefficient for stress of top slab is different from that of bottom slab at the cross section of the skewly supported three-span continuous box girder. The skew coefficient for stress of top slab is smaller than that of bottom slab. Skew coefficient for stress decreases with the increasing of the skew angle. Because of the shear lag effect, the minimal skew coefficient for stress of flanges occurs at the free tip of cantilever slab while the maximal skew coefficient occurs at the intersection of web and flange slabs.

Spatial Stress Analysis of Long Span Prestressed Concrete Box Girder Bridges

2012 ◽  
Vol 256-259 ◽  
pp. 1693-1696
Author(s):  
Xian Lin Yu ◽  
Jian Shu Ye ◽  
Wen Qing Wu
Keyword(s):  
Prestressed Concrete ◽  
Shell Element ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Girder Bridges ◽  
Long Span ◽  
Principal Tensile Stress ◽  
Concrete Box Girder ◽  
Concrete Box Girder Bridges ◽  
Spatial Stress

A FEA program using 8 nodes and 40 freedoms degenerated solid shell element was developed to analyze the spatial stress of long span prestressed concrete box girder bridges during construction stage and finished stage. The maximum principal tensile stress positions on box girder section and shear lag coefficient were researched according to spatial stress results. It presented suggestions on prestressed concrete box girder bridges anti-crack design.

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