Nonlinear Finite Element Analysis Package Research Articles

Numerical investigation of elastic-plastic buckling performance of circular arched cellular steel beam using nonlinear finite element analysis method

This study presents a numerical investigation of the in-plane elastic-plastic performance, post-buckling mode, and arched web-post shear resistance of a pinned end circular arched cellular steel beam using ABAQUS nonlinear finite element analysis package. The trustworthiness of the finite element analysis results was confirmed by comparing them to the existing experimental investigation results. The main study parameters, such as the effect of a rise-to-span ratio, the radius of curvature, the impact of opening, the types of loading on elastic-plastic performance, and the buckling mode of an arched cellular steel beam, were investigated. Furthermore, the arched web-post finite element model was proposed and the shear resistance of the arched web-post was investigated. Also, the appropriateness of the currently existing different web-post shear resistance analysis approaches was reviewed and evaluated in determining the shear resistance of arched web-posts. The results showed that the web post-structural stiffness of a circular arched cellular steel beam was improved as the rise-to-span ratio increased under the mid-span concentrated load regardless of the rise-to-span ratio. However, under uniformly distributed vertical load, increasing a rise-to-span ratio beyond 0.35 or 140° subtended angles reduces the stiffness of circular arched cellular steel beams. The web post shear resistance analyzing approaches proposed by Panedpojaman et al. and SCI P-100 overestimate and yield unsafe results in determining the web-post shear resistance of arched web post cellular steel of low rise-to-span ratio.

Investigation of Proposed Concrete Filled Steel Tube Connections under Reversed Cyclic Loading

Concrete-filled steel tube (CFT) columns are used in the primary lateral resistance systems. The objective of this research is to analyse the behavior of the steel beam to CFT column connections. A three-dimensional numerical model for simulating the behavior of CFT connections was developed with the aid of the general purpose nonlinear finite element analysis package ABAQUS. In this paper, 90 CFT connection specimens include simple and moment connections that were tested under reversed cyclic loading. Shear capacity of joint, moment-drift response, energy absorption, and displacement ductility were studied in those models. The results have indicated that, the hysteresis curve of CFT columns was plump; no pinch phenomenon can be found; the damage and degradation degree of the strength and stiffness of specimens is lower; and high energy dissipation capacity can be achieved. Improvement in the behavior of CFT connection depends on the beam characteristics and column features.

Assessment of design methods for punching through numerical experiments

The work is intended to demonstrate that the loss of bond between concrete and flexural steel which led in recent years a number of flat-slab structures to punching collapse under service loading conditions is also relevant to ultimate limit-state design. It is based on a comparative study of the results obtained from numerical experiments on flat slab-column sub-assemblages. The slabs were designed for punching either in compliance with the EC2 code requirements, which do not allow for such loss of bond, or in accordance with the compressive force-path method which considers the loss of bond between concrete and the flexural reinforcement in tension as the primary cause of punching. The numerical experiments are carried out through the use of a nonlinear finite element analysis package for which, although ample published evidence of its validity exists, additional proof of its suitability for the purposes of the present work is presented.

NONLINEAR FE MODELLING OF ANCHORAGE BOND IN REINFORCED CONCRETE

The transfer of forces from the surrounding concret e to the reinforcing bars in reinforced concrete (R C) can be influenced by several parameters. In this paper an attempt has been made to study the influence of specimen geometry, bar di ameter, strength of concrete, lateral confinement and embedment length on the bon d properties of concrete. The embedment length of t he bar was varied between 50mm and 400mm by varying the diameter of the bar, strength of concrete and lateral confinement. The d ifferent bar diameters of 16, 20 and 25mm were selected along with three differen t concrete strengths of 25, 40 and 65MPa. The speci mens with the above parameters were modeled by using a nonlinear finite element analysis package. It has been found that fthe same geometry, the specimens with small bond length exhibited high bon d strength. With the range of bar diameters conside red the bond strength of concrete decreases as the diameter of the bar incre ases. The splitting failure has been observed in un confined concrete, while the pullout failure was predominant when the concrete l aterally confined. In case of large embedment lengt h, the post peak plateau is prolonged with small diameter bars when compared to the large diameter bars. The descending branch of the bond stress-slip response with large diameter bars has been found to be steep.

Automatic Generation of User Material Subroutines for Biomechanical Growth Analysis

The analysis of the biomechanics of growth and remodeling in soft tissues requires the formulation of specialized pseudoelastic constitutive relations. The nonlinear finite element analysis package ABAQUS allows the user to implement such specialized material responses through the coding of a user material subroutine called UMAT. However, hand coding UMAT subroutines is a challenge even for simple pseudoelastic materials and requires substantial time to debug and test the code. To resolve this issue, we develop an automatic UMAT code generation procedure for pseudoelastic materials using the symbolic mathematics package MATHEMATICA and extend the UMAT generator to include continuum growth. The performance of the automatically coded UMAT is tested by simulating the stress-stretch response of a material defined by a Fung-orthotropic strain energy function, subject to uniaxial stretching, equibiaxial stretching, and simple shear in ABAQUS. The MATHEMATICA UMAT generator is then extended to include continuum growth by adding a growth subroutine to the automatically generated UMAT. The MATHEMATICA UMAT generator correctly derives the variables required in the UMAT code, quickly providing a ready-to-use UMAT. In turn, the UMAT accurately simulates the pseudoelastic response. In order to test the growth UMAT, we simulate the growth-based bending of a bilayered bar with differing fiber directions in a nongrowing passive layer. The anisotropic passive layer, being topologically tied to the growing isotropic layer, causes the bending bar to twist laterally. The results of simulations demonstrate the validity of the automatically coded UMAT, used in both standardized tests of hyperelastic materials and for a biomechanical growth analysis.

The finite-element deformation modeling of superplastic Al-8090

The deformation behaviors of an Al-Li-Cu alloy (Aluminum 8090) during uniaxial and biaxial stress states were modeled using the nonlinear finite element analysis package ABAQUS 5.8. Two different material models were used for the purpose of comparison and to propose a valid and accurate superplastic material deformation behavior. Using a power law strain hardening model, the material was modeled with either constant or variable properties of strain-rate sensitivity and strain-hardening exponent. Results from the numerical models were compared to experimental results by Chen and Huang, who investigated the uniaxial and biaxial states of stress. Experimental data were primarily used to acquire the needed uniaxial material parameters for the model. The strain-rate sensitivity and strain-hardening exponent were dependent on the strain and strain rates. Comparing the two material models for both stress states indicated that the material model with variable properties better represented the true behavior of the material when compared to the experimental results.

Simplified non-linear analysis of plates subjected to hydrocarbon explosions

An elastic Lagrangian formulation for an unstiffened plate subject to blast loading is presented. Building on a previous formulation, which accounted for membrane strains from purely out-of-plane displacement, the addition of in-plane stretching highlights the importance of membrane action. Numerical results of the resulting system of non-linear differential equations from the new model are compared with a non-linear finite element analysis package in terms of the various displacements and membrane strains, with good correlation.

Finite Element Modeling of Reinforced Concrete Beam-Column Connections

The application of a nonlinear finite element analysis package to the modeling of external beam-column connections is investigated. The behavior of the finite element model is compared with the results from 19 experimental tests. A parametric study was conducted to evaluate the effects of the main variables on both joint capacity and joint behavior. Details of the effects of column load on one of the connection details have been included. The study validates the suitability of both the software package and the applied modeling technique.

Non-linear analysis of blast walls and stiffened panels subjected to hydrocarbon explosions

This paper presents results on the response of a typical blast wall and a tee-stiffened panel subjected to hydrocarbon explosions with geometries typical of those used in current offshore structures. The panels have been modelled using a non-linear finite element analysis package (DYNA3D) with thin shell elements for both the plate and stiffener components accounting for the effects of plasticity, strain-rate and buckling. Correlation with previous experimental work is presented together with a parameter study highlighting the effect of an increasing peak pressure and the shape of the pressure-time curve. The effect of boundary restraints is shown to have a significant influence on both the torsional response of the stiffeners and the overall panel deformations. The results are also compared with a simple single degree of freedom (SDOF) dynamic model where good correlation is obtained in the region where only limited plastic deformations occur.