Vipulkumar Ishvarbhai Patel

Numerical analysis of circular concrete-filled steel tubular slender beam-columns with preload affects

This paper presents a new numerical model for the nonlinear analysis of circular concrete-filled steel tubular (CFST) slender beam-columns with preload effects, in which the initial geometric imperfections, deflections caused by preloads, concrete confinement and second order effects are incorporated. Computational algorithms are developed to solve the nonlinear equilibrium equations. Comparative studies are undertaken to validate the accuracy of computational algorithms developed. Also included is a parametric study for examining the effects of the preloads, column slenderness, diameter-to-thickness ratio, loading eccentricity, steel yield stress and concrete confinement on the behavior of circular CFST slender beam-columns under eccentric loadings. The numerical model is demonstrated to be capable of predicting accurately the behavior of circular CFST slender beam-columns with preloads. The preloads on the steel tubes can affect significantly the behavior of CFST slender beam-columns and must be taken into account in the design.

A Validated Numerical Model for Residual Stress Predictions in an Eight-Pass-Welded Stainless Steel Plate

Welding processes create a complex transient state of temperature that results in post-weld residual stresses. The current work presents a finite element (FE) analysis of the residual stress distribution in an eight-pass slot weld, conducted using a 316L austenitic stainless steel plate with 308L stainless steel filler metal. A thermal FE model is used to calibrate the transient thermal profile applied during the welding process. Time-resolved body heat flux data from this model is then used in a mechanical FE analysis to predict the resultant post-weld residual stress field. The mechanical analysis made use of the Lemaitre-Chaboche mixed isotropic-kinematic work-hardening model to accurately capture the constitutive response of the 316L weldment during the simulated multi-pass weld process, which results in an applied cyclic thermo-mechanical loading. The analysis is validated by contour method measurements performed on a representative weld specimen. Reasonable agreement between the predicted longitudinal residual stress field and contour measurement is observed, giving confidence in the results of measurements and FE weld model presented.

Finite Element Modelling of Welded Austenitic Stainless Steel Plate With 8-Passes

The current paper presents a finite element analysis of an eight-pass groove weld in a 316L austenitic stainless steel plate. A dedicated welding heat source modelling tool was employed to produce volumetric body power density data for each weld pass, thus simulating weld-induced thermal loads. Thermocouple measurements and cross-weld macrographs taken from a weld specimen were used for heat source calibration. A mechanical finite element analysis was then conducted, using the calibrated thermal loads and a Lemaitre-Chaboche mixed work-hardening model. The predicted post-weld residual stresses were validated using contour method measurements: good agreement between measured and simulated residual stress fields was observed. A sensitivity analysis was also conducted to identify the boundary conditions that best represent a tack-welded I-beam support, which was present on the specimen back-face during the welding.Copyright

Nonlinear analysis of biaxially loaded high strength rectangular concrete-filled steel tubular slender beam-columns, part II: applications

This paper presents the verification and applications of a numerical model developed for biaxially loaded high strength thin-walled rectangular concrete-filled steel tubular (CFST) slender beamcolumns with local buckling effects. The accuracy of the numerical model is established by comparisons of numerical results with existing experimental data. The verified numerical model is employed to investigate the effects of four parameters including concrete compressive strength, loading eccentricity, depth-to-thickness ratio and columns slenderness on the strength reduction factor and steel contribution ratio of CFST slender beamcolumns under biaxial bending. The results obtained indicate that increasing each of the four parameters decreases the strength reduction factor. The steel contribution ratio is found to decrease with an increase in the concrete compressive strength and depth-to-thickness ratio but increase with increasing the loading eccentricity and column slenderness ratios. It is shown that the numerical model is efficient and accurate for predicting the load-deflection curves and strength envelopes for thin-walled rectangular CFST slender beamcolumns under biaxial loads. Benchmark numerical results given in this paper provide a better understanding of the local and global interaction buckling behavior of high strength thin-walled rectangular CFST slender beam-columns and are useful for the development of composite design codes.

Nonlinear inelastic behavior of circular concrete-filled steel tubular slender beam-columns with preload effects

This paper presents a numerical model based on fiber element formulations for predicting the nonlinear inelastic behavior of circular concrete-filled steel tubular (CFST) slender beam-columns under eccentric loading.