A 13-point sampling point scheme for 20-node brick elements

A new sampling point scheme with 13 evaluation points was introduced in this research study for 20-node brick elements. The new sampling points were located inside the brick element at the edges and the center point of the 20-node brick element. This integration scheme can be assumed to be an imitation of the Gaussian integration scheme. Standard benchmark problems were chosen from the different research works and compared with our proposed scheme. Finally, the proposed integration scheme achieves good results for 20-node brick elements on different performance parameters of finite element analysis.

Parametric Evaluation of Stress Concentration Factor (SCF) at Brace – Chord Intersection of a Ring Stiffened Tubular Joint

Tubular joints are common in offshore framed structures such as jackets. These joints are subjected to fatigue due to cyclic loads from waves. Stress concentration factor plays a major role in the estimation of fatigue life. Studies have been carried out in the past on stress concentration factors for these joints. However, literature on ring stiffened joints is limited. In the present study, numerical simulations have been carried out on ring stiffened tubular joints, especially the T joints, subjected to axial tension load using finite element method in linear analysis using ABAQUS software. A solid type 20-node quadratic brick element (C3D20R) has been used in the study. Stresses in hotspot locations at brace/chord intersection, ring/chord intersection and ring inner edge are examined. The numerical model has been validated using published experimental data and Lloyd’s register recommendations. Further parametric study has been carried out with 20 models, which includes geometric parameters of ring stiffener such as width of stiffener, thickness of stiffener and spacing between the ring stiffeners. The results of parametric study show a significant reduction of SCF at saddle location by placing ring stiffeners in unstiffened T joint. A set of new parametric equations are developed to calculate SCF for ring stiffened T joint at saddle location for axial tensile load.

Modal Analysis of FSW Plate Considering the Residual Stresses Effect

In this paper, a modal analysis of the FSW plate is performed to identify the modal parameters such as: frequencies and eigenvectors. A finite element simulation is carried out by using ANSYS commercial software. The brick element called SOLID70 is used to model the weld joint in order to represent the welded structure with good precision thus determined the residual stresses in the plate. The modal analysis is use to extracting the vibration behavior of the FSW plate made of AA6061-T6 aluminum alloy with consideration the residual stresses effect on the modal parameters of the plate. The numerical results found in the friction stir welding simulation are compared by a reference plate to analyze the influence of residual stresses on the fundamental frequencies and modal deformations. The study concluded that the presence of residual stresses induced by the FSW process influences the modal behavior of the welded plates.

Seismic hazard assessment of existing reinforced concrete bridge structure using pushover analysis

The present paper focuses on the nonlinear static pushover analysis of a 3-span existing RC bridge located in Indian seismic Zone IV as per IS1893-2016 using the Finite Element Method (FEM). The 3D model of the RC bridge is simulated using the FEM technique and pushover analysis is performed to analyze the structure for modal mass participating ratio, performance level, spectral demand, and capacity of the structure. The bridge pier and longitudinal girder are modeled using the two noded beam element and bent cap and abutment of the bridge structure is modeled using the 8 noded brick element. The base of the column is assumed fixed condition. The pushover analysis is performed using Displacement Modification (FEMA 440) and Capacity Spectrum Method (ATC 40). The outcomes of results appear that the considered bridge has inadequate capacity to cope up with any of the desired performance levels because spectral demand is greater than the spectral capacity. The modal analysis of the 3D bridge exposes that it has many closely-spaced modes. The mass participating ratio for the higher modes is not very high. After performing pushover analysis of the exiting RC bridge structure it has been concluded that the existing bridge structure does not meet seismic criteria of spectral demand as per the ATC 40 and FEMA 440, therefore retrofitting is required for bridge component i.e. piers, abutment, and bent cap.

Evaluation of stiffness matrix in finite element analysis using element edge method for the 8-node brick element

An element edge method is developed for the evaluation of stiffness matrix for the 8-node brick element. Handling of large data leads to take more computational time in finite element analysis. The new set of quadrature consist of 13 sampling points and weights out which 12 points are at the edges of the brick element and one point is considered at the center of the element. The new set of sampling points is a mimic of Gauss numerical integration method. Finally, the proposed element edge method is evaluated using the standard benchmarked problems and compared the results with conventional Gauss integration method and found that CPU execution time for the evaluation of finite element problems are found to be reduced considerably without compromising in the results mainly consist of accuracy of values and convergence rate.