VM-LSDYNA-SOLVE-022

VM-LSDYNA-SOLVE-022
Statically Indeterminate Reaction Force Analysis

Overview

Reference: Timoshenko, S.P. (1995). Strength of materials: Part I: Elementary theory and problems. (3rd ed.). D. Van Nostrand Co. pp.22 and 26.
Analysis Type(s): Linear Static Structural Analysis
Element Type(s): Solid

Test Case

An assembly of three prismatic bars is supported at both end faces and is axially loaded with forces F1 and F2. Force F1 is applied to the face between Parts 2 and 3, and F2 is applied between Parts 1 and 2. Find the reaction forces in the Y direction at the fixed supports.

This test case also appears in the Workbench Verification Manual. See VM-WB-MECH-001.

Figure 89: Problem Sketch

Problem Sketch

Material PropertiesGeometric PropertiesLoading

E = 2.9008e7 psi

ν = 0.3

ρ = 0.28383 lbm/in3

Cross section of all parts

= 1 x 1 in

Length of Part 1 = 4 in

Length of Part 2 = 3 in

Length of Part 3 = 3 in

Force F1 = –1000 lbf (Y direction)

Force F2 = –500 lbf (Y direction)

Analysis Assumptions and Modeling Notes

The assembly is modeled with solid elements using elform 1. MAT_ELASTIC is used in the FEA model, and LOAD_NODE_SET is used to apply force on each node of the defined node sets. The total force applied on the face between Part 1 and Part 2 is 500 lbf, and the force applied between Part 2 and Part 3 is 1000 lbf. An implicit analysis has been performed to obtain a static solution. And the reaction force at the bottom and top supports are extracted using keyword card *DATABASE_NODAL_FORCE_GROUP of node sets 1 and 4.

Results Comparison

ResultsTarget LS-DYNA SolverError (%)
Y Reaction Force at Top Fixed Support (lbf) 900900.780.0867
Y Reaction Force at Bottom Fixed Support (lbf) 600599.22–0.13