Composing a stiffness matrix

*To*: mathgroup at smc.vnet.net*Subject*: [mg20328] Composing a stiffness matrix*From*: "Toshiyuki (Toshi) Meshii" <meshii at mech.fukui-u.ac.jp>*Date*: Fri, 15 Oct 1999 20:20:51 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I am wondering whether we can use Mathematica to systematically compose a stiffness matrix in Finite Element Method. Please give me an advice on this problem. An example problem is as follows: I know Eq (1) {f1,f2}={{ka,-ka},{-ka,ka}}・瘢雹{u1,u2} Eq (2) {f2,f3}={{kb,-kb},{-kb,kb}}・瘢雹{u2,u3} and want to construct Eq (3) from these two equations systematically. Eq (3) {f1,f 2,f3}=K・瘢雹{u1,u2,u3} Here, matrix K is called a stiffness matrix and it's elements are K={{ka,-ka,0},{-ka,ka+kb,-kb},{0,-Kb,Kb}} How can we construct matrix K in Eq (3) from Eq (1) and Eq (2) by using Mathematica's commands ? ******************************************************* Toshiyuki (Toshi) Meshii meshii at mech.fukui-u.ac.jp Associate Professor, Department of Mechanical Engineering Fukui University, 3-9-1 Bunkyo, Fukui, 910-8507, JAPAN Tel & Fax +81-776-27-8468 *******************************************************