function [Kt,Elem] = tangStiffMtxUL(Model,Anl,Elem,U)
%根据位移向量更新节点位置后得到的单元刚度矩阵
    Kt = zeros(Model.neq,Model.neq);
    for i = 1:Model.nel
        % Elastic, geometric and tangent stiffness matrices
        ke = elasticStiffMtxUL(Elem(i),U);%U影响节点坐标进而影响单元长度
        kg = geometricStiffMtxUL(Anl,Elem(i),U);
        kt = ke + kg;
        % Store elastic stiffness matrix to be used in computation of internal forces
        Elem(i).ke = ke;
        % Rotation matrix from local to global coordinate system
        angle = elemAngle(Elem(i),U);%%U影响节点坐标进而影响单元角度
        c     = cos(angle);
        s     = sin(angle);
        rot = [ c -s  0  0  0  0;
                s  c  0  0  0  0;
                0  0  1  0  0  0;
                0  0  0  c -s  0;
                0  0  0  s  c  0;
                0  0  0  0  0  1 ];
        % Tangent stiffness matrix in global system
        k = rot * kt * rot';
        % Assemble element matrix to global matrix
        gle = Elem(i).gle;
        Kt(gle,gle) = Kt(gle,gle) + k;
    end
end