function [K, F] = Linear_Elasticity(Nodes, Elements,N_ID_p1, Boundary,Patch)
global E u SD q0
Ne=size(Elements,1);
Nnod=size(Nodes,1);
Width=1;%平面应力单元的厚度

% 初始化结果存储空间
K = zeros( 2 * Nnod , 2 * Nnod );
F = zeros( 2 * Nnod , 1 );
for i=1:Ne
    ke=ele_stiff_matrix(i,Nodes,Elements,E,u,Width);
    ENodes( : , 1 ) = Elements( i , : ); 
    %组装为整体刚度阵
    iEnum = size( ENodes , 1 );      % 单元的结点总数 
    iDOFnum = 2 * iEnum;              % 单元的总自由度数 
    iDof = zeros( 2 * iEnum , 1 );   % 各节点自由度编号 

    for il=1:iEnum 
      inod = ENodes( il ); 
      iDof( 2 * il-1 : 2 * il) = 2 * inod-1 : 2 * inod; 
    end
    % 拼装：ir为行局部编号, irg为对应整体编号 
    for ir = 1 : iDOFnum %row
      irg = iDof( ir ); 
      % ic为列局部编号, icg为对应整体编号 
      for ic = 1 : iDOFnum %column
        icg = iDof( ic ); 
        K( irg , icg ) = K( irg , icg ) + ke( ir , ic ); 
      end 
    end
end
%施加荷载边界条件%均布荷载
% if Patch==2
%     iLenElt = size(N_ID_p1,1);          %均布荷载所在单元编号
%     for ie = 1:iLenElt
%       for ind = 1:2                   % ind结点自由度编号
%         iNode = N_ID_p1(ie,:);           %获取单元结点
%         irow = (iNode-1)*2+ind;
%         Pe = UniLoad(ie,N_ID_p1,q0,Nodes,Elements,Width);    % 3级子程序：EquivalentLoad(ie)
% 
%         F(irow) = F(irow)+Pe(ind:2:end,:);
%       end
%     end
% end
if Patch==2
    iLenElt = size(N_ID_p1,1);          %均布荷载所在单元编号
    for ie = 1:iLenElt
      for ind = 1:2                   % ind结点自由度编号
        iNode = N_ID_p1(ie,:);           %获取单元结点
        irow = (iNode-1)*2+ind;
        Pe = UniLoad(ie,N_ID_p1,q0,Nodes,Elements,Width);    % 3级子程序：EquivalentLoad(ie)
        F(irow) = F(irow)+Pe(ind:2:end,:);
      end
    end
end

%施加支座边界条件    
iBct = size( Boundary , 1 ); 
for ib = 1 : iBct
    iNode = Boundary( ib , 1 );       % 结点编号
    iType = Boundary( ib , 8 );
    if iType == 1             % 固定点边界条件
        for ind = 1 : 2
            irow = ( iNode-1 ) * 2 + ind;
            if ( Boundary( ib , ind + 1 ) == 1 )
                K( irow , : ) = 0.0;
                K( : , irow ) = 0.0;
                K( irow , irow ) = 1.0;       % 划零置一法
                F(irow)=0.0;
                %         gKA( irow , irow ) = 1.0e+20;  % 乘大数法
            end
        end
    end
end