You can also use the http://moi3d.com/download/3dmCurves2DXF.zip converter by Michael
and import a dxf file in Sketchup

and wait a minut that I refound the plug who merge the lines inside sketchup ;)


Ok Here the plug to put inside the folder Plugins of Sketchup ;)
http://www.crai.archi.fr/RubyLibraryDepot/Ruby/EM/repair_broken_lines.rb