Shadows problem with PolySoup

I have a road street, the final exported mesh its compose for various meshes. like this

start01
giroUno2
streetOne2
steetTwo2



i am using polysoup for the collision, buts the shadows are not working.
i have spend all my day try to search , why the shadows do not appear, and finally, i discovered that the object receive shadows only for the first element .( or the first element on the Subtree 0
giroUno2 --> Object giroUno with following details: 2)

this is my problem




why is that, the collision works fine with all the elements, but it receive shadows with one element?????