In the case of a truss bridge, a post-tensioned slab bridge, or a box girder bridge the sections are often floated to the bridge and then lifted into place by cranes on barges or cranes sitting over piers.
The very good reason why the word communism is so commonly associated with these revolutionary, anti-liberal, anti-democratic Marxists is that political parties with communist in the name were pretty much invariably of that bent throughout the 20th century, whereas parties called socialist or social democrat or labor varied enormously in ideology.
Socialism and communism are ideological doctrines that have many similarities as well as many differences. One point that is frequently raised to distinguish socialism from communism is that socialism generally refers to an economic system, and communism generally refers to both an economic system and a political system.