The chinese were able to build suspension bridges and pagodas because of the development of

Iron and steel casting discovery
 
the casting of iron into steel through the removal of carbon, which made it hard and durable as it could not rust easily was a fundamental breakthrough in the metal industry. Chinese were able to cast their iron, which involves removal of carbon as early as the eight  century which enabled them to improvise bamboo suspension bridges into steel bridges.

He made the polygraph too,but thomas edison was not falsely credited for the light buld