University of Pittsburgh
Univ. Of Pitt: Glossary of Medieval Art and Architecture
Here at the University of Pittsburgh is a definition, a list of parts, and a diagram for an arch.
Merriam-Webster
Merriam Webster: Dictionary Illustration: Types of Architectural Arches
Labeled illustrations of different styles of arches along with an illustration of the principal parts of an arch: pier, impost, springer, voussoir, and keystone.
Cleveland State University
Cleveland Memory Project: Bridges of Metropolitan Cleveland
Here's an ebook with descriptions, locations, and pictures of bridges all over the Cuyahoga Valley.