Try the ASME B.30 series:
B30.2 "Overhead and Gantry Cranes (Top Running Bridge, Single or Multiple Girder, Top Running Trolley Hoist)"
B30.17 "Overhead and Gantry Cranes (Top Running Bridge, Single Girder, Underhung Hoist)"
also:
ANSI A1264.1-1995, Safety Requirements for
Workplace Floor and Wall Openings, Stairs, and
Railing Systems
Publisher: American Society of Safety Engineers
(ASSE), 1800 East Oakton Street, Des Plaines, IL
60018-2187
CMAA Specification No. 74, Revised 2000,
Specification for Top Running and Under Running
Single Girder Electric Overhead Traveling Cranes
Utilizing Under Running Trolley Hoist
Publisher: Crane Manufacturers Association of
America (CMAA), 8720 Red Oak Boulevard, Suite
201, Charlotte, NC 28217
These guys are good: