Investigation of Load Capacity and Serviceability of Assembled Concrete Blocks (Dox Plank)

This paper presents a literature survey of roof and floor slab systems constructed of assembled concrete blocks as manufactured in the 1940s, 1950s, and 1960s with a retrospective on load capacity considerations and serviceability. Assembled concrete blocks were formed by assembling a row of lightweight hollow core concrete blocks into a prestressed plank. The most common system, which came to represent the industry, was Dox Plank named for its inventor Bernard A. Doc Vander Heyden. Mr. Vander Heyden patented improvements in the planks and the methods of constructing them in 1954 and 1965. This survey of United States patents, manufacturers' design data, and design theory will aid the forensic engineer in an investigation of the load capacity and serviceability of existing systems. This survey identifies the original design parameters, such as the allowable unit stresses, area of embedded steel, material properties, etc.