Prefabrication experiments - 365 - Modern structural archetypes - 05 - J.H. Gray Column

 

The construction of tall buildings implies the efficient and economical use of materials to minimize dead loads for compounded stories. Weight and functional loads from each floor plate are transferred to columns that transmit them down to foundations. Steel works particularly well for tall buildings as structural elements can be profiled to reduce material use and increase span to weight ratio both horizontally and vertically. The iconic H shape of columns and beams depicts this type of material efficacy. The assembly of rolled posts and beams in platform structures became an iconic representation of the early Chicago or New York City style skyscrapers. 

 

The Reliance Building designed by Burnham and Root with Charles Atwood in the early 1890s is often cited as the archetype of the towering brace framed steel skeleton. The fourteen-story structure built in (1894-1895) with a floor plate of 56 by 85 feet exemplified the modern canon of separate structure and skin; glass and glazed terracotta panels were hung or even cantilevered from the steel grid foreshadowing the development of lightweight modular curtain walls. Recognized for its use of projected bays, the building's simple façade demonstrated what would become the commercial urban glass building of the twentieth century. 

 

An expression of industrialization's advances in mechanization (elevators) and pig iron's refinement into steel, the tall building skeletons were devised as large-scale kits-of-parts. The Reliance Building's structure is a basic assembly of a type of balloon frame where continuous pillars carry floor plates composed of primary and secondary beams. The chief innovation in terms of structure was the use of an open web column invented by civil engineer J.H. Gray. Contrary to the Z-bar riveted closed iron columns that had become common in steel assemblies, Gray invented an open trellis framework, a type of rising chase, that would allow for electrical and piping distribution. The posts were made by riveting plates at 30-inch intervals to 12-foot long continuous angles; columns were spliced at every 12 feet. The open web concept reduced column weight, increased accessibility for fireproofing and straight edges made standardized assemblies for beams and columns more efficient. 

Reliance building sketch and J.H. Gray column details