Many concrete contractors have worked on older-style (pre-1980) steel-frame buildings that had enough strength to support all the loads from deck forming and pouring operations without anything else to brace or hold them. Currently designed frames frequently lack that strength in the steel members and only achieve adequate design strength when the fully cured concrete is in place.
Changes in the steel construction and design codes allow much lighter steel frames before concrete than previously considered practical. This is done by using thinner, narrower steel sections and by allowing higher stresses in them.
