Structures: The Sum of Their Parts

Structures—whether they are bridges or buildings—are comprised of structural members interconnected by joints. Cast-in-place reinforced concrete is one of the most common structural systems in common use today.

Cast-in-place reinforced concrete construction is one of the most economical building systems. It is also one of the most inherently redundant building systems. This means that if one member is weakened, it is likely that other members can take the load.

Floor Systems

Basically, a building is a series of floors held up by columns and walls. There are a number of standard floor/roof structural systems used in cast-in-place reinforced concrete construction.

• Two-way flat plate system. There are no beams between the columns. Instead, the floor is heavily reinforced in both directions. In addition there is reinforcing steel in the floor at the columns to transfer the loads.
• Two-way flat slab with drop panels. This system is similar to the two-way flat plate system except there is a drop panel to provide extra thickness around the columns. This strengthens the column-floor connection. The rest of the floor can be slightly thinner with less dead weight.
• One-way beam and slab. The floor loads are transferred to the beams, which are then transferred to the columns.
• One-way joist slab. The joists act like small beams. This floor system is very economical because the formwork is readily available, and less reinforcing is need. Because there's only a small span between each joist, the slab can be thinner.
• One-way wide module joist slab in the lower middle is a variation on the one-way joist slab.
• Two-way joist slab, also called a waffle slab. Because there are joists in both directions, this floor system is the strongest and will have the least deflection. It's typically used when stiffness is important or if there are abnormally heavy loads.

	CRSI Design Handbook Chapters 7 through 10 provide load tables and design examples for reinforced concrete floors systems.
	Engineering Data Report 37: Reinforcing Steel in Slabs-on-Grade Slabs-on-grade are used for industrial and commercial floors, residential floors, parking lots, pavements, airport slabs and other applications.  This report outlines the need for reinforcing steel in slabs-on-grade and provides design examples.
	Engineering Data Report 43: One-Way Concrete Joist Construction Understand the important factors in one-way concrete joist construction: a monolithic combination of regularly-spaced joists (ribs) and a thin slab of concrete cast-in-place to form an integral unit with the supporting beams, columns and walls.
	Engineering Data Report 46: Wide-Module Joist Systems - Revisited Provides typical dimensions for wide-module joist systems, along with information on how this structural system is constructed, including construction dimensions, supporting reinforcement, and design and detailing aids.

Columns

Columns transmit the loads from a structure's roof and floors down to the foundation. The design of reinforced concrete columns consists of:

• Determining the critical load combinations and resulting factored moments and loads for each,
• Selecting a column cross section satisfying all design assumptions for the materials used under loads and moments equal to or larger than the factored loads and moments, and
• Ensuring that slenderness effects do not reduce capacity.

	CRSI Design Handbook Chapters 2 through 4 provide load tables and design examples for rectangular and round columns.

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