Title: Macro-Cracking and Crack Control in Concrete Structures--A State of the Art
Author(s): Edward G. Nawy
Publication: Symposium Paper
Appears on pages(s): 1-32
Keywords: beams (supports); concretes; cover; cracking (fracturing); crack propagation; crack width and spacing; flexural strength; fracture properties; macrocracking; microcracking; post tensioning; prestressing; pretensioning; reinforced concrete; shrinkage; sta
This paper presents the state of the art in evaluating flexural crack development and control of macrocracking. It is based on extensive research over the past five decades, in the United States and overseas, in the area of macrocracking in reinforced and prestressed concrete beams and in two-way action slabs and plates With the advent of limit states theories that generally lead to economic proportioning of members, control of cracking has become essential to maintain the integrity and esthetics of concrete structures. The trend is stronger than ever in better utilization of current concrete strengths, use of higher strength concretes that include super-strength concretes of 20,000 psi (138 MPa) compressive strength and higher, and increased application of prestressed concrete concepts. All these trends require closer control of serviceability requirements in cracking and deflection. Design expressions are given for the control of cracking in reinforced concrete beams and thick one-way slabs; prestressed, pretensioned, and post-tensioned flanged beams; and reinforced concrete two-way action structural floor slabs and plates. In addition, recommendations are given for the maximum tolerable flexural crack widths in concrete elements.