IS NO-TENSION DESIGN OF CONCRETE OR ROCK STRUCTURES ALWAYS SAFE?--FRACTURE ANALYSIS

Unreinforced concrete structures and rock structures--such as dams and retaining walls or tunnels and rock slopes, respectively--are designed by elastic-perfectly plastic analysis in which the tensile yield strength of the material is zero. The author examines the safety of such a design in light of the finiteness of the tensile strength of concrete and the tensile strength of rock between the joints. Examples demonstrate that: 1) the calculated length of cracks or cracking zones can correspond to an unstable state; 2) the uncracked ligament of the cross section, available for resisting horizontal shear loads, can be estimated much too large, compared to the fracture mechanics estimation; 3) the calculated load-deflection diagram can lie lower than that obtained by fracture mechanics; 4) the no-tension load capacity for a combination of crack face pressure and loads remote from the crack front, computed by elastic analysis on the basis of allowable compressive stress, can be higher than that derived by fracture mechanics; and 5) an increase in the tensile strength of the material can cause the load capacity of the structure to decrease. Based on size effect, these facts are true for zero fracture toughness as well as finite fracture toughness, provided the structure is large enough. Several prior studies on the safety of no-tension design are reviewed. The author concludes that if the no-tension limit design is employed, the safety factors of concrete or rock structures cannot be guaranteed to have the specified values.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/07339445
• Corporate Authors:

  American Society of Civil Engineers

  345 East 47th Street
  New York, NY  United States  10017-2398
• Authors:
  • Bazant, Z P
• Publication Date: 1996-1

Language

• English

Media Info

• Features: Appendices; Figures; References;
• Pagination: p. 2-10
• Serial:
  • Journal of Structural Engineering
  • Volume: 122
  • Issue Number: 1
  • Publisher: American Society of Civil Engineers
  • ISSN: 0733-9445
  • Serial URL: http://ascelibrary.org/loi/jsendh

Subject/Index Terms

• TRT Terms: Concrete; Elastoplasticity; Fracture mechanics; Rocks; Safety factors; Structural design; Tensile strength; Toughness
• Uncontrolled Terms: Elastic plastic analysis
• Subject Areas: Bridges and other structures; Design; Geotechnology; Highways; Safety and Human Factors; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00715363
• Record Type: Publication
• Files: TRIS
• Created Date: Jan 18 1996 12:00AM