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.


  • English

Media Info

Subject/Index Terms

Filing Info

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