EFFECT OF SUSTAINED LOAD ON THE LOAD-DEFORMATION CURVE OF CONCRETE

A project was undertaken to study the effect of age on the elastic properties of stressed and unstressed concrete. A part of this investigation was to determine the effect of sustained load on the load-deformation curve of concrete as compared with that of unstressed concrete. Specimens were made with various aggregate/cement and water/cement ratios in different batches in order to study the effect of these variations. The main specimens consisted of 30 in. long prisms having a cross-section of 3-1/2 in. x 3-1/2 in. with an axial circular hole of 0.85 in. Diameter. In most of the hatches there were four main specimens, two of which were kept under sustained load while the other two were unloaded. All the test specimens were kept under controlled conditions of temperature and humidity. In some cases the specimens were sealed with wax after an initial period of curing but in most cases they were unsealed. Specimens in a few batches consisted of pure cement paste. The specimens were kept under sustained load by prestressing . Steel bars were placed in the axial hole cast in the specimen and were stressed against the concrete by means of a 30 ton (centre hole type) simplex jack through an end block. The specimens were kept under sustained loads ranging from about 15% to 50% of the ultimate strength of the specimens for periods ranging from 100 to over 300 days in different batches. At the end of the sustained load tests, each main specimen was cut into three pieces, two being 7 in. long and one about 14 in. long. Seven inch long pieces were used for determining the compressive strength while on the longer pieces defrmation readings for various loads up to about 80% of f1c were taken with an 8 in. Demec gauge. These tests were carried out both for sustained load as well as companion unloaded specimens. This investigation revealed that the load-deformation curve was modified under sustained load and the specimens showed an elastic behaviour up to a higher value of stress when compared with unloaded companion specimens. The shape of the load-deformation curve of loaded and unloaded specimens has been explained in terms of microcracking induced in the material (a). The number of the covering abstract of the conference is IRRD abstract no 213776. /TRRL/

  • Supplemental Notes:
    • Presented at the First Australian Conference on Engineering Materials.
  • Corporate Authors:

    University of New South Wales

    School of Civil Engineering, Anzac Parade
    Kensington, New South Wales  Australia  2033
  • Authors:
    • Khalifa, S
  • Publication Date: 0

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 19 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00129547
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Conf Paper
  • Files: ITRD, TRIS
  • Created Date: May 14 1976 12:00AM