Now showing 1 - 3 of 3
  • Publication
    Expansive fracture agent behaviour for concrete cracking
    (Institution of Civil Engineers/Thomas Telford Publishing, 2010-06) ; ; ; ; ;
    Increasing concerns regarding litigation and terrorism provide a strong dual motivation to decrease high explosives usage in the construction industry. This paper provides parameter considerations and initial guidelines for the application of expansive fracture agents, typically used for concrete and soft rock removal. This approach may be especially appropriate near environmentally and historically sensitive sites. Thirty-three unreinforced blocks (approximately a cubic meter each) of varying strengths composed of sand, cement, and flyash were tested under various temperature environments, with differing expansive agents, confinement levels, and post-cracking treatments. Cracking characteristics such as crack initiation and crack expansion were analyzed. Although the performance of expansive cement was dependent upon a highly complex set of variable interactions, higher ambient temperatures, higher agent mixture temperatures, and chemical configuration designed for colder temperatures decreased the time to first crack and hastened the extent of cracking. Conversely, higher strength material required more time to first crack, as well as an extended time to achieve a 25.4 mm wide crack. Manual interference with the normal material volume expansion slowed the cracking process but did not truncate it, while the manufacturer’s recommendation to introduce water post-cracking actually reduced and slowed the extent of cracking.
    Scopus© Citations 50  1741
  • Publication
    Predicting reinforced concrete frame response to excavation induced settlement
    (American Society of Civil Engineering (ASCE), 2009-11) ; ; ;
    In many tunneling and excavation projects, free-field vertical ground movements have been used to predict subsidence and empirical limits have been employed to evaluate risk. Validity of such approaches given the reality of two-dimensional ground movements and the influence of adjacent applied loads has been largely unknown. This paper employed analytical and large-scale experimental efforts to quantify these issues, in the case of a reinforced concrete frame structure adjacent to an excavation. Nearly half of all soil and building movements occurred prior to installation of the first tie-back, even when conservative practices were applied. Free-field data generated a trough half the size of that recorded near the building frames. Empirically based relative gradient limits generally matched the extent and distribution of the damage. Application of various structural limits also generally reflected global experimental response but did not fully identify local damage distribution. Fully free-field data or failure to include accurate two-dimensional soil displacements under-predicted building response by as much as 50% for low-rise concrete frames without grade beams.
      2562Scopus© Citations 36
  • Publication
    A new multi-parallel condition assessment scale for estimating tunnel-induced damage
    Traditional means to predict tunnel-induced damage for large groups of potentially affected above ground structures has generally focused on creating a settlement trough and estimating subsequent building response limited by rudimentary aspects of each building’s geometry, structural system, foundation type, and soil bearing capacity. Historically, the procedure is done without consideration for a building’s condition. In this paper, a supplementary step is proposed – one focused on the building’s current state of repair. The presented system employs at its core a widely adopted crack evaluation scale. The main focus is application to unreinforced masonry buildings as they are simultaneously, disproportionately present in urban areas and vulnerable to tunnel movements. The proposed system is herein outlined and applied to a future tunnelling project in Ireland.
      1063