Browsing by Subject "Concrete beams"

Now showing 1 - 3 of 3
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    Measurements of intact and cracked concrete structural elements by the SASW method
    (1994) Kalinski, Michael E. (Michael Edward), 1963-; Stokoe, Kenneth H.
    Research was conducted to apply the Spectral-Analysis-of-Surface-Waves (SASW) method to the identification of internal cracking in concrete structural elements such as beams and columns. The SASW method is a nondestructive technique which involves the propagation of surface stress waves along the exposed face of a structural element. By yielding the relationship between wave velocity and wavelength of the surface wave energy, the SASW method provides information about how the stiffness of a material varies with depth. SASW measurements were made on intact and cracked concrete structural elements. Surface waves propagated through cracked concrete at consistently lower velocities. These velocity reductions corresponded to the presence of visibly detectable cracking and, in some cases, occurred in the absence of visible cracking. This result demonstrated the ability of the SASW method to detect otherwise hidden damage. When the cracks were reclosed by the application of a compressive load, the surface waves propagated at velocities comparable to those of uncracked concrete. In addition to performing velocity measurements, material damping measurements were made on intact and cracked concrete structural elements. These measurements revealed that the presence of cracking can be qualitatively assessed through an increase in observed surface wave material damping, with material damping ratios ranging from less than 1% in undamaged concrete to around 3% in damaged concrete
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    Rehabilitation of poorly detailed RC structures using CFRP materials
    (2006-05) Kim, InSung; Jirsa, J. O. (James Otis)
    In many reinforced concrete structures built in the 1970's and earlier, bottom beam reinforcement is not continuous and if a column support is lost due to terrorist attack or other unexpected action, the structure could be vulnerable to progressive collapse. The use of CFRP material may provide a solution for rehabilitating such structures. CFRP materials cannot develop full tensile capacity unless they are properly anchored to the reinforced concrete structure. The intent of this study is to find an effective method of anchoring CFRP material to a reinforced concrete beam so that the ultimate tensile strength of the CFRP is realized. In this study, ten reinforced concrete beams rehabilitated using different configurations of anchors were tested to assess the effectiveness of the anchors. Both CFRP anchors and CFRP U-wraps were investigated. The rehabilitated beams were loaded until failure of the CFRP material or anchor occurred. Different failure modes, strengths and deformation capacities of the rehabilitated beams were observed depending on the configurations of anchors. The maximum capacity was obtained using a combination of CFRP anchors and U-wraps.