Entity

Time filter

Source Type

Kansas City, KS, United States

Darwin D.,University of Kansas | O'Reilly M.,University of Kansas | Browning J.,University of Kansas | Locke C.E.,University of Kansas | And 6 more authors.
Journal of Materials in Civil Engineering | Year: 2014

Techniques for making epoxy-coated reinforcement more corrosion resistant, including epoxies with increased adhesion to the steel; concrete with a decreased water cement ratio; concrete containing calcium nitrite or one of two organic corrosion inhibitors; bars with a primer coating containing microencapsulated calcium nitrite applied prior to epoxy application; and bars coated with zinc prior to epoxy application are compared based on the chloride content required to initiate corrosion and corrosion losses using the southern exposure and cracked beam tests. The coatings on all bars are penetrated prior to testing to simulate damage in the field. The results indicate that, even when damaged, conventional epoxy coatings result in much higher concrete chloride contents at corrosion initiation and much lower corrosion losses than exhibited by conventional reinforcement. A reduced water-cement ratio, corrosion inhibitors, and the primer coating containing microencapsulated calcium nitrite provide protection in uncracked but less or no protection in cracked concrete. The bars coated with zinc prior to epoxy application exhibit relatively high corrosion rates because of preferential losses to the zinc, and no improvement in corrosion performance is observed for epoxies with increased adhesion. © 2014 American Society of Civil Engineers. Source


Kim Y.,Hyundai Engineering | Quinn K.,Haris Engineering Inc. | Ghannoum W.M.,University of Texas at Austin | Jirsa J.O.,University of Texas at Austin
ACI Structural Journal | Year: 2014

Sixteen reinforced concrete T-beams were tested to evaluate the shear performance of beams strengthened externally with carbon fiber-reinforced polymer (CFRP) laminates and CFRP anchors. Monotonically increasing load was applied to the reinforced concrete members at three different shear span-depth ratios until shear failure. Other test variables included the amount of transverse steel, the layout and amount of CFRP laminates, bond between the CFRP laminates and the beam surface, and inclination of CFRP anchors. All specimens were 24 in. (610 mm) deep. Beams strengthened with anchored CFRP laminates showed a much larger shear strength increase than those strengthened with unanchored laminates. In all cases, CFRP anchors increased the contribution of the CFRP laminates to the shear capacity. Test results indicate that current design procedures for external CFRP shear strengthening should be modified to account for interactions between concrete, steel, and CFRP. Copyright © 2014, American Concrete Institute. All rights reserved. Source


Guo G.,Haris Engineering Inc. | Joseph L.M.,Thornton Tomasetti
ACI Structural Journal | Year: 2013

Part I of the study compares five concrete shortening prediction models, and the B3 model is considered to be the most appropriate model. Part II of the study provides detailed procedures to estimate post-tensioned (PT) concrete floor shortening. Different relative humidity values during and after construction are used to simulate the actual conditions concrete floors experience. For typical PT construction, concrete floor shortening due to elastic compression, concrete creep, and shrinkage can be estimated as approximately 1 in. (25 mm) per 100 ft (30.5 m). If different relative humidity values during and after construction are considered, the construction period can affect total floor shortening by more than 15%. Total shortening is minimized by longer construction exposure in regions with high relative humidity and shorter construction exposure in regions with low relative humidity. The helpful effect of pour strips in reducing PT floor shortening is studied and appears rather limited for typical construction. Copyright © 2013, American Concrete Institute. Source


Guo G.,Haris Engineering Inc. | Joseph L.M.,Thornton Tomasetti
ACI Structural Journal | Year: 2013

For post-tensioned (PT) concrete floors, shortening occurs due to elastic compression, concrete creep, concrete shrinkage, and temperature change. The longer the continuous concrete slab, the greater the cumulative shortening effect. More commonly, some restraints to shortening exist, such as shear walls and stocky columns. At best, restraint to shortening (RTS) can induce cracks and spalls that affect aesthetics and durability. At worst, it can affect structural safety. Therefore, appropriate models and procedures that can predict shortening are quite necessary. In the first part of this study, five concrete creep and shrinkage models are compared for both ultimate values and relative shortening rates. The B3 model is considered to be the most appropriate model. Adjustments to the B3 model are introduced by using equivalent concrete age to account for high early concrete strength frequently used in PT construction. Part II of this study covers detailed procedures to estimate PT concrete floor shortening. Copyright © 2013, American Concrete Institute. Source

Discover hidden collaborations