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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 234 Abstracts search results
February 1, 2021
Xingxing Zou, Chris Moore, and Lesley H. Sneed
Externally bonded (EB) steel reinforced grout (SRG) composites have the potential to improve the flexural
and shear performance of existing concrete and masonry structural members. However, one of the most commonly
observed failure modes of SRG-strengthened structures is due to composite debonding, which reduces composite
action and limits the SRG contribution to the member load-carrying capacity. This study investigated an endanchorage
system for SRG strips bonded to a concrete substrate. The end anchorage was achieved by embedding the
ends of the steel cords into the substrate. Nineteen single-lap direct shear specimens with varying composite bonded
lengths and anchor binder materials were tested to study the effectiveness of the end-anchorage on the bond
performance. For specimens with relatively long bonded length, the end-anchorage slightly improved the performance
in terms of peak load achieved before detachment of the bonded region. Anchored specimens with long bonded length
showed notable post-detachment behavior. Anchored specimens with epoxy resin achieved load levels significantly
higher than the peak load before composite detachment occurred. For specimens with relatively short bonded length,
the end-anchorage provided a notable increase in peak load and global slip at composite detachment. A generic load
response was proposed for SRG-concrete joints with end anchors.
January 1, 2021
Abheetha Peiris and Issam Harik
Following an over-height truck impact, Carbon Fiber Reinforced Polymer (CFRP) fabric was used to
retrofit the exterior girder in a four-span Reinforced Concrete Deck on Girder (RCDG) Bridge on route KY 562 that
passes over Interstate 71 in Gallatin County, Kentucky. The impacted span (Span 3) traverses the two northbound
lanes of Interstate 71. While the initial retrofit was completed in May 2015, a second impact in September 2018
damaged all four girders in Span 3. The previously retrofitted exterior girder (Girder 4) suffered the brunt of the
impact, with all steel rebars in the bottom layer being severed. Damage to Girders 1, 2, and 3 was minor and none of
the bars were damaged. A two-stage approach for the containment and repair of the damaged girders following an
over-height truck impact was implemented when retrofitting the bridge. The repair and strengthening of all the girders
using CFRP fabric was the economical option compared to the alternative option of replacing the RCDG bridge. The
initial CFRP retrofit was found to have failed in local debonding around the impact location. The CFRP retrofit
material that was not immediately near the impact location was found to be well bonded to the concrete. The removal
of this material and subsequent surface preparation for the new retrofit was time consuming and challenging due to
traffic constraints. In Girder 4 all but one of the main rebars were replaced by removing the damaged sections and
installing straight rebars connected to the existing rebars with couplers. One of the rebars could not be replaced. A
heavy CFRP unidirectional fabric, having a capacity of 534 kN (120,000 lbs.) per 305 mm (1 ft.) width of fabric, was
selected for the flexural strengthening and deployed to replace the loss in load carrying capacity. A lighter
unidirectional CFRP fabric was selected for anchoring and shear strengthening of all the girders, and to serve as
containment of crushed concrete in the event of future over-height impacts. The retrofit with spliced steel rebars and
CFRP fabric proved to be an economical alternative to bridge replacement.
April 1, 2020
John M. Kulicki and Gregg A. Freeby
Dr. Dennis Mertz was involved with the AASHTO LRFD Bridge Design Specifications  for 30 years. Starting with the original development of the specifications and continuing with maintenance and related course development and presentations. His last major contribution to the Specifications was to serve as Principal Investigator for the reorganization of Section 5, Concrete Structures. This presentation summarizes the changes to the structure of the Section including the increased emphasis on design of “B” and “D” regions of flexural members and introduces new and expanded material on beam ledges and inverted T-caps, shear and torsion, anchors, strut and tie modeling and durability. The product of this work was included in the 8th Edition of the Specifications as a complete replacement of Section 5.
March 1, 2020
John S. Ma
The U.S. Nuclear Regulatory Commission (NRC) defines seismic Category 1 structures as the structures (buildings) that should be designed and built to withstand the maximum potential earthquake stresses for the particular region where a nuclear plant is sited. Seismic Category 1 structures have been designed for ground-shaking intensity associated with a safe-shutdown earthquake (SSE) – the intensity of the ground motion that will trigger the process of automatic shutdown of the reactor in operation. The SSE generates floor response spectra at different floor elevations in a building, and these spectra and their associated forces are used for the design of piping and piping anchors and equipment and equipment anchors at their floor locations. The NRC policy requires that the seismic Category 1
structures whose collapse could cause early or/and large release of radioactive materials into the atmosphere to be
analyzed/designed for “no collapse” during the ground-shaking intensity of a review-level earthquake (RLE), which
is 1.67 times that of an SSE. Most seismic Category 1 concrete structures, such as containment and shield buildings
(curved cylindrical wall; see Figs. 1 and 2 in the next section) and containment internal structures (straight wall; see
Fig. 1), use walls to resist earthquakes.
This paper presents guidelines for the performance-based seismic design for these wall-typed structures that could
meet the NRC policy. The method consists of (1) proportioning wall thickness based on shear stress of 6√fc’ (0.5√fc’ megapascals (MPa)) generated by SSE ground motions, (2) limiting vertical compressive stress in walls to less than
0.35 fc’, (3) providing minimum percentage of reinforcement of 1.0 percent to prevent steel reinforcing bar fracture,
(4) subjecting the building design to nonlinear dynamic response analyses under RLE ground motions, (5) identifying
any members and their connections in the building that have failed or collapsed during the RLE ground motions,
(6) increasing reinforcement or wall thickness, or both, to provide additional strength or/and ductility for the failed or
collapsed members and their connections, and (7) resubjecting the revised building design to the nonlinear dynamic
response analyses as stated in step (4) until no collapse of the building and its members and their connections. This
performance-based seismic design method is a direct, transparent, and scientific answer to whether these important
seismic Category 1 structures meet the NRC’s policy that they will not collapse during the RLE ground motions.
Examples of using the nonlinear dynamic response analyses are cited and described. Guidelines for the performance-based
seismic design of seismic Category 1 concrete Structures are listed at the end of this paper.
January 23, 2020
Widianto; Jameel Khalifa; Erik Åldstedt; Kåre O. Hæreid; Kjell Tore Fosså
An offshore concrete Gravity-Based-Structure (GBS) is a massive concrete structure placed on the seafloor and held in place strictly by its own weight, without need for anchors. This paper focuses on concrete GBSs used as the base of integrated oil drilling and production platforms. The summary of key distinct structural features of several major GBSs, since the first Ekofisk GBS (installed in the North Sea, offshore Norway, in 1973) until the latest Hebron GBS (installed in the Grand Banks, Canada, in 2017), is presented. This paper also discusses several unique loads that GBSs have to resist. An overview of structural analysis and design methodology is described in detail. Key considerations for preliminary sizing of GBS structural components are presented. Typical construction phases, methods, and the importance of constructability are explained. Finally, potential future research topics that would result in a more cost-effective offshore concrete GBS are discussed.
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