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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 1-10 of 228 Abstracts search results
July 1, 2019
Keith Kesner and Kevin Coll
Evaluation of an existing structure is a task commonly performed by licensed design professionals. An evaluation can be required by a façade inspection ordinance, as part of a due-diligence process prior to the purchase of a structure, or prior to the development of rehabilitation or repair measures. Each of these project types will have differences in the evaluation protocol and portion of the structure to be examined – but in each example, the licensed design professional is expected to provide a minimum “standard of care” to the client and to protect the public. Therefore, in developing the evaluation protocol, a critical question facing the licensed design professional is how much investigative effort is required to complete the evaluation and ensure the evaluation provides a minimum standard of care.
The standard of care for an evaluation of existing structures can broadly be defined as the level of effort that a reasonable and prudent licensed design professional would be expected to provide under similar circumstances. Given the range of structure types that can be encountered and the varying levels of damage and exposure conditions, determination of the scope of evaluation can be a difficult task for a licensed design professional. The following sections examine approaches used in industry codes and ordinances to help define a minimum standard of care for the evaluation of existing structures. Industry codes and ordinances to be examined will include the ACI 562-16 Code for Assessment, Repair and Rehabilitation of Existing Structural Concrete, FHWA bridge inspection requirements and building façade inspection standards and ordinances. Based upon these documents, items to be considered in establishing a “Standard of Care” in the evaluation of existing structures will be summarized.
February 1, 2019
Tarek Omar and Moncef L. Nehdi
Bridge deck condition assessment is commonly conducted through visual inspection by bridge inspectors. Considering the colossal backlog of aging bridge structures, there is a need to develop cost-effective and innovative solutions to evaluate bridge deck conditions on regular time intervals, without interrupting traffic. This makes remote sensing technologies viable options in the field of bridge inspection. This paper explores the potential for applying infrared thermography (IRT) using unmanned aerial vehicle (UAV) to detect and quantify subsurface delaminations in concrete bridge decks. The UAV-borne thermal sensing system focuses on acquiring thermal imagery using a UAV and extracting information from the image data. Two in-service concrete bridge decks were inspected using a high resolution thermal camera mounted on a UAV. The captured images were then enhanced and stitched together using a tailored procedure to produce a mosaic view of the entire bridge deck, indicating the size and geometry of the detected delaminated areas. The results were validated by conducting hammer sounding and half-cell potential testing on the same bridge decks. The findings reveal the capability of the technology to provide measurements comparable to those derived from traditional hands-on inspection methods. Thus, it can be an excellent aid in efficient bridge maintenance and repair decision-making.
November 1, 2018
Mohammad Moravvej and Mamdouh El-Badry
Utilization of fiber-reinforced polymers (FRPs) in concrete structures, particularly bridges, has promised
a safe and satisfactory performance. However, the structural performance of FRP-reinforced bridges can be affected
by occurrence of various types of damage. This paper presents structural damage identification in FRP-reinforced
bridge truss girders tested under static and fatigue loading. The proposed technique combines discrete wavelet
transforms (DWTs) and spectral entropy in a relative procedure to detect and quantify the damage-induced
disturbances in the measured vibrational signals of the girders. Various types of test-induced damage were identified
using the vibrational signals obtained only from the damaged state of the girders. Results of damage identification
were verified by data obtained through instrumentations and by visual inspection of the actual state of damage in the
girders during and after the tests. The results show that the technique can be implemented in a protective structural
health monitoring (SHM) system to identify imminent failure. It can also help with the decision-making process
regarding maintenance of FRP-reinforced concrete bridges. The technique is a practical means for damage
identification in in-situ cases, where the normal operation of bridges cannot be interrupted, and the data obtained
from a reference state of bridges are not available.
American Society of Concrete Contractors (ASCC) Technical Committee
Designing slopes at the maximum limits required for compliance with the Americans with Disabilities Act (ADA) often results in unnecessary rejections of constructed sidewalks and ramps. To accommodate for the accuracy of the inspection tool and the effects of local surface roughness, the ASCC Technical Committee recommends that designers specify maximum slopes that are slightly less than the ADA requirements. This article provides the committee’s recommendations for specifying and measuring slopes for walks and ramps.
September 12, 2018
Paolo M. Calvi, Giorgio T. Proestos, David M. Ruggiero
Much of the post-war reinforced and prestressed concrete infrastructure in North America and Europe is reaching its design life and engineers are in need of tools that can be used to assess the shear behavior of these structures. The Compression Field Theory (Collins, 1978) and the Modified Compression Field Theory (Vecchio and Collins, 1986) form the basis of a suite of design procedures and software that engineers can use to assess concrete structures subjected to shear. The complexity of these tools varies from simple hand calculations, such as the sectional design procedures or strut-and-tie procedures in CSA A23.3-14 and AASHTO-LRFD, to sectional software tools, such as Response-2000, and full finite element programs such as VecTor2. This paper describes how such tools can be used to evaluate shear-critical structures in the context of assessing inventories of bridge structures. A preliminary crack assessment procedure, capable of providing estimates of the residual capacity of bridge girders based on crack slips and crack widths, is also presented. This procedure is based on the Pure Mechanics Crack Model and builds on existing compression field approaches. The tool is envisioned as a means of moving from traditional bridge inspection procedures to more complex methods, based on the theoretical advancements that have been made over recent decades.
August 10, 2018
This paper reviews the background, inspection and refurbishment of a hyperbolic cooling tower located at the Opole Power Station in Poland. The cooling tower is 132 m high with a base diameter 100,00 m. It was erected in 1977-1982. On the inner surface of the RC shell serious damage to the concrete and protective coating occurred as a result of an unexpected shut-down of the unit at low ambient temperature in winter 2010. It manifested itself by spalling, loss of the concrete, corrosion of the reinforcement and deterioration of the protective coating. For this reason, the tower was subjected to the detailed inspection and technical assessment in 2013 which resulted in required repair and protection of the RC shell of the cooling tower. General view of the concrete shell and columns of the cooling tower is displayed in Fig.1.
May 1, 2018
Mauricio Diaz Arancibia and Pinar Okumus
Recurrent service problems and uncertainties in load distribution have been frequently reported by Departments of Transportation for skewed bridges. Service problems, such as deck cracking or excessive bridge racking can lead to bridge deterioration, and indicate the need of a better understanding of the structural response of high skew bridges to service loading. This paper presents the instrumentation and load testing of a three-span, medium span length, prestressed concrete bridge with 64° of skew to understand service, analysis and design problems associated with skew. The instrumentation plan for the bridge was developed based on service problems observed in concrete bridges with high skew such as deck cracking and displacements, as reported by the literature and by regular bridge inspections. Complete understanding of skew related responses required both short-term testing and long-term load monitoring. Structural responses of the key areas of the bridge to live and temperature loads and shrinkage were measured. The effects of certain bridge details on live load distribution were determined using finite element models validated through short-term load testing data. The evolution and magnitude of bearing movements and deck strains were captured for long periods of opposite thermal tendencies.
June 1, 2017
Anil Patnaik, Prince Baah, Perry Ricciardi, and Waseem Khalifa
Bridge deck cracking is a common problem in the United States, and affects the durability and service life
of reinforced concrete bridges. Physical inspections of three-span structural slab bridges in Ohio revealed cracks
wider than ⅛ inch (3.2 mm). ACI 224R-01 recommends a maximum crack width of 0.007 inch (0.18 mm) for
members exposed to de-icing chemicals. The primary objective of this study was to investigate the effects of fiber
addition on crack resistance. In an attempt to minimize deck cracking, slab specimens with basalt MiniBar or
polypropylene fiber were also investigated in the test program. Slab tests revealed that the specimens with
longitudinal epoxy-coated bars developed first crack at smaller loads, exhibited wider cracks and a larger number of
cracks, and failed at smaller ultimate loads compared to the corresponding test specimens with uncoated (black)
bars. Test specimens with fiber exhibited higher cracking loads, smaller crack widths, smaller mid-span deflections
and higher ultimate failure loads compared to identical specimens without fiber. Addition of fiber to concrete with
no changes to internal steel reinforcement details is expected to reduce the severity and extent of cracking in
reinforced concrete bridge decks demonstrating that fiber addition improves crack resistance of bridge decks.
October 1, 2016
Raymond Messer and Enrique Vaca
Current building codes require unbonded tendons to be fully encapsulated to provide improved corrosion resistance. To minimize construction problems, ensure design compliance, and eliminate or minimize failure mechanisms and tendon placement issues, all unbonded tendons have to be inspected. Tendon handling and placement considerations, concrete blowouts, corrosion-induced failures, and personnel qualifications are covered.
October 1, 2015
Post-Tensioning Institute staff
1) During a concrete repair project to a post-tensioned (PT) structure, we removed the patching material in the stressing pocket and noticed cracking in the wedges. Do the wedges need to be replaced? 2) I’m an inspector for a municipal building department, and I recently encountered a foundation subcontractor that insisted on placing reinforcing bars just ahead of the flow of concrete coming out of the pump hose. Is that acceptable?
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