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International Concrete Abstracts Portal

Showing 1-5 of 225 Abstracts search results

Document: 

SP-344_05

Date: 

October 1, 2020

Author(s):

Constantin E. Chalioris, and Chris G. Karayannis

Publication:

Symposium Papers

Volume:

344

Abstract:

Recently the use of special reinforcement arrangements has been extended in reinforced concrete members under torsion. These arrangements include (a) continuous rectangular spiral reinforcement, (b) epoxy bonded Carbon Fiber Reinforced Polymer (C-FRP) sheets as external transverse reinforcement and (c) short steel fibers as mass reinforcement. In this study an extended experimental program of 14 beams tested under torsion is presented. All specimens have the same geometrical characteristics but different transverse reinforcement arrangements. Six beams are used as pilot specimens; three of them have no transverse reinforcement and three have conventional steel stirrups. Further, two specimens have continuous steel spirals; four specimens have steel fibers as mass reinforcement and two specimens have externally bonded C-FRP sheets. The torsional behavior of these specimens is presented and compared to the behavior of the pilot specimens. Discussion and explanatory design examples about the application of these reinforcements are also included.


Document: 

SP-337_08

Date: 

January 23, 2020

Author(s):

Anthony Devito; Alex Krutovskiy and Leszek Czajkowski

Publication:

Symposium Papers

Volume:

337

Abstract:

The purpose of the LaGuardia Runway Extension Project is to extend existing runways 4-22 and 13-31 into Flushing Bay, at the inshore end of Long Island Sound, to support Engineered Material Arresting System (EMAS) - a crushable material installed at the end of each runway to reduce the risk of a plane overrun during takeoff.

The new runway deck extensions are marine concrete structures which utilize precast prestressed pile caps with a pre and post-tensioned composite precast deck and cast-in-place concrete topping slab. The concrete decks are supported by 250 ton (227 tonnes) 24 inch (61cm) diameter epoxy coated closed end concrete filled steel pipe piles with specialized wraps and sacrificial zinc anodes for corrosion protection. The piles are approximately 100 feet (30m) long and driven in about 30 feet (9m) of water through soft organic clay and dense glacial soils and founded on bedrock.

This paper provides an overall description of the runway extensions and a detailed account of both the technical and logistical challenges. Challenges included a prestressed composite deck design for both the aircraft impact and braking loads. Maintaining and replacing the lightbars of the Approach Lighting Systems (ALS) used to visually identify the runways was required, along with optimizing the pile hammer selection and driveability with wave equation analyses and dynamic pile driving PDA testing. Extensive coordination was necessary with the PANYNJ, FAA and various other stakeholders involved in this fast-paced design build project.


Document: 

SP331-02

Date: 

February 1, 2019

Author(s):

Ian Shaw, Hang Zhao and Bassem Andrawes

Publication:

Symposium Papers

Volume:

331

Abstract:

Fiber reinforced polymer (FRP) composites have emerged as a lightweight and efficient repair and retrofit material for many concrete infrastructure applications. FRP can be applied to concrete using many techniques, but primarily as either externally bonded laminates or near-surface mounted bars or plates. This paper presents the results of direct shear pull-out tests performed on aged concrete specimens reinforced with glass FRP (GFRP) and carbon FRP (CFRP) externally bonded laminates and near surface mounted (NSM) bars. An accelerated aging scheme consisting of freeze/thaw cycling in the presence of a deicing salt solution is implemented to determine the effect of long-term environmental exposure on the FRP/concrete interface in regions that experience aggressive winter environments. The results show that the NSM bar technique is superior to externally bonded laminates in terms of efficiency in the use of FRP material and the effects of accelerated aging. Generally, the performance of GFRP is affected less than CFRP after freeze/thaw cycling for both externally bonded laminates and NSM bars. For high strength NSM FRP bar applications, a spalled or cracked concrete surface caused by freeze/thaw cycling may drastically reduce the capacity of the FRP/concrete interface by inducing failure at the concrete/epoxy filler interface.


Document: 

SP327-09

Date: 

November 1, 2018

Author(s):

Ruo-Yang Wu and Chris P. Pantelides

Publication:

Symposium Papers

Volume:

327

Abstract:

A rapid repair or replacement method is developed for severely damaged concrete bridge columns due to cyclic loading. A carbon fiber-reinforced polymer (CFRP) shell and headed steel bars are used to relocate the column plastic hinge. The technique employs a steel collar with steel studs to increase bond of the original column to repair concrete inside the CFRP shell. Two bridge columns were damaged including concrete crushing and longitudinal steel bar pullout under quasi-static cyclic loads. One of the specimens required additional epoxy injection of the cracks; for the other specimen, the column and cap beam were decoupled before repair to simulate replacement of a column which sustained unrepairable damage. The technique successfully relocated the plastic hinge and restored strength and displacement capacity. Failure of the repaired specimens included concrete crushing and bar fracture. The technique is an accelerated bridge construction method and could be used to repair columns with repairable damage or replace columns with unrepairable damage.


Document: 

SP327-28

Date: 

November 1, 2018

Author(s):

Salah Altoubat, Abdul Saboor Karzad, Mohamed Maalej

Publication:

Symposium Papers

Volume:

327

Abstract:

This paper is part of an on-going research project on the behavior of damaged Reinforced Concrete (RC) beams repaired and strengthened with Externally Bonded Fiber Reinforced Polymer (EB-FRP). A total of seven full-scale rectangular beams; fully-damaged in a previous study, were repaired and retested to failure. The repair methodology consists of filling the cracks with epoxy, and then wrapping the beams with FRP discrete strips with two different thicknesses (1 layer and 2 layers). Out of the seven beams, four beams were strengthened using 2 layers of EB-FRP discrete strips; two beams were strengthened with 1 layer of EB-FRP; and the remaining beam was only repaired by crack injection with epoxy without wrapping with FRP. The beams were instrumented and tested to failure in three-points loading setup. The measured test parameters were the beams deflection and the maximum load-carrying capacity. Furthermore, the mode of failure was also observed and reported in this study. The test results revealed that the use of EB-FRP strips along with epoxy injection is an effective repair method that not only recovers the original strength (strength of the beams tested in previous study, considered as the reference beams), but also significantly increases their shear capacity. Comparing the shear capacity of the repaired beams to that of the reference beams, revealed that 2 layers of EB-FRP increased the shear strength by up to 95%, while the use of 1 layer of EB-FRP increased the shear strength by up to 66%. Moreover, comparison of the test results with existing predictive models (ACI 440.2R and fib TG-9.3) showed that both models reasonably predict the EB-FRP contribution to the shear strength of repaired and strengthened damaged beams.


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