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International Concrete Abstracts Portal

Showing 1-5 of 10 Abstracts search results

Document: 

SP331

Date: 

March 1, 2019

Author(s):

ACI Committee 345, ACI Committee 201, Yail J. Kim, Isamu Yoshitake, and Mark F. Green

Publication:

Symposium Papers

Volume:

331

Abstract:

Sustainability is one of the salient requirements in modern society. Structures frequently deteriorate because of aggressive service environments; consequently, federal and state agencies expend significant endeavors to maintain the quality of the structures. Among many factors, durability plays a major role in accomplishing the concept of sustainability. Extensive research has been conducted to understand the deterioration mechanisms of concrete and to extend the longevity of concrete members. Over the past decades, the advancement of technologies has resulted in durable construction materials such as advanced composites. This Special Publication (SP) contains nine papers selected from two technical sessions held in the ACI Spring Convention at Detroit, MI, in March 2017. All manuscripts were reviewed by at least two experts in accordance with the ACI publication policy.


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: 

SP331-06

Date: 

February 1, 2019

Author(s):

Abheetha Peiris and Issam Harik

Publication:

Symposium Papers

Volume:

331

Abstract:

An exterior girder of a prestressed concrete bridge over Interstate 65 in Kentucky was damaged due to an over-height truck impact. The damaged section spanned two of the three northbound lanes of the highway. Two prestressing strands were severed and two additional strands were damaged by the impact. In addition, shear reinforcing bars in the vicinity of the impact were cut-off. CFRP Rod Panels (CRPs) were deployed to restore some of the load carrying capacity lost due to the severed prestressing tendons. CRP 195, with CFRP rods of 3.96 mm (0.156 in) diameter, having a capacity of 867 kN (195,000 lbs.) per 305 mm (1 ft.) width of panel, was selected for the flexural strengthening. A triaxial braided quasi-isotropic CFRP fabric was selected for shear strengthening and served as containment of crushed concrete in the event of future over-height impacts. Since the ACI and AASHTO Codes or Guides do not directly address the design with CRPs, strain limits based on debonding of the rods similar to externally bonded CFRP (EB-CFRP) are imposed when determining the retrofitted beam capacity. The load rating evaluation of the impacted beam, the retrofit analysis and design, and the field repair stages are presented and discussed.


Document: 

SP331-03

Date: 

February 1, 2019

Author(s):

Ali S. H. Zerkane, Yasir M. Saeed, and Franz N. Rad

Publication:

Symposium Papers

Volume:

331

Abstract:

Use of fiber reinforced polymer (FRP) material has served as a proper solution to overcome the weakness of concrete members caused by substandard design, changes in the load distribution, or to correct the weakness of concrete structures subjected to hostile weather conditions. Concrete beam-column joints designed and constructed before 1970s were characterized by weak joints. Lack of transverse reinforcement within the joint reign, hence lack of ductility in the joints could be one of the main reasons that many concrete buildings have failed during earthquakes around the world. In the present work, carbon fiber reinforced polymer (CFRP) sheets were used as Externally Bonded FRP System to compensate for the lack of transverse reinforcement in the beam-column joints in order to retrofit the joint region and to transfer the failure to the concrete beams. Six specimens of approximately one-third scale were designed, constructed, and tested. A new technique of rehabilitation scheme is proposed for retrofitting. The scheme proved to be effective in improving the behavior of non-ductile beam-column joints, and to change the final mode of failure. The comparison between beam-column joints before and after retrofitting is presented by load versus deflection, load versus CFRP strain, energy dissipation, and ductility.


Document: 

SP331-07

Date: 

February 1, 2019

Author(s):

Yasir M. Saeed and Franz N. Rad

Publication:

Symposium Papers

Volume:

331

Abstract:

This paper presents the experimental investigation of concrete beams pre-tensioned with Carbon Fiber Reinforced Polymer (CFRP) strands. Four rectangular prestressed concrete beams were fabricated and tested under cyclic loading, and then the beams were loaded monotonically until failure. All beams were prestressed with one 0.5-in. diameter (13 mm) CFRP strand. The results showed that bond failure between CFRP strands and surrounding concrete was the main cause of early and brittle failures. Adding extra steel stirrups improved the slippage resistance capacity but was not adequate to prevent slippage at higher loads. A new technique was developed and used by anchoring the CFRP strand at the ends using a steel-tube anchorage system. The new technique prevented the slippage and improved the flexural moment capacity by 39%. An analytical computer model was created to predict the load vs. deflection responses of the beams. The behavior of beams with CFRP strands were compared to beams with steel strands using the same computer program. It was found that CFRP beams had more flexural strength but lower ductility if both beams were designed to carry the same service loads.


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