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International Concrete Abstracts Portal

Showing 1-5 of 12 Abstracts search results

Document: 

SP264-02

Date: 

October 1, 2009

Author(s):

S.P. Gross, J.R. Yost, and D.J. Stefanski

Publication:

Symposium Papers

Volume:

264

Abstract:

An experimental study was conducted to evaluate the increase in crack width occurring over time in FRP-reinforced concrete as a result of sustained loading. Twelve beams (eight GFRP, two CFRP, and two steel-reinforced) were maintained under a constant sustained service load for nearly three years. Three flexural cracks were monitored on each beam over the duration of the test. The observed increase in flexural crack widths over the study was greater in the FRP-reinforced specimens than in the steel-reinforced specimens. On average, flexural crack widths in FRP-reinforced concrete specimens were observed to double over one year of sustained loading. A simple design approach, based on modification to the existing ACI 440 (2006) crack control procedure, is proposed to account for this observed increase in crack widths with time.

DOI:

10.14359/51663258


Document: 

SP264

Date: 

October 1, 2009

Author(s):

Editors: Carlos Ospina, Peter Bischoff, and Tarek Alkhrdaji / Sponsored by: ACI Committee 440

Publication:

Symposium Papers

Volume:

264

Abstract:

This CD-ROM consists of 11 papers that were presented by ACI Committee 440 at the ACI Spring 2009 Convention in San Antonio, TX, in March 2009. The papers focus on experimental evaluation and analytical predictions related to deflection and cracking. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-264

DOI:

10.14359/51663287


Document: 

SP264-11

Date: 

October 1, 2009

Author(s):

J.J. Kim, A.M. Said, and M.M. Reda Taha

Publication:

Symposium Papers

Volume:

264

Abstract:

This paper presents an alternative approach to examine uncertainty in predicting deflections of fiber-reinforced polymer-reinforced concrete (FRP-RC) beams. The use of nonspecificity of concrete cracking as a measure of cracking variability is proposed. Non-specificity is a type of uncertainty associated with having multiple alternatives to define variables (e.g. modulus of rupture, tensile strength to describe cracking). Nonspecificity in cracking can be described by considering cracking strength interval. Using a cracking strength interval, deflection intervals of FRP-RC beams are calculated. Deflection is modeled using cracked plane frame analysis integrated with recent models describing concrete tension stiffening with fiber reinforced polymers (FRP) reinforcement. A deflection database of FRP-RC beams is developed and examined. The uncertainty in deflection prediction is evaluated by comparing the measured deflection from the database with respect to the predicted deflection interval. The significance of deflection prediction parameters on the uncertainty in predicting deflection of FRP-RC beams was analyzed. It is shown that when the applied moment to cracking moment ratio gets close to unity, the uncertainty in predicting deflection of concrete beams reinforced with FRP increases.

DOI:

10.14359/51663267


Document: 

SP264-10

Date: 

October 1, 2009

Author(s):

A. Mirmiran, H. Erdogan, and A. Singhvi

Publication:

Symposium Papers

Volume:

264

Abstract:

While most studies have focused on short term behavior of fiber reinforced polymer (FRP)-reinforced concrete (RC) members, it is important and necessary to study their time-dependent behavior, if FRP is to be used as a viable alternative reinforcement for the infrastructure. The present study provides an analytical tool to assess serviceability issues of FRP-RC beam-columns under sustained loads. The analytical model accounts for creep of FRP-RC beams and beam-columns. The model is based on age-adjusted effective modulus method for concrete and Findlay’s model for FRP reinforcement. The model has been verified against the FRP-RC beam tests by the authors, as well as those from the literature. A detailed parametric study is then carried out to determine the effects of different types of FRP reinforcing bars on the creep of slender FRP-RC columns, and whether the ACI 318 design provisions for creep of slender RC columns is adequately safe for FRP-RC construction.

DOI:

10.14359/51663266


Document: 

SP264-07

Date: 

October 1, 2009

Author(s):

H.A. Rasheed and H. Charkas

Publication:

Symposium Papers

Volume:

264

Abstract:

The use of externally bonded FRP plates and sheets has been established as an effective mean to strengthen concrete beams in flexure and shear. Several investigators have shown that the direct use of Branson equation does not yield conservative deflection results especially after steel yielding. The authors have developed an analytical solution that generates closed form expressions for deflection in simple beams. These expressions were shown to reproduce results that compared well with experiments. These expressions were dependent on the loading condition while Branson equation is not load specific. Branson equation is modified by replacing the cracked section moment of inertia with an effective moment of inertia at steel yielding to evaluate deflections at the service load levels. This revised formula could be easily implemented in the ACI 440.2R format. The predictions are compared against Branson equation and experimental evidence. Furthermore, another new modification to Branson equation is proposed for the region covering response from steel yielding and up to ultimate capacity.

DOI:

10.14359/51663263


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