ABOUT THE 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.

International Concrete Abstracts Portal

Showing 1-5 of 9 Abstracts search results

Document: 

SP258-04

Date: 

December 1, 2008

Author(s):

Ayman S. Mosallam, Ph.D., P.E., M.ACI

Publication:

Symposium Papers

Volume:

258

Abstract:

The paper discusses the potential use of fiber reinforced polymer composites for repair and retrofit of existing reinforced concrete (RC) column-tie beam assemblies. Results of an experimental program performed on large-scale specimens repaired and strengthened with two types of wet lay-up composite systems are presented. Each column-tie beam assembly specimen was subjected to a constant axial load simulating gravity loads, and incremental cyclic lateral loads simulating potential seismic forces. Displacements, strains and loads were continuously monitored and recorded during all tests. Evaluations of the observed strength and ductility enhancements of the strengthened specimens are made and limitations of such retrofit methods are highlighted for design purposes. Experimental results indicated that the two composite systems used in this study succeeded in enhancing the strength, stiffness and the ductility of the column-tie beam assembly. As compared to the unstrengthened specimens, the strengths of the retrofitted specimens were 152% and 154% for carbon/epoxy and E-glass/epoxy composite systems, respectively.

DOI:

10.14359/20251


Document: 

SP258-02

Date: 

December 1, 2008

Author(s):

Murat Engindeniz, Lawrence F. Kahn, and Abdul-Hamid Zureick

Publication:

Symposium Papers

Volume:

258

Abstract:

This paper presents the performance of a full-scale reinforced concrete cor¬ner beam-column-slab specimen that was first severely damaged under bidirectional quasi-static loading, then rehabilitated and retested. The specimen was built using the pre-1970s construction practices including the use of low-strength materials ( =3000 psi [21 MPa], Grade 40 reinforcing bars) and deficiencies in reinforcement detailing. The rehabilitation process consisted of: (1) epoxy injection, (2) addition of a bar within the clear cover of the column at the inside corner, and (3) external application of a multilayer composite system made of unidirectional carbon-epoxy layers placed at different orienta¬tions. The carbon fiber-reinforced polymeric system was heat-cured at a temperature of 80°±10°C (176°±18°F) for 6 hours. The performance was evaluated both before and after rehabilitation based on the progression of damage and the hysteretic behavior including the changes in the strength, stiffness, and energy dissipation characteristics. The results indicated that even a severely damaged corner joint can be effectively rehabilitated using CFRP to achieve a ductile beam failure mechanism. The joint was upgraded to withstand story drift ratios of up to 3.7% applied simultaneously in both directions.

DOI:

10.14359/20249


Document: 

SP258-08

Date: 

December 1, 2008

Author(s):

Feifei Lu and Ashraf Ayoub

Publication:

Symposium Papers

Volume:

258

Abstract:

Externally bonded carbon fiber reinforced polymer (CFRP) is a feasible and economical alternative to traditional methods for strengthening and stiffening deficient reinforced and prestressed concrete bridge girders. The behavior of bond between FRP and concrete is the key factor controlling the behavior of these structures. Several experiments showed that debonding failure occurs frequently before FRP rupture and therefore the FRP strength can not be fully utilized. For design accuracy, the FRP strength must be reduced. This paper analyzes the effect of the bond properties on the response and failure modes of FRP-strengthened RC beams. A nonlinear RC beam element model with bond-slip between the concrete and the FRP laminates is used to analyze a test specimen subjected to monotonic and cyclic loads typical of seismic excitations, and to investigate the corresponding failure mode, and whether it is due to FRP rupture, debonding, or concrete crushing. The model is considered one of the earliest studies to numerically evaluate the behavior of FRP-strengthened girders under seismic loads. The model was also used to study the reduction factor of FRP tensile strength of simply supported strengthened RC girders due to debonding failure. This reduction factor seems to be directly affected by the bond strength between FRP and concrete interface. The study concludes with a numerical evaluation of the current ACI-440 guidelines for bond reduction factors.

DOI:

10.14359/20255


Document: 

SP258-03

Date: 

December 1, 2008

Author(s):

S. Rocca, N. Galati, and A. Nanni

Publication:

Symposium Papers

Volume:

258

Abstract:

This paper presents the results of an experimental investigation on the axial behavior of medium and large scale Reinforced Concrete (RC) columns of circular and non-circular cross-sections strengthened with unidirectional Carbon Fiber Reinforced Polymer (CFRP) wraps. A test matrix was developed to investigate the effect of different variables, such as the geometry of the specimen cross-section (circular, square, and rectangular), the side aspect ratio, and the area aspect ratio. A total of 22 specimens were divided into six series of three specimens each and two series of two specimens each. The largest and smallest columns featured cross-sectional areas of 0.8 m2 (9 ft2) and 0.1 m2 (1 ft2), respectively. All the specimens were subjected to pure axial compressive loading. The experimental results are compared with available data on RC specimens with one minimum dimension of the cross-section of 300 mm (12 in.). This evaluation allowed confirming that among circular and non-circular specimens of the same cross-sectional area and FRP volumetric ratio, the level of confinement effectiveness decreases as the side aspect ratio increases. Additionally, size effect within specimens of circular cross-section does not appear to be significant; however, for the case of non-circular specimens, scatter and limitation of data-points does not allow at the present time to draw a definite conclusion. A new analytical method that allowed estimating the confining pressure in non-circular cross-sections from the transverse strains at the corners is proposed. The obtained confining pressures and experimental results from this study allowed calibrating a strength model, which was validated with the available experimental data in the literature. Finally, the predictions of this strength model were compared to the ones by the model of Lam and Teng yielding close agreement.

DOI:

10.14359/20250


Document: 

SP258

Date: 

December 1, 2008

Author(s):

Editors:Tarek Alkhrdahi and Pedro Silva / Sponsored by: ACI Committee 440

Publication:

Symposium Papers

Volume:

258

Abstract:

This CD-ROM consists of eight papers that were presented by ACI Committee 440 at the Spring Convention in Atlanta, BA, in April 2007. Papers include: Seismic Retrofit of Reinforced Concrete Beam-Column T-Joints in Bridge Piers with FRP Composite Jackets Performance of an RC Corner Beam-Column Joint Severely Damaged Under Bidirectional Loading and Rehabilitated with FRP Composites Experimental Evaluation of Non-Circular Reinforced Concrete Columns Strengthened with CFRP

DOI:

10.14359/56364


12

Results Per Page