Date of Award

Fall 2004

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering - (Ph.D.)

Department

Civil and Environmental Engineering

First Advisor

C.T. Thomas Hsu

Second Advisor

William R. Spillers

Third Advisor

Dorairaja Raghu

Fourth Advisor

Walter Konon

Fifth Advisor

Pedro Munoz

Abstract

The new technique of using Fiber Reinforced Polymer (FRP) materials to repair and strengthen various concrete members is becoming more and more popular in structural retrofitting field. Among all the confining materials, Carbon Fiber Reinforced Polymer (CFRP) fabric jackets are identified as an effective way to enhance the strength and ductility of concrete members due to its superior mechanical properties. This study investigates the detailed structural behavior of confined concrete members using CFRP fabric jackets by both analytical and experimental approaches.

A series of CFRP wrapped concrete cylinder tests were conducted to study the compressive stress-strain behavior for CFRP confined concrete members, Based on the test results, the CFRP system can significantly increase the ductility and ultimate compressive strength of normal concrete specimens. Also, a complete stress-strain equation was derived to model the fabric-confined concrete and verified by various experimental tests results.

In order to fully apply this new technique to structural engineering, more experiments were conducted by wrapping CFRP fabric to the large structure members such as beams and columns in this study. The flexural behavior of the large concrete beams wrapped by CFRP fabrics was investigated based on the experiments at the NJIT Structures Laboratory. Different wrapping methods were applied. Test results show that the CFRP confinement can significantly increase the ultimate flexural strength of Reinforced Concrete (RC) beams. However, the contribution of fabrics may vary due to the different wrapping methods applied. Experimental results are compared with the finite element modeling using the ANSYS computer program. A practical design method similar to ACI strength method is also proposed to predict the ultimate strength of the beam specimens. Good agreements are achieved for both methods.

Structural behavior of the RC slender columns wrapped with CFRP fabrics under combined axial load and biaxial bending were also investigated in this research. Seven slender columns with different wrapping methods were tested and analyzed. It can be concluded that both longitudinal and transverse fabric do help increase the load capacity of the column specimens, although the longitudinal fabric tends to decrease the deformability of the columns. The columns with both wrapping methods applied achieve a better strength and ductility performance. A modified computer program accounting for the proposed stress-strain equation for fabric-confined concrete has been used to verify the present experimental results. A satisfactory agreement is attained for both ascending and descending branches of the load-deformation curves.

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