Date of Award

Spring 1995

Document Type

Dissertation

Degree Name

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

Department

Civil and Environmental Engineering

First Advisor

Farhad Ansari

Second Advisor

Edward G. Dauenheimer

Third Advisor

C.T. Thomas Hsu

Fourth Advisor

John R. Schuring

Fifth Advisor

Ali Maher

Abstract

The main objective of this dissertation is to develop a simple non-linear fracture mechanics model for the determination of fracture mechanics parameters for concrete, such as fracture process zone length (rp), critical fracture energy release rate (Gic), critical stress intensity factor (KO and fracture energy (GF). The fracture process zone (FPZ) is modeled as a damaged non-elastic cohesive band where the extent of damage due to microcracking varies from no damage at the boundary of FPZ to complete crack surface separation at the notch or macro-crack tip. The proposed method can predict theoretically both the pre-peak and post-peak load versus crack mouth opening displacement (P-CMOD) and load versus load point deflection (P-δ) behaviors for a three point bend (3-PB) single-edge notch (SEN) beam. To apply this method, one only needs to measure peak load (Pu) and corresponding crack mouth opening displacement (CMODu) of a 3-PB SEN beam, and cylinder compressive strength. This method does not require post-peak load-deflection or CMOD data. Furthermore, it does not require information as to the unloading characteristics of a beam. The testing machine need not be very stiff. This makes the testing procedure greatly simplified and makes it suitable not only for the testing laboratory but also for work sites where a closed-loop testing machine is not available. A microcomputer based simple numerical model is also developed based on the proposed fracture model. This model is verified by comparison with numerous experimental results as well as with other available methods from the literature.

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