Philip C. Perdikaris

Kinetics of Crack Growth in Plain Concrete

The number of load cycles, N, load-point displacement (LPD) and crack- mouth-opening displacement (CMOD) compliance were measured in a series of fatigue tests on single-edge-notched concrete beams (SENB) under 4-point bending to investigate the kinetics of crack propagation in plain concrete. The prenotched beams were subjected to either a constant or variable pulsating load up to a maximum load level of about 75% of the static ultimate strength. Typically, the crack growth rate, dl/dN decreased for the first 8 mm of crack extension. The crack growth rate and the strain energy release rate, GI, are plotted versus the crack length to beam depth ratio, which is determined from the CMOD compliance measurements. The crack speed varied considerably along the crack path but increasing strain energy release rates produced on the average an increase in the crack speed. Finally, kinetic data from three beams subjected to a constant amplitude repeated loading is compared to the Paris model.

Design of Reinforced Concrete Infilled Frames

AbstractThe work presented in this paper aimed to evaluate the diagonal strut model for the design of reinforced concrete (RC) infilled frames, already broadly used as a design tool in the case of masonry infilled RC frames. The assumptions on which the strut model provisions in codes are based are reviewed. In parallel, some of the results of an experimental study on the response of eight 1/3-scale RC infilled frames subjected to quasi-static cyclic horizontal displacements are summarized. Two different aspect ratios and different types of connection of the infill to the frame have been investigated. Design provisions for infilled frames included in codes are applied to describe the behavior of the specimens tested in terms of stiffness, ultimate strength, and expected mode of failure. The results are discussed and some suggestions are made for improving the design procedures.