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ACI Committee 544's repeated drop-weight impact test for concrete is often criticized for large variations within the results. This paper identifies the sources of these large variations and accordingly suggests modifications to the ACI test. The proposed modifications were evaluated and compared to the current ACI test by conducting impact resistance tests on 40 specimens from two batches of polypropylene fiber-reinforced concrete (PPFRC). The results obtained from both methods were statistically analyzed and compared. The variations in the results were investigated within the same batch and between different batches of concrete. The impact resistance of PPFRC specimens tested with the current ACI test exhibited large coefficients of variation (COV) of 58.6% and 50.2% for the first-crack and the ultimate impact resistance, respectively. The corresponding COV for PPFRC specimens tested according to the modified technique were 39.4% and 35.2%, indicating that the reliability of the results was significantly improved. It has been shown that, using the current ACI test, the minimum number of replications needed per each concrete mixture to obtain an error below 10% was 41 compared to 20 specimens for the modified test. Although such a large number of specimens is not good enough for practical and economical reasons, the reduction presents a good step on the development of a standard impact test.

It is well known that arching action in reinforced concrete slabs resulting from surrounding restraining elements is responsible for much greater collapse loads than those estimated considering flexural effects only. However, the subject needs to be better understood and simplified if it is to be reliably applied in broader practice. This thesis presents a rational treatment of the problem. By limiting the scope of investigation to one-way slab systems, for the first time an explicit method of calculating the load-carrying capacity of elastic- plastic slab strips with a laterally rigidly restrained boundary condition is derived. Application of the proposed model to specimens selected from four experiment programs proves its reliability in ultimate strength calculations. The proposed model is then employed in a parametric study of structural responses of deck slab strips. The parametric study shows that a longer span, lightly reinforced deck slab system is still adequate in strength if it is cast in higher strength concrete and sufficient lateral restraint is available.

It is well known that arching action in reinforced concrete slabs resulting from surrounding restraining elements is responsible for much greater collapse loads than those estimated considering flexural effects only. However, the subject needs to be better understood and simplified if it is to be reliably applied in broader practice. This thesis presents a rational treatment of the problem. By limiting the scope of investigation to one-way slab systems, for the first time an explicit method of calculating the load-carrying capacity of elastic- plastic slab strips with a laterally rigidly restrained boundary condition is derived. Application of the proposed model to specimens selected from four experiment programs proves its reliability in ultimate strength calculations. The proposed model is then employed in a parametric study of structural responses of deck slab strips. The parametric study shows that a longer span, lightly reinforced deck slab system is still adequate in strength if it is cast in higher strength concrete and sufficient lateral restraint is available.

The research reported in this thesis was carried out in two phases to investigate the behaviour of reactive powder concrete (RPC) columns. In the first phase of this study, six steel fibre reinforced RPC columns of 150 mm square cross section were tested to failure under various loading eccentricities. The RPC mix contained 2 percent (by volume) of straight steel fibres with a concrete strength of about 150 MPa. The columns contained either 4 or 7 percent of longitudinal reinforcement but no tie reinforcement in the test region. All the columns failed in a controlled manner and no buckling of the longitudinal steel or cover spalling was observed, even well beyond the peak load. The tests revealed that stirrups can be significantly reduced for steel fibre reinforced RPC columns, which could lead to an increase in the speed of construction with an associated potential reduction in construction costs. In the second phase, 17 RPC columns were tested with 16 confined using carbon fibre reinforced polymer (CFRP). The concrete mix contained either no fibres or 2 percent (by volume) of straight steel fibres with concrete strength of approximately 160 MPa. The columns contained no conventional steel reinforcement. For the concentrically loaded specimens, failure occurred at or close to the peak loading and the CFRP increased the strength by 19 percent compared with the unconfined specimen. The tests showed that the formulae developed to predict the peak strength of concentrically loaded FRP confined conventional strength concrete columns, in general, overestimate the load carrying capacity of FRP confined RPC specimens. The CFRP was shown to be effective in controlling the failure for the eccentrically loaded specimens. There was no evidence, however, that the use of CFRP in the hoop direction significantly increased the strength of the columns. Three dimensional nonlinear FE analyses of the test specimens were undertaken using the program DIANA. The FE analyses showed a reasonable comparison with the experimental results for the specimens tested under eccentric loading.

Dissertation (PhD)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "January 2007." Includes bibliographical references. Also available via the World Wide Web.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 288-293). Also available in electronic version.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Adelaide, 1990. / Errata inserted. Includes bibliographical references (leaves 336-358).