Abstract:
Increasing popularity of the strut-and-tie methodology among research communities and practising engineers is due to its rational analytical approach and its superiority, compared to the conventionally employed empirical methods for analysing disturbed regions in structural systems. Nevertheless, this analysis methodology is not used as a routine procedure in design offices, primarily because of the perceived ambiguity and complexity involved in appropriate model formulation. In addition, until recently application of the strut-and-tie methodology has been limited to the prediction of strength, with utilisation of this modelling technique to capture nonlinear structural deformation being rather minimal [ACI Bibliography (1997)].
The research project reported herein represents an original contribution to the development of the strut-and-tie methodology by providing a systematic approach for applying this modelling technique to nonlinear structural concrete analyses. The study proposes a orginally developed computer-based strut-and-tie model formulation procedure that permits prediction of the nonlinear monotonic and cyclic response of structural systems with distinct reinforcement details. The procedure being presented in this thesis is a refined version of that reported previously [To et al. (2001 &.2002b)]and the accuracy of the analytical modelling is verified using experimental data.
Several issues pertaining to model formulation are thoroughly investigated. These issues include the strategy of model formulation for Bernoulli (or beam) and disturbed regions of structural systems, the satisfactory positioning of model elements, the appropriate stress-strain material models for concrete and reinforcing steel, the suitable effective strength of model elements, the inclined angle of diagonal concrete struts in beam and column members, and the concrete tension carrying capacity and associated tension stiffening effect.
In addition, the seismic response of various prototype structures when subjected to the experimentally employed cyclic forces and the time-history earthquake loadings was predicted using the originally developed cyclic strut-and-tie models. A summary encapsulating the findings of this project and recommendations for future research work in the area of nonlinear strut-and-tie modelling is also presented.