Seismic design of bridge piers
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis is concerned with the seismic design of bridge piers. Particular attention is given to lifeline bridges with reinforced concrete hollow columns. Development of an analytical model to predict the stress-strain behaviour of reinforcing steel under dynamic cyclic loading is presented. Model predictions agreed well with previous tests on mild and high strength steel specimens. A generalised stress-strain model for plain or confined concrete under dynamic cyclic axial compression loading is presented. To verify the model, axial compression tests were carried out on 15 circular columns with spiral reinforcement, 16 rectangular walls and five square columns with rectilinear hoops. Theoretical predictions compared well with the experimental behaviour of the near full size specimens. A ductile design methodology for lifeline bridges is presented. Inelastic response spectra for "maximum credible" earthquake motions were derived for structures with concrete columns. These design spectra can be used to assess ductility demand of column hinges. Using the steel and concrete stress-strain models, a theoretical model is developed to predict the lateral load-deformation behaviour, and thus ductility capability, of reinforced concrete columns under axial load and cyclic flexure. Design charts are prepared to enable the rotational capacity of columns with confined concrete to be assessed. Finally, an experimental investigation into the seismic performance of ductile hollow reinforced concrete columns is described. Four specimens, 40 percent full size, containing different amountsof confining steel in the plastic hinge zone were subjected to a constant axial load and cyclic lateral displacements. An assessment of the effect of axial load and the amount of confining steel on the rotational capacity of the plastic hinge is made. The specimens performed satisfactorily, obtaining member ductilities between 6 and 8, without any significant strength degradation under cyclic loading. Predictions from the proposed lateral load- deformation model are found to compare well with the experimental results.