Seismic modeling, analysis and design of structural concrete pile-deck connections

Abstract

This dissertation encompasses three primary efforts related to the assessment of the seismic behavior of shallow embedment, structural concrete pile-deck connections: (i) the implementation and validation of a computational model that includes the resulting rotations due to slip of reinforcing dowels at the pile-deck interface, (ii) the evaluation of damage indices reported in the literature, for use in characterizing the ensuing nonlinear behavior, and (iii) a parametric study of structural interactions affecting pile-deck connections. Initially, a fiber-based computational model, comprising nonlinear distributed pile elements and a zero-length rotational spring, is developed to model dowel connection slippage at the pile end. A comparison with four, full-scale experimental specimens shows good agreement, at both the sectional and element levels, with this simplified model, which represents the prestressed concrete pile as a cantilever supported by the cast-in-place deck. The observed damage in these specimens also correlates well with earlier reported measures, such as the Park and Ang damage index. While additional research could be required to extend and verify this damage measure for high-strength concrete, the moment-rotation envelopes needed for implementation in lumped plasticity models have already been developed. A more refined computational approach then includes full-length piles, and thus soil-structure interaction and in-ground nonlinear effects are accounted for. Rotational ductility is identified as a critical parameter to assess the structural behavior of pile-deck connections at a moderate to severely damaged state. A factorial-based statistical analysis demonstrates the importance of interactions between concrete strength, spiral reinforcement, and axial force. Global and local effects, either due to concrete- or steel-controlled structural behavior, are summarized in a series of curves generated using relationships revealed by the factorial analysis. The collective work forms the basis for potential revisions to PCI and other code equations, where the amount of spiral reinforcement can now be prescribed as a function of rotational ductility.