International Concrete Abstracts Portal

The seismic design of pile-supported marine structures such as piers and wharves is largely governed by their unique structural configuration and the special loading conditions associated with the operations that take place on the structure. The operation of heavy equipment and the stacking of heavy loads -usually well in excess of the self-weight of the structure- have significant implications on the seismic analysis and design of this type of structures. This paper reports a series of recommendations for the seismic analysis and design of piers, wharves and platforms supported on prestressed concrete piles, in presence of massive mobile equipment and/or stacked containers. Because of their significance in terms of structural safety and impact on construction costs of container and bulk handling terminals, emphasis is given to the evaluation of the percentage of live load to be considered as a source of seismic mass and a detailed discussion is presented on the need to rationalize the process of combining live loads with dead and earthquake loads as part of the definition of extreme load combinations in the seismic analysis and design of elevated platforms supported on piles. The paper includes a review of the treatment given to these loading aspects by specialized marine infrastructure design codes and offers specific recommendations.

This paper discusses the results of an experimental program carried out at the Englekirk Structural Engineering Center of the University of California in San Diego (UCSD) to provide data for the performance-based seismic design of vertical pile-supported marginal wharves. Strong earthquake-induced inertial lateral loading may cause significant damage to the wharf in two critical locations (i) at the pile-cap connection, and (ii) at the location of the pile maximum bending moment below the ground. Two pile-cap assemblies, representative of the two most critical piles of a marginal wharf and the surrounding quarry-run fill, were built at full-scale and tested under quasi-static reversed cyclic loading to large lateral displacements. The piles in the test units were precast pretensioned and were connected to the deck through grouted dowels and were also embedded in quarry-run fill, as is often the case in these marine structures. The test units displayed a very stable hysteretic response. This paper describes the test specimens, their hysteretic response together with the predicted response, the progression of damage in the test units, and the distribution of the applied lateral force among the two piles. The paper also highlights the most relevant implications for performance-based design of marginal wharves.

This CD consists of 8 papers that were presented at a technical session sponsored by ACI Committees 357, 423, and 543 at the ACI Convention in Minneapolis, MN, in April 2013. The papers cover key aspects relevant to seismic analysis, design, detailing and experimental testing of precast prestressed concrete piles as substructure elements of marine structures. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-295

Pile-supported marginal wharves have geometrical characteristics that make them prone to torsional response when subjected to earthquake induced inertial forces. Because of expected early system non-linear response due to the soil-structure interaction, lateral displacement demands on the piles cannot readily be estimated from conventional elastic modal response spectrum analyses and modal combination techniques. These displacement demands may be obtained using non-linear time-history analysis. Nevertheless, modeling the non-linear response of the wharf is still impractical in many design offices. For this reason, simple approximate methods that can estimate the critical pile displacement demand as the spectral displacement corresponding to a predominant translational (transverse) mode natural period of the wharf multiplied by a Displacement Magnification Factor (DMF) is adequate for design purposes. This paper revisits the earlier work of Benzoni and Priestley (2003) and computes, through non-linear time-history analysis, DMFs of short, long and linked segment wharves. Furthermore, the paper also reports shear key forces observed in the non-linear analyses of linked segment wharves. Finally, equations are proposed for calculating the DMFs and to estimate the forces for the design of shear keys.

Pile-supported marginal wharves are a critical component of port infrastructure. A primary region of post-earthquake structural damage is the connection between the pile and the wharf deck. Review of prior experimental studies into state-of-the-practice connections indicates these can sustain cyclic deformation demand but at the cost of deterioration in resistance and significant damage. Damage within the connection is difficult to access and its repair is costly. Therefore, there is an interest in reducing the damage under moderate levels of seismic demand while sustaining the capacity under large cyclic drifts. An experimental study was undertaken to investigate mechanisms to limit damage while maximizing strength and deformation capacities of precast piles and their connections. Several structural concepts were investigated including (1) intentional debonding of the headed reinforcing bars, (2) supplemental rotation capacity through the addition of a cotton duck bearing pad above the head of the precast pile and (3) supplemental material to sustain the lateral deformations while minimizing deck damage. The final design incorporated all of these concepts. The results show significantly reduced damage. A design method is proposed to facilitate adoption of the proposed connection design in structural engineering practice. A comparison with other connection designs is made via fragility functions to assess their seismic performance.