Design Of Wharves Research Articles

Experimental study on dynamic response of pile-supported wharf under wave and ship berthing collision

Pile-supported wharf is widely used in deep-water port engineering, which is inevitably subject to joint action of wave and ship berthing collision in marine environment. The evaluation of dynamic response of pile-supported wharf under wave and berthing collision is particularly essential for the design of deep-water port infrastructures. In this study, a wave flume experiment was carried out to investigate the dynamic response of pile-supported wharf embedded in a saturated sand stratum under a given wave and a three-stage pendulum steel ball collision. The pendulum collision was applied at the corner and edge midpoint of the wharf deck, respectively. A variety of representative responses are explored, including time histories of acceleration, displacement, hydrodynamic pressure, pore water pressure, and strain, which characterize the important aspects of dynamic behavior of pile-supported wharf-ground system. Acceleration and displacement of deck as well as acceleration of sand stratum are dominated by the berthing collision; hydrodynamic pressure on piles and pore water pressure of sand stratum are controlled by the wave action; and strain and bending moment on piles are depended on the joint action of wave and collision. It should be noted that dynamic response characteristics of pile-supported wharf will change significantly due to the decreasing of pile effective buried depth near berths induced by the berthing collision energy accumulation. Furthermore, pile group effects including wave scour around piles, collision energy propagation in a sand stratum, and peak bending moment on piles are explored. For comparison, dynamic response of a single pile-ground system and free field are also discussed. Dynamic response of sand stratum around single pile induced by berthing collision on wharf deck is greater than that of free field at the same distance. Experiment techniques and insights from this study may be of significance to the design and maintenance of pile-supported wharves.

Seismic performance evaluation of a pile-supported wharf system at two seismic hazard levels

This study presents a framework for assessing the seismic performance of a pile-supported wharf at different seismic hazard levels. A refined Three-Dimensional (3D) Finite Element (FE) model is conducted using the open-source computational platform OpenSees. The modeling strategies of the refined numerical model are given in detail, including refined modeling of free-field boundaries and soil-pile interaction. Two seismic hazard levels adopted by the design standard for seismic design of piers and wharves (ASCE 2014) are considered, namely, Contingency Level Earthquake (CLE) and Design Earthquake (DE). The seismic performance of the wharf-ground system is systematically explored in the following two aspects. First, the evaluation of seismic performance is based on the time history response for CLE (and DE) motion. Second, the seismic performance is assessed by averaging maximum response for all 28 DE and CLE motions. The results from this study reveal that (i) the seismic response of the wharf-ground system is larger under a DE motion than under a CLE motion; (ii) the pile foundation with a short free length is more vulnerable to damage for both seismic hazard levels; and (iii) the fiber strains of piles are significantly lower than the strain limits in the design standard (ASCE 2014).

A simplified reliability estimation method for pile-supported wharf on the residual displacement by earthquake

Pile-supported wharves undergo lateral displacement as well as structural damage due to earthquakes. Therefore, residual displacement and structural safety assessment are necessary for earthquake-resistant design of pile-supported wharves. This study introduces a simplified reliability estimation method for pile-supported wharves, involving the residual displacement caused by earthquakes and the variation of earthquake ground motions. As the residual displacement of wharves is strongly affected by the deformation of subsoil caused by earthquakes, a soil-structure system finite element earthquake response analysis was performed. To reduce the computational load for the evaluation of a probability distribution of residual displacement, a first-order second-moment method estimating the probabilistic response of structures with a small number of trials was applied. Thefinite element analyses demonstrate that the summed squared Fourier amplitudes (SSFAs) of the input seismic motion for a cumulative probability frequency band better estimated the residual displacement. A simplified reliability estimation method utilizing three results of finite element analyses is proposed following the demonstration of its applicability.

Evaluation of virtual fixed points in the response spectrum analysis of a pile-supported wharf

Response spectrum analysis is widely employed in the seismic design of pile-supported wharves, as it can easily determine the maximum response of a structure. The analysis typically uses virtual fixed points to model the structure, without modelling the ground, as the structure is assumed to be a frame. Virtual fixed points can adequately simulate pile responses under horizontal static loads; however, pile responses under seismic loads have not been well studied. Therefore, the dynamic centrifuge tests evaluate the applicability of response spectrum analysis, using virtual fixed points, to the seismic design of a pile-supported wharf. Comparison of results from scale models (3 × 3 groups of piles from sections of Pohang New Port, Korea) with those from the analysis showed that the response spectrum analysis using virtual fixed points does not adequately simulate the natural period or pile bending moment of a pile-supported wharf system.

Time-dependent probabilistic capacity degradation assessment of prestressed concrete piles in marine environment

As coastal infrastructure systems are continuously exposed to deterioration, it is increasingly crucial to analyse their current and future serviceability performance. This paper investigates effects of chloride corrosion on the lateral force capacity and ductility of a wharf-supporting prestressed concrete marine pile and provides new insights into the state of marine structures. A probabilistically generated finite element modelling approach is developed for piles, which includes discrete concrete pile cross-sectional models connected to steel tendon non-linear elements via a series of non-linear springs that simulate bonding behaviour. Moreover, a prestressed material model is established that incorporates alternate failure modes including stress corrosion cracking and brittle failure to capture chloride-induced pitting corrosion in piles. It is shown that various failure modes cause an overall decrease in the maximum force capacity as piles age. Specifically, the alternate failure modes result in 31 and 56% reductions in the maximum capacity of the pile and associated top pile displacement, respectively, as the age of the pile increases from 25 years to 75 years. The presented methodology and results can greatly assist in decision-making for repair or replacement of wharves and aid in the design of new wharves considering their future performance.

Equivalent damping for displacement-based seismic design of pile-supported wharves with soil–pile interaction

Displacement-based seismic design methods have been used in port industry for decades. For determining demand displacements of pile-supported wharves, the substitute structure method, a nonlinear static demand analysis methodology, is used in current practice. In the method, the estimation of equivalent damping does not account for damping from soil–pile interaction. In view of this, a new damping equation for pile-supported wharf system as a whole based on the total energy dissipation of soil and structure is proposed. The energy dissipated by soil is quantified by the p–y curves of soil springs and Masing hysteretic rule, and energy dissipated by structure is the sum of energy dissipated by all plastic hinges appeared in piles. Then, the equivalent damping of wharf as a whole is derived by Jacobsen's approach for steady-state harmonic response. To figure out the contribution of soil–pile interaction on system damping as well as the accuracy and rationality of the equation, a case study is presented. It is found that the soil–pile interaction contributes significantly to the dissipated energy of wharf system, and the displacement demands of wharf based on the proposed equation are closer to those based on time-history analyses than other equations in current practice.

Equivalent Damping Ratio Equations in Support of Displacement-Based Seismic Design for Pile-Supported Wharves

This study primarily proposes new equivalent damping ratio equations based on Jacobsen’s approach for displacement-based seismic design of pile-supported wharves to account for wharf configurations and soil-pile interaction. It is found that Pivot hysteresis model and Masing rule can accurately capture nonlinear behavior of concrete and steel wharves, respectively. To verify applicability of proposed equations, analyses were conducted to three typical wharves to make a comparison of maximum displacements obtained from nonlinear time-history analyses and substitute structure method with various damping equations. The verification reveals proposed equations are better than those in practice for their higher precision in determining displacements.

Seismic performance of improved pile-to-wharf deck connections

Ports, a vital link in the transportation of goods worldwide, are often located in high seismic regions and are susceptible to strong ground motions and potentially devastating physical and economic damage. It is important that ports are designed to withstand strong ground motions with minimal damage. Moment-resisting prestressed concrete pile-to-wharf connections are commonly used in the seismic design of marginal wharves. These connections can sustain significant damage and deterioration of resistance starting at small seismic deformations. This study developed and tested an improved connection for prestressed concrete piles. Findings indicated that the use of a bearing pad over the head of the pile significantly delays pile and connection damage without reducing maximum resistance or inelastic deformation capacity. Additional findings suggested that flexible joint sealant wrapped around the perimeter of the embedded pile segment effectively eliminates spalling of the wharf deck. The authors developed and presented a design procedure for the improved moment resisting connection.

Corrosion of Steel Sheet Piles in Port Structures

A two‐staged analysis of service reserves of sheet piles has been developed and proposed for design of marine wharves. The discussion is based on the results of bulkhead inspections, carried out in the ports of Israel during 1976–1981. First, the conventional structural approach, currently used in design practice and based on an estimation of the allowable loss of thickness, is considered. Specific inspection findings related to the structural calculations, such as asymmetrical corrosion of flanges and real distribution of corrosion rates, are also examined. In the analysis stress is placed on the fact that maintenance problems on inspected wharves began during a relatively early stage of their service life due to the leakage of fill through corrosion holes. Description of typical corrosion perforations, as well as an estimation of their possible rates, engineering consequences and methods of repair are given. It is shown that complete verification of service reserves of sheet piles may be accomplished on...