Page 26

2014SumShotcreteEMag

Marine Structures: Pier Projects By Tommy Pirkle and Randell Ogburn MWhile composite materials, steel, treated the ever-changing tides cause a number of issuesamount of marine repair work requires physicallybeing on the water underneath the structure itself,arine piers are abundant in the UnitedStates and are generally made of concrete. wood support piles, and thick rubber fender sys- not confronted on more conventional job sites, tems are commonplace, concrete remains the main including shortened work days and a work component of most pier structures. The majority schedule that is constantly changing according to of these structures were constructed long ago, and the tide (Fig. 1). given their constant exposure to destructive ele- There are two main types of tides: spring tides ments, they require routine maintenance. This and neap tides. Spring tides (which, contrary to includes repairing the deteriorated concrete, which their name, do not have anything to do with the is exacerbated by inclement weather, freezing-and- season) are very strong and occur when the moon thawing cycles, continuous wetting and drying is full or new. Neap tides occur during the quarter from tidal action and, especially, the chlorides in moon phases and are very weak. This results in a salt water, which will eventually take a heavy toll smaller difference between high and low tides on concrete and its embedded reinforcement. The during a neap tide. shotcrete process has been the restoration method Another key factor to take into consideration of choice by many to restore the concrete on a during the bidding process for pier work is access. large number of these facilities seeking to combat Using work floats to navigate throughout the site the accelerated deterioration process that is part is preferred, but simple, provisional decking made and parcel of concrete marine structures. out of lumber or cables and scaffold boards works The single most important factor when bidding well on higher-volume jobs or where the work is or working on a saltwater pier is having a com- too high to reach safely from the float stage. Float plete understanding of the perpetually changing platforms are the most cost effective if the work tides. Each day, as the sun, moon, and earth is accessible at both low and high tide. However, interact with each other, ocean levels fluctuate, many times a wide float will not be able to get yielding two high tides and two low tides. The around the existing piles or can become grounded ocean is constantly moving from high tide to low on unseen impediments in the water as the tide tide and then back to high tide, and there are lets out. This is especially true in situations where approximately 12 hours and 25 minutes between additional piles were installed to support today’s the two high tides. Given that a considerable heavy cranes that are necessary to unload the ships’ cargo (Fig. 2). Port Elizabeth Elizabeth Marine Terminal is located on the Newark Bay in Jersey City, NJ. It is operated by the NY/NJ Port Authority. This port is the 22nd busiest in the world and is the largest container port in the eastern United States. Port Elizabeth is comprised of a large pier with 10,128 ft (3088 m) of ship berth space. Work must be per- formed around docked ships from all over the world, which are in a constant state of loading and unloading their cargo. The design engineer’s method of repair for this concrete structure is shotcrete, and the work generally consists of pile cap and underside deck repairs. The scope of work includes deteriorated con- crete removal, cleaning or replacement of severely rusted reinforcement, and the installation of welded wire reinforcement with anchors. Fig. 1: Night work as a result of the constantly changing schedules Shotcrete is then applied and cured. Where the 24 Shotcrete • Summer 2014


2014SumShotcreteEMag
To see the actual publication please follow the link above