Reinforced plastics prevail on the waterfront

Reinforced plastics prevail on the waterfront Few materials can withstand the onslaught infrastructure

needs regular maintenance.

durable replacement

of the sea for long and marine Reinforced plastics can provide a more

for the wood, steel and concrete materials traditionally

used.

George Marsh reports. then

poison

ability

of

marine exploiting

life, the unsustainrainforest

woods - species like teak being

ere sea meets land is a zone of strife and unruly forces. Few materials can long survive the unrelenting onslaught of sea waves, wash and impact from vessels, corrosive salts, sand and pebble erosion, high atmospheric humidity, inter-tidal wetting and drying, sun and marine borers exacerbated by the immense forces of tempest and storm. Marine infrastructure constantly has to be buttressed and renewed. One class of materials that is helping it to last longer is reinforced plastics, To contribute in this harsh environment, fibre reinforced plastics (FRPs) have to substitute for or augment one or more of the traditional marine infrastructural materials - wood, steel and concrete. Drivers for replacing the most ubiquitous, wood, include the rapid deterioration of most woods, the leaching out of preservatives like creosote and chromated

30

copper arsenate

REiNFORCEDplastics

(CCA) which Ju n e 2 0 0 2

ate post-war

years, Disposing

the best

vative-treated

wood accounts

of preserfor a signifi-

wood burns. Steel spalls and corrodes away whilst even concrete, though it will never be displaced as a key material, can break up and eventually disintegrate.

cant proportion of this and the Navy wants any replacement to be environmentally benign as well as strong and cost effective. A multidisciplinary research team led by the Naval Research Laboratory but also involving the Naval Facilities

Wood

Service Centre, the United States Forestry Service, the Universities of Washington

According to one informed estimate, over US$l billion needs to be spent on piers in New York alone, where old wooden structures are falling prey to general marine wear and tear plus the depravations of

State, Maine and Honeywell Inc and been investigating plastic composites. University’s Wood

marine borers, particularly Teredo worm which devour woods from the inside by

eering Laboratory (WMEL), for instance, brings its acknowledged expertise in inno-

eating along the grain. Perversely, these organisms are thriving as a result of water clean-up programmes. With several piers

vative structural systems utilising the collaboration.

for resisting aggressive waterfront tions - and the readiness with

Railings at Niagara Falls, produced by the pultrusion process. (Picture courtesy of Owens Corning: www.owenscoorning.com.)

date back to World War II or the immedi-

hardcondiwhich

in Brooklyn, for instance, almost completely consumed by borers, agencies have been looking to alternative materials like recycled plastic and FRP as a remedy. Steel and concrete are too damaging for boats coming alongside but, like wood, pliable polymer materials yield momentarily to contact. Authorities in New York and around the world are keeping a close eye on US Navy efforts to reduce maintenance costs for its large amounts of waterfront infrastructure, which includes everything from isolated piers and jetties to full harbour installations. The Navy currently spends $40-50 million annually on replacing treated wood structures, many of which

Pennsylvania State; Strandex Corp have a number of woodWashington State Materials and Engin-

wood to

The US Navy currently spends $40-50

million

annually on replacing treated wood structures. One approach being investigated is to recycle ground wood and plastic materials into synthetic deckings, facings and pier support ‘timbers’. In some composites of wood with plastics like PE and polyvinyl lose/lignin

chloride (PVC), wood structure

the celluconstitutes

the fibrous reinforcement while in others man-made fibres are added. Resistance of

0034-36 17fO2/$ - see front matter 0 2002 Nsevier Science Ltd. Ail rights reserved.

Reinforced

such

composites

moisture,

to biological

fire, chemicals

attack,

and other haz-

ards can be impressive

while an advan-

tage of several reinforced

thermoplastics

is that they can be extruded. One company using recyclate sively

is

Virginia-based

International and

Inc

whose

SEAPILE products

recycled

polyester

exten-

matrix

a 100% reinforced

with glass fibre. This GRP system,

said

to offer good abrasion resistance and with ultraviolet (UV) inhibitors incorporated, tropical

is offered wood

as a substitute

for

and timbers

and

pilings

has been used for protecting

bridge and

dock piers. Another

company

active in replacing

maritime wood infrastructure is Hardcore Composites. As an example, it produced composite piles used in reconstructing historic New Castle pier in Delaware. Composite tubular piles of 12 and 18 inch (30 and 45 ?m) diameter designed to carry a new main timber deck were driven in over the remains of the original wood piling and then filled with concrete. Hardcore produced the piles using an adaptation of vacuum-assisted resin transfer moulding (VARTM) and points out that they will not rust or spall, or be affected by the water, weather or marine borers. They should serve, according to the company, for 30-40 years without major repair or replacement, and do not require resurfacing or painting. Similar advantages apply to a replacement for a sheet-metal protected timber pile dolphin that Hardcore produced for the end of another pier, at Lewes, Delaware. diameter

Forty four composite

18 inch piles

(45 cm) installed

together and filled with concrete form a reaction block capable of absorbing the forces generated by 2100-ton ferries moving at three knots. The company has also developed monopiles, an impressive example being a single 80 ft (24 m) long, 5 ft (1.5 m) diameter pile used to replace a cluster of almost a dozen timber piles at Cape May, New Jersey. This can absorb more energy from berthing ships than the previous timber cluster, deflecting

(79 cm)

under

a force

on the waterfront

of

240 000 lbs (110 000 kg). In what was claimed ever use of hybrid piling,

Seaward SEATIMBER

utilize

31 inches

plastics prevail

composites

this company

ed cradle supports beaches,

using

composites. lation,

to be the first

for major outfalls near

E-glass and carbon

Benefits include

fewer supports, outfall

ricated using

finishing

maintenance.

produced

Army Corps of Engineers and glass-carbon

fibre

rapid instal-

minimal

work and low ongoing stormwater

for marine

has also construct-

A

for the US

has 168 glass

pilings which were fab-

with a vacuum Dow Derakane

infusion vinyl

process

ester

resin

and Johns Manville polyisocyanurate foam in a sandwich construction. Stringent

performance

requirements,

driven by anticipated wave loads, were met by using heavy quadraxial glass and hybrid fabrics from Brunswick Technology Inc. Carbon (Zoltek) was used to confer the stiffness needed to minimize deflection in long spans. Piles were finished with a sand-loaded epoxy coating to promote frictional adhesion with sand and underlying soil. Although composite components for this multimillion dollar project cost nearly three times more than standard timber and concrete equivalents would have done, estimates suggest that reduced installation and associated expenses brought total project cost down to 65% less than for a standard installation. There are signs of progress in Europe too. In UK, for instance, a study by HR Hydraulics at Wallingford, UK, called ‘Use of Timber in Coastal and Fluvial Engineering’ is embracing consideration of potential alternatives. A spokesman indicated a number of early uses for FRP wood substitutes in fendering and the meeting faces of dock gates - an example of the latter being in use at Shoreham, a port on England’s south coast. In France, a project in which wooden lock gates have been substituted more completely was the construction of major GRP parts for Voies Navigable de France as part of its restoration of the French canal system. DCN Lorient laid up the woven glass-reinforced isopolyester components

Seapile composite marine piling installed as a replacement to a traditional wood fender pile at a large oil tanker terminal.

by hand in open moulds to create solid laminate gate sections which were then mounted in stainless steel frames. The resulting gates weighed 50% less than conventional units, facilitating their handling, mounting and control in use. Around the world, builders of marina pontoons could be willing prospects for any economically and functionally viable replacement that might emerge for wood decking, which degrades, and concrete which degrades more slowly but is less ‘user friendly’. One such, France’s Poralu Marine, is a leader in composite decking and recently won a contract to supply its product for the Commonwealth Games.

Metal Sea walls are often of metal, generally steel though aluminium has been used too. American designer of aluminium sea walls for more than two decades, Barry Hansen, has more recently engineered

June 2002

REINFORCEDplastics

31

Reinforced

plastics prevail

on the waterfront

other

materials

different

sites,” Hansen there

to the

two

distinctly

corrosive environments comments.

is the saline

tures built in or close to sea water, includ-

environment

of sea-

panels

have

been

driven

muck.”

forcing

intended

pre-stressing

for waterfront

bar (rebar),

applica-

of a suitable along

with

reindesign

track record,

swimming

as

part

of

Strengthening

-

pools

its

Mbrace

Composites

System.

Design using composite rebar requires some adaptation, a fact that has so far inhibited

most designers

instead preferred

to remain

who have

with familiar

creates prospects for a major niche market accounting for many tons of rein-

steel reinforcement.

forced plastic material.

likely to take over from corrosion

Composite

bar is

creep, rupture

Mechanisms

or concrete

such as

crushing

are

as the

immune to the destructive moisture and salt attack which can corrode conventional steel bar, causing it to swell and crack the concrete around it. Experience shows that sometimes even epoxycoated steel rebar is not an adequate

primary failure mechanisms. Fortunately design codes are emerging. The American Concrete Institute’s ‘Guide for and Construction of the Design Concrete Reinforced with FRP Bars’ (ACL 440 lR-01) can be helpful as can

answer while stainless steel, which could be, is too expensive. A representative product which answers the need is C-BARTM from Marshall Industries of Lima, Ohio. Marshall’s patented process combines pultrusion and compression moulding of

‘Eurocrete Modifications to NS3473 When Using FRP Reinforcement’ in

GRP, the resulting rod core being given an outer skin of a urethane-modified vinyl ester which has high resistance to moisture and chemicals, including the alkaline According

surroundings of concrete. to Marshal Industries, C-BAR

has twice the tensile

J u n e 2 0 02

floating

roads and buildings

also offshore platforms,

uses for com-

and

codes and with a growing

REINFORCEDplastics

canals,

and aquariums. Another product is Mbar CFRP rebar rod offered by Master Builders

is reinforcing

concrete

32

walls, piers, jetties,

structures,

the

tion. The development

residential property on a river island. “Composites have better resistance than

retaining

soil that

One of the most promising

composite panels produced by Creative Pultrusions and Alum Bank, Gator has constructed a number of sea walls including one to stop shoreline erosion near a pumping station and another to protect

ing quays,

caissons, decks, piles, bulkheads,

posites

Gator Using

as C-BAR,

“At the first

Concrete

GRP sea walls for his employer, Dock and Marine Inc of Florida.

resistance advantages

this product is said to be suitable for struc-

water and salt air, and at the second, the into is an acidic, organic

Composite piling being used for CIdock installation in Rotterdam. (~icrure courtesyof SeawardInternational/PC Jansen Marine Agencies.)

corrosion

at these

strength

of conven-

Europe and ‘Construction of Concrete Structures Using Continuous Fibre Reinforcing Materials’ in Japan. The USbased Rebar Manufacturers Council offers advice and support for end users. Canada, too, is actively developing the use of FRP substitute for steel reinforcement, which is now seriously corroded in a wide range of concrete infrastructure older than about 30 years. One manifestation of this is the appointment of Professor Brahim Benmokrane, an

tional epoxy-coated steel rebar, at only a quarter the weight. In addition, the composite’s coefficient of thermal expansion is closer to concrete than that of steel. As a bonus, the rebar has a low dielectric constant, making it suitable for applications requiring magnetic transparency, such as foundations for magnetic resonance imaging facilitation, aircraft compass calibration pads, and computer and laser testing facilities. Addressing the same need is ISOROD@ from Pultrall Inc and marketed by Concrete Protection Products Inc of Dallas. With the same weight and

Seapile composite marine piling being installed at US Naval Station in San Diego, California.

Reinforced

plastics

prevail

on the

waterfront

Piles for Pier 12 were made eight

lengths

of cable into

by laying the casting

frame for each pile. These lengths secured

were

at their ends in steel bulkheads

and pre-tensioned after which concrete

with hydraulic

jacks,

was poured into the

frames and allowed to cure. advantage

carries

over glass that it is

impervious

to the alkaline

of concrete.

Dr George Warren, who was

operational

loads

from vehicles and truck-mounted in service. A similar

preferred

over

strengthener rods

accept

attaching

CFRP

out-of-plane

and are buried,

adopted

cranes, solution, sheet

to the deck surface because loads

including

base.

FRP strips and plates less, increasingly

more

has since been

for other installations

a Trident submarine

surroundings

lead engineer for the Pier 12 upgrade, points out that glass fibres, even when

heavy

remained

readily

Carbon, despite its higher cost, has the important

which

used

range

of deteriorating

tures,

as has been

are, neverthefor repairing concrete

reported

a

struc-

previously

protectively coated, tend to lose strength when exposed to an alkaline environment

in Reinforced Plastics. Light composites

and that carbon will therefore be the natu-

need

ral choice

equipment

for pre-stressing

applications.

can be placed by hand, for

bulky that

eliminating

materials might

the

handling

otherwise

pre-

Glass composites, though, will have a major role in piling (albeit sometimes in a hybrid with carbon) and for ancillary items such as gratings and hand rails. The Pier 12 piles are expected to last

vent ship docking and other operations while remedial work is in progress. Downtime is minimal, composites

international specialist in composite materials for infrastructure, as holder of a

50 years, whereas steel cables begin to corrode in less than ten. A report entitled

new industrial research chair at the University of Sherbrooke in Quebec. His mandate is to study FRP composite rein-

‘Demonstration of Advanced Composite Cables for Pre-stressing Applications in Concrete Waterfront Structures’ issued by

in hours. Low weight repairs are also in earthquake zones advantageous where any extra loading on supporting

forcement for concrete infrastructure, and to incorporate monitoring intelligence. As a researcher on the Canadian Intelligent Sensing for Innovative Structures (ISIS)

the US Army Corps of Engineers which collaborated on the project, concluded

Navy

pier structure

made using pultrusion.

(Picture courtesy of Owens Corning:

www.mvensc*rn-

ing.com.)

project Benmokrane, working with industrial partners, embedded fibre-optic sen-

that it had ‘clearly demonstrated the viability, practicality and potential cost-

sors within composite materials used to repair Sherbrooke’s Joffre Bridge. This

effectiveness of using fibre-reinforced composite cables in pre-stressed concrete structures subject to corrosive environments.’ The report included guidelines

enabled strains and other forces to be monitored remotely in real-time, an innovation that the Professor expects will

for the design and construction of composite products, but acknowledged what is still a drawback for composites - the

become important in future composite/concrete programmes. In the USA the armed services have been as proactive as any organization in bringing composites and concrete together. Using glass and carbon fibre

lack of long-term performance industry-wide standards.

hybrid cables to pre-stress concrete is a technique that has been evaluated at the waterfront testbed facility of the US Naval Facilities Engineering Service Center at Port Hueneme, California. In one trial carbon fibre cables were used to internally reinforce 60 ft (18 m) piles

wharf in Pearl Harbour, Hawaii. Epoxy encapsulent was poured into slots cut in the concrete deck, without disturbing underlying steel rebar. The composite rods were then laid and rolled into the

supporting a 1200 ft (365 m), 55 year old pier in the Navy shipyard in San Diego.

34

REINFORCEDplastics

Ju n e 2 0 0 2

being bonded to concrete with epoxies which can reach design strengths with-

data and

Repair and upgrade Similar CFRP rods were Restoration of California

used by ACE to upgrade a

epoxy, which subsequently cured. The slots were topped off with a layer of sand in epoxy binder. It proved possible to carry out the work while the wharf,

Navy pier application: waterfront test site. Structure made by pultrusion. (picture cowtesy of Owens Corning: I

www.owenrcorning.com.) 1

Reinforced

members

can

precipitate

failure

at

times of seismic stress. Another of composites

repair exploiting

the virtues

is the bonding

of pultrud-

ed glass or carbon

fibre

reinforced

provided

is highly

and was given the task of building

resistant

to fatigue and can be

economic

repair,

beams below pier decks. Such beams typ-

tium

ically weigh less than a third the weight

GRP profile

of steel equivalents

replace

and can be lifted into

offers

a European

that

reinforced

concrete.

jacks. A repair of this sort was made as

four

years

part of the Pier 12 experiments

Fiberline

mentioned,

workmen

in

without

conjunction

CFRP tow sheet bonded

glass, carbon

confinement

jackets

Diego)

are used

strength

and

hybrid

Tomorrow’s

at San

be made

with

complex

geometric

and

bridge

the

shear

project

manufactured

over by

AS of Denmark

Infrastructure),

profiles

large cross sections

ASSET was developed

supports,

shapes.

Spain’s IETCC and a work site;

and KTH in Sweden for material ty testing and academic advice.

HIM the

proper-

Looking further ahead, the US Navy faced

with

having

to replace

60% of its pier infrastructure

entirely over the

next decade or two - is considering large (730-740 m long by 30-40 m wide) double-deck

other waterfront structures too. UK’s Mouchel, as leader of the EU project, designed the system. Other partners included Skanska, Sweden, which

a first

deck surface material; providing test facilities

than be supported

for the

solution

England; developing

can

Although

primarily

physical

bridge in Oxfordshire, from the Netherlands,

and

rapid replacement of bridge decks it can, according to Fiberline proprietor Henrik Thorning, be used for jetties and

especially in seismic zones such as in California and Japan. Mitsubishi Chemical Corporation, for instance, targets its REPLARKTMCFRP sheet system at the seismic repair and upgrade market. Elastic modulus is said to be 70% that of steel (105%‘if prepreg is used) but weight

VACUUM

and

Composites

it can

Developed

Reichhold ASSET using resins, (Advanced Structural System for

with

the deck.

(also tried

to increase

of piles

already also

under

Additionally,

using

extruded

is so strong

an EU Brite-Euram

by

consor-

a revolutionary

under

position

are beyond

the overall

on the waterfront

is only a fifth that of steel. The material applied to complex shapes. Finally, for decks that

‘I’

plastics prevail

Navy wants century

and

piers that

will float rather

on piles. Because the

a service life of well over a maintenance

80%

lower

than with conventional piers, advanced composites are likely to figure strongly in the ’21st Century Pier’ being developed under the Navy’s Hybrid Waterfront Structure programme. But this aspect of waterfront engineering must, for the time being, remain another story. n

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