018 civil engineering structures
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Construction and Building Materials 17 (2003) 405437
0950-0618/03/$ - see front matter 2003 Elsevier Ltd. All rights reserved.doi:10.1016/S0950-0618(03)00041-2
A model specification for FRP composites for civil engineering structures
Lawrence C. Bank *, T. Russell Gentry , Benjamin P. Thompson , Jeffrey S. Russella, b a a
Department of Civil and Environmental Engineering, Room 2206, University of Wisconsin, Madison, WI 53706, USAa
College of Architecture, Georgia Institute of Technology, Atlanta, GA 30332, USAb
A proposed model specification for FRP composite materials for use in civil engineering structural systems is described in thisarticle. The model specification provides a classification systems for FRP materials, describes admissible constituent materials
and limits on selected constituent volumes, describes tests for specified mechanical and physical properties, specifies limitingvalues of selected properties in the as-received condition and in a saturated state, and provides a protocol for predicting long-termproperty values subjected to accelerated aging based on the Arrhenius model. The model specification is included as an appendixto the article. 2003 Elsevier Ltd. All rights reserved.
Keywords: Accelerated aging; Acceptance criteria; Arrhenius model; Classifications; Mechanical properties; Minimum properties; Physicalproperties; Specifications; Test methods
It is widely recognized that in order for fiber rein-
forced polymer (FRP) composite materials to be usedin the construction of civil engineering structures suchas buildings and bridges a uniform procedure for speci-fying these materials is required. Standard specificationsexist for all commonly used materials in the civilengineering construction. These specifications ensurethat materials used in civil engineering projects aredefined in specific classes, are tested using standardprocedures, are certified in a uniform format and providespecific properties for their intended use. A consensus-based general material specification for FRP materialsfor use in civil engineering structural applications does
not exist at this time. A model specification has beendeveloped by the authors, under sponsorship of the USFederal Highway Administration (FHWA) and in coor-dination with the American Association of State Trans-portation and Highway Officials (AASHTO). Thespecification has not yet been approved by either AASH-TO or the America Society for Testing and Materials(ASTM). This article describes the development of themodel FRP material specification and the key elements
*Corresponding author. Tel.: q1-608-262-1604; fax: q1-608-262-5199.
E-mail address: email@example.com (L.C. Bank).
that the specification contains. The Appendix to this
article contains the model specification itself. The spec-
ification is titled Standard Specification for Fiber Rein-
forced Polymer (FRP) Composite Materials for
Highway Bridge Applications as per the requirements
of the contract under which it was developed.
The model specification was developed by a team of
researchers who have extensive experience and expertise
in the use of FRP materials for civil engineering struc-
tures and extensive prior expertise in the development
of material specifications. The model specification was
developed in the following steps: (a) technical literature
on the subject of characterization of the mechanical and
physical properties of FRP composite materials for both
short-term and long-term properties was studied fromthe perspective of writing a specification; (b) existing
material and design codes and specifications for com-
posite materials were reviewed and evaluated; (c) exist-
ing design codes for conventional materials were
reviewed to determine their relationship to material
specifications; (d) key elements for a FRP material
specification for civil engineering structures were iden-
tified in consultation with design professionals and end-
users, state and federal officials; and (e) draft
specifications and commentaries were developed at 30,
60 and 90% completion targets for review.
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From a detailed review of codes and specificationsfor composite materials a number of key sources wereidentified as a basis for the development of the modelFRP material specification for civil engineering appli-cations. These documents, detailed below, provide pro-cedures for material characterization, methods for
prediction of long-term properties and performance, andacceptance criteria. The American National Standard forLadders w1x, the specification for reinforced plasticladders, provides detailed procedures for testing andminimum properties for acceptance of FRP materials foruse in ladders. Tests for physical properties (e.g. density,maximum water absorption and cure) and mechanicalproperties subjected to dry, wet, elevated temperatureand weathered conditions are stipulated. The Internation-al Conference of Building Officials (ICBO) AcceptanceCriteria AC-125 w2x specifies selected physical andmechanical properties to be measured and reported for
composite materials used for repair and retrofit ofconcrete structures. While no minimum properties arespecified for use, limits on minimum property retentionvalues following conditioning for 1000 and 3000 h arestipulated. The US Department of Defense MilitaryHandbook 17 w3x provides procedures for obtainingproperties for design for FRP composites for aerospaceapplications, as well as property data for specific com-posite material systems. Finally, specifications of theAmerican Society of Testing and Materials (ASTM)related to fiberglass tanks, pipes and poles (e.g. ASTMD2997, D3754, D4021 and D4923) provide guidanceon test methods, acceptance criteria and methods for
prediction of long-term properties of FRP compositesw4x.
Key sections of the specification are discussed in thetext that follows. The order of the discussion followsthat of the specification, which is organized and pre-sented in the generally-accepted format provided byASTM w5x: scope, classification, materials, manufactur-ing, qualification testing, acceptance testing, reportingand quality assurance. Sections on terminology, orderinginformation, keywords and product marking are con-tained in the specification but are not discussed in thearticle. References to tables, figures and text sections
that are numbered with the decimal point (e.g. Section9.5.2) refer to elements of the specification and not tothe article itself.
According to ASTM, a specification is an explicit setof requirements to be satisfied by a material, product orsystem. A material specification serves three main pur-poses: (1) to aid in the completion of purchasingagreements between materials suppliers and purchasers,so that all batches and lots of a material conform to therequirements; (2) to define standard classes and forms
of the material; and (3) to identify performance datathat must be disclosed as part of the material purchasew5x.
In addition, the FRP materials specification was devel-oped to apply to a wide range of FRP compositematerials for numerous different uses, while still ensur-
ing quality and promoting durability. The specificationfocuses on materials most likely to meet AASHTOsstated goals of providing a 75-year life in its structures.It was determined that the specification should, at aminimum: (1) classify FRP materials into groups sothat similar materials will be tested in an identicalmanner and will meet the same minimum performancerequirements; (2) require that material manufacturersprovide sufficient property data for structural designusing the FRP materials; (3) ensure that high qualityconstituent materials and well-controlled manufacturingprocesses are used to produce the FRP materials; (4)
provide long-term data on mechanical property retentionand a method for service life prediction; and (5) providequality assurance procedures so that agencies procuringthe material can verify that FRP materials meet thespecification.
FRP composite parts covered by the specification aremade of one or more qualified laminates. The quali-fying procedure includes a number of mechanical andphysical screening tests. In the specification itself andin this article, the term qualification implies a set oftests that are completed on trial laminates or on lami-nates cut from production parts. The qualification testsare Procedure A, which provides a wide range of test
data and screens for key properties, and Procedure B,which provides long-term property retention data on thematerial. The parts themselves are accepted if thetesting completed on coupons cut from production partsshows that the material properties are essentially equiv-alent to those of the qualified laminates. The testingregime for part acceptance is a small subset of the testsrequired for laminate qualification. The acceptance testsare Procedure C, which provides a comparison test toshow that the material being accepted is substantiallythe same as the qualified (Procedure A) material, andProcedure D, which requires that the material retain key
mechanical and physical properties in a hotwet envi-ronment. The step-by-step procedure for qualificationtesting and subsequent acceptance testing is describedin Fig. 1.
It is important to note that the materials specificationonly covers coupon-level properties. In some applica-tions a materials specification alone will be sufficient tospeci