1GRC mechanical properties for structural applications J . G. Ferreira, F. A. Branco1 (1) Instituto Superior Tcnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal ABSTRACT GRC - Glass Fiber Reinforced Concrete - is a material made of a cementitious matrix in whichshortlengthglassfibersaredispersed.Ithasbeenwidelyusedintheconstruction industryfornon-structuralelements,especiallyinfaadepanels.Thispaperpresentsthe results of a research program aiming the implementation of GRC as a structural material. For this, GRC was associated with continuum carbon and/or stainless steel reinforcement, leading to an innovative material characterized by its lightness, impact strength and high durability characteristics. The evaluation of the mechanical properties of the material are described in thispaper.Thisresearchworkleadtotheindustrialproductionofdifferentstructural elements, such as communication towers, pedestrian bridges and roof elements. RSUM GRC(delanglaisGlassFiberReinforcedConcrete)estunmatriaucomposdune matrice de mortier base de ciment avec des fibres de verre de petit longueur disperses dans son intrieur. Ce matriau a t utilis dans des lments non-structurelles, surtout dans des lments de faade. Cet article prsent les rsultats dun programme de recherche ayant par objectiflutilisationstructurelledeleGRC.PourcelaleGRCatrenforcavecdes lments continus de carbone et/ou dacier inoxydable : on obtient un matriau caractris par sa lgret, rsistance limpact et durabilit. Les proprits mcaniques de ce matriau sont dcrives.Letravaileffectudanslecadredeceprogrammederechercheaconduitla productionindustrielledeplusieurslmentsstructurellescommetoursde tlcommunications, ponts pitonnier et lments de couverture. 21. INTRODUCTION GlassFiberReinforcedConcrete(GRC)consistsbasicallyofacementitiousmatrix composedofcement,sand,waterandadmixtures,inwhichshortlengthglassfibersare dispersed.Theeffectofthefibersisreflectedintheincreaseofthetensionandimpact strength of the material. This composite material has been used for over thirty years in several non-structural elements, namely faade panels (about 80 % of the GRC production) [1]. In the early times of the GRC development one of the most concerning problems was the durability of the glass fibers, which became fragile with time, especially because of the alkalinity of the cement mortar. Since then, significant progresses have been made, with the development of new types of alkali resistant glass fibers and of mortar additives to prevent the chemical and physical processes that lead to the embrittlement of GRC [1,2]. Studiestousethismaterialinstructuralelementswererecentlydeveloped[3].The structural advantages of GRC arise from a reduced weight and a higher impact and tensile strength as compared with concrete. To obtain a corrosion free material with high durability, thestructuralelementsstudiedweredesignedwithreinforcementofcarbontendonsand stainless steel bars. Two main production techniques of GRC were initially analyzed, namely the classical projection and premixing. The later, however, proved to be much better for use in structural elements due to the homogeneity of the material obtained, and the speed of production. Although some of the mechanical and physical properties of GRC can be found in the literature [4,5], there are important reasons that justify its experimental determination: For structural applications, a much more complete and precise characterization is needed, when compared with non-structural elements; It is necessary to know the specific values for the material actually produced in each case, so the final quality of the structure can be assured; Some properties, such as the cyclic loading behavior, were unknown. 3ExperimentaltestswereperformedonGRCspecimenstodetermineitsmechanical strength,Youngmodulus,creepandshrinkagebehaviorandstress-straindiagramsunder static and cyclic loading. The cementitious matrix was tested either plain or with glass fibers and reinforced with carbon or glass tendons or with steel elements. The GRC compositions werestudiedalsointermsoflengthandpercentage of fibers. The ageing effect was also analyzed with accelerated ageing tests. These tests led to a characterization of the production conditions to obtain optimized material properties. 2. TYPES OF GRC TherearetwomainproductiontechniquesofGRC,usuallyreferredasspray-up(or shotcreted) and premix [2]. In the process of producing GRC by shotcreting, the mortar is produced separately from the fibers, which are mixed only at the jet of the spray gun, as shown in Fig. 1. The glass fiber tendons are cut within the spray gun to the required size, typically between 25 mm and 40 mm, and constitute about 5 % of the GRC total weight. The subsequent compaction with a cylindricalrollguaranteesthemouldofGRCintheform,theimpregnationofthefibers withinthemortar,theremovaloftheairretainedwithinthemixandthearisingofan adequate density. Figure 1 Production of element with spray-up GRC [6].4In the GRC production method by pre-mixture, mortar and pre-cut fibers are previously mixed. The quantity of fibers added to the mortar is usually around 3.5 % in terms of weight. Thelengthofthefibersisgenerallyaround12mm.Longerfibersleadtoanexcessive reductionofthemixsworkability.ProductionwithpremixGRCmayinvolveseveral techniques such as injection and vibration, pressing or shotcreting. InTable1thevaluesofsomeGRCcurrentpropertiesreferredinliterature[4,5]are presented for effects of comparison with those experimentally obtained in this paper. PropertyGRC spray-upGRC premix Dry density (kN/m3)19-2119-20 Compression strength (MPa)50-8040-60 Young modulus (compression) (GPa)10-2013-18 Impact strength (Nmm/mm2)10-258-14 Poisson ratio0.240.24 Bending: Limit of linearity (MPa)7-115-8 Maximum strength (MPa)21-3110-14 Direct tension: Maximum strength (MPa)8-114-7 Maximum extension (%)0.6-1.20.1-0.2 Table 1 Typical values of some GRC properties. 3. COMPRESSION BEHAVIOR 3.1 Young modulus Tests were performed to determine the Young modulus of GRC, following the national standard LNEC E397 [7], for concrete. The cylindrical specimens had a diameter of 15 cm and were 90 cm high (Fig. 2). The material was produced with spray-up technique, with the followingcomposition:WhitecementtypeBRI42,5R:100kg;Sand:100kg;Polymer Primal MC 76 S: 6,0 liters; Fluidizer type Sikament: 163: 10,0 liters; Water: 34 liters. Fiber: 4% to 5% Cem-FIL 53/76. ValuesofYoungmodulusforspray-upGRCbetween16,0GPaand17,0GPawere obtained, which are in the range of the technical data. 5 Figure 2 Tests to determine Young modulus. 3.2 Compression strength For assessment of the GRC compression strength different tests were carried out, either onSpray-upandPremixspecimens.Thecompositionsofeachproductiontechniquewere optimized based on former experience and on workability tests. The aim of these tests was to assess the compression strength of GRC and to evaluate the role of the fibers. Five series of specimens were tested, as follows: Series A 9 specimens of premix GRC (2,5% of 12 mm fibers); Series B 8 specimens of spray-up GRC (4% to 5% of 31 mm or 63 mm fibers); Series C 13 specimens of spray-up GRC (4% of 31 mm fibers); Series D 10 specimensofpremixmortar(withoutfibers);SeriesE6specimensofspray-upmortar (without fibers). All specimens were produced with standard dimensions. Spray-up GRC mortar was composed as referred in 3.1, while premix GRC mortar was produced with the following the composition: White cement type BR I 42,5R: 100 kg; Sand: 67 kg; Polymer Primal MC 76 S: 1,8 liters; Fluidizer type Sikament: 163: 1,0 liters; Water: 29 liters. 6Fig. 3 shows the set-up of the tests, performed following the national standard LNEC E226 [8], for the evaluation of concrete compression strength. Figure 3 Compression tests set-up. The plain mortar specimens (without fiber reinforcement) practically exploded when the maximum force was achieved, while the GRC ones, despite the crack pattern showed on their surface, almost maintained their initial shape, denoting a much more ductile behavior (Fig. 4). This distinct type of GRC behavior, when compared to plain mortar, is relevant for structural use and is reflected in the stress-strain diagrams (Fig. 6). Figure 4 GRC and plain mortar ruptured specimens. Basedonthestrengthtestsresults,theaveragevalue,standarddeviationand characteristic value at 95% were determined for each series. A numerical treatment of the cubic specimens values was carried out [9,10] to refer them to cylindrical specimens tests. In Table 2 the results for all tested series are presented. 7Seriesfcm (MPa) (MPa)fck (MPa) A (9 premix GRC)40.92.9136.1 B (8 spray-up GRC)37.42.9332.6 C (13 spray-up GRC)57.03.4851.3 D (10 premix mortar)51.80.7050.6 E (6 spray-up mortar)58.38.9243.7 Table 2 Statistics of compression tests results, referred to cylindrical specimens. These results show that GRC strength is comparable to that obtained for good quality concrete. The lower values of series A (premix GRC), when compared with series D (premix GRC mortar), are probably related to a lesser compaction or excess of water. The average strength of series E (spray-up GRC mortar) is higher than that of series B and C (spray-up GRC),butitscharacteristicstrengthpresentsanintermediatevaluebecauseofthelow numberofspecimens.Theresultsshowthatthepresenceoffibersmayimplyalossof compression strength of the material. 3.3 Stress-strain diagrams Five tests were performed to determine the stress-strain behavior in compression. Three of these specimens were composed by premix GRC (series F), while the other two (series G) were made of plain mortar. AllstandardcylindricalspecimensofseriesFandGwereproducedfollowing, respectively,thecompositionsofseriesAandEindicatedin3.2.Thetestset-upandthe general procedure adopted in these tests was identical to those indicated in 3.2. Thestrainwasmeasuredbymeansofeitherelectricaldisplacementtransducersand strain gauges, as showed in Fig. 5. In the initial phase of tests the strain gauges readings are considered due to their higher accuracy. The displacement transducers may read deformation far beyond the working limit of the strain gauges, allowing the evaluation of the post peak behavior. 8 Figure 5 Measurement of specimens deformation. Fig.6showsthestress-straindiagramsobtainedinthesetests,thatclearlyreflectthe differenttypeofcollapsemodedependingwhetherthefibersarepresentornot.Itis particularly evident the greater ductility of GRC when compared with plain mortar that, as previously referred, disintegrates when maximum force is reached. Although the presence of the fibers leads to a reduction of compression strength, it ensures a better behavior in the post-peak zone, namely preventing its fragmentation. 010203040500 2000 4000 6000 8000 10000Strain(m/m)Stress (MPa)

010203040500 2000 4000 6000 8000 10000Strain(m/m)Stress (MPa) Figure 6 Stress strain diagrams of. premix GRC and of plain mortar. 4. TENSION BEHAVIOR The tension behavior of GRC is one of the most important mechanical parameters when considering its structural use. A large number of experimental tests was carried out to analyze differentaspectsontensionbehavior,suchasproductiontechniques,compositions, continuous reinforcement or ageing.The main set-up used to perform tension testsis showed in Fig. 7. 9 Figure 7 Tension tests set-up. The test specimens were 30-35 cm long, with rectangular cross-section of 1 cm x 4-5 cm. 4.1 Spray-up GRC Thecompositionusedinthespray-upGRCspecimenswasbasicallysimilartothat referred in section 3.1. The different series are distinguished by the type (53/76 or 250/5), quantity and length of dispersed fibers, the sand used (regular, sieved or siliceous), the type (or absence) of continuous reinforcement and the previously accelerated ageing. Within each series all the specimens have identical characteristics. The series were divided in four groups, being the first made of plain GRC specimens, the second with carbon tendons reinforcement, the third presenting glass-fiber tendons and, the last, made of specimens previously subjected to accelerated ageing by immersion in hot water. Tables 3 to 6 present a description of each series within each group. SeriesN spec.Description 1105.2% fiber 53/76, 63 mm long (non sieved sand) 2104.0% fiber 53/76, 31 mm long (non sieved sand) 3104.4% fiber 53/76, 31 mm long (non sieved sand) 4104.6% fiber 53/76, 63 mm long (non sieved sand) 555.0% fiber 53/76, 31 mm long (non sieved sand) 655.0% fiber 53/76, 63 mm long (non sieved sand) 754.0% fiber 53/76, 63 mm long (non sieved sand) 854.0% fiber 53/76, 31 mm long (non sieved sand) 9105.0% fiber 53/76, 31 mm long (sieve 0.6 mm) 10105.0% fiber 53/76, 31 mm long (sieve 0.3 mm) 11105.0% fiber 250/5, 31 mm long (sieve 0.6 mm) 12105.0% fiber 250/5, 31 mm long (sieve 0.3 mm) Table 3 Series of plain spray-up GRC specimens. 10SeriesN spec.Description 1315 5% fiber 250/5, 31 mm long, inox grid, 1 longitudinal carbon tendon (sieve 0.6 mm) 1410 5% fiber 250/5, 31 mm long, inox grid, 1 longitudinal carbon tendon (sieve 0.3 mm) 1595% fiber 250/5, 31mm long, wet carbon fiber at 45 (sieve 0.6 mm) 16105% fiber 250/5, 31mm long, 4 wet sinusoidal carbon tendons (sieve 0.6mm) 1795% fiber 250/5, 31mm long, 5 longitudinal wet twisted tendons (sieve 0.6mm) 1811 5% fiber 250/5, 31mm, inox grid, 3 longitudinal wet twisted tendons (siliceous sand) 1995% fiber 250/5, 31mm long, 3 wet sinusoidal carbon tendons (siliceous sand) 2010 5% fiber 250/5, 31mm long, 3 longitudinal wet twisted carbon tendons with knots every 5 cm (siliceous sand) Table 4 Series of spray-up GRC specimens with carbon fiber tendons reinforcement. SeriesN spec.Description 2154% fiber 53/76, 31 mm long, 1 longitudinal fiber tendon (non sieved sand) 2211 5% fiber 250/5, 31mm long, inox grid, 3 longitudinal wet twisted glass fiber tendons (siliceous sand) 23105% fiber 250/5, 31mm long, 3 wet sinusoidal glass fiber tendons (siliceous sand) 2410 5% fiber 250/5, 31mm long, 3 longitudinal wet twisted glass tendons with knots every 5 cm (siliceous sand) Table 5 Series of spray-up GRC specimens with glass-fiber tendons reinforcement. SeriesN spec.Description 255 5% fiber 250/5, 31 mm long, inox grid, 1 longitudinal carbon tendon (sieve 0.6 mm) 265 5% fiber 250/5, 31 mm long, inox grid, 1 longitudinal carbon tendon (sieve 0.3 mm) 2755% fiber 250/5, 31 mm long (sieve 0.6 mm) 2855% fiber 250/5, 31 mm long (sieve 0.3 mm) 2955% fiber 53/76, 31 mm long (sieve 0.6 mm) 3055% fiber 53/76, 31 mm long (sieve 0.3 mm) Table 6 Series of spray-up GRC specimens subjected to accelerated ageing. Toanalyzecontinuousreinforcingtendons,differentpatternswereconsidered,as indicatedintheprevioustables,attemptingtoachieveoptimizedadherencetothematrix. Sinusoidal layout indicates a longitudinal pattern where the same tendon passes different times along the length of the specimen, without being cut at its ends. When fiber at 45 is indicated,thetendonsarepositionedobliquelytothelongitudinalaxes.Thispatternsare illustrated in Fig. 8. Sinusoidal pattern Fiber at 45 pattern 11Figure 8 Patterns of continuous reinforcement. Theartificialageingprocessconsistedofsubmergingthespecimensin75Cwater during 17 days, whatcorresponds, in accordance with[11], to 22 years of natural ageing. Fig.s 9 to 12 show the average and characteristic values of tension strength obtained for each tested series. 024681012Series 1Series 2Series 3Series 4Series 5Series 6Series 7Series 8Series 9Series 10Series 11Series 12Tension strength (MPa)Average value Charact. value Figure 9 Tension test results. Plain spray-up GRC. 024681012141618Series 11Series 12Series 13Series 14Series 15Series 16Series 17Series 18Series 19Series 20Tension strength (MPa)Average value Charact. value Figure 10 Tension test results. Spray-up GRC with carbon fiber reinforcement. 02468101214Series 2Series 11Series 12Series 18Series 20Series 21Series 22Series 23Series 24Tension strength (MPa)Average value Charact. value Figure 11 Tension test results. Spray-up GRC with glass fiber reinforcement. 12024681012Series 9Series 10Series 11Series 12Series 13Series 14Series 25Series 26Series 27Series 28Series 29Series 30Tension strength (MPa)Average value Charact. value Figure 12 Tension test results. Accelerated aged spray-up GRC. These figures show that the use of carbon tendons increases the tension strength of the specimens,althoughitseffectivenessdependsontheanchortype.Thesinusoidalpattern provedtobethebestanchoringsystem,followedinsequencebythesimplelongitudinal layout,theknotarrangementandthe45pattern.Twistingthetendonsdidntleadto noticeableincreaseofthestrength.Thetotalstrengthofthecarbontendonswasnever completely mobilized. The inox grid used in various series didnt show practically any effect because its intrinsic strength was not significant. Tension strength is not clearly affected by the type of dispersed glass fibers. The use of glass-fiber tendons shows similar effects but is less effective. 4.2 Premix GRC The composition of premix specimens was similar to that referred in section 3.2, but with afiberincorporationofonly2,5%.Thischangeprovedtobenecessarytoincreasethe workability and facilitate the fiber dispersion. The different series are distinguished by the type (or absence) of continuous reinforcement. In Table 7 the premix GRC series tested in tension are described. 13 SeriesN spec.Description 3118Plain GRC, cross-section 50mm x 15mm 3214Plain GRC, cross-section 40mm x 10mm 3317GRC with 1 carbon tendon, cross-section 50mm x 15mm 3413GRC with 1 carbon tendon, cross-section 40mm x 10mm 357GRC with 1 carbon tendon and 1 3 mm steel bar, section 50mm x 15mm 3616GRC with 1 3 mmsteel bar, cross-section40mm x 10mm Table 7 Series of premix GRC specimens subjected to tension tests. Fig. 13 show the average and characteristic values of tension strength obtained for the various tested series. 02468Series 31Series 32Series31/32Series 33Series 34Series 35Series 36Tension strength (MPa)Average value Charact. value Figure 13 Tension test results. Spray-up GRC with glass fiber reinforcement. Theanalysisoftheresultsshowsthatthecontinuousreinforcementincreasesthe specimenstensionstrength.ConsideringthattheplainGRCtensionstrengthvalueisnot changed by the presence of continuous reinforcement, the force exerted on these elements was determined in each case. Based on such considerations it was concluded that the carbon tendons are tensioned to 11%-13% of their capacity. In the case of steel bars this value is worth 59%, in the series with carbon tendons, and of 29% without carbon. This phenomenon is related to the reduced length of the specimens, that prevents the adequate anchoring of continuousreinforcingelements.ThisfactisillustratedinFig.14,wheretheslipofthis elements is evident. 14 Figure 14 Slipping of continuous reinforcing elements in GRC specimens. 5. CYCLIC BEHAVIOR Different tests on GRC specimens were performed to characterize its cyclic behavior and collect data to incorporate in numerical models to be developed for structural analysis. The cyclic behavior is particularly important when considering the GRC structural use in seismic zones or in windy areas. The tested specimens were produced with premix GRC, being their composition equal to tat referred in 4.2. Fig.s 15 to 17 show the cyclic stress-strain diagrams obtained from rectangular specimens tested under a cyclic increasing positive (tension) displacement history. In these figures, togetherwiththecyclicpath,thecurvesrespectingseveralmonotonictestsundersimilar specimens are presented. -4.0-2.00.02.04.06.00 1000 2000 3000 4000 5000 6000 7000 8000Strain (m/m)Stress (MPa) Figure 15 Cyclic test on plain GRC specimen. 15-6.0-4.0-2.00.02.04.06.00 1000 2000 3000 4000 5000 6000 7000 8000Strain (m/m)Stress (MPa) Figure 16 Cyclic test on GRC specimen with 1 carbon tendon. -12.0-8.0-4.00.04.08.012.00 5000 10000 15000 20000Strain (m/m)Stress (MPa) Figure 17 Cyclic test on GRC specimen with 1 carbon tendon and 1 3 mm steel bar. The analysis of the results show that the stiffness gradually decreases along the test; the cyclic diagrams of plain GRC and of GRC with 1 carbon tendon are approximately delimited by the monotonic ones; the specimens with a steel bar show a more favorable behavior, with higher stress values and an envelope diagram outside the monotonic lines. Fig. 18 shows the cyclic stress-strain diagram obtained from a cylindrical specimen tested under a cyclic increasing negative (compression) displacement history, together with curves respecting monotonic tests under similar specimens. 160510152025303540450 2000 4000 6000 8000 10000Strain (m/m)Stress (MPa) Figure 18 Compressive cyclic test on GRC specimen. The results obtained show the following aspects: the material stiffness in cyclic regimen, because of damage accumulation, is greater than in monotonic tests; the monotonic diagrams approximatelyenvelopethecyclicpath;themaximumcyclicstrengthwassimilartothe monotonic one. 6. CREEP BEHAVIOR SincesomeofthestructuralusesofGRCunderdevelopmentincludedpre-stressed elements, an assessment of creep behavior was needed to evaluate long-term losses. Creep tests were performed on 3 cylindrical specimens of spray-up GRC. To ensure the stability of appliedcompressivestress,thespecimensweresubjectedtoagravityloadof85kN,as shown in Fig. 19. Figure 19 Specimens subjected to creep test. 17The specimens designated by S1 and S2 were loaded 8 days after casting. In the 28th day thespecimenS2wassubstitutedbyspecimenS3.Thespecimensdeformationswere measured with strain gauges.Fig. 20 shows the tests results, where (t) represents the creep coefficient(definedasthereasonbetweencreepandelasticstrain).Theseresultswere obtained considering the difference between the values measured on the tested specimens and theaveragedeformationofcontrolunloadedspecimens,keptundersimilarenvironment conditions.Thisprocedureaimstocompensatethedeformationcomponentscausedby shrinkage and by atmosphere moisture. 0.00.51.01.52.02.53.03.50 20 40 60 80 100 120 140 160Age (days)(t)S1 S2 S3 Figure 20 Creep tests results. The creep coefficient values are comparable to those usually obtained in concrete. 7. CONCLUSIONS Theexperimentaltestprogramcarriedoutallowedtheassessmentofthemain mechanical parameters of GRC concerning its structural use. Though some indicative values oftheanalyzedparametersaregiveninliterature,theassessmentoftheGRCactually producedwasabsolutelynecessary,aiminganadequatecontrolandknowledgeofthe fabricated structural elements. 18The GRC compositions of the tested specimens result from adjustments established in fabricationtests,consideringtheactualproductionconditionsandsomespecificstructural elements. Thisstudyalsoprovidedimportantdatarespectingtheeffectivenessofcontinuous elements reinforcement introduced in GRC. Partoftheexperimentaldataobtainedwaslaterincorporatedinnumericalmodelsto analyze the structural behavior of the elements produced with GRC. 5. ACKNOWLEDGEMENTS The authors wish to thank the financial support of the FCT (Fundao para a Cincia e Tecnologia)andoftheEuropeanCommissionfortheresearchdevelopedwithinproject PRAXIS/P/ECM/14046/1998,BetoReforadocomFibrasdeVidroAplicaes Estruturais. 6. REFERENCES [1]Bentur,A.,Mindess,S.,FibreReinforcedCementitiousComposites,(Elsevier Applied Science, London 1990). [2]Cem-FIL GRC Technical Data, Cem-FIL International Ltd, (Vetrotex, UK 1998). [3]Ferreira,J .,Structuralcharacterizationofglass-fiberreinforcedconcrete(GRC). Applicationtotelecommunicationstowers,availableinPortuguese,PhDthesis, (Instituto Superior Tcnico, Lisbon 2002) [4]Knowles, E., Recommended Practice for Glass Fibre Reinforced Concrete Panels, PCI Committee on Glass Fibre Reinforced Concrete Panels, (PCI, USA 1987). [5]Bijen,J .,J acobs,M.,PropertiesofGlassFibreReinforcedPolymer-Modified Cement, J ournal of Materials and Construction, Vol. 15, 1982. 19[6] Glass fiber reinforced cement, J ournal of Portuguese Producers of Precast Concrete Products (anipc), (available in Portuguese),Year 2, n 4, (anipc, Lisbon 1998) . [7]Laboratrio Nacional de Engenharia Civil (LNEC), E397 standard - Assessment of compressive Young modulus in concrete, (available in Portuguese) (LNEC, Lisbon 1993). [8]LaboratrioNacionaldeEngenhariaCivil(LNEC),E226standardCompression tests in concrete, (available in Portuguese) (LNEC, Lisbon 1993). [9]Concrete Core Testing for Strength,Report of a Concrete Society Working Party, Concrete Society Technical Report N 11, The Concrete Society, 1976. [10]Guide to Assessment of Concrete Strength in Existing Structures, British Standards Institution, BSI, BS 6089, (British Standards, UK1981). [11]Litherland, K., Oakley, D., Proctor, B., The Use of Accelerated Ageing Procedures to PredicttheLongTermStrengthofGRCComposites,CementandConcrete Research, Vol. 11, 1981. [12] REBAP Portuguese code for reinforced concrete structures, Decreto-Lei 349-C/83, (available in Portuguese) (Imprensa Nacional Casa da Moeda, Lisbon 1986). 20 BIOGRAPHIC NOTES JooFerreiragraduated in Civil Engineering and received his MASc and Ph.D. degrees at IST-TechnicalUniversityofLisbon,Portugal,whereheisanAssistantProfessor.His researchworkdealswithnewstructuralmaterials,steelstructures,andexperimental assessment of structural behavior. Fernando A. Branco is Full Professor of Civil Engineering at IST - Technical University of Lisbon, Portugal. He is Vice-Chairman of the IABSE Technical Commission, Member of ACI CommitteeN342onEvaluationofConcreteBridgesandmemberoftheCSCEand RILEM. His primary research interests deal with the behavior of bridges and other public works.