Fourth International Conference on FRP Composites in Civil Engineering (CICE2008) 22-24July 2008, Zurich, Switzerland

- 1 -

1 INTRODUCTION

Primary supporting elements made from pultruded glass-fiber reinforced polymers (GFRP) have already been employed successfully for some years in bridge building (in particular in the USA and Asia). GFRP-bridge decks, consisting of E-glass reinforcement imbedded in a matrix of isophthalpolyester resin, open up a very easy and rapid construction method with absolute cor-rosion resistance, corresponding minimum maintenance costs and high strength properties. On the other hand, a low modulus of elasticity and the problem of fiber-related jointing are disad-vantages.

As well as the geometrical layout of the new deck with orthotropic material parameters, the laminate composition, consisting of roving, unwoven fabrics, woven fabrics and mats, is treated. The deck elements are dimensioned with beam-grid models, FE analyses and designed with the aid of the laminate theory as well as a special strength hypothesis.

Experience from other projects, e.g. the European ASSET Project [1] and the CLAP-Deck development with RWTH Aachen [2], is directly applied to the new developments.

After the production of the newly developed deck elements in the pultrusion operational works of the company Fiberline Composites A/S, the decks are examined at Delft TNO in an extensive test program with regard to material properties, connection systems, concentrated wheel loads and combined loading. The entire test program is aligned with first priority to ex-periments guaranteeing sufficient fatigue resistance according to NEN 6788: 1995.

The first bridges with this new pultruded, glass-fiber reinforced plastic decks have already been built in the Netherlands in the year 2007.

The new lightweight bridge deck FBD300 made from pul-truded fiber-reinforced composites for traffic bridges W. Sobek, H. Trumpf Werner Sobek Ingenieure International, Stuttgart, Germany

ABSTRACT: The project partners Fiberline Composites A/S, Kolding (DK), Haasnoot Brug-gen, Katwijk (NL), and Werner Sobek Ingenieure, Stuttgart (D) are developing new decks for traffic bridges for different load classes made from glass-fiber reinforced polymers. Since the application of glass-fiber reinforced polymer decks for bridges, in particular in case of pedes-trian bridges and traffic bridges with low bridge classes, is already far advanced in the Nether-lands, the decks are calculated initially in accordance with the Dutch Standard NEN 6788, in order to carry out a classification according to Eurocode 1 in a subsequent step. In this contribu-tion, the development of the new bridge deck "Fiberline Bridge Deck 300" -FBD 300- for the Bridge Class 300, according to the Dutch standard NEN 6788:1995, is explained and the pedes-trian-cyclist bridge "Holländerbrücke" in Reinbek near Hamburg is presented.

- 2 -

The deck elements, with a maximum support span of 1.3 m, are laid on a prepared frame of steel girders with a maximum span of 30.0 m. All steel construction elements are coated with a duplex corrosion protection system, in order to guarantee maximum low-maintenance service life duration for the steel girders as well.

The entire bridge building work is already completely finished at the works, including the steel coating, protective coating of polymer concrete, the decking coating and the railing instal-lations. Bolted and/or bonded joints are employed for the connection of the decking elements to the steel girders. Every single element of the deck has to be bolted and/or bonded to the steel girder. The erection of the bridges is realized in a few hours on prepared abutments, with the aid of a light mobile crane.

The combinations of lightweight and sophisticated materials like steel and GFRP are very competitive in comparison to conventional pre-stressed concrete or composites structures.

This very economical and durable construction method, in association with demanding archi-tecture, is explained in the example of the new “Holländerbrücke” crossing for pedestrians and cyclists in Reinbek near Hamburg.

2 REQUIREMENT

For the development of the new FBD 300 bridge deck, the following boundary conditions were stipulated in order to fulfill the requirements of the Dutch road authorities with a high degree of prefabrication, with simultaneously optimized construction performance:

- Bridge Class 300 "Load Class 300", in accordance with NEN 6788:1995; three-axle ve-hicle with 300 kN, 4 wheels per axle, distributed load 2 kN/m², cf. Fig. 1

- Placement of the decking on a support grid of steel with bonded and/or screwed connec-tions, no composite action is considered, cf. Fig. 2

- Laying of the decking elements in transverse direction with spans up to 1300 mm, where the first deck element is supported by a cross beam in each case

- Take-up of the temperature expansion differences and bending of approx. ∆ = 0.3 mm between steel and GFRP (∆Steel = 12 * 10-6, αGFRPy = 18 * 10-6) in the joints

- Deflection limitation - SLS Limit L/200 - Application of a special deck coating (primer with mineral layer) for sufficient grip and

surface roughness - Prefabrication of the entire superstructure in the works, including railings and decking

coating, loading of the segments or the entire bridge onto trucks, placement of the fin-ished superstructure on pre-assembled abutment with a mobile crane

An additional coating with a polymer concrete is recommended for protection of the decking elements concerning local peak pressures induced by wheel patches.

Fig. 1: Load arrangement "Load Class 300" according to NEN 6788: 1995 [9]

- 3 -

Fig. 2: Schematic draft of FBD 300 decking on HEB 300 steel main supports – steel beams in longitu-dinal direction of the bridge, bridge deck is placed in transverse direction with the stronger pul-trusion orientation and a maximum span of 1300 mm

3 GEOMETRIC LAYOUT

First of all, a decking element was proposed by Haasnoot Bruggen with an installation height of approx. 60 mm in analogy to the 40 HP planks open out below as in Fig. 3, in order to provide a simple bolted fixing with polyurethane cores. These planks were developed for pedestrian bridges with light traffic vehicles with max. distributed load of 5 kN/m² and have in the mean-time become a standard product for pedestrian bridges. Those planks open to below can be con-nected very simply with the steel beams by means of inserted pre-assembled polyurethane cores and stainless steel bolts.

Fig. 3: Open plank 40 HP for pedestrian bridges (Graphics: Fiberline Composites A/S)

This open profile geometry with vertical webs cannot withstand existing high local wheel patch loads and horizontal breaking loads, according to "Load Class 300". Therefore a closed profile section with three cores, sloping webs as reinforcing props and a tongue and groove connection in the impact area, was developed in several static optimization steps for the take up the vertical forces, cf. Fig. 4.

- 4 -

Fig. 4: Cross section of the FBD 300 in mm (B = 333 mm, and H = 80 mm) with groove and tongue connection on both sides

Due to the low installation height of the section, the static layout is implemented with focussing on compliance with the maximum shear stresses.

The existing profile section with three cores and a high fiberglass content requires a very high technical outlay by the Fiberline Composites A/S pultrusion operational works, in order to achieve the exact reinforcement positioning, the layout of the core tools and the fixing of the mandrels, as well as the resin supply in the closed system.

4 LAMINATE LAYOUT

The layout of the orthtropic laminate composition in the individual sectional view parts is im-plemented in accordance with the load stressing type and direction (normal stresses, shear stresses and combinations) and load stressing extent, with consideration of positive and negative values. This means that the laminate is designed exactly to accommodate the decisive stressing states from the individual load case combinations.

The laminate is considered in micro-mechanics and macro-mechanics as a multiple-layer compound, and the stiffness matrix is set up according to the classical laminate theory, for which the following prerequisites apply:

- Linear-elastic material behavior (Hooke's Law) - Sectional view remains straight and vertical to the rod axis (Bernoulli's Hypothesis), full

jointing of the single layers - Normal expansion perpendicular to the reference area is neglected (εz = 0) - Sectional view normal to the plate central surface remains normal (Kirchhoff''s Theory),

i.e. transverse shear deformations γxz = γyz = 0. Roving, unwoven fabrics, woven fabrics and mats are employed as reinforcement fibers. On

the basis of the properties of the single components of matrix and fiber, the compound proper-ties to be expected are determined in micro-mechanical aspects as constants of the locally-oriented single layer. The single layer is considered as a heterogeneous and unidirectional ma-trix-fiber compound (UD layer), whose properties are stipulated with mixing rules.

In macro-mechanical aspects, the properties of the overall laminate / multiple-layer com-pound, consisting of the single layers, are determined. The properties of the single layers are considered layer-related as a quasi-homogenized continuum, with anisotropic characteristic be-havior due to the fiber orientation. Furthermore, the expansions and stresses in the single layers can be determined with specification of stress demands and deformations.

The transformed single layer, depending on the respective position k and layer thickness t situation, are composed to form a total stiffness matrix, symmetrical to the main diagonal, in ac-cordance with equations (1) and (2).

( ){ } [ ] ( ){ } [ ] { } { }( )κ+ε⋅=ε⋅=σ zCzCz 0kkk (1)

80

333

- 5 -

κκκγεε

=

κε

=

xy

y

x

xy

y

x

665646

565545

464544

362616

262515

161514

362616

262515

161514

332313

232212

131211

12

2

1

12

2

1

0

P

K

K

S

cccccccccccccccccc

ccccccccc

ccccccccc

MMMNNN

,CC

CC

MN (2)

with

( ) 3,2,1j,izzctcc 1kk

n

1kkj,i

n

1kkj,ij,i =−⋅=⋅= −

==∑∑ (3)

( ) 3,2,1j,izzcc 21k

2k

n

1kkj,i3j,i =−⋅= −

=+ ∑ (4)

( ) 3,2,1j,izz31cc 3

1k3

k

n

1kkj,i3j,3i =−⋅= −

=++ ∑ (5)

The four quadrants can be represented as three different lower matrices: - Membrane stiffness matrix or disk quadrant [ ]SC , - Bending strength matrix or plate quadrant [ ]PC , - Coupling stiffness matrix and coupling quadrant [ ]KC .

The multiple-fiber break criterion according to Puck [3] represents a physically-based failure

hypothesis for fiber and intermediate fiber break, according to the strength hypothesis of Mohr for brittle materials. The basic idea of the break hypothesis is that the tensile strength of a mate-rial is determined by the stresses in the break level (effect-level-related intermediate fiber-failure criterion).

Fig. 5: Effect-level-related intermediate-fiber break criterion in UD layer according to [3]

a) Spatial stress state in the (1,2,3) coordinate system

b) Stress transformation on all effect levels in the (1,n,t) coordinate system

c) Search of the effect level with the highest stressing → failure level

- 6 -

From further research and development projects, e.g. the European ASSET Project [1] or the CLAP Deck (Composite Lightweight Aachen Profiles) [2], a lot of experience has been gained in dimensioning the laminate layout.

The laminate composition in the individual section parts is subject to Fiberline Composites A/S company confidentiality and thus cannot be represented or explained by calculation or graphic means.

From the laminate theory, the strength criterion and the verifying material investigations, in accordance with the requirements of EN 13706 [4], the following global characteristic nominal and dimensioning values can be indicated for the overall cross section, Table 1 (section size de-termination at the orthtropic beam grid). In the individual sectional parts, these global material parameters deviate as a function of the stress demand (stress analysis with FE methods), accord-ing to the local laminate composition.

The "Losipescu Test", according to ASTM D 5379, was applied as an extension for the inter-laminary shear strength of the sloped web sections. The characteristic interlaminary shear strength in these section parts can be accordingly assumed as τm,Rd = 48 N/mm².

Table 1: Global characteristic nominal and dimensioning values

Material parameter Unit Testing method Mean value

Characteristic value

Effective bending module Eeff N/mm² EN 13706 27000

Axial tensile module Etx N/mm² EN ISO 527-4 27000

Transverse tensile module Ety N/mm² EN ISO 527-4 10000

Axial compressive module Ecx N/mm² EN ISO 14126 27000

Transverse compressive module Ecy N/mm² EN ISO 14126 10000

Axial tensile strength ftx N/mm² EN ISO 527-4 300

Transverse tensile strength fty N/mm² EN ISO 527-4 50

Axial compressive strength fcx N/mm² EN ISO 14126 280

Transverse compressive strength fcy N/mm² EN ISO 14126 100

Interlaminary shear strength τm N/mm² EN ISO 14130 30

Modulus in torsion G N/mm² ISO 15310 3000

From the expert appraisals, which are presently under preparation for the attainment of a general construction supervision certification [5], and publication regarding the "stability of plane struc-tures made from pultruded fiber-reinforced polymer profile sections" [6], dimensioning regula-tions and safety coefficients can be used, cf. Table 2.

No reduction is necessary, in case of the existing construction works, to take into account the long-term behavior characteristics A1, special environmental conditions A2 and thermal stresses (> 80°C) A3 according to the BÜV Recommendation [7].

Table 2: Safety coefficients, determined according to EN 1990 Appendix D [5] and [6]

Verification Mγ

Sectional view of load-bearing capacity 0,Mγ

1.35

Stability

(dents, buckling, torsional-flexural buckling) 1,Mγ

1.5

Bolted connections 2,Mγ

1.5

- 7 -

In the Fig. 6 the finished deck element FBD 300 is shown from the first charge of the pultrusion process. The pultrusion process is always in the longitudinal direction of the profile, which is the transverse direction of the bridge.

Fig. 6: First charge FBD 300 from the pultrusion process (Photograph: Fiberline Composites A/S)

5 STATIC VERIFICATION

The deck is always placed in pultrusion direction (longitudinal direction of the profile itself) on the steel beams. Therefore, the deck is spanning in transverse direction of the bridge. The following loads were applied in the dimensioning of the deck in accordance with NEN 6788:1995 [9]:

- Vehicle with Q300 = 300 kN and three axles, 4 wheels per axle, with Q300,Wheel = 25 kN with a wheel contact area of 160 mm * 250 mm, distributed load q300 = 2 KN/m²

- Horizontal breaking load QB300 = 100 kN, per wheel QB300 = 8.33 kN - Temperature load cases ∆TN,neg/ N,pos = ∆Te,min/ e, max - ∆T0 = +/- 35°C and ∆TN = +/- 15°C - Snow and wind loads are not dimensionally relevant for the decking

For ULS and SLS the following load case combinations were considered: I. 300300ULS,Sd q5,1Q5,1G5,1N ⋅+⋅+⋅= , V. 300,B300300ULS,Sd Q2,1q2,1Q2,1G2,1N ⋅+⋅+⋅+⋅= , XII. 300,BULS,Sd Q5,1N ⋅= , XXL. 300,B300300ULS,Sd Q5,1q5,1Q5,1G5,1N ⋅+⋅+⋅+⋅= (own combination, decisive), and iiSLS,Sd q0,1Q0,1N ⋅+⋅= . Within the framework of the global static analysis, orthtropic support grids with different

support spans were generated and stress analyses carried out. A loading situation is represented in Fig. 7 for the traffic load Q300 consisting of two axes.

For the local stress analysis, a plank as single-span beam was generated by means of FEM subject to centrally-applied and eccentric local wheel loads, with elastic support conditions. For the support springs HEB-profiles have been considered, which are typical steel beams for these kind of bridges. This numerical analysis is used in particular for the more precise determination of the shear stress distributions in the flanges and in the webs, Fig. 8.

The local static analysis was performed on a single span girder instead of using a continues action for the global static analysis. Therefore the results of the local analysis are conservative compared to the real behaviour of the deck.

- 8 -

Fig. 7: Global static analysis: Traffic load situation for the maximum moment (two axles with 4 wheels in each case) – span has been varied for the analyses

Fig. 8: Local static analysis: Shear stress distribution in the FEM analysis Under the assumed conditions, taken with more conservative values to be on the safe side

(e.g. unfavorable load case combination, disregarding the curvature radii, conservative material strength properties etc.) the capacity utilization of the sectional view is:

max σS,d = 70 N/mm² < σR,d = 220 N/mm² min σS,d = of -61 N/mm² < σR,d = -205 N/mm² max τS,d = 33 N/mm² < τR,d = 35 N/mm² (layout of the sectional view on max τS,d) max w = 5.02 mm < L/200 = 6.5 mm

A loading span curve for the FBD300 is represented in Fig. 9.

Z

XY

DY = 999.0

DX = 250.0 DX = 250.0

DX = 250.0 DX = 250.0

DX = 1250.0

- 9 -

Fig. 9: Loading span curve FBD 300 The static three-point bending tests on the first charge, carried out within the framework of

the internal monitoring of the company Fiberline Composites A/S, indicated that the material strength properties and stiffnesses assumed in the static calculations are above expectations.

For the support of the deck, a combination of bolted and/or bonded connections is recom-mended, which is to be verified in an investigation program with regard to the fatigue limit and durability. For the bonded connection, a verification with a two-component epoxy resin was im-plemented according to the theory of Volkersen [8]. The layout of the bolted connections was implemented conventionally according to the relevant steel construction standards and own ex-perimental results [5].

6 INVESTIGATION PROGRAM WITH ORIENTATION TO THE ENDURANCE LIMIT

Since, for the existing laminate and the geometric details, there exist any "Woehler Curves" (S-N Curves), no serious fatigue limit verification can be provided. Furthermore, no standard-based dimensioning regulations or verification concepts exist. From internal experiments from further projects, e.g. [1] and [2], only an estimate of the fatigue limit can be implemented. Thus the process "Design by Testing" is referred back to for the fatigue verification.

The investigation program was initially coordinated with the "Institute for Lightweight Struc-tures B.V." at TNO Delft, with a view to the special specifications of the Dutch government au-thorities. Fatigue experiments with orientation towards significant dimensioning details will be carried out, e.g. webs under shear stresses, support of the decking plank on the steel beam and finally experiments verifying the overall system, Fig. 10.

- 10 -

Fig. 10: Excerpt from the verification fatigue experiments on the overall system

7 HOLLÄNDERBRÜCKE

In Reinbek near Hamburg, a replacement construction works is currently being planned for the pedestrian and cyclist bridge the "Holländerbrücke", with an overall length of 99.0 m and a width of 3.5m; Fig. 11 and Fig. 14. The object and structure planning is being carried out by the office Werner Sobek Ingenieure.

The bridge building work with support spans 12.0 m - 12.0 m - 16.0 m - 18.0 m and 12.0 m was projected, considering urban development, as a discreet and filigree construction works. The sight screen on the south side of the construction works is adapted into the draft without at-tracting attention. Technically imposing structures and constructions with complicated appear-ance were intentionally avoided in case of this draft. Through the optically demanding design of the details and tactile qualities, people accept the construction works as a bridge for "touching and experiencing". The carefully differentiated coloring and few gloss lines support this high aesthetic quality.

The minimization of the construction outlay and the number of different component parts, as well as the utilization of corrosion-proof materials in lightweight construction, enable very eco-nomical implementation and low maintenance costs.

The decking elements FBD300 are not bonded with the steel girders and enable a span of 1.80 m between the longitudinal girders. Thus only two longitudinal girders are necessary, which are set into the superstructure shadow and, due to dirt accumulation problems from birds, are developed as closed profile sections.

The sloping rail with the demandingly-structured handrail can be implemented optionally with lighting (neon tubes or LED).

Fig. 11: View of the new Holländerbrücke

- 11 -

Fig. 12: Sectional view of the new “Holländerbrücke”

Fig. 13: Visualization of the entire bridge with environment development

Fig. 14: Visualization of the cross-section of the bridge with integrated lighting

- 12 -

8 SUMMARY

This contribution presents the development of the new bridge deck FBD 300 for the Bridge Class 300 according to the Dutch Standard NEN 6788: 1995. The project partners Fiberline Composites A/S, Haasnoot Bruggen und Werner Sobek Ingenieure International thus extend the use of glass-fiber reinforced plastic decking for pedestrian and light traffic bridges, which has been successfully employed up to now.

The layout of a very economical bridge construction as a complete finished part is enabled by the lightweight construction method, using the combination of steel girders with attached deck-ing of glass-fiber reinforced polymer profile sections without composite action. The geometric layout of the driveway deck is implemented with special regard given to a very economical in-stallation and restraint-free supports. The FBD 300 placed throughout transfers the local traffic loads, via support spans of 1300 mm, into the main support mechanism of steel girders, which ensures the overall stiffness and load-bearing capacity.

Due to the low installation height, the static layout is implemented with a view to compliance with the maximum shear stresses in the webs. In a global analysis using a beam-grid and an ex-tended FEM analysis with orthtropic stiffness values the necessary static verification is imple-mented. The first static, three-point bending experiments give results with greater safety factors than the assumptions made.

In extended experiments on details and on the overall system, the necessary verification is carried out with regard to the fatigue reistance in an extensive test program.

The generation of the first bridge structural works with the new FBD 300 bridge deck on a steel support frame was already completed in the Netherlands in the year 2007.

In the case of the new pedestrian and cyclist bridge "Holländerbrücke" in Reinbek near Ham-burg, the new FBD300 decking element is also employed. The bridge deck with an installation height of 80 mm enables the utilization of only two longitudinal girders, which are arranged set back from the outer edge within the shadow of the superstructure. As well as enabling a very economical and durable construction, this structure provides pleasing aesthetic qualities with its filigree architecture.

9 BIBLIOGRAPHY

[1] Luke, S., Canning, L., Collins, S., Knudsen, E. Brown, P. Taljsten, B., Olofsson, I.: „Advanced Composite Bridge Decking System – Project ASSET“; Structural Engineering International, SEI Volume 12, Number 2; May 2002

[2] Beye, S.: „Entwicklung einer orthotropen Fahrbahnplatte aus pultrudierten glasfaserverstärkten Polymeren mit Hilfe der klassischen Laminattheorie“; Diplomarbeit am Lehrstuhl für Stahlbau, RWTH Aachen; Aachen 2004

[3] Puck, A.: “Festigkeitsanalyse von Faser-Matrix-Laminaten”; Carl Hanser Verlag; München 1995 [4] EN 13706: “Reinforced plastics composites – Specifications for pultruded profiles”; Part 1,2 and

3; CEN European Committee for Standardization; Brussels June 2002 [5] Sedlacek, G., Oppe, M., Trumpf, H.: „Gutachterliche Stellungnahme als Hilfestellung für eine

allgemeine bauaufsichtliche Zulassung für pultrudierte glasfaserverstärkte Langerzeugnisse aus Kunststoffverbundwerkstoffen der Firma Fiberline Composites A/S“; Lehrstuhl für Stahlbau, RWTH Aachen; Aachen 2004 – unveröffentlicht –

[6] Trumpf, H.: Stabilitätsverhalten ebener Tragwerke aus pultrudierten faserverstärkten Polymer-profilen; Schriftenreihe des Lehrstuhls für Stahlbau und Leichtmetallbau der RWTH Aachen; Shaker Verlag Heft 59; Aachen 2006

[7] BÜV-Empfehlungen: „Tragende Kunststoffbauteile im Bauwesen [TKB] – Entwurf, Bemessung und Konstruktion –“, Diskussionsentwurf; Fassung Oktober 2002

[8] Volkersen, G.. Die Schubkraftverteilung in Leim-, Niet- und Bolzenverbindungen, Energie und Technik, 1958

[9] NEN 6788: 1995: „Het ontwerpen van stalen bruggen – Basiseisen en eenvoudige rekenregels (VOSB 1995); Nederlands Normalisatie-instituut; Delft, 1995