State-of-art of asphalt surfacings on long-spanned orthotropic steel deck in China

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State-of-art of Asphalt surfacings on long-spanned orthotropic steel deck in

China

Xianhua C H E N ' , Xueyan Liu^, Zhendong Qian^, Zhang Lei^ 1 School of Transportation, Southeast University, Nanjing, China, 210096

2 CITG, T U Deft, Delft, the Netherland, CN2628 3 ITS Center, Southeast University, Nanjing, China, 210096

Abstract: Reliable and durable asphalt surfacing systems still remain to be desired for the long-spanned orthotropic

steel bridges as the nationally and internationally reports on distresses in deck pavement. Based on ten-year research

works, this paper has presented a brief review and discussion of the Chinese practices and experiences of deck

pavement on long-spanned steel bridges, including issues of typical surfacing materials and their properties, main

distresses in asphalt surfacing, and the basic characteristics o f asphalt surfacing on orthotropic steel bridge decks. It is

concluded that the behaviours of deck pavement on oithotropic steel bridge deck under truck load are coinplex

contributed by geometric and material-dependent nonlinearity, coupling the global dynamic effects of the whole

bridge systems. More efficient computational techniques are still desirable to couple global effects into local

responses, to count the interfacial effects and interaction, and to evaluate the effect of predominant distress of fatigue

cracking and de-bonding on the service life of this type of structure.

Keyword: long-spanned steel bridge, orthotropic steel decks; asphalt surfacing system, local deflection behaviour;

composite action; fatigue cracking

1 Introduction

Orthotropic steel deck systems with cross-beams and longitudinal ribs have been widely used in modern

long-span bridges to reduce the weight and depth o f the girders[l]. The oithotropic steel deck plate of highway bridges

requires a wearing surface for skid resistance, for smooth riding, and for corrosion protection. The wearing surface is

subjected to the heavy impact of loaded truck wheels imposed by the passage of millions of ti'ucks during the several

decades of its service life, acts as skid-resistant pavement for the vehicles and, as well as load-spreadmg layer and corrosion protecting layer for the steel superstructure. It should be watertight, resisting cracks and well bonded to

steel deck plate, besides provide a smooth riding surface with high skid resistance for the vehicles passing through the

bridges[2].

Bituminous materials such as gussasphalt or mastic asphalt, epoxy asphalt concrete and Stone Matrix Asphalt

have adopted as the surfacing materials for a long-time as due to their flexibility, deformation compliance and good

water resistance. However, premature distress of asphalt surfacing have been frequently reported world-wide within recent twenty years, such as cracking of steel deck plates, rutting and cracking of asphalt surfacing materials, loss of

bond between the surfacing layer and the steel bridge decks. The severity o f the problems is enhanced by the

considerable increase in traffic in terms of number of trucks and heavier axle loads. Asphalt surfacing acts

compositely with the steel deck plate by the bonding membrane and must be regarded as an integral part of the

structural deck system [3]. A better understanding of the behaviour and the interaction of the surfacing layers and the

steel decks are of paramount importance for the effective design of steel bridges. Innovative methodologies offer

' Corresponding author: Xianluia CHEN(1976-), Ph.D, Associate Professor, Tel.: +86 25 837 90522, Email: chenxhfg.seu.edu.cn Foundation Item: project(50908053) supported by National Natin-al Science and Foundation of China.

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opportunities to mitigate material response degradation and fatigue related problems in this type o f structures

contributing thus to significant extension of the service life of steel bridges.

In this paper, consideration is given to the requirements for a bright future for the asphalt surfacing on orthotropic

steel bridge decks by carefully analysing recent trends. The state of the art o f asphalt surfacing system, and the

considerations towards a bright future in Chinese long-spanned steel bridge construction could be useful also to

various other countries, in particular, countries with heavy duty traffic and long-spanned orthotopic steel bridges.

2. Asphalt surfacing on orthotropic steel bridge in China

2.1 Long spanned steel bridge with orthotropic deck plates

The application of orthotropic steel deck plate in highway bridges in China can be dated back to 1970s. However,

great achievements have been accomplished within twenty years after Xiling Yangtze River Bridge. More than

twenty long-spanned steel bridges with orthotropic deck plates have been constructed to meet the requirements of

rapid economy developments and travel demands.

Table L Cable-supported steel bridges in the mainland of China

Year Main steel box-girder _deck trapezoidal ribs _original

Bridge Name _span

(m) length (m) height (m) width (m) plate

(mm) rib wall _(mm) depth _(mm) width at top rib spacing _{(mm) (mm)}rib span _(m)

deck pavement Taizhou Under constr. 1080x2 2160 3.5 39.1 14/16 6/8 280 300 600 3.2 Xilioumen* 2009 1620 2220.8 3.51 36 14 8 280 300 600 3.6 Figlb OT <U Zhujiang Huangpu 2008 1108 1108 3.5 38.6 16 8 280 300 600 3.2 Figlb brid g Runyang-South 2004 1490 1490 3 38.7 14/12 6 280 300 600 3.22 Figlb pensio n Yichang Yanbtze 2001 960 1187 3 30 12 6 280 300 590 4.02 Figlc 3 Haicang 2000 648 2000 3 28.8 12 6 280 300 600 3.5 Figlc Jiangyin 1999 1385 1385 3 36.9 12 6 280 300 600 3.2 Figla Humen 1997 888 1997 3 33.6 12 8 260 320 620 4 Fig2c Xiling 1996 900 900 3 21.4 12 6

_-

320 640 2.54 Edong 2010 926 901 3.8 38 16 8 300 300 600 3.0 Figlb Jingyue 2010 816 1204 3.8 38.5 14/16 8 300 300 600 3.0 Figlb bridge s _Minpu*** ₂₀₁₀ ₇₀₈ ₇₀₈ ₉ _{43.6/27 14/16} ₈ ₃₀₀ ₃₆₀ ₇₀₀ _15.1 _Figlb bridge s Shanghai Yangtze 2009 730 1430 4 51.5 16 8 300 300 600 3.75 Figlb

•a _Jingtang ₂₀₀₉ ₆₂₀ ₁₂₁₀ ₃ _30.1 ₁₄ ₈ ₂₈₀ ₃₀₀ ₆₀₀ _3.5 _Figlb

Cable-st i Sutong 2008 1088 2088 4 41 16/14 8 300 300 600 4 Figlb Cable-st i 3rd Nanjing 2005 648 1288 3.2 37.2 14/16 8 280 300 600 3.75 Figlb Cable-st i 2nd Nanjing 2001 628 1238 3.5 37.2 14 6 280 300 600 3.75 Figlb Bashazhoii 2000 618 904 3 30.2 12 8 260 320 640 6** i M g l c * 1. Twin-box gu^der;

**2. With a hansverse rib in between two adjacent cross-beams;

***3. a.) Mam ghder is truss beam with double decks for highway traffic; b.) With three transverse ribs in between two adjacent cross-beams;

The deck system of long-spanned steel bridges in China normally consists of a deck plate, 12-14 mm thick and

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in Table 1. The steel decks are sand-blasted and then coated with zmc primer and waterproof membrane /bonding

coat prior to the construction of 50-80 mm thick asphah surfacing layers. In order to minimize the fatigue problems

of the superstructure, the deck plate at outside lane of the newly built bridges is thickened even up to 16mm or 18mm.

2.2 Typical structure of deck pavements on orthotropic deck plates

Typical structures o f deck pavement used m China are shown as in Fig. 1. Gussasphalt or Mastic Asphalt(MA),

Epoxy Asphalt Concrete(EAC) and Stone Matric Asphalt(SMA) are the commonly candidate surfacing materials for

those steel bridges. Their properties are also different, as illustrated in Table 2 according to the research results of

Southeast University[4].

30-«liiIii SM witli SBS

a) Gussasphalt b)epoxy asphalt concrete c) Stone Matrix Asphalt

Fig. 1 Typical structures of deck pavement used in China

Table 2 Propeities o f asphalt surfacing materials used in China

Properties SMAIO GA EAC

Binder content 6.2 8.2 6.1

Air Void/% 3.0 0.6 2.2

Marshall Stability 10 -- 58

Dynamic Stability(60°C,0.7MPa, i:^-mm ') 4846 1276 17671

Flexural strength(-15°C,lmm/min, MP a) 10.31 13.72 24.18

Flexural strain(-15°C,lmm/min, 10'^) 3.09 8.26 3.72

TSR(%) 88.3 95.7 91.8

Expansion at 15°C~-15°C(10-^°C"') 2.25 2.14 1.52

EAC is a thermo-set material by using a reaction-curing material o f epoxy asphalt which will not inelt or soft under

70°C temperatures, which has been ineasured on orthotropic deck pavement in 2nd Nanjing Bridge. EAC is proved to

be the super durable surfacmg material for heavy duty traffic and extremely high temperahare, and now it is widely

used in China although its construction cost is 2-3 times that SMA. M A are demonstrated suitable for long-spanned

suspension bridges for a better flexibility, compliance and water resistance. The binder of M A are normally Pmb 25

with a soft point higher than 85 °C or straight hard bitumen with penefration grade of 30-40. The blend of natural lake

asphalt is about 10% to 40% dependent on the durability requirements. Warm mixing additive such as organic

polymer wax is also adopted to decrease the viscosity for the purpose of construction.

3 The performance of typical asphalt surfacing system in China

The performances of asphalt surfacing on steel bridge decks in Chhia vary from excellent to poor depending

largely on local climate, deck plate flexibility, volume of heavy truck traffic, and the type and sftucture of the

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In general, comparing witli the M A and SMA systems, the performance and condition of EAC systems is better and

its mean service life is much longer than other systems.

3.1 Fatigue Cracking

Fatigue cracking has been recorded in all type of pavement on orthotropic steel bridges decks. These cracks are

located on the surface of the pavements near the conjunction ribs of the longitudinal and transverse stiffeners. The

cracks were observed to propagate in depth and in length fustly, several weeks later, a second parallel longitudinal

cracks could be initiated i f the original one be not been sealed or repaired on time. And alligators or block crackmg will be inevitable within several months, as shown in Fig. 2.

over crossbeam Propagate in Length

Fig. 2 Fatigue Cracking and the propagation of pavements on orthotropic steel decks

3.2 disintegration of slippage and de-bonding

Slippage of deck pavements were mainly observed in the surfacing system of SMA and M A at hot summer. The U

-shaped cracks occur with the corrugation and shoving of the pavement. The cracks generally have a width o f 2 cm to

10 cm covering at least lane, as shown in Fig. 3.

Fig. 3 Slippage cracking of SMA asphalt layer

Localized de-bonding has also been observed in the surfacing system of gussasphalt and SMA as shown in Fig. 4.

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penetrate down to steel deck plate surface. Experiences also indicate that large area of the pavements will soon fail

once the deck pavements system loses bond strength at the interface.

Fig. 4 Debonding at the interface of asphalt surfacing and steel bridge decks

3.3 Rutting, shoving and corrugations

Rutting, shoving, and corrugations are common distresses o f the surfacing systems with thermal-plastic bmder

such as M A and dense graded asphalt concrete with polymer modified asphalt. Severe rutting has also occurred in the surfacmg system of SMA. These problems could become even worse as the occurrence of fatigue cracking, the rapid

increase of heavy duty traffic and the absence of efficient fighting against overloadmg, despite of higher performance

grade polymer modified asphalt was adopted or natural hard asphalt was blended.

3.4 Bubbles and hair cracks

Bubbles and irregular micro-cracks were mostly found in the surfacing system o f EMA. The bubble can be easily

recognized with two or thi-ee radial micro-cracks as shown m Fig. 5. A ring crack of 15cm to 30cm in diameter w i l l

then develop withm several weeks i f the bubble crack be not properly repaired and sealed, and consequently, a

pothole will form from bubbles as shown in Fig. 5.

Fig. 5 Bubble cracking and development of pothole

hregular micro-cracks have also been observed on the surface o f EAC with a length of 5cm to 15cm, as shown in Fig. 6. This type o f cracks may be a conhibution of differential construction temperature and compaction, and

chemical reaction between the cure agent and epoxy resin. However, the real reason is still unknown to us as no visible feature could be summarized.

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Fig. 6 Irregular micro-cracks in E A C

4 The behaviours of Asphalt surfacing on orthotropic steel bridge decks

4.1 general analysis

Considering tiie overall behaviors, the complex stress field in the surfacing o f an orthotropic deck is the result o f

three actions[3]: (1) Prknary stresses arismg fi'om the mam gh-der effect. These membrane stresses are due to the

bending o f the main girder, when the orthotropic deck is simply considered as the upper flange; (2) Secondary

stresses arising fi'om the distribution o f the loads correspondmg to the rigidities o f the ribs and cross beams; (3) Tertiary stresses arising from the local bending of the isoft-opic deck plate under dhect wheel loading. To include the

global effects o f the cable-supported system and the mam girders, a multi-scale approach[7] has been proposed

recently by the research group o f Southeast University, as illustrated in Fig. 7. A 10 to 20 percentage o f increase in

maximum transverse tensile stress has been reported according to the analysis of Taizhou Bridge[8].

levels

Fig. 7 A multi-scale approach to simulate the behaviours asphalt surfacing on orthotropic steel bridge decks[7-8]

4.2 Local responses of asphalt surfacing on steel bridge decks

The behavior o f paved steel orthotropic decks under heavy truck traffic and envkomnental conditions is veiy

complex with localization characteristics, and dependent on the geometry o f the decks, the wheels position, wheel

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obtained are strongly dependent on the geometric configuration of the deck, position of the wheels, and composite

contribution of the surfacing and other uncertain factors [9].

4.2.1 Wheel load positions

One of the characteristics of orthotropic bridge decks is the relatively large local deflection caused by the passage

of fruck wheel loads, as shown in Fig. 8. The transverse stress response o f a typical orthotropic deck with varies load

positions are shown in Fig. 9. Load case I (dual-tyre crawls on one rib) and load case I I (dual-tyre crawls on one webs

of a rib) are critical position, under which larger local displacement and transversal tensile stress will occur, and in particular, for negative bending in load case I I . Critical points under different load case with large tensile sti'esses are

shown as in Fig. 10 with red circle marks. Transverse tensile stress occurs at the top of pavement over webs of ribs

adjacent to wheel load, and for longitudinal tensile stress, the max value occurs at the top of pavement over webs of

diaphragms near to wheel load.

load c a s e : I I I

1.1111 H i l l

U U U I W W U

Fig. 8 Vertical displacement of deck pavement under dual-wheel load

load c a s e ; I I I

U

'U'

U I W

0 ""

W

I W

J"U

V

Fig. 9 Transverse Stress of deck pavement under dual-wheel load

J 0 . 3 0 5 0. : o E I 0. 10 E 0 . 0 0 £ 0 . 7 0 S 0 . 6 0

I

0 . 5 0

I

Q.W

I

" - S O c 0 . 2 0 : 0 . 1 0 g 0 . 0 0 r: 0 . 2 5 c-Z •J. 0 . 2 0

i

• J 0. 15

I

0 . 1 0 I 0 . 0 5 Ê 0 . 0 0 ' t i a i i ï v e n a l - lonojtudinal 0 50 100 150 200 250 D i s t a n c e to t h e iieai-est d i a p h g i - a i i i , c n i 0 50 100 150 200 250 D i s t a n c e t o tlie n e a r e s t d i a p h g r a m . c m 0 50 100 150 20O 250 D i s t a n c e t o t h e n e a r e s t d i a p h g r a m . c m

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4.2.2 load effects

As equivalence of multi-axle loads into standard single axle load is a key aspect in pavement design, CHEN and

Qian[10] investigated the equivalent factors o f multi-axle loads for pavement on steel bridge decks through the

concepts o f axle interaction factors and dissipated energy based on fatigue equivalence principle. The responses o f

asphalt pavements on orthotropic bridge decks under single, tandem axle and tri-axles were sunulated with 3-D FEM.

The time history stress response with varied adjacent axle distance has been calculated as shown m Fig. 11. The

effect o f adjacent axle on the stress responses can be negligible when the adjacent axle distance o f a multi-axle is

great than half span o f longitudinal ribs. Three composite beams samples composed o f epoxy asphah concrete and

steel plate were loaded with the simulating block loads. The dynamic responses o f composite beams were measured

and the dissipated energies o f epoxy asphalt concrete were calculated with measured shess-strain hysteresis loops,

shown as in Fig. 12. Equivalent factors o f multi-axle loads were determined with interaction factors o f different axles

and their dissipated energies as 1.39 and 1.86 for tandem axle and tri-axle respectively.

2 " axle

-0.1 L

Time, X 0.078s

Fig. 11 Time history stress response with varied adjacent axle distance

single axle tandem-axle tri-axle

Fig. 12 Energy dissipation of standards single axle and multi-axle loads in composite beam fatigue test

4.2.3 Temperature effects

Asphalt surfacing, whether theiTnal-plastic materials as SMA or M A , or thermal-setting materials as EAC, are

temperature dependent materials. With temperature changes fi-om high temperature to low temperature, the modulus

of asphah matenals decreases as tested by Xianhua CHEN[11]. Transversal tensile stress, which causes longitudmal

cracks is dominate stress at room temperature to high temperature. However, numerical results reveal that

longitudinal tensile stress becomes critical at low temperature, which w i l l contribute to transversal cracks, as shown

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J ^ 4000 3 s i a l i c l o a d i i i : 20 40 Temperature, "C 200 400 600 Modulus Ratio(Steel/H\lA)

Fig. 13 Temperature effect on modulus of E A C and the maximum tensile stress of E A C system 4.3 Interaction between E A C and steel deck plates

Focuses have been made to the mteraction between asphalt surfacing layers and orthotropic steel bridge decks as

it is also a key factor to the responses of asphalt surfacing layers, as well as to the orthotropic steel decks. As the behaviour o f EAC is to some degrees different with M A and SMA, and the bonding membrane of epoxy asphalt is

totally different with the membrane of rubberized asphalt or mastic asphalt, CHEN and HUANG[11] explore the

interaction of epoxy asphalt surfacmg system hi laboratory. They adopted an equivalent simply supported beam

loaded at mid-span to characterize the local hog moment o f surfaced orthotropic deck plate under a double-wheel

load at the critical position. Strain distributions along thickness o f the composite beam were tested and the results at

room temperature are shown as in Fig. 14. A new model to describe interface behaviors of simply supported

composite beams was developed by defining a parameter named of bonding membrane stiffiiess incorporated with the

classic linear-elastic partial interaction theory[12]. A simple mathematical procedure was developed and verified to

predict the flexure responses of the beam.

-500 0 500 1000 1500 2000

compressive tensile .Moasureed s t r a i n (p £ )

Fig. 14 Test set-up of composite beam and the strain distribution of E A C composite beam specimen

5 Conclusion

This paper presented state of the art o f asphalt surfacing on long-spanned orthotropic steel bridge decks. Issues of

typical surfacing materials and their properties, mam disfresses in asphalt surfacing, and the basic characteristics of

asphalt surfacing on orthotropic steel bridge decks have been overviewed. The behaviours of deck pavement on

orthoh-opic steel bridge deck under truck load are complex contributed by geometric and material-dependent

nonlinearity, couplmg the global dynamic effects of the whole bridge systems. More efficient computational

techniques are still desirable to couple global effects into local responses, to count the interfacial effects and hiteraction, and to evaluate the effect of predominant distress of fatigue cracking and de-bonding on the service life o f

this type of structure. A successful deck pavement design should be based on sufficient understanding the shuctural

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pavement design into superstructure design of the bridges. In addition, improvement of the integral performance of

deck pavement, paying much attention to the aspects of construction and ensuring the designed inaterials to be

constructed with designing specification are all important factors to lead to a successftil deck pavement project.

State-of-art of asphalt surfacings on long-spanned orthotropic steel deck in China