Effectiveness of Continuity Diaphragm for Skewed Continuous Prestressed Concrete Girder Bridges Aziz Saber, Ph.D., P.E. Associate Professor Louisiana Tech University Ruston, La.

Freddy Roberts, Ph.D., P.E. Professor Louisiana Tech University Ruston, La.

Walid Alaywan, P.E. Senior Structures Research Engineer Louisiana Transportation Research Center Baton Rouge, La.

Continuity diaphragms have caused difficulties in detailing and construction when used in bridges composed of prestressed concrete girders supported on skewed bents. This study investigates the effect of full-depth continuity diaphragms on the deflection of, and stress in, skewed precast, prestressed concrete girders. Bridge models used in this study had the following parameters: girder type and spacing, bridge skew angle, span length, and diaphragm type. As either the skew angle increases or the girder spacing decreases in these types of bridges, construction becomes more difficult and the effectiveness of the diaphragms becomes questionable. If diaphragms are determined to be unnecessary as an outcome of this research, the construction and maintenance costs of these types of bridges could possibly be reduced. The objectives of this research were to determine the need for continuity diaphragms in skewed, precast, prestressed concrete girder bridges; study the load transfer mechanism through full-depth continuity diaphragms; and determine the minimum skew angle at which a diaphragm becomes ineffective in performing its function.

T Joseph Toups U.S. Army Corps of Engineers Jacksonville, Fla. 108

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he majority of highway bridges in the United States are built with cast-in-place (CIP) reinforced concrete slabs on precast, prestressed concrete girders. Composite action between the CIP concrete slab and precast concrete girders is ensured by the interface shear between the tops of the girders and the slab. Bridge design guidelines in section 8.12 of the American Association of State Highway and PCI JOURNAL

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Transportation Officials’ (AASHTO’s) Standard Specifications for Highway Bridges1 indicate that diaphragms should be installed for T-girders but may be omitted where structural analysis shows adequate strength without diaphragms. However, the design of the girders does not account for the effects of diaphragms. Continuity diaphragms cause difficulties in detailing and construction when used in bridges composed of prestressed concrete girders supported on skewed bents. As the skew angle increases or the girder spacing decreases in these types of bridges, construction becomes more difficult and the diaphragms become less effective in carrying and distributing the loads. The objectives of this research were to determine the need for continuity diaphragms in these types of bridges, to study the load transfer mechanism through full-depth continuity diaphragms, and to determine the minimum skew angle at which a diaphragm becomes ineffective at transferring and resisting loads.

Diaphragm

Bridge girder

Bridge girder

Fig. 1. Partial plan view for continuity diaphragm.

DESCRIPTION OF DIAPHRAGMS

LITERATURE REVIEW Using various analytical methods to analyze load distributions in highway bridges, the following assumptions have been made to simplify bridge modeling and to allow for a manageable solution: • Slab-and-girder bridges are assumed to be plate structures stiffened by girders; and • Orthotropic plate theory assumptions are used for bridges with closely spaced girders. Although an approach based on these assumptions has been popular in analyzing slab on girder bridges, the method has limitations in the cases of continuous and skew bridges, or bridges with diaphragms, and more elaborate methods may be necessary in such cases. Wong and Gamble3 indicate that while the diaphragms may improve the load distribution characteristics of some continuous slab and girder highway bridges that have large beam March–April 2007

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Bridge deck

Reinforcements

Bridge girder Bridge girder

Diaphragm

Fig. 2. Partial section at continuity diaphragm.

Centerline of roadway

Girders

The AASHTO LRFD Bridge Design Specifications2 defines a diaphragm as a member that resists lateral forces and transmits loads to points of support. For many years, diaphragms were believed to contribute to the overall distribution of live loads in bridges. Consequently, most bridges built in the United States have included diaphragms that are either continuous or simple. Some diaphragms are post-tensioned, while others, depending on the type of bridge, have nonprestressed reinforcement. CIP concrete diaphragms are most commonly used in prestressed concrete I-girder bridge construction. Full-depth diaphragms are terminated at the end of the sloping portion of the bottom flange, as shown in Fig. 1 and 2. Generally, the diaphragm is integrated with the deck through continuous reinforcement and tied to the girders with anchor bars (Fig. 2). For this study, the skew angle of the bridge was defined as the angle ß between the centerline of a support and a line normal to the roadway centerline, as shown in Fig. 3.

Normal to centerline of roadway

Centerline of support

Fig. 3. Bridge skew angle. 109

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Table 1. Bridge Parameters

spacing–to–span ratios, diaphragms should be eliminated from prestressed concrete I-beam bridges unless required for erection purposes. Another study investigated the effect of diaphragms on prestressed concrete slab-and-girder bridges by varying span length, skew angle of the bridge, diaphragm stiffness, and location and number of diaphragms.4 In this study, the diaphragms distributed the load more evenly, but diaphragms never significantly reduced the governing design moment for the girders. Results from research on simply supported bridges were the basis for much of the present AASHTO design criteria on live load distribution. Provisions for the design of negative moment regions were inferred from the behavior of the positive moments. Because of the difference in effective span length due to the negative moment at the interior support of a continuous bridge, a direct comparison between the results of an analysis of a simply supported bridge and a continuous bridge are difficult. Because most highway bridges are continuous, analyses of the effects of diaphragms on continuous bridges will undoubtedly provide new data as well as supplement the current data on the design of slab-and-girder bridges. Marx et al.5 developed wheel load distribution equations using finite element analysis of 108 simply supported, skewed–slab-and-girder bridges. The research included models for the concrete bridge deck and prestressed girders as an eccentrically stiffened shell assembly. Kennedy and Grace studied the effects of diaphragms in skew bridges that had been subjected to concentrated loads and concluded that diaphragms enhance the distribution of point loads.6 Nutt, Zokaie, and Schamber analyzed multigirder composite steel bridges using equivalent orthotropic plate and ribbed plate models.7 Simplified equations were developed, modified, and included in the 1994 AASHTO LRFD Bridge Design Specifications. Background information on the development of wheel load distribution factors can be found in Hays et al., Sanders and Elleby, and Stanton and Mattock.8–10 Chen studied load distribution in bridges with unequally spaced girders. AASHTO empirical formulas for estimating live-load distribution factors were compared with the results from the refined method.11 Parametric studies were conducted with a number of nonskewed, simply supported bridges that had no diaphragms. Load distribution equations were proposed. Subsequent work by Chen and Aswad12 sought to review the accuracy of the formulas for live load distribution for flexure contained in the AASHTO LRFD Bridge Design Spec-

Y

Z

B1

B2

Bridge Group

Bridge AASHTO DiaSkew Girder Span Girder phragm Angle, Spacing, ft Length, ft Type Condition Degrees II II II II II II II II IV IV IV IV IV IV IV IV

A B C D E F G H

10 10 10 10 20 20 20 20 10 10 10 10 20 20 20 20

5 5 9 9 5 5 9 9 5 5 9 9 5 5 9 9

75 75 55 55 75 75 55 55 111 111 92 92 111 111 92 92

Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No

Note: AASHTO = American Association of State Highway and Transportation Officials;1 ft = 0.3048 m.

ifications for prestressed concrete I-girder bridges. Research conclusions stated that the use of a finite element analysis led to the reduction of the live-load distribution factor in Ibeams when compared with the simplified LRFD guidelines. Tarhini and Frederick13 presented additional revisions to the load-distribution equations. Contrary to the AASHTO Standard Specifications for Highway Bridges assumptions, the finite element analysis revealed that the entire bridge superstructure acts as one unit rather than a collection of individual structural elements. Bakht reported on a simplified procedure by which skewed bridges could be analyzed to acceptable design accuracy using methods originally developed for the analysis of straight bridges.14 The study concluded that beam spacing and skew angle are important criteria when analyzing a skewed bridge. Results from error analysis using experimental data indicated that the process of analyzing a skew bridge as an equivalent straight bridge is conservative for longitudinal bending moments but not for longitudinal shear forces. Using the results from previously published experiments, Nassif and Nowak attempted to quantify the dynamic load factor (DLF) associated with the trucks available in the United States.15 The study concluded that the DLF decreases as

B3

B4

B5

B6

X G2

G3

G4

G5

G6

G7

Fig. 4. Cross section of bridge models with a 5 ft (1.5 m) girder spacing. 110

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Y B1

B2

B3

B4

X

Z

G1

G2

G3

G4

G5

Fig. 5. Cross section of bridge models with a 9 ft (2.7 m) girder spacing.

the static stress in each girder increases. The lateral stability of prestressed concrete girders was investigated by Saber in analyses for long-span, simply supported, nonskewed bridges.16 Results indicated that the AASHTO 1996 recommendations were conservative, involving T-girder construction for one intermediate diaphragm at the point of maximum positive moment of spans in excess of 40 ft (12.2 m). Barth and Bowman studied the effect of diaphragm details on the service life of bridges and found that even though some fatigue cracking might occur in certain locations, cracking did not reduce the service life of the bridge.17

analysis software, version 25. Figure 6 shows a typical girder and deck FEM configuration. The maximum aspect ratio for the FEM is four. The boundary conditions for the end and

Deck element

Eccentricity

ANALYTICAL STUDIES The objectives of the research presented in this paper were to determine the need for continuity diaphragms in skewed, precast, prestressed concrete girder bridges; to study the load transfer mechanism through full-depth continuity diaphragms; and to determine the minimum diaphragm skew angle at which a diaphragm becomes ineffective at transferring and resisting load. The bridge parameters considered in this study were based on results of a survey sent to all 50 U.S. state bridge engineers. Bridge parameters included girder type (AASHTO Type II and Type IV), bridge skew angle (10 degrees and 20 degrees), girder spacing (5 ft and 9 ft [1.5 m and 2.7 m]), span length (55 ft, 75 ft, 92 ft, and 111 ft [16.8 m, 22.9 m, 28 m, and 33.8 m]), and diaphragm conditions (full depth and without diaphragms). The bridge width and slab thickness remained constant at 30 ft (9.1 m) and 8 in. (200 mm), respectively. In evaluating the stresses and deflections in the girders, bridges were grouped based on the bridge parameters. Table 1 lists the 16 combinations of bridge configurations included in this study. For all cases, the bridge deck is continuous over the intermediate supports. For the cases in which diaphragms were not used, the bridge girder was continuous over the intermediate supports.

Space truss member Y Girder element Z

X

Fig. 6. Typical plate and girder finite element configuration.

Span 1

14 ft

36 ft

14 ft

6 ft 3 ft 6 ft

METHOD OF APPROACH

5 ft 8000 lb

Significant advances in computer technology have made finite element modeling one of the most popular methods for constructing and analyzing complex structures. The finite element models (FEM) developed in this investigation simulated the behavior of skewed continuous-span bridges. Figures 4 and 5 present the girder and diaphragm labels as used in models generated using GTSTRUDL structural design and March–April 2007

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32000 lb

Fig. 7. Placement of the axle loads on span 1 of the bridge. Note: 1 ft = 0.3048 m; 1000 lb = 4.4 kN. 111

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Table 2. Results for Comparison of Diaphragm to No-Diaphragm Models

76

A

0.4

0.1

2.8

0.1

B

1.0

0.2

0.7

0.0

C

0.5

0.0

3.5

0.0

D

1.2

0.2

0.5

0.1

152

228

60

8.8

40

5.9

20

2.9

0

0.0

-20

-2.9

-40

-5.9

Stress, ksi

Change Change Tensile CompresChange Change Stress over sive Stress Maximum Critical TenFirst Inunder Deflection, sile Stress, % termediate Truck % Support, % Load, %

Stress, MPa

Bridge Group

Distance along bridge, ft 0

-8.8

-60 0

22.8

45.6

68.4

Distance along bridge, m

E

0.3

0.0

1.0

0.0

F

0.1

0.1

0.6

0.0

G

0.3

0.1

1.0

0.0

51

7.4

H

0.6

0.0

0.3

0.0

48

7.0

45

6.6

42

6.1

39

5.7

36

5.3

33

4.8

AASHTO LRFD Bridge Design Specifications loading conditions were used in this investigation. The applied loads were dead load, HL 93 vehicular load, surcharge load for future overlays, and wind load. The location of the axle loads that would produce the maximum moment was determined based on influence line analyses, as shown in Fig. 7.

DISCUSSION OF RESULTS

30

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Stress, MPa

Effects on Maximum Stress

112

2

3

4 5 6 Girder number Diaphragm No diaphragm

Stress, ksi

7

Fig. 9. Maximum stress at the bottom of the girder, group A.

The results of all bridge configurations listed in Table 1 were examined to determine the effects of continuity diaphragms on skewed, continuous, precast prestressed concrete girder bridges.

The study of the effects of continuity diaphragms on the maximum stresses in the girders was investigated in two parts. The first part focused on the stresses in the critical girder as a function of the distance along the bridge. The maximum compressive stress in the top fiber of the girder occurred in span 1 where the applied load was placed and the maximum tensile stress occurred over the first intermediate support in the negative moment region (Fig. 7). The general behavior of stress in the critical girder for all bridge configurations followed the same pattern as the stress in the critical girder (girder 5) of group A, as shown in Fig. 8. The stress in the top fiber of the critical girder of the bridge configurations in group A is shown on the vertical

4.4 1

48

7.0

45

6.6

42

6.1

39

5.7

36

5.3

33

4.8

30

4.4

27

3.9

24

3.5

21

3.1

18

2.6

15

Stress, ksi

AASHTO Loading

Stress, MPa

intermediate support nodes for the girders were modeled as simple and continuous supports, respectively.

Fig. 8. Stress in critical girder as a function of distance, group A with diaphragm.

2.2 1

2

3 4 Girder number Diaphragm No diaphragm

5

Fig. 10. Maximum stress at the bottom of the girder, group B. PCI JOURNAL

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Span length, ft 92

111 134.9

600

112.4

400

89.9

300

67.4

200

Bridge skew angle 20

100

45.0 Bridge skew angle 10 Bridge skew angle 20

Compression force, kip

Compression force, kN

500

Bridge skew angle 10

22.5 0.0

0 28.0

34.0 Span length, m

Fig. 11. Axial force in diaphragms for bridge groups E, F, G, and H. Note: Skew angle in degrees.

axis in Fig. 8, and the distance along the span is shown on the horizontal axis. Saber et al.18 contains all the plots of the stress distribution along the girders for each bridge configuration group. Table 2 shows the percentage change in stress between each model within the bridge configuration groups. Due to the use of the continuity diaphragms, there was little difference in the magnitude of the tensile stresses. The differences in the tensile stresses between the diaphragm and the no-diaphragm conditions ranged from 0.0 ksi to 0.01 ksi (0.0 MPa to 0.07 MPa), and the maximum tensile stress increased 1.2%. Due to the use of the continuity diaphragms, the differences in the compressive stresses were less than 0.02 ksi (0.14 MPa) and the maximum compressive stress decreased 0.2%. Based on the small changes in stress in the girders, the effects of continuity diaphragms on the maximum stress in the girders were determined to be negligible. The second part of the study focused on the maximum tensile stresses over the first intermediate support in the top fibers of the critical girder. Two patterns were observed in this study. Bridge configurations with a girder spacing of 5 ft (1.5 m) (groups A, C, E, and G) followed the first pattern for the bridge configuration group A, as shown in Fig. 9. The maximum tensile stress is shown on the vertical axis in Fig. 9, and girder number is represented on the horizontal axis. The middle girder (girder 4) was the critical girder for all cases, and the tensile stresses in the remaining girders were similar in magnitude for all diaphragm conditions (approximately 7.3 ksi [50 MPa]). The second stress pattern was observed in the bridge configurations with girder spacing of 9 ft (2.7 m), groups B, D, F, and H, as shown in Fig. 10. The maximum tensile stress is shown on the vertical axis of Fig. 10, and the girder number is shown on the horizontal axis. The critical girder for all diaphragm conditions was girder 3, which was located in the center of the bridge configurations. The tensile stresses in each of the girders were similar in magnitude for all of the diaphragm conditions. March–April 2007

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As shown in Fig. 10, the tensile stresses over the first intermediate support behaved as expected for all diaphragm conditions, with the critical stresses occurring in the center girder. The tensile stresses in the top fibers of the girders over the first support for all diaphragm conditions were of the same magnitude (about 6.5 ksi [45 MPa]). Saber et al. contains the graphs of the maximum tensile stress in the girder top fibers for all of the bridge configuration groups. Again, Table 2 shows the percentage change in maximum tensile stress between each model within the bridge configuration groups. Bridge configurations with a 5 ft (1.5 m) girder spacing (groups A, C, E, and G) with or without a diaphragm had critical tensile stresses in girder 4. The maximum tensile stress for bridges with a diaphragm increased 3.5% compared with the no-diaphragm condition. Bridge configurations with a 9 ft (2.7 m) girder spacing (groups B, D, F, and H) had critical stresses in girder 3. The maximum tensile stress for bridges with a diaphragm increased 0.7% compared with the no-diaphragm condition. Again, the effects of continuity diaphragms on the maximum stress in the girders were determined to be negligible. Effects on Maximum Deflection The bridge configurations listed in Table 1 were evaluated to determine the effect of continuity diaphragms on deflection. The behavior of the girder deflections for all of the bridge configurations was as expected: the maximum deflection occurred in span 1 near the truck axle loading. Table 2 presents the percentage change for deflection data between each model within a bridge configuration group. As the diaphragm condition changed from the skew condition to the no-diaphragm condition, the maximum increase in deflection was 0.1%. This suggested that continuity diaphragms did not contribute to reducing girder deflection. Therefore, the effects of continuity diaphragms on the maximum deflection of the girders were determined to be negligible. Effects of Skew Angle on Axial Force in the Continuity Diaphragms The axial forces in the continuity diaphragms for all bridge configurations listed in Table 1 were evaluated to determine the minimum diaphragm skew angle at which a diaphragm becomes ineffective. The results of the analyses that were performed indicated that for AASHTO’s critical loading condition, Strength I Maximum, the axial force in the diaphragm decreased as the skew angle increased. Results for the bridge configuration groups E, F, G, and H considered in this study are presented in Fig. 11. Based on the analyses in this study, it can be concluded that a continuity diaphragm with a skew angle larger than 20 degrees will be ineffective in performing its function.

CONCLUSIONS AND RECOMMENDATIONS This study investigated the load transfer mechanism through full-depth continuity diaphragms. The effect of continuity diaphragms on the maximum stress in the girders and maximum deflection of the girders was negligible. This 113

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indicated that continuity diaphragms could be eliminated from skewed, continuous, precast prestressed concrete girder bridges. Thus, continuity diaphragms are ineffective and full-depth diaphragms are not needed to control deflections or reduce member stresses but may be needed for construction, lateral stability during erection, or resisting/transferring earthquake or other transverse loads. The theoretical results of this investigation were based on finite element analysis to determine the effects of full-depth continuity diaphragms for skewed, continuous, precast prestressed concrete girder bridges. Based on the study of the load transfer mechanism through full-depth continuity diaphragms, it is recommended that laboratory tests and field measurements be compared with the theoretical results. Further research is needed to instrument similar bridges, perform field load tests, and compare measured strains and deflections with data reported in this study. The outcome of this research has the potential to reduce the construction and maintenance costs of bridges throughout the United States.

ACKNOWLEDGMENTS Support for this work was provided by the Louisiana Transportation Research Center under research project number 011ST and state project number 736-99-0914. The contents of this study reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein. Study conclusions do not necessarily reflect the official views or policies of the Louisiana Department of Transportation or the Louisiana Transportation Research Center. This paper does not constitute a standard, specification, or regulation. The assistance provided by the Civil Engineering Program at Louisiana Tech University is gratefully acknowledged and appreciated.

REFERENCES 1. American Association of State Highway and Transportation Officials (AASHTO). 1996. Standard Specifications for Highway Bridges. 16th ed. Washington, DC: AASHTO. 2. AASHTO. 1994. AASHTO LRFD Bridge Design Specifications. 1st ed. Washington, DC: AASHTO. 3. Wong, A., and W. Gamble. 1973. Effects of Diaphragms in Continuous Slab and Girder Highway Bridges. Civil Engineering Studies Structural Research Series No. 391. Urbana, IL: University of Illinois. 4. Sengupta, S., and J. E. Breen. 1973. The Effect of Diaphragms in Prestressed Concrete Girder and Slab Bridges. Research Report 1581F. Austin, TX.: Center for Highway Research, University of Texas at Austin. 5. Marx, H. J., N. Khachaturian, and W. L. Gamble. 1986. Development and Design Criteria for Simply Supported Skew Slab-and-Girder Bridges. Civil Engineering Studies Structural Research Series No. 522. Urbana, IL: University of Illinois. 6. Kennedy, J. B., and N. F. Grace. 1983. Load Distri114

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bution in Continuous Composite Bridges. Canadian Journal of Civil Engineering, V. 10: pp. 384–395. 7. Nutt, R.V., T. Zokaie, and R. A. Schamber. 1987. Distribution of Wheel Loads on Highway Bridges. National Cooperative Highway Research Program Report (NCHRP) No. 12-26. Washington, DC: Transportation Research Board, National Research Council. 8. Hays, C. O., L. M. Sessions, and A. J. Berry. 1986. Further Studies on Lateral Load Distribution Using a Finite Element Method. Transportation Research Record No.1072, pp. 6–14. Washington, DC: Transportation Research Board. 9. Sanders, W. W., and H. A. Elleby. 1970. Distribution of Wheel Loads on Highway Bridges. National Cooperative Highway Research Program Report No. 83. Washington, DC: Highway Research Board. 10. Stanton, J. F., and A. H. Mattock. 1986. Load Distribution and Connection Design for Precast Stemmed Multibeam Bridge Superstructures. National Cooperative Highway Research Program Report No. 287. Washington, DC: Transportation Research Board. 11. Chen, Y. 1995. Refined and Simplified Methods of Lateral Load Distribution for Bridges with Unequally Spaced Girders: I. Theory and II. Applications. Computers & Structures, V. 55, No. 1: pp.1–32. 12. Chen, Y., and A. Aswad. 1996. Stretching Span Capability of Prestressed Concrete Bridges under AASHTO LRFD. ASCE Journal of Bridge Engineering, V. 1, No. 3: pp. 112–120. 13. Tarhini, K. M., and G. R. Frederick. 1995. Lateral Load Distribution in I-Girder Bridges. Computers and Structures, V. 54, No. 2: pp. 351–354. 14. Bakht, B. 1988. Analysis of Some Skew Bridges as Right Bridges. ASCE Journal of Structural Engineering, V. 114, No. 10: pp. 2307–2322. 15. Nassif, H. H., and A. S. Nowak. 1995. Dynamic Load Factor for Girder Bridges. Transportation Research Record No. 1476. Washington, DC: National Academy Press. 16. Saber, A. 1998. High Performance Concrete: Behavior, Design and Materials in Pretensioned AASHTO and NU Girders. Ph.D. diss. Georgia Institute of Technology, Atlanta, GA. 17. Barth, A. S., and M. D. Bowman. 1999. Fatigue Behavior of Intermittently Welded Diaphragm-toBeam Connections. In Structural Engineering in the 21st Century: Proceedings of the 1999 Structures Congress, April 18–21, 1999, New Orleans, Louisiana, ed. R. Richard Avent and Mohamed Alawady, pp. 805–808. Reston, VA: American Society of Civil Engineers. 18. Saber, A., J. Toups, L. Guice, and A. Tayebi. 2003. Continuity Diaphragm for Skewed Continuous Span Precast Prestressed Concrete Girder Bridges. LTRC project no. 01-1ST and state project no. 736-99-0914. Baton Rouge, LA: Louisiana Department of Transportation and Development and Louisiana Transportation Research Center. PCI JOURNAL

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Mark Your Calendar for the

National Bridge Conference October 22 – 24, 2007 Hyatt Regency Phoenix/Phoenix Civic Plaza Convention Center, Phoenix, Ariz. Cosponsored by the Precast/Prestressed Concrete Institute and the Federal Highway Administration • Featuring the Arizona Department of Transportation

Bridges For LIFE® Featuring High Performance Bridges The PCI National Bridge Conference (NBC) is the premier national venue for the exchange of ideas and state-of-the-art information on concrete bridge design, fabrication, and construction—particularly for precast, prestressed concrete bridges. Concrete continues to grow as the material of choice for the nation’s bridges. The continued interest in high-performance concrete and the growing excitement about methods for rapid construction promise to fuel this growth even more and dictate the need for this conference. Public agencies and industry have joined forces and are committed to bringing together the nation’s most experienced, expert practitioners. Experience has shown the value of technology transfer that takes place at the National Bridge Conference. The NBC will be held in conjunction with the PCI Annual Convention and Exhibition.

Pre-Conference Sunday, October 21 A 60,000-square-foot exhibit hall opens with a grand reception. This year’s “Spotlight State,” the Arizona Department of Transportation, is featured here and in the technical sessions. Exhibitors display the materials, supplies, services, and consultants used in all facets of the industry. PCI’s active and historic Committee on Bridges continues its exciting program during an all-day meeting, which NBC registrants are invited to attend. The meeting is a premier venue for the discussion of timely technical topics on the AASHTO Design Specifications and issues facing all designers. Numerous sub-committees will also meet to continue work on new technical publications and on solutions to design challenges.

209 West Jackson Boulevard I Suite 500 I Chicago, IL 60606 Phone: 312-786-0300 I Fax: 312-786-0353 I www.pci.org

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Conference Schedule Monday, October 22 Keynote Address General Session Afternoon “Spotlight State” Plenary Session Concurrent Afternoon Technical Sessions Tuesday, October 23 Concurrent Morning Technical Sessions Afternoon Technical Sessions Meeting of the AASHTO Technical Committee on Concrete Design Wednesday, October 24 Concurrent Morning Technical Sessions

Social Events and Gatherings Throughout the event, you’ll have ample time to network with colleagues and establish or renew acquaintances. Social events include an opening reception gala, lavish buffet luncheons sponsored by our exhibitors, and a dinner/dance banquet. Above all, you’ll have the opportunity to immerse yourself in the state-of-the-art of concrete bridges. An exciting program of tours and activities for accompanying guests is also available.

Special Bonus Those registering for the National Bridge Conference also have the opportunity to participate in all the exciting educational sessions of the PCI Annual Convention and Exhibition.

Call for Papers PCI is currently accepting submissions for the NBC program, which will include approximately 11 technical sessions comprised of 44 papers, plus an additional session with papers devoted to the “Spotlight State” of Arizona. Conference proceedings will be provided to all registrants on CDROM and will also be available to others following the event.

Suggestions for topics of interest include: • Beams with Integral Decks • Bridge Aesthetics, Coatings, and Colors • Bridge Repair and Rehabilitation • Creative Concrete Bridge Solutions • Contractor Alternates, Value Engineering, and Design-Build • Designing and Retrofitting for Seismic Forces • Designs to Facilitate Fast Construction • Hauling and Transporting Studies • High Performance Concrete/High Performance Solutions • Innovative Concrete Bridges • LRFD Issues, Research, and Monitoring • Materials—SCC, Light Weight, High Strength • Plant Forming/Production Reports • Post-Tensioning Technology/Applications • Precast Bridge Decks • Precast Substructures • Project Case Studies • Research in Action • Spliced Girder Solutions A technical committee will review submissions. Abstracts must be no longer than one, double-spaced, typewritten page and must adequately describe the topic. It must state the author’s willingness to present the paper at the National Bridge Conference if the reviewers choose the paper. If multiple authors are listed, the statement must identify the presenter. The deadline for receipt of abstracts is April 6, 2007. Abstracts should be submitted electronically according to the instructions at www.pci.org. Selected authors will be notified April 18, 2007, and final written papers are due July 2, 2007. Requirements for papers can be found at www.pci.org. For more information, contact John Dick; Tel.: (312) 360-3205; Fax (312) 786-0353; or Email: [email protected].

U.S. Department of Transportation Federal Highway Administration

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