Precast Prestressed Concrete Short Span Bridges

precast prertrerred concrete

5HORT )PP\N BRI DOU

r.pam ‘to 100 feet

Introduction BRIDGE CLOSED! A sad sign for any traveler. Do you have any such signs in your part of the country? There are more than 600,000 bridges on highways, roads, streets, and railways in the United States and Canada. Two-thirds of these are located on county, secondary, municipal, and rural roads. It has been estimated that there are 133,000 structurally deficient and functionally obsolete bridges of which 117,000 are on roads maintained by counties and other local jurisdictions. Precast prestressed concrete INTEGRAL DECK COMPONENTS offer a unique solution for replacing or widening deficient existing bridges or constructing new ones. LOCALLY MANUFACTURED prestressed concrete efficiently combines very high strength steel with high strength concrete to produce a quality structural component at low cost. Prestressed concrete bridges have proven to be low in first cost, low in maintenance, high in durability and fire resistance, and they have good riding characterisitics.

Precast concrete bridges can be installed during all seasons and opened to traffic MORE RAPIDLY than any other permanent type of bridge. In addition, their low depth-to-span ratios and clean, attractive lines, help bridge designers meet the most demanding environmental requirements. The precast integral deck sections illustrated and described in the following pages make good sense for bridge construction anywhere. The purpose of this booklet is to help in the selection of the best solution to bridge problems for spans up to 100 ft.

WEIGHf LIMITS ONTHIS BRIDGE GROSS WEIGHT

SINGLE TRUCK TRUCK AND SEW-TRAILER TRUCK AND TRAILER 0

TONS TONS TONS

Wide use and acceptance Prior to 1950 there were no prestressed concrete bridges in America. Thousands of prestressed bridges have now been built and many more are under construction in all parts of America. They range in size from short span bridges to some of the largest bridge projects in the world. The design of prestressed concrete bridges is covered by AASHTO and AREA specifications. Precast prestressed concrete bridges have gained wide acceptance because of: 1. Proven economic factors: a. b. c. d.

low initial minimum fast easy minimum

cost maintenance construction traffic interruption

2. Sound engineering reasons: a. b. c. d.

simple design minimum depth-span ratio assured plant quality durability

3. Desirable esthetics - precast prestressed bridges can be designed to be very attractive.

_,-__

_.. _.

.’

.a...

Low initial cost Bridge designers are often surprised to learn that precast prestressed bridges are usually lower in first cost than other types of bridges. Coupled with savings in maintenance, precast bridges offer maximum economy. An old bridge located on a main logging road in Idaho was replaced with the prestressed concrete bridge shown in the photo immediately below. The bridge consists of integral deck beams on precast concrete abutments and wing walls. The heavy spring runoff dictated the need for a shallow superstructure and the load capacity of the bridge had to be sufficient to carry off-highway logging trucks which weigh as much as 110 tons each. The precast prestressed bridge system offered

two principal advantages: it was economical and it provided minimum downtime for construction. Project duration was three weeks including one week lost due to bad weather. In another case, the City of Tulsa saved money by replacing a collapsed steel truss and wood deck bridge with the prestressed concrete bridge shown immediately below. The city engineer stated, “The total cost of this bridge was half the cost of replacing it with a steel truss and wood deck bridge.” Similar cases can be cited at locations throughout America, and the resulting bridges are economical as well as attractive as evidenced by the three bridges shown below.

Minimum maintenance

On the Illinois Toll Highway, the superstructures of 224 bridges are precast prestressed concrete beams. These bridges, built during 1957 and 1958 have withstood heavy traffic and severe weathering and yet require practically no maintenance. Other projects in all parts of North America have exhibited similar experience - little or no maintenance has been required on precast prestressed concrete bridges. The overall economy of a structure is measured in terms of its life-cycle cost. This includes the initial cost of the structure plus the total operating cost. For bridges, the operating cost is the maintenance cost. Precast prestressed concrete bridges de signed and built in accordance with AASHTO or AREA specifications should require very little, if any, maintenance. Because of the high quality of materials used, prestressed members are particularly durable. Fatigue problems are minimal because of the minor stresses induced by traffic loads. Of course, no painting is needed. Some bridge engineers estimate the life-cycle cost of re-painting steel bridges to be 10 to 2096 of the initial cost. Painting bridges over busy highways, overstreams, or in rugged terrain is especially expensive. One of the reasons for selecting integral deck prestressed concrete for the two bridges shown be low was low maintenance.

i

Fast easy construction Precast prestressed concrete bridge components are easy to erect, particularly when the tops of the units form the entire deck slab (integral deck component). Formwork of the superstructure is eliminated. Connections between the deck elements and the substructure are simple. Connections between adjacent units often consist of welding matching plates and grouting the keyway. Carefully planned details speed the construction process and result in overall economy. An example: August 13: A steel truss bridge south of Creston, Washington, collapsed under the load of a harvest truck. August 74: The County Engineer decided to replace the bridge quickly with 60-ft precast prestressed concrete integral deck components and precast concrete abutments and wingwalls. August 75: While plans were being prepared for the new bridge, the old one was being removed. August 20: Shop drawings were approved by the County Engineer. August 27: First deck unit was cast and preparations made for precasting the substructure units. August 30: Precast abutments and wingwalls were delivered to jobsite, placed on temporary footing pads, and the footings were poured encasing the reinforcement protruding from the precast units. (Photo, upper right)

August 31: Precast deck units were set on the precast walls and fastened together. (Two center photos) September 6: On the 23rd calendar day after the collapse, the new bridge (designed for HS20-44 loading) was opened to traffic. Because precast concrete integral deck bridges with precast abutments can be erected in cold weather, as shown at the left, they can be opened to traffic sooner. Note the open space in the abutment to be used for future widening.

Minimum traffic interruption

Maintaining traffic and eliminating detours is a difficult problem faced by bridge departments. With precast concrete integral deck bridges, traffic interruption can be minimized because of the availability of plant-produced sections and the speed of erecting and completing the bridge. For instance, consider this case study:

April 27: Flood waters undermined a bridge located on U.S. Route 36 and Illinois Route 96. The bridge was closed to traffic creating about 40 miles of adverse detour.

April 24: The Illinois Department of Transportation concluded that the fastest way to replace the two spans was to use precast, prestressed concrete.

April 25: Engineers in the Bridge and Traffic Section began design of the deck units for the 46-ft and 60-ft spans.

April 28: Design plans were completed. May 3: The contract was awarded for 16 precast prestressed concrete deck units. May 30: Erection of the deck units was complete. The steel truss shown in the photos at the right was used as a runway to “slide” the units across the stream. May 31: The project was completed and the bridge was back in service the next day.

In Ketchikan, Alaska, a bridge on the only highway to the north was washed out when an old dam gave way on October 26. Integral deck girders were selected for the 85-ft span. The 12 girders were designed and precast in the state of Washington, then shipped by rail and barge to Alaska. The girders were installed (left photo) and the bridge was completed and opened to traffic on December 19 - less than eight weeks after the wash out - despite the problems of design, remote location, great distances, and adverse weather conditions!

Simple design Replacement of substandard bridges can be easily accomplished with precast prestressed sections. In some cases, existing abutments can be used, but in others, it is easier and more economical to build new ones as shown below, or to utilize precast abutments and wing walls supported on cast-inplace footings, as shown at the right.

The pedestrian overpass, below, exemplifies the simplicity of precast prestressed bridges. The 7-ft wide integral deck unit, supported on cast-in-place piers, spans 81 ft. Erection of the superstructure took two hours on a Sunday morning without interruption of traffic. Thus a standard prestressed concrete unit created a simple solution to the complex problems of economy, aesthetics, traffic interruption, and low maintenance.

Minimum depth/span ratio

\

A common requirement of many bridges is that the superstructure be as shallow as possible in order to provide maximum clearance and minimum approach grades. Through the technique of prestressing, the designer can utilize the minimum possible depth-span ratio. Depth-span ratios as low as 1:32 can be achieved with solid slabs, voided slabs, box beams, multi-stemmed units, or bulb-tee sections. Even though deeper sections will require less prestressing steel, the overall economy of a project may dictate the lowest possible depth-span ratio. Precast prestressed concrete integral deck girders were selected to provide a shallow superstructure for a bridge in a scenic park in Colorado (upper left photo). Even though the bridge must carry frequent heavy truck traffic, the total depth of the girders is only 3 ft., including the 3-in. wearing surface, for a span of 80 ft. The skewed deck on the bridge shown in the center photo illustrates the low depth-span ratios possible with integral deck prestressed concrete. Two bridges with low depth-span ratios are shown below, the one at the left is in the state of Washington, and the one at the right is in Alberta, Canada.

Assured plant quality

Precast prestressed concrete products are inspected and quality controlled at the precasting plant. In fact, each operation in the manufacturing process provides an opportunity for inspection and control. During manufacture, portions of prestressed concrete beams are subjected to some of the highest stresses they will ever encounter as structural members. So, in a sense, prestressed members are pre-tested during manufacture. Prestressed concrete is economical because it makes efficient use of high strength steel and high strength concrete. To take advantage of this efficiency, precasting plants have developed sophisticated quality control programs which assure the customer that the end product meets his exacting demands. Suggested tolerances for dimensions, tensioning procedures, material properties, and other details for controlled plant operations are given in the PCI Manual for Quality Control for Plants and Production of Precast Prestressed Concrete Products.

Durability

Bridges are subjected to an assortment of hostile environments as well as repeated impact loading. They must withstand not only the freezing and thawing provided by nature but artificial cycles of weathering induced by man through the use of de-icer chemicals. High strength prestressed concrete has excellent freeze-thaw resistance, as demonstrated by the performance of prestressed concrete piles. Prestressed concrete bridges are not easily damaged by fire as evidenced by the structural integrity of the bridge in Minneapolis shown below that was exposed to the inferno caused by a burning gasoline truck beneath the bridge. Note that the fire was hot enough to consume the metal bridge rail, yet only cosmetic repairs were needed to restore the bridge to its original condition.

Attractive

Prestressed concrete bridges offer an attractive view from above, below, and from the side because of the simple clean shapes of the members used. Strong, tough, durable, yet graceful bridges result from the low depth-span ratios possible through the use of prestressing. The late eminent structural engineering educator, Professor Hardy Cross once said, “Any bridge that is not beautiful is a disgrace. ” It is unfortunate that Professor Cross did not live to see the thousands of attractive prestressed concrete bridges like the one below. Citizens in Lake Forest, Illinois, were dismayed when they learned that a landfill and culvert was being proposed to replace a dilapidated bridge. The landfill proposal was slightly less in first cost than a prestressed bridge but much less desirable aesthetically. The bridge at the upper right shows how the natural beauty of a wooded ravine was preserved by a handsome prestressed bridge. The two prestressed bridges at the left blend harmoniously with their park-like surroundings.

General information @for designers

The advantages of prestressed concrete for short span bridges have been shown on the preceding pages. The pages that follow show a variety of precast prestressed sections available for short span bridges in the United States and Canada. Also shown are typical bridge layouts, details of deck member shear connections, bearings, end diaphragms, curbs, and guard rails. Helpful suggestions for specifications and methods of reducing costs are included. In addition to the types of sections shown on these pages, many other sections are available. The sections described have integral decks unless otherwise noted. Precasting plants in your geographical area will be pleased to furnish you with information on the sections they are equipped to make most economically. In the tabulated data, the weights are based on concrete weighing 150 lb per cu ft. These weights should be modified if lightweight concrete or concretes heavier than 150 lb per cu ft are used. In general, the spans are based on the application of a future wearing surface of 20 psf and on camber-deflection limitations to assure proper riding characteristics. Amount and detailing of reinforcement shown are only diagramatic; each concrete section must be designed individually. The many details shown on the following pages will assist you in planning bridge layouts. Many variations of these details are available. Most precasting plants have standardized on the details shown in this booklet or have developed others which they are best equipped to supply. They will furnish information on these details on request. Many bridge engineers have found it advantageous to specify precast concrete for the substructure as well as for the superstructure. The substructure can consist of prestressed concrete piles with precast pile caps or precast abutments, wingwalls, and piers. Design information and suggestions on details are included for prestressed piles and other substructure components.

Solid slabs

Solid slabs for bridges are available in nearly all locations in the United States and Canada. They are often economical for spans of less than 30 ft. The former AASHO-PCI standards include the 12-in. deep sections, in widths of 3 ft and 4 ft.

TYPICAL SECT 3N PROPERTIES m -!iFTTK 3

10

375

360

3 3

12

450

14

525

4 4 4

10

500

12 14

432

3,000 5,184

600 864

504

8,232

1176

600

480 576

4,000 6,912

800 1152

700

672

10,976

1568

$* 1 ii 1 ii; l

Railway trestle slab

-I

l/r

b

4

0

10

20

30

APPROXIMATE MAXIMUM SPAN, FEET - HS20

B

40 LOADING

Ii 1 ,,

TYPICAL KEYWAY

DETAILS

.

Voided slabs 8

Voided slabs are similar to solid slabs except that they are cast with cylindrical voids to reduce dead load. The sections tabulated be low are the former AASHO-PCI standards which can span up to 50 ft for HS20 loadings. Sections with widths and depths other than those tabulated are available from some precasting plants.

-I--

I

TYPICAL KEYWAY

1/2"

b P 11 , 4 3

TYPICAL

DETAILS

LONGITUDINAL

SECTION

TYPICAL SECTION PROPERTIES Void Dia. Width

Depth

No. of

ft

in.

Voids

DI

02

3

15

-

18 21

2 2 2

8

3 3

10 12

4 4 4

15 18 21

3

8

3 3

10 12

in.

Net Weight

Arm

Ibift

in.2

-

457 511 552

439 491 530

8 10 10

593 654 733

569 628 703

12,897 21,855 34,517

1720 2428 3287

25

5 0

30 20 APPROXIMATE MAXIMUM SPAN, FEET - HS20 10

40 LOADING

50

Box beams The box beams shown are the former AASHO-PCI standard sections. They can be used either as adjacent units with or without an added wearing surface or spaced apart in which case the deck slab is cast-in-place. Box beams for railway loadings have been standardized by AREA.

7 Width

I, F’L’-----II F7 1

TYPICAL

TYPICAL Width Depth

SECTION

Net Weight Area

L----j LONGITUDINAL

SECTION

PROPERTIES

Ix

St

in.4

yb in.

Sb in.3

in.3

Tape

ft

in.

Iblft

in.2

B l-36

3

27

584

561

50,334

13.35

3770

3687

B II-36

3

33

647

621

85,153

16.29

5227

5096

B Ill-36

3

39

709

681

131,145

19.25

6813

6640

B IV-36

3

42

740

711

158,644

20.73

7653

7459

8 l-48

4

27

722

693

65,941

13.37

4932

4838

B II-48

4

33

784

753

110,499

16.33

6767

6629

B III-48

4

39

847

813

168,367

19.29

8728

8542

B IV-48

4

42

878

843

203,088

20.78

9773

9571 TYPICAL KEYWAY

45

25 APPROXIMATE MAXIMUM SPAN, FEET - HS20

LOADING

DETAIL

Single stemmed bridge sections Width

Single stemmed bridge sections are available in depths of 24 to 51 in. and widths of 4 to 6 ft for spans up to about 120 ft carrying HS20 loading.

TYPICAL SECTION PROPE ITIES Width

Depth

Weight

Area

ft

in.

Ib/ft

in.2

‘x in.4

4 4 4

24 38 48

448 548 648

430 528 822

18,555 81,058 139,038

16.98 24.76

1094 2466

2634 5434

32.01

4344

8695

5 5 5

24 38 48

531 831 731

510 608

19,788 85,873

17.53 25.80

1129 2545

3059 6440

702

150,543

33.45

4504

10,353

8

820 720

595

20,782

17.94

1158

3431

8

24 38

891

89,323

26.62

2604

8

48

820

787

180,146

34.64

4623

7388 11,987

--

20

40

60

yb in.

I

sb in.3

I

80

APPROXIMATE MAXIMUM SPAN, FEET - HS20 LOADING

s, in.3

100

Single stemmed bridge sections

a

(Cast-in-place deck)

Width

Single stemmed bridge sections are widely available throughout the United States and Canada. With a thin flange, these units serve as formwork for cast-in-place deck slabs which act compositely with the precast sections. Overall depths range between 24 and 48 in. and widths between 4 and 6 ft. Prestressing plants will furnish dimensions and properties of the sections made locally.

f.,i+~f>j~Ti;i:.i$l

?I

A

6 St P

1

TYPICAL SECTION PROPERTIES (PRECAST SECTION ONLY) Stem

T

-r

Slab

Width

Depth

C

A

B

weight

Arm

ft 4 4 4

in. 24 30

in. 8 12

in. 2

in. 3

Iblft 317

in.2 304

in.4 17,106

2

3

4 4

36 36 42

8 12 12

1.5 2 2

2.74 3 3

481 402 556

462 386 534

41,501 51,325 69,108

4 4

48 48

1.5 2

2.74 3

631 502

606 482

106,304 113,616

5 5

36 48

8 12 8

1.5 1.5

3.18 3.18

6 6 6 6

36 40 44

1.5 1.5 1.5

3.62 3.62 3.62

1.5

3.62

48

8 8 8 8 8

‘x

yb in.

sb in. 3

15.86 17.97

1079 2309

in.3 2101 3450

22.20 21.14

2312 3269

3720 4651

St

24.27

4379

5997

3975 5637

5851 7485

2424

4445

706

678

154,350

28.58 27.38

442

424

56,470

23.30

542 486 520

520 467 499

124,791 61,124 81,881

29.88

4176

6888

24.30 26.60

2516

5223

553 586

531 563

106,548 135,384

28.89

3078 3688

6110 7051

31.13

4349

8025

APPROXIMATE MAXIMUM

SPAN, FEET - HS20 LOADING

Channel sections a Many precasting plants manufacture prestressed concrete channel sections for use in 20 to 60-f-t span bridges. These plants will furnish you with information on the sections thev _ pro. duce.

TYPICAL SECTION PROPERTIES Slab

Stems

Width

Depth

T

A

in.

in.

in.

in.

40

21

5

3.25

6

C i

n

. 30

s,

Weight

Arm in.2

‘x

Iblft

in.4

yb in.

sb in.3

in. 3

362

348

11,495

14.37

800

1734

42

25

5

3.5

6

30

417

400

20,105

16.98

1184

2507

46

23

5

4.62

6

36

438

421

18,507

15.46

1197

2453

60

27

5

3.75

5.75

48

530

509

28,886

19.27

1499

3739

36

20

5.5

7

28

358

344

12,283

12.37

993

1610

48

20

6

7.5

40.5

461

443

14,663

13.05

1123

2110

48

27

4.5

8

36

536

515

31,216

17.85

1748

3410

60

35

4

8

48

688

660

67,648

23.86

2835

6074

36

24

7

9.25

27

488

469

24,24 1

14.00

1731

2425

66

21

7.75

9.75

48

640

614

22,051

13.90

1586

3106

66

27

7

9.75

48

730

701

43,738

17.82

2454

4764

66

35

6

9.75

48

844

810

87,469

22.96

3810

7265

35

APPROXIMATE MAXIMUM SPAN, FEET - HS20

LOADING

Channel sections

l

Width

(Cast-in-place deck)

Precast channel sections can be placed side by side and serve as formwork for a cast-in-place concrete deck slab. Spans of 20 to 70 ft can be achieved with precast sections 14 to 36 in. deep and 30 to 66 in. wide.

AZ s 6

TYPICAL SECTION PROPERTIES (PRECAST SECTION ONLY)

5 E Width I in.

F:: :

r

Depth

Arm

in.

in.2

‘x in.4

vb in.

166

2,900

8.99

322

579

12.81

676

1205

32

14

2

3.25

5.25

40

20

2

3.5

54

24

2

4

60

24

2

3.75

5.75

60

36

2

6

9

48

656

66

18

2

7.75

9.75

48

429

s, in.3

24

173

4.5

30

233

224

8,659

6

48

342

328

17,986

15.44 1165

2102

48

343

329

17,943

15.87

1131

2207

630

76,151

21.35 3567

5197

412

12,774

11.99 1152

1849

501

27,399

14.61

1876

2917

z ;

sb in.3

66 66

24 30

2 2.5

67

9.75 8

48 54

522 573

550

47,952

18.71 2563

4247

66

32

2

6

9.75

48

630

605

57,441

19.42 2957

4568

36

24

18

12 20

30

40

50

60

APPROXIMATE MAXIMUM SPAN, FEET - HSZO LOADING

70

Double stemmed bridge sections Width

integral deck double stemmed bridge sections are available in depths of 18 to 36 inches and widths of 5 to 8 ft. “Heavy” sections can span 60 ft and more with HS20 loading while lighter sections can be used for shorter spans.

TYPICAL SECTION PROPERTIES

F ti v)

Width ft

t 5 3 :

k z ;

Stems

Slab

g

Depth

T

A

C

E

Weight

Area

in.

in.

in.

in.

in.

Iblft

5 6 6 8 8

27 23 27 27 35

5 5 5 5 5

4.50 4.50 4.50 3.75 3.75

8 6.50 8.00 5.75 6.50

36 36 36 48 48

5 6 7 8

36 35 35 35

6 5 5 5

6 6 6 6

8 9.75 9.75 9.75

6 7 8

27 27 27

5 5 5

7 7 7

6 7 8

21 21 21

5 5 5

7.75 7.75 7.75

in.2

‘x in.4

yb in.

sb in.3

St in.3

599 582 662 718 820

575 558 635 689 787

33,740 21,366 35,758 32,888 72,421

18.60 16.61 19.15 20.64 26.20

1812 1286 1866 1593 2764

4020 3345 4560 5171 8230

30 48 48 48

812 876 938 1001

780 840 900 960

90,286 90,164 95,028 99,299

23.69 23.30 23.91 24.45

3811 3870 3974 4061

7334 7706 8569 9412

9.75 9.75 9.75

48 48 48

761 824 886

731 791 851

45,084 47,486 49,566

18.09 18.58 19.00

2492 2556 2609

5060 5640 6196

9.75 9.75 9.75

48 48 48

671 733 796

644 704 764

22,720 23,903 24,920

14.11 14.48 14.80

1610 1651 1684

3298 3666 4019

15 20

30

40

50

APPROXIMATE MAXIMUM SPAN, FEET - HS20

60 LOADING

70

Double stemmed bridge sections Width

(Cast-in-place deck) With a cast-in-place deck slab, double stemmed precast sections eliminate the need for deck formwork. A variety of double-stemmed precast sections are available throughout the United States and Canada. Prestressing plants in your area can provide you with the dimensions and properties of the double stemmed units they produce most economically.

E

I

TYPICAL SECTION PROPERTIES (PRECAST SECTION ONLY) B

F P F 5 F 5 E ;

5 ,4 I

Slab Width

Depth

Stems

T

A

C

Weight

Area

in.

F in.

lb/h

in.2

‘x in.4

yb in.

sb in.3

St in.3

ft

in.

in.

in.

8 8 8

24 24 32

2 2 2

3.75 4.25 4.5

5.75 6.25 8

48 48 48

418 441 591

401 423 567

20,985 22,661 54,522

17.15 16.83 21.34

1224 1347 2554

3064 3160 5117

5 6 6 7 8 8

24 24 32 32 18 24

2 2 2 2 2 2

4.5 4.5 4.5 4.5 5.87 4.87

8 8 8 8 8 8

36 36 48 48 48 48

411 436 541 566 431 495

395 419 519 543 414 475

20,902 22,230 49,616 52,177 12,363 25,389

15.36 15.80 20.45 20.92 12.39 16.38

1361 1407 2426 2494 998 1550

2419 2710 4296 4708 2205 3331

6 6 6

18 24

2 2

7.75 7

9.75 9.75

48 48

442 534

424 513

13,185 28,229

11.26 14.80

1171 1907

1956 3070

7 7 7 8 8 8

32 18 24 32 18 24 32

22 2 2 2 2 2

6 7.75 7 6 7.75 7 6

9.75 9.75 9.75 9.75 9.75 9.75 9.75

48 48 48 48 48 48 48

467 643 559 668 492 584 692

448 617 537 641 472 560 664

59,021 13,942 29,776 62,005 14,623 31,192 64,775

19.65 11.57 15.17 20.07 11.84 15.51 20.47

3004 1205 1963 3089 1235 2011 3164

4779 2167 3373 5200 2374 3674 5618

25

20 15

20

30 40 50 APPROXIMATE MAXlMUMSPAN,FEET

60 - HS20 LOADING

70

Multi-stemmed sections a.

Multi-stemmed bridge sections are especially suitable for spans of 25 to 55 ft for HS20 loading. The sections shown here are available in some areas; other sections are available elsewhere. Designers wishing to take advantage of the low depth-span ratios possible with multi-stemmed sections should determine if these sections are available locally.

TYPICAL SECTION PROPERTIES

Depth

Weight

Area

‘X

in.

Iblft

in.2

in.4

16

438

420

18

538

516

12,674

23

606

582

25,699

14.21

8,751

yb in.

St

Sb in.3

in.3

9.94

880

1445

11.26

1126

1879

24

APPROXIMATE MAXIMUM SPAN, FEET - HS20 LOADING

2922

Bulb tees integral deck bulb tee bridge sections are efficient and economical for spans of 60 ft or more. T h e sections shown here are available only in some parts of the United States and Canada. Designers wishing to use bulb tee sections should determine if they are available within an economical hauling range. In some areas, depths of 53, 65, and 77 in. are available for spans up to about 180 ft. Because of the high section modulus to weight ratio (particularly when lightweight concrete is used for the top flange) the use of bulb tees for bridge construction is gaining wide acceptance. Thin-flange bulb tees are also highly efficient for use with cast-in-place concrete decks.

TYPICAL SECTION PROPERTIES+ Width

l

Depth

C

Weight

Area

in.

Iblft

0

627

in.2

‘x in.4

yb in.

Sb in.3

s, in.3

602

68,310

20.38

4340

6,480 6,093

ft 4

in. 34

5

29

1

708

680

64,110

18.48

3470

5

34

0

690

662

95,180

21.39

4450

7,548

5

41

1

771

740

157,840

26.18

6029

10,652 6,866

6

29

1

771

740

67,790

19.13

3544

6

34

0

752

722

100,600

22.25

4520

8,550

6

41

1

833

800

166,390

27.11

6139

11,975

7

29

1

833

800

70,930

19.68

3604

7,611

7

41

1

896

860

173,760

27.90

6228

13,265

These sections are sometimes made with normal weight concrete web and bottom flange and lightweight concrete deck, in which case the weight and section properties differ from those shown.

44

40 i . $

36

32

28 60

70

80

90

APPROXIMATE MAXIMUM SPAN, FEET - HS20

100 LOADING

l-Girders - PCI Standards a

(Cast-in-place deck)

Thousands of bridges have been built utilizing the former standard AASHO-PCI l-Girders shown here. The cast-in-place deck provides composite action with the girders. Many states have developed additional l-girder sections. Producers of prestressed concrete will be glad to furnish you with the dimensions and properties of the sections made locally. Stay-in-place prestressed concrete soffit slabs which span between girders are available for use with l-girders. They serve both as formwork for the cast-in-place slab concrete and as transverse positive moment reinforcement.

SECTION DIMENSIONS (INCHES)

91

GIRDER SECTION PROPERTIES Depth Weight Type II III IV

Area

Ix in.4

yb in.

=b in.3

=t in.3

369

50,980

15.83

3220

2528

560 789

125,390 260,730

20.27 24.73

6186 10543

5070 8908

in.

Ib/ft

in.2

36

384

45 54

583 822

Type II

Type III

40

50

60

70

80

APPROXIMATE SPAN RANGE, FEET - HS20

90 LOADING

loo

Piling

Wire Spiral* Prestressing Strandf

SQUARE SOLID

OCTAGONAL SOLID OR HOLLOW

SQUARE HOLLOW

TYPICAL

*Wire spiral varies with pile size.

ELEVATION

+ Strand pattern may be circular or square.

Allowable

SECTION PROPERTIES “I Moment of Section

Core Size

Dia.

in.

in.

Araa i n .2

Weight

Inertia

Iblft

in.4

Radius

Modulus of Gyration in. i n .3

Conan-

tric *vita Load, Tonr(2) for f; of

POrimetar

5ooo

5ooo

ft

mi

pri

3.33 4.00 4.67 5.33 6.00 6.67 6.67 8.00 8.00 8.00 800 L

73 105 143 187 236 292 222 420 338 308 291

89 129 175 229 290 358 273 515 414 377 357

2.59 2.76 3.09 3.31 3.60 3.87 4.12 4.42 4.61 4.97 5.15 5.52 5.84 5.52 5.66 6.08 6.53 6.08 6.17 6.63 7.23 6 . 6 3

60 86 118 154 195 241 172 292 195 348 219

74 106 145 189 240 296 211 359 240 427 268

SQUAREE PILES 10 12 14 16 18 20 20 24 24 24 2

i I

4 10 12 14 16 18 20 20 22 22 24 24

Solid Solid Solid Solid Solid Solid 11 Solid 12 14 15

100 104 144 150 196 204 256 267 324 338 417 400 305 318 600 576 463 482 422 439 3 9 9 4 1 5

833 1,728 3,201 5,461 8,748 13,333 12,615 27,648 26,630 25,762 25,163

OCTAGONAL PILES Solid Solid Solid Solid Solid Solid 11 Solid 13 Solid 15

83 119 162 212 268 331 236 401 268 477 300

85 125 169 220 280 345 245 420 280 495 315

555 1,134 2,105 3,592 5,705 8,770 8,050 12,837 11,440 18,180 15,696

111 189 301 449 639 877 805 1167 1040 1515 1308

I I

(1) Form dimensions may vary with producers, with corresponding variations in section properties. (2) Allowable point bearing loads based on N=Ac(0.33fk - 0.27fpe); fge = 700 psi. Check local producer for available concrete strengths. See Sec. 1.4.4 (E) of AASHTO Standard Specifications for Highway Bridges for ground capacities of piles unless subsoil investigations are conducted.

Sheet pile abutments

Prestressed concrete sheet piling can serve as abutments and wingwalls, as shown above. Sheet piles are available in various sizes ranging up to four feet in width and two feet in thickness, but most are about 30 in. wide and 8 to 12 in. thick. Sheet piles are usually made with tongue-and-groove sides. In addition, the foot of the pile is beveled on one side so that the tip is forced against the adjacent pile during driving or jetting. The bridge shown above consists of the following components: 1. 2. 3. 4. 5. 6. 7.

Prestressed concrete sheet pile abutments and wingwalls. Prestressed concrete piling pier. Reinforced concrete abutment and wingwall caps. Precast or cast-in-place concrete pile cap. Precast concrete curb unit. Prestressed concrete deck unit. Precast concrete guard posts.

Precast abutments and whgwalls On-site labor can be substantially reduced by using precast bridge abutments and wingwalls. In addition, the bridge can be completed on schedule by minlmizing delays due to bad weather. Illustrated at the left is one such precast abutment and wingwall

system which

goes together in the following sequence. 1. Concrete erection pads are cast in place to proper elevation and location. 2. Deedmen

footings are cast in place with steel dowel rods projecting from the deadmen to facilitate welding of the braces.

3. Formwork for the cast-in-place footing is positioned. 4. Precast abutment and wingwall set in place by crane.

panels are

5. Steel shims are used as required to set the top elevation of the abutment and wingwalls. 6. Erection braces are attached to the deadmen and panels after each piece is erected. 7. After auxilliary horizontal reinforcement is positioned the footings are cast. When the footing concrete has attained strength, the abutment acts as a cantilever retaining wall and is no longer dependent on the tie back braces.

NOTES: A. Abutments and wingwall panels are dapped 2 in. and the reinforcing bars protrude from the panels into the footing. B. Weld plates anchored into the panels provide for joining of adjacent panels and welding of erection braces. C. Dowel sleeves, 3-in. diameter, provide for anchorage of the precast concrete bridge deck members which offer additional strut

support to the abutment walls.

Abutment and wingwall panels are usually 8, 10, or 12 in. thick depending on the wall height. They are generally cast in four sections as shown but can be as large as permitted by locally available

equipment. Many other types of precast abutment and wingwall systems are available. Precasting plants will be pleased to furnish you with information on the types that are most suitable for your area.

Deck member shear connections

RECESSED CONNECTIONS - NO TOPPING REQUIRED Flat bar 314” f th.*

Flat bar 314” f th.*

grout. Cover for curing

Cover for curing SECTION - SLAB MEMBERS

SECTION - FLANGED MEMBERS *See plan views

NON-RECESSED CONNECTIONS - REQUIRES WEARING SURFACE Flat bar 314” f th.*

Flat bar 314” * th.*-

L

/-

Fill with approved grout. Cover for curing

-L 3/S” f th.*

SECTION - FLANGED

f th.+

SECTION - SLAB MEMBERS

MEMBERS *Sea plan views

PLAN VIEW - RECESSED AND NON-RECESSED CONNECTIONS

Rebar anchors lapped or welded

,i’ hl/t- Deformed bar anchor a1

& 4&J1

k-\\ L-1-w

1111

a

-Lit --

or headed \\., anchor stud

‘Q

III

II

anchor stud or deformed bar anchor

I

Slab width

*

PLAN PLAN RECESSED CONNECTION

PLAN NON-RECESSED CONNECTION

RECESSED OR NON-RECESSED CONNECTION

Bearing and diaphragm details Fill sleeves with grout Poured joint filler -I

Fill sleeves with grout at fixed end and bitumen at expansion end Poured joint filler

joint fil er *m

grouted in sleeve

PIER

ABUTMENT

This bearing detail for slab or box units employs smooth bar dowels to retain the deck members transversely.

- Creosoted plank or precast slab eric

&double nuts .yq.jg~lastomeric . . .. Pad

ABUTMENT

SECTION THRU DECK MEMBER

Double bolt connection for stemmed members, bulb tees or l-beams. Connections may be used on all beams or on exterior beams only, and can be fixed or expansion. An expansion bearing may consist of a tetrafluorethylene (TFE) plate between an elastomeric pad and a stainless steel face plate. Slotted holes are required with expansion bearings.

ABUTMENT

SECTION THRU DECK MEMBER

This connection differs from the bolted type at the left in that keeper bars rather than bolts retain the member. A bearing plate is cast into the cap. The plate over the pad is welded to the plate cast in the deck member. Keeper bars are welded at the site. This connection is used where uplift forces need not be resisted.

Bearing and diaphragm details :...;..:..‘ . ..*’.(... ‘_ . .:: . . . . ‘r . ..-I? ‘f.7 *:-< :.-::. i,! ;.i.:;; 1 ! F-f-

Poured

Bond-

:::.:.t.: . ...1. .” m. ._ . . _. ..: : -7

” joint filler L SECTION THRU DECK MEMBER

ABUTMENT

SECTION THRU PIER

This bearing employs only elastomeric pads. The deck members are retained transversely by steps cast at the ends of the abutments and piers. The end diaphragm shown may be either cast onto the deck member in the precasting plant or field poured.

- Approach slab 7 Premolded joint filler \ Channel nosing

-/ /-

/-Z

L 3/8” k th.

- Precast end diaphragm Plate cast in deck unit

Precast concrete end diaphragms are attached through weld plates. Diaphragms can be attached to each bridge member at the precasting plant or at the bridge site.

Intermediate diaphragms can be added to bridge members at the precasting plant, in which case matching weld plates are needed. Concrete is cast through holes formed in the top flange. As an alternate, intermediate diaphragms made of steel angles can be bolted or welded to plates embedded in the bridga members.

Guard rail and post details Structural w railings

Guard rail welded to plates which are bolted to posts Wide flange post 7

tube

Structural tube post

- Precast curb acing S

r

structural This concept allows an easily drained curb without cutting down on the roadway width.

tube

Above is a simple method for attaching side mounted railing to stemmed deck members.

Corrugated metal rails are functional and economical. Steel can be galvanized, painted, or weathering type. SIDE MOUNTED POSTS

3 7 ITI L ’ rp r

‘i;

Aluminum or steel rails

I&-

4

I ” tf ‘1

Steel or aluminum post

Square or rectangular concrete rail

:I I

Square or rectangular concrete post

1 I Jk I 1 \ II II

Ii 4 c-

I

b

L Low profile aluminum or steel pipe railing mounted on high curb. Curb may be added in plant or at site.

t

Three-rail design. Rails may be oval, round, rectangular tubes, or channels.

Reinforced concrete rails can be developed in a variety of designs.

POSTS MOUNTED ON CURBS Structural -/- tube railina

Structural tube

Structural - tube post

Wide flange Post

Block out during casting of bridge member

-f

Wide -flange post

Inset deck Bolts may be stud welded to anchor plate. Assembly should be retained in slab with U shaped reinforcing bar.

washer

MISCELLANEOUS POST MOUNTING METHODS

Corbel form is attached after bridge member has been removed from form. Concreting is then completed.

Curb details Construction

joint Wl -

For top mounted railings minimum width is 12 in. For side mounted railings width may be 10 in.

Top of precast unit or topping

Ht - Normally 6 to 12 in.

FOR USE WITH HIGH TOP OR SIDE MOUNTED RAILINGS

w2-

For sidewalk curbs minimum width is 36 in.; normally 3’6” to 6’6”.

H2

/- Construction

1. -1

For non-sidewalk curbs minimum width is 12 in.; normally 18 in. to 24 in.

I

H2 -

18 in. minimum for low profile railings.

- Top of precast unit or topping HI

/

FOR USE WITH LOW PROFILE TOP MOUNTED RAILINGS O R SIDEWALKS

Outside curb optional depending on railing detail Top of precast unit or topping

‘O.. . . . , 0 ‘0 . . : .

*-.& . ...’ .;. 0..O* * . .-:,_* e .. . . . . . . . . _ _ , . . .

SAFETY CURB FOR SIDEWALKS AT ROADWAY LEVEL NOTE: Curbs may be cast on deck members in plant or at the jobsite; plans should specify. Contact precasting plant for information on local practice.

Precast curb and guard barriers

l

Front face contour is the shape of a standard median barrier. No guard rail is required

L 80lt or insert

In addition to the sections shown, prestressed concrete piles (cast with risers for drainage) in a horizontal position have been used as low-cost curbs.

,-- Grout pocket flush

Insert for rail posts

Precast abutment caps and pier caps

-8”-

-8”. b 4

t 1-7: 12” (min.) _I:&+

1:

i’

j;7Tk As req’d by pile size I ;

b

I. Abut. pile spacing

Abut. pile spacing

*

rll

c

I : 1 I

ELEVATION PRECAST ABUTMENT CAP

Width as req’d

L

-rjk

8” it-

8”

t fFT’r 12” (min.)

i-y-i

4

Q

t-

Ic-3 I I Pier pile spacing

: 9 h(

I-T-, I ; ,

L

I

-t-

-i ELEVATION PRECAST PIER CAP

NOTE: Dimensions on this page are approximate.

.h ---7 \ b&i;b kll END VIEW ABUTMENT CAP

“t--=-i ---&:&?to m Ir-7\ END VIEW PIER CAP

Caps shown are intended for use with square pretensioned piling. Piles must be carefully driven to design locations. Prestressed piles can be cut to proper elevation with a pneumatic hammer. After placing cap on piles and leveling with shims or wedges, sockets are dry-packed from below with a rich concrete mix. Precast caps can also be designed with sockets extending to top of cap. Cap can be placed on steel channel yokes bolted to piles at correct elevation (see illustration at right). Sockets can then be concreted from above.

concrete after setting

Lay wood or steel form on yoke prior to setting cap-

Reinforcing we

- hestressed pile cut off as required

Channel yoke bolted to proper soffit elevation ALTERNATE CAP - PILL CONNECT(ON

Suggested specification provisions GENERAL: These specifications cover materials, fabrication, transportation, and erection of all precast concrete bridge components as shown on the plans.

MATERIALS: It is recommended that materials conform to the following requirements. Where ASTM specifications are cited, the latest edition is applicable unless otherwise indicated. Prestressing strands, 270 ksi, seven-wire . . . Reinforcing bars . . . . . . . . . . . . . . . . . . . . . Welded wire fabric . . . . . . . . . . . . . . . . . . . Normal weight aggregate . . . . . . . . . . . . . . . . Lightweight aggregate. . . . . . . . . . . . . . . . . . Portland cement, Type I, I I, or I I I . . . . . . . .

- ASTM A416 - ASTM A615 -ASTM Al85 - ASTM C33 - ASTM C330 - ASTM Cl50

Concrete compressive strength of at least 3500 psi at transfer of prestress and 5000 psi at 28 days is recommended. Concrete exposed to freezing and thawing while wet, such as bridge decks, piling, and abutments, should have an air content of 4% * l%%.

DESIGN: The bridge should be designed in accordance with AASHTO Standard Specifications for Highway Bridges for HS20-44 loading. It is recommended that the design provide for a future wearing surface of 20 psf unless otherwise noted.

FABRICATION OF PRECAST CONCRETE UNITS: It is recommended that bridge members be fabricated in plants in accordance with the “Manual for Quality Control for Plants and Production of Precast Prestressed Concrete Products,” PCI Publication MNL 116-70. Except for precast abutments, diaphragms, wingwalls, and pile caps, the use of steel forms founded on concrete casting beds is recommended. Voids may be formed by any approved material, must be securely held in place during casting, and should be vented during casting and curing. Box-beam voids should be fitted with bottom drain tubes. All exposed corners should be chamfered or rounded preferably % in. Dimensional tolerances should conform to those suggested in PCI MNL 11670. Chairs, spacers, or bar supports in contact with forms should be plastic tipped or made of plastic. The top surface of precast sections that will receive cast-in-place topping are to be roughened with a stiff bristle broom. A wood float finish or a light broom finish at right angles to the length of the section is recommended for the top surface of precast integral deck units.

TRANSPORTATION AND ERECTION: During handling, flexural members must be maintained in an essentially upright position at all times and picked up only by means of approved devices at locations indicated on the plans. During transport, the members should be supported only at locations near the pick-up points.

Suggestions for reducing costs PLANNING: 1. Use locally available precast concrete members. The hauling distance for precast concrete bridge members is generally limited to about 200 miles except under unusual circumstances. Precasting plants are equipped to furnish certain types of members. For short span bridges, designs utilizing available types of members will result in lower bid prices than unique designs.

9. Use integral deck girders to eliminate the need for cast-in-place concrete deck slabs and to speed construction.

DETAILING: 1. Eliminate projections from the sides of the girders. Most precast prestressed concrete members are cast in precision made steel forms. Projections can be accommodated only by modifying the forms. It is better practice to utilize details that permit attachment by use of threaded inserts, weld plates, or through bolts, as shown in other parts of this booklet.

2. Make precast members identical. Economy in precasting results from the production of identical sections. As an example, if a bridge consists of different span lengths, it may be better to design all of the precast units with the same cross section rather than to design each span for an optimum depth-span ratio.

2. Use standard details recommended by local prestress manufacturers. Those are the details that can be made most economically.

3. Work closely with local prestress manufacturers throughout the planning stages. Ask for cost estimates as soon as sufficient data or plans are available so that cost savings can be incorporated well before bids are taken.

3. To save considerable field labor and time, use precast concrete diaphragms which are made integral with the bridge member at the pre casting plant. Steel diaphragm systems have proven to be economical in some areas.

4. Set up bridge replacement programs to group several bridges into single contracts for optimum savings in fabrication, hauling, erection, and supervision.

4. Minimize the amount of reinforcing steel in prestressed concrete members. There is a tendency to a’dd more reinforcing bars and welded wire fabric than is needed “just to be safe.” Often the added reinforcement merely creates congestion making consolidation of the concrete difficult without contributing to the structural strength or behavior.

5. Utilize county or municipal work forces and equipment, when available, to perform most of the site work on small bridges. 6. For prestressed concrete bridges with cast-inplace deck slabs, use diaphragms only if required for erection purposes. Recent studies* have shown that diaphragms contribute very little to the distribution of static or dynamic loads. End diaphragms, i.e., those over sup ports, are useful in stiffening the slab edge.

5. Use elastomeric pads instead of metal bearing assemblies. Elastomeric pads, properly designed and installed, require no maintenance and will permit movements (due to temperature, shrinkage, and loads) to occur without distress.

7. Avoid skews wherever possible. If a skew is necessary, limit the skew to 30” or less. It may be less costly to lengthen the bridge slightly than to use an extreme skew angle in order to fit the bridge site exactly. l

8. Use prestressed piles to double as foundations and piers. If pile foundations are warranted, prestressed concrete piles can .serve as piers and abutments, thereby reducing the amount of on-site forming and concreting.

Wong, A.Y.C., and Gamble, W.L., “Effects of Diaphragms in Continuous Slab and Girder Highway Bridges,” Civil Engineering Studies. Structural Research Series NO . 391, University of Illinois, Urbana, Illinois. May, 1973. Sengupta. S., and Breen, J.E., “The Effect of Diaphragms in PrimstrB)sBd Concrete Girder and Slab Bridges,” Reseerch Report 15*1F. Center for Highway Reseerch, The University of Tom l t AuCin, Oct., 1973.

12’6” Tvo.

-------

------

d---B -----

-------------a-------

/

BRIDGE PLAN

\ i0 0

‘v> ‘v’

Precast abutment .___cI I

SECTION A-A

C8x 11.5x O’-8” w/4 - ll2”fp. x 1.-O” weld studs

PRECAST SECTION

Grout Flat bar 2” x 314” x 3-l 14”

/ 4-A

SECTION C-C

x 2 ” x 318” x O ’ - 4 ” w/2 - 1 l2”d1 x 8” weld studs (flair at 30”)

NOTES:

314”

threaded inser

SECTION D-D GUARD RAIL POST

Nosing angle ,Dowel and sleeve SECTION E-E

i

!

1

1.

Concrete for precast sections shall have a compressive strength of at least 3500 psi at transfer of prestress and 5000 psi at 28 days. Air content of the concrete shall be 4%% f 1X%.

2.

Prestressing steel shall be ‘/-in. diam. 270 ksi seven-wire strand and shall conform to ASTM A416.

3.

Grouting between precast concrete sections shall be done when air temperature is above 40°F and no traffic shall be permitted on the bridge until the grout has cured for 3 days.

4.

Design and construction shall be in accordance with AASHTO Standard Specifications for Highway Bridges for HS20-44 loading.

5.

Deck surface of the precast sections shall be given a light broom finish transverse to the length of the sections.

6.

Dimensional tolerances of precast sections shall be in accordance with “Manual for Quality Control for Plants and Productions of Precast Prestressed Concrete Products,” PCI Publication MNL 116- 70. Adjacent units shall be brought to the same elevation prior to welding.

C 8 x 11.5 x O’-8” WI4 - 112” l$ x l’-0” weld studs ‘thick aphragm

L

/

Flat bar 3/8” .x 3 ” x O’-8” each face

end diaphragm

SECTION B-B DIAPHRAGM CONNECTION

One-span skewed bridge

5118” bp 318” to l/2” joint clearance I

PRECAST PRESTRESSED SINGLE STEMMED MEMBERS with PRECAST ABUTMENTS AND WlNollyALLS

Abutment

and

wingwalls

I L-----JL----,_:~ r - - - - - - 7 - - ---II i’ I i I L-----AL------J1 c---~,

-------r--r--1 I L----,-I-L-- -----: t

-

-

-

-

-

-

i

I --

--d

t

-

I

1 -

-

- -

-

-

-

I

I

I’ -----

Precast box beams BRIDGE PLAN

recast concrete pier cap Prestressed

concrete

Precast concrete sheet pile abutment and wingwalls ELEVATION

3” rj~ dowel sleeves fill with grout at fixed

(

L 2-112” x 2” x4”wM- l/: x 6” weld stud (flair at 30”)

II boxbeam SECTION A-A

SECTION B-B

connections

NOTES: Concrete - Normal weight for prestressed members, fhi = 3500 psi @ transfer fk = 5000 psi @ 28 days for reinforced concrete, f;: = 4000 psi @ 28 days Strand - l/2” t#~ 270 ksi, 7-wire, ASTM A416. Loading - HS20-44 urb and metal rail

Nosing angles

3” #dowel x 3-1 f4”

-7

sler

1” 4 dowel

I

I

SECTION D-D

Bar

ti I I

WELDING

SECTION C-C

DETAIL

Three-span bridge ADJACENT PRECAST PRESTRESSED CONCRETE BOX BEAMS with PRECAST PRESTRESSED PILE ABUTMENTS WINGWALLS AND PIERS