study of in-service bridges constructed with prestressed ...continuity of action between beams,...

STUDY OF IN-SERVICE BRIDGES CONSTRUCTED

WITH PRESTRESSED PANEL SUB-DECKS

by

Harry L. Jones Engineering Research Associate

and

Howard L. Furr, P.E. Research Engineer

Research Report 145-1

A Study of Prestressed Panels and Composite Action in Concrete Bridges Hade of Prestressed Beams, Prestressed

Sub-deck Panels, and Cast-in-place Deck

Research Project No. 2-5-70-145

Sponsored By

The Texas High\vay Department in Cooperation \vi th

The U. s. Department of Transportation, Federal Highway Administration

July, 1970

TEXAS TRANSPORTATION INSTLTliTE Texas A&H University

College Station, Texas

ABSTRACT

This report describes the results of a field inspection and load

test of three prestressed concrete highway bridges which have a pre-

stressed panel subdeck. The panels, which are precast and pretensioned,

span from beam-to-beam and serve as the bottom form for a cast-in-

place concrete deck. The bridges examined were located in Grayson

County, Texas, and were opened to traffic in August of 1963.

Crack patterns in the surface of the cast-in-place deck of two of

the bridges were mapped. With only a few exceptions, the cracks found

coincided with a butt joint between prestressed panels. The cracks

were judged to extend approximately halfway through the cast-in-place

deck. No cracks were found in the prestressed panels. Soundings to

detect delamination between prestressed panel and cast-in-place deck

were taken in one traffic lane of one of the bridges. No significant

delamination was found. Core samples were taken from one span of one

bridge, and an examination of these cores revealed no bond failure

between panel and cast-in-place deck.

Electrical resistance strain gages were placed on a span of one

bridge to measure transverse and longitudinal strains in the prestressed

panel and cast-in-place deck. The instrumented span was subjected to

both static and dynamic forces from a loaded truck. The results of

these tests indicated continuity of action between prestressed beam,

panel and cast-in-place deck was present.

ii

SUMMARY

A recent innovation in prestressed concrete highway bridge con-

struction utilizes prestressed concrete panels as bottom forms for

the conventional cast-in-place deck. The precast, prestressed panels

are placed on top of the prestressed beams, spanning the distance

between adjacent beams. This type of construction is particularly

attractive where placement and removal of conventional form work is

difficult and costly.

In the design of these bridges, it is assumed that composite

action between prestressed beams, prestressed panels and cast-in-place

deck is present, causing these three separate elements to act as a unit.

The work reported herein is a field study of three existing

highway bridges constructed in 1963 using prestressed concrete panels.

The study was undertaken to determine the condition of these structures

after seven years of service, and to see if any evidence of a lack of

continuity of action between beams, panels and deck could be detected.

The study included mapping of crack patterns in the cast-in-place deck,

soundings to detect delamination between prestressed panel and cast-in--

place deck, corings and load tests.

No evidence of distress or noncomposite action was found in the

bridges studied. Some transverse cracking was found in the cast-in-

place deck of two of the more heavily traveled structures. With only

a few exceptions, the cracks coincided with transverse butt joints

iii

between prestressed panels. Core samples showed these cracks to extend

approximately halfway through the cast-in-place deck.

iv

IMPLEMENTATION STATEMENT

The research effort reported here is only the first phase of a

more thorough study to be completed in August of 1971, and therefore,

an unqualified statement concerning the implementation of this type

of bridge construction would be premature. However, the results of

this study indicate that the bridges investigated are performing

satisfactorily, and their structural behavior agrees with that assumed

in their design.

v

TABLE OF CONTENTS

Page

I. Introduction . . . . . 1 II. Description of Bridges 1

III. Inspection of Bridges 6

IV. Load Tests 16

v. Discussion 28

VI. Conclusions 34

References . 35 Appendix A. Crack Patterns 36

Appendix B. Load Test Strain Readings 47

The opi.ni.ons, findings, and conclusions expressed in this report

Figure

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

LIST OF FIGURES

St. Louis-San Francisco Railroad Overpasses ••

Span Layout of St. Louis-San Francisco Railroad Overpasses . . . . . . . . . . . . . . . . . .

Arrangement of Prestressed Panel, Cast-in-place Slab and Prestressed Beam • • •

Prestressed Panel Layout for 40 ft Span

Prestressed Panel Layout for 50 ft Span

Reinforcing in Cast-in-place Slab

Typical Prestressed Panel . . . . Typical Transverse Cracks in Cast-in-place Deck

Core Sample No. 1

Core Sample No. 2

Core Sample No. 3

Core Sample No. 4

Discoloration of Concrete at Crack in Cast-in-place deck

Shear Test of Core Sample

Location of Strain Gage Patterns on Stran 2NB

Location of Strain Gages in Pattern No. 1

Location of Strain Gages in Pattern No. 2

. . . .

. . . .

Typical Strain Gage Installation on Top of Cast-in-place Deck • • • • • • • • . . . . . Typical Strain Gage Installation on Underside of Prestressed Panels • • • • • • • • • • • •

vii

Page

3

4

5

7

8

9

10

12

14

14

15

15

17

18

20

21

21

22

22

Figure

20

21

22

23

24

Location of Strain Gages and Strain Readings in Core Hole No. 1 • • • •

Dial Gage Installation to Detect Slippage Between Prestressed Beam and Panel

Dial Gage Installation to Detect Relative Displacement Between Two Adjacent Prestressed Panels

Test Vehicle

Dimensions and Wheel Loads of Test Vehicle

25 Position of Test Vehicle for Static and

26

27

28

A.l

A.2

A.3

A.4

A.5

A.6

A.7

A.8

A.9

A.lO

Dynamic Load Tests

Reference Positions of Test Vehicle Relative to Strain Gage Being Recorded • • • • • •

Arrangement of Load and Assumed Transverse Strip for Strain Calculations • • • • • • • • • • • •

Transverse Support and Loading Assumptions for Strain Calculations • • • • • •

Cracks in Cast-in-place Deck, Span lNB

Cracks in Cast-in-place Deck, Span 2NB




Cracks in Cast-in-place Deck, Span lSB

Cracks in Cast-in-place Deck, Span 2SB




viii

Page

23

23

24

26

27

27

29

33

33

37

38

39

40

41

42

43

44

45

46

Figure Page

B.l Strain Readings, Top and Bottom Transverse Gages No. 1, Pattern No. 1 . . . . . . . . . . . 48

B.2 Strain Readings, Top and Bottom Transverse Gages No. 2, Pattern No. 1 . . . . . . . . . . . 48

B.3 Strain Readings, Top and Bottom Tr_ansverse Gages No. 3, Pattern No. 1 . . . . . . . . . . . . 49


B.5 Strain Readings, Top and Bottom Transverse Gages No. 5, Pattern No. 1 . . . . . . . . . . 50

B.6 Strain Readings, Top and Bottom Longitudinal Stages No. 6, Pattern No. 1 . . . . . . . . . . . . . 50

B.7 Strain Readings, Top and Bottom Longitudinal States No. 7, Pattern No. 1 . . . . . . . 51

B.8 Strain Readings, Bottom Longitudinal Stage No. 8, Pattern No. 1 . . . . . . . . . . . . 51

B.9 Strain Readings, Top and Bottom Longitudinal Gages No. 9, Pattern No. 1 . . . . . . . . . . 52

B.lO Strain Readings, Top and Bottom Longitudinal Gages No. 10, Pattern No. 1 . . . . . . . 52

B.l1 Strain Readings, Top and Bottom Transverse Gages No. 1, Pattern No. 2 . . . . . . . . . . . 53

B.12 Strain Readings, Top and Bottom Transverse Gages No. 2, Pattern No. 2 . . . . . . . . . . . . . . 53


B.14 Strain Reiiidings, Bottom Transverse Gages No. 4, Pattern No. 2 . . . . . . . . . . . . . . . 54

B.l5 Strain Readings, Top and Bottom Transverse Gages No. 5, Pattern No. 2 . . . . . . . . 55

B.16 Strain Readings, Top and Bottom Longitudinal Gages No. 6, Pattern No. 2 . . . ' . . . . . . . . 55

ix

Figure Page

B.l7 Strain Readings, Top and Bottom Longitudinal Gages No. 7, Pattern No. 2 . . . . . . . . . . . 56

B.l8 Strain Readings, Top and Bottom Longitudinal Gages No. 8, Pattern No. 2 . . . . . . . . . . . . 56

B.l9 Strain Readings, Top and Bottom Longitudinal Gages No. 9, Pattern No. 2 . . . . . . . . . . . . 57

X

I. INTRODUCTION

Some of the more recent prestressed concrete highway bridges have

incorporated a prestressed panel subdeck into the design. This panel,

which is precast and pretensioned, serves as the bottom form for the

cast-in-place concrete deck. The elimination of conventional bottom

forming for the cast-in-place slab is a major advantage where form

placement and removal are difficult and costly.

In the design of these bridges it is assumed that composite action

between prestressed beams, prestressed panel and cast-in-place deck is

present, causing these three separate elements to act as a unit. This

composite action is attained through the bond of the cast-in-place slab

to the prestressed panels and beams.

A study is currently underway to determine the behavior of highway

bridges constructed with prestressed panels. One phase of this study

included a general visual inspection of three existing bridges and a

load test of one to see if any evidence of distress or noncomposite

action between panel, slab and beam could be detected. This report

presents the results of that inspection and load test.

II. DESCRIPTION OF BRIDGES

The three bridges examined were located in Grayson County, Texas,

One is an overpass, carrying Farm Road 902 over U. S. Highway 75, and

the other two are parallel structures carrying U. S. Highway 75 over

1

the St. Louis-San Francisco Railroad. The three overpasses were opened

to traffic in August of 1963.

1. Farm Road 902 Overpass: This bridge consisted of four spans;

two end spans 45 ft. long and two 60 ft. interior spans. Four Type B

prestressed beams, spaced at 6 ft.-8 in. on center, were used in each

span. The prestressed panels were 6 ft.-2 in. long, 4 ft.-Oin. wide

and 3 in. thick. The panel details and the arrangement of reinforcing

in the cast-in-place deck were similar to those used in the St. Louis-

San Francisco Railroad overpasses.

2. St. Louis-San Francisco Railroad Overpasses: Figure 1 is a

view of the two parallel structures, with the north-bound lane in

the foreground. The north-bound and south-bound structures were

identical, with each overpass consisting of two 40 ft. end spans and

three 50 ft. interior spans as shown in Fig. 2. Six prestressed beams,

spaced laterally at 7 ft.-3 in. on center were used in all spans. Type

B beams were employed in the two 40 ft. spans, while Type C beams were

used in the 50 ft. spans.

The arrangement of prestressed panel, cast-in-place slab and

prestressed beam is shown in Fig. 3. Continuity between panels, slab

and beams was provided by the bond of the cast-in-place slab to the

panels and beams, and by mechanical shear connectors embedded in the

upper face of the panels and the top flange of the beams. The prestressed

panels rested on continuous fiberboard strips and therefore did not bear

directly on the prestressed beams.

2

Figure 1. St. Louis-San Francisco Railroad Overpasses.

3

·.23o'- o"

V>

CAST -IN-P\.../1-CE. SLAB

PRESTRESSED PANE-L

'r

•M

CAST-IN-PLACE. SLAB I PRESTRESSED PANlf.L

. . .

...-5"' DIAPHRAM _J

7'-3"

o o -... -.-~---...- ..- • • .-:-~T-;-;---.-

7'-3"

.r----- 2-$5

"4 51-lEAR Ca-lf.JECTORS •>10" O.C.

PRESTRESS STRAt.JDS ~NO 5" INTO SU'B -TYPICI'.L

SEE. FiGURE. C. FOR SL"B RElNF.

C0\4\INVOUS ~·\I-lK. FIBERBOARD STRIP

/ /--PRESTRESSE-D CONCRETE ~ BEAM.

The prestressed panels were 6 ft.-9 in. long, 3 in. thick, and

varied in width from 1 ft.-5 in. to 5 ft.-2 in. The arrangement and

width of panels used in the 40 ft. and 50 ft. spans are shown in Figs. 4

and 5, respectively. All panels employed 3/8 in. diameter, 7-wire

prestressing strands, spaced at 4-1/2 in. on center at mid-depth, with

an initial prestress force of 14,000 lbs. per strand. Number 2 plain

bars at 6 in. on center were layed on the strands to provide transverse

reinforcing for the panels, while No. 5 deformed bars located as shown

in Fig. 6 were used in the cast-in-place slab. A design strength of

f' = 3,000 psi was used for the concrete and F 33,000 psi for the c y

conventional reinforcing. Additional prestressed panel details are

contained in Fig. 7.

III. INSPECTION OF BRIDGES

A visual inspection of the three structures was first conducted to

determine their general condition. Based upon these preliminary findings,

more detailed studies, which included mapping of crack patterns, soundings

to detect delamination, and core samples were undertaken where deemed

advisab-le. This portion of the work was carried out by Texas Highway

Department personnel.

The Farm Road 902 overpass exhibited the least amount of wear. No

significant cracks were found in the cast-in-place deck, nor in the

prestressed panels. For this reason, the more detailed studies were

limited to the two more heavily traveled overpasses on U. S. Highway 75.

6

4o'- o''

zo'-o " 20'-ci' \

\\ - . \\

M~ I u 4'-o" ~ t-

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;i

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TYPICAL

5'-z•

Figure 4. Prestressed Panel Layout for 40 ft Span·

so·-o·

!'----\

..---1 __. ..- I

I I

II I .--11 p-----·---1

__. II I I I - I I __._,r 11-------lr-----,

--- I I I I I I I -1r I 1--' ----~ L-- -- ~ 1---- .... -~

-- II II Ill II I I 11 1 ( Jt---- -----j I lj 11 1

I II 11--------l r·-------,1---·------1 1---------JI---- ---1 I II 11 i I 11 II I I 11 1 1----------l 1--- ---{ ~----- ~ L-------J ~------~ I 11 I 1 I l I I : I 'l I I II I I 1 L _______ J._ -- -- _j L .,------- J L--- ___ j :_ ______ j r----- -, r--- ----. r--- ---,,------, r-----...., --, I II II II I I I I 11 I I II I I l r-- ----- i I--- __ ...] ~- -----11--- ---~ :------ _j I II 11 lj I I I I II It I I I I : ~--- ---J 1---- __ _j L --- --~ ~------J 1----- _...J ~"==.:-'-~=f- lj -~ IJ ~-- ----: l- --- ---1-{:-J-- -- -~ ~----- --l ~ I I I t:.&>-£:--t I I 11 1 I II ' J I I L _____ J L ----- __ __.J L_ ---- __ j L_ -- ___ j L ---- _...l r- ---, r---- --, r·- -------, r--- -----1 r-- -----. I II 11 II 1 I I I II 1 I II 11 I r- -- - -, r -- -- -- -i ~- - - -- - --j 1- - - - - - -l l- - - - - -l I I II I I I I I I I II IL-----Jl--------1 ~------'1-------~L----...jl II I I 11 II ~~-----~~ J I II II II II ... ------

lr ~------1 rl-1-- --- 1---- - --! I .-II II I I _ __.-- .

L _____ .J~---·- ----11 Jt./ . I II I' ......... J __ -- -·- ---- J I .J L-- __. __. I II __...-1

I __.-J l--1 __.. _ ....

L.----

9

~ 0

. "'

"'2. BAR~ ("TYP.)

Figure 7. Typical Prestressed Panel.

10

s' CABLC. E.'X,TlO.l--1'5\0N T...-PlC!>.L ALL P.O.l-.lE.L"'

1. Mapping of Crack Patterns: Some transverse cracking was

visible on the cast-in-place decks of both the north-bound and south-

bound overpasses. The position of those cracks which could be detected

were determined by measuring their distance from one end of a span and

by measuring their length. Each span of the two bridges has been

assigned the identifying number shown in Fig. 2, and the crack patterns

that were obtained are presented by span in Appendix A. Figure 8

shows cracks typical of those found in the decks of both structures.

2. Soundings to Detect Delamination: Serious deterioration and

delamination in the interior portion of a monolithic concrete slab

can usually be detected by tapping the surface of the slab. A sharp,

solid sound is characteristic of sound concrete, while a hollow

sound indicates the presence of delamination. For the prestressed

panel and cast-in-place slab construction, a bond failure and delamina-

tion between panel and slab would be perceptible th~ough soundings.

An electronic device(l)* operating on the principle of differences

in sound was used to inspect the right lane of the north-bound overpass.

This device was rolled along the deck and gave a continuous ins~ection

of a nine inch wide strip of slab.

The results of these soundings were almost completely negative.

Only two small areas of delamination were found; the first occurred

on the north approach to the bridge, a few inches from the end of span

1!\B, and the second was located adjacent to the center traffic stripe

in span 3NB. No delamination was found in the vicinity of any of the

transverse cracks in the cast-in-place slab.

*Superscripts refer to entries in the list of references.

11

Figure 8. Typical Tranverse Cracks in Cast-in-place Deck.

12

3. Core Samples: The north end span of the north-bound overpass

was chosen for coring, and four, 4 in. diameter cores were taken at

the locations indicated in Fig. A.l.

Core No. 1 was taken in an uncracked region at the center of a

prestressed panel. The core dropped through the deck, fell approxi-

mately 5 ft. onto the sloping concrete abutment below and rolled to

the bottom. The sample, which remained intact after the fall, is shown

in Fig. 9. The visible face of the core is the top of the cast-in-

place deck.

The second and third cores were taken over a joint between two

prestressed panels, at a point where a crack occurred in the cast-in-

place slab. The second core, like the first, fell through the deck.

It broke into several pieces, which were reassembled for the photograph

shown in Fig. 10. The sample split vertically through the crack in the

cast-in-place slab and horizontally along part of the interface of the

slab and prestressed panel. The bond between these two elements to

the left of the vertical.split remained secure.

The third sample, shown in Fig. 11, lodged in the coring bit and

was broken at the interface of the precast and cast-in-place concrete

when attempts were made to pry it from the coring tool. The concrete

over the face of separation was clean, which indicated a new break, not

an old one.

The fourth core was taken from an area slightly offset from a

crack, and was drilled only through the cast-in-place portion of the

deck. It was broken from the precast panel by a·wedge driven into the

cut. The break was clean at the interface of precast and cast-in-place

13

14

N

~ 0)

.-<

~ U)

0) ... 0 u

~ 0)

.-<

~ U)

0) ... 0 u

15

0 z ru .... ~

Ul

ru H 0 u

0 z

concrete, and the drill operator estimated that it took about as much

force to break it as was his experience to use. in breaking out a core

from a monolithic pour. An inspection of the exposed upper face of the

prestressed panel gave no indication of an unbending or delamination

between slab and panel. The core sample is shown in Fig. 12.

The position of the second and third cores over a crack in the

cast-in-place slab permitted an estimate of the depth of such cracks

by observing the extent of the discoloration of the concrete. Figure 13

shows core sample No. 2, layed open along the vertical crack shown in

Fig. 10. The top surface of the deck, visible in Fig. 10, is at the

top of Fig. 13. It appears that the crack in the cast-in-place slab

extended approximately half way through the slab, based on the depth

of darkened concrete visible.

Core sample No. 1 was subjected to a direct shear test(Z) to deter-

mine an average bond stress between prestressed panel and cast-in-place

slab. Two forces, parallel to the interface between slab and panel

(see Fig. 14) were applied until separation of these two elements

occurred. A force of 3600 lbs. was required, l

Figure 13. Discoloration of Concrete at Crack in Cast-in-place Deck.

17

~-PRE STRE.SSE..D PAN!:.\-

CAST-IN-PLACE. SLAB

Figure 14. Shear Test of Core Sample.

18

the frequency of cracks in the cas t-in-place deck was typical of the

other 50 ft.-0 in. spans. The instrumentation consisted of electrical

resistance strain gages and two dial gages. The strain gages were

arranged in two similar patterns, as shown in Fig. 15. The locations of

the gages within each pattern are shown in Figs. 16 and 17. Wherever

possible, pairs of gages were used; one on the top of the cast-in-place

deck and another directly belmv it on the underside of the prestressed

panel.

The position of each gage ~Vas determined by measurements from the

edge of the curb and from the expansion joint at the end of the span.

The concrete surface beneath the gage was cleaned with acetone and a

stiff bristle brush. A layer of polyester resin, just thick enough

to provide a smooth surface for the gages, was then brushed onto the

cleaned area and allowed to harden. The strain gages were attached to the

resin surface using Eastman 910 contact cement, and a waterproofing com-

pound was placed over the gages. Figure 18 and 19 show typical strain

gage installations.

In addition to the gages used in patterns No. 1 and 2, strain gages

were mounted on the walls of core hole No. 1, to measure strains through

the depth of the slab, and dial gages were positioned on the underside

of the bridge to detect differential movement bet\Veen elements of the

structure. Six strain gages were placed in the core hole at the loca-

tions shown in Fig. 20, to measure strains in both the longitudinal and

transverse directions. The dial gages used were sensitive to 1/1000 in.

and '\-Jere placed near midspan of 2NB. The gage shown ln Fig. 21 m(.:..asun ... ·J

19

I l-a 0 z

~

20

2 4 uJ dl

z a: ww C) I-

~~ ~

'w > .... ' .II)

I I I I

J!.-8"

--f-1---1 3 4

I CRACKS IN CI\ST-IN-: PLACE DEcK..---~

I

Figure 18. Typical Strain Gage Installation on Top of Cast-in-place Deck.

Figure 19. Typical Strain Gage Installation on· Underside of Prestressed Panels.

22

I I f - ,; CA!i>T-_q : .. . o· ' .. ·ti:

• . ;, . : , . ·. .. ' •. • -VDIA.L GAG ,_ •;> {li

" I" i DIAL GAuE. 1-!0LD'E.R .......__

,,. ~!i:>\RESSE.D BEAM (_ cf' . • ~

Figure 22. Dial Gage Installation to Detect Relative Displacement Between Two Adjacent Prestressed Panels·

24

\

Il---l-PLACE. SLAB

slip between prestressed panel and beam, and that shown in Fig. 22

was used to measure relative vertical movement between two adjacent

prestressed panels.

A set of static readings were taken from the strain gages in

patterns No. 1 and 2, core hole No. 1, and from the dial gages mounted

under span 2NB. The loaded dump truck shown in Fig. 23 \vas used as the

test vehicle. The truck had a total weight of 71,800 lbs., and the

wheel loads and axle spacings indicated in Fig. 24. The wheel loads

were detained by.weighing each wheel independently. Strain readings

were taken from each gage pattern with the two rear wheels adjacent

to the gages, as shown in Fig. 25. For readings from the gages in the

core hole, the truck was positioned to the west of the hole, and with

its rear-most axle even with it. The distance between the outside

line of wheels and the edge of the hole was approximately 12 in. The

two dial gages were monitored while the truck was aligned with gage

pattern No. 2.

Dynamic strain readings were taken from the gages in patterns No. 1

and 2 with the test vehicle moving at approximately 20 mph., along the

path indicated in Fig. 25. All strain traces were recorded by a Honey-

well Visicorder oscillograph and amplifier system, capable of recording

the output from 12 gages simultaneously. Thus, four passes with the

test vehicle were needed to record the strains from all gages. On a

single pass, all top or all bottom gages in one of the patterns were

read. The left lane of the north-bound overpass remained open to

traffic during the load test and on several occasions cars passed over

25

Figure 23. Test Vehicle.

26

0 4'-2'' L4'-4"

. 2.3

1-B" 1

27'-lo"

3S'- 5"

'o CJ c:J c:J c:J CJ c:J .. CJ,..CJ 7ZO~ 7100 esoo azoo""'

iO sooo"" -+--CJ

SIOO"' CJ CJ

7tDOo"~ CJ CJ

BIM 7500# CJ CJ = =

CJ

=

Figure 24. Dimensions and Wheel Loads of Test.Vehicle.

r----APPROXIMATE. PA"TI-l OF VEHICLE WHEELS -DYI-lAMJC TE.ST -- -- -- -- -- -- ---T GAG>E. PATTE~ --

-- · -- II I II =-t=· CO TO 12. lN. = = = = c::l_CJ_ -------=-=- --------

NOR"TK

Figure 25. Position of Test Vehicle for Static and Dynamic Load Tests.

27

the bridge while readings were being taken. However, precautions were

taken to see that no trucks crossed the bridge during these times.

The strain readings from the static and dynamic load tests are

presented in Appendix B. The strains recorded from each pair of top

and bottom gages in a pattern are plotted against the estimated truck

position, relative to these gages. Three reference lines, labeled A,

B, and C, have been included on each plot and correspond to the rela-

tive truck positions shown in Fig. 26. The horizontal dashed lines on

each graph are the strains recorded during the static test.

One set of static readings was taken from the gages mounted in

core hole No. 1. The test vehicle was positioned as shown in Fig. 26,

truck position C. The resulting strains are shown in Fig. 20. No

dynamic strain readings were taken from these gages.

There were no differential movements between prestressed panel and

beam, or between adjacent panels recorded by either of the dial gages.

V. DISCUSSION

With only a few exceptions, the cracks found in the cast-in-place

deck Coincided '~ith transverse butt joints between pres tressed panels.

They occurred between prestressed beams, usually along the path of tlw

wheels of a vehicle in the right traffic lane. The cracks were more

numerous in the shorter, end spans, and in all spans were more frequent

towards the ends of the span. Based upon the core samples taken, the

cracks appeared to .extend approximately halfway through the cast-in-

place slab.

28

I I P-a A A u..__GA.GE BEING. RE.A.D

TRUCK PDSITION A

l A GAJ

I 9 If-._ GAGE BEING READ

TRUCK POSITION B

l--(A)· A

I Cit n....__GAGE. BEING RE.A.D

TRUCK POSITION "C

Figure 26, Reference Positions of Test Vehicle Relative to Strain Gage Being Recorded.

29

The prestressed subdeck panels had the effect of controlling the

spacing of transverse cracks since these cracks occur almost exclusively

over the joints between adjacent panels. The predominant panel width

in the bridges under investigation was 4 ft.-0 in. It is of interest

to compare this frequency of transverse cracking with that occurring in

decks of comparable bridges constructed with monolithic slabs. A recent

survey(3

) of the general condition of all bridge decks in the state of

Texas reports that for bridges \>ith prestressed beams and monolithic

cast-in-place slab, 69 percent had transverse cracks at average intervals

of 4 ft.-0 in. or less.

There was no evidence of service bond failure at the interface of

precast concrete and cast-in-place concrete. The breaks that occurred in

the cores were due to impact from falling or from a hammer and wedge.

In each core, the finishing marks in the concrete at the interface

between slab and panel were well defined. If slippage along this inter-

face had occurred, these projections would probably have been ground

smooth. Some discoloration was noted on the interface of core No. 3,

possibly from oil or curing compound present on the top face of pre-

stressed panel prior to pouring of .the cast-in-place slab. This may

have. contributed to the partial separation of the core along this

interface. The one core sample \-lhich was removed intact and subjected

to a direct shear test exhibited substantial bond strength.

The strains recorded by the gages in patterns No. 1 and No. 2,

and presented in Appendix B of this report, were taken to test the

continuity of action between prestressed panels and cast~in-place slab.

Only qualitative results were sought from these tests because of the

30

inherent inaccuracies involved in measuring small strains in concrete

structures in the field under rapidly fluctuating temperature conditions.

The rapid temperature fluctuations in this test resulted from inter-

mittent clouds briefly shading the bridge surface from the sun, and

from gusts of wind blowing over the deck. It was anticipated that a

lack of continuity between prestressed panel and slab would be reflected

by a sudden jump or discontinuity in the strain trace from one or· more

gages. A similar result was expected from those gages measuring trans-

verse strains on either side of a panel joint if the transfer of wheel

loads between adjacent panels was uneven. No such jumps or discontinuities

were found in the strain traces recorded.

In general, those gages mounted on the top of the cast-in-place

slab exhibited a greater sensitivity to changing wheel position, as

evidenced by the five distinct peaks in the strain traces corresponding

to the passage of each of the five axles of the test vehicle. The strain

readings from those gages attached to the bottom of the prestressed

panels tended to peak only at the two instances where the pairs of

vehicle trailer. axles passed by the gages. With the exception of gage

10 in pattern No. 1, only compressive strains were recorded by gages

mounted on the top of the cast-in-place slab.

Among those gages reading stra.ins in the transverse direction

(gages 1 through 5 in both patterns), several trends were observt'd.

The strain traces from gages located on either side of a panel joint

(gages 1 and 2, and 4 and 5 in both patterns) show a smooth transfer of

wheel loads from panel to panel. These gages recorded strains before

31

a vehicle wheel came in contact with the panel to which they were

attached, and after all wheels had passed beyond the panel. The traces

had similar shapes, as seen from comparing Figs. B.l and B.2, B.4 and

B.4, B.ll and B.l2, and B.l4 and B.l5.

Gages 6 through 10 in patterns No. 1 and No. 2 measured longi-

tudinal strains. With the exception of the top gage number 10 in

pattern No. 1, all top gages recorded only compressive strains through-

out the test. The longitudinal gages on the bottom of the panels,

however, fluctuated betHeen tension and compression, with approximately

equal maximum values of each. The strain traces from the 6 in. gages

(numbers 6, 7, and 8) appear to be more uniform than those from the

0. 5 in. gages (numbers 9 and 10).

The six gages mounted in core hole No. 1 provided strain profiles

through the slab and panel, in both the transverse and longitudinal

directions. As expected, the strains in the longitudinal direction

were all compressive, with the largest value occurring at the top of

the cast-in-place slab and decreasing almost linearly t•ith depth. The

strains in the transverse direction varied from compressive in the top

of the slab to tension at the bottom of the panel, with approximately

zero atmmid-depth.

A rough calculation was run to determine the expected static

strains for transverse gages 1 through 5 in gage pattern 2. The

calculations assumed that complete continuity of action betHeen pre-

stressed panel and cast-in-place slab Has present so the two elements

behaved as a monolithic slab of equal thickness. A transverse strip

32

STIE. 5TI2'.A.IH GjAGfE:-5

M

4. 21 \V( K-in.)

\V::.qK (L.oAO FROM 13Crp.l AlCL..E6)

A'Y->UM~D t='IX "5UPPOI2'T

Figure 28. Transverse Support and Loading Assumptions for Strain Calculations.

33

of slab whose width was equal to one and one-half panel widths (72 in.)

was assumed to carry the loads from the wheels of the two rear axles.

Figure 27 _shows the position of the wheel loads relative to the strip.

The sum of the two axle loads (approximately 17,000 lbs.) was assumed

to be distributed transversely over a 20 in. wide strip as shown in

Fig. 28. The resulting transverse moment at midspan, assuming each

end of the slab to be fixed, was 52 k-in. Using a slab strip width of

72 in., a thickness of 6 in. and a modulus of elasticity of 5 millions

psi. for the concrete gives a computed midspan transverse strain of

24 micro-inches. This compares favorably with the value of 21 micro-

inches obtained from averaging the top and bottom static strain readings

from gages l through 5 in pattern No. 2.

VI. CONCLUSIONS

Based upon the results of the inspection and load tests performed,

the following conclusions have been drawn regarding the condition and

performance of the three bridges studied:

1. No cracking or distress is present in the prestressed panels.

2. A secure bond between prestressed panel and cast-in-place

slab is present, causing these two elementS to act as a

unit.

3. The bridges are in sound condition and show no signs of dis-

tress.

4. In view of the observed effect of panel width on transverse

crack spacing, greater panel widths would be desirable.

34

REFERENCES

1. Moore, William, Swift, Gilbert, and Milberger, Lionel, "An Instrument for Detecting Delamination in Concrete Bridge Decks," Research Report 130-4, Texas Transportation Institute, Texas A&M University, College Station, Texas, August 1970.

2. Furr, Howard, Ingram, Leonard, and Winegar, Gary, "Freeze-Thaw and Skid Resistance Performance of Surface Coatings on Concrete," Research Report 130-3, Texas Transportation Institute, Texas A&M University, College Station, Texas, October 1969.

3. Darroch, J. G., and Furr, H. L., "Bridge Deck Condition Study -Part 2 - Relative Frequency Tables Displaying Associations Between Structural Characters and Deck Conditions," Research Report 106-lF, Part 2, Texas Transportation Institute, Texas A&M University, College Station, Texas, Submitted for approval April 1970.

35

APPENDIX A

CRACK PATTERNS

36

""' ...,

~--.--r---r--~ [-,----,----, r--T--Tr--, \ 1 1ol-1o·· ~ I ·? I I I 1 I 1 j \

·-:- 1 1 I"' I I II 1 1 1 \ \ I I o I I ! ~ I 1 \ \ I 1 C.ORIE HOLE• No.1 I I I I L _ _._ _______ 1..- ___ l ___ J_ __ ..J L ___ ,_ ___ L..l- ---~

\---~~-[' c::El- --~~-;oR:~~. --l ; --tT -4-: ~~ -1-C -\ \ HOLE HOLE. I I ; 0 \' i \

\ No 3 No. 2 11 • ~' jf \ \ I ' I I CORE. 11-\(JLE.I· ~ \

I I N LJ I I \.. __ ,_ ---L-------"----1 L---'--~-~--~J. ___ __l \--- -- ---;---1--l i---r---r--;--~--\ \ ~\1 :: I ' :r \

\__ -- ___ .L. ___ l __ j ~---- __ l _ _ .J __ l_- -~ \: ___ !_(_\ ___ :--~ ;---:---r--;--r -1~- -\

\ I I I I ' I ' II I \ ' ' I I ' I I \ I ' 1 : I I I \ L- L .J __ L --..!. __ _j :...._ __ .!_ __ j_ __ ..L ---'- J. ___ __, \----~-~---~ --l r -- -~--~-- -~---r-- T -\ \ I I I I I I I I I I \ I 1 I I I I I 1 . I I \ \ 1 I I 11 I 1 : I 1 \

I I I I I I I I \ \.._ _ _..! _L __ ..L- _J L __ J.- --'-- _j_- _.L_ -L -- _ _.

Figure A.l. Cracks in Cast-in-place Deck, Span lNB.

..-- I _..-,, I

__..-.- II I ____ ...,,- lr-------,

_..-.- II II I -.., ( - I L--- ·- -~ r---- -1

_..- I II . II ---;i-- :~- -~:---------111 ______ _]11 ..---- IL------.JI II I : li :r~-1 1---------jl-------l ~- - -- - -- ~ 1·· ·- ·;...:;; --11 1 I II I ~ -- -- -- -~ l- -- ·- -- .. -~ : -j L - --- J L --- --- -J I 'I Jl 11 II I : :I . 11 II II I L--- -- ---' L_ ____ -- ___ j L_ ___ -- _j L --- _____ j L- ---- _j ,----- -l r ----- --· r·----~ r- -----, r-------, I I' I' II II I I II II II II ~-----~~-----~~-----~~-----~r-----~ I II I! I i II : · J! II II II I ,--------1 -------- _J >----- -----, r- ----- ---j ~-- -----1 1 :: :I 'I 11 I : 11 1: 11 II I r- ----------; :- •·· · · "1 : r - .... ~ l ~ ------ ...j I 1 I I I 1 I II I I II II I I . II I L _____ .J L -- -· __ .. _] L ______ .J L. _ .• __ •. _ J l- .. _ --- - J r··---- -~ :-------, r- ------- -~ r- ·- ----, r-- --·---, I II II 1: II I i I I ~I I I 11 I r--- --·-- -i L ••· --u '-1 \------,1- -·- ---- -j : :: . 1: I I 11 I : II II 1>--------d------, 1----- -- - --1 t. ••• • · ---.1 1 - -1 I II I 1 I II 1 J-· , --11 j I II I II I I ! II I _.-~---- --1J·· I> 0" U"'-~~~---i: ___ ;1..--1 1 1 I I 1.-.- .- .-L-------JI- -jl ...J I II II ~-----JI J~--1 II _.--

1 11 ..-1 .J'-.--I ..- .-1.-.-

38

"' z N

. "" u Q) 1=1 Q) u

"' ..-! p. 1: .... I

+J

"' "' u

--1 .......... ... -__ .....,1 I .-.- II I

-..., ... lr----- -~ ---- II II I

~..,r 'L-----~~-----1 --- II jl . 'I ...,.- I f··- -------< ------ _J __ ,, 1--' ' ' • -II I I I

11 11 I 11 I ll-------'1 II I

I II I I I . J 1

11 1r----,·-------ir·------

f------~~--------~~ II II I L--- -- ~~--- -- --~ ~-------1 L ____ j L _____ l : :1 jl 1! II I I II II ,I II I I _______ J L. .. -- ____ J L ________ J L ____ _j L- --- J ,--- ----l r-- ----1~-- -- "l r-- ---11-----1 1 II I • 11 II 1 1 11 II , I i 1 ~-----~l _____ _JL-----~1------~r-----J

II II I I I I I II II I• I I \ J! II If II r·---- --j~----- -- ~ :--------- -,~-- -- ··-J ~-- ----- --l I I! II I I I I I : 11 11 11 II I r--------IL "1 1-- __ Jr--------11-------l

' 1 I I I : 1 1 II 1 I I 1 II I I II II I L .. ____ . .J 1------ • _J L ... ---- _) L _________ j [_ ----- J r·· -- -----: :·- ·c- -----q- -------- -~~--- ----, r··-- -----, I II II II I I I : II ! I 11 1 I . I :-----'----I L.. -1 L I I• • -- ---,1------ -j I II I I I 1 II 11 1l I I I I II 11--·-,-----Ji-------l t_ -- - - - - ~ L. -' 1 - -I I I I I I 11 lj 1!-·--------ll j I II I. I II .-1 11 11 . I 1 --1 _______ --II- _____

11., ., ,.,. --j I _;l---

: :1 ,1 11L- - __. ' I I -

'-- - -·· -- - - _J 1- --- -- - - -j -I 11 11 I I · ~-----~1 )~-1 I I ...--1 I I _. ...-I _ • .J ,_

I / ::----L-#-~

-----39

. -"' 0 " A " 0 "' .-! "" &

•.-! I

'-' ., "' u

.... 0

,----T ..... -r --:----y----T-----, r------ -l--- -,----, ~---y--~ -- ... \ \

I I 1 • 1 I I I J I I· • 1 I I I . I i I I I I I I

~ I I 1 ' 1 I 1 1 IJ 1 i \ I I I I 11 I I I II I I

\ I 1 I I 1 I I I · I ! II 1 1 \ I J 1 I I I :! I I I 11 ' 1 \ \_ __ L __ L --'--- _j __ -- J.-- -~ '--- _]_-- _l_ --- L __ _J '--- __ l __ L ____ _, ,-----.---,-- --r-- -,---1 r-- -,----,----.---, r-- ,-,--r- \ \ • J 1 I '1 I I I 1' ~ : \

I I I I i I I i ' ! I \ l I I fl ' l I 1: ! ! \ \ ! I I f1 1 I I~ I 1 \ \"-- _i ____ L __ j ___ J ~ __ _]_ ___ L ___ L __ J ~ __ _1_j_ -~ _ --~ \- --l·--- ---r .... --·,;-- ~~.-- -:---:---: i- --,, - -~,- --,. --\

\ , I I I I . \ \ J I : II \ I ' I I · \ 1 I i I I I : ! ·

1 \

'---'--- ___ ;_ __ _j :_ ___ I ___ .J ___ I __ _j [_ __ _.:. __ _! __ _,_- ---" ~---,-r-T--Ir--,--~---,--,,--,--,--T-r-1

\ I I I I I I I I II I l i. I \ \ I 1 1 , 1 I 1 I I I I 1 \ I 'I 1 I , I I : \ I : i i I I i I II I I I I \ \ I i i ! I 1 I 1 I I I I I \ \. __ L_l_.l ___ j i__ __ J ___ _]_ __ L __ .J L __ L _ J. __ _i_L __ -~ ~---T-T ___ i ~--,--- ;-- ,--~ r- -~--~- --~-~--~--~ I I I , , I · I 11 1 : 1 I 1 I \ I 1 j l ! I I i ; I l 1 I 1 \ \ I I i ! , I I . I ' I I I I I \ \ I I 'l I I I ' I I I I 1 I j 1 I I I II j ! I I : \ L_.L_...L __ .J L __ l_ __ L ___ L _ _j L~ _, ___ :.._ __ L__t _ _,_ ___ -'

Figure A.4. Cracks in Cast-in-place Deck, Span 4NB.

-- _, _.- I

_. I _.,1" I ------ II ---r( II-'-- ----l

----- II II I _. _ _, ( 11- - -- - - -j I I

_....- II 1~------JL----~ _.., ( I -~--!I I' I

_..---- :1 11 11 II I _ .,. .. -; I . I I . I

II ~~-- --~r--·---l I 1 r- ---.....- J I 11 I I r----~1 :1 11 1: I 1 - - - _J r- ... ·· ·· 1------ -; 1- --- - --l r· - -- --! I II :: 1: II I I II 11 l1 II I I-- ---i!- ..... ~""""1t----1 r ·-----l 1-------1 I 11 11 II J1 I I 11 II II II 1 L----- .JL ___ JL~- .JL _______ JL ______ _j ,----- -l r---- -l 1"~--.. l r··---- --I,-------, I 11! 11 II 11 I I I l1 11 . II I L_ -- -l !-.., ., '• -l1-- -1 f------ -1 r- --·--l : IJ II . IJ II I

l 1: _:: :: . 1: I ,------- -i 1- --- i ~--- -i r- -----~~- ----~ I IJ 11 II ~~---~ I II II 11----, 1 1 1------f~f---- -Jl ~ I I ,, ......... ,, ,,--------·I _ ......

II 11 1, II _ _.

I II II-_._ 1 I J f...--L-- ---~~ 11 11 _.-1 It 11 !.-_..--1 1!-~l, ___ J I Jl II.-_._. 1------tl ,..J II II _. ---1 J!.---1 L-_.

41

"" tJ Q) Cl

Q) tJ

"' .... "' b •.-i I .., "' "' u

""'" "'

,----r ---r- -T---~----r-:---, ,--:--:-:-' \ I I l I I I I I I I \ \ I I I : l !I I 1 1 \ \ I I I I I I ! I : 1 \ \ __ l ___ L ___ L __ J ___ l __ j i_ ___ ~ ___ ;__l ____ ~ \---,-r---~---~---.---: r--T--~-~-~-~

\ I ! I ! : ! I I ! I I \ \ : I I l I I I I I I I \ \ I I . I l I l I . • I \ \ __ ..J_l ___ ~ __ j ___ ~ __ J L __ j ___ l_ -~1-- -~ \---I---~, ---

1~----r~. --ll--1---,--; --:--\

\ !! : I I I ; I \ \ f ~( I I I I : If \ \ I I I I I li \ '----'~-.l ___ .L ___ j_ ___ j L __ J.. __ l _ _ _j __ .1.. -- -~ \---r~-,---r--1 ;--;---T--;--r ~--\ \ t i II t I . I) \ \ I I I I I f I I I 1\ \ \ I I I I l I I I I I \ L- L__l __ L __ _:_ __ _j ..__ __ .L __ _,_ -- .L ---'- ...L ___ _, ,---~-r---r---, r- -~---,-- -~---,-- T -, \ I I I I I I I I I I \ \ 1 I 1 I I I 1 l l I \ \ i I l jl I I I I I \

I I I I I I I I \ \_ _ _I _L __ .L __ ...I L __ ....I.-- -.1..- _j_- -.L- _.L -- --'

Figure A.6. Cracks in Cast-in-place Deck, Span lSB·

.,.. "'

r----T~-r --,- ---r-:----T----; ~---~-- -----.-- -~ ~---~--~ -- ... \ I • I I ' I ' I ' \ \ : I I I I I I I ' I I I

' I I I I I I I I I I \ \ I I I I I . I • \ ' ; I I I I I I i I I \ ! 1 I I 1 I I 1 I I 1 \ I i 1 I I I II I I I 1: I : \

·\\... __ L __ L _ _J_ ___ J ___ .L ___ J L-- _L ___ .l ___ l_ ---.1 ,_ ___ L --L- -- _ _, \.-- ---;---r-- -r-- -r- --, r---.-- --~-- --.---, r- -.,--~--~- \ 1 i I I I I I I I 1 I I I · I \ ' I I I I I I I I I ' I I I I I I ' I \ \ I I I I I I I I I I I • \ \ • I 1 I ! I 1 1 I 1 : 1 I ! \ \ ! I I I I I 1 I I 1 : 1 I I 1 \..._~_j ___ L--~---~L--~---L ___ L __ JL--j-~--L---~ ,- --r--r---r----, ~--1-- -T- --~- --~ r- -T---,-- -T -, \ ! I I I! I .I I II I ! l \

\ I I ! I I I ' I I · • \ \ I I I I I I I II I \ I I I I 1 I I 1 I \ 1 I I I ! I I I I 1 I , · \ \_ _ _l __ .l ___ L __ _j L ___ L --~--_I __ _j L __ j __ _j __ l_ ___ ..1 \---,-r-·--~~--,--,---.--,,--r--:--T-r-,

\ I I l ll I 1 t II ~ 1 ! I \ \ : I : ! : I II ' I I \ \ I I : I I i I I . I \ \ : : i : I 1 I 1 I I I \ \ ___ L_.t _ __l ___ J L __ j_ __ .J. __ L __ .J L_ __ L _ __L -- _l _]__ ___ _\ ,---r-T----; ;---,-- ;-- ·--~ r- -~--~---~--,-,--, \ I I I I I ; I II I I I I I I \ I I I I I ' I I 1 I I 1 1 I \ \ I 1 11 ! I I • I 1 \ \ 1 1 1 1 I 1 I II I I I 1 I \ \ I I 1 1 I I I I I : I I I 1 \ \__.L _ _i- _ _j L __ L __ L_ -L- _J L- -1--- L __ L_I _ _I.

Figure A.7. Cracks in Cast-in-place Deck, Span 2SB •

........ 1 .... ,-- _. I

_. .... ....-,, I _.....- ,, I

,... .... ..., r I r-- ---1 ,....-.- I I II I

_.,( lL-----~r-----1 _....- IJ II . II

_. .... - I f---"" •.• _, ______ .J ,... .... 1 1 1- ------ ~ I I I

_............ '' IJ II II I ,.. Jl-----.J 1 1 1 1 : :: :r--·;, ",, '" ·- j~-----l }---------~~-------11 11 II . I L, ________ ::------~~-------1~ JL ______ j : :I 11 1l II I 1 Jl i1 Jl II I t.. _____ .! '---- _____ J L ________ J L _____ _j L- ---- _j r--- ----1 r --- -----,~- ----~ r--- -, r----, I I' J, I I I I I : 1: II 11 l1 ,-------~------.JL, • ~ ~ ..... --lr--------J

,, II II I I ,, II II II I : Ji II II II ,--- --~ ,------- ~ i-- ----, ,---- ----j f--------1 I Jf I 'I Jl I : Jl 1: 11 II I r- -------< L __ - ---1 r---- _.J r----- --11------ --l

II I I I : IJ II 11 I 1 11 II IJ II I L .. - ____ J L. _ --·-- .J L __ ----- .J L .... _____ j l_ ------- J r--------: r --------, r·- ------lr- -----v-- -----~ I II II II II I : 11 l1 IJ 11 I r----- --- -i ~--- ------1: - ~ f- ------------, r- -------- -j I : 1 11 11 1l I : ,, ,, 11-----------jl----'--·---~ 1-------1'-------.Jl-. ·---il II I 11 lj If;. --.,,.. -.ll j : I: II 11 Jl ,......-1 ______ ~1-----~1- _,, _;~---: ,: ,I 'I ................ L-----..J~---·-----jl __.1!.- · I II II l I .-1---------'1 )I.-I II ~--J II _.. I ) 1.--- _. -I _.. .-

J t.- .....

44

~ 0 Q)

"" Q) 0

"' r-i "" b ·rl I _._,

"' "' u

. a-.

45

..,.. a-

\--- -r--T- -T---~----~--~ r-- T- -~ -r-' \ I I I I I I 1 I I I \ \ I 1 i ! I I ! 1 1 I \ \ I I I I I I: I I 1 \ 1L_l ___ l ___ ~ __ j ___ l __ _j L---~---L .. L---~ \---l-1--1- --~---~--~ ~--T-- ~-~-~-I \ 1 I I ! I I I l ! 1 1 \ \ l I I I I I I I I I I \ \ · I I l I I \ \ I I l I I I I I I I I

\.._..J_l ___ L ___ l ___ ,_ __ ...J L ---'---~- -~1-- _.J

\,~--~1.-T-T--rl!_T_r_l_T\ \ I 1 I l I \1 1 \ L-..J-_.L ___ ,_ ___ l ___ j L __ ..L __ l __ _j __ J.. ----1

\~--rrr-Flrr-~ --,--fF\ \ I I l l \ I 1 1 1 I \ L-L..l--L--.1-_....J '---.1...---'- --..1..--..L....l. -----' \---~-i---~--~ r --T---,-- -~---~---:- -, \ I I I I I I I I I : \ I 1 I 1 I l I 1 I I l \ \ 1 I ! 11 I 1 1 I I \ \ 1 I I I I 1 I I

\..._ ..J_L __ .l, __ ..J L __ ..J.- -..L-- .l_ -.I...- _.J... -- _:.

Figure A.lO. Cracks in Cast-in-place Deck, Span 5SB.

APPENDIX B

LOAD TEST STRAIN READINGS

47

-40

-20

~

z I -10

0 It !2 ~ 0 2 ;( C( +10

Iii +20

+.30

T40

-40

-50

-zo

? I -10

0 I!! 'd l 0 z :;( It +10

~

+20

--~o

A B c

TOP GAGE.

/". I -

7 -

7 r'\ - "STAIIC

1\ v ' } \_ TRUCK ..... ~ ~ _/

POSITION (SEE FIG..~)

' ' I ------ ----- --------- -------STAIIC

BOTIOM GAGE

:-· igure B .1. Strain Readings, Top and Bottom Transverse Gages No. 1, Pattern No. 1.

A B c

lOP GAGE

-t--~------·----·----------·-

TRUCK

POSITION (SEE FIG.. 2G>)

----t------------· -------·-

·c-igure ll. 2. Strain Readings, Top and Bottom Transverse Gages No. 2, Pattern No. 1

48

z .GE

... 1\ - ··-·· ·- ------·-~----

___ ,_ ~------ --------STATIC

.

/ -.......J J .

\ ~ ~

\ TRUCK ~ A / P0'51TION " (>«-·~'I . "\ r-' \ J ------ i- ---- --------- ---------STATIC

BOTTOM GAGE.

Figure B.3. Strain Readings, Top and Bottom Transverse Gages No. 3, Pattern No. 1.

A c -·

TOP GAGE

• ~- -

~w -- IV - STATIC

1--·

v ~ ....,.J _-_; "'-- TRUcK ----- /\ ~

POSITION

~ (SEE. FIC..2C.)

----- v \ ~STATic··---

··-·--. --------------------- -- ···- ----

BOTTOM GAGE.

-- . Figure B.4. Strain Readings, Top and Bottom Transverse Gages

No. 4, Pattern No. 1.

49

-30

-20

:z ::;: a: +10 1--

-40

-20

......... z

I -\0 0 a: !d 6 0 z ~ tr tiO Iii

-t!>O

-+40

A

!I f----- ---!+

I ~ I 1 r I I

I I '--"" ~---J /""'\. r-- -~

c

-- - TOP GA.GE

1-Jr-- ------ ----- ----~'TA"TIC II ·. n r, "

,, J I l \ I I I

i I v ~ ~ ~:;?\ t\ h :. !RUcK ru-- - ~ v . - S'TA.'TIC. PoSITION (SEE "'\C... 2

-40

-'30

-20

z I -\0

0 (t \<

_; 0

2

-40

-30

-20

" z I -10 c a: f,!

6 0

+30

r-

A

-

l'J.. 11\ -v~ ' _...J

-........ ~ -'V v

-- 1"--

----

c. .

TOP GA.GE.

-

-

1'1 [_/'\_ _..:...~-STATIC_·~---- .. ___ --~-

~ TRUCK /

. POSITION (sEE. 1'\CO.Zt.)

~ v -- - --ST"A"IIC BOTTO IV\ GI'.GE.

------

Figure B.ll. Strain Readings, Top and Bottom Transverse Gages No. 1, Pattern No. 2.

-40

-30

-20

~

z I -10 0 It ~

-6 0 z ~ It 410 f-

A B c

A lOP G~E.

-30

-20 ·----f-

2

-40

-30

-20

2 I -\0 @ \,!

.; 0

z ~ a: +10 Iii ~20

+40

1-----

--1-----

A B c

TOP G,AGE. . .

~ -\--------SIAliC. r----1'- ~--_;-

v '-..,.../ TRUCK

""" ~ / POSITION

(SEE. l"\0..21.>)

"' "-./'

---- ------- j- ------- -'=>TA>IC 8DTTOM GAG'E.

Figure B.lS. Strain Readings, Top and Bottom Transverse Gages No. 5, pattern No. 2.

-40

-50

-20

~

6 I -10

~ S! 1- 0 z 4: (!. +10

~

+'20

+40

I \ I

f-----· ~:-i"\1

~ l! .. '\ ----- f-----

.

B c

~ ,, ~ I 1 II - -- \DP G.AG'E.

II i i I I 1\ " II i I I '\ I j I j f.L~~~ -\------ --SIA>IC ~I \ \~ . -- >RUCIS\T\ON

(SE"E. FIG. '21,)

-------- 1----------STA>Ic.

-

-- BOITOIV\ G./>.GE-

Figure B.l6. Strain Readings, Top and Bottom Longitudinal Gages No. 6, Pattern No. 2.

55

-"'a -3o

-20

:2

I -\0 0 cr ld

2- 0 :z (( a: +10 {n

+20

~40

1-----1 I

/ .L..

~,

r-----

A c

~ ft II " Ill H II ,I ---TOP GA.GE I I q I jl I j I I• I\ I I I • I I I I , I I I I '· . tr--...l- ,-- -- ..... ,_ iL I i -------- STA.\\C

ll f \ I I .

LA J" \J ~ .... _ . !RUCk _._,..;__

______ ..;.. __ y.._ ___ ---- -STAIIC. POSITION

(SEE F\G.21c)

- BO\TOM Gk;.'f.

Figure B.l7. Strain Readings, Top and Bottom Longitudinal Gages No.7, Pattern No.2·

-40

-30

-zo

1 f -\0

0 it. 11 1 0

'-..-'

2

~ +10 ~

+20

+30

+40

A

!\ ~ ',', ! I d I I I ---ToP GAGE ,.,, 1 lt• ,,,, ,,,, 1\J\ /vi

-- ---f ---+ -\----+-- -\----- ---'STA)IC I / ..._ ..... .._,.J \

--- -· ---~ ---------v..__--------"2.>rAIIC TRUe«

PosiTION (bEE. FIG.. 2~)

t----t-----t-----------------------·--------1

----' BOTTOM G~E.

Figure B.l8. Strain Readings, Top and Bottom Longitudinal Gages No. 8, Pattern No. 2 ·

56

-40

-30

-20

I -10 0 ct u

.1:. 0

..-:5o

+4o

A B c -----r=-- ------

---lOP GAGE

,__ ___ ---1- -----,.- ---------STA"TIC (-),f~ ~Jv: I~\ ·~~ ...-: -:..!. ~ .... __ ....... \ TRUck

iJ 'V' " -- --o;::,"TA\IC. Po5\TION

l"-'CE 'FIG.. '2")

----- -------------

- 13DT"IDM GJ>c.t. Figure B.l9. Strain Readings, Top and Bottom Longitudinal Gages

No. 9, Pattern No. 2 .

57

145-1 a145-1 b

study of in-service bridges constructed with prestressed ...continuity of action between beams,...

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