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Field Strengthening and Validation of FRP Composites Technology in Missouri

David J. Holdener1, John J. Myers2, Antonio Nanni3

1 Graduate Research Assistant, Center for Infrastructure Engineering Studies, Department of Civil, Architectural & Environmental Engineering, Univ. of Missouri–Rolla, Rolla, MO

2 Associate Professor, Center for Infrastructure Engineering Studies, Department of Civil, Architectural & Environmental Engineering, Univ. of Missouri–Rolla, Rolla, MO

3 Lester and Gwen Fisher Endowed Scholar Professor and Chair Department of Civil, Architectural & Environmental Engineering, Univ. of Miami, Coral Gables, FL

Abstract Strengthening of the existing highway bridge infrastructure with fiber reinforced polymer (FRP) has become a viable option in recent years. Five structurally deficient Missouri bridges have recently been retrofitted with FRP technologies with the intent to validate the overall in-situ performance under a variety of tests. These tests focus on Nondestructive testing (NDT) techniques as a means of conducting these tests without damaging the existing structures. This examination includes testing practices for proper installation of FRP such as: surface roughness, fiber alignment, bond strength and FRP delaminations. In order to monitor the strengthened bridges new technologies in crack sensors and strain gages were applied and monitored. Load tests were also conducted to determine relative deflection changes prior to and after FRP strengthening. This paper will discuss the methods of NDT techniques utilized on the project known as “Preservation of Missouri Transportation Infrastructure: Validation of FRP Composite Technology through Field Testing” and provide the current findings for this on-going project. Introduction Fiber-reinforced polymer (FRP) technology continues to make strides in structurally deficient bridge strengthening applications primarily due to its corrosion resistance, high strength to weight ratio and rapid installation process1. However, durability validation and inspection criteria need to be implemented before FRP will gain widespread acceptance throughout the engineering and infrastructure community. The five-bridge project entitled: “Preservation of Missouri Transportation Infrastructure: Validation of FRP Composite Technology through Field Testing”, uses Nondestructive testing (NDT) techniques to evaluate the use of these FRP materials.

This paper is broken down as follows. First, an overview of composite strengthening techniques will be presented followed by background information on the individual bridges. Second, NDT techniques utilized on this project associated with the installation performance of FRP such as fiber alignment, surface roughness and debonding will be analyzed. Next strain measurement and crack sensor monitoring applications will be explored in connection with bridge P-962. Finally, load testing of these bridges utilizing non-contact advanced surveying equipment for deflection measurement will be presented and discussed. Composite Background Information

Currently there exist a number of composite strengthening techniques available for implementation on bridges. It is important to have an understanding of each of these individual

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techniques because their uses can be project specific in nature with each having their merits. Manual FRP lay-up is the process of adhering rolled sheets of FRP to concrete with two part resin. The types of FRP include Glass (GFRP), Aramid (AFRP) and, the most common for structural applications, Carbon (CFRP). Care must be taken to ensure a good bond by roughening the existing concrete surface with sandblasting or by other similar techniques. In some cases smoothing and leveling of the concrete surface with putty may be required. Corners must also be rounded in the case of shear strengthening with U-wraps to prevent localized stresses in the FRP.

Pre-cured laminates are plates of the resin and fiber matrix that have been cured prior to application. These plates are applied to the prepared concrete surface with a two part epoxy in a similar manner as the sheets. However, pre-cured plates need to be properly supported during installation to a soffit to ensure that there is proper contact and a solid bond.

Near surface mounted (NSM) bars are rectangular or circular bars applied by cutting grooves into the existing concrete surface where an increase in moment capacity is required. These grooves are filled with epoxy then the bars are pushed into the grooves causing excess epoxy to seep out. Additional epoxy is then applied where required over the bars and the surface is finished.

Steel reinforced polymer (SRP) is very similar to FRP with the primary difference being that SRP contains high strength steel wires instead of carbon, glass or aramid. SRP is applied the same way as FRP sheets; it is impregnated with resin and applied to the prepared concrete surface.

The final technology associated with bridge strengthening is mechanically fastened fiber reinforced polymer (MF FRP). MF FRP is essentially pre-cured laminate plates with pre-drilled holes that are fastened to the concrete surface with mechanical bolts. This strengthening technique is fast for installation purposes since the concrete surface does not need to be prepared.

The above strengthening techniques have their merits and shortcomings and need to be evaluated on a project basis before they are selected for use. Each of these technologies was implemented on the five bridges studied for this project. Project Background The Preservation of Missouri Transportation Infrastructure-Validation of FRP Composite Technology through Field Testing project is a current research project underway at the University of Missouri-Rolla (UMR) focusing on FRP strengthening validation. It is a joint project between the Missouri Department of Transportation (MoDOT), the University Transportation Center, and a private sector funding initiative2. The purpose of the project is to help make the technology of FRP strengthening available to bridge owners and engineering professionals2. The project duration spans five years, from April 3, 2003 to June 1, 2008, to allow for long-term field validation through load testing.

The project was not competitively bid by the University due to the integrated research nature of the project. Therefore the repair, strengthening, and long-term monitoring costs of the project were not representative of a typical commercial project. For this reason, the financial aspects of the project are not presented.

The individual bridge strengthening was completed in 2003 and involved utilizing five different composite strengthening techniques on five different structurally deficient bridges throughout the state of Missouri. Each of these structurally deficient bridges was load posted and visually rated prior to strengthening. The construction dates, daily traffic, load posting

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information and inspection ratings are all summarized in Table 1. The bridges were also scattered around the state of Missouri with no two bridges lying on the same route. The relative location of the bridges within Missouri and the composite strengthening techniques utilized on the bridges are provided in Fig. 1 and Table 2 respectively. It may be noted that FRP manual lay-up strengthening was used on every bridge. The following sections will outline the different characteristics of each individual strengthened bridge; for more detailed information the Preservation of Missouri Transportation Infrastructure: Validation of FRP Composite Technology through Field Testing – Volume I & II2.

Table 1: Bridge information prior to strengthening2 Load Posting Visual Inspection Rating

Bridge code

Year Built

Average Daily

Traffic

Truck Weight (Tons)

Speed (mph)

Deck Rating SuperstructureSubstructure

T-0530 1937 200 21 15 5 5 5 X-0495 1948 300 19 15 6 6 7 X-0596 1946 2000 18 18 6 5 5 P-0962 1956 350 18 15 7 6 6 Y-0298 1937 1100 18 15 5 5 5

Figure 1: Location of bridges strengthened with composites in Missouri2

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Table 2: Composite strengthening utilized2

Bridge Code

CFRP Sheets by Manual Lay-Up

Pre-cured CFRP

Laminates

CFRP NSM Bars

SRP by Manual Lay-Up

MF FRP Laminates

T-0530 YES YES X-0495 YES YES X-0596 YES YES P-0962 YES YES YES Y-0298 YES YES

Bridge X-596 Bridge X-596 is located on Hwy C and spans Lander’s Fork Creek in Morgan County, Missouri. This bridge was originally constructed in 1946 and consists of three simply supported reinforced concrete spans of lengths 42.5 feet, 52.5 feet, and 42.5 feet with a roadway width of 20 feet. The load testing is currently being conducted on the center 52.5 feet span. The 6 inch deck is supported by three tee beams spaced 9 foot centers2.

The condition of X-596 prior to strengthening was such that there were cracks in the exterior girders with exposed reinforcement. Fig. 2 depicts the bridge and Fig.3 shows the condition of the substructure with exposed rebar. In addition there were cracks at the connection between girders and the intermediate diaphragms and bents. The end bents were in overall good condition aside from rusty steel bearing plates.

X-596 was strengthened using NSM bars for flexure and FRP manual layup for flexure and shear. In order to accomplish the installation of these composites, 116 cubic feet of deteriorating concrete needed to be removed and the new surface cleaned. The surface was then prepared by rounding corners and roughening necessary surfaces with sandblasting for the placement of FRP via manual layup2.

Figure 2: Bridge X-5962

Figure 3: Bridge X-596 substructure2

Bridge T-530 Bridge T-530 is located on Hwy M and spans Crooked Creek in Crawford County, Missouri. This bridge was originally constructed in 1937 and consists of five simply supported spans all 47 feet long with a roadway width of 23 feet. The load testing was conducted on the second span from the North abutment. The 6 inch deck is supported by four tee beams spaced 6.5 foot on center.

Exposed Rebar

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The bridge is shown in Figures 4 and 5 before strengthening. Prior to strengthening of bridge T-530 the concrete exhibited some spalling along the edges of the bridge. The concrete in the deck and beams was noted to be in good condition with minor cracks that required no injection. The piers and abutments were in good condition and the bents showed some deterioration due to steel corrosion2.

T-530 was strengthened in flexure using both manual layup and precured laminates on the deck and girders. Ten cubic feet of concrete needed to be removed and from deteriorated areas and the surfaces were then prepared and the reinforcement was placed.

Figure 4: Bridge T-5302 Figure 5: Bridge T-530 substructure2

Bridge X-495 Bridge X-495 is located on Hwy C and spans Crane Pond Creek in Iron County, Missouri. This bridge was originally constructed in 1948 and consists of three simply supported spans of lengths 42.5 feet, 52.5 feet, and 42.5 feet with a deck width of 24 feet. The load testing was conducted on the center 52.5 foot span. The 6 inch deck is supported by three tee beams spaced 9 foot on center3.

Prior to strengthening the condition of the beams, abutments and piers were noted to be in good condition. Of the bridges tested in this project this bridge was in the best condition when considering its overall age and average rating2. Figs. 6 and 7 illustrated the visual details of the bridge prior to strengthening.

X-495 was strengthened in flexure using NSM bars and manual FRP lay-up. Due to the good condition of this bridge, concrete repair work did not require the removal of deteriorated concrete. The surface was prepared in accordance with accepted practice for installation of FRP via manual layup and NSM bars2.

Figure 6: Bridge X-4952 Figure 7: Bridge X-495 substructure2

Bridge P-962 Bridge P-962 is located on Hwy B and spans Dousinbury Creek in Dallas County, Missouri. This bridge was originally constructed in 1956 and consists of three simply supported spans all 42.5 feet long with a 23 foot wide deck. The load testing was conducted on all three spans with

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primary monitoring focused on span 1. The 6 inch deck is supported by three tee beams spaced 9 feet on center3.

Prior to strengthening the condition of the beams and piers were noted to be in good condition as shown in Figs. 8 and 9. The Abutments were not in good condition and the deck required some repairs2.

P-962 was strengthened in flexure using NSM bars manual FRP lay-up and SRP. In order to place the SRP and FRP on bottom of the bents 20 cubic feet of concrete needed to be removed. In addition cleaning and substrate preparation was required for the SRP and FRP sheets.

Figure 8: Bridge P-9622

Figure 9: Bridge P-962 substructure2

Bridge Y-298 Bridge Y-298 is located on Hwy U and spans Crews Branch Creek in Pulaski County Missouri. This bridge was originally constructed in 1937 and consists of two continuous spans each 15’ long, 7 inches deep and 27 feet wide. The load testing was conducted on both spans.

Prior to strengthening it was noted that the east span was in poor condition, especially close to the edge of the bridge due to poor drainage. Also upon visual inspection the east span shows some deflection. The west span has sound concrete; however, due to improper concrete cover the structure has some exposed reinforcement as illustrated in Figs. 10 and 11 for the visual appearance of Y-298 before strengthening.

Y-298 employed the use of two strengthening techniques for flexure. The first was FRP manual lay-up, which was difficult to install due to the poor condition of the concrete substrate. The second strengthening involved the use of MF FRP laminates. These were mechanically fastened to the substrate and provided a quick means to strengthen the bridge; however, the long-term performance of this strengthening technique is not yet documented.

Figure 10: Bridge Y-2982

Figure 11: Bridge Y-298 substructure2

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Table 3: FRP strengthening schedule and analytical capacity increase4 Bridge ID Span # Girder Flexural Reinforcing Description (Girder) Capacity Increase

X-596g 2 Interior ML: 4 Plies 20" Wide; NSM Bars: 4 Total 42% X-596g 2 Exterior None NA X-596g 1, 3 Interior ML: 4 Plies 20" Wide; NSM Bars: 4 Total 44% X-596g 1, 3 Exterior ML: 2 Plies 16" Wide 16% T-530g 1, 3, 5 Interior ML: 4 Plies 16" Wide 29% T-530g 1, 3, 5 Exterior ML: 2 Plies 16" Wide 15% T-530g 2, 4 Interior 1 Laminate Plate: 12" Wide 29% T-530g 2, 4 Exterior 1 Laminate Plate: 12" Wide 15% X-495g 2 Interior ML: 5 Plies 20" Wide 40% X-495g 2 Exterior None NA X-495g 1, 3 Interior ML: 5 Plies 16" Wide; NSM Bars: 2 total 44% X-495g 1, 3 Exterior ML: 2 Plies 16" Wide 16% P-962g 1, 2 Interior ML: 5 Plies 16" Wide plus 4 NSM Bars 56% P-962g 1, 2 Exterior ML: 3 Plies 16" Wide 25% P-962g 3 Interior SRP 3X2: 3 Plies 16" Wide 54% P-962g 3 Exterior SRP 3X2: 3 Plies 16" Wide 49%

Bridge ID Span # Type Flexural Reinforcement Description (Slab) Capacity IncreaseX-596s 2 NSM Tape 2 Per Groove @ 12" O/C 78% X-596s 1, 3 Manual Layup 1 Ply 6" Wide @ 15" O/C 61% T-530s 1, 3, 5 Manual Layup 1 Ply 9" Wide @ 15" O/C 141% T-530s 2, 4 Laminate Plates 1 Plate 3" Wide @ 15" O/C 143% X-495s 1, 2, 3 Manual Layup 1 Ply 6" Wide @ 14" O/C 65% Y-298s 1, 2 Manual Layup 2 Plies 8" Wide @ 12" O/C 23% P-962s 3 SRP 3X2 1 Ply 4" Wide @ 20" O/C 62% P-962s 1, 2 Manual Layup 1 Ply 6" Wide @ 14" O/C 64%

Bridge ID Span # Girder Shear Reinforcing Description (Girder) Capacity IncreaseX-596g 2 Interior ML: 1 Ply Continuous U-Wrap 26% X-596g 2 Exterior None NA X-596g 1, 3 Interior ML: 2 Plies Continuous U-Wrap 52% X-596g 1, 3 Exterior None NA X-495g 2 Interior ML: 1 Ply Continuous U-Wrap 30% X-495g 2 Exterior None NA X-495g 1, 3 Interior ML: 2 Plies Continuous U-Wrap 51% X-495g 1, 3 Exterior ML 1 Ply 12" Wide U-Wrap @ 24" O/C 18% P-962g 1, 2 Interior ML: 4 Plies Continuous U-Wrap 64% P-962g 1, 2 Exterior ML: 1 Ply Continuous U-Wrap 24% P-962g 3 Interior SRP 3SX: 3 Plies Continuous U-Wrap 63% P-962g 3 Exterior SRP 3SX: 1 Ply Continuous U-Wrap 36% Key: s-slab/deck strengthening; g-girder strengthening; ML-manual layup; NSM-near surface

mounted bar; SRP-steel reinforced polymer

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The strengthening for the above bridges was designed utilizing ACI 440.2R-022. Table 3 presents a detailed reference for the type and amount of strengthening applied to each span and the analytical capacity increase in either flexure or shear gained by adding the composites. Testing measures were required to ensure proper installation had been performed. The following section covers these testing techniques in detail. NDT for Installation Quality Control Nondestructive Testing Techniques are valuable in that they do not damage existing structural elements. The following NDT techniques were utilized on bridge P-962 to evaluate the performance of FRP systems. Surface Roughness The roughness of the concrete surface plays a vital role in its bond performance with the FRP. If the surface is too smooth or rough the bond will be poor and the FRP structural system may ultimately fail. One way of measuring roughness is to compare plastic specimens of varying roughness with the concrete until the desired roughness is achieved2. This can be extremely ambiguous and user dependent. Thus, a new technology involving the use of laser striping technology was developed at UMR and utilized. The laser profilometer projects thin strips of laser light at an angle of 45 degrees onto concrete surface5; see Fig. 12. A high resolution camera perpendicular to the concrete surface then records a video that is digitized and sent to a computer for analysis. The roughness can then be quantified based upon the average pixel to pixel angles; this is called an average inclination angle5.

For bridge P-962 these measurements were taken on 12 inch centers in four prepared locations prior to placement of the FRP. The average value of the inclination angle for all points was roughly 8 degrees whereas the target value was 12 degrees. Therefore, the concrete surface was not as rough as optimum, this could be due to the small amount of material removed by the sandblasting2.

Figure 12: Laser profilometer5

Fiber Alignment Improper installation of FRP components by more than 5 degrees from the intended alignment can significantly reduce the performance of the strengthening system8. In order to measure this variance the FRP is installed with a tracer woven into it and clear epoxy is used for attachment in order for the tracer to be visible. A chord is then stretched across the installed FRP in the

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direction of the correct alignment. Imaging software is then utilized to determine the angle differences8.

A total of 421 fiber alignment tests were conducted on bridge P-962’s deck in the above mentioned manner. The mean error was determined to be 3.6 degrees; however, approximately 25% of the measurements were above the recommended 5 degree threshold. This can be attributed to the fact that the FRP strips used were thin and difficult to place along the correct alignment8. FRP Delaminations Surface delaminations or voids between the FRP and concrete surface can be detrimental to the strength of the FRP System. These delaminations can be caused by moisture, fluctuating temperatures and improper installation6. According to ACI 440.2R-027 any delamination over 25 square inches should be repaired by means of cutting away and patching the FRP sheet. In addition if the FRP delaminations are between 25 and 2 square inches in size they can be injected with resin for repairs. In order to test and monitor these delaminations on bridge P962 the following NDT procedures were conducted.

First surfaces were created with artificial delaminations on non critical structural components as shown in Fig. 13. This was accomplished by installing FRP via manual layup on one abutment and one bent and forcing air under the FRP sheets and then releasing the air once the epoxy cured. These constructed areas were then monitored utilizing the two systems described below.

Figure 13: Artificial delaminations6

The first method involved the use of impact echo testing. An Olsen Instruments impact

echo tester used frequency domain analysis to locate the delaminated areas. The testing located all forced delaminations and some small delaminations that were not deliberately placed. The testing was determined to be fairly time consuming, requiring 30 minutes to test a 2.75 square foot area8.

The second method enlisted the use of near-field microwave NDT techniques. The testing apparatus consisted of a microwave probe, signal processing station, and 2D scanning platform. To work the system transmitted an incident signal from the probe which was then reflected from the surface and used to generate an image of the scanned area6. This method was shown to be quick and effective at discerning the location of the delaminations6.

Artificially formed defects for long-term growth monitoring.

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Strain Gages & Crack Sensors Strain gages and crack sensors provided internal monitoring of bridge P-962’s structural components. Traditional electrical resistance and new fiber optic strain gages were mounted in parallel with the reinforcement of the central span of bridge P-962. Fiber optic strain sensors enjoy several attractive features such as robustness, low profile, sensitivity, and can be directly embedded within concrete. Preliminary tests, conducted by loading P-962 with a light truck, showed the results of both strain gages to be in agreement with each other9. Strain data collection during load-testing and analysis is on-going and will continue throughout the duration of the project.

Cracks formed in concrete can cause significant attrition due to water damage, and chloride attack10. It is important to know when and where significant cracks occur so they may be properly treated before significant damage has occurred. Two crack sensors were installed on the deck of bridge P-962 as a means of monitoring for these cracks. To date, new cracks have not been found during load testing of this bridge11. The crack sensors will continue to be monitored during load tests until the end of the project. Load Testing Utilizing Non-Contact Deflection Monitoring Load testing represented an imperative step in validating the effectiveness of the FRP composites in the field. The first series of load tests began July of 2003 and have been conducted semi annually since, once each fall and once each spring.

Four of the five bridges for this project were located in areas such that traditional deflection monitoring equipment, such as Linear Variable Displacement Transducers (LVDT) and String Transducers, would be extremely difficult to utilize due to the height of the bridge spans above the creek beds. It was decided that optical laser surveying equipment would be ideal for the measurement of deflections under static load testing of these bridges. Research conducted by Merkle and Myers11 showed the Leica TCA 2003 Total Station to be accurate to 0.005 inches at distances of 200 ft to the target or less which is comparable to the traditional deflection monitoring equipment4. However, the total station requires approximately one minute to statically measure each point elevation, whereas, an LVDT can record data points continuously4. The additional time the total station required to measure points was more than compensated for when considering the required time to setup LVDTs. Load testing setup for the total station was easily accomplished in half an hour; whereas setup for LVDTs with bridge spans less than fifteen feet can easily take several hours11. Load Test Setup The load testing procedure for the five bridges involves the static placement of two loaded H20 dump trucks provided by MoDOT3. The weight of these trucks needed to be recorded since large variances in weight between load tests can cause a considerable difference in deflection4. Load tests utilizing loaded dump trucks have been conducted in the past and are an effective and simple means to evaluate bridges12. This method utilized a Leica TCA 2003 Total Station and optical surveying prisms for both targets located on the bridge and reference points; see Fig. 14 for a load test setup example.

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Figure 14: Load test setup

Iron plates were first epoxied to the underside of the bridges at select locations and given

time to cure prior to load testing. This was only required once since the plates remained for future load tests. Magnetized target prisms were then attached to these plates through the use of a range pole. During this time a location for the total station was selected. The location was selected to avoid direct sunlight on the total station or the potential for future sunlight as the test progressed. The total station was set atop a tripod that was well founded in the ground and then leveled. The total station operator then made certain the target prisms were visible through the sight. Next, three reference prisms were placed in locations far apart from each other and directed at the total station. These reference prisms served as guides for determining if the total station had exhibited any movement or settlement in between readings. Load Test Procedure The total station was set up to automatically record the locations of all prisms. This was accomplished by first locating and naming all targets in a sequential order that was well documented in a field book. The total station was set to record each of these data points three times and any discrepancy between two points by more than 0.005 inches was later removed during post processing. Traffic over the bridge was then stopped and the elevations of the points were determined for the unloaded condition for the establishment of a baseline. Next, the loaded dump trucks were placed in stop 1 which is the maximum shear configuration, the bridge was given five minutes to settle under the load and the total station recorded the new elevations. The trucks were then moved off of the bridge and traffic was allowed to pass. Stops 2, 3, 4, and 5 were then performed in a similar fashion with the trucks positioned as shown in Fig. 15. After stop 5 the bridge was given five more minutes to rebound and a final no load run was conducted to determine if the bridge elevation had changed from the first reading. This concluded a typical

Reference Prism

Reference Prism

Target Prism

Total Station

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load test; the total station, reference prisms and target prisms could now be taken down and the data could be processed.

Figure 15: Stop positions for bridge P-962

16Hp

16Hp 8Hp

16Hp

16Hp 8Hp

T r u c k # 2

T r u c k # 1Test 1Maximum

Shear

Test 2Maximum

Moment

Test 3Maximum

Shear

Test 4Overload

Exterior Girder

Test 5Overload

Interior Girder

Truck #1 is centered in Lane 1 facing East with the centroid of its rear axles over the first stop line; Truck #2 is centered in Lane 2 facing East with the centroid of its rear axles over the first stop line

1st. Stop Line 2nd. Stop Line 3rd. Stop Line

20'

10'

5'10

'5'

5'5'

52'-6"5'-9" 20'-6" 5'-9"20'-6"

Centerline of Lance 1

Centerline of Bridge

Centerline of Lance 2

Truck #1 is centered in Lane 1 facing East with the centroid of its rear axles over the second stop line; Truck #2 is centered in Lane 2 facing East with the centroid of its rear axles over the second stop line

Truck #1 is centered in Lane 1 facing East with the centroid of its rear axles over the third stop line; Truck #2 is centered in Lane 2 facing East with the centroid of its rear axles over the third stop line

Truck #1&2 are centered about the bridge (roadway) centerline back-to-back at the second stop line (Midspan)

Truck #1&2 are centered in line 2 back-to-back at the second stop line (Midspan)

16Hp

16Hp 8Hp

16Hp

16Hp 8Hp

T r u c k # 2

T r u c k # 1

16Hp

16Hp 8Hp

16Hp

16Hp 8Hp

T r u c k # 2

T r u c k # 1

16Hp

16Hp 8Hp

16Hp

16Hp8Hp

T r u c k # 1

16Hp

16Hp 8Hp

16Hp

16Hp8Hp

T r u c k # 2

T r u c k # 1 T r u c k # 2

N

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Load Test Results The results produced by the total station were transferred into a database program and used to generate deflection plots of the bridge. These deflections were determined by taking the difference between the loaded condition and the baseline condition. The reference point elevations were also considered at this time. If all of the reference points showed signs of movement during the course of the test by roughly the same amount, then it was probable that the total station had undergone some movement. To compensate for this movement, the elevation change was incorporated into the deflection of the bridge.

The exterior girder deflection of bridge P-962 with the trucks located in stop 3 configuration is shown in Fig. 16. Note that test 1 is the before the bridge was strengthened with FRP, and tests 2 through 8 are the after strengthened case. Also note that tests 4, 5 and 7 show a larger deflection than the before strengthened state. Part of this can be attributed to differing truck weights (see Table 4) between tests; in fact for tests 4, 5 and 7 the combined truck weights have a percent increase from test 1 of approximately 7%, 4% and 6% respectively. Future data analysis will look at normalizing the deflection of the bridge with respect to truck loads. Thus far the load tests have not shown a large increase in deflection in comparison to the before strengthened load test 1. Three more load tests will be conducted in the next year an a half with further deflection results.

Figure 16: Longitudinal deflection of exterior girder

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Table 4: Bridge P-962 total truck weight percent change from test 1

Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Truck 1 & 2 Total

Wt (Kips) 112.34 112.32 112.34 120.50 117.48 132.24 119.22 124.06

Percent change from Test 1 NA -0.02% 0.00% 7.26% 4.58% 17.71% 6.12% 10.43%

Project Summary NDT results conducted thus far on the five bridges project have shown satisfactory results with no growth in intentional or non-intentional defects. The effect of surface roughness on the long-term bond performance of the FRP externally bonded materials is on-going with no bond related issues observed to date. Fiber alignment tests associated with FRP during installation have documented the typical installation level that may occur and yielded reasonably acceptable results for bridge P-962. Furthermore, this project has yielded additional tools for use by the inspector/owner to verify installation compliance.

The strain gages and crack sensors are on going and results thus far have not indicated any unusually high levels of strain in the FRP nor any new crack development. Currently the load tests conducted have not found any significant changes in bridge stiffness; future work will focus on normalizing the data for the effects of truck weight variance between load tests. Future testing will be conducted until the summer of 2008. Other work that has been completed or is in progress includes specification documentation for design and installation, guidelines for the selection of candidate bridges for FRP strengthening, and modeling to predict the life expectancy of FRP bridges in Missouri. Acknowledgements This work has been supported by the University Transportation Center (UTC) at UMR and a grant from the Missouri Department of Transportation (MoDOT). The Industry members of NSF I/U CRC also based at UMR have been responsible for supplying materials and construction. References 1. Nanni, A. and A. Lopez. (2004) Validation of FRP Composite Technology through Field Testing. In The e-

Journal of Nondestructive Testing & Ultrasonic, Vol. 9, No. 1, 9 pp. 2. “Preservation of Missouri Transportation Infrastructure: Validation of FRP Composite Technology Through

Field Testing – Vol. I & II”, http://campus.umr.edu/utc/research/r098/, 1/2/2007 3. Merkle, W.J., 2004 Load Distribution and Response of Bridges Retrofitted with Various FRP Systems, MS

thesis, Univ. of Missouri-Rolla, Rolla, Mo. 4. Merkle, W.J. and J. J. Myers. (2006) Load Testing and Load Distribution Response of Missouri Bridges

Retrofitted with Various FRP Systems Using a Non-Contact Optical Measurement System. Transportation Research Board, 85th Annual Meeting January 22nd – 26th, Washington, D.C. CD 22 pp.

5. Maerz, N., P. Chepur, J. J. Myers, and J. Linz (2001) Concrete Roughness Characterization using Laser Profilometry for Fiber-Reinforced Polymer Sheet Application. In Transportation Research Record, no, 1775, pp. 132-139.

6. Stephen, V., S. Kharkovsky, J. Nadakuduti, and R. Zoughi. (2004) “Microwave Field Measurement of Delaminations in CFRP Concrete Members in a Bridge”. 16th World Conference on Nondestructive Testing. Montreal, Canada.

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7. ACI 440.2R-02. “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures,” American Concrete Institute, Farmington Hills, MI, 2002.

8. Maerz, N., Galecki, G. and A. Nanni. (2004) Experimental Nondestructive Testing of FRP Materials, Installation and Performance. In The e-Journal of Nondestructive Testing & Ultrasonic. Vol. 9, No. 11, 8 pp.

9. Fonda, J.W., and S.E. Watkins. (2004) “Embedded Fiber Optic Sensing For Bridge Rehabilitation”. 16th World Conference on Nondestructive Testing. Montreal, Canada.

10. Chen, G., (2004) “Novel Cable Sensors for Crack Detection of RC Structures”. Proceedings of the Structural Materials Technology: NDE/NDT for Highway and Bridges. Buffalo, NY.

11. Merkle, W.J., and J. J. Myers. (2004) Use of the Total Station for Load Testing of Retrofitted Bridges with Limited Access. Proceedings of SPIE – Smart Structures and Materials: Sensors and Smart Technologies for Civil, Mechanical, and Aerospace Systems, Vol. 5391 pp.687-694.

12. Stone, D.K., 2002 Investigation of FRP Materials For Bridge Construction, Ph.D. dissertation, Univ. of Missouri-Rolla, Rolla, Mo.