8.0 running a load test using sts-wifi completerichard/bridge/bdi/8.0 running a load test... ·...

8888.0 .0 .0 .0 Running a Load Test using STSRunning a Load Test using STSRunning a Load Test using STSRunning a Load Test using STS----WiFiWiFiWiFiWiFi

8.0 RUNNING A LOAD TEST USING STS-WIFI

BRIDGE DIAGNOSTICS, INC. – STS-WIFI OPERATIONS MANUAL

8.3

TABLE OF CONTENTS

8.1 INTRODUCTION ............................................................................................................. 8.5

8.2 DEVELOPING AN INSTRUMENTATION PLAN................................................................ 8.6

8.3 INSTRUMENTING THE STRUCTURE .............................................................................. 8.7

8.4 COLLECTING TEST VEHICLE INFORMATION.............................................................. 8.8

8.5 MARKING THE LOAD PATHS........................................................................................ 8.9

8.5.1 Zero Reference Point ......................................................................................................... 8.9

8.5.2 Lateral or “Y” Positions................................................................................................... 8.11

8.5.3 Longitudinal or “X” Positions ......................................................................................... 8.12

8.5.3.1 Tracking Longitudinal Position using the AutoClicker ............................................ 8.12

8.5.3.2 Tracking Longitudinal Position using Roadway Marks ........................................... 8.13

8.5.3.3 Tracking Longitudinal Position using a Marked Tire............................................... 8.14

8.6 RUNNING SEMI-STATIC LOAD TESTS........................................................................ 8.16

8.7 LOAD TEST DOCUMENTS ........................................................................................... 8.18

8.7.1Recommended Packing List ............................................................................................. 8.18

8.7.2 Field Test Information ..................................................................................................... 8.19



8.4



8.5

8.1 INTRODUCTION

The following section outlines how to run a typical diagnostic load test on a short- to medium-

span highway bridge up to approximately 300 ft (100m) in length. With only minor modifications,

these directions can be applied to railroad bridges (use a locomotive rather than a truck for the load

vehicle), lock gates (monitor the water level in the lock chamber), amusement park rides (track the

position of the ride vehicle) and other structures in which the live load can be applied easily.

Longer-span bridges can be more difficult to test due to logistical difficulties in applying a

controlled live load heavy enough to induce significant strains.

The basic scenario is to first instrument the structure with the required number of sensors, run

a series of tests, and then removing all the sensors. These procedures can often be completed

within one working day depending on field conditions such as access and traffic. If the bridge is to

be instrumented one day and then tested later and it might possibly rain, the STS-WiFi Nodes will

need to be protected.



8.6

8.2 DEVELOPING AN INSTRUMENTATION PLAN

Developing an instrumentation plan depends upon the type of testing being performed and

what exactly is trying to be obtained from the results. There are two general testing scenarios- (1)

localized structural effects and (2) global responses.

In the case of localized effects, sensors will likely be concentrated in a particular area, such as

a connection or a round a cracked area. In these cases the instrumentation plan will be very

specific to the situation.

Generally, when discussing instrumentation plans the user will be conducting a diagnostic

load test and will be using the measurements to help calibrate a finite element model of the

superstructure. In this type of testing, the sensors will be located throughout the superstructure so

that the load paths throughout the structure, particularly the lateral distribution, can be understood.

For examples on how to develop instrumentation plan, please see “The Integrated Approach to

Load Testing – Instruction Manual”. This is available for download on BDI’s website at:

http://www.bridgetest.com/support/docs/IntegratedApproach.pdf.



8.7

8.3 INSTRUMENTING THE STRUCTURE

By this stage it is assumed that the user(s) are very familiar with how to install the equipment

and operate the WinSTS software and also should have been through at least one field training

session by BDI.

Since every structure has slightly different field conditions, the user will need to adapt the

following general steps for successfully completing the diagnostic load test.

Once the transducers have been mounted, they should be connected into an STS-WiFi Node.

The Nodes should be placed near the gage locations on the bridge in such a manner to allow four

transducers to be plugged in. Since the Intelliducers will identify themselves to the system, there

is no special order that they must follow. The only information that must be recorded is the

Intelliducer serial number and its location on the structure. Once all of the sensors and STS-WiFi

components have been attached to the structure and the signal strengths have been verified, the top

of the bridge can now be set up for testing.

If questions arise during installation, please consult Chapter 5 for sensor installation

procedures of the various sensor types, Chapter 6 for WinSTS instructions and Section7 for STS-

WiFi equipment installation information.

Notes!

If the structure is concrete and no flanges are available to set the units on, they can be “hung”

using transducer tabs, L-brackets, masonry screws along with tie wire or zip ties. Remember that

if there is traffic below the bridge, effort will need to be made to hang the Nodes up as high as

possible. Section 7 outline the various attachment techniques for bot the Nodes and Base Station.



8.8

8.4 COLLECTING TEST VEHICLE INFORMATION

The next piece of vital information to collect is the axle spacing of the test vehicle. Simply

measure center-to-center between each of the axles. Also obtain the center-to-center width of both

the front and rear wheels. Since the rear axles typically have a set of duallies, measure center-to-

center of the duallies.

Sometimes, tests are run with two testing vehicles at the same time. If possible, use a tow

chain between the vehicles and have the front truck tow the rear truck across the structure. With

this configuration, the measurement from the rear axle of the lead truck to the front axle of the

following truck will need to be recorded. By keeping the chain tight, this measurement can be kept

constant during the truck passage. For side-by-side passes, it is best to instruct one driver to hold a

constant speed, and then tell the other driver to keep up with that first truck rather than have them

try to keep a certain speed. This is a good test of truck driver skill!

After the vehicle has been measured, the user must obtain its axle weights, not just the gross

weight. The best option is to use portable scales and weigh the individual wheels. However, this

is often not possible and the truck will need to stop at local scales. Usually, the tandem rear axles

cannot be separated on the scale, but it is sufficient to take a total rear weight and divide that by

two.

Finally, the wheel circumference is needed. To do this, mark the tire and the pavement where

the tire is touching the ground. Note that the wheel circumference is needed on the tire that the

AutoClicker is going to be mounted over. Have the truck roll five wheel revolutions and stop at

the point where the mark is touching the ground again and mark the pavement. Using a 100’

(30m) tape measure, measure the distance between the two marks on the pavement. When this

procedure is performed it is important that the truck drives in a straight line to increase the

accuracy of this measurement.

The Field Check list found in 8.7.2 has a place for all of these measurements to be recorded.



8.9

8.5 MARKING THE LOAD PATHS

8.5.1 ZERO REFERENCE POINT

Reference points and lines will need to be located on surface of the bridge deck in order to

track the position of the vehicle as it crosses the structure. While setting up the reference system,

keep in mind that the truck will need to travel in the same direction for all tests. This significantly

simplifies not only the data reduction, but helps provide a good basis for helping determine data

quality.

The first step is to determine the zero reference point for the (X, Y) coordinate system. This is

commonly referred to as the “Beginning of World” or just “BOW”. For girder-type bridges (steel

or concrete) this will usually correspond to the point on the deck directly above the abutment

bearing and the centerline of one of the fascia beams. All other measurements on the deck will

then be related to this zero reference point. For concrete T-beams, box beams, and slabs, this can

correspond to where the edge of the slab or the beam web meets the face of the abutment. If the

bridge is skewed, the first point encountered from the direction of travel is used. In any case, it

should be a point that can be easily located on the drawings for the structure. Once this point is

located it should be clearly marked on the structure using marking paint and should also be noted

in the gage plans. The pictures below shows the “BOW” marked on a structure and it being noted

on the gage plans.



8.10

In order to obtain baseline or “zero” data before the truck gets on the bridge, measure back at

least 10 feet from the zero reference point and extend a line or set of marks perpendicular to the

roadway with marking crayons or spray paint. This will be the start line for all tests and can be

seen in the picture below.

BOW

Starting Line

10ft



8.11

8.5.2 LATERAL OR “Y” POSITIONS

Once the zero reference location is known, the lateral load placements for the vehicle need to

be determined. Often, the painted roadway lines can be used for the driver to follow if they are in

convenient locations. For example, for a two-lane bridge, a northbound shoulder line can

correspond to Y1 (passenger-side wheel), the center dashed line to Y2 (center of truck), and the

southbound shoulder line to Y3 (driver’s side wheel). If the lines are not in useful locations or if

there are no lines at all, then some kind of line for the driver to follow will need to be applied to

the roadway. This is easily done by stretching a kite string or tape measure the length of the bridge

plus at least one or two truck lengths past each end and making a mark with paint or chalk every 8-

15 feet.

The number of Y locations will vary with each bridge and will typically be the number of

lanes plus one. In general, it is best to have the truck travel in each lane (at least on the lane line),

down the center line of the structure and approximately two feet from each shoulder or sidewalk.

Often, the structure will be symmetrical with respect to its longitudinal center line. If this cases, it

is good practice to have symmetric truck paths so that data quality can be confirmed by comparing

symmetric gage locations. The picture below shows the lateral positions mark on a two lane

bridge.

Y1

(fog line)

Y2 (offset ½ truck

width for centering

truck down bridge)

Y3

(fog line)



8.12

8.5.3 LONGITUDINAL OR “X” POSITIONS

Longitudinal position can be tracked in three ways- (1) by the AutoClicker, (2) marking

reference points on the bridge deck, and (3) marking the side wall of the test vehicle tire. The next

three subsections will explain these techniques.

8.5.3.1 TRACKING LONGITUDINAL POSITION USING THE AUTOCLICKER

By far the most precise way of tracking the longitudinal position of the vehicle, the

AutoClicker is designed to send a “click” to the WinSTS software via a wireless connection. A

complete instruction manual for the AutoClicker can be found in Section 5.6.

The rest of this subsection assumes that the user understands the functionality of the

AutoClicker. The instruction below will be used in conjunction with Section 8.6 to perform a load

test.

Instructions for inserting “clicks” into the data stream while running a test:

1. Position the truck on the proper starting position for the lateral location being tested

(i.e. Y1, Y2, etc.).

2. Attach either the reflective tape or AutoClicker Clamp so that it is facing the starting

position marked on the bridge. (see picture below).

3. With WinSTS in “Monitor Mode”, back the truck up until the reflector passes the

sensor and ensure WinSTS receives the transmitted “click”.

AutoClicker

Paddle



8.13

4. The WinSTS operator will communicate that the “click” was received at which point

the truck operator will communicate back that “The truck is in position on Y1 (or

whatever lateral position the testing is on) and ready for testing”.

5. The WinSTS operator will begin running a test and let the truck operator know that

“The test has begun”.

6. At this point the truck operator will signal to the driver to begin moving and each time

the reflector passes the sensor the AutoClicker will automatically send a “click” to the

WinSTS software.

7. The truck operator will need to keep the truck on the lateral position until the truck is

completely off the bridge at which point communicate to the WinSTS operator that the

testing is complete and “Stop Test”.

8. Once the truck has stopped, remove the reflective tape or AutoClicker Paddle from the

tire and back the truck up to the next testing position (return to Section 8.6).

8.5.3.2 TRACKING LONGITUDINAL POSITION USING ROADWAY MARKS

If the Manual Clicker is being used, hash marks can be placed with chalk or paint along the

length of the bridge on each Y line in even increments. For spans less than 100-ft (30.5-m), 10-ft

(3.05-m) increments can be used, although for very short spans (25ft or less), use 5-ft (1.5-m). For

spans longer than 100ft, marks can be placed at 20-foot (6.1-m) intervals. The diagram below

shows a typical deck layout when roadway marks are used.

The instruction below will be used in conjunction with Section 8.6 to perform a load test.



(i.e. Y1, Y2, etc.).

2. Back the truck up approximately 1/2 wheel rev.



8.14

3. Communicate to WinSTS operator the following: “The truck is in position on Y1 (or




5. At this point, signal to the driver to begin moving and when the tire is touching the

starting position depress the clicker button to send a “click” to the WinSTS software

6. Press the clicker button at each mark until the truck is completely off the bridge at

which point communicate to the WinSTS operator that the testing is complete and

“Stop Test”. Back the truck up to the next testing position (return Section 8.6).

8.5.3.3 TRACKING LONGITUDINAL POSITION USING A MARKED TIRE

Using a marked tire is very similar to the procedures of roadway marks except that a piece of

tape will be adhered to the tire instead of putting marks on the road. The instruction below will be

used in conjunction with Section 8.6 to perform a load test.



(i.e. Y1, Y2, etc.).

2. Adhere a piece of tape to the tire where the tire is touching the ground (see below).

3. Back the truck up approximately 1/2 wheel rev.

4. Communicate to WinSTS operator the following: “The truck is in position in Y1 (or




Tape



8.15

6. At this point, signal to the driver to begin moving and when the tape side of the tire is

touching the ground depress the clicker button to send a “click” to the WinSTS

software.

7. Press the clicker button each time the tape hit the ground until the truck is completely

off the bridge at which point communicate to the WinSTS operator that the testing is

complete and “Stop Test”. Back the truck up to the next testing position (return

Section 8.6).



8.16

8.6 RUNNING SEMI-STATIC LOAD TESTS

After the structure has been instrumented and the reference system laid out on the bridge deck,

the actual testing procedures can now be completed.

1. Start WinSTS and allow all the Nodes to “check-in”.

2. Verify the number of sensors in the Monitor screen and zero the sensors.

3. Test the AutoClicker or Manual Clicker while in the Monitor Mode to verify that the

“Clicks” are being received.

4. Select the desired test length, sample rate, and output file name. In general, a longer

test time than the actual event is selected. For most bridge tests, a ten minute test

length will suffice since the test can be stopped manually as soon as the truck crosses

completely over the structure.

5. Instruct the truck driver that the test vehicle must be kept in the proper location on the

bridge. For example, the left front wheel needs to be kept on the white line for the

shoulder tests. Another important point to emphasize to the driver is that the vehicle

maintains a constant rate of speed of 2-4mph (3-7kph) during the entire test!

6. When all personnel are ready to commence the test, traffic control should be initiated.

The WinSTS operator should let the other personnel know that they are about to begin

a test.

7. See Instructions for the type of Clicker that is being used in Section 8.5.3.

8. Once the vehicle has driven off the bridge the user can then hit Stop Test and it should

immediate begin downloading the remaining data collected during the test. This

should only take a short while.

9. The next data file to be recorded will have been named already if “Auto Number Files”

has been selected in WinSTS.

10. Tests can also be run with a second truck, usually one with a significantly different

axle weights and configurations.

11. Dynamic tests can also be run with one or both trucks. It’s a good idea to get a “high

speed” pass at for the truck crossing at least one of the “Y” positions that was used for

the static tests as this will make for a direct comparison so that an impact factor can be

determined. The sample rate can be increased to 40 Hz if desired. Remember to

remove the AutoClicker from the vehicle if being used. To record the dynamic data,

put the system in its “activated” state with “Run Test” when the truck is several

hundred yards before the bridge. Using either the supplied manual clicker switch (the

cord switch that plugs directly into the STSII power supply) or one of the radios, hit

the first click when the truck is at least 100-200 feet before the bridge. This will allow

some initial data to be stored. Keep running the test for a few seconds after the truck

has crossed so that any vibratory motion can be captured.

12. After all tests have been completed, the data is backed up to a floppy disk. If the data

files are large, they can be compressed into one “zip” file and backed up.



8.17

13. It is important to record the field notes very carefully. Having data without knowing

where it was recorded is worse than having no data at all! Intelliducer location and

serial numbers must be recorded accurately. All future data handling in BDI analytical

software is then accomplished by keying on the Intelliducer number. This system has

been designed to eliminate the need to track channel numbers by keeping this process

in the background. However, the STSII unit and the Intelliducers connector numbers

are recorded in the data file if needed for future hardware evaluations if required.

14. Remove the instrumentation and the transducers as outlined in “Removing

Transducers” and carefully replace the system into the transit cases.



8.18

8.7 LOAD TEST DOCUMENTS

8.7.1RECOMMENDED PACKING LIST

STS-WIFI FIELD PACKING LIST – PROJECT

ORDERED: � Glue/Accelerator

PAPER WORK: � Clipboard

� Field Data Sheets

� Scrap Paper

STS-WIFI

EQUIPMENT: _____ STS-WiFi Node(s)

_____ Mobile Base

Station(s)

_____ Antennas

_____ LAN Cable � AutoClicker

� Switches

SENSORS: _____ Intelliducers

_____ LVDT’s

_____ String Pots

_____ Other

_____ Displacement

Hardware

POWER: _____ STS-WiFi Batteries

_____ Fast Chargers

_____ Grinder Batteries

_____ Grinder Chargers � Power Strip (2)

TESTING KIT: � Pens/ Pencils

� Clicker

Paddle/magnet

� Clicker Receiver

� Reflective Tape

� Manual Clicker

Button

� 4 x 9V Batteries

� 3 x AA Batteries

� PCMCIA WiFi Card

STEEL BRIDGES: � Extra C-Clamps

PERSONAL ITEMS:

� Earplugs

� Work Boots

� Safety Glasses

� Dust Masks/Filters

� Hardhats/ Liners

� Reflective Roadway

Vests

� Camera

� Field PC

� Coveralls

� Gloves

� Work Belts

� GPS

R/C BRIDGES: � ¼-20 Threaded Studs

� Socket for Studs

� Fender Washers

(500+)

___ Gage Extensions

� Extension Jig

� L-Brackets (Box

Hangers)

� Chalk Line

� Hammer Drill/ Bits

(5/32”)

� Makita Drill

� Extra Hammer

� Scrap Cardboard for

Skewed Slabs (Angle

Saver)

� Paint Brushes

OTHER TESTING

EQUIPMENT: � Power Inverter

� Surge Protector

� Sun Visor for

Computer

� 100ft Clicker Cable

� 3 Radios +Chargers

HARDWARE LIST: � Paint

� 5-gallon bucket(s)

� Acetone

� Compressed Air (RC

only)

� __________________

� __________________

� __________________

8.7.2 FIELD TEST INFORMATION

BDI FIELD CHECKLIST (For use with AutoClicker)

�� DATE:____________________

�� STRUCTURE:_________________

�� VERTICAL MEASUREMENTS BETWEEN GAGES:_____________________

�� ZERO REFERENCE POINT (B.O.W.):__________________________________________

�� TEST STARTING LINE LOCATION:____________________________________________

�� TEST VEHICLE DIRECTION:_______________________

�� AUTOCLICKER LOCATION ON TRUCK:________________________________________

�� WHEEL ROLLOUT DISTANCE / 5 REVS:_____________

�� LATERAL VEHICLE POSITIONS: Y1= Y2= Y3= Y4=

�� AXLE WEIGHTS: FRONT= REAR= GROSS=

TRUCK 1:

STATIC TEST FILES Y- POSITION COMMENTS

*****Set sample rate to 100Hz***** HIGH-SPEED FILES Y- POSITION SPEED COMMENTS

�� BACK UP DATA FILES (FLASH DRIVE+)

�� TAKE PICTURES OF ALL GAGE LOCATIONS

1965 57th

Court North, Suite 106

Boulder, CO 80301

USA

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