Granville Street Bridge Preliminary Assessment report

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DRAFT

Revision Record Sheet

Rev.No

Date Changes ImplementedOriginated

ByVerified

ByApproved

By


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Amendments Record Sheet


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Executive Summary

This preliminary assessment report investigates the condition and alternatives for

rehabilitating the expansion bearings in the steel truss spans of the Granville Bridge. The

feasibility and costing of alternatives to recondition the expansion bearings are examined.

There are a total of fourteen steel roller type bearings in the steel truss spans of the

Granville Bridge. In general, the bearings have been well maintained and are in goodworking condition, but the potential for PCB spills and contamination of the environment has

become a concern. The bearings included an oil bath, using Aroclor 1248 which is a

synthetic oil product comprised of Poly-Chlorinated Biphenyls (PCBs), to clean and

lubricate the steel rollers contained inside the bearings. To mitigate potential contamination,

the oil from the bearings has been drained and transferred to a hazardous waste facility for

disposal.

For all of the rehabilitation options considered, the cleaning and encapsulation of the pier

caps has been included as a measure to reduce the potential for PCB contamination. Any

options that retain the bearings will include decontamination of the steel portions to a

predetermined level. Materials used or removed from the site that are contaminated with

PCBs will be disposed of at a hazardous materials disposal facility.

Key options considered include the reduction of PCB contaminated materials at the bridge

site, through decontamination or material removal. The continued use of lubricating

materials that would be constantly present in the bearings is not considered as a long term

option.

The alternatives assessed for rehabilitating the expansion bearings include: maintaining the

existing bearings without an oil bath; replacing all the existing bearings; and replacing the

smaller bearings while reconfiguring the larger expansion bearings as fixed bearings instead

of replacing them.

The existing bearings may be retained. However, it may not be possible to completely clean

the interior of the bearings such that they can be considered free of contamination. In this

case, the future maintenances costs will need to account for handling the bearings as

contaminated by PCBs. s.13(1); s.17(1)(c), (d), (e) & (f) and s.21(1)


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All of the bearings can be replaced with conventional expansion bearings to remove allcontaminated steel components from the bridge. However, the four largest bearings will be

technically very difficult and very costly to remove and replace with new bearings, in particular,

the two largest bearings at Pier M7. s.13(1); s.17(1)(c), (d), (e) & (f) and s.21(1)


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Table of Contents

1 Introduction...........................................................................................................................1

1.1 Description of Bridge Expansion Bearings....................................................................11.2 Current Condition at the Bridge Expansion Bearings....................................................4

1.2.1 Expansion Bearings...........................................................................................4

1.2.2 Surfaces on the Pier Tops.................................................................................51.3 Bearing Decontamination Trial......................................................................................5

2 PCB Contamination Mitigation..............................................................................................7

2.1 Decontamination of Existing Bearings...........................................................................72.1.1 Flushing Existing Bearings................................................................................72.1.2 Removing Bearing Boxes & Flushing Existing Bearings ...................................82.1.3 Removing Existing Bearings to Clean Off-site...................................................8

2.2 Decontamination of Pier Caps.......................................................................................83 Bearing Revitalization.........................................................................................................10

3.1 Recondition Existing Bearings.....................................................................................103.1.1 Periodic Lubrication.........................................................................................103.1.2 New Oil Bath....................................................................................................11

3.2 Structurally Alter Bearings...........................................................................................113.2.1 Typical Bearing Replacement..........................................................................113.2.2 Bearing Options at Piers M2 and M7...............................................................13

4 Load Rating Analysis ..........................................................................................................18

4.1 Computer Modeling.....................................................................................................184.2 Loading........................................................................................................................18

4.2.1 Dead Load.......................................................................................................184.2.2 Live Load.........................................................................................................194.2.3 Wind Load.......................................................................................................204.2.4 Temperature Effects........................................................................................20

4.2.5 Earthquake Load.............................................................................................214.3 Load Combinations.....................................................................................................224.4 Member Demands.......................................................................................................224.5 Member Capacities .....................................................................................................224.6 Pier Demands..............................................................................................................234.7 Comparison Summary.................................................................................................23


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6 Recommendations..............................................................................................................27

6.1 Bearing Revitalization Programme..............................................................................276.2 Staged Revitalization...................................................................................................27

6.2.1 Engineering .....................................................................................................286.2.2 Stage 1............................................................................................................286.2.3 Stage 2............................................................................................................286.2.4 Stage 3............................................................................................................28

Appendix A..................................................................................................................................29

Appendix B..................................................................................................................................33

Appendix C .................................................................................................................................34


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1 Introduction

This preliminary assessment report investigates alternatives for rehabilitating the

expansion bearings for the steel truss spans of the Granville Bridge. To provide a

comprehensive assessment: the existing condition, environmental concerns, bearing

alternatives, load rating of the steel trusses, staged construction and cost estimates

are considered and discussed.

1.1 Description of Bridge Expansion Bearings

The Granville Bridge was constructed in 1954. The bridge has seven spans, from

Piers M1 to M8, constructed of structural steel (see Figure 1). These structural steel

spans consist of an arrangement of steel trusses with appropriate placement of fixed

bearings, expansion bearings and internal pins to provide a statically determinate

system for expansion and vertical load.

s.15(1)(l) and s.19(1)(b)


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s.15(1)(l) and s.19(1)(b)


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The expansion bearings were originally designed to be kept in an oil bath, as showninFigure 2. The oil bath served to both lubricate the internal steel components of the

bearing and protect them from corrosion and contaminates that may get inside the

bearing box.

Expansion bearings of this type are susceptible to water entering the bearing box

through leaks or condensation. Originally, the oil bath used whale oil that, because

of its relatively lower density, allowed water entering the bearing box to sink to the

bottom. As water continued to enter the bearing box the oil could eventually be

displaced and overflow from the box. To avoid this condition, the lubricating oil used

in the expansion bearings was substituted with Aroclor 1248 (a synthetic oil product

comprised of Poly-Chlorinated Biphenyls, or PCBs) in the early 1960s, selected for

its unique quality of being denser than water. By using this dense lubricating oil, any

water entering the bearing box would float on top of the oil bath and be spotted

during regular inspections to be removed.s.15(1)(l) and s.19(1)(b)


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1.2 Current Condition at the Bridge Expansion BearingsIn general, the expansion bearings are well-maintained and in good working

condition.

1.2.1 Expansion Bearings

The primary issue concerning the expansion bearings was the consequence of a

potential oil spill from leaking bearings. When Aroclor 1248 was selected for use,

sometime during the early 1960s, PCBs were not recognized as a hazardous

material and government environmental regulations concerning PCBs did not exist.

PCBs are now known as a hazardous material and the disposal of PCBs and PCB-

contaminated materials are regulated by environmental legislation.

s.13(1); s.15(1)(l) and s.19(1)(b)


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To mitigate the environmental damage potential and attempt to satisfy environmentalregulations, the PCB-contaminated oil from all expansion bearings was drained in

2006. The cost of draining and disposing of the PCB-contaminated oil was on

average $5,000 per bearing.

1.3 Bearing Decontamination Trial

A pilot project to develop a protocol for the removal of the PCB-contaminated oil at

the expansion bearings and subsequent decontamination of the bearings was

s.13(1); s.15(1)(l) and s.19(1)(b)


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The West expansion bearing at Pier M8 was selected for the pilot project. Theprotocol, methods, testing and results are contained in the Envirochem Services Inc.

report Pilot Project Decontamination of the Granville Bridge Bearing Boxes

Containing PCB dated J une 2006 (draft). In summary, the decontamination process

included:

rinsing the bearing box with kerosene to dissolve residual oil after draining,

flushing the bearing box and bearing components three times with about 20 litresof kerosene each time, which is about 10% of the original volume,

filling the bearing box with kerosene to soak,

draining the kerosene from the bearing box,

filling the bearing box again with kerosene,

draining the kerosene, and

wiping down the accessible internal surfaces with absorbent pads.

The test results for residual PCB contamination, for the Pilot Project, indicated that

the interior surfaces of the M8 bearing could not be decontaminated sufficiently to

reduce the PCB concentrations to acceptable levels, but were dramatically reduced

from the untouched state. The PCB levels were reduced to 2800 mg/kg PCB in the

kerosene solvent removed in the final rinse. It has been learned that, proposedregulations will require the PCB level to be below 500 mg/kg by 2014. Further

flushing is to be undertaken at the Pilot Project bearing in an attempt to achieve the

proposed regulation level.

s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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4 Load Rating AnalysisThis section is a summary of the load rating analysis of Granville Bridge to date. It is

a detailed assessment of the effects of the modified bearing configuration on the live

load distribution in the steel truss bridge spans, compared to that of the existing

structure. In addition, wind, temperature, and seismic loads are also considered.

The assessment accounts for the seismic rehabilitation of the steel truss spans that

was completed in 1994, but does not account for any potential deterioration of thestructural elements.

Assessment of the steel bridge truss components was carried out using CAN/CSA-

S6-00, Canadian Highway Bridge Design Code (S6-00) design loads and capacities.

The bridge floor system (i.e., deck slabs, stringers, floor beams, etc.) is not affected

by the proposed bearing modifications and therefore was not included in the

assessment. The substructure is assessed by comparison of demands in thecomponents of the piers for the two cases of the M2 and M7 bearings being fixed or

in the present condition.

4.1 Computer Modeling

The computer analysis model originally developed for the 1992 seismic rehabilitation

design was used in this analysis. There have been no modifications to the structure

since that time that would warrant modifications to the computer model.s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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5 ConclusionsIn general, the steel roller expansion bearings have been well maintained and are in

good working condition. The steps that the City of Vancouver has taken to safely

drain and dispose of the PCB contaminated oil from the expansion bearings has

greatly mitigated potential environmental damage due to leaks from the bearing

boxes.

Alternatives that clean and retain the existing roller bearings in service have the least

present costs. However, these options have long-term maintenance costs

associated with handling the bearing components as items contaminated with

hazardous materials. Also, it may not be possible to get the PCB level to an

acceptable level under the regulations.s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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6 Recommendationss.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)

s. ; s. ; s. c , an s.


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s. ; s. ; s. c , an s.


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s. ; s. ; s. c , an s.


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s. ; s. ; s. c , an s.


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s. ; s. ; s. c , an s.


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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s. ; s. ; s. c , an s.


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s.13(1); s.15(1)(l); s.17(1)(c), (d) & (f) and s.19(1)(b)


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Documents

Granville Street Bridge Preliminary Assessment report