Accelerated bridge construction chapter 11 a review of chapters, river bridges, and conclusions

Accelerated bridge construction chapter 11 a review of chapters, river bridges, and conclusions Accelerated bridge construction chapter 11 a review of chapters, river bridges, and conclusions Accelerated bridge construction chapter 11 a review of chapters, river bridges, and conclusions Accelerated bridge construction chapter 11 a review of chapters, river bridges, and conclusions Accelerated bridge construction chapter 11 a review of chapters, river bridges, and conclusions

489 Accelerated Bridge Construction http://dx.doi.org/10.1016/B978-0-12-407224-4.00011-3

CHAPTER

A Review of Chapters, River

Bridges, and Conclusions

11.1 Introduction to chapter 11

This final chapter is divided into two parts

Part 1: It deals with the summary and review of the first 10 chapters

Part 2: It deals with rapid construction on rivers, using alternative float-in method to transport assembled bridge to the bridge site and timber and aluminum bridges

Part 2 is followed by overall conclusions

Part 1

11.1.1 Summary of earlier chapters

For early completion or for rapid construction, the main factors and issues discussed in the earlier chapters may be summarized as the five M’s, namely:

Management team of design-build engineers,

Modern materials using high-performance steel (HPS), high-performance concrete (HPC), and composites,

Method of assembly of modular construction in factory or on site,

Method of transport using self-propelled modular transporters (SPMT), and

Method of erection by lifting into position, roll-in, roll-out or lateral slide-in

For bridges on rivers, a float-in method can be used

Both full and partial accelerated bridge construction (ABC) methods are discussed

Partial ABC is a compromise between conventional and ABC methods It is applicable when ticated transport and lifting equipment is not available and where the bridge owner wants to keep the in-charge consultant Some factory fabrication of girders would still be used

sophis-Since the scope of each project is slightly different, full ABC may not always be applicable The following types of conditions would exist:

1 A new bridge on a new highway Coordination with highway construction on one or both sides of

the bridge will be required Bridge construction activities may not be on the critical path Also, no demolition work is needed

2 Existing bridge requiring superstructure replacement only Only superstructure demolition may be

required The ABC can be done using staged construction with limited lane closure

3 Existing bridge requiring both superstructure and substructure replacement Staged construction

may be required since existing footing width may interfere with the new footings Demolition of entire abutment footing would require shutting down of the entire bridge rather than lane

closure

11

4 Construction duration for deep foundations such as minipiles or long piles or drilled shafts/

caissons will not change for full or partial ABC

5 Funding will be unaffected in each case.

Construction season may be geared to local weather and factory manufacture in doors will be an advantage Also, roll-in, roll-out method may be more expensive than lateral slide-in but has the advan-tage that the assembled bridge can be lifted and placed over the bearings without relocating the existing utilities

Training programs in ABC may be necessary Use can be made of the Federal Highway tion (FHWA) conferences, and lunchtime seminars organized by FIU and other universities engaged in research in the new technology

Administra-A variety of case studies are presented for superstructure or substructure replacement using rication, self-propelled modular transporters, roll-in and roll-out methods, and lateral slide-in methods

prefab-A glossary of prefab-ABC terminology applicable to all the chapters is listed for ready reference in prefab-Appendix

2 ABC

Part 1 will provide brief summaries of the chapters and will be the review of Chapters 1–10.The chapters that follow this introductory chapter on modern ABC will cover the following themes:

Sections 11.2 address coordination with highway construction schedule

Sections 11.3 to 11.8 address scour issues related to river bridges and design of countermeasures The details related to scour are based on author’s textbook on Bridge and Highway Structure published by McGraw=Hill 2010

Section 11.9 provides details of case studies

Section 11.10 is for the conclusion of the chapter 11

In addition, Section 11.11 discusses future developments of ABC

Finally, Section 11.12 discusses acknowledgements and future revisions of codes/

Section 1 Innovative Construction Methods (chapters 1 to 4)

(Chapter 2), Recent developments in ABC concepts

(Chapter 3), Research and training in ABC structural systems

(Chapter 4), Introducing innovative ABC techniques

(Chapter 5), Modular bridge construction issues

Section 2 Recent Developments in ABC Concepts (chapters 5 to 7)

(Chapter 6), Rapid bridge insertions following failures

(Chapter 7), Planning and resolving ABC issues

(Chapter 8), ABC Prefabrication of the superstructure

Section 3 Modular Bridges (chapters 8 to 11)

(Chapter 9), Prefabrication of the substructure and construction issues

(Chapter 10), Alternative ABC methods and funding justification

Chapter 1 presents an introduction to modern ABC with discussion of the many advantages and

deterrents Deterrents include administrative and planning bottlenecks, construction easements and right-of-ways, permit approvals, and utilities relocation issues Timely labor availability, weather prob-lems, and the large storage yard areas required at the site are addressed In addition, the need exists for certification and training, laboratory testing related to the structural behavior of field connections of

491 11.1 Introduction to chapter 11

subassemblies, and mathematical modeling Design and construction codes, continuous funding, heavy cranes, and erection equipment such as trolleys and SPMTs are required to properly implement ABC.Major benefits include reducing traffic impacts, and the use of prefabricated bridge components made of HPS, HPC, and other new materials and equipment Application of the latest techniques in concrete manufacture, including the use of lightweight concrete and other hybrid materials, will con-tribute to durability and possibly early completion of projects

It was shown that applying the ABC methodology will result in 50% more completed bridges each year This will help the economy by reducing wasted man-hours due to traffic jams during construction; commuters will get to work faster, which will benefit commerce by promoting faster delivery of goods.Primary and secondary consideration for the selection of suitable projects for ABC, in terms of benefit, are addressed Tables 1.2(a) and 1.2(b) give a format of criteria and allocating points in the point system

Please see references to FHWA publications in Appendix 1 (Bibliography) for Chapter 1 for details

In Chapter 2, we address recent developments in ABC concepts and their application to

infrastruc-ture We noted that it might be possible to reduce the number of failures with ABC by applying recent advancements in technology and innovative methods The failed bridges that were built using old tech-nology can be rebuilt on a fast track using ABC

It appears that there are hiccups that may be holding up a more rapid switch to ABC A slow but gradual shift from conventional methods to full ABC (with many projects utilizing a partial ABC approach) has been observed Each management subsystem, such as partial ABC, can be used to accommodate different circumstances and physical conditions ABC-related design needs to be made part of the American Association of State Highway and Transportation Officials (AASHTO) and state bridge design codes and specifications Deterrents and bottlenecks such as maintenance and protection

of traffic (MPT), construction easements, right-of-way, permit approval, and utilities relocation need to

be resolved, and administrative procedures further simplified to facilitate ABC

There are many feasible applications of the latest techniques in concrete manufacture, composites, HPS, and hybrid materials that need to be promoted Integrated software that would cover all aspects

of ABC, including design calculations and drawing preparation, should be investigated and developed

to save engineering man-hours

A surge has been seen in the manufacturing of bridge components and construction machinery worldwide FHWA has prepared a comprehensive ABC manual AASHTO grand challenges by the AASHTO Technical Committee for Construction (T4) present additional goals to strive for For bridges located on rivers, a survey of scour countermeasures that are being used nationwide was conducted A form was successfully developed to assist in the field assessment of scour at bridges Introducing more rapid inspections to identify deficient bridges by using remote sensors is emphasized

Full-scale testing of joints in precast curved decks for both rectangular and curved decks is required Modifications to analytical methods applicable to discontinuities of components need to be developed.Chapter 2 also addresses design-build contracting system and the role of the Design-Build Institute

of America (DBIA) in promoting ABC Construction Manager/General Manager system is described in Chapter 2

Chapter 3 emphasizes ABC logistics and training and research aspects For promoting ABC,

design-build method of construction management is described in this chapter The role of the tation agency in patronizing and promoting ABC is the most critical The consultant and specialized subconsultant roles come next; they introduce key innovations in design and field connections

transpor-This chapter reviews bridge rating procedures to identify deficient bridges and how to prioritize bridge repair Structural health monitoring methods using remote sensors will help prioritize bridges for rehabilitation The key factors dictating a particular type of delivery method include time restraints, level of risk, budget, and level of quality.

Preparing an evaluation matrix for selecting the type of fix or replacement would be helpful vative techniques need to be popularized and adopted as routine bridge construction Most accidents occur during bridge construction; hence rapid constructability requirements during erection need to be met, and preventive measures in design and construction to prevent failures need to be introduced.ABC planning, analysis, and implementation methods vary for each of the structural systems and lead to many diverse applications for small, medium, and long spans, each of which has different con-struction durations and their own specialized construction methods

Inno-Constraints in implementing ABC include MPT, approach slab construction, permits, and utility relocation; these are unavoidable constraints and should be on critical path for early completion.The nature of manufacturing precast products creates a proprietary system and monopolistic envi-ronment, which may lead to unemployment of some number of construction workers Overemphasis of incentives/disincentives may pressure the contractor into adopting unrealistic schedules at the expense

of quality control

Certain improvements for economical design include the following:

• An upgrade to most modern construction equipment would be required

• Current plan preparation and presentation should reflect ABC

• Payment and accounting of pay items need to be accelerated

• Arching action in deck slabs should be utilized—there is reserve strength that is being neglected

• Deck overlays for riding surface quality—latex-modified concrete (LMC) or corrosion inhibitor aggregate concrete may be used

• Bridge deck expansion joints for precast deck units should be investigated

• Compliance with permitting regulations—environmental permits may hold the start of

construction

• Insurance against risk and liabilities is critical

Chapter 3 describes training programs in ABC organized by DBIA It also addresses construction permits issues for air quality and water quality etc to be award by the Department of Environmental Protection (DEP) Chapters 7 and 9 also describe environmental issues Chapters 3 and 4 and Appendix

1 (Bibliography) provide a list of relevant references on all aspects of ABC

Chapter 4 discusses how maintaining the right-of-way philosophy is achievable through

innova-tive ABC techniques The chapter deals with design-build construction management, addressing modern concrete technology and the philosophy of maintaining the right-of-way at all times for all citizens There has to be a reward to promote innovation and encourage the undertaking of some risk The most recent initiatives and innovative techniques are described; they are promoted by federal agencies like FHWA and AASHTO as well as individual states, which are promoting the implemen-tation of ABC for faster bridge delivery This chapter discusses a comparative study of conventional and innovative methods, along with a review of new design methods and the development of diverse repair technologies

We look at modern construction equipment, the use of recyclable materials, and examples of recent ABC applications in the United States The scope of design-build (D-B) contracts and considerations

493 11.1 Introduction to chapter 11

of engineering ethics are also addressed We also discuss the important issue of ensuring adequate returns of the hundreds of billions of dollars of yearly investments in infrastructure through rapid bridge delivery

Innovations help in upgrading the quality of construction and in completing the project in a timely manner A list of advancements in ABC methods include:

• Preventing bridge failures by minimizing the identified deficiencies through maintenance

• Use of advanced methods, including computer-aided analysis and design techniques

• Closer interaction between design documents and construction

Continued research efforts are required in resolving technical issues Common examples of tive concepts that require continued study are ground-penetrating radar (GPR), staged construction, overhead and utility lines, environmental permits, road closures versus detours, precast and composite decks, and the use of stainless steel

innova-On the administrative side, new procedures for asset management, award of simultaneous multiple contracts, and accelerated highway construction (AHC) to accompany ABC were introduced in this chapter Using nanotechnology to reveal cracks and corrosion, searching for photographic evidence of defects, and using remote sensing technologies would certainly help in rapid bridge inspection and SHM.There have been developments in the use of self-consolidating concrete (SCC), lightweight aggre-gate concrete (LWAC), recycled concrete aggregate (RCA) concrete, accelerated cure cast-in-place (ACCIP) concrete, blended cement concrete (BCC), fiber mesh concrete (FMC), reactive powder con-crete (RPC), and rapid setting concrete (RSC)

Researchers have developed special repair materials They include nonshrink, multipurpose and high-strength repair mortar Cementations materials concrete utilizes fly ash, blast furnace slag, and silica fume

Examples of proprietary bridge systems include the robotic steel beam assembly system by Zeman, which has added a new dimension of structural steel fabrication and erection The system is designed for fully automated assembling, tack-welding, and full welding of structural steel elements Other sys-tems include recycled plastic lumber bridges, lightweight titanium pedestrian bridges, Inverset, Effideck bridge decks, Exodermic bridge decks, and full-depth precast concrete deck panels (FDDP)

Chapter 5 addresses construction and rehabilitation using prefabrication, prefabricating bridge

ele-ments and systems (PBES) and various other improveele-ments in the manufacture of ready-made bridges Prefabrication of bridges and their technical issues are discussed in Chapter 5 There are many bridge companies in this area, such as CON/SPAN and Mabey-type temporary bridges Modular design and prefabrication have a number of benefits, including shorter production cycles and enhanced sustain-ability This results in lower production costs, with savings to be passed on to the client The use of eco-friendly materials and prefabricated design also make these modular structures ideally suited to the changing demands of the transportation industry

Consider sample projects using the following bridge elements as guidance in the absence of an ABC code of practice:

• Precast foundation elements

• Precast pile and pier caps

• Precast columns

• Precast full-depth deck slabs

• Cored slabs and box beams

• NEXT beams and deck girders

• Full-span bridge replacement units with precast deck

• Bridges installed with SPMTs

Cost evaluations are important and should be accurate They should include the following categories:

• Time and materials estimates

• Roadway user costs

• Maintenance of traffic costs

• Safety costs

• Agency costs

• Life cycle costs

If the cost of ABC is not greater than 30% of the conventional bridge construction cost, strongly consider ABC The benefits are in early delivery, improved quality, and longer bridge life Take advan-tage of existing technologies, such as Inverset and prefabricated fiber-reinforced polymer (FRP) deck.ABC methods have evolved ahead of the design codes Research is required in many aspects, including:

• Developing strengthening methods and corrosion mitigation techniques, including fabricating stronger girders by eliminating the need for shear stiffeners with the use of folded web plate in steel girders

• New methods to monitor and strengthen foundations against scour, earthquake, and impact

• Developing and reviving the concept of full canopy on bridges to facilitate mobility, improve drainage, prevent skidding, and eliminate the use of deicing agents

Chapter 6 deals with rapid bridge insertions following failures This chapter addresses the reasons

for numerous failures of bridges in United States and abroad, which can be prevented by the tion of new technologies of ABC Maintenance can avoid failures or at least warn of failures in advance Use of remote sensors to monitor structural health is desirable Early failures in conventional construc-tion can be attributed to a variety of reasons, both administrative and technical Studies shows failures resulting from inadequate oversight of projects, a lack of supervision at the site, design errors, lack of comprehensive codes, contractor’s last-minute decisions to meet hasty schedules, and limited resources Most failures occur during construction due to lack of redundancy in design, inadequate construction, and lack of contracting experience and knowhow Alternate ABC contracting methods are described in Chapters 6 and 9

introduc-As discussed in this chapter, bridges on rivers failed more than those located on intersections, due

to soil erosion Use of HEC-23 countermeasures is on the rise Deep foundations are preferred over shallow foundations for bridges that are scour critical Scour countermeasures need to be designed according to HEC-23 and provided to protect footings When replacing an existing superstructure, deck elevation may be raised by 1–2 ft Some progress has been made in making bridges seismic resistant by using lightweight materials and isolation bearings The large volume of site work in conventional con-struction is minimized by ABC, which requires as much work offsite as possible

495 11.1 Introduction to chapter 11

Use of modern technology: Bridge engineering is changing with time New technology and tive ideas developed in the last two years need to be adopted In planning bridges, cost is still the main criteria Much of the cost goes into the foundation and substructure concrete construction

innova-The use of new and stronger construction materials such as HPS, HPC, and Ultra HPC and FRP decks should be encouraged, as these are more durable Shallow-depth girders will result, which are lighter in weight Galvanizing will reduce corrosion Currently, rolled sections in HPS 70W and 100W are not available or are too expensive Welded girders in HPS are being used

Prestressed concrete box girders are stronger in torsion and cost-effective, especially with the use

of lightweight concrete; they also lower maintenance costs Also, composite construction, for example using the Inverset system, is more economical and on the rise Precast integral abutment construction requires greater attention Peak stress and deformation can be checked prior to lifting The location of cranes needs to be identified on contract drawings

Project management, quality control, and MPT are of critical importance It was observed that the professional relationship between owners, contractors, and consultants needs improvement through increased communication ABC design-build methods are a step in the right direction

Widening of highways in urban areas is not always an option Right-of-way and legal issues are involved to acquire new land Hence, underpass and/or double-deck highways are often used to over-come the additional lanes problem and traffic congestion once and for all

Safety checklists: It is critical for personnel to be safe and healthy at construction sites A checklist

of do’s and don’ts needs to be prepared and issued

Erection methods for curved girders are also described in Chapter 6

Chapter 7 addresses ABC planning and construction issues Our failing infrastructure and

trans-portation problems are discussed in this chapter Before launching a multimillion dollar project, it is the professional responsibility of engineers to conduct an effective planning exercise The continued and ever-increasing infrastructure difficulties faced by the public are highlighted The economic and public comfort benefits derived from early completion of projects are reviewed A survey of ABC projects successfully completed in many states illustrates an increased interest in adopting the new technology Major contractors and fabricators have welcomed the increased responsibility of the design-build sys-tem in which their decision making is appreciated The progress of design-build system and MPT issues are described in Chapter 7

Various aspects of the contractors’ role such as that of Construction Manager/General Manager are described in Chapter 7

Partial ABC: For rehabilitation of an existing bridge, an engineer’s options are restricted as pared to the options available for design of a new or replacement bridge But partial ABC is still pos-sible The huge funding issues can be partly overcome by public-private partnerships

com-The focus of Chapter 8 is on bridge superstructure prefabrication, several aspects of prefabrication

of the superstructure and includes the stakeholders of ABC The reasons for its success are as follows:

• The contracting industry is not afraid to take the lead in the management of small- and sized projects and is willing to take the necessary risks and meet challenges that inevitably arise

• There have been developments in special transportation methods for long and wide loads using SPMT In addition, heavy capacity cranes for lifting and erection are now available

• Organizations such as FHWA (with their Every Day Counts Program and ABC Handbook), Transportation Research Board (TRB) and AASHTO have been a motivating factor.

• The design-build contract system helps in the adoption of prefabrication According to SHRP2 Project R04, ABC is the clear choice Life cycle costs are significantly reduced

Promoting modular construction: European practice is to standardize the design of bridges on cal intersections (limiting them preferably to two spans) and wherever possible on river bridges as well The location of abutments can be adjusted to utilize standard precast girder lengths The location of field connections are also kept unchanged as determined from analysis

typi-A list of recent innovations is presented for selection and for further action and implementation, such as:

• PBES

• Connection details for PBES

• NEXT beams, spliced girders, bulb tee, and Wolf girders

• Structural placement methods

• Launching, sliding, and heavy lifting

On-site construction under open sky is far more difficult than factory manufacture New bridges have become more complex since the bridge practice of a century ago, when cast-in-place (CIP) con-struction was the only option Today a medium-size factory would likely have the necessary facilities for indoor fabrication Some of the difficulties involved in on-site construction include:

Extreme events and climatic hazards: Most of North America has a subzero cold climate for four months of the year, and southern states have high temperatures in the summer This may slow down the speed of outdoor work In large factories, temperature change does not affect the schedule for construction Also, activities on the critical path are not affected

Labor availability at remote locations: Most bridge sites are located on distant highways dreds of members of the labor force cannot be relocated The factory is their regular workplace

Hun-Storage of construction materials: A special building is required on-site for storing construction materials such as aggregates, cement bags, ladders, machinery, and dozens of other appliances Temporary pathways need to be constructed This adds to the schedule

Formwork: This is an expensive item of CIP construction It needs to be erected for the deck slab and for the CIP girders This adds to the cost of work and affects the schedule

Exposure to rain and sunlight: Due to the exposure of steel and cement to the elements, corrosion of steel and wetting of cement, etc., takes place, which lowers the quality of work and is not desirable

Mobilization: For CIP, a temporary administration building needs to be set up This adds to the overhead

Other issues covered in Chapter 8 include the following:

Wider use of the P3 system: With the P3 approach, required funding is made available to replace hundreds of these bridges more quickly

Introduction of new maintenance and planning techniques: The causes of structural deficiencies, functional obsoleteness, and bridge failures need to be investigated Methods to prioritize the planning of structural systems and introduce rapid construction need to be researched

Structural health monitoring (SHM): This is a new technology for bridge inspections that uses lasers and remote sensors Bridge inspectors need to be trained in the use of computer software

497 11.1 Introduction to chapter 11

that operates such remote sensors, as well as radar technology and Lidar techniques that can quickly obtain information about the fatigue and stress-strain history of a bridge This approach will make bridges safer and reduce life cycle costs

Overload prevention and review of live loads: In light of the latest advancements in the truck industry, it has become important to assess the magnitude of axle loads on highway bridges and also update the military live loads on military routes due to new tanks American Society of Mechanical Engineers design codes need to be reviewed

Use of high-friction surface: Introducing the British-invented surface treatment on asphalt

pavement to create a high-friction surface and favorable friction properties between vehicle tires and bridge deck surfaces will help in braking and prevent skidding Binders such as thermosetting epoxies are used Maryland has successfully introduced plates on their intersections

Chapter 9 deals with substructure prefabrication techniques and construction management The

progress in using prefabrication has been slower for substructure construction compared to that for superstructure construction, especially for longer span bridges It is easier to transport horizontal bridge beams and slab panels on an SPMT than vertical pier bents due to their size Also, post-tensioning may

be required for the substructure panels to make them watertight

For emergency bridge replacements on important routes after floods, earthquakes, or accidents, etc., prefabrication of both pier and abutment members would help Other key aspects of prefabricated sub-structure planning and management include:

Soil report: Since foundation design requires soil investigation, this operation should be started well in advance by the owner even before the award of the contract

Utility pipes: Advance coordination with the utility companies for supporting their pipes and transferring from pavement elevation to deck elevation is required

Deck drainage: The method of disposal of rainwater from the deck into public sewers also needs

to be planned

Electrification: If deck lighting is provided, the power supply needs to be arranged from the electric supply company and negotiations need to be started in advance, as the prefabrication activity is in progress

Precasting concrete and welding: Although prefabrication in a factory may not take as much time

as cast-in-place construction under the site conditions, the time required for the plan layout of rebars, the curing of concrete components, and the welding of steel members, etc., remains unchanged

Planning: The additional time required to plan a route, obtain permits for heavy and wide loads, and apply for police escort, as well as the hauling distance for the prefabricated bridge from the factory to the site need to be taken into consideration

Hauling heavy loads: Loading prefabricated components onto the SPMTs and unloading them at the site as well as the required lifting and placing operations by the special cranes on-site need to

be taken into account in the overall schedule

Stay-in-place formwork: The additional time and cost for hauling, lifting, and placing needs to be analyzed in comparison to the cast-in-place construction erection time for temporary formwork or using permanent stay-in-place formwork to make prefabrication as economical as possible

Modular construction: The greatest benefit of prefabrication is for small spans, where the hauling and lifting problems are fewer and pier construction is avoided Arch structures combine super-structure girders with substructure curved columns and are more aesthetically pleasing

Leading prefabrication companies: There are a wide variety of bridge manufacturing companies

in the United States who have developed specialized bridges for repeated use Examples include High Steel Structures, Acrow, Jersey Precast, and CON/SPAN

Need for standardization: AASHTO specifications have recommended minimum vertical and horizontal clearance requirements Similarly, many states have developed standard details for lane widths, shoulder widths, and bicycle tracks, spaces for plants and flowers, etc Span length

alternatives to conform to the width of the highway can be used to standardize bridge lengths Such ready-made standard span structures using concrete and steel can be made available off the shelf and ready for delivery to sites, as required A choice of colors is also available for aesthetic requirements

Quality control: Construction drawings for precast substructures are more specialized than tional construction drawings Typical review comments on reinforced concrete detailing of abutment walls, pier caps, and columns are therefore necessary Examples of necessary quality control measures are review by expert bridge engineers of the connection details, location of hinges, seismic detailing, lifting points, etc Case studies of a variety of bridges using PBES for the substructure in the United States are summarized in Chapter 9

conven-Foundation drawing reviews: Expert reviews can raise a number of issues and lead to various

recommendations Some of these include the following:

• Foundation design is too expensive; footings are too big/deep Review soil report

• Monitor compaction before placing footings Consider soil improvement techniques

• Always get soil borings and a geotechnical report before foundation design and have geotechnical oversight and testing during construction

• Use deep piles or drilled piers

• Use caissons or auger piles

• Use tied spread footings

• Check for retaining wall failure from settlement and overturning

Alternate ABC contracting methods are also described in Chapter 9

Various aspects of engineering management are presented, such as asset management (Chapters 2 and 10), disaster management (Chapter 3), design-build (Chapter 4), bridge failures and risk manage-ment (Chapter 6), and construction management (Chapter 9)

Chapter 10 addresses evaluation criteria for deficient infrastructure and alternative ABC methods

ABC technology is still developing, although significant progress has been made in prefabrication This chapter highlights important alternatives to the well-established use of factory prefabrication and SPMT, such as transportation by barges and lateral slide-in methods The many impacts of rapid con-struction and traffic volume and lane closures are also given in Chapter 10

In some cases it may be warranted to use lateral slide-in methods due to the limitations of ing large bridges by road or on rivers for long distances and fitting them on SPMTs or barges The method consists of site casting adjacent to the existing bridge on temporary bents, followed by the use

transport-of mechanical devices for sliding or the use transport-of cranes to lift the superstructure in position Case studies have shown that many states have successfully used this modern technology

A few states like Utah and Oregon have developed special provisions as part of their construction specifications In some cases it is possible to construct abutments prior to slide-in of the new bridge, leading to further time savings

499 11.1 Introduction to chapter 11

The use of new types of concrete materials for deck slab will enhance deck life and reduce life cycle costs Examples are Exodermic decks, Effidecks, and FRP and HPC deck panels Several types of lightweight precast girders such as NEXT beams, Wolf girders, and T-Bulbs have helped in providing rapid delivery of bridges and reducing initial and life cycle costs

The important and sensitive issue of generating additional funding through the P3 system is also discussed in this chapter Public investment has promoted much needed and timely reconstruction of thousands of structurally deficient (SD) bridges

The ASCE Report Card for infrastructure has put pressure on federal and state governments to take the necessary measures to replace, repair, and rehabilitate the growing number of deficient and obsolete bridges nationwide FHWA’s “Every Day Counts” Program and FIU seminars on ABC have been train-ing bridge engineers in new technology Also, courtesy of FHWA, Website resources are now available These will help in training of contractors in the use lateral slide-in methods The conclusions for this chapter are presented at the end of the chapter A wide range of appendices are presented on the follow-ing topics and are referred to in the text in the chapters:

Bibliography

ABC Glossary

Bridge Inspection Terminology

Three-Credit University Course in ABC

Training Courses and Workshops in ABC

Survey Form for Structural Countermeasures

ASCE Report Card—Innovations and New Technology

Rapid Construction of Timber, Aluminum, and Lightweight Bridges

TEMPLE-ASCE One-Day Course on Rapid Bridge Construction

A three-credit course syllabus shows the importance of theoretical and practical aspects and how the AASHTO Load and Resistance Factor Design (LRFD) Specifications and Load and Resistance Factor Rating (LRFR) Provisions need to be supplemented

The salient features of the topics of the course are as follows:

Introduction and Objectives of Rapid Bridge Construction

Overview of Highway User’s Comforts; Examples of Bridge Failures, Deficient and Functionally Obsolete Bridges; ASCE Report Card on Infrastructure

Problems with Detour and Lane Closures for Considerable Length of Time

Initiatives for ABC by FHWA, TRB, Selected States and Universities

Bridge Inspections, Site Surveys, Testing, Alternates and Preliminary Designs

11.1.2 Funding aspects

Economic Considerations in Planning, Value Engineering, Public-Private Partnership (P3)

11.1.3 Project management aspects

(Lump-sum, Design-bid-build, Design-build, CMAR etc.)

DBIA Recommendations

11.1.4 Accelerated construction techniques

Use of SPMT, Slide-in, Roll-in, roll-out, Float-in, Bridge in a Back Pack, partial ABC

High-capacity cranes, Rollers, etc

11.1.5 Modern durable construction materials

Concretes in Deck, Prestressed Girders, Abutments, Piers and Foundations (HPC, UHPC, FRPC, CFRPC, GFRPC, etc.)

Steel Girders (50W, HPS 70W, HPS 100W)

11.1.6 Type of superstructure and geometry of bridge

Slab-beam, Truss, Arch, Segmental, Cable-Stayed etc

• Insurance, Warranty, and Surety Issues

11.1.10 Project management aspects

Technical Proposal to Client, Structural Planning, Feasibility Studies, Preliminary and Final designs, Post design Services

Part 2

11.2 Coordination with highway maintenance schedule

Maintenance and protection of traffic is a primary requirement during reconstruction Work on the bridge would affect traffic flow on the highway and vice versa The volume of tasks for fixing the high-way pavement and resurfacing takes much more time than required for the bridge repairs itself

In practice, highway maintenance requires the following tasks, which can be performed parallel to those on the bridges to avoid frequent lane closures

• Cracks may happen in the road surface due to frequent rains and snow

• Due to accidents, the median barrier can get damaged

• Variable message sign structures may be added

501 11.3 ABC applications for bridges located on rivers

Bridges are essential parts of the highway Both the highway and the bridges require maintenance

If a number of bridges need to be fixed on a busy highway, the work will most likely be done in the window available in the same construction season The schedule needs to be planned by the highway agency

11.2.1 Construction season restrictions

For deck repairs, longitudinal joints require cast-in-place concrete pours All outdoor work, which involves minor or major repairs (both for highway and for bridges), must be carried out in reasonable weather conditions Weather may vary according to the location of each state Work will not be possible

if it rains the day wet concrete is planned for use or in extreme cold or hot weather The bridge tion schedule and activities on the critical path must be planned while keeping an eye on highway repair work and severe weather conditions

construc-When bridges on a given highway are due to for repairs or replacement, often some of the highway sections and pavements also require fixing Generally, bridge deficiencies and highway wear and tear

go together In the interests of minimizing adverse impacts on the traveling public, the owner would like to perform both the highway and bridge work at the same time using the same contractor, who can deploy its resources (equipment and labor) in an efficient manner This enables all of the work to be done in the shortest possible time

A review of research challenges by a key AASHTO subcommittee (T-4) on this developing subject presented some areas still in need of further investigation For more efficient project management and faster implementation, improved coordination and communication skills need to be researched so that ABC methods can be made more economical A comprehensive construction code that spells out prac-tical steps based on past experience for a refined and rapid type of construction needs to be developed

11.3 ABC applications for bridges located on rivers

Application of ABC for construction of bridges on rivers is possible, but the scope of work is greater and it may take longer to complete than for bridges located at intersections This is due partly because banks of flowing rivers are subject to erosion and scour Deep foundations, including longer piles, are required, which increases the duration of construction Moreover, the foundations need to be shielded against erosion during floods, which requires special items such as river training, scour countermea-sures, and retaining walls along the eroded banks For the slide-in method, temporary bents adjacent to the existing bridge need to be constructed in the river conditions The additional work for extra items gets added to the construction schedule and is discussed below

Environmental Permit requirements: For continuous span bridges, piers are required in the

mid-dle of rivers An application for a construction permit should be made to the state DEP, well ahead of the start of the project Otherwise, objectives of ABC will be defeated

Documents need to be prepaid in support of the application forms for review by DEP Meetings are held to minimize obstructions to the flood flow such as eliminating piers and increasing opening sizes Cofferdams for foundation construction are required, and in some cases the river needs to be diverted through an auxiliary bridge Prefabricated members may not require SPMTs for the entire distance, but

transportation on barges will shorten the distance of travel from the factory to the site Deep tions, scour countermeasures, retaining walls, use of barges, etc., are major items that will increase the overall duration and cost of the project Nevertheless, the ABC design-build method will still be a great help compared to the conventional method.

founda-11.3.1 Scour and erosion of foundations at river bridges

In the United States, over 36,000 bridges are either scour critical or scour susceptible Some examples

of recent bridge failures are:

• Schoharie Creek Bridge, located on the New York State Thruway, in 1987

• US 51 Bridge over Hatchie River in Tennessee in 1989

• Damage to bridges located on the Mississippi River in 1993

• Interstate 5 NB and SB bridges over Los Gatos Creek in California in 1995

• Route 46 Bridge on Peckman’s River Bridge in Passaic County in New Jersey in 1998

• Ovilla Road Bridge located in Ellis County in Texas in 2004

In this chapter the latest technology for scour countermeasures is introduced Applications for FHWA Circulars HEC-18 and HEC-23 are discussed Since scour is a major problem for bridges located on waterways, familiarity with the methods presented will benefit the engineer in terms of safety and economical foundation design and also assist in solving constructability issues According

to the AASHTO LRFD Specifications (Section C3.7.5):

Scour is the most common reason for the failure of highway bridges in the United States.

Scour excavates and carries away material from the bed and banks of a stream Small brooks, streams, rivers, and oceans all possess different degrees of kinetic energy Scour or soil erosion at a bridge is caused by the dynamic effects of water in motion

Erosion is a very old subject that is currently analyzed using scientific disciplines such as:

The type of countermeasure is dependent upon:

• The nature of scour contraction or local

• Clear water or live bed

• Aggradation or degradation

• Meander or

• Debris accumulation

503 11.3 ABC applications for bridges located on rivers

Scour-critical bridges across the United States are currently being retrofitted using different dards for countermeasures The design procedures depend on individual bridge owners, representing hundreds of city, county, and state government agencies Design guidelines are being applied differ-ently in different states for old bridges

stan-The author carried out research on this subject for a joint publication with Anil Agrawal with a goal

of developing a “Handbook for Scour Countermeasures.” The NJDOT Bureau of Research sponsored the project, and a detailed report is now available on their Website for general use Some of the coun-termeasure details provided in this chapter are based on the handbook See http://www.state.nj.us/transportation/refdata/research/reports/FHWA-NJ-2005-027.pdf

11.3.2 Factors affecting magnitude and rate of scour

Soil profiles for typical scour-critical bridges: The soil profile for a particular bridge site should be based on boring logs While detailed geotechnical and borehole testing needs to be carried out to obtain site-specific information, studies will often utilize existing maps and information available with the state and the U.S Geological Survey (USGS) Different soil and rock materials will exhibit different rates of scour The kind of geologic material, coupled with the intensity and duration of a flood, will determine scour depth

Soil classification: Soil types are broadly classified as:

• Noncohesive (e.g., gravels, sands, and silts)

• Cohesive (silts, clays) materials

The magnitude of scour for cohesive and noncohesive soils is different, but scour takes much longer

in cohesive soils, resulting in longer bridge life In cohesive soils such as clay, both the local scour and contraction scour magnitudes may be similar, but scour takes place considerably later than in the non-cohesive sand The threshold of movement of particles of both cohesive and noncohesive materials depends on:

• Particle size

• Density

• Shape

• Packing and orientation of bed material

Noncohesive sediments: Examples are sands, gravels, and silts that have a granular structure Such

soils are considered to be the most susceptible to scour The unbounded individual particles are tible to erosion when the applied fluid forces (drag and lift) are greater than the stabilizing forces (grav-ity and friction with adjacent bed particles)

suscep-Most fine-grained sediments (clay, silty clay, and clay mixtures) possess some cohesion, the clay content being of great importance Cohesive sediments typically require relatively large forces to detach the particles and initiate movement, but relatively small forces to transport the particles away

Type of bed material: The bed material is comprised of sediments (alluvial deposits) or other

erod-ible material If bed materials are stratified, there is a greater risk of scour breaking through the more resistant layer into the less resistant layer A survey of U.S bridges indicates that bridges founded in sand have the most scour problems, as summarized in NCHRP 24-7

The clay content in the soil increases cohesion, and relatively large forces are required to erode the riverbed Higher pulsating drag and lift forces increase dynamic action on aggregates until the bonds between aggregates are gradually destroyed and aggregates are carried away by the flow An approach estimating scour in cohesive soil is to couple erosion rate with the cumulative duration of flows that exceed the threshold velocity for particle movement.

Soil types: Jean-Louis Briaud at Texas A&M University has proposed the SRICOS method of scour

measurement Streambeds that either consist of bedrock or contain a high percentage of oversized cobbles and boulders are the most scour-resistant materials To determine rock quality careful evalua-tion is needed to assess factors such as:

11.3.4 Damage from flood scour

Minimal marine life disruption and quick construction are being achieved by gabion baskets, lated concrete, or cable-tied blocks in lieu of traditional riprap Sheet piles were used for the new Schuylkill River Bridge and SEPTA’s 30th Street Station Bridge (by the author) The author

articu-Table 11.1 Soil Types with Scour Problems (NCHRP 24-7)

505 11.4 Planning of bridges over rivers

prepared a “Handbook for Scour Countermeasures” for NJDOT jointly with CUNY, which was approved by FHWA, and helped developed Sections 45 and 46 of the NJDOT Bridge Design Manual

11.3.5 Structures on water crossings

Study of scour critical bridges in the Northeast USA: In the past twenty years, the author investigated the effects of flash floods and 50-year floods and the many damages caused to the superstructure, sub-structure and foundations

Research reports were prepared for the identified scour critical bridges in Massachusetts, New Jersey, Pennsylvania, Delaware and Maryland

Some of the findings are presented here

• Unless founded on rock, all structures crossing water shall be supported on piles or have other positive protection to prevent scour of the substructure

• Cofferdams should be evaluated with regard to need, type, size, constructability, and cost

Alternative types of construction such as causeways, caissons, or drilled shafts should be ered and compared to conventional cofferdam costs

• The estimated maximum depth of scour should be used to determine overall structure stability Piles should be socketed into rock if scour can affect their stability Recommendations for details will be contained in the foundation design report (FDR)

• In addition to areas for repairs identified in the last underwater inspection and evaluation report, a field inspection and a new underwater inspection need to be carried out for field verification of the latest substructure conditions underwater

Figure 11.1 shows damage to pier concrete due to fast moving flood water making the bridge unsafe for heavy traffic

11.4 Planning of bridges over rivers

Use of Float-in Method: The modular substructure and superstructure transportation problem to the

river site will be solved by the float-in method (as shown in Figure 11.1 to avoid non-composite concrete cracks) It will help immensely in conducting complex construction over rivers Existing continuous spans may be replaced by a single span, using high-strength construction material such as HPS and HPC that are fabricated in the factory rather than on the site

The latest methods for repairing deteriorated concrete and repointing mortar joints, the applicable design details from AASHTO, and the applicable state bridge design manual can all be used as neces-sary If the current NBIS rating given in the inspection report is higher for the abutments than for the piers, the load rating will be upgraded by performing the recommended repairs

Perform substructure repairs both above and below the waterline for the following conditions:

• Abutment showing deterioration

• Abutment back wall with wide cracks at the north and south ends

• Concrete aprons at the piers exhibiting wide cracks

• Deteriorated expansion joint and back wall elements

• Removal of buildup of sand debris at piers

• Removal of any tree trunks or tree roots between piers

• Tooth dam at abutment not functioning and needs to be replaced

An estimate of the cost and repair quantities is required in each case for scour-critical bridges Unlike the HS-25 live loads, which are defined fairly accurately, flood magnitudes are unexpected and

of unpredictable magnitudes and are difficult to compute accurately for the required 50-, 100-, and 500-year intensity floods

StreamStats hydraulic analysis software: There is a need for preparation of several databases

(including demography changes in urban river locations) as required by the latest STREAMSTATS software, which is developed using hydrologic studies on rivers in each state by the USGS Updates are required for the following reasons:

• The Rational Formula for computing flood discharge (which generally has been used) is mate and has led to failures of bridges subjected to floods nationwide

• Also, HEC-18 provisions have recently been revised

• DM-2 and DM-4 specifications for flood computations and countermeasures design based on the old version of HEC-18 need to be updated so that foundations of bridges located on rivers can be safe in accordance with the new specifications

Due to increased corrosion of steel bridges on waterways due to daily evaporation, the life of such bridges is adversely affected During floods, countermeasures should not get displaced Sediment deposits in some rivers require dredging and clearing of stones under bridges before it is too late Hence, frequent inspections may be required

FIGURE 11.1

Damage to pier concrete due to fast moving flood water making the bridge unsafe for heavy traffic.

507 11.5 Issues of scour-critical bridges

11.5 Issues of scour-critical bridges

Examples of original planning defects are narrow openings and shallow foundation depths Old bridges are likely to have planning defects as compared to new bridges The effects of floods include both aggradations and degradation In earlier days there were no scour analysis criteria As per AASHTO it

is now required to conduct such analysis There is a considerable increase in velocity due to increase in discharge or reduction in flow area under the bridge

where V = Peak flood velocity

Q = Flood discharge and

A = Cross-sectional area of bridge opening

Potential issues include the following:

• The original design of the flow area may be inadequate

• The river has meandered over a long period and direction of flow is skewed

• Debris may accumulate during floods, reducing the size of the opening

• Heavy storms, increased snow and subsequent melting, global warming of glaciers, and changes

in demography will increase discharge

When both Q increases and A decreases simultaneously, the magnitude of increase in velocity will

make the bridge “scour critical.”

Scour is very much a site-specific issue as no two rivers are alike even though bridges may be alike Physical parameters include:

River configuration types

• Restrictions from environmental agencies in placing piers in riverbeds, resulting in longer spans

• Difficulties in designing and constructing deep foundations in flowing water

• Difficulties in maintaining bridge substructure underwater and in painting of corroded girders

11.5.1 Scour analysis

Codes and design guidelines: The following FHWA and AASHTO publications serve as major resources for scour analysis and design:

Riverine Flow HEC-18, “Evaluating Scour at Bridges”

HEC-20, “Stream Stability at Highway Structures”

HEC-23, “Countermeasures”

Tidal Flow HEC-25, “Tidal Hydrology, Hydraulics, and Scour at Bridges”

AASHTO LRFD Bridge Design Specifications

Model Drainage Manual (AASHTO)

Also, the Maryland, New Jersey, Pennsylvania, and Florida state codes, among others, can be consulted NCHRP materials and CIRIA (British code) may also be useful

11.5.2 Design floods

The aim should be to design bridges for all times and for all occasions AASHTO (LRFD) load binations for extreme conditions are applicable The extreme-event limit states relate to flood events with return periods (usually 100 years) in excess of the design life of the bridge (usually 75 years) Foundations of new bridges, bridges to be widened, or bridges to be replaced should be designed to resist scour based on 100-year-design flood criteria, reviewing conditions that may create the deepest scour at the foundations The author designed Peckman’s River Bridge on Route 46 in North Jersey after Hurricane Floyd had subsided Figure 11.2 shows damage even to the girders from overtopping

com-Check flood for bridge scour: The foundation design should be reviewed using a 500-year check flood, or 1.7 times a 100-year flood, if 500-year flood information is not available

FIGURE 11.2

Hurricane Floyd High water elevation causing damage from over topping.

(Photo by the author during peak floods.)

509 11.5 Issues of scour-critical bridges

11.5.3 Evaluation of the need for countermeasures

1 Post-flood inspection in shallow water

2 Post-flood inspection in deep water

The location of a bridge influences the formation of scour at its foundation Bridges located on a straight, meandering, or sloping thalweg, at a confluence, or downstream of a dam will all have differ-ent degrees of scour

Bridge footings: Countermeasures are required for scour-critical bridges Ideally, a

recommended scour countermeasure will permanently eliminate a bridge’s potential ability to scour damage for the peak floods A permit from the state is required to install armoring

vulner-Periodic inspections after major floods or coastal storm surge

Bridge Scour Evaluation: A nationwide survey was conducted by the author’s research team

for the types of scour countermeasures being used by each state Appendix 9 shows a questionnaire survey form for scour countermeasures The feedback received gave useful information on the type

of countermeasure used and its performance Scour-critical bridges located on streams with high flood velocities can cause major foundation settlements Bridges with narrow waterway openings and soft erodible soils contribute to bridge collapse

The magnitude and depth of erosion depend upon discharge volume and velocity Rivers, rivulets, streams, brooks, and channels are all subjected to scour to varying degrees A channel, for example, may have a small discharge but a high velocity Hence, scour is present in all types of rivers, narrow or wide The two main issues are hydraulics and soil science, i.e., the interaction between water and soil Nonerodible rock will not be subjected to scour

The following items discuss procedures for the assessment of scour at all bridges that are 20 ft or greater in length that spans water There are two basic types of assessment:

• Field-viewed bridge site assessments, for which USGS personnel visit the bridge site

• Office-reviewed bridge site assessments, for which USGS personnel compile data and do not visit the bridge site

Both types of assessments are primarily focused at meeting the requirements of the FHWA date Date of bridge construction and the accessibility of the bridge substructure units for inspection determine which type of assessment a bridge receives

man-Pennsylvania State Scour Code: A web-based Scour-Critical Bridge Indicator (SCBI) Code as

developed by USGS is used The SCBI Code indicates the vulnerability of the bridge to future scour It

is based on the FHWA code (NBI Item 113) (FHWA 1989) and PennDOT’s interpretation of the FHWA Code (Bryan Spangler, PennDOT, written communication, 1999)

The SCBI Code contains a whole number between 9 and 2 Each code number has one or more cases Scour Assessment Rating (SAR) is computed from select collected and compiled structure com-ponents, and hydrologic and hydraulic data Agency personnel assign the final SCBI Code and an SAR (between 0 and 100) on the basis of their review of all data

The SCBI Code and SAR calculator use various factors from the field or office scour evaluations to determine the SCBI Code for individual subunits and the bridge Field view, soil maps, and previous

inspection reports are required The calculator allows inspection personnel in Pennsylvania to mine overall bridge rating when:

• Review of bridge reports identify undetermined historical data or revised field data

• Site conditions change

• New scenarios have developed

• New bridges are constructed

11.5.4 Types of scour

According to HEC-18, general scour is a lowering of the streambed across the stream or waterway at the bridge This lowering may be uniform across the bed or nonuniform General scour may result from contraction of the flow or other general scour conditions such as flow around a bend Total scour is the sum of long-term degradation, general (contraction) scour, and local scour

Contraction scour is the component of scour resulting from a contraction of the flow area at the bridge It causes an increase in velocity and shear stress on the bed at the bridge If the abutments are located outside the width of a channel, no contraction takes place and there will be no contraction scour.The initial scouring in low flows is known as “clear water” scour Clear water scour is scour at the pier or abutment (contraction scour) when there is no movement of bed material upstream of the bridge crossing at the flow causing bridge scour If the flow continues to increase, “live bed” scour can occur, which is general movement of the bed Live bed scour depth increases with the increase in the size of bed material D50 in the riverbed, while clear water scour decreases as mean bed material size Dmincreases The increased velocity affects the stability of the streambed For HEC 18, scour depth is computed from Laursen’s equation for channel contraction within the total bridge opening In terms of magnitude, it may be higher at the piers or at the abutments

Local scour is removal of material from around piers, abutments, spurs, and embankments caused

by an acceleration of flow and resulting vortices induced by obstructions to the flow Local features at

a bridge such as abutments, piers, weirs, cofferdams, and dikes may obstruct and deflect the flow The substructures increase the local flow velocities and turbulence levels, giving rise to vortices that may increase the erosion of the riverbed

At the piers, local scour is computed using the Colorado State University (CSU) equation It is dependent upon many factors including length of pier, width of pier, and the angle of attack Abutment scour is computed from Froehlich’s and Hire’s equations It is dependent upon many factors including length of embankment

The flow of water is on both sides of a pier, generating vortices and eddy currents, while the flow is

on one side only for abutments This results in higher scour depths at piers than that seen for local scour

511 11.5 Issues of scour-critical bridges

Scour analysis and

Detailed countermeasures design

The complete original procedures for determining the SCBI Code can be found in Cinotto and White (2000) The SCBI Code algorithm used by the web-based SCBI Code and SAR calculator was modified from Cinotto and White (2000) to eliminate the comparisons of USGS and PennDOT data

Geotechnical: Both boring information and grain size analysis would be needed for accurate

deter-mination of scour Collection and processing of geomorphic, hydrologic, and hydraulic data for ment of scour at bridges require borehole information for soil characteristics

assess-The size of the opening or degree of obstruction from abutments, piers, and foundations will ence the velocity of water The catchment area of a river, its source of supply, demography, storms, and melting of glaciers will influence the volume of discharge and erosion The use of a gabion mat and baskets on a New Hampshire project for scour analysis on Monatiquot River is shown in the author’s textbook “Bridge and Highway Structure Rehabilitation and Repair” published by McGraw-Hill, 2010.Figure 11.3 shows use of Gabion Mat between abutment walls

influ-A

Flow Monatiquot river

A Plan

58.7'

1.0' TO 2.0' 3' × 3' Gabion wire basket Anchor block (TYP.) Section A–A East abutment

40.0'

FIGURE 11.3

Use of gabion mat between abutment walls.

11.6 Rapid repairs and replacement of bridges on rivers

11.6.1 NBIS condition rating

The overall condition of substructures of 19 bridges was assigned the following NBIS condition rating:

Very good condition: No problems noted

Good condition: Some minor problems

Satisfactory condition: Structural elements show some minor deterioration

Fair condition: All primary elements are sound, but may have minor section loss, cracking, or spalling

Poor condition: Advance section loss, deterioration, or spalling of primary structural elements.Aggradation is a common problem due to the tree environment close to the river banks

11.6.2 In-depth bridge inspections

The purpose of the inspections is to identify levels and areas of deterioration of all structural and structural substructure elements in order to develop repair recommendations and details This effort also includes correlating probing measurements taken near the pier edges with the previous substruc-ture inspections FHWA has adopted three diving inspection intensity levels The first two levels can be described as follows:

non-Level I: Visual, tactile inspection (100% “swim-by” at arm’s length)

Level II: Detailed inspection with partial cleaning (100% “swim-by” with 10% cleaning)

FHWA Level II requires that portions of the structure be cleaned of marine growth to identify sible damaged and/or deteriorated areas that may be hidden by surface growth The cleaning must be performed on at least 10% of all underwater elements The equipment used to inspect the majority of the bridges consists of a small boat, sounding rod, hand tools, and line-tended SCUBA

pos-FHWA Level III diving inspections: This is a highly detailed inspection with nondestructive testing Testers are inspecting a critical structural element where extensive repair is contemplated Based on under-water inspection reports, the defects in Table 11.2 are typical of what may exist for a scour-critical bridge

11.6.3 Concept study report and plans

Based on the findings of the condition assessment, potential repair/remediation recommendations will

be developed Fluctuating river elevations will be taken into account when developing repair mendations and reviewing the construction feasibility

recom-Evaluation shall include but not be limited to:

• Evaluation of constructability and construction staging

• Community impacts during construction: impacts to emergency vehicle response, tourist industry, traffic delays, pedestrians and bicyclists, local businesses, and noise

• Development of construction cost estimates for each feasible alternative along with the anticipated construction schedule

513 11.6 Rapid repairs and replacement of bridges on rivers

• MPT schemes shall be prepared for each feasible alternative

• Right-of-way requirements

• Environmental impact to the waterway and endangered species

A Draft Concept Study Report, including plans and recommendations, should be created to vide a concise aggregation of the important elements of the condition evaluation and an overall

pro-Select bridge location and span

Is bridge location acceptable to scour?

Structural planning for waterway opening

Field data collection.

Obtain river x-sections.

Obtain hydraulic & flood data Obtain geo-technical data.

Check stream stability

hydrologic analysis river or tidal Hydraulic analysis.

Identify abutment or pier Perform scour analysis.

Inspection & maintenance

HEC-18

HEC-20

AASHTO LRFD, Section: 2 & 9 Geo-technical Report

FEMA Insurance Study AASHTO Model Drainage Manual

Field Surveys

No risk NO

YES

Check bridge for AASHTO Extreme loads.

Set Foundation elevation Design Spread Footing or Deep Foundations.

FIGURE 11.4

Flow diagram for scour analysis.

synthesis of conclusions and recommendations The Draft Concept Study Report shall include but not be limited to:

• Condition assessment

• Scour vulnerability assessment

• Discussion of alternatives, including a discussion of potential impacts for each alternative

• Recommended repairs/remediation including supporting justification

• Requirements for design including required surveys, geotechnical evaluations, and hydraulic analysis

• A list of applicable permits including the permit cost and the anticipated duration to obtain the permit in the light of many requirements, including a discussion of required temporary construc-tion easements, if any

• MPT requirements including sketches and/or conceptual plans for construction staging and detours

• Construction costs

• Anticipated construction schedule

• Plans with details to a level sufficient to clearly demonstrate the repair/remediation type and location along with construction staging and construction access

11.6.3.1 Constructability review

After the Draft Concept Study Report, a one- or two-day workshop may be held with the team members

to review the concept study options The goal of the workshop is to provide review comments in advance of presenting a preferred design concept

Table 11.2 Underwater Inspection Results

11 Spalls in abutment concrete Surface repairs with approved

patch material

22 Delaminations and cracks in

substructure concrete above water Pressure grouting

33 Voids in breast wall Epoxy grouting Nonshrink grout

44 Debris accumulation Clean debris

55 Mortar loss in masonry joints Repoint mortar

66 Undermining Plug with concrete Use grout bags

77 Broken stone masonry Place stone and fill with mortar

88 Cracks in tremie concrete below water Pressure inject masonry cracks

99 Spalling in foundation Pressure grouting

110 Missing or broken riprap Replace by R-8 size stone

111 Cracks in apron around piers Repair concrete apron Place riprap

around piers

112 Silting Dredging

113 Advance section loss of structural

members Strengthen member Underpinning

515 11.6 Rapid repairs and replacement of bridges on rivers

11.6.4 Condition evaluation and countermeasures design

• Subsurface feature description

• Streambed description: Grain size analyses are conducted on one sample from the streambed The grain size distribution curves are given in the laboratory soil test results

• Field survey results (example): A field survey by an interdisciplinary team of licensed structural, hydraulic, and geotechnical engineers should be carried out The team should record visual observations (Table 11.3), which may be summarized as:

• Any scour holes in the bridge area that need to be clogged

• Location of thalweg of the main channel; if it has moved toward one of the abutments, increased scour will result

• Top of footing elevation if exposed; bottom of footing elevations need to be investigated

• If mortar is missing from joints of stone, masonry needs to be fixed

• Deposit of stones from earlier floods at both upstream and downstream sides

Other steps include:

• Preparation of photographic documentation

• Evaluation stream and waterway characteristics and roughness coefficients of the channel

• Due to the diverse nature and extent of data collection, a collection procedure is followed:

• Compile an inventory of already available data of a reliable nature

• A list of remaining data necessary to perform scour analysis and the methods, extent, and duration of obtaining such data Roughness coefficient values are as described in “Open Channel Hydraulics” by Chow for scour only

Table 11.3 Data Collection Items for Scour Study Example

Field surveys Waterway opening Yes Observations and

measurements Two daysUnderwater surveys Scour holes Yes Probing One day River cross-

sections HEC-RAS model Yes Surveying instruments Two daysSoil parameters Roughness

coefficients Inspection and photos Characteristics of banks and bed One dayFoundation details Size and scour

damage Inspection and photos Probing exposed footings One dayTest boring Depth of footing /rock Boring logs Drilling/Coring One day