National Academies Press: OpenBook

Bridge Demolition Practices (2019)

Chapter: Chapter 2 - Literature Review

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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Suggested Citation:"Chapter 2 - Literature Review." National Academies of Sciences, Engineering, and Medicine. 2019. Bridge Demolition Practices. Washington, DC: The National Academies Press. doi: 10.17226/25478.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

6 The literature review process began with a bibliographic search of the Transportation Research Information Database for documents related to bridge demolition practices. Keywords and phrases in the search included “bridge demolition practices,” “bridge demolition specifications,” and “bridge demolition engineering.” There was also a search of the OSHA website for engi- neering investigative reports of bridge demolition incidents. AASHTO’s current LRFD bridge construction specifications (2017a) were reviewed for additional information or references, and Internet searching was performed to find documentation from individual transportation agencies on their demolition provisions. To date, there is limited published research or literature on the topic of bridge demolition practices. Overview Bridge demolition includes both full bridge removal and partial removal required to modify or rehabilitate an existing bridge. Either of these may be performed as phased demoli- tion such that one portion of the structure remains under traffic while the other portion is demolished. The emphasis of this synthesis is the practice used by bridge owners to manage and administer those bridge demolition activities. Provisions of OSHA govern safety practices for all construction activities, including demolition. Some states have additional safety and health regulations. Conformance with both federal and local OSHA regulations is mandatory for all contractor operations, and thus safety requirements are not part of the literature review. Current Manuals and Specifications for Demolition Section 2 of AASHTO’s LRFD bridge construction specifications addresses partial or total removal and disposal of bridges and other major structures. The published standard requires submittal of drawings showing the methods and sequence of removal when structures or portions of structures are removed and salvaged, when removal is over or adjacent to public traffic or railroad property, or if removal is specified in the contract documents. Work is not to begin until the drawings have been approved. The remainder of the section addresses construction aspects such as foundation cut-off elevations, bolt and rivet removal when salvag- ing structures, and requirements such as sawcuts and concrete removal when executing partial removals. No requirements on submittal drawings content, supporting engineering calculations, or demolition procedure narratives are provided. Chapter 8 of Engineering for Structural Stability in Bridge Construction (Garlich et al. 2015) provides recommendations for the content of bridge removal plans. Section 8 of the chapter C H A P T E R 2 Literature Review

Literature Review 7 notes that demolition submittals should be similar to bridge erection submittals, “in reverse,” and includes a demolition checklist to augment the erection checklist provided in Section 7. The manual provides information on verifying crane stability, lifting capacity determination, and rigging design. Methods for computing girder stability, including the effects of loss of composite action and load redistribution during demolition are provided, as are considerations for design of temporary bracing and shoring systems. AASHTO’s manual for bridge evaluation (AASHTO 2018) sets forth criteria for load rating existing bridges. Since it provides criteria for existing structures, including those constructed to older design specifications and with older materials, the manual is well suited for use in evalu- ating bridge capacity under loads that may be applied by demolition equipment and activities. Bridge demolition projects located over or adjacent to railroads must satisfy the individual railroad requirements as well as the bridge owner requirements. Submittal requirements for the Norfolk Southern Railway Company are contained in Norfolk Southern Railway Company’s Public Projects Manual (2013) and include the following: • Plan showing location of the bridge, tracks, overhead utilities, adjacent structures, and so forth. Show crane locations and operating radii. • Rating sheets for crane and rigging capacities showing adequacy for 150% of the actual crane lift. • Calculated weight of each crane lift. • Sketch of rigging configuration and component capacities. • Complete demolition procedure, including the order of removal with lifts, allotted time, and crane repositioning. • Design calculations for temporary support and stability of the structure during temporary conditions. • Plans and calculations prepared by a licensed professional engineer in the state where work takes place. • Predemolition meeting with contractor’s key personnel. • Design requirements for overhead debris shield. The Norfolk Southern Public Works Manual also provides detailed requirements for the use of explosives in demolition. The requirements in the BNSF Railway Guidelines (BNSF 2008) are similar to those of the Norfolk Southern but also include the following provisions: • Prior to beginning removal, the sealing engineer, or that person’s authorized representa- tive, shall inspect all temporary support components and certify in writing that they are satisfactory. • Contractor shall verify that site soils can adequately support crane loads while lifting. • Front-end loaders and backhoes cannot be used for lifting. • No blasting is allowed on railroad right-of-way. • Safety provisions for cutting torches are provided. Demolition Practices There is limited literature addressing bridge demolition practices, and the majority of what is available discusses specific techniques for demolition activities such as concrete sawing, hydro-demolition, controlled explosives, or the effects of those techniques on the remaining structure. NCHRP Synthesis of Highway Practice 169: Removing Concrete from Bridges (Manning 1991) provides a summary of eight methods for complete removal of concrete

8 Bridge Demolition Practices during bridge rehabilitation and four methods for partial removal. The equipment and con- struction procedures for each method are presented, along with advantages and limitations on their use. A chapter on contract preparation and execution is included; however, the chapter primarily addresses the effects of partial concrete deck removal methods on the durability of subsequent repairs. Abudayyeh, Sawhney, El-Bibany, and Buchanan (1998) discussed eight methods used for concrete bridge demolition. The authors describe each method, along with its application, advantages, disadvantages and production rates. Safety issues are presented, including the need for a demolition plan, protection of underground and overhead utilities, and measures to monitor and protect adjacent structures. Their conclusions included placing more emphasis on engineering of demolition projects. Barsottelli and Avci (2013) stressed the need for checking the structure’s strength and stability at each stage of removal. The authors noted that demolition has become far more sophisticated than the wrecking ball method. Loading from demolition equipment can be significant if economical procedures are employed. This requires engineering analysis. FHWA’s Manual on Use of Self-Propelled Modular Transporters to Remove and Replace Bridges (2007) notes that removal of bridges using self-propelled modular transporters (SPMTs) is just the reverse of installation, though unless scheduled to be reused, some damage to the bridge resulting from removal should be acceptable. Examples of bridge removals using SPMTs on I-4 in Florida and I-10/LA 35 in Louisiana are in the manual. In the I-4 project, the two center spans over traffic of the prestressed concrete girder bridge were removed by using SPMTs after conventional demolition of the approach spans. The spans were each 70.5 feet long and were moved to a nearby location for subsequent demolition. An overweight load had damaged the I-10 east and I-10 west bridges over State Route 35 (SR-35) in Louisiana. The damaged spans were composed of 60-foot pretensional concrete girders. Each span was removed by using two sets of SPMTs and transported to a nearby location for conventional demolition. Partial demolition often includes concrete deck removal. It is important that the removal technique not cause damage to the supporting girders. Improper sawing has resulted in cuts to girder flanges, necessitating repairs. Overaggressive use of impact breaking may cause tears, denting, and distortion of steel flanges and fracturing of concrete girder flanges. Phares, Shane, Dahlberg, and Dang (2014) reported on various concrete deck removal methods for steel girders as well as methods of damage repair, including grinding and welding (Figure 1). A survey of state DOT practices conducted as part of their report indicated that sawing, percussive tools, and hydrodemolition were the primary concrete removal techniques, and 10 of the 28 states responding had special provisions covering full-depth removal. They noted that special provisions typically addressed limits on percussive equipment size and locations of sawcutting. Most of the states responding to the survey require submission of a deck removal plan, including proposed removal methods and equipment. Assad and Morcous (2016) provided guidance on deck removal from precast/prestressed concrete I-girders with wide and thin tip flanges. They noted the increased potential for damage to thin style girders and the minimal existing guidelines or specifications addressing means to minimize damage. Lindsell (1994) discussed various issues that may arise in demolition of prestressed concrete bridges (Figure 2), noting that a detailed structural assessment, including consideration of the original construction sequence, may be needed to determine a safe demolition sequence. Systems of prestressing or posttensioning have changed over time, and the system type and installation

Literature Review 9 Source: Courtesy of the Walsh Group. Figure 1. Deck removal. Source: Courtesy of the Walsh Group. Figure 2. Prestressed box girder demolition.

10 Bridge Demolition Practices details may not be known without field investigation. Some of the items they identified as requiring consideration include • The prestressing system, tendon locations at critical sections, points of cutting tendons during demolition. • The condition of the tendons and grout, if present, should be determined. • Redistribution of forces as the structure is demolished or selective cutting takes place. • Requirement for special analysis such as finite element modeling. • Assessment of remaining levels of prestress. • Original sequence of prestressing for staged stressing. • A detailed method statement, including calculations and checks of structural stability at each stage of demolition design of any temporary works required. Lindsell noted that the owner should outline likely acceptable demolition techniques and site constraints within the drawings and specifications and that contractors be prequalified. The contractors, as part of their bid documents, should include a preliminary work plan. Both partial and total demolition are frequently conducted using equipment such as hydraulic breakers placed on the existing bridge deck (Figure 3). Engineering guidance for those situations is provided by Avci and Barsottelli (2017), including a worked design example of demolition of a three-span continuous steel bridge. The authors stressed the importance of accurate exist- ing bridge condition information for use in the analysis and that analysis for partial demolition should be conservative to assure no damage is done to the remaining structure. The authors also noted that determining the load effects of demolition equipment and distribution to the girders has not been well established. Analysis for complete demolition may be in accordance with the allowable stress design methods of the American Institute of Steel Construction’s Specification for Structural Steel Buildings (ANSI/AISC 360-16) (American Institute of Steel Construction 2017) or the American Concrete Institute’s Building Code Requirements for Struc- tural Concrete (ACI 318-14) (American Concrete Institute 2014). Partial demolition, however, must adhere to the AASHTO bridge design specifications. The authors noted that, in their experience, the extent of submittal requirements and review for demolition engineering vary from state to state. Source: Courtesy of the Walsh Group. Figure 3. Demolition equipment working atop the bridge.

Literature Review 11 Failure to account properly for demolition equipment loads on the deck and load changes during deck removal has resulted in failures, according to Ayub (2006), Jauregui (2014), and Ayub (2015). In the failure reported by Jauregui, the original bridge design drawings included a deck removal procedure; however, the contractor changed the procedure to accelerate the deck removal, leading to a lateral torsional buckling failure of the girders. Collapse of the Grandview Triangle Bridge in Kansas City, Missouri (Ayub 2006), was also attributed to the contractor’s failure to recognize the changed structural behavior as demolition progressed, coupled with the loads from demolition equipment. The collapse near Cincinnati, Ohio, of the bridge onto southbound Interstate 75 (Ayub 2015) was a stability failure attributed to the demolition equip- ment loads on the deck, coupled with poorly designed and installed temporary girder tie-downs at the abutment. The report also criticized the owner for not questioning the contractor about the method and sequence of demolition at the site. Demolition Plan Requirements While the literature includes numerous articles on bridge projects that included partial or full demolition, they contain minimal information on demolition submittals requirements. A synthesis report published in 2011 by CTC & Associates LLC was prepared for the Wisconsin DOT Bureau of Structures. The report informed about possible changes to Wisconsin’s then- current demolition plan provisions. The report found that 26 DOTs provided plan requirements for bridge removal in their standard specifications, construction manuals, or special provisions, while the remaining DOTs provided only bridge removal language in their standard specifica- tions. The report noted that standard specifications may be supplemented by project specific special provisions, citing projects in California, Texas, and Nebraska as examples. Removing Old Structures, a Wisconsin DOT special provision, is included as an appendix to the synthesis report. Garber (2016) prepared a survey of bridge demolition experience and practices. Although initially intended to address issues related to accelerated bridge construction projects, the survey was expanded to cover traditional delivery methods. Twenty-eight states responded to the survey. Forty three percent (43%) had experienced an unintentional collapse in the previous 15 years, with only two incidences attributed to accelerated bridge construction projects. Approximately one-half of the respondents required demolition plans for either full or partial demolition. The remainder only requires them on what may be termed higher risk projects such as when blasting may be used, railroads are involved, or removal may affect live traffic. Detailed demolition plans were found to not be required for prestressed concrete girder bridges, small structures, box culverts, bridges not being demolished over a public road, and cases where adjacent structures were not affected. Responses indicated that the design engineer’s involvement is generally limited to preparation of specifications or special provisions, unless the structure is complex, and review of contractor submittals. An engineer retained by the contractor engineered the demolition plan. Just over 60% of the respondents always required demolition plans to be signed by a professional engineer, while others required it on a case-by-case basis. The survey did not inquire as to owner specified engineering criteria for use in preparing demolition plans. Approximately 20% of respondents do provide limits on the hammer size or energy of demolition equipment, a measure intended to limit damage to any remaining structure or deck. Field oversight is predominantly left to the contractor, with one-half of the respondents requiring a predemolition meeting. Only 20% of respondents required a contingency plan with the demolition submittal, though this may be addressed in the predemolition meeting as well. Information on demolition plan preparation and on submittal requirements was also obtained as part of developing the Engineering for Structural Stability in Bridge Construction

12 Bridge Demolition Practices manual (Garlich et al. 2015). An 18-question survey was sent to the DOTs of all 50 states, asking about their experiences and requirements for bridge superstructure erection and demolition engineering. Thirty-three states (66%) responded. Most states require that a demolition plan be submitted for other than small or simple span structures. Work over or adjacent to live traffic, bridge complexity, bridge length, and proximity to railroads was a common trigger of demolition plan submittals. Approximately twenty-two states (70% of respondents) require demolition plans to bear a professional engineer’s seal. Specific design criteria for use in preparing demolition plans were rarely provided. State Departments of Transportation Provisions Various state DOT standard specifications and manuals were reviewed to determine the types and range of provisions they included for demolition plan preparation and submittal, as well as for review and field oversight. The degree to which bridge demolition is addressed in those documents was found to vary considerably, with most states providing limited requirements. The several DOT provisions highlighted in this section demonstrate this range in demolition requirements, along with examples of DOT guidance for field oversight and design drawing preparation. In Section 7.2.11, Demolition of Existing Bridge, in the New Jersey design manual for bridges and structures (2016) provides a list of the minimum information to be included in the contract plan to assist bidders in determining the extent of the work. Major items include a plan, elevation and typical sections with key dimensions and elevations, the extent of removal, staging, and quantity estimate, along with other information that “in the judgment of the engineer” may be of use. When available, at least the original bridge plan and elevation sheets are included. The following note is placed on the contract drawing: “The information presented hereon is for informational purposes only and is not guaranteed to be correct. Bidders shall visit the site before submitting bids to ascertain the extent of the work.” A limited review of other states’ design manuals did not disclose similar design provisions. Bridge demolition in the Idaho Standard Specifications (Idaho Transportation Department 2017), Arizona Standard Specifications (Arizona Department of Transportation 2008), Nebraska Standard Specifications (Nebraska Department of Roads 2017), and Michigan Standard Specifica- tions (Michigan Department of Transportation 2012), as well as several other states, is addressed within provisions for removal of structures and obstructions. These provisions cover demoli- tion of buildings, walls, and other structures that might be part of right-of-way preparation or roadside development as well as bridges, culverts, and miscellaneous structures. Specification provisions typically require removal in accordance with the contract documents, that is, that portions of structures to remain are not damaged and, if so, that repairs are made, backfilling any excavations and properly disposing of materials. Requirements for disposition of salvaged materials are generally included. Preparation and submittal of demolition plans or procedures was not addressed. Some of these specifications (Idaho 2017, Nebraska 2017, and Michigan 2012) include separate provisions for removal of bridge decks. Typical provisions that are addressed allow methods of concrete removal such as impact hammer sizes or hydrodemolition equipment, debris removal, cleanliness of remaining reinforcing steel, sawcutting depths, and repair of any girder damage. The limits of removal are to be in accordance with the contract drawings. The Connecticut Standard Specifications (Connecticut Department of Transportation 2017) address both full and partial removal in Section 5.03, Removal of Superstructure. The provisions

Literature Review 13 primarily address construction methods and operations for concrete removal and contractor measures to prevent damage to the structure to remain. It does include a requirement for the contractor to submit written procedures and drawings for removal operations but does not provide requirements for their contents. The Oklahoma Standard Specifications (Oklahoma Department of Transportation 2009) under the section removal of buildings, structures, and obstructions require removal as required by the contract to ensure the remaining portions of the structure continue to function as intended. This suggests that specific project requirements may be contained in the contract drawings or project specifications. The section requires the resident engineer to be informed of the proposed methods prior to starting removal, but no specific requirements are included. Removal of foun- dations to 1 foot below grade is specified, along with backfilling all excavations. When structures that are removed are to remain the property of the department, they shall be dismantled at the original field splices, supported on false work, and matchmarked. The dismantling operations are subject to approval by the resident engineer. Demolition requirements may be located under several specification sections. The New York Standard Specifications (New York State Department of Transportation 2016) include partial or total removal of bridges, culverts, and other structures, as well as buildings under the section Removal of Structures and Obstructions. An engineering survey of the structure must be completed by a “competent” person prior to demolition. For bridges longer than 20 feet, the competent person shall be a registered professional engineer with experience in bridge design or demolition. A removal plan, including a description of the type, size, weight, and location of all equipment and sequence of removal, is required. The competent person must periodi- cally observe the demolition activities and recommend appropriate actions should evidence of unanticipated performance be found. If so, the removal plan shall be revised accordingly and provided promptly to the state’s engineer. Various safety and environmental requirements are provided. Provisions for dismantling structures include dismantling without damage, match- marking pieces to permit reassembly and protected storage. Removal of structural concrete is covered under Section 580, Structural Concrete Removal, which notes that concrete shall be removed as indicated on the plans. Saw cuts are to be located as shown on the plans with maximum 45-pound chipping hammers, having less than 1,600 blows per minute, used for removal where adjacent concrete is to remain. Bridge members damaged by removal operations shall be repaired. Partial demolition of structural steel is covered under Section 589, Removal of Existing Steel. This section provides specific workmanship requirements for fastener removals, cutting, and disassembly of welded connections. A written work plan setting forth expected structure temporary support requirements, disconnection procedures, and any adjustments to the steel to remain must be submitted. The limit of demolition work shall be in accordance with the contract plans. The Pennsylvania Standard Specifications (Pennsylvania Department of Transportation 2016) under Section 1018, Removal of Existing Bridges or Culverts, require submittal of a plan describing the demolition and removal methods to be used. The plan shall include methods of protecting the general public and public utilities. Work cannot begin until the plan has been reviewed and accepted. For removal of bridges over roadways or removal of bridges with spans over 80 feet, the plan must be signed and sealed by a professional engineer. For structures over or under a railroad, the accepted plan shall be submitted to the railroad by the contractor and written acceptance by the railroad must be provided to the department prior to any work. All excavated areas are to be backfilled. In addition to the specifications, the Project Office Manual (Pennsylvania Department of Transportation 2017) contains predemolition meeting require- ments, including who should be in the meeting, a meeting agenda, and inspector duties during

14 Bridge Demolition Practices demolition. The manual also includes provisions for the demolition plan, noting its complexity will vary with the complexity at the structure being demolished. The plan, at a minimum, must address the following: • Methods of protection of the public, construction, and inspection personnel, including traffic control and fall protection. • Location and methods of protection of utilities. • Phasing and sequence of activities, including equipment types and locations, along with catalog data sheets for any equipment operating on the structure. Crane operating radius and associated load capacities are required. • Rigging calculations and catalog data for rigging components. • Location and weight of equipment or materials staged or stockpiled on the structure. • Removal sequence with analysis to assure stability of the structure at all stages during demolition. • Temporary support system design required to assure stability. The manual requires the inspector to have a copy of the accepted demolition plan in the field to ensure the contractor is in compliance at all times. Any changes require resubmission of the plan. All equipment and rigging should be verified to conform to the plan before any lifts, and lifting over live traffic is prohibited. The West Virginia Bridge Design Manual (West Virginia Department of Transportation 2016) require submittal of a demolition or dismantling plan by the contractor under Section 203, Dismantling of Structures. This section applies to all structure types designated in the contract plans for removal. The contractor is responsible for determining the current condition of the structure and that the file location of available bridge condition reports is provided. The demoli- tion plan is to include a complete structural analysis for all phases of the work, accounting for existing conditions. The analysis shall be completed in accordance with AASHTO’s Standard Specification for Highway Bridges (AASHTO 2002) or the LRFD bridge design specifications (AASHTO 2017b). The design loads shall match those applied by the contractor’s means and methods of demolition. The plan shall be prepared and sealed by a West Virginia registered professional engineer who is experienced in bridge design. The plan must be submitted at least 7 calendar days before the start of work. It is not clear whether the plan is returned, but submittal is stated to not constitute review or approval. Requirements of the Illinois Standard Specifications (Illinois Department of Transportation 2016) in the section titled Removal of Existing Structures only require submittal of a demolition plan when the work is adjacent to or over an active roadway, railroad, or waterway designated as “public waters.” The specification applies to bridges and drainage structures. The plan includes an assessment of the condition of the existing structure and an evaluation of its capacity and stability during demolition and must be sealed by an Illinois licensed structural engineer. A protective shield is required to prevent injury or damage from fallen debris during any deck removal. The protective shield must be able to carry a 200-pound-per-square-foot live load, and design drawings and calculation are required. Equipment for partial removal of bridge decks is limited to 15-pound pneumatic impact hammers within 1 foot of the required saw cuts and 45-pound hammers beyond that. For complete removal, breakers with energy up to 1,200-foot pounds may be used. Provisions for concrete removal using hydrodemolition are also included. In addition to the specifications provisions, whenever the contractor’s means and methods for demolition apply loads to the structure or change its structural behavior, a structural assess- ment report for contractor’s means and methods is required as part of the demolition plan. This analysis must show that no portions of the structure to remain are compromised as a result of the demolition activities. Each stage of the work must be addressed, and the assessment must

Literature Review 15 be based on the existing structure condition. The evaluation is conducted in accordance with the AASHTO Manual for Bridge Evaluation (AASHTO 2018). Loads applied to portions of the structure to remain shall not exceed the inventory level, while for portions being removed the loads shall not exceed the operating level. All engineering analysis shall be signed and sealed by an Illinois licensed structural engineer. The Washington State Standard Specifications (Washington State Department of Trans- portation 2018) contain requirements for a bridge demolition plan showing all stages of demolition along with crane foundation stability analysis and crane load capacity calculations. The requirements further stipulate that when the contractor’s removal method for a truss involves use of cranes to pick, lift, and remove the truss, the contractor shall confirm the truss dead load. The dead load shall be confirmed by using jacks or other means to break the truss free from its supports at each end. The means of performing these requirements shall be included in the submitted demolition plan. The provisions of Utah’s specification for concrete bridge deck removal of the Standard Specifications (Utah Department of Transportation 2017) address demolition of bridge decks where the supporting structure is to remain. The section requires submittal of a detailed demo- lition plan, including a written work sequence as well as drawings. Equipment locations, lifting calculations, and equipment data are required, as are calculations demonstrating satisfactory stability and strength of the remaining structure. Caution is provided to account for loss of composite action due to deck removal in girder analysis. Repair procedures for any damage to girders as a result of concrete removal are also required as part of the submittal. The specifica- tion includes general flange repair guidelines to be used in developing the repair procedures. Provisions for various types of concrete deck removal equipment are included. The contractor is to allow 14 calendar days for submittal review. No deviations from the approved drawings are permitted unless authorized in writing by the state. The Bridge Construction Records and Procedures Manual, Section 124-2 (California Depart- ment of Transportation 2017a) addresses demolition plan reviews and includes the following items to check prior to demolition. They are • Contractor should obtain as-built plans and investigate as-built conditions. • Contractor to submit a complete bridge removal/demolition plan, prepared by an engineer who is a registered civil engineer in the State of California. • The removal/demolition plan should detail the procedures and sequence for removing portions of the bridge, including all features necessary to remove the bridge in a safe and controlled manner. • For partial demolition of bridge decks, barriers, et cetera, the maximum striking energy of concrete removal equipment shall not exceed 1,200 foot-pounds. • A pre-job meeting is required to review specification requirements, safety, and shoring. • A contingency plan is to be submitted. • Design calculations must demonstrate the stability of the structure during all stages of the removal operations. • Contractor’s equipment list, weights, and locations shall be provided. The California DOT’s Construction Manual (California Department of Transportation 2017b) provides guidance to the field inspector. Under Section 4-6003B, Removing Bridges, the inspector should do the following: • The contractor must submit bridge removal work plans. Construction’s (Caltrans) represen- tative on site has responsibility and authority for reviewing all authorizing bridge removal work plans and overseeing bridge removal work.

16 Bridge Demolition Practices • When removal is adjacent to public traffic or railroad property, review contractor’s traffic handling around or through the area. • Review protective shielding plans to ensure contractor meets the specified requirements. • Assure removal sequence protects facilities from damage. • Verify that the registered engineer who signed the bridge removal work plan is present at all times during bridge removal activities and prepares a daily inspection report that is available at the job site. Standard procedures for documenting construction projects are to be followed for demolition activities. Summary AASHTO’s LRFD bridge construction specification provides limited requirements for bridge demolition. While the specification requires submittal of demolition drawings for structures or portions of structures, when removal is over or adjacent to public traffic or railway property, or if specified in the contract documents, the specification provides no requirements for the contents of those drawings. The Engineering for Structural Stability in Bridge Construction manual (Garlich et al. 2015) does address demolition activities and provides guidance for demolition plans and supporting calculations. DOT specifications, however, did not reference the manual. Limited research and technical information are available addressing bridge demolition practices other than for specific demolition techniques such as hydrodemolition or chemical demolition. The limited technical literature on engineering analysis for demolition and inves- tigation of unintended collapses by OSHA and others demonstrates the benefits of detailed analysis as part of the preparation of demolition plans and procedures. OSHA investigations of demolition incidents also note the benefit of knowledgeable field oversight. State standard specifications vary widely in the extent to which they address demolition activities. Specification requirements are often limited to general descriptions of the work, though requirements for deck demolition or removal may be more prescriptive in order to limit unintended damage. While many states require a demolition plan submittal, few states provide requirements for its contents. For larger or more complex projects, detailed requirements are provided by use of special provisions. Limited guidance on demolition oversight of field operations was found in state construction manuals.

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TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 536: Bridge Demolition Practices documents practices used by bridge owners to manage and administer bridge demolition in construction projects.

Each year hundreds of bridges are rebuilt or are entirely replaced as part of highway construction projects. Bridge reconstruction or replacement work often entails demolition of part or all of the bridge structure.

Unintended events resulting in injury, project delays, and traffic disruptions can occur and have occurred during bridge demolition activities. The intention of this synthesis report is to assist in better understanding how to reduce risk associated with bridge demolition.

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