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17 Overview To understand better the current bridge demolition practices used by state transportation agencies, a survey of practice was conducted through NCHRP in cooperation with AASHTO. Each of the voting members of the AASHTO Subcommittee on Bridges and Structures was contacted by e-mail for the survey. The subcommitteeâs voting members were encouraged to forward the survey to the individual in their agency who would be most familiar with that agencyâs bridge demolition practices. E-mail reminders were sent to encourage participation. Forty-two state DOTs completed the survey, an 84% response rate. Because some questions are only applicable if the answer to the previous question is yes, the number of respondents to a particular question may not always be 42. This chapter summarizes the current practices as derived from the survey. The information is in various formats and includes tables and graphs, as appropriate. The survey questionnaire that was electronically distributed is in Appendix B. Appendix C presents participant agency responses. Survey Content Survey questions were organized into the following three categories: â¢ Organizational policy on bridge demolition. This section of the survey focused on whether a participantâs agency has any specification provisions or other guidance documents that address bridge demolition. Specifically, participants were asked what information is provided in bid documents for projects that include bridge demolition. â¢ Bridge demolition submittal. This section of the survey focused on the submittal of the bridge demolition plan. The first question of this section asked participants whether their agency requires a submittal of a demolition plan for bridge projects. Respondents that answered âyesâ were then asked what the content requirements are, if there are any design or analysis requirements, and if there is an owner review practice. The following demolition submittal content requirements were investigated: whether the requirements vary with project delivery methods, what type of bridge demolition (total, partial, phased, or other) requires a submittal, and what elements are required as part of the submittal. Use of the following design or analysis requirements was investigated. The requirements were AASHTOâs LRFD Bridge Design Specifications, American Institute of Steel Construction (AISC), Specification for Structural Steel Buildings, American Concrete Institute (ACI 318-14), Building Code and Commentary, AASHTOâs LRFD Bridge Construction Specifications, AASHTOâs Stan- dard Specifications for Highway Bridges, 17th ed., and other design provisions. C H A P T E R 3 State of the Practice
18 Bridge Demolition Practices The following owner review practices were investigated: â¢ Who prepares the demolition plan submittal? â¢ Whether a licensed design professional is required to sign and seal the demolition plan. â¢ Who provides the review of the demolition plan? â¢ Whether the reviewer is required to have training or experience and what kind. â¢ Whether review comments are provided to the contractor and if they are resolved prior to the start of demolition. â¢ Bridge demolition field oversight and case examples. The first question in this section asked participants whether their agency provides field oversight of demolition activities. If so, participants were asked over what percentage of the demolition activity is oversight provided, who provides it, and whether those providing it have any special training or experience in demolition activities. The participants were also asked whether a predemolition meeting is required prior to starting demolition and whether there is a standard agenda. Finally, participants were asked if they require contingency plans identifying specific responses to unanticipated occurrences, whether they prohibit the use of any types of demolition methods, and what methods are used to document the progress of demolition activities. The survey also asked agencies about bridge demolition projects that could be potential case examples. Additional information was then collected on those specific bridge demolition projects, including why, and whether, they ended successfully. Representatives from five state DOTs were interviewed by phone or e-mail to develop case examples of specific bridge demolition projects. The case examples are in Chapter 5. Bridge Demolition Policy Of the 42 state DOTs that responded to the survey, 37 (88%) reported that their agency has specification provisions or other guidance documents addressing bridge demolition. For the contractor to estimate, bid, and construct a project construction, documents developed by the owner are provided to the contractor. For projects involving demolition activities, the contractor also uses these documents to prepare any required demolition plans and submittals. Regarding information provided in bid documents, of the 42 state DOTs, Figure 4 displays what information is in bridge documents for bridge demolition projects. In addition to agency design plans and specifications, nearly all DOTs provide existing bridge plans when available. The existing plans are important, particularly if structural analysis of demolition operations is required. Providing special provisions (nearly 60% of respondents) is important when standard specification provisions for demolition are limited or provide only general guidance. Bridge condition reports or load rating calculations assist the contractor in evaluating the type and placement of equipment on the structure during demolition. Bridge Demolition Submittal Much of the survey focused on the submittal of a bridge demolition plan. Of the 42 partici- pants that were asked if they required a demolition plan for bridge projects, 83% or 35 said that they do. To learn more about submittal requirements for those 35 state DOTs, information was gathered in three categories. Submittal Content Requirements Project delivery method is defined as a system used by an agency for organizing and financ- ing design, construction, operations, and maintenance services for a structure or facility. Some
State of the Practice 19 common examples are âdesignâbidâbuild,â âdesignâbuild,â and âpublicâprivate partnership.â Part of the purpose of this section of the survey was to gauge whether, of the 35 state DOTs that require a submittal of a bridge demolition plan, it is common practice to vary demolition submittal requirements with project delivery methods. Eight (23%) of the state DOTs do vary the requirements with project delivery methods. Of those eight state DOTs, one reason provided was âdesignâbuild jobs may negotiate a different process for removal,â but the overwhelming response was that complex structures or larger bridges, which may or may not also affect the type of delivery method used, were greater factors in what is required for the submittal of a demolition plan. Bridge demolition can be a total bridge demolition, or a partial demolition, both of which may be a phased demolition. Of the 35 state DOTs that require submittal of a demolition plan, the type of demolition for which they require a submittal is shown in Figure 5. Most state DOTs require a demolition plan submittal on every bridge demolition type, including demolitions over bodies of water or demolition that specifically requires blasting. Michigan and Iowa require the submittal of a demolition plan only when dealing with a âcomplexâ or âuniqueâ structure, respectively, while Louisiana and North Carolina only require a submittal for partial or phased demolition, and five state DOTs only require a submittal for one of the three demolition types. Figure 6 displays the elements required by the 35 state DOTs as part of their demolition submittals. The common elements required as part of the submittal were a sequence of work narrative and demolition drawings, as indicated by 30 and 25 of the 35 agencies, respectively. The other often-cited elements were temporary support and bracing drawings, supporting engineering 83% 90% 57% 19% 9% 0 5 10 15 20 25 30 35 40 Agencies (42 Respondents) Load rating calculations Bridge condition report(s) Special provisions for demolition Existing bridge plans (if available) Agency design plans and standard specifications Figure 4. Information included in bid documents.
20 Bridge Demolition Practices 86% 83% 83% 17% 0 5 10 15 20 25 30 35 Agencies (35 Respondents) Other Phased demolition Partial demolition Total bridge demolition Figure 5. Required demolition submittals per demolition type. 83% 74% 86% 66% 77% 60% 11% 9% 17% 0 5 10 15 20 25 30 35 Agencies (35 Respondents) Other Demolition contractorâs field superintendent resume Condition assessment of existing structure Traffic control Temporary support, bracing drawings Equipment data, lifting capacity Sequence of work narrative Supporting engineering calculations Demolition drawings Figure 6. Elements required as part of the demolition submittal.
State of the Practice 21 calculations, equipment date and lifting capacity, and traffic control. Some agencies selected âotherâ with the following explanations: â¢ A demolition plan is required for the selected method of removal; for hydroblasting, the method of control of water or slurry runoff and measures for safe containment of concrete fragments must be shown. â¢ Vibration monitoring plan, debris containment methods, and utility protection methods. â¢ No standard requirements. â¢ Protective measures for traffic material stockpile locations. â¢ Submittal of a removal plan per standard specifications. Design Calculation or Analysis Requirements Further investigation into the contents of each agencyâs demolition submittals identified if there are design calculation or analysis requirements and there are code or specification requirements. Of the 35 state DOTs that require a demolition submittal, 18 or 51% said that they do not require design calculations for demolition activities to be performed, in accordance with AASHTOâs LRFD Bridge Design Specifications. Of those 18 agencies, Figure 7 identifies which codes or specifications they specify or allow. The common design specification specified or allowed by the 18 respondents is AASHTOâs Standard Specifications for Highway Bridge, 17th ed., as indicated by 13 of the agencies. The other often-cited specifications were AASHTOâs Bridge Construction Specifications and âother.â The agencies that selected other had the following explanations: â¢ Section 402 of [North Carolina DOTâs] Standard Specifications. â¢ AASHTOâs Guide Design Specifications for Bridge Temporary Works, 2nd ed. (AASHTO 2017c). â¢ Not specified. 6% 6% 44% 72% 39% 0 2 4 6 8 10 12 14 Agencies (18 Respondents) Other AASHTOâs Standard Specifications for Highway Bridges, 17th ed. AASHTOâs LRFD Bridge Construction Specifications ACI 318-14, Building Code and Commentary AISC, Specification for Structural Steel Buildings Figure 7. Codes that are specified or allowed other than AASHTOâs LRFD Bridge Construction Specifications, 4th ed.
22 Bridge Demolition Practices â¢ Guide Spec (not defined). â¢ The need for design calculations would be on a case-by-case basis. In general, âweâ allow any reasonable set of design specifications to be used. â¢ Complex demolition usually requires PE [professional engineer] stamped demolition plans and [calculations]. (They state that the code is not specified.) Owner Review Practices With varying degrees of content in a demolition plan submittal from different specifications to different design calculations and analyses, it is important to understand the agency review process of the demolition submittals. For all 35 agencies, the demolition contractor prepares the demolition plan submittal. The respondents were then asked whether their agency requires a licensed design professional to sign and seal demolition submittals. Figure 8 shows the answers to this question. Twenty of the 35 state DOT respondents require a professional engineerâs seal, while another 13 sometimes do. Agencies that answered âsometimesâ commented that the decision to require a licensed design professional usually depends on the complexity and size of the bridge demolition but could also depend on public safety and right-of-way concerns. Each of the 35 agencies was asked to answer who provides review of demolition submittals. Of those agencies, 63% or 22 said the agency (or consultant) bridge designer provides the review, while 34% or 12 said it was agency construction staff. Only one state said âotherâ but did not provide a comment with their response. Furthermore, each of those agencies was asked what type of training or experience the reviewer is required to have specifically related to demolition activities, and how that training or experience is obtained. Of the 35 agencies, 23% or eight said that they do require those charged with reviewing demolition submittals to have specific training or experience in demolition activities. Figure 9 displays how those eight respondents obtain the training or experience. All eight agencies said the experience or training is obtained from on-the-job experience in design, while five of the eight respondents (63%) said on-the-job experience is also obtained in the field. No agency said it is obtained from formal training programs. The 35 agencies that require a demolition plan submittal were asked if written comments from the review are provided to the demolition contractor and, if they are, whether the comments 20, 57% 2, 6% 13, 37% Yes No Sometimes Figure 8. Agencies that require a licensed design professional to sign and seal demolition submittals.
State of the Practice 23 are resolved with concurrence by the contractor prior to the start of demolition. As displayed in Figure 10, 91% or 32 of the respondents said written reviews are provided to the demolition contractor. Additionally, of those 32 agencies, all of them said comments must be resolved with concurrence by the contractor prior to starting demolition. Owner Practices for Field Oversight of Demolition An important aspect in construction projects is the oversight process. From meetings to inspections and general supervision, whether by the owner or a consultant, a series of checks and balances can reduce the chance for mistakes. All 42 agencies were asked whether they provide 0% 100% 63% 0 1 2 3 4 5 6 7 8 9 Agencies (8 Respondents) On-the-job experience in field On-the-job experience in design Formal training program Figure 9. How bridge demolition training and experience are obtained. 32, 91% 3, 9% Yes No Figure 10. Agencies that provide review comments to the demolition contractor.
24 Bridge Demolition Practices field oversight of demolition activities. Of those 42 agencies, all but one agency responded that they do. Among the 41 agencies that do provide field oversight of demolition activities, 55% or 22 provide full-time oversight, while 17% or seven provide between 75% to 100% oversight (Figure 11). Of the 41 agencies, 63% or 26 provide oversight with a combination of agency staff and a consultant, and only one agency provides oversight with just a consultant. As to the training or experience of oversight staff, 60% or 25 of 41 agencies responded that they do not have any special training or experience in demolition activities, while 39% or 16 have field oversight staff with special experience in demolition activities (Figure 12). As part of the oversight process, many engineering projects will have a preconstruction meeting, but predemolition meetings may not be as common. Of the 42 agencies, 52% or 22 responded that they do require an on-site predemolition meeting. Of those 22 respondents, 91% or 20 said there is no standard agenda for the meeting. However, many of the respondents that do not have a standard agenda commented that there are discussions regarding public and worker safety at each meeting. Agencies were asked whether they require a contingency plan identifying a specific response to unanticipated occurrences, including those leading to stoppage of work. Twenty-four percent or 10 of 42 responded that they do. Of the 10 agencies, activities requiring a contingency plan primarily involved working near critical areas, such as around traffic or around other structures. One agency mentioned contingency plans for catastrophes, and one agency responded that it depends on adjacent utilities. Of the agencies that responded that they do not require a contin- gency plan (76% or 32), a few commented that, while they do not require a plan, they do have standards that act as general contingency plans on projects. Respondents were asked whether their agency prohibits the use of any types of demolition methods and, if so, to provide examples of which types and why. Sixty percent or 25 of the 42 responding agencies prohibit the use of at least some type of demolition method. The common demolition method mentioned was explosives. Several states prohibit the use of explosives due to environmental or safety concerns except in special circumstances. Several of 22, 55% 7, 17% 4, 10% 4, 10% 3, 8% Full time 75%-100% 50%-75% 25%-50% 0-25% Figure 11. Percentages of demolition activity in which oversight is provided by an agency or by a consultant, or by a combination of both.
State of the Practice 25 the agencies that commented also limit the type, size, and locations of equipment like concrete impact breakers. The common reason for the limitations is to protect bridge members that will remain from damage. An important part of oversight on any project is documentation. Agencies were asked what methods they use to document the progress of demolition activities. Figure 13 displays the 39% 1% 60% 0 5 10 15 20 25 30 Agencies (41 Respondents) No YesâTraining YesâExperience Figure 12. Whether field-training staff have special training or experience in demolition activities. Figure 13. Agency methods used to document the progress of demolition activities. 93% 52% 21% 7% 19% 5% 0 5 10 15 20 25 30 35 40 45 Agencies (42 Respondents) OtherâPlease describe Drawing mark-up Time lapse photography Video logs Photo logs Inspector Daily Report/Diary
26 Bridge Demolition Practices responses. The common method is the inspector daily report or diary, with 93% or 39 of the agencies using this method. Just over one-half of the agencies (22 of 42) also use photographic logs to document demolition activities progress. Two agencies responded with âother.â One agency commented that photographs and videos are sometimes attached to inspector daily diaries, and the other agency commented that the method varies from none to all of those listed depending on the project size. Summary Forty-two agencies completed survey responses, an 84% response rate among state DOTs. The primary findings of the survey of the state of the practice are summarized as follows: â¢ Eighty-eight percent of responding agencies have specifications, provisions, or other guidance documents that address bridge demolition. â¢ In addition to the agency design plans and standard specifications, 90% also provide an existing bridge plan if available. â¢ Fifty-seven percent of respondents provide special provisions for demolition. â¢ Eighty-three percent require submittal of a demolition plan. â¢ Of those agencies that require a demolition plan, many agencies responded that the submittal requirements do not vary with project delivery methods and that submittals are required for phased, partial, or total bridge demolition. â¢ Elements that are frequently required as part of the submittal are sequence of demolition nar- rative; demolition drawings; temporary support, bracing drawings; supporting engineering calculations; equipment data, lifting capacity; and traffic control plans. â¢ Thirty-six percent require design calculations supporting demolition activities to be performed in accordance with AASHTOâs LRFD Bridge Design Specifications. â¢ Of those agencies that do not require design calculations supporting demolition activities to be performed in accordance with AASHTOâs LRFD Bridge Design Specifications, 13 of 18 agencies require design calculations in accordance with AASHTOâs Standard Specifications of Highway Bridges, 17th ed., and eight agencies require design calculations in accordance with AASHTOâs LRFD Bridge Construction Specifications. â¢ The demolition contractor prepares the demolition plan for all 35 agencies that require a demolition plan. â¢ Most of the agencies require a licensed design professional to sign and seal demolition submittals. â¢ Sixty-three percent (63%) of agencies have an agency or consultant bridge designer reviewing the demolition submittals, while 34% use an agency construction staff member. â¢ Twenty-four percent of agencies require the reviewer to have specific training or experience in demolition activities. All obtain the training or experience through on-the-job experience in design, while two-thirds also have on-the-job experience in the field. â¢ Providing the demolition contractor with written review comments for the demolition submittal is common among the agencies surveyed, with 91% of the agencies providing such comments. â¢ Among those agencies that do provide review comments, all of them require the comments to be resolved by the contractor prior to starting demolition. â¢ All but one state agency provides field oversight of demolition activities, and among those state agencies that do, all but one state agency provides that field oversight with either agency staff or a combination of agency staff and a consultant. â¢ Among the state agencies that do, almost three quarters provide oversight of demolition activity at least 75% of the time, while among those 75%, just over one-half provide oversight full time.
State of the Practice 27 â¢ On-site predemolition meetings are required prior to the start of demolition by approximately one-half of the agencies, but only two agencies have a standard agenda. â¢ Only 10 agencies require a contingency plan identifying specific responses to unanticipated occurrences. â¢ Sixty percent of respondents prohibit the use of certain types of demolition methods, the common one being explosives, along with limitations on types and sizes of equipment allowed. â¢ The majority (93%) of the agencies document demolition activity with an inspector daily report or diary, with one-half also using photographic logs. â¢ Only 40% of state DOTs provide special experience or training in demolition to field staff. â¢ Five agencies provided case examples of bridge demolition projects (see Chapter 5).