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1 The objective of this synthesis was to document practices used by bridge owners to manage and administer bridge demolition in construction projects. Each year there are numerous bridges partially demolished or totally demolished as part of rehabilitation or replacement. 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 bridge owners in better understanding how to manage those projects to reduce risk associated with bridge demolition. Information for this synthesis was obtained from several sources. The rehabilitation and expansion of the highway infrastructure include the reconstruc- tion or replacement of hundreds of bridges each year. Many of these projects are demolition activities ranging from bridge deck removal to complete structure removal. The contract documents typically provide the limits of demolition and construction requirements to preclude damage to portions of the structure that remain. The contractor then develops the specific demolition procedures. AASHTOâs load and resistance factor design (LRFD) bridge construction specifications contain limited requirements for demolition (AASHTO 2017a). Surveys by Garber (2016) and by CTC & Associates LLC (2011) found that state require- ments for contractor-developed demolition procedures, submittals, and reviews, as well as administration of demolition projects, varied. A literature review was performed to provide background information and uncover pre- vious research on this topic. A survey was distributed to voting members of the AASHTO Subcommittee on Bridges and Structures that requested information on their practices for bridge demolition. Forty-two state departments of transportation (DOTs) responded to the survey, an 84% response rate. Telephone interviews with representatives from five DOTs were conducted to acquire additional information and learn more about practices for administering bridge demolition projects. See Chapter 5 for case examples. Telephone and e-mail interviews with seven bridge construction contractors were also conducted to acquire information on their interactions with ownersâ requirements. The five DOTs selected for the phone interviews were chosen based on their expressed willingness to provide additional information, type of demolition activities, and geographic location. The contractors for the interviews included mid-size and large bridge contractors, and a specialty demolition contractor, all who work for multiple state DOTs. Their demolition experiences included a wide range of bridge types and sizes as well as project delivery methods. The literature review found that available manuals and specifications used for bridge design and construction provide limited criteria for bridge demolition activities. Provisions in AASHTOâs LRFD Bridge Construction Specifications, 4th ed. (2017a) require submittal of drawings showing methods and sequence of removal when structures or portions of S U M M A R Y Bridge Demolition Practices
2 Bridge Demolition Practices 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. Requirements for drawing content, however, are not provided. Engineering for Structural Stability in Bridge Construction (Garlich et al. 2015) provides guidance on cranes and lifting design, as well as considerations in evaluating structure stability during demolition. The manual also includes recommendations for the contents of demolition plans. Owners, however, did not reference the manual. The rigorous requirements for demolition plans were found to be from railroad owners and, in cases where highway bridges cross railroads, those requirements will normally control the demolition. Limited research or technical information was found that addresses bridge demolition practices other than specific demolition techniques, that is, hydrodemolition. The literature consists of project descriptions with minimal technical content. The few technical papers available and the Occupational Safety and Health Administration (OSHA) accident reports stress the need for an engineering evaluation of demolition activities and good field oversight. A review of various state DOT specifications shows a range of requirements for demo- lition. Requirements for partial demolition of bridge decks are provided and sometimes contain detail on equipment limitations and construction practices, particularly to limit damage to the remaining structure. For extensive demolition or total removal, a demolition plan is requested, but only a few states provide specific requirements on what the plan is to include. Provision of specific design criteria for conducting a structural assessment of the demolition sequence is rarely provided. Forty-two states responded to the survey of practice. All but two survey respondents have specifications or special provisions addressing bridge demolition, and 83% require submittal of a demolition plan. Submittal requirements generally do not vary with delivery methods, and submittals are required for partial, phased, or total demolition. The contractor prepares submittals, and the majority of states require them to be signed and sealed by a registered professional engineer. Most agencies provide field oversight of demolition using either in-house staff or a consultant. Less than one-half of the agencies indicated that they provide training in demolition activities to field staff. Approximately one-half of the states conduct a pre- demolition meeting, and 25% require contingency plans. Documentation of fieldwork is through the inspectorâs daily report. The responses of the contractors confirm that most owners require a demolition plan and that the contents vary, becoming greater for larger or more complex projects, as do requirements for engineering analysis of demolition stages. Contractors stated they prepare a demolition plan whether or not the owner requires one. Contractors also noted that design criteria for developing the demolition plan are not specified. The case examples illustrate the use of both standard specification and special provisions for demolition projects, as well as varying submittal requirements. The case examples show that unintended events may occur and that agencies do revise their requirements based on past experiences. The results of the synthesis indicate some knowledge gaps in the current practices. Those gaps could be addressed with research that â¢ Identifies design criteria and guidance applicable to analysis of structures under demolition. â¢ Identifies critical steps for field oversight of demolition activities. â¢ Establishes load distribution criteria for equipment operating on structures during demolition activities.