Expedited Concrete Box Girder Bridge Removals Over the Interstate in One-Night Interstate Closures
Attachment 1 - E 9th - Evening Before Demolition
Attachment 2 - Access Holes On Deck To Remove Wooden Forms
Attachment 3 - View of E 9th Bridge Removal at 1:00 PM Sunday afternoon
Attachment 4 - Slotted Top Deck
Attachment 5 - Excavator Hammering at the Barrier Rail
Attachment 6 - Separate Debris Pile for Steel Rebar
Attachments 7 & 8 - Damage to roadway caused by equipment
Attachment 9 - Pre-drilled Holes for Explosives
Attachment 10 - Columns wrapped with fencing and fabric
Attachment 11 - Deck Wrapped only over Pier Caps and Sidewalk
Attachment 12 - Longitudinal saw cuts in the deck
Attachment 13 - 18" Holes drilled into the Deck
Attachment 14 - Columns Before Wrapped
Attachment 15 - Cut Horizontal Rebar
Attachment 16 - An outside girder after the implosion
Attachment 17 - An inside girder after the implosion once outside girder was removed
Special Provision For
Removal of Concrete Box Girder Bridges
October 2, 2001
- DESCRIPTION OF WORK
This item shall consist of removal from the project of all portions of an existing structure, except the portions that may be required or permitted to be left in place. Unless otherwise provided, all structures or parts of structures to be removed shall become the property of the Contractor.
Work shall be performed in accordance with these special provisions, or as directed by the Engineer, and Section 2401 of the Standard Specifications.
- BRIDGE REMOVAL
The Contractor shall submit a complete bridge removal plan to the Engineer detailing procedures and sequence for removing portions of the bridge, including all features necessary to remove the bridge in a safe and controlled manner. The removal plans, indicating detailed sequences of operations, shall be submitted to the Engineer, at least, thirty (30) calendar days prior to start of removal operations of the existing bridge. The bridge removal plan shall include the following:
- The bridge removal sequence for the entire structure, including staging of bridge removal;
- Equipment locations on the structure during removal operations;
- Temporary support shoring or temporary bracing if required;
- Locations where work is to be performed over traffic; and
- Details and locations of protective covers or other measures to assure that bridge removal will not endanger the public.
The following additional requirements apply to the removal of portions of the existing bridge that are over or adjacent to roadways that may be closed to public traffic for only brief periods of time:
- The closure of roadways to public traffic shall conform to the Traffic Control Plan.
- Prior to closing of a roadway to traffic to accommodate bridge removal operations, the Contractor shall have all necessary workers, materials, and equipment at the site as needed to proceed with the removal work in expeditious manner. While the roadway is closed to public traffic, work shall be pursued promptly and without interruption until the roadway is reopened to public traffic.
- All removal operations shall be performed during periods of time that the roadway is closed to the public traffic except as specified herein for preliminary work.
- Preliminary work shall be limited to operations that will not reduce the structural strength or stability of the bridge, or any element thereof, to a level that in the judgement of the Engineer would constitute a hazard to the public. Such preliminary work shall also be limited to operations that cannot cause debris or any other material to fall onto the roadway. Protective covers may be used to perform preliminary work such as chipping or cutting the superstructure into segments, provided the covers are of sufficient strength to support all loads and are sufficiently tight to prevent dust and fine material from sifting down onto the traveled way. Protective covers shall extend at least 1.2m beyond the limit of the work underway. Bottom slabs of box girders may be considered to be protective covers for preliminary work performed on the top slab inside the limits of the exterior girders.
- Temporary support shoring, temporary bracing, and protective covers shall not encroach closer than 2.4m horizontally from the edge or 4.6m vertically above any traffic lane or shoulder that is open to public traffic.
- During periods when the roadway is closed to public traffic, debris from bridge removal operations may be allowed to fall directly onto the lower roadway provided adequate protection is furnished for all highway facilities. The minimum protection for paved areas shall be a 0.6-m thick earthen pad or a 25-mm thick steel plate placed over the area where debris can fall. Prior to reopening the roadway to public traffic, all debris, protective pads, and devices shall be removed and the roadway swept clean with wet power sweepers or equivalent methods.
- The removal operations shall be conducted in such a manner that the portion of the structure not yet removed remains in a stable condition at all times.
Concrete superstructures may be removed by any means consistent with regulations regarding safety and protection of adjacent property. Where portions of existing substructures lie wholly or in part within limits for a new structure, they shall be removed as necessary to accommodate construction of the proposed structure.
The Contractor shall submit working drawings, with design calculations, to the Engineer for the proposed bridge removal plan. The bridge removal plan shall be prepared by a Professional Engineer registered in the State of Iowa. The design calculations shall be adequate to demonstrate the stability of the structure during all stages of the removal operations. Calculations shall be provided for each stage of bridge removal and shall include dead and live load values assumed in the design of protective covers. At a minimum, a stage will be considered to be partial removal of the top slab, the sidewalk, or portions of the superstructure, in any span; or bent caps, or columns at support locations.
The Contractor's registered engineer shall be present at all times when bridge susperstructure removal operations are in progress. The Contractor's registered engineer shall inspect the bridge removal operation and the status of the remaining structure. Should an unplanned event occur, the Contractor's registered engineer shall submit immediately to the Engineer for approval, the procedure of operation proposed to correct or remedy the occurrence.
Full compensation for conforming to requirements of this special provision shall be considered as included in the contract lump sum price paid for bridge removal and no additional compensation will be allowed.
- REMOVAL METHODS
Cutting / Shearing: Existing bridge superstructure and pier columns may be reduced into smaller sections to allow for partial removal. Smaller sections may be lifted by cranes or dropped on the pavement below provided that all the requirements of this Special Provision are met.
Blasting: The Contractor may be permitted to use explosive provided the requirements outlined in this Special Provision are satisfied.
Other Approved Methods
- USE OF EXPLOSIVES
The following requirements shall apply:
- Pre-blast Crack and Damage Survey
The Contractor shall arrange with property owners affected by the project the rights-of-entry to their properties in order to engage in a pre-blast and post-blast property damage survey. The locations of the affected properties are included in the estimate reference information of the bridge plans. The Contractor shall submit written reports to the Iowa DOT District 1 Engineer to confirm a visual investigation of the buildings on these properties.
The investigation shall consist of visually inspecting and recording all existing defects in the structures. The structures shall be thoroughly inspected from top to bottom, inside and out. The report shall include names of inspectors, date of inspections, and descriptions and locations of defects. In addition, the Contractor shall mark existing cracks in such a way that future observations would indicate whether cracks continue to open or spread. Photographs shall be used in verifying written descriptions of damaged areas. The Contractor shall arrange for professional photography capable of producing sharp, grain-free, high-contrast pictures with good shadow details for construction monitoring at the properties.
Before any blasting operations for demolition, the Contractor shall have record photographs taken of the portions of all the buildings affected by the proposed bridge demolition.
Photographs shall be taken and developed so that details of the buildings will be clear and well defined. The intent is to procure a record of the general physical condition of the buildings' exterior walls and foundations. Camera location shall be changed for each of the photographs and shall be varied so that all portions of the buildings' exterior surfaces will be covered by the view.
Each photograph shall contain the following information:
I-235, Polk County
Photographs shall be eight by ten inches, black and white glossy, mounted on paper with a flap for binding. Three prints of each view and the negatives shall be supplied to the Iowa DOT District 1 Engineer within two weeks after the exposure has been made. Rights for subsequent use shall become the property of the Iowa DOT.
The Contractor shall conduct a second inspection of each affected property once blasting is complete. He shall visually inspect and photograph each structure to verify the post-blast condition. The Contractor shall follow the same inspection procedures as outlined herein before for the pre-blast survey.
The final written report of each property shall be typed on bond paper and be in text form, headings, indexed, etc., and shall become the property of the Iowa DOT.
Work under this item shall consist of furnishing a seismograph and employing a trained operator to continuously monitor ground vibration near buildings during controlled blasting. The purpose of the monitoring is to assess potential damages to adjacent structures due to blasting activities.
The seismograph shall be a continuous monitoring instrument capable of producing a continuous strip recording of the seismic readings, or a continuous dated report of all seismic events exceeding a predetermined threshold. The seismograph shall be supplied with all accessories necessary for making seismographic observations.
The Contractor, in the presence of the Iowa DOT District 1 Engineer, or his representative, shall take seismograph readings prior to blasting to establish an ambient index.
The seismograph shall be placed to continuously monitor all blasting activities or as directed by the Engineer. Attentive observation of the seismographic readings shall be made during all blasting operations. If blast activities generate ground vibration with maximum peak particle velocity of greater than 12.7 mm (0.50 inch) per second at frequencies below 40 Hz, or 50.8 mm (2.0 inches) per second at frequencies greater than 40 Hz; or alternatively, a maximum of 12.7 mm (0.50 inch) per second peak particle velocity below 10 Hz, and a maximum of 50.8 mm (2.0 inches) per second above 40 Hz, and a maximum of 0.20 mm (0.008 inch) displacement between 10 and 40 Hz, the Contractor shall stop the operation in progress and adjust explosive quantities and/or type or other methods to reduce vibrations to allowable levels.
Ground vibration shall be measured as the particle velocity. Particle velocity shall be recorded in three mutually perpendicular directions. The maximum allowable peak particle velocity shall apply to each of the three measurements.
The final recorded seismograph charts and/or reports shall become the property of the Iowa DOT.
- Pre-blast Crack and Damage Survey
- ROAD CLOSURE LIMITS
Depending on the method of removal employed, the Contractor will be allowed to close I-235 to traffic using one of the following traffic control schemes outlined below:
- The Contractor will be allowed to close I-235 to traffic between 9 PM Saturday and 11 AM Sunday to allow for complete superstructure removal over the traveled way. Additional one lane closure may be allowed between 11 AM Sunday and 7 AM Monday to complete the bridge removal operation; during this period the Contractor will be limited to performing debris removal and clean up.
- The Contractor will be allowed to close I-235 to traffic between 9 PM and 6 AM weekdays to allow for partial removal of the structure.
- METHOD OF MEASUREMENT AND BASIS OF PAYMENT
Removal of all material from the bridge, including removal in stages, will be measured as a single lump sum. No measurement will be made of individual items on the bridge.
The lump sum price bid for "Removal of Existing Structures" shall be full compensation for furnishing all material, equipment, and labor and for performance of all work including removal plans as required, safety and protective measures, cleanup, and disposal of non-salvaged materials.
If explosive is used, the following items should be considered incidental: surveying each property twice, providing the written report, providing three mounted black and white glossy prints and the negative for each view photographed, furnishing a seismograph, an operator, accessories, and for furnishing all labor, equipment and incidentals necessary to complete the work.
Attachment B - typical cross-section of a concrete box girder showing the tracks of the excavator remaining over the girders
Attachment C (page 1 of 2) - Westbound traffic counts from February at Penn Ave Bridge.
Attachment C (2 of 2) - Eastbound traffic counts from February at Penn Ave Bridge.