Article 1 — Description
Raise and support existing structures as shown on the plans . Raising a bridge may be associated with permanent raising to increase vertical clearance or temporary raising to accomplish other work.
Article 2 — Construct Ion
Submit detailed plans to raise structure. Approval of plans is required before beginning raising work. A licensed professional engineer must sign and seal the plans. Clearly indicate the methods, materials, cribbing, falsework or other supports, and equipment proposed. Repair or replace by an approved method any portions of the structure damaged by the raising operation. Approval of these plans does not relieve the Contractor from responsibility for the completion of the work nor from liability for repair or replacement of damaged portions of the structure due to the methods approved and employed.
2.1 Preparation of Plans. Apply vertical and horizontal loads such that the load capacities in bearing, shear, and flexure are not exceeded for any material or member carrying the load. Indicate jack positions and capacities and temporary hardware attachments on the plans.
Avoid jacking against the bottom of the slab. Use a jack with a minimum capacity of two times the unfactored dead load. Higher jacking capacity may be required if a single member is to be lifted individually in a multi- girder unit. Prohibit traffic on the structure until the structure is supported by cribbing, falsework, or temporary supports, or has been lowered onto the final supports. If traffic is to be returned on a partially raised bridge affecting roadway elevation, obtain approval of all scenarios of raised condition. Provide suitable cribbing, falsework, or other supports until the span or unit is resting on its final supports to prevent the various spans or units from dropping due to jack failure or other causes during the lifting operation.
2.2 Temporary Support Load Factors . Factor dead, live, and horizontal loads, including dynamic load
allowance, in accordance with AASHTO LRFD Bridge Design Specifications . Design temporary supports to carry two times the dead load if traffic will not be allowed until permanent supports are in place. It is not necessary to factor dead, live, and horizontal loads if design capacities of temporary supports incl ude minimum safety factors of 2.0. Documentation of proprietary or project -specific temporary supports must include acceptable loads and safety factors.
2.3 General Construction Requirements . Verify anchor bolts, closed joints, or other appurtenances do not
restrict vertical movement before jacking. Jack spans and beams from the existing bent cap or temporary falsework unless otherwise shown on the plans. Limit the amount of lift as specified below unless the approved engineering plans allow otherwise. Loosen and remove all anchor bolt nuts or cut the anchor bolts as approved to allow free vertical movement before raising. Replace all damaged or cut anchor bolts either by butt welding to existing bolts or by drilling into the existing concrete cap a minimum of 12 in. and grouting in new bolts. Do not damage the bent cap reinforcing steel when installing new anchor bolts. Replace all damaged or lost anchor bolt nuts. Weld in accordance with Item 448, “Structural Field Welding.” Repair or replace by an approved method any portions of the structure damaged by the raising operation. Repair concrete damage in accordance with Item 429, “Concrete Structure Repair.” 763 2.4. Raising of Spans . Provide adequate guides or force to ensure vertical lifting and prevent drifting of the structure during the jacking operation. Immediately cease jacking operation if lifting causes damage to any portion of the structure. Provide continuous support until pedestals and bearings are installed. Support may be removed only after pedestals have been installed and full contact with supporting member is achie ved.
2.4.1 Simple Spans with an Expansion Joint in the Deck at Every Bent . Raise the span by jacking as shown
on the plans. Raise all the beams on one side of the bent simultaneously. Do not raise one end of a simple span more than 4 in. before raising the opposite end.
2.4.2 Simple Beam Spans with a Continuous Deck o ver the Bent . Raise all beams on both sides of the bent
simultaneously by jacking as shown on the plans. Do not raise one end of a span more than 2 in. before raising the opposite end of the span.
2.4.3 Continuous Beam Span s. Raise the unit by jacking as shown on the plans. Raise all beams at a single bent
simultaneously. The unit may be raised incrementally from bent to bent. Do not raise the unit more than 2 in. at any bent before raising it at the adjacent bents.
2.5 Raising Beams. Raise beams to allow for other work as shown on the plans. Do not raise beam more than
1 in. higher than adjacent beams.
2.6 Support Structure . Raise and provide temporary support of existing structure as needed to complete repair
work as shown on the plans. Provide adequate material for foundation of shoring and prepare subgrade to prevent settlement for shored structure.
Article 3 — Measurement
This Item will be measured by the lump sum or each structure.
Article 4 — Payment
The work performed and materials furnished in accordance with this Item and measured as provided under “Measurement” will be paid at the unit price bid for “Raising Existing Structure” and “Support Existing Structure,” and when paid by each, for the structure description by reference number. This price is full compensation for shoring, falsework, jacking, labor, tools, equipment , and incidentals for all materials except new pedestals. Pedestals will be paid for in accordance with Item 442, “Metal for Structures ,” or Item 420, “Concrete Substructures .”