RESIDENT ENGINEERING INSPECTION FOR
MOVEABLE BRIDGE REHABILITATION

Henry W. Hessing, PE
Senior Project Officer
O’Brien Kreitzberg


Key words:::: Resident Engineer Moveable Bridge, Construction Inspection


Abstract: This paper describes resident engineering and construction inspection services for bridge rehabilitation projects to insure compliance with plans and specifications.

1.0 INTRODUCTION
· Using a hypothetical example, an owner intends to rehabilitate a moveable bridge that was constructed sixty or seventy years ago over a navigable waterway in New York City. The cross section has narrow lanes, some of which are out of service. The multi-span structure can be described as having concrete cellular spans, deck trusses, through trusses and a moveable, lift span. Similarly, the moveable part could be bascule, lift or swing bridge design. The owner wants a proposal for construction inspection and/or construction support services for deck replacement.

As consulting engineers, we can develop an approach to by identifying the key issues:

· What does the bridge link? What are the traffic characteristics? What is the vehicular and pedestrian maintenance of traffic scheme caused by construction rehabilitation?
· Will commercial or recreational marine traffic require planning and coordination? What are the Coast Guard requirements for maintaining marine traffic?
What are the Coast Guard’s material handling requirements?
· Does the bridge have several layers of lead/chromium based paint? The removal process must adhere to current environmental regulations, sensitivity to the waterway and the surrounding community.
· Rehabilitation of the bridge structural members including the moveable span will require expertise and manpower familiar with and capable of performing the required tasks in the bridge environs and the above constraints outlined.

Typical construction monitoring and construction support services are well defined by practice, the owner’s request for proposal and the consultant agreement. The technical approach presented herein will focus on the most important and critical issues involved in constructing the project.

2.0 TECHNICAL APPROACH

2.1 Construction Monitoring and Construction Support
To accomplish construction, a consultant will provide Construction Inspection and Construction Support services to the owner. The most important and critical issues are:

· An organization with a clear-cut chain of command and responsibilities;
· Qualified and sufficient staff;
· Quality Control/Quality Assurance (QA/QC) program;
· Complete familiarization with the construction documents and references, the work plan, construction schedule, and staging environs, and client expectations;
· Inspection, documentation, and Construction schedule; Long lead items; Community affairs/relations; Lift span balancing; Electrical installations;
Lead/chromium based paint removal and new coating.

2.2 Maintenance and Protection of Traffic (MPT)
For each construction stage, the MPT scheme is prescribed. Daily and holiday restrictions along with information and directional signs and protection devices to be used are included in the contract documents. The Resident Engineer will assure that lane closures signs and protective devices are installed, maintained and used as required to be effective. Any deviation or unsatisfactory results, such as excessive queuing, accidents or complaints will be recorded and analyzed. The owner will be notified immediately and the appropriate action(s) will be taken to correct the problem, first by the field staff, and if necessary by engaging construction support services.

2.3 Marine Traffic
Working over water requires sensitivity to two items. Is the bridge over a navigable waterway? Is there a possibility of water contamination resulting from the contractor’s operation?
Marine traffic must be maintained according to the mandates of federal law, which state that at no time can a navigable waterway be closed or restricted or can a horizontal clearance be reduced or altered without written permission. The consultant will monitor the contractor’s compliance with government regulations and see that he secures all permits. Other steps may include reviewing and making recommendations concerning the contractor’s “fail safe plan” to prevent debris from entering the waterway; posting an observer to notify workmen of a vessel’s approach; the installation of battery or power operated lights if the permanent bridge or fender navigational lighting cannot be maintained; and posting warning signs to mark the location of work platforms.

2.4 Construction Schedule
The contractor has primary responsibility for developing the detailed construction schedule. The Resident Engineer will review the schedule for conformance with the lead contract documents as to level of detail; activities included, i.e., procurement, delivery, and submittals; conformance and milestones. He will look for the schedule to recognize MPT stipulations, shop drawing status, and long lead items, seasonal weather conditions, and the contractor’s capabilities to complete the job. He will also review the schedule for a logical sequence of events, reasonableness of goals set, and opportunities for getting back on track. He will make recommendations for improvements.

2.5 Long Lead Items
Beginning with his initial review of the contract documents, the RE will identify long lead items including material and fabrications that take a long time to be delivered to the construction site as well as other intangible items that may have the potential of delaying construction. Such items may include permits; requests for information (RFIs) design changes, disputes, and undefined agreements, and the like. Potential long lead items will be closely correlated with the CPM schedule.

2.6 Community Affairs
To minimize the impact to the surrounding area, the RE will be proactive, monitor the project schedule, review actual progress made vs. the CPM, and assess deviations. He will communicate his findings with the Resident Engineering’s liaison Officer who will keep the public appraised of the project’s status.

2.7 Bascule, Lift or Swing Span Balancing
Before construction commence, the balance of the bridge must be verified, using strain gauge testing and electrical current readings on the drive motors. This will establish a benchmark accomplishing two objectives: 1) if the bridge is not balanced, immediate action can be taken to balance it; and 2)a reference will be established against which the bridge will be checked through all phases of construction. When the movable span is out of balance there may be serious effects on the operating systems; i.e., the bridge was originally designed to be slightly span heavy (the mass of the span is slightly more than the mass of the counter weight). This allows the bridge to remain firmly seated under live load. The mechanical and electrical systems were sized according to the designed imbalance. The electrical drives and motors are sized to overcome the AASHTO wind and Ice loads, friction forces, and the imbalance of the span. The counter weight ropes and sheaves were designed to withstand the forces generated under these conditions (the same is true for other components of the mechanical and electrical systems). When the span is further out of balance than intended, more force must be used to open and close the span. This translates into heavier loads on the operating machinery and the electrical system. If the bridge becomes too far unbalanced, it may not be possible to operate the movable span at all. The existing circuit breakers, drives and electric motors that move the bridge have an overload rating. If the forces to move the span exceed the overload ratings the electric drive system could fail. It will be the Resident Engineer’s responsibility to make sure that the contractor stays within safe operating limits of the drive system and within the specified ranges of the contract.
Critical to the safety of the entire project is keeping the span balanced. The contractor must record the weight and location of all members removed and added to the lift span in specific detail. This should be performed each day. The Resident Engineering staff will review this data on a daily basis and will confirm the information provided by the contractor with data supplied by the strain gauge system. In doing so, the span will be kept in balance throughout the entire project to the extent that a range of 1,000 to 10,000 lbs. weights will be kept at each corner of the lift span at all times. Within 24 hours of receiving such data from the contractor, the RE will assess the implications and confirm it by means of strain gauges if openings occur. He will advise the contractor of any adjustment he must make to bring the imbalance within the appropriate range in each location. Any serious situation, which cannot be quickly and easily addressed by the contractor, will be brought to the attention of the client’s Engineer immediately.

The post tensioning of the trunnion shafts must be performed in an accurate manner to ensure tension is gradually and evenly applied to the tensioning studs. This will ensure that the load is evenly distributed in the bearing plates and the trunnion shaft is properly post tensioned to minimize cycles of extreme fiber tension to prevent fatigue. The RE will oversee the entire post tension operation at each trunnion shaft, document each operation with listings of personnel present, sequences followed, problems encountered, and dates and times of each occurrence.
In addition to balancing the bridge, it is necessary to check that the total mass of the movable span does not exceed the limitations of the operating systems of the bridge. There will be many modifications to bridge structure under this contract i.e., addition of a median barrier, replacement stringers, grating, and other structural members. It is vital that the new dead load of the bridge remains within the safe operating limits of the operating systems.

2.8 Electrical Installations
Attention to detail and rigorous closeout of non-conformances are key to the success of an electrical system for it to be safe, complete and in a maintainable condition. The RE will ensure that all electrical work meets the established standards and codes, and progresses on schedule in a safe and orderly manner. The RE staff of inspectors must be familiar with the National Electric Code, and AASHTO Standards for Highways and Bridges.

In the hypothetical example, electrical work includes new 5,000-volt feeders, a manual transfer switch, a 5,000-volt switch gear, street lighting, new traffic gates, traffic gate bypass switches, a new traffic signal system, and the removal and reinstallation of limit switches on counter weight sheaves. To safely install the new lighting and gantry systems successfully, the RE will:

· Approve a construction sequence that removes conflicts between work items
· Review the contractor’s demolition work to prevent damage;
· Review the contractor’s pre-installation preparations;
· Monitor the receipt and storage of equipment in safe, secure and clean spaces;
· Monitor that the correct tools, equipment and method are used for handling
and installation of new systems;
· Inspect and check all work to monitor nonconformance;
· Work with the contractor during testing to ensure completeness; and
· Control the energizing of systems from source to load in set steps.

The RE will give particular attention to the manual operation of all operating mechanisms to make certain that they operate freely. He will monitor nicks or rings in conductors due to insulation stripping; grounding; conduct a cleanout and pull through test for conduit; expansion fittings across expansions joints; data sheets for installation materials; protection of cables during pull-in; identification of wire, cable, and terminations. The RE will monitor safety clearances around equipment; check the tightness of connections, insulation resistance testing; ensure protection of personnel from access to live equipment, and safety interlocking for the movable bridge control system. Balanced and smooth operation of new traffic warning gates; the incorporation of a traffic warning system with bridge controls; correct setting of cams and mounting of the removed counter weight sheave limit switches will be monitored. The RE team will check foot-candle illumination levels at roadways and sidewalks after new street lighting has been installed. The RE will monitor the safe transfer of main power with the new manual transfer switch; and will perform a complete functional test of the movable bridge interlocking and control system, utilizing normal and out of sequence testing.

Prior to testing the electrical-mechanical work of the span, it will be necessary to have permanent traffic gates operating. Additional MPT requirements may be required to provide for testing and debugging the mechanical, power and control systems.

2.9 Lead/Chromium Paint Removal and New Coating
The locations and extent of lead/chromium paint removal will be identified via visual inspection, sampling and testing. The RE will ensure the contractor is removing the lead/chromium paint in accordance with the contract documents, applicable laws, codes, rules and regulations, the OSHA lead in construction, standard 29CFR 1926.62 and applicable waste disposal regulations. He will oversee the lead/chromium removal process to ensure that all lead/chormium material is contained within the work area and that the contractor’s activities do not result in contamination with dust of any surrounding areas.