Bridges-the Bayonne, Goethals and Outerbridge Crossing (see box)-the Port Authority made a comprehensive investigation into their structural integrity. The expected increase in bridge traffic from the new arterial highway network, and the investigation findings led to a combined major work program of structural repairs and modifications and an improved ramp and tolls plaza system. Most of the work was completed in time for the opening of the Verrazano-Narrows Bridge, in November 1964, and the timely repairs and alterations averted serious traffic delays as the expected increases in traffic began to materialize. Last year, for example, the three bridges served a combined total of nearly 19 million vehicles. In making the investigation, the Port Authority's engineering department reported that the three bridges, which were completed during the period 1928 through 1931, were generally in good condition. But the Staten Island bridges are almost 40 years old, and although that is not considered old in the life cycle of a steel bridge, each bridge requires more and more maintenance. The nature of the defects uncovered prompted the department to suggest that a systematic inspection and maintenance program would aid in discovering and correcting most defects before they became serious. Structural integrity maintenance has traditionally been an engineer's responsibility, adequately fulfilled by on-site engineering inspections and surveys. The economics of high time costs for engineers, together with the typically slow deterioration of structural integrity dictate that the engineer's inspection be performed at periodic intervals supplemented by specific requests by maintenance personnel for spot checks, usually of an emergency nature. All too often the specific requests are simply the most expeditious method of handling reports of unusual or poorly defined defects. The end result of this situation is that costly engineering spot checks are frequently made on a demand basis and without the benefit of background data. Kavanagh and Johnson have succinctly stated three "facts of life" about structural maintenance (see Civil Engineering, May 1965, page 52): 1. "There is hardly a structure in existence in which there are not defects that could have been prevented by better engineering and more careful construction. In the main, these defects are not serious, but they exist and inevitably shorten the service life of the structure. 2. "The same problems consistently recur in similar structures under similar conditions of exposure. This recurrence appears to be the result of an inadvertent but repeated use of unsuitable details and/or practices in design and construction. It indicates that design engineers, in general, are not aware that such details and practices have previously proved unsatisfactory. 3. "Defects are seldom detected before they become so serious that repair must be accomplished on a rush basis. The result, at best, is that management's planning and maintenance budgets are upset and, at worst, that the facility is put out of service while repairs are being carried out." Empirical evidence confirms the obvious conclusion that structural defects develop progressively with age and that certain components are more susceptible than others. Maintenance personnel traditionally agitate for so called maintenancefree components to replace the bothersome old-fashioned features that require perpetual care. Today's new structural materials and design features are far better than those of 40 years ago, but to rebuild a structure or replace components after every material or design innovation is extremely costly. The question is-can a comprehensive program of structural maintenance, inspections, lubrication, and the technical reports, management controls, manpower resources and other factors be brought together in a workable program within realistic and economical proportions? The answer is not obtained easily. Many meetings with groups who shared the common problem led to the formulation within the Port Authority of ground rules for an effective program. The primary considerations are that structural integrity, by definition alone, must remain the engineer's responsibility, and that maintenance work, as defined in job classifications, belongs to the local facility maintenance forces. The solution to the problem was to write a program of inspections so precise that a skilled structural mechanic could act as the eyes and ears of the engineer. The mechanic would feed back an abundance of quantitative date that would, in turn, enable the engineer to ascertain and document the total structural picture without the need for frequent field inspection. Programming maintenance The writer's rule of thumb for programming structural integrity maintenance is "if it moves, measure it; if it rubs, lubricate it; and if it does neither, inspect it." Perhaps this rule is an over-simplification of very complex systems, but maintenance people understand it and that is half a solution to the problem. The programming of structural integrity maintenance effectively transfers the critical judgment factor from the field to the decision making atmosphere of the engineering office. The transfer is effected by the series of preplanned inspections and measurements which record the vital statistics of the structure's soundness and vitality. The technical language barrier between engineer and skilled mechanic is overcome by writing instructions in journeymen's jargon supplemented with more pictures than a typical daily newspaper. Thus, in concept, the program is analogous to a periodic medical examination, in which a nurse or technician measures and records such variables as weight, blood pressure, and temperature that the doctor then analyzes before diagnosing. Inspection and maintenance guides The complete program contains 71 field work routines encompassing a wide range of activities and skills, such as inspections, lubrications, technical measurements, structural cleaning, access rigging, and spot painting. All work routines are defined in the inspection and maintenance guides, which features 220 on-site photos of typical defects and measurement directions, tool and equipment requirements, special notes, and a specific condition report form for each routine. See Fig. 1. A performance schedule, which cycles every three years, assures that seasonal, cyclical, and weather-restricted routines are effectively incorporated. Two skilled structural mechanics perform the scheduled work and fill out the condition report by following the step by step instructions. The reports are reviewed by the local facility management and then sent to the engineering staff of the tunnels, and bridge department for analysis and recording. Time-lapse principles Structural defects, other than the types caused by accidents, usually progress very slowly. Consequently, they frequently exist unnoticed by field observers or are considered dormant. But through the maintenance program developed, the project engineer can give a systematic review to a series of reports on the same work routine-arranged chronologically and containing the critical measurements and observations made and figuratively speed up the effects on the structure of slow weathering and seasonal temperature cycles. This "time-lapse principle" thus provides an objective source of information showing both normal and abnormal expansion and contraction movements, progressive deterioration characteristics, and structural alignment and defects. OPERATIONS STANDARDS DIVISION Direction Туре or Lean Displacement Condition Routine Number 8332 OBC Y-2 Description: Inspect main span expansion roller nests. Check pivot bar bolts for Equipment Required: spring return steel measuring tape, chipping hammer, wire Measurements: Top pin east or west of center line of base and distance between center line of top pin and center line of base. Measure approach span pin and rocker according to directions for routine 8301 OBC. Note: Detailed drawings of the Main span measurement locations and bearings can NO FIG. 1. Typical inspection and maintenance guide, or work routine. Where certain defects, such as bent lacing, prove to be superficial, recording the defect will prevent repeated engineering inspections due to subsequent reporting of the same defect. For example, the inherent problem of span racking, usually caused by frozen bearings, can be diagnosed early with simple calculations and symmetry checks and compared with previous readings at various temperatures. Concrete pier cracks are periodically recorded and sketched in the field and analyzed by the engineers with the aid of previous sketches to detect movement or to verify dormant conditions. If a serious problem does begin to develop it will be caught early and thereby eliminate frustrating, unplanned, rush repair jobs or the worst stituation, mentioned earlier, in which a facility is put out of service while repairs are being carried out. As a fringe benefit the standardized reporting guide is also used as a reference format by maintenance personnel to transmit meaningful information on suspected emergency conditions via telephone. The extensive photographs in the indexed program guides provide a ready reference of critical measurements or anticipated defects using specific identifying nomenclature. After receiving such a call, the engineer can quickly review the history and development of conditions in the area of the suspected defect before making a field trip or a decision. Occasionally, new maintenance personnel who are unfamiliar with the structure report conditions of bent lacing or other abnormalities that have previously been detected, investigated and classified superficial. In that case, the engineer can verify the duplication by telephone and perhaps eliminate a trip. The inspection and maintenance guides will provide a perpetual means of communicating with the maintenance staff and achieving management objectives for structural integrity and maintenance. They also provide the basis for the first formal training tool for skilled structural mechanics in this highly specialized field. Management decision making and structural research should also benefit by the accumulation of information stored in the program records. A comprehensive analysis of the present painting cycle is planned using the spot paint data on each condition report. These data will objectively reveal corrosion and paint deterioration cycles in critical areas. Such information may lead to an improved spot painting system and, hopefully, may extend the overall bridge painting cycle; a one-year delay of a nine-year cycle would yield a theoretical 11 percent savings in total painting cost. The concept of programming structural integrity maintenance is not limited to steel bridges and concrete piers. A similar program is now being written for the Holland and Lincoln Tunnels-the Port Authority's two Hudson River vehicular tunnels which link New York with New Jersey. Other potential applications on structures operated and maintained by the Port of New York Authority include: huge aircraft hangars, pile supported runways over water, and aircraft taxiways over express highways; marine piers, terminals and warehouses; bus terminal and elevated parking structures. The diligent performance of this program-a unique combination of the methods of civil engineering, traditional preventive maintenance, and management sciences will help fulfill the agency's responsibility for assuring the structural integrity of those increasingly vital bridges, and serve as a pilot project for future innovations in structural integrity maintenance techniques. The CHAIRMAN. Before you continue, I would like to have the record reflect the presence this morning of students of Gaithersburg,, Md., Junior High School. I always for the record take cognizance of the attendance of young men and young women who come to these subcommittee or committee hearings. Because they are from the State of Maryland, I have had checked the record for the number of bridges that are now in use in your State. There are 1,537 bridges over which motor vehicles pass. That is on what we call the Maryland State system which would apply to your major highways, the interstate, the primary and secondary roads. It would not include those roads that are local in nature but all of those that have Federal-State participation—1,537. I am not going to compare States this morning but I did want to welcome the young men and young women of the junior high school in Gaithersburg. |