Usually, highway bridge structures remain in service for forty years or more, and are generally retired for becoming functionally obsolete as to width, as often as they are replaced because of structural inadequacy. Highway engineers generally project traffic trends twenty years into the future as a basis of design. As more experience is gained, such projections become more accurate and admittedly, engineers have been too conservative in forecasting traffic growths in the past. They have been expecting that traffic growth increases will level off, and this has never occurred. Highway engineers are also gathering important data at this time on those factors that might affect or modify conventional traffic growth projections, because of a change in the character, land use, or environment of the area traversed, that might be indicated from socioeconomic or planning studies. Often, unanticipated developments occur, such as new industries moving into an area, which can cause traffic far in excess of traffic forecasts made earlier. Question 2. Yesterday we were told that the 1965 9th edition, Standard Specifications for Highway Bridges, was the official standard for bridges on the Interstate System. Is this 1965 Standard Specifications also used in the design of highway bridges not on the Interstate System? Answer. The AASHO Standard Specifications for Highway Bridges are used as the official design specifications for bridges on the Interstate System, and for bridges not on the Interstate System. In fact, these specifications are used by all governmental levels, consulting engineers, or anyone else designing highway bridges. Question 3. The subcommittee staff has been advised that the 1964 An Information Guide for Maintenance Inspectors prepared by the AASHO Committee on Maintenance and Equipment is a guideline only as opposed to the 1965 Standard Specifications for Highway Bridges. What is the exact status of the 1964 Informational Guide .? Answer. With reference to Chapter 6 of the 1964 AASHO Informational Guide for Maintenance Inspectors, this particular Chapter dealing with bridge inspec tions was developed by the AASHO Committee on Bridges and Structures for inclusion in the Guide that was issued by the AASHO Committee on Materials and Equipment. The Standard Specifications for Highway Bridges is an "official policy" of our Association, and deals with engineering design and is used by all of the State highway departments. In contrast, an "informational guide" is for the guidance of a highway department in developing its own administrative, managerial or operational procedures, and department manuals. AASHO is composed of all of the State highway departments which, in turn, are official agencies of the several soverign States. There has been a strong feeling, on the part of the State highway departments, that they should have the prerogatives and privilege of determining their own practices and procedures dealing with operations for their own departments. An AASHO "informational guide" is issued to aid the States and to give them guidance in the development of such procedures and practices, if they so wish. Question 4. We note that the 1964 An Informational Guide for Maintenance Inspectors does not specify any maximum or minimum period between bridge inspections. Could you tell us why no such time intervals were established? Answer. With reference to Chapter 6 of the Informational Guide for Maintenance Inspectors, AASHO did not specify any maximum or minimum periods for bridge inspections, but only sets forth those things that should receive special consideration or attention in the inspection. It was felt that over the years, the individual State highway departments had determined appropriate intervals for inspections which are best suited to their individual conditions. Question 5. It has been suggested that maintenance is in a relatively low priority position when competing for qualified manpower and funds. What is the typical staffing pattern of State highway maintenance and inspection organizations insofar as highway bridges are concerned? Answer. The several State highway departments spend between one-and-a-half and two billion dollars annually on maintenance, and it is a major budget item in every State highway department. The maintenance of the highway plant should have first call on available funds, inasmuch as it is the primary responsibility of the State highway departments to protect its investment in highways, and to keep the roads and bridges in a safe and satisfactory condition for the user. Most of the States which have a sizeable inventory of major structures have specialized bridge inspection personnel to check such structures. A specialist of this type is usually a graduate Civil Engineer, with specialized post-graduate studies in structures, and one who has gained extensive experience in bridge design, bridge construction and bridge maintenance. For the multiplicity of simple structures that are a part of all State highway systems, regular maintenance forces are usually trained to make the necessary periodic inspections of such structures, and to seek expert evaluation from bridge specialists if something unusual is noted. Question 6. Maintenance is the responsibility of the States. What is being done to upgrade maintenance procedures? What consideration is being given to the design and construction of more maintenance-free highway bridges? What might the Federal Government do to assist the States in these important areas? Answer. The maintenance of the State highway systems is the sole responsibility of the individual States, however, the maintenance of any facility that was built as a federal-aid project is subject to a periodic inspection by Bureau of Public Roads personnel, and if found inadequate, must be corrected. Much is being done to improve maintenance procedures and much is being done to assure the safety of the public and maintenance personnel on the highway where maintenance operations are in progress. New improved maintenance equipment is being developed and utilized, as well as some new materials. A State highway department will have many, many bridges of the various types and designs, and in the process of inspecting and repairing them over the years, those things that cause maintenance problems are noted and are being corrected in subsequent structures, to the extent possible. Much of the maintenance and repair is caused by the thermal expansion and contraction of the bridge structure, or its components. The structural failure of a major component of a bridge is a rarity. Most of the maintenance and repair, other than that caused by vehicles colliding with the structure, result either from this thermal movement, or the effect of deicing treatments and is generally relatively minor. In order to assure that bridge structures can move with temperature changes, improvements are constantly being made in expansion devices. As to what the Federal Government might do to assist the State highway departments in the matter of bridge inspection and maintenance, it might be constructive to include a safety standard requirement in the State traffic safety program on the subject of bridge inspection procedures. The States do not want federal aid for maintenance. They believe that maintenance responsibility is closely associated with ownership and the roads and bridges making up the State highway systems belong to the individual States. Question 7. What would be a normal procedure for making a safety inspection of an existing highway bridge? Answer. The inspection of a bridge for safety would involve the evaluation of the various components of the structure to continue to carry the loads and to function as designed. Inspection of the substructure should be made concerning scouring around the foundations and the general structural condition of the pier. Determination as to the extent of scouring and undermining around footings, if any exist, may be measured by taking soundings around the pier footing and for a distance of approximately 100 feet each way from the pier. Soundings and elevations of pier footings should be plotted on paper to determine the extent of scour and to reveal any undermining. If undermining does exist, further study should be made with underwater inspections to determine the method of repair required. Structural condition of pier shafts and caps should be checked for cracks, spalls and general deterioration of concrete. Particular attention should be directed to condition of caps around and under superstructure bearings. The condition of the superstructure should be noted with regard to the bearings, main supporting members, roadway surface, railings, expansion devices and paint. Main supporting members, composed of concrete, should be inspected for cracks in beams and arches at the mid span and over the bearings. Particular attention should be paid to the concrete around and over the bearings for any signs of deterioration. The ability for expansion plates to move and their relative location on the cap as compared to when built should be checked. Any end bearing or edge bearing caps should be noted. Main supporting members of structural steel should be checked for condition of steel, cracks and breaks in paint, severe rustings at connections and around bearings. Movements in joints of trusses, indicated by movements from original position of paint line, should be noted. Condition of bolted connections as to rust and alignment should be noted. Signs of fatigue in members will sometimes be noted by small cracks in the paint on the surface of the steel. Actual stresses in these truss members should be checked to determine frequency of stresses and amount. Pin connections, rocker expansion shoes and expansion plates should be checked for corrosion, ability to rotate and position as compared to that when built. Expansion devices should be checked for structural soundness and ability to perform as designed. General paint sondition should be checked for breaks in paint surface and around rivets and bolts. Condition of paint around bearings should be checked and noted. All points of stress raiser, such as at the end of welded partial cover plates, should be examined for fatigue failure. Superstructure decking should be checked and inspected for cracks and general deterioration in concrete that would permit water, salt and brine to enter. Freezing and bursting of the concrete would allow rusting of the reinforcing steel. Any undue damage to the members should be checked with the Bridge Design Division to determine adequacy of the existing facility. A record should be kept of the inspection report with particular attention to creep and other deficiencies for future record and reference. Question 8. What role does age play in the safety of a highway bridge? Answer. Age of a bridge indicates that two things have possibly occurred to the bridge. Number One: The bridge has been exposed to continuous detrimental actions of the elements of nature upon the concrete and steel and the deicing chemicals of men. Number Two: The continuous traffic upon the bridge, increasing at an increasing rate each year, has produced wear, fatigue, stress reversals in members and vibration on the structure. The action of rusting, freezing and thawing cycles tends to produce cracks and permit deterioration in concrete and steel. Steel sections will be reduced in size over a period of years and strength reduced materially without proper maintenance. Traffic upon a bridge with a high frequency of heavy traffic loads tends to produce movement in joints, connections and materials. Fatigue stresses will in some cases set in to produce a weakened bridge member. 91-955-68 RELATIVE STRENGTHS, MAINTENANCE REQUIREMENTS, AND COST BETWEEN STEEL RATED AT A-7, A-36, AND 1 None of these steels are recommended for use in an exposed condition without painting. The chemical composition of A-441 can be altered to provide a steel for use in an unpainted condition known as Weathering Steel. 2 The atmospheric corrosion resistance of A-441 Steel is approximately twice that of structural carbon steel (A-7 and A-36). 8 United States Steel Structural and Plate Product Section, December 1, 1967. Note.-AASHO specifications included A-7 steel until 1962 when A-36 was also included. Since 1962 A-7 has been replaced with A-36 and A-7 is no longer used and A-36 is the present specification for carbon steel for bridges and buildings. Weighted average unit prices for structural steel (material, fabricated, erected, and painted) in Arkansas for calendar year 1967 Structural Steel in Beam Spans (A36).. Structural Steel in Plate Girder Spans (A441)_ Cents per pound 15. 8 27.0 Cost of steel in the main structural elements of a bridge in proportion to the total cost Type superstructure of the bridge I-Beam and Plate Girder with Concrete Deck__ Percent of total cost 30 45 Percentages shown are averages. I-Beam and Plate Girder Construction is generally used in situations where optimum, that is the most economical span lengths, can be used. Truss and Arch Construction is generally used in situations where spans longer than the optimum are required to provide clearances for navigation, etc. This is the major reason for the difference in the two percentages shown. 33% is the approximate percentage for all ranges of spans. (Whereupon, at 11:40 a.m., the subcommittee recessed, to reconvene at 10 a.m., Wednesday, March 20, 1968.) BRIDGE INSPECTION, MAINTENANCE, AND DESIGN WEDNESDAY, MARCH 20, 1968 U.S. SENATE, SUBCOMMITTEE ON ROADS, Washington, D.C. The subcommittee met at 10 a.m., pursuant to recess, in room 4200, Senate Office Building, Senator Jennings Randolph (chairman of the subcommittee) presiding. Present: Senators Randolph, Spong, Cooper, Fong, Jordan of Idaho, and Baker. Also present: Richard B. Royce, chief clerk and staff director; M. Barry Meyer, committee counsel; Bailey Guard, assistant chief clerk (minority); and Martin Baker, staff assistant. The CHAIRMAN. Good morning, ladies and gentlemen. This, as you know, is the first day of spring. You look very cheerful. I am delighted to have the opportunity to continue the hearings. Our first witness is Mr. Frank Masters. Mr. Masters, Junior, please. Are you going to have anyone accompany you? Mr. MASTERS. No, sir. The CHAIRMAN. Thank you, Mr. Masters. If you will, identify yourself, sir. STATEMENT OF FRANK MASTERS, JR., CONSULTING ENGINEER, FIRM OF MODJESKI & MASTERS, HARRISBURG, PA., REPRESENTING THE CONSULTING ENGINEERS COUNCIL Mr. MASTERS. Mr. Chairman, members of the committee, my name is Frank Masters, Jr. I am a partner in the firm of Modjeski & Masters, a consulting engineering firm specializing in design of long- and medium-span highway and railroad bridges, as well as design of highways,fexpressways, dock facilities, and subaqueous foundations. The CHAIRMAN. I think you did the Ben Franklin Bridge; is that correct? Or did you? Mr. MASTERS. No, sir; my predecessors did. I was in diapers at the time. The CHAIRMAN. How about the Huey Long Bridge then? Mr. MASTERS. The Huey Long Bridge-I was a young pup running around the house, and I heard an awful lot about it, because many nights I was aware of my father pacing the floor while they were doing the foundations there. The CHAIRMAN. And the Calvert Street Bridge in Washingtonwhere were you then? Mr. MASTERS. I was in grade school at the time of that one. |