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27 Years of Bridge Engineering with Federal Highway Administration
When compared to the years of service of some BPR (sorry FHWA) engineers, I am a Johnny-come-lately. However, if I can pay a few debts and even an old score or two it will be worth the effort. Perhaps a few words in explanation of how I became associated with FHWA in the first place are in order.
At the conclusion of Word War II, I was in the market for a new job. Although enjoying reemployment rights with the Kansas City District of the Corps of Engineers, I had no great desire to return to them. The work in planning and office engineering was in many respects analogous to FHWA Federal-aid work, and even then I was prejudiced against that type of activity and favored a more direct involvement in the technical aspects of engineering. During my several years with the North Dakota State Highway Department, off and on, I had been exposed to the old BPR through the medium of the approximately monthly inspections made on Federal-aid projects in that State by the equivalent of today's engineer. His name escapes me, but he was a very friendly and personable middle aged gentleman and he made a lasting impression on me. So it was that after a close brush with going to work in private engineering (via the Austin Company of Cleveland, Ohio), when the Personnel Officer in FHWA in Washington, D.C., indicated an interest in hiring me, I was quite receptive.
The first offer was to the South Dakota Division Office in the capacity of Division Bridge Engineer, which I hurriedly refused on the basis of desiring to relocate to the far west. Actually, I had already had enough long, cold winters to last a lifetime. So my application was sent to the then Western Headquarters, FHWA, in San Francisco, California, and to what is now the Regional Office, FHWA, in Portland, Oregon. The San Francisco office tactfully expressed no interest on the grounds of limited bridge design experience (which was true). Ironically, it was only 13 years later that I gladly accepted the position of Chief, Western Bridge Design office there, after Mr. H. R. Angwin had announced his intention to retire.
It was Mr. R. B. McMinn, then first assistant to R. B. Wright, the equivalent of today's regional bridge engineer, who saw some possibilities in my application and was instrumental in that office offering me a position as Associate highway Bridge Engineer which I accepted with alacrity in 1946. Thus began an association of 27 years with one of the finest, if not the finest, agency in the Federal Government.
Mr. Leslie Schureman, then Personnel Officer for FHWA in Washington, D.C., recruited me. He was an engineer and how he became assigned to personnel work is still a mystery to me. Perhaps it was his lot always to be miscast, because he went from bad to worse when, probably in desperation over personnel work, he became interested in the then virgin field of computer applications in structural engineering. In any event, it was his program for the analysis of continuous beams of prismatic selection, utilizing the classical three moment equations, that sparked a nationwide interest in the use of computers in all fields of engineering and resulted in his many years of servitude to the computer. Of course, levity aside, he made a most significant contribution to the reduction of drudgery in the engineering profession. The fact that, in my opinion, the resulting widespread infatuation with ADP is a two-edged sword does not detract from his pioneering accomplishments.
There probably are many younger generation bridge engineers today in FHWA who do not know the name R. B. McMinn. It is their loss because he was one of the giants in bridge engineering for several decades. (He retired in 1961 from the position of Regional bridge Engineer, Portland.) He was largely a self-made man, and his exploits and accomplishments considering his humble beginning and the great gaps in his formal education are almost incredible. Here is a man who never completed grade school-he was forced to drop out after the sixth grade; who never spend a day in high school, but who, after a few years helping his father in a family building construction business, successfully passed a special entrance examination to the University of Oregon. Low on funds, he and another student lived in a tent and did their own cooking. Five years later he graduated with a Bachelor of Science degree in Civil Engineering.
Unhampered by the gaps in his formal education, Mr. McMinn was and is well read, articulate, and knowledgeable. His fore lay in the overall conception of bridge projects and the practical aspects of their design and construction, rather than in highly technical bridge design. Actually, his lack of interest in this one area of bridge engineering was probably a Godsend, because it enabled him to concentrate on the other equally important phases of bridge engineering, i.e., overall planning and layout, type selection, and construction. He left the designing and detailing to the "mechanics" (his word, not mine). He could and did move freely in the company of the Nation's bridge designers and enjoyed their respect and confidence. This is amply demonstrated by the fact that he, in addition to a full load of regular duties, was for several years the Secretary of the AASHO Bridge Committee. As such he was personally responsible for the updating and subsequent publication of several editions of the AASHO Standard Specifications for the Design and Construction of Highway Bridges. This single book was and is the most authoritative source for bridge design and construction specifications in the U.S. and enjoys almost worldwide acceptance also.
A hard worker himself, one of his idiosyncrasies was setting deadlines for the completion of tasks. The fact that sometimes these were a bit unreasonable never fazed him. I remember one incident when I was due to go to an annual two week tour of active duty for training with my reserve army unit. The Seward-Anchorage Highway in Alaska was being planned and there were many long trestle type bridges involved. Mr. McMinn told me "Sure you can take your two weeks military leave, if you design and prepare a standard plan for these bridges," and he proceeded to allow me one week. The fact that they involved bridges on both tangent and varying radius curves, were to be of precast concrete stringer construction with cast in place concrete decks, that the most economical spacing of pile beings had to be determined, etc., and the standard drawings and estimates prepared in such a short period, was immaterial. It was done, but now without resorting to burning a lot of midnight oil.
This brings up one of Mr. McMinn's early important accomplishments, that of recognizing the potential in ease of construction when precast concrete units are yard fabricated and field assembled into virtually monolithic units. The prototype of today's practically innumerable short and moderate span precast slab and girder bridges was constructed about 1929 on a Forest Highway section of the Oregon Coast highway. Slab units precast in Portland by a structural steel fabricator were hauled to the project and placed on the field-constructed substructure. One of the great grandchildren of this small project, the twenty-mile long lake Ponchartrain Bridge in Louisiana, might have been constructed anyway, but we will never know.
Precast concrete box culverts were formed from mass produced rectangular units for top, sides, and bottom, and field bolted together; precast concrete quarter circular segments were formed into semi-circular rings when installed in the field on cast-in-place footings and low walls to become part of the tunnel lining for tunnels (the rings were spaced about 10 feet on centers and provided support for plywood forms begin which concrete was placed against the tunnel bore thus eliminating the usual maze of tunnel lining falsework; precast concrete semi-circular rings were set on cast-in-place concrete footings and low wall to form large diameter two hinged arch culverts; and many other original conceptions featuring precast concrete elements were products of Mr. McMinn's fertile imagination.
Always ready to embrace the new and different, Mr. McMinn early recognized the potential for prestressed concrete. He became a leader in the west in encouraging use of this new material borrowed from European origins. The Ten Mile Creek Bridge on a Forest Highway section of the Oregon Coast Highway was one of the earliest prestressed concrete girder bridges in the west. The Kenai River Bridge in Alaska with its entirely precast superstructure (precast prestressed I-girders, precast and field prestressed diaphragms, and precast deck slab and curb units) was another conception of his. The Baker River Bridge on a Washington Forest Highway project embodying an all precast superstructure of stringers, slab, and curb units all welded together to form a monolithic unit for each span by a minimum of cast-in-place concrete was yet another product of this indefatigable engineer. Considering that today the vast majority of short and moderate span highway structures are composed of precast and/or prestressed main supporting members and that Mr. McMinn was a leader in this field in the west is a monument to itself.
Perhaps Mr. McMinn's most crowning achievement was his original conception for a crossing of blue Creek bay, an arm of Lake Coeur d' Alene in Idaho, on a Forest Highway section of a transcontinental and now Interstate highway. After estimating the cost of a 1,300 foot long suspension bridge with unloaded backstays, already designed and ready to proceed to contract ($2,000,000 and in 1948 that was a lot of money) , he was dismayed. A fill across the bay with a height of 120 feet of which 100 feet was in the water had been considered and discarded. Soils engineers had estimated annual settlements of 4 to 5 feet requiring annual topping off and repaving for many years. Similarly a floating bridge had been considered and discarded when its cost exceeded that of the suspension bridge.
Mr. McMinn arrived at the office one morning after a sleepless night with a new idea. Simply stated it involved constructing several structural steel towers (182.5 feet on centers) in the bay from the lake surface down through 100 feet of water and 200 feet of bay sediment to and into underlying bedrock. The upper portions of the towers (a maximum of four stories of 29 feet each) would be erected story by story between a pair of barges and lowered into the water. After reaching the mud line and sinking into the lake mud to the desired elevations, the towers would become templates for driving piles through the remaining 180 feet more or less of mud to rock. The inside of the cylindrical piles, one at each corner of each tower, would be cleaned out, holes drilled into underlying rock by an inside cutter, the cylindrical piles driven into those holes, the cylindrical piles cut off from the inside after a 20 foot overlap with the cylindrical tower legs, a steel H pile set from top to the bottom of the holes in the rock, and the entire tower leg and the cylindrical pile filled with small aggregate concrete.
This time I had ten whole days to examine the conception for feasibility, prepare a preliminary design for substructure and superstructure complete enough to make a reasonably accurate estimate of quantities and cost, and prepare a report complete with a scheme for erection to lay before higher echelons. It crowded me a little bit but it was done, approved by Mr. McMinn and also approved by Mr. Lynch, the Regional Engineer, by Mr. Andrews his deputy and principal assistant for direct construction, and also by Mr. Archibald the FHWA Chief Bridge Engineer. Although some details of the preliminary design and report were modified during final design in Mr. Angwin's office of western bridge design, the original conception was basic and the bridge was constructed in 1949-1950 at half the estimated cost of the suspension bridge and within a few perfect of the estimated cost based on the preliminary study and report. The excellence of the project was demonstrated 20 years later when another independent two lane bridge was constructed parallel and contiguous to the original by the State of Idaho as a Federal-aid project.
I would like to say that the Blue Creek bay substructure became the prototype for the many oil well drilling platforms that have been constructed in deep offshore ocean waters. However, it appears that about the same time Mr. McMinn had his brain child, one or more oil companies independently arrived at a very similar conception. It is a fact the Blue Creek Bay bridge and the first oceanic oil well platform were independently conceived and constructed at about the same time. It must be apparent by now that I had and still have the highest regard for Mr. McMinn as an engineer, as a gentleman, and as a friend.
At this point I have covered in capsule fashion a few of Mr. McMinn;s many accomplishments and achievements during his long (approximately 42 years) service with the Bureau of Public Roads. If this capsulated recital is long it is because even to discuss briefly a few of the examples of his enlightened leadership and brilliant conceptions in the field of bridge engineering warrants it.
There is still, however, an area totally untouched outside of his bureau of Public Roads' service. This is his service and contributions toward two world famous toll bridges constructed by the Washington Toll Bridge Authority. His recommendations to simplify the design of the floor system were adopted by the rest of the board of consulting engineers and the Toll Bridge authority, and the plans were changed. During the course of the construction of the bridge he made other significant contributions in connection with the main tower foundations, and other matters.
In 1938, a project for a new route running easterly from Seattle was in the planning stage. Existing routes went around each end of lake Washington adding miles of unnecessary travel if a direct crossing of the lake could be built. Mr. Lacey morrow, then Director of highways, State of Washington, felt that a direct crossing of the lake combined with a road on mercer Island and a tunnel on the Seattle end might be feasible. He informally consulted with Mr. McMinn and asked to consider undertaking an engineering feasibility study for the tunnel and water crossing portions.
At that time there were several floating bridges in existence scattered over the world, but none of the magnitude of the one being considered, and none were wave action was as severe. Mr. Murrow suggested a floating bridge and during the interview made a simple line sketch showing Viking style ships as possible pontoon supports.
Recognizing the vast advantages of a floating bridge in deep water where conventional piers were impractical and being himself of an innovative and inventive mind, Mr. McMinn proceeded to study the problem. In a short time he conceived the plan of constructing reinforced concrete pontoons rectangular in plan and a cross section which could be built in a graving dock, towed to the site, and fastened together to form a continuous floating bridge. It could be anchored at intervals on each side to provide longitudinal stability, with vertical movement virtually eliminated by rigidity of the continuous pontoon system.
Since such a continuous floating structure would constitute a virtual dam to surface traffic on the lake, two navigation openings were suggested. One of these would be a full pontoon length (350 feet) floating draw span which could be retracted into a special widened pontoon section. The other would be a 378 foot tied arch fixed elevation span in conjunction with several deck truss spans also of fixed elevation except at the floating bridge end. The draw span would provide for deep draft/high clearance requirement vessels, and the fixed arch and deck truss spans would accommodate the vastly greater number of low draft/low clearance craft.
Mr. McMinn's work in preparing the engineering feasibility study culminated in its adoption by the Washington Toll Bridge Authority, and he was again selected as one of a four member consulting engineering board. During the detailed design, preparation of plans, and construction of the Lake Washington Floating Bridge and Tunnel, he made many recommendations which were incorporated in the final plans in the areas of concrete type and strength, pontoon connections details, anchoring system details, etc. He also gave much advice during the construction on such matters as pontoon connection methods, pontoon casting methods, tensioning anchor cables, etc. Completed in 1940, this outstanding and famous floating bridge is alive and well today. During its 35 years of service to date not one drop has ever been pumped out of the bridge pontoons.
Another bridge engineer who left the position of Chief Bridge Engineer with the Louisiana Highway Department to become Chief Bridge Engineer for FHWA about 1949 has left an indelible imprint on me and many others. This was Mr. E. L. Erickson, soft spoken, deliberate, completely knowledgeable in all aspects of bridge engineering, incorruptible, and a true gentleman. He is also a stubborn Swede, and it used to be quite a show when Mr. Erickson, who represented FHWA on the AASHA Bridge Committee for many years, would rise during deliberations of the regional meetings of that body and unequivocally state the FHWA policy on bridge design and construction matters. Respected by all and liked by most, he could still be exasperating when he had taken a stand for good and excellent reason and would not be moved from it.
Mr. Erickson cast a very long shadow in the field of prestressed concrete. The Walnut Lane Bridge in Philadelphia was constructed in 1949 and was the first major prestressed concrete bridge in the U.S. When it didn't fall down, consulting engineers, States, and the FHWA were all competing for honors in the early days of 1950. Trying to keep up with the Joneses had led to a veritable jungle of slightly different but essentially similar design criteria, allowable stresses, etc. Mr. Erickson took the bull by the horns and sought to bring order into the maze of conflicting and scattered data which was all the poor bridge designer had when trying to design in prestressed concrete. He set up a study group in his office in Washington, D.C., composed of several engineers who first assembled prestressed concrete data from all sourced, both the meager information at home and the vastly greater amount from abroad. They collated, analyzed, discarded, cussed and discussed this mass of information and shortly came up with a brief three page effort called "Criteria for the Design of Prestressed Concrete Bridges." It was immediately accepted by the Nation's bridge engineers and was the first positive and sketchily comprehensive guide to the bridge designer. It was augmented and improved over the course of the next several years and became a small bound pamphlet published by FHWA containing criteria for design, a guide for construction, and a discussion of underlying concepts. This was published in 1954 and had the force of law for the next few years.
Not to be outdone, the American Concrete Institute and a study group of the AASHO Bridge Committee, belatedly joined forced and produced in 1958 "Tentative Recommendations for Prestressed Concrete." Tentative or not, this was adopted virtually in total by the AASHO Bridge Committee and was incorporated into the national bridge design specification where it remains, slightly improved and modified, to this day. But it was Mr. Erickson's pioneering effort that produced the first reasonably complete and comprehensive guide to the bridge designer and allowed him a firm foundation for the phenomenal use of prestressed concrete in our country's bridges and highway structures.
Mr. Erickson's next effort in this field was not immediately as successful but ultimately produced the desired effect. One of the things and perhaps the most important thing that hampered more extensive use of prestressed concrete (after the criteria for design had been prepared and widely disseminated) was the extreme variety and multiplicity of beam cross sections that immediately developed.
Accustomed to cast-in-place concrete where each element of the bridge is individually formed, there was little incentive to select common beam widths, depths, prestressing hardware, etc. One of the important advantages of prestressed concrete, however, is that bridge beams can be and indeed should be precast, with only the current physical limitations of lifting, hauling, and erecting these members governing their size. Also, pretensioned prestressed concrete requires a most sizeable investment in the casting bed, tensioning abutments and equipment, concrete mixing and placing equipment, and, of course, forms.
When every designer had a free hand to select dimensions of structural members, the reuse of forms for many members of many bridges was almost non-existent. Mr. Erickson reasoned that it should be possible and was certainly desirable to select a representative number of sizes for bridge beams and other elements (piles, slabs, box girders, etc.) and drastically reduce the costly duplication of forms resulting from the hodge podge of cross sections all essentially similar but varying in minor details.
Accordingly, as early as 1952, he set about accomplishing this in his office by having his men design a coordinated series of I-shaped prestressed beams of sufficient range in span length to encompass the needs for precast (both post- and pre-tensioned) members. The result was a family of eleven sizes of members with overlapping span capabilities up to about 80 feet. A few of his beam sections were adopted by a few States and are in use today., Most of the States, however, wishing to preserve their independence, immediately set about standardizing their own sections. The AASHO Bridge Committee recognized that the State Standards were a step in the right direction, but that national standards were what was needed. This is precisely what Mr. Erickson had wanted. The end result was a combined effort of the AASHO Bridge Committee and the Prestressed Concrete Institute which led to the selection of four standard sizes of precast prestressed concrete beams. These four sizes were adopted by the vast majority of all the States and by FHWA and are still in use. Their number has now grown to six, and similar standards for box beams, piles, and solid and voided slabs have long since been developed and adopted. Mr. Erickson, however, in my opinion deserves the credit for sparking the effort for standardization. This single thing did more to popularize and encourage the widespread use of precast prestressed concrete bridge elements on a national scale than any other thing (with the exception of preparation of the original design criteria).
My reminiscences of outstanding bridge engineers in FHWA that I have known and admired during these 27 years would not be complete without mentioning Mr. L. A. Herr. Mr. Herr came to Portland in 1949 as a neophyte bridge engineer. His knowledge ability, professional competency, restrained aggressiveness, enthusiasm, and overall friendliness quickly focused the attention of the higher echelons of the Regional Office on him. Mr. Herr is now serving as Chief of the Bridge Division in the FHWA Headquarters.
Several pages ago I started on these excerpts from the past with the intention of keeping this word picture of a few highlights and persons short and sweet. I am sorry it didn't turn out that way. I am also sorry to have made no mention of the significant contributions made by many other FHWA bridge engineers. No disrespect or lack of appreciating of their roles is implied or intended.
This page last modified on 04/07/11