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In his excellent treatise Bridges and their Builders, D. B. Steinman closes his text with a section called “The Bridge Builder in Contemporary Civilization.”In this final chapter, he defines the role of the modern bridge engineer (circa1957) as a metallurgist, mathematician, foundation expert, steel erector, artist,and leader of mankind. While leader of mankind may be stretching the point a bit, the breadth of scientific and engineering knowledge involved in bridge design is formidable, yet as we shall see, quite definable.

Through the efforts of bridge engineers involved in projects such as those described in , the past 40 years have yielded a set of design standards that allows today’s engineer the luxury of not having to reinvent the wheel for each project. However, do well-defined standards and sets of details stifle creativity? Perhaps on a more fundamental level, the proper question is: Who are today’s bridge designers anyway? In the United States, highway bridge design is typically undertaken by two principal groups :

- Municipal Agencies. These could be local agencies, but for the most part they are design groups for a state or county transportation agency or autonomous agency in charge of a specific branch of highway.

- Private Consultants. The majority of private civil engineering consulting firms that engage in bridge design are medium (15 to 100 person)to large (100 plus persons) size firms specializing in highway design work in general and highway bridge design in particular.

In the United States a highway bridge project is usually slated for construction by the owner (the agency), after which design is either under-taken by an outside consulting firm or the in-house design department of the owner. Once the appropriate reviews are completed, the project is then listed in an advertisement in response to which several contractors will bid on the job. The contract is then awarded to the lowest bidder, although this is not always the case.

An intriguing alternative to this process is under the term design-build (sometimes called value engineering) under which approach, a consultant or the owner prepares a preliminary plan of the bridge to be constructed which includes only basic information such as physical location, basic dimensions, design loading and specifications, alignments, clearances, etc. Based on these preliminary plans and specifications, contractors then propose their own design and construction costs. The design is either completed by an in-house engineering department of the con-tractor or a hired consultant. Once the design and price proposals are submit-ted to the owner, a group of independent or check engineers review the plans and the costs, and along with the owner,decide which design and its contractor will construct the project. The decision is not based on cost alone but on the overall solution and its impact on every-thing from aesthetics to environmental concerns (so called technical evaluation).Design-build proponents believe that their approach creates a competitive atmosphere that stimulates the various parties to provide better solutions for the client, which leads to innovative and more economical designs for the owner [Ref. 1.8]. Since there is only a single party responsible for design and construction, the cost and schedule should be improved. Any problem, either from design or construction, can be resolved easily. From the owner’s perspective,he or she only needs to deal with one party who takes responsibility of engineering, cost, schedule, and quality.

There are several problems which engineers in the United States have with this approach. First and foremost is the belief that competitive bidding for engineering services is considered to be unethical. The thinking behind this belief is that, in trying to save costs to impress a panel on the design of a project, the engineer will be tempted to sacrifice safety of the structure in order to minimize construction expense.The other major problem U.S. engineers have is with the notion that the contract will not be based solely on price. Municipal agencies, who must ultimately report to the public, would have to make an extraordinary case for choosing a more expensive design just because it looks better or fulfills some abstract criterion of the panel. Under the design-build approach, contracts are awarded on a lump sum basis, which means that the owner and contractor must have an extraordinarily good working relationship for this type of arrangement to be successful. In many cases, an outside consulting firm is hired by the owner to supervise and to approve the contractor’s design, and to over see the construction for the owner.

The opponents argue that with respect to the contractors, having to submit design proposals (in most cases, 30% to 50% complete drawings) is a costly venture, especially when they may not be awarded the project. In some instances there are monies available to compensate all bidders for their design proposals, but if this is not the case, the costs that contractors incur preparing these proposals will just be passed along to the consumer on subsequent projects. In this instance the consumer is the owner and the public they serve.That also indicates that the future maintenance of any constructed project that is part of an overall infrastructure, be it a bridge or highway, cannot be so easily dismissed as to say that an independent design under the design-build approach will “meet the maintenance needs of the owner.” To do so means following, to a certain degree, a set of standard details and specifications that in and of itself puts a constriction on creativity.

As with any argument, the answer most likely lies somewhere in the middle. Design-build does spur the participants on to more creative designs. It reduces the cost and overall project time. However, competitive engineering presents many dangers which cannot be ignored. Also, owners need to do more in the way of working with consultants and contractors within their present system to foster innovation in design, something they have not done well in the past (see Design Perspective, on facing page). If all parties involved recognize that the three fundamental goals of any highway bridge project are low costs, quality and safety, and longevity of the structure, then much has already been accomplished in securing the completion of a successful project,regardless of the way in which it is undertaken.

At present, only a few states in the U.S. have adopted the design-build approach as an alternative contract method for large or high profile projects.So far, their results seem to be positive, and as a result, more and more states are considering joining this group to have the design-build as an alternative contract method to save project costs, speed up the projects, or choose the best design for high profile projects.

THE BRIDGE ENGINEERING LEXICON

So far, we have examined the major components of a highway bridge structure and, in the process, obtained a general understanding of the nomenclature employed by bridge engineers. Provided below is a more detailed lexicon of the bridge engineer’s daily vernacular. To be sure, it would be impossible to compile a complete list of all the expressions and terms used in the profession. The items listed below, however, represent the common expressions used throughout this text. An attempt has been made to de-regionalize the terms used in this book. It should be understood by the reader that each geographic region maintains its own distinct flavor of design, and to a certain extent, the terminologies used for bridge elements. Complicating this situation is that many designers refer to elements by manufacturers’ brand names. While there is nothing inherently bad about this except that we should not specify any brand name in our design, it does tend to confuse young engineers.

It may seem to the reader that a good many of the entries in the lexicon are repeated definitions from the preceding (and following) text. The lexicon is meant to act as a handy reference for the reader to flip back to while reading the text. While it is certainly hoped that the book is read from cover to cover,a measure of reality would suggest that many readers will be moving about the book in a somewhat nonlinear fashion. So, for example, if the term weep tube is used liberally in a section, the reader will not have to hunt down the exact point of definition in the text but rather can refer back to the entry below. It is recommended that newcomers to bridge design spend time familiarizing themselves with the definitions below before moving on to the subsequent sections. The definitions provided herein are within the context of bridge engineering in general and this text in particular.