GENERAL BACKGROUND
The perceptions of a beautiful bridge and its suitability to the landscape have varied through the years along with its technological development. Stability and durability (stone arches) were the highest values in the earlier days, whereas lately one strives for slender structures (slim girders and arches, suspension and stayed cable bridges). However, there are certain "eternal" criteria that apply for a bridge well fitting the landscape: well adapted to the purpose, harmonious proportions, length, height, colors, materials and surface treatment, all suitable for the landscape. In earlier days the financial and technical possibilities were more limited than today. But nevertheless results were often achieved.The Finnish National Road Administration has designated this year, 1996, The Year of the Environment. This means, among other things, that more than ever before, even the users will be invited to evaluate the appearances of bridges and their suitability to the landscape. The following introduces some general principles that Finnra considers to be essential in producing a successful outcome.
THE EXTERNAL FEATURES OF A BRIDGE
For the designer to be able to choose the proper proportions for a bridge, an artistic eye and a wide experience are required. A correct choice of dimensions forms a logical connection between the load and the dimensions, the structure expressing the strength of materials and their static function, i.e. the dissipation of load through the supportive structures down to the ground. Good proportions also fulfill the requirements of harmony, ie. the various parts of the bridge are in tune with one another, and together form a harmonious whole. Using symmetry is one possible way to achieve harmony.In addition to having good proportions, a beautiful bridge should be uncomplicated. The main lines of the bridge should be clean, fluent and continuous. One should avoid structures protruding in several directions. The design should not be overly decorative but all forms should have a logical explanation.
The Lumberjack's Candle Bridge in winter appearance.
A well-proportioned bridge might still need some finishing touches. Steel bridges require paint to prevent corrosion unless weatherproof steel is used. The choice of color is important to the overall appearance. Concrete surfaces can also be given various finishes. There are many ways for that: brushing, chipping, grooving or using any number of patterning, covering the surface with stone or ceramic tiles, painting or coating, using dyed concrete, among other things. The choice of railings, light fixtures and lighting columns can add a lot to the final appearance of the bridge. See Fig. 1, The Lumberjack's Candle Bridge and Fig. 2, The Saame Bridge.
INTEGRATING THE BRIDGE TO THE ENVIRONMENT
Good looks are not enough to create a successful overall effect. A bridge must also be in harmony with the surrounding landscape and the buildings in the vicinity.Through inventory of the bridge site and its surroundings a conclusive picture is formed of the scenic and ecological conditions, land use and conservation areas or objects, and their joint effect on the positioning, length and type of the bridge.
Bridges over waterways are often subject to special concern since the surroundings usually have considerable scenic value. These bridges are often large and visible from a long distance. A bridge should be long enough to leave the shore lines free in order to preserve a land passage. When crossing wide straits or bays it might be necessary to build ledges or embankments in the water. These should be integrated in the surroundings using gentle curves and landscaping. See Fig. 3, The Lietvesi Bridge and Fig. 4, The T�htiniemi Bridge.
Surroundings of flyover bridges usually are not very significant unless they are located in densely populated areas. Often they are continuous reinforced concrete slab or girder bridges. Flyover bridges are mainly viewed from the underpass level. The speed of the passers-by causes the focus points to be the main lines rather than the details of the bridge.
Flyover bridges crossing a particular stretch of road tend to become too similar. The monotony can be broken by choosing one bridge, in a carefully considered spot, to have distinctly different design and surface treatment than the other bridges.
Foot bridges and pedestrian underpasses have some factors in common: they are situated in areas with busy traffic, they are viewed at close range and at a slow pace. One must pay special attention to their appearance and finishing touches. Underpasses can be vivified in many ways: with paintings, ceramic tile and brick surfaces, patterning, etc. See Fig. 5, an underpass in Jyv�skyl�.
Finnra has dealt with issues involving the appearance and the surroundings of bridges in its directives; A bridge and its environment; How to design the surroundings of a bridge; and The aesthetics of flyover bridges.
THE FINISHING TOUCHES OF BRIDGE SURROUNDINGS
Adapting a bridge into its environment cannot be successful without the proper finishing of the immediate surroundings. Well executed finishing is also cost-effective since it makes the maintenance of the surroundings so much easier.The ways of finishing bridge's surroundings include landscaping, surface treatment of cones and ramps, structures pertaining to the bridge (stairs, supportive walls, fixtures), plants, drainage of the bridge site, etc.
A variety of methods for finishing the bridge surroundings has been introduced in Finnra's Bridge Repair Manual.
HOW DOES FINNRA PROMOTE BRIDGE DESIG THAT FIT THE ENVIRONMENT?
INVESTING IN THE PRE AND GENERAL PLANNING
How the bridge will affect its surroundings, and also the major part of its building costs. are determined during the initial planning phases. When a bridge is planned for a site of significant value, various visual aids are used in comparing alternative bridge designs and their suitability to the environment. These include perspective drawings, photo montage, scale models and videos. The modern CAD methods are a great help in creating visual aids and in comparing the alternatives.
Well executed visual presentations are excellent marketing tools when a project is introduced to the public and various interest groups, and the media. See Fig. 6, a photo montage of The K�rkistensalmi Bridge.
CLASSIFICATION OF BRIDGE SITES
In order to clarify and make it easier to take into consideration the environmental aspects in bridge planning, Finnra has developed aclassification system for bridge sites. The site's classification can be best determined at the inventory phase. There are four categories. Their characteristics define, among other things, how much the construction costs on various sites can exceed the cheapest alternative. It is a worthwhile notion that a bridge that is good-looking and well suited to its environment does not always require extra cost.
OPEN AND INTERACTIVE PLANNING PRACTICE
All the interest groups are represented in the project group in charge. In addition to the road engineer, the bridge expert, the landscape engineer and, if necessary, the architect, all participate in the project from the start. There are presentations to the public at suitable phases of the project, using a sufficient amount of visual aids. Relevant feedback is taken into consideration. The goal is to handle the administrative tasks as smoothly as possible, i.e. to win public acceptance for the good solutions even if they in some cases, would be more expensive to construct than the cheapest alternatives.DESIGN CONTESTS
In cases of particularly demanding bridge projects, idea contests in the general planningphase have brought in good results. Competitions can be open competitions or by invitation only. For instance, the Lumberjack's Candle Bridge in Rovaniemi, the T�htiniemr Bridge in Heinola and the K�rkistensalmi Bridge in Korpilahti (under construction), are results of competitions. However, it is usually necessary to develop further the won design.
Finnra has produced a publication describing the planning and construction phases of the Lumberjack's Candle Bridge in Rovaniemi (TIEL 3200085).
QUALITY REQUIREMENTS FOR THE CONTRACTORS' ALTERNATIVE DESIGNS
If contractors are given the possibility to present designs deviating from the basic designs made, the minimum requirements for the visual effects should be clearly indicated in the invitation to tender.GUIDANCE
Finnra has produced a number of directives on visual and environmental aspects of bridge design to serve as an aid to designers, see page 8 of this FinnContact issue.
OLLE KAROLA
Finnra