Notification No.3, dated the 29^th January, 2005

Subject: Amendment to IRC:SP:54-2000 "Project Preparation Manual for Bridges"

IRC:SP:54-2000 "Project Preparation Manual for Bridges" was published in April, 2002 and Reprinted in September, 2003.

The Indian Roads Congress has decided to amend the above document and accordingly Amendment No.1 annexed herewith is hereby notified. This Amendment shall be effective from the 1^st March, 2005.

Encl. As above

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Amendment No.1 to IRC:SP:54-2000 "Project Preparation Manual for Bridges" (First published in April, 2002 and Reprinted in September, 2003)

Sub Clause 5.7.8. Aesthetic considerations (page 22)

Add: "A brief guidelines in this regard is given at Appendix-I." At the end of the Sub Clause and add Appendix -1 attached herewith at the end of the document.

The above amendment shall be effective from the 1^st March, 2005.




Aesthetic Design of Bridge Structures
1. Why Aesthetic Design?
1.1. Aesthetic design is a contributor to society mainly through the intangible mechanism of enhancing the quality of life. It is readily acknowledged that engineers have not taken sufficient cognizance of this issue. It is also recognised that synergy has not been achieved between engineers and architects leading to mutually independent and often contradictory conception of the parameters of bridge design. When bridge aesthetics gets completely amputated from structural design consideration what results is an uninspiring bridge and some times even ugly ones most unsuited for the environment.

1.2 There is a need to acconunodate aesthetics in bridge design for the dual purpose of enhancing the quality of life as well as to resurrect the image of bridge engineers. The difficult-to-quantify benefit as regards the quality of life has to be correlated with the nuts-and-bolts aspect of project execution including costs.

2. Issues of Aesthetic Design of Bridges
2.1. In considering aesthetics of bridges, one of the important factors is the location from which the bridge will be viewed and also the background and foreground vistas. The relative importance/occurrence of the viewpoint is also a matter of major significance.

2.2. The abstract structural form, by itself as well as in conjunction with the environment, is a major issue of aesthetic design. The issues influencing the structural forms contributions to aesthetic designs can be characterised in terms of efficiency, harmony and aesthetic shapes.

3. Efficiency
3. 1. Engineers are conditioned to think of efficiency of structures mainly in terms of optimal use of material. But from the viewpoint of aesthetics, the visual expression of efficient structural function is the fundamental criteria of elegance in bridge design. It may be mentioned that these two conceptaulisations may not be at odds with each other, as in most cases, tree flow of forces is the major requirement for both. Visual expression of efficiecy is related to the level of transparency and slenderness.

3.2. The parameters of transparency are well understood to correlate with the appearance of the bridge from the various viewing angles, suitably weighted. Even the perceived instability of a structural form (for example, a single round column for a bridge span) is visually unacceptable forcing a compromise between transparency and perception of stability. Transparency can be achieved even in situations not readily amenable, for example, .long bridges with many short spans.

Slenderness, expressed as a ratio of span length to girder depth, is not a reliable measure of visual slenderness, dependent highly as it is on the viewing position and also the interplay between light and shadow. Visual slenderness is the perceived ratio of the uninterrupted length of the superstructure to the perceived dimension in the orthogonal directions. Therefore, it is evident that the bridge superstructure dimension in three principal directions are the controlling measures in achieving the desired visual slenderness.

4. Harmony
Harmony amongst all elements of a bridge makes major contributions to aesthetic design and is achieved through visual means, such as, symmetry, order and regularity and also through technical means by property defining the structural function of each component, etc.

5. Structure and Environment
The character of the landscape should be reflected in the structural form. Topographical features that enhance the appearance of bridges should be identified and, if possible, incorporated into the form.

6. Factors of Aesthetic Design
6.1. It is clearly understood that a stern cost-benefit analysis cannot be carried out in the matter as the factors on one side are tangible and quantifiable, and on the other, they are not. But general guidelines can be developed as to how to strike a balance between the contending factors. One of the guidelines could be a general restriction on increase of cost of the project. This limit is to be decided by the owner(s) based on his/their financial capability. It can also be tied to the cost of the most economical alternative, though a marginally more expensive alternative might have been adopted based on some other considerations.

6.2. The other factor is the constructability of the structure as demanded by considerations of aesthetics. It is agreed that variety and diversity adds spice to the environment. However, such concerns should not impose unjustifiable efforts on the I constructability of the bridge. Classical and efficient erection/construction techniques alone can restrict the escalation of construction costs.

6.3. A rational aesthetic design should advocate use of locally available material. In addition to perhaps contributing to reduction in cost, such a philosophy imparts a local colour to the structure, certainly an added feature of aesthetic design as it implicitly advocates congruence between the structure and the immediate environment. Tendency to adopt an alternative merely to arrest the attention of the viewers or be willingly provocative, with no consideration towards implications on cost, constructability and -use of appropriate material should be generally avoided.

7. Conclusions
7.1. An aesthetic bridge proclaims itself through its own visual, as well as structural expression, in concert with the environment. Incorporating aesthetic features, though these are highly subjective, do not lead to excessive additional cost. Ingenuity lies in limiting the extra cost due to aesthetic factors.

7.2 While considering aesthetic aspects of a bridge, the design of bridges should follow function and definitely not fancy. Illogical forms, driven as they may be by vanity of any and all concerned with a bridge project, should be avoided, bearing in mind that originality without structural efficiency and elegance is eccentricity. "Structural architecture" is the name given to aesthetic design that achieves a commendable balance amongst structural, functional and aesthetic demands on the bridge.

7.3. Cost considerations have to be taken into account. Guidelines that may be developed based on value engineering analyses suitably adjusted to account for the subjectivity inherent in aesthetic considerations may be allowed to be violated only marginally and that too only on rare occasions.

7.4. The presence of scale effect is an antidote to the sometimes overbearing concern as to the cost of the structure and helps in not stifling creativity and artistic expression on that score. An innovative concept can be tested, or going beyond, even demonstrated in a small bridge, say of the kind of a pedestrian bridge, whose function is very well defined as to the type of loads it will be called on to carry. The additional cost of any exceptional solution - structurally consistent and aesthetically outstanding of a small facility is easily justifiable and might not cause dissonance. In fact, we often come across such 'signature' small bridges, usually pedestrian facilities.