BRIDGE AESTHETICS

Aesthetics in Bridge Design

•The conventional order of priorities in bridge design is safety, economy,

serviceability, constructability, and so on. Somewhere down this list is aesthetics.

There should be no doubt in an engineer’s mind that aesthetics needs a priority

boost, and that it can be done without infringing upon the other factors.

•The belief that improved appearance increases the cost of bridges is unfounded and

oftentimes the most aesthetically pleasing bridge is also the least expensive.

•The additional cost is about 2% for short spans and only about 5% for long spans

•It is not necessary that everyone agrees as to what makes a bridge beautiful, but it is

important that designers are aware of the qualities of a bridge that influence the

perception of beauty

Definition Aesthetics and

Beauty •Aesthetics is the study of qualities of beauty of an object and of their

perception through our senses.

•Even if this particular aesthetic air be the last quality we seen in a bridge, its

influence nonetheless exists and has an influence on our thoughts and

actions. ( Santayana )

Qualities of Aesthetic Design “ There are not HARD & FAST rules or formulas for aesthetics of

bridge design. It finally gets down to the responsibility of each

designer on each project to make personal choices that will lead to

a more beautiful structure “

•Function

•Proportion

•Harmony

•Order & Rhythm

•Contrast & Texture

•Light and shadow

Function •For a bridge design to be successful, it must always safely perform its function.

•For example, a bridge is designed that fulfills every requirements of aesthetic

consideration and other requirements such as economy, constructability etc. but is

somehow unable to perform the function for which it was designed, then however

beautiful it is, it won’t be appealing.

•The very first notion of beauty in a bridge is that it performs its function efficiently and

people using it are satisfied.

•Moreover, the IMPORTANCE of function also enhances the BEAUTY or

AESTHETICS of the BRIDGE.

•For Example: A bridge across straits of Bosporus at Istanbul. This bridge replaces a

slow ferry boat trip, but it also serves the function of connecting two continents (Asia

and Europe).

Proportion

•Good proportions are fundamental to achieving an aesthetically pleasing bridge

structure

•It is generally agreed that when a bridge is placed across a relatively shallow

valley, the most pleasing appearance occurs when there are an odd number of

spans with span lengths that decrease going up the side of the valley.

•The bridge over a deep valley again should have an odd number of spans, but

should be of equal length. And slender girders and the tall, tapered piers can add to

the aesthetic pleasure

•Another consideration is the proportion between piers and girders. From strength

viewpoint, the piers can be relatively thin compared to the girders. However, when

a bridge has a low profile, the visual impression can be improved by having

strong piers supporting slender girders.

•Slender girders can be achieved if the superstructure is made continuous. Infact,

the superstructure continuity is the most important aesthetic consideration

•The proportions of a bridge change when viewed from an oblique angle.

Proportion

Harmony •Harmony means getting along well with others. The parts of the structure must be in

agreement with each other and the whole structure must be in agreement with its

surroundings.

Harmony between the elements of a bridge:

•It depends on the proportions between the span lengths and depth of girders, height

and size of piers, and negative spaces and solid masses.

Harmony between the whole structure and its surroundings

•The scale and size of a bridge structure should be relative to its environment.

•For Example, a long bridge crossing a wide valley can be large because the

landscape is large. But when a bridge is placed in an urban setting, the size must be

reduced.

Order and Rhythm

•Repeating similar spans too many times can become boring and monotonous

•It can also become aggravating to be driving down the interstate and seeing the

same standard over crossing mile after mile. The first one or two look just fine,

but after a while a feeling of frustration takes over the pleasing affect of however

the beautiful the construction.

•There is a place for contrast, as well as harmony in bridge aesthetics.

•All bridges do not have to blend in with their surroundings. “ when a bridge is

built in the middle of the country, it should blend in with the country side, but

very often, because of its proportions and dynamism, the bridge stands out

and dominates the landscape”

•The dominance seems to be specially true in case of Cable-stayed and

suspension bridges.

•There can also be contrast between the elements of a bridge to emphasize

the slenderness of the girders and the strength of the piers and abutments.

Contrast and Texture

•Texture can also be used to soften the hard appearance of concrete and

make certain elements less dominant.

•Large bridges seen from a distance must develop contrast through their form

and mass, but bridges with smaller spans seen up close can effectively use

texture.

Contrast and Texture

Light and Shadow

•Designer must be aware of how the shadows occur on the structure throughout

the day

•If the bridge is running north and south the shadows will be quite different than

if it is running east to west.

•For Example: When sunlight is parallel to the face of a girder or wall, small

imperfections in workmanship can cast deep shadows. Construction joints in

concrete may appear to be discontinuous and hidden welded stiffeners may no

longer be hidden.

•One of the most effective ways to make a bridge girder appear slender is to put

it partially or completely in shadow.

•Creating shadow becomes especially important with the use of solid

concrete safety barriers that make the girders look deeper than they

actually are.

•Shadows can be accomplished by cantilevering the deck beyond the

exterior girder.

•The effect of shadow on a box girder is further improved by sloping the

side of the girder inward.

Light and Shadow

BOX GIRDER

Clark Bridge in Alton, IL

Dames Port Florida

Dames Port Florida

Moveable Bridge

BRIDGE ARCHITECTURE BY R.S.RAKSHIT