Learning Objectives To gain a comprehensive understanding of

Learning Objectives To gain a comprehensive understanding of bridge loading To develop a critical appreciation and comprehensive understanding of methods of structural Idealisation and analysis of bridge structures. To develop a critical awareness of bridge inspection and assessment.

Lecture-1 Bridge Definition Types of Bridges Bridge Components Aesthetic in Bridge Design Selection criterion of a Bridge Type Quiz

What is a Bridge? Bridge is a structure which covers a gap Generally bridges carry a road or railway across a natural or artificial obstacle such as, a river, canal or another railway or another road Bridge is a structure corresponding to the heaviest responsibility in carrying a free flow of transport and is the most significant component of a transportation system in case of communication over gaps for whatever reason such as aquatic obstacles, valleys and gorges etc.

Bridge is the KEY ELEMENT in a Transportation System

Structures for Transportation Beauty can be expressed in the structural efficiency, simplicity, and repetition of a bridge.

Substructure Superstructure Foundation (Pile/Spread footing) Any structure above bearing Wearing surface Pier (Column) Abutment

Bridge Planning Traffic Stu dies Hydro tec hnical Studies Geotechnical Studies Environmental Considerations Alternatives for Bridge Type Economic Feasibility Bridge Selection and Detailed Design

Short span : 6 -30 m Medium span: 30 -100 m Long span: >100 m Span>6 m Span<6 m Bridge Culvert

Material Usage Span Structural form Steel Concrete Timber Hybrid Stone/Brick FRP Pedestrian Highway Railroad Short Medium Long Slab Girder Truss Arch Suspension Cable-Stayed

Material and Fabrication Materials Fabrication Masonry (brick, rock) Precast (RC, PC) Timber Cast in place (RC, PC) Reinforced Concrete Pre tensioned (PC) Prestressed Concrete Post tensioned (PC) Iron Prefabricated (Steel) Steel Rivet (steel) Composites Bolted (steel, timber)

Bristol Bridge, Bristol, UK

London Millennium Footbridge, UK Electric Wharf Footbridge, UK

Thames Ditton Railway bridges The Forth Railway Bridge, Scotland

Basic types based on structural form: Arch Beam Cantilever Truss Cable Stayed Suspension

Types of Bridges Arch Bridge Arch bridges are one of the old est types of bridges and have great natural s trength. Instead of pushing straight down, the weight of an arch bridge is carried out ward along the curve of the arch to the support s at each end. These supports, called tments, the abu carry the load and keep the ends of from t he bridge spreading out.

Beam/Girder Bridge The most basic type of bridge Typically consists of a beam simply supported on each side by a support and can be made continuous later Typically inexpensive to build Forces When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

Beam/Girder Bridge Currently, most of the beam bridges are precast (in case of RC and PC) or prefabricated Most are simply-supported Some are made continuous on site Simply supported Cantilever Continuous

Cantilever Bridge In a cantilever constructed out directions at the weight on both each other bridge, the roadway is from the pier in two same time so that the sides counterbalance Notice the larger section at the support to resist the negative moments Firth of Forth Bridge, Scotland 521 m span

Truss Bridge All beams in a truss bridge are straight. Trusses are comprised of many small beams that together can support a large amount of weight and span great distances. Typical Span lengths: 40 m-500 m

Suspension Bridges Suspension bridge needs to have very strong main cables Cables are anchored at the abutment London Tower Bridge (1894), UK

Types of Bridges Cable-stayed Bridge All the forces are transferred from the deck through the cables to the pylon Roadway deck can be : (prestressed) Concrete Box Deck Steel Truss Deck

Consider the following: Span length Bridge length Beam spacing Material available Site conditions (foundation, height, apace constraints) Speed of construction Aesthetics Cost Access for maintenance

An ugly bridge, however safe, serviceable and inexpensive, is not a good bridge Long span bridge over a river can be a land mark: thus aesthetics should be an important factor Bridge should blend with the environment Smooth transition between members Determinant of bridge’s appearance (in order of importance) • Vertical and Horizontal geometry relative to surrounding topography and other structures • Superstructure type and shape • Pier/abutment placement and shape • Color, surface texture, Signing, Lighting & landscaping

Context Comprehensive Cost Constructability Adapted from “Restore Aesthetics as Design Priority” by Jeffery Grob

Context All projects from a simple creek bridge to the longest multi span water crossing must first be considered with a view to the context in which it is located. Comprehensive The designs that work best are those that take aesthetics in to account right from start.

Cost No discussion of design considerations can be conducted realistically without asking “How much is it going to cost? ”. Constructability No discussion of aesthetics is complete without considering constructability.

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

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.

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 an odd number of spans with span lengths that decrease going up to 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. Slender girders and the tall, tapered piers can add to the aesthetic pleasure The proportions spandrel, arch important on such bridges. of etc. are parapet, very Runnymede Bridge, River Thames (1962)

Slender girders can be achieved if the superstructure is made continuous. In fact, the superstructure continuity is the most important aesthetic consideration Byker Viaduct, Tall, slender divided piers, straight haunches and a shallow deck. Athlone Bypass Bridge, Ireland A shallow deck, straight haunches extended into piers and broad , shallow cutwaters combine to give a strong and distinctive effect.

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 environment. A 9 Dornoch Firth Bridge, Scotland. Constant depth box on simple supports, a low key solution suiting a shallow estuarial crossing. River Camel Viaduct, Wadebridge, Cornwall: Simple constant depth girder viaduct with clean and neat lines. its

Developing a rhythm to the bridge is also important. For example, spans should match where possible or at least demonstrate a consistent order. The cumulative effect of all bridge elements including lighting columns, barrier support and pier should be considered. For example, outer spans of this bridge are not the same dimension and the symmetry of the bridge is affected.

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” For Example: When the deck line is not expressed, the scale looks odd due to paucity of detail. Also the coursing of the stone or brick then follow neither the arch, the deck nor the parapet, so invariably it tends to be horizontal. G-Mex bridge, Manchester Metrolink. The steel structure contrasts boldly with its surroundings. Avon Bridge, M 40, Warwick A lack of much detailing gives ‘wallpaper’ effect

Establish requirements Understand context Design Refinement Setting design objectives and principles Implementation Plan Develop design Analysis of design

Bridge Design Process • Function (To bridge or not? Replace or remove? ) • Who is User? • Where is best spot? Specs, • Plans, Estimates. • Many decisions. • Project Funding and Scope finalized.

Quiz Question 1: What are the oldest type of Bridges? A. Beam B. Arch C. Cable-stayed D. Suspension

Quiz Question 2: Which type of bridge is normally the longest type? A. Beam B. Arch C. Cable-stayed D. Suspension

Quiz Question 3: Which type of bridge is the cheapest? A. Beam B. Arch C. Cable-stayed D. Suspension

Quiz Question 4: Which Quality of Aesthetic Design is the most important? A. Rhythm B. Function C. Proportion D. Harmony

Quiz Question 5: During this step, the designs are studied based on their merit in relationship to strength, cost, market appeal, and manufacturability. A. Identify Problems B. Modify the Implementation C. Determine Constraints D. Analysis of Design