Bridge engineering


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Bridge engineering

  1. 1. Learning Objectives <ul><li>To gain a comprehensive understanding of bridge loading </li></ul><ul><li>To develop a critical appreciation and comprehensive understanding of methods of structural Idealisation and analysis of bridge structures. </li></ul><ul><li>To develop a critical awareness of bridge inspection and assessment. </li></ul>
  2. 2. Lecture-1 <ul><li>Bridge Definition </li></ul><ul><li>Types of Bridges </li></ul><ul><li>Bridge Components </li></ul><ul><li>Aesthetic in Bridge Design </li></ul><ul><li>Selection criterion of a Bridge Type </li></ul><ul><li>Quiz </li></ul>
  3. 3. What is a Bridge? <ul><li>Bridge is a structure which covers a gap </li></ul><ul><li>Generally bridges carry a road or railway across a natural or artificial obstacle such as, a river, canal or another railway or another road </li></ul><ul><li>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. </li></ul>
  4. 4. What is a Bridge? Bridge is the KEY ELEMENT in a Transportation System
  5. 5. Structures for Transportation Beauty can be expressed in the structural efficiency, simplicity, and repetition of a bridge. Millau Viaduct, France
  6. 6. <ul><li>Substructure </li></ul><ul><li>Foundation (Pile/Spread footing) </li></ul><ul><li>Pier (Column) </li></ul><ul><li>Abutment </li></ul><ul><li>Superstructure </li></ul><ul><li>Any structure above bearing </li></ul><ul><li>Wearing surface </li></ul>Bridge Components
  7. 7. Bridge Components
  8. 8. Bridge Planning <ul><li>Traffic Studies </li></ul><ul><li>Hydro technical Studies </li></ul><ul><li>Geotechnical Studies </li></ul><ul><li>Environmental Considerations </li></ul><ul><li>Alternatives for Bridge Type </li></ul><ul><li>Economic Feasibility </li></ul><ul><li>Bridge Selection and Detailed Design </li></ul>
  9. 9. Span>6m Bridge Span<6m Culvert <ul><li>Short span : 6-30m </li></ul><ul><li>Medium span: 30-100m </li></ul><ul><li>Long span: >100m </li></ul>Bridge Span Length
  10. 10. Types of Bridges Steel Concrete Timber Hybrid Stone/Brick FRP Pedestrian Highway Railroad Short Medium Long Slab Girder Truss Arch Suspension Cable-Stayed Material Usage Span Structural form
  11. 11. Material and Fabrication <ul><li>Materials </li></ul><ul><li>Masonry (brick, rock) </li></ul><ul><li>Timber </li></ul><ul><li>Reinforced Concrete </li></ul><ul><li>Prestressed Concrete </li></ul><ul><li>Iron </li></ul><ul><li>Steel </li></ul><ul><li>Composites </li></ul><ul><li>Fabrication </li></ul><ul><li>Precast (RC, PC) </li></ul><ul><li>Cast in place (RC, PC) </li></ul><ul><li>Pre tensioned (PC) </li></ul><ul><li>Post tensioned (PC) </li></ul><ul><li>Prefabricated (Steel) </li></ul><ul><li>Rivet (steel) </li></ul><ul><li>Bolted (steel, timber) </li></ul>Types of Bridges
  12. 12. Bristol Bridge, Bristol, UK Highway Bridges
  13. 13. Electric Wharf Footbridge, UK London Millennium Footbridge, UK Pedestrian Bridges
  14. 14. The Forth Railway Bridge, Scotland Thames Ditton Railway bridges Railway Bridges
  15. 15. <ul><li>Basic types based on structural form: </li></ul><ul><li>Arch </li></ul><ul><li>Beam </li></ul><ul><li>Cantilever </li></ul><ul><li>Truss </li></ul><ul><li>Cable Stayed </li></ul><ul><li>Suspension </li></ul>Types of Bridges
  16. 16. Types of Bridges <ul><li>Arch Bridge </li></ul><ul><li>Arch bridges are one of the oldest types of bridges and have great natural strength. </li></ul><ul><li>Instead of pushing straight down, the weight of an arch bridge is carried outward along the curve of the arch to the supports at each end. </li></ul><ul><li>These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out. </li></ul>
  17. 17. Forces When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart. <ul><li>Beam/Girder Bridge </li></ul><ul><li>The most basic type of bridge </li></ul><ul><li>Typically consists of a beam simply supported on each side by a support and can be made continuous later </li></ul><ul><li>Typically inexpensive to build </li></ul>Types of Bridges
  18. 18. <ul><li>Beam/Girder Bridge </li></ul><ul><li>Currently, most of the beam bridges are precast (in case of RC and PC) or prefabricated </li></ul><ul><li>Most are simply-supported </li></ul><ul><li>Some are made continuous on site </li></ul>Simply supported Cantilever Continuous Types of Bridges
  19. 19. <ul><li>Cantilever Bridge </li></ul><ul><li>In a cantilever bridge, the roadway is constructed out from the pier in two directions at the same time so that the weight on both sides counterbalance each other </li></ul><ul><li>Notice the larger section at the support to resist the negative moments </li></ul>Firth of Forth Bridge, Scotland 521m span Types of Bridges
  20. 20. <ul><li>Truss Bridge </li></ul><ul><li>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. </li></ul><ul><li>Typical Span lengths: 40m-500m </li></ul>Types of Bridges
  21. 21. <ul><li>Suspension bridge needs to have very strong main cables </li></ul><ul><li>Cables are anchored at the abutment </li></ul>Suspension Bridges London Tower Bridge (1894),UK Types of Bridges
  22. 22. Types of Bridges <ul><li>Cable-stayed Bridge </li></ul><ul><li>All the forces are transferred from the deck through the cables to the pylon </li></ul><ul><li>Roadway deck can be : </li></ul><ul><li>(prestressed) Concrete Box Deck </li></ul><ul><li>Steel Box Deck </li></ul><ul><li>Steel Truss Deck </li></ul>
  23. 23. <ul><li>Consider the following: </li></ul><ul><ul><li>Span length </li></ul></ul><ul><ul><li>Bridge length </li></ul></ul><ul><ul><li>Beam spacing </li></ul></ul><ul><ul><li>Material available </li></ul></ul><ul><ul><li>Site conditions (foundation, height, apace constraints) </li></ul></ul><ul><ul><li>Speed of construction </li></ul></ul><ul><ul><li>Aesthetics </li></ul></ul><ul><ul><li>Cost </li></ul></ul><ul><ul><li>Access for maintenance </li></ul></ul>Which Type Should I Use?
  24. 24. Selection of a Bridge Type by Span Lengths
  25. 25. <ul><li>An ugly bridge, however safe, serviceable and inexpensive, is not a good bridge </li></ul><ul><li>Long span bridge over a river can be a land mark: thus aesthetics should be an important factor </li></ul><ul><li>Bridge should blend with the environment </li></ul><ul><li>Smooth transition between members </li></ul><ul><li>Determinant of bridge’s appearance (in order of importance) </li></ul><ul><li>Vertical and Horizontal geometry relative to surrounding topography and other structures </li></ul><ul><li>Superstructure type and shape </li></ul><ul><li>Pier/abutment placement and shape </li></ul><ul><li>Color, surface texture, Signing, Lighting & landscaping </li></ul>Aesthetics : What it means?
  26. 26. Aesthetics : What it means?
  27. 27. <ul><li>Context </li></ul><ul><li>Comprehensive </li></ul><ul><li>Cost </li></ul><ul><li>Constructability </li></ul><ul><li>Adapted from “Restore Aesthetics as Design Priority” by Jeffery Grob </li></ul>The Four “C’s” of Bridge Aesthetics
  28. 28. <ul><li>Context </li></ul><ul><li>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. </li></ul><ul><li>Comprehensive </li></ul><ul><li>The designs that work best are those that take aesthetics in to account right from start. </li></ul>The Four “C’s” of Bridge Aesthetics
  29. 29. <ul><li>Cost </li></ul><ul><li>No discussion of design considerations can be conducted realistically without asking “How much is it going to cost?”. </li></ul><ul><li>Constructability </li></ul><ul><li>No discussion of aesthetics is complete without considering constructability. </li></ul>The Four “C’s” of Bridge Aesthetics
  30. 30. <ul><li>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 </li></ul><ul><li>Function </li></ul><ul><li>Proportion </li></ul><ul><li>Harmony </li></ul><ul><li>Order & Rhythm </li></ul><ul><li>Contrast & Texture </li></ul>Qualities of Aesthetic Design
  31. 31. <ul><li>For a bridge design to be successful, it must always safely perform its function. </li></ul><ul><li>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. </li></ul><ul><li>The very first notion of beauty in a bridge is that it performs its function efficiently and people using it are satisfied. </li></ul>Function
  32. 32. <ul><li>Good proportions are fundamental to achieving an aesthetically pleasing bridge structure </li></ul><ul><li>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 to the side of the valley. </li></ul><ul><li>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 </li></ul>Runnymede Bridge, River Thames (1962) <ul><li>The proportions of parapet, spandrel, arch etc. are very important on such bridges. </li></ul>Proportion
  33. 33. <ul><li>Slender girders can be achieved if the superstructure is made continuous. In fact, the superstructure continuity is the most important aesthetic consideration </li></ul><ul><li> </li></ul>Athlone Bypass Bridge, Ireland A shallow deck, straight haunches extended into piers and broad ,shallow cutwaters combine to give a strong and distinctive effect. Byker Viaduct, Tall, slender divided piers, straight haunches and a shallow deck. Proportion
  34. 34. <ul><li>Harmony between the elements of a bridge: </li></ul><ul><li>It depends on the proportions between the span lengths and depth of girders, height and size of piers, and negative spaces and solid masses. </li></ul><ul><li>Harmony between the whole structure and its surroundings </li></ul><ul><li>The scale and size of a bridge structure should be relative to its environment. </li></ul>A9 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. Harmony
  35. 35. <ul><li>Developing a rhythm to the bridge is also important. For example, spans should match where possible or at least demonstrate a consistent order. </li></ul><ul><li>The cumulative effect of all bridge elements including lighting columns, barrier support and pier should be considered. </li></ul>For example, outer spans of this bridge are not the same dimension and the symmetry of the bridge is affected. Order and Rhythm
  36. 36. <ul><li>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” </li></ul>Avon Bridge, M40,Warwick A lack of much detailing gives ‘wallpaper’ effect 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. Contrast, Texture & Finishes
  37. 37. Establish requirements Setting design objectives and principles Develop design Engineering Process Analysis of design Design Refinement Implementation Plan Understand context
  38. 38. Bridge Design Process Project Scope Location/Survey Final Design Construction Preliminary Design <ul><li>Function (To bridge or not? Replace or remove?) </li></ul><ul><li>Who is User? </li></ul><ul><li>Where is best spot? </li></ul><ul><li>Many decisions. </li></ul><ul><li>Project Funding and Scope finalized. </li></ul><ul><li>Plans, Specs, Estimates. </li></ul>
  39. 39. Quiz <ul><li>Question 1: </li></ul><ul><li>What are the oldest type of Bridges? </li></ul><ul><li>A. Beam </li></ul><ul><li>B. Arch </li></ul><ul><li>C. Cable-stayed </li></ul><ul><li>D. Suspension </li></ul>
  40. 40. Quiz <ul><li>Question 2: </li></ul><ul><li>Which type of bridge is normally the longest type? </li></ul><ul><li>A. Beam </li></ul><ul><li>B. Arch </li></ul><ul><li>C. Cable-stayed </li></ul><ul><li>D. Suspension </li></ul>
  41. 41. Quiz <ul><li>Question 3: </li></ul><ul><li>Which type of bridge is the cheapest? </li></ul><ul><li>A. Beam </li></ul><ul><li>B. Arch </li></ul><ul><li>C. Cable-stayed </li></ul><ul><li>D. Suspension </li></ul>
  42. 42. Quiz <ul><li>Question 4: </li></ul><ul><li>Which Quality of Aesthetic Design is the most important? </li></ul><ul><li>A. Rhythm </li></ul><ul><li>B. Function </li></ul><ul><li>C. Proportion </li></ul><ul><li>D. Harmony </li></ul>
  43. 43. Quiz <ul><li>Question 5: </li></ul><ul><li>During this step, the designs are studied based on their merit in relationship to strength, cost, market appeal, and manufacturability. </li></ul><ul><li>A. Identify Problems </li></ul><ul><li>B. Modify the Implementation </li></ul><ul><li>C. Determine Constraints </li></ul><ul><li>D. Analysis of Design </li></ul>