Metallic Bridges Str403
Total Page:16
File Type:pdf, Size:1020Kb
METALLIC BRIDGES STR403 Sherif A. Mourad Professor of Steel Structures and Bridges Faculty of Engineering, Cairo University Lecture 1 – February 2020 Sherif A. Mourad 1 Introduction Course: STR403 Instructors: Prof. Sherif Ahmed Mourad. Prof. Mohammed Hassanein Soror. Lecture: Monday 8:30-10:00 or 10:15-11:45 Grading: 70% final 15% midterm 15% term work Sherif A. Mourad 2 STR403 - Metallic Bridges Winter 2020 1 Introduction Why a course in steel bridge design? Sherif A. Mourad 3 Lecture Outline • Definition of a bridge. • Historical background. • Bridge forms. • Classification of bridges (Structural system, Material of construction, Use, Position, Span, …). • Design considerations. • Course outline. Sherif A. Mourad 4 STR403 - Metallic Bridges Winter 2020 2 Definition of a Bridge A bridge is a structure that carries a service (which may be highway or railway traffic, a footpath, public utilities, etc.) over an obstacle (which may be another road or railway, a river, a valley, etc.), and then transfers the loads from the service via the superstructure through the bridge substructure to the foundation level. Sherif A. Mourad 5 Definition of a Bridge Sherif A. Mourad 6 STR403 - Metallic Bridges Winter 2020 3 Historical background The historical development of bridges best illustrates the progress of structural engineering from ancient times up to the present century. In particular the development in steel bridges equates with the progress in structural analysis, theory of strength of materials and materials testing, since all of them were increasingly stimulated by the need for bridging larger spans and building more economically with the new construction method. Sherif A. Mourad 7 Historical background The simplest type of a bridge is stepping stones, so this may have been one of the earliest types. People from the stone age also built a form of boardwalk across marshes that are around 6000 years old. Undoubtedly ancient peoples would also have used log bridges; that is a timber bridge that fall naturally or are intentionally felled or placed across streams. Sherif A. Mourad 8 STR403 - Metallic Bridges Winter 2020 4 Historical Background Probably the oldest form of bridges to cross waterways is the stepping stone bridges. Sherif A. Mourad 9 Historical Background Some of the first man-made bridges with significant span were probably intentionally felled trees. Sherif A. Mourad 10 STR403 - Metallic Bridges Winter 2020 5 Historical Background There is a drawing displayed on a monument of Sethos I at Karnak. According to this drawing the strong place of Khetam was situated on both banks of the river Nile and the two opposite parts of the fortress were joined by a great bridge. A “Qanthareh” as it is called in Arabic. Sherif A. Mourad 11 Historical Background The Indian Epic literature Ramayana provides mythological accounts of bridges constructed from India to Sri Lanka by the army of Sri Rama, the mythological King of Ayodhya. The recent satellite photograph depicts the existence of this bridge, referred to in Ramayana. Sherif A. Mourad 12 STR403 - Metallic Bridges Winter 2020 6 Historical Background Holzbrücke Rapperswil-Hurden is a wooden pedestrian bridge between the city of Rapperswil and the village of Hurden crossing the upper Lake Zürich (Obersee) in Switzerland. The prehistoric timber piles discovered to the west of the Seedamm date back to 1523 BC. Sherif A. Mourad 13 Historical background The oldest datable bridge in the world still in use is the slab-stone single-arch bridge over the river Meles in Izmir (formerly Smyrna), Turkey, which dates from c. 850 BC. Remnants of Mycenaean bridges dated c. 1600 BC exist in the neighborhood of Mycenae, Greece over the River Havos. Sherif A. Mourad 14 STR403 - Metallic Bridges Winter 2020 7 Historical Background Chinese built big bridges of wooden construction, and later stone bridges, and the oldest surviving stone bridge in China is the Zhaozhou Bridge built around 605 AD during the Sui Dynasty. This bridge is also historically significant as it is the world’s oldest open- stone segmental arch bridge. Sherif A. Mourad 15 Historical Background The ancient Romans were great bridge builders. Ancient Romans used cement (called pozzolana) consisting of water, lime, sand, and volcanic rock to provide bond between stone elements. Sherif A. Mourad 16 STR403 - Metallic Bridges Winter 2020 8 Historical background The discovery of a new material, iron, and later steel, contributed a lot to the design and construction of bridges. However, by the time the new material was ready for use in larger structures there already existed a quite highly developed technology in bridge building, namely for bridges in timber and bridges in stone. Sherif A. Mourad 17 Historical background It is important to mention that the technologies of bridge building at that time were based on individual intuition of outstanding "masters" and on the experience passed down through the generations rather than on rules of mechanics and mathematics. The significance of preserving the knowledge of bridge building and of extending it was closely connected with military purposes and the interests of trade in ancient times. Sherif A. Mourad 18 STR403 - Metallic Bridges Winter 2020 9 Historical background The Romans even established a separate caste - the "pontifices" (bridge makers) - headed by the "pontifex maximum", which was also one of the titles of the Roman emperors. Similar reasons motivated the French kings, e.g. Louis XIV, and later Napoleon, to support the new engineering schools (Ecole de Ponts et Chaussés and Ecole Polytechnique). Sherif A. Mourad 19 Bridge Form Bridges may be classified according to the form by which they support the loading into two main types: 1. Bridges which carry loads mainly in flexure. 2. Bridges which carry loads mainly as axial forces. Sherif A. Mourad 20 STR403 - Metallic Bridges Winter 2020 10 Bridges carrying loads in flexure The majority of bridges are of this type. The loads are transferred to the ground by slabs or beams acting in flexure, i.e. the bridges obtain their load carrying resistance from the ability of the slabs and beams to resist bending moments and shear forces. This type of bridge is referred to generally as a girder bridge. A wide range of structural forms is possible, as shown in the next Figure which indicates a typical elevation of a girder bridge with a number of terms being defined. Sherif A. Mourad 21 Bridges carrying loads in flexure Sherif A. Mourad 22 STR403 - Metallic Bridges Winter 2020 11 Bridges carrying loads as axial This type can be further subdivided into those bridges in which the primary axial forces are compressive (arches) and those in which these forces are tensile (suspension bridges and cable stayed bridges), or a combination of both (trusses). Such forces normally have to be resisted by members carrying forces of the opposite sense. Figures 2a to 2d show the basic structural systems for some typical layouts.. Sherif A. Mourad 23 Bridges carrying loads as axial Note that flexure is also important in such structures. Certainly, in most suspension bridges, flexure of the stiffening girder is not a primary loading in that overstress is unlikely to cause overall failure; however, in cable stayed bridges (particularly if the stays are widely spaced) flexure of the girder is a primary loading. Similarly, in arch bridges, non-uniform loading of the rib can cause primary bending moments to be developed in it and may well govern the arch design. Sherif A. Mourad 24 STR403 - Metallic Bridges Winter 2020 12 Bridges carrying loads as axial Sherif A. Mourad 25 Arch stability The arch is made up of blocks, and will stand with nothing attaching them together. The central block stays up because it is wider at the top than at the bottom, so to fall down it would have to push the neighboring blocks outwards. As long as these are held securely, the central block can’t fall down. So by the combination of friction and strong abutments holding the sides of the arch, the arch remains stable. Sherif A. Mourad 26 STR403 - Metallic Bridges Winter 2020 13 Bridge Classification Material of Construction • Concrete. • Steel. • Stone. • Masonry. • Timber. Sherif A. Mourad 27 Material of Construction Why steel bridges? What are the steel grades? What are the mechanical properties? Sherif A. Mourad 28 STR403 - Metallic Bridges Winter 2020 14 Egyptian Standard Specifications Steel Egyptian Specifications STR403 - Metallic Bridges Winter 2020 15 Steel Egyptian Specifications Steel Egyptian Specifications STR403 - Metallic Bridges Winter 2020 16 Steel Egyptian Specifications Steel Egyptian Specifications STR403 - Metallic Bridges Winter 2020 17 Bridge Classification Use • Roadway Bridges. • Railway Bridges. • Footbridges. • Pipeline Bridges. • Conveyor Bridges. Sherif A. Mourad 35 Roadway Bridges Sherif A. Mourad 36 STR403 - Metallic Bridges Winter 2020 18 Railway Bridges Sherif A. Mourad 37 Pedestrian Bridges Sherif A. Mourad 38 STR403 - Metallic Bridges Winter 2020 19 Pipe Bridges Sherif A. Mourad 39 Conveyor Bridges Sherif A. Mourad 40 STR403 - Metallic Bridges Winter 2020 20 Bridge Classification Traffic Level Moving Bridges are classified according to the position of bridge floor into: • Deck • Through Sherif A. Mourad 41 Deck Bridge Sherif A. Mourad 42 STR403 - Metallic Bridges Winter 2020 21 Through Bridge Sherif A. Mourad 43 Bridge Classification Bridges are classified according to the structural system of the main girder into: • Beam/Plate Girder Bridges. • Frame Bridges. • Arch Bridges. • Truss Bridges. • Cable-Stayed Bridges. • Suspension Bridges Sherif A. Mourad 44 STR403 - Metallic Bridges Winter 2020 22 Beam Bridges Beam Bridges may be: • Rolled section or Plate Girder. • Simply-supported or Continuous. • Straight or Haunched. • Steel or Composite. • I-section or box. Sherif A. Mourad 45 Frame Bridges Sherif A. Mourad 46 STR403 - Metallic Bridges Winter 2020 23 Arch Bridges Sherif A. Mourad 47 Truss Bridges Sherif A. Mourad 48 STR403 - Metallic Bridges Winter 2020 24 Cable-Stayed Bridges Sherif A.