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Bridge Engineering

Cantilever Bridges – Types, Advantages & Disadvantages

A cantilever bridge comprises structures that protrude horizontally into space and are only supported on one end. A cantilever is something like a balcony that protrudes from a building. The cantilevers on small footbridges may be simple beams; however, major cantilever bridges designed to handle road or rail traffic require structural steel trusses or prestressed concrete box girders. The steel truss cantilever bridge was a great engineering accomplishment initially implemented. It can span over 460 meters (1,500 feet) and be built more simply at challenging crossings due to the lack of falsework (temporary supports). The Hassfurt Bridge spans the Main River in Germany and has a central span of 38 meters (124 feet), considered the first contemporary cantilever bridge.

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Types of Bridges

Introduction
Bridges can be basic structures or massive, awe-inspiring pieces of art – or everything in between. A bridge serves a single purpose as long as it transports us across a gap that would otherwise be difficult (or even impossible) to cross. Bridges have played a significant part in developing our earliest civilizations, the diffusion of knowledge, local and global trade, and the emergence of transportation during the previous several thousand years.

Initially made out of most simple materials and designs, bridges soon evolved and enabled the carrying of wide deckings and spanning of large distances over rivers, gorges, inaccessible terrain, enormously elevated surfaces and pre-built city infrastructures. Starting with the 13th century BC Greek Bronze Age, arched stone bridges quickly spread worldwide, eventually leading to the rise of steel, iron and other materials in bridges that can span kilometres.

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Use of Ancient Titan’s For Development of New Suspension Bridge

By
Shubham Sunil Malu

ABSTRACT
Suspension means to suspend something as system of spring and shock absorbers which supports vehicles on its wheels and make it more comfortable to write. In likely suspended bridge is a bridge which is suspended from cables running between the towers. We have discussed here how the bridge works and the force accounted in the bridge due to various load acting on it like wind, water, moving vehicles.
Here we discus the construction sequence in suspension bridge & have discussed the disaster in Tacoma narrow bridge in detail.

1.0 INTRODUCTION
“Suspension bridge is one where cables or ropes or chains are stung across the obstacle & the deck is suspended from these cables”

Anatomy of a Bridge

Deck –  For pedestrian, train, and / or automobile traffic.
Supports – The towers are the supports.
Span – Describes the distance between towers.
Foundations – The supports rest on the foundations.
Approaches – The approaches are the roads leading up to the bridge.
Long wire cables – are strung over the towers and secured to the anchors on land.
Hangers – run from the cables to the deck hold it up.

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Bridge Design Practice in North America – An Overview

By
Isidro P. Buquiron

Introduction
The primary objective of code specifications in bridge design is public safety. Thus, in the United States, the American Association of State Highway Officials (AASHO) was formed in 1914 which later on issued the first edition of the Standard Specifications for Highway Bridges and Incidental Structures in 1931 [1]. The concept of safety provided in this document is to guarantee that all structural element in the system in part and as a whole must have minimum resistance that will exceed the load and demand applied to the structure during its specified years of service. In Canada, specifically in Ontario, the American Association of State Highway and Transportation Officials (AASHTO) specification was widely used, however unofficially before the first edition of the Ontario Highway Bridge Design Code (OHBDC) was issued in 1978 [2].

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Lateral Torsional Buckling of Long Span Suspension Bridge: Geometrically Nonlinear Analysis Under Wind Load

By
D.Ishihara, H.Yamada, H.Katsuchi, and E.Sasaki
Yokohama National University

Abstract
There are plans of constructing bridges longer span like Messina strait bridge. This trend causes the necessity of discussing on the problems of instability analysis such as lateral-torsional buckling. However, lateral torsional buckling analysis of long span bridge is not sufficiently taken yet. For that reason, we apply the Abaqus/Standard to solve the high nonlinear problem. The analysis object is Akashi-kaikyo Bridge which is the longest bridge in the world. This paper presents how to analyze the lateral-torsional buckling of long span bridge applying wind load.

Keywords
Lateral Torsional Buckling, Suspension Bridge, Aerodynamics

Introduction
By now, a lot of long span suspension bridges have built and their lengths keep growing. As a result, their girder stiffness is relatively reduced and their strengths for wind force are also decreasing. Therefore, numerous futter analysis and experiments were executed. On the other hand, it is as well as important to investigate the lateral torsional buckling strengths of suspension bridges, but the investigations have never been made for decades. Certainly, we just use Hirai-Okauchi formulation that was proposed around 60’s to confirm the stability against the problem. It contains a theoretical equation and ideal boundary conditions so the application of the formulation is limited. Therefore, the need of modern examination of lateral torsional buckling of suspension bridge is increasing. A long span suspension bridge shows quite nonlinear behavior and shows non linearity when its initial condition and wind load are applied. Therefore it needs some techniques. We present the way of modeling bridges using the structural elements and making initial conditions under gravity. After this we present how to analyze the lateral-torsional buckling of long span bridge applying wind load. The wind load is calculated by the static coefficient of wind force. Finally, the result is showed and the conclusion is presented.
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