Welcome to civil engineering world: Cantilever Bridges

Welcome to civil engineering world: Cantilever Bridges: (note : people are bit confused with  the cantilever bridges in dental with cantilever in engineering. so pls check it out.) CANTILEVER ...

Cantilever Bridges

(note : people are bit confused with  the cantilever bridges in dental with cantilever in engineering. so pls check it out.)

CANTILEVER BRIDGES

A structure at least one portion of which acts as an anchorage for sustaining another portion which extends beyond the supporting pier.

                                                        -- john alexander low waddel

A cantilever bridge is constructed using cantilevers, which are horizontal structures supported only on one end.cantilevers may be simple beams for small bridges and for large bridges cantilevers are trusses which are made from structural steel.

A balanced cantilever is another technique for spanning long distances. In this situation, engineers construct a pier in the middle of the river. They then anchor two cantilevers on the pier, each facing the opposite direction from the other. These cantilevers, or anchor arms, meet with other cantilevers anchored in the ground or another pier to create one whole bridge.

function of  cantilver bridges :

The first step in building a cantilever bridge is to build and connect the arms to the shore. River piers for balanced cantilevers should not be built until the cantilevers that touch the land are completed. If a beam bridge or truss bridge is necessary, it cannot be added until the cantilevers are ready. The beam bridge is often built off-site and lowered with a crane into position.

A simple cantilever span is formed by two cantilever arms extending from opposite sides of the obstacle to be crossed, meeting at the center. With a suspended span, the cantilever arms do not meet in the center; instead, they support a central truss bridge which rests on the ends of the cantilever arms. The suspended span may be built off-site and lifted into place, or constructed in place using special traveling supports.

with as balanced cantilever, the span is balanced by cantilevers going in the opposite direction. If these are anchored into solid foundations, they are called anchor arms. In a bridge built on two foundation piers, there are four cantilever arms: two which span the obstacle, and two anchor arms which extend away from the obstacle. Because of the need for more strength at the balanced cantilever's supports, the bridge superstructure often takes the form of towers above the foundation piers. The Commodore Barry Bridge is an example of this type of cantilever bridge.

Steel truss cantilevers support loads by tension of the upper members and compression of the lower ones. Commonly, the structure distributes the tension through the anchor arms to the outermost supports, while the compression is carried to the foundations beneath the central towers.

Prestressed concrete balanced cantilever bridges are often built using segmental construction.

List of famous cantilver bridges in the world:

1.Quebec Bridge (Quebec, Canada) 1,800 feet (549 m)

2.Forth Bridge (Firth of Forth, Scotland) 2 x 1,710 feet (521 m)

3.Minato Bridge (Osaka, Japan) 1,673 feet (510 m)

4.Commodore Barry Bridge (Chester, Pennsylvania, USA) 1,644 feet (501 m)

5.Crescent City Connection (dual spans) (New Orleans, Louisiana, USA) 1,575 feet (480 m)

6.Howrah Bridge (Kolkata, West Bengal, India) 1,500 feet (457 m)

7.Veterans Memorial Bridge (Gramercy, Louisiana, USA) 1,460 feet (445 m)

8.San Francisco – Oakland Bay Bridge (East Bay Span) (San Francisco, California, USA) 1,400 feet (427 m)

9.Horace Wilkinson Bridge (Baton Rouge, Louisiana, USA) 1,235 feet (376 m)

10.Tappan Zee Bridge (South Nyack, New York & Tarrytown, New York, USA) 1,212 feet (369 m).

( A post on cable bridges will be published soon  :)

Difference between architecture and civil engineering

Many of us don't know the difference between architecture and civil engineering. Good number of  websites and authors had tried to tell the difference between these two through many forms, Iam also trying to do that but in an interesting and simple manner covering all the aspects araised till date!!

Architecture :

Architecture is mainly a practice of designing structures with aesthetics and spatial functionality in mind. Architects may have the basic to advanced knowledge of structural mechanics but their primary focus is always, first and foremost, the creativity, look and feel, and functionality of the design. Structural vision starts in the field of architecture.

Civil engineering :

Civil engineering, also referred as structural engineering, specializes in the structural elements of systems, ensuring that facilities can withstand normal and extreme loading conditions. Civil engineers work closely with architects and they are responsible for making the vision of architects into a realization. Civil engineering deliberates on the physics involved in the construction process of the architect’s design.

NOTE : 

•  Architecture is more into the creativity of designs. Civil engineering focus on innovation to realize that design.
• Architects will need engineers help to make their designs work. Civil engineers will be guided by the architectsÂ’ outlines and dimensions.
• Architecture involves the design of structures with the focus on aesthetics and functionality. Civil engineering will not normally care about those things; Civil Engineers will rather deliberate and plan the methodology to construct the design.
  
• Architecture initiates the project through architects’ drafts. Civil engineering involves studying drafts and examining the practicality of the design; civil engineers ensure that the design can withstand normal and extreme loading conditions.
  
  (Economical values of the respective fields and salaries will be discussed in the coming post.)

Architectural engineering

An architectural engineer helps create efficient buildings and building systems. Architectural engineers often work on projects with other professionals, including construction workers and architects. 

it has three sub disciplines in it namely 

Structural engineering : 

Structural engineering involves the analysis and design of physical objects (buildings, bridges, equipment supports, towers and walls). Those concentrating on buildings are responsible for the structural performance of a large part of the built environment and are, sometimes, informally referred to as "building engineers". Structural engineers require expertise in strength of materials and in the seismic design of structures covered by earthquake engineering. Architectural Engineers sometimes practice structural as one aspect of their designs; the structural discipline when practiced as a specialty works closely with architects and other engineering specialists.

Mechanical, electrical, and plumbing (MEP) :

MEP room in a building

Mechanical engineering and electrical engineering engineers are specialists, commonly referred to as (mechanical, electrical, and plumbing) when engaged in the building design fields. Also known as "building services engineering" in the United Kingdom, Canada, and Australia.[1] Mechanical engineers often design and oversee the heating, ventilation and air conditioning (HVAC), plumbing, and rain gutter systems. Plumbing designers often include design specifications for simple active fire protection systems, but for more complicated projects, fire protection engineers are often separately retained. Electrical engineers are responsible for the building's power distribution, telecommunication, fire alarm, signalization, lightning protection and control systems, as well as lighting systems.

Bridges and its types (part-1)

Bridges:

Tensile bridges are the largest clear span structures in the world.

In the following diagrams, only the white struts are intended to be capable of sustaining compressive loads - all other elements are tensile.

Hexagonal Geodesic Domes - Bridges

HEXDOME

The hyperboloid is a simple tensile structure, which I believe has - or should have - substantial significance for bridge builders.

The hyperboloid is one of the two "doubly ruled" structures. Its surface consits entirely of straight lines, the roles of which can be conveniently played by cables. The degree of central constriction can be varied - by placing cables at different angles.

Practical constructions often consist of two sets of cables - one twisting to the left, the other twisting to the right.

The cables can be woven togther, using rectangular or triaxial weaving patterns.

Also, the two sets of cables can sometimes be placed at slightly different angles to the main axis of the bridge - so that neither set of cables is quite straight. This causes the two concentric sets of cables to press into each other dynamically.

Facts about bridges?

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  Common types of bridges include beam bridges, arch bridges, suspension bridges, cantilever bridges, truss bridges, and cable-stayed bridges.
• Bridge designs depend on their intended function, financial resources and also the type of terrain where they are constructed. While an arch bridge might be suited in one situation, a suspension bridge might be suited in another.
• The Zhaozhou Bridge is the oldest standing bridge in China and the world’s oldest stone segmental arch bridge. Built in 605 AD, it is still standing strong today, over 1400 years later.
• The Inca civilization in South America made use of rope bridges in the Andes Mountains before the Europeans colonized in the 1500’s. These rope bridges spanned canyons and gorges, allowing easy access to otherwise difficult to reach areas. While they were strong and reliable, repairing the bridges was a dangerous job that often ended in death.
• During the Industrial Revolution of the 19th century wrought iron was introduced into the design of large bridges. Wrought iron was later replaced by steel because it has a higher tensile strength.
• The first welded road bridge was designed by Polish engineer Stefan Bryla in 1927.
• The Sydney Harbour Bridge in Australia can rise or fall up to 18 cm (7.1 inches) depending on the temperature due to the steel expanding or contracting. It also features 6 million rivets and weighs 39006 tonnes.
• The Brooklyn Bridge in New York, USA joins Manhattan and Brooklyn over the East River. When completed in 1883, it was the longest suspension bridge in the world (remaining so until 1903). It features average daily traffic of around 145000 vehicles.
• The Golden Gate Bridge in San Francisco, USA is a well known suspension bridge that was completed in 1937. It has a total length of 8981 feet (2737 metres) and features 80000 miles (129000 kilometres) of wire in its two main cables.
• The longest suspension bridge in the world (as of 2010) is the Akashi Kaikyo Bridge in Kobe, Japan. It opened in 1998 and spans an incredible 1991 metres 

what is CIVIL engineering?

 First of all ..being a civil engineering student i can say that civil engineering is such type of professional engineering discipline in which design,construction and maintenance of environment of your surroundings.
                         

ya ofcourse iam a student in civil..but the comments which i have recieved from several people is this profession will not let you to earn more.but that is totally wrong! you can't decide anything of your own.talent matters, if you are very passionate about your respective profession.undoubtledly it'll help you to gain more..so keeping this apart!

Generally a civil er. deals with how to design a building, construction, environmental issues. Ofcourse civil engg  It is traditionally broken into several sub-disciplines including architectural engineering, environmental engineering, geotechnical engineering, control engineering, structural engineering, earthquake engineering, transportation engineering, forensic engineering, municipal or urban engineering, water resources

(please see the nextpost for getting info about those sub disciplines in detail . thank you!!)