Welcome to civil engineering world: TRUSS BRIDGES

Welcome to civil engineering world: TRUSS BRIDGES:  We can see the  beam bridges every where, but the difference from one another will be its type of design.The key differences, however, all...

TRUSS BRIDGES

 We can see the  beam bridges every where, but the difference from one another will be its type of design.The key differences, however, all come down to the design, location and composition of the truss.


"A truss bridge is that in which truss will be the load supercomposing structure"

SIMPLE DEF : Truss is a formation produced by triangular components, in accordance with the truss bridge drawings, and coupled at joints known as nodes. The triangular units forming the truss are slim and straight in form.

.The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads.

STRUCTURE AND DESIGN :

The structure and design of the truss bridge has been done by using newtons' laws of motion according to statics. Int he bridge vertical members are in tension,lower horizontal members in tension, shear, and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension.

The truss may carry its roadbed on top, in the middle, or at the bottom of the truss. Bridges with the roadbed at the top or the bottom are the most common as this allows both the top and bottom to be stiffened, forming a box truss. When the roadbed is atop the truss it is called a deck truss (an example of this was the I-35W Mississippi River bridge). When the truss members are both above and below the roadbed it is called a through truss (an example of this application is the Pulaski Skyway), and where the sides extend above the roadbed but are not connected, a pony truss or half-through truss.

THROUGH  TRUSS

A single beam spanning any distance undergoes compression and tension. The very top of the beam gets the most compression, and the very bottom of the beam experiences the most tension. The middle of the beam experiences very little compression or tension. This is why we have I-beams, which provide more material on the tops and bottoms of beams to better handle the forces of compression and tension.

DECK TRUSS

And there's another reason why a truss is more rigid than a single beam: A truss has the ability to dissipate a load through the truss work. The design of a truss, which is usually a variant of a triangle, creates both a very rigid structure and one that transfers the load from a single point to a considerably wider area.

TRUSS USED IN BRIDGES:

Allan truss :

 It is  on the based on the Howe truss.

Bailey bridge :

Designed for military uses, the prefabricated and standardized truss elements may be easily combined in various configurations to adapt to the needs at the site. In the image at right, note the use of doubled prefabrications to adapt to the span and load requirements. In other applications the trusses may be stacked vertically.

BALTIMORE BRIDGE : 

The Baltimore truss is a subclass of the Pratt truss. A Baltimore truss has additional bracing in the lower section of the truss to prevent buckling in the compression members and to control deflection. It is mainly used for rail bridges, showing off a simple and very strong design.

Bowstring arch truss :

The bowstring arch through truss bridge was patented in 1841 by Squire Whipple. While similar in appearance to a tied-arch bridge, a bowstring truss is a truss and thus has diagonal load-bearing members. These diagonals result in a structure that more closely matches a Parker truss or Pratt truss than a true arch.

CANTILEVER TRUSS :

Most trusses have the lower chord under tension and the upper chord under compression. In a cantilever truss the situation is reversed, at least over a portion of the span. The typical cantilever truss bridge is a "balanced cantilever", which enables the construction to proceed outward from a central vertical spar in each direction. Usually these are built in pairs until the outer sections may be anchored to footings. A central gap, if present, can then be filled by lifting a conventional truss into place or by building it in place using a "traveling support".

cantilever bridge(click to open about cantilever bridge)

Howe truss :

A truss having upper and lower horizontal members, between which are vertical and diagonal members; the vertical web members take tension, and the diagonal web members are under compression.

(TYPES OF TRUSS BRIDGES WILL BE CONTINUED IN THE NEXT POST:)

welcome to civil engineering world: BRIDGES

welcome to civil engineering world: BRIDGES: Well  there are very few posts about bridges on net. i'd like to provide the info about the bridges to my blog's visitors.    &...

welcome to civil engineering world: CABLE STAYED BRIDGES (one of the most innovative i...

welcome to civil engineering world: CABLE STAYED BRIDGES (one of the most innovative i...: A complete look over the cable stayed bridges. "Cable-stayed bridges may look similar to suspension bridges—both have roadways that...

CABLE STAYED BRIDGES (one of the most innovative in man creations.)

A complete look over the cable stayed bridges.

"Cable-stayed bridges may look similar to suspension bridges—both have roadways that hang from cables and both have towers." 

. Cable-stayed bridges differ from their suspension predecessors in that they don't require anchorages, nor do they need two towers. Instead, the cables run from the roadway up to a single tower that alone bears the weight.

 The tower of the bridges will play a major role in balancing compressional forces.The cables attach to the roadway in various ways. For example, in a radial pattern, cables extend from several points on the road to a single point at the tower, like numerous fishing lines attached to a single pole. In a parallel pattern, the cables attach to both the roadway and the tower at several separate points.

PARALLEL ATTACHMENT PATTERN

RADIALLY ATTACHMENT PATTERN

Today in this modern world, these bridges are the first choice for every civil engineer.due to its less cable requirement, faster to build which inturns gives the best result.

HOW DO IT WORK :

Stand up and hold your arms out horizontally at each side. Imagine that your arms are a bridge, and your head is a tower in the middle. In this position, your muscles are holding up your arms. 

Try making cable-stayeds to support your arms. Take a piece of rope (about five feet long), and have a partner tie each end of the rope to each of your elbows. Then lay the middle of the rope on top of your head. The rope acts as a cable-stayed and holds your elbows up. 

Illustration of person with rope supporting arms Have your partner tie a second piece of rope (about 6 feet long) to each wrist. Lay the second rope over your head. You now have two cable-stayeds. Where do you feel a pushing force, or compression? Notice how the cable-stayeds transfer the load of the bridge (your arms) to the tower (your head).

BRIDGES

Well  there are very few posts about bridges on net. i'd like to provide the info about the bridges to my blog's visitors.

   "A bridge is a structure built over a river, seas, and so on, that allows people or vehicles to cross from one side to the other." 

     
It is a structure which is used to span the physical obstacles like sea,rivers,etc.different designs will be used for construction of bridges that suits the  topography of that particular place. Designs of bridges vary depending on the function of the bridge.

TYPES OF BRIDGES :

Classification of bridges depends on the structure and its functions bridges and by how the forces of tension, compression, bending, torsion and shear are distributed through their structure.

BEAM BRIDGE :

Beam bridges are horizontal beams supported at each end by substructure units and can be either simply supported when the beams only connect across a single span, or continuous when the beams are connected across two or more spans. When there are multiple spans, the intermediate supports are known as piers. The earliest beam bridges were simple logs that sat across streams and similar simple structures. In modern times, beam bridges can range from small, wooden beams to large, steel boxes. 

TRUSS BRIDGE :

A truss bridge is a bridge whose load-bearing superstructure is composed of a truss. This truss is a structure of connected elements forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by nineteenth and early twentieth century engineers. A truss bridge is economical to construct owing to its efficient use of materials.

TRUSS BRIDGE (click here for full info)

CANTILEVER BRIDGE :

Cantilever bridges are those which gets it support on only from side.

 Most cantilever bridges use a pair of continuous spans that extend from opposite sides of the supporting piers to meet at the center of the obstacle the bridge crosses. Cantilever bridges are constructed using much the same materials & techniques as beam bridges. The difference comes in the action of the forces through the bridge.

CANTILEVER BRIDGES(click here for full info)

ARCH BRIDGE :

Arch bridges have abutments at each end. The weight of the bridge is thrust into the abutments at either side. The earliest known arch bridges were built by the Greeks, and include the Arkadiko Bridge.

TIED ARCH BRIDGES :

Tied arch bridges have an arch-shaped superstructure, but differ from conventional arch bridges. Instead of transferring the weight of the bridge and traffic loads into thrust forces into the abutments, the ends of the arches are restrained by tension in the bottom chord of the structure. They are also called bowstring arches.

SUSPENSION BRIDGES :

Suspension bridges are suspended from cables. The earliest suspension bridges were made of ropes or vines covered with pieces of bamboo. In modern bridges, the cables hang from towers that are attached to caissons or cofferdams. The caissons or cofferdams are implanted deep into the floor of a lake or river. Sub-types include the simple suspension bridge, the stressed ribbon bridge, the underspanned suspension bridge, the suspended-deck suspension bridge, and the self-anchored suspension bridge.

CABLE STAYED BRIDGES :

These are just like suspension bridges which are held by cables from the  towers of the bridge .The only difference is cable usage can be reduced in this bridge . And the towers holding the cables are proportionally higher.

CABLESTAYED BRIDGES(click here for full info)

( EXPLANATION INDETAILED  FOR THE ABOVE BRIDGES  WILL BE VERY SOON :)

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?

• 
  
  
  
  
  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!!)