BRIDGES

BRIDGES:

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.

TYPES OF BRIDGES

BEAM BRIDGES

The beam bridges are horizontal beams supported at each end by abutments, hence their structural name of simply supported. When there is more than one span 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 are large box steel girder bridges.

CANTILEVER BRIDGES

Cantilever Bridges are built using cantilevers horizontal beams supported on only one end. 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.

ARCH BRIDGES

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.

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.

MOVABLE BRIDGES

Movable bridges are designed to move out of the way of boats or other kinds of traffic, which would otherwise be too tall to fit. These are generally electrically powered.

TACOMA NARROWS:

The Tacoma Narrows Bridge is a pair of twin suspension bridges in the U.S. state of Washington, which carry State Route 16 (known as Primary State Highway 14 until 1964) across the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. Historically, the name "Tacoma Narrows Bridge" has applied to the original bridge nicknamed "Galloping Gertie" which opened in July 1940 but collapsed due to aero elastic flutter four months later, as well as the replacement of the original bridge which opened in 1950 and still stands today as the westbound lanes of the present-day twin bridge complex.

The first Tacoma Narrows Bridge opened to traffic on July 1, 1940. Its main span collapsed into the Tacoma Narrows four months later on November 7, 1940, at 11:00 AM (Pacific time) due to a physical phenomenon known as aero elastic flutter caused by a 42 miles per hour (68 km/h) wind. The bridge collapse had lasting effects on science and engineering. In many undergraduate physics texts the event is presented as an example of elementary forced resonance with the wind providing an external periodic frequency that matched the natural structural frequency (even though the real cause of the bridge's failure was aero elastic flutter. Another reason in why the bridge was destroyed 4 months later was due to not only aero elastic flutter, but its solid sides, not allowing wind to pass through the bridge's deck.

Tacoma bridge video

Tunnels

TUNNELS:

A tunnel is an underground passageway, completely enclosed except for openings for ingress and egress, commonly at each end.

A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. Other uses include routing power or telecommunication cables, some are to permit wildlife such as European badgers to cross highways. Secret tunnels have given entrance to or escape from an area, such as the Cu Chi Tunnels or the smuggling tunnels in the Gaza Strip which connect it to Egypt. Some tunnels are not for transport at all but rather, are fortifications, for example Mittelwerk and Cheyenne Mountain.

In the United Kingdom, a pedestrian tunnel or other underpass beneath a road is called an underpass subway. In the United States that term now means an underground rapid transit system.

The central part of a rapid transit network is usually built in tunnels. Rail station platforms may be connected by pedestrian tunnels or by foot bridges.

CONSTRUCTION:

Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk management.

There are three basic types of tunnel construction in common use:

Cut and cover tunnels, constructed in a shallow trench and then covered over.

Bored tunnels, constructed in situ, without removing the ground above. They are usually of circular or horseshoe cross-section.

Immersed tube tunnels, sunk into a body of water and sit on, or are buried just under.

VARIANT TUNNEL TYPES

DOUBLE-DECK TUNNEL

Some tunnels are double-deck, for example the two major segments of the San Francisco – Oakland Bay Bridge (completed in 1936) are linked by a double-deck tunnel, the largest diameter bore tunnel in the world. At construction this was a combination bidirectional rail and truck pathway on the lower deck with automobiles above, now converted to one-way road vehicle traffic on each deck.

ARTIFICIAL TUNNELS:

Over-bridges can sometimes be built by covering a road or river or railway with brick or steel arches, and then leveling the surface with earth. In railway parlance, a surface-level track which has been built or covered over is normally called a covered way.

Snow sheds are a kind of artificial tunnel built to protect a railway from avalanches of snow. Similarly the Stanwell Park, New South Wales steel tunnel, on the South Coast railway line, protects the line from rockfalls.

HAZARDS:

Owing to the enclosed space of a tunnel, fires can have very serious effects on users. The main dangers are gas and smoke production, with low concentrations of carbon monoxide being highly toxic. Fires killed 11 people in the Gotthard tunnel fire of 2001 for example, all of the victims succumbing to smoke and gas inhalation.

THE LONGEST TUNNELS

·       The Delaware Aqueduct in New York USA is the longest tunnel, of any type, in the world at 137 km (85 mi). It is drilled through solid rock.

·       The Gotthard Base Tunnel will be the longest rail tunnel in the world at 57 km (35 mi). It will be totally completed in 2017.

·       The Seikan Tunnel in Japan is the longest undersea rail tunnel in the world at 53.9 km (33.5 mi), of which 23.3 km (14.5 mi) is under the sea.

·       The Channel Tunnel between France and the United Kingdom under the English Channel is the second-longest, with a total length of 50 km (31 mi), of which 39 km (24 mi) is under the sea.

·       The Lötschberg Base Tunnel opened in June 2007 in Switzerland was the longest land rail tunnel, with a total of 34.5 km (21.4 mi).

·       The Lærdal Tunnel in Norway from Lærdal to Aurland is the world's longest road tunnel, intended for cars and similar vehicles, at 24.5 km (15.2 mi).

·       The Zhongnanshan Tunnel in People's Republic of China opened in January 2007 is the world's second longest highway tunnel and the longest road tunnel in Asia, at 18 km (11 mi).

·        The longest canal tunnel is the Rove Tunnel in France, over 7.12 km (4.42 mi) long. 

Hydrology

HYDROLOGY

Is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability. A practitioner of hydrology is a hydrologist, working within the fields of earth or environmental science, physical geography, geology or civil and environmental engineering.

Domains of hydrology include hydrometeorology, surface hydrology, hydrogeology, drainage basin management and water quality, where water plays the central role. Oceanography and meteorology are not included because water is only one of many important aspects within those fields.

Hydrological research can inform environmental engineering, policy and planning.

Branches of hydrology

Chemical hydrology: Is the study of the chemical characteristics of water.
Eco hydrology:  Is the study of interactions between organisms and the hydrologic cycle.
Hydrogeology: Is the study of the presence and movement of ground water.

Hydro Informatics: Is the adaptation of information technology to hidrology and water resources applications.

Hydrometeorology: Is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere.

Isotope Hydrology: Is the study of the isotopic signatures of water.

Surface hydrology: Is the study of hydrologic processes that operate at or near Earth´s surface.

Drainage basin: Management covers water-storage, in the form of reservoirs, and flood-protection.

Water quality: Includes the chemistry of water in rivers and lakes, both of pollutants and natural solutes.

Hydrologic cycle

All the amount of water that exists on world is divided into three main sources: oceans, continents and atmospheres in which there is a continuous circulation. The movement of water in the hydrological cycle is maintained by the sun's radiant energy and the force of gravity. The hydrological cycle is defined as the sequence of events through which water passes from the earth's surface in the vapor phase into the atmosphere and returns to its liquid and solid phases. The transfer of water from the surface of the Earth into the atmosphere, water vapor, is due to direct evaporation, perspiration by plants and animals and by sublimation (direct passage of solid water to water vapor).

The hydrological cycle can be seen, on a planetary scale, as a gigantic system of distillation spread throughout the planet. The warming of the tropical regions due to solar radiation causes continuous evaporation of ocean water, which is transported in the form of water vapor by the general circulation of the atmosphere, to other regions. During transfer, part of the water vapor condenses due to cooling and forms clouds which cause the precipitation.

The hydrologic cycle

Applications of hydrology

·       Determining the water balance of a region.

·       Determining the agricultural water balance.

·       Mitigating and predicting flood, landslide and drought risk.

·       Real-time flood forecasting and flood warning.

·       Designing irrigation schemes and managing agricultural productivity.

·       Part of the hazard module in catastrophe modeling.

·       Providing drinking wáter.

·       Designing dams for water supply or hydroelectric power generation.

·       Designing bridges.

·       Designing sewers and urban drainage system.

·       Analyzing the impacts of antecedent moisture on sanitary sewer systems.

·       Predicting geomorphological changes, such as erosion or sedimentation.

·       Assessing the impacts of natural and anthropogenic environmental change on water resources.

·       Assessing contaminant transport risk and establishing environmental policy guidelines.

Geotechnical Engineering

GEOTECHNICAL ENGINEERING

The branch of civil engineering concerned with the engineering behavior of earth materials. Geotechnical engineering is important in civil engineering, but is also used by military, mining, petroleum, or any other engineering concerned with construction on or in the ground. Geotechnical engineering uses principles of soil mechanics and rock mechanics to investigate subsurface conditions and materials; determine the relevant physical/mechanical and chemical properties of these materials; evaluate stability of natural slopes and man-made soil deposits; assess risks posed by site conditions; design earthworks and structure foundations; and monitor site conditions, earthwork and foundation construction.

A typical geotechnical engineering project begins with a review of project needs to define the required material properties. Then follows a site investigation of soil, rock, fault distribution and bedrock properties on and below an area of interest to determine their engineering properties including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include the assessment of the risk to humans, property and the environment from natural hazards such as earthquakes, landslides, sinkholes, soil liquefaction, debris flows and rock falls.

GEOTECHNICAL ENGINEER

A geotechnical engineer then determines and designs the type of foundations, earthworks, and/or pavement subgrades required for the intended man-made structures to be built. Foundations are designed and constructed for structures of various sizes such as high-rise buildings, bridges, medium to large commercial buildings, and smaller structures where the soil conditions do not allow code-based design.

Foundations built for above-ground structures include shallow and deep foundations. Retaining structures include earth-filled dams and retaining walls. Earthworks include embankments, tunnels, dikes, levees, channels, reservoirs, deposition of hazardous waste and sanitary landfills.

WORKING SITES

Geotechnical engineers work with government, commercial, industrial and private organizations and developers to assist with projects such as highways, bridges, dams, tunnels, tanks, public infrastructure improvement.

Geotechnical engineers are a subset of civil engineers who focus on materials in and below the earth's surface mainly soil and minerals.

OTHER SPECIALITES:

GEOTECHNICAL AND GEOLOGICAL ENGINEERING

Geological engineers identify and try to solve problems involving soil, rock and groundwater, and design structures in and below the ground, using the principles of earth science and engineering. Geological engineering includes a number of ground engineering specialties such as geotechnical engineering.

GEOLOGICAL ENGINEERS MAY PERFORM THE FOLLOWING TASKS:

Investigate the engineering feasibility of planned new developments involving soil, rock and groundwater plan and undertake site investigations for proposed major engineering works such as bridges, dams and tunnels design measures to correct land contamination and salination.

The Pavements

PAVEMENTS

Pavement engineering is a branch of civil engineering that uses engineering techniques to design and maintain flexible (asphalt) and rigid (concrete) pavements. This includes streets and highways and involves knowledge of soils, hydraulics, and material properties. Pavement engineering involves new construction as well as rehabilitation and maintenance of existing pavements. Maintenance often involves using engineering judgment to make maintenance repairs with the highest long-term benefit and lowest cost. Pavement engineer is the process of designing paved surfaces to meet the needs of traffic, pedestrians, and the environment. Some pavement engineer professionals may work to help to develop and test new asphalt and concrete mixtures.

CONCRETE PAVEMENTS WITHOUT SUBBASES FOR LIGHT TRAFFIC

The necessity of a sub-base (a layer of granular material placed on a prepared subgrade) depends on the frequency of heavy truck loadings.

This pumping is the forceful ejection of a mixture of soil and water from under slab edges and joint It is caused by frequent slab deflections under heavy wheel loads.

FAST FULL-DEPTH PAVEMENT REPAIR

Requires removing and replacing at least a portion of a slap to the bottom of concrete to can restore areas of deterioration and extend the pavement service life.

PROPER USE OF ISOLATION AND EXPANSION JOINTS IN CONCRETE PAVEMENTS

The joints are only necessary in four cases:

·       When the pavement is divided into long panels.

·       Constructed in temperatures below 40°F.

·       When the contraction are allowed to be infiltrated.

·       When the pavement is constructed with high expansion materials

Dams

DAMS:

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations.

TYPES OF DAMS

Arch dams:

An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes into its foundation or abutments.

These masonry or concrete dams are ideal for narrow and/or rocky locations because their curved shape easily holds back water via gravity without the need for a lot of construction materials.

Embankment Dams:

An embankment dam is a massive artificial water barrier. It is typically created by the emplacement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a dense, waterproof core.

These are large dams made out of soil and rock which use their weight to hold back water. To prevent water from moving through them, embankment dams also have a thick waterproof core. Embankment dams have a triangular-shaped profile.

Gravity Dams:

Is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water against the canyon rock walls, providing the force to compress the dam. It combines the strengths of two common dam forms and is considered a compromise between the two. They are generally made of reinforced concrete which provides more strength compared to normal concrete, consist of thick, vertical walls of concrete built across relatively narrow river valleys with firm bedrock. Their weight alone is great enough to resist overturning or sliding tendencies. these are difficult and expensive to build.

Buttress dam:

These can have multiple arches, but unlike a traditional arch dam, they can be flat as well.  These dams are essentially hollow constructed of steel-reinforced concrete or timber.

Function Dams:

·       Power Generation

·       Water supply

·       Stabilize water flow/ irrigation

·       Flood prevention

·       Land reclamation

·       Water diversion

·       Navigation

·       Recreation and aquatic beauty

Reservoirs: A reservoir is a man-made lake that is primarily used for storing water. They can also be defined as the specific bodies of water formed by the construction of a dam.

The biggest dams in the world

·       Three Gorges 18,460 MW, China.

·       Itaipu 14,750 MW, Brazil/Paraguay.

Colombian’s Dams

·       Chivor´s Dam.(Boyacá)

·       Jaguas’ Dam. (Antioquia)

·       Betania’s Dam. (Huila)