Bridge Materials and Manufacturing Methods in the US
Introduction
Approximately 600,000 bridges have been established in both water ways, dry land depressions and other types of roads in United States. Various bridges use complex designs of constructions such as arches, cables or triangular shaped filled trusses to connect the road space between towers or columns. Nevertheless the work horse of any highway bridge system is comparatively modest and cheap solid beam balance. Also termed as Girder Bridge a beam bridge is used to cover a maximum distance of 76 meters. If the distance is longer several girder bridges may be connected in a series to cover that distance, commonly known as continuous span (Xiang, et al, pg. 973).
Girder Bridge
A girder bridge is composed of a horizontal slab which has some supporters at the both ends. The other objects are elevated vertically in order to support the support the columns which have less weight compared to arch’s. The world’s longest bridge known as pontchartrian causeway in Louisiana is made from pairs of continuous series of simple beams. The bridge is estimated to be 38 kilometers’ long
A bridge consists three main elements which includes substructure which is the basically the foundation. The foundation is used to transfer the impacts of the weight impacted by the bridge to the ground. Foundation is made of columns and abutments.an abutment is simply a connection between the terminal of the bridge and the earth’s surface. The abutment provides some strong support to the terminals of the bridge. The other structure is the deck which is an extensional surface added to the super structure and is used as the traffic carrying surface area
History of bridges
Ancient man began building of bridges by copying the modeling of nature. They usually found it comfortable when walking on trees to cross over small streams of water. They could place pieces of stones or slabs across rivers to use it as bridges. The first bridge to be established was in 480, Bc. The bridge was composed of wood supported by large pieces of stones as columns and was constructed across the Euphrates river. The bridge is very popular due to its arches modeled from stones and concretes built by the great roman architects. Actually is the oldest Roman Bridge established across river Euphrates. The art of bridge building initiated the transformation of art science in 1700 after French engineer wrote documentation on the process of bridge building. (Xiang, et al,pg.973).
Construction materials and their processing
Mostly, road beam bridges are made from mortar and steel. Earlier, the romans used a mixture of concrete, red volcanic soil and lime in their beams while constructing bridges. This mixture hardened very quickly even when under water and had a high level of strength and stoniness. The mixture was also believed to be water proofed.in the European middle age, lime water was used but in a soluble form. After some years, the todays popular cemented was invented from a mixture of lime and clay by an English brick producer called joseph Aspidin. Even after its discovery, cement was not used as base building material until the start of 1900. Don't use plagiarised sources.Get your custom essay just from $11/page
Concrete contains sufficient strength to support and survive compression but its weak when impacted with tensional force. Both Europe and United States made several tests in integrating concrete with steel or iron to increase its level of strength.an ideal brand of concrete was invented in 1880s by François hennebique who incorporated some strengthening bars made of steel and iron. The first bridge made of concrete and steel to be established was Alvord Lake Bridge located in sans Francisco Golden Gate Park. The bridge was completed and opened for operation in1889 and is still under operation up to today (Kim, et al, pg. 49).
The other advancement which was made to improve the efficiency and effectiveness of concrete was the development of prestressing. The concrete beams were press stressed by pulling on steel bars passing through the beam and the forced on to the beam when a load is placed in it. Press stressing is applied on beams which was manufactured in the factory and then transferred to the construction site. Press stressing can also be used on a concrete poured in the beams final location or point. Pressure is then applied to the iron bars before the concrete is set. This method is also known as pre tensioning. Alternatively, the concrete can be set around the tube having the less tensional steel bars and then apply tension after the concrete is ready.
Design and modeling
Every bridge should be modeled and designed by qualified professional before the actual construction is intiated.the professionals must check on certain factors which includes the general landscape, direction of water currents, direction and strength of wind, possibilities of earthquakes, soil factors. The frequency of expected traffic and cost benefit implications
The design of the bridge should guarantee its effectivines.to achieve this, the engineers should evaluate, assess and analyze the different tensional forces acting on the structure of the bridge. These forces emanate from three kinds of weight exerted to the bridge. Dead load is the term used to describe the weight of the bridge itself. Live load is the total weight of the traffic the bridge is supposed to support. Environmental load describes the other environmental forces such as wind, earthquakes and storms and then any possible collisions of the traffic and the bridge surfaces. Over the years the level of redundancy in modeling and design of bridges has been largely permitted. The bridge is modeled so that the failure of one of the professionals would stop the progress of the project. If there any cost incurred and one of the professionals is held liable, then the fellow professionals will help on compensation of the loss.
Manufacturing process
Since each bridge is constructed for specific purpose and for a particular location the mode and the process of construction differs from one bridge to another. The procedure outlined below visualizes the basic steps followed in construction process of for fairly typical strengthened concrete running across a shallow river ( Eckel& Edwin,pg.12).
Substructure
A coffee dam is built around each column point in the base of the river. The water is forced out from the enclosure then some shafts are drilled on the riverbed to reach the bedrock. An auger is used to pump out the soil from the shafts. A clay solution is the pumped back into the holes to replace the soli and prevent the shaft from falling .After the shafts are 24 meters in depth; some cylindrical shaped steel cages are lowered in the shafts. The cylindrical shaped steel cages are about two meters in diameter. Concrete is the poured to the base of the shaft. As the shaft feels with concrete, the slurry is ejected out and tapped for future use (yeppes, et al, pg. 123).
Two bridge abutments are then established around each column point within the river base, exactly on the surface area on which the bridge should lie. A concrete back wall is made and connected between the bank and base of the river. This acts as a maintenance wall for the soil exceeding the terminal of the bridge. A flat base for the seat lie on is developed on the top base of the back wall. Wing wall extension is also developed to maintain the fill dirt for the bridge extent.(Xiang, et al,pg.973).
A cross- section view of a simple concrete beam bridge.
Super structure
A crane is used in placing the steel or press tensioned concrete girders between successive series of columns across the extent of the bridge. The girders are then fixed to the columns by use of bolts and mortar. For most bridges in United States of America each girder is estimated to be 1.8 meters tall and up to 40 meters long and weighing up to fifty four tones.5 steel panels are embedded across the girders to make a strong solid flat base, hence completing the bridge superstructure (Black, et al, pg.12).
Deck
After forming the super structure, a wet barrier is placed at the top base, for instance, a hot polymer modified asphalt. Steel bars are then elevated on the top of the hot polymer modified asphalt. The bars are then enclosed in a concrete slab. A concrete layer is then poured with a thickness of 20 to 30cm.in some incidences whereby forms are used as superstructure framework concrete is set on them. A slip-form machine can be used since it spreads mixes and smoothens the concrete in one single operation. Flexible filler is used to seal the gaps and joints.
Use of cover dams in creating a solid substructure
Quality control
The modeling and construction of a bridges process must meet some international standards of building and construction quality control. These standards were planned and established by various agencies including the American association of states highway and the transportation officials, the American concrete institute and the American society for testing and materials (yeppes, et al, pg. 123).
Conclusion
Various government institutions and manufacturing associations’ support and finance industrial and scientific research focused on improvement of bridge construction process. These studies are also targeted on the improvement of construction materials. The main goal and objective of this institution is to increase the durability of these materials. The quality assurance and control institution are focused on reducing the weight of the materials and the performance of the materials. Polymer based materials which are lighter are in the design process for future use
Work Cited,
Black, J. Temple, and Ronald A. Kohser. DeGarmo’s materials and processes in manufacturing. John Wiley & Sons, 2017.
Eckel, Edwin Clarence. Cements, limes and plasters: Their materials, manufacture and properties. Routledge, 2015.
Kim, Kyong Ju, et al. “Life cycle assessment based environmental impact estimation model for pre-stressed concrete beam bridge in the early design phase.” Environmental Impact Assessment Review 64 (2017): 47-56.
Yepes, Víctor, José V. Martí, and Tatiana García-Segura. “Cost and CO2 emission optimization of precast–prestressed concrete U-beam road bridges by a hybrid glowworm swarm algorithm.” Automation in Construction 49 (2015): 123-134.
Xiang, Ziru, et al. “Synergic identification of prestress force and moving load on prestressed concrete beam based on virtual distortion method.” Smart Structures and Systems 17.6 (2016): 917-933.