Limitations Of Precast Cantilever Construction Method-
In cantilever method construction procedure is very complex.
It require great care to maintain stability of structure during construction.
Special attention is required for precast segments as they have joints. An epoxy agent is used to the joint before putting it in the superstructure.
Size and weight of precast elements are limited by capacity of placing and transportation.
Success of this process relies strongly on accurate geometry control.
Large heavy equipments are needed for erecting the segments.
Pre-casting yard needs investment in equipments.
Segments are fabricated in factories and are taken to the site with the help of transportation ,it may be costly if large distance from construction site.
Components Of an Open Spandrel Arch Bridge
Abutments
Foundation
Road deck
Floor Beam
Spandrel Columns
Arch Ribs or Barrel
Springing lines
Extrados and Intrados
Crown and Rise
Arch axis
Sidewalk
Concrete Requirements
As my structure is an open spandrel Arch bridge that is made up of Reinforced concrete i.e. concrete as well as steel reinforcement hence it can be benefited by using unconventional concrete that is High Strength or High Performance concrete (HSC or HPC). HSC is that concrete which satisfies all the requisites in terms of all the critical fabrication and utilization at the lowest possible cost.It is a new type of concrete that needed unconventional techniques and componenets.It offers high strength as well as durability to the structure.
Now a days HPC is expensive than conventional concrete. It require additional materials in some quantities as to meet specified performance.These additional materials are cement,silica fume,...
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...xibility to engineers and architects. It is often used in prestressed and precast girders which allows logger spans in bridge designs.
Disadvantages:-
Mixture is more prone to early drying problems and Shrinkage cracking.
It require additional admixtures and materials that may be a difficult task to implement them.
High Volume Fly Ash Mixtures
Advantages
Eliminate the problem of balling that was in silica fume
Improve structural strength, reduces bleeding, less cost, more resistant to chemical and sulfate attacks, and it is environmental friendly.
Gives superior finish to structure
Disadvantages
Should be handled properly otherwise may be dangerous
Require better quality control, good knowledge of mix proportions and mixing and good curing at least for 7 days.
Comparing above these two methods for HSC we should use high volume fly ash mixtures for the bridge design.
For almost as long as civilizations began they have been fighting against each other. Often times these wars come down to who has the better military equipment. When one army creates an elite war machine another army is sure to soon copy or improve it. For example the U.S. Army Signal Corps purchased the first ever military aircraft in 1902 (Taylor). Two years later the Italians were also using aircrafts. The trebuchet catapult is no exception; it was one of the most destructive military machines of its time (Chevedden, 2000). A trebuchet works by using the energy of a falling counterweight to launch a projectile (Trebuchet). In this research paper I intend to explain the history and dynamics of a trebuchet catapult.
According to Suspension bridges: Concepts and various innovative techniques of structural evaluation, “During the past 200 years, suspension bridges have been at the forefront in all aspects of structural engineering” (“Suspension”). This statement shows that suspension bridges have been used for over 200 years, and that people are still using them today because they are structurally better bridges. This paper shows four arguments on the advantages of suspension bridges, and why you should use one when building a bridge. When deciding on building a suspension bridge, it has many advantages such as; its lightness, ability to span over a long distance, easy construction, cost effective, easy to maintain, less risk
Coating the bearings of high speed motors since allows for the even distribution of lubricating oil.
Current modifications to the design are making them have antiseptic and antimicrobial coatings. Some have a third channel to infuse saline. There have also been efforts to make the surface as smooth as possible to reduce bacterial infections.
Most people may not realise but concrete plays a vital part in our lives daily. It shapes and creates the built environment in which we are surrounded by, such as schools, bridges, roads, housing, hospitals, dams and so much mores. Concrete is the most used man made material in the world, averaging around 3 tonnes annually for each person. In comparison with other building materials such as wood, steel, plastic and aluminium, over twice as much concrete is used globally than any of these materials. It is the material choice of most purposes due to its strength, durability, thermal mass and its cost.
Prefabrication -Haas et al (2000), prefabrication normally involves a single skill or trade, such as electrical, or piping, and this can be defined as “a manufacturing process, which generally takes place at a specialized facility, in which various materials are joined to form a component part of a final installation” (Tatum et al., 1987). Components manufactured off-site and is not a complete system can be referred to as prefabricated components. Furthermore Jaillon & Poon (2009) proceed to describe prefabrication as, a manufacturing process, commonly conducted at a specific facility, in which numerous materials are combined to form a component which is part of a final installation. The manufacturing process may be undertaken in different environments such as, a factory environment (factory prefabrication) or (site-prefabrication) on site under the open sky. The term off-site fabrication is utilized when prefabrication and pre-assembly is integrated (Jaillon & Poon, 2009). Gibb (1999) defines off-site prefabrication as a process which integrates prefabrication and pre-assembly. This process includes the design and the manufacture of units or modules, typically away from the work site, and their installation. “Off-site fabrication requires a project strategy that will change the orientation of the project process from construction to manufacture and installation”, (Gibb, 1999). (Klerk, 2013)
Based on the above data and the requirements that are to be achieved for the construction of the dam are analyzed. Self compacting concrete has been used mostly in the design of major parts of the dam.For the first time China used new type of admixture known as Glenium type PCE admixture (PCE-3) for the mix used in constructing the power house.The SCC mixture contains large content of limestone powder to increase fluidity,cohesiveness and limit heat generation.These materials are less reactive and reduces the problem of fluidity loss of concrete.Three types of mixes have been used they are....
The preferred alternative of ODOT is to widen and improve the structural integrity of the Yaquina Bay Bridge. The widening of the bridge shall follow the AASHTO LRFD Bridge Design Specification (Baker, 2008, p.3) using steel pier cap extensions (Quesnell Bridge Widening). The structural integrity of the bridge is to be enhance by improving the fatigue life of welds (Bennett, Matamoros, Barett-Gonzalez, & Rolfe, 2014, p.8)
The three most basic types of bridge structures are girder bridges, arch bridges, and suspension bridges (“Bridge Technology,” 2007). The girder structure consists of a chain of beams that are interconnected and supported vertically through the use of well allocated piers. The arch structure utilizes curved elements to disperse the applied forces downwards into end abutments. Finally, the suspension structure exploits the superior tensile strength of steel cables in order to help carry the massive loads applied to the bridge. While some bridges are built basic in structure, others are made through a combination of the structural forms mentioned above (“Bridges,” 2008).
The materials used for the construction of the designed plan is steel of grade415 and to that for coloums and beams is concrete where grade of concrete for coloums is M40 and for beams is M30.
Bachmann, H., & Steinle, A. (2011). Precast concrete structures / Hubert Bachmann, Alfred Steinle. Berlin: Ernst & Sohn, c2011.
High performance concrete is a concrete mixture, which possess high durability and high strength when compared to conventional concrete. This concrete contains one or more of cementious materials such as fly ash, Silica fume or ground granulated blast furnace slag and usually a super plasticizer
Constituent materials are the fundamental materials required to produce concrete. The constituent materials of concrete consist of mainly three materials which are cement, aggregate and water, with admixtures included as addictive to alter the characteristics of the concrete (Scalenghe et al., 2011). “Cement is the chemically active constituent but its reactivity is only brought into effect on mixing with water” (Dhir & Yap, 1984). According to Bye (1999), in the industry, Portland cement, which was developed in 1824 by using calcium carbonate found in calcareous rocks, namely limestone or chalk and silica, alumina, and iron oxide found in sedimentary rock, namely clay or shale. Bye (1999) said that cement is produced by grinding the quarried limestone to powder form, blending it with water and heat with pulverized coal to drive out water at 100°C, carbon dioxide at 800°C and clinker at 1400°C, which is then cooled, grounded and mixed with 1%-5% gypsum to alter it fineness and goes through final grinding and the cement is ready to be distributed to the market. According to Sismondo & Sergio (2009), aggregate, which builds up the majority of the volume stability and the durability of the resulting concrete and is of lower price than cement, is always used to the maximum extend as possible in the production of concrete for maximum profit. Aggregates ar...
It produces total quality work the concrete formed with such formwork systems is more durable.
In Proceedings of the International Workshop on Sustainable Development and Concrete Technology, Beijing, China, 20-21 May 2004. Edited by Kejin Wang. Ames, IA: Center for Transportation Research and Education, Iowa State University