Metal constructions due to the possibility of assembling the skeleton, before install and perform simultaneously and without interruption of the skeleton, in comparison with other structures have a higher operation speed. Because of homogeneous beam, column and cross brace as the main members, the skeleton of metal structures has a more appropriate integrity than the other structures. And also for this reason, to the result of constructional calculations has closer distance to the actual resistance of metal structures.
Metal structures and application of Nano-technology in it
Metal structures made via Nano-technology has a unique specifications, this technology can be used in many of the processes of manufacture and design of steel structures to be used. These unique specifications are capable to solve the current problems in the building and make changes in the process of manufacture. The progress of science in the field of nano metal particles and great achievements in this field improve the characteristics of structural metals such as steel. To add Nano-particles like copper, molybdenum and vanadium has been caused improvement of the mechanical properties of steel and reduce the cost of manufacturing. Creating of nano-cables, Nano-coverage such as titanium dioxide and the use of Nano-technology in creating and production of bolts and nuts has made a huge transformation in the structures.
Nanotechnology and steel
One of the most important building material is steel. Characteristics such as strength, resistance to corrosion and its welding capability in the design and structure are very important . These features make the role of steel in the structure industry very important.
Use of steel in restructure industry:
– In the building of the metal skeleton buildings as column, cross brace and floor plate, on buildings and concrete structures as rebar
– The bases and the floor of the bridges, full strength stretching cables
– Pipes for water, gas and oil
– The internal components of the buildings like doors and Windows, screws and connectors
– Use of facades
Disadvantages of steel:
Fatigue and cracking, corrosion in the vicinity of cement, the consequential effects of welding, require higher resistance, higher elasticity, the need for greater resistance against scratching, removing metal surfaces contamination, etc.
Steel and Nano-particles:
Fatigue is a significant issue that can lead to the structural failure of steel subject to cyclic loading, such as in bridges or towers. This can happen at stresses significantly lower than the yield stress of the material and lead to a significant shortening of useful life of the structure. Stress risers are responsible for initiating cracks from which fatigue failure results and research has shown that the addition of copper Nano-particles reduces the surface unevenness of steel which then limits the number of stress risers and hence fatigue cracking. Advancements in this technology would lead to increased safety, less need for monitoring and more efficient materials use in structure prone to fatigue issues .
Nano-technology and welding:
Welds and the Heat Affected Zone (HAZ) adjacent to welds can be brittle and fail without warning when subjected to sudden dynamic loading, and weld toughness is a significant issue especially in zones of high seismic activity. Weld and HAZ failures led to the re-evaluation of welded structural joints in the aftermath of the 1994 Northridge earthquake in the Los Angeles area and current design philosophies include selective weakening of structures to produce controlled deformation away from brittle welded joints or the deliberate over-sizing of structures to keep all stresses low. Research currently under way, however, has shown that the addition of Nano-particles of magnesium and calcium makes the HAZ grains finer (about 1/5 the size of conventional material) in plate steel and this leads to an increase in weld toughness. This is sustainability as well as a safety issue, as an increase in toughness at welded joints would result in a smaller resource requirement because less material is required in order to keep stresses within allowable limits .
The coatings incorporating certain nano-particles or nano-layers have been developed for certain purpose. It is one of the major applications of nanotechnology in structure. For example, TiO2 will break down and disintegrate organic dirt through powerful catalytic reaction . The photocatalytic function involves two processes simultaneously with different practices:
1. Photochemical process in which energy is provided by radiation.
2. A catalytic process that affects the reaction speed.
High strength steel cables are used to build bridges, especially suspended bridges. Using strong cables reduces costs and time to build structures. Studies and researches in the field of the cementite phase correction (Fe3C) of steel in nano have led to the production of strong cables .
Nano and Bolts:
Tall metal structures require high-strength connections, that this issue in turn requires strong bolts and nuts. The value of high strength of the bolts and nuts is usually achieved through quenching (cooling) and tempering (annealing).
These products include martensite microstructure (hard structure steel) tempering. When the tensile strength of steel includes tempered martensite, became more than MPa1200, even the existence of a small amount of hydrogen makes border of seeds getting the brittle and as a result, lead to the failure of steel materials in use. This phenomenon is known as the failure due to delay, prevents an increase in strength of metal bolts.
Their highest strengths range is from 1000 to 1200 MPa. Researches on vanadium and molybdenum nanoparticles have shown that these materials can improve lag failure in bolts and nuts. In fact, the nanoparticles increase the strength of the bolts and nuts by reducing the hydrogen brittleness and improvement of steel microstructure by decreasing the intergranular cementite phase .
Discussion and conclusion:
The use of nanotechnology in structures such as bridges and towers has increased the mechanical properties of these structures. The use of copper nanoparticles in the manufacture of steel increases its strength and melting point. Also, these types of steels have more flexibility and shine. Steel containing copper nanoparticles has been used a lot in the structure of bridges, because this type of steel has a considerable corrosion resistance. It is worth mentioning that nanoparticles in steels cause an increase the proportion in strength-to-weight. The use of nano metals technology in structure has led to the production of lighter composites and more robust structure constructions. It also produces nano coatings that require less maintenance and repair. Adding nanoparticles like molybdenum and vanadium to steel bolts and nuts increases the strength of these equipments.
Metal structure | High strength metal structure:
The resistance of the metal parts is high and the resistance -to-weight ratio is higher than concrete aggregates, which is why in the openings of the industrial sheds and high-rise buildings, buildings that are loose in the land, are the great importance.
Metal structure | Uniform Properties of Metal Structures
Metal has been produced in large metal factories under the strict supervision, uniformity of its properties can be assured and unlike concrete, its properties are not affected by external factors, ensuring the uniformity of properties of materials is effective in choosing a small coefficient of reliability, which saves consumption of materials.
1. Zhi Ge, Zhili Gao “Applications of nanotechnology and nano materials in construction” Advancing and Integration Construction Education, Research & Practice, 2008, Karachi, Pakistan.
2. Saurav “Application of nanotechnology in building materials” International Journal of Engineering Research and Applications, Vol. 2, Issue5, pp.1077-1082, (2012).