ROOF SYSTEM HISTORY
ROOF SYSTEM HISTORY
Space Roof Systems
SPACE ROOF The material used consists of steel pipes, cones, bolts and nuts. These are obtained by screwing the rod pipes to steel spheres of various diameters. This global construction is called a sphere. The pressure force generated on the pipes is transferred to the spheres through the bolts and the pulling force is transferred by the bolts. The load on the space roof is calculated by a special program called "framecad". Space System The space frame makes the most convenient way, as soon as possible, with advanced technology information and computer aided technology support
Advantages of space roofing Quick drawing, fabrication and assembly Low-cost application in the short term Contemporary solutions in the projects Variable modules and heights Functional use possibility Easy application with lighting and ventilation systems Free drawing Aesthetic appearance High corrosion resistance Different application with all kinds of roofing material possibility to create decorative image in interior and exterior environment Possibility of easy transportation and storage of system elements Advantage of quickness in installation on the ground and in the air Space roof is a three dimensional very rigid structure. This means that large openings can be crossed with low system heights.
Prefabricated Steel Space Cage Systems and Application Problems
Nowadays, the covering of wide open spaces is usually carried out by space cage systems. Economical, fast, aesthetic and safe solutions for space cage construction are possible with prefabricated steel space systems. Thus, prefabricated steel space systems, contemporary technology, are offered to the service of the architect. In space cage systems, each node is held in three directions with rods. For this reason, knot points have a high degree of hyperostability, so the articulation of the joints is the right approach. Beyond the large openings, systems such as traditional steel roof constructions have now left their place in prefabricated steel space systems. There are companies manufacturing and assembling about twenty prefabricated steel space frame systems in medium and large scale in our country. A large number of prefabricated steel space frame structures are being built by these companies every year, in the country, and abroad. On the other hand, it is also a fact that the prefabricated steel space cage system construction, whether for a small number of reasons or not, is completely or partially displaced due to various reasons. In this study, the problems encountered in the practice of not being able to obtain more economical and safer solutions in the prefabricated steel space frame systems from the beginning to the end of the assembly will be discussed and some suggestions will be made.
"Prefabricated steel space frame systems" have a very high stability. Wide openings in various geometries provide a very economical solution for the indoor use without collar. Moreover, since these systems are prefabricated from standard elements, the design, fabrication and assembly times are very short and the problems arising especially from workmanship errors are minimized. Space lattice systems are formed by screwing in the nodal points formed in special geometric shapes, the nodules opening on riveted, welded or nodal points. The first application of three dimensional lattice systems was carried out by Graham BELL in 1907. The tower built by BELL is a simple space cage system. Multi-storey space cages in Germany were built by MENGERIN-GHAUSEN in 1942. In this system, 18 rods can be connected to the specially manufactured knot points without forming eccentricity. Since this system has a lot of rigidity, it has found use in many buildings.
Prefabricated Space Frame Systems are modular systems consisting of union of three-dimensional rods that are not in the same plane at one point, unlike steel scissor systems. These systems, which have been widely used in Europe and America for almost forty-five years, have a wide range of applications. Previously used prestressed concrete, classic steel roof constructions or similar systems used in the passage of large openings left their place today with space cage systems. Space lattice system designs are based on open space (one-way or two-way large openings), one-way large open spaces such as warehouse, hangar, factory etc. it can be done as a space beam in a structure, or a space frame system can be formed which is a combination of modules for two-way large openings. This system can be pyramid, spherical shell, cylindrical or multi-storey depending on architectural or static construction.
Due to the fact that it can be applied as industrial facilities, factories, airplane-helicopter hangars, swimming pools, sports halls, warehouses, tribunes, theaters and opera houses, cinemas, petrol stations, exhibition stands, shops, classrooms, school buildings, laboratories and exhibition departments, It allows to use in different places and is also very convenient and economical for applications in these structures. Having a decorative structure has expanded its usage area. It has the feature of being able to pass through large openings because it is a three-dimensional light structure. Because the two-way can pass through large openings, the center can be used comfortably by increasing the area of use. According to the situation of construction, more than 15m consoles can be arranged from all sides. It provides great facilities due to its small number of different elements for manufacturing and assembly. The desired form can be given to the roof with the space system. Constructions in the form of sloping roof, cradle roof, spherical roof, vault, pyramid can be realized easily in one direction or in two directions.
Air conditioning ducts, plumbing and electrical pipes can easily pass through the space system. Natural lighting can be provided. Any roof covering can be applied on it and the suspended ceiling can be easily arranged on the interior. It has a more flexible structure than other systems due to heat exchange. The node displacements are very small because the rod tongues are close to each other.
Because the production is prefabricated, it is possible to easily change the location of the building by demounting it. Installation is very easy. By using only a nut key, thousands of square meters of space systems can be built. Mounting can be done on site as well as on site. This is an important criterion in terms of suitability for different construction conditions. Since the production and assembly times are very short, the price increases that are taking place over time are prevented. In addition, the level of economic efficiency is high because it removes the cost of scaffolding, mold, natural concrete, wooden roof construction, veneer and tile cover in the conventional systems. Taking the plant to operate in a shorter time provides a great contribution to the investor and also to the economy of the country.
STEEL SPACE SYSTEMS
Steel Dome Systems
The entrance of the steel dome came into existence in 1811. After the first years of use of iron or coarse iron elements, we can see that steel dome systems of various types are used in the 19th century when large openings are covered in the rapid development of steel production technology. The London dome, covering the Royal Albert Hall built during this century (1867-1871) and still standing, has an oval plan of 76 and 56 m. Steel domes are often referred to by designers. Föble, Zimmerman, Fuller, Mohr Kebelerlerini can give as an example.
Classification of Steel Dome Systems
According to Makovski, steel dome systems are classified into four main groups.
a- Single-line domes
b- Double line domes
c- Dented leather-type domes
d- Domes with special form surface
The classification of steel dome systems still causes confusion in this area. This is because it is difficult to get to a certain standard in classification because of the necessity of constantly getting new geometry of the cube in the new form, and also the use of different constructions and knot systems in the carrier system. According to the classification above, the first type is dominant. They are usually used to pass openings up to 100 m. The second type of domes are used to pass more than 100 m openings. To give an example of the second type, the net span of the world's largest dome covering the New Orleans sports stadium is 213 m.
On the other hand, if the steel dome built in the last two decades is examined, it can be seen that in practice, four or five types are used most frequently. These are Ribbed dome, Schwedler dome, Grid dome in three directions, Parallel-lamella dome, Geodesic dome, Double line dome.
Space Cage Carrying Systems
Space lattice systems are planes or curved lines of two parallel rods, which are interconnected by rods that connect these nets to each other's nodal points. It is not compulsory that both rods have the same shape. This carrier system has been a rapid development since 1950 with the work of Le Ricolais in the United States, S. du Chateau in France and Z. Makovski in England. .
Initially, the node points were implemented as bullets or welds as traditional combinations. Gradually, it has been seen that a number of special combination arrangements have emerged that provide an attractive industrialization to this carrier platform. This technological development naturally led to the standardization and the ready-made. Ready-made is based on simple elements such as nodal points and rods, or composite elements such as triangular or tetrahedral. The modulating facilitates the transformation of the carrier arrangements.
Space cage systems have many advantages. Two of the most important ones are lightness, rigidity.
Due to the fact that there is almost no bending element in the case of the failure of an element in
order to create a high degree of hyperactivity in the case of an element failure, the most convenient
utilization from the material, the great freedom in the shaping and drawing, the ease of assembly
and assembly, the ease of dismantling and replacing, the initial inconveniences have been phased out
. The technological challenges arising from the combination of different space-widening bars have
been solved by a large number of construction systems on the market. Account difficulties are no
longer a hindrance after the widespread use of computers. Node Systems in Steel Space Systems One
of the biggest challenges in the manufacture of steel space systems is the creation of node points. A
convenient nodal point has a significant effect on ease of installation and cost of the system.
Particularly in the construction of the domes, providing the appropriate node is a very important
problem. Prefabricated steel space cage structures use many knot systems. Some of these are
VVachsman, Oktaplatte, S.D. C, Triodetic, Varitec, Unistrut, Gero, Mero and Nodus nodal point
PROBLEMS APPLICABLE TO APPLICATION
In our country, mostly prefabricated steel space cage system construction is being constructed or controlled by the Ministry of National Education, Ministry of Public Works, General Directorate of Geçitlik ve Spor, Special Provincial Administrations, Municipalities and Private Sector. In particular, a number of prefabricated steel space lattice systems are being constructed within the control of the Ministry of Public Works, General Directorate of Late Autumn and Sports. When any prefabricated steel space cage system construction is on the agenda, the person or institution concerned sends the request to the company that manufactures the prefabricated steel space frame system together with the characteristics of the demand. The manufacturer evaluates the request and projects it before making the production at the factory or at the workshop. then completes the prefabricated steel space cage system construction by assembling. As can be understood from the above statements, the construction of a prefabricated steel space cage system comes to three main stages. These are projecting, production (manufacturing) and assembly stages. Therefore, it will be correct to analyze the problems encountered in practice according to these stages.
In our country, prefabricated steel space frame system static projects are usually implemented using the Framecad program. The necessary architectural information is given to the relevant Civil Engineer and static project works are started by using Framecad program in the frame of this information. Even if the computer programs used are considered to be correct solutions, the professional formation of the engineer who will do the static design will affect the accuracy of the solution made by the features such as program dominance positively or negatively. Here, you should immediately underline your facts. In most of our universities, there is no training for branching. As a result, there is no adequate training on steel structures, or more particularly prefabricated steel space frame systems. Therefore, an engineer who will work on prefabricated steel space cage systems has to train himself after university. It is obvious that there is not a healthy approach to this. It is sufficient for very few of the civil engineers who work in the prefabricated steel space cage system companies. The need for trained staff in prefabricated steel space cage systems companies is always a major problem, as the civil engineering of craftsmen, due to the staffing policies of the companies or other reasons, has moved into other professions.
On the other hand, both the legal gaps in our country, market conditions, both the prefabricated steel space cage system companies and the contractors or subcontractors cause them to move within the framework of making money at any cost. In this case, it is regrettable that in static design, the aim is not to establish a safe and economical structure. The fact that there are not enough civil engineers in this area in the control organizations also makes it easier for those who want to gain unfair advantage. If the legal gaps are not resolved shortly and the necessary regulations are not made and the related personnel are not trained in this area, it will be inevitable that the construction of the prefabricated steel space frame system will be carried out every few years.
Often it is shown in the architectural project of a building to be closed with a prefabricated steel space cage system, not in accordance with the prefabricated steel space cage system technique, but forbidden. The most important reason for this is that our architects who are preparing the architectural project are also foreign to the prefabricated steel space cage system. They also do not know how the geometry of our architects' structure affects the behavior of the prefabricated steel space frame under different loads. In other words, while the architectural project is being prepared and the static system of the basic structural system to carry the prefabricated steel space frame system is being prepared, it is treated independently of the prefabricated steel space frame system. For example, if you are designing a gym with a 40-50 m span as a single slope and want to close it with a prefabricated steel space cage system, you will have to migrate to the steel roof in the face of unexpected effects, such as snow loads, which accumulate in a particular area of the roof. I would like to remind you here that the Ministry of Public Works and the General Directorate of Geçitlik ve Spor should take care of the type projects. If there are building types that invite demolition in terms of both architectural features and reinforced concrete carrier system, the necessary precautions should be taken as soon as possible.
In order for a prefabricated steel space cage system to be suitable both for economic and safety reasons, the accuracy of the computer program primarily used, the professional formation of the engineer who prepares the static project and the dominance of the program are of great importance. The loads on the project must reflect the truth. Due to various reasons; it is also a fact that projects are either overloaded or under-loaded. For this reason, the solutions made are either below the safety limits, or they have heavy construction. Sometimes we are faced with structures that are both heavier and below safety boundaries. It is not possible to say that steel structures such as TS 498, TS648 and TS3357, which are in force in our country, are sufficient to design safe steel structures. These requirements should be rearranged in accordance with the needs of the day and scientific developments, or the use of European specifications should be made compulsory. Because, under current conditions, it is not possible to say that a steel structure that is static designed according to the specifications of steel constructions such as TS 498, TS648 and TS3357 which is in force in our country is a safe structure. The situation is even worse in terms of prefabricated steel space cage systems. Although there are technical specifications of a prefabricated steel space frame system that are introduced by companies, it is not possible that this requirement is sufficient. The extent to which this specification is binding for companies is also a separate matter. At this point, our recommendation. In the short term, a "Prefabricated Steel Space Lattice System Specification" compliant with other relevant specifications should be prepared and put into practice. Because, in developed countries, different specifications are used for different constructions. As long as the loads, the deflection, the stresses and other constructive principles to be taken in the calculations are not clearly revealed, an unfair competition environment is created and unsafe or uneconomical constructions are made.
Prefabricated steel space cage system production is a production requiring precision workmanship. If the project is prepared correctly and the work orders are properly transmitted to the factory or the workshop, it is very unlikely to make a mistake during production. If there is any mistake made, this error will occur at the time of installation and the structure will be removed before use. On the other hand, in the course of production, unfair competition conditions or the desire to earn a lot of money push manufacturers to make some wrong choices. At the beginning of these wrong choices is the use of faulty pipes. Poor pipes, deformation, corrosion due to corrosion, paint thinned or insufficiently painted without adequate sanding. In particular, pipe welds of cones are also found to be faulty. Sometimes low quality conical elements are also used. One of the most important elements of prefabricated steel space frame systems is the node point elements. The mero node system is generally used in our country. In full sphere systems, tooth scrapes are found in the bulls and sphere explosions are found in the empty spheres. In particular, under direction-changing loads, emptyspherical systems must be well-validated. As is known, spheres are elements that are heated up to plastic sheathing and then stamped on the press. In the process of bringing plastic material into the mold, an overheating process will adversely affect the quality of the material. On the other hand, adequate heating or irregular tattooing will also affect the quality of the clutch and therefore the bearing power in the negative. Another node system element used in prefabricated steel space cage systems is bolts and pins. These are usually taken from the market. In particular, it is necessary to attach great importance to the quality of these elements. Because of the reasons for the migration of prefabricated steel space cage systems, bolts cutting and tooth scraping are at the beginning.
Prefabricated steel space cage systems are one of the reasons for the failure of the assembly process. Even if you have a perfect project, perfect production, mistakes that can be made during the assembly phase can cause your building to collapse. Unfortunately, manufacturers often find it difficult to check for errors during assembly. Removal of defects in the mounting system during the assembly phase, which would take place in the prefabricated steel space cage system, is an important problem. If the prefabricated steel space cage system is not fitted to the system to carry it properly, as projected in the project, the members will lose their carrying capacity by exceeding the prescribed limits of strength in the project and the structure may be displaced. The most common mistakes in assembly are; lack of proper use of the pins in the nodal points, failure to use the pins, no proper positioning of the support points on the support plates, no proper positioning of the support plates on the main bearing system members, no tightening of the support plate bolts, neglect of paint finishes, is that the module is deformed in modular assembly.
RESULTS AND RECOMMENDATIONS
The purpose of designing a structure is to ensure that it is economically and functionally safe to provide any kind of effect that may occur during its useful life. The purpose is the same for prefabricated steel space cage systems. In our country, in the field of steel structures, the number of engineers and other technical personnel trained in terms of quality and quantity has not reached the point that steel structure applications deserve due to reasons such as the lack of necessary habits about steel structure in the sector. Therefore, according to developed countries, progress in this area is very slow. Prefabricated steel space lattice systems are common systems in our country in the last twenty years. Due to various reasons, there are not enough technical staff to control both production and application as well as work done. The prefabricated steel space cage system work is a workplace with its own characteristics in the case of a subdivision of the steel construction science branch. For this reason, especially the state control agencies, have to train enough staff in this area.
Prefabricated Steel Space Frame System Constructions usually find application areas in Ministry of National Education, Ministry of Public Works, General Directorate of Late Night and Sports, Special Provincial Administrations and Municipalities in a few cases built by Private Sector. On the other hand, most of the structures made under the control of the Ministry of National Education, the Ministry of Public Works, the General Directorate of Late Autumn and Sports are the types. In total, when the number of these types does not exceed it, even two structures with the same property in the same region vary greatly between the steel material removal in the unit area; accordingly, the costs increase at an abnormal rate. If we compare this with the structure of the private sector in the same feature, the price difference between them is much bigger. In this case, our recommendation should be to have the production of the Prefabricated Steel Space Lattice System Projects according to the type of structures and especially the investor organizations, which we regard as the above, by preparing or preparing the prefabricated steel space lattice system projects and giving them to the production companies. Those who work in this field know how much the state will benefit from this work. Thus, it will be possible to produce economical and safe prefabricated steel space frame systems in our country as well as unfair competition among the companies in the sector will be lifted. People and organizations that do not have adequate naval and personnel will also be removed from the sector.
Source: : TMH - TURKEY ENGINEERING NEWS ISSUE 418
Author: : Y. Doç. Dr. Zeki AY, İnş. Müh. Gülhan DURMUŞ