Master's Thesis
Civil-Structural Engineering
Abstract
Divergent bracing frames are considered earthquake-resistant systems for steel structures. These braces have a suitable hardness and very high plasticity. Using honeycomb as a link beam makes use of the properties of honeycomb beams. Honeycomb beams increase by 50% of the height of the original iron beam, if there is no change in the thickness and wing, as a result, in this case, according to the h/t regulation and control, the section is no longer a compact section. Also, due to the weakening of the honeycomb beam, these beams have less resistance to shearing efforts. Therefore, it is forbidden to use honeycomb beams as graft beams. The purpose of this research is to find a new method for using honeycomb beams as connecting beams in countries where there is no access to deep rolled sections to use the characteristics of honeycomb beams and divergent bracing frames at the same time. By conducting research on this type of beams, it was observed that by using a shear cell that follows the post-buckling mechanism like a shear wall, these beams can be used as a link beam. Also, the results showed that this built model has the required stability and energy dissipation and good flexibility. Keywords: honeycomb beam, divergent braced frames, link beam, cells Barshi
Chapter one:
General information about the honeycomb beam
1-1 Introduction
. Introduction
In areas where it is not possible to access profiles or deep rolled steel sections, the use of honeycomb beams in steel structures is an economical solution and It is common. The main advantage of using these beams compared to ordinary beams is to increase the section modulus without increasing the weight. Another advantage of honeycomb beams is the ability to pass electrical and mechanical facilities. from among the holes in the beam and as a result of that there is a general decrease in the height of the floor to the floor. Combined system divergent braced frames It is one of the advantages of bending frames and converging bracing frames (Figure 1-1). If these frames are designed correctly, during a severe earthquake, the connecting beam area will act like a fuse and prevent damage to other components.
The research topic of this article is whether it is possible to install or assemble a connecting beam (fuse) along the length of the honeycomb beam? According to the existing rules, on the one hand, the joint beam must be of a compact section type without any opening, which is not considered as a compact honeycomb section, on the other hand, due to the increase of 1.5 times the height of the normal beam, the instability of the beam is inevitable. Therefore, the use of honeycomb beams in diverging frames is invalid according to the existing standards.
It seems that if it is possible to think of measures to solve the problem of the compression of the section, especially the instability of the beam, it may be possible to use honeycomb beams in divergent bracing frames, especially as connecting beams. In the following, solutions will be provided to solve this issue.
Since World War II, many efforts have been made by structural engineers to find new ways to reduce the price of steel structures. As a result, many new methods were used to increase the hardness of the steel member without any increase in the weight of the steel. Honeycomb beams (castle-shaped) were one of these methods. Therefore, this method can be an important move towards the concept of "Ideal arrows" To be noted, in the discussion of economic design, there is a need for most of the materials of a bending component to be placed as far away from the neutral axis as possible. Honeycomb beams were made from standard I-shaped sections by cutting the web along an alternating pattern as shown in Figure 2-1.
(Images can be seen in the main file)
The main advantage of using these beams (versus full section beams) is to increase the section modulus and stiffness without increasing the weight. In addition, these sections are more efficient in long lengths. Another advantage of honeycomb beams is the ability to pass electrical and mechanical facilities.Among the holes in the beam, and as a result of that, there is a general decrease in the height of the floor to the floor (Figure 3-1). 1-2 History of Honeycomb Beams According to Boyer (1964), the name of the castle beams is derived from the design of the holes in the beam blade, and it means building like a castle, having a tower, or ordinary holes in the wall. is In the author's country of Iran, these poles « Honeycomb» They have been called which means having holes with a pattern similar to beehive houses [1]. Their commercial use in large sizes began after World War II and when industrial mass production with relatively low construction costs became important and saving materials through such methods was considered. In England, this process was first described by G. M. Boyd (1949) and produced by the Appleby-Fordingham Steel Company as a factory in a branch of the United Steel Company. The Litzka process and equipment was also developed by the Litzka stahlbu company in Germany, which allowed economic mass production in large sizes, thus reducing the unwanted distortions that occurred in production.
b) Beams with uniform or variable cross-sections in plate frames with inclined beams (frames known as sheds in our country)
c) Beams of single-layer lattice grids
i) Beams and mixed beams in concrete
n) Longitudinal or transverse deck beams Bridges (with steel mesh floor or mixed with concrete floor)
f) Compression members (columns) and compression-bending members (beams-columns)
e) Beams of construction machinery
-4 Area process
Honeycomb beams are made of I-shaped beams. The cross-sections are cut by various methods according to an alternating and sometimes non-alternating pattern. One of the cutting methods is cold-punching (3). Figure 5-1 shows one of the first devices of this method. After five, a part of the body of the arrow is removed, and with the development of empty spaces in the body, a zig-zag pattern appears in the body of the arrow. Panj operation is usually done by hydraulic press. The mentioned method is almost no longer used due to the low speed of execution and the loss of a large part of life.
Another method is the use of rollers with blades. This method is very popular especially in our country. Beam using roller The input enters the machine, the blade roller cuts the beam, and then it is ironed (smoothed) by the output roller and led out. Almost smooth cut edges, high execution speed, the possibility of working on site are the characteristics of this method. Figure 6-1 shows an example of this device.
One of the best and most standard methods is the use of gas flame in an automatic and controlled manner. The advantages of this method include smooth cut edges, fully controlled cutting, high execution speed, mass production and factories. Figure 7-1 shows an example of this method.
Sometimes they use a gas flame manually, in such a way that they first draw the appropriate pattern on the beam, then manually cut the beam using gas. Despite its simplicity, low cost, and the possibility of working on site, this method has disadvantages such as the slow execution speed of very irregular edges and the reduction of resistance due to the uncontrolled heat of the flame.
1-5 cutting patterns
Regardless of the cutting method, the cutting pattern also has many variations, including hexagonal, cellular and sinusoidal cutting patterns. Below are their types in detail:
Hexagon pattern: This pattern is very popular in our country. According to the design goals, the angle is between 450 and 650. Below are two types of commonly used angles that are given as standard patterns in the tenth chapter.
Sources:
[1] SHAHROKH MALLEK.