Steel frame – Code 2800, design of buildings against earthquakes
rose roofing:Code of Design of Buildings Against Earthquake or Standard 2800 (Code 2800) is a set of structural rules for the seismic design of various structural systems against earthquakes.
These regulations in the forties, which were later included in a chapter of Iran’s 519 standard, were a step in the way of strengthening structures against destructive earthquakes in Iran. The approval and mandatory implementation of the 4th edition of the 2800s regulations against earthquakes (2800 standard) in 1366 and 1367 also gave legal formality to the Iranian government’s national determination and program with a scientific image.
Compilation of the 2800 regulations led to the development of engineering regulations in the country’s construction process, and at the same time, the effort to implement it comprehensively and prevent violations was very effective in reducing the damages caused by earthquakes.
The government has entrusted the Ministry of Housing and Urban Development (Building and Housing Research Center) with revising the “Building Design Code against Earthquake” to be done every 5 years. Currently, the fourth edition of the 2800 regulations has been published.
The purpose of Regulation 2800 is to determine the minimum criteria and regulations for the design and implementation of concrete frame buildings, steel frame buildings, wooden buildings and buildings with building materials against the effects of earthquakes and special structures such as dams, bridges, piers It does not include marine structures and nuclear power plants.
In addition, for the seismic design of various pit stabilization methods such as anchorage, shielding, mutual restraint, nailing, truss guard structure, Berlin wall and diaphragm wall, as well as different bed improvement methods such as deep mixing Soil (DSM), high-pressure injection (jet grouting), pile, vibrating sand column, dynamic compaction, micro pile (micropile), reinforced soil (geosynthetic) should be referred to relevant regulations such as FHWA.
Of course, in the top-down (top-down) construction method, regulation 2800 and related regulations such as FHWA should be considered.
Types of irregularities in the structure
One of the most important structural issues discussed in the 2800 regulations is the determination of the earthquake force on the building and the control of irregularities in the structure.
Types of irregularities in the structure
Geometric irregularity: the plan in a building should be symmetrical with respect to the earthquake-resistant structural elements (frames) in the plan. According to this point, if there is a depression or setback in the building plan, if its size in one of the corners of the building in two directions is more than 20% of the length of the plan in that stretch, the building has a geometric irregularity.
Torsional irregularity: In structures, if there is a distance between the center of mass and the center of stiffness, the lateral force of the earthquake causes torsional anchoring in the floors, and the structure can be considered as torsionally irregular. According to the fourth edition of the 2800 standard, in an irregular structure with a lot of torsion, the maximum relative displacement at one end of the building (including random torsion and assuming Aj=1) is greater than 20% of the average relative displacement at both ends of the building. Is.
In cases where this difference is higher than 40%, the building is of severe twisting irregularity. Torsional irregularity control has a significant effect in determining Aj coefficient. This coefficient is used to determine random eccentricity. Accidental eccentricity at the level of each floor is considered in order to account for the possibility of accidental changes in mass and stiffness distribution on the one hand and the force caused by the twisting component of the earthquake on the other hand.
Irregularity in the diaphragm: in cases where there is a sudden change in the area of the diaphragm to the extent of the total opening levels more than 50% of the floor level, or a sudden change in the hardness of the diaphragm, to the extent of more than 50% of the hardness of the adjacent floor.
Out-of-plane irregularity: In cases where there is a discontinuity in the lateral force transmission path (such as a plane change), in at least one of the lateral bearing components in the floors, in the lateral bearing system.
Irregularity of non-parallel systems: in cases where some vertical components of the lateral bearing are not parallel to the main orthogonal axes of the building.
Regulations for the design of buildings against earthquakes
Earthquake is one of the natural phenomena that has terrified people many times throughout the history of human life and caused the destruction of cities and villages, along with human casualties. In line with the national determination and the government’s plans to reduce the damage caused by this phenomenon, the effective and constructive role of the “Building Design Code against Earthquake” in promoting safe construction is not hidden from anyone.
A few years have passed since the approval and implementation of the third edition of Iran Standard 2800 and the occurrence of severe earthquakes in Iran and other parts of the world, caused changes in building design regulations against earthquakes. It also makes different regulations unavoidable.
For this reason, revision and revision of this regulation should be done every five years and all study activities and scientific and technical investigations in this regard with the aim of “updating the regulation according to the analysis, design and construction methods of the country.” Taking into account the risks caused by the occurrence of accidents, also by taking advantage of scientific advances, local and global study-research achievements, it should be designed and planned.
In the fourth edition, by passing a work experience, the following executive policies were considered to carry out different stages of revision.
The vast country of Iran is located in one of the earthquake-prone regions of the world, on the path of the Alpine-Himalaya earthquake belt. The existence of many faults throughout the crust of Iran and the frequent occurrence of devastating earthquakes throughout history is a fact that we must accept whether we like it or not.
