Irregularity in lateral resistance
The resistance of a floor is the maximum force that the floor can withstand before it becomes unstable. In general, determining the exact value of the resistance of a floor requires non-linear analysis because the way the floor becomes unstable cannot be predicted from the beginning, however, sometimes approximate relationships are provided in steel and concrete reference books to determine the resistance of a floor. The point that we should pay attention to is that factors such as creating an opening in the shear walls and removing the bracing on the floor, which we mentioned in the discussion of irregularity in hardness, can also cause a decrease in the strength of the structure. Of course, note that due to the difference in the concept of hardness and resistance, in general, the amount of change in hardness and resistance in these cases is different from each other. The regulations are sensitive to the reduction of resistance in the structure’s floors, similar to the reduction of hardness, and they consider it one of the examples of creating irregularities in the height of the structure. According to the fourth edition of the 2800 standard, the reduction of resistance in the floors of the structure should be controlled, according to which if the lateral resistance of the floor is less than 80% of the lateral resistance of the floor above it, that floor causes an irregularity in height and as a result the whole building is irregular in height. .
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