The most common work of construction units is to test steel bars.
Occasionally, such a thing happened. The main tendons of the beams made the workers tie the steel bars with a diameter of 25 to a diameter of 22 mm.
Change it, all the steel bars are tied up, the template is also supported, but also to remove the template, the real is too troublesome.
Later, a remedy method was adopted, and a steel bar with a diameter of 12 mm was added. The diameter of the steel bar was small and easy to penetrate. This problem was handled easily.
In fact, a method is used here: steel bar replacement.
How to replace steel bar? What else is substitution?
That's the topic today.
1. Equal Section Substitution
For example, Xiao Zhang went to the supermarket and bought two sets of noodles, each 1.2g, a total of 2.4kg.
When I got back, I felt inappropriate. 1.2g meal was not enough, and two meals were not enough. It was very inconvenient.
3 The total of 0.8g is still 2.4kg, which is called isosection substitution.
The following is the time to reveal the secret. Why can a steel bar with a diameter of 25 mm be replaced by a steel bar with a diameter of 22 mm and a diameter of 12 mm?
There is one thing that must be clearly stated. The cross-section of steel bar is circular. The cross-section area of this circular steel bar is called the cross-section area of steel bar.
As you can see from the table, the cross-sectional area of 25mm steel bar and 22mm steel bar is 490.9 and 380.1 respectively. The difference between them is 110.8.
The section area of 12mm steel bar is 113.1 > 110.8
3. What we need to pay attention to most is actually one point.
Knowing what equal strength substitution is, let's use equal strength substitution to save money.
For example, the cast-in-situ steel bar is designed to be 8mm in diameter, 1st grade steel and 100mm in spacing. It's too tedious to tie up in this way. Replace it. The diameter is 20mm, the third grade steel is 1000mm apart.
So excuse me? Cast-in-place floor, only a steel bar is placed 1 metre away, will it collapse?
What about that? In fact, the design countries of reinforced concrete are standardized. There are design criteria for what kind of components you are, the minimum reinforcement ratio, the spacing of reinforcement, the force difference between the 1 and 2 rows of reinforcement, and so on.
Therefore, any steel bar replacement, it is necessary to deal with the design of hexagram documents.