How to set the distance of the positioning grid

The positioning axis is the line used to determine the position of the main structure, such as the line that determines the spacing, depth or span of the building.

The anchor grid should coincide with the main grid axis. The distance between the positioning lines (e.g., span, column spacing, floor height, etc.) should conform to the modular dimensions to determine the position and elevation of the structure or components, etc. The connection between the structural components and the plane positioning line should be conducive to the unification and interchange of horizontal component beams, plates, roof trusses and vertical component walls and columns, and make the structural components reasonable and the structure simplified.

Measurement to properly control the verticality deviation of the building, and at the same time, to correctly position the floor and set off the line.

At present, in the construction of high-rise buildings at home and abroad, the commonly used axis vertical transmission measurement methods include theodolite projection point measurement method, laser measurement method, theodolite zenith measurement method, theodolite top-down measurement method and hanging hanging line pendant method, etc., which are introduced as follows.

Section 1 Theodolite projection point measurement method.

Theodolite projection point measurement method is a traditional measurement method, and it is also a relatively common method used in building construction. It mainly uses general instruments J2 and J6 theodolite for projection.

1. Advantages of theodolite projection point measurement method.

1. The measurement accuracy is generally higher, such as the climate, the location of the adjacent house, the scaffolding and other objective conditions are better, and the accuracy of the measurement will be higher when the closed wire is set up on the floor.

2 J2, J6 theodolite can be solved by the general construction unit, no need to read the angle during the measurement operation, so the operation is relatively simple, and the projection speed is faster.

3. Because the projection is not transmitted layer by layer, there will be no accumulation error, so the accuracy of measurement and positioning is improved.

Second, the shortcomings of theodolite projection point measurement method.

1. When the height of the building is high, due to the elevation relationship, the measurement distance should be long, and the construction in the urban area is narrow, and the on-site measurement and design work is difficult.

2. It is greatly affected by the climate, and it is not suitable to carry out measurement operations under sunny days, windy, rainy days and other climatic conditions, otherwise the accuracy will be affected.

3. The following problems should be paid attention to when using theodolite projection point measurement method.

1. The instrument should be fixed for each measurement, and the instrument should be strictly inspected before each measurement, especially the horizontal tube shaft of the alignment part, which should be strictly perpendicular to the vertical axis to prevent measurement errors caused by the defects of the instrument itself.

2. Special attention should be paid to the leveling accuracy of the instrument during each measurement. When measuring and setting, the measurement and setting methods of forward and reverse mirrors should be adopted. At the same time, the size of the elevation angle of the line of sight should be controlled, which should not be greater than 45 degrees, otherwise, the elbow eyepiece should be prepared on the theodolite to improve the observation conditions, because the elevation angle is too large, not only the operation is inconvenient, but also will reduce the measurement accuracy.

3. The measurement time should be selected before the sun comes out in the morning when there is no wind, cloudy day, to avoid natural conditions affecting the accuracy of measurement and design.

4. The ground control pile should be stable and properly protected.

5. Pay attention to the measurement error caused by the settlement of the foundation, and the settlement difference of the foundation should be measured frequently during construction, and it should be corrected in time once found.