Checking verticality works would encounter during building construction at several stages such as during installing vertical formworks of columns and transferring levels up successive floors of multi storey structures. Various methods which to control or check verticality works during building construction are discussed.
Fig.1: Verticality Works During Building Construction
Methods to Control Verticality of Structure during Building Construction
Methods used to check or control verticality works include:
- Plumb-bob technique
- Spirit level
- Optical plummet
1. Plumb-Bob Technique
Plumb-bob as shown in Figure 2 consist of a weight with pointed tip on the bottom attached to end of a string. The heavy weight will hang under gravity and offer a precise vertical line which is called plumb line.
Fig.2: Plumb-Bob Tool
This method is applied for checking or controlling vertical line of structural elements especially indoors such as lift shaft. Added to that, it is used to control verticality of foundation, walls, and columns.
Fig.3: Checking Verticality of Structural Elements
Fig.4: Checking Verticality of Columns
The plumb line or vertical line of plumb-bob is influenced by wind force and it will lose its accuracy and precision. Small to moderate lateral movement of plumb-bob can be reduced satisfactorily by damping it in oil or water.
If the height of structural member is large, then it is possible to replace the string with a long wire, but substantial cautions should be plasticized so as to avoid imposing risks to the personals working below.
2. Spirit Level Method
This tool is appropriate for controlling verticality of small scale works for example checking formworks and door frames. If spirit level is employed for approximate checks, then it is required to check the verticality with more accurate technique.
Fig.5: Spirit Level
3. Theodolite Method
Theodolite is substantially powerful instrument which can be used to check verticality works during construction with great precision and accuracy.
It is suitable for checking or controlling verticality of towers as shown in Figure 8, wall, foundation and columns as shown in Figure 9; specifically large number of columns along a one grid line.
It is possible to measure the slope of out of plumb line of the member by using Theodolite in combination with a tape.
The procedure used to check column verticality includes:
- Setting up the digital Theodolite centered on a peg that installed 500 mm from the column grid.
- After Theodolite set up accurately the laser beam will be turned on and focused it to the steel tape which is held to the formwork.
- Take the reading of the steel tape through the telescope.
- Take the readings of two positions at the same level on both top and bottom levels of the formwork. By taking two readings at the same level any curvature on the surface can be identified. These steps are illustrated in Figure 9.
Fig.6: Checking Verticality Using Theodolite
Fig.7: Checking Column Verticality Using Theodolite
4. Optical Plummet Method
It is an instrument that sight directly down or directly up. Optical plummet has an automatic compensator which increases its accuracy significantly compare with other methods used for controlling verticality.
Fig.8: Optical Plummet
Fig.9: Optical Plummet to Check Structure Verticality