The elevation value of the supporting surface of the positioning axis and supporting steel column exceeds the allowable deviation value of the specification, which is often seen in the steel structure engineering construction. How does the deviation occur?Which construction technology and process is misoperation?Today, the 3D steel structure editor will give you an analysis of the causes and preventive measures for the foundation positioning axis and support surface elevation of steel structure engineering,

 1、 The causes are as follows:

 　　1.There are errors and deviations in the basic survey control network, foundation survey setting out and elevation finding. 

Foundation positioning axis and supporting surface of steel structure engineering

　　2.The formwork of foundation support is not firm, the pouring concrete blanking is too high, and the concrete vibration impact makes the formwork displacement, resulting in the deviation of datum line.

 　　3.The use of steel ruler, theodolite and level gauge has not been verified and there are errors.

 　　4.Wrong construction drawings, wrong axis, no strict inspection.

 　　5.The surface of the poured concrete has not been plastered and leveled for the second time, resulting in the settlement, shrinkage and settlement of the concrete.

 　　6.The embedded steel plate (or support) is not fixed.

 In the process of construction and installation of steel structure engineering, because the foundation positioning axis and bearing surface are out of tolerance, the column installation axis and bearing elevation will be out of tolerance, which will affect the quality of the whole steel structure installation project.

 2、 Preventive measures:

 (1) The accuracy of the basic survey control network, the instruments and measuring tools used for setting out and leveling of the foundation survey shall be accurate. They must be checked or verified by the measurement department before use. If problems are found, they shall be adjusted in time to prevent errors or accumulated errors, resulting in the axis and elevation exceeding the allowable deviation.

 (2) The foundation formwork must be firmly supported with sufficient strength and rigidity.When pouring concrete and vibrating, it is necessary to prevent the impact of formwork and displacement.In the process of concrete pouring, the positioning axis and elevation shall be checked regularly with measuring tools or suspension wire. If any deviation is found, the pouring and vibration shall be stopped, and the reinforcement and adjustment shall be carried out after elimination.Before the final setting of concrete, the surface of foundation concrete shall be plastered and leveled twice.The elevation and levelness of the embedded steel plate or support shall be adjusted twice, and the bottom concrete shall be dense.The steel plate or support of foundation supporting column shall be provided with necessary fixing device to ensure the correct position and elevation

 (3) When the elevation and levelness of the steel plate or the bearing surface of the vertical and horizontal axis of the foundation and the column bearing surface are out of tolerance, the measures shall be taken according to the deviation degree.When the out of tolerance is not serious, it can be solved by shifting the column base, enlarging the hole and filling the base plate.If it is out of tolerance seriously and cannot be adjusted, it shall be studied with relevant departments and a feasible correction scheme shall be worked out before handling.

 3、 Standard error of foundation positioning axis and supporting surface of steel structure engineering

 Code for acceptance of construction quality of steel structures

 Article 10.2.1 the positioning axis, foundation axis and elevation of the building, the specification of anchor bolt inspection and its fastening position shall meet the design requirements.

 Article 11.2.1 the positioning axis of the building, the positioning axis and elevation of the column on the foundation, the specification and position of the anchor bolt inspection (bolt tracing), and the fastening of the anchor bolt (tracing bolt) shall meet the design requirements.When there is no design requirement, it should be in accordance with the provisions of Table 2.1 (steel structure engineering of single storey workshop can be referred to).

Article 10.2.2 when the top surface of the foundation is directly used as the bearing surface of the column and the embedded steel plate or support on the top surface of the foundation is taken as the bearing surface of the column, the allowable deviation of the bearing surface and the position of the anchor bolt inspection (bolt tracing) shall comply with the provisions in table 2.2.

The allowable deviation of bedded propeller pad shall be in accordance with Table 2.3