Selection of tachymetry spacing in the process of monitoring of construction projects

The urbanization of territories and the increase in density of urban development cause the necessity of introduction of improved structural solutions into the construction practice. This is also connected with both the erection of higher buildings with longer span structures and the use of non-standard methods for the analysis of structures. The introduction of modern structural patterns lessens considerably the weight of structures, reduces the consumption of materials and cuts the construction production costs. At the same time, the responsibility for the construction projects enhances. A systematic control over the state of structures including a quasi-continuous one, allows us to reveal the very beginning of destructive processes and to take measures for their liquidation. One of monitoring methods is the tachymetry survey of positions of a number of adjusting marks fixed at the structural elements. The non-reflection mode of operation of tachymetry survey allows lifting the restrictions for the number of points under observations. The combination of the afore-said factors determines the urgency of the use of the tachymetry as a tool for monitoring the state of the construction project. The subject of the study: the subject of the present research work is the methodology of selection of tachymetry spacing during the deformation monitoring of a construction project. The tachymetry can be carried out both in the mode of focusing on pre-established marks, and in the non-reflection mode through the points on the structure. The disadvantage of the first method is the need of installation of light-reflecting marks, which is not always possible due to some technical and/or aesthetic reasons and may lead to a significant increase in the cost of monitoring. The disadvantage of the second method is a reduced accuracy of the measurements. A wide incremental step may lead to the failure of detection of deformation processes, a narrow step means a considerable increase in the monitoring time and an unjustified rise in the cost of monitoring. Objectives: the purpose of this research work is the optimization of tachymetry spacing, which will reveal all deviations of structural elements from their permanent positions by a value exceeding the accuracy of measurements. Materials and methods: the initial material for the study included the results of geodetic observations carried out at various construction projects, in particular, the tachymetry results. The method of study includes the comparing of the limiting admissible curvature value to the minimum deformation value measured with the tachymeter accuracy. Results: a methodology is suggested for the selection of the tachymetry survey step. On its basis, a formula for the determination of a step value is offered that takes into account the geometry of the structure, the strain capacity of the material and the accuracy of the survey. Conclusions: the obtained results allow us to optimize the number of the observation points during the tachymetry survey and to ensure the detection of all destructive effects associated with structural geometry changes at the construction project. The descriptions of the methodology are recommended for their application in the development of geodetic monitoring programmes.