Calculation Methodology of Translucent Construction Elements in Buildings and Other Structures

The paper proposes a calculation methodology of translucent structures elements in buildings and other structures under distributed or concentrated load. The authors describe calculations sequence and introduce formulas used to determine tensile and shearing stresses influencing glass and sheet glass deflection. Mechanical loads to which translucent structures are subjected should be calculated with account of the SP 20.13330.2016 requirements, "Loads and impacts". The task of calculating the translucent part of the structure is reduced to determining maximum stresses in the glass under the calculated load q. This value should not exceed calculated stress values under bending R and the glass used. Triplex should be calculates as two independent glasses under 0.5 values of the total load. In multilayer glasses (triplex) the thickness of sheets should be taken as identical, being not more than 10 mm of each sheet. According to this methodology, the calculation error of sheet glass in translucent constructions of buildings and structures does not exceed 10%.


Introduction
More and more buildings around us are covered with translucent shells, allowing to penetrate the sunlight not only in the buildings, but also into the streets of cities. Airiness, transparency of the facades make it possible to turn a stone jungle into a space filled with air and light.

Materials and methods
The applied translucent structures should provide not only protection from environmental impacts such as cold, noise, water, dust, but also to perceive mechanical loads on the facades of buildings and structures.In connection with this, a technique is proposed for calculating the translucent structures of buildings and structures under the action of a

Results
The calculation of translucent structures begins with the definition of the type of load: distributed q, or concentrated P , and the location of its application.
Mechanical loads acting on translucent structures must be determined taking into account the requirements of SP 20.13330.2016"Loads and effects".Having determined the magnitude and type of the load, the strength and deformation calculation of the transparent part of the translucent structure is immediately performed.When using laminated glasses (triplex), the thickness of all sheets should be the same and not more than 10 mm each sheet.
The triplex should be calculated as two independent glasses under 0.5 times of the total load.
The task of calculating the translucent part of the structure is to determine the maximum stresses in the glass from the action of the calculated load q.This value should not exceed the calculated values of stresses in bending R и of the applied glass.
The calculated value of the voltage R и depends on the strength of the used glass in the bend R ри and the importance class of the building: in which -R иcalculated sress of the glass under bending; R риultimate resistance of sheet glass under bending, experimentally measured (glass strain at the sample fracture); сassurance factor, depending upon the importance calss of the building and measured in Table 1.We calculate the sheet thickness as the first step.As there are two unknown values: the thickness of the sheet and the stress in the glass.This value is assumed to be equal to the thickness of the glass presented in the translucent structure, or presented by the formula: The calculation is carried out in the following consequence: The thickness of the glass (2) in the interval between from 3 to 10 mm (3,5 ,6, 8, 10 mm), depending upon the value of the calculated load or a triplex made of these sheets.
The following coefficients are used : We identify the value of the tensile stress σ рn in the angular zone: We identify the value of the sheer stress: We measure the value of the reduced tensile stresses in the angular zone: The obtained value of the reduced tensile stresses is compared with the design value of the stresses in the glass: If the value of the reduced tensile stresses is greater than the calculated values of the stresses R и , increase the thickness of the glass h or the number of sheets, the calculation until σ р пр is less than R и 10%.In all the above formulas: a, b, hlength, width and thickness of the sheet, mm.The deflection of the sheet glass, supported along the contour, is determined by the formula in which: fdeflection of the central part of the sheet, mm; qcalculated equally distributed load on one of the sheets, kPa; Emodulus of elsticity, MPa; a, blong and short sides of the sheet, mm; hthickness of one sheet, mm; μ -Poisson's ratio of the glass; γcoefficient, regarding the change of the rigidity of the sheet under load.
The deflection of the sheet under the calculated load should not exceed 1/150 of the long side.If the deflection is greater than this value, it is necessary to increase the thickness of the glass, the number of sheets or provide rib stiffeners.
Under the action of the concentrated load in the central zone of the plate, the total tensile stresses are determined by the formula: in which: σ рп -tensile stress in the glass with the power, MPa; Рconcentrated force, influencing one sheet, kH ; αcoefficient, corrects for the location of conditional bearings; λcoefficient, considering the state of neutral axis; γcoefficient, considering the change of the sheet rigidity under the influence of concentrated force.
The results of the exploitation of testing sheet glass showed the coefficients and computing formulas.
For relatively thick sheets, in which ζ ≤ 100, coefficient α is regarded equal to α = 0,37, ζ > 100 according to the formula: (0,8 40) 100 The obtained value of tensile strain is compared with the calculated value of glass tensile:

.
central partof the sheet under the influence of concentrated force is measured by the formula: Deflection at the rated load should not exceed 1/150 of the long part of the sheet.If the deflection is bigger than the present value, you should increse the glass thickness, number of sheets or to preview the stiffering ribs.

Table 1 .
Factor of safety of glass durability