For all supports and connections the direct contact of glass and steel or glass and glass has to be avoided under all circumstances, since small

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2 For all supports and connections the direct contact of glass and steel or glass and glass has to be avoided under all circumstances, since small roughness and dirt at contact points can lead to dangerous excess loads. In between there is always to place a soft polymeric component (EPDM, Neoprene, Epoxy). Also the support has to be such, that no loads to constraints appear due to temperature differences, support deformation or tolerance problems. 3 4

3 Thermal crack due to highly absorbing foil. Areal crack due to bad dimensions. Delamination of PVB foils by weathering. Excess load in the support of the hand railing. Edge crack due to constrained supports. 5 6

4 Glazing is in generally supported by one of the following types: linear force transmission point transmission of force Adhesive bonding bearing type shear connection frictional bonding Pressure cap (Pressleiste); Post and rail facade (Pfosten Riegelfassade) In civil engineering, glass is predominantly used as membrane or plate. Therefore allsided supports are advantageous. Point transmission of forces are the most difficult ones, since tolerance problems can lead to constraint forces. However the gap between glass sheets can be much smaller than in the case of linear force transmission. Point supports need pre stressed glass, since the global stress field gets superposed by the local excess loads of the support. 7 8

5 Architects love point mountings. Basically there are different systems with cylindrical and countersunk bold fixings. Countersunk holes can be used to obtain a smooth surface for optical reasons, the load carrying capacity however is smaller than for clamped point mountings with clamping plate. The systems can additionally be fixed or made with a hinge to allow for constraint free mounting. If the dead load of a vertical facade is transmitted through a hinge in the window plane, it can be supported without inducing bending moments. 9 10

6 Point support with clamping at the edges can as well be used for suspended facades and the sheets do not get weakened by boreholes

7 Adhesive joints realize an almost continuous load transmission. The behavior of connections is regulated by adhesive properties and thickness. Thin layers result in stiff connections with high stresses in adhesive layers, thick ones can deform more strongly. A good adhesive is silicon due to its durability, good adhesion to glass and chemical compatibility e.g. with PVB interlayers and cast resin. Driving rain = Schlagregen A neat application of adhesive bondings for vertical glazing is structural Sealant Galzing (SSGS). Glass sheets are glued with silicon adhesives on frames. The bondline is sealing and has to take short term loads (eg. Wind suction). The dead load however is in generally transmitted mechanical via brackets. Advantage: Optically plain, undisturbed surface without pressure caps and glazing beads. No shadows on edge zones (thermal stress), simple cleaning and not holes. Problems: Quality of silicon bondline needs to be assured

8 The dead load typ 1 and 2 is transmitted via blocks. Safety factor is 6!! European Technical Approval Guidelines (ETAGs). The design stress for those adhesive are for dynamic load (wind) σ_rd=0.14 MPa for tension and τ_rd=0.11 MPa for shear. Values for static loads are significantly smaller

9 Direct glass contact is avoided by bushings made of polymers. There are pre fabricated and casted ones. Prefab are simpler to mount, but require smaller tolerances. For multilayer laminated glass this is problematic. Thickness is about 4mm and width >12mm. The design follows the one of steel components. Frictional type connections depend on pre stress

10 One classifies vertical glazing up to an inclination of 10. This classification is needed, due to different loading and load bearing types at different angles. For vertical glazing, typically the dead weight of the glass itself acts in the glass plane, while in horizontal glazing it acts perpendicular and the glazing has to act as a plate. However if one has to expect static loads perpendicular to the glass plane (e.g.. Snow), vertical glazing have to be designed also by the stricter rules of horizontal glazing. Vertical glazing lower than 4m above ground (shop windows) do not need to be designed, as well as roof windows smaller than 1.6m 2. In glass constructions, right now the safety concepts are transferred into semiprobabilistic concepts. These are based on a statistic description of input variables. Instead of global safety factors, partial safety factors are applied, that allow for a more detailed consideration of uncertainties. The concept is called semi probabilistic, since partial safety factors are used, that are obtained in a probabilistic way. However the proof of conformity is made by deterministic equations. The partial safety factor for the action considers disadvantageous deviations, as well as imprecise model assumptions for actions and uncertainties in determining their effect. The partial safety factor for the capacity considers disadvantageous deviations of characteristics like material, product properties, tolerances as well as uncertainties in geometric properties and in the model

11 Typical vertical glazing are curtain walls. They have to separate climatically, energetically, and acoustically and need to control permeability of light, air and heat. Additionally they have to protect against falling, fire, intrusion or explosions. In glass constructions different types of facade systems were developed that differ by the way they transmit load. An other criterion for classification is the support of glass sheets. The support can be maid by rails, posts, tethers, space frames etc. Rail constructions have linear or point supports of glass sheets. Free form surfaces are possible, but they miss transparency compared to tethered systems. Hanging facades take the dead load of the entire faces via point supports into the stiff roof construction. Wind load is transmitted via tethers or glass sheets. In vertical cable net walls glass is placed by spiders on tethers. Wind loads are transmitted by deformation of the cable net. Many other types exist. Vertical glazing is the most prominent case of application. In general there are no requirements of remaining load carrying capacity after fracture and laminated as well as toughened glass can be used. If tilted facades could bring a danger of injury to public zoned underneath, they have to be designed like an overhead glazing. For vertical glazing in general one has to design for load carrying capacity and usability for dead load and wind load Climatic load only for insolation glass For buildings with particular requirements, safety glasses might me needed

12 Curtain facade with tethered steel cables

13 Example Maximilian Museum in Augsburg. Point supports transmit compressive forces of glass sheets and fix the cable net. For overhead use, a passive fall protection is required: Even after fracture, for a certain time, no large fragments are allowed to fall on persons. With laminated glass made of annealed glass or heat strengthened glass this requirement can be met. If tempered glass is used, point supports can only prohibit falling sheets for a certain time and for linear supported types, the sheets can entirely slip out of the clamping zone due to large deflections and fall

14 For horizontal glazing the construction needs to be evaluated via: Load bearing capacity and usability for dead load, wind and snow Climatic loading if insolation glass Remaining loading capacity after fracture Impact resistance for hard impacts (falling ball test) 27 28

15 The used polymers in laminated glass have less durability than the glass itself. Delaminations, void formation, dulling of foils by chemical reactions with water, biodegradation etc can occur. In particular horizontal glazing with free edges need care e.g. by drainage edges. Contact of PVB with certain silicons also leads to chemical reactions and delamination

16 Cat A: Edges have to be protected from impact. Room high glazing, french windows without railing. Single glazing has to be laminated glass, insolation glass needs combinations with laminated glass. Cat B: Single laminated glass, clamped at the bottom. A continuous hand rail protects the upper glass edge and takes horizontal loads. In generals hand rails are fixed to side poles or walls to assure fall protection. Glass sheets <30mm distant can be consideres as arris protection. C1: Have to be from laminated glass. C2: This is the category of post rail facades

17 Balcony at the Willis Tower in Chicago/USA, 103.rd floor. Laminated toughened clear glass (3x12mm), heat soak tested with PVB interlayers, mounted on a stell frame on top. Everythin else is mouted with point supports. Dead load of 680kg (1,40mx3.7mx3.2m) for load of 5t and wind load of 6kN/m2. Heating at the lower edges of the glass to avoid iceing and ice cone formation. The entire balcony can be pulled in for cleaning purposes. Requirements for walk on glazing are of course static loads and enough remaining capacity after glass failure, impact protection against hard impacts. One needs to prove load bearing capacity and usability under dead and live loads Hard impact remaining capacity after failure. For walk on glazing laminated glass with at least 3 glass layers is used. The top layer is a wear layer that is not considered for the calculation. Shear interaction between different sheets is not allowed to be considered. The elements are connected by adhesive bonding, frictional type connections with stainless steel connections, bearing type connections or point mountings

18 Frosted wearing layer psychological reasons view protection anti-slip protection (DIN 51130) 35 36

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22 Bemessung und Konstruktion von hinterlüfteten Aussenwandbekleidungen ist in DIN geregelt. Gamma=specific weight 43 44

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28 Insolation glass effect: convex or concave pillow shaped deformation of glass by: Meteorological pressure changes Temperature changes Pressure and temperature difference between fabrication and installation site

29 Load combinations for the calculation of the isochoric pressure are worst case combinations. If glasses with a total absorption degree >30%<50% are used, this leads to additional heating (+9K*3kPa). Solar protection inside (+9K*3kPa), Absorption >50 (+18K*6kPa), thermal insolation behind the sheet (+35K*12kPa), not heated in winter ( 12K* 4kPa). TRLV 57 58

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