Analysis of Resistance to Wind Suction of Flat Roof Coverings Glued with Polyurethane Adhesives
Abstract
:1. Introduction
- The type and power of the chemical interaction with the glued surfaces—adhesion—if the adhesive reacts chemically with the substrate forming chemical bonds with it; typically, such a weld is more resistant to being formed by adhesives that penetrate only into the glued surface;
- The penetration depth into the glued material—the higher, the better, but if the adhesive penetrates too deep, it can damage the glued material’s structure; the penetration depth can be increased by raising the roughness of the glued material’s surface;
- The mechanical strength of the adhesive layer, cohesion, depends on the chemical structure of the adhesive;
- The size and shape—the larger the adhesive bond area and the more irregular its shape, the stronger it becomes.
2. Materials and Methods
2.1. Materials
- -
- Product 1—polymerisation of monocomponent polyurethane adhesive under moisture, open time ca. 30 min, complete curing time ca. 90 min, density 1.11 g/cm3, dry matter content 99%, thermal resistance from −30 °C to +120 °C, application temperature between +5 °C and +40 °C;
- -
- Product 2—polymerising of monocomponent polyurethane adhesive under moisture (polyurethane prepolymer), skin—over time ca. 80 min, open time ca. 40 min, complete curing time ca. 60 min, thermal resistance between −40 °C and +90 °C, application temperature from 0 °C to +35 °C.
- ➢
- Substrates, consisting of two elements for each test specimen, size 1.25 m × 2.5 m, with a gap over the entire length of the test specimen, approximately 4 mm ± 1 mm wide and over the full height of the substrate, placed in parallel to the side of a pressure chamber:
- (a)
- Concrete slabs, C 30/37;
- (b)
- Galvanised trapezoidal steel sheets T55.
- ➢
- Thermal insulation materials:
- (a)
- PIR ETX 50 boards (rigid cellular polymeric product mainly of polyisocyanurate groups), 50 mm thick, consisting of a thermal insulation core made of rigid PIR foam, density 30 kg/m3, covered on one side with glass fibre tissue (ETX); hardness and resistance to damage σ10 = 150 kPa, λ = 0.027 W/mK;
- (b)
- EPS 100 boards (expanded polystyrene), 50 mm thick, compressive stress: 100 kPa, flexural strength: 150 kPa, λ = 0.036 W/mK.
- ➢
- Roof covering materials:
- (a)
- PVC membrane (polyvinylchloride membrane)—roofing membrane made of pliable PVC, 1.2 mm wide, laminated on the underside of the nonwoven polyester roll, tensile mechanical characteristics 1100 N/50 mm, at elongation ≥ 15%, flexibility at low temperature −30 °C.
- (b)
- Laminated EPDM membrane (terpolymer of ethylene, propylene and a diene with residual unsaturated portion of diene in the side chain membrane), 2.3 mm thick, laminated with non-reinforced synthetic membrane formed from two EPDM layers with a total thickness of 1.3 mm. The membrane is laminated with nonwoven polyester fabric, 160 g/m2 mass per unit area. Maximum tensile force of membrane 400 N/50 mm, at elongation < 40%, flexibility at low temperature < −40 °C.
- (c)
- EPDM membrane—not laminated, with non-reinforced synthetic membrane formed from two EPDM layers (i.e., synthetic rubber—ethylene-propylene-diene-monomer) with a total thickness of 2.0 mm.
- (d)
- Bituminous primer, bitumen content ca. 65%, density: 0.85–0.95 kg/L, VOC content 350 g/L.
- (e)
- Vapour barrier—elastomeric reinforced bitumen sheet, 3.8 mm thick, with a glass fabric insert with aluminium coating. Maximum tensile force 500/400 N/50 mm (+/−100/100), at elongation 4/4% (+/−2/2), flexibility at low temperature −15 °C.
- (a)
- For concrete substrates:
- (b)
- For substrates of trapezoidal sheets:
Set No. | The Arrangement of the Layers (Stacking Order) | ||
---|---|---|---|
Substrate | Thermal Insulation Boards | Covering Layer | |
Set I | Concrete primed with a bitumen liquid + vapour control layer (reinforced bitumen sheet) glued to the substrate over the surface. | PIR ETX, 50 mm thick, glued to the substrate with polyurethane adhesive—product 2, strips applied every 15–20 cm. | Laminated PVC membrane, glued to the substrate with polyurethane adhesive—product 1, all over the surface |
Set III | Laminated EPDM membrane, 2.3 mm thick, glued to the substrate with polyurethane adhesive—product 1, all over the surface | ||
Set II | EPS 100, 50 mm thick, glued to the substrate with polyurethane adhesive product 2, strips applied every 15–20 cm. | Laminated PVC membrane, glued to the substrate with polyurethane adhesive—product 1, all over the surface | |
Set IV | Laminated EPDM membrane, 2.3 mm thick, glued to the substrate with polyurethane adhesive—product 1, all over the surface | ||
Set V | Galvanised trapezoidal steel sheet T55. | PIR ETX 50, 50 mm thick, glued to the substrate with polyurethane glue—product 2, two strips on each upper flange of the sheet steel (along the edge). | Laminated PVC membrane, glued to the substrate with polyurethane adhesive—product 1, all over the surface |
Set VII | EPDM membrane (not laminated), 2.0 mm thick, glued to the substrate with polyurethane adhesive—product 1, all over the surface | ||
Set VI | EPS 100, 50 mm thick, glued to the substrate with polyurethane adhesive—product 2, two strips on each upper flange of the sheet steel (along the edge). | Laminated PVC membrane, glued to the substrate with polyurethane adhesive—product 1, all over the surface | |
Set VIII | EPDM membrane (not laminated), 2.0 mm thick, glued to the substrate with polyurethane adhesive—product 1, all over the surface |
2.2. Methods
2.2.1. Laboratory Tests
2.2.2. Numerical Investigation
- A roof surface for a standard industrial structure, at a roof slope α < 11.5° (i.e., 20%).
- Dimensions of the building:
- -
- Length d = 30.0 m;
- -
- Width b = 15.0 m;
- -
- Height h = 10.0 m (typical height of double-storey industrial facilities), an altitude A = 1100 m above ground level.
- Dimension e = min (b, 2 h) = 15.0 m.
- The basic value of the wind base velocity according to EN 1991-1-4 [30]:
- Directional factor (unknown wind direction): cdir = 1.0.
- Seasonal factor: cseason = 1.00.
- Wind base velocity: vb = cdir·cseason·vb,0 = 32.56 m/s.
- Reference height: ze = h = 10.00 m.
- Terrain category I roughness coefficient:
- Coefficient of topographic profile (orography): co(ze) = 1.00.
- Mean wind velocity:
- Turbulence intensity: Iv(ze) = 0.145.
- Air density:
- Velocity pressure peak value:
- Construction coefficient (building less than 15 m high): cscd = 1.000.
- External pressure coefficient cpe = cpe,10 = −1.8.
3. Results
3.1. Results of Laboratory Tests of Wind Suction Resistance
3.2. Results of Numerical Calculations
4. Discussion
5. Conclusions
- The tests confirmed that some polyurethane adhesives used for the adhesive of PVC and EPDM membranes on flat roofs with an up to 20% slope ensure high resistance of complete systems to wind suction, characterised by values of up to 8 kPa (Table 3).
- The roof cover sets laid on concrete (C30/37) substrates reveal resistance to pulling off as a result of wind suction (pulling at 7.5–8.0 kPa pressure) greater than those glued to the trapezoidal sheet substrate, i.e., galvanised trapezoidal steel sheets T55 (pulling off in the pressure value range between 1.5 kPa and 7 kPa).
- A comparison of the results of wind suction resistance for laminated membranes and membranes without additional reinforcement of the surface underside reveals a significant adhesion increase in the adhesive bond when polyurethane adhesive can partly penetrate the glued layer, meaning the underside laminating layer, together forming a rigid structure. The interlayer cohesion forces within the formed adhesive bond do not exceed the adhesion values between the laminating layer and the membrane without compromising adhesion in this plane; de-bonding (pulling off) occurs in the thermal insulation layer.
- The adhesive bond formed between an EPS board and a roof covering made of a plastic (PVC) or rubber membrane (without laminating on the underside of the surface) is the weakest spot in the analysis of covering sets glued with polyurethane adhesives.
- Wind impact simulated in fatigue cycles described in this manuscript, in the 0–4 kPa range, corresponds to the averaged values occurring in a ca. 1.5 m wide range in the edge and corner zones, determined assuming extreme weather impacts on a flat roof.
- The values of the resistance of the roof coverings to wind obtained in calculations performed according to EN 1991-1-4 [30], even under stringent computational assumptions, do not reflect the actual pressure distribution, which typically has parabolic shapes and local extremes occurring at the edges of the roof.
- The external pressure coefficient plays an important role in analysing a building’s wind load; the coefficient depends on the shape, dimensions and size of the surface analysed. Basic and mean wind velocities are significant but do not determine the final pressure distribution on the building surface.
- In the case of complicated geometry and complex wind load, in order to correctly design covering solutions for a specific structure, it is recommended to compare the results obtained in the testing method described in this manuscript with the values obtained in the calculations performed to EN 1991-1-4 [30], supplemented with those determined in CFD numerical simulations.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
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Number of Test Cycles | Applied Test Pressure in kPa |
---|---|
4 | 1.0 |
1 | 1.5 |
1 | 2.0 |
1 | 2.5 |
1 | 3.0 |
1 | 3.5 |
1 | 4.0 |
No. | Test Variant Number | Substrate Type | Strengthening the Membrane’s Underside by Lamination | Test Result, kPa | Failure Modes | |
---|---|---|---|---|---|---|
Up to the Value of 4.0 kPa | Failure at Pressure Value | |||||
1 | I | Concrete primed with a bitumen liquid + vapour control layer (reinforced bitumen sheet) glued to the substrate over the surface | Yes | + | 8.0 | De-bonding of PVC membrane from PIR board |
2 | II | + | 8.0 | De-bonding of PVC membrane from EPS board | ||
3 | III | + | 8.0 | EPDM membrane de-bonded from PIR board | ||
4 | IV | + | 7.5 | EPDM membrane de-bonded from EPS board | ||
5 | V | Trapezoidal galvanised steel sheet T55 | + | 7.0 | De-bonding of PVC membrane from PIR board | |
6 | VI | + | 7.0 | De-bonding of PVC membrane from EPS board | ||
7 | VII | None | + | 5.5 | EPDM membrane de-bonded from PIR board | |
8 | VIII | - | 1.5 | EPDM membrane de-bonded from EPS board |
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Francke, B.; Szulc, J.; Sieczkowski, J.; Piekarczuk, A.; Dobrev, J.W.; Schabowicz, K. Analysis of Resistance to Wind Suction of Flat Roof Coverings Glued with Polyurethane Adhesives. Materials 2023, 16, 7135. https://doi.org/10.3390/ma16227135
Francke B, Szulc J, Sieczkowski J, Piekarczuk A, Dobrev JW, Schabowicz K. Analysis of Resistance to Wind Suction of Flat Roof Coverings Glued with Polyurethane Adhesives. Materials. 2023; 16(22):7135. https://doi.org/10.3390/ma16227135
Chicago/Turabian StyleFrancke, Barbara, Jarosław Szulc, Jan Sieczkowski, Artur Piekarczuk, Joanna Witkowska Dobrev, and Krzysztof Schabowicz. 2023. "Analysis of Resistance to Wind Suction of Flat Roof Coverings Glued with Polyurethane Adhesives" Materials 16, no. 22: 7135. https://doi.org/10.3390/ma16227135