Brief Description — Structural Concept & Roof Geometry
For the ETFE structures, this pre calculation report has been prepared. The aim of the pre calculation report is to check the conceptional design of structure and load conditions.
MACHS Stadium
Roof cover by ETFE cushions for MACHS
Area1,500 m²
FabricETFE
CityDammam
Year2023
SectorSports
Project overview
The MACHS Stadium is the sports stadium of Mohammed Al-Mana College for Health Sciences (MACHS) in Dammam. Its long-span arched roof is built from double-layer ETFE cushions covering more than 1,500 m². TMSI's scope was design, supply and installation, and the project is dated 2023.
The cushions are held permanently at 250–300 Pa by an air handling unit with two fans for load sharing and redundancy; non-return valves hold pressure in the system. The trapped air gives the roof its stiffness and an insulating cavity, with a U-value of approximately 2.9 W/m²K for the two-layer build-up. The cushion grid was laid out so that no rectangular cushion exceeds the 3.5 m guideline span, and individual cushions can be replaced without disturbing the rest of the roof.
The primary structure is a grid of rolled tubular steel arches, fabricated, trial-assembled and coated in the TMSI factory for the coastal Eastern Province environment, then pre-assembled at ground level and lifted into place. Each ETFE cushion was test-inflated and inspected in the factory before dispatch.
Project photos
PROJECT 03
ETFE Double Layer Cushion System · Dammam, Saudi Arabia
Project data
| Project | MACHS — Mohammed Al-Mana College for Health Sciences |
|---|---|
| Location | Dammam, Saudi Arabia |
| System | ETFE double layer cushions |
| Approx. area | 1,500+ m2 |
| Cushion pressure | 250 – 300 Pa |
| Inflation | Air handling unit, dual fan |
| Structure | Rolled tubular steel arch grid |
| Scope | Design, supply and install |
Scope of works
- Structural design of the long-span arched roof and cushion layout
- Factory rolling, welding and pre-assembly of the tubular steel arch grid
- Fabrication of double-layer ETFE cushions with welded perimeter keder
- Installation of aluminium extrusion, cushions and air distribution pipework
- Inflation plant installation, pressure commissioning and handover
System description
- 01Double-layer ETFE cushion system providing a U-value of approximately 2.9 W/m2K.
- 02Cushions permanently inflated to 250–300 Pa, giving structural stiffness and an insulating air cavity.
- 03Air handling unit with dual fans for load sharing and redundancy, plus non-return valves to hold pressure.
- 04Fully integrated aluminium perimeter extrusion with air inlet and integral water seal.
- 05Rolled tubular steel arch grid fabricated in the TMSI factory and pre-assembled before lifting; individual cushions can be replaced without disturbing the remainder of the roof.
MACHS — Fabrication & Installation
Every panel is engineered, patterned and welded in our Dammam factory, then delivered to site as a finished, numbered assembly. The sequence below follows the actual production and installation route used on this project.
- 01 Form Finding & Cushion LayoutArch geometry and cushion grid are developed together so no rectangular cushion exceeds the 3.5 m guideline span, analysed for Dammam wind and thermal load.
- 02 Pipe Rolling & Steel FabricationTubular sections are rolled to radius, cut and welded into arch segments, then verified against the setting-out template.
- 03 Arch Assembly & CoatingSegments are trial-assembled on a jig to prove the full profile, then blast-cleaned and coated for the coastal Eastern Province environment.
- 04 Pre-Assembly on SiteArches are re-assembled at ground level adjacent to the building, complete with lifting points and rigging, ready for a single lift.
- 05 Lifting & ErectionComplete arches are craned into position, aligned and bolted down, with temporary bracing retained until the grid is closed.
- 06 Secondary Steel & SurveySecondary members are installed and the grid surveyed so the extrusion line matches the fabricated cushion dimensions exactly.
- 07 Extrusion & Air InletsThe perimeter extrusion is installed with clamping profiles, gaskets, air inlet spigots and the integral gutter and water seal.
- 08 Cushion FabricationUpper and lower foils are patterned and thermally welded with a keder edge. Each cushion is test-inflated and inspected in the factory before dispatch.
- 09 Cushion InstallationCushions are lifted, the keder is fed into the extrusion on all sides and clamping plates are torqued to the specified sequence and value.
- 10 Inflation & CommissioningAir pipework is run to every cushion from the dual-fan air handling unit. Pressure is balanced, alarms proven, and the system handed over with as-built records.
DESIGN & ENGINEERING
MACHS – Design & Engineering
Structural Drawings — Plan & Elevation
Loadings — Dead, Collateral & Live Load
The dead load of the structural elements have been taken into calculation by the software. The collateral load is taken into calculation as 0.4 kN/m² × 4.5 m = 1.8 kN/m.
The live load is taken into calculation as 0.24 kN/m² as per ASCE 7-16.
Wind Loading — Velocity Pressure (ASCE 7-16 / SBC 301)
The wind load is taken into calculation as 152 km/h as per SBC 301.
- Structure type
- Arched Roofs
- Velocity
- 42 m/s · 94 mph · 152 km/h
- Ground elevation
- 0.00 m
- Mean height
- 13.30 m · 43.64 feet
- Velocity pressure exposure coefficient Kz
- 0.78
- Topographic factor Kzt
- 1.00
- Wind directionality factor Kd
- 0.85
- Ground elevation factor Ke
- 1.00
- Velocity pressure qh
- 0.72 kN/m² · 15.1 psf
- Net design wind pressure P
- 0.61 kN/m² · 12.8 psf
qz = 0.613 KzKztKdKeV² (N/m²); V in m/s (26.10-1.si) · P = qz · G
ASCE 7-16: Minimum Design Loads and Associated Criteria for Buildings and Other Structures.
Sliding Support — Maximum Displacements & Detail
Steel System Analysis — Zone A Design Ratios
Cable Design — Internal Forces
Cable Design Calculation — Member Sizing
Definitions, symbols and values — 28 rows
| Definitions | Symbol | Unit | Value | Formulation |
|---|---|---|---|---|
| Cable tension | Nges | [kN] | 376.00 | |
| Quantity of cables | n | [-] | 1 | |
| Cable tension in the single cable | Nseil | [kN] | 376.00 | |
| Design Criteria | LRFD | |||
| Load Safety Factor | γf | [-] | 1.00 | |
| Material Safety Factor | γR | [-] | 1.00 | (usually 1.0) |
| Cable Type | 1X37 | |||
| Cable Diameter | d | [mm] | 36 | |
| Tensile Strength | Rr | [N/mm²] | 1770 | |
| Youngs Modulus for variable action | EQ | [kN/cm²] | 15000 | |
| Filling load factor | f | [-] | 0.750 | |
| Equavalent Diameter Factor | fed | [-] | 0.866 | |
| Equavalent Diameter (Sap2000) | de | [mm] | 31.18 | =de*fed |
| Reduction dirilling | k | [-] | 0.883 | |
| Self Weight factor | w | [kg/cm²] | 0.830 | |
| Breaking Load Factor | K | [-] | 0.520 | = π*f*k/4 |
| Metallic Cross Sectional Area | Am | [cm²] | 7.634 | |
| Nominal Metallic Areac Factor | C | [-] | 0.590 | |
| Stifness Single Cable | EA | [MN] | 114.511 | |
| Stifness All cables | EAges | [MN] | 114.511 | |
| Cable Weight | g | [kg/m] | 6.34 | =Am*w |
| Minimum Breaking Load Cable | Fmin | [kN] | 894.6 | = K*d2*Rr/1000 |
| Socet Type | Swaged Socket | |||
| Loss factor (Due to cable fitting) | ke | [-] | 0.90 | |
| Characteristic value of the resistance | Fuk | [kN] | 805.2 | =Fmin*ke |
| Design Value of the cable tension | FEd | [kN] | 376.00 | =Nseil*γf |
| Design value of the cable resistance | Frd | [kN] | 536.78 | =Fuk/1.5*γR |
| Verification in the ultimate limit state | Fed/Frd | [-] | 0.70 | OK |
Cable Design — Reference Tables (Unit Weight & Breaking Force)
ETFE Foil Design — Warp & Weft Direction Forces
Connection Design — Pinned Support
- Steel
- S235
- Concrete
- 4000 psi, C30
- Analysis
- Stress, strain / simplified loading
- Design code
- AISC — LRFD 2016
Members — geometry — 1 row
| Name | Cross-section | β – Direction [°] | γ - Pitch [°] | α - Rotation [°] | Offset ex [mm] | Offset ey [mm] | Offset ez [mm] | Forces in |
|---|---|---|---|---|---|---|---|---|
| M1 | 1 - CHS323.9/10.0 | 0,0 | -90,0 | 0,0 | 0 | 0 | 0 | Node |
Connection Design — Bolts Verification
Bolts — 8 rows
| Item | Grade | Loads | F t [kN] | V [kN] | φR n,bearing [kN] | Ut t [%] | Ut s [%] | Ut ts [%] | Status |
|---|---|---|---|---|---|---|---|---|---|
| B1 | M24 8.8 - 1 | LE7 | 22,8 | 46,8 | 311,0 | 11,2 | 38,4 | - | OK |
| B2 | M24 8.8 - 1 | LE8 | 40,3 | 46,5 | 311,0 | 19,8 | 38,1 | - | OK |
| B3 | M24 8.8 - 1 | LE8 | 20,0 | 47,0 | 311,0 | 9,8 | 38,6 | - | OK |
| B4 | M24 8.8 - 1 | LE8 | 0,2 | 47,3 | 311,0 | 0,1 | 38,8 | - | OK |
| B5 | M24 8.8 - 1 | LE8 | 0,6 | 47,7 | 311,0 | 0,3 | 39,0 | - | OK |
| B6 | M24 8.8 - 1 | LE8 | 0,2 | 47,7 | 311,0 | 0,1 | 39,1 | - | OK |
| B7 | M24 8.8 - 1 | LE11 | 0,0 | 50,0 | 311,0 | 0,0 | 41,0 | - | OK |
| B8 | M24 8.8 - 1 | LE11 | 23,7 | 49,9 | 311,0 | 11,6 | 40,9 | - | OK |
Design data — 1 row
| Grade | φR n,tension [kN] | φR n,shear [kN] |
|---|---|---|
| M24 8.8 - 1 | 203,4 | 122,0 |
Connection Design — Weld Verification
Welds — 32 rows
| Item | Edge | Xu | T h [mm] | L s [mm] | L [mm] | L c [mm] | Loads | F n [kN] | φR n [kN] | Ut [%] | Status |
|---|---|---|---|---|---|---|---|---|---|---|---|
| PP1a | RIB1a | E70xx | 4,0 | 5,7 | 74 | 9 | LE8 | 5,7 | 11,6 | 49,2 | OK |
| E70xx | 4,0 | 5,7 | 74 | 9 | LE11 | 6,4 | 11,5 | 55,2 | OK | ||
| B1-arc 5 | RIB1a | E70xx | 4,0 | 5,7 | 155 | 10 | LE11 | 4,0 | 9,2 | 43,6 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE8 | 4,3 | 9,1 | 47,0 | OK | ||
| PP1a | RIB1b | E70xx | 4,0 | 5,7 | 74 | 9 | LE10 | 6,2 | 11,7 | 53,1 | OK |
| E70xx | 4,0 | 5,7 | 74 | 9 | LE10 | 6,5 | 11,3 | 57,6 | OK | ||
| B1-arc 13 | RIB1b | E70xx | 4,0 | 5,7 | 155 | 10 | LE10 | 4,4 | 9,3 | 47,3 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE10 | 4,7 | 9,2 | 51,0 | OK | ||
| PP1a | RIB1c | E70xx | 4,0 | 5,7 | 74 | 9 | LE1 | 6,5 | 11,5 | 56,7 | OK |
| E70xx | 4,0 | 5,7 | 74 | 9 | LE1 | 6,2 | 11,8 | 52,3 | OK | ||
| B1-arc 21 | RIB1c | E70xx | 4,0 | 5,7 | 155 | 10 | LE1 | 4,4 | 9,4 | 46,7 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE1 | 4,8 | 9,2 | 51,8 | OK | ||
| PP1a | RIB1d | E70xx | 4,0 | 5,7 | 74 | 9 | LE12 | 5,7 | 11,5 | 49,3 | OK |
| E70xx | 4,0 | 5,7 | 74 | 9 | LE4 | 4,2 | 10,9 | 39,0 | OK | ||
| B1-arc 29 | RIB1d | E70xx | 4,0 | 5,7 | 155 | 10 | LE12 | 3,4 | 9,3 | 36,2 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE12 | 3,9 | 9,1 | 42,8 | OK | ||
| PP1a | RIB1e | E70xx | 4,0 | 5,7 | 74 | 9 | LE12 | 4,7 | 10,6 | 44,1 | OK |
| E70xx | 4,0 | 5,7 | 75 | 9 | LE8 | 5,2 | 12,1 | 43,0 | OK | ||
| B1-arc 37 | RIB1e | E70xx | 4,0 | 5,7 | 155 | 10 | LE8 | 4,2 | 9,3 | 45,6 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE11 | 4,7 | 9,1 | 51,9 | OK | ||
| PP1a | RIB1f | E70xx | 4,0 | 5,7 | 75 | 11 | LE10 | 7,5 | 13,6 | 55,5 | OK |
| E70xx | 4,0 | 5,7 | 75 | 11 | LE10 | 7,5 | 13,5 | 55,4 | OK | ||
| B1-arc 44 | RIB1f | E70xx | 4,0 | 5,7 | 155 | 10 | LE10 | 5,6 | 9,5 | 59,1 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE10 | 5,0 | 9,9 | 50,4 | OK | ||
| PP1a | RIB1g | E70xx | 4,0 | 5,7 | 75 | 11 | LE1 | 7,6 | 13,5 | 56,5 | OK |
| E70xx | 4,0 | 5,7 | 75 | 11 | LE1 | 7,7 | 13,6 | 56,7 | OK | ||
| B1-arc 53 | RIB1g | E70xx | 4,0 | 5,7 | 155 | 10 | LE1 | 5,0 | 9,9 | 50,6 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE1 | 5,6 | 9,5 | 59,3 | OK | ||
| PP1a | RIB1h | E70xx | 4,0 | 5,7 | 74 | 11 | LE8 | 4,5 | 13,5 | 33,6 | OK |
| E70xx | 4,0 | 5,7 | 74 | 11 | LE11 | 6,3 | 13,4 | 46,8 | OK | ||
| B1-arc 60 | RIB1h | E70xx | 4,0 | 5,7 | 155 | 10 | LE12 | 4,4 | 9,1 | 48,3 | OK |
| E70xx | 4,0 | 5,7 | 155 | 10 | LE12 | 3,6 | 9,5 | 38,3 | OK |
Connection Design — Strain & Equivalent Stress Check
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