2014 WEA Conference Seismic Design of Wine Tanks

Introduction & Scope Current Design Codes, –What they are. –What they do and do not cover. –What all the figures mean. What Wine Tank Owners need to consider and specify when ordering a tank. Type of wine tank designs (pros and cons, limits) Review of some of the common failures and learning’s from Marlborough –Legs –Plinths – conventional –Cast in place Q & A Content

Introduction and Scope Cliff Ellery –NDA/Crown. General Manager and Senior Engineer. CPEng with 18 years experience in Tank fabrication for Wine, Dairy, Tare Treatment and Pharmaceutical industries. Design tanks 500m3 to 5 litre and over 100 tanks in the last year alone. Seismic design of wine tanks. (for the non Engineer) –Atmospheric storage vessels for non toxic, food grade products. –For this class of tank seismic strength and restraint is the governing design condition. Excludes –Pressure Vessels –HASNO vessels. –Water storage tanks for domestic and fire fighting purposes.

Common Questions, Why is there no code covering wine tanks design? Why did my tanks fail when they where designed to a code? The tanks come with a compliance statement so I don’t need to worry about anything else. I‘m not a Engineer so how can I be expected to specify what the seismic requirements are for my tanks. Should I bolt my tanks down? I heard it was best to let them move around?

Tank Design Codes. The NZ code structural codes ‘Earthquake Action” excludes tanks, but it also excluded bridges, dams retaining walls and off shore structures all of which are designed to withstand earthquakes. For Tanks we therefore use 2 codes for seismic design. –AS/NZS “Earthquake actions New Zealand” – For the size of earthquake. –NZ National Society for Earthquake Engineering (NZNSEE) “Seismic Design of Storage tanks: – for how important the tank is and how strong it needs to be to withstand the design earthquake.

Why did my tanks fail when they where designed to a code The goal of the codes is to 1.Save lives. (Prevent full or part structural collapse that would prevent evacuation of people). 2.Protect society. 3.Protect the Environment. 4.Protect Adjacent Property. –Risk of property on same site is at owners discretion.

Design State Tanks are designed to “U ltimate limit state”. Meaning some bending and distortion is ok but ultimate failure or collapse is not.

Some distortion is Acceptable Provided tank does not collapse or spill content or harm people. Diamond BucklingElephant foot Buckling

Not Acceptable Tank and walkway collapse poses a serious risk to wine staff personnel and is not code compliant.

What to Specify Tank Location –Using NZS – Hazard factor (size of earthquake) –Marlborough and Hawke’s Bay =0.4

What to Specify Soil Type –AS/NZ 1170:5 creates five classes – –Strong Rock [A] –Rock [B] –Shallow soil [C] –Deep or soft soil [D] (Default in Marlborough) –Very soft soil [E] Geotechnical site report, or council recommendation.

Design Life Design period which structure/tank intended purpose is without major structural repair. Less than 6 months 5 years 25 Years – can be applicable for some applications 50 Years – NZSEE recommendation. 100 Years or more

Importance Level, & 4 Building/structural code definitions difficult to apply to tanks. AS/NZS are Building Definitions (containing people) Importance Level 1 – structure presenting low risk – Farm Buildings. Importance Level 2 – Normal structures – single family dwellings. Importance Level 3 – structures containing crowds. (schools, airports etc) Importance Level 4 – Post disaster functions or hazardous materials, Hospitals.

Tank code – Risk based approach. Seismic Design of Storage tanks: Risk based approach. Risk of failure Importance Level 1 – Negligible or slight Importance Level 2 – Moderate Importance Level 3 – Serious Importance Level 4 – Extreme.

Tank Content Schedule 4 – Water, Milk, Wine Schedule 3 – Substances presenting low danger Schedule 2 - Substances presenting medium danger Schedule 1 - Substances presenting High danger

Risk to Life Schedule 4 (Wine), Number of people within 50m –Less than 10 – slight – Level 1 –Less than 100 – Moderate – Level 2 –More than 100 – Serious – Level 3

Risk to Environment Schedule 4 (Wine), –Low to High – Level 1

Risk to Community –Risk = Negligible to slight – Level 1

Risk to Adjacent Property Adjacent property within 50m –Less than $1 million - slight – Level 1 –Less than $10 million – Moderate – Level 2 –More than $100 million – serious - Level 3

Risk to your Property Your property –slight – Level 1 –Moderate – Level 2 –serious - Level 3 Your call. Your own business risk.

Client Design Specification Design Codes –AS/NZS “Earthquake actions New Zealand” –NZ National Society for Earthquake Engineering (NZNSEE) “Seismic Design of Storage tanks: Design Variables –Design Life 50 years. –Percentage Full = 100% –SG of Product = 1.05 –Soil Type D. –Location = Napier (Hazard Factor = 0.38) –Important Level 1 (2 if supporting working platforms) or ? to meet your business risk for that tank.

MARLBOROUGH 2013 EARTHQUAKES Lessons learnt Observations Improvements

Tanks on Leg Pro Easy to install. Easy to move. Cons Seismically weak. Requiring –Large number of legs – cross bracing. Difficult to effectively attached thin wall vessels to legs.

Tanks on Legs Legs weak, require cross bracing Legs tend to tier tank at point they attach to tank.

Bolt all tanks down. Especial tanks on legs Load from earthquake taken by downwards load on one legs and upwards load on opposite leg Not bolting legs down increases load on the one leg, leading to failure & risk to people.

Bolt tanks to foundations with i.a.w designer specifications

Plinth Mounted Tanks Wine Industry standard for large tanks. Suitable for tank of all sizes. Cons Cost of installation higher than leg design. Difficult to move tanks or remove old concrete plinths.

Plinth mounted tank Seismic Performance If skirts do not extend to the ground then tanks will bend at floor knuckle and settle in and earthquake. Gap

Tanks on Plinths If skirts do not extend to the ground then tanks will bend at floor knuckle and settle in and earthquake.

Plinth mounted tank Seismic Performance Extending the skirt to the ground eliminates this issue. Or retro fit chairs that extend to the ground. Skirt extends to Foundations

Extend skirts to ground Ensure base plates are correctly grouted across full width and circumference.

Or Cast in place Plinths Tank skirt is pumped full of concrete fully supporting floor and knuckle. This design worked well in the 2013 Earthquakes

Cast in Place Plinths

Bolt failures For necked hold down bolt, material needs to be ductile (stretchy) therefore high tensile material not suitable. Large M24 and M30 Hold down bolts need to be embedded up to 300mm into the foundations.

Summary – Key Find from Marlborough2013 Personnel safety is key – safe walkways and platforms are required by law. Above 15kl, tanks on plinths with skirts that extend to the foundation performed the best. Bolt your equipment, tanks and platforms down. Ensure your holddown bolts are installed in accordance with manufactures recommendations. Fully embedded into the foundations.

Produce a specification for your Tanks. Specify the conditions and level of product risk you want your tanks built for. Design Variables –Design Life 50 years. –Percentage Full = 100% –SG of Product = 1.05 –Soil Type D. –Location = Napier (Hazard Factor = 0.38) –Important Level 1, 2 if supporting walkways, or ? to meet your business risk for that tank.

Any Questions