How to solve for footing designs?

Designers are faced with unique challenges during upfront engineering to scope up concrete footings sizes to meet project requirements. It’s a bit like guesswork at the start.

This is exactly the problem faced by Greg, a Principal Piping Designer at a reputable process firm based in Australia. Greg was responsible for preparing the initial field layouts for a new flowline for an existing onshore gas plant. The layout required the detailing of the DN100 flowline from the existing pressure vessel to new offtake valve approx 200m away. The pipe needed to be supported every 10m according to piping engineers and maintain a height of 0.8m above the ground.

Greg first worked out how much permanent load was on the footing. He quickly estimated steel pipe was 16kg/m and hence for 10m span there was 160kg of dead load. He then determined the pipe support self weight was about 100kg and hence the total permanent load was 260kg.  The max content load based on water filled was 8kg/m and for 10m span meant only 80kg of content. Greg also worked out the max horizontal load on the pipe from pipe & wind loads to be 1.7kN acting horizontally at top of support. The support was 0.5m above the footing and hence giving 0.9kN.m overturning moment at base of pipe support.

Greg had heard about Think Structural’s concrete footing design template that satisfied for a range of pre-determined design loads. He pulled up the range of concrete footings and selected the 1t concrete footing. For a permanent load of less than 2T, the 1t concrete footing allowed for overturning moment of 3.1kN.m and satisfied the expected design loads. The footing dimensions was 1.2m x 1.2m x 0.3m deep and included a 3D model.

The final design was checked by a Senior Structural Engineer to ensure it meet all client and code requirements and overall the design resulted in a smooth project from start to finish.

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