for engineers

CONTAINERS

There is a misconception that most shipping containers are decommissioned because of some structural defect, or that their framework designs vary substantially. Mainly there is just a surplus at the ports, because we import 4 times from China what we export. Contractors are instructed on container selection criteria to minimize any variability. Wind and Watertight condition ensures there is no significant material deficit from corrosion. 


The service loads for the columns and floors in shipping are many times those in residential use. Even then, contractors perform load tests to demonstrate the new assembly is sound. The rigging process is straightforward, however it’s definitely intended for contractors with a certain skill level, which helps ensure overall quality. 


The model house has passed preliminary foundation, floor and roof load tests! 

The connection techniques and load tests are clear and foolproof, and very easy to safely assess remotely. There is much redundancy and design safety built into the system. The houses can resist wind uplift from dead weight alone, based on the configuration and strength of the connections, and the foundation increases the hurricane and tornado resistance. All container metal is made from Corten steel (ASTM A588), which has an ultimate tensile strength of 70 ksi as opposed to A36, with 58 ksi. The 14-gauge thickness of the roof means the entire roof is 1.5 stronger than a 16-gauge Simpson strap! 

The entire house, roof and foundation could be picked up from the uppermost container in one piece with four chains. This high degree of composite action explains the exceptional seismic and extreme wind performance. 


Since much of the design is proprietary, please contact us directly for additional details. 


FOUNDATION 

The foundation allows relatively flexible cut and fill for several reasons. The excavator weighs 18,000 lbs, and design of the footings obliges the machine to pass around them many times, thus stabilizing the perimeter. Contractors are instructed to backdrag periodically. The foundation is leveled and the footings are inset from the edges, increasing stability and frost-/moisture-resistance. 

Though harder to model, recycled crushed concrete is VASTLY superior to clean 57 and pea gravel as a leveling course and filler medium.* On the leveling course of RCC, contractors lay out a base of rubble stone 4’x6’ for each footing. They fill the gaps with more recycled crushed concrete and hand tamp. No machine compaction is necessary. 


The difficulty in modeling is overcome by a simple proof test. The bunker blocks have a footprint of 2x4 feet, therefore, the assertion that the block can distribute its weight over a footprint of soil 4x6 feet under the rubble-stone with a deliberately conservative presumptive load-bearing capacity of 500 psf can be proven by applying a “proof- compaction” load of the self-same footing block weighing 2400 lbs, and the additional weight of 4 bunker blocks, (9600 lbs) for a total of 12,000 lbs, distributed over 24 square feet. Each stack is documented with a simple picture. 


This foundation offers a clear path to code compliance: the proof stack of 5 recycled pre-cast blocks weighing 12,000 lbs over a footprint of 8 square feet (here referring to the immediate plane under the bunker block as opposed to the distributed base) satisfies the IBC and IRC requirements of 1,500 psf for in-place soils, even though the in-place soils may be substituted with free-draining non-frost susceptible, 95% recycled crushed concrete instead. 


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*Recycled crushed concrete has superior particle angularity, gradation, and ductility, increasing angle of repose and internal friction. Engineers are invited to dump three 5-gallon buckets, each containing RCC, clean 57 and pea gravel onto the ground and stand on each to feel the difference in stability. Even compared to crusher run, crushed concrete: -fractures along planes of original aggregate reinforcement for a more knurled texture. -pulverizes into more silts and fines, to fill gaps more densely. -is more ductile than stone...particles grab better and don’t slide... (all three of these are simply functions of flexural and compressive properties vs. stone) It’s also recycled, and 1/3 of the price.

 

Please contact us directly for additional information regarding modeling the recycled crushed concrete/rubblestone composite. 

Contact us for more information