Interesting construction techniques

posted Aug 20, 2015, 8:56 AM by Amy Stone   [ updated Aug 21, 2015, 1:45 PM ]
So, Outlier is always interested in learning new things, better ways to solve a problem or even alternate ways to solve a problem.  One of the new ways Structural Engineering is changing is the growing use of progressive collapse analysis.  One way to state progressive collapse resistance is that the building must remain standing after one or more major support elements have been severely compromised.  A typical, non- terrorist scenario is a bridge that gets hit by a dump truck and one of the columns is broken.  The bridge must remain standing.  It doesn't have to remain functional, just standing until it can be evacuated.
Following this thought, I've gathered some pictures of really shoddy construction that will fulfill the same purpose.  The masonry walls are non-structural.  The method is called rubble infill, actually, which tells you the quality of the bricks, blocks or rocks used between the reinforced concrete beams and columns.  
If one of the columns or beams is removed, the wall can support enough load for the occupants to safely evacuate the building.  I agree that the building may be unusable after that.  Also, the period of time the building remains standing after damage occurs is anyone's guess.  Evacuation should take only minutes, though.  

interesting structural engineering solutions
This first picture is one bay of a building from the outside.  The yellow to the left and right are separate buildings.
You can clearly see the beam and column construction.
rubble infill
Here's a snap showing multiple bays and multiple levels.  The bays are about 10' apart, as is the floor to floor height.  They very consistently display poor construction techniques on the masonry and use lots of mortar used to close the gap between the column and the infill wall.  Note that they did use running bond patterns. Funny enough, running bond pattern is the most important thing that would assist the rubble wall as a bearing wall in the case of progressive collapse.

rubble infill structural engineering
Here's a bit of a close-up on the left hand side showing the mortar around the column.    

during construction
Here's a building under construction showing that the beams and columns are reinforced appropriately for their size.  This is a different building to you sharp eyed observers.

honeycomb blocks
These blocks are typical for a new construction infill wall.  You can see that they are a version of clay product bricks.  The extra thickness and hole pattern would enhance air as a thermal barrier.  With these wall blocks considered rubble infill, the poor manufacture matters less.

spacer blocks
These are floor tiles.  They are placed within a cast-in-place floor horizontally to allow for electrical conduit placement. Within a concrete floor, there are often several 'rows' of these to run future conduits through. 

Here's a final shot.  On the left is the same wall as earlier.  On the right is a similar wall, but with finish materials added. 
I hope this tour has been interesting to you.  It certainly was to me.  At first sight, it seems these buildings couldn't possibly withstand a stiff breeze, much less any heavier loading.   However, this method has been used for some decades- although not IBC 2012 compliant.   Interestingly this method, though old, provides resistance to the newest thing in structural engineering!

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