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EVALUATE AND REFINE STRUCTURE
EVALUATE AND REFINE
STRUCTURE
Now, look over the model again, this time with
an eye on structure. The legs, beams, and seat
form a structural frame that resists the gravity
loads when people are seated. As people sit
down on and get up from the bench, they also
put dynamic, lateral forces onto the bench
structure. The seat forms a diaphragm within
the frame, keeping the bench square and rigid
as people take a seat. The four feet prevent the
legs from splaying outward, giving the bench
enough strength to support those who are
seated.
In examining the overall proportions, beam
depth, and leg dimensions, we see that the
bench might benefit from a bit of structural
reinforcement. To give our structural frame
additional strength, we will add an extra beam
along the center of the bench. Adding this
beam allows the seat to act like a torsion box,
which helps the seat to handle a long span and
to keep the bench rigid.
ADD A CENTER BEAM
11A: Copy the front part; then move it toward
the center of the bench and align its top mid-
point with the center of the seat.
11B: Delete the legs; they’re unnecessary—
we’ll leave only the beam that locks into the
side parts. Figure 4-13 shows the bench with
the center beam added.
FIGURE 4-13
Copy and modify the
front piece to form a
center beam
102
DESIGN FOR CNC
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