Right now, I'm involve in a design of a 4-storey residential
structure. The east-west bays are in 3.2-2.5-3.2m center to center column
dist. and the north-south are in 5-4.24m spacing. The design was done in a
fast manner with due care. I got a column of 500 x 350mm for the center post
with 12-20mm. The architect said this was really large. I tried to argue
that the large column size was due to the large load it would carry (like
the water tank @ the rooftop, stairs with 125mm thick slab) and it would
carry much of the EQ forces since the 500mm dimension is along the east-west
direction. They said that for a seven storey building, they were only
getting a 500x500 column.
I tried to review my loadings. I computed the weight W with
accuracy. I also assumed that the 800 gallons of water located at the
rooftop would add to the earthquake force.
Am I right on my assumptions? Also, I computed the tie spacing as
per ACI / NSCP Seismic provision. For the confinement region, I'm getting a
50-mm tie spacing (10-mm bar). I am confused on the spacing of the ties /
hoops outside the confinement region. Code provision says it should not be
greater than 150 mm. Don't you think this is to conservative? I specified
200mm spacing of ties.
I hope you could guide me on this. An EQ struck my country yesterday
at Agusan in Mindanao. I don't want my designs to fail in anyway even if no
lives are lost.
By the way, I lost much of guidance from my bosses since Nick and
Boss Apeng have parted ways. I feel like it's all by myself now not like
before when I was in the consultancy office.