16
STORY OFFICE BUILDING IN CONCRETE
1. Building Description and Loading
This 16 storey office building typical floor
consists of flat plates and a number of beams near the core
walls. On the perimeter, the floor slab cantilevers 3 feet
beyond the column lines and in the front edge of the slab
the cantilever is 6.5 ft. The vertical structural elements
are columns and shear wall with pilasters. In the X-direction
much of the seismic forces are resisted by shear walls,
while in Y- direction they are resisted by rigid frames
formed by flat plates and columns. For typical floor layout
see figure A.
Fig. A
The
floor live load is 80 psf, floor dead load 11 psf, plus
the slab. The structure is to be designed by the American
Concrete Institute "Building Code Requirements for Structural
Concrete" (ACI) and the seismic forces to be computed by
the Uniform Building Code.
The design of flat plate floors is often governed by punching
shear around columns. This problem can be resolved by investigating
different slab thickness, column sizes, or by introducing
drop panels, column capitals, shear heads or by changing
concrete strength. With AMECO-17, the optimum solution
was found in one hour by redesigning the structure
some 7 or 8 times with different slab thicknesses, different
minimum column sizes and with drop panels over selected
columns, etc. Since for each design AMECO calculates for
the whole structure the exact construction costs, it was
easy to identify and select the least cost design. Each
AMECO-17 design execution took 9 seconds.
The input commands for the optimum design solution
of the structure are shown in Fig. B. No member sizes were
input, no loads manually calculated, no loading cases or
combinations selected. Basically, only loading parameters
and member connectivitiies, and their spans were input,
plus the trial minimum dimensions for columns and slabs.
If
you wish to familiarize yourself with the basics of the
AMECO-17 input language, it would be helpful to read the
next section. Otherwise, proceed to section 3.
2. Input Commands
The command USE ACI-99 calls for the American Concrete Institute
Building code using the USD method for designing members.
No other criteria is given, therefore AMECO-17 standard
criteria values will be used for concrete and steel strength,
for unit prices of materials, etc. The values used can be
seen later in the output result file. The LIST and SUPPRESS
are entered to select desired results.
LEVEL 17 defines the penthouse framing, a very simple structure;
on to the main floor input.
LEVELS 16 TO 1 implies that the subsequent data given is
the same for all 16 levels. Note that does not mean that
the member sizes selected by AMECO-17 will be the same on
all levels.
PROJECT- OAK PLAZA
STRUCTURE- 16 STOREY OFFICE BUILDING
CLIENT- NORK ENTERPRIZES LTD.
REVISION- D
INPUT- FB
$
USE CODE ACI-99, USD
CYCLE MAX 2
LIST ALL
SUPPR ENVELOPES FOR LEVELS 17 TO15 13 to 9, 7 TO 1
LIST FRAME FORCES EQ LEVEL 15 2 1
$
LEVEL 17 $ PENTHOUSE
DESIGN BEAMS
USE SPANS 24 SLAB 8 FLL 65
B101 WALL201 TO 301
B401 TO 501 12 101
DESIGN COLS SQ 14, L 11-0
C8 TO 9 201 401 C13 TO 14 301 401R
$
LEVELS 16 TO 1
DESIGN TWO WAY SYSTEM
USE SLAB 8, FDL 11, FLL 80 SPANS 24
USE FL PROJ 36, CANTILEVERS 3.
S101 19 S102 S103 FL NS 6-6 S104
S201 TO 202 19 WALL203 S204 TO 304
S401 19 S402 TO 404 S501 TO 502
USE SPANS 22
S601 OFFS -5 S602 S603 TO 703 OFFS 5
S801 23-6 LCANT 6.5 B802 2(6 1101) 22 fll 100
S803 23-6 S804 TO 904
S1001 TO 1004 DL W .4
B1101 24 REQ 2 OP FS FLL 100
$
DESIGN COLS SQUARE 16, L 11-6
EQUATE COLS 1 5 16 21 23
EQUATE COLS 7 12
EQUATE COLS 10 15 20
C1 TO 5 101 601 C6 TO 10 201 602
C11 TO 15 301 603 C16 TO 20 401 603R
C21 TO 23 501 804R
C8 TO 9 RECT 16 30, C13 TO 14 RECT 16 30
C18 TO 19 DROP 8-0 8-0 12
$
COMPUTE TORSION UBC
COMPUTE EQ FORCES UBC Z .15
EXECUTE |
Fig. B - Input Commands |
USE SLAB 8, FDL 11 (floor dead load 11 psf), FLL 80 (floor
live load 80 psf) SPANS 24 (24 ft span will be applied to
all subsequent slabs unless other value is entered). The
subsequent lines list the slabs and beams with their spans.
Slab marks are prefixed with the letter S and beam marks
with B. An exterior wall load is applied on slabs S1001
to 1004; DL W .04 (0.4 kips/ft.).
DESIGN COLS SQUARE 16, L 11-6 requests column size selections,
starting with 16 in. EQUATE COLS 1 5 16 21 23 requests that
all five columns be the same. C1 to 5 101 601 connects 101
to 104 to the columns in X- direction and members 601 701
801 901 1001 in Y- direction. This is a typical statement
for connecting slabs and beams to columns.
C8 to 9 RECT 18 30 enters the pilaster size. C18 TO 19 DROP
8-0 8-0 12 enters 8 ft. square drop panel with total thickness
of 12 in.
COMPUTE TORSION UBC invokes mass eccentricity amplification
& COMPUTE EQ FORCES requests static earthquake computations
as per UBC code with Z= 0.15 |
3. Analysis and Design Process
Based on the input commands of Fig. B, AMECO-17 generates
the geometry in 3D, initializes member sizes, models joints,
calculates floor dead and live loads on each member, calculates
seismic forces, sets up loading cases and combinations and
through an iterative cyclic analysis/design process designs
the whole structure .
Fig.
C
AMECO-17 cyclical process
4.
Analysis and Design Execution Time
This structure has 512 slabs, 67 beams, 384 columns and
34 walls, or a total of 981 members. Non-linear analysis
was executed for 17 dead load cases (produced by construction
simulation), 576 live load cases (number of beams and slabs)
and 2 seismic load cases. This structure was designed
and optimized in 12 man-hours--from the input preparation
to the review of the design results. The AMECO-17 design
execution per design run was 9 seconds.
5. Analysis and Design Results
In this section, representative pages are displayed
out of the total of 354 Design Result pages. This design
was done in English units, therefore all member forces and
moments are ft kip units; member dimensions and displacements
in inches; floor and formwork areas in sq.ft.; ASTM standard
reinforcing bars invoked by the ACI code.
The following results are listed level by level:
