DESIGN OF A 4 LEVEL STEEL BUILDING

1. Description of Structure and Loads

This 4 level Calcinatory Building in an Iron Ore Concentrator plant is frames in the long direction (see Fig. A). On the lower three levels, all pin connected beams are to be composite. The roof has a snow load of 67 psf, while the floors have a superimposed dead load of 18 psf and a live load of 200 psf. The seismic region has zonal velocity ratio V=0.20. 30% of live load is to be included in the mass for seismic considerations. The self-weight (dead load) of all members is computed by AMECO-17. AMECO-17 automatically generates a rigid floor diaphragm at each level, unless otherwise instructed.

The input commands for AMECO-17 to design the structure are shown in Fig. B. It took 3 hours to prepare this input. No member sizes had to be input, no loads had to be manually calculated, no loading cases or combinations needed to be specified. Basically, only loading parameters and member connectivitiies and member spans had to be specified.

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 Command Description (see Fig. B)
After the Job Title Statements, general data for the entire structure is entered.

USE CODE NBC-95, LSD, follows the command AMECO STEEL specifying the National Building Code with LSD method for member design. This also loads the steel shape tables available in Canada. The next 4 lines select desired result files. CYCLE MAX 3 limits the global analysis/design cycles to 3. The member data is entered level by level, starting from the top. The DESIGN BEAMS command requests beam size selection and sets beam spans to 18'-0. Data common to a group of members (e.g. 18'-0) is given in a command (statement stating with a verb). USE SLAB 6, FDL 18 FLL 67 specifies floor dead and live load in psf. USE FL PROJECTION 18 extends the floor slab 18" beyond the column lines all around the floor. Beam entries consist of beam marks followed by their spans, when the spans are different from 18'-0. By default, beam end connections are hinged. ABR denotes an A-brace below a beam, e.g. B401. The DESIGN COLUMNS command request size selection and sets all columns 12'-6 long, which defines the storey height. RESTRICT limits column depth to min 10". Column marks are prefixed with the letter C. The next 2 lines define connectivity between columns and beams. A column stack supporting a number of levels is given the same column mark at all levels. LEVEL 3 TO 1 implies that data for these 3 levels is the same. DESIGN BEAMS, RG 1 sets beam end connections fully rigid. Next line calls for Composite Design for all beams pinned at ends. USE RG 0 sets beam ends from now on pinned. The line "B401 11 301, ABRACE" states that beam 401 supports at 11' the left end of beam 301 and an "A" brace is placed below 401.

$ A) JOB TITLE STATEMENTS $ PROJECT LOREDO MINES CLIENT ABC ENGINEERING STRUCTURE CALCINATOR BUILDING FILE LOREDO JOB 76EX7 INPUT- L.D. $ B) GENERAL DATA FOR WHOLE STRUCTURE $ AMECO STEEL USE CODE NBC-95 LSD LIST ALL SUPPRESS LIST GEOM DATA SUPPRESS NONLINEAR ANALYSIS CYCLE 1 LIST FRAME FORCES FOR EQ CYCLE MAX 3 DESIGN ALL $ $ C) MEMBER DATA LEVEL BY LEVEL LEVEL 4 $ DESIGN BEAMS, SPANS 18-0 RESTRICT DEFLECTIONS TO L/360 USE SLAB 6, FDL 18 FLL 67 USE BRACING SHAPES WT B101 TO 301 RG 1 B401 22 ABR B402 14 B501 22 XBR B502 14 $ DESIGN COLUMNS, LENGTH 12-6 RESTRICT XDIM TO MIN 10 C1 TO 2 101 401 C5 TO 6 201 402 C9 TO 10 301 402R $ LEVEL 3 TO 1 $ DESIGN BEAMS, RG 1 USE COMPOSITE IF RG LE .1 USE SLAB 8, FDL 50 FLL 200 USE FLOOR PROJECTION 18 B101 TO 103 B201 TO 203 B301 TO 303 RG 0 B801 USE RG 0, SPAN 22 B401 11 301 ABRACE, B402 14 B501 11 302, B502 14 B601 11 303 B701 11 303R XBRACE $ DESIGN COLUMNS LENGTH 15 EQUATE COLS 3,4,7,8 C1 TO 4 101 401 C5 TO 8 201 402 C9 TO 10 801 402R USE SUBGRADE MODULUS 200 $ COMPUTE TORSION NBC COMPUTE EQ XFORCES NBC V .20 R 4 MF .3 COMPUTE EQ YFORCES NBC V .20 R 2 MF .3 $ EXECUTE

C1 to 4 101 401 means that columns 1 to 4 support beams starting with 101 in X- direction and beams 401 501 601 701 in Y- direction. In the USE SUBGRADE command, the modulus of 200 psi/in. represents a soil of medium strength. In AMECO-17, default subgrade is rock.

COMPUTE TORSION NBC invokes eccentricity amplification for seismic analysis as per NBC code. The last two COMPUTE commands request earthquake computation for zonal velocity ratio of 0.20. The R factor is set to 4 in the direction of rigid frames and R=2 in the direction of the bracing. MF 0.3 sets 30% of live load to be included in the seismic mass.

3. Analyses 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 a cyclic analysis/design process designs the whole structure. For this structure, the AMECO-17 design execution time was 2 seconds on a 1.3 GHz PC. To prepare the input, execute AMECO-17 and to review the output took a total of 7 man-hours.

Fig. C
AMECO-17 Cyclical Process

4. Analysis and Design Results
In this section, representative pages are displayed out of the total 61 Design Result pages. This design was done in English units, therefore all member forces and moments are ft ­kip units; floor and fire protection areas are in sq.ft., member cross-section dimensions and displacements in inches; steel shapes available in Canada are used, invoked by the NBC code.

The following results are listed level by level: