[GEN] Seismic Design for Reinforced Concrete Building

0. Contents 

1. Summary

1-1 Overview

This example problem is meant to demonstrate the design of a Reinforced Concrete building structure subjected to floor loads, wind loads and seismic loads.

1-2 Description

Seismic Design Data

• Dual system (special reinforced concrete structural walls with special moment frame) in the transverse direction

• Special moment frame in the longitudinal direction

• Assigned to a high seismic zone

1-3 Methodology

• Response spectrum analysis

• P-Delta analysis

1-4 Model

Reinforced Concrete Building Model

Typical Floor Plan

Longitudinal Section

2. Design Procedure

2-1 Material & Section Properties Input

Material

• Concrete fc’ = 4,000 psi

• Reinforcement fy = 60,000 psi

Section

• Edge columns 24×24 in.

• Interior columns 30×30 in.

• Beams 20×24 in.

• Walls 18 in. (In-plane & Out-of-plane)

Material & Section Properties Input

2-2 Create Model

Units : Length > ft

Set UCS to X-Y Plane

Origin : 0, 0, 16

Change View Direction > (on)

Set Line Grid

Grid Name = 2F

X-Grid Lines

Relative > (on)

‘7@26’

Y-Grid Lines

Relative > (on)

‘3@22’

Add/Modify Grid Lines

Define Grids

Line Grid, Line Grid Snap (toggle on)

Create Grid Lines

Grid Lines in X-Y Plane

Generate Floor Plan

Hidden, Node Number, Element Number (toggle on)

Create Elements

Element Type = General Beam / Tapered Beam

Section Name = 3 : Beam

Draw Elements as shown (Refer Figure below)

Floor Plan

Generate Columns

Change to GCS

Select All

Extrude Element

Node → Line Element

Reverse I-J > (on)

Element Type = Beam

Material = 1 : Grade C4000

Section = 1 : Edge column

dx, dy, dz = 0, 0, -16

Generate Columns

Change Properties of Interior Columns

Work > Properties > Section : 1 : Edge column = Active

Display > Property > Property Name > (on)

Isometric View (Refer Figure below)

Top View > Select Window > Select Interior Columns

Work > Properties > Section = 2 : Interior column

Drag & Drop (Refer Figure below)

Inactivate Beams

“Drag & Drop” Interior Column Properties

Generate Walls

Hidden (toggle off) ;    Node Number (toggle on)

Display > Property > Property Name > (off)

Select Window (Refer Figure below)

Active

Create Elements

Element Type : Wall

Membrane > (on)

Wall ID > Auto Inc. > 1

Material Name > 1:Grade C4000

Thickness > 1:1.5000

Intersect Node > (on)

Nodal Connectivity > 50, 42, 10, 18 (Refer on Figure below)

Select Single > Wall Element 1

Translate Element > Copy

Equal Distance (dx, dy, dz) > 130, 0, 0

Wall ID Increment = 1

Location of Wall Element

Nodal Connectivity of Wall Element

Generation of Wall Element

Building Generation

Select All

Structure > Building > Control Data > Building Generation

Number of Copies = 11

Distance(Global Z) = 12

Building Generation

Generate Story Data

Structure > Building > Control Data > Story

Generation of Story Data

2-3 Boundary Conditions Input

The lower ends of the columns are assumed fixed.

Boundary > Supports > Define Supports

D – All > (on)

R – All > (on)

Select Window

Boundary Supports

2-4 Loading Data Input

Load > Static Load > Create Load Cases > Static Load Cases

• Dead Load

• Live Load

• Wind Load (X-direction)

• Wind Load (Y-direction)

• Earthquake Load (X-direction, Eccentricity direction-Positive)

• Earthquake Load (X-direction, Eccentricity direction-Negative)

• Earthquake Load (Y-direction, Eccentricity direction-Positive)

• Earthquake Load (Y-direction, Eccentricity direction-Negative)

Loading Data Input

Self Weight

Load > Static Loads > Structure Loads/Masses > Self Weight

Z = -1

Self Weight Load

Floor Load

Load > Initial Forces/Misc. > Assign Floor Loads > Define Floor Load Type

• Name > Typical Floor : DL = -30 psf, LL = -75 psf 

• Name > Roof Level : DL = -10 psf, LL = -20 psf 

Load > Initial Forces/Misc. > Assign Floor Loads > Assign Floor Load

• Load Type > Typical Floor

• Two Way Distribution

• Copy Floor Load > (on)

• Axis > z (on)

• Distance > 10@12

• Assign Nodes Defining Loading Area > (1, 8, 32, 25)

Similarly, assign floor load at roof level :

• Load Type > Roof Level

• Copy Floor Load > (off)

• Assign Nodes Defining Loading Area > (386, 387, 417, 410)

Assign Floor Loads

Floor Load Distribution

Wind Loads

Load > Static Loads > Lateral > Wind Loads

• Load Case Name > WX

• Wind Load Code > IBC2012 (ASCE7-10)

• Alternate Method > (on)

• Basic Wind Speed > 85 mile/h

• Exposure Category > B

• Scale Factor in Global X > 1

• Scale Factor in Global Y > 0

• Load Case Name > WY

• Scale Factor in Global X > 0

• Scale Factor in Global Y > 1

Input Wind Loads

Convert Model Weight & Loads to Masses

Structure > Type > Structure Type

• Structure Type > 3-D (on)

• Convert Self-weight into Masses (on)

• Convert to X, Y (on)

• Gravity Acceleration > 32.1719 (ft/sec²)

Convert Model Weight to Masses

Load > Static Loads > Structure Loads/Masses > Nodal Masses > Loads to Masses

• Mass Direction > X, Y (on)

• Load Type for Converting > All (on)

• Gravity > 32.1719 (ft/sec²)

• Load Case > DL

• Scale Factor > 1

• Load Case > LL

• Scale Factor > 0.25

Covert Model Loads to Masses

Static Seismic Loads

Load > Static Loads > Lateral > Seismic Loads

• Load Case Name > EXP

• Seismic Load Code > IBC2012 (ASCE7-10)

• Seismic Design Category > E

• Site Class > C

• Ss = 1.0

• S1 = 0.3

• Importance Factor (I) = 1

• Period (Code) > X-Dir. = 1.2 ; Y-Dir. = 0

• Response Modification Coef. (R)

> X-Dir. = 8 (Special moment frame),

    Y-Dir. = 8 (Dual system: special reinforced concrete structural walls with special moment frame)

• Scale Factor in Global X = 1

• Scale Factor in Global Y = 0

• Accidental Eccentricity in X-direction > Positive (on)

• Accidental Eccentricity in Y-direction > Positive (on)

• Load Case Name > EXN

• Period (Code) > X-Dir. = 1.2 ; Y-Dir. = 0

• Scale Factor in Global X = 1

• Scale Factor in Global Y = 0

• Accidental Eccentricity in X-direction > Negative (on)

• Accidental Eccentricity in Y-direction > Negative (on)

• Load Case Name > EYP

• Period (Code) > X-Dir. = 0 ; Y-Dir. = 1.2

• Scale Factor in Global X = 0

• Scale Factor in Global Y = 1

• Accidental Eccentricity in X-direction > Positive (on)

• Accidental Eccentricity in Y-direction > Positive (on)

• Load Case Name > EYN

• Period (Code) > X-Dir. = 0 ; Y-Dir. = 1.2

• Scale Factor in Global X = 0

• Scale Factor in Global Y = 1

• Accidental Eccentricity in X-direction > Negative (on)

• Accidental Eccentricity in Y-direction > Negative (on)

Input Static Seismic Loads

Response Spectrum Load

Load > Seismic > Response Spectrum Data > Response Spectrum Functions

Design Spectrum

• Design Spectrum > IBC2012 (ASCE7-10)

• Site Class > C

• Ss = 1.0

• S1 = 0.3

Response Spectrum Loads

Load > Response Spectrum Analysis Data > Response Spectrum Load Cases

• Load Case Name > RX

• Direction > X-Y

• Excitation Angle = 0 (deg.)

• Scale Factor (I/R) > 1/8 = 0.125

• Period Modification Factor = 1

• Function Name (Damping Ratio) > IBC2012(ASCE7-10) (0.05) > (on)

• Interpolation of Spectral Data > Linear (on)

• Accidental Eccentricity > (on)

• Modal Combination Type > SRSS

• Load Case Name > RY

• Excitation Angle = 90 (deg.)

• Modal Combination Type > SRSS

Response Spectrum Analysis

2-5 Analysis

Analysis > P-Delta Analysis Control

• Number of Iterations = 5

• Convergence Tolerance = 1e-005

• P-Delta Combination > Load Case > DL ; Scale Factor > 1

• P-Delta Combination > Load Case > LL ; Scale Factor = 0.25

Analysis > Eigenvalue Analysis Control

• Type of Analysis > Eigen Vectors (on) > Subspace Iteration (on)

• Number of Frequencies = 10

• Number of Iterations = 20

• Subspace Dimension = 0

• Convergence Tolerance = 1e-010

Perform Analysis

P-Delta and Eigenvalue Analysis Control

2-6 Design Input

Results > Combinations

Concrete Design > Auto Generation

• Option > Add (on)

• Design Code > ACI318-11

• Scale Up Factor = 1.48 ; RX 

• Scale Up Factor = 1 ; RY 

Generation of Load Combinations for Concrete Design

Compare RX (RY) with EX (EY)

RX (RY) :

Results > Tables > Result Tables > Story > Story Shear (Response Spectrum Analysis)

• Spectrum Load Cases > RX(RS) (on) & RY(RS) (on) 

• Shear Force (Without Spring)

Story Shear (Response Spectrum Analysis)

EX (EY) :

Load > Static Loads > Lateral > Seismic Loads

Load Case > EXP > Modify > Seismic Load Profile

• Story Shear (on)

Similarly, select Load Cases EXN, EYP & EYN

Story Shear (Static Seismic Loads)

Design > General > General Design Parameter >Definition of Frame

• X-direction > Unbraced | Sway (on)

• Y-direction > Braced | Non-Sway (on)

• Design Type > 3-D

• Auto Calculate Effective Length Factors > (on)

Definition of Frame

Design > General > General Design Parameter > Modify Live Load Reduction Factor

General Tab

• Option > Add/Replace (on)

• Applied Components > Axial Force (on)

• Top View > Select Window

• Interior columns: Reduction Factor = 0.56

• Edge column: Reduction Factor = 0.69

• Corner column: Reduction Factor = 0.88

Modify Live Load Reduction Factor

• Unbraced Length (L, Lb)

• Option > Add/Replace (on)

• Unbraced Length > Ly=0 ; Lx=0

• Laterally Unbraced Length > Do not consider (on)

• Select All 

• Equivalent Moment Correction Factor (Cm)

• Option > Add/Replace (on)

• Moment Factor > Calculate by Program (on)

• Select All 

Unbraced Length

Equivalent Moment Correction Factor

Design > Design > RC Design > Design Code

• Design Code > ACI318-11

• Apply Special Provisions for Seismic Design > (on)

• Select Frame Type > Special Moment Frames (on)

Concrete Design Code

Design > Design > RC Design > Strength Reduction Factors

Update By Code

Strength Reduction Factors

Design > Design > RC Design > Design Criteria for Rebars (Refer Figure below)

Design Criteria for Rebars

Design > Design > RC Design > Modify Concrete Materials

Select material ID #1

Rebar Selection

• Code > ASTM (RC)

• Grade of Main Rebar > Grade 60

• Grade of Sub-Rebar > Grade 40

Modify Concrete Materials

2-7 Design Output

Design > Design > RC Design > Concrete Code Design > Beam Design

Sorted by > Member (on) 

Concrete Beam Design

Design > Design > RC Design > Concrete Code Design > Beam Design

Sorted by > Member (on) 

Concrete Column Design

Design > Design > RC Design > Concrete Code Design > Wall Design

Sorted by > Wall ID + Story (on)

SEL (Select) > WID (Wall ID) = 1 ; Story = 1F

Graphic

Concrete Wall Design

Typical Output of Concrete Wall Design