Analysis & Design Using ETABS

Analysis and Design of Buildings using ETABS

ACECOMS, AIT 1

Analysis and Design of Buildings Using ETABS 9.5

Dr. Naveed Anwar, Keerati Tunthasuwat, Thuang Htut Aung

Asian Center for Engineering Computations and Software, AIT Asian Institute of Technology

Users’ ForumManila, 2009

About ACECOMS and AITThe Asian Center for Engineering Computations and Software (ACECOMS) is a part of the Structural Engineering Field in the School of Engineering and Technology (SET) at the Asian Institute of Technology (AIT), Thailand.

AIT is a postgraduate international institute established in 1959 with the mission “to develop highly qualified and committed professionals who play leading roles in the region's sustainable development and its integration into the global economy”.

The Structural Engineering Field is one of the first programs to be established at AIT and has been as a strong academic and research program for almost fifty years. The program is well known for excellence in academic, research and industry partnership.


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About ACECOMS and AITACECOMS was established in 1995 as one of the first not-for-profit, self-sustaining outreach center in then the School of Civil Engineering to provide and interface between academic and research activities and the professional practice. Since its establishment., ACECOMS has been contributing significantly in the development and effective applications of computational technologies in structural and civil engineering through its activities

ACECOMS Carry-out research and development in engineering computational technology and software.Carry-out research and provide consultancy for the applications of computing tools on the real world problemsProvide general and specialized consulting services and support for project design, system development, review and investigation etc. Provide trainings and technical support for development of knowledge, information and skillsEstablish networks and associations with regional academic institutions and professional organizationsDisseminate practical information and knowledge· Encourage active participation of professionals


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AgendaOverviewHandling Materials, Sections, LoadsHandling Special BehaviorCreating Complex ModelsAnalysis for various purposesInterpreting and evaluating resultsSpecific QuestionsWhat is Coming Next?Discussion

Software Discussed

ETABSSAP2000SAFECSICOL

GEARGRASP


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Overall Process

Define the Parameters and PropertiesQuick ModelingImport, Draw and EditSelect and AssignAnalyze and UnderstandDesign and Check

Define and PreferencesBasic Parameters to be used in Analysis and Design


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Define Coordinate System/GridsFor a regular or general system, the coordinate system is defined using an origin and orientation relative to the Global coordinate system. All coordinate systems follow the right-hand rule. The grid lines for a regular system are defined relative to X and Y (Cartesian) or r and theta (cylindrical). The grid lines for a general system are defined relative to X and Y only.A regular system is any coordinate/grid system having a Cartesian (rectangular) or cylindrical grid system. A general system is a system comprised of arbitrarily defined grid lines. The Global coordinate system always exists, and has its own grid. All other systems are user defined with respect to the Global system.

Define Coordinate System/GridsConfiguration of alternate coordinate systems

Locate the system origin


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Define Coordinate System/GridsConfiguration of alternate coordinate systems

Define Coordinate System/GridsHow to determine regular system or general system

To determine if a previously defined system is a regular or general system, access the Coordinate/Grid Systems form and highlight the system name in the Systems display area. If the Convert to General Grid check box is NOT checked (with the system name highlighted), the grid system is a regular system.

Regular system General system


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Define Coordinate System/GridsGeneral System

In general system, we can draw the arbitrary grid lines which does not need to perpendicular each other.

Define Coordinate System/GridsGeneral System

General System


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FunctionsResponse SpectrumTime History

FunctionsResponse Spectrum FunctionFor Seismic Analysis

From Code (IBC2006, AASHTO, EuroCode 8 …etc.) User Define from File

Response Spectrum Function for UBC97


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FunctionsTime History Function

From Built-in (Sine, Cosine, Ramp, Sawtooth…etc.) User Define from File

Time History Function for Sine Function

Quick ModelingUsing Parametric Structures and Templates


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Templates

Steel Deck System


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Staggered Truss System

Flat Slab System


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Flat Slab with Perimeter Beams

Waffle Slab System


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Ribbed Slab System

Template

Add template to existing modelAble to add the components from template to the existing model


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Export, Draw and EditCreating Complex Geometry Efficiently

Import & Export

Capability to import data from many structural engineering software to create the modelExport the model to SAFE and other drawing software


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Export to AutoCAD .dxf File

Export to AutoCAD .dxf File


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Drawing and EditingPoints

Nodes, Supports etc.Lines

Frames, Beams, TrussesCables

AreasPlate, Shell, Membrane

MoveReplicateExtrudeEdit PointsDivideMesh

ReplicateGenerating a large model from a small model when the objects and/or joints form a linear or radial pattern or are symmetrical about a plane or story. Different from Cut, Copy and Paste commands.Replicate command replicated the assignments and loads on the objects but Cut, Copy and Paste commands are NOT capable of copying the assignments or loads.Four types of replication

LinearRadialMirrorStory


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Extrude

Sweep selected objects through space to create new objects of higher dimension

Extrude points to linesModel circular-shaped beam

Extrude lines to areasModel the ramp

Extrude

Model circular shaped beam by radial extrusion of point object


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Extrude

Model circular shaped ramp by radial extrusion of line object

Edit PointMerge joints

Merge the joints outside the auto merge tolerance.To eliminate the extraneous joints that may occur if the elements are drawn with snap turned off.

Align pointsIf the floor area is manually meshed in irregular pattern and the different pattern loading is to be assigned, the edge of area elements should be aligned along the border of the pattern loading.


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Edit Point - Merge

Select the points to merge

Merge tolerance must be greater than distance between the points

Edit Point - Align

Live load = 2 kN/m2 Live load = 5 kN/m2

To assign different pattern loading on irregular shaped

meshed floor

Draw the line along the border of pattern loading. Select the

line and the points to be aligned

The floor elements are aligned along the

border of different pattern loading


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Edit Lines

Divide framesJoin framesTrim/Extend framesEdit curved frame geometryEdit cable geometryEdit tendon profile

Edit LinesDivide frames

Divide the frame intersect with selected frames.

Select the frame object to bed divided and select the

intersecting objects

Join framesJoin the selected frame objects and remove the unused joints.


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Edit Areas - Divide

Divide into the number of objects specified using the edit box for each edge.

Edit Areas - Divide

Divide area into objects of given maximum size

10 elements


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Edit Areas - DivideDivide area based on points on area edges

Divide based on specified lines and points. Program will not extend the selected line to make it intersect an edge; the selected line must already intersect an edge of the selected area object. The selected point must also intersect an edge of the selected object, not inside the selected object.

Edit Areas - DivideDivide area using cookie cut based on selected straight line objects

The selected line object does not need to intersect with the edge of the selected area object .


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Edit Areas - DivideDivide area into given number of objects

The selected point object must lie either on the edge or inside the selected area object. The rotation in degrees of dividing lines can be specified from original local 1 and 2 axes.

Edit Areas - DivideDivide area using general divide tool based on selected points and lines

Divide the area object based on specified maximum dimension.The division lines intersect the selected points and concurrent with the selected lines.


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Edit Areas - DivideLocal axes for added points

Specify that the local axes definitions for new points added along the edges of an area object are the same as an adjacent area object corner point if the local axes definition for the adjacent corners are identical.Specify that the local axes definition for the new points on the face of the area object are set the same as a corner point of the area object if the local axes definitions for all of the corner points of the area object are identical.

Edit Areas - Divide

Added points on the edge of original element have the same local axes with original element.

If the second check box is checked, local axes of added points on the face of original element will be same.


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Edit Areas - DivideRestraints and constraints for added points

Specify that a restraint degree of freedom (or constraint) is added to new points on the edges of the area object if both adjacent corners have that degree of freedom restrained (constrained) and the local axes definitions for the adjacent corners and the new point are identical.Specify that a restraint degree of freedom (or constraint) is added to new points on the face of the area object if all area object corners have that degree of freedom restrained (constrained) and the local axes definitions of all corners and the new points are identical.

Edit Areas - Divide

Added points on the edge of original element have the same restraints with original element. If the second check box is checked, restraints of added points on the face of original element will be same.


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Edit Areas-MergeSelected areas essentially in the same plane and sharing a common edge or with overlapping area edges will be merged.Areas that lie one on top of the other or that share no common or overlapping edges will not be merged.Choose an area that has assignments suitable for the merged area.

Edit Areas-Merge

Area 6

Area 7

Maintain the assignments for Area 7


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Edit AreasExpand/Shrink areas

A positive value expands the area and a negative value shrinks the area. The offset distance is measured perpendicular to the area edge.

100 100

100

100

Offset all area edges

Select the edge or whole area

Edit Areas

Offset selected area edges only

Select the edge

100


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Edit Areas

Offset selected points of selected areas only

100

Select the point and areaThe offset for points is measured along a bisector angle formed by the area edges adjacent to the

selected point(s).

Edit AreasAdd point to area edge

Add points to the edges at the midpoint between the existing points of the selected object.This procedure can do repeatedly as many times as needed.


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Edit AreasRemove points from area

Select the area and the point to be removed.If the point was not colinear with the remaining points, the area object will be reshaped.

Special ToolsHandling Special Problems and Behavior


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Basic Modeling Techniques -Behavior

Constraints RestraintsSpringsNonlinear LinksNonlinear HingesElement End ConditionsDummy elements

Link/Support ElementA Link element is a two-joint connecting link. A Support element is a one-joint element

Support Element

Link Element


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Link/Support ElementType of Link/Support Element available in ETABS

LinearDamperGapHookPlastic1Isolate1Isolate2

Link/Support Element

Damper ElementGap Element

Compression only (for example Spread Footing)

Hook ElementTension only (for example Tie Rod)


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DiaphragmsIn ETABS: Only diaphragms is available as

constraint option for joint and shell element

DiaphragmsRigid Option

Fully rigid diaphragm is assumed


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DiaphragmsSemi Rigid Option:

The in-plane rigidity of the diaphragm comes from the stiffness of the objects that are part of the diaphragmUsed to calculate the dimension of diaphragm in application of the wind/static equivalent earthquake loading

Select and AssignConnecting Geometry with Defined Parameters


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Select and Assign

Many tools to select the drawn objectsMany types of assignments

SectionsLoads, Temperature, Joint PattersConstraints, Restraints, ReleasesSpecial modificationsAxis, Insertion Points, OffsetsLocal material changes

Analyze and UnderstandGetting the Required Response and Understanding Behavior


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Analysis Case

StaticLinear StaticNonlinear Static (Included Push Over)Staged Construction

Response SpectrumTime History

Linear Time HistoryNonlinear Time History

Analysis CaseStatic:

Linear: The most common type of analysis. Loads are applied without dynamical effects.Nonlinear: Loads are applied withoutdynamical effects. May be used for pushoveranalysis, and other types of nonlinearproblems. (Pushover + P-Delta)Nonlinear Staged Construction: The definition of a nonlinear direct-integration time-history analysis case for staged construction.


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Analysis Case

1

2

3

NonlinearStaged Construction

Analysis Case

Modal:Calculation of dynamic modes of the structure using the Eigenvector or Ritz-vector method. Loads are not actually applied, although they can be used to generate Ritz vectors.


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Analysis CaseResponse Spectrum.Statistical calculation of the response caused by acceleration loads. Requires response-spectrumfunctions.

Response Spectrum Function

Analysis CaseTime History:

Linear Time History. Time-varying loads are applied.Requires time-history functions. All objects behave linearly.Period. Specify a single cycle of the periodic function and assumes that the specified cycle continues indefinitely. All objects behave linearly. Nonlinear Time History. Time-varying loads are applied. Requires time-history functions. Nonlinear dynamic properties assigned to link elements are considered.


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Pushover Analysis

Pushover Analysis

Available Hinge PropertiesAxial PShear V2Shear V3Moment M2Moment M3Torsion TInteraction P-M2-M3


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Pushover AnalysisHinge Property Data

Displacement Controlled

Pushover AnalysisPushover Curve

Resultant Base Shear vs Monitored Displacement


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Pushover AnalysisPushover Curve

ATC-40 Capacity Spectrum ATC-40 Capacity Spectrum

Show Response Spectrum CurveCreate from Time History Case at Particular Joint

Frequency or PeriodVersus

Spectral DisplacementSpectral VelocityPseudo Spectral VelocitySpectral AccelerationPseudo Spectral Acceleration


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Show Plot Function

Energy FunctionInput, Kinetic, Potential Modal DampingLink Damper, Energy ErrorBase FunctionJoint Displacement/ForcesFrame ForcesPier ForcesSpandrel Forces

Show Plot Function

Displacement FunctionBase Function


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Energy/ Virtual Work FunctionFigure "a," that has lateral loads P1 and P2 at the Roof and Second story levels, respectively. Also note the displacedshape, D, associated with this structure and loading, whichis shown as a dashed line.

Energy/ Virtual Work FunctionFigure "b", with a single load P (typically a unit load) appliedto it and a resulting displaced shape, d, shown as a dashed line. Maxwell's Reciprocal Theorem states that:

Pδ = P1 δ roof + P2 δ second


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Energy/ Virtual Work FunctionIn this very simple example, the equation above could be reduced to an element level where the elements are illustrated in Figure "c" as:

P δ = [P1 δ roof - P1 δ second] + [(P1 + P2) δ second]

Energy/ Virtual Work FunctionP δ = [P1 δ roof - P1 δ second] + [(P1 + P2) δ second]

ETABS show the energy diagram, it reports the equivalentof the values shown in brackets in the above equation of the background information for each element in the structure.

Note the following about the energy values that ETABSreports:


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Energy/ Virtual Work FunctionP δ = [P1 δ roof - P1 δ second] + [(P1 + P2) δ second]

They are based on all six degrees of freedom of the element, not just the one degree of freedom described in the Figure and the associated equations in the backgroundinformation.

They are determined as follows:ETABS determines the energy per unit volumeassociated with each element in the structure.ETABS normalizes all of the calculated energy valuessuch that the largest one has a value of 100.

Energy/ Virtual Work FunctionSample of Energy/ Virtual Work Diagram due to Wind Load


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Time History TracesAvailable Functions for Time History Traces

Input FunctionEnergy FunctionBase FunctionPoint Displacement/ ForcesLine Element ForcesPier ForcesSpandrel Forces

Time History TracesInput Function = Input Time History Function


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Time History TracesEnergy Function

Time History TracesEnergy Function


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Time History TracesBase Function = Total Base Reaction Function

Time History TracesPoint Displacement/ ForcesLine Element ForcesPier ForcesSpandrel Forces

Displacement/ Forcesat Particular Element and

Location

Point Line Pier Spandrel


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Time History TracesPoint Displacement/ ForcesLine Element ForcesPier ForcesSpandrel Forces

Displacement/ Forcesat Particular Element and

Location

Element ID

Force ComponentLocation

Outrigger System

OutriggerNo Outrigger


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Shear Force in Beams due to Lateral Load (No Outrigger Wall)

3.14 T 3.25 T 4.24 T

Shear Force in Beams due to Lateral Load (Outrigger Wall)

2.58 T 2.41 T 2.95 T


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Axial Force in Columns due to Lateral Load (No Outrigger Wall)

623 T 350 T 383 T

Axial Force in Columns due to Lateral Load (Outrigger Wall)

746 T 580 T 484 T


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Bending Moment due to Lateral Load (No Outrigger Wall)

8.3 8.6 11.3

40.2 38.3 36.9

Bending Moment due to Lateral Load (Outrigger Wall)

6.9 6.4 7.9

33.7 31.1 29.1


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Top Displacement due to Lateral Load

Top Displacement = 75 cm Top Displacement = 40 cm

Construction Sequence Analysis


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Deflected Shape due to DL (Linear Analysis) Deflected Shape due to DL

(Construction Sequence Analysis)


Axial Force due to DL at the Base (Linear Analysis)

Axial Force due to DL at the Base (Construction Sequence Analysis)

1018 T 16135 T 1141 T 1011 T 1101 T 15333 T 1248 T 1035 T


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Bending Moment due to DL (Linear Analysis)

Bending Moment due to DL (Construction Sequence Analysis)

11.3 12.4


Shear Force due to DL (Linear Analysis) Shear Force due to DL (Construction Sequence Analysis)

8.9 9.3

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Analysis & Design Using ETABS