SEISMIC ANALYSIS AND DESIGN OF FOUR STOREY REINFORCED CONCRETE BUILDING (EQUIVALENT LATERAL FORCE) USING STAAD PDF

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SEISMIC ANALYSIS AND DESIGN OF FOUR STOREY REINFORCED CONCRETE BUILDING (EQUIVALENT LATERAL FORCE) USING STAAD AND SPREADSHEET JP Bersamina, MSCE, RCE October 11,2018 2 Contents 1 COMPUTER AIDED DESIGN USING STAAD AND SPREADSHEET 5 2 INTRODUCTION 7 2.1 Project Description . . . . . . . . . . . . . ....

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SEISMIC ANALYSIS AND DESIGN OF FOUR STOREY REINFORCED CONCRETE BUILDING (EQUIVALENT LATERAL FORCE) USING STAAD AND SPREADSHEET JP Bersamina, MSCE, RCE October 11,2018

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Contents 1 COMPUTER AIDED DESIGN USING STAAD AND SPREADSHEET

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2 INTRODUCTION 2.1 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Importance of STAAD and Spreadsheet . . . . . . . . . . . . . . . . . . . . . 2.3 Design Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Setting up design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Modeling of Structure in STAAD . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Adding loads in structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Design of Gravity Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.1 Stair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.2 One way slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.3 Two way slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.4 Intermediate Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Design of seismic resisting members . . . . . . . . . . . . . . . . . . . . . . . 2.8.1 Girder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.2 Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 Design of Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10 Compiling the result in structural Design Report for submission in City Hall

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3 SETTING UP THE DESIGN CRITERIA 3.1 Reference Code . . . . . . . . . . . . . . . . 3.2 Dead Loads . . . . . . . . . . . . . . . . . . 3.3 Live Loads . . . . . . . . . . . . . . . . . . 3.4 Seismic Loads . . . . . . . . . . . . . . . . . 3.5 Wind Loads . . . . . . . . . . . . . . . . . . 3.6 Material strength . . . . . . . . . . . . . . . 3.7 Design Constants . . . . . . . . . . . . . . .

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13 13 14 14 15 19 20 21

4 BUILDING THE MODEL 4.1 Modeling the Ground Floor Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Building Upper Floors using Translational Repeat . . . . . . . . . . . . . . . . . . . . . . 4.3 Defining section properties and assigning to structure . . . . . . . . . . . . . . . . . . . .

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5 ASSIGNING SUPPORT 5.1 Support for Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Support for Footing using Finite Element Model . . . . . . . . . . . . . . . . . . . . . . .

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6 CREATING GROUPS IN STAAD 6.1 Group for Exterior Girder . . . . . 6.2 Group for Interior Girder . . . . . 6.3 Group for Interior Column . . . . . 6.4 Group for Exterior Column . . . . 6.5 Group for Exterior Node support . 6.6 Group for Interior Node Support .

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CONTENTS

7 DEFINING PRIMARY LOADS AND 7.1 Adding Dead Load . . . . . . . . . . . 7.1.1 Adding Exterior Wall Load . . 7.2 Adding Live Load . . . . . . . . . . .

ASSIGNING . . . . . . . . . . . . . . . . . . . . . . . . . . .

TO STRUCTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41 42 48 50

8 DEFINING SEISMIC LOAD

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9 GENERATING AUTOLOAD COMBINATION

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10 RUNNING ANALYSIS AND VIEWING 10.1 Earthquake Base Shear Result . . . . . . 10.2 Exterior Column Forces . . . . . . . . . . 10.3 Exterior Girder Forces . . . . . . . . . . . 10.4 Support Reactions . . . . . . . . . . . . . 10.5 Displacement . . . . . . . . . . . . . . . . 10.6 Storey Drift . . . . . . . . . . . . . . . . . 10.7 Errors and Warnings in Analysis . . . . .

RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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11 DESIGN OF STAIR

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12 DESIGN OF ONE WAY SLAB 12.1 Design Using Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Design Using Finite Element Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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13 DESIGN OF TWO WAY SLAB 13.1 Design Using Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Design Using Finite Element Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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14 DESIGN OF INTERMEDIATE BEAM

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15 DESIGN OF GIRDER 15.1 Getting Result from STAAD Postprocessing Tab . . . . . . . . . . . . . . . . . . . . . . . 15.2 STAAD Parameters for Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3 Design of Girder in Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87 87 91 96

16 DESIGN OF COLUMN 99 16.1 Getting Result from STAAD Postprocessing Tab . . . . . . . . . . . . . . . . . . . . . . . 99 16.2 STAAD Parameters for Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 16.3 Design of Column in Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 17 DESIGN OF ISOLATED FOOTING 17.1 Getting Result from STAAD Postprocessing Tab . . . . . . . . . . . . . . . . . . . . . . . 17.2 Design of Footing in Spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Design Using Finite Element Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1 Bersamina

109 113 115 119

Chapter 1

COMPUTER AIDED DESIGN USING STAAD AND SPREADSHEET In the advent of technology or faster computer capacity, analysis and design of building is now done very quickly. Undergraduate students are trained in Theory of Structures to analyse indeterminate frame using Moment Distribution Method or Slope Deflection Method. Reinforced Concrete Design teaches design of beam and column using Strength Design Method. All of these can be packaged in one software like STAAD. The background of structural analysis in STAAD is Stiffness Method because it can be programmed using computer. The use of software STAAD will help the student analyze the building and design it quickly thus focusing on overall behavior of structure which the traditional manual calculation cannot produce in a seconds. However, the goal of this course does not want the student to rely solely on sofware. There must be a way to check the software result to allow the student scrutinize the software calculation and avoid the familiar GIGO situation or ”Garbage In, Garbage Out”.

Figure 1.1 5

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CHAPTER 1. COMPUTER AIDED DESIGN USING STAAD AND SPREADSHEET

Figure 1.2 Thus, a spreadsheet must be prepared by the student to verify the software result.

Chapter 2

INTRODUCTION 2.1

Project Description

Our structure is a four storey school building.

Figure 2.1: Elevation View of Structure

Figure 2.2: East West Elevation 7

8

CHAPTER 2. INTRODUCTION

Plans were downloaded from DPWH website. We will model this in STAAD and assume some parameters to show features of STAAD and use of our spreadsheet.

2.2

Importance of STAAD and Spreadsheet

We will use STAAD software together with our spreadsheet to design or investigate our project structure. STAAD is only used for analysis. It has no capability to design members in compliance to Earthquake Provision of NSCP. Most design firms actually do that. They have separate checking of members to comply with earthquake provision. Structura engineers in the Philippines should be aware of these provisions because we are in an earthquake prone country. We expect our structure to be subjected to earthquake during its lifetime and seismic resisting members will surely undergo inelastic deformation. Thus, seismic detailing of these members are important part of design and the spreadsheet does that for you. Figure below shows typical details for seismic resisting members. Images are from Google search.

Figure 2.3

2.3

Design Process

Design and analysis of structure is normally done in the following procedure:

2.4

Setting up design criteria

This is discussed in chapter 3. Design criteria needs to be consistent with the design drawing, specifications and design report.

2.5

Modeling of Structure in STAAD

This is discussed in chapter 4. Modeling of structure and idealization of members should be consistent with the design intent of the structural engineer.

2.5. MODELING OF STRUCTURE IN STAAD

Figure 2.4

Figure 2.5

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2.6

CHAPTER 2. INTRODUCTION

Adding loads in structure

This is discussed in chapter 7. Loads applied in the model should be consistent with the design criteria established.

2.7 2.7.1

Design of Gravity Members Stair

This is discussed in chapter 11. Stairs location and length are configured by the architect.

2.7.2

One way slab

This is discussed in chapter 12. Both one way and two way slabs contribute to most of dead weight of structure. Establishing its thickness is required and thus affects general structural framing of building.

2.7.3

Two way slab

This is discussed in chapter 13.

2.7.4

Intermediate Beam

This is discussed in chapter 14. Intermediate beams are the immediate support of slabs before transferring load to the girder.

2.8 2.8.1

Design of seismic resisting members Girder

This is discussed in chapter 15.

2.8.2

Column

This is discussed in chapter 16. Note that this is a separate spreadsheet because interaction diagrams are programmed using macros in excel to consider biaxial bending of column.

2.9

Design of Foundation

This is discussed in chapter 17. Foundation design is dependent on the soil bearing capacity of the soil as obtained by Geotechnical Engineer. They normally set the initial embedment of footing in the ground where hard strata is present. Otherwise, ground improvement will be needed if soil is found with insufficient strength to carry loads from the building.

2.10

Compiling the result in structural Design Report for submission in City Hall

Finally, when all members are designed, you can easily print out each tab in the spreadsheet to generate a design report.

2.10. COMPILING THE RESULT IN STRUCTURAL DESIGN REPORT FOR SUBMISSION IN CITY HALL11

Figure 2.6

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CHAPTER 2. INTRODUCTION

Chapter 3

SETTING UP THE DESIGN CRITERIA Design Criteria tab of the spreadsheet shows the parameters used in the whole design of the structure. What are these parameters? These are the following:

3.1

Reference Code

In the Philippines, its NSCP which is the reference code but this is actually referenced from UBC 1997 from the USA. Modifications of UBC to adapt to local conditions is made however.

Figure 3.1 13

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3.2

CHAPTER 3. SETTING UP THE DESIGN CRITERIA

Dead Loads

These are the permanent loads in the structure. Values in red are input values. That means these will be referenced by other design sheets of the spreadsheet to guarantee uniformity of values.

Figure 3.2

Figure 3.3: dead load

3.3

Live Loads

For residential building, a typical floor has 1.90 kpa of live load. For our school project, 2.4 Kpa is required live load by code. Exit facilities like stair required 4.8 Kpa.

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3.4. SEISMIC LOADS

Figure 3.4

Figure 3.5: live load

3.4

Seismic Loads

Engineer will need to refer to NSCP Chapter 2 to determine seismic parameters. For seismic parameters, just input the distance of the site from the nearest seismic fault line, importance factor, ductility coefficient and soil profile, then the spreadsheet will come up with proper seismic values. Thus, site location of the project is required to determine proximity in nearest fault line which will affect seismic intensity of building.

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CHAPTER 3. SETTING UP THE DESIGN CRITERIA

Figure 3.6

These parameters in the figure below are incorporated in the spreadsheet.

Figure 3.7: seismic parameters

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3.4. SEISMIC LOADS

Figure 3.8: seismic formulas

Figure 3.9: ductility coefficient values

18

CHAPTER 3. SETTING UP THE DESIGN CRITERIA

Figure 3.10: seismic map

Observe that almost whole Philippine area is under seismic Zone 4 region and you need to realize that any building structures designed here will be subjected to nonlinear behavior thus deforming beyond elastic region.

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3.5. WIND LOADS

Figure 3.11: seismic zone in philippines

3.5

Wind Loads

For wind load, you need to choose the zone factor of the site location and corresponding wind velocity also the roughness exposure of the site.

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CHAPTER 3. SETTING UP THE DESIGN CRITERIA

Figure 3.12: wind load

Figure 3.13: wind map

3.6

Material strength

The red input for concrete strength will be linked to other design tabs of the spreadsheet like the slab design, stair and beam design. Rebar strength will be referenced in designs of slab, beam and girders.

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3.7. DESIGN CONSTANTS Structural Steel strength Soil data will be linked to footing design tab under chapter 17.

Figure 3.14

3.7

Design Constants

Since you have inputted material values above, design constants will be automatically computed by the spreadsheet. These are important in design procedures of structural elements. Because you will need to determine the max and minimum reinforcement ratio, from these parameters that will be used for beam, slab, girder and foundation design.

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CHAPTER 3. SETTING UP THE DESIGN CRITERIA

Chapter 4

BUILDING THE MODEL We refer first to architectural drawing and check column location before inputting the coordinates in STAAD. In general, column location will be coordinates in STAAD. Note we are talking about global axis x,y, and z coordinates.

Figure 4.1

Click on New structure. Check Space Option, Input Filename, Select Folder location and Set units Meter and KN then click Next. Observer global axis x, y and z directions shown in bottom left of figure. 23

24

CHAPTER 4. BUILDING THE MODEL

Figure 4.2

Figure 4.3

Below shows architectural elevation. This will be used to determine global z values in the STAAD model.

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Figure 4.4

Input coordinates in geometry.

Figure 4.5

Figure 4.6

Below shows a sketch of plan and frame elevation showing column to column spacing and column height each floor. Top left column serves as location of 0,0 coordinates.

26

CHAPTER 4. BUILDING THE MODEL

Figure 4.7

4.1

Modeling the Ground Floor Beams

It is common practice to model the ground floor first especially if you have typical floor layout from ground to roof beam level.

4.2. BUILDING UPPER FLOORS USING TRANSLATIONAL REPEAT

4.2

Building Upper Floors using Translational Repeat

Once bottom floor is modeled, we can use translational repeat to model the upper floors.

Figure 4.8

Figure 4.9

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28

CHAPTER 4. BUILDING THE MODEL

Figure 4.10

Figure 4.11

4.3. DEFINING SECTION PROPERTIES AND ASSIGNING TO STRUCTURE

Figure 4.12

4.3

Defining section properties and assigning to structure

Refer to schedule of column and beam to define section properties in our model.

Figure 4.13

Assume column dimension of 450x450mm.

29

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CHAPTER 4. BUILDING THE MODEL

Figure 4.14

Figure 4.15

Click on beam properties then assign to beam in the model. To select all beam member quickly. Click Select–Beams Parallel to X. Repeat this for Beams Parallel to Z to select all beam members.

4.3. DEFINING SECTION PROPERTIES AND ASSIGNING TO STRUCTURE

Figure 4.16

To assign properties for column, select beams parallel to Y then assign.

Figure 4.17

Click on rendered view to check if all properties are assigned in structure.

31

32

CHAPTER 4. BUILDING THE MODEL

Figure 4.18

Chapter 5

ASSIGNING SUPPORT 5.1

Support for...