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Success with ModelSmart3D Pre-Engineering Software Corporation Written by: Robert A. Wolf III, P.E. Copyright 2003, Pre-Engineering Software Corporation, All Rights Reserved Tower - Show 1

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 2 Series Outline Show # 1 I.Possible benefits II.Introduction to towers Show # 2 III.Model towers IV.Using ModelSmart3D V.Extra for Experts Show # 3 VI.Optimization VII.Printing Show # 4 VIII.Building Your Model

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 3 I. Possible Benefits 1.Practical application for math and science. 2.Create a feel for engineering. 3.Foster innovation. 4.Re-label mislabeled students 5.Efficient method for experimenting Motivation and Enhancement

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 4 II. Introduction to Towers Why build a tower? To support something or someone above ground level.

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 5 Example Towers Observation Radar

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 6 More Examples Communications Hotel

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 7 More Examples Water Supply

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 8 Definition What is a tower? Its a tower if W H

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 9 The Job of a Tower To safely support people, materials, and equipment at the design height.

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 10 Classified by Direction Vertical – Acting up or down Horizontal – Acting left or right (also forward of back ward) (Diagonal forces can be resolved into vertical and horizontal components.) = Types of Loads on a Tower

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 11 Vertical Load Vertical (Gravity) Loads Dead Load – Immovable Materials (the structures self- weight) Live Load – People and moveable things

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 12 Horizontal Load Horizontal (Lateral) Loads: Wind Earthquake Flowing water

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 13 Design Concept The Cantilever Analogy One way to think about a tower is by considering a cantilever truss with a vertical load (P) that acts up and down and horizontal loads (C) that cause compression in both the top and bottom chords. P (+ or -) C C Cantilever Truss Top Chord Bottom Chord

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 14 Which load is greater? What if the vertical (lateral load if the tower was standing up) load was the greater load? What shape would the tower take? P (+ or -) C C

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 15 Wind Direction Varies? Remember, we are really designing a tower and the P load might be a load caused by wind or earthquake and thus could act in either direction. P (+ or -) C C

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 16 A Tower is Born? That looks like a tower! ±P C C

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 17 Which load is greater? What if the horizontal load was the greater load? What shape would the tower take? Chunkier Columns? P C C

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 18 Column Size Usually there is a mix of lateral and vertical load. Maybe we could widen it a bit to take care of the some lateral load and make the columns chunkier to take the vertical load.

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 19 Getting the Most out of Your Columns If your column is long it could buckle. Where might you hold it to keep it from buckling?

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 20 Secondary Buckling Mode Now how do we keep it from buckling?

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 21 How Many braces Do We Need? Each time we add the support midway between the existing (lateral) supports. Equal Spaces

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 22 Column Failure Modes. Crushing of the material Buckling

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 23 A Columns Critical Unbraced Segment Length. Start with a short column. Keep increasing its length until the mode of failure is by buckling. The critical length is the maximum length the column before it fails due to buckling. Approximate Critical Length

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 24 Bracing the Column Provide bracing such that no column segment exceeds the critical length of the column? Have I done that here?

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 25 Use Diagonal Bracing For stability against sidesway you might want to add diagonal bracing.

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 26 Other Diagonal Bracing Schemes X- Braced Inverted V V with and Inverted V at base Invent One ! ?

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 27 Designing the Lateral Braces How do we design an optimal bracing configuration? Lets assume the wind comes from the left. If the wind only came from the left, we could place the diagonals such that each bracing element was in tension. A tension or pulling internal force P

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 28 Procedure for Designing X-Braces Design the diagonals to resist the tension created by the window coming from the left. Reverse the direction of the wind and design tension bracing again neglecting the existing braces.

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 29 Why are X-Braced Towers so popular? It is usually more efficient to design redundant tension bracing than to design a single element (member) that can act both as a tension brace and a compression strut.

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Success with ModelSmart3D - Series 2 (towers) - Show 1 Slide No. 30 End of Show 1 Series 2

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