STRUCTURAL SYSTEMS

January 15, 2013

Presented by AIA-Pittsburgh’s Young Architects’ Forum (YAF)

Exam resources are available at AIA-PGH YAF ARE Review

http://yafpghare.wordpress.com/

ARE Blackout Period

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an estimated eight week blackout

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for the ARE beginning July 1, 2013.

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Agenda

� 5:30 Introduction/ Division Overview

� 5:35 Graphic Vignette Review

� 6:00 Multiple Choice Content Review

� 7:00 Break (if desired)

� 8:00 Questions?

Division StatementIdentification and incorporation of general structural and

lateral force principles in the design and construction of

buildings.

Exam Structure� 125 Multiple-Choice Questions (3 hours, 30 mins)

� Break (15 minutes)

� 1 Graphic Vignette (1 hour)

� Structural Layout

Test Day…

� Introductory Tutorial 0:15

� Multiple-Choice Questions 3:30

� Scheduled (Mandatory) Break 0:15

� Introductory Tutorial 0:15

� Graphic Vignettes 1:00

� Exit Questionnaire 0:15

� TOTAL APPOINTMENT TIME 5:30

Content Areas� GENERAL STRUCTURES (38-42% of scored items)

� Principles

� Materials and Technology

� Codes and Regulations

� SEISMIC FORCES (28-32% of scored items)

� Principles

� Materials and Technology

� Codes and Regulations

� WIND FORCES (14-17% of scored items)

� Principles

� Materials and Technology

� Codes and Regulations

� LATERAL FORCES – GENERAL (13-16% of scored items)

� Principles

� Materials and Technology LATERAL FORCES

55 – 65% of scored items

By the numbers…

� 125 questions…

� 3 hour, 30 minutes testing time…

…1 minute, 41 seconds per question

�By content area:

General Structures…….…………..……………47 - 53 questions

Seismic Forces…………..…………………..…..35 - 40 questions

Wind Forces………………………………….…...17 - 22 questions

Lateral Forces (General)……….…….……..…16 - 20 questions

LATERAL FORCES…………….………...…68 - 82 QUESTIONS

What’s actually on the test?� Gravity loads – Reduction to live loads

� Foundations/ Retaining Walls and soil types

� Bolted connections

� Scales of measurement for tornados, hurricanes, earthquakes

� Heavy Focus on Lateral Forces (both wind and seismic)� Wind Exposures

� Seismic Categories

� Diaphragms/ Shear Walls

� Center of Mass / Center of Rigidity

� Formulas – Section Modulus, Moment of Inertia, Radius of Gyration, Slenderness Ratio, Base

Shear (note: many are not provided as references)

� Factors in formulas (the ones that are usually determined by a table)

� Some force diagrams (similar to trusses but not as complex)

� Beams (tension / compression forces, moment and shear)

� Minimal calculations/ equations on the test

� Minimal focus on engineering exemplars/ notable buildings

GRAPHIC VIGNETTE

STRUCTURAL LAYOUT

Design a schematic framing plan for a

one-story building with a multi-level roof.

PROGRAMCreate a two-level framing solution (Upper Roof Plan and Lower Roof Plan) for a given background drawing. The solution should locate all structural elements such as load-bearing walls, columns, beams, and joists, and be responsive to the floor plan layout defined on the background (i.e., no new walls can be added). Framing for the Upper Roof needs to be depicted on the Lower Roof, and then carried through to the floor plan/ foundation.

GRAPHIC VIGNETTE

Program Requirements

Program

The preliminary floor plan for an urban mini-mall has been completed and approved, and you are

now required to develop a roof framing layout for the building or portion of the building shown on

the work screen. The layout must accommodate the conditions and requirements given below.

Site/Foundation

1. The site has no seismic activity and wind pressures are negligible.

2. The soils and foundation system should be assumed adequate for all standard and

normal loads.

3. The distribution of concentrated or special loads need not be considered.

Construction/Materials

1. Structural steel/open web steel joist construction has been chosen for the roof structure type.

2. Steel beam sections are to be rolled or built-up.

3. The metal roof deck is capable of carrying the design loads on spans up to and

including 4 feet.

4. Joists are sized to carry roof loads only.

Program Requirements, cont.General Requirements

1. All portions of the roof framing are flat.

2. Cantilevers are prohibited.

3. Structural members must not extend beyond the building envelope, except to frame a designated

covered entry.

4. Columns may be located within walls, including the window wall and the clerestory window wall.

5. Walls shown on the background floor plan may be designated as bearing walls. Additional bearing

walls are not allowed.

6. Lintels are required to be shown in bearing walls only. Other lintels shall not be indicated.

7. The opening located between the common area and the seating area must be unobstructed and

column-free.

8. The common area must be column-free.

9. The window wall and the clerestory window extend to the underside of the structure above. All

other openings have a head height of 7 ft above finish floor.

10. The roof over the high ceiling space must be higher than the roof over the low ceiling spaces.

1. The common area requires a high ceiling with a top of structure height of 18 ft.

2. The remaining spaces require a low ceiling with a top of structure height of 12 ft.

11. The structure must accommodate a clerestory window to be located along the full length

of the north wall of the common area.

Structural Layout – Step-by-Step(Note: Steel framing method shown – see NCARB’s Exam Guide for the Bearing Wall method)

STEP #1 Start at the top, work your way down.

Set Current Layer to “Upper Roof Plan”

STEP #2 Place columns at the corners of the high-bay space.

STEP #3 Place additional columns to reduce spans.

STEP #4 Add beams (at wall centerlines – zoom in, use the Check tool!).

Structural Layout - Step-by-StepSTEP #5 Draw Joists and Decking

STEP #6 Use the Check tool to be sure that beams, decking, etc, are

centered on walls below.

Upper Roof Plan is now complete.

STEP #7 Move on to the Lower Roof Plan.

Set Current Layer to Lower Roof, set other layer to visible.

Structural Layout - Step-by-StepSTEP #8 Extend columns from upper level to lower level.

STEP #9 Add columns supporting lower roof areas.

STEP #10 Draw beams.

Structural Layout - Step-by-StepSTEP #11 Draw joists and decking.

STEP #12 Don’t forget the covered entry!

Lower Roof is now complete.

Structural Layout

Sample PASSING Solution

(Lower Roof)

Structural Layout

Sample PASSING Solution

(Upper Roof)

Structural Layout

Sample FAILING Solution

(Lower Roof)

Structural Layout

Sample FAILING Solution

(Upper Roof)

General Tips…

Clear your head.

Remember – it’s not AutoCAD…

… or design studio.

Practice makes perfect…

… but don’t over-practice!!

Take your time.

Follow all of the instructions!!

Don’t second-guess yourself.

MULTIPLE CHOICE

Common Materials

Structural Steel

AISC 360

IBC Chapter 22

Fy = 50,000 psi (W and HSS shapes); 36,000 psi (angles, channels)

E = 29,000,000 psi

Standard Shapes – W, C, HSS, L

Reinforced Concrete

AISC 318 and 301

IBC Chapter 19

f’c = 3,000 psi to 6,000 psi

Fy (steel) = 60,000 psi

Typically non-standard shapes

Flexural and Shear Reinforcement

Shrinkage and temperature Reinforcement

Cover

Common Materials

Reinforced Masonry

AISC 530

IBC Chapter 21

f’m = 1,500psi to 3,000 psi

Fy (steel) = 60,000 psi

Composite properties of cmu, grout, mortar and steel

Reinforcement can be at face or centered in wall

Bond beams

Wood

National Design Specification (NDS)

IBC Chapter 23

Unique design methods due to non-uniform properties

(Fb, Fv, Fcll, Fc, Fcbbbb, Emin)

Sectional Properties

Moment of Inertia (I) = bh3/12

Sectional Modulus (S) = I/c

c = h/2

Area (A) = bh

Radius of gyration (r) = [I/A]1/2

b

h

Foundations

Deep

Caissons (Drilled Pier) Auger-cast Piles

Load Transfer Types

Other Types: Micro-piles, driven piles

Foundations

Shallow

Wall Footing

Differential Settlement

Soil Stabilization – Aggregate Piers, CMCs, Soil Compaction, etc.

Gravity Forces/Systems

Live, Snow, Dead, Soil, and Hydrostatic

Live Load Reduction (LLR)

LLR = Lo[25 + 15/(KLLAT)]1/2

Lo = Unreduced Live Load

AT = Tributary Area

KLL = Live Load Element Factor

Flexure: Fb = M/S

Shear: Fv = V/A

Deflection: ∆∆∆∆

wL2/8

wL/2

5wL4(12)3/384EI

Uniform Load

Vleft = Pb/L

Vright = Pa/L

PL3(12)3/48EI(P at center of beam: a=b)

Pab/L

Point Load

P

ba

L

Beams

Trusses / Joists

King Post TrussPratt Truss

Howe Truss

Standard Steel Joist

Beams

Composite Beams

STEEL

SIPs Panels

Other Types Include:

Pre-stressed and Post-Tensioned Concrete

Standard Reinforced Concrete

Reinforced Masonry

Columns

fc = P/A

fc is dependent upon

Slenderness Ratio = KL/r

Smaller will increase the fc

K - Effective Length Factor

LRFD vs. ASD

Load Resistance Factor Design

Ultimate Strength Method

Factors placed on Loads and Stressed to Capacity

Live Load = 1.6 and Dead Load = 1.2

Allowable Stress Design

Member stressed to percentage of yield stress

Steel: Fb = 0.66Fy and Fy = 0.40 Fy

Wood: Duration Factors (Cd):

Live = 1.0, Dead = 0.9, Wind = 1.6, Snow = 1.2

Industry has moved to LRFD

Loads vs. Structural Systems

WOOD BEAMS/ JOISTS

STEEL AND CONCRETE JOISTS

ONE-WAY CONCRETE (SLABS AND BEAMS)

STEEL BEAM

COMPOSITE STEEL BEAMS

TWO-WAY CONCRETE SYSTEMS

LONG SPAN TRUSSES

LOAD INCREASE

Basement and Retaining Walls

Basement Wall Retaining Wall

Simple span cantilever

Wind

Main Wind Force Resisting Systems vs. Components and

Cladding

Loads are based upon historical analysis and probability

90 percent of U.S. designed for 90 mph

Factors which affect pressure:

Special considerations:

Pressures increase with building height

Non-enclosed structures, escarpments, parapets,

overhangs, etc.

Importance factor

Building height

Wall/roof zones (comp./cladding)

Exposure Category

Wind

Wind base shear (V) = wind area x wind pressure

Windward and leeward pressures are included

Collected at the floor diaphragms

� https://courses.cit.cornell.edu/arch264/calculators/seismic-wind/index.html

Seismic

Need to understand:

Site Class A through F

Occupancy Category

Seismic Design Category

Importance Factor

Seismic Force-Resisting System

Response Modification Factor

Seismic base shear (V) = CsW (Equivalent Lateral Force Method)

Seismic response coefficient (Cs) = SDS/(R/I) but not < 0.01

SDS = Design Spectral Acceleration

R = Response Modification Factor

I = Seismic Occupancy Importance Factor

W = Effective Seismic Weight

(includes dead, % of LL, partition, heavy snow loads)

Lateral Forces/Systems

Braced Frames Eccentric Braced

Frame

Base Shear

P

P

P

P

4P 4/3P

P

P

P

P

2/3P 4/3P 2/3P

Portal Method

(Moment Frame)

P-Delta (P∆) Effect

P∆ about a structure

P-δ effect (P-"small-delta“) , is associated with local deformation

relative to the element chord between end nodes.

P-Δ effect (P-"big-delta“), is associated with displacements relative to

member ends.

Diaphragms

Center of Mass and Center of Rigidity

L/2 L/2

Sh

ea

r w

all

Sh

ea

r w

all

Center of Rigidity

L/2 L/2

Sh

ea

r w

all

Sh

ea

rw

all

Center of Mass

> L/2 < L/2

e

Design should minimize eccentricity (e) in order to reduce additional

shear stress as a result of torsion (“twisting”)

Drift

Inter-story and overall drift shall be limited for

serviceability requirements. Primary consideration will

be façade materials.

H/400 for masonry facades

H/200 for curtain wall, EIFS and

metal panel facades

Examples

Questions on the sample test?

Additional Examples…..

Example 1

12

12

A B

C

P = 75 kips

Example 2

12

12

A B

C

P = 75 kips

D

Example 2

12

12

A B

C

P = 75 kips

D

Example 3

6,000 pounds

20’

I = 2

50 in

4

I = 2

50 in

4

I = 250 in4

20

’

Example 4

9,000 pounds

I = 4

00

in4

I = 4

00

in4

I = 400 in4

20’

Example 5

PP P

A B C

Example 6

A

2L

B

1 1/2L

Example 7

A

B

C

Example 8

A B

Example 915 kips

5’5’

E = 1,500,000 psi

I = 2,000 in4

750 pounds per foot

20’

E = 29,000,000 psi

I = 750 in4

Example 10Y

X

Y

X

10’

15’

P

General Tips…Study comprehensively…

Review study materials from other related divisions

Don’t get stuck…

Skip or mark items and come back to them

Don’t get stressed if you mark a lot of questions.

Once you review them they seem easier the second time around.

Or another question you answered triggers a question you skipped

Answer every question!

Even a guess is a chance at a correct answer…

Make the most of your break.Clear your head, relax, and get focused on the next section.

Take a quick walk, eat a snack, splash water on your face… whatever works for you.

Don’t stress on what you think you missed.

Take your time… you paid for the full appointment!

Follow all of the instructions!!

Don’t second-guess yourself.

Suggested Resources� “References Available During the Test”

� The Architect’s Studio Companion

� Simplified Engineering for Architects and Builders

� AISC Steel Manual

� Notes from college classes

� FEMA, Chapter 4 and 5 (lateral forces)

� YouTube’s “WikiEngineering” channelhttp://www.youtube.com/user/wikiengineering

� Step-by-step vignettehttp://www.dustingoffron.com/ARE/HowtoApproachtheStructuralSystemsVignette.pdf

QUESTIONS…?

THANKS!