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twelve design methods, structural codes Methods & Codes 1 - - PowerPoint PPT Presentation

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E LEMENTS OF A RCHITECTURAL S TRUCTURES : F ORM, B EHAVIOR, AND D ESIGN ARCH 614 D R. A NNE N ICHOLS S PRING 2019 lecture twelve design methods, structural codes Methods & Codes 1 Elements of Architectural Structures S2019abn Lecture 12

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SLIDE 1

S2019abn Methods & Codes 1 Lecture 12 Elements of Architectural Structures ARCH 614

twelve

design methods, structural codes

lecture ELEMENTS OF ARCHITECTURAL STRUCTURES: FORM, BEHAVIOR, AND DESIGN

ARCH 614

  • DR. ANNE NICHOLS

SPRING 2019

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SLIDE 2

S2019abn Methods & Codes 2 Lecture 12 Elements of Architectural Structures ARCH 614

Design

  • factors out of the designer’s control

– loads – occurrence

  • factors within the designer’s control

– choice of material – “cost” of failure (F.S., probability, location) – economic design method – analysis method

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SLIDE 3

S2019abn Methods & Codes 3 Lecture 12 Elements of Architectural Structures ARCH 614

Design Methods

  • different approaches to meeting

strength/safety requirements

– allowable stress design (elastic) – ultimate strength design – limit state design – plastic design – load and resistance factor design

  • assume a behavior at failure or other

threshold and include a margin of safety

http://mceer.buffalo.edu

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SLIDE 4

S2019abn Methods & Codes 4 Lecture 12 Elements of Architectural Structures ARCH 614

Load Types

  • D = dead load
  • L = live load
  • Lr = live roof load
  • W = wind load
  • S = snow load
  • E = earthquake load
  • R = rainwater load or ice water load
  • T = effect of material & temperature
  • H = hydraulic loads from soil (F from fluids)
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SLIDE 5

S2019abn Methods & Codes 5 Lecture 12 Elements of Architectural Structures ARCH 614

Weight of Materials

  • for a volume

– where is weight/volume – for an extruded area with height of t

V W  

tA W  

t A

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SLIDE 6

S2019abn Methods & Codes 6 Lecture 12 Elements of Architectural Structures ARCH 614

Building Codes

  • documentation

– laws that deal with planning, design, construction, and use of buildings – regulate building construction for

  • fire, structural and health safety

– cover all aspect of building design – references standards

  • acceptable minimum criteria
  • material & structural codes
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SLIDE 7

S2019abn Methods & Codes 7 Lecture 12 Elements of Architectural Structures ARCH 614

Building Codes

  • occupancy
  • construction types
  • structural chapters

– loads, tests, foundations

  • structural materials, assemblies

– roofs – concrete – masonry – steel

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SLIDE 8

S2019abn Methods & Codes 8 Lecture 12 Elements of Architectural Structures ARCH 614

Prescribed Loads

  • ASCE-7

– live load (not roof) reductions allowed

  • International Building Code

– occupancy – wind: pressure to static load – seismic: shear load function of mass and response to acceleration – fire resistance

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SLIDE 9

S2019abn

Code Reduction of Live Loads

  • for (ordinary) live loads

– factored area supported  400 ft2 – reduction can’t exceed

  • 0.5Lo (one floor) or 0.4Lo (more)
  • for live loads > 100 lb/ft2

– live load reduction of 20% on columns

  • for (ordinary) roofs:

– 12 lb/ft2  Lr  20 lb/ft2

         

T LL

  • A

K . L L 15 25

2 1R

R L L

  • r 

Methods & Codes 9 Lecture 12 Elements of Architectural Structures ARCH 614

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SLIDE 10

S2019abn Methods & Codes 10 Lecture 12 Elements of Architectural Structures ARCH 614

Structural Codes

  • prescribe loads and combinations
  • prescribe design method
  • prescribe stress and deflection limits
  • backed by the profession
  • may require design to meet

performance standards

  • related to material or function
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SLIDE 11

S2019abn Methods & Codes 11 Lecture 12 Elements of Architectural Structures ARCH 614

Structural Codes

  • Design Codes

– Wood

  • NDS

– Steel

  • AISC

– Concrete

  • ACI
  • AASHTO

– Masonry

  • MSJC
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SLIDE 12

S2019abn Methods & Codes 12 Lecture 12 Elements of Architectural Structures ARCH 614

Design Methods

  • probability of loads and resistance
  • material variability
  • overload, fracture, fatigue, failure
  • allowable stress design
  • limit state design

– design loads & capacities

. S . F f f A P f

capacity allowed actual

  

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SLIDE 13

S2019abn Methods & Codes 13 Lecture 12 Elements of Architectural Structures ARCH 614

Allowable Stress Design

  • historical method
  • a.k.a.

working stress, strength design

  • stresses stay in

ELASTIC range

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SLIDE 14

S2019abn Methods & Codes 14 Lecture 12 Elements of Architectural Structures ARCH 614

ASD Load Combinations

  • D
  • D + L
  • D + (Lr or S or R)
  • D + 0.75L + 0.75(Lr or S or R)
  • D + (0.6W or 0.7E)
  • D + 0.75L + 0.75(0.6W or 0.7E) +

(0.75Lr or S or R)

  • 0.6D + (0.6W or 0.7E)

ASCE-7 (2010)

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SLIDE 15

S2019abn Methods & Codes 15 Lecture 12 Elements of Architectural Structures ARCH 614

Limit State Design

  • a.k.a. strength design
  • stresses go to limit (strain outside

elastic range)

  • loads may be factored
  • resistance or capacity

reduced by a factor

  • based on material behavior
  • “state of the art”
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SLIDE 16

S2019abn Methods & Codes 16 Lecture 12 Elements of Architectural Structures ARCH 614

Limit State Design

  • load and resistance factor design (LRFD)

– loads:

  • not constant,
  • possibly more influential on failure
  • happen more or less often

– UNCERTAINTY  - Resistance factor  - Load factor for (D)ead & (L)ive load

n L L D D

R R R     

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SLIDE 17

S2019abn Methods & Codes 17 Lecture 12 Elements of Architectural Structures ARCH 614

LRFD Load Combinations

  • 1.4D
  • 1.2D + 1.6L + 0.5(Lr or S or R)
  • 1.2D + 1.6(Lr or S or R) + (L or 0.5W)
  • 1.2D + 1.0W + L + 0.5(Lr or S or R)
  • 1.2D + 1.0E + L + 0.2S
  • 0.9D + 1.0W
  • 0.9D + 1.0E
  • F has same factor as D in 1-5 and 7
  • H adds with 1.6 and resists with 0.9 (permanent)

ASCE-7 (2010)

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SLIDE 18

S2019abn Methods & Codes 18 Lecture 12 Elements of Architectural Structures ARCH 614

Load Tracing

  • how loads are

transferred

– usually starts at top – distributed by supports as actions – distributed by tributary areas

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SLIDE 19

S2019abn Methods & Codes 19 Lecture 12 Elements of Architectural Structures ARCH 614

Load Tracing

tributary area

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SLIDE 20

S2019abn

 

width tributary area load w        

Methods & Codes 20 Lecture 12 Elements of Architectural Structures ARCH 614

Load Tracing

  • tributary load

– think of water flow – “concentrates” load of area into center

width

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SLIDE 21

S2019abn Methods & Codes 21 Lecture 12 Elements of Architectural Structures ARCH 614

Load Paths

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SLIDE 22

S2019abn Methods & Codes 22 Lecture 12 Elements of Architectural Structures ARCH 614

Load Paths

  • wall systems
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SLIDE 23

S2019abn Methods & Codes 23 Lecture 12 Elements of Architectural Structures ARCH 614

Load Paths

  • openings & pilasters
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SLIDE 24

S2019abn Methods & Codes 24 Lecture 12 Elements of Architectural Structures ARCH 614

Load Paths

  • foundations
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SLIDE 25

S2019abn Methods & Codes 25 Lecture 12 Elements of Architectural Structures ARCH 614

Load Paths

  • deep foundations