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ARCHITECTURAL STRUCTURES:

FORM, BEHAVIOR, AND DESIGN

ARCH 331

DR. ANNE NICHOLS

FALL 2013

fourteen

system assemblies

& load tracingLoad Tracing 1

Lecture 14

Architectural Structures

ARCH 331

lecture

reed.tamu.edu

Load Tracing 2

Lecture 14

Foundations Structures

ARCH 331

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Structural Loads

• gravity acts on mass (F=m*g)

• force of mass

– acts at a point

• ie. joist on beam

– acts along a “line”

• ie. floor on a beam

– acts over an area

• ie. people, books,

snow on roof or floor

Load Tracing 3

Lecture 14

Foundations Structures

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Concentrated Loads

Load Tracing 4

Lecture 14

Foundations Structures

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Distributed Loads

2

Load Tracing 5

Lecture 14

Foundations Structures

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Equivalent Force Systems

• replace forces by resultant

• place resultant where M = 0

• using calculus and area centroids

dx

w(x)

x

L

loadingloading

L

0AdAwdxW

dx

y

x

elx

Load Tracing 6

Lecture 14

Foundations Structures

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Area Centroids

• Table 7.1 – pg. 242

b

h

3

b

right triangle only

Load Tracing 7

Lecture 14

Foundations Structures

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Equivalent Load Areas

• area is width x “height” of load

• w is load per unit length

• W is total load

x

x/2

W

x/2

x

2x/3

W/2

x/3

x

x/2

W

x/6 x/3

W/2

0

Wxw w w 22

Wxw

w

2w

Load Tracing 8

Lecture 14

Foundations Structures

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Distributed Area Loads

• w is also load per unit areaw

3

Load Tracing 9

Lecture 14

Foundations Structures

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Load Tracing

• how loads are

transferred

– usually starts at top

– distributed by

supports as actions

– distributed by

tributary areas

Load Tracing 10

Lecture 14

Foundations Structures

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Load Tracing

• areas see distributed

area load

• beams or trusses

see distributed line

loads

• “collectors” see

forces

– columns

– supports

Load Tracing 11

Lecture 14

Foundations Structures

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Load Tracing

tributary area

Load Tracing 12

Lecture 14

Foundations Structures

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Load Tracing

• tributary load

– think of water flow

– “concentrates” load of

area into center

widthtributaryarea

loadw

width

4

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Lecture 14

Foundations Structures

ARCH 331

Load Tracing

Patcenter

Rogers 1986

www.columbia.edu

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Lecture 14

Foundations Structures

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Load Tracing

Alamillo Bridge

Calatrava 1992

http://en.structurae.de

Load Tracing 15

Lecture 14

Foundations Structures

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Load Paths

• floors and framing

Load Tracing 16

Lecture 14

Foundations Structures

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Load Paths

• wall systems

5

Load Tracing 17

Lecture 14

Foundations Structures

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Load Paths

• openings & pilasters

Load Tracing 18

Lecture 14

Foundations Structures

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Load Paths

• foundations

Load Tracing 19

Lecture 14

Foundations Structures

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Load Paths

• deep foundations

Load Tracing 20

Lecture 14

Foundations Structures

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Spans

• direction

• depth

6

Load Tracing 21

Lecture 14

Foundations Structures

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Levels

• determine span at top level

• find half way to next element

• *include self weight

• look for “collectors”

• repeat

• one:

Load Tracing 22

Lecture 14

Foundations Structures

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Levels

• two:

• three:

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Irregular Configurations

• tracing still ½ each side

Load Tracing 23

Lecture 14

Architectural Structures

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Load Tracing 23

Lecture 14

Foundations Structures

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Slabs

• edge support

• linear and uniform distribution

7

Load Tracing 24

Lecture 14

Foundations Structures

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Girders and Transfer

• openings

– no load & no half way

• girder actions at beam supports

+

+ +

+

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Lecture 14

Foundations Structures

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Sloped Beams

• stairs & roofs

• projected live load

• dead load over length

• perpendicular load to beam:

• equivalent distributed load:

cosww

cos

w.adj

w

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Framing Diagrams

• beam lines and “dots”

• breaks & ends

Load Tracing 27

Lecture 14

Architectural Structures

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Spanning direction of decking or reinforcement

Load Tracing 25

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Foundations Structures

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• purpose

– retain soil or other material

• basic parts

– wall & base

– additional parts

• counterfort

• buttress

• key

Retaining Walls

8

Load Tracing 26

Lecture 14

Foundations Structures

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Retaining Wall Types

• “gravity” wall

– usually unreinforced

– economical & simple

• cantilever retaining wall

– common

Load Tracing 27

Lecture 14

Foundations Structures

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Retaining Wall Loads

• gravity

W = V

• fluid pressure

p = ’ h

P = ½ p h at h/3

• friction

F = N

• soil bearing pressure, q

Load Tracing 28

Lecture 14

Foundations Structures

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Retaining Wall Equilibrium

• sliding - overcome friction?

• overturning at toe (o) - overcome mass?

o

P

R

W251

goverturnin

.M

MSF resist

2251 .F

FSF

sliding

resisthorizontal

Fresist

Load Tracing 29

Lecture 14

Foundations Structures

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• want resultant of load from pressure inside

the middle third of base (kern)

• triangular stress block with pmax

• x = 1/3 x width of stress

• equivalent force location:

Pressure Distribution

32

3 xxpxW max

a

W

x

Wpmax

2

3

2

when a is

fully stressed

9

Load Tracing 30

Lecture 14

Foundations Structures

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Wind Pressure

• distributed load

• “collected” into V

• lateral loads

must be

resisted

V

Load Tracing 31

Lecture 14

Foundations Structures

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Bracing Configurations