pdf.io >> Free >> ELEMENTS OF ARCHITECTURAL STRUCTURES:.pdf

ELEMENTS OF ARCHITECTURAL STRUCTURES:

 FileName: lect26.pdf
[previewonline]


 FileSize: 1913 KB download
 Shared by: faculty_arch_tamu_edu 40 month ago
 Category: Free
 Tag: ELEMENTS OF ARCHITECTURAL STRUCTURES
 Report us: delete it


Abstract: ELEMENTS OF ARCHITECTURAL STRUCTURES:FORM, BEHAVIOR, AND DESIGNARCH 614DR. ANNE NICHOLSSPRING 2012lecturetwenty sixconcrete construction: www.tamu.edufoundation design

ELEMENTS OF ARCHITECTURAL STRUCTURES:
FORM, BEHAVIOR, AND DESIGN
ARCH 614
DR. ANNE NICHOLS
SPRING 2012
lecture
twenty six
concrete construction: www.tamu.edu
foundation design
Foundations 1 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Foundation
• the engineered interface between the
earth and the structure it supports that
transmits the loads to the soil or rock
Foundations 2 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Structural vs. Foundation Design
• structural design
– choice of materials
– choice of framing system
– uniform materials and quality assurance
– design largely
independent of
geology, climate, etc.
Foundations 3 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Structural vs. Foundation Design
• foundation design
– cannot specify site materials
– site is usually predetermined
– framing/structure predetermined
– site geology influences foundation choice
– no site the same
– no design
the same
Foundations 4 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Soil Properties & Mechanics
• unit weight of soil
• allowable soil pressure
• factored net soil pressure
• shear resistance
• backfill pressure
• cohesion & friction of soil
• effect of water
• settlement
• rock fracture behavior
Foundations 5 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Soil Properties & Mechanics
• compressibility
– settlements
• strength
– stability
• shallow foundations
• deep foundations
• slopes and walls
– ultimate bearing capacity, qu finehomebuilding.com
qu
– allowable bearing capacity, qa
S.F.
Foundations 6 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Soil Properties & Mechanics
• strength, qa
Foundations 7 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Bearing Failure
• shear
slip zone punched wedge
punched wedge
Foundations 8 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Lateral Earth Pressure
• passive vs. active
active
(trying to
move wall)
passive
(resists movement)
Foundations 9 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Foundation Materials
• concrete, plain or reinforced
– shear
– bearing capacity
– bending
– embedment length, development length
• other materials (piles)
– steel
– wood
– composite
Foundations 10 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Basic Foundation Requirements
• safe against instability or collapse
• no excessive/damaging settlements
• consider environment
– frost action
– shrinkage/swelling
– adjacent structure, property lines
– ground water
– underground defects
– earthquake
• economics
Foundations 11 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Generalized Design Steps
• calculate loads
• characterize soil
• determine footing location and depth
• evaluate soil bearing capacity
• determine footing size (unfactored loads)
• calculate contact pressure and check
stability
• estimate settlements
• design footing structure* (factored loads)
Foundations 12 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Types of Foundations
• spread footings
• wall footings
• eccentric footings
• combined footings
• unsymmetrical footings
• strap footings
Foundations 13 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Types of Foundations
• mat foundations
• retaining walls
• basement walls
• pile foundations
• drilled piers
Foundations 14 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Shallow Footings
• spread footing
– a square or rectangular footing supporting
a single column
– reduces stress from load to size the ground
can withstand
Foundations 15 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Actual vs. Design Soil Pressure
• stress distribution is a function of
– footing rigidity
– soil behavior
RIGID RIGID
sand clay
• linear stress distribution
assumed
Foundations 16 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Proportioning Footings
• net allowable soil pressure, qnet
– qnet qallowable h f ( c s )
– considers all extra weight (overburden)
from replacing soil with concrete
– can be more overburden
• design requirement
with total unfactored
load: P
qnet
A
Foundations 17 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Concrete Spread Footings
• plain or reinforced
• ACI specifications
• Pu = combination of factored D, L, W
• ultimate strength
– Vu Vc : 0.75 for shear
• plain concrete has shear strength
– Mu Mn : 0.9 for flexure
Foundations 18 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Concrete Spread Footings
• failure modes
shear
bending
Foundations 19 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Concrete Spread Footings
• shear failure
one way shear two way shear
Foundations 20 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Over and Underreinforcement
• reinforcement ratio for bending
As
–
bd
– use as a design estimate to find As,b,d
– max from steel 0.004
– minimum for slabs & footings of uniform
thickness As 0.002 grade 40 / 50 bars
bh
0.0018 grade 60 bars
Foundations 21 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Reinforcement Length
• need length, ld
– bond
– development of yield strength
Foundations 22 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Column Connection
• bearing of column on footing
– Pu Pn 0.85 f cA1
0.65 for bearing A1
A2 1
– confined: increase x A2 2 2
A1
• dowel reinforcement
– if Pu > Pb, need
compression
reinforcement
– min of 4  #5 bars
(or 15 metric)
Foundations 23 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Wall Footings
– continuous strip for load bearing walls
– plain or reinforced
– behavior
• wide beam shear
• bending of projection
– dimensions usually dictated
by codes for residential walls
– light loads
Foundations 24 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Eccentrically Loaded Footings
• footings subject to moments
P P
e
M=Pe
by statics:
– soil pressure resultant force may not
coincide with the centroid of the footing
Foundations 25 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Differential Soil Pressure
– to avoid large rotations,
limit the differential soil P
pressure across footing M
– for rigid footing,
simplification of soil
pressure is a linear
distribution based on
constant ratio of pressure to settlement
Foundations 26 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Kern Limit
• boundary of e for
no tensile stress
• triangular stress
block with pmax
wpx
volume N
2
2N
pmax
wx
Foundations 27 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Guidelines
– want resultant of load from pressure inside
the middle third of base (kern)
• ensures stability with respect to overturning
P
M resist R x M
SF 1.5
M overturning M
x R
– pressure under toe (maximum) qa
– shortcut using uniform soil pressure for
design moments gives similar steel areas
Foundations 28 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Combined Footings
– supports two columns
– used when space is tight and spread footings
would overlap or when at property line
– soil pressure might not be uniform
– proportion so pressure will uniform for
sustained loads
– behaves like beam lengthwise
Foundations 29 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Combined Footing Types
– rectangular
– trapezoid
– strap or cantilever
• prevents overturning of exterior column
– raft/mat
• more than two columns
over an extended area
Foundations 30 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Proportioning
– uniform settling is desired
– area is proportioned with sustained column
loads
– want the resultant to coincide with centroid
of footing area for uniformly distributed
pressure
P1 P2
assuming a
rigid footing
qmax qa y
R = P1+P2
Foundations 31 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Walls
• purpose
– retain soil or other material
• basic parts
– wall & base
– additional parts
• counterfort
• buttress
• key
Foundations 32 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Walls
• considerations
– overturning
– settlement
– allowable bearing pressure
– sliding
– (adequate drainage)
Foundations 33 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Walls
• procedure
– proportion and check stability with working
loads for bearing, overturning and sliding
– design structure with factored loads
M resist
SF 1.5 2
W M overturning
Fx
Fhorizontalresist
o
Fresist
SF 1.25 2
R F sliding
Foundations 34 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Wall Proportioning
• estimate size
– footing size, B 2/5  2/3 wall height (H)
– footing thickness 1/12  1/8 footing size (B)
– base of stem 1/10  1/12 wall height (H+hf)
– top of stem 12” t
H
b
hf
B
Foundations 35 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Walls Forces
• design like cantilever beam
– Vu & Mu for reinforced concrete
– Vu Vc : 0.75 for shear
– Mu Mn : 0.9 for flexure
Foundations 36 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Wall Types
• “gravity” wall
– usually unreinforced
– economical & simple
• cantilever retaining wall
– common
Foundations 37 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Retaining Wall Types
• counterfort wall
very tall walls (> 20  25 ft)
• buttress wall
• bridge abutment
• basement frame wall (large basement areas)
Foundations 38 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Deep Foundations
• usage
– when spread footings, mats won’t work
– when they are required to transfer the
structural loads to good bearing material
– to resist uplift or overturning
– to compact soil
– to control settlements of spread or mat
foundations
Foundations 39 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Deep Foundation Types
– piles  usually driven, 6”8” , 5’ +
– piers
drilled, excavated,
– caissons concreted (with or
– drilled shafts without steel)
– bored piles 2.5’  10’/12’
.
– pressure injected piles
Foundations 40 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Deep Foundation Types
Foundations 41 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Deep Foundations
• classification
– by material
– by shape
– by function (structural, compaction...)
• pile placement methods
– driving with pile hammer (noise & vibration)
– driving with vibration (quieter)
– jacking
– drilling hole & filling with pile or concrete
Foundations 42 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Piles Classified By Material
• timber
– use for temporary construction
– to densify loose sands
– embankments
– fenders, dolphins (marine)
• concrete lift hooks
– precast: ordinary
reinforcement or prestressed
– designed for axial capacity
and bending with handling
Foundations 43 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Piles Classified By Material
• steel
– rolled HP shapes or pipes
– pipes may be filled with concrete
– HP displaces little soil and may either
break small boulders or displace them to
the side
Foundations 44 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Piles Classified By Function
– end bearing pile (point bearing)
Pa A p fa
for use in soft or
soft or loose loose
layer
materials over a
dense base
“socketed”
Rp
– friction piles (floating)
P common in both P tapered:
clay & sand sand & silt
Rs =ƒ(adhesion) T
N
RP 0
Foundations 45 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Piles Classified By Function
– combination friction and end bearing
P
– uplift/tension piles
structures that float, Rs
towers
Rp
– batter piles
angled, 1:12 to P
cost more, 1:3 or 1:4
resist large
horizontal loads
Foundations 46 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Piles Classified By Function
– fender piles, dolphins, pile clusters
large # of piles
in a small area
– compaction piles
• used to densify loose sands
– drilled piers
• eliminate need for pile caps
• designed for bearing capacity (not slender)
Foundations 47 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
Pile Caps and Grade Beams
– like multiple column footing
– more shear areas to consider
Foundations 48 Elements of Architectural Structures S2012abn
Lecture 26 ARCH 614
 Related pdf books
 Mechanics of Materials
 10 L = ? 10
 ARCH 331 Note Set 27.2 F2010abn
 Method of Sections for Truss Analysis
 ARCH 614. Study Guide for Quiz 3  Texas A&M University
 ARCH 631. Topic 1 Reading Notes
 MECHANICS OF MATERIALS AND DESIGN APPLICATIONS ARCH 252 ANNE ABELL
 ARCH 631. Topic 5 Reading Notes
 Technical Notes on Brick Construction
 NEW TERMINAL AREA MADRIDBARAJAS  Texas A&M University
 Loading Stages
 ELEMENTS OF ARCHITECTURAL STRUCTURES:
 ARCH 631 Note Set 21.1 F2011abn
 Structural Glossary
 ARCHITECTURAL STRUCTURES I: S M Beams TATICS AND TRENGTH OF ...
 APPLIED ARCHITECTURAL STRUCTURES  Texas A&M University
 Kansai International Airport Terminal
 Popular epubs
 ELEMENTS OF ARCHITECTURAL STRUCTURES:
 ELEMENTS OF ARCHITECTURAL STRUCTURES  Texas A&M University
 ELEMENTS OF ARCHITECTURAL STRUCTURES
 SHELL ELEMENTS OF ARCHITECTURAL CONCRETE USING FABRIC FORMWORK
 CHAPTER 5 ILLUSTRATED GLOSSARY OF ARCHITECTURAL ELEMENTS OF STYLE
 Architectural Elements of Integrated MicroSensors for ...
 Title: Basic Elements Of Landscape Architectural Design
 Sequence stratigraphy and architectural elements of the Giant ...
 Chapter 23 Architectural Elements of Resource Sharing Networks
 6.1 ARCHITECTURAL RELATIONSHIPS AND ELEMENTS THE DESIGN OF ...
 10/03/2011
 ARCHITECTURAL STRUCTURES III:
Download the ebook