Luis garcia - wall-design-2009

Wall design Luis E. Garcia

Outline DESIGN OF REINFORCED CONCRETE STRUCTURAL WALLS
by: Luis Enrique García
President American Concrete Institute – ACI – 2008-2009 Partner Proyectos y Diseños Ltda., Consulting Engineers Professor of Civil Engineering, Universidad de los Andes, Bogotá, Colombia

Generalities Structural wall systems Behavior of wall systems ACI 318-08 Requirements Earthquakeresistant design Boundary elements

Structural wall systems in Latin America
Before 1910 almost everything was masonry walls The arrival of reinforced concrete brought the use of moment resisting frames In the 1960s walls reappear with tunnel formwork systems such as the French Outinord In the 1970s Structural Masonry (USA inspired vertical perforation block) make an appearance. In the 1980sBox-Type formwork types appear (Contech y Western) Story drift restrictions in the seismic codes makes its use more widespread

Wall vs. Column
Some Codes differentiate them based on geometry. For example, based on section side dimensions, slenderness ratio, etc. In some instances by the presence on an inflection point in the moment diagram within the story floor height. Then it classifies ascolumn when present and wall when not. In ACI 318 it is done using the vertical reinforcement steel ratio. If it is greater than 1% transverse ties are required as in columns.

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Wall design Luis E. Garcia

Wall Terminology (very confusing)
In English:
Shear walls Structural walls Curtain walls (a glass facade in many instances) Core walls

Wall based structural systems
Bearing wallsIn Spanish:
Muros Muros de cortante Muros cortina Pantallas Paredes estructurales Tabiques estructurales

Wall based structural systems
Box system

Wall based structural systems
Dual system

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Wall design Luis E. Garcia

Wall based structural systems
Core systems

Wall based structural systems
Some core types

(a)

(b)

(c)

Wall based structural systems
Tubesystems
Actual stresses

Shear-lag transfer
Stresses without shear-lag Actual stresses Lateral load direction

Only lateral load Stresses shown

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Use of structural systems for wind as the dominant lateral load
No. stories
75 65 55 50 35 20

Coupled walls

FRAME

SHEAR WALLS

DUAL

EXTERNAL TUBE

TUBE IN TUBE

MODULAR TUBE

Behavior ofcoupled walls

Tunnel forms system

(a)

(b)

(c)

There is ample experimental evidence that the slab-walls joint reinforced with welded wire reinforcement fails when subjected to cyclic moment Demands In the nonlinear range. This means that this system requires Walls in both direction in plan.

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Wall design Luis E. Garcia

General behavior of wall systems
hf

Effectiveflange
b
⎧ 4 ⎪ b ≤ min.of ⎨16 ⋅ h f + b w ⎪s + b w ⎩

Building configuration in plan Building configuration in height Type of foundation Amount of wall with respect to floor area Wall section shape

bw
hf b

s
⎧ 12 + b w ⎪ b ≤ min.of ⎨6 ⋅ h f + b w ⎪ ⎩s 2 + b w

s
bf b
hf ≥ bw 2

bw
⎧4 ⋅ b w b ≤ min.of ⎨ ⎩b f

hf

bw

Moment frame vs. wall system

Fixed base vs. flexiblefoundation
2m 3m 3m Wall 3m 3m 3m 3m Rocking Stiffness 10 m 9m 9m

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Wall design Luis E. Garcia

Definition of stiffness
1m P1 1m P2

WALL BASE SHEAR
1.0 0.9 09

/ Vtotal V
wall

0.8 0.7 0.6 06 0.5

Infinitelly rigid wall

Flexible fixed-base wall Wall Stiffness

0

Rocking Stiffness

1 10 100 1 000 10 000 100 000 ROCKING STIFFNESS / WALL STIFFNESS

LATERALDEFLECTION - TOP OF BUILDING
1.2% Top Deflection / Total Heigh D ht 1.0% 1 0% 0.8% 0.6% 0.4% 0.2% 0.0% 0 1 10 100 1 000 10 000 ROCKING STIFFNESS / WALL STIFFNESS 100 000

LATERAL DEFLECTION
6
FIXED

5 4 STORY 3 2 1 0
0.00 0.05
FREE

WALL ROCKING STIFFNESS RATIO
FREE 1 10 100 1000 2000 5000 10000 50000 100000 1000000 FIXED

Lateral Deflection (m)

0.10

0.15

0.20

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