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RD, Max CD

The document discusses the strut-tie model (STM) used to analyze concrete structures where plane sections assumption does not hold. STM models the concrete as a truss with compression struts and tension ties. It describes different types of nodes in the STM based on whether they contain compressive struts or tension ties. It provides equations from Eurocode and AASHTO specifications for calculating the maximum stress allowed at different node types.

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BALRAJ
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45 views3 pages

RD, Max CD

The document discusses the strut-tie model (STM) used to analyze concrete structures where plane sections assumption does not hold. STM models the concrete as a truss with compression struts and tension ties. It describes different types of nodes in the STM based on whether they contain compressive struts or tension ties. It provides equations from Eurocode and AASHTO specifications for calculating the maximum stress allowed at different node types.

Uploaded by

BALRAJ
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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1.

Introduction
 Strut & Tie Model (STM)

 As per ACI SP 208 – “A hypothetical Truss consisting of concrete Struts stressed in


compression, steel Ties stressed in tension, joined together at joints referred to as
Nodes.”

 Used for – “D” regions.

 Plane section do not remains plane.

 Non-uniform shear stress distribution.

 Lower bound plastic theory

 Stresses are within yield limit

 Equilibrium is maintained

2. STM –

i. Node

Classification of Nodes:

 CCC – All Compressive Struts

 CCT – Two Compressive Struts and One Tie

 CTT – One Compressive Strut and Two Ties

 TTT – All Tension Ties

Node – Euro code Provisions

The maximum stress at the edge of the Node:

 Rd, max = k ’f c d

Where:
’ = 1-f c k /250

f c d = 0.85 x f c k /1.5

f c k – Concrete Cylinder strength

CCC CCT CTT


k 1.00 0.85 0.75
 Rd, max 0.57 ’fck 0.48 ’fck 0.43 ’fck

Node – AASHTO LRFD Provisions

fcu = m  f ’c

f ’c = Compressive strength of concrete

m = confinement modification factor 2/ 1 but not more than 2.

 = Concrete Efficiency Factor (0.45  0.65)

Node – Dimensioning as per AASHTO


ii. Strut

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