1. Structural Bracings Presentation by V. G. Abhyankar
For Knowledge sharing sessions

2. Objectives
To understand various types of structures and bracing systems and their behavior
To explain the advantages of braced systems
To discuss the limitations of Braced frames
To study the method of Detailing bracing systems
To highlight advanced theories – in – bracing design

3. Types of Structural Framing systems
Bare Frame (Moment Resistant / Rigid jointed frame)
In-Filled frame
Equivalent bracing system
Braced frame (Pin Jointed / Truss)

4. Types of Loads Vertical / Gravity Loads Lateral Loads Special Loads
Self-weight
Imposed Load
Live loads
Snow load
Lateral Loads
Wind
Earthquake
Wave / Current forces
Friction
Special Loads
Lack of fit
Sinking supports
Tsunami
Blast Load / Vibrations / Dynamic Loads
Fatigue
Shrinkage / Creep

5. Behavior of Structural Framing Systems under various types of loads
COLUMN
BEAM
DEFLECTED SHAPE
LATERAL LOAD
SWAY
BARE FRAME UNDER LATERAL LOAD
BRACED FRAME UNDER LATERAL LOAD
VERTICALLOAD
BARE FRAME UNDER GRAVITY LOAD
BRACED FRAME UNDER GRAVITY LOAD
PIN JOINT
RIGID JOINT

6. Comparison of Rigid Jointed / Pin Jointed Framing System
RIGID JOINTED FRAME
BRACED FRAME
Advantages
More free space (allows openings)
Less numbers of Members
More sway as compared to braced frame
Full cross sectional area is utilized as members are mainly axially loaded
Simple connections, simple behaviors (direct load transfer)
Lesser sway
Easy to analyze
Capable of resisting accidental loads, twisting etc.
Easy to modify
Aesthetically appealing
Economical
Disadvantages
The flanges only resist the moment. Stress diagram is triangular (less utilization of area)
Connections are difficult to fabricate
Bulky sections are required
More number of members
Difficult to provided openings
Heavy bracings are required for long spans
Loads need to act essentially on joints
Design load for the Bracing design is always debatable

7. Types of Braced Frames
Single Diagonal Brace (Tension / Compression Both)
X – Cross Brace (Tension / compression only)
Chevron Brace (K-brace)
A – Chevron brace
Inverted chevron
Braced Chevron Brace
Braced Single Brace
Knee brace

8. A few facts regarding Bracings
1) Force in Bracings
Compression only Bracings – Concrete
Tension only Bracings – Steel
Pre-stressed bracings are also used for industrial structures (wire-ropes)
Vertical Load carrying braces
Horizontal Load carrying braces
Seismic bracing
Wind bracing
2) Slenderness of bracing
Effective length for In-Plane action
Effective length for out-of Plane action
Wind load for out-of-plane bending need not be checked (but the wind acting on braces is transferred to the connected joints)
Stiff-bracings
Flexible bracings

9. Cont /- . . . 3) Torsion Control with bracings is effective
4) 2D-Plane - Portal frames when connected with braces demand wind braces
5) Design loads on braces are usually 2.5% to 3% Lateral loads of the respective vertical loads
6) Bracings are effective in resisting Seismic forces than bare frame. Plays major role in seismic retrofitting
7) It is difficult to provide opening at the location of bracing
8) In case of In-filled frame, the stiffness of Infill walls can be simulated in the structural model by means of equivalent brace. This philosophy was proposed by Mr. V. V. Bertero

10. Slotted connection
Slotted connections are provided if the bracing is expected to resist the load in a particular direction only.
RCC BEAM WP
GUSSET PLATE
SLOTTED CONNECTION
STEEL BRACING

11. BRACING SYSTEMS
ELEVATIONAL BRACING
SECTIONAL BRACING
PLAN BRACINGS

12. Technical Reference “Structures” – by Daniel Schodeck
AISC Presentations
Tall steel Buildings –
Steel Designers Manual
Steel Detailers Manual
SP-40
V. V. Bertor’s articles
Standard detail drawings - Toyo Engineering

13. Structural Bracings Presentation by V. G. Abhyankar
For Knowledge sharing sessions