This document discusses long span structures, which are buildings with unobstructed column-free spaces greater than 15-20 meters used for stadiums, arenas, and pools. Steel is commonly used due to its ability to span large distances. Prestressed concrete is also used, which involves pre-tensioning or post-tensioning tendons to put concrete into compression and improve its strength. Pre-tensioning tensions tendons before pouring concrete, while post-tensioning does so afterwards. Segmental and composite construction are also discussed as methods to achieve long spans.

1. ADVANCED BUILDING CONSTRUCTION-IX
LONG SPAN STRUCTURES
RISHABH JAIN
B.ARCH(9THSEM)
1/16/FPA/B.ARCH/005

2. CONTENTS
1. INTRODUCTION TO LONG SPAN STRUCTURES
2. STRUCTURAL SYSTEM TO LONG SPAN : APPLICATION IN BUILDING AND
ASSOCIATED ISSUES
3. PRE AND POST TENSIONING
4. SEGMENTAL CONSTRUCTION
5. COMPOSITE CONSTRUCTION

3. WHAT ARE LONG SPAN STRUCTURES ?
Long span structures create
• unobstructed,
•column-free spaces greater than 15-20 metres for a
variety of functions
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4. Long span structures are buildings are
 stadium
 sport hall
 swimming pool
 ice tracks
 indoor athletics , etc.
Steel is the most common structural material used in such construction.
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5. Pre-Tensioning
and
Post-Tensioning

6. FORMS OF THE PRESTRESSED STEEL:
1: Wires:
It is a single unit made of steel.
2: Tendons:
Tendons are wires and a group of strands is wound to form a prestressing strand.
3: Strands:
Strands are two, three or seven wires that are wound to form a prestressing strand.
4: Cable:
Cables are the series or group of tendons.
5: Bars:
The tendons are simply made up of a single steel bar and the diameter of this steel bar us
larger than that of wire.

7. Pre-Tensioning :
 In Pre-tensioning,wires or strands, called tendons( cables inside plastic ducts or
sleeves), are tensioned before the concrete is cast.
 The tendons are temporarily anchored using hydraulic jacks against some
abutments and then cut or released after the concrete has been placed and
hardened.
 The prestressing force is transferred to this concrete by the bond along
the length of the tendon.

11. A method of prestessing concrete in which tendons
are tensioned before the concrete is placed.
SO WE CAN ALSO DEFINE PRE TENSIONING AS :

12. Post-Tensioning :
 After adequate curing of concrete, reinforcing tendons (placed in side the
voids of the structure) are tensioned/stretched by jacks on the sides
 These spaces are then pumped full of grout to bond steel tightly to the
concrete.
 tendons are coated with grease or a bituminous material to prevent them
from becoming bonded to concrete. Another method used in preventing
the tendons from bonding to the concrete during placing and curing of
concrete is to encase the tendon in a flexible metal hose before placing it
in the forms. The metal hose is referred to as sheath or duct and remains in
the structure.

14. A method of prestessing concrete in which tendons
are tensioned after the concrete is placed.
SO WE CAN ALSO DEFINE POST TENSIONING AS :

15. Application
 This concrete is used in large-span distance between
which is not possible through the normal RCC
construction because rcc will make slab thickness more.
 Prestressed concrete is used in bridges to increase the possible
span of the bridge and to make the structure more durable
under moving traffic conditions.
 Used for office buildings where larger span, column free
spaces are required.
 Used for the metro construction.

16. Difference Between Pre-Tensioning and Post-Tensioning
PRE-TENSIONING POST-TENSIONING
 Pre-tensioning is done in the factories
thus suitable for precast construction
works
 Post-tensioning can be done in
factories as well as on the site
 Small sections are to be constructed  Size of a member is not restricted,
long-span bridges are constructed
by post-tensioning
 It is cheaper because the cost of
sheathing is not involved
 It is costlier because of use of
sheathing
 It is more reliable and durable  The durability depends upon the
two anchorage mechanism

17. SEGMENTAL CONSTRUCTION

18. SEGMENTAL CONSTRUCTION
 A Segmental Construction is built in short sections (called
segments), that is one piece at a time. And then segments
are erected to make the component.
 This type of construction is either cast-in-place or precast.

21. COMPOSITE CONSTRUCTION

22. COMPOSITE CONSTRUCTION
 Composite construction refers to two or more load-carrying structural
members that are integrally connected and deflect as a single unit.Use for
longer span, thinner slab.
 concrete is good in compression and steel is good in tension. Combining
these two materials structurally enhances their strengths, which can be
exploited to create a highly efficient and lightweight design.
 Composite systems also offer benefits in terms of speed of construction.
The floor depth reductions that can be achieved using composite
construction can also provide significant benefits in terms of the costs of
services and the building envelope.

23. Types of composite elements :
Composite slabs
Composite columns

24. BIBLOGRAPHY
• civiljungle.com
• theconstructor.org
• GOOGLE IMAGES
• SLIDE SHARE
• wikipedia.org
• steelconstruction.info