ADVANTAGES OF CONTINOUS MEMBERS

TOPIC 1

EVEN DISTRIBUTION OF MOMENTS

• Between center of span and supports

• Lesser span moments

• Longer spans

REDUCTION OF SIZE

• Vertical load carrying capacity is more

• Lighter structures

• Economical

HIGHER LOAD CARRYING CAPACITY

• Redistribution of moments

• Reduced cross sectional dimensions

INCREASED STABILITY

• Redundancy in load path

• Formation of hinges in extreme events

PRECAST UNITS CONNECTED BY PRESTRESSED CABLES

• Segmental construction

• Precast units

• Connected by pre-stressed cable

SUITABLE POSITIONING OF CURVED CABLES

• In post tensioned girders

• Resist span and support moments

REDUCTION IN NO: OF ANCHORAGES

• One pair of post tensioned anchorages

• A single stressing operation

• Less maintenance

SMALLER DEFLECTIONS

• Higher load carrying capacity

• Even distribution of moments

• Safer

DISADVANTAGES

• Secondary stresses

• Losses

• Skill of workmanship

• Analysis and design

• Concordant cables

METHODS OF ACHIEVING CONTINUITY

TOPIC 2

USING STRAIGHT CABLES

• Wide web necessary

• Large anchorage blocks

• Form work

• Skilled workmen

• High strength threaded

rods

USING CURVED CABLES

• Higher resistance to

stress

• Longer spans

• Cracking over piers

eliminated in multistage

post-tensioning

USING CAP CABLESNegative moment taken care of

USING STRAIGHT TENDONSLimited length

COMPOSITE CONSTRUCTION

• Beam ends embedded in

cast-in-situ diaphragms

• Reinforcement for

negative moment within

deck thickness

• SS under major loads

COUPLING

• Pre-tensioned precast members

• Optimized strands• Top strands at adjacent

interior members coupled

• Performance of full length post tensioning

• Lesser cost

TWO TYPES

FULLY CONTINOUS

• Using straight cables

• Using curved cables

• Larger size tendons

• Secondary reinforcements

• Expensive

PARTIALLY CONTINOUS

• Using cap cables

• Using straight tendons

• Tendons not used to

achieve continuity

• Negative moment at

supports

• Cheaper

EFFECT OF PRESTRESSTOPIC 3