02-construction stages and column shortening analysis in tall buildings
TRANSCRIPT
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis and Column Shortening in Tall Buildings
Midas IT Technical Seminar
17th February 2012
Ravi Kiran
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
• In general structures are analyzed assuming that the structure is built and loaded in a moment.
• Construction of structures is a time taking process and during this period Material Properties,
Loads and Boundaries conditions may change.
Construction Stage Analysis
Why Construction Stage (CS) Analysis
Construction Sequence
Self weight of slab
Other Dead Loads (Partions, Finishes)
Completed Structure
Dead Load + Live Load
Wind
Earthquake
LL,WL,EQ Acts
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Construction Stage Analysis
Conventional Analysis Vs. Construction Stage Analysis
Case 1 – Conventional Analysis Case 2 – CS Analysis
Stage 1 Stage 2
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Construction Stage Analysis
Conventional Analysis Vs. Construction Stage Analysis
Case 1 – Conventional Analysis Case 2 – CS Analysis
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Construction Stage Analysis
Where CS Analysis is Required
Long Span Trusses
Long Span Slabs, Beams constructed in multiple stages
Prestressed concrete Structures
CS analysis should be performed for all structures where there is a change in
Support Conditions, Loading and varying material properties (Concrete).
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
σ
When any member is loaded with Axial Load, it undergoes axial deformation
E = (σ / ε)
ΔL = (PL/A E)
Why is
this
Important
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
P1, ΔL1
P2, ΔL2
The differential shortening happening between the vertical members may cause
additional forces and stress in Beams and Slabs
Column Shortening and Related Issue
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Steel Structures
- Linear elastic Behavior
Stress ∞ Strain
Strain is constant for a given Stress
during loading & unloading
E = (σ / ε)
ΔL = (PL/A E)
σ
Column Shortening and Related Issue
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Concrete Structures - Nonlinear Inelastic Behavior
- But in general analysis and design behavior of concrete is treated as Linear Elastic Material
Neither Stress ∞ Strain
Nor Strain is constant for a given Stress
During loading & unloading
Elastic Strain + Inelastic Strain
Column Shortening and Related Issue
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Concrete Structures
Elastic Shortening
Modulus of Elasticity changes with time.
Ei = (σ / ε)
ΔL = (PL/A Ei)
Inelastic Shortening
σ
σ
Creep Shortening.
Shrinkage Shortening.
Column Shortening and Related Issues
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
With increased height of structures the effect of column shortening (Elastic & Inelastic)
take on added significance and need special consideration in design and construction.
Elastic Shortening of 80 Storey Steel Structure ~ 180 mm to 255 mm.
Elastic Shortening of 80 Storey Concrete Structure ~ 65 mm.
Total Shortening of 80 Storey Concrete Structure ~ 180 to 230 mm.
Inelastic Shortening ~ 1 to 3 times Elastic shortening.
Column Shortening and Related Issue
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
Two basic prerequisites for accurately and efficiently predicting these effects
are
Reliable Data for the creep and shrinkage characteristics of the particular concrete mix
Analytical procedures for the inclusion of these time effects in the design of structure.
Some of the popular predictive methods for predicting creep and shrinkage
strains are
ACI 209 -92
Bazant – Bewaja B3
CEB – FIP (1978, 1990)
PCA Method (Mark Fintel, S.K.Ghosh & Hal Iyengar)
GL 2000 (Gardner and Lockman)
Eurocode
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
The total strain at any time t may be expressed as the sum of the
instantaneous, creep and shrinkage components:
Where,
εe (t) = Instantaneous strain at time t,
εc (t) = Creep strain at time t,
εsh (t) = Shrinkage strain at time t.
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
The instantaneous strain in concrete at any time t is expressed by
Where,
σ (t) = stress at time t,
Ec(t) = Elastic modulus of concrete at time t, given by
fct = Compressive strength at any time t, given by
α & β are constants depending on Type of Cement & Type of Curing
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
Inelastic Shortening = Creep + Shrinkage
Shrinkage Creep
Shrinkage is the time-dependant decrease in concrete
volume compared with the original placement volume
of concrete.
Drying Shrinkage is due to moisture loss in concrete.
Autogenous Shrinkage is caused by hydration of
cement.
Carbonation shrinkage results as the various cement
hydration products are carbonated in the presence of CO
Creep is time-dependent increment of strain under sustained
stress.
Basic creep occurs under the condition of no moisture
movement to and from the environment.
Drying creep is the additional creep caused by drying.
Drying creep has its effect only during the initial period of load.
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
Factors affecting the Creep & Shrinkage of Concrete
Concrete
(Creep & Shrinkage)
Concrete Composition
Cement Paste Content
Water – Cement ratio
Mixture Proportions
Aggregate Characteristics
Degrees of Compaction
Initial Curing
Length of Initial Curing
Curing Temperature
Curing Humidity
Member Geometry and Environment
(Creep & Shrinkage)
Environment Concrete Temperature
Concrete Water Content
Geometry Size and Shape
Loading
(Creep Only)
Loading History
Concrete age at load Application
During load Period
Duration of unloading Period
Number of load Cycles
Stress Conditions
Type of Stress and distribution across
the Section
Stress/Strength Ratio
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Column Shortening and Related Issue
Inelastic Shortening = Creep + Shrinkage
Shrinkage Creep
As per ACI 209R-92 the creep coefficients are predicted
as =
As per the ACI 209R-92, shrinkage can be predicted by
Where,
t = time in days after loading.
vu = Ultimate creep coefficient = 2.35 c
c = Product of applicable correction factors
After 7 days for moisture cured concrete
After 1-3 days for steam cured concrete
Where,
t = time in days after the end of Initial Curing
(sh)u = Ultimate Shrinkage Coefficient = 780 sh x 10-6 m/m
sh = Product of applicable correction factors
Column Shortening
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Effects of Column Shortening
Absolute shortening is rarely of practical interest.
Differential shortening between adjacent vertical elements is the most important factor for
engineer.
Axial Shortening of vertical elements
will not effect those elements very much,
horizontal elements like beams and slabs
and non structural elements are affected.
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Effects of Column Shortening
Cracks in Partition Walls.
Cracks in Staircases
Deformation of Cladding.
Mechanical Equipment.
Architectural Finishes.
Built in Furnishings.
These non structural elements are not
intended to carry vertical loads and are
therefore not subjected to shortening.
Slabs may not be truly horizontal after some time.
Beams could be subjected to higher bending moments.
Load transfer.
Structural Effects
Non Structural Effects
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Effects of Column Shortening
Deformation and breakage of Facades, windows &
Parapet walls…
Reverse Inclination of Drainage Piping System
Deformation of Vertical Piping System
Deformation and breakage of internal partitions
Column Shortening
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Movement Related to Construction Sequence
• Pre-slab installation shortenings
– Shortenings taking place up to the time of slab installation
• Post-slab installation shortenings
– Shortenings taking place after the time of slab installation
① :Compensation
② : Design Level
③: Pre-slab Installation shortening
④: Post-slab Installation shortening
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Procedure for Accounting Column Shortening
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Procedure for Accounting Column Shortening
?
Climatic Condition
Conditions
Loading Condition
Construction Progress
Other Conditions
Pre-Analytical
Prediction &
Continuous
Monitoring
Experimental
Measurements
&
Construction
Survey
Precise prediction of shortening
Correctio
n
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Procedure for Accounting Column Shortening
Analytical Measurement
Reflection of physical properties in calculation from material experiment: Young’s Modulus, Poisson’s Ratio, Mean Compressive strength, Volume to Surface ratio, Shapes, sizes etc. Reflection of effects of Climate on shortening: Average Temperature , RH etc. Construction Sequence: Stage duration, Additional Steps, Member Age, Load activation age, Boundary activation age etc. Reflection of the above effects on site master-schedule.
Installation of sensors or gages in members for
determining the actual shortening.
Understanding and noting the following:
Curing procedure / Temperature,
Actual Shortening,
Change in Ambient Temperature (Important),
Actual Humidity,
Deviation from Defined Construction Stages,
Manipulation of factors in analytical Calculation,
Re-Analysis…
Experimental Measurement
Using Software or Manually
(Manual calculation is almost impossible)
Field Measurements
Method has Limitation
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Procedure for Accounting Column Shortening
Determination of Installation location Installation of Gauge After Installation
After Installation of Gauge
After Casting of Concrete Field data collection
Field Measurements
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Procedure for Accounting Column Shortening
Manipulation of the construction stage as per site condition
Construction stage of each group
Activation of Construction stages
Perform 3D CS Analysis
Engineering Re-Analysis
Column Shortening
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Compensation at Site
Column Column
1st correction
2nd correction
1st correction
Column Shortening
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Column Shortening
Compensation at Site
SLAB THK.
B (= Height of correction
filler
Height of correction
Column Rebar
CON'C Casting face
The order of construction
installation of column forms
insertion of FILLER
insertion of correcting FILLER
Installation of SLAB forms
securing the thickness of slab.
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Construction Stage Wizard for Building Strcuture
The wizard readily allows us to define the timing of elements created and loadings applied in the construction
stages during the erection of a building.
You may find it more convenient to first click the [Automatic Generation] button to define the basic
construction stages and modify them as necessary.
Useful Features for CS Analysis
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Construction Stage Analysis for Composite Members
Define an analytical model for each construction stage by assigning activated or inactivated sections corresponding to
each construction stage of a composite section.
By using Composite Section for Construction Stage, we can consider the construction sequence with creep and
shrinkage effect.
Useful Features for CS Analysis
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Material Stiffness Changes for Cracked Sections
Specific stiffness of specific member types may be reduced such as the case where the flexural stiffness of lintel beams
and walls may require reduction to reflect cracked sections of concrete.
Section stiffness scale factors can be included in boundary groups for construction stage analysis. The scale factors are
also applied to composite sections for construction stages
Useful Features for CS Analysis
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Point Spring Support (Linear, Comp.-only, Tens.-only, and Multi-linear type)
Surface Spring Support (Nodal Spring, and Distributed Spring)
Springs can be activated / deactivated during construction stage analysis.
Spring Supports For Soil Interaction
[Nonlinear point spring support]
[Nodal Spring and Distributed Spring] [Surface Spring Support] [Pile Spring Support]
Useful Features for CS Analysis
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar
Pre-stress load can be considered in construction stage analysis.
Tendon primary / secondary forces are provided with pre-stress loss graph
Useful Features for CS Analysis
Tendon Loss
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Project Applications
Burj Khalifa (Dubai, UAE)
Height 705 m
No. of floors 160
Location Dubai, United Arab Emirates
Function / Usage Office Building & Residential Building
Designer Adrian D. Smith
Architect Skidmore, Owings & Merrill
General Contractor Samsung Development
ove
rvie
w
CS:1
CS:30
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Project Applications
SK S-Trenue (Seoul, Korea)
Area 39,600 m2
No. of floors 36
Location Seoul, Korea
Function / Usage Office Building
Structure Type Composite Structure
Foundation Type Mat Foundation
Lateral load resisting system RC Core + Steel + RC Composite Frame
ove
rvie
w
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Project Applications
Keangnam Hanoi Landmark Tower (Hanoi, Vietnam)
Height 345m
No. of floors 70 fl., 49 fl.
Location Hanoi, Vietnam
Function / Usage Hotel, Office, and Residential building
Structure Type Reinforced Concrete Structure
Architect Heerim, Samoo, Aum & Lee, Hellmuth Obata + Kassabaum
Contractor Keangnam
ove
rvie
w
Midas Gen – One Stop Solution for Building and General Structures
Construction Stage Analysis
Column Shortening & Related Issues
Effects of Column Shortening
Procedure for Accounting
Compensation at Site
Useful Features for Construction Stage Analysis
Project Applications
Live Demonstration
Contents
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Live Demonstration
Structural Plan
Typical Floor Plan
Storey's :- 40
Storey Height :- 3.15 m
Total Height :- 126.85 m
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Live Demonstration
Material and Sectional Properties
Level fck
Size Wall Thk. C1 C2
1st to 10th 50 1200 x 1200 900 x 900 500
11th to 20th 40 1000 x 1000 800 x 800 500
21st to 30th 35 800 x 800 700 x 700 500
31st to 40th 30 600 x 600 600 x 600 500
Girder 30 900 x 600 -
Link Beam 30 700 x 500 -
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Live Demonstration
Construction Schedule
Stage 1
Stage 4 Final Stage
Partition Load : 5 weeks after first slab casting. Finish Load : 5 Weeks after Partition Wall Construction.
One Stop Solution for Building and General Structures Midas Gen – Technical Seminar Live Demonstration
Procedure
Time Dependant Material Properties
•Define Creep and Shrinkage Properties .
•Define time Dependant Material Properties.
•Define Time Dependant Material Link.
•Change Element Dependant Material Property
Define Construction Stage
•Define Construction stages using Building Wizard for CS analysis
•Create LL group and add LL to LL group.
•Define CS for LL
Perform Analysis
Results
•BMD’s and SFD’s for different CS.
•Deformations for different CS.
•Column Shortening Graph.
Midas Gen – One Stop Solution for Building and General Structures
Q & A