1. SELECTION CRITERIA FOR ELEVATED RC TANKS CONSTRUCTION
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SELECTION CRITERIA FOR ELEVATED RC TANKS CONSTRUCTION
Mohamed Darwish, PhD, PEng
Karim Kamel, BSc
Omar Balbaa, BSc
Ahmed El-feel, BSc
Jwanda Elsarag, BSc
Mohamed Tawfeek, BSc
Ahmed El-Embaby, BSc
Ghadir El-Shaer, BSc
Omar Montasser, BSc
Reem Aboali, BSc r
Presented by:
Reem Aboali, BSc

2. Introduction

3. Concrete Shaft Construction: Climbing (Jump) Forms
Applications: suitable for construction of multi-storey vertical concrete elements in high-rise structures, such as shear walls, core walls, lift shafts, stair shafts and water towers shafts.
Three Types of Jump Work
Normal Jump/Climbing Form: forms dismantled using a crane to move it to next level of construction.
Guided Climbing Jump Form: units remain anchored to the structure but lifted with a crane to the next level of construction.
Self Climbing/ Jump Form: No crane is used, pushed on rails by hydraulic Jacks.

4. Concrete Shaft Construction: Climbing (Jump) Forms
Construction Sequence
Formwork and working platforms are assembled on the ground
Formwork is then lifted by a crane and fixed to anchors and the climbing brackets which are bolted to the wall below
Steel Fixation
Pouring concrete
5. Formwork dismantling after setting up of the concrete and raised by a crane to the next level ( for the self-climbing form, this is done by the hydraulic jacks).

5. Concrete Shaft Construction: Slipforms
Similar to Jump form, but is a continuous process where hydraulic jacks are pushing the formwork upwards at a constant rate while the concrete is being poured inside the formwork.
Slip Formwork System has three Platforms
Upper Platform : Storage and distribution area
Middle Platform : Working Area at the top of the poured concrete level
Lower Platform : Concrete Finishing

6. Shaft Construction: Selection Criteria
Construction Method
Conventional Formwork
Normal Jump Forms
Guided Jump Forms
Self-Climbing Forms
Slipforms
Cost
Cost-saving for small heights
Cost-saving for medium – large heights
Only Cost saving for large heights
Safety
Least safe
Better safety due to more advanced components
Surface Finish
Normal
Fare-faced concrete
Adjustability
Adjustable
Non-Adjustable
Need for Crane
Always Needed
Only during concrete supply
Site Congestion
Most Congested
Less Congested
Least Congested
Labor
Semi-skilled
Skilled
Highly skilled
Time
Slowest
Medium speed
Medium-High speed
High speed
Fastest
Formwork Durability
Least Durable
Durable
Needed Concrete Characteristics
Typical conventional concrete
Preference when fast setting is possible
The rate of pouring should be equal to that of setting

7. Tank Vessel Construction
Massive structured false work :
Construct concrete shaft.
Assemble false work and formwork.
Place reinforcement &/or pre-tensioned tendons and pour concrete.
Suspended false work :
Construct concrete shaft.
Suspend false work structure from shaft and assemble formwork.
Place reinforcement &/or pre-tensioned tendons and pour concrete.

8. Tank Vessel Construction
False work lift (pushed) method:
Assemble false work on ground.
Construct vessel on ground.
Vessel raised by the jacks while shaft is constructed.
Construct transition & rest vessel.
Lift Slab Method:
Construct concrete shaft.
Assemble false work on ground.
Construct vessel on ground.
Suspend tendons from shaft.
Lift vessel & construct transition.

9. Tank Vessel Construction: Selection Criteria
Construction Method
Conventional Massive False Work
Suspended False Work Method
False Work Lift Method
Liftslab Method
Cost
Cost-saving for limited heights
Cost-saving for medium heights
Cost-saving for medium and large heights
Risk
High probability of worker fall-off
Special precautions required during lifting
Accessibility limitation
Not limited
Limited
Equipment
Simple
Requires special equipment
Labor
Semi-skilled
Skilled
Time
Slowest
Medium
Fastest
Design Considerations
None
Special design considerations should be taken into account
Quality Control
Moderate
Better Quality

10. Case Study 1: 2 Million Gallons Tank, Frankfurt Kentucky, USA
Owner: Frankfort Electric and Water Plant Board
Consultant: The Crom Corporation
Capacity: 7570 m3
Total height: 130 feet (40 meters)
Tank Diameter: 35 m
One of the first four all concrete elevated tanks in the United States.

11. Elevated tank components
Dome:
35m span
Ring beam
Tank Vessel: height is 13 m
Transition
thickness varies from 0.6 to 1.2 m.
Concrete shaft
diameter of the wall is 9.75 m with a height of 27.5m
Raft foundation
a dimension 14m*4m by depth 1.8

12. Construction Sequence1
Raft Foundation 2
Concrete shaft using jump forms 3
Transition section 4
Tank vessel formwork and pouring 5
Ring beam 6
Dome
Inner Vertical members
Compression members
Outer vertical members
Tension members

13. Case Study 2: Disney Road Elevated Water Storage Tank
Owner: Anne Arundel county department of public works
Consultant: O’Brien and Gere
Capacity: 7570 m3
Total height: 59.1 m
Bowl diameter: 30.5 m

14. Case Study 2: Construction Procedure
Construct Foundation
Construct 1st 3.9 m using conventional forms
Construct the remaining 33.1 m of shaft by slipforms
Construct the thicker wall, inner columns and staircases.
Construct the Vessel on the ground
Lift the tank using the lift slab method
Construct transition ring beam
Release lifting tendons
Construct tank roof slab

15. Case Studies: Methods Evaluation
Using slip forms to construct the shaft of the 2nd project while normal jump forms were used in the 1st project as the 2nd tank was higher than the 1st tank.
The higher height of the 2nd tank is the major reason giving preference to the lift slab method to construct the tank vessel as having the tank false work constructed at the top of the shaft would be time-consuming and cost-consuming while the situation was different for the 1st tanks.
The verticality of the walls of the 2nd tank vessel made the construction using the suspended formwork much more difficult than constructing it on the ground then lifting it using the lift slab technique while the walls of the 1st tank were slanted easing the use of suspended false work.

16. Conclusion
When examining the methods applied in the two cases discussed in this paper against the developed selection criteria, the selection criteria proved that it covered the different aspects governing the selection of the most suitable methods for different elevated RC tank construction cases.
It is highly recommended when using the selection criteria matrix to take all the factors governing the method selection into account as neglecting some of them could cause real problems.

17. Acknowledgements
Department of Construction and Architectural Engineering in the American University in Cairo.

18. References
ACI Committee 371. (2008). Guide for the Analysis, Design, and Construction of Elevated Concrete and Composite Steel-Concrete Water Storage Tanks. Farmington Hills: American Concrete Institute. Anne Arundel County Department of Public Works. (2011, December). Disney Road Elevated Water Storage Tank. Retrieved December 4, 2014, from Anne Arundel County Department of Public Works: Bennett, C. P., & D'Alessio, M. S. (1996). Falsework/Shoring. In R. Ratay, Handbook of Temporary Structures in Construction (2nd ed., pp ). New York, NY, USA: McGraw-Hill. Camellerie, J. F. (1996). Slipforming. In R. T. Ratay, Handbook of Temporary Structures in Construction (2nd ed., pp ). New York, NY, USA: McGraw-Hill. Copley, J. D., Ward, J. S., & Bannister, H. (2007, June 22). 2.0-Million Gallon Prestressed Concrete Elevated Tank Frankfurt, Kentucky. Retrieved December 4, 2014, from Bentley.com: ftp://ftp2.bentley.com/dist/collateral/Web/Building/Frankfort_Paper_1.pdf Destil, F. (2008, April 22). Cassaforma rampante Destil. Retrieved November 27, 2014, from wikipidea: Gregory, K. (1996). Concrete Formwork. In R. T. Ratay, Handbook of Temporary Structures in Construction (2nd ed., pp ). New York, NY, USA: McGraw-Hill. Kim, H. S., Kim, Y. J., Chin, W. J., & Yoon, H. (2013, August). Development of Highly Efficient Construction Technologies for Super Long Span Bridge. Engineering, 5, Masih, R., & Hambertsumian, V. (1999, February). Dynamic Liad Effect on Lift Slab Structures. JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES, Peurifoy, R. L., & Oberlender, G. D. (2011). Formwork for Concrete Structures. New York: McGraw-Hill. Peurifoy, R. L., Schexneydar, C. J., & Shapira, A. (2006). Construction Planning Equipment and Methods. New York: McGraw-Hill. VSL International LTD. (1983). Concrete Storage Structures - Use of the VSL Special Construction Methods. Bern, Switzerland: VSL International LTD. Zallen, R. M., & Grossf, B. (2002, November). Effective Length of Lift-Slab Columns. JOURNAL OF PERFORMANCE OF CONSTRUCTED FACILITIES,

19. Thank you