1. We are reviewing Chapt. 1&2 and we assigned Chapt. 3 & 4 for
FORMWORK DISASTERS
CHAPTER 2
We are reviewing Chapt. 1&2
and we assigned Chapt. 3 & 4 for
reading assignment!!!
Chapter One- Introduction to Forming
Chapter Two- General Objectives in
Formwork Building
Chapter Three-Overall Planning for
Formwork
Chapter Four-Materials, Accessories,
Proprietary Products

2. What is forming and formwork?
FORMWORK COST AND CONSIDERATIONS
What is forming and formwork?
What is its purpose?
What are the objectives of any form design?
The form design must provide,
THE BEST QUALITY
SAFETY
ECONOMICS
What kind of nomenclature or terminology
is associated with forming?
Discussion of some Case Studies
on Pages 2-4 to 2-8

3. New York Coliseum FORMWORK DISASTERS
Concrete was placed on the Main Exhibition Floor of the
New York Coliseum
Forms for the floor slab were being supported on two tiers of shores
Bottom shores were wood 4x4s, capped with horizontal 4x4s and cross –braced horizontally.
Adjustable metal shores were placed directly over the 4x4 posts to form the second tier
There was little diagonal cross-bracing or horizontal bracing on the adjustable shores.
At the time of the collapse there were eight or nine motorized buggies transporting concrete to the area
A horizontal thrust developed through the combined effect of the movement and sudden stopping of the buggies

4. FORMWORK DISASTERS
New York Coliseum
New York Coliseum where rapid deliveries of power buggies introduced lateral forces

5. Increased diagonal bracing was added
FORMWORK DISASTERS
New York Coliseum
Increased diagonal bracing was added
to all remaining shoring for the New York Coliseum following partial collapse of formwork

6. Bailey’s Crossroads in Virginia
FORMWORK DISASTERS
Bailey’s Crossroads in Virginia
14 workers were killed
Flat plate apartment building had 26 stories plus penthouse and four –story basement
Columns were normal weight concrete, and slabs were lightweight concrete, 8 in thick.
One floor was cast per week. Forms were supported by floor 7 days old or older, which in turn was propped to a floor 14 days old or older.
24th Floor was being cast when collapse occurred.
24th Floor was shored to the 23rd Floor which was only about 5 days old.
Workmen began knocking out the shores supporting that 5 day old floor (the 23rd), even though 2 full floors of shoring was required in the design
The overloaded 23rd floor failed in shear around one or more columns, triggering a collapse throughout the bldg.

7. Bailey’s Crossroads in Virginia
FORMWORK DISASTERS
Bailey’s Crossroads in Virginia
14 workers were killed

8. More Accidents in Forming
FORMWORK SAFELY
More Accidents in Forming
15 injuries and one death
Contractor taking risk for economic reasons

9. Preventive Measures FORMWORK SAFELY
High Shoring with a heavy load at the top is vulnerable to eccentric or lateral loadings.
Diagonal bracing improves the stability of such a structure, as do guys or struts to solid ground or completed structure

10. SHORES AND RESHORES
Book Overview
Read Chapt. 5
Chapter Five- Loads and Pressures

11. What are the loads experienced in
formwork?
Vertical Dead Load
Weight of reinforced concrete (DL)
Average unit weight of concrete is
considered 150 pcf (includingrebar)
For slabs we use 12.5 #/sq ft.per
one inch of slab thickness
Vertical Live Load
Weight of material, workmen, and
equipment (LL)
minimum LL is 50 psf (includes
workmen, runways, screeds, & equip.
minimum LL is 75 psf when motorized carts are used

12. What are the loads experienced in
formwork?
Vertical Live Load & Dead Load
Regardless of slab thickness, minimum DL+LL is 100psf, and
125psf if motorized carts
Forms and shores must be joined securely and attached to base support to insure against uplift loads
(see p. 5-3)

13. How do shores and reshores function
within our design?
Shores and Reshores
shores that support freshly placed concrete may be supported by floors that are exceeding there full design strength, therefore shores must be developed in as many floors as can support the capacity
10 considerations for shoring are mentioned on p. 5-3

14. How do shores and reshores function
within our design?
Reshores
Reshores replace shores after stripping
The sequence is as follows
Set up forms and shores for new concrete
remove reshores at lowest floors and forms and shores from next level above
replace reshores snugly under the slab just stripped, but without reshores carrying any load when they are first placed

15. How do shores and reshores function
within our design?
Reshores and Shoring Sample problem
review assumptions for hand calculation
review table 5-2

16. Wooden ReShores from Text 4-68

17. Adjustable Shores from Text 4-70

18. Horizontal Bracing of Shores
@ 77 Hudson St.
Preparing for Fresh Pour on Top Floor

19. Metal Adjustable Shores @ 77 Hudson St.
Preparing for Fresh Pour on Top Floor

20. 77 Hudson St.
Supporting Floors that have been recently
poured and hardened

21. Metal Adjustable Shores @ 77 Hudson St.
Supporting Hardened Concrete Floor

22. Metal Adjustable Shores @ 77 Hudson St.
Next to open wooden form stairwell

23. Metal Adjustable Shores @ 77 Hudson St.
Wood Formed Stairwell

24. Calculations for Shoring and Reshoring
Two levels of shoring and one level of reshoring

25. Calculations for Shoring and Reshoring

26. Calculations for Shoring and Reshoring
One level of Shoring and Two levels of Reshoring

27. Rules of Calculating Shoring Diagrams
Rule#1 – Freshly Poured Concrete transmits it full load to shores below
Rule#2 – Hardened Concrete does not deflect until shores are removed
Rule#2a – Hardened Concrete does not transmit it loads into columns until shores are removed (taking it own load)
Rule#3– Hardened Concrete that deflects and is not connected to ground by shores, shares the load with other floors that are connected.
Rule#4– Loads are rebounded (lossed) in Hardened Concrete when connected floors are disconnected by removing shores