Collapse of concrete structures during construction has been happening since concrete has been placed in formwork. Cases and causes of these type of failures have been documented and recorded in many texts, articles and journals. This installment will try and focus on a few of them, starting with The New York Coliseum on May 9, 1955, 2000 Commonwealth Ave. on January 5,1971, Skyline Plaza in Bailey's Crossroads on March 2, 1973, The Harbour Cay Condominium in Cocoa Beach, Florida in March 1981 and ending with The Tropicana in Atlantic City on October 30, 2003.The focus will be on what has been learned over time from these failures and what has been done to keep these type of tradgedies from occurring in the future.

Key Words: New York Colliseum, 2000 Commonwealth Ave., Skyline Plaza, Harbour Cay Condominiums, Tropicana Casino Parking Garage, punching shear, formwork failures.

Case Studies:

Although there were many cases of concrete failures during construction prior to the New York Coliseum collapse as illustrated in (McKaig 13-27, 1962), only a few will be looked at after this point because of the changes and progressions being made in the construction industry at this time in history.

New York Coliseum on May 9, 1955

The construction method was a flat plate waffle slab with solid slabs at the column caps. It was one of the first times the use of motorized buggies had been used in the pouring of this type of structure. The floor that collapsed was the first floor above grade supported on two tiers of shores at a total of 22' high. See Figure 1 for view of collapse. The buggies weighed about 3000 lb loaded, ran at about 12 mph, and there were eight of them at the time of the failure with about 500 cubic yards of concrete already placed (Auburn University). The investigation that followed put the blame solely on inadequate provisions in the formwork to resist lateral forces, it even went on to say that "if there had been sufficient diagonal, horizontal, and end bacing of the temporary supporting structure, the collapse could have been prevented entirely,...", (McKaig 15-16, 1962). After the collapse the district attorney called attention to the lack of inspections and made recommendations to revising the building code with respect to formwork because of the new advances.
Figure 1: N.Y. Coliseum Collapse, National Archives

2000 Commonwealth Avenue: January 5, 1971

This was a progressive collapse of a cast-in-place reinforced concrete flat-slab structure. Punching shear was determined to have been the triggering mechanism but the real problem was in the numerous errors and omissions by every party involved in the project (Delatte 133-143). The investigating committee determined that if the construction had had a proper building permit and had followed codes, then the failure could have been avoided (Delatte 142). Some of the problems leading to the collapse are
  1. Not following the structural engineers specifications for shoring and formwork
  2. Lack of concrete design strength
  3. Lack of shoring or removed too soon
  4. Improper placement of reinforcement
  5. Little construction control on site
  6. Owner changed hands many times
  7. Almost all jobs were sub contracted
  8. No architectural opr engineering inspection done
  9. Inadequate inspection by the city of Boston
  10. The general contractors representative was not a licensed builder
  11. Construction was based on arrangements done by the subcontractors
  12. No direct supervision of subcontractors
Figure 2: Typical flatplate with uniform distributed loading
Figure 3: Punching shear failure diagram

Skyline Plaza: March 2,1973
Figure 4: Skyline Plaza at Bailey's Crossroads, National Archives

Skyline Plaza in Bailey's Crossroads is an example of a catastrophic collapse of a 30 story cast-in-place reinforced concrete structure. This was also a flat-plate design structure that failed due to punching shear on the 23rd floor and resulted in a progressive collapse. Some of the reasons for this failure again were 1) premature removal of shores and reshores, 2) insufficient concrete stength, 3) no preconstruction plans of concrete casting, formwork plans, removal of formwork schedules, or reshoring program (Kaminetzky 66-67).
For more information go to:

Harbour Cay Condominium: March 1981

Built just 10 years after 2000 Commonwealth Ave. and 8 years after Skyline Plaza, was another cast-in-place reinforced concrete structure that collapsed during construction. It was determined that the most important factor towards its failure was a design error coupled with a construction error of the wrong size rebar and chair height. The designer never performed any calculations to check for punching shear, the most common form of failure in these type of structures (Feld & Carper 18).
For more information go to:

The Tropicana Casino parking garage in Atlantic City, N.J.: October 30,2003

The structure collapsed during construction killing another four construction workers and and leaving more than 30 others injured. Larry Bendesky, Mongeluzzi's partner of the Philadelphia law firm Saltz, Moongeluzzi, Barrett & Bendesky, P.C, the lead counsel for the litigation with Paul D'Amato of the D'Amato Law Office and a member of the trial team, said that "the simple explanation of the cause of the collapse is that the floors were not connected to the walls with the required reinforcing steel. Built without the necessary steel, it is no wonder it collapsed like a house of cards." (pr newswire) The vertical columns left standing and the fact that the floors were not connected implies that this was another punching
Figure 6: Tropicana Casino; Parking Garage Picture taken from
shear failure.
Figure 5: Tropicana Parking Garage Collapse; photo taken from OSHA website
Figure 5: Tropicana Parking Garage Collapse; photo taken from OSHA website

Codes & Regulations:

OSHA, The Occupational Safety and Health Administration is the main federal agency charged with the enforcement of safety and health legislation. For all of the failures that have occurred, lives lost and countless individuals who have been injured or crippled for life, the "Handbook of OSHA Construction Safety and Health" (Reese & Edison) only dedicates less than two pages to cast-in-place concrete. The first sentence reads "Formwork is designed, fabricated, erected, supported, braced, and maintained so that it will be capable of supporting, without failure, all vertical and lateral loads that are anticipated to be applied on the formwork." This appears to be a statement that does not need to be printed, for why else would formwork be installed if it is only expected to fail. This statement among others do not give many specifics and could be interpretted by others differently.
ACI, The American Concrete Institute's origins started in 1905 with its first building code
Figure 7
published in 1910 and changing its name to the current designation in 1913. ACI's first design handbook came out in1939 and the first building code titled ACI 318 came out in 1941. The beginning volumes of ACI were less tha fifty pages with the current code specification being nearly 470 pages of design specifications and commentaries (ACI 318). This clearly shows the history of ACI is closely tied to the ever changing demands of concrete construction and technology. The ACI sees itelf as an expanding, alert,and informed organization prepared to stimulate imaginative applications of concrete and better knowledge of its properties and uses, and will take an increasingly active part in solving problems affecting the public welfare (History of ACI).

Lessons Learned:?

Starting with the N.Y. Coliseum the construction industry learned that shoring systems should be well braced to resist lateral loads and to consider the effect of power or motorized buggies/carts on the formwork (Auburn University).
From 2000 Commonwealth Ave. the industry learned that this type of failure is a critical failure mechanism for flat-plate-slab concrete construction. Structural safety depends on adequate slab thickness,proper placement of reinforcement,
and adequate concrete strength (Delatte 144).
Six lessons learned from the colloapse of Skyline Plaza at Bailey's Crossroads are listed in (Kaminetzky 67) as 1) the contractor should prepare formwork drawings showing details of the formwork, shores, and reshores. 2) The contractor should prepare a detailed concrete testing program, to include cylinder testing, before stripping forms. 3) The engineer of record should ascertain that the contractor has all the pertinent design data (such as live loads, superimposed dead loads, and any other information which is unique to the project). 4) Inspectors and other quality control agencies should verify that items 1 and 2 above are being adhered to. 5) Uncontrolled acceleration of formwork removal may lead to serious consquences. 6) Top and bottom rebars running continuously within the column periphery must be incorporated in the design.
The Harbour Cay Condominiums presented the industry with six more lessons learned in this type of construction also listed in (Kaminetzky 77-78). This tradgedy happened only eight years after the Skyline Plaza tradgedy and yet some of the same lessons are listed again, they are 1) A punching shear strength check s critical to the success of a flat-slab, since punching shear is the most common failure mode of concrete slabs. 2) Minimum depth of a flat-slab must be checked to assure proper strength and acceptable deflections. 3) Reinforcing bars, both at the top and at the bottom of the slab, should be placed directly within the column periphery to avoid progressive collapse. This can easily be accomplished routinely in all flat-slab jobs at no additional cost at all. 4)Proper construction control must be provided in the field, including design of formwork by professionals. This must include shoring and reshoring plans, procedures, and schedules, with data on minimum allowable stripping strength of the concrete. 5) When there are failure warning signs of any type on a construction site, work must stop. All aspects of the project must be carefully evaluated by experienced professional help. Immediate evacuation of the structure must be considered. 6) Special care must be taken during cold weather to evaluate the actual in place strength of the concrete. It is also a fact that the level of construction carelessness increases in the winter months.
The Tropicana lessons learned have not yet been published in any documented form that I have been able to ascertain, but from articles such as the one from ASQ Newsletter published in the summer of 2004, one can reasonably determine that all of the above lessons learned will be revisited. The article states that all of the errors were remarkably simple, Engineering 101". Contractor failed to tie rebar in the frames floor beams to the columns and shear walls in several places was only one reason as listed in (ASQ Newswire 11-12).

It can be seen from the lessons learned in bold print from the above cases that the same type of errors keep repeating themselves through history. Are the lessons really being learned, or is there something more that has to be done to ensure the lives and safety of our working men and women?


Statistics released in 1984 by the National Safety council reported over 2200 deaths were reported for the construction industry for that year, and 220,000 disabling injuries, the largest total for the eight major industries surveyed (Carper 312).

Over $1.6 billion is lost annually in the U.S. due to construction accidents (Carper 312)

Forty-nine percent of falsework collapse happens during concrete placing (Hadipriono & Wang 115)

Untimely removal of falsework is the second most significant event related toconcrete failure (Hadipriono & Wang 116)

Investigations prove that many accidents causing thousands of dollars worth of damage could have been prevented if only a few hundred dollars hadbeen spent on diagonal bracing for the formwork structure (University of Washington).


OSHA, ASCE, and ACI have all responded to these as well as many other accidents and issues with activities, publications and codes aimed at improving construction safety and the welfare of our construction workforce; however, these organizations alone cannot be responsible for all construction related activities and failures.
The safety record in the construction industry can be and must be improved in all phases. As C. Roy Vince has stated, many construction accidents are the result of ignorance, carelessness, and greed (Carper 133). The lessons learned from above being repeated over and over again can only point to the fact that this statement is precisely true. "As long as structures are constructed by humans, using imperfect materials and procedures, failures are likely to continue. Many of these failures will occur during the process of construction, endangering the lives of construction workers." (Carper 143) There is no way to break everyone of their bad habits but awareness has to be raised and the consequences have to be sharply increased.
More focus has to be placed on required education of all construction personel beyond certain levels of responsibility, this is to include the workers themselves who are actually assembling these structures. Better licensure requirements, more stringent inspections, and increased factors of safety during construction (because it is at this time when the structure will be likely to see its most significant loading), should also be considered to help prevent these ttradgedies from reoccurring. From the initial design phase to maintainance of the structure after completion everyone involved needs to pay strict attention to all details and warning signs of impending failures. There can be NO SHORTCUTS if we are to protect the safety and lives of the individuals who provide us with all of the essential structures in our lives.
Most often it is not their mistake that cost them their life and the misery of the families who lost them too soon.


American Concrete Institute. “History of ACI” <> (October 10, 2009)
ACI Committee 318, (2008). ACI 318-08 “Building Code Requirements for Structural Concrete and Commentary” pp. 81-82
ACI Committee 318, (1963). ACI 318-63 “Building Code Requirements for Structural Concrete and Commentary” pp. .
Arthur H. Nilson, David Darwin and Charles W. Dolan, (2004). “Design of Concrete Structures” pp. 12-17
The ASQ Newsletter. “Extracts from Engineering News Record” OSHA Report Claims that Atlantic City Garage Contractors Failed to Tie Rebar and Properly Shore <> (summer 2004), (October 10, 2009)
Auburn University. “Lateral Stability of Structures” New York Coliseum <> (2009), (Sept. 18, 2009)
Charles D. Reese and James Vernon Eidson, (2006). “Handbook of OSHA Construction Safety and Health” pp. 181-183
Fabian C. Hadipriono,1 M. ASCE and Hana-Kwang Wang2, (March/April 1986). “Analysis of Falsework Failures in Concrete Structures” J. Constr. Engrg. Mgmt. 112(1), pp. 112-121.
Jacob Feld and Kenneth L. Carper, ((1997) “Construction Failure” pp. 242-274
Kaminetzky D. (1991). “Design and Construction Failures” Lessons In Forensic Investigations pp. 67-78
M. ASCE, (August 1987). “Structural Failures During Construction” J. Perf. Constr. Fac., ASCE, 1(3), pp. 132-144.
McKaig T. (1962). “Building Failures” Case Studies in Construction and Design
Norbert J. Delatte Jr., Ph.D., P.E. (2009). “Beyond Failure” Forensic Case Studies For Civil Engineers pp. 129-155
PR Newswire. “$101 Million Settlement in Deadly 2003 Tropicana Parking Garage Collapse That Killed Five Workers” <> (October 10, 2009)
University of Washington. “CM 420 Course Lecture 1” Temporary Structures <> (Spring Quarter 2002), (Sept. 18, 2009)
Zallen Engineering. “Collapse of Flying Formwork During Concrete Placement
<> (July 2002), (Sept. 18, 2009)