2000+Commonwealth+Avenue+-+Boston

toc ​ **2000 Commonwealth Avenue, Boston Massachusetts (January 25, 1971)** //Kevin T. Wigton, BAE/MAE, Penn State, 2009// //Additional Peer Review in Progress//

Introduction
 The structural failure and eventual collapse of the 2000 Commonwealth Avenue building occurred January, 25 1971. Failure occurred in three stages beginning with punching shear in the uppermost floor of the 16 story building. This was followed by the collapse of the roof slab and the eventual progressive collapse of the east side of the building. Four workers were killed and 20 injured as a result of this failure (Kaminetzky 1991). Immediately after the collapse occurred, rescue efforts were delayed due to uncertainty of structural stability for the remaining building as well as other concerns for rescue workers safety (Blake 1971).

Cause of the building collapse was unknown for some time with three possibilities initially suspected. Formwork collapsing on the upper floors under the weight of freshly poured concrete was one of the first suspected causes of the building collapse. Second, a witness to the building failure named a welding compressor the trigger mechanism to the collapse when it fell from a crane onto an upper floor. Finally, the third theory was that the strength of concrete previously placed in the building was much lower than specified due to the cold weather that Boston had been experiencing in the days prior to January 25 (Cause 1971).

It would eventually be determined that punching shear of the floor slab at an upper level column was the initial trigger mechanism for the collapse (King, Delatte 2004). Many factors played into the weakened shear strength at this location. Improper shoring of floors, low concrete strength and improper concrete detailing all contributed to the punching shear failure. From the early stages of this building project, there were numerous procedural erros that could have signaled the building's eventual collapse. Followed by flaws in construction procedure, the disregard for standard building practices became one of the major contributors to the collapse. Only one employee was present on site for the general contractor resulting in nearly no quality control or inspection of work. The project suffered greatly from changes in ownership and design professionals during early stages of the project. The lack of controls and monitoring throughout all stages of the building process is atributed to being the underlying cause of the collapse at 2000 Commonwealth Avenue.



Keywords
Punching Shear, Flat Plate, Construction Failure, Coordination, Progressive Collapse, Condominium, Boston

General Description of the Building
When construction began at 2000 Commonwealth Avenue plans were for a new multi story apartment building. The building was to be constructed as cast in place reinforced concrete project with flat slab floors. The building would include 16 upper level floors with a mechanical penthouse, 5ft above the roof slab, and two below grade parking levels (Heger 1972).

This final iteration of the building varied substantially from earlier building plans at this site. Early attempts for the building on this site included a seven story apartment building and then later a 14 story apartment building (King, Delatte 2004). The first permit lapsed due to delays in construction and the second project was never issued a permit for construction due to insufficient information on the application (King, Delatte 2004). With no permit being issued this would later be deemed an abandoned project by the building department. After numerous changes in ownership a building permit is granted in September of 1969 and construction begins. Lack of consistent designers and owners through this process as well as the irregularities in the permitting process were an early sign of the construction failure that would occur just over a year later.

Construction Activities at the Time of Collapse
Structural concrete work had been completed through floor 16 including the main roof level. Exterior wall masonry work was being performed on the 16th floor. On the morning of January 25th concrete was being placed for the mechanical penthouse floor slab with placement proceeding from west end and moving toward the east (Heger 1972). For an overview of the building floor plan at the failure location see Figure 1.

Collapse Summary
After investigation and interviews conducted by the mayor's Investigation Commission of eye witnesses, it was agreed that collapse of the building happened in three phases. The first phase was the punching shear of the main roof slab at column E5 (King, Delatte 2004). The initial failure was observed by several of the workers at the upper levels. They watched as the sag in the slab around column E5 slowly increased. This was followed by the complete collapse of the east side of the roof slab. See Figure 2 for the initial punching shear failure location. The structure remained in this condition for approximately 10 to 20 minutes, which allowed many of the workers to exit the building or reach safety (Heger 1972). This was followed by the total progressive collapse of the east side of the building, which left the floor plates stacked in the basement of the structure. Figure 3 shows the extent of the collapse on the building's east side.



Investigation and Findings
The primary investigation of the disaster was called for by the Mayor of Boston to find the cause of the fatal collapse. The mayor’s investigating commission enlisted the help of Professor William Litle, Associate Professor of Structural Design at M.I.T. to assist with the structural assessment. An additional notable investigator of the failure was Simpson Gumppertz and Heger Inc. (SGH) primarily conducted by Frank Heger. The SGH report was originally prepared for an insurance adjustor involved in the project.

The mayor’s investigating committee issued their report identifying a number of flaws contributing to the building failure and collapse. Key issues are summarized below.

As previously mentioned there were a number of irregularities associated with the permitting process for the building. The architect or the structural engineer of record did not seal any of the drawings for the project (King, Delatte 2004). Many of these issues can be attributed back to the numerous changes in ownership and designers on the project.

Procedural issues were largely to blame on this project. There was a general contractor for the project but they only had one employee on site during construction. Many of the contracts were issued from the owner directly to the subcontractors (King, Delatte 2004). Given this situation there was next to no inspections or quality control measures on site. The confusion over various design and construction responsibilitis was a considerable issue on this project, considered by many to be a contributing factor to the collapse.

There were many deficiencies associated with the concrete mix, reinforcement, placement, and 28 day compressive strength. The mix designs did not meet the necessary prequalification required by the Boston Building Code (King, Delatte, 2004). During the investigation it was found that reinforcement was not correctly placed in many areas and may have contributed to the final collapse of the building (Heger, 1972). After concrete was placed no protection against cold was provided. The roof slab was placed in early December and in the days following the average temperature was 25 degrees Fahrenheit (Heger 1972). As a result of these contributing factors the 28 day compressive strength of concrete was as low as 700 psi (Feld 1997). A final straw was missing special shoring at the area of the initial collapse (Heger 1972).

The design of the project was determined to have been adequate to carry the structural loads of the building. Slab thickness did not meet the deflection criteria but all strength requirements were met (King, Delatte 2004). The investigating committee deemed that the failure would not have occurred if the necessary regulations and procedures were followed (Kaminetzky 1991).

Lessons Learned
Unfortunately, 2000 Commonwealth Avenue would not be the last project that suffered from faulty construction practices leading to a punching shear failure and progressive collapse of the building. Skyline Plaza was one of the first major failures to follow Commonwealth Avenue. Similar to the collapse in Boston this 30 story concrete structure failed due to early removal of shores, insufficient concrete strength, and improper construction planning. Harbour Cay Condominium was another case of a building project that resulted in a collapse during construction. Again procedural errors were largely to blame leading to a punching shear failure and progressive collapse during construction. Immediately following the collapse a summary of the failure at Commonwealth Avenue was available but the details were not widely known. Skyline Plaza and Harbour Cay both could have benefitted from the timely dissemination of information about this failure. For a further discussion of similar failures please review Concrete System Collapses and Failures During Construction.

In recent years the public has questioned if engineers have learned from the mistakes of improper construction practices (Daley 2006). The Commonwealth Avenue collapse would not be the last flawed construction project in Boston. The John Hancock Tower drew scrutiny when the windows did not perform as expected and began to fall from the building. Again in 2006 a major construction project failure struck Boston. A concrete panel fell from a tunnel ceiling on Interstate 90 as a result of a connection failure. In both cases improper detailing lead to poor material performance.

Conclusions
A variety of lessons can be learned from the 2000 Commonwealth Avenue collapse. The project, which was flawed from the beginning, went through many stages where deficiencies could have been caught. The culmination of errors on the project from the initial permitting of the building through construction procedures resulted in a major building failure. This failure brought to light the importance of construction controls and inspections on a project. If measures were taken to ensure that the original design was carried out the collapse would not have occurred. The Boston Building Department became aware of the pivotal importance of their role in a construction project with this collapse. There were a number of opportunities for deficiencies to be spotted and all of them went unnoticed.

Annotated Bibliography
Delatte, N. J. (2008). //Beyond Failure, forensic case studies for civil engineers,// ASCE, Reston, VA. (133-144)

A synopsis of the building failure that reviews causes, collapse details, and implications on the construction industry.

Feld, J. (1968). //Construction Failure//, Wiley, New York. (242-243), (265-274), (422-429)

Three chapters from there book are useful in researching the collapse. Failures in flat plate construction as well as those resulting from formwork and low material strengths are discussed here.

King, S., and Delatte, N. J. (2004). “Collapse of 2000 Commonwealth Avenue: Punching Shear Case Study.” //Journal of Performance of Constructed Facilities,// 18(1), 54-61.

The original article which appears agin in //Beyond Failure.// This article contains additional information regarding the construction proceedings.

Kaminetzky, D. (1991). //Design and construction failures: Lessons from forensic investigations//, McGraw-Hill, New York (37-38, 67-72, 572-573)

This book Discusses the collapse as well as design and responsibility issues on the project.

“Cause of fatal Collapse unknown.” (1971). Engineering News Record, Feb. 4,13.

This article appeared shortly after the collapse and summarizes the three likely causes that were suspeced at that time.

Blake, A. F. (1971). “16-story building falls in Brighton.” //The Boston Globe//, Jan. 26.

The front page headline of //The Boston Globe// which gave the first reports of the building failure

Heger, F. (1972). “Investigation of Collapse During construction of Reinforced Concrete Apartment Building Located at 2000 Commonwealth Avenue Boston, Massachusetts” Simpson Gumpertz & Heger Inc., Cambridge, Massachusetts.

This is an extensive report by Frank Heger that was prepared for an insurance company during the investigation that followed the collapse.

Litle, W. A. (1972). “Boston collapse.” //Structural failures: Modes, causes, and responsibilities,// ASCE, New York. (98)

This is a short summary by William Litle which was made public shortly after the collapse and gives the main causes of the building failure.

Daley, B. (2006). "Back to the drawing board." //The Boston Globe,// July 17.

In this news article, several Boston construction failures are discussed along with the engineering community response that follows.

Additional Resources:

Granger, R.O., Peirce, J. W., Protze, H. G., Tobin, J. J., And Lall, F. J. (1971). “The building Collapse at 2000 Commonwealth Avenue, Boston, Massachusetts, on January 25, 1971.” //Rep. of the Mayor’s Investigating Commission,// Mayor’s Investigating Commission, of Boston.