Big+Blue+Crane+Collapse

Lampson Transi-Lift "Big Blue" Crane Collapse: toc //** Brian Riewestahl, E.I.T., M.S., Penn State, 2010 **//

= Abstract: =

On July 14, 1999, while lifting a section of the retractable roof for the Milwaukee Brewers new stadium, the Lampson Transi-Lift crane nicknamed 'Big Blue' suddenly collapsed. As a result of the collapse, three workers died, five more were injured, and the opening of Miller Park was delayed for a season. The litigation stemming from this accident has also resulted in sizable monetary penalties. Directly following the collapse, a number of various theories were offered as possible reasons for the failure. Theories included faulty crane parts, poor soil conditions under the crane, and wind loads on the crane. Upon investigation of the various theories, the prevailing belief is that the primary factor of the collapse was the high wind loads acting on the section of roof being lifted, and lack of consideration of those loads on the crane's rated capacity.

Background:
Miller Park is the current home the Milwaukee Brewers major league baseball team. Miller Park came about from the need to replace an aging Milwaukee County Stadium. Lobbying for the stadium started under the previous owner, Bud Selig, back in the 1980's. Lobbying continued through the 1990's as a way to finance became the biggest issue holding back the new stadium [Ballparks of Baseball, 2010]. After the financing issue had been resolved, via a 5 county sales tax increase, designs and planning could begin, culminating with the ceremonial groundbreaking for the new stadium in November of 1996 [Munsy & Suppes, 2007].

The project team consisted of;
 * Owner:** Southeast Wisconsin Professional Baseball District, and the Milwaukee Brewers
 * Architect:** HKS, Inc., NBBJ, and Eppstein Uhen Architects
 * Construction:** Huber, Hunt & Nichols, Inc, Clark Construction, Hunzinger Construction, and Mitsubishi Heavy Industries

Construction of the stadium continued without major incident until July 14th, and the failure of the Lampson Transi-Lift crane that had been nicknamed 'Big Blue'.

Crane Failure:
Prior to the lifting of the roof panel on the 14th, all of the necessary rigging for the lift was completed, along with moving Big Blue in to proper position to begin the lift. The morning of the lift, the lifting plan was completed along with routine daily crane maintenance before the rest of the workers arrived on site. At 6:30am a pre-lift meeting was held in which procedure and the general lift plan was covered with the roughly 40 workers from all the different contractors that were involved with the lift. Starting at 7am, upon inspection of the rigging and verification of radio contact, the lifting of the roof panel began. As of 9:30, the panel had been lifted 6'-8' and was held there to verify the orientation of the roof panel as it needed to be precisely lifted in the correct orientation to match up with the connection locations. While this was occurring, it was noted by the lift superintendent that the front crawler was sinking into the ground. Upon noticing this, he directed the crane crew to move the crane onto more stable ground. This deviation from the original lift plan now meant that the roof panel would need to be lifted over the existing roof panels already installed. Once the crane moved to more suitable ground, the roof panel was hoisted to approximately 300 feet, and the crane prepared to move to the final 'set point' location. During this move, the lift superintendent wanted updates regarding the wind speeds from an anemometer mounted on the crane. These readings varied between 17mph and 20mph over the course of the move. After the crane had completed its approximately 500' travel to the set point, workers went to work on stabilizing the roof panel while the crane operator assisted under the direction of the lift supervisor to move the boom counter to the action of the now swinging roof panel. It was during this phase of the lift that the crane's boom buckled at approximately the mid-point of the boom [NIOSH, 1999]. (see Figure 1 and 2).

Lifted Load vs. Crane Capacity
The very first thing to review in a crane failure is the simplest. That is, was the crane trying to lift more than its capacity? In this case, this factor can very easily be dismissed based on the fact that the crane had a rated capacity of 1500 tons in the most ideal setup [LaBar, 07/15/1999]. At the time of the failure and configuration of the crane, the capacity chart for the crane indicated a rated load of 1040 kips [Ross et. al, 2006]. While this is significantly less than the most ideal rating, and almost at capacity (96.2%=1000000lbs/(1040*1000lbs)) for that configuration, it still did not go over the rated capacity. The idea that the lift was nothing out of the normal range for the crane is backed up by the statement of Lawrence Shapiro, an engineer with Howard I. Shapiro & Associates, "For a Lampson Transi-Lift, 400 tons is a yawn," [Jagler, 1999]. Based on the crane's various lift ratings, previous track record of the crane, and the observation of the video of the collapse, it can be determined that the pure weight of the lift alone was not the cause of the crane's failure. media type="file" key="bigblue.wmv" width="508" height="426" align="left"

(Figure 3 : Video of crane collapse - Courtesy of OSHA)

Ground Subsidence
Another theory that was proposed following the crane's failure was that the ground simply could not support the weight of the load the crane was attempting to lift. "The ground was prepared specifically for the travel of the Transi-Lift under full load from the assembly site to the roof section placement locations. Borings and a soils engineering study were conducted for this effort... A runway was built with two 10-ft. wide by 2-ft. deep concrete grade beams on 7ft. of compacted fill with an 8in. overlay of gravel" [Ross et. al, 2006]. It was stated that two of the workers running the lift at the time of the failure saw one side of the crane's tracks sinking just prior to the accident [Shapiro, 1999]. Ground failure is also noted as a possible factor in the official National Institute for Occupational Safety and Health (NIOSH) report of the incident as a possible contributing cause. Another interesting fact discovered during the investigation of the failure was a broken 12" diameter water main about 6 feet below and 20 feet away from the base of the crane. It was noted at the time of the investigation that there was little evidence to suggest the water main has broken prior to the crane's failure [Jagler, 1999] . The discrepancy between these two sources unscores the complexity of finding a root cause of the collapse versus what may have be secondary damage as a result of the collapse.

[[image:crane_tip_over_NIOSH.jpg align="right" caption="Figure 4 : Photo of Miller Park, during crane failure (Photo courtesy of NIOSH FACE report 99-11 with credit to John A. Thraen)"]]Wind loads
The two main competing theories upon initial investigation of the failure were; a theory that high wind loads during the lift were the principle cause of the failure versus a theory of a structural failure in components of the crane itself as the proximate cause of the collapse.

"Large structures such as the ill-fated roof panel at Miller Park should not be lifted by cranes in winds of 20 to 32mph, according to two veteran crane accident investigators." [Jagler, 1999]. The reason behind this statement is the inherent dangers in operating a crance, and trying to place a suspended load when even a person trying to stand still at ground level has a hard time staying in one place. This statement serves as simplest explanation of the theory that the wind loads on the day of the failure and the failure of the people responsible for the lift to account for such loads were at the heart of the collapse of Big Blue. Wind speeds taken at various sites around the Milwaukee area varied in measurements at the time of the failure, but an average wind speed was concluded to be 23mph with gusts up to 35mph [Ross et. al, 2006]. However, wind speeds at the crane's anemometer located approximately 180 feet about the ground, which the workers using a reference, only recorded wind speeds topping out at 20mph [NIOSH, 1999]. The winds at elevations above grade were so noticeable that the day of the failure, group of ironworkers left the job site around noon refusing to work at elevation due to concern over their personal safety [Ross et. al, 2006]. It was also noted that some of the people on the site wanted to cancel the lift due to the wind conditions as well [WISN-12, 2009]. During the investigation, two monitoring devices on the crane that were designed to trigger an alarm if the wind speeds were excessive or the load was off kilter, were found to have dead batteries [LaBar, 07/15/1999].

Crane Structural Failure
The dueling theory to wind loads as the cause of the failure, was a failure of the cranes structural components as the primary cause of the collapse, more specifically flaws in the crane's center pin. The center pin of the crane is the physical member that connects the tub to the front crawler on the crane. The center pin (also called the king pin) on Big Blue was a 12 inch diameter, 11 foot long, solid steel member made out of American Iron and Steel Institute (AISI) grade 4340 steel with a yield strength of 103,000 psi [Kenner et. al, 2006]. (see Figure 5). During the course of normal crane operations, this center pin functions only as a pivot point for the crane works, but when the crane is subjected to excessive loading from the sides, the center pin can function as a tension and flexural member that keeps the crane from tipping [Kenner et. al, 2006]. As part of the design of the crane, a side load of 2% of the rated load should be and was considered. The basis of this theory was that there were side loads acting on the side of the crane, but that the design and original drawings for the crane's king pin didn't match the actual configuration of the king pin in the field, and that "connection" was the root cause of the collapse. The original design had a large nut at the top and bottom ends of the king pin. The design subsequently changed to include a two inch thick split ring and three-quarter inch locking ring both made out of A514 steel (100,000 psi yield strength) at the bottom connection of the king pin. [Kenner et. al, 2006]. However, during the investigation a half inch bronze (19,000 psi yield strength) spacer was found along with a change in the thrust bearing material from CDA 836 brass (17,000 psi yield strength) to a CDA 863 bronze (68,000 psi yield strength) thrust bearing [Kenner et. al, 2006]. It was noted that the spacer was added to facilitate a more complete connection of king pin to the crane's tub [Ross et. al, 2006].

The core contention of the theory was that the weak 1/2 inch bronze spacer that was added to the bottom end of the king pin connection assembly was the primary cause for the failure. This weak link in the connection fractured under the "moderate wind loads", as described by the crane's contractor lawyers, the day of the failure which led to those pieces from the fractured spacer to be thrown out of the connection, resulting in a 4000 kip dynamic jolt to the crane works that caused the overturning [Ross et. al, 2006]. Witnesses at the base of the crane were reported to say they saw "...the center pin lock ring flying up in the air, followed a couple of seconds later by the center pin shooting out." [LaBar, 07/29/1999].

OSHA's Initial Findings
After Big Blue's failure, investigations into the cause of the collapse started. The first investigation to be completed was the one by the U.S. Labor Department's Occupational Safety and Health Administrations (OSHA). However, the OSHA investigation was limited in scope due to time constraints. Per the Occupational Safety and Health Act, the department has six months from the date of the accident to issue citations for safety violations [OH Editorial Staff, 2000]. Given this compressed timeline, the OSHA investigation was focused on the workplace safety violations, and not the root cause of the failure. As a result of their investigation, the crane's operator, Mitsubishi Heavy Industries America, Inc., was cited with penalties totaling $240,500. The crane's designer, Lampson International Ltd., was cited for $131,000. The ironworker's company, Danny's Construction Company Inc., was cited $168,000 [OSHA, 2000]. The Mitsubishi citations covered numerous areas including, exceeding the crane's rated load, failure to factor in wind conditions during crane operations, failure to follow requirements relating to ground conditions, not keeping workers clear of the suspended load, and hoisting workers in personnel platforms in dangerous weather conditions [OSHA, 2000]. The Lampson citations were based on overloading of the crane and failing to factor in wind conditions [OH Editorial Staff, 2000]﻿. The citations issued to Danny's stemmed from hoisting workers in dangerous weather conditions, not keeping workers clear of the lift, and not ensuring crane operators were at the prelift meeting ﻿[OSHA, 2000]. Even though the OSHA findings only addressed workplace safety violations, at the time of the release of the citations, OSHA's Milwaukee office director, George Yoksas, was quoted saying, "wind is a contributing factor" to the accident [OH Editorial Staff, 2000].

Civil Lawsuit and Trial
As the result of the failure, a lawsuit was filed on August 12, 1999 against the numerous parties by the 3 widows of the workers killed in the collapse [Wisconsin Curcuit Court, 1999]. As is typical with suits in the construction industry, everyone associated with the project including parent companies was named as a defendant, but in the end the scope of the trial focused on Mitsubishi Heavy Industries, Lampson International Ltd, and the construction company, and ultimately the two different theories of the cause of the collapse. The essence of the trial was, is Mitsubishi to blame for lifting the load in the high wind conditions, or is Lampson to blame for providing inadequate strength in their crane?

The case lasted seven weeks [Cranes Today, 2000]. During the trial, lawyers argued and presented evidence trying to blame the other side for the cause of the failure. Lampson lawyers argued that the high winds and Mitsubishi lifting the load in the those high winds without accounting for the loads it would put into the crane was the cause, while Mitsubishi lawyers argued that the half inch spacer plate Lampson put into the crane's king pin connection was a weak point in the crane, and that had the weaker bronze spacer plate not been there, the lift would have gone according to plan even in the high winds [Cranes Today, 2000].

In the end, the jury assigned a 97% negligence for the accident to Mitsubishi, and 3% to Lampson [Cranes Today, 2000]. The result of this verdict was that each of the widows was awarded 1.75 million dollars for the "loss of companionship", and "pain and suffering" of their husbands [Cranes Today, 2000]. On top of these amounts, Mitsubishi was assessed punitive damages of an additional 94 million dollars [Cranes Today, 2000]. This case ended up being appealed and partially over turned [Wisconsin District Court of Appeals, 2003]. Even during the course of the appeals process, lawyers continued to debate whether Mitsubishi's alleged misuse of the crane in the high winds or Lampson's alleged omissions in design and rating calculations where the root cause [Wisconsin District Court of Appeals, 2003].

Conclusions:
"Long after this project is built, no one will remember us. If someone dies, they will remember that forever." [Smith, 1998]. That quote from Mitsubishi's director of safety, given months prior to the collapse of Big Blue is a tell-tale reminder that safety is really the most important factor in any project. However, as projects progress, attitudes can shift from being more concerned about the safety and details, to costs and construction schedules. Thus, a drive to finish the project 'on time' and 'on budget' can lead to a situation like this case, where workers are so focused in on the project deadlines, that they don't have time to ask questions to other project members or notice the 'fine print' on crane rating charts. In the quest to keep the project moving, the crane operator's pushed what they believed to be the limit of the crane lifting the roof panel in high wind conditions. Also contributing to this collapse was a lack of communication between the crane's designers and the crane's operators. In a perfect case, the crane's designers would have explicitly notified the operators of the inclusion of the spacer plate in the king pin connection, and more importantly, that the crane load charts did not include provisions for wind loads on the piece being lifted, only on the crane itself, and that the cranes wind speed meter was not at the height of the actual load. A result of the NIOSH investigation, a number of recommendations were made to help prevent this type of accident from occuring again.

The following are the paraphrased recommendations from NIOSH's report; [NIOSH, 1999]
 * Employers hould implement specifically engineered lift plans designed by professional engineers based on rated capacity, measured weight of the load, thorough study of the wind speed and its effect on the load, and consideration of ground conditions and dynamic forces on the crane's stability.
 * Cranes and work areas should be equipped with wind instrumentation at or near the elevation of hoisted loads.
 * Suspended personnel platforms should not be used in adverse weather conditions which may endanger workers.
 * Provide alternate observations methods for locations not easily visable from the ground.
 * Only use personnel necessary to safely complete the lift in hoisted platforms.
 * Cranes should be equipped with correct instrumentation to monitor all parameters affecting a safe lift
 * Designers and erectors should evaluate worker risk when figuring out construction and hoisting methods.

Had these recommendations been used during the construction of Miller Park, this collapse mostly likely would have never occured. Ultimately, the decision to lift the roof panel in the high winds fell to the crane's operators. Their decision to lift the panel, even with workers on site objecting to working in such high winds, without thoroughly reviewing the provisions of the crane's load charts, can be concluded to be root cause of the crane's collapse, even with the other compounding mitigating factors.

References:
1. Ballparks of Baseball. (2001-2010). "Miller Park". []
 * Brief history and facts about Miller Park.

2. Cranes Today. (December 2000). "Mitsubishi faces $99m damages as court finds it to blame for Big Blue's collapse". //Cranes Today//. Issue 313. p2-p3
 * An article providing the summary of the results of the court outcome followed by some highlights of testimony given and reasoning behind the verdict

3. Jagler, Steven. (July 23, 1999). “Investigators blame wind, not Big Blue”. //The Business Journal of Milwaukee//. []
 * Interview by Jagler with two veteran crane accident investigators roughly a week and half after the accident occurred discussing the wind speed at the time of the collapse

4. Kenner, Matthew T., P.E., Wilkinson, John A., P.E., and Morin, Charles R. P.E. (2006). “The Miller Park Crane Collapse – Analysis of the King Pin Failure”. 2006 ABAQUS Users’ Conference. []
 * In depth analysis of the crane’s king pin failure via finite element analysis software.

5. LaBar, Gregg. (July 15, 1999). “Three Workers Die When 'Big Blue' Falls at Stadium”. //EHSToday//. []
 * Initial news details and report of the crane collapse accident

6. LaBar, Gregg. (July 29, 1999). “Crane's Base May Be at Fault in Miller Park Accident”. //EHSToday//. []
 * Initial theory of a king pin failure on the crane which caused the collapse.

7. Munsey & Suppes. (April 2007). "Miller Park". []
 * Brief background on Miller Park

8. NIOSH. (1999). "Three Iron Workers Die After Heavy-lift Crane Tips Over - Wisconsin. NIOSH In-house FACE Report 99-11. []
 * Summary of the crane accident and recommendations resulting from it to increase workplace safety in the future.

9 . OH Editorial Staff. (January 13, 2000). "Violations in Crane Collapse Top $500,000". //EHSToday//. []
 * Summary of the citations issued by OSHA following the crane collapse

10. OSHA. “Big Blue Crane”. []
 * A video by OSHA safety inspector on site the day of the collapse.

11. OSHA. (January 12, 2000). "Three Firms Fined For Total of Over Half-Million Dollars". []
 * News release by OSHA regarding the citations issued as a result of the accident. Does not include damages resulting from the subsequent court cases.

12. Ross, Bernard, McDonald, Brian, and Vijay Saraf. (2006). “Big Blue Goes Down. The Miller Park Crane Accident”. //Engineering Failure Analysis//, Vol. 14, Issue 6, p942-p961
 * Comprehensive review of the accident, competing failure theories at the time and just following the accident, and determined causes of the accident upon review by multiple parties.

13. Shapiro, Mark. (November, 26 1999). "'Ground Failure' Seen In Collapse". //Chicago Tribune//. p2
 * Newspaper article with the crane operator's statement that ground failure occured prior to the crane's failure.

14. Smith, S L. (October 1998). "In a League of Its Own". //Occupational Hazards//. Vol. 60, Issue 10, p97-p100, p105
 * An article about the general overview of safety measures and programs in place on the Miller Park construction site, written before the crane accident.

15 . Wisconsin Circuit Court. (1999). "Milwaukee County Case Number 1999CV006553". Patricia Wischer et al vs. Mitsubishi Heavy Industries et al. []
 * Court records for the civil trial resulting from the crane collapse.

16. Wisconsin District Court of Appeals. (2003). "Patricia Wishcer v Mitsubishi Heavy Industries". []
 * Appeal court record of its decision in the case of the appeal of the civil trial.

17. WISN-12. (July 14, 2009). “Fatal Crane Accident 10 Years Ago At Miller Park Remember”. WISN-12, Milwaukee, WI. []
 * A retrospective look at the accident by a reporter who covered the accident when it occurred. Also includes a few quotes from people about their thoughts regarding the accident.

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= = Keywords: = crane collapse, Miller Park, wind loads, king pin failure, ground subsidence, OSHA, NIOSH