B1/2003Y Roof of multi-purpose hall collapsing at Mustasaari, on January 17, 2003

On January 17, 2003, at 16.51 hrs, an incident took place in Mustasaari municipality where the roof of a multi-purpose hall – designed among other things, for sports activities – collapsed above the spectator stand, over an area of more than 150 square meters.

At the time of the incident, there were football practices going on and individual sportsmen practising on the running track and elsewhere in the hall. Moreover there were in the stand some parents of children practising football on the ground. According to the estimates, altogether 130 persons were in the hall when the incident occurred.

First a noise was heard as coming from the roof. It was identified as the noise of snow falling down from the roof. Such falling down of snow in big rafts from the roofs of buildings is a regular yearly phenomenon, and hence the noise was quite familiar. The noise lasted for a few seconds and then a crash was heard and two separate beam lattices of steel in between the girders of the hall, collapsed. At the same time profiled steel sheet, insulation materials, plastic roof coating materials and about two truck-loads of snow penetrated into the hall.

Quite soon an ambulance arrived at the scene of the incident, as well as two rescue units of Mustasaari Rescue Service. Altogether 20 rescue service, ambulance and police units had been called to the scene of the incident. At first uncertainty prevailed as to whether someone had been buried by the collapsed structures and layers of snow. But soon it became evident that no personal injuries had resulted from the incident.

The direct cause of the collapsing of the roof was that the fastening brackets of the beam lattices mounted between the hall girders detached from their weldings. The fastening brackets used in the collapsed hall differed from the brackets in the earlier hall; in fact they had been designed insufficiently without due consideration of the loads they would have to endure. Actually the strength of the brackets had not been ensured by design calculations in the planning and design phase, and the plans had been checked only by the planner himself. Therefore this design error in the planning of the component detail could freely move on through the entire construction process and finally cause the roof to collapse.

Furthermore the relevant investigation disclosed shortcomings in the calculations of the loads to be endured by the beam lattices mounted between the girders, in the dimensioning of the structural components connected in the damaged joint, and in the overall bracing of the hall. These secondary shortcomings nevertheless had no direct impact on the collapsing of the roof.

This investigation report is included in the same publication as the investigation report on the collapsing of the roof of an exhibition hall in Jyväskylä, on February 1st, 2003. The corresponding recommendations based on both investigations and drawn up jointly, are included in a separate Recommendations Part of the publication referred to.

B1/2003Y Report (pdf, 1.11 Mt)

B1/2003Y Report (pdf, 0.68 Mt)

Recommendations

This Part III of the Investigation Report specifies the safety recommendations that are drawn up on the basis of the investigations on the building incidents on January 17, 2003 at Mustasaari, Finland, and on February 1, 2003 in Jyväskylä, Finland. The relevant Investigation Reports B 1/2003Y and B 2/2003Y have already been published.The corresponding safety recommendations envisioning a prevention of similar incidents are elaborated jointlyby the Accident Investigation Committees.

At Mustasaari on January 17, 2003, an incident occurred where the roof of a multipurpose hall, designed e.g. for sports activities, collapsed above the spectator stand over an area of about 150m². About two weeks later, another building incident took place where the roof of a recently built fair center collapsed over an area of about 2500m². This incident occurred on February 1, 2003 in Jyväskylä. The incidents generated no personal injury.

The incidents referred to reveal inadaquacies and deficiencies in the mutual cooperation within the construction organization. Therefore the Investigation Committees recommend that the organizations active in the building business develop such methods that ensure an adequate cooperation among the different parties engaged in a building project. Both of the incidents discussed display failing joints of the support constructions, and hence the Investigation Committees recommend that such methods ought to be designed and developed for the construction business that enable an identification of any safety critical details in a building project. In addition, the instructions for the prevention of a progressive collapse should be harmonized so as to enable the same instructions to be applicable to all building materials. This recommendation is based on the collapse of the Fair Center roof in Jyväskylä.

Furthermore the Investigation Committees recommend that the building inspection authorities and the labour protection authorities work in close cooperation, which was not the case in the construction of either one of the halls discussed. The Investigation Committees believe that building incidents could also be prevented by the creation of a database with information on incidents and hazardous situations in the building business – that is, by learning from errors.

To secure an appropriate quality standard of European planning and design instructions, it is recommended that a corresponding drawing up and maintenance system be generated so as to permit a rapid response to any safety critical error or shortcoming.

B1/2003Y Report (pdf, 1.3 Mt)