B2/2003Y Fair center roof collapsing in Jyväskylä, on 1 February, 2003
On Saturday February 1st, 2003, at 9.39 hours, an incident took place in Jyväskylä, Finland, where a Fair Center roof collapsed over an area of about 2,500 m², with the exterior wall also collapsing over a width of about 20 meters. The building was quite new with its B hall of altogether 7,766 m² having only been opened and introduced into service about two weeks earlier.
The previous day, a training and education fair organized in the Fair Center had ended, and on Saturday morning there were 12 Fair Center employees and exhibitors’ representatives stripping the stands in the B hall. Suddenly a loud bang was heard from the roof of the hall, and some of the people inside went to see where the noise came from. Then someone discovered that one of the tie beams of the roof truss pair made of laminated timber had broken in its narrow part close to the end of the roof truss. The observers understood that the roof would possibly collapse and they yelled to the others to leave the hall. In an estimated two minutes time, the roof truss pair referred to, as well as the three following roof truss pairs and the roof elements supported by them, collapsed and fell down. All people had managed to leave the hall and no-one was injured.
Already before the collapse, one person in the hall had called the Emergency Exchange. The collapse actually took place during that call, and hence the Emergency Exchange was immediately informed of the incident. Numerous rescue units and ambulances were called out to the scene of the incident. In about half an hour it had been ascertained that there was no-one left buried under the ruins.
The collapsing roof trusses made of laminated timber featured a length of 55 meters which is exceptionally great. The trusses had been mounted in the plant by an interconnection of the laminated timber parts by dowel joints. In the dowel joints two steel plates penetrated the timber and 4 to 48 steel dowels – as depending on the size of the joint - had been installed perpendicularly to them. The truss pair consisted of two identic trusses interconnected in parallel by screws.
Already at the initial phase of the investigation of the incident, it became evident that according to the eye-witnesses, one joint of the truss of the roof truss pair having first collapsed, only had 7 dowels while according to the plans, their number should have been 33. In fact the collapse commenced as caused by this quality control negligence by the truss manufacturer. At the time of the incident the snow load was measured as being about 25% (i.e. 50 kg/m²) of the load having served as the basis in the planning, and only one truss of the truss pair displayed missing dowels. Hence the damage ought to have been limited only to one of the trusses. But a collapse was generated and it proceeded as the major dowel joints yielded in a cleavage fracture, that is, the joint section had torn off the timber along the outer rows of the dowel group. The European planning instructions implemented in the planning of the trusses, fail to consider such a type of breaking, and therefore the strength of the biggest joints only featured about 50% of the planned rates. According to the investigation commission, the errors discovered in the instructions imply deficiencies in the drawing up of the norms, in their adoption and implementation, and in the communication of their detection. Already several years before the incident, the errors had in fact been corrected in a more recent draft of the instructions and the problematic issues had been discussed in a Finnish technical journal. Hence the errors were well known by a limited circle of experts.
Jointly with the investigation commission studying the collapsing of the roof of a multipurpose hall at Mustasaari on January 17, 2003, the investigation commission drew up recommendations that target a prevention of such incidents in the future. The recommendations are presented in a separate part to be published simultaneously with both of the relevant Investigation Reports.
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.