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*Collapse of a Warehouse [#x7705cd2] **1.Field of application [#t9b854df] >A single-storey warehouse hall. **2.Circumstances of Repair and Detail of loading [#d60ca787] >Collapse was under construction. When the concrete mix was conveyed to the roof by a pump situated outside the building, the west part of the roof collapsed under the weight of the concrete. **3.Types of structure [#e0ecd8fe] >This hall was composed of 70 x 30m in plan ([[Fig.1>#fig1]]) and about 12m high with internal built-in structure. Its principal load-bearing structure consisted of reinforced concrete columns, steel primary beams and reinforced concrete and steel diaphragms with steel roof trusses span 30m and were designed as a simple system with alternating diagonals and verticals, spaced at 3m. The columns and roof trusses were usually spaced at 6m, with the exception of the west part of the hall where the spacing was 5.5m and then 8.5. The truss was made of box chords individually welded of 14mm thick steel plate with a single continuous fillet welds only 4mm wide. Moreover, the stresses in the welds were increased by the effect of additional shearing forces and moments due to eccentric jointing of the diagonals called for in the design. According to the design, the truss bars did not intersect in the customary manner in the neutral axis of the lower or upper chords, but in the axis of their lower ([[Fig.2>#fig2]]) and upper faces respectively. &br; CENTER:&aname(fig1);&attachref(Wareho33.gif);&br; &br; &br; CENTER:&aname(fig2);&attachref(Wareho34.gif);&br; &br; CENTER:Fig.2 Intersection of diagonals on the lower chord. &br; **4.Description of damage [#rd80de7c] >The truss adjacent was heavily deformed, but did not collapse. However, the geometry of the adjacent bay was heavily disturbed, as a result of which all roof panels in the three west bays collapsed, and the adjacent frame members and outside wall panels were distorted. The direct cause of the collapse was the failure of the poor fillet welds connecting the individual parts of the box section truss and the connection detail between the first tensile diagonal and the chords, which lacked gusset plates ([[Fig.3>#fig3]]). The welds were unable to transfer the force from the diagonal to the webs of the closed box section. &br; CENTER:&aname(fig3);&attachref(Wareho35.gif);&br; &br; CENTER:Fig.3 Unsatisfactory fillet welds caused the collapse. &br; **5.Repair method applied [#rfba6c98] >The centerlines of the diagonals did not intersect on the lower face of the lower chord nor the upper face of the upper chord, but at a distance of several centimeters below the lower chord ([[Fig.4>#fig4]]). Therefore, the diagonals had been shortened and re-welded to facilitate mounting of the trusses on their supports. Additionally, damaged members of the frame structure needed to be replaced and the damaged trusses in the last two west rows had to be accurately designed, manufactured and assembled. The gussets of two new trusses were fitted with plates to transfer the forces from the diagonals to the chord ([[Fig.5>#fig5]]). The trusses were provided with additional diagonals intersecting with the existing diagonals in the neutral axis of the lower chord ([[Fig.6>#fig7]] and [[7>#fig7]]). The roof structure was also provided with additional wind bracing in the form of a vertical diaphragm in the longitudinal axis of the hall and two horizontal diaphragms in the roof plane. >The centerlines of the diagonals did not intersect on the lower face of the lower chord nor the upper face of the upper chord, but at a distance of several centimeters below the lower chord ([[Fig.4>#fig4]]). Therefore, the diagonals had been shortened and re-welded to facilitate mounting of the trusses on their supports. Additionally, damaged members of the frame structure needed to be replaced and the damaged trusses in the last two west rows had to be accurately designed, manufactured and assembled. The gussets of two new trusses were fitted with plates to transfer the forces from the diagonals to the chord ([[Fig.5>#fig5]]). The trusses were provided with additional diagonals intersecting with the existing diagonals in the neutral axis of the lower chord ([[Fig.6>#fig6]] and [[7>#fig7]]). The roof structure was also provided with additional wind bracing in the form of a vertical diaphragm in the longitudinal axis of the hall and two horizontal diaphragms in the roof plane. &br; CENTER:&aname(fig4);&attachref(Wareho36.gif);&br; &br; &br; CENTER:&aname(fig5);&attachref(Wareho37.gif);&br; &br; &br; CENTER:&aname(fig6);&attachref(Wareho38.gif);&br; &br; &br; CENTER:&aname(fig7);&attachref(Wareho39.gif);&br; &br; CENTER:Fig.7 Undamaged trusses provided with additional diagonals. &br; **Reference [#td8c1779] >Kratene J., Krejci H., Collapse of a Warehouse and Its Repair, '''Structural Engineering International''', vol. 5, No. 3, 1995. &br; &br;
