Assessment of damage to the ceilings and sprinkler downpipes of an industrial plant from the 2012 7.6Mw Sámara earthquake in Costa Rica
This paper presents field observations on the performance of ceilings and sprinkler downpipes in a manufacturing facility 30 km west of San José, Costa Rica, during the Mw 7.6 Sámara earthquake on September 5th, 2012. The ground motion intensity was MM VI at the site and IX near the epicentre, 137 km away. The structure is a typical single-storey industrial steel gable frame with a combination of braces and portal frames in the short spans, and houses injection moulding, laboratories, clean rooms, a warehouse and office facilities. There was no structural damage observed and the production facilities were operational immediately after the event, while the office area and cafeteria required repairs due to fallen ceiling tiles. Focus is on performance of the ceilings and the sprinklers downpipes in the office and cafeteria area, and the damage inflicted by sprinkler heads on ceiling tiles. It was observed that the lateral restraints used in pipe and ceiling bracing did not prevent some sprinkler heads boring into the ceilings and enlarging the original circular perforation. The enlargement was several centimetres long and it was observed in clusters rather than isolated cases. One sprinkler drop broke at the upper thread causing water damage to the cafeteria ceiling. A large proportion of the perimeter ceiling tiles and tees in the open-plan office area fell down, while little damage was observed in smaller rooms. The drawings called for closely-spaced bi-directional “V” bracing of the Tee grid with galvanised wire, but these were found during the survey to be much further apart with most hangers being fairly vertical. A comparison between as-drawn, as-built and state-of-the-art code details is undertaken, and the observed damage is compared with expected damage using state-of-the-art fragility curves. Finally, conclusions about possible improvements are made.
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