To ensure the safety of steel structure prefabricated cabin units in multi-compartment substations under transformer fires,a construction method utilizing autoclaved lightweight concrete slabs as additional fireproof layers for enclosure materials was proposed.This construction method,designed in the context of advancing industrialization in the building sector,allows for both prefabrication in factories and simple and rapid on-site assembly.Based on the hydrocarbon fire temperature-time curve,fire tests lasting 3 h were conducted on the composite wall panels used in existing multi-compartment substations and the proposed additional fireproof layer construction.The design of the five additional fireproof layer specimens took into account various parameters such as repeated fire exposure,hook bolt anchorage length,plate thickness,dry density grade,and panel joining method.Results indicated that due to the thermal bridge effect,the temperature rise at the back-fire surface measurement points of the composite wall panel specimens reached 180℃after 107 min,failing to meet the insulation requirements for the scenario.In contrast,the specimens with the proposed additional fireproof layer met both insulation and integrity requirements after 3 h of fire exposure,with the least favorable specimen's back-fire surface temperature rise peaking at 143.8℃.Additionally,the flush connection method demonstrates advantages over the staggered connection method in terms of insulation performance and construction convenience;shorter anchor length of hook bolts reduces the thermal bridge effect;higher dry density grade is beneficial for improving the fire resistance;the 100 mm thick ALC board already provides sufficient safety redundancy.
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