鋼構建築在火災中，鋼材強度與勁度隨溫度上升而快速衰減，結構易在數十分鐘內喪失承載力並發生漸進倒塌，是火場重建的重要對象。然而，既有火害分析多將火災與結構視為單向流程：先以標準火災曲線給定受熱條件，再分析結構反應，未考慮倒塌後的幾何改變會反過來影響火勢發展。此一單向假設，使重建難以反映真實火災中結構與火場相互演變的過程。 為此，本研究建立一套整合火災動力學模擬、結構熱傳分析、高溫失效判斷與幾何回饋的火場重建框架，其核心為雙向耦合的迭代機制：每一輪由火場受熱驅動結構失效，失效後的倒塌幾何再回饋至下一輪火災模擬，使火勢能反映倒塌所造成的開口擴大與阻擋改變；當關鍵構件失效或失效比例達門檻時，即觸發下一輪迭代，並將前一輪的火場狀態延續帶入，維持多輪之間的物理連續性。 以2015年新屋保齡球館火災為案例，框架重現了自局部受熱、漸進倒塌至鋼構架崩塌的完整因果鏈。分析顯示，結構倒塌所形成的開口確實改變了後續火勢的通風與煙流路徑，最終產生之倒塌單元多集中於起火區附近，證實火災與結構之間存在雙向耦合，而非單向的火災至結構關係。此雙向耦合的迭代框架為本研究的核心貢獻，有別於既有的單向流程，並可作為事故調查、消防訓練與建築防火設計改善的科學基礎。;In fire， the strength and stiffness of steel degrade rapidly as temperature rises， so steel-framed buildings can lose load-bearing capacity within tens of minutes and undergo progressive collapse， making them an important subject for fire-scene reconstruction. Existing structural-fire analyses， however， largely treat the fire and the structure as a one-way process: the thermal exposure is prescribed from standard fire curves and the structural response is then analyzed， without accounting for the way the post-collapse change in geometry in turn alters the development of the fire. This one-way assumption makes it difficult for a reconstruction to capture the mutual evolution of the structure and the fire environment that occurs in a real fire. To address this， the present study develops a fire-scene reconstruction framework that integrates fire dynamics simulation， structural heat transfer analysis， elevated-temperature failure assessment， and geometry feedback. At its core is a bidirectionally coupled iterative mechanism: in each round the fire-driven thermal exposure produces structural failure， and the resulting post-collapse geometry is fed back into the next round of fire simulation， so that the fire can reflect the enlarged openings and altered obstructions caused by the collapse. When a critical member fails or the failure ratio reaches a prescribed threshold， the next round is triggered， and the fire-environment state from the previous round is carried forward， maintaining physical continuity across successive rounds. Using the 2015 Xinwu Bowling Alley fire as a case study， the framework reproduces the complete causal chain from localized heating and progressive collapse to failure of the steel frame. The analysis shows that the openings formed by structural collapse redirect the ventilation and smoke-transport paths of the subsequent fire and drove the progressive collapse， where collapse units are concentrated near the ignition zone， confirming a two-way coupling between fire and structure rather than a one-way fire-to-structure relationship. This bidirectionally coupled iterative framework， distinct from existing one-way pipelines， is the central contribution of this study， and it can serve as a scientific basis for accident investigation， firefighter training， and improvements to building fire-safety design.
