本研究以一棟鋼筋混凝土（RC）構架廠房為分析對象，針對兩台大型離心式壓縮機配置於建築物一樓筏基板上方之情境，系統性地進行靜力安全性評估與動力反應分析。在靜力設計層面，依據 ACI 318-19 對筏基板進行土壤承載力、彎矩強度及衝切強度之檢核；在動力設計層面，依據 ACI 351.3R-18 及 ISO 20816-3 進行頻率避振校核、軸承位置振動反應及筏基板頂面振動反應之評估。
在建模方案的發展上，本研究首先觀察壓縮機之實體外觀與細部構造，發現其在結構上可區分為上方之各旋轉組件（馬達、齒輪組、轉軸）與下方之空心箱型承載基座兩個層次。基於此一構造特徵，本研究建立「長方形鋼製模型」作為第一種建模方案：以 A36 鋼材板元素模擬壓縮機下方箱型基座之幾何形態（尺寸 3 m × 8 m × 2 m），保留其對頂層樓板所貢獻之局部幾何剛度，靜態自重以均佈載重方式施加於模型頂面，並以等效正弦激振力取代上方各旋轉組件之幾何建模，直接施加於對應軸承位置之節點。考量工程實務中對快速評估工具之需求，本研究進一步建立「剛性連結模型」作為第二種建模方案：將壓縮機整體視為無限剛性體，靜態自重以節點載重方式施加於主節點，並以剛性約束集中質量並傳遞動態力，此方案符合 ACI 351.3R-18 規範對機器基礎簡化建模所允許之假設型式，建模程序簡便且計算效率高。動態不平衡力依據 ISO 1940/ANSI S2.19 G6.3 平衡品質等級計算，放大係數設定為 2.0，兩台設備採同相位同時啟動以涵蓋最不利之疊加情境。地基邊界條件採用 Winkler 彈性基礎模型，依黏土地層特性設定土壤彈簧剛度參數。
靜力安全性檢核結果顯示，土壤承載力、X 向與 Y 向彎矩強度及衝切強度之需求承載比（DCR）分別為 0.73、0.846、0.864 及 0.058，均符合 ACI 318-19 之規範要求，確認筏基板對兩台壓縮機之靜態集中載重具備充裕之承載能力。特徵值分析結果顯示，兩種模型之前三階主振型頻率差值均在 0.0064 Hz 以內，且遠低於壓縮機運轉頻率危險區間下限 22.66 Hz，均判定為 Low Tuned 結構。動力歷時分析結果顯示，低速組件（Motor、Bull Gear）之軸承位置最大水平位移均落於 ACI 351.3R-18 之 A 區（No faults）；高速組件（LS、HS）之振動速度 RMS 值均位於 ISO 20816-3 之 Zone Green；筏基板頂面之最大振動位移（Motor 2.553 μm、Bull Gear 1.605 μm）依 Reiher-Meister Chart 判定為「Barely Noticeable to Persons」等級，所有檢核項目均通過，確認此配置方案在靜動力雙重層面之工程可行性。
兩種建模方案之比較結果顯示，前三階主振型頻率差值均在 0.0064 Hz 以內，軸承位置與筏基板頂面之振動反應差異亦極小，所有規範安全判定結論完全一致。就建模特性而言，剛性連結模型建模效率高，適合作為設計初期之快速規範合規性篩查工具；長方形鋼製模型因保留壓縮機基座之幾何剛度與連續質量分布，物理描述較為完整，可作為詳細設計階段之輔助參考。惟須指出，兩種模型結論一致，並不足以推論兩者均精確反映真實結構行為，此一一致性亦可能係兩種假設在本研究特定載重條件下均足夠保守所致；在缺乏現場量測數據校核之前提下，兩模型之絕對預測精度仍待後續實驗驗證確立，此為本研究之主要方法論限制。

This study investigates the static and dynamic behavior of two large centrifugal compressors installed directly above the first-floor raft foundation slab of a reinforced concrete (RC) industrial building. Two finite element modeling approaches were developed and analyzed using MIDAS Gen software, with static safety verified against ACI 318-19 and dynamic responses evaluated against ACI 351.3R-18 and ISO 20816-3 standards. The development of the two modeling approaches was motivated by direct observation of the compressor's physical configuration. The machine can be structurally decomposed into two distinct layers: the upper rotating components (motor, gear train, and rotor shafts) responsible for power transmission, and the lower hollow box-type base frame that supports all rotating parts and serves as the force transfer interface with the foundation slab. Based on this structural characteristic, the Rectangular Steel Model was first established as the more physically representative approach: A36 steel plate elements were used to replicate the geometry of the lower base frame (3 m × 8 m × 2 m), preserving its local geometric stiffness contribution to the raft slab, with static self-weight applied as a uniformly distributed load over the top surface, while the dynamic unbalance forces of each rotating component were applied as equivalent sinusoidal excitation functions directly at the corresponding bearing nodes. To further explore the reliability of a more highly simplified approach commonly adopted in engineering practice, the Rigid Link Model was subsequently introduced: the entire compressor is treated as an infinitely rigid body, with static self-weight applied as a nodal load and mass concentrated at master nodes, with forces transmitted to slave nodes through rigid constraints. This approach conforms to the simplified modeling assumptions permitted by ACI 351.3R-18 and offers significantly higher modeling efficiency. Static safety assessment results show that the demand-to-capacity ratios (DCR) for soil bearing capacity, flexural strength (X and Y directions), and punching shear strength are 0.73, 0.846, 0.864, and 0.058, respectively, all satisfying ACI 318-19 requirements. Eigenvalue analysis results indicate that the dominant modal frequencies of both models fall well below the compressor's operating frequency danger zone, confirming a Low Tuned structural classification, with differences between the two models within 0.0064 Hz for the first three modes. Time-history analysis results show that maximum horizontal displacements at bearing locations for low-speed components fall within Zone A (No faults) of ACI 351.3R-18, and RMS vibration velocity values for high-speed components remain within ISO 20816-3 Zone Green. Maximum displacements at the raft slab surface (2.553 μm for Motor, 1.605 μm for Bull Gear) are classified as "Barely Noticeable to Persons" according to the Reiher-Meister Chart, and all code-stipulated assessment criteria are satisfied. Regarding the modeling comparison, both approaches yield completely consistent safety determinations across all code-stipulated criteria. However, this consistency alone does not confirm that either model precisely captures true structural behavior, since both sets of assumptions may simply be sufficiently conservative under the specific loading conditions considered; the absolute predictive accuracy of both models remains subject to field measurement validation, which constitutes the main limitation of this study.

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