火害前後之六層樓鋼造抗彎構架模擬與耐震分析

Abstract

當鋼結構發生火災時，其受熱區在冷卻後會發生材料性質上的改變，還可能導致構件的嚴重變形。許多研究顯示，火害後對於鋼材材料性質的影響中，降伏強度最為顯著。然而進行火害相關等研究，不但試驗成本耗費過高，還可能導致人身安全的危險。除此之外，若還要考慮地震作用下的影響，將使得試驗難度大幅度的提升。因此找到一個精確理想的建模方法，用來模擬火災後鋼結構受到地震動力的影響，是我們首要完成的目標之一。 首先，本研究使用Sepulveda（2024）於台灣國家地震研究中心15米高反力牆進行的複合模擬試驗，作為未受火害構架的模型依據。該實尺寸試體是由四跨六層樓抗彎構架中，一二樓的構件所組成。其他部分則使用Opensees軟體進行數值計算。試驗使用之構件皆使用熱軋H型鋼製作。接著，本研究使用PISA3D和ETABS軟體用來模擬該試驗結果。背骨曲線為一種預測構件在塑鉸處行為的方法，尤其是因局部屈曲引起塑鉸達極限強度後之行為，會有強度遞減的現象產生。如今，使用數值軟體計算此強度遞減行為是一項挑戰。然而，隨著分析技術的進步，本研究嘗試將背骨曲線輸入至模型桿件的塑鉸中，並進行非線性動力歷時分析。 最後，使此模型在靜態和動態分析結果中，皆接近Sepulveda（2024）複合模擬試驗結果，即可假設火害後對整體構架模型造成的影響，本研究僅改變火害區域之鋼材材料降伏強度。此折減方法已被許多研究使用與證實。本研究火災位置為整個一二樓層，並將DBE和MCE級別的近斷層地震輸入於此模型中，以診斷不同火災後情境的結果。結果顯示，火害後導致背骨曲線參數的折減，可以預測構件於動力歷時中的遲滯行為，並於火害與地震等級交互作用之下，造成抗彎構架在基底剪力以及層間位移上的影響。

Post-fire effect in the steel structure change the properties of the material and cause the deformation of the steel component. Many research indicated that significant effect is yield strength. But post-fire test is very expensive and dangerous. Furthermore, considering the earthquake after the fire situation. So the effective way to find a precisely ideal modeling method to simulate the post-fire effect in the steel structure are our most important thing. First of all, this study’s model use Sepulveda（2024）hybrid simulated test（HS）at the NCREE lab. This test specimen is a full-scale subassemblage of four bay six story special moment frame. This building is all composed of deep wide flange steel section. Secondly, the study aim to construct numerical model to simulate the result from HS test. Backbone curve is one way to predict the component behavior at the hinge response. The special part is degrading behavior cause by the local buckling Nowaday, use software to calculate the degrading behavior in model is challenging. However, the technique is more and more progressive, so this research try to use backbone curve input into the numerical software in the hinge and run the nonlinear dynamic time history analysis. Once find the most appropriate model that static and dynamic result fit the result from Sepulveda（2024）HS test. Aim to assume the post-fire model is to change the yielding strength. That way is confirm by many research that discuss below. The fire position is the whole first and second story, and input DBE and MCE level near-fault earthquake into this model to diagnose the result from different post-fire scenario. The result show the backbone curve parameter can predict the collapse behavior of steel structure that affect by post-fire.