鋼梁接箱型柱之內橫隔斷裂試驗與有限元素模型分析研究

Fracture Tests and Finite Element Analysis of Diaphragm Connection in Steel Beam-to-Box Column Joints

吳忠哲(Chung-Che Wu) ； 李昭賢(Chao-Hsien Li) ； 蔡青宜(Ching-Yi Tsai) ； 林克強(Ker-Chun Lin) ； 莊勝智(Sheng-Jhih Jhuang) ； 蔡克銓(Keh-Chyuan Tsai)

《結構工程》 33卷4期 (2018/12) Pp. 29-61

https://doi.org/10.6849/SE.201812_33(4).0002

摘要

鋼箱型斷面柱構件具有雙強軸的特性，因此國內鋼建築結構中應用非常普遍。為傳遞梁端彎矩至柱構件，箱型柱內與梁翼同高處須配置與梁翼同厚的橫隔板。內橫隔板與柱板間焊接常使用電熱熔渣焊(Electro Slag Welding, ESW)工法，此種焊道施作便利且效率高，已大量使用於國內鋼結構製造廠。然而，ESW施做時的高入熱量恐導致其焊道及其周圍母材結晶過大與抗衝擊性質較差，此現象亦常導致梁柱發生非預期的脆性破壞。為避免ESW發生脆性破壞及量化ESW破壞之機制，本研究採用既有的鋼材斷裂預測模型，利用有限元素模型對試體進行斷裂預測分析。本研究進行三組梁柱接頭試驗，藉由變化試驗之載重歷時與ESW施工儲倉口截面形狀，探討試體破壞時機並驗證鋼材斷裂預測模型之可行性。實驗結果顯示證實累積塑性應變大小確實影響其破壞時機；ESW儲倉口截面由矩形變為喇叭口形時，顯示若增加ESW之熔透範圍可增加接頭試驗耐震性能。為應用斷裂預測模型，藉圓周刻痕拉伸(Circumferential Notched Tensile, CNT)試驗與有限元素模型分析，將所得之材料參數對ESW元件試驗與梁柱接頭試驗進行斷裂預測分析。分析結果顯示，ESW之幾何形狀及相對位置對於破壞時機影響甚大，因此顯示破壞預測分析與CNT試驗之可行性，以及焊道超音波檢測(Ultrasonic Test, UT)之重要性。

關鍵字

鋼箱型柱 ； 電熱熔渣焊 ； 鋼材斷裂預測模型 ； 鋼梁柱接頭 ； 有限元素分析 ； 圓周刻痕拉伸試驗 ； 電熱熔渣焊儲倉口

並列摘要

Steel box columns are widely used in steel building structures in Taiwan due to the strong axes in two directions. In order to transfer the beam end moment to column, diaphragm plates of the same thickness and elevations as beam flanges are usually welded inside box column. Electro-slag welding (ESW) process is typically used in attaching the diaphragms to column flanges. This ESW process has been widely used in steel beam-to-box column joints in Taiwan because of its' convenience and efficiency. However, ESW may increase the hardness of the welds and heat affected zones (HAZs), while reduce the Charpy-V Notch (CVN) strength in HAZ. This situation could cause the diaphragm to column flange weld to suffer premature fracture before a large plastic rotation is developed in beam-to-box column joints. In order to quantify the critical eccentricity and the effectiveness of predicting the fractures, this study utilizes the fracture prediction model and finite element model (FEM) analysis to correlate the test results. In this study, three beam-to-box column connection subassembly tests have been conducted with a different loading protocol or the shape of ESW chamber. Test results show that the fracture instances can be predicted based on the cumulative plastic deformation in the HAZs. Tests confirm that the possible fracture of the diaphragm to column flange welds can be mitigated by enlarging the chamber of the ESW. When the fracture prediction model is applied, the material parameters were firstly established from the Circumferential Notched Tensile (CNT) tests and FEM analysis. Subsequently, these parameters were used to predict the fractures observed in the ESW component tests and beam-to-box column connection subassembly tests. The fracture locations and instances can be reasonably well predicted by a suitable FEM model analysis. Thus, the effectiveness of CNT and the fracture model are confirmed. Analytical results also show fracture instances and locations are sensitive to the relative locations of the ESW and the beam flange. Thus, the importance of ultrasonic test in assuring the quality of the ESW is evident.

並列關鍵字

steel box column ； electro-slag welding ； heat affected zone ； fracture prediction model ； steel beam-to-box column connection ； finite element model analysis ； circumferential notched tensile test ； ultrasonic test