柱失效方程中荷載相關特性對承載力抗震設計可靠度的影響

蔣友寶 孫國衡 周成玉 張建仁

摘要：以豎向荷載和水平地震作用組合下的鋼筋混凝土柱和鋼柱為對象，研究了失效方程中荷載相關特性對柱承載力抗震可靠性的影響。根據現行《混凝土結構設計規范》和《鋼結構設計規范》分析了不同柱彎矩軸力相關曲線的特性。結合多個框架結構實例，對比了柱失效方程中荷載相關曲線與規范考慮情形的異同。實例分析表明：水平地震和豎向荷載組合作用下，小偏壓RC柱和工字型鋼柱的荷載相關曲線與規范考慮的情形較為符合，均近似為負相關的直線；水平地震和豎向荷載組合作用下，大偏壓RC柱的荷載相關曲線則與規范考慮的情形有較大出入，存在明顯的正相關段部分。在此基礎上，考慮失效方程復雜特性，依據已有的荷載和抗力變量概率模型，采用Monte Carlo法分析了水平地震和豎向荷載組合作用下柱的可靠性。結果表明：鋼柱和小偏壓RC柱的承載力抗震可靠度隨軸壓力荷載效應比值的變化幅度較小，與規范模式計算結果較接近；大偏壓RC柱的承載力抗震可靠度隨軸壓力荷載效應比值的變化會有較大幅度波動，與規范模式計算結果差異較大；當軸壓力荷載效應比值為負時，大偏壓RC柱的承載力抗震可靠度會低于規范計算值較多，現行柱可靠性設計方法會偏于不安全。

關鍵詞：結構設計；可靠度；柱抗震承載力；荷載相關曲線；荷載效應比值

中圖分類號：TU312.1

文獻標志碼：A 文章編號：1674-4764（2016）03-0025-10

Abstract： The concrete and steel columns subjected to a combination of vertical load and horizontal earthquake action are used to study the influence of correlations between loads in failure function on design reliability of seismic capacity of columns. According to the current Code for Design of Concrete Structures and Code for Design of Steel Structures， the correlations between moment and axial force are analyzed for different columns. Through comparisons of different columns in several frame structures， the similarities and differences are investigated between the load interaction curves and those considered in codes. It is indicated that the load interaction curves under this combination match well with those considered in codes for RC columns with compression failure and steel columns with I-shaped section， and they are all negatively correlated straight lines approximately； the load interaction curve of RC column with tension failure is largely different from that considered in codes， and obviously has some positive correlation parts. Based the complex failure function， reliability of columns under this combination is analyzed with the Monte Carlo method and current statistics of load and resistance. The results show that： （1）the reliability indexes of seismic capacity vary lightly with different load effect ratios based on axial force for steel columns and RC columns with compression failure， and are close to those based on the codes； （2）the reliability indexes vary greatly with different load effect ratios based on axial force for RC columns with tension failure， and are also largely different from those based on the codes； （3）the reliability indexes are lower than those based on the codes for RC columns with tension failure when the load effect ratio based on axial force is negative， as a consequence， the current reliability-based design method of columns may be unsafe in this case.

Keywords：structural design； reliability； seismic capacity of column； interaction curve of loads； load effect ratio

中國近年接連發生了幾次地震災害，如2008年汶川地震、2010年玉樹地震等。……