188宝金博页面版

www.springer.com/journal/13296International Journal of Steel Structures 15(1): 17-30 (2015)DOI 10.1007/s13296-015-3002-8Influencing Factors Analysis of Degradation andDamage and the Effect on Steel FrameMeng Wang 1, *, Yongjiu Shi 2 , Yuanqing Wang 2 , and Weiguo Yang 11 School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, China2 Department of Civil Engineering, Tsinghua University, Beijing, 100084, ChinaAbstractIn order to discuss the influencing factors of damage and degradation and the effect on steel frame subject to strongearthquakes, firstly, a constitutive model was proposed for 3D finite element models to calculate the seismic behaviors of steelframe more accurately. The model was proved correct and applicable due to typical quasi-static tests. Then, based on theverified model, the damage and degradation factors were discussed by parametric analyses, including the panel zone, loadinghistory, loading amplitude, the width to thickness ratio and yield strength. The cumulative damage phenomena of steel frameconnections were further studied and the degradation distribution curve was obtained. Finally, the traditional beam elementmodel and proposed shell element model of structure were established by ABAQUS for time history analysis. The effect ofdamage and degradation on seismic behaviors of steel frames were compared and discussed. The tests and analysis resultsrevealed that: panel zone strength, loading amplitude and width-thickness ratios of plates had significant impact on damage anddegradation behaviors and failure modes of connections. Premature weld cracking would lead to earlier damage and degradationunder “strong to weak” earthquake, which would seriously affect the overall mechanical properties of the structure. Once localbuckling caused damage, the results of the beam element model and accurate shell element model were remarkably different.Beam element model without considering damage and degradation underestimated the structural deformations, which shouldbe paid more attention for design safety.Keywords: steel frame, influencing factors, degradation and damage behaviors, constitutive model, time history analysis1. IntroductionAt present, two research fields have been focused onfor earthquake failure analyses of structures, which arethe monotonic peak failure study and accumulative damagefailure study (Li, 2002). The existing seismic analyses werewidely based on the former without considering the effectof accumulative damage. However, with the frequentoccurrence of strong earthquakes, the devastating earthquakes(e.g. Wenchuan and Yushu in China, Sendai in Japan,etc.) have brought huge economic losses and threats oflife safety. The impact of the aftershocks sometimes wasimmensely greater than the one caused by main earthquake,indicating the disasters of seismic cumulative damage andcollapse occurred more and more often (Wang et al.,2009). Therefore, the studies of the structure cumulativedamage have been concerned gradually.An interactive process exists in cumulative damage andthe seismic response of structures (see the cycle in Fig.1), containing two core issues: 1) How much damage thestructure subjected to the earthquake would impact onlocal region? 2) How the local damage would affect thebehaviors of the overall structure? For the first question,the level of structural damage is not only proportional tothe earthquake intensity but also is related with thecharacteristics of the structure itself, the loading time andloading patterns. In order to study the influencing factorsof cumulative damage, a large amount of test data areneeded. However, there were not enough tests carried outfor damage and degradation of members and connections,and it was difficult to conduct the parametric analyses ofdamage only by test method. Therefore, it is necessary todevelop the effective parametric analyses using moreactual finite element method. For the second question, thedamage and degradation of members or connection regionswould directly affect and change the overall seismicperformances of structures, resulting in redistribution ofinternal forces. Due to the limits of experimental techniquesReceived April 10, 2012; accepted June 30, 2014;published online March 31, 2015© KSSC and Springer 2015*Corresponding authorTel: +86-10-62792330; Fax: +86-10-62782708E-mail: wangmeng1117@gmail.com