胶粉掺量对橡胶改性沥青低温性能的影响

通过弯曲梁流变(BBR)试验分析不同掺量橡胶改性沥青以及胶粉复合SBS改性沥青的低温性能。结果显示,随着胶粉掺量的增加,橡胶改性沥青的劲度模量逐渐下降,蠕变速率逐渐增加,沥青逐渐变软,低温变形以及应力消散能力逐渐提升,低温性能逐渐提升;当胶粉掺量达到18%时,其低温PG分级相较于基质沥青可提升一个等级。对于胶粉复合SBS改性沥青,随着SBS的加入,橡胶改性沥青的劲度模量稍有提高,然而蠕变速率也增加,说明加入SBS使得橡胶改性沥青变硬的同时,也提升了其低温变形能力以及应力消散能力;当胶粉掺量从5%增加至18%时,其低温劲度模量降低约50%。

Research on Limiting Value of Interlayer Displacement Angle of Underground Structure in "Repairable" State

In China, two-stage seismic design is generally adopted for the underground structures. The target of seismic fortification is generally "not damage in moderate earthquake, repairable in major earthquake", which is higher than ground structures. The performance index of "repairable in major earthquake" in the specification is expressed as the interlayer displacement angle, but the basis for determining the limiting value of interlayer displacement angle is not clear. Taking this seismic performance index of the underground structure in the "repairable" state as the research object, firstly, the limiting values of interlayer displacement angle in the "repairable" state in the common seismic design specifications at home and abroad are compared, and the reasons for the difference between the performance indexes of the different specifications are analyzed. Then, according to the statistic results of pseudo static tests of frame structures and shear wall structures at home and abroad, the rationality of the limiting value of interlayer displacement angle in "repairable" state in the seismic specification of China is evaluated. Finally, taking a metro station and a ground frame structure as the examples, the laws of damage and failure of the underground and ground structures are compared and studied by pushover analysis. The difference of the limiting values of interlayer displacement angle in the "repairable" state between the underground structure and the ground structure is compared. The research results can be referred for the revision of underground seismic design specification.