圆高强钢管UHPC梁抗弯性能研究

以含钢率和套箍系数为参数，开展5根圆高强钢管超高性能混凝土(UHPC)梁和2根圆普通钢管UHPC对比梁的纯弯试验；而后，采用已验证的有限元模型，对套箍系数进行了参数分析。试验研究表明，高强钢管UHPC梁发生延性破坏，组合截面满足平截面假定，受压区高强钢管对核心UHPC的套箍作用应被考虑。较普通强度的钢管，高强钢管能更及时地约束UHPC的横向膨胀。随着套箍系数的增加，钢管混凝土梁达抗弯承载力时，中性轴趋近截面中线，受拉区钢管应力减小，受压区钢管和混凝土的应力则增大。承载力计算分析发现，对于高强钢管UHPC梁而言，现有中国规范GB50936?2014的实用计算方法存在不准确且离散性较大等问题，为此该文提出了新实用计算方法。

STUDY ON VERTICAL SEISMIC DESIGN SPECTRA OF NEAR FAULT AREA BASED ON CHINESE CODE

Due to the lack of vertical seismic design spectra for the structural design in near-fault regions, the near-fault vertical seismic design spectra are studied, which took the near-fault vertical ground motions as the research object and the format is compatible to the code for the building seismic design in China. The vertical components of 198 near-fault pulse-like ground motions are used to develop the near-fault response spectra. Results given by the comparison of the near-fault response spectra and code-specific near-fault design spectra in China show that the effects of near-fault vertical ground motion are not fully considered in Chinese seismic design code. What the amplitudes of the code-specific near-fault design spectra are smaller than that of the response one in some periods leads to difficulties in the safety of structures in near-fault regions. According to the results, a reasonable near-fault vertical seismic design spectrum, based on the code-specific seismic design spectra in China, is proposed with a spectral amplitude amplification coefficient of 1.5, restricted characteristic periods to no less than 0.40 s for frequent earthquake and 0.45 s for rare earthquake and a decreased attenuation coefficient. The proposed seismic design spectra are useful for the design of structures in near-fault regions.