基于项目组合管理理论的研发项目管理流程研究

运用美国太平洋地震工程研究中心开发的OpenSees软件，采用纤维梁柱单元建立圆柱式节段桥墩模型，进行拟静力加载过程分析，研究预应力筋布置形式和使用耗能钢筋及钢套管加固对桥墩抗震性能的影响。结果表明：预应力钢束均匀布置在四周比布置在中心具有更好的抗震性能，在墩底增设钢套管时，对节段桥墩抗震性能的提高帮助不大；钢套管厚度的变化对桥墩拟静力性能影响不大；在墩底设置耗能钢筋能改善桥墩的抗震性能，耗能钢筋长度以穿过塑性铰区为宜；随着耗能钢筋配筋率的增加，空心节段桥墩强度退化加快，延性能力减弱；对耗能钢筋配筋率较高而耗能能力不好的节段桥墩，可通过降低耗能钢筋屈服强度有效延缓其强度退化，提高延性能力。

Research on R&D Project Management Process Based on Project Portfolio Management Theory

The model of segmental precast bridge piers with circular hollow section is set up utilizing fiber beam column element with the OpenSees program developed by the Pacific Earthquake Engineering Research Center of the U.S. to analyze the pseudo static behavior and investigate the effect of different configuration of strands and addition of steel tubes and energy dissipation bar in plastic hinge zone on seismic performance of piers. The results show that: piers with strands configuring in the peripheral direction uniformly have better seismic performance than those with strands configuring in centre; steel tubes in plastic hinge zone can effectively prevent early spalling of cover concrete, and the thickness of steel tubes has little influence on seismic performance of piers; energy dissipation bar in plastic hinge zone can improve the seismic performance of bridge columns, and energy dissipation bar with the length through plastic hinge zone is advisable. The strength degradation speeds up and ductile ability weakens with the increase of energy dissipation bar''s ratio, and reduction of yield strength of energy dissipation bars can effectively delay strength degradation and improve ductile ability of piers.