To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element i...To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity （or supply） of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.展开更多
Triblock copolymer of poly（p-dioxanone） and polyethylene glycol end-capped with pyrene moieties（（Py-PPDO）_2-b-PEG） was synthesized and used as modifier for multi-wall carbon nanotubes（MWCNTs）.Nano-aggregates（...Triblock copolymer of poly（p-dioxanone） and polyethylene glycol end-capped with pyrene moieties（（Py-PPDO）_2-b-PEG） was synthesized and used as modifier for multi-wall carbon nanotubes（MWCNTs）.Nano-aggregates（（Py-PPDO）_2-b-PEG@MWCNTs） with shish-kebab like partially wrapped morphology and very good stability were obtained by incorporating the copolymer with MWCNTs.The bare MWCNT sections of（Py-PPDO）_2-b-PEG@MWCNTs were able to induce n-n interactions with graphene（GE） and resulted in a novel GE/（Py-PPDO）_2-b-PEG@MWCNTs hybrid.The dispersity of GE in solution or polymer matrix was therefore greatly improved.The PCL nanocomposite films using GE/（Py-PPDO）_2-bPEG@MWCNTs as hybrid nanofiller exhibited obviously improved mechanical properties especially at very low hybrid nanofiller content.The influence of the nanofiller content and feed ratio of GE/MWCNTs on the mechanical properties of composites films was evaluated.When the feed ratio of GE to MWCNTs is 2：8 and the total loading of nanofiller is only 0.01 wt%,the tensile strength of the composite film increased by 163%and the elongation at break increased by 17% compared to those of neat PCL These results can be attributed to fine dispersion of the nanofillers in PCL matrix and the hybrid interactions between GE and MWCNTs.Therefore,this work provides a novel method for preparing polymer nanocomposites with high mechanical performance and low nanofiller loading.展开更多
基金Supported by the Natural Science Foundation of China and the Natural Science Foundation of Guangxi Autonomous Region (No0249001 )the Graduate lnnovation Foundation of Guangxi Autonomous Region
基金National Natural Science Foundation of China Under Grant No.50878147
文摘To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity （or supply） of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.
基金financially supported by the National Natural Science Foundation of China(No.21474066)the Foundation for Young Scientists of State Key Laboratory of Polymer Materials Engineering(No.sklpme2014-3-09)
文摘Triblock copolymer of poly（p-dioxanone） and polyethylene glycol end-capped with pyrene moieties（（Py-PPDO）_2-b-PEG） was synthesized and used as modifier for multi-wall carbon nanotubes（MWCNTs）.Nano-aggregates（（Py-PPDO）_2-b-PEG@MWCNTs） with shish-kebab like partially wrapped morphology and very good stability were obtained by incorporating the copolymer with MWCNTs.The bare MWCNT sections of（Py-PPDO）_2-b-PEG@MWCNTs were able to induce n-n interactions with graphene（GE） and resulted in a novel GE/（Py-PPDO）_2-b-PEG@MWCNTs hybrid.The dispersity of GE in solution or polymer matrix was therefore greatly improved.The PCL nanocomposite films using GE/（Py-PPDO）_2-bPEG@MWCNTs as hybrid nanofiller exhibited obviously improved mechanical properties especially at very low hybrid nanofiller content.The influence of the nanofiller content and feed ratio of GE/MWCNTs on the mechanical properties of composites films was evaluated.When the feed ratio of GE to MWCNTs is 2：8 and the total loading of nanofiller is only 0.01 wt%,the tensile strength of the composite film increased by 163%and the elongation at break increased by 17% compared to those of neat PCL These results can be attributed to fine dispersion of the nanofillers in PCL matrix and the hybrid interactions between GE and MWCNTs.Therefore,this work provides a novel method for preparing polymer nanocomposites with high mechanical performance and low nanofiller loading.
