Response of the Fatih Sultan Mehmet Suspension Bridge under spatially varying multi-point earthquake excitations

The study aims at investigating the structural behavior of the Fatih Sultan Mehmet Suspension Bridge, i.e. the second Bosphorus Bridge in Turkey, under multi-point earthquake excitations, and determining the earthquake performance of the bridge based on the results obtained from this analysis. For this objective, spatially varying ground motions in triple direction were produced for each support of the bridge considering the Mw=7.4 scenario earthquakes on the main Marmara Fault. In order to simulate the ground motions, modified stochastic finite-fault technique was utilized. Taking the ground motions into account, non-linear time-history analysis was carried out, and the results obtained from the analysis were compared to those from uniform support earthquake excitation to identify the effects of multi-point earthquake excitations on the seismic performance of the bridge. From the analysis, it was determined that modal response of the towers and the deck was mostly effective on dynamic response of the entire bridge rather than other structural elements, such as cable and approach viaduct. Compared to the results obtained from simple-point earthquake excitation, noticeable axial force increase in the cable elements was obtained under multi-point earthquake excitation. The changes at the main cable and the side span cable were determined as 21% and 18%, respectively. This much increase in the cable elements led to increase in axial force at the towers and in shear force at the base section of the tower column. These changes in the structural elements were closely related to response of the deck and the towers since they had considerable contribution to response of the entire bridge. Based on the findings from the study, spatially varying ground motions has to be considered for long span suspension bridges, and the multi-support earthquake analysis should be carried out for better understanding and obtaining reliable results necessary for retrofitting and performance evaluation.     

基于虚功原理的悬索桥隧道式锚碇边坡稳定性分析

本文基于虚功原理,结合工程地质勘察资料,在岩层层面和不利结构面组合切割下,由于锚碇工程荷载作用,研究坝陵河大桥西岸隧道式锚碇边坡的整体稳定性。本文的力学分析模型采用多个块体破坏机构的分析方法,假定块体的底面和侧面均达到了极限平衡状态,安全系数可通过功能平衡的虚功原理表达式来求解。功能平衡方程中仅有安全系数一个未知数,条块底部和界面上的法向压力和切向摩擦力并不出现,求解大为简化。     

紫菜细胞悬浮培养

用酶解技术获得条斑紫菜离体细胞并对其进行细胞悬浮培养研究;对藻休不同部位的细胞分化发育方式,不同悬浮器具培养效果及不同起始培养的细胞密度进行了探索。结果表明:用气升式生物反应器培养细胞效果最佳,起始培养的细胞密度可达l×10~5细胞/ml,细胞存活率达85%。     

Field measurements of snow-drift threshold and mass fluxes,and related model simulations

Field measurements were carried out to calculate the threshold friction velocity for snow saltation, and mass fluxes during snow drift. The wind was measured in three components by an ultrasonic anemometer, and the mass fluxes were determined using an optical sensor (snow particle counter), acoustic sensors (Flowcapt) and mechanical traps. The threshold friction velocity was found to be correlated to the grain size (R²=0.75). The mass flux measurements were compared with numerical simulations of snow drift, and it was demonstrated that the maximum snow transport takes place at shear stress values of roughly two times the average shear stress over 20 min. By implementing a probability distribution for the shear stress the mass flux was simulated with only the mean measured value of the shear stress as input. This procedure enables the future use of the numerical model for operational applications.     

拖网配纲形状合理性检验

为正确分析和改进设计网具,采用悬链线与拖网配纲形状比较的方法,引伸配纲形变系数对设计网配纲进行合理性检验。并对有关计算方法进行推导和论证。     

Filtrate Quality from Different Filter Operations

A brief review of the literature on filtrate quality obtained in constant and variable declining rate operation systems is presented, with the general conclusion that both systems usually produce filtrate of similar quality, assuming the flow‐rate controllers in the constant flow rate system operate properly. A mathematical model of CR (constant rate) filters and VDR (variable declining rate) filters based on the model by Mackie and Zhao (1999) has been described and used to investigate filtrate quality under different operating conditions. A similar quality of filtrate was achieved in computations carried out for both modes of operation, while the total head loss was much lower in the VDR mode. For the same time of filter runs slightly better filtration quality resulted from CR operation, but for different filter runs resulting from the same head loss of flow just before a backwash, the VDR control system produced lower turbidity filtrate.     

大跨度悬索桥振动控制的双向TMD参数研究

用时域内的逐步积分法对无ＴＭＤ和带有不同参数ＴＭＤ的悬索桥进行了时程分析,结果表明,ＴＭＤ的参数对结构的动力特性的抑振效果均有较大的影响,ＴＭＤ的频率不仅影响振动控制的效果也影响结构的表观阻尼,扭转振动的控制可由侧向ＴＭＤ来实现。     

基于挂钩政策下的山东省农村建设用地整理潜力及重点区域

在分析山东省农村建设用地现状基础上,提出全省农村建设用地整理潜力;采用人均定额指标法,预测城镇工矿用地需求量;结合新一轮土地利用总体规划中城乡建设用地控制指标,提出全省可用于挂钩的农村建设用地整理潜力;采用双因素分级法,提出城乡建设用地增减挂钩的重点区域。     

An experimental study on using MR damper to mitigate longitudinal seismic response of a suspension bridge

In this paper, the seismic response reduction performance of magnetorheological (MR) damper is experimentally investigated for a suspension bridge. First, the force–displacement and force–velocity curves under a range of excitation frequencies, amplitudes and currents are obtained by mechanical behavior test of the RD1097 type MR damper. Then a new non-linear hysteretic model is proposed to model the mechanical behavior of the MR damper and the model parameters are identified from test data. An experimental method, as well as a set of testing setups with the MR damper for longitudinal seismic response reduction of a SDOF generalized system representing the fundamental longitudinal mode of suspension bridge, is developed. Finally, the seismic response reduction experiment subject to three kinds of earthquake excitations, including the Pingsheng Bridge earthquake wave, the El-Centro wave and the Taft wave, is carried out, and nine control cases, including uncontrolled, six passive control schemes with different input currents and two semi-active Bang–Bang control schemes, are tested. The results verify that the seismic response reduction experimental method is feasible and the good performance of seismic longitudinal response reduction of the suspension bridge can be achieved by MR damper. It is also shown that the passive control with optimum input current outperforms the semi-active Bang–Bang controls.     

Does thermal history influence the tolerance of temperate gorgonians to future warming?

To date, several studies have provided evidence that thermal stress affects the growth, survival and physiology of tropical and temperate macroinvertebrate species. However, few studies have focused on subtidal temperate species and the potential differential thermal tolerances of populations dwelling under contrasting temperature conditions. To assess the role that environmental history has on the response of the temperate gorgonian Eunicella singularis to thermal stress, we compared populations dwelling in the coldest and warmest areas of the NW Mediterranean Sea. Our results show that E. singularis populations from both areas exhibited a high resistance to thermal stress; however, populations from warmer areas had an increased tolerance to thermal stress. Specifically, the upper thermal limits found for cold and warm populations were 28 and 29 °C, respectively. The higher resistance of E. singularis colonies to thermal stress found in this study compared to the field temperature conditions during recent mass mortality events highlights that performing further thermotolerance experiments under contrasting levels of feeding is necessary to fully assess the tolerance thresholds displayed by both study populations. To our knowledge, this study provides the first evidence for the role of thermal history in shaping the thermotolerance responses of Mediterranean marine invertebrates dwelling under contrasting temperature environments.