Effect of vehicle weight on natural frequencies of bridges measured from traffic-induced vibration

Recently,ambient vibration test(AVT)is widely used tu estimate dynamic characteristics of large civil struc- tures.Dynamic characteristics ean be affected by various envirnnmental factors such as humidity,intensity of wind,and temperature.Besides these environmental conditions,tire mass of vehicles may change the measured valnes when traffic-in- duced vibration is used as a source of AVT tor bridges.The effect of vehicle mass on dynamic characteristics is investigated through traffic-induced vibration tests on three bridges;(1)three-span suspension bridge(128m+404m+128m),(2) five-span continuous steel box girder bridge(59m+3@ 95m+59m),(3)simply supported plate girder bridge(46m). Acceleration histories of each measurement location under normal traffic are recorded for 30 minutes at field.These recor- ded histories are divided into individual vibrations and are combined into two groups aceording to the level of vibration;one by heavy vehicles such as trucks and buses and the other by light vehicles such as passenger cars.Separate processing of the two groups of signals shows that,for the middle and long-span bridges,the difference can be hardly detected,but,for the short span bridges whose mass is relatively small,the measured natural frequencies can change up to 5.4%.

Expression of Endothelial Nitric Oxide Synthase Traffic Inducer in the Placenta of Pregnancy Induced Hypertension

The expression of endothelial nitric oxide synthase traffic inducer （NOSTRIN） in the placenta of the patients with pregnancy induced hypertension （PIH） was detected and its role in the pathogenesis of PIH was studied. The pathological changes in placental vessels were observed by HE staining. NO2-/NO3- , the stable metabolic end products of NO, was measured with nitrate reductase. The eNOS activity in placental tissues was assayed by spectrophotometry. Western blot analysis was applied to detect NOSTRIN expression. The incidence of thickening and fibronoid necrosis of placental vessels was significantly higher in women with PIH than in the normal group （P〈 0.01）. The levels of placental NO2-/NO3- in PIH patients （27. 53±7.48 μmol/mg） were significantly lower than in normal group （54. 27±9.53 μmol/mg, P〈0.01）. The activity of eNOS was significantly decreased in PIH group （12. 826±3.61 U/mg） as compared with that in normal group （21. 72±3.83 U/mg, P〈0.01）. Western blot analysis revealed that both groups expressed 58 kD NOSTRIN, but the protein level was significantly higher in women with PIH than in the normal group （P〈0.01）. A significant negative correlation existed between the expression of NOSTRIN protein and the activity of eNOS in placental tissue of women with PIH （r=-0.57, P〈0.01）. It was concluded that the level of NOSTRIN expression in placenta of women with PIH was increased, which may play an important role in the pathogenesis of PIH.

Changes in Human Umbilical Vein Endothelial Cells Induced by Endothelial Nitric Oxide Synthase Traffic Inducer

This study investigated the changes in human umbilical vein endothelial cells （HUVECs） induced by overexpression of endothelial nitric oxide synthase traffic inducer （NOSTRIN） and its role in cellular injury. Recombinant NOSTRIN-expressing and empty vectors were transfected into cultured HUVECs, and factor Ⅷ-related antigen was examined by using immunohistochemical analysis. Growth curves were generated for both transfected and untransfected cells and these indicated that the prolifera- tive ability of cells overexpressing NOSTRIN was significantly decreased. The expression of NOSTRIN and eNOS proteins was detected by using Western blot analysis, endothelial NOS （eNOS） activity was assayed by using spectrophotometry, and NO2-/NO3- levels were measured usin~ nitrate reductase. Immunohistochemical analysis demonstrated that all groups expressed NOSTRIN in the plasma mem- brane and cytoplasm, and Western blot analysis confirmed that NOSTR1N levels were significantly higher in cells transfected with the NOSTR1N plasmid （P〈0.01）. The activity of eNOS and the levels of NO2-/NO3 were significantly decreased in NOSTRIN overexpressing cells as compared with empty vector and untransfected cells （P〈0.01 and P〈0.01, respectively）. Morphological and ultrastructural changes were observed under light and electron microscopy, and it was found that NOS- TRIN-overexpressing cells were elongated with deformities of the karyotheca, injury to the plasma membrane, increased lipids in the cytoplasm, and shortened microvilli. This study showed that overex- pression of NOSTRIN had a significant effect on eNOS activity in HUVECs and resulted in significant cellular damage.

Key Technologies of Urban TIA and Their Application

With the high speed development of Chinese economy, urban traffic problems have become increasingly serious. Based on an analysis of the significance and function of TIA (Traffic Impact Analysis), the characteristics, procedure and key techniques of TIA are elaborated according to the overseas experience. Then, in combination with the domestic practice, the standard of executing TIA, the prediction of traffic volume, the standard of appraisement, etc ., are discussed in detail. Finally, construction of the commercial pedestrian street of Chunxi road in Chengdu city is taken as an example for analysis.