Applied Mechanics and Materials Vols. 90-93

Abstract: That there existed time and spatial variation for winter wheat water use efficiency (WUE) in different scales in irrigation area could be concluded by studying winter wheat WUE in small scale, middle scale and large scale in irrigation area in 2004~2006 in this paper. It indicated that winter wheat WUE were much more different in the small, the middle and the large scales in different years, which were 1.61kg/m³, 1.30kg/m³ and 0.88kg/m³, respectively. With up scaling, winter wheat WUE was declining in 2004, while increased firstly and then declined in 2005 ~2006.

Abstract: In order to study the influence of the structural and operating parameters on device performance of the self-excited pulsed jet in low-press and Amount-flux, a great deal of experiments on structural and operating parameters of the self-excited pulsed jet was carried out by independently developed testing system. Under the certain upper nozzle diameter and cavity diameter, the changes of the lower nozzle diameter and cavity length and working pressure have an effect on the hitting power of the pulsing jet and pulsing effect. Experimental results showed that for the different lower nozzle diameter and under each working pressure the influence of the cavity length changes on the hitting power is different, there is the optimal range of cavity length and working pressure while the lower diameter is fixed, and with the increase of the lower nozzle diameter, the range of the optimal cavity length and working pressure also has a gradually increasing trend.

Abstract: An experimental research on interference of two risers with suppression device was conducted. The arrangement of the two risers is side-by-side, one is bare and another is a riser with triple strakes. Centre-to-centre distances from 3 to 10 diameters of the risers were studied. The riser model was a 18mm diameter organic glass with wall thickness of 2 mm. The current velocity ranges from 0.3 to 0.8 m/s, with approximate increments of 0.1 m/s. Dynamic strain records were obtained through the dynamic strain gauges which were sticked on the surface of the risers. The experimental data were contrastive studied by dynamic response, amplitude and frequency, respectively. The experimental results indicate that interference have little effect on the oscillatory characteristic of the riser with triple strakes while have important effect on the oscillatory characteristic of the bare riser with different distances.

Abstract: As one of the main configurations of the riser, top tensioned riser(TTR) encounters harsh environment in its whole service life. In order to ensure that the riser will fulfil its intended functions, a fatigue assessment should be carried out for each representative riser, which is subjected to dynamic fatigue loading. The fatigue life of TTR under the combination excitation of random waves, current and vessel motion is analyzed in this paper. The long-term stress histories of the riser are calculated and the mean stresses, the number of stress cycles and amplitudes are determined by rain flow counting method. The Palmgren-Miner rule for cumulative damage theory with a specified S–N curve is used to estimate the fatigue life of the riser. The corresponding numerical programs which can be used to calculate the response and fatigue life of the riser are compiled. The significant influences of internal flow velocities and low frequency motion of the vessel are analyzed in detail.

Abstract: Caofeidian reclamation work may have great influence on the hydrodynamic enviorment. Based on the four-year field survey on water depth, the batymetric maps of different years of Caofeidian are obtained. Through annalying field measurements, a series of comparisons of topography changes in cross section and profile sections are made. Because of the intensed promontory effects, the scour intensity is fierce near the cape but weak with the distance from the cape in the cross-section direction.

Abstract: By studying the geological structure and seepage character, in YanJin bridge reservoir region the harmful geological structure had been reinforced with anchor cable. To establish constitutive law and yield-dstroy critertion of anchorage zone, working state of anchor cable was simulated with FLAC software. With two states of no seepage and Stress-seepage coupling in the reservoir, the anchor cables and the state of the dam abutment rock was computed, but the mechanic character of the harmful geological structure and anchor cable was studied. The deformation stability was accurtely appraised in the high slope rock of dam abutment, by comparing with the state of unreinforce rock, analysing the loading effect of the structure face in anchor cables and the stability regular of slope rock . The computing results have the greater practical values for the reservoir work.

Abstract: The basic theory of temperature field and stress field of concrete and 3D FEM combining with cooling pipe discrete model and iteration method are used to carry out the dynamic simulation analysis of the temperature filed and stress field of a concrete gravity dam of South-to-North Water Diversion Project. The impacts on cracking mechanism of the surface insulation, internal cooling and environmental climate are considered in calculation. The change laws of temperature field and thermal stress with time and their distributions are analyzed, reasonable temperature control measures are put forward for reference. The results show that good effect of temperature control and cracking prevention is achieved, the proposed measures should have great reference significance to the similar concrete dam in future.

Abstract: A parametric finite element (FE) model was developed to allow a broad investigation into the influence of various parameters, such as load conditions, stacking sequence and the number of steps on the performance of the stepped-lap repairs in composite laminated cylindrical shells. And the peak stresses determined with respect to changes in stacking sequence and the number of steps. Furthermore, the adhesive stress distribution resulting from joining mismatched laminate cylindrical shells was investigated. The results of this investigation provide further insight into the stresses that develop in stepped repairs of composite structures under load. This insight may lead to improve design and analysis techniques of stepped repairs in composite structures.

Abstract: Several typical sections of some embankment were studied by the method of environmental isotopes in the paper. The leakage sources of groundwater were ascertained. The result showed that the groundwater of No.1 borehole at Jiangdu dockyard, No.23 borehole at Xiaocaitan section and No.29 borehole at Lianmengzhuang dock was recharged by river water, the water of Heiyutang pond near No.5 borehole was recharged by the local precipitation or groundwater forming by recent precipitation, and the groundwater of No.7 borehole at Wanshougong section was the mixture of river water and local precipitation. Then the analysis of fuzzy clustering was performed by applying fuzzy clustering method that environmental isotopes and hydrochemistry values were taken as index characteristic values and endued different weights. The quantitative analysis result was in agreement with the conclusion qualitatively judged by environmental isotopes and hydrochemistry.

Abstract: The physical explanation of shear lag is given in this paper. The shear lag effects can be attributed to the abrupt change of shear stress at web-flange junction. The abrupt change at the junction of shear stresses changes the magnitude of the flange bending stresses, which attenuates gradually with increasing distances from the web. Meanwhile, the abrupt change of shear stresses from zero to the flange shear stress also influences the bending stress state at the centerline of the flange. The method to determine the shear lag effects has been given, which is based on the Euler-Bernoulli elementary theory of bending, and the calculated results are in good agreement with the experimental results. Considering the transversal distribution of the shear stress at the junction, the flange real bending stress could be calculated on the section. The change of the shear stresses decreases the magnitude of the bending stresses in tension, but increases the magnitude of the bending stresses in compression. The shear lag effects in continuous box girder are different from that in the simply supported box girder. The reaction force of the continuous support would generate an abrupt change of the shear forces between the two sides of the support, and the real bending stresses beside the support would vary significantly due to shear lag effects. The ratio of real bending stress to standard bending stress is not the proper index to reflect the shear lag effects, but the real bending stresses could represent the shear lag effects and should be paid more attention to in design.