Papers by Keyword: Preloading

Abstract: To join components of fiber reinforced polymers (FRP) to metals or FRP, too, bolted joints are used regularly. Reliability, affordability, and disassembly are the drivers for dissemination of this joining technique; despite some disadvantages. For bolted joints of metals it is well known, that a preloading of the bolts increases the efficiency drastically. Therefore, preloaded screws are the standard in mechanical engineering. Prerequisite is a load transfer by friction of the joining partners induced by a preload of the bolt. However, when joining FRP components a preloading of the bolts is usually not considered since a force release is afraid due to creeping of the polymeric matrix. Furthermore, the load transfer by friction of FRP is not investigated sufficiently. The limiting parameters of preloaded bolted joints of different FRP materials are investigated here. Particularly these are the allowed contact pressure at the bolt heads or washers, the coefficient of friction in the joining zone, and the release behavior of the preloading. The load transfer capability of bolted joints under optimized conditions is presented.

Abstract: Aiming at gear in dynamic analysis simulation system often appears oscillation problem the phase of high-frequency. An method of eliminating the initial loading of oscillation system bases on dynamic relaxation, which is presented. In this paper, preloading dynamic relaxation process was carried out in the gear system. Also, the application method of dynamic relaxation based on LS-DYNA is proposed. and on account of LS-DYNA platform which proposes dynamic relaxation method in the application to dynamic simulation method of gear system. Finally, investigating the efficacy of method by simulation example.

Abstract: The effect of defined preloading in the tensile and compressive regime on the near surface (residual) stress distributions, which result from laser surface hardening, is systematically studied in-situ, i.e. under the applied preload and after unloading. Samples made of steel grade AISI 4140 are defined surface hardened by means of a high-power diode laser (HPDL) system during uniaxial compressive elastic loading at-300 MPa as well as during uniaxial elastic tensile loading at 300 MPa using a custom designed 4-point-bending device, which can be mounted on an X-ray diffractometer. The results of X-ray stress analysis were compared to data derived for a sample state unaffected by any preload. Without external loading compressive residual stresses are induced inside the process zone that are balanced by tensile residual stresses outside this zone. The investigations show that external loading in the tensile and compressive regime has a strong impact on the resulting lateral residual stress distribution in loading direction. The results further indicate that undesirable tensile residual stresses outside the process zone can even be suppressed by using a defined appropriate preloading in the tensile regime.

Abstract: Nanjing-Hangzhou Railway Passenger Dedicated Line is a high-speed railway of the speed 350 km/h in coastal soft area without railway track ballast. The settlement of soft foundation is quite great and the strict control standards of the settlement after construction of the high-speed railway that the settlement observation in construction phase is very strict. Through the settlement observation data analysis of Nanjing-Hangzhou Railway Passenger Dedicated Line on-site, the author found that the preloading can rapidly accelerate the settlement of the soft soil subsidence, the settlement is quite great during the embankment construction and the later three months, there is a preloading critical height, the foundation generally does not rebound when load was removed, the settlement trends are consistent with the three-point analysis. These conclusions are certain referential significance for the settlement control of the coastal soft soil area of high-speed passenger dedicated .

Abstract: Yangpu Port has inhomogeneous soft soil with the properties of high water content, high void ratio, high compressibility and low shear strength. Based on soft soil ground treatment engineering practice, the geological characteristics are summarized, the ground treatment methods are comparatively analyzed, static-dynamic drainage consolidation method is chosen to treat the soft soil ground, the reinforcing mechanism of vertical and horizontal drainage system are discussed, the design of drainage system, preloading and dynamic consolidation are researched and the surface settlement monitoring, pore water pressure monitoring, side piling displacement monitoring, laboratory soil test and plate loading tests are carried out. The results show that average surface settlement is 1170.8 mm, the physical and mechanical properties of soft soil are improved and the characteristic value of foundation bearing capacity is greater than 120kPa.

Abstract: Dredge materials with the water content more than 80% have been used for land reclamation in Tianjin, China. The dredge is transferred by pipeline to the reclamation place and then strengthened with the vacuum preloading technique. It has been found that with the thickness of the filled dredge layer becomes larger and larger, the quality of soil improvement is not as good as expected. Field investigation shows that after vacuum preloading the vane test strength can reach 50kPa at the ground surface, but decreases along with depth dramatically. The model test is carried out to detect the factors that may influence the efficiency of using vacuum preloading to improve dredge soil foundation. The water content, vacuum pressure and undrained strength are measured during the test.

Abstract: According to the monitoring results of soft clay treated by preloading with plastic drainage pipe, the consolidation settlement effect of soft clay with 50kPa preloading load, 21m plastic pipe, 1.2m and 1.5m distance was compared with that of 30kPa preloading load, 6m plastic pipe, 1.5m and 2.0m distance. The analysis showed that, the preloading method with deep plastic drainage pipe can accelerate the dissipation of excess pore water pressure in deep soft soil. The over-flow penetration may occur in the confined water. The elastic deformation appears and recoveries after unloading. This is not conducive to the consolidation of soft clay layer 4. The plastic drainage pipe whose depth and distance should be 18~20m and 1.5m respectively to the consolidation soft soil in Pudong.