Papers by Keyword: Load Stress

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Authors: Wolfgang Kowalski, Markus Dammer, Frank Bakczewitz, Olaf Kessler
Abstract: Stents are medical implants, which are applied to keep cavities in the human body open, e.g. blood vessels. Typically they consist of tube-like grids of suitable metal alloys. Typical dimensions depend on their applications: outer diameters in the mm-range and grid bar thickness in the 100 µm range. Before implantation, stents are compressed (crimped) to allow implantation in the human body. During implantation, stents are expanded, usually by balloon catheters. Crimping as well as expansion causes high strains and high stresses locally in the grid bars. These strains and stresses are important design criteria of stents. Usually, they are calculated numerically by Finite Element Analysis (FEA) [1,2]. The XRD-sin²ψ-technique is applied for in-situ-determination of stress conditions during crimping and expansion of stents of the CoCr-alloy L-605. This provides a realistic characterization of the near-surface stress state and an evaluation of the numerical FEA results. XRD-results show an increasing compressive load stress in circumferential direction with increasing stent expansion. These findings correlate with the numerical FEA results. Further residual stresses after removing the expansion device have been measured.
Authors: Yan Wang, Zhi Feng Liu
Abstract: Semi-rigid base asphalt pavement has well load-bearing capacity if no cracks occur. But cracks appear inevitably at the weak part of the structure. Models under different working conditions are set up with the finite element method (FEM) to analyze the stress distribution in the structure while the cement-stabilized macadam-base asphalt pavement encounters different crack states and interface conditions. The analysis indicates that the interlayer cohesion is the key factor affecting the spread of cracks. When the cohesion between the surface and base is weak, the tensile and shear stresses at the bottom of the surface course increase rapidly and both transverse cracks from the bottom to the top and longitudinal cracks in traffic direction come into being in the asphalt surface even though the base doesn’t crack; those transverse cracks which haven’t spread through the base in depth direction will reflect to the surface course under load. The reflected cracks can be reduced and stayed if the surface course is covered after the shrinking cracks in the base course have fully spread and been cured.
Authors: Song Lin Ma, Song Yue, Zheng Yang Zhao
Abstract: This paper, in terms of structure design, mainly considers the unfavorable load position of cement concrete pavements and the finite element software is used to establish three-dimensional solid model for analysis and calculation of load stress. The results show that fatigue stress along the transverse direction is much larger than that along the longitudinal direction, and slabs are most likely to have cracking along the longitudinal direction under the combined effect of load and temperature. It is of certain significance for the prevention of longitudinal cracking of concrete pavements and the extension of pavement life.
Authors: Xing Zhong Weng, Xiang Cheng Yan, Wen Lu Liu, Lei Liang, Xin Qiang Li
Abstract: In order to study the influence of interface bond condition between new and old cement concrete pavement on overlay performance, the three-dimensional finite element model of the airport double-layer pavement was established. The pavement overlay's load stress and deflection were analyzed, the coupling coefficient between new and old cement concrete pavement was calculated based on the bottom of overlay deflection basin shape factor. The results show that the coupling coefficient reflects the degrees of interface bond condition well. Poor interface bond condition increases the overlay's load stress and deflection. The points that more closely distance from the wheels load center, the bigger the pavement overlay's load stress and deflection is. Therefore, more attention should be paid to the interface bond condition during the airport pavement overlay's designs and constructions.
Authors: Bin Yang, Wei Liang, Xiang Xin Zeng, Jin Hua Huang
Abstract: The vehicle load stresses of the cement concrete pavement structure with/without flexible functional layer were contrastively analyzed by numerical simulation with using ANSYS software. The results showed that the load stress of the cement concrete pavement structure with flexible functional layer was much lower than that without flexible functional layer under the vehicle load. Consequently, the force condition of the pavement structure was effectively improved by the flexible functional layer.
Authors: Yong Hong Wang, Xiong Jun He, Hong Sheng Qiu, Xi Ming Tan
Abstract: For the old concrete pavement with large proportion damage, it can be reconstructed by paving asphalt surface after cracked and stabilized with punching technique. But there is great difference in adopting the cracked size of pavement slab in every place and there is no relational theory basis. So the authors use 3-D finite element method to analyze the relationships of cracked size of concrete slab and load stress, thermal stress, coupling stress in asphalt overlay and pressure stress on the base surface. The results show that the influence of cracked size on thermal stress and coupling stress is much greater than load stress. With the decrease of cracked size, the thermal stress and coupling stress in asphalt overlay decrease rapidly, the stress centralization at joints and cracks lessens evidently, while the pressure stress on base surface increases. Considering the factors synthetically, it is reasonable for the cracked size from 80cm to 100cm.
Authors: Hua Cai, Ke Jiang, Jian Miao, Jian Gang Liao
Abstract: Aiming at the problems of the concrete pavement transverse joint, and the characteristics of prestressed concrete pavement and continuously reinforced concrete pavement, a transversely prestressed continuous concrete pavement with oblique-reinforced is presented. ABAQUS software is adopted to establish respectively two three-dimensional finite element models of plain concrete pavement and transversely prestressed continuous concrete pavement with oblique-reinforced for calculating mechanical behavior under the standard load. The results show that, with a concrete pavement slab transversely prestressed, a finite prestressing force exist in longitudinal by bonding among oblique-reinforced and concrete, and there isn’t tensile stress under the load, so the possibility of slab breakage due to tensile stress is low. Due to its excellent performance, in addition its great load-carrying capacity and overall stability, the investigation is valuable for the research of seamlessly prestressed pavement.
Authors: Bin Yang, Li Jun Suo, Chun Ren Zhou, Kai Liang Dong
Abstract: With the goal of exploring the impact of pavement structure parameters on load stress of super-thick cement concrete pavement, this paper, based on the Quanxing freeway in Guangxi, analyzes the load stress in the situation of the separated type and combined type contact between the cement concrete slab and the lean concrete base by using three-dimensional finite element model. Computational results show that the variation of different pavement structure parameters have various impacts on the load stress of super-thick cement concrete pavement. The load stress σc1 of super-thick cement concrete pavement slab declines with the increase of slab thickness h1 and base thickness h2 and decreases with the reduction of slab length L and the increases of base modulus E2 and subbase modulus Et. Among them, the variation of slab thickness h1 has the greatest impact on the pavement load stress. Thus, there is a quite obvious effect in reducing the pavement load stress by increasing the slab thickness.
Authors: Dong Qing He, Yi Ming Wang, Chang Lu
Abstract: The finite element model for the basalt fiber reinforced concrete(BFRC)-roller compacted concrete(RCC) composite pavement structure is formed, by the model the influence of the BFRC and RCC panel thickness, elasticity modulus and foundation Equivalent Resilient Modulus on the complex road load stress can be summarized as: with the increasing of the composite pavement slab thickness, the stress at the end of the below plate shows decreasing trend, but the above end of the plate stress increased with the increasing of relative thickness of laminates; the increasing of concrete elastic modulus will make the stress in the end of this laminate increase, while the end of the adjacent laminates stress will reduce; with the increasing of the equivalent modulus of elasticity of roadbed top, the stress of laminates decreases. The results of the analysis are available as the reference to optimize the design of BFRC-RCC composite pavement.
Authors: Li Jun Suo, Xin Wu Wang
Abstract: In order to analyze load stress of roller compacted concrete base of asphalt pavement, first of all, threedimension finite element model of the flexible pavement is established. The main objectives of the paper are investigated. One is calculation for stress of roller compacted concrete base in asphalt pavement, and the other is analysis for relationship between load stress of roller compacted concrete base and parameters, such as thickness, modulus. The results show that stress, which is caused by load that is located in the middle of longitudinal joint of roller compacted concrete base of asphalt pavement. Maximum load stress decrease, decrease and increase respectively with increase of the surfaces thickness, bases thickness and ratio of bases modulus to foundations modulus.
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