基于海量点云的钢结构形变分析

常规的钢结构健康监测方法效率低,不能满足钢结构形变分析的要求。三维激光扫描技术具有采集速度快、点位精度高等技术优势使其适用于钢结构的形变分析中。本文采用三维激光扫描仪通过分段闭合扫描路线采集特高压南阳变电站海量点云数据,并详细介绍了海量变电站点云数据的去躁、配准、重建过程,实现了变电站整体数字化重建。同时,根据挠度分析法讨论了站内钢架结构的挠度偏移,基于坐标分量中误差评价了钢架结构的健康程度,实现了变电站钢架结构的挠度形变分析。

50 MeV负氢回旋加速器主磁铁设计研究

本文介绍了50MeV负氢回旋加速器(CYCIAE-50)的总体设计考虑和主磁铁系统的优化设计过程及结果。确定了CYCIAE-50主磁铁的主要尺寸参数,建模计算出满足等时性的主磁铁中心平面磁场。通过调整参数,优化了主磁铁的峰值磁场、局部饱和等,以控制建造及运行成本。优化了磁极张角与磁气隙高度等参数,使负氢离子满足轴向和径向的聚焦要求,避免穿越有害共振。最后对主磁铁的结构进行形变校核,并估计了形变对束流动力学的影响。设计结果表明,CYCIAE-50的主磁铁设计符合要求,可为后续其他系统的设计和建造提供重要参考。

Deformation-based freeform feature reconstruction in reverse engineering

For reconstructing a freeform feature from point cloud, a deformation-based method is proposed in this paper. The freeform feature consists of a secondary surface and a blending surface. The secondary surface plays a role in substituting a local region of a given primary surface. The blending surface acts as a bridge to smoothly connect the unchanged region of the primary surface with the secondary surface. The secondary surface is generated by surface deformation subjected to line constraints, i.e., character lines and limiting lines, not designed by conventional methods. The lines are used to represent the underlying informa-tion of the freeform feature in point cloud, where the character lines depict the feature’s shape, and the limiting lines determine its location and orientation. The configuration of the character lines and the extraction of the limiting lines are discussed in detail. The blending surface is designed by the traditional modeling method, whose intrinsic parameters are recovered from point cloud through a series of steps, namely, point cloud slicing, circle fitting and regression analysis. The proposed method is used not only to effectively and efficiently reconstruct the freeform feature, but also to modify it by manipulating the line constraints. Typical examples are given to verify our method.

Parameter Variations of Identified Model for Static Deformation Analysis of Arch Dam

The structural health monitoring of a dam is important for maintaining the safe operation and longevity of the dam system. The structural health of a large dam can be monitored from the measured static deformation. This paper presents an investigation of the parameter variations of the identified model of the measured long-term static deformation for the structural health monitoring of Fui-Tsui Dam, which is located in a very active seismic zone of Taiwan. The measured static deformation is characterized as a function of the measured physical parameters, including the effects of hydrostatic pressure and temperature variation. The identified parameters, associated with the effects of hydrostatic pressure and temperature variation, change with environmental factors, such as flooding, earthquake and foundation change.

Structural Optimization of Lap Link Based on Elastoplastic Finite Element Analysis

Based on finite-deformation elastoplastic theory, a scheme to solve the structural problems of the lap link by using ANSYS is proposed. The analysis results show that the maximum deformation exists at the loading spot of the lateral pin and the stiffness of this area needs to be enhanced; the maximum stresses occur at the two sides adjacent to the loading spot and the intensity around this region should be strengthened;the materials at the pole and pinhole with relatively low stress are redundant and removing excessive weight is possible. Based on the analysis, corresponding improvements are tentatively made, and the simulation results prove that, the stiffness and intensity of the new structure are improved. Furthermore, the reliability and validity of this design are verified by tensile tests of two types of structure.

A meshfree method and its applications to elasto-plastic problems

Standard finite element approaches are still ineffective in handling extreme material deformation, such as cases of large deformations and moving discontinuities due to severe mesh distortion. Among meshfree methods developed to overcome the ineffectiveness, Reproducing Kernel Particle Method (RKPM) has demonstrated its great suitability for structural analysis.This paper presents applications of RKPM in elasto-plastic problems after a review of meshfree methods and an introduction to RKPM. A slope stability problem in geotechnical engineering is analyzed as an illustrative case. The corresponding numerical simulations are carried out on an SGI Onyx3900 supercomputer. Comparison of the RKPM and the FEM under identical conditions showed that the RKPM is more suitable for problems where there exists extremely large strain such as in the case of slope sliding.

Deformation Analysis Due to Early Loading of Concrete Buildings

The building industry has experienced in recent years a strong growth in demand in general and in the case of reinforced concrete buildings this increase has been more marked. This fact has also contributed to accelerate all stages of the production process of these constructions with more pronounced effects on the methodologies used in the constructive steps that influence directly the structural design of the building. Structures loaded at ever earlier ages, in which the strength and deformation properties of materials are not yet sufficiently mature. It is a variable that needs to be taken into account already in the design phase so that the concrete structure behaves within acceptable level of reliability taking into account design code recommendations for service life. To understand the importance of constructive effects and to assess its magnitude in the execution of reinforced concrete buildings, this paper presents result from nonlinear analyses using finite element method adopting an approach commonly referred as staged construction applied to a typical building found in the practice. The effects of creep and shrinkage were considered and the results obtained demonstrate that the strains due to constructive effects can, in certain cases, assume representative values which, if ignored, can lead to important pathologies in the building.

New Activity of the Tanlu Fault Zone in the South of Huaihe to the Nvshanhu Segment since the Late Quaternary

Taking the Huaihe to the Nvshanhu segment of the Tanlu( Tancheng-Lujiang) fault zone as the main research target to explore whether there has been new activity since the late Quaternary,and based on the interpretation of remote sensing images and repeated surface investigations,we excavated trenches at the sections where the tectonic landform is significant,identified and recorded the deformation patterns of the fault and analyzed the activity behavior. Samples of new activity and deformation were collected and oriented slices were ground based on the samples ' original state to make the micro structural analysis and demonstration. All of the above research shows very clear linear tectonic geomorphology along the fault,three trenches across the fault zone all revealed new deformation traces since late Quaternary. The latest stratum dislocated by the fault is the late Quaternary and Holocene. The main slip mode is stick slip,as represented typically by fault scarps,wedge accumulation,the faults and the filled cracks and so on. In general,it shows the characteristics of brittle high-speed deformation and belongs to the prehistoric earthquake ruins. The above understanding was confirmed partially by microscopic analysis. In addition,the similarities and differences and the possible reasons for the characteristics of the latest activities of the Tancheng-Lujiang fault zone in the north and south of the Huaihe River regions are also discussed in this paper.

NUMERICAL SIMULATION OF THE STRUCTURAL STRESS FIELD OF BEIYA GOLD DEPOSIT

Based on the study about the geological background of Beiya Gold Deposit, numerical simulation was conducted about the three-dimensional structural stress field for Beiya Gold Deposit by applying finite element theory and by employing a linear elasticity model. Results of the simulation indicate that the Beiya syncline is a faulted basin, and a hidden fracture occurs in the west wing of the syncline.Under the action of the EW-trending compressive force, four nearly NS-trending fractures (groups) were generated in the stress stretching areas of the two wings of the syncline, and these fractures constitute favorable tectonic positions for the upward intrusion of porphyry magma and the occurrence of Au-Pb-Zn polymetallic deposits.

Features and genesis of micro-nanometer-sized grains on shear slip surface of the 2008 Wenchuan earthquake

In coseismic surface rupture zones caused by the 2008 Mw 7.9 Wenchuan earthquake, some thin-layered fault gouges with strong deformation were observed in different locations. In this paper, fault gouge samples were taken as research objects from the Bajiaomiao village in the south-west segment of the principal rupture and the Heshangping village and the Shaba village in the north-east segment of the principal rupture where larger displacements were measured. Fabric characteristics of the fault gouge samples and the morphologies and structures of micro-nanometer grains on Y-shear surfaces were then analyzed by using a stereoscope and SEM. Observation results showed that obvious Y- and R-shears and obvious scratches were well developed in coseismic gouges caused by the 2008 Wenchuan earthquake. Micro-nanometer grains in the fault gouge of the Wenhcuan earthquake were formed mainly due to breaking, grinding, and powdering of fault slipping friction surface. Heat caused by fault slipping(maybe also including heat caused by thermal decomposition) played an important role in producing micro-nanometer sized grains. Existence occurrence state of micro-nanometer sized grains on fault slip surface includes singled grains and their complexes with shapes of ball, silkworm, pancake and mass. The structures mainly include dispersed and close-packed structures besides a few of striped and layered structures. All these structures were formed at the extreme unbalance conditions caused by rapid deforming during an earthquake. There always exist some voids between structures due to loosely contact. Only alienated grains are included in the stripped structure. But there are some singled grains with no deformation in dispersed and close-packed structures besides complexes of grains with morphologies of ball, silkworm, pancake and mass. The striped and close-packed structures are the results of plastic deformation, and the dispersed and layered structures are the results of brittle deformation whereas loose contact of different structures was caused mainly by discontinuous dynamic friction(fault stick-slipping). The structures of the micro-nanometer sized grains in coseismic fault gouge caused by the Wenchuan earthquake are the geological records of seismic fault slipping(it is not pseudotachylite), which could be used as an index of paleo-seismic events.