体外预应力锚固横梁拉应力域法配筋

针对体外预应力混凝土桥端锚固横梁内侧承受较大拉应力且传统配筋方法有所欠缺的现状,提出一种新方法——"拉应力域法"配筋:对于承受主拉、压应力,存在有规律的二维"拉应力域"实体结构,可连续划分二维"拉应力域切片",通过对各切片网格配筋的方式以承担混凝土拉应力的正交分量,并以"拉应力域深度"控制网格的纵向布置区域.以某体外预应力端锚固横梁为例,建立有限元模型,并考虑锚固端横、竖向预应力的影响.应用拉应力域法配筋的分析结果表明,锚固端横、竖向预应力对于配筋量有较大影响,原设计竖向钢筋过多,横向钢筋分布不尽合理,而拉应力域法可根据实际应力分布来配筋,结果更准确.

基于拉应力域的波形钢腹板组合梁承载力配筋计算

针对波形钢腹板组合箱梁配筋方法的不足,提出了基于空间网格分析方法和"拉应力域"的设计方法。结合工程案例,将网格配筋、设计配筋及规范配筋结果进行了对比并描述了截面关键板件纵向配筋趋势。结果表明:基于拉应力域的配筋计算方法可以实现波形钢腹板组合梁桥顶板和底板的面内、面外精细化配筋,验证了网格模型模拟波形钢腹板组合箱梁的准确性。空间网格模型和拉应力域设计方法可为波形钢腹板组合箱梁提供精细化的设计思路和方向。

统一强度理论在杆管柱力学中的适用性和具有SD效应材料的安全应力域

在油气井杆管柱力学中广泛应用Von Mises屈服准则和Tresca屈服准则,而在岩土力学中则普遍采用统一强度理论。统一强度理论是否囊括了Von Mises屈服准则和Tresca屈服准则,在油气井杆管柱力学中应用统一强度理论是否比应用Von Mises屈服准则和Tresca屈服准则更好等问题,是值得澄清和探讨的。在分析统一强度理论、Von Mises屈服准则和Tresca屈服准则所考虑的因素、数学表达式和适用材料后认为,在一般的油气井杆管柱力学计算中,Von Mises屈服准则比统一强度理论更完备;在特定条件下Tresca屈服准则比统一强度理论更简明;Von Mises屈服准则和双向应力椭圆理论充分地考虑了中间主应力效应;油气井杆管柱力学中一般不需要考虑SD效应;统一强度理论没有考虑材料的冷作硬化效应和屈强比。建立了具有SD效应材料的安全应力域。

基于应力可行域法的斜拉桥合理成桥状态确定

现有确定斜拉桥合理成桥状态的方法主要有影响矩阵法和分布算法,但各自都有其局限性,鉴于此,提出将最小弯曲能量法和应力可行域法相结合形成分布算法,确定斜拉桥合理成桥状态。首先计算主梁恒载下的应力及其所有可变作用效应的应力包络图;其次根据预应力产生的应力和主梁可变作用效应的应力包络图,分别计算出主梁截面上、下缘在恒载作用下的应力可行域,形成应力判别图;然后根据应力判别图中主梁恒载应力与应力可行域的相互关系,调整成桥索力,使主梁恒载应力落在应力可行域中居中的位置,得到合理成桥状态。将该方法应用于一座单塔斜拉桥,计算结果表明该方法方便有效,整个优化过程将定性判断和定量判别相结合,优化效果直观。

地下道路分叉节点段结构受力分析与配筋设计

研究地下道路分叉节点段结构整体结构的受力性能及配筋设计,针对顺德区环湖路地下回旋通道分叉节点段,利用ABAQUS有限元计算软件建立分叉节点段三维精细化分析模型,重点计算结构顶板、底板、侧墙局部受力最大区域。利用“拉应力法”对顶板、底板、侧墙进行配筋设计,并与二维框架计算模型进行对比分析。结果表明,按二维框架模型计算配筋设计偏大,甚至受力钢筋位置会出现错误。本文计算结果对类似地下道路分叉结构配筋设计具有一定参考价值。

接触压力和循环应力幅对45号钢微动疲劳特性影响

研究了接触压力对调质45号钢微动疲劳特性的影响.随着接触压力增大,在低接触压力阶段,微动疲劳寿命急剧下降;然而,在高接触压力阶段几乎保持不变.随着循环应力幅升高,微动疲劳寿命下降.实验中,微动接触面上出现磨损并形成凹坑.在高接触应力情况下,主裂纹萌生在凹坑外边缘处;在低接触应力情况下,主裂纹萌生在微动接触面的中间部分.

市政预制梁桥横向合理构造分析

超载情况下,T梁、预制小箱梁结构横向联系成为病害集中爆发的部位。选择35 m跨度的桥梁结构,以板单元建立有限元模型,利用MIDAS Civil程序的移动荷载追踪功能寻找最不利工况,对不同超载系数的超载车辆按拉应力域配筋的设计方法进行分析。对横隔板开裂情况进行对比分析,从而确定不同桥梁类型的横向联系的合理构造。

Geostress measurements near fault areas using borehole stress-relief method

To minimize negative effects of geostress distribution on mining safety near the fault areas, the UPM40 triaxial geostress testing system was introduced to conduct in-situ geostress measurements at three sites and nine points by the borehole stress-relief method. The results of strain?confining pressure curves show that rock masses at the three measuring sites exhibit comprehensive linear elasticity in spite of various fissures or cracks within rocks. Horizontal and vertical stress components distribute discrepantly near the fault areas, and the maximum lateral pressure coefficient is as high as 6.15. The maximum principle stress ranges from 8.01 to 14.93 MPa, and stress directions are in the range of N78.07°W?N17.55°W. Geostresses near fault areas are dominated by the horizontal tectonic stresses, while the lower values, compared to those under similar geological conditions are due to stress release by the fault. Additionally, the fault and shear stress nearby are partially responsible for asymmetric elongation and southwesterly migration of orebodies.

The launch of a large regional gravity information system in China

We developed the China Regional Gravity Information System（RGIS） using mixed language programming in Visual Basic,Visual C＋＋,and FORTRAN.The software is based on the MapInfo platform with OLE technology.With this system,we achieve visual data management for the database with spatial geography,geology data and gravity data as well as graphical data editing and data table operations over the whole of China.We are able to perform normalized gravity reduction,gravity and magnetic field transforms,gravity anomaly inversion and interpretation,thematic mapping and so on.

Numerical analysis of water inrush from working-face floor during mining

Confined water in the Ordovician limestone is one of the hidden troubles that threaten safe production of mines in north China. A numerical model of the key strata was developed. It included the structural characteristics and mechanical properties of the floor rock at the working face of a particular coal mine. The model was used to predict failure modes and to help establish rules for safe mining above the aquifer. The distribution of deformation, failure and seepage was simulated by using Dilian Mechsoft's Real- istic Failure Process Analysis (RFPA2D) program. The stress distribution, the deformation and the flow vectors were also obtained. The results indicate that: 1) The original balance of the stress and seepage fields is disturbed due to coal mining; and 2) As the working face advances different deformation, or failure, appears in the surrounding rocks, the water-resisting strata in floor may be destroyed and the passage of water from the aquifer into the mine may occur. The combined action of mining stress and water pressure ultimately lead to water inrush from the floor.

Modern tectonic stress field deeply in Xuzhou Coal Mine

By inverting fault slip data, the parameters of 12 tectonic stress tensors in the mine region can be determined. The following characteristics can be obtained for recent tectonic stress fields, which are found deep in the study region. The results show that the recent tectonic stress field mainly presents the characteristics of near NWW-SSE maximum compressional stress and near NE-SW minimum extensional stress, while the stress regimes are mainly of strike slip, part of the reverse-fault type. Recent tectonic stress field in the region is characterized by horizontal components. The maximum principal compression stress direction was from NEE to SEE, the average principal compression stress direction was near NWW-SSE maximum compres- sional stress and near NE-SW minimum extensional. The recent tectonic stress field of the studied area can be controlled by a large tectonic stress area.

空间阶梯肋环型钢屋盖多管相贯节点试验研究

江阴市民水上活动中心的屋盖钢结构采用了阶梯式肋环型钢管网格结构体系。对该屋盖体系中的多管汇交相贯节点进行足尺试验研究,系统地总结了试验过程中的若干关键问题,包括最不利节点荷载选取、加载装置设计、加载制度确定以及试件测点布置等。根据节点足尺试验结果,分析节点域在设计荷载下的应力分布、刚度变化以及极限承载力。为了与试验结果进行比较,进行了该节点在试验条件下的有限元数值分析,确定了节点的极限承载力,为结构设计提供了可靠的数据及建议,可为类似复杂空间钢结构多管相贯节点的结构设计或试验提供参考。

Origin of the regional stress field along the Liquine-Ofqui Fault Zone(LOFZ),Southern Chilean Andes by means of FE Simulation

The Liquine-Ofqui Fault Zone(LOFZ) of southern Chilean Andes is one of the largest active strike-slip fault zones.There is an ongoing debate regarding the origin of the stress field along the LOFZ due to its complex geometry.This paper represents a study of the origins of the LOFZ regional stress field.Stress fields are calculated by finite element(FE) analysis.The two possible stress origins, i.e., oblique plate convergence and ridge collision/indenter tectonics of Chile ridge against Peru-Chile trench, have been emphasized in the present study.Three types of boundary conditions for the three particular models have been applied to calculate stress fields.Models are assumed to be elastic and plane stress condition.Modeling results are presented in terms of four parameters, i.e., orientation of maximum horizontal stress(σ H max ), displacement vector, s train distribution, and maximum shear stress(τmax ) contour line within the model.The results of the first model with oblique plate convergence show inconsistency between the geometric shape of the LOFZ and the distribution of the four parameters.Although more realistic results are obtained from the second model with normal ridge collision, there are few coincident in the LOFZ geometry and regional stress field.The third model with normal and oblique ridge collision is reasonable in understanding the origin of stress field and geometrical condition in the lithosphere of the LOFZ.

Simulation of astronomical solar radiation over Yellow River Basin based on DEM

Based on the developed distributed model for calculating astronomical solar radiation (ASR), monthly ASR with a resolution of 1 km×1 km for the rugged terrains of Yellow River Basin was calculated, with DEM data as the general characterization of terrain. This model gives an all-sided consideration on factors that influence the ASR. Results suggest that (1) Annual ASR has a progressive decrease trend from south to north; (2) the magnitude order of seasonal ASR is: summer>spring>autumn>winter; (3) topographical factors have robust effect on the spatial distribution of ASR, particularly in winter when a lower sun elevation angle exists; (4) the ASR of slopes with a sunny exposure is generally 2 or 3 times that of slopes with a shading exposure and the extreme difference of ASR for different terrains is over 10 times in January; (5) the spatial differences of ASR are relatively small in summer when a higher sun elevation angle exists and the extreme difference of ASR for different terrains is only 16% in July; and (6) the sequence of topographical influence strength is: winter>autumn>spring>summer.

Prediction on rock stratum stability using numerical simulation

Numerical simulation, which is one of the important methods for tectonic simulation, can be successfully applied into the stability analysis of rock stratum in mining engineering. With numerical simulation, the characteristics of stress deformation field of the area study can be well discovered, the stress concentration regions can be clearly located and the mechanism and effect of the stress concentration can be analyzed. The results of these studies offer fundamental data for evaluation of the rock stability and prediction of the tunnel wall stability in the working area.

Surrounding rock deformation regularity of roadway under extremely complicated geological conditions in deep mine and its control

By combining the practices of deep mine mining in Changguang Mine field and using the Universal Distinct Element Code 3 0(UDEC3 0) numerical computing method, the distribution characteristics of deformation field and stress field as well as the surrounding rock deformation regularity of soft rock roadway are analyzed under extremely complicated geological conditions, a technical principle of bolting to control the surrounding rock of roadway is put forward. And also using a dynamic control for surrounding rocks designing method, the supporting parameters and implement plan are rationally determined. The experimental tests have obtained a good controlling result of surrounding rock.

悬浇钢筋混凝土拱桥合理成桥状态的确定分析

悬浇钢筋混凝土拱桥在我国西部山区修建越来越多,但目前相关该类桥梁合理成桥状态的确定分析相对较少。文章介绍了合理成桥状态的确认内容和方法,并采用Midas Civil有限元软件对某悬浇钢筋混凝土拱桥建立了主拱圈一次落架和施工阶段模型,通过对比计算结果和实际施工的测试结果,分析了两者偏差产生的原因,论述采用"应力可行域"作为控制条件来检验一次落架法确定悬浇钢筋混凝土拱桥合理成桥状态的可行性和合理性,为该类桥梁设计、施工和监测提供借鉴。

Research on inspection of stability of subsiding area in composite rock-mass roadway

The research concentrates mainly on the development of failure process in composite rock-mass through acoustic emission, convergence inspection, stress measurement, subside area measurement, level measurement in the process of stability and safety monitoring as well as inspecting of subside area in composite hard rock. In terms of the modern signal analysis technology, various aspects are discussed. The monitoring result and the stability of rock mass can be synthetically evaluated and inferred, and the location of acoustic origin according to the acoustic emission regularity can be successfully detected. Finally the key factors of the deformation can be inferred from in subside area.

Inversion of Stress Fields in the Middle Section of the Xiaojiang Fault and Its Adjacent Area

With waveform data of 613 earthquakes with ML ≥ 2. 5 in the middle section of the Xiaojiang fault and its adjacent area which occurred during January,1998 to September 2007,focal mechanisms were calculated by the direct wave amplitude ratio of S /P in the vertical component and their characteristics were analyzed. According to regional tectonic features of the middle section of the Xiaojiang fault and its adjacent area,the study region was partitioned into two zones with the Xiaojiang fault as the boundary,e. g. zone A and zone B (including the Xiaojiang fault). In order to research the faults stress in detail,the Xiaojiang fault zone was picked out for independent analysis. The study region was also partitioned into 1°× 1° cells with a 0. 5° step. The stress fields of zone A,B and the fault zone were inverted with the FMSI method (Gephart,1990). The results show that first, the faults are mainly of strike-slip in the middle section and its adjacent area,amounting to 81. 28%,69. 23% and 72. 97% in the A,B and fault zones,respectively. Secondly,the stress inversion also indicates that the directions of maximum principal stress σ1 in the A, B,and fault zones are approximately NNW,NWW and NWW,the stress action is mainly horizontal,and strike-slip faulting is dominant in the study area. On the other hand,the direction of the principal stress field in the central Yunnan block changed from NNW to NWW,however,in the region between the Yuanmou and Pudu River faults,the azimuth of the main compressive stress shows that the north-south slip is obvious. While the direction of the main compressive stress of the Xiaojiang fault zone is nearly NW; in the east of the Xiaojiang fault,the direction of principal compressive stress is NW to NNW in the eastern Yunnan block.

Analysis of Contact Stress Distribution and Strength in Pin-Loaded Orthotropic Plates

The development of an analytic solution in terms of laminate parameters is presented for contact stresses and joint strength in pin-loaded orthotropic plates. This involved the determination of complex stress functions required to compute stresses in terms of a set of unknown coefficients for the specified displacement expressions satisfying the prescribed boundary conditions. The assumed Coulomb friction between the plate and the pin was used to provide the solution and iteration was also used to determine the extent of contact region. The results from present study showed good agreement with the available results in literature for all the joint configurations evaluated.