Pushover analysis of reinforced concrete frames considering shear failure at beam-column joints

Since most current seismic capacity evaluations of reinforced concrete （RC） frame structures are implemented by either static pushover analysis （PA） or dynamic time history analysis, with diverse settings of the plastic hinges （PHs） on such main structural components as columns, beams and walls, the complex behavior of shear failure at beam-column joints （BCJs） during major earthquakes is commonly neglected. This study proposes new nonlinear PA procedures that consider shear failure at BCJs and seek to assess the actual damage to RC structures. Based on the specifications of FEMA-356, a simplified joint model composed of two nonlinear cross struts placed diagonally over the location of the plastic hinge is established, allowing a sophisticated PA to be performed. To verify the validity of this method, the analytical results for the capacity curves and the failure mechanism derived from three different full-size RC frames are compared with the experimental measurements. By considering shear failure at BCJs, the proposed nonlinear analytical procedures can be used to estimate the structural behavior of RC frames, including seismic capacity and the progressive failure sequence of joints, in a precise and effective manner.

Vertex centrality of complex networks based on joint nonnegative matrix factorization and graph embedding

Finding crucial vertices is a key problem for improving the reliability and ensuring the effective operation of networks,solved by approaches based on multiple attribute decision that suffer from ignoring the correlation among each attribute or the heterogeneity between attribute and structure. To overcome these problems, a novel vertex centrality approach, called VCJG, is proposed based on joint nonnegative matrix factorization and graph embedding. The potential attributes with linearly independent and the structure information are captured automatically in light of nonnegative matrix factorization for factorizing the weighted adjacent matrix and the structure matrix, which is generated by graph embedding. And the smoothness strategy is applied to eliminate the heterogeneity between attributes and structure by joint nonnegative matrix factorization. Then VCJG integrates the above steps to formulate an overall objective function, and obtain the ultimately potential attributes fused the structure information of network through optimizing the objective function. Finally, the attributes are combined with neighborhood rules to evaluate vertex's importance. Through comparative analyses with experiments on nine real-world networks, we demonstrate that the proposed approach outperforms nine state-of-the-art algorithms for identification of vital vertices with respect to correlation, monotonicity and accuracy of top-10 vertices ranking.

Seismic Behaviour of Beam-Column Joints of Precast and Partial Steel Reinforced Concrete

A beam-column joint of precast and partial steel reinforced concrete( PPSRC) is proposed for precast reinforced concrete frames. The PPSRC consists of partial steel and reinforced concrete. The partial steel is located in the core joint region and the connections between concrete members. This paper presents an experimental study of a series of PPSRC specimens. These specimens are tested under low cyclic loading.Experimental results demonstrate that the bearing capacity of the PPSRC specimens is 3 times that of the ordinary reinforced concrete( RC) beam-column joints. The strength and stiffness degradation rates are slower compared with that of the RC beam-column joints. In addition,the strength of the core joint region and the connections is higher than other parts of the PPSRC specimens. Beam failure occurs firstly for the PPSRC specimens,followed by column failure and connections failure. The failure of the core joint region occurs finally.Test results show that the seismic performance of the PPSRC is better than that of the ordinary RC beam-column joints.

Analysis of the stress intensity factor of welded joints under prior corrosion and complex stress fields

Taking cruciform welded joints under different corrosion degrees, together with 45° inclined angle and full penetration load-carrying fillet, as the research object, the stress intensity factor of a quarter-circular comer crack of welded joints is calculated based on FRANC3D with ABAQUS. Effects of different corrosion pit sizes, crack aspect ratios, and crack depths on stress intensity factor are analyzed. The results show that pit depth plays a major role in stress intensity factor, while the effect of pit radius is relatively small. The cracking modes of the surface and the deepest point are mode I, and mixed modes I and II, respectively. Effects of pit depths, crack aspect ratios, and crack depths on the stress intensity factor at the surface point are greater than at the deepest point.

COMPLEX VARIABLE-VARIATIONALMETHOD OF SOLUTION FOR BI-METALLAMINATES WITH INTERFACE CRACKSAND ITS APPLICATION IN GLUED JOINTS

In this paper, the eigen function expansions of displacements and stresses of bi-metal laminates with interface cracks are obtained. Furthermore, the stress intensity factors are determined by the variational method to satisfy the boundary conditions and there are only line integrals in the variational equations due to the previous satisfaction of all basic equations. The computations show that this method of solution has the advantages of rapid convergency and time-saving. The results obtained by this method for homogeneous material agree with the known ones very well.

Low Complexity Joint Hybrid Precoding for Millimeter Wave MIMO Systems

In millimeter wave(mmWave) multiple-input multiple-output(MIMO) systems, hybrid precoding has been widely used to overcome the severe propagation loss. In order to improve the spectrum efficiency with low complexity, we propose a joint hybrid precoding algorithm for single-user mmWave MIMO systems in this paper. By using the concept of equivalent channel, the proposed algorithm skillfully utilizes the idea of alternating optimization to complete the design of RF precoder and combiner. Then, the baseband precoder and combiner are computed by calculating the singular value decomposition of the equivalent channel. Simulation results demonstrate that the proposed algorithm can achieve satisfactory performance with quite low complexity. Moreover, we investigate the effects of quantization on the analog components and find that the proposed scheme is effective even with coarse quantization.

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete （SRUHSC） columns and steel reinforced concrete （SRC） beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirIup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete （SRC） frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

Seismic performance and global ductility of RC frames rehabilitated with retrofi tted joints by CFRP laminates

This paper presents a new FRP retrofi tting scheme to strengthen local beam-column joints in reinforced concrete(RC) frames.The new retrofi tting scheme was proposed following a preliminary study of four different existing retrofi tting schemes.A numerical simulation was conducted to evaluate the effectiveness of FRP-strengthened reinforced concrete frames by bridging behavior of local joints to the whole structure.Local confi nement effects due to varying retrofi tting schemes in the joints were simulated in the frame model.The seismic behavior factor was used to evaluate the seismic performance of the strengthened RC frames.The results demonstrated that the new proposed retrofi tting scheme was robust and promising,and fi nite element analysis appropriately captured the strength and global ductility of the frame due to upgrading of the local joints.

Surgical Repair of Dorsal Capsulo-Ligamentous Complex for Dislocation of the Thumb Carpometacarpal Joint

Background: Acute dislocation of the thumb carpometacarpal (CMC) joint is a rare and challenging injury, and its treatment remains controversial. The purpose of the study was to evaluate the clinical outcome after surgical repair of the dorsal capsulo-ligamentous complex. Materials and methods: Eight patients with a mean age of 39.8 years (range, 23 - 56 years) treated for the thumb CMC joint were treated in our hospital between 2008 and 2018. The ruptured dorsal capsulo-ligamentous complex was repaired using suture anchors in all patients, and the joint was immobilized with a Kirschner wire pinning and splint for 3 weeks. The clinical outcome was assessed by measuring the range of motion of the thumb CMC joint and the Japanese Society for Surgery of the Hand version of the Quick Disability of the Arm, Shoulder, and Hand (Q-DASH-JSSH) score. Results: The mean radial abduction of the thumb CMC joint was 66°, and the volar abduction was 63°. The mean Q-DASH-JSSH score was 4.8 (range, 0 - 15.6). There were no cases of infection, nerve disturbance, or osteoarthritis. Anatomical reduction was observed in seven patients at the final follow-up and in a rugby football player at 6 months of follow-up;however, subluxation of the thumb CMC joint at 12 months of follow-up due to reinjury was observed. Conclusion: Surgical repair of the dorsal capsulo-ligamentous complex with suture anchors is a reliable and simple treatment for acute unstable dislocation of the thumb CMC joint.

Clinical study on the surgical treatment of atypical Lisfranc joint complex injury

BACKGROUND Lisfranc injuries have not received much attention by orthopedic doctors in the past,and there is little related research on the diagnosis and treatment of these injuries.In recent years with the rise in foot and ankle surgery,doctors are now paying more attention to this type of injury.However,there is still a high rate of missed diagnosis due to insufficient attention causing treatment delays or inadequate treatments,which eventually result in greater sequelae;including long-term pain,arthritis,foot deformity etc.In particular,for cases with a mild Lisfranc joint complex injury,the incidence of sequelae is higher.AIM To select an active surgical treatment for an atypical Lisfranc joint complex injury and to evaluate the clinical efficacy of the surgical treatment.METHODS The clinical data of 18 patients,including 10 males and 8 females aged 20-64 years with Lisfranc injuries treated in our department from January 2017 to September 2019 were retrospectively analyzed.All patients were treated with an open reduction and internal fixation method using locking titanium mini-plates and hollow screws or Kirschner wires.X-ray images were taken and follow-up was performed monthly after the operation;the internal fixation was then removed 4-5 mo after the operation;and the American Orthopedic Foot and Ankle Society(AOFAS)score was used for evaluation on the last follow-up.RESULTS All patients were followed up for 6-12 mo.A good/excellent AOFAS score was observed in 88.9%of patients.CONCLUSION For atypical Lisfranc joint complex injuries,active open reduction and internal fixation can be performed to enable patients to obtain a good prognosis and satisfactory functional recovery.

Finite Element Analysis (FEA) for the Beam-Column Joint Subjected to Cyclic Loading Was Performed Using ANSYS

This paper analyses the seismic performance of exterior beam-column joints strengthened with unconventional reinforcement detailing. The beam-column joint specimens were tested with reverse cyclic loading applied at the beam end. The samples were divided into two groups based on the joint reinforcement detailing. The first group (Group A) of three non-ductility specimens had joint detailing in accordance with the construction code of practice in India IS456-2000, and the second group (Group B) of three ductility specimens had joint reinforcement detailed as per IS13920-1993, with similar axial load cases as the first group. The experimental studies are proven with the analytical studies carried out by finite element models using ANSYS. The results show that the hysteresis simulation is satisfactory for both un-strengthened and ferrocement strengthened specimens. Furthermore, when ferrocement strengthening is employed, the strengthened beam-column joints exhibit better structural performance than the un-strengthened specimens of about 31.56% and 38.98 for DD-T1 and DD-T2 respectively. The analytical shear strength predictions were in line with the test results reported in the literature, thus adding confidence to the validity of the proposed models.

颞下颌关节盘前移位患者盘-髁复合体MRI特征及盘周附着半量化评级研究

目的通过盘-髁复合体磁共振成像(magnetic resonance imaging,MRI)特征分析及盘周附着半量化评级法,探讨颞下颌关节可复性盘前移位(anterior disc displacement with reduction,ADDWR)与不可复性盘前移位(anterior disc displacement without reduction,ADDWoR)中关节盘形态、髁突形态及盘周附着处之间的相关性。材料与方法回顾性分析2021年5月至2022年9月于福建省级机关医院行MRI检查确诊为颞下颌关节盘前移位74例患者共114侧,分为ADDWR组39侧和ADDWoR组75侧,比较关节盘形态Ⅰ~Ⅳ类型、髁突形态3类别及盘周附着处半量化评分分级6级。采用Kruskal-Wallis检验比较两组中不同关节盘形态类型、髁突形态类别及盘周附着分级之间差异。采用Mann-Whitney U检验比较两组之间关节盘形态、髁突形态、盘周附着处总评分及各处附着评分差异。采用Spearman秩相关分析关节盘形态、髁突形态、盘周附着处总评分及各附着与盘-髁复合体可复性与否的相关系数。采用二元logistic回归方法对盘周附着的模型筛选出独立危险因素,作为盘-髁复合体是否可复性的预测。结果除Ⅲ型与Ⅳ型外,两组关节盘形态类型差异均有统计学意义(P<0.05)。两组髁突形态类别差异均有统计学意义(P<0.05)。除1级至4级、5级/6级外,两组盘周附着评分分级差异均有统计学意义(P<0.05)。关节盘可复性与否和关节盘形态、髁突形态及盘周附着处总评分存在较强的正相关性(r分别为0.824,0.626及0.827,P<0.05)。盘周附着处的logistic回归预测模型筛选发现下板附着处是关节盘可复性与否的独立危险因素,回归系数为2.979(OR=19.672,P<0.05)。结论基于盘-髁复合体MRI征象分析及半量化评级法,能有效地评估关节盘可复性与否的相关性因素,为临床治疗提供可靠的影像学参考。

复杂场景下多模态点云数据配准技术

针对复杂环境下多模态点云数据获取难,以及对点云数据配准、三维模型构建精度的要求越来越高的情况。本文以南通大剧院实景三维建模为例,当初始点云和校准点云两组多模态融合点云位置差较大时,采用ICP算法进行点云配准易导致局部最优问题,利用所提出的基于控制点辅助约束的最近点迭代(CPA-ICP)算法通过对点云数据进行配准,并与其他3种点云配准算法的试验进行对比,可知该方法的配准精度和配准效率较高,对复杂场景下的多模态点云数据融合有较好的参考意义。

络合沉淀法—硫化沉淀法联合处理铜氰贫液试验研究

针对某黄金生产企业产生的铜氰贫液,采用络合沉淀法—硫化沉淀法联合进行回收处理。在络合沉淀法五水合硫酸铜投加量3.0 g/L、焦亚硫酸钠投加量2.0 g/L,硫化沉淀法九水合硫化钠加药量0.35 g/L条件下,铜氰贫液中总氰化合物、铜和硫氰酸盐质量浓度从150.84 mg/L、121.46 mg/L、252.65 mg/L降至0.44 mg/L、86.17 mg/L、1.23 mg/L,回收金、银、铜的产值为116.62元/m^(3),扣除药剂成本后产生经济效益55.44元/m^(3)。研究结果为类似氰化企业铜氰贫液的净化处理提供参考。

复杂断块油藏井震联合建模数模一体化技术研究

【目的】为解决复杂断块油藏面临的油藏构造碎小、低序级断层数量多、准确识别难度大和油藏描述效率低等问题。【方法】充分应用地震资料、测井数据等储层信息,开展井震联合建模数模一体化技术研究,利用三维地震资料,结合现场生产动态响应情况开展断层精细解释、断裂系统精细刻画,准确落实低序级断层发育及组合方式,在精细地层对比研究的基础上,建立三维地质模型,利用数值模拟与模型互检,迭代修正更新模型,尽可能保证模型精准,以便厘清剩余油分布规律,指导后期开发。【结果】该技术在胜利油田复杂断块区D块、L块等多个区块先后进行了应用,结果显示,断点吻合率均达到100%,数模含水拟合率达到90%以上。【结论】该技术能够实现复杂断块构造的精细描述,对特高含水期自然断块剩余油潜力认识、提高老区采收率具有重要意义,对其他同类型油藏的剩余油挖潜具有指导意义和良好的推广价值。

苏州某大型复杂商业连体结构设计

苏州某大型商业综合体项目位于7度抗震设防烈度区,为体型重叠建筑。通过5道防震缝将建筑整体划分为购物中心A区、购物中心B区、停车楼、商业街A区、商业街B区五个独立结构单元。购物中心A区为复杂连体高层建筑,1~5层采用框架-剪力墙结构,两个单体在3~5层中区由钢桁架相连,顶部(6层)钢桁架结构与两个单体通过成品球铰支座连接,形成强连体结构。充分考虑了周期比、位移比双指标平衡后对购物中心A区剪力墙布置进行了优化;屋顶钢桁架结构支座采用变刚度设计,局部设置滑动支座解决恒载下杆件应力比较高的问题。通过性能化设计,该复杂结构连体部位可以满足中震弹性、大震不屈服的性能目标要求。性能化设计及专项分析表明,影院钢结构具有良好的抗震性能、楼盖舒适度及防倒塌性能。

下肢重复蹬伸至力竭过程中肌肉功能网络拓扑特性

背景:表面肌电已经被广泛用于监测肌肉疲劳,但传统肌电指标通常针对于单块肌肉,无法评价一组肌肉在疲劳过程中的变化。目的:建立肌肉功能网络,提取复杂网络参数,研究不同疲劳程度下的肌肉功能网络拓扑特性变化,为疲劳的监测、预防提供理论和方法依据。方法:11名受试者进行直到力竭的50%1RM单腿下肢蹬伸运动,同步采集股直肌、股外侧肌、股内侧肌、股二头肌长头、胫骨前肌、腓肠肌外侧肌、腓肠肌内侧肌7块肌肉的肌电信号,以及心电信号和Borg CR-10量表评分;根据Borg CR-10量表评分划分为轻度、中度和重度三个疲劳阶段,采用心率和心率变异性验证疲劳阶段划分的有效性;以7块肌肉为节点,使用肌肉信号的相干性构建肌肉功能网络,提取聚类系数、平均加权度、全局效率、特征向量中心性4个复杂网络参数;提取肌电信号的均方值振幅、中位频率、瞬时平均频率和共激活比4种指标,并在3种疲劳程度下进行比较。结果与结论:①3种疲劳阶段在心率及心率变异性上产生显著性差异,证明了疲劳阶段划分的有效性;②对于不同肌肉在3种疲劳程度下的肌电指标:均方值振幅和共激活比未表现出差异,中位频率在股外侧肌、股内侧肌和股二头肌长头表现出稳健的疲劳趋势,瞬时平均频率则在股直肌、股外侧肌、股内侧肌和股二头肌长头表现出稳健的疲劳趋势;瞬时平均频率的性能优于中位频率和均方值振幅,但三者仅在主要工作肌群能够获得较好的稳健趋势,共激活比不受疲劳因素的影响;③股外侧肌-股内侧肌、股外侧肌-股二头肌长头、股外侧肌-腓肠肌内侧肌和股内侧肌-股二头肌长头连接强度逐渐增加,平均加权度、聚类系数和全局效率在疲劳后表现出显著差异,并且与疲劳程度之间显著相关。结果表明:肌肉功能网络内的连通强度变化能够反映疲劳过程中肌肉间的协同性和互补性;聚类系数、平均加权度、全局效率可作为一组肌肉疲劳的监测指标。

某航站楼钢屋盖复杂节点有限元分析

节点设计是空间钢结构设计的重要环节.某国际机场航站楼的钢结构屋盖为空间方管桁架体系,节点构造较为复杂,现有规范并未给出相关的承载力计算方法,为验证节点的安全性,采用ABAQUS有限元软件对关键节点进行力学性能分析,并在分析过程中考虑几何非线性和材料非线性的影响.有限元分析结果表明,本工程的节点在检验荷载作用下,节点承载力总体满足设计要求;对于承载力不满足设计要求的节点,合理设置加劲板可以有效缓解节点区的应力集中,增大节点安全储备.

南昌文体中心大跨度重型钢结构桁架设计关键问题分析

南昌文体中心项目采用大跨度重型钢结构桁架实现了最大99m的无柱空间。为了阐述大跨度重型钢结构桁架的设计思路,考察设计、施工中各因素的影响,通过理论分析和数值模拟细致地讨论了涉及的关键问题,包括杆件布置、支承条件、关键节点构造、施工过程的影响等。结果表明:腹杆布置形式对弦杆内力的影响较小;重型桁架两支承端的连接处理至关重要,应注意保证弦杆轴力在极限承载状态下的有效传递,并弱化弯矩的影响;整体提升施工方案对结构内力分布影响较大,“后激活”部分杆件的方法可以考虑提升过程中桁架端面的转动效果,更为准确地体现施工过程的影响。

钢轨焊缝复杂曲面打磨机器人选型及打磨工艺

钢轨焊缝焊筋的处理一直由人工使用砂轮机进行打磨,轨腰焊筋处于被保留状态。轨腰焊筋处常出现推凸挤入、表面划伤、热裂纹等,这些缺陷在探伤时很容易被判定为焊筋波而造成误判。鉴于当前机器人的功能发展完善,钢轨复杂曲面打磨可以选用具备全回转、自动调节角度功能的工业六轴机器人来进行功能控制程序设计实现仿人工打磨,并研究刀具、磨料、磨削工艺对焊接接头焊筋处理的影响因素以及磨削过程中刀具正常损耗对磨削精度的影响因素,确定工艺标准。钢轨焊接后复杂曲面打磨机器人实现了对钢轨焊缝形态一致性偏差打磨轨迹的主动兼容与适应,使焊筋与母材圆(平)顺过渡,完全消除焊筋波,可完全替代人工打磨。采用仿造人工Z字形连续和局部重叠打磨,最大程度上降低了对母材造成的损耗。打磨机器人刀具在给定的打磨力120 N,转速6000 r/min,打磨进给量0.2 mm/r参数下,单次打磨即可满足磨削质量要求。