Improving Fatigue Properties of 316L Stainless Steel Welded Joints by Surface Spinning Strengthening

The surface spinning strengthening(3S)mechanism and fatigue life extension mechanism of 316L stainless steel welded joint were systematically elucidated by microstructural analyses and mechanical tests.Results indicate that surface gradient hardening layer of approximately 1 mm is formed in the base material through grain fragmentation and deformation twin strengthening,as well as in the welding zone composed of deformedδ-phases and nanotwins.The fatigue strength of welded joint after 3S significantly rises by 32%(from 190 to 250 MPa),which is attributed to the effective elimination of surface geometric defects,discrete refinement ofδ-Fe phases and the appropriate improvement in the surface strength,collectively mitigating strain localization and surface fatigue damage within the gradient strengthening layer.The redistributed fineδ-Fe phases benefited by strong stress transfer of 3S reduce the risk of surface weak phase cracking,causing the fatigue fracture to transition from microstructure defects to crystal defects dominated by slip,further suppressing the initiation and early propagation of fatigue cracks.

Experimental Study on Seismic Behavior ofSeismic-damaged Lateral Joints in CompositeFrame Consisting of CFSST Columns and SteelBeams Strengthened with Enclosed ReinforcedConcrete

A new composite strengthening method of seismic-damaged lateral joints in composite frame consisting of Concrete-Filled SquareSteel Tubes （CFSST） columns and steel beams strengthened with enclosed Reinforced Concrete （RC） at the ends of columns andwelding steel plates at the ends of beams was presented. Based on the current design specifications, one half scaled models of 4lateral joints in composite frame consisting of CFSST columns and steel beams were designed and manufactured. One model wasoriginal control specimen, one was strengthened by enclosed RC, and the others were strengthened after pre-damage. The destructiontests under lateral cyclic load on the models were carried. The effectiveness of seismic-damaged joints strengthened with enclosedRC and the reinforcement effect on different levels of seismic damage were studied. The test results show that seismic- damagedjoints in composite frame consisting of CFSST columns and steel beams strengthened with enclosed RC meets the strongcolumn-weak beam joints requirement of seismic design, and the failure modes are of all joints are the bending failure of steel beam.The reinforcement with enclosed RC has a significant on increasing the ultimate capacity and the seismic behaviors of joints. Thestudy indicated the rehabilitated joints recover the level of their original seismic performances before seismic damage in a certainextent damage level. Based on the test data, namely the ultimate capacity, limit displacement, ductility, the energy consumptioncoefficient, limit displacementthe strengthening method of seismic-damaged joints by strengthened with enclosed RC is an effectivemethod for seismic strengthening.

Experimental study on aseismic behaviors of Chinese ancient tenon-mortise joint strengthened by CFRP

In order to well protect Chinese ancient buildings, aseismic behaviors of Chinese ancient tenon-mortise joints strengthened by carbon fibre reinforced plastic （CFRP） are studied by experiments. Based on the actual size of an ancient building, a wooden frame model with a scale of 1 ： 8 of the prototype structure is built considering the swallow-tail type of tenon-mortise connections. Low cyclic reversed loading tests are carried out including three groups of unstrengthened structures and two groups of structures strengthened with CFRP. Based on experimental data, moment-rotation angle hysteretic curves and skeleton curves for each joint are obtained. The energy dissipation capability, stiffness degradation and deformation performance of the joints before and after being strengthened are also analyzed. Results show that after being strengthened with CFRP, the tenon value pulled out of the mortise is reduced; the bending strength and the energy dissipation capabilities of the joint are enhanced; stiffness degradation of the joint is not obvious; and the deformation performance of the joint remains good. Thus, the CFRP has good effects on strengthening the tenon-mortise joints of Chinese ancient buildings.

Rapid Repair of Earthquake Damaged RC Interior Beam-wide Column Joints and Beam-wall Joints Using FRP Composites

This paper studies the seismic performance of FRP-strengthened RC interior non-seismically detailed beam-wide columns and beam-wall joints after limited seismic damage.Four eccentric and concentric beam-wide column joints and two beam-wall joints,initially damaged in a previous study,were repaired and tested under constant axial loads(0.1fc′Ag and 0.35fc′Ag) and lateral cyclic loading.The rapid repair technique developed,aimed to restore the original strength and to provide minimum drift capacity.The repair schemes were characterized by the use of:(a) epoxy injections and polymer modified cementitious mortar to seal the cracks and replace spalled concrete;and(b) glass(GFRP) and carbon(CFRP) sheets to enhance the joint performance.The FRP sheets were effectively prevented against possible debonding through the use of fiber anchors.Comparison between responses of specimens before and after repair clearly indicated reasonable restoration in strength,drift capacity,stiffness and cumulative energy dissipation capacity.All specimens failed with delamination of FRP sheets at beam-column joint interfaces.The rapid repair technique developed in this study is recommended for mass upgrading or repair of earthquake damaged beam-column joints.

Micro-mechanical properties of 2219 welded joints with twin wire welding

Nanoindentation method was adopted to investigate the distribution regularities of micro-mechanical properties of 2219 twin wire welded joints, thus providing the necessary theoretical basis and guidance for joint strengthening and improvement of welding procedure. Experimental results show that in weld zone, micro-mechanical properties are seriously uneven. Both hardness and elastic modulus distribute as uneven sandwich layers, while micro-mechanical properties in bond area are much more uniform than weld zone;In heat-affected zone of 2219 twin wire welded joint, distribution regularity of hardness is similar to elastic modulus. The average hardness in quenching zone is higher than softening zone, and the average elastic modulus in solid solution zone is slightly higher than softening zone. As far as the whole welded joint is concerned, metal in weld possesses the lowest hardness. For welded specimens without reinforcement, fracture position is the weld when tensioning. While for welded specimens with reinforcement, bond area is the poorest position with joint strength coefficient of 61%. So, it is necessary to strengthen the poor positions--weld and bond area of 2219 twin wire welded joint in order to solve joint weakening of welding this kind of alloy.

增设角部阻尼器箍头榫木节点的抗震性能

为了给广府木结构的修复提供理论依据,采用菠萝格木材设计制作了5个箍头榫节点试件。考虑到榫卯构造尺寸的影响,首先进行了未加固无损节点的拟静力试验。然后,采用对原有外观影响较小的雀替型阻尼器对上述节点损坏试件进行加固,以尽可能保留建筑的原始风貌。最后,对加固节点进行拟静力试验,以研究节点的抗震性能变化以及阻尼器的加固效果。结果表明:采用阻尼器加固后的节点试件在加载至破坏时,榫卯处压痕明显,梁外榫外侧劈裂、脱榫现象明显,阻尼器脚部的橡胶与钢板有一定的脱离现象;对节点增设阻尼器能够弥补节点初期损伤导致的受力性能下降,为残损榫卯节点提供较好的后期刚度,提高节点的承载能力和耗能能力;与未加固试件相比,增设阻尼器后,试件的后期刚度、极限承载力、总滞回耗能均有所增加,分别提高18%、19%、20%以上。文中还在已有简化力学模型的基础上,结合OpenSees,提出了一种应用于箍头榫木结构的宏观模型建模方法。采用该方法得到的节点滞回曲线与试验结果吻合良好,可以有效模拟阻尼器加固的箍头榫木节点的滞回耗能特性。

非对称加强与狗骨式削弱型钢框架节点抗震性能数值模拟

为有效防止梁柱节点处发生脆性破坏并提高节点抗震性能,提出一种非对称加强与狗骨式削弱型钢框架节点。以边柱节点为例,利用ABAQUS有限元软件对非对称加强与狗骨式削弱型节点、非对称加强型节点、狗骨式削弱型节点和普通型节点共4个节点模型进行抗震性能对比分析,研究了节点的破坏形态、滞回曲线、骨架曲线、延性、耗能能力和刚度退化等方面的区别。研究表明:非对称加强与狗骨式削弱型节点能够有效实现塑性铰外移,防止节点发生脆性破坏,同时不仅能够提高节点的耗能能力和延性,还可以保持较好的承载能力。

What are the Special Plant Ingredients from Each Province of China Used in Cosmetics?

“Encourage and support the use of modern science and technology in the cosmetics R&D,with the help of China’s traditional advantage projects and special plant resources”.This is a clear voice in the Regulation on the Supervision and Administration of Cosmetics often quoted as the evidence that China’s special plant resources are highly recommended by the country and enjoy a good external development environment.The Work Plan for Stabilizing the Growth of Light Industry(2023-2024),jointly issued by the Ministry of Industry and Information Technology,the National Development and Reform Commission and the Ministry of Commerce,also advocates“strengthening the development and innovation of special plant ingredients,promoting the scale production of bioactive ingredients,and extending the application of special plant ingredients in the food,cosmetics and other industries”.

淮安某学校风雨操场体育馆结构设计

淮安某学校风雨操场体育馆由主馆和训练馆组成,为大跨空间结构,主体结构采用钢筋混凝土框架结构,屋盖采用平面管桁架轻钢屋面。针对本工程特点,论文采用PKPM和3D3S两种软件对结构进行整体计算分析,两种软件的计算结果表明,结构各项参数、屋盖强度、稳定性及变形等指标均满足规范要求,同时,还介绍了钢管桁架连接节点做法、桁架支座与主体结构连接方式以及超长结构的加强措施。

间歇式膨胀加强带在净水厂工程中的应用

为了控制超长水池裂缝的发展,通过对反冲洗水池壁板裂缝统计分析,提出了采用间歇式膨胀加强带代替连续式膨胀加强带的施工措施,并进行了现场试验性应用。结果表明:采用间歇式膨胀加强带可进一步限制和控制池体裂缝发展;间歇式膨胀加强带间歇时间7d~10d是合适的,实际施工间隔时间可根据现场实际情况适当微调,但不宜小于7d。可为同类水池、泵房类构筑物的变形缝设计提供参考。

Moiré method analysis for tensile strain field of 2024 aluminum alloy welded joint

Using experimental mechanics method of moiré analysis, strain field distributions of 2024 aluminum alloy welded joints under different conditions were investigated. The results show that moiré stripes of welded joint without trailing peening just before fracture are not only few and scattered but also uneven, and the stress mainly concentrates on the poor position welded toes during the tensioning process with the relatively poor mechanical properties of welded joints; When the method of welding with trailing peening is adopted, moiré stripes of welded joint just before fracture are relatively thick and even due to the strengthening welded toes during the welding process, and fracture position transfers from the welded toes to weld, at the same time the mechanical properties of welded joints are improved greatly than conventional welding which can show that the technology of trailing peening is effective to strengthen welded joints of aluminum alloy with high strength.

雀替型阻尼器加固箍头榫木框架结构的抗震性能

为研究广府古建筑木结构的抗震性能及加固方法,采用菠萝格木材,设计并制作了两榀不同结构形式的典型广府木祠堂箍头榫框架,提出并制作了用于木结构榫卯节点加固的雀替型阻尼器,对雀替型阻尼器加固前后的木框架进行低周往复荷载试验,研究结构的抗震性能及阻尼器的加固效果。研究结果表明:阻尼器可以弥补初次加载产生的损伤,在转角不大时给残损的榫卯节点提供较高的初始刚度,并在榫卯节点自身开始闭合时与之协同受力,提高节点刚度、极限承载能力和耗能能力,使得加固试件的极限承载能力高于未加固试件;未加固试件经过加载,出现了榫卯脱离、榫卯局部压屈现象,加固试件的破坏形式主要为榫卯脱离、榫卯局部压屈和竖向顺纹劈裂裂缝;各节点的滞回曲线呈现明显的“捏缩”现象,榫卯节点强度退化系数均大于0.83,在循环荷载作用下表现出稳定的承载性能,随节点转角的增大,各节点的环线刚度、等效粘滞阻尼系数呈现逐渐减小并趋于稳定的趋势;边跨框架试件节点的等效粘滞阻尼系数逐渐稳定于0.1~0.2,而中跨框架试件节点的等效粘滞阻尼系数逐渐稳定于0.05~0.1,且经过阻尼器加固,边跨框架与中跨框架试件的总滞回耗能分别提高了67%和19%。

强化膝关节控制训练对脑卒中后膝过伸的疗效研究

目的观察脑卒中后膝过伸患者采用强化膝关节控制训练的效果。方法选取2021年1—10月期间中山市中医院收治的60例脑卒中后膝过伸患者为研究对象,采用随机数字表法分为对照组(30例,常规康复训练)与治疗组(30例,常规康复训练联合强化膝关节控制训练),2组患者均训练2周。训练结束时,对比2组患者治疗效果、平衡功能[采用Berg平衡量表(BBS)评估]及步行功能[采用“起立-行走”计时测试(TUGT)评估]、下肢运动功能[采用Fugl-Meyer运动功能量表(FMA)评估]。结果2组治疗有效率对比,差异无统计学意义(P>0.05)。治疗前,2组患者BBS评分、TUGT时间及FMA评分对比,差异无统计学意义(P>0.05);治疗后,2组BBS评分、FMA评分升高,TUGT时间缩短,且治疗组患者BBS评分、FMA评分高于对照组,TUGT时间短于对照组,差异有统计学意义(P<0.05)。结论脑卒中后膝过伸患者在常规康复训练基础上联合强化膝关节控制训练的效果显著,利于改善下肢运动功能,提高平衡功能及步行能力,值得借鉴。

高烈度区古建筑木构架的拉结加固方法

榫卯节点是木构架构件连接的关键构造,也是地震中容易损伤的部位,其抗震加固是降低木构架地震损伤程度、提升整体稳定性能的重要措施。依据GB/T 50165—2020《古建筑木结构维护与加固技术标准》的抗震鉴定要求,以构架的柱与梁枋拉结加固、构架间连接加固为研究重点,针对榫卯节点以及屋盖构件连接的薄弱构造和损伤特征,提出了高烈度设防区木构架整体拉结加固的实用方法,研制了相应的加固装置。该方法根据木构架在地震中的变形特点,确定了拉结加固的重点部位,以及加固装置的布置形式。所研制的加固装置源于传统铁件加固工艺并进行了性能改善,采用现代防锈蚀钢材制作连接件和紧固件,可延长装置的使用期限;采用降低连接件弯曲刚度的构造措施,可减少对榫卯节点半刚性转动性能的影响。为了推动抗震新技术在古建筑中的运用,介绍了一种布置在木构架额枋与柱之间的雀替式加固装置,可有效地提升高烈度区木构架的变形控制与能量耗散性能。

上海体育场2021年世俱杯改建结构设计与研究

上海体育场作为承办2021年世俱杯开闭幕式和总决赛的场地,按照国际足联(FIFA)相关的场地要求,需对现有场地及相应的设施进行改建。改建主要有四个方面:接待区域升级、场芯下挖1.7m、首层看台上抬约1.8m和屋盖钢结构悬挑向内延展16.5m,其中屋盖改建方案填补了国内在既有空间钢结构上进行大比例悬挑延伸改建的空白。为实现屋盖如此大比例的悬挑延展,既有屋盖钢结构在新增结构施工前,进行了负载状态下的加固,包括改变结构体系的加固、受力转换的加固和杆件与节点的补强加固,保障了结构的安全。同时为了体育场与科技的完美融合,设计中在新增悬挑段中满布设置了LED天幕和南北侧两块大屏,给观众更好的观赛体验。

施工缝加固后铁路重力式桥墩的抗震性能试验研究

为研究施工缝加固后铁路重力式桥墩的抗震性能,选用玄武岩纤维布加固墩身施工缝,采用拟静力试验研究施工缝加固前后桥墩的抗震性能,从加固前后桥墩的破坏特征,滞回曲线和骨架曲线,以及承载力、累积耗能、刚度等指标对桥墩进行抗震性能分析。试验结果表明:采用玄武岩纤维布加固墩身施工缝后,桥墩的破坏面出现在墩底,施工缝区域未发生破坏;与未加固的桥墩相比,施工缝加固后的桥墩的极限承载力、耗能能力和刚度都得到了提升。

胜利黄河大桥病害高强螺栓节点修复及桥面板补强技术

胜利黄河大桥主桥为(60.5+136.5+288+136.5+60.5)m连续钢箱梁斜拉桥,桥面板采用正交异性钢桥面板,钢箱梁节段横缝采用摩擦型高强螺栓(Friction-type High-Strength Bolt,FHSB)连接。受人为和自然环境因素影响,该桥运营33年后出现了横缝FHSB节点锈蚀、接触面磨光、正交异性钢桥面板U肋焊缝开裂与脱落、横缝折角等病害。对该桥病害进行统计及成因分析,并提出病害FHSB节点修复及超高性能混凝土(Ultra-High Performance Concrete,UHPC)桥面板补强技术。拆除横缝位置处的原连接U肋拼接板,按照“纵横对称间隔拆除”的原则拆除原桥螺栓群,喷砂处理节点接触面,螺母侧朝下重新栓接更换的拼接板,栓焊新增的U肋拼接板,最后铺装UHPC桥面板。通过理论分析及数值模拟,对比分析了加固前、后横缝FHSB节点的抗滑承载力及主梁结构性能,并进行全桥荷载试验。结果表明:加固后,横缝FHSB节点抗滑承载力恢复至设计值,修复施工阶段桥梁结构安全可靠,改造后主梁结构性能满足规范要求。

与连续倒塌相关的T型钢连接破坏模式和梁柱子结构抗力机制研究

关于T型钢连接破坏的研究已有很多,但与连续倒塌相关且关注弱轴效应的并不多见。利用非线性有限元软件ABAQUS进行了数值模拟,探讨了与结构连续倒塌相关的T型钢节点的连接性能和梁柱子结构的抗力机制。考虑了材料塑性与损伤演化,力求准确预报T型钢连接梁柱子结构在中柱失效条件下的破坏行为,重点考察了弱轴方向节点连接类型、节点构造和连接板尺寸效应对结构破坏模式和抗力机制转换的影响。分析结果表明:弱轴方向采用梁-板连接类型可以明显提升结构抗连续倒塌性能;加肋型节点能有效提升节点的变形能力和承载能力,表现出良好的抗连续倒塌性能;为避免结构抗倒塌性能下降,应合理选择弱轴连接板厚度。

强筋活血复元汤对急性踝关节骨折伴三角韧带损伤患者术后关节功能恢复的影响

目的:观察强筋活血复元汤对急性踝关节骨折合并三角韧带损伤患者术后关节功能恢复的影响。方法:选取2020年1月至2022年2月在新干县人民医院接受手术治疗的急性踝关节骨折合并三角韧带损伤患者56例,应用计算机按1~56编号分组,对照组全单号,试验组全双号,每组各28例。两组患者均给予骨折内固定手术治疗,对照组患者术后早期给予常规治疗,试验组患者术后早期在对照组治疗的基础上给予强筋活血复元汤治疗。观察两组患者临床疗效、踝关节功能评分、疼痛视觉模拟评分(visual analogue score, VAS)、凝血因子[D-二聚体(d-dimers, D-D)、全血血小板计数(platelet count, PLT)、血浆纤维蛋白原(fibrinogen, FIB)]及并发症等。结果:试验组有效率96.43%,对照组有效率为78.57%,试验组有效率高于对照组,差异有统计学意义(P<0.05)。试验组治疗后踝关节功能评分高于对照组,差异有统计学意义(P<0.05)。试验组治疗7 d、14 d后VAS评分低于对照组,差异有统计学意义(P<0.05)。试验组治疗后D-D、PLT、FIB水平低于对照组,差异有统计学意义(P<0.05)。试验组并发症发生率为0.00%,对照组并发症发生率为14.28%,试验组并发症发生率低于对照组,差异有统计学意义(P<0.05)。结论:强筋活血复元汤能促进急性踝关节骨折合并三角韧带损伤患者术后关节功能恢复,减轻疼痛,降低并发症发生率。