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.

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.

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.

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.

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。

肌力强化训练在半月板损伤关节镜术后患者中的应用效果

目的探讨肌力强化训练在半月板损伤关节镜术后患者中的应用效果。方法将94例半月板损伤关节镜术后患者随机分为对照组(47例)和观察组(47例)。对照组采用常规康复训练,观察组采用肌力强化训练,两组均持续训练干预3个月。比较两组的膝关节肌力、本体感觉及膝关节功能恢复情况。结果干预后,观察组的屈肌、伸肌峰力矩(PT)值及Lysholm膝关节评分系统(LKSS)评分均高于对照组,轨迹误差和平均负重力量差低于对照组(P<0.05)。结论肌力强化训练可有效改善半月板损伤关节镜术后患者膝关节肌力、本体感觉,促进其膝关节功能恢复,值得临床借鉴应用。

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。

碳纤维加固震损混凝土框架节点抗震性能的初步研究

首先对 4个十字形混凝土梁板柱节点进行破损加载 ,模拟中小地震中的损伤 ,然后进行灌缝修复和粘贴碳纤维加固。加固试件和对比试件的低周反复荷载试验结果表明 ,采用的加固修复方法非常有效 ,受损试件加固后的抗震性能要优于对比试件。

中国古建筑木结构榫卯节点加固的试验研究

通过对3个按照《营造法式》制作的二等材殿堂式木构架的缩尺模型,以及3个碳纤维布和2个扁钢加固榫卯节点的构架模型在水平低周反复荷载作用下的试验研究,得到了未加固构架、碳纤维布加固构架及扁钢加固构架的破坏特征、滞回曲线、骨架曲线、强度和刚度退化规律、变形及耗能等性能。试验结果表明:所有构架的梁、柱构件完好无损,破坏均发生在榫卯节点;未加固构架、碳纤维布加固构架及扁钢加固构架的滞回曲线有明显的不同;碳纤维布和扁钢加固后构架强度和刚度增加,而耗能能力却有所降低;木构架具有非常好的变形能力。扁钢加固适合于强度或刚度明显不足且较隐蔽的榫卯节点,而碳纤维布加固适合于破损程度较小的榫卯节点。

核心区外碳纤维布增强混凝土框架节点抗剪性能试验研究与机理分析

由于直交梁的存在,混凝土空间框架节点核心区无法象平面框架一样直接加固。针对这一工程难题,采用两种碳纤维布加固核心区外侧梁、柱端的方法,进行了五个足尺混凝土框架节点的低周反复加载试验,以检验加固后节点核心区抗剪性能的改善效果,并针对不同加固方法,对碳纤维布的增强机理进行了分析研究。

聚合物砂浆嵌缝加固石墙灰缝抗剪性能研究

根据条石砌筑石墙的砌筑和构造特点,提出了采用聚合物砂浆对石墙进行嵌缝抗震加固的方法。通过对12片聚合物砂浆嵌缝加固的双剪试件和12片有垫片干砌甩浆砌筑的对比试件进行抗剪性能试验研究,探讨采用聚合物砂浆嵌缝加固对石墙通缝抗剪承载能力的提高效果,分析不同砂浆强度、不同压应力水平下的嵌缝加固情况。试验结果表明,聚合物砂浆嵌缝加固能有效提高石墙灰缝的抗剪承载能力和剪切变形能力。在低砂浆强度、低压应力水平的情况下,其加固效果更明显。在试验的基础上,提出了聚合物砂浆嵌缝加固后石墙通缝的抗剪强度计算公式,计算值与试验值吻合良好。本文提供的内容可供石墙抗震加固研究和工程应用借鉴参考。

碳纤维布加固梁柱节点试验研究

通过 4个足尺的梁柱节点 (其中 2个用碳纤维加固 )在低周反复荷载作用下的试验研究 ,比较分析了用碳纤维布加固钢筋混凝土梁柱节点的破坏形态、承载能力、滞回曲线和延性系数等。试验结果表明 。

焊接工艺对奥氏体不锈钢焊接接头应变强化性能的影响

用等离子焊、埋弧焊和气体保护焊对不同厚度的国产304不锈钢板进行焊接,通过三种工艺焊接接头应变强化前后的力学性能和组织变化来研究焊接工艺对奥氏体不锈钢焊接接头应变强化性能的影响。结果表明:板材和三种焊接接头应变强化后,屈服强度均增大,板材和等离子焊焊接接头的其他性能基本不受影响,埋弧焊和气体保护焊的焊接接头的塑性有不同程度的降低,低温冲击韧性有一定幅度变化,组织都没有发生马氏体相变;焊缝余高和焊缝一次返修对气体保护焊焊接接头的应变强化性能基本没有影响。

嵌缝加固条石砌筑石墙抗震性能试验研究

针对条石砌筑石墙的砌筑特点、薄弱环节和对保持质朴美观风貌的要求,提出对条石砌筑石墙进行嵌缝加固的方法。通过5个干砌甩浆石墙加固试件和未加固对比试件的低周反复加载试验,研究嵌缝加固方法对提高石墙抗震性能的加固效果。加固对象包括新砌石墙和灰缝滑移破坏的损伤石墙。其中,新砌石墙采用钢筋-聚合物砂浆嵌缝加固;发生灰缝滑移破坏的损伤石墙在破坏灰缝中嵌入聚合物砂浆和剪力键进行加固。基于试验结果,分析加固前后石墙的承载能力、变形性能和刚度退化等规律。试验结果表明,嵌缝加固后石墙的开裂荷载得到明显的提高,极限承载力也有一定程度提高,墙体的整体性能和抗震能力有明显改善。研究成果可为后续研究和石结构抗震加固提供参考。