Experimental Investigation on the Seismic Performance of Beam-Column Joints Reinforced with GFRP Bars

Glass fiber-reinforced polymer (GFRP) reinforcing bars were used recently as main reinforcement for concrete structures. The noncorrodible GFRP material exhibits linear-elastic stress-strain characteristics up to failure with relatively low modulus of elasticity compared to steel. This raises concerns on GFRP performance in structures where energy dissipation, through plastic behavior, is required. The objective of this research project is to assess the seismic behavior of concrete beam-column joints reinforced with GFRP bars and stirrups. Two full-scale exterior T-shaped beam-column joint prototypes are constructed and tested under simulated seismic load conditions. One prototype is totally reinforced with GFRP bars and stirrups, while the other one is reinforced with steel. The experimental results showed that the GFRP reinforced joint can sustain a 4.0% drift ratio and can recover its deformation without any significant residual strains. This indicates the feasibility of using GFRP bars and stirrups as reinforcement in the beam-column joints subjected to seismic-type loading.     

Experimental Evaluation of Seismic Performance of Squat RC Structural Walls with Limited Ductility Reinforcing Details

This article describes an experimental study carried out on of reinforced concrete (RC) walls of less confining reinforcement than that recommended by ACI 318. A total of eight RC walls with boundary elements comprising of five walls with aspect ratio of 1.125 and three walls with aspect ratio of 1.625 were tested by subjecting them to low levels of axial compression loading and simulated seismic loading, to examine the structural performance of the walls with limited transverse reinforcement. Conclusions are reached concerning the failure mode, drift capacity, strength capacity, components of top deformation, and energy dissipation characteristics of walls on the seismic behavior with limited transverse reinforcement. The influences of axial loading, transverse reinforcement in the wall boundary elements, and the presence of construction joints at the wall base on the seismic behavior of walls are also studied in this paper. Lastly, reasonable strut-and-tie models are developed to help in understanding the force transfer mechanism in the walls tested.     

南京狮子山段损伤城墙的加固对策研究

为探索南京城墙科学保护对策及加固技术方法,针对狮子山的地形特征和城墙建造特点,通过城墙本体损伤调查和山体地质勘探,对狮子山段城墙再次发生局部坍塌原因进行了分析;采用传统造城工艺与现代加固技术修复坍塌墙体,恢复了城墙与山体的排水系统;对墙体裂缝病害进行安全监测,改善了该段城墙的生存环境.此方法可为进一步研究同类城墙保护提供技术参考.     

含氟聚合物加固保护纸质文物研究

为探讨用含氟聚合物FEVE和HDI三聚体对纸质物进行加固保护的有效性,用FEVE树脂溶液和HDI三聚体对纸质物加固保护后,分别进行了拉伸强度、光泽度、耐酸水解性及抗干热老化性等一系列试验,并用扫描电镜进行观察分析。结果表明,采用FEVE(浓度5％)和HDI三聚体(浓度20％)对纸质物的加固保护后,提高了纸张的机械强度,缓解、抑制了酸和热对纸质物的侵蚀,具有较好的效果。     

韩城大禹庙藻井画脱酸与加固保护研究

韩城大禹庙始建于1301年,1579年重建,其佛龛顶部藻井画共168格,内容为花鸟人物,色彩饱和,具有很高的历史文化价值。近年来由于自然环境的影响,藻井画出现了大面积剥离、脱落、污染、起翘、鼓泡、撕裂、脆化等病害,使该批藻井画濒临自毁,如不及时抢救修复,将永远消失。为此,在对其病害进行调研的基础上,研究了藻井画脱酸和颜料加固的方法和材料。通过实验对模拟纸样进行处理,测试了脱酸加固前后、老化前后,纸张的抗张强度、耐折度等各物理性能。结果表明,脱酸加固剂能够在保持藻井画的原貌、色泽、质感的情况下,使保护后的藻井画各物理性能有较大提高,大大延长了藻井画的保存寿命。研究结果可为韩城大禹庙藻井画的修复、提供科学依据。     

HDI三聚体加固材料对纸质文物字迹保护性能研究

以HDI三聚体化学加固材料对纸质文物中字迹保护效果为研究对象,选用纸质档案中常见的墨汁、碳素墨水、蓝黑墨水、纯蓝墨水、红色墨水、铅笔字迹等材料,根据加固前后字迹的颜色变化、扩散现象,以及与壳聚糖、羧甲基纤维素、明胶-甘油溶液加固材料所做的对比,对HDI三聚体加固纸质文物字迹的安全性进行评估,并依据耐酸性、耐碱性、耐氧化性和耐干热老化性能对其耐久性做出综合分析,进而探究HDI三聚体加固材料对字迹的保护效果。结果表明：在安全性上,HDI三聚体相比其他加固材料性能更优;在耐久性上,其对墨汁、碳素墨水字迹的保护效果较好,对蓝黑墨水、纯蓝墨水、红色墨水、铅笔字迹的保护效果相对较差。另外,依据字迹材料特点,选取适当质量分数加固溶液方能达到理想的加固效果。     

Kauramin法加固饱水古木件的机理

利用FT IR、DSC以及形态组织观察等方法,初步探讨了Kauramin(MF树脂)法渗透加固16世纪饱水古船残块(古像木)的过程与机理。结果表明,MF树脂可填充在橡木细胞组织的各层中,与其中的纤维素、木质素等形成大量氢键,高度交联,最终形成网络状整体,从而使古木件的机械性能得以改善。     

浙江萧山跨湖桥独木舟遗址加固保护试验研究

为了保证所用加固材料对跨湖桥独木舟遗址土壤加固的有效性,使用改性水性环氧和正硅酸乙酯两种加固材料,分别于该遗址隐蔽部位进行了小面积加固试验,通过测试加固前后的土壤密度、pH值和色差以及强度等,对加固效果进行了评价。结果表明加固后的土壤干密度有所提高,土壤更加密实,仍处于原来的中性环境,保持土壤原貌,抗剪强度也有所提高。     

Seismic Resistant Effects of Composite Reinforcement on Rockfill Dams Based on Shaking Table Tests

In this article, the seismic resistant effect of a new reinforcement measure on rockfill dams, the Composite Reinforcement, is investigated based on 1-g large-scale shaking table tests. A 1 m high rockfill dam, which is scaled from the Yele rockfill dam in China, is tested by inputting a series of motions designed from a realistic Wenchuan earthquake record. The model dam is divided into two sections, with one section representing a normal rockfill dam (RD) while the other section employing the Composite Reinforcement (composite reinforced rockfill dam (CRRD)). The seismic-resistant effect of the Composite Reinforcement is investigated by comparing the recorded dynamic response of the two dams, in terms of the peak acceleration amplification factor distribution along the dam core, the crest settlement, and the visualized failure pattern. Results show that the application of the Composite Reinforcement can effectively mitigate the seismically induced deformation of the rockfill dam by reducing the peak crest acceleration and residual crest settlement by 18% and 55%, respectively, when subjected to a 0.5 g input motion. The investigation of the captured failure pattern on the two dams further indicates the effective reinforcing effect of the Composite Reinforcement on preventing the sliding failures of rockfill materials in the top 20% height of the dam body.     

Confidence Factor?

Eurocode 8 Part 3 (EC8-3) is devoted to assessment and retrofitting of existing buildings. In order to take into account the uncertainty in the knowledge of structural properties, EC8-3 defines, analogously to the ordinary material partial factors, an adjustment factor, called “confidence factor (CF),” whose value depends on the level of knowledge (KL) of properties such as geometry, reinforcement layout and detailing, and materials. This solution is plausible from a logical point of view but it cannot yet profit from the experience of its use in practice, hence it needs to be substantiated by a higher level probabilistic analysis accounting for and propagating epistemic uncertainty (i.e., incomplete knowledge of a structure) throughout the seismic assessment procedure. This article investigates the soundness of the format proposed in EC8-3. The approach taken rests on the simulation of the entire assessment procedure and the evaluation of the distribution of the assessment results (distance from the limit state of interest) conditional on the acquired knowledge. Based on this distribution, a criterion is employed to calibrate the CF values. The obtained values are then critically examined and compared with code-specified ones. The results pinpoint a number of deficiencies that appear to somewhat invalidate the approach. The methodological significance of the work extends beyond the assessment procedure in EC8-3, since similar factors appear in other international guidelines (e.g., the knowledge factor of FEMA356).