RPC混凝土梁施工工艺及验收标准研究

RPC混凝土梁在我国铁路桥梁结构中为新型结构,叙述了该种结构设计、施工、架设的要点,并结合实桥制作经验,提出了主要技术指标和设计参数,确定了施工工艺和验收标准,为新技术及材料推广提供了可靠的技术支撑。     

钢纤维与聚丙烯纤维混杂活性粉末混凝土的力学性能

为了改善活性粉末混凝土的力学性能,采用在活性粉末混凝土中混合掺加高模量的钢纤维和低模量的聚丙烯纤维的方法。通过两种纤维掺量的改变,研究二者混杂对活性粉末混凝土抗压强度、抗折强度力学性能的影响。从试验结果可以看出:两种纤维混杂使得活性粉末混凝土的力学性能得到一定程度的改善和提高。     

钢纤维掺量对RPC抗压强度影响的试验研究

设计了6组钢纤维掺量的RPC试件,进行抗压强度试验,建立了钢纤维掺量与RPC抗压强度之间的定量关系式,研究结果表明：在水胶比较低时,钢纤维对RPC抗压强度的增强效果随钢纤维掺量的增大而增大;在水胶比较高时,钢纤维的掺量变化对RPC抗压强度几乎无增强作用,另外,对最佳配合比进行了调整。     

活性粉末混凝土高温后冲击力学性能研究

摘　要：利用分离式Hopkinson压杆系统,采用铅片作为整形器,分别对常温下、400℃、600℃及800℃高温过火后的RPC试样进行单轴冲击压缩实验。研究高温后钢纤维对RPC材料动态力学性能及吸能特性的影响规律。结果表明,高温过火前后钢纤维对RPC均有增强和增韧的作用。高温后因RPC塑性流动性能的增强,导致钢纤维的增韧作用减弱。RPC动态抗压强度高温后损失的速率高于韧性指标。分析RPC材料冲击压缩过程的能量机制,发现钢纤维提高了RPC的能量吸收率,因此能量吸收能力也得到了增强。利用SEM扫描电镜,从RPC材料微观结构变化的角度分析了其高温后宏观力学性能降低的原因。     

基于平钢板连接件的钢-RPC组合桥面板抗剪试验研究

该文提出了采用平钢板剪力连接件连接的钢-RPC组合桥面板结构,该结构不仅能解决公路钢桥沥青铺装层的病害,还能有效地提高桥面横向刚度,有助于缓解U肋加劲处应力集中和疲劳开裂现象。为了掌握该组合结构界面抗剪性能,连接件板厚分别取10 mm和4 mm,进行了两组平钢板连接件的推出试验,试验考察了平钢板连接件厚度对抗剪破坏形态及承载力的影响。结果表明：平钢板厚度较小时,表现为平钢板连接件根部受拉屈服;厚度较大时表现为连接件附近混凝土被压碎,工作机理类似于型钢连接件。10 mm板厚连接件相比4 mm板厚抗剪承载力提高了43.6%,抗剪刚度提高了35%,同时延性略有下降,但两组试件的延性系数均大于3.5。最后给出了平钢板连接件的抗剪承载力简化计算公式,计算结果相比试验结果偏于安全,可供设计参考。     

标准养护条件下铁尾矿制备RPC力学性能研究

标准养护条件下,采用固体废弃物铁尾矿砂代替石英砂设计制备RPC,研究其引入对RPC工作性能、强度和弯曲韧性的影响,通过XRD和SEM研究其对RPC水化反应和微观结构的影响.结果表明,标准养护条件下,铁尾矿砂RPC28d抗压强度和抗弯拉强度可分别达到117.5 MPa和24.2 MPa;铁尾矿砂的引入可降低RPC流动度、...     

Detector physics and simulation of resistive plate chambers

We present a simulation model suited to study efficiency, timing and pulse-height spectra of Resistive Plate Chambers. After discussing the details of primary ionisation, avalanche multiplication, signal induction and frontend electronics, we apply the model to timing RPCs with time resolution down to 50 ps and trigger RPCs with time resolution of about 1 ns.     

The I-meter, a distributor unit for the OPERA RPC HV system

The OPERA RPC HV system has been implemented using custom current measurement/distribution systems developed by the LNF Electronics Workshop.

Each system features eight inputs and 24 outputs (1–3 modularity). The current on each channel is measured with 100 pA sensitivity and 3% accuracy in the 1 nA– range.

In the paper we describe the measurement circuit as well as the results of the tests we have carried out to qualify the system.     

RPC200塑性与各向异性损伤耦合本构建模研究

针对活性粉末混凝土 (RPC200：Reactive Powder Concrete 200MPa)的非线性行为,将连续损伤力学和塑性力学结合起来,建立了RPC200的弹塑性各向异性损伤耦合本构。在有效应力空间内,采用非关联流动法则和非均匀等向强化法则建立了RPC200的塑性本构。基于损伤能释放率建立了损伤准则,并由正交法则给出损伤演化法则,同时采用两个不同的损伤硬化法则来描述拉、压性能不同的损伤硬化。证明了该文所建模型与热动力学基本原理的相容性。最后,给出了RPC弹塑性各向异性损伤耦合本构模型数值计算流程,并以简单例证证明了所建模型的预测能力。     

Influence of RPC Parameters on the Precipitation of Nb in Microalloyed Steel

Thermo-simulation test, metallographic analysis, measurement of hardness, TEM(including diffraction contrast technique and nano-beam anylasis)along with calculating software of Metlab, etc. were used to study the influence of RPC parameters(relaxation time, aging time)on the precipitation of Nb in microalloyed steel. Following work was undertaken in this study:Strain-induced precipitation in Nb-bearing multi-microalloyed steel was monitered and analyzed. The interaction between dislocation evolution and precipitates in deformed austenite was directly observed(an Fe-Ni-Nb alloy was employed to simulate austenite in steel). The(a low carbon microalloyed steel only by Nb was adopted)effect of relaxation of deformed austenite on aging behavior occurring in bainite was investigated. Finally, the thermal stability and variation of composition of carbonitride precipitates during dissolving process in Nb-Ti microalloyed steel were alsodetected. These results indicate:(1)During the stress relaxation, the process of precipitation happened in deformed austenite of multi-microalloyed steel can be divided into three stages, i. e. nucleation, growth and coarsening. In the final stage of relaxation, Mo atoms would enter the lattice of(Nb,Ti)(C,N)precipitates and its concentration in the precipitates increases with the relaxation time.(2)In the earlier stage of relaxation, the dislocations in deformed austenite demonstrate twisted and distribute randomly. The precipitates have the tendency to occur along those dispersed dislocations. The dilocation cells would form gradually with the relaxing time prolonged and would become more stable by the subsequent precipitates formed on them in the later relaxation period. The paralleled dislocations in dislocation cells exhibit the same Burgers vector. The dislocations get rid of pinning by the bypassing mechanism.(3)When the samples are reheated to hold isothermally at 525℃,which are relaxed for different time in deformed austenite followed by accelerated cooling, their microstructures evolve very slowly with the aging time but two hardness peaks can be found one each hardness-time curves. The position of hardness peaks nearly raimains unchanged while their height varies obviously with the relaxation time. In no relaxtion samples, only one hardness peak could be observed. During the process of aging at 525℃, The growth and coarsening of as-existed strain-induced precipitates formed in deformed austenite contribute to formation of the first hardness peaks. While the second hardness peaks result from the further precipitates which nucleate in a phase after γ→α transformation(after aging for about 10 hours).(4)It was found that the precipitates formed during solidification are monophase(Ti,Nb)(C.N)rather than TiN enclosed with NbC. With addition of Ti to the steel, the thermal stability of the carbonitrides would enhance remarkably.