Analysis on Regional Power Grid Load Characteristics and Rational Allocation of Capacity Load Ratio

The reasonability of the adopted capacity load ratio numerical value in urban power grid planning determines the economy of planning level yearly power grid.Too large capacity load ratio will result in the increasing investment in the early period of power grid construction, however, too small capacity load ratio will make the power grid have poor adaptability, affecting the power supply. Reasonably determining the adopted regional power grid capacity load ratio quantitative numerical value in planning has a strong guiding significance for constructing reliable and economic power grid and preventing power grid from excessive advance or lagging behind the load development. This paper, through the statistics and analysis of a certain regional power grid 2010-2012 three years＇ power grid daily load characteristics and the investment benefit evaluation of three years＇ 220KV power grid individual project, makes a preliminary analysis and puts forwards the specific advice on the reasonable values of power ~rid 35-220KV power transformation capacity load ratio.

Effects of ceria/zirconia ratio on properties of mixed CeO_2-ZrO_2-Al_2O_3 compound

A series of CexZr0.50-xAl0.50O1.75(0.05≤x≤0.45) mixed oxides with different Ce/Zr ratio were prepared by co-precipitation method and characterized by means of X-ray diffraction(XRD),Brunauer-Emmet Teller method(BET),temperature-programmed reduction(H2-TPR) and oxygen pulsing technique.The XRD results showed that all samples kept the single CeO2 cubic fluorite structure after calcination at 600 and 1000 oC for 5 h.The results of BET revealed that CexZr0.50-xAl0.50O1.75 with Ce/Zr molar ratio 1/1 exhibited hi...

Influence of Axial Load Ratio on Shear Behavior of Through-Diaphragm Connections of Concrete-Filled Square Steel Tubular Columns

Nonlinear finite element analysis and parametric studies were carried out to study the influence of axial load ratio on the shear behavior of the through-diaphragm connections of concrete-filled square steel tubular columns. The analysis reveals that smaller axial load ratio can improve the shear bearing capacity and ductility while larger axial load ratio will decrease the shear behavior of the through-diaphragm connections. The parametric studies indicate that the axial load ratio should be limited to less than 0.4 and its influence should be considered in the analysis and design of such connections.

Determination of the load bearing capacity of pre-stressed expandable props for ground support in underground mines

This paper aims to determine the load bearing capacity of pre-stressed expandable props with different geometries and load eccentricities for flexible support in underground mining or excavation.It is deduced that the expandable device could have much higher strength(>89 MPa)by laboratory tests,and the load bearing capacity of the expandable prop may depend on the stability of the supporting steel pipe structure.A good agreement was found between the laboratory test and numerical results in terms of the load bearing capacity and the final macro-bending failure pattern for expandable props with heights of 1.5 and 2.7 m,and the theoretical calculation for the strength of traditional steel structures is not directly suitable for the expandable props.Moreover,additional numerical simulations were performed for the expandable props with different normalized slenderness ratiosλ_(n)and loading eccentric distances e.The variation of stability coefficient of the expandable prop is in line with the Perry-Robertson equation and its correlation coefficients are fitted as a of 0.979 and b of 0.314.For estimating the load bearing capacity of the expandable props,the strength equation for traditional steel structures is improved by introducing a bending magnification factor and by modifying the normalized slenderness ratio to a converted slenderness ratio.Based on the underground field monitoring for the strength of expandable props with different heights,the empirical eccentric distances were back calculated,and a safety factor is introduced to obtain the designed strength of the expandable prop.In addition,a four-step design procedure is proposed for the expandable prop.

Experimental Study on Concrete Columns Confined by BFRP-PVC Tubes Under Uniaxial Loading

This paper presents an experimental study on the behavior of circular concrete columns reinforced by BFRP-PVC tubes under uniaxial loading.A total of six specimens were prepared and tested under uniaxial loading.The main parameters varied in the tests were strengthening ratio and strengthening approach of BFRP.The performance,such as failure modes,ultimate bearing capacity and stress-strain curves,was investigated in details and a formula was proposed to predict the compressive ultimate strength.The results show that this kind of confined columns obviously improves the ultimate bearing capacity,and the ultimate bearing capacity increases with the strengthening layers.The formula proposed is applicable and efficient for prediction of the ultimate bearing capacity as well.

Bearing capacity and mechanical behavior of CFG pile composite foundation

CFG pile (i.e., pile constructed by granular materials of cement, fly-ash and gravel) composite foundation is applied in subsoil treatment widely and successfully. In order to have a further study of this kind of subsoil treatment technology, the influencing factors and calculation methods of the vertical bearing capacity of single CFG pile and the CFG pile composite foundation were discussed respectively. And based on the obtained solutions, effects by the cushion and measurements to reduce negative friction area were analyzed. Moreover, the developing law of settlement and bearing capacity eigenvalue controlled by the material strength with the increase of load were given for the CFG composite foundation. The in-situ static load test was tested for CFG pile. The results of test show that the maximum test load or half of the ultimate load is used from all the points of test, the average bearing capacity eigenvalue of single pile is 390 kN, and slightly greater than the design value of bearing capacity. The bearing capacity eigenvalues of composite foundation for 3 piles are greater than 300 kPa, and the mechanical properties of CFG pile composite foundation are almost identical in the case of the same load and cushion thickness. The pile-soil stress ratio and the load-sharing ratio can be adjusted through setting up cushion thickness.

Combined Bearing Capacity of Spudcans on a Double Layer Deposit of Strong-Over-Weak Clays

An extreme sea storm process can lead to a jack-up rig under the combined loading condition of vertical load(V), horizontal load(H), and moment(M) to have stability problems. This paper presents the analysis of combined bearing capacities of a circular spudcan on layered clays with a strong layer overlying a comparatively weaker layer. Numerical models combined with displacement-based load tests, swipe tests, and constant ratio displacement probe tests are adopted to calculate the uniaxial bearing capacities, failure envelopes in combined V-H, V-M planes, and failure envelopes in a combined V-H-M load space, respectively. A parametric study on the effects of vertical load level V, the layer strength ratio s_(u,t)/s_(u,b), and the hard layer thickness t_1 on the bearing capacities is then performed. Results show that the vertical load level is a key factor that influences the values of H and M and the size of the H-M failure envelope. The existence of the underlying weak clay decreases the bearing capacities in all directions, and the vertical capacity Vult is affected more than the horizontal(H_(ult)) and moment(M_(ult)) capacities based on a single uniform deposit. The influence of the underlying weak clay on H-M failure envelope is mainly shown where H and M are coupled in the same direction. In contrast, little difference is observed when H and M are coupled in opposite directions.

Investigation of Excavator Performance Factors in an Open-Pit Mine Using Loading Cycle Time

This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.

Non-Euclidean Geometry and Regulated Characteristics of Limited Capacity Power Supply

The restriction of load power, two-valued regulation characteristic, and interference of several loads are observed in power supply systems with a limited capacity of voltage sources. In this paper, the definition of regime in an invariant form through different parameters, of changes of transformation ratio and voltage load is grounded for these circuits with two loads. The approach for interpretation of changes or ＂kinematics＂ of load regime is presented by using the conformal and hyperbolic plane. To simplify the task and reveal the basic moments of influence of the limited source power, the static regulation characteristics and idealized models of voltage converters are considered. Geometrical interpretation of a simplified model of multichannel power supply system allows basing the definition of operating regime parameters. Results can be useful for electric circuit theory education and for voltage coordinated control of given loads. Non-Euclidean geometry is a new mathematical apparatus in the electric circuit theory, adequately interprets ＂kinematics＂ of circuit, and provides a validation for the introduction and definition of the proposed concepts. From the methodological point, the presented approach is applied for a long time in other scientific domains, as mechanics and biology.

Semi-Deep Skirted Foundations and Numerical Solution to Evaluate Bearing Capacity

Semi-deep foundations are a remarkable solution in conditions where the soil beneath the foundation is loose to a great depth and there is no possible way to use any way of soil improvement and applying piles would not be a logical way considering their cost and time of enforcing. Skirted foundations are a type of semi-deep foundations that can penetrate to the soil up to two times of their breadth. Estimating bearing capacity of these foundations is a long geotechnical problem for engineers whether under absolute or combined loading because of their usage in offshore and onshore projects. For estimating the vertical bearing capacity of these foundations, series of finite element analyses were performed for a range of embedment ratios to investigate the effect of the length of the skirt. The foundation has been modelled with two different types of soil and the results validated with previous analytical, numerical and experimental researches. In addition, the bearing capacity of a skirted foundation under combined loading in V-H space has been analyzed by this approach and the 2-dimentional failure envelope has been presented.

震后RC桥墩竖向承载力最优工程需求参数的选取方法

桥墩结构的震后竖向承载力是评估梁式桥梁震后通行功能的重要指标,但其难以测量。为了快速定量地评估桥梁结构的震后通行能力,对评估梁式桥梁结构震后竖向承载力的最优工程需求参数(EDP)进行了系统地研究。首先选取与墩柱残余侧移和损伤相关的5个EDPs,通过对考虑了材料不确定性的RC桥墩进行Pushover分析和动力时程分析得到5个EDPs,进一步对震后的桥墩进行Pushdown分析获取震后竖向承载力。然后采用回归模型对所选EDPs与震后竖向承载力损失比的关系曲线进行回归分析,选取竖向承载力损失比关系曲线的最优回归模型为在ln(x)-y坐标系中的正态累积函数模型,进一步通过最优EDP评价准则对评估竖向承载力损失比的5个EDPs进行评价分析。评价结果表明:当考虑震后可计算性时,峰值侧移率最优;当考虑震后可测性时,残余侧移率最优;当考虑余震时,改进的Park-Ang指标最优。通过选取的最优EDP可以建立桥梁结构功能指标与抗震性能指标之间的联系,为进一步发展和完善桥梁结构的抗震韧性评估和设计提供参考。

考虑容重比的车辆配载优化综述

零担货运具有货物品种多样,体积和重量变化大的特征,基于容重比的车辆配载优化可同时提升车辆载重率和容积利用率,进而大幅度降低物流成本,在交通和物流行业具有重要的研究价值。首先,介绍了考虑容重比的车辆配载优化问题及其数学规划模型,再针对求解该问题的算法进行分析归纳予以综述。目前,求解算法大多集中于精确算法和启发式算法以及智能优化算法。随着人工智能的发展,还可以考虑机器学习思想在相关方面的应用。最后对于考虑容重比的车辆配载优化在当前形势下面临的新挑战,提出几个未来在研究该问题时可以考虑研讨方向,期望能为考虑容重比的车辆配载优化研究提供参考。

水电站中长期多尺度调峰能力计算方法研究

调峰能力是衡量水电站调峰性能的重要特性指标。对含风光等新能源的区域电网,开展水电站的中长期调峰能力研究对提高新能源消纳、促进电网长期稳定运行具有重要意义。以多时间尺度对应的历史典型日负荷过程为基础,利用快速搜索与发现的密度峰值聚类算法提取各尺度下的典型日负荷比例,进而确定日调峰电量的计算方法,作为确定各尺度调峰能力的依据。以调峰电量最大为目标建立相应计算期和时间尺度的调度模型,开展年内月尺度、月内旬尺度和旬内日尺度的逐层优化调度研究。以具有年调节能力的龙滩水电站为研究对象开展实例研究表明,本方法可为区域电网开展中长期电力电量平衡,合理安排梯级水电站各时间尺度的调峰电量提供决策参考。

计及P2G的综合能源系统CCUS容量规划

考虑到碳捕集利用与封存(CCUS)是对电转气(P2G)过程中二氧化碳(CO_(2))来源的细化,文中提出对综合能源系统(IES)进行电-氢-氧-甲烷-二氧化碳和虚拟二氧化碳等P2G过程的定性定量建模,以及对风-光-电动汽车-负荷等随机源荷进行时空聚类以深度挖掘IES氢源碳源潜力的CCUS设备容量规划模型。以阶梯正负碳交易、弃风弃光惩罚和年设备投资成本等的年综合成本最低为目标,以碳捕集、碳存储和甲烷化等CCUS设备功率容量限值为全局变量对电气平衡和能量耦合进行二次约束,经过混合整数线性化处理后利用Cplex求解。算例分析表明,源荷时空聚类可在典型日场景缩减时保留IES廉价碳源氢源特征,合理规划后的CCUS设备可兼具弃风消纳和碳减排功能,使P2G制取的天然气更具市场竞争力。

荷载和氯盐环境下RC梁非均匀锈蚀与承载力劣化试验

为考察持续荷载与氯盐干湿循环共同作用对钢筋混凝土(RC)梁抗弯性能的影响,先后进行19根钢筋混凝土梁的腐蚀试验和抗弯承载力试验,研究不同持续荷载等级和干湿循环天数对裂缝分布、钢筋质量锈蚀率以及受腐蚀构件受弯性能的影响,并分别总结纵筋最大和平均质量锈蚀率与承载力降低比的关系.研究结果表明:纯弯段的钢筋锈蚀程度较高,纵筋锈蚀程度沿圆周分布不均匀;纵筋质量锈蚀率的极值点位置与初始横向裂缝的出现位置无必然关联性;纵筋最大质量锈蚀率随荷载等级和干湿循环天数的增加而增大,受干湿循环天数的影响更明显;腐蚀后梁峰值荷载呈下降趋势;当纵筋锈蚀率较小时(平均值≤3%或最大值≤6%),锈蚀率与承载力降低比的相关度较低,且最大质量锈蚀率的相关度小于平均质量锈蚀率;当纵筋锈蚀率较大时(平均值>3%或最大值>6%),质量锈蚀率与承载力降低比的相关度提高;在纵筋平均质量锈蚀率相同时,采用自然腐蚀试件的承载力降低程度高于采用外加电流腐蚀的试件.

高轴压比下小剪跨比剪力墙的抗震性能试验研究

通过5片不同轴压比下小剪跨比剪力墙构件的低周反复荷载试验,研究了高轴压比对小剪跨比剪力墙的破坏模式、受剪承载力、延性、刚度特征及耗能能力的影响,并对加载全过程中剪力墙腹板双向钢筋的受力情况及传力机制进行分析。研究结果表明:所有构件均发生了剪切破坏,并在高轴压力作用下发生了平面外的错动;高轴压比阻碍了裂缝的产生及发展,提高了构件的受剪承载力,但在构件达到峰值荷载后,强度和刚度退化剧烈,极限位移小,提高边缘约束构件配箍率可以有限地提高构件的变形能力、延性及耗能能力,但对破坏模式、传力机制的影响不大。轴压比对构件的传力机制有着显著的影响,当轴压比较小时,桁架作用明显,水平钢筋与竖向钢筋对受剪承载力的贡献相当,均能充分发挥作用;当轴压比较高时,拱作用明显,水平钢筋未能充分发挥作用,对受剪承载力的贡献有限,竖向钢筋主要对拱作用有贡献。

UHPC预制拼装综合管廊的抗弯性能试验

针对预制拼装钢筋混凝土(RC)管廊自重大和吊装难的问题,通过试设计超高性能混凝土(UHPC)预制拼装管廊主体构造,并进行1∶2模型的静力试验;得到UHPC综合管廊的顶底板和侧墙在不同荷载作用下的破坏形态、荷载-变形关系、钢筋和混凝土应变,并对整体受力机制、破坏模式和极限承载力进行分析.结果表明,UHPC管廊重量可减少30%,破坏模式与RC管廊基本一致,均为弯曲破坏,但UHPC管廊的开裂荷载和变形能力明显提高.在实测数据的基础上,通过简化拉压区应力分布图形,建立UHPC综合管廊抗弯极限承载力的计算方法,得到的计算值与实测值吻合良好,误差在10%左右.提出的计算公式可为UHPC综合管廊的设计计算提供参考.

多电压等级交流电网容载比计算方法

现有的容载比计算方法未考虑不同电压等级对交流电网的影响,导致交流电网可靠性与经济性无法同时达到最优,因此在考虑电压等级的基础上,提出多电压等级交流电网容载比计算方法。分别计算高压与低压模式下交流电网的供电能力,根据供电能力利用离散粒子群优化算法计算不同电压等级的容载比粒子数,得到多电压等级交流电网的最优容载比计算结果,从而实现多电压等级交流电网容量配置优化。实验结果表明,该方法能够使变压器容载比达到最优,优化后的交流电网供电可靠性、经济性及满意度均较高。

基于PVsyst软件模拟发电量数据的光伏电站电能损耗的分析方法研究

电能损耗是光伏电站非常重要的综合性指标,对其进行分析可以为光伏电站能效管理提供数据支持。在电能损耗的计算过程中,最大负荷损耗小时数的选取非常关键。提出了一种基于PVsyst软件模拟所得的发电量数据来分析光伏电站电能损耗的方法,结合工程实际情况给出了精确计算年最大负荷损耗小时数的改进算法数学模型,并对采用不同算法得到的年最大负荷损耗小时数进行了比较分析;以山西省大同市鸦儿崖乡100 MW光伏电站为算例,对其电气设备及线缆的电能损耗进行详细分析,验证了所提出光伏电站电能损耗分析方法的正确性。研究结果表明:1)由于光伏电站容配比的影响,应分别计算光伏电站直流侧和交流侧的年最大负荷损耗小时数,直流侧和交流侧的电能损耗也需要分别计算。2)该方法基于PVsyst软件模拟得到的光伏电站全年各小时的发电量数据,可准确计算出光伏电站的年最大负荷损耗小时数,在数学逻辑上合理,可以提高光伏电站电能损耗计算的准确度。该方法也可应用于其他实际运行的发电项目的电能损耗分析。

桩网结构路基动静承载性状分析

为研究桩网结构路基在静动荷载作用下的承载性状,采用有限元分析方法对桩网结构路基在静动两种荷载下的承载特性、荷载传递机理、土拱形成及发展规律进行了数值计算。通过分析静动两种工况下桩土应力、桩周土压力分布、桩土应力比及土拱效应,并与试验结果进行了对比分析。结果表明:静载作用下基桩轴向应力约为400 kPa,最大土压力出现在路基中部,且沿路基横向向外逐渐减小;动载作用下沿路基横向布置的桩体的动应力在埋深方向呈先增大后减小趋势,其竖向应力最大值约为静载下的160%;动载下路基内部土拱效应较静载有大幅削弱,其中削弱最大的为四桩中心处的空间土拱效应,其桩土应力比约为静载的29.3%。