Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations—Ⅱ: Experiment

The possibility of using a multi-stage pendulum mass damper （MSPMD） to control wind-induced vibration of a single column tower of a cable-stayed bridge during construction was studied theoretically in part I of this work. In this paper, the performance of the MSPMD for reducing bridge tower vibration is studied experimentally. A MSPMD model and a tower model of the bridge with geometry scaling of 1：100 were designed and manufactured. Calibration of the MSPMD model with different wire lengths is conducted to verify the analytical model of the damper. A series of tests for the uncontrolled freestanding tower, tower with cables, and tower with MSPMD model are then performed under harmonic and white noise excitations. The experimental results show that the responses of the tower model significantly decrease with the installation of the MSPMD model, which demonstrates the effectiveness of the M SPMD to mitigate the vibration of the bridge tower.

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations——I:Theory

In this paper, wind-induced vibration control of a single column tower of a cable-stayed bridge with a multi- stage pendulum mass damper （MSPMD） is investigated. Special attention is given to overcoming space limitations for installing the control device in the tower and the effect of varying natural frequency of the towers during construction. First, the finite element model of the bridge during its construction and the basic equation of motion of the MSPMD are introduced. The equation of motion of the bridge with the MSPMD under along-wind excitation is then established. Finally, a numerical simulation and parametric study are conducted to assess the effectiveness of the control system for reducing the wind-induced vibration of the bridge towers during construction. The numerical simulation results show that the MSPMD is practical and effective for reducing the along-wind response of the single column tower, can be installed in a small area of the tower, and complies with the time-variant characteristics of the bridge during its entire construction stage.

Performance of CO_2 absorption in a diameter-varying spray tower

The application of spray towers for CO2 capture is a development trend in recent years. However, most of the previous jobs were conducted in a cylindrical tower by using a single spray nozzle, whose configuration and performance is not good enough for industrial application. To solve this problem, the present work proposed a diameter-varying spray tower and a new spray mode of dual-nozzle opposed impinging spray to enhance the heat and mass transfer of CO2 absorption process. Experiments were performed to investigate the mass transfer performance （in terms of the CO2 removal rate （η） and the overall mass transfer coefficient （KGae）） of the improved spray tower under various operating conditions. Experimental results showed that the liquid to gas ratio and mole ratio of MEA to C02 are major factors, which affect the absorption performance and the maximums of η and KGae that are 94.0% and 0.574 kmol. m^-3·h^-1·kPa^-1, respectively, under the experimental conditions. Furthermore, new correlations to predict the mass transfer coefficient of the proposed spray tower are developed in various CO2 concentrations with a Pearson Correlation Coefficient over 90%.

基于速率模型的胺法碳捕集系统吸收塔内传热传质耦合模型

为研究化学吸收法碳捕集系统吸收塔内CO_(2)化学吸收过程中,搭建了一套基于速率模型的传热传质耦合模型,用以分析塔内热质耦合过程和吸收塔吸收性能。与Aspen Plus工艺模拟软件比对后,验证了模型的准确性。基于模型对某电厂CCUS示范项目中,吸收塔气液比、填料高度对传热传质、吸收性能的影响进行研究。结果表明,增大气液比与填料高度可提高吸收性能,过大则会引起CO_(2)吸收速率降低,导致吸收性能提升不再明显。研究为吸收塔内复杂的热质耦合过程研究提供新方法,对实际工程应用中吸收塔工艺参数优化有指导意义。

钢管密闭塔水平圆管降膜热质传递规律研究

冷却塔通过热质交换将高温介质的热量从系统排放到大气,从而达到冷却效果。对钢管密闭式冷却塔水平圆管降膜蒸发器传热传质的影响因素进行研究与分析,搭建逆流式密闭塔水平圆管降膜传热传质性能研究可视化实验台,主要研究气流速度、喷淋密度、喷淋水温度对横管降膜蒸发传热传质性能的影响。在给定实验工况下,得出当最佳喷淋密度为0.0416 kg/(m·s),对应的最大总换热系数为1625.01 W/(m^(2)·K);当最佳喷淋水温度为16.82℃,对应的最大总换热系数为1736.86 W/(m^(2)·K);最佳气流风速在1~2 m/s之间。

主塔C60大体积混凝土配合比设计及性能研究

研究了粉煤灰单掺、粉煤灰与矿渣粉或降黏剂复掺对主塔C60大体积混凝土工作性、力学性能、绝热温升和收缩性能的影响。结果表明:掺入适量降黏剂提高了混凝土的流动性,而掺入矿渣粉降低了混凝土的流动性,但仍满足施工要求;与单掺粉煤灰的试验组相比,复掺适量降黏剂提高了混凝土的抗压强度和弹性模量,降低了绝热温升和自收缩,对劈裂抗拉强度和干燥收缩的影响较小,而复掺适量矿渣粉后,混凝土的7 d抗压强度略有降低,28 d、60 d抗压强度增大,弹性模量增大,绝热温升和干燥收缩降低,28 d劈裂抗拉强度和自收缩变化不大。

大型漂浮式风机塔架系统固有频率快速评估方法

漂浮式风机塔架为细长高耸柔性结构,受风、浪、风轮旋转等多源复杂激励作用,塔架固有频率和模态的准确评估是漂浮式风机系统设计的关键环节。针对当前漂浮式风机塔架的模态分析大多基于塔底固定假设,未考虑浮式基础和风机正常作业的影响。提出了一种准确高效的大型漂浮式风机塔架固有频率快速评估方法,分析了漂浮式风机塔架固有频率的变化特性及规律。结果表明:当风机处于停机状态时,塔底固定的简化模型得出的塔架固有频率存在约10%的偏差,塔架固有频率评估需考虑浮式基础的影响;当风机处于运转状态时,上部风轮气动附加质量效应导致塔架的固有频率略有减小。研究结果可为漂浮式风机塔架以及控制策略的设计提供参考。

基于APDL风机塔筒MTMD系统参数敏感性分析

为了研究MTMD(多重调谐质量阻尼器)对风机塔筒振动控制时,各参数对振动控制效果的影响,基于ANSYS参数化设计语言(APDL)进行MTMD系统参数敏感性分析。首先在风机塔筒有限元模型的基础上,进行MTMD-塔筒耦合模型的建立,对塔筒进行谐响应分析,得到塔筒塔顶质量点位移频谱图。基于APDL改变TMD(调谐质量阻尼器)参数,进行“再建模-再分析”,以塔筒塔顶位移峰值为评价指标,对各参数进行敏感性分析。研究结果表明:单TMD系统减振效果随质量比、阻尼比增大而增大,且在频率比接近1时,减振效果达到最优;在MTMD在质量、刚度、阻尼参数发生偏移时,减振效果随TMD个数的增加而减弱,参数敏感性增强。

某大底盘多塔超高层结构分析与设计

某项目为1栋带3座塔楼的大底盘多塔超高层结构,塔楼均匀分布于裙房北侧,分别为部分框支剪力墙和剪力墙结构体系。针对塔楼偏置问题进行了分析,并采用盈建科、PERFORM3D、ETABS等软件对结构进行了多塔模型和单塔模型的整体计算对比、罕遇地震下的动力弹塑性分析及温度效应分析。多塔与单塔模型整体指标吻合较好,内力接近,同时根据分析结果对结构构件采取相应的构造加强以满足性能目标。结果表明,项目结构形式及构件截面合理,具有良好的抗震性能。

深圳某超高层结构设计重点及难点分析

深圳某超B级高度的超高层塔楼,采用钢管混凝土框架柱+钢筋混凝土框架梁+钢筋混凝土核心筒结构。塔楼相对于裙房部分有较大的偏心,同时因为建筑功能要求存在有多处跃层透空空间。采用盈建科、ETABS等软件对项目进行了整体计算、构件设计及楼板应力分析。针对塔楼偏置、楼板不连续、核心筒收进等不规则项,对于结构构件采取适当的构造加强,以满足抗震性能目标。对于外框梁不闭合的问题,采取对比分析,确保水平地震剪力可有效传递。结果表明,项目结构体系选择恰当,结构布置、构件截面取值合理,具有良好的抗震性能。

Free flexural vibration of a partially wet tapered Timoshenko beam with intermittent mass and stiffness variations, eccentric tip mass and non-classical foundation

A compliant tower is modeled as a partially dry, partially tapered, damped Timoshenko beam with the superstructure modeled as an eccentric tip mass, and a non-classical damped boundary at the base. The foundation is modeled as a combination of a linear spring and a torsional spring, along with parallel linear and torsional dampers(Kelvin-Voigt model). The superstructure adds to the kinetic energy of the system without affecting the potential energy, thereby reducing the natural frequencies. The weight of the superstructure acts as an axial compressive load on the beam, reducing its natural frequencies further. The empty space factor due to the truss-type structure of the tower is included. The effect of shear deformation and rotary inertia are included in the vibration analysis; with the non-uniform beam mode-shapes being a weighted sum of the uniform beam mode-shapes satisfying the end condition. The weights are evaluated by the Rayleigh-Ritz(RR) method, and verified using finite element method(FEM). The weight of the superstructure acts as an axial compressive load on the beam. Kelvin-Voigt model of structural damping is included.A part of the structure being underwater, the virtual added inertia is included to calculate the wet natural frequencies. A parametric study is done for various magnitudes of tip mass and various levels of submergence. The computational efficiency and accuracy of the Rayleigh-Ritz method, as compared to the FEA, has been demonstrated. The advantage of using closed-form trial functions is clearly seen in the efficacy of calculating the various energy components in the RR method.

石灰石粉对主塔大体积混凝土性能的影响

以水泥、粉煤灰和石灰石粉为胶凝材料,制备了一种低温升主塔大体积混凝土,研究了石灰石粉掺量(5%、10%、15%)对砂浆流变性能和混凝土绝热温升、干燥收缩性能、力学性能、抗渗性能的影响,采用SEM观察了水化产物的微观形貌,并与水泥-粉煤灰-矿渣粉胶凝体系(对照组)进行了对比。结果表明:与对照组相比,掺入石灰石粉可以降低砂浆的塑性黏度和屈服应力,延缓胶凝材料的水化进程,降低混凝土的绝热温升;石灰石粉的掺量越大,抑制混凝土干燥收缩的作用越显著;随着石灰石粉掺量的增加,混凝土的抗压强度下降,但掺5%石灰石粉混凝土的抗压强度较对照组高;与对照组相比,掺石灰石粉混凝土的抗渗性能较好,且掺量为5%时性能最好。

湿法脱硫喷淋塔强化传质提效技术及减碳探讨

为了深入挖掘燃煤电厂湿法脱硫喷淋塔能效,寻找电厂超低改造后新面临的煤质硫分升高及机组负荷变化大的问题解决办法,通过分析脱硫反应物理化学过程及脱硫喷淋塔传质存在的问题,提出采取应用较多的托盘技术、旋汇耦合技术、FGDplus技术(含湍流管栅技术)、新型混沌器技术4种脱硫强化传质提效技术。分析对比结果显示,4种技术均可以有效强化SO_(2)吸收传质过程,降低液气比,提高CaCO_(3)利用率,有效节省石灰石用量,从而降低电厂CO_(2)排放量,实现碳减排。同时借助CFD模拟技术,对塔内提效构件增加前后以及增加不同提效构件的效果进行全面的模拟研究,最终确定技术经济性最佳的改造技术。

抗裂材料在桥梁主塔大体积混凝土施工中的应用研究

为研究大体积混凝土的开裂原因、开裂类型,以及常见的裂缝控制措施,文中依据某斜拉桥主塔,通过建模计算分析大体积混凝土的温度应力状态,在现场施工过程中利用镁质抗裂剂、玄武岩纤维等抗裂材料选取试验段进行研究,解决现场主塔塔柱开裂问题。结果表明,利用氧化镁作为抗裂剂,可以有效补偿大体积混凝土的温度收缩裂纹,有效解决主塔塔柱开裂问题,从而提升工程质量。

钢制风力机塔架非线性预应力调谐质量阻尼器振动控制性能研究

悬吊式调谐质量阻尼器原理明确、安装简便,已在高层建筑、高耸输电塔等众多结构中得到了广泛应用,近年来在钢制风力机塔筒方面也逐步得到广泛关注。预应力调谐质量阻尼器(prestressed tuned mass damper,PS-TMD)通过附加下拉索并施加预拉力,可采用摆长和预拉力两个参数进行振动控制调谐,在高柔钢制风力机塔架振动控制中能充分发挥作用。但PS-TMD中拉索变形会引起非线性响应,进而影响控制性能。鉴于此,基于动力学原理建立考虑柔索效应的PS-TMD非线性运动方程,推导了拉索发生变形情况下PS-TMD动力系数及分支共振点频率比;通过优化分析给出了PS-TMD最佳调谐参数的选择方法;某3.2 MW风力机塔筒数值算例结果表明,考虑柔索效应后PS-TMD的动力系数幅值小于同参数下线性PS-TMD,共振响应下减振性能和能量耗散能力更为突出。5组风载荷下振动控制结果表明,考虑柔索效应后PS-TMD对塔架结构的风致响应振动控制效果优于相应线性PS-TMD系统。

热源塔传质特性的分析和实验研究

通过分析供冷/热设备的特点,指出了热源塔热泵供冷/热的优异性。对热源塔中不同进口空气参数和不同进口溶液温度下传质的4种模式进行了理论分析,并对叉流热源塔在不同进口参数时潜热百分比、进出口空气含湿量差和换热量的变化规律进行了实验研究。实验结果表明:进口溶液温度从-2℃升高到4℃,潜热百分比从27%降低到无潜热交换;提高风量和进口空气温度能同时满足降低潜热百分比和增加总换热量的目的;溶液流量从2.9 L.min-1上升到6.4 L.min-1,潜热百分比从15%升高到28%,系统的换热量也随之增加近50%。实验数据表明热源塔换热中潜热百分比基本上小于30%,为溶液浓度控制和溶液再生提供了实验依据。

θ环填料塔中单乙醇胺吸收CO_2传质性能研究

在乱堆θ环不锈钢填料的自制填料塔中,使用单乙醇胺（MEA）作为吸收剂,研究MEA脱除CO2的去除率和总体积传质系数KGav,考察了贫液中CO2负载量、吸收剂浓度、液体流量、吸收温度等不同参数对总体积传质系数的影响.实验结果表明,KGav随贫液中CO2负载量的增大而减小,随吸收剂浓度、液体流量的增大而增大;且进料温度在30~50℃时,KGav随温度的增大而增大.

逆流热源塔传热传质模型建立与凝水调节的可行性

为探讨通过调节运行参数对热源塔内凝水量进行控制的可行性,在建立逆流热源塔内溶液与空气间热质传递数学模型并对其验证的基础上,深入研究了以乙二醇水溶液为工作介质热源塔的入塔空气湿度和入塔溶液温度对塔内凝水量的影响规律.结果表明:当热源塔入塔空气含湿量从4.9 g/kg减小至2.2 g/kg时,塔内凝水量从1.98 g/s减小至-0.40 g/s;当入塔溶液温度从-5℃升高到-1℃时,塔内凝水量由0.56 g/s减小至-0.07 g/s.通过降低入塔空气湿度或者提高入塔溶液温度,可减少热源塔内凝水量,甚至实现溶液浓度再生,从而为减少系统溶液再生需求,高效解决热源塔热泵的溶液再生问题提供了新思路.

沼气提纯过程中醇胺溶液吸收CO_2传质性能

醇胺溶液吸收CO2是沼气提纯领域重要的研究课题。在实验填料吸收塔中,以乙醇胺（MEA）、二乙醇胺（DEA）为吸收剂,研究了吸收剂浓度、进气流量、CO2浓度、进液温度对吸收过程转化率η、吸收速率N以及气相总体积传质系数KGae的影响。结果表明,吸收剂浓度增加可有效提高η、N及KGae;进气流率增加,η逐渐降低,N先增加后降低,KGae先增加后降低最终趋于稳定;随着CO2浓度增加,η和KGae不断降低,N逐渐增加;随着进液温度升高,η和KGae均先升高后降低;MEA、DEA的最佳进液温度在40～60℃之间,并随CO2负载量增大而逐渐降低。研究结果对于醇胺溶液吸收法沼气提纯技术的研究开发和实际应用有参考作用。