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Model testing of tripod caisson foundations in silty clay subjected to eccentric lateral loads

《结构与土木工程前沿（英文）》 2023年第17卷第3期页码 467-476 doi: 10.1007/s11709-023-0933-6

摘要： In this study, model tests were conducted to investigate the bearing capacities of tripod caisson foundations subjected to eccentric lateral loads in silty clay. Lateral load–rotation curves of five eccentric-shaped tripod suction foundations were plotted to analyze the bearing capacities at different loading angles. It was observed that the loading angle significantly influenced the bearing capacity of the foundations, particularly for eccentric tripod caisson foundations. Compared with eccentric tripod caisson foundations, the traditional tripod foundation has a relatively high ultimate lateral capacity at the omnidirectional loading angle. By analyzing the displacement of the caissons, a formula for the rotational center of the tripod caisson foundation subjected to an eccentric lateral load was derived. The depth of the rotation center was 0.68–0.92 times the height of the caisson when the bearing capacity reached the limit. Under the undrained condition, suction was generated under the lid of the “up-lift” caisson, which helps resist lateral forces from the wind and waves.

关键词： tripod caisson foundation silty clay eccentric lateral capacity model tests

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Applicability of the Arrhenius model for Ammonia Oxidizing Bacteria subjected to temperature time gradients

Alberto MANNUCCI,Giulio MUNZ,Gualtiero MORI,Claudio LUBELLO,Jan A. OLESZKIEWICZ

《环境科学与工程前沿（英文）》 2015年第9卷第6期页码 988-994 doi: 10.1007/s11783-014-0751-0

摘要： The aim of this work is to identify the range of applicability of Arrhenius type temperature dependence for Ammonia Oxidizing Bacteria (AOB) subjected to temperature time gradients through continuous titrimetric tests. An innovative online differential titrimetric technique was used to continuously monitor the maximum biologic ammonia oxidation rate of the biomass selected in a pilot scale membrane bioreactor, as a function of temperature time gradients. The monitoring technique is based on the measurement of alkalinity and hydrogen peroxide consumption rates in two parallel reactors operated in non-limiting substrate conditions for AOB; both reactors were continuously fed with mixed liquor and in one of them AOB were inhibited with allylthiourea. The effects of temperature decrease rates in the range 1 to 4°C·h were evaluated by controlling the titrimetric reactor in the temperature range 10°C–20°C. The dependence of growth kinetics on temperature time gradients and the range of applicability of Arrhenius model for temperature dependency of AOB growth kinetics were assessed. The Arrhenius model was found to be accurate only with temperature gradients lower than 2°C·h . The estimated Arrhenius coefficients ( ) were shown to increase from 1.07 to 1.6 when the temperature decrease rate reached 4°C·h .

关键词： nitrification rate temperature effect continuous titrimetric tests time-gradient temperature variations Ammonia Oxidizing Bacteria (AOB)

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Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams subjected

Antonio MARÍ,Antoni CLADERA,Jesús BAIRÁN,Eva OLLER,Carlos RIBAS

《结构与土木工程前沿（英文）》 2014年第8卷第4期页码 337-353 doi: 10.1007/s11709-014-0081-0

摘要： A mechanical model recently developed for the shear strength of slender reinforced concrete beams with and without shear reinforcement is presented and extended to elements with uniformly distributed loads, specially focusing on practical design and assessment in this paper. The shear strength is considered to be the sum of the shear transferred by the concrete compression chord, along the crack, due to residual tensile and frictional stresses, by the stirrups and, if they exist, by the longitudinal reinforcement. Based on the principles of structural mechanics simple expressions have been derived separately for each shear transfer action and for their interaction at ultimate limit state. The predictions of the model have been compared to those obtained by using the EC2, MC2010 and ACI 318-08 provisions and they fit very well the available experimental results from the recently published ACI-DAfStb databases of shear tests on slender reinforced concrete beams with and without stirrups. Finally, a detailed application example has been presented, obtaining each contributing component to the shear strength and the assumed shape and position of the critical crack.

关键词： shear strength mechanical model reinforced concrete design assessment shear tests

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两座大型斜拉桥索塔锚固区模型试验及对比研究

刘钊,孟少平,吕志涛

《中国工程科学》 2003年第5卷第12期页码 48-54

摘要：

简要介绍了两座大型斜拉桥（南京长江第二大桥南汊桥和润扬长江公路大桥北汊桥）索塔锚固区的节段足尺模型试验，研究了索塔锚固区的抗裂安全系数和极限承载力；同时，还对索塔锚固区预应力索的合理布置形式、索塔节段模型对索塔整体的仿真效果等进行了研究，对于斜拉桥索塔设计具有理论指导意义和实用价值。

关键词：斜拉桥索塔模型试验设计研究

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预应力混凝土简支箱梁足尺模型试验及非线性全过程分析

方志,唐盛华,何鑫

《中国工程科学》 2012年第14卷第10期页码 73-81

摘要：

对一片30 m跨的预应力混凝土小箱梁和一片20 m跨的预应力混凝土空心板进行了足尺模型试验，破坏模式分别为预应力筋拉断和顶板混凝土压碎，按能量的观点计算的延性指标小箱梁和空心板分别为1.99和1.23。基于平截面假定，采用有限条带法编制了非线性计算程序，可对包括卸载过程在内的全过程受力性能进行分析。重点介绍了卸载曲线如何在应力-应变、弯矩-曲率及荷载-位移3个层面进行计算。通过程序，对预应力筋配筋量、预应力筋张拉系数对结构的承载力、变形性能及延性的影响进行了分析。

关键词：预应力混凝土箱梁足尺模型试验非线性分析承载力延性

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Study of base friction simulation tests based on a complicated engineered bridge slope

Liu HE, Guang WU, Hua WANG

《结构与土木工程前沿（英文）》 2012年第6卷第4期页码 393-397 doi: 10.1007/s11709-012-0174-6

摘要： In this paper, a physical base friction test model of a slope is established. The model is based on similarity principles and the geological conditions of a complicated bridge slope during construction, deformation and failure. The behavior of the slope in both its natural state and during excavation loading is qualitatively analyzed through base friction tests. The base friction test results are then subjected to comparison and analysis using finite element numerical simulation. The findings show that the whole engineered slope tends to stabilize in its natural state, whereas instabilities will arise at faulted rock masses located near bridge piers during excavation loading. Therefore, to ensure normal construction operation of bridge works, it is suggested that pre-reinforcement of faulted rock masses be performed.

关键词： base friction test slope stability evaluation bridge slope

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Strain localization analyses of idealized sands in biaxial tests by distinct element method

Mingjing JIANG, Hehua ZHU, Xiumei LI,

《结构与土木工程前沿（英文）》 2010年第4卷第2期页码 208-222 doi: 10.1007/s11709-010-0025-2

摘要： This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method (DEM). In addition to the dilatancy and material frictional angle, the principal stress field, and distributions of void ratio, particle velocity, and the averaged pure rotation rate (APR) in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization. The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio, strain and APR, and distortions of stress field and force chains. In addition, both thickness and inclination of the shear band change with the increasing of axial strain, with the former valued around 10–14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.

关键词： idealized sand strain localization numerical analyses distinct element method (DEM)

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Extension of pilot tests of cyanide elimination by ozone from blast furnace gas washing water through

Ismael Matino, Valentina Colla, Teresa A. Branca

《化学科学与工程前沿（英文）》 2018年第12卷第4期页码 718-730 doi: 10.1007/s11705-018-1771-2

摘要：

For improving wastewater quality, one of the dare of steelworks is reducing cyanide in wastewater of gas washing treatment of blast furnaces. Costs of existing treatments, stringent environmental regulations and changeable composition of water from gas treatment, have led to study how available treatments can be modified and to examine new ones. Ozonation is one of cyanide treatments, tested within a European project. A process model was set up with Aspen Plus^®, to assess operating conditions and wastewater distinctive characteristics and to demonstrate treatment robustness. Process was modeled by theoretical reactors, taking into account all more affecting reactions. A genetic algorithm was exploited to find kinetic parameters of these reactions. After validation, the model was used to analyse scenarios, by considering also real contexts. Pilot tests were extended, process knowledge was enhanced and suggestions were obtained. To promote cyanide removal with ozone, temperature and pH values were 30°C and 10, respectively. With an ozone (mg/h)/water (L/h) ratio of 100 mg/L, batch mode ensure reaching cyanide regulation limit (0.2 mg/L) after maximum 4.5 h, if initial amount was less than 20 mg/L. Higher removal was obtained than in continuous mode due to constraints related to this last run. Higher wastewater contamination needed further time and more ozone.

关键词： blast furnace cyanide removal gas washing water modeling and simulation ozonation

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砂质边坡安全保障新技术研究

牛笑笛,杨广庆,刘伟超

《中国工程科学》 2017年第19卷第6期页码 86-91 doi: 10.15302/J-SSCAE-2017.06.013

摘要：

砂质边坡稳定性差，常规防护措施的防护效果较差。为了有效地对砂质边坡进行防护，笔者研制了一种新型固砂剂——TD–1。为了验证TD–1的固砂效果，笔者进行了配比优化试验、渗透试验、干湿循环试验和现场试验。试验结果表明：在磷酸硅、硅酸锂、硅溶胶掺入比例相同的条件下，固砂试样的强度随钾水玻璃模数的增加而增大；钾水玻璃的最佳添加量为固化砂质量的3%；加入改性剂的试样，强度有明显的增长；使用低模数钾水玻璃的试样，渗透能力相对更好；随着干湿循环次数的增加，试样的强度逐渐下降，经过3次循环之后，试样的强度基本趋于稳定。TD–1固砂剂还可与客土喷播技术结合使用，进行边坡绿化防护，固化产物有利于植物生长。

关键词：砂质边坡固砂剂室内试验现场试验

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高铁闪锌矿精矿加压浸出半工业试验研究

王吉坤,周廷熙,吴锦梅

《中国工程科学》 2005年第7卷第1期页码 60-64

摘要：

高铁闪锌矿经二段加压浸出，锌浸出率97.09%，铁浸出率15.2%，元素硫产率93%，浸出液残酸3.95g/L，经简单中和、净化，生产合格硫酸锌新液供应锌电积。为了研究比较，闪锌矿经一段加压浸出，锌的浸出率98.09%，铁浸出率37.88%，元素硫产率96%，浸出液残酸高（46.4g/L），可并入现有传统湿法炼锌工艺流程处理。

关键词：高铁闪锌矿加压浸出半工业试验元素硫

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Seismic tests of post-tensioned self-centering building frames with column and slab restraints

Chung-Che CHOU, Jun-Hen CHEN

《结构与土木工程前沿（英文）》 2011年第5卷第3期页码 323-334 doi: 10.1007/s11709-011-0119-5

摘要： Post-tensioned (PT) self-centering moment frames have been developed as an alternative to typical moment-resisting frames (MRFs) for earthquake resistance. When a PT frame deforms laterally, gaps between the beams and columns open. However, the gaps are constrained by the columns and the slab in a real PT self-centering building frame. This paper presents a methodology for evaluating the column restraint and beam compression force based on the column deformation and gap openings at all stories. The method is verified by cyclic tests of a full-scale, two-bay by one-story PT frame. Moreover, a sliding slab is proposed to minimize restraints on the expansion of the PT frame. Shaking table tests were conducted on a reduced-scale, two-by-two bay one-story specimen, which comprises one PT frame and two gravitational frames. The PT frame and gravitational frames are self-centering throughout the tests, responding in phase with only minor differences in peak drifts caused by expansion of the PT frame. When the specimen is excited by a simulation of the 1999 Chi-Chi earthquake with a peak ground acceleration of 1.87 g, the maximum interstory drift and the residual drift are 7.2% and 0.01%, respectively.

关键词： post-tensioned frame frame expansion column restraint sliding slab frame test shake table test

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enhancement for implementation in purification of modal frequency for extremely noisy ambient vibration tests

Hassan YOUSEFI, Alireza TAGHAVI KANI, Iradj MAHMOUDZADEH KANI, Soheil MOHAMMADI

《结构与土木工程前沿（英文）》 2020年第14卷第2期页码 446-472 doi: 10.1007/s11709-019-0605-8

摘要： The main purpose of the present study is to enhance high-level noisy data by a wavelet-based iterative filtering algorithm for identification of natural frequencies during ambient wind vibrational tests on a petrochemical process tower. Most of denoising methods fail to filter such noise properly. Both the signal-to-noise ratio and the peak signal-to-noise ratio are small. Multiresolution-based one-step and variational-based filtering methods fail to denoise properly with thresholds obtained by theoretical or empirical method. Due to the fact that it is impossible to completely denoise such high-level noisy data, the enhancing approach is used to improve the data quality, which is the main novelty from the application point of view here. For this iterative method, a simple computational approach is proposed to estimate the dynamic threshold values. Hence, different thresholds can be obtained for different recorded signals in one ambient test. This is in contrast to commonly used approaches recommending one global threshold estimated mainly by an empirical method. After the enhancements, modal frequencies are directly detected by the cross wavelet transform (XWT), the spectral power density and autocorrelation of wavelet coefficients. Estimated frequencies are then compared with those of an undamaged-model, simulated by the finite element method.

关键词： ambient vibration test high level noise iterative signal enhancement wavelet cross and autocorrelation of wavelets

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Axial compression tests and numerical simulation of steel reinforced recycled concrete short columns

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

《结构与土木工程前沿（英文）》 2022年第16卷第7期页码 817-842 doi: 10.1007/s11709-022-0844-y

摘要： To research the axial compression behavior of steel reinforced recycled concrete (SRRC) short columns confined by carbon fiber reinforced plastics (CFRP) strips, nine scaled specimens of SRRC short columns were fabricated and tested under axial compression loading. Subsequently, the failure process and failure modes were observed, and load-displacement curves as well as the strain of various materials were analyzed. The effects on the substitution percentage of recycled coarse aggregate (RCA), width of CFRP strips, spacing of CFRP strips and strength of recycled aggregate concrete (RAC) on the axial compression properties of columns were also analyzed in the experimental investigation. Furthermore, the finite element model of columns which can consider the adverse influence of RCA and the constraint effect of CFRP strips was founded by ABAQUS software and the nonlinear parameter analysis of columns was also implemented in this study. The results show that the first to reach the yield state was the profile steel in the columns, then the longitudinal rebars and stirrups yielded successively, and finally RAC was crushed as well as the CFRP strips was also broken. The replacement rate of RCA has little effect on the columns, and with the substitution rate of RCA from 0 to 100%, the bearing capacity of columns decreased by only 4.8%. Increasing the CFRP strips width or decreasing the CFRP strips spacing could enhance the axial bearing capacity of columns, the maximum increase was 10.5% or 11.4%, and the ductility of columns was significantly enhanced. Obviously, CFRP strips are conducive to enhance the axial bearing capacity and deformation capacity of columns. On this basis, considering the restraint effect of CFRP strips and the adverse effects of RCA, the revised formulas for calculating the axial bearing capacity of SRRC short columns confined by CFRP strips were proposed.

关键词： steel reinforced recycled concrete CFRP strips short columns axial compression behavior recycled aggregate concrete

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新冠病毒肺炎疫情肆虐——抗原检测能否挽救局面？

Peter Weiss

《工程（英文）》 2021年第7卷第1期页码 3-5 doi: 10.1016/j.eng.2020.12.002

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基于非参数检验的高原反应影响因素分析

常海娟,刘猛,庞丽萍,杨鹏 ,王浚

《中国工程科学》 2009年第11卷第2期页码 65-69

摘要：

用一年的时间随青藏铁路列车采集了2 882样本数据，随机抽取其中的1 693份，利用非参数检验及相关分析的方法从统计学上对可能影响耐缺氧反应的因素做分析，最后发现以前到高原时缺氧反应严重程度、性别、吸烟习惯、肥胖度、年龄５个因素对个体的抗缺氧能力有着不可忽视的影响。该结论不仅可以为减少旅客高原反应提供指导性意见，为高原旅客列车供氧系统设计和改进提供重要依据，也可以为后续的医学研究提供统计学基础。

关键词：高原反应影响因素青藏铁路非参数检验个体抗缺氧能力