Quantum Chemistry Calculation on Oxygen and Nitrogen Adsorption in Carbon Nanotude

Oxygen and nitrogen adsorption in single walled carbon nanotube (SWCNT) is studied by density function and discrete variational (DFT-DVM) method.The models of O 2 and N 2 adsorption in the SWCNT are optimized based on the energy minimization.The calculated results of density of state,populations and energy gaps of the molecular orbitals show that oxygen adsorption in SWCNT increases the carbon nanotube`s electrical conductivity more notably than nitrogen adsorption,which is consistent with the experiment.

Shear resistance performance of steel-concrete-steel composite shear wall

For a deeper understanding of the shear resistance performance of the steel-concrete-steel composite shear wall, the main influence factors such as the thicknesses of the steel plates and the concrete, the strength grades of the concrete and the span-depth ratios of the composite wall, which have impacts on the shear resistance performance of the composite shear wail, are analyzed by the numerical simulation method. Meanwhile, the simplified calculation formulae of the initial elastic lateral-resisting stiffness and the shear bearing capacity of the composite shear wall are also proposed. The research shows that with the increase in the thicknesses of the steel plates and the concrete and the increase in the strength grades of the concrete, the shear performance of the shear wall improves obviously; the span-depth ratios of the composite wall have a significant effect on the initial elastic lateral- resisting stiffness, but a small effect on the shear bearing capacity. Comparing the results of the simplified calculation formulae with those of the nonlinear finite element method, it is obvious that the presented formulae are reasonable and meet the real force state of the structure. These conclusions can serve as a preliminary design reference for the steel-concrete- steel composite shear wall.

Wall pressure analysis in squat silos

Rankine theory and Coulomb theory are not suitable for the calculation of wall pressure by bulk materials, so this paper studies the actual distribution and calculation methods for the wall pressure in squat silos. Based on the limits equilibrium theory, the force on unit width of wall exerted by bulk materials is obtained, and the distribution of wall pressure is obtained by accurate mathematical deduction. It is proved that the results are in good agreement with those of the full-sized silo experiment, whether the top of the stored bulk materials is a horizontal plane or a conical pile.

DEVELOPMENT OF CALCULATING MODEL APPLICABLE FOR CYLINDER WALL DYNAMIC HEAT TRANSFER

In the calculation of submarine air conditioning load of the early stage, the obtained heat is regarded as cooling load. The confusion of the two words causing the cooling load figured out is abnormally high, and the change of air conditioning cooling load can not be indicated. In accordance with submarine structure and heat transfer characteristics of its inner components, Laplace transformation to heat conduction differential equation of cylinder wall is carried out. The dynamic calculation of submarine conditioning load based on this model is also conducted, and the results of calculation are compared with those of static cooling load calculation. It is concluded that the dynamic cooling load calculation methods can illustrate the change of submarine air conditioning cooling load more accurate than the static one.

The Application of Pile Foundation Bearing-Retaining Wall Combination Structure in a Mountainous Urban High Fill Project

Pile foundation bearing-retaining wall combination structure is a new type of support structure developed in recent years.This article focuses on the characteristics,advantages,and application scope of the support structure,while combining a variety of algorithms,according to different geological conditions and slope stability,as well as summarizes the pile foundation bearing-retaining wall combination structure force analysis and design methods,taking a high-fill road project in Chongqing as an example.The application of this support structure under special conditions,such as thicker soil layer,steeper sliding surface,weak foundation,and limited slope release conditions,is presented,which illustrates the technical advantages of this support structure and proving that it has several other advantages,including clear force mechanism as well as economic and reasonable structure,thus providing reference for similar projects.

新型再生泡沫混凝土的Tilt-up建筑体系墙体保温P-Temp分析

设计一种应用于Tilt-up建筑体系的新型再生泡沫混凝土保温墙体。利用二维温度场计算软件P-Temp建模,与再生混凝土保温墙体进行对比,证明新型再生泡沫混凝土保温墙体具有良好的保温性能,符合我国建筑节能规范。

Analysis and seismic tests of composite shear walls with CFST columns and steel plate deep beams

A composite shear wall concept based on concrete filled steel tube （CFST） columns and steel plate （SP） deep beams is proposed and examined in this study. The new wall is composed of three different energy dissipation elements： CFST columns; SP deep beams; and reinforced concrete （RC） strips. The RC strips are intended to allow the core structural elements - the CFST columns and SP deep beams - to work as a single structure to consume energy. Six specimens of different configurations were tested under cyclic loading. The resulting data are analyzed herein. In addition, numerical simulations of the stress and damage processes for each specimen were carried out, and simulations were completed for a range of location and span-height ratio variations for the SP beams. The simulations show good agreement with the test results. The core structure exhibits a ductile yielding mechanism characteristic of strong column-weak beam structures, hysteretic curves are plump and the composite shear wall exhibits several seismic defense lines. The deformation of the shear wall specimens with encased CFST column and SP deep beam design appears to be closer to that of entire shear walls. Establishing optimal design parameters for the configuration of SP deep beams is pivotal to the best seismic behavior of the wall. The new composite shear wall is therefore suitable for use in the seismic design of building structures.

适应锅炉调峰运行的水冷壁高温腐蚀预测模型

随着可再生能源大规模并网,传统火电机组作为调配能源的地位显著增强,这对锅炉灵活调峰运行的安全稳定性提出了更高要求。本文耦合烟气侧与工质侧传热,结合管壁温计算,形成水冷壁壁温分布耦合计算方法。同时,建立了用于确定还原性气氛下的燃料硫释放以及含硫组分的相互转化过程的SO_(x)生成模型。综合炉膛数值模拟、水冷壁壁温耦合计算以及包含时间维度的管壁高温腐蚀模型,提出了一种适应锅炉调峰运行的水冷壁高温腐蚀预测模型并基于Matlab GUI开发了对应软件。选取一台超临界600MW四角切圆燃煤锅炉为研究对象,结果表明:采用壁温耦合计算模型和SO_(x)生成模型得到水冷壁的壁温分布和近壁面H_(2)S浓度分布准确度高,为水冷壁高温腐蚀的准确预测提供了良好基础。不同负荷下水冷壁高温腐蚀特征存在差异,壁面腐蚀程度整体上随负荷降低而降低。100%BMCR与75%THA负荷下前墙水冷壁燃烧器与SOFA之间的区域腐蚀最为严重,最大年腐蚀深度分别为276μm和233μm;50%THA与35%BMCR负荷下高温腐蚀深度在燃烧器区域的上部迅速增加至最大值,分别为224μm和256μm。多工况运行水冷壁高温腐蚀状态表现为各工况腐蚀状态的时空叠加。运用水冷壁高温腐蚀预测模型可实现通过锅炉运行参数和运行时间预测多工况下水冷壁高温腐蚀状态程度的时空分布。

西安国际文化传播中心大跨斜幕墙支承结构设计

西安国际文化传播中心大跨斜幕墙支承采用竖向张弦桁架结构体系,结构造型独特新颖。对其结构选型和受力特点进行了重点介绍。采用MIDAS Gen软件建立有限元模型,进行非线性静力及抗震分析计算,同时采用ANSYS软件对考虑几何与材料双重非线性的结构整体稳定性进行了详细分析,探讨了安全系数取值等。分析结果及实际使用效果表明,幕墙支承满足正常使用的各项要求,并具有良好的抗震性能。

框桁式墙体抗震性能试验及影响因素研究

为研究新型框桁式墙体抗震能力,设计4片框桁式墙体试件进行拟静力试验,对比分析了墙体试件的破坏形态、滞回曲线、承载力、延性及性能特征点。并应用ABAQUS软件建立墙体的非线性数值模型,考虑了轴压比、混凝土强度、配箍率和配筋率等因素的影响,计算得到了荷载-位移曲线,分析了承载力及延性变化特征。结果表明:各墙体试件破坏过程为,内部桁杆先于外框墙肢发生变形并耗能,而后桁杆与外墙肢的底部相交处形成塑性区并破坏;在桁式杆件中配置角钢、增大混凝土强度、配箍率和纵筋配筋率也可提高试件延性,而配置角钢时,配筋率对承载力的影响不明显,混凝土强度较高时,其延性不再明显提高;增大轴压比可提高试件的承载力,但会使试件的延性降低。研究结果可为框桁式墙体抗震设计提供依据。

铁路路基挡墙碳减排方案优选及降碳策略研究

铁路路基挡墙在铁路路基全生命周期产生的碳排放不可忽视。为探析不同类型挡墙碳排放水平,选取3种典型挡墙展开研究,提取碳减排最优方案并剖析不同策略组合对其碳排放影响,进而提出碳减排综合策略。首先基于LCA理论,将加筋土挡墙、重力式挡墙及土钉墙全生命周期碳排放分为建材生产、建材运输、施工建造与运营维护4个阶段,基于功能单位,利用碳排放因子法并依据碳排放计算模型测算各类型挡墙各阶段与总碳排放量。研究结果表明,加筋土挡墙因边坡植被固碳能力使其全生命周期表征出固碳效应,且固碳量为197.300 t,重力式挡墙与土钉墙总碳排放量分别为489.344 t和51.834t,故将加筋土挡墙作为碳减排最优方案。然后以加筋土挡墙为研究对象,提取其设计阶段碳排放影响因素,并利用敏感性分析方法识别出其碳排放最敏感的因素为边坡植被类型,其次为挡墙坡度。最后选取百喜草、结缕草、黑麦草3种植被与1∶0.4、1∶0.5、1∶0.6、1∶0.7这4种坡度,分析不同策略组合对加筋土挡墙全生命周期碳排放综合影响。研究表明,对碳汇能力较强的百喜草,降低坡度可提高全生命周期固碳量;对碳汇能力一般的结缕草,避免不利坡度以提高全生命周期固碳量;对碳汇能力较弱的黑麦草,提升坡度可提高挡墙全生命周期固碳量。研究成果可为铁路挡墙降碳设计提供理论依据。

低周反复荷载下T型双波纹钢板混凝土组合剪力墙受力性能试验研究

为研究低周反复荷载下T型双波纹钢板混凝土组合剪力墙的受力性能,对5个T型双波纹钢板混凝土组合剪力墙进行了低周反复加载试验。基于试验数据,分析了T型组合剪力墙的破坏模式、滞回曲线、变形能力及耗能能力,重点研究了边缘约束条件、波纹类型以及轴压比不同变化参数对T型组合剪力墙抗震性能指标的影响规律。研究结果表明:T型双波纹钢板混凝土组合剪力墙破坏模式主要有压屈破坏和压弯破坏两种;设置边缘约束构件是提高T型双波纹钢板混凝土组合剪力墙承载能力和变形能力的关键因素;纵向窄波纹钢板对内部混凝土的约束能力更强,在低周反复荷载下两者协同工作性更优,而横向窄波纹钢板试件强度退化最严重;采用全截面塑性设计方法进行T型双波纹钢板混凝土组合剪力墙正截面承载力计算,试验值与计算值吻合良好;T型双波纹钢板混凝土组合剪力墙具有较好的承载能力和变形能力,可适用于高层及超高层建筑结构中。

自攻螺钉与拉铆钉混合连接受剪承载性能试验

为改善自攻螺钉连接的构件在地震作用下易发生拉脱导致结构严重破坏的缺点,提升冷弯薄壁型钢组合墙体抗破坏能力,分析了组合墙体层间连接处的传力机理,针对自攻螺钉的破坏模式,提出拉铆钉与自攻螺钉混合连接。为研究混合连接的抗剪性能,共进行了48组连接接头抗剪性能试验,包含冷弯薄壁型钢结构常用的5种连接板厚度,不同搭接板厚比(变化范围1.0~2.0),包含纯自攻螺钉连接、纯拉铆钉连接及混合连接的连接方式。观察混合连接的破坏模式,自攻螺钉未发现拉脱破坏,其破坏模式主要表现为:板承压破坏与螺钉倾斜组合破坏、铆钉剪断破坏及板承压与铆钉部分剪断组合破坏3种;相较单一连接方式,混合连接荷载–位移曲线表现出更长的塑性阶段;当板厚比大于1.5且组合板厚小于3.0mm,混合连接的承载力及延性较单一连接增长明显;利用现有计算方法对混合连接的承载力进行累加计算,与试验结果对比,计算结果偏保守。研究发现:混合连接能较好地弥补拉铆钉和自攻螺钉受剪过程中的缺陷,有效改善自攻螺钉拉脱破坏,从而提升连接的承载力及延性;板厚和板厚比是影响混合连接破坏模式及承载力的重要因素,与单一连接相比,板厚比越大,承载力提升越大;排布方式对混合连接的力学性能及破坏机理影响有限;在本文试验工况下,结合混合连接的破坏模式,在现有计算方法的基础上,提出改善后的计算方法,其计算结果更合理。

粉煤灰泡沫混凝土墙体面外偏压承载力数值模拟及简化计算

目的 提出一种粉煤灰泡沫混凝土墙体结构,对墙体进行平面外偏压力学性能研究及参数分析,为该墙体在村镇低、多层建筑中的推广应用奠定基础。方法 设计3种粉煤灰泡沫混凝土墙体模型,采用ABAQUS有限元分析软件对墙体平面外偏压力学性能进行研究;建立104个墙体模型并展开参数化分析,研究高宽比、内置冷拔钢丝间距、冷弯薄壁C型钢厚度等关键参数对墙体平面外偏压力学性能的影响规律;最后建立适用于不同截面参数及高宽比的粉煤灰泡沫混凝土墙体平面外偏压承载力简化计算式。结果 有限元分析所得墙体损伤位置基本与试验结吻合,墙体极限承载力有限元分析值与试验值之比在1.114~1.147;墙体截面参数中冷拔丝间距对平面外偏压承载力相关曲线的影响为正相关,高宽比、冷弯薄壁型C钢厚度为负相关。结论 平面外偏压承载力简化计算式计算结果基本位于有限元分析曲线内部且曲线趋势一致,可以较为准确地预测粉煤灰泡沫混凝土墙体平面外偏压承载力,为墙体在工程实践中的设计提供一定理论依据。

Advanced Sheet Pile Curtain Design: Case Study of Cotonou East Corniche

This paper delves into the critical aspects of sheet pile walls in civil engineering, highlighting their versatility in soil protection, retention, and waterproofing, all while emphasizing sustainability and efficient construction practices. The paper explores two fundamental approaches to sheet pile design: limit equilibrium methods and numerical techniques, with a particular focus on finite element analysis. Utilizing the robust PLAXIS 2016 calculation code based on the finite element method and employing a simplified elastoplastic model (Mohr-Coulomb), this study meticulously models the interaction between sheet pile walls and surrounding soil. The research offers valuable insights into settlement and deformation patterns that adjacent buildings may experience during various construction phases. The central objective of this paper is to present the study’s findings and recommend potential mitigation measures for settlement effects on nearby structures. By unraveling the intricate interplay between sheet pile wall construction and neighboring buildings, the paper equips engineers and practitioners to make informed decisions that ensure the safety and integrity of the built environment. In the context of the Cotonou East Corniche development, the study addresses the limitations of existing software, such as RIDO, in predicting settlements and deformations affecting nearby buildings due to the substantial load supported by sheet pile walls. This information gap necessitates a comprehensive study to assess potential impacts on adjacent structures and propose suitable mitigation measures. The research underscores the intricate dynamics between sheet pile wall construction and its influence on the local environment. It emphasizes the critical importance of proactive engineering and vigilant monitoring in managing and mitigating potential hazards to nearby buildings. To mitigate these risks, the paper recommends measures such as deep foundations, ground improvement techniques, and retrofitting. The findings presented in this study contribute significantly to the field of civil engineering and offer invaluable insights into the multifaceted dynamics of construction-induced settlement. The study underscores the importance of continuous evaluation and coordination between construction teams and building owners to effectively manage the impacts of sheet pile wall construction on adjacent structures.

某600MW机组锅炉主汽出口抽汽方案安全性分析

供热抽汽是形势所趋,本文以某60万千瓦锅炉主汽出口管道最大抽汽量方案进行核算,分别就30%、40%和50%锅炉负荷、在保证发电量不变的基础上,通过壁温计算模型的建立,最终理论计算出三个负荷下最大的理论抽汽量,可为后续供热抽汽改造方案设计提供一些参考。

双钢板混凝土组合墙偏心受压性能试验研究

为了研究双钢板混凝土组合墙在偏心受压荷载下的结构性能,设计制作了5个试件,以偏心距离和墙板厚度作为研究参数,进行偏心受压试验.利用ABAQUS软件对试件进行有限元分析,并采用截面分析法计算试件在轴力与弯矩共同作用下的截面承载力.试验结果表明,试件最终出现钢板局部屈曲与混凝土受压破坏.根据试验荷载-位移曲线,计算得到试件延性系数为1.28~1.92.墙厚相同时,随着加载偏心距离的增加,承载力逐渐下降.偏心距离相同时,增加墙体厚度可以有效提高试件承载能力.偏心受压试件的截面应变分布满足平截面假定.承载力试验值与有限元模型计算值和理论计算值的最大误差分别为4%和9%.

冷弯薄壁C型钢-混凝土组合梁抗弯性能试验研究及有限元分析

为探究冷弯薄壁C型钢-混凝土组合梁受弯性能,制作并设计了5个不同断面组合形式的组合梁试件,并对其进行抗弯性能试验研究,分析其承载性能、破坏机理。在试验基础上,通过有限元分析软件ABAQUS对此组合梁进行非线性分析,对其进行参数分析,研究材料、尺寸对组合梁性能的影响。基于试验研究与有限元模拟分析,建立冷弯薄壁C型钢-混凝土组合梁的承载力模型,对其承载力、刚度进行理论分析。结果表明:各组合梁的主要破坏形式均属于延性破坏;采用ABAQUS建立的组合梁有限元模型能较好地模拟冷弯薄壁C型钢-混凝土组合梁的受力过程。随着C型钢屈服强度的增加,极限荷载最高提高56.5%;C型钢厚度每增加1mm,极限荷载平均提高28.5%;截面高度每增加50mm,极限荷载提高20%左右。但是提高混凝土的强度等级对组合梁的承载力影响较小;推导出了适用于此种冷弯薄壁C型钢-混凝土组合梁的抗弯承载力及其刚度计算方法,发现计算结果与试验结果吻合较好。

考虑套筒灌浆随机缺陷的装配式剪力墙结构可靠度评估

在装配整体式剪力墙结构中,由于套筒灌浆连接的质量具有一定的随机性,势必影响结构的竖向连接性能和结构抗震性能。根据不同缺陷程度的套筒灌浆拉拔试验,建立了一套等效套筒灌浆缺陷连接承载力模型,并基于某实际工程结构,建立了装配整体式剪力墙结构有限元模型。通过考虑灌浆缺陷的随机性,赋予连接接头相应缺陷程度的力学连接性能,来反映套筒灌浆中可能存在的缺陷。通过非线性有限元分析并结合概率密度演化方法(probability density evolution method,PDEM)进行了结构随机非线性反应分析和可靠度评估。结果表明:在动力作用下,结构非线性与随机性具有明显的耦合效应;缺陷的随机性会随着时间的推移,逐渐放大对结构响应的影响;在不同的安全域内,结构的整体可靠度将存在较大的差异。

不同工况下水库大坝固化灰浆防渗墙防渗效果数值分析

针对山东东营孤东水库坝体渗漏问题,提出了大坝的防渗加固方案,对加固后的大坝渗流及稳定性进行数值计算。结果表明,固化灰浆防渗墙方案能很好地解决大坝渗漏问题,加固后设计蓄水位下出逸比降低于允许渗透比降。在水位骤降的条件下,大坝内部压力水头线下降,安全系数提高到1.40;在地震荷载的工况下,安全系数提高到1.32~1.44。加固后围坝的安全系数满足规范值,保证满足大坝的防渗要求,各工况的安全系数也都符合规范要求,可为类似加固工程提供可靠参考。