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Wind-Induced Failure Analysis and Retrofit of an Existing Steel Structure 某既有钢结构风致失效分析与改造
Pub Date : 2018-07-23 DOI: 10.4236/OJCE.2018.83021
Chrysanthos Maraveas, Z. Fasoulakis
The “Dimitrios Vikelas” athletic center in Ermoupolis of Syros, Greece, consists of two buildings. Building B has a steel superstructure that was constructed approximately 35 years ago. It was initially used as a boat shelter and no design calculations were made. It contains steel columns with varying cross section heights. The spans are bridged via trusses and I-beams. Significant geometrical inconsistencies are noted among the existing steel connections and failures have been recorded as a result of buckling in several beams and bracings during the service life of the athletic center. The current study presents an investigation performed in order to diagnose building structural problems and propose strengthening and intervention measures. The goal of this study was to improve the load-carrying capacity of the structure in order to comply with the current design codes. Moreover, enhancement of the dynamic properties of the strengthened structure was demonstrated using modal analyses. The structural behavior was determined in a more precise manner via non-linear wind time-history and incremental static analyses. The analytical results explain the development of failures in the existing structure.
“Dimitrios Vikelas”运动中心位于希腊Syros的Ermoupolis,由两栋建筑组成。B楼的上层结构是钢结构,大约建于35年前。它最初被用作船棚,没有进行设计计算。它包含不同截面高度的钢柱。跨度由桁架和工字梁架起。在体育中心的使用寿命期间,现有的钢连接之间存在显著的几何不一致,并且由于几个梁和支撑的屈曲而记录了失效。本研究提出了一项调查,以诊断建筑结构问题,并提出加强和干预措施。本研究的目的是为了提高结构的承载能力,以符合现行的设计规范。此外,利用模态分析证明了增强结构的动力性能。通过非线性风时程和增量静力分析,更精确地确定了结构的性能。分析结果解释了现有结构中破坏的发展。
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引用次数: 1
The New Formula of Seismic Rigidity Method 地震刚度法的新公式
Pub Date : 2018-07-20 DOI: 10.4236/OJCE.2018.83025
A. S. Aleshin
This publication is a revised version of the previous article. Seismic rigidity method despite its widespread use is the object of harsh criticism from scientists who oppose it to the methodology and results of seismological registration of earthquakes and microseisms. The article substantiates the original approach based on the solution of the direct problem of seismic microzonation for the model of real soil thickness. A new formula of the seismic rigidity method is proposed, taking into account the lithological, hydrogeological and spectral features of the soil mass, as well as the position of the new seismic scale of the SSI. The formula was tested on the example of the correct description of the features of macroseismic effects on the territory of Leninakan at the Spitak earthquake in 1988. Linear estimates according to the formula of seismic rigidity in the seismic microzoning area represent changes in seismic intensity in the most contrast way. It is shown that the real estimates of seismic intensity under strong seismic effects (by I > VII degree) will not exceed those given by the formula of the seismic rigidity method.
本出版物是前一篇文章的修订版。地震刚度法尽管得到了广泛的应用,但却受到了科学家们的严厉批评,他们反对地震和微地震的地震学登记方法和结果。本文在求解地震微区划直接问题的基础上,对实际土壤厚度模型进行了验证。考虑土体的岩性、水文地质和波谱特征以及SSI新地震尺度的位置,提出了一种新的地震刚度法公式。以1988年斯皮塔克地震对列宁纳坎地区宏观地震效应特征的正确描述为例进行了验证。根据地震微区划的地震刚度公式进行线性估计,最能反映地震烈度的变化。结果表明,强震作用下(I > VII度)的地震烈度的真实估计值不会超过地震刚度法公式给出的值。
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引用次数: 1
Major Determinants of Prices Increase of Building Materials on Ghanaian Construction Market 加纳建筑市场建筑材料价格上涨的主要决定因素
Pub Date : 2018-05-09 DOI: 10.4236/OJCE.2018.82012
H. Danso, N. K. Obeng-Ahenkora
Prices increase of building materials is a common trend in both developed and developing countries. The prices increase of building materials results in high cost of housing.The aim of this study is to identify the major determinants of prices increase of building materials on Ghanaian construction market, and also to assess the relationship between the independent variables of the prices increase. A five-point Likert scale was used for the study; from strongly disagree (1) to strongly agree (5). The variables in the questionnaire were ranked based on the response of the participants of the study using Mean Response Analysis (MRA) statistics. Spearman correlation matrix was used to determine the relationship between the variables of prices increase of building materials. Crude oil prices, energy cost, local taxes and charges, cost of fuel and power supply, high running cost, high prices of raw materials, cost of transportation and the high cost of labour were found to be the major determinants of prices increase of building materials on Ghanaian construction market. The study further found multicollinearity relationship among variables of prices increase of building materials, of which the highest correlation coefficient was found between fast-growing demand due to high global economic growth and over-dependence on imported building materials. The study recommends that further research should be carried out to determine the control measures of increase prices of building materials in Ghana.
建筑材料价格上涨是发达国家和发展中国家的共同趋势。建筑材料价格上涨导致住房成本高企。本研究的目的是确定加纳建筑市场上建筑材料价格上涨的主要决定因素,并评估价格上涨的自变量之间的关系。这项研究采用了李克特五点量表;从强烈不同意(1)到强烈同意(5)。问卷中的变量根据研究参与者的反应使用平均反应分析(MRA)统计进行排序。采用Spearman相关矩阵确定建筑材料价格上涨各变量之间的关系。原油价格、能源成本、当地税费、燃料和电力供应成本、高运行成本、高原材料价格、运输成本和高劳动力成本被认为是加纳建筑市场上建筑材料价格上涨的主要决定因素。研究进一步发现建筑材料价格上涨的变量之间存在多重共线性关系,其中全球经济高速增长带来的快速需求与过度依赖进口建筑材料之间的相关系数最高。该研究报告建议,应进行进一步的研究,以确定加纳建筑材料价格上涨的控制措施。
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引用次数: 17
Properties and Thermal Stress Analysis of Blended Cement Self-Compacting Concrete 掺合水泥自密实混凝土性能及热应力分析
Pub Date : 2018-05-09 DOI: 10.4236/ojce.2018.82009
Benson Kipkemboi, S. Miyazawa
Self-Compacting concrete is a concrete that is able to flow and consolidate under its own weight, completely fill the formwork even in the presence of dense reinforcement, whilst maintaining homogeneity and without the need for any additional compaction. Self-Compacting concrete is achieved by using high proportions of powder content and super plasticizers. Due to this, pronounced thermal cracking is anticipated. Thermal cracking in concrete structures is of great concern. The objective of this research is to carry out experiments and investigate fresh and hardened properties of SCC developed using a blend of ordinary Portland cement and ground granulated blast furnace slag (GGBFS), to evaluate the applicability of Japan Concrete Institute (JCI) model equations and to find out any similarities and differences between Self- Compacting concrete and normal vibrated concrete—Portland blast furnace slag concrete class B. Thermal stress analysis of the proposed Self-Compacting concrete and normal vibrated concretes were investigated by simulation using 3D FEM analysis. To carry out these objectives, concrete properties such as autogenous shrinkage, adiabatic temperature rise, drying shrinkage, modulus of elasticity, splitting tensile strength and compressive strength were determined through experiments. From experimental results, it was observed that except for the fresh properties, the hardened properties of Self-Compacting exhibit similar characteristics to those of normal vibrated concrete at almost similar water to binder ratios. It was also established that Self-Compacting concrete at W/B of 32% with a 50% replacement of ground granulated blast furnace slag has better thermal cracking resistance than SCC with 30% GGBFS replacement. It is also found that provided the relevant constants are derived from experimental data, JCI model equations can be applied successfully to evaluate hardened properties of Self-Compacting concrete.
自密实混凝土是一种能够在自身重量下流动和巩固的混凝土,即使在存在密集钢筋的情况下也能完全填满模板,同时保持均匀性,无需任何额外的压实。自密实混凝土是通过使用高比例的粉末含量和超级增塑剂来实现的。因此,预计会出现明显的热裂。混凝土结构中的热裂是人们关注的问题。本研究的目的是开展实验,研究使用普通硅酸盐水泥和磨碎的粒状高炉矿渣(GGBFS)的混合物开发的SCC的新鲜和硬化性能。为评价日本混凝土协会(JCI)模型方程的适用性,找出自密实混凝土与法振混凝土的异同点——b级波特兰高炉矿渣混凝土,采用三维有限元法对所提出的自密实混凝土与法振混凝土进行了热应力模拟分析。为了实现这些目标,通过实验确定了混凝土的自收缩、绝热温升、干燥收缩、弹性模量、劈裂抗拉强度和抗压强度等性能。实验结果表明,在水胶比相近的情况下,自密实混凝土除具有新鲜性能外,其硬化性能与普通振动混凝土相似。研究还表明,自密实混凝土在W/B为32%时,掺加50%的磨粒级炉渣,其抗热裂性能优于掺加30% GGBFS的自密实混凝土。如果相关常数由试验数据导出,则JCI模型方程可以成功地用于评价自密实混凝土的硬化性能。
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引用次数: 0
Rutting Resistance of HMA Rehabilitated with Micro-Surfacing 微表面修复HMA的抗车辙性能
Pub Date : 2018-05-09 DOI: 10.4236/OJCE.2018.82019
Arbia Garfa, A. Carter, A. Dony
The work presented here is a study on the measurement and prediction of the rutting resistance of previously rutted asphalt mixes rehabilitated with a layer of micro-surfacing manufactured with virgin and recycled aggregates at different stages of aging. The experimental procedure consisted of rutting tests on hot mix asphalt slabs already degraded and repaired with virgin and recycled micro-surfacing. Then, the evolution of the behavior of micro-surfacing cast on the hot mix asphalt slabs is observed according to loading cycles of the pavement rutting tester MLPC. Before rutting tests, slabs are subjected to 24 hours at 50°C and aged for 2 days and 5 days at 85°C in the oven. The results showed rutting percentages of 6.3% for hot mix asphalt slabs aged for 2 days and 7.2% for 5 days. These hot mix slabs repaired with virgin micro-surfacing have rutting percentage of about 9.2 % for 2 days of aging and 6.5% for 5 days of aging. While, the HMA slabs repaired with recycled micro-surfacing have rutting percentage of about 8.1% for 2 days of aging and 5.9% for 5 days of aging. These results allowed the development of a prediction model based essentially on three predictor variables including cycle number, rutting state and percentage of water in the micro-surfacing material. The developed model shows a strong correlation between the predicted rutting values and the rutting values measured with the MLPC rut tester. Thermal aging in oven has a positive impact on the resistance to permanent deformation of new asphalt mixes and those rehabilitated with micro-surfacing. The parameters of rutting state and contribution water are significant in the rutting prediction model, while the cycle number remains a non-significant parameter in the model but determinant.
本文研究了在不同老化阶段用原始和再生骨料制成的微表面层修复以前车辙的沥青混合料的抗车辙性的测量和预测。实验过程包括对已经退化的热拌沥青板进行车辙试验,并使用原始和再生微表面进行修复。然后,根据路面车辙试验装置MLPC的加载周期,观察热拌沥青路面微浇筑物的行为演变。在车辙试验之前,板坯在50℃下放置24小时,在85℃下放置2天和5天。结果表明:热拌沥青板2 d车辙率为6.3%,5 d车辙率为7.2%;这些用原始微表面修复的热拌板在2天时效下车辙率约为9.2%,在5天时效下车辙率约为6.5%。而采用再生微堆焊修复的HMA板,时效2天车辙率约为8.1%,时效5天车辙率约为5.9%。这些结果使得基于三个预测变量的预测模型得以发展,包括循环次数、车辙状态和微表面材料中水的百分比。该模型表明,车辙预测值与MLPC车辙测试仪实测车辙值具有较强的相关性。烘箱热老化对新沥青混合料和微表面修复沥青混合料的抗永久变形性能有积极的影响。车辙状态和贡献水量参数在车辙预测模型中具有显著性,而周期数在模型中不具有显著性,但具有决定性。
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引用次数: 6
Analysis of Road Embankment Slope Stability 公路路堤边坡稳定性分析
Pub Date : 2018-05-09 DOI: 10.4236/ojce.2018.82010
Chunyuan Liu, Ulysse Sèho F. Hounsa
The stability of earthworks (cuttings, embankments, dikes) and natural slopes is a problem that is of concern to geotechnicians, both practitioners and researchers. The disorders generated by breaking the slopes are usually spectacular, often destructive and sometimes murderers. Many methods of calculating stability have been proposed. These are differentiated by the assumptions accepted by their authors (methods of calculation in equilibrium limit, methods of calculation at break, deformation calculation methods) and the ease of their implementation (calculations using charts, automatic calculations using software), but they all agree to define an overall factor of safety according to which the stability of the studied slope is considered to be insured or compromised, or by safety factor spartial effects on the one hand, applied stresses and, on the other hand, the mechanical properties soil. Various embankment strengthening techniques have been developed. They are differentiated by the process of their realization, their cost and their durability. The main objective of this study is to present the problems of both natural and artificial slope stability on construction projects. In this regard, special emphasis is given to the sensitivity of the calculation model input parameters (soil, load), which should contribute to raising awareness about this issue, as a prerequisite to make the right decisions and optimal technical solutions in this area.
土方工程(岩屑、堤防、堤防)和天然斜坡的稳定性是岩土技术人员(从业人员和研究人员)关注的一个问题。破坏斜坡所产生的混乱通常是壮观的,往往是破坏性的,有时是谋杀。人们提出了许多计算稳定性的方法。这些方法根据其作者接受的假设(平衡极限计算方法、断裂计算方法、变形计算方法)及其实施的便利性(使用图表计算、使用软件自动计算)进行区分,但它们都同意定义一个总体安全系数,根据该系数,所研究的边坡的稳定性被认为是得到保证或损害的,或者一方面是安全系数的局部影响。施加应力,另一方面,土壤的力学特性。各种路堤加固技术已经发展起来。它们根据实现的过程、成本和持久性来区分。本研究的主要目的是提出建设工程中天然边坡和人工边坡的稳定性问题。在这方面,特别强调了计算模型输入参数(土壤,荷载)的敏感性,这应该有助于提高对这一问题的认识,作为在该领域做出正确决策和最佳技术解决方案的先决条件。
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引用次数: 3
Determination of an Equivalent Loading Circle Which May Represent the Loading of the Dual Wheels 可表示双轮载荷的等效载荷圆的确定
Pub Date : 2018-05-09 DOI: 10.4236/OJCE.2018.82018
B. Thiam, Fatou Samb, A. Dione
This work aims to look for a simplifying surface that can represent the effect of the dual wheels on the variation of the stress and deformation state prevailing during the passage of traffic loads. This was facilitated by the results of Thiam (2016) [4] obtained on the distribution of the vertical contact stress in the space described by the dual wheels. The analysis of the results of this study, on all the loading circles considered, shows that the radius loading circle equal to 0.181 m makes it possible to most probably represent the effect of the dual wheels. With this new surface, the effect of the dual wheels can be determined in 2D. The choice of this load is confirmed by a study in case of overload. Thus, the single axle with dual wheels is represented by a simplified diagram equipped on each side by a disk of radius 0.181 m. These results are obtained using a numerical simulation under Cast3M with a gravelly lateritic pavement.
本工作旨在寻找一种简化的表面,可以表示双车轮对交通荷载通过过程中普遍存在的应力和变形状态变化的影响。Thiam(2016)[4]对双轮所描述的空间中垂直接触应力分布的研究结果为这一点提供了便利。对所考虑的所有加载圆的研究结果进行分析表明,半径为0.181 m的加载圆最可能代表双车轮的影响。利用这种新的表面,可以在二维上确定双轮的效果。在超载情况下的研究证实了这种载荷的选择。这样,双轮单轴就可以用一个简化的图来表示,每边都有一个半径为0.181 m的圆盘。这些结果是通过在含砾红土路面上使用Cast3M进行数值模拟得到的。
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引用次数: 1
Analysis of Rooftop Rainwater Harvesting in Kabul New City: A Case Study for Family Houses and Educational Facilities 喀布尔新城屋顶雨水收集分析:以家庭住宅和教育设施为例
Pub Date : 2018-05-09 DOI: 10.4236/OJCE.2018.82013
O. Rahimi, K. Murakami
The Afghan government has planned the project of Kabul New City (KNC) to cope with the rapid growth of Kabul, an existing capital city. Due to climatic and topographical reasons, it is supposed that KNC suffers from a water scarcity problem. This study investigates the feasibility of a rooftop rainwater harvesting system in KNC to relieve the water scarcity problem. An applicability of the rooftop rainwater harvesting system was discussed for several types of residential houses and schools, using 11 years rainfall data. This study also examined the cost-effectiveness of the system by considering the service life of the system. Furthermore, an optimal size of the rainwater storage tank was discussed based on the balance among harvested rainwater volume, non-potable water demand, and cost-effectiveness.
阿富汗政府为应对现有首都喀布尔的快速发展,计划建设喀布尔新城(KNC)。由于气候和地形的原因,人们认为KNC存在缺水问题。本研究探讨了KNC屋顶雨水收集系统缓解水资源短缺问题的可行性。利用11年的降雨数据,讨论了屋顶雨水收集系统对几种类型的住宅和学校的适用性。本研究还通过考虑系统的使用寿命来检验系统的成本效益。此外,在收集雨水量、非饮用水需求和成本效益平衡的基础上,讨论了雨水储罐的最佳尺寸。
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引用次数: 2
The Pedagogic Capacity of Architecture the Macro Project University Citadel—University of Atlántico Barranquilla—Colombia 建筑教学能力宏观项目大学Citadel-University of Atlántico Barranquilla-Colombia
Pub Date : 2018-05-09 DOI: 10.4236/OJCE.2018.82011
C. Lemus, Mayra Alejandra Rivero Bueno
Urban agenda nowadays puts pedestrians as the axis of urban design, and pedestrians are the most important thing in the city. The architect takes that idea and applies it in the project, and he focuses on prioritizing the pedestrian over the cars. Public spaces filled with green zones are a main element, water treatment is a design determinant, buildings use natural illumination as much as possible and culture and arts are reinforced through new scenarios.
当今的城市议程将行人作为城市设计的轴线,行人是城市中最重要的东西。建筑师采纳了这个想法并将其应用到项目中,他专注于优先考虑行人而不是汽车。充满绿化带的公共空间是一个主要元素,水处理是设计的决定因素,建筑尽可能地使用自然照明,文化和艺术通过新的场景得到加强。
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引用次数: 0
The Reduction in the Swelling Potential of the Foundation Ground of Togblécopé in Togo by the Stabilization with Binders and Sands 用粘结剂和砂土稳定降低多哥togblaco<s:1>地基的膨胀势
Pub Date : 2018-05-09 DOI: 10.4236/ojce.2018.82017
Kossi Bolanigni Amey, Komi Mawutodzi Sounsah, K. Amoussou, K. Neglo
The present study aims at helping to search for preventive solutions to pathologies of constructions in Togblecope in Togo, by the reduction in the withdrawal and swelling of foundation grounds through their stabilization. Togblecope’s clay taken from 1 m, 2 m and 3 m deep, and mixed with four binding materials (cement, sea sand, silty sand and lime). Tests of identification and free swelling with odometer are carried out on pure and stabilized materials. What emerges from these tests is that the limits of liquidity and plasticity are rising along with the rate of stabilizers while the index of plasticity is falling. Cement and lime cause a reduction in the index value of plasticity by almost 50%. The more the sand’s grain size, the more the reduction in the plasticity index. The swelling potential is reduced by 60% for cement and lime, 30% for sea sand and 20% for silty sand. The present study is a contribution to the reduction in deflations from 20% to 60% of some parts of constructions in order to limit cracks.
本研究的目的是通过稳定地基来减少地基的退缩和膨胀,从而帮助寻找预防多哥Togblecope建筑病态的办法。Togblecope的粘土取自1米、2米和3米的深度,并与四种粘结材料(水泥、海砂、粉砂和石灰)混合。用里程表对纯稳定材料进行了鉴定和自由膨胀试验。试验结果表明,随着稳定剂用量的增加,流动性极限和塑性极限呈上升趋势,而塑性指数呈下降趋势。水泥和石灰使塑性指数值降低了近50%。砂的粒度越大,塑性指数的降低幅度越大。水泥和石灰的膨胀潜力降低了60%,海砂降低了30%,粉砂降低了20%。目前的研究是一个贡献减少通货紧缩从20%到60%的某些部分的建设,以限制裂缝。
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引用次数: 0
期刊
Open Journal of Civil Engineering
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