High-Rise Residential Reinforced Concrete Building Optimisation

In the last few decades structure optimisation has become a main task in a civil engineering project. As a matter of fact, due to the complexity and particularity of every structure, the great amount of variables and design criteria to considerate and many other factors, a general optimisation’s method is not simple to formulate. As a result, this paper focuses on how to provide a successful optimisation method for a particular building type, high-rise reinforced concrete buildings. The optimization method is based on decomposition of the main structure into substructures: floor system, vertical load resisting system, lateral load resisting system and foundation system;then each of the subsystems using the design criteria established at the building codes is improved. Due to the effect of the superstructure optimisation on the foundation system, vertical and lateral load resisting system is the last to be considered after the improvement of floor. Finally, as a case example, using the method explained in the paper, a 30-story-high high-rise residential building complex is analysed and optimised, achieving good results in terms of structural behaviour and diminishing the overall cost of the structure.

Modeling of environmental influence in structural health assessment for reinforced concrete buildings

One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.

Slenderness Ratio Influence on the Structural Behavior of Residential Concrete Tall Buildings

The main concern of this paper is to study the influence of the building slenderness ratio on the structural behavior of the residential concrete tall buildings aiming to deepen structure and architect designers understanding for such type of buildings. The study is emphasized only on Kuwait city design conditions for wind and seismic loadings. The paper presents an actual case study for adding two thirty stories residential towers with two different slenderness ratios to an existing residential complex. Wind loading is considered using both code values and wind tunnel results. Three dimensional finite element techniques through ETABS software are used in conducting analysis for structures presented here. A serviceability study is performed to ensure that buildings have sufficient stability to limit lateral drift and peak acceleration within the acceptable range of occupancy comfort. In addition, an ultimate strength study is carried out to verify that all the structural elements are designed to withstand factored gravity and lateral loads in a safe manner according to the international building codes. Analysis results are presented and discussed. A brief idea about foundation design of the new towers and its connection to the existing foundation is presented. Finally conclusions are summarized as guidelines for the structural professions of concrete residential tall buildings.

Defects in Concrete Elements: A Study of Residential Buildings of 30 Years and above in Onitsha Metropolis, Anambra State, Nigeria

Building defect is an issue in existing buildings that needs urgent tackling to prevent further problems. This study assessed the defects in concrete elements in residential buildings of 30 years and above in the Onitsha metropolis of Anambra State, Nigeria. Data collection instruments in the study include structured questionnaire, interviews, visual inspection/observations, archival records, recordings, photographs;and non-destructive testing of the concrete elements in an existing building in the study area. The population of this study constituted of the construction registered professionals and the existing buildings in study area. The sample for the study was based on the calculated sample size using Taro Yamani Formula. A total of 158 registered professionals were sampled from the population of 260. The questionnaires were purposively distributed to the registered professionals up to the required sample sizes of 158 and 129 questionnaires were properly filled and returned. The study used the SPSS and Microsoft Excel to analyze the data. The results were analyzed in percentages and figures using descriptive statistics and presented in the form of pie charts and tables. The finding of the study revealed that the causes and effects of structural defects on the concrete elements in existing buildings in the study area according to the rating are;exposed/corrosion of the embedded metals, faulty workmanship, overload and impacts, chemical attack, freeze-thaw deterioration, fire/heat, restraint to volume change. The visual observation revealed that the structural elements are characterized by heavy defects such as deep vertical, horizontal and diagonal cracks, exposed/ corrosion of the embedded metals, spalling of the concrete slabs. The existence of defects in the concrete members led to the low compressive strength of the concrete elements and the structural instability of the existing buildings as revealed by the non-destructive test. The non-destructive test result revealed that most of the tested concrete elements have low compressive strength value and such were remarked poor as they did not satisfy the assumed value. Essentially, the study concluded by recommending that regular monitoring, inspections and non-destructive testing of concrete elements should be conducted on existing aged and defected buildings to detect the structural stability of the buildings;and it is imperative to evacuate occupants from heavy structurally deteriorated and defected buildings since most of them have lost their residual design life span and ability to sustain imposed loads.

The Structural Behavior of Low/Medium/High Rise Concrete Office Buildings in Kuwait

The main concern of this paper is to provide an extensive study for the structural behavior of low/medium/high rise office buildings aiming to deepen structure and architect designers understanding for such type of buildings. The study is performed on reinforced concrete and emphasized only on Kuwait city conditions for wind. Regular layout plan building with different heights ranging from five to fifty typical office stories are investigated in this study. Three dimensional finite element techniques through ETABS software are used in conducting analysis for structures presented here-in. A serviceability study is performed to ensure that buildings have sufficient stability to limit lateral drift and peak acceleration within the acceptable range of occupancy comfort. In addition, an ultimate strength study is carried out to design and verify that all the structural elements are designed to withstand factored gravity and lateral loadings in a safe manner according to the international building codes. The building slenderness ratio and the building core size and location are the studied parameters since they are the key drivers for the efficient structural design. Analysis results are presented and discussed and finally conclusions are summarized as guidelines for designers of concrete office buildings in Kuwait.

Load Distribution Assessment of Reinforced Concrete Buildings During Construction with Structural Characteristic Parameter Approach

High-rise reinforced concrete buildings are in great demand in developing countries with rapid urbanization. Construction engineers are facing more and more safety control challenges. One major issue is the understanding of the load distributions, especially the maximum slab load, of structures under construction, which is time dependent. Previous methods were mainly targeted to specific examples, providing specific solutions without addressing the fundamental issues of finding general solutions for load distributions in reinforced concrete buildings with different geometrical and material characteristics during construction. The concept of a structural characteristic parameter is used here to parametedze the main geometrical and material characteristics of concrete structures for generalized assessments of load distributions during construction. The maximum slab load for 20 different construction shoring/reshoring schemes is presented. The results indicate that the traditional simplified method may underestimate or overestimate the maximum slab load, depending mainly on the shoring/reshoring schemes. The structural characteristic parameter approach was specifically developed to assist construction engineers to estimate load distributions to assure safe construction procedures.

Influences of Shrinkage,Creep,and Temperature on the Load Distributions in Reinforced Concrete Buildings During Construction

Site measurements have shown that slab loads re-distribute, between the slabs during the concrete curing, while the external Ioadings and structural geometry remain the same. Some have assumed that this is caused by concrete shrinkage and creep, but there have been no studies on how these factors exactly influence the load distributions and to what degree these influences exist. This paper analyzes the influences of concrete shrinkage, creep, and temperature on the load re-distributions among slabs. Although these factors may all lead to load re-distribution, the results show that the influence of concrete shrinkage can be neglected. Simulations indicate that shrinkage only reduces slab loads by a maximum of 1.1%. Creep, however, may reduce the maximum slab load by from 3% to 16% for common construction schemes. More importantly, temperature variations between day and night can cause load fluctuation as large as 31.6%. This analysis can, therefore, assist site engineers to more accurately estimate slab loads for construction planning.

Elastic-plastic study on high building with SRC transferring story

A new type of transferring structure for steel reinforced concrete (SRC) beams is used in high building. The pushover analysis method was used to study the failure mechanism and ductility of SRC transferring structure through consulting pseudo-static test results for the structure. And, the occurrence order and position of the plastic hinge, the weak story and seismic capacity of high building with SRC transferring story were also studied through consulting shaking table test results for the high building, showing that the seismic behavior of high building with SRC transferring story is good.

Seismic design and analysis of a high-rise self-centering wallbuilding:Case study

Post-tensioning self-centering walls are a well-developed and resilient technology.However,despite extensive research,the application of this technology has previously been limited to low-rise buildings.A ten-story selfcentering wall building has now been designed and constructed using the state-of-art design methodologies and construction detailing,as described in this paper.The building is designed in accordance with direct displacement-based design methodology,with modification of seismic demand due to relevant issues including higher-mode effects,second order effects,torsional effects,and flexural deformation of wall panels.Wall sections are designed with external energydissipating devices of steel dampers,and seismic performance of such designed self-centering walls is evaluated through numerical simulation.It is the first engineering project that uses self-centering walls in a high-rise building.The seismic design procedure of such a high-rise building,using self-centering wall structures,is comprehensively reviewed in this work,and additional proposals are put forward.Description of construction detailing,including slotted beams,flexible wall-to-floor connections,embedded beams,and damper installation,is provided.The demonstration project promotes the concept of seismic resilient structures and contributes to the most appealing city planning strategy of resilient cities at present.The paper could be a reference for industry engineers to promote the self-centering wall systems worldwide.

装配式配筋砌块砌体结构技术与应用

当前在国家大力倡导建筑业采用装配化建造方式的背景下,装配式混凝土结构、装配式钢结构等建筑新技术不断涌现并在工程建设中大量应用,而砌体建筑在这次装配化建造大潮中比较沉寂。砌体结构领域的工作者一直也在积极探索,介绍了砌体结构中一种配筋砌块砌体结构实现装配化建造的技术,该技术先以标准化生产的砌块产品组装成个性化需求的墙构件,再将墙构件经绑扎后在施工现场吊装并在安装中穿入竖向钢筋,最后用混凝土灌孔连接形成整体结构。该技术是基于理论试验研究及工程实践验证后得出的新成果,已有近20万m^(2)规模的工程实践应用,具有成本低、工艺简、安全性好、效率高等特点,为采用装配化方法建造房屋提供了新的选择。

乌兹别克斯坦9度区某超高层建筑结构设计与优化

对于9度设防地区的超高层建筑,其结构设计基本由地震作用控制,因此抗震设计尤为重要。建筑消能减震技术可在提高结构地震安全储备的同时,降低整体工程造价,是结构优化设计的有效措施。对位于9度区的超高层建筑进行了结构方案选型对比、结构方案优化、减震设计方案比选、剪力墙内嵌钢板优化。结果显示,钢骨混凝土框架⁃核心筒方案相对于钢框架⁃支撑方案具备更高的成本优势;框架⁃核心筒方案可通过精细化设计作进一步优化;在此基础上,对钢骨混凝土框架⁃核心筒方案采用两种消能减震方案进行比选,结果表明,采用黏滞阻尼器方案的结构抗震性能明显优于采用黏滞阻尼墙方案;最后通过增大剪力墙竖向分布钢筋配筋率,对低区核心筒墙肢中的内嵌钢板进行了优化。

高延性混凝土加固单层砖木结构农房振动台试验研究

为提高我国农村砌体房屋的抗震性能水平,采用高延性混凝土(HDC)条带加固的方法,设计了两个缩尺比为1∶2的砖木结构模型,对加固模型与未加固模型进行振动台同台对比试验。对比分析了地震作用下两个模型结构的加速度响应、位移响应、扭转效应和破坏形态,并对其抗震性能进行评估。试验结果表明:单层砖木结构农房的整体抗震性能较差,结构的自振频率低、位移反应较大,扭转效应明显,在8度设防地震作用下接近倒塌;经HDC条带加固的模型结构自振频率增大,位移反应相比未加固模型更小,山墙外闪现象得到明显控制,结构扭转效应的破坏作用明显减轻,在9度罕遇地震作用下HDC面层只出现轻微受损,可达到“大震可修”的性能目标。采用HDC条带加固法可有效延缓结构在强震作用下的刚度退化,增加结构的耐损伤能力,并有效提高此类砌体结构的整体抗震能力。

装配式型钢混凝土叠合框架梁连接节点构造设置与安全分析

住房和城乡建设部印发《“十四五”建筑业发展规划》提出大力发展装配式建筑、推动生产和施工智能化升级的主要任务。而国内目前采用的预制叠合框架梁存在着跨度大自重大吊装成本高、预制梁柱节点位置易发生钢筋碰撞吊装定位难度大等问题,限制了装配式建筑结构的发展。结合实际工程项目,提出一种新型的装配式型钢混凝土叠合框架梁,并对该叠合梁的构造设置、连接方式及安全性进行分析,从而为装配式框架结构、框架—剪力墙结构等装配式建筑中框架梁的深化设计提供一种新的拆分方案。

冷却塔定向拆除时剩余支柱的轴力计算方法

为了使冷却塔的定向拆除更加安全可控,对冷却塔保留柱轴向力的计算方法展开研究。根据力的相似关系给出支柱轴向力与其Z向力之间的关系式,基于平截面假定推导保留柱Z向力的计算公式;利用有限元研究环梁和支柱的弹性模量、支柱高度、保留柱数量以及相邻柱柱顶所对应的圆心角5种参数对保留柱Z向力的影响;根据有限元的结果对保留柱Z向力的计算公式进行修正,并研究修正后公式的适用性。结果表明:爆破后的冷却塔在所有保留柱上并不满足平截面假定;在实际工程范围内,上述5种参数不影响保留柱Z向力的分布规律为Z向力沿着y轴方向上的分布形态始终“两端受压,中间受拉”,且保留柱中的最大压力始终出现在第n排保留柱上,最大拉力始终出现在第(n-4)排保留柱上;当爆破圆心角为200°~240°时,修正后计算值的相对误差在21%以内,且该公式在不同冷却塔上具有良好的适用性。保留柱轴向力的计算公式从力学角度为冷却塔的拆除提供了理论支撑,增加了拆除工作的安全性。

装配式钢结构在闽南古建筑保护中的应用

将现有的装配式钢结构技术应用于闽南古建筑的修缮保护项目,基于质量、工期、成本等目标,与传统钢筋混凝土结构进行对比,研究结果表明:装配式钢结构用料更经济,总造价节约近20%,成本优势明显;总工期节约近40%,工期优势明显;施工现场不断校准,加工精度高,工程质量优势明显。

钢筋桁架楼承板在钢筋混凝土框架结构中的应用

钢筋桁架楼承板作为主体结构和外围护结构中常见的预制构件而被广泛应用。本研究基于徐庄高新区某工程总承包项目,研究了钢筋桁架楼承板在钢筋混凝土框架结构体系中的应用,总结了工程施工中的重难点,并提出了相应的施工措施,取得了较好的社会效益和经济效益。

基于BIM技术的钢筋混凝土结构课程教学改革

传统钢筋混凝土结构课程中,学生往往通过施工图纸来学习各类构件的截面尺寸和配筋,但是图纸上内容繁多的标注以及与实际三维建筑结构的差别,让学生掌握起来较为费力。为了回归建筑的三维属性,帮助学生直观地学习本课程的相关知识,文章将BIM技术引入到课程教学中,基于BIM正向设计,在建模过程中将课程内容进行串联,实现从二维结构施工图到三维建筑模型的跨越,在激发学生积极性的同时,提升教学效果。

房屋建筑中装配式钢筋混凝土结构施工技术研究

本项目以装配式钢筋混凝土结构为研究对象,以实际工程为背景,研究其在房屋建筑中的应用优势。研究成果表明,房屋建筑中装配式钢筋混凝土结构作为一种新型的结构形式,具有施工效率高、造价低、绿色环保等优点,满足了现代住宅建设的发展需求,具有较高的推广价值。将该技术应用于建筑工程,能使工程施工质量得到较大提升,特别是应用于房屋建筑工程中,既能提升施工水平,又能降低资金投入。

现有建筑结构抗震鉴定及混凝土结构加固设计研究

虽然现有建筑结构具有较好的抗震表现,但是结构抗震性能依然是建筑设计中的重要内容,只有对建筑结构抗震鉴定和加固设计进行深入研究,才能进一步提升建筑的安全性。下面论述了现有建筑结构抗震鉴定流程和方法,分析了现有建筑结构抗震鉴定内容,并讨论了混凝土结构加固设计内容和方法,最后分析了加固设计的注意事项,并进行了总结。

配筋混凝土肋空心砖组合楼板防坠落技术应用

本着最小干预、保证文物建筑原真性、加固措施可逆的原则,在对文物建筑修缮加固方案选择上,应选择最恰当的加固方案。配筋混凝土肋空心砖组合楼板常见于建造年代较为久远的各类文物建筑中,在经历长时间使用后,容易出现肋部混凝土酥松脱落、钢筋外露锈蚀、空心砖粉化等问题,严重影响后续结构使用安全。通过加固方案适应性分析,选用“钢框架+镀锌钢丝网”组合承托式加固方案,既解决了楼板因荷载产生挠度过大的问题,又起到了防止局部块体坠落的作用,可为今后类似工程提供参考。