Potential Use of Strain Hardening ECC in Permanent Formwork with Small Scale Flexural Beams

Utilizing pre-cast ECC panels as participating permanent formwork of concrete members, and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied. In the process, totally two kinds of ECC with different tensile properties, 7 series of flat panels with different top surface figures and 3 U-shape panels with different inner surface forms were investigated. To evaluate the performance of the permanent formworks, small ECC-concrete composite beams were cast and tested mechanically. The 4-point bending test results show that the use of pre-cast ECC panels as permanent formwork can significantly improve the load capacity and toughness of a concrete member, effectively dispersing single widely opened crack in concrete into multiple ones in ECC. Most permanent formworks show perfect bond with the concrete cast on them, while the ones with partially debonded zone achieve the best mechanical performance. The U-shape permanent formworks show better performances than the flat ones, achieving much betler improvements in both the load capacity and toughness, together with better crack width control.

Reinforcement by polyurethane to stiffness of air-supported fabric formwork for concrete shell construction

By spraying concrete on inner surface,air-supported fabric structures can be used as formwork to construct reinforced concrete shell structures.The fabric formwork has the finished form of concrete structure.Large deviation from the desired shape of concrete shells still remains as central problem due to dead weight of concrete and less stiffness of fabric formwork.Polyurethane can be used not only as a bonding layer between fabrics and concrete but also as an additional stiffening layer.However,there is little research on mechanical behaviors of the polyurethane shell structure.This paper presents experimental studies on an inflated fabric model with and without polyurethane,including relief pressure tests,vertical loading tests and horizontal loading tests.Experimental results show that the additional polyurethane layer can significantly enhance the stiffness of the fabric formwork.Compared with the experiment,a numerical model using shell layered finite elements has a good prediction.The reinforcement by polyurethane to improve stiffness of air-supported fabric formwork is expected to be considered in the design and construction of the concrete shell,especially dealing with the advance of shape-control.

Formwork lateral pressure of precast normal-concrete composite shear walls infilled with self-compacting concrete

Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete(SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.

Interactions between Superplasticizer and Release Agents at the Concrete/Formwork Interface

Improving the knowledge of rheological and tribological characteristics of fresh concrete is important to contribute to the progress of construction sites and the final quality of the work. The objective of this study is to identify the effect of a superplasticizer based on polycarboxylic ether on the tribological behavior of fresh concrete at the concrete/formwork and concrete/oil/formwork interfaces. Friction tests on fresh concrete were carried out using a plan/plan tribometer. In order to study the behavior of the superplasticizer close to the formwork, three concretes with 30% of paste and different dosage of superplasticizer were formulated. The results show that the increase of the dosage of superplasticizer reduces the friction stress. The properties of the superplasticizer generate a deflocculating action of concrete grains and lead to a stabilisation of the soap-oil micellae present in the vicinity of the formwork. Thus, the efficiency of superplasticizer depends on the quantity of fines, on the quantity of soap formed and so, on the release agent formulation.

Discussion Based on Formwork Construction of Box Girder Formwork Design Scheme

Formwork construction has been the important and difficult of the construction process, so the design plan is very important. This paper relies on the Shun Ping Yu subordinate Fertgbo bridge rebuilding project, detailing the cast-in-place box beam formwork support system safety special construction plan, focuses on box girder formwork design scheme of foundation design, box girder bracket design and box girder formwork design, to provide a reasonable reference for similar projects.

Cost Comparison of Different Types of Formworks

Formwork is the temporary moulds in the construction which is fabricated based on the drawing and design of the structure and into which the concrete is poured to form the required structure.Formwork is an essential part of the construction as it has been used by the Romans.The formworks must be strong enough to withstand all types of loads.The joint must be in proper condition to avoid any kind of leakages.The materials used for the formworks should be economical,easily available and durable.The formworks can be made up of different materials such as plywood,steel,aluminum,composite material,etc.In steel formwork the plates used for the slab support are made up of galvanized steel and these are fabricated as per the requirements.Aluminum plates are used in the aluminum framework along with the other components made up of aluminum.The selection of a suitable framework is important in any project because it bears about 25%to 30%cost of the total cost of construction.In the present study,different types of formworks such as steel,plywood and aluminum were studied in a project and a comparison was made on the reusability and easiness in handling and maintenance.Also,a comparison of the formwork used in the construction of the 5th and 11th-floor tower based on the specific plan and drawing was done.The results showed that the aluminum formwork was found to be efficient and suitable among all formworks,although the cost was higher compared to other formwork materials.

THE EVALUATION OF CHANGE IN CONCRETE STRENGTH DUE TO FABRIC FORMWORK

Fabric,as a flexible formwork for concrete,gives builders,engineers,and architects the ability to form virtually any shape.This technique produces a superb concrete surface quality that requires no further touch up or finishing.Woven polyolefin fabrics are recommended for this application.The texture of this fabric allows water from concrete mix to bleed,and therefore reduces the water-cement ratio of the mix.Due to the reduction in the water-cement ratio,a higher compressive strength in fabric-formed concrete is achieved,which is also suggested by earlier studies.The current research study was conducted to investigate and document the changes in concrete strength and overall quality due to these woven polyolefin fabrics.Use of fabric formwork will result in a decrease in construction cost,construction waste,and greenhouse gas emissions.Two sets of tests were conducted in this research study:a comparison of the compressive strength of fabric-formed versus PVC-formed concrete cylinders,and a comparison of the behaviour of the fabric-formed columns versus cardboard-formed reinforced concrete columns.Variables in this research were limited to two types of fabric that included one with coarse and one with a more refined texture,and two types of concrete that included ordinary and flyash concrete.The laboratory results revealed that the effects of fabric formwork on concrete quality in a large member are limited mostly to the surface zone and the core of the concrete remains the same as a conventionally formed concrete.Even though fabric-formed cylinder tests showed an average of a 15%increase in compressive strength of the concrete samples,the compressive strength of the reinforced columns did not dramatically change when compared to the companion cardboard formed control columns.This research confirmed that fabric formwork is a structurally safe alterna-tive for forming reinforced concrete columns.

Application of Mobile Formwork Cast-In-Situ Beam Technology in Bridge Construction

The application of mobile formwork cast-in-situ beam technology is conducive to providing quality assurance for bridge constructions.At the same time,it can improve the overall mechanization level of the construction process and further accelerate the construction progress,so as to shorten the construction period and improve the economic benefits of enterprises.In fact,this construction method has been widely applied.In order to assure a positive outcome from the use of this technology,this paper analyzes the application of mobile formwork cast-in-situ beam technology in bridge construction to provide reference.

基于EMI-CNN的建筑施工模板支撑体系节点健康监测

为预防模板坍塌引发建筑施工安全事故风险,提出一种基于压电阻抗法(EMI)和卷积神经网络(CNN)的模板支撑体系节点智能监测方法。首先,利用压电陶瓷传感器(PZT)的机电耦合特性及其集驱动-传感于一体的特点,建立PZT-节点耦合系统的机电阻抗传感机制模型;其次,基于EMI法,以与待测结构耦合的PZT片电导信号为监测指标,确定模板支撑体系节点松动的发生;然后,以敏感频段内PZT片的801个原始电导信号为模型输入,9个节点松动程度为模型输出,构建162组学习样本和27组测试样本,建立EMI-CNN模型,确定节点松动程度;最后,以一个实际工程中的建筑施工模板体系节点为例,验证EMI-CNN模型的有效性,并对比分析EMI-BP模型。研究结果表明:EMI-CNN模型经过85次迭代达到收敛,预测准确率达到100%,相较于EMI-BP模型提高29.63%。该监测方法可实现对建筑施工模板支撑体系节点健康状态实时、准确、无损监测。

扣件钢管单面支撑体系设计与施工

随着我国城市建设土地减少,新建筑大多数都紧贴用地红线而建,而且很多新建筑地下室外墙厚度越来越厚,常规双面支模无法施工,因此越来越多的地下室外墙采用内侧单面支模的方法施工。虽然扣件钢管排架斜撑在单面支模施工中有一定的应用,但相关设计计算与施工经验不足。细致剖析单侧支模支撑形式多种类型及其特点,针对某具体工程的地下室外墙单侧支模工程,创新性地引入了一种优化后的扣件排架斜撑搭设策略。通过对该单侧支撑体系的研究,构建了精细的有限元模型,并进行了深入的应力、变形及稳定性评估,可为类似单侧支模支撑体系的设计与施工提供参考。

地下室外墙新型工具式单侧支模体系设计及应用

通过对建筑工程地下室支模体系历史沿革进行研究,分析总结常用单侧支模体系优缺点;围绕快速装拆、提高材料复用率、减少现场吊运量、增强结构防水质量等关键指标,进行新型工具式单侧模板创新优化设计。利用ETABS软件进行模板力学分析,采用现场试验进行变形及应力测定及验证。基于分析及试验结果,进行迭代优化,由此形成新型工具式单侧支模体系。工程应用效果表明,该体系较传统单侧支模体系在技术、经济方面均有大幅提升,为未来地下室外墙支模问题提供了解决方案。

落地与悬挑组合式支模体系在高位逐层外悬挑结构施工中的应用

高位逐层外悬挑混凝土结构造型奇特、受力复杂,在建造过程中普遍存在技术难度大、安全风险高、措施费用高、施工工期长等突出问题。以光谷人民医院项目塔楼单侧高位逐层外悬挑混凝土结构支模体系实施为例,从安全性、经济性、可实施性等多方面进行方案综合比选,采用落地与悬挑组合式支模体系。分析结构荷载传递路径和多种施工工况,对支模体系进行精细设计和验算。严格按设计方案指导现场支模体系搭设和拆除。实践表明,提出的落地与悬挑组合式支模体系可安全、便捷、高效地完成高位逐层外悬挑混凝土结构施工。

高层建筑电梯井道液压自爬升筒架模架体系的研发

针对高层建筑电梯井道传统施工方法的缺点与不足,研发了一种高层建筑电梯井道液压自爬升筒架模架体系,以提升建筑电梯井道施工的灵活性和安全性能。通过在工程项目的实际应用,高层建筑电梯井道液压自爬升筒架模架体系能够满足井道结构的施工作业要求,实现了高层建筑电梯井道内剪力墙机械化、智能化施工,提高了施工的安全性与可靠性,并获得了良好的社会效益与经济效益。

基于BIM的桥梁高支模三维可视化智能设计系统

为提高桥梁高支模支撑结构的设计效率和设计质量,利用BIM的二次开发技术对桥梁高支模设计系统进行研究。在实现桥梁及高支模BIM模型的参数化快速建模基础上,研究开发系统内嵌的高支模空间分布设计、受力分析验算、设计冲突分析、工程量校核、设计合理性校验、施工模拟以及集高支模结构三维模型、设计图纸和工程量清单自动生成,高支模交互设计功能于一体的桥梁高支模三维可视化智能设计系统。该系统在多个桥梁实际工程项目的高支模设计中得到成功应用,有效解决传统高支模设计方法存在的图纸表达不够清晰完整、方案修改工作量大、设计效率低下、设计合理性校验不便等问题。

BIM技术辅助空间异型薄壁混凝土结构施工技术

为高效且精确地完成现浇空间异型薄壁混凝土结构的施工,以熊猫基地扩建工程熊猫门建筑施工为载体,分析了BIM技术在施工过程中的应用。利用BIM建立空间曲面薄壁结构三维模型,并对曲面弧形结构进行有限元划分;通过建立模板支撑体系三维模型,导入MIDAS GEN后应用有限元分析计算,优化支架搭设方式,实现支撑体系的深化设计。结果表明:利用BIM技术辅助空间异型薄壁混凝土结构施工,提高了混凝土施工效率,节约了施工时间与成本。

型钢悬挑高支模系统的设计与应用

随着更多高档住宅小区不断追求建筑形式的立面效果,使建筑物外立面的设计更加具有特色和复杂化,如大跨度挑檐、阳台错层布置、外伸屋面等。对于高层建筑而言,传统的施工工艺已不能满足现代建筑的施工要求,同时在建筑结构施工中也成为施工质量、安全控制的难点。以所建项目为例,阐述了高层大跨度外伸屋面实际应用的型钢悬挑高支模支撑体系施工的要点与相关注意事项,旨在为类似工程提供借鉴。

MSS50移动模架吊挂系统有限元分析

利用ANSYS有限元分析软件,分别建立移动模架吊挂系统合模和开模工况下的有限元模型,研究吊挂系统在静载和过孔工况下的应力分布和变形情况,为确保其在施工状态下结构的安全可靠性,需校核移动模架吊挂系统最大受力工况下的结构强度、刚度及屈曲稳定性。有限元分析结果表明:移动模架吊挂系统满足强度、刚度及屈曲稳定性要求,研究成果可为移动模架的设计与安全施工提供参考。

塑料模壳密肋楼盖在大型地下室中的应用

可拆式塑料模壳密肋楼盖体系因具有良好的经济效益,在各种大型建筑物以及大跨度构筑物中得到普遍应用。此受力结构由可拆式模壳及密肋梁板体系构成,具有可周转使用、造价低、施工速度快、外形美观等诸多优势,近几年已经逐步取代传统有梁板结构体系。该文简要介绍和分析了塑料模壳密肋楼盖系统在大型地下室工程实际应用中的施工结构设计、材料选择、工序安排、模板与支撑体系、模壳排布安装及拆除工艺、主肋梁,次肋梁板钢筋施工、混凝土浇筑与养护等主要施工方法,可供参考。

Experiments in Modernizing Cob Construction

This paper will discuss experiments using various forming systems combined with utilizing mechanical equipment,from cement mixers to excavators and skid steers with attachments,to accelerate construction of cob homes and greatly reduce the labor involved.Cob is a colloquial term for monolithic adobe,and refers to a masonry building technique used since ancient times that uses locally-sourced clay as a binder,with various aggregates from sand to small grit or stone,woven together with straw or other fiber and built in continuous layers to form a monolithic structure.

高空外挑大直径钢筋混凝土斜圆柱施工技术

为实现建筑新颖特异的外观并满足其使用功能的需要,建筑结构设计也随之变得新颖,如钢筋混凝土结构中大量采用斜柱、圆柱或斜圆柱等,施工存在一定难度。以深圳某未来科技城项目为例,针对其高空外挑大直径钢筋混凝土斜圆柱施工难题,设计模板支撑体系,分析施工工艺,研究关键技术措施,并总结一套高空外挑大直径钢筋混凝土斜圆柱施工方法。