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.

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.

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.

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.

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.

拼接成型UHPC免拆模板钢筋混凝土柱的抗震性能

为研究超高性能混凝土(UHPC)免拆模板钢筋混凝土(URC)柱的抗震性能,选取UHPC免拆模板拼接方式和表面处理方式为试验设计参数,制作并完成了9个URC柱和1个钢筋混凝土(RC)柱的拟静力加载试验。模板拼接方式为螺栓加角钢连接、螺栓连接和环氧树脂砂浆连接;表面处理方式为光面处理、气泡膜印花处理和设肋处理,通过拟静力试验研究了模板拼接方式及表面处理方式对该类柱抗震性能的影响。此外,基于平截面假定,提出了URC柱的正截面偏压承载力计算式。结果表明:峰值荷载前,UHPC模板与核心混凝土黏结面无明显破坏,URC柱表现出良好的整体性,尤其是采用螺栓加角钢连接的URC柱,即使加载至极限位移时,也没有发生界面黏结失效破坏;与普通RC柱相比,URC柱的承载力提高了6.4%~43.3%,延性提高了11.4%~48.7%,耗能能力提高了27.7%~85.3%;三种连接方式中,采用螺栓加角钢连接的URC柱承载力最高,连接最可靠。最后,基于平截面假定提出的公式计算值与试验值吻合较好,可为工程应用提供参考。

3D打印混凝土永久模板叠合柱的抗压性能数值模拟研究

为深入研究3D打印混凝土永久模板叠合柱的抗压性能,基于3D打印混凝土永久模板叠合柱及同尺寸整体现浇对照柱试验建立构件数值模型,模拟分析其轴压荷载-位移响应及失效形态。针对界面粘结性能、现浇混凝土抗压强度、打印模板厚度、荷载偏心距等参数开展3D打印混凝土永久模板叠合柱的抗压性能计算分析,研究表明:叠合柱轴压极限承载力随着薄弱界面剪切强度、刚度及现浇混凝土抗压强度的增大而增大。由于打印材料的抗压强度高于现浇混凝土,叠合柱抗压极限承载力提升率与打印模板厚度呈近似线性关系,叠合圆柱的抗压极限承载力随着荷载偏心距的增大而降低,呈近似线性负相关。此外,偏心距对叠合圆柱极限承载力下降幅度的影响大于现浇圆柱。

大跨度混凝土钢筋框架梁挠度超限研究

根据大量的工程实践,大跨度钢筋混凝土框架梁由于设计不合理引起大跨度梁超限的工程案例很少,大多数是施工原因导致挠度超限。以某工程挠度超限的大跨度钢筋混凝土梁为例,根据设计资料和现场检测资料,从设计和施工两方面,利用数值计算和有限元模拟,验证分析大跨度钢筋混凝土框架梁挠度超限的原因。验证分析表明,梁板混凝土实际浇筑厚度超限与梁模板起拱高度不足可能引起梁挠度增加。当梁下立杆稳定承载力不足时,梁也易随立杆屈曲变形产生较大挠度。

岩棉复合保温外模板承载力及温度效应分析

为了提高建筑外围护结构施工效率及解决传统外保温系统长期存在的易脱落和易着火问题,提出了一种集保温和建筑模板于一体的岩棉复合保温外模板(RW-CIEF)体系。RW-CIEF由内到外依次为内侧加强层、岩棉保温芯材、黏结层、保温过渡层以及外侧加强层。以哈尔滨市为例,基于全寿命周期成本(life cycle cost,C lc)确定了岩棉保温芯材的最佳厚度。采用有限元分析与理论计算相结合的方法探求了RW-CIEF在工程中的可行性,分析了RW-CIEF的抗弯性能、施工承载力及温度效应下的应力和变形,讨论了开槽形式、开槽宽度、开槽深度以及开槽间距对RW-CIEF抗弯性能的影响。结果表明:RW-CIEF的抗弯性能理论计算结果与有限元分析结果有较高的一致性;开槽处理可有效提高RW-CIEF的抗弯性能,综合抗弯性能、热工特性及加工角度,建议开槽形式选用对应开井字槽或对应开纵槽,开槽深度和宽度均为10 mm,开槽间距为150 mm;设计的RW-CIEF满足施工承载力,可保证外围护结构保温工程施工质量;由温度效应产生的最大拉应力和压应力均未超过RW-CIEF的外侧加强层承载力,反映出RW-CIEF出现夏季空鼓或冬季开裂现象的可能性极小。提出的RW-CIEF体系可为外围护结构保温工程及建筑模板工程未来研究方向提供一种新的思路和方法。

预制模壳填芯混凝土悬臂盖梁承载力分析

盖梁的轻量化发展是实现全预制桥梁的必然要求。基于已有的预制模壳填芯混凝土悬臂盖梁静力试验,采用有限元软件ABAQUS对试件PRC1进行数值分析,有限元计算结果和试验结果吻合较好,验证了有限元模型的可靠性。通过修改已验证的有限元模型参数,进一步分析外壳混凝土强度、纵筋配筋率和交界面接触设置对预制模壳填芯混凝土悬臂盖梁力学性能的影响。基于钢筋混凝土一般构件的承载力计算方法建立试件的理论计算公式,并对提出的计算公式进行验证。研究结果表明:当外壳材料为普通混凝土时,混凝土强度等级从C35增加到C60,峰值承载力仅提高1%,而当外壳材料为超高性能混凝土(UHPC)时,峰值承载力相较C35提高了22%。纵筋配筋率与峰值承载力呈线性增长趋势,当顶部第1排纵筋直径从14 mm增加到22 mm时,峰值承载力提高了34%。交界面接触设置为绑定约束比面面接触的峰值承载力更接近试验值,且后者是相对保守的。基于钢筋混凝土一般构件建立的承载力计算方法所计算结果与试验结果和有限元分析结果吻合较好。

一种新型预制装配式免拆模板设计与开发

为克服传统建筑模板施工质量不高、工序多、周转率低和现场环境乱等质量缺陷,在总结现有免拆模板的基础上设计、开发了一种可实现装饰装修一体化的新型预制装配式免拆模板。本文介绍了新型装配式免拆模板的基本构造及施工要点,为新型装配式免拆模板的推广应用提供一定的借鉴和参考。

大采高工作面柔模沿空留墙掘巷技术

柔模混凝土沿空留巷技术已应用多年,在中厚煤层和薄煤层开采下均取得了较好的支护效果,但在厚煤层大采高工作面,因巷道高、巷旁支护压力大、混凝土早期强度低易受压损坏难以有效支撑顶板。大采高工作面矿压显现剧烈,巷旁维护难度大,故此提出一种新型的预浇墙柔模混凝土沿空留墙掘巷新技术,即在上工作面回采前,刷煤扩帮后提前预浇柔模混凝土墙体,提高煤帮整体支撑力的同时,解决柔模混凝土墙短期无法有效承载顶板来压的难题;待回采一定距离后,再沿墙滞后掘进下工作面回采巷道,且掘进方向与上工作面回采方向一致,缓解接续紧张,最终实现无煤柱开采。以王庄煤业3503工作面回采留设预浇墙为工程背景,建立了沿空留墙掘巷围岩结构力学模型,理论计算得出墙体力学支护参数,并通过现场应用验证了该技术的可实施性。结果表明:理论计算分析确定了墙体高宽比为5 m×1.5 m,混凝土强度C30即可满足留墙支护要求;沿墙掘进巷道总体变形量小,顶底板和两帮最大移近量仅为260 mm和125 mm,墙体最大受压18 MPa,小于墙体自身承载力;下工作面临近巷道掘进115 m后即趋于稳定。该技术应用全阶段效果良好,满足巷道使用要求,有效解决了大采高工作面沿空留巷重大技术难题,也可为相似工况无煤柱开采提供技术借鉴。

特急曲线水利隧洞针梁台车设计与施工

水利基础设施建设过程中,特急曲线水利隧洞具有弯多、弯急的特点。普通针梁台车在此类隧洞工程施工中,出现弯道碰壁、受压变形等诸多问题,传统施工装备与技术的适应性难题亟待解决。以金沙江向家坝灌区北总干渠一期工程望江岩隧洞衬砌施工为依托,在传统全圆针梁台车既有设计方法的基础上,开展加大单次衬砌长度、整体快速拆合、优化结构形式、改变脱模方式、实现高通用性等方面研究;研制特急曲线水利隧洞全圆针梁台车,创新台车不同状态下的施工工法,解决了台车在曲线处行走时会触碰隧洞壁,台车过特急曲线隧洞需重复拆卸及安装,衬砌完成后上、下侧模在受力状态下出现模板反向咬合等问题,有效推动了特急曲线隧洞施工装备设计方法革新。实际应用结果表明,所开发的特急曲线水利隧洞全圆针梁台车及其相关施工技术大幅度提高了特急曲线水利隧洞施工效率,降低了施工成本,保证了施工安全和工程质量。

Experimental study on flexural behavior of ECC/RC composite beams with U-shaped ECO permanent formwork

To enhance the durability of a reinforced concrete structure, engineered cementitious composite (ECC), which exhibits high tensile ductility and good crack control ability, is considered a promising alternative to conventional concrete. However, broad application of ECC is hindered by its high cost. This paper presents a new means to address this issue by introducing a composite beam with a U-shaped ECC permanent formwork and infill concrete. The flexural performance of the ECC/RC composite beam has been investigated experimentally with eight specimens. According to the test results, the failure of a composite beam with a U-shaped ECC formwork is initiated by the crushing of compressive concrete rather than debonding, even if the surface between the ECC and the concrete is smooth as-finished. Under the same reinforcement configurations, ECC/RC composite beams exhibit increases in flexural performance in terms of ductility, load-carrying capacity, and damage tolerance compared with the counterpart ordinary RC beam. Furthermore, a theoretical model based on the strip method is proposed to predict the moment-curvature responses of ECC/RC composite beams, and a simplified method based on the equivalent rectangular stress distribution approach has also evolved. The theoretical results are found to be in good agreement with the test data.

柔模墙沿空留巷灾害一体化防治技术研究

在煤炭保供和工作面限员双重压力下,将煤矿灾害分别进行治理的理念和技术已不能适应新时代煤矿发展要求。通过工业性试验研究提出一种紧跟回采工作面浇筑1道饱满密实接顶且可即时承载的柔模混凝土连续墙,密闭采空区,保留原有巷道,并将保留下来的巷道作为灾害一体化防治工程平台。给出了利用该平台进行矿井水、火、瓦斯、顶板、热害、强矿压等重大灾害综合治理的技术途径,总结了该技术的适用条件,介绍了该技术在国家能源集团、潞安化工集团、陕煤集团等单位的灾害一体化防治效果。

多级孔LaNiO_(3)制备及其在苯酚加氢脱氧反应中的催化性能

采用无皂乳液聚合法制备聚甲基丙烯酸甲酯(PMMA)和聚苯乙烯(PS)胶体晶体模板剂,以制备的模板剂和经处理的P123为模板分别制备LaNiO_(3)钙钛矿氧化物。采用XRD、SEM、H 2-TPR等表征手段考察模板剂种类对LaNiO_(3)钙钛矿氧化物的晶体结构、表面形貌、还原性能以及孔径分布等的影响。结果表明,不同种类模板剂制备的样品均形成了明显的钙钛矿结构,孔径分布以介孔-介孔多级孔结构为主。孔径分布和比表面积的差异影响样品的还原性能和表面形貌。聚甲基丙烯酸甲酯为模板剂制备的LaNiO_(3)钙钛矿氧化物具有较高比表面积,还原性能较好,在0.1 MPa、350℃和40 mL·min-1氢气流量下,苯酚单程转化率达到22.48%,主要发生直接脱氧反应,产物以苯为主。

钢-PVA混杂纤维增强水泥基复合材料永久模板叠合RC单向板短期刚度计算方法

钢-PVA混杂纤维增强水泥基复合材料(HFRCC)具有良好的受拉韧性和耐久性能,是永久模板的理想材料。首先探究了PVA纤维掺量对HFRCC工作性能和抗折强度的影响,随着PVA纤维掺量增加,HFRCC的工作性能显著减弱,抗折强度先增大再减小,最终选用含有1.5%钢纤维和0.25%PVA纤维的HFRCC来制作永久模板。随后对六个HFRCC永久模板叠合RC单向板和一个RC单向板进行了四点受弯试验,探究了HFRCC-RC界面处理方式和配筋率对叠合板受弯性能的影响。试验结果表明:抹平、等距凹槽和钢钉拉毛三种界面处理方式对叠合板受弯性能的影响可以忽略;HFRCC模板能够有效限制裂缝发展,减小裂缝宽度和间距,叠合板的开裂弯矩相比于普通混凝土板提高了20.1%~31.7%。分别采用刚度解析法和有效惯性矩法建立了HFRCC-RC叠合板短期刚度计算方法,两种方法均有较高的计算精度且离散性较小。

水泥聚苯保温模壳混凝土柱的抗震性能试验

为进一步了解水泥聚苯保温模壳混凝土柱的抗震性能,制作了单侧设置水泥聚苯保温模壳、周边设置保温模壳的2个混凝土柱试件,以及相应的2个普通混凝土柱对照试件,采用拟静力加载方式对各试件的抗震性能进行试验。试验中考虑不同混凝土柱截面尺寸、单侧设置保温模壳及四周设置保温模壳对混凝土柱抗震性能的影响,分析各试件的滞回性能、骨架曲线、延性、刚度退化、耗能能力以及破坏特征等。结果表明:水泥聚苯保温模壳可以延缓混凝土开裂,混凝土柱角先于保温模壳发生破坏,且保温模壳与混凝土柱交界面无损伤,模壳与试件协同受力,形成整体;单侧设置保温模壳的试件,其承载力、延性、累积耗能分别提高了5.0%、6.0%、10.7%;周边布置保温模壳的试件,分别提高了17.0%、26.0%、23.3%。在混凝土柱中设置水泥聚苯保温模壳不仅可以起到保温、隔热的作用,还可以显著提高结构的抗震性能。

旧古建筑墙型钢组合单面支模施工技术的研究与应用

研究主要介绍古旧建筑墙新做现浇混凝土结构加固单面支模的相关施工技术,通过工程实例的应用提出了一种创新的型钢组合单面支模施工技术,成功解决了工程中的保留古旧砖墙新增现浇结构加固单面支模的施工技术难题,最大程度地保留墙体原始建筑风貌及特点,符合工程形象提升要求。