UHPC免拆模板钢筋混凝土柱抗震性能参数分析及承载力计算

为研究UHPC免拆模板钢筋混凝土柱在不同参数影响下的抗震性能,基于ABAQUS软件中混凝土塑性损伤(CDP)模型,考虑模板与后浇混凝土的界面接触滑移建立了数值分析模型;讨论了轴压比、普通混凝土强度、配筋率和模板厚度等参数对UHPC免拆模板-RC柱承载力和延性的影响;基于平截面假定,给出了UHPC免拆模板-RC柱的承载力计算公式。结果表明:建立的有限元模型能较好地模拟试件的承载力、骨架曲线和混凝土损伤情况;随着轴压比的增大,试件的承载力和延性均先增大后减小,轴压比为0.7时承载力和延性均最高;随着混凝土强度的提高,试件的承载力逐渐增大,但增长幅度却逐渐降低;提高配筋率可以提高试件的承载力,但对延性影响不大;模板的厚度对试件的承载力和延性影响显著,当模板厚度从10 mm增加到25 mm时,试件的承载力提高了24.1%,但其延性降低了43.8%,在保证试件拥有足够的承载力和变形能力下,建议UHPC模板厚度选择15~20 mm;基于平截面假定得到的承载力计算方法可以很好地预测试件的承载能力,计算值与模拟值(试验值)的比值均值为0.97,标准差为0.04。

超大截面加腋梁板、承台基础一次成型施工工艺研究

针对无地下室独立承台、梁板结构,设计梁板下及承台处有防水处理,承台顶标高与基础梁底标高存在高差并有斜向加腋的形式进行研究,从垫层施工、防水施工、钢筋绑扎、混凝土浇筑等各工序介绍了能够一次施工成型的施工方法,解决了常规依次施工工序穿插较多,易造成劳动力窝工、防水难以衔接,难以保证施工质量的问题。

高层建筑工程铝合金模板设计研究

铝合金模板具有施工较便利、施工效率较高、稳定性强、较强承载能力、铝模施工周期短等优势,得到了迅猛发展。基于此,本文主要针对高层建筑工程铝合金模板设计进行研究,结合实际工程案例,分析了铝模板设计方案及技术要点,希望能为相关人员提供参考。

桥梁高墩施工中液压提升爬模技术

为满足车辆快速平稳地运行,需要在河流、山谷上修建大跨度高墩桥梁,考虑其整体性强、跨越能力大,多使用液压提升爬模技术开展施工。基于此,以某大桥为例,简要阐述液压提升爬模技术特点,结合工程情况,开展液压提升爬模结构荷载分析、结构计算及改进设计,以此为基础,提出施工技术应用措施,以期为相关工作者提供参考。

屋面花架悬挑结构高空支模施工技术的应用

屋面花架在提高建筑结构空间层次方面发挥着重要作用,但是悬挑结构的高空支模施工面临着很大难度。首先对工程案例进行详细介绍,分析了悬挑结构高空支模的主要施工技术流程以及整体方案。重点从预埋件埋设,挑梁、连梁安装施工,防护脚手架搭设,支模架搭设,支模架拆除等方面详细介绍了关键施工技术。实践经验表明,所述的高空支模施工方案是有效的,为工程项目的顺利推进创造了良好条件。有效积累了悬挑结构高空支模的施工技术经验,可以为国内其他工程案例提供有效的经验借鉴。

铝合金模板施工技术在装配式建筑中的应用研究

文章选取南京某装配式住宅试点项目作为案例,重点分析铝合金模板与装配式建筑结合的设计与施工管理措施,特别是深化设计阶段的同步协调、节点部位的加强和优化等关键技术点。通过工程实践,解决集成化工艺中的问题,发现集成化施工技术的应用缩短施工周期约15%,同时提高了施工质量水平。

避难层悬挑支模模块化节点施工技术

为了解决超高层避难层的悬挑支模问题以及爬架爬升的工序交叉问题,采用了在避难层竖向结构施工时预埋螺栓或者预留穿越螺栓的孔洞,待爬架爬升到避难层上方五层左右之后,开始施工避难层的支模系统,其支模系统采用标准的钢牛腿支撑承担支模荷载的钢梁。研究和实际应用表明:通过在避难层竖向结构施工阶段预埋螺栓或预留穿越螺栓孔,后期进行避难层结构施工,能够有效保证主体结构的连续施工,避免技术间隙时间,同时无需重新搭设爬架。支模系统采用标准钢牛腿支撑承担支模荷载的钢梁,传力简单、可靠,且钢牛腿可循环使用,节约造价。进一步研究及应用结果表明,在墙体上采用预留孔洞时,其连接牛腿的螺栓同样可循环使用,进一步节约工程成本,且标准牛腿也可用于其余悬挑支模施工。该技术为施工现场的一线技术人员提供了可参考的解决方案。

铝合金组合模板在云埔爱特城项目中的应用与监理

随着科技的发展,建筑施工方式得到了进一步创新与优化。铝合金组合模板凭借其卓越的物理性能和环保特性,正逐步取代传统的木质和钢质模板,成为建筑工程中的重要构件。对此,以云埔爱特城项目为例,探究铝合金组合模板在其中的应用与监理,旨在为类似工程提供参考和借鉴。

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.

城市中小桥梁维修加固技术研究

桥梁工程普遍存在梁底混凝土剥落和钢筋腐蚀的问题。针对该问题提出吊模结构胶的修补技术,以强化梁体结构;对于承载力大幅下降的空心板结构,则采取梁板更换方案;对于钢筋混凝土结构的开裂问题,分析裂缝成因和评估承载力,探讨使用裂缝修补技术替代粘贴钢板加固法,缩短工期和节约成本。文章深入分析了低净空与复杂交通环境下的城市中小型桥梁加固维护策略,选取某地三座桥梁作为案例,重点研究城市中小桥梁维修加固技术,以期为桥梁工程运行水平提升奠定基础。

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.

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.

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.

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。

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。

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.

织物增强混凝土永久模板叠合试件抗氯离子渗透性能研究

织物增强混凝土(TRC)由高性能细骨料混凝土基体与纤维网组成,TRC永久模板与核心混凝土组成叠合试件。为揭示叠合试件氯离子渗透作用规律,确定永久模板最佳厚度范围,以TRC永久厚度、耐碱纤维网层数以及界面处理方式为变量,进行叠合试件抗氯离子渗透性能试验研究和计算分析。结果表明:与未设置永久模板相比,当TRC永久模板厚度为10~50 mm时,叠合试件氯离子扩散系数分别降低73.2%~95.6%。耐碱纤维编网对永久模板抗氯离子渗透性能没有增强作用。水泥净浆涂刷、表面凿毛、短切纤维插入三种界面处理方式对叠合试件氯离子渗透系数和渗透深度的影响不显著。结合Duracrete模型定量分析,给出了海洋环境不同工况下TRC永久模板厚度建议范围。