竹筋混凝土构件不宜用于承重结构

我国盛产竹子,近年由于钢材及塑料使用增多,使竹材滞销积压。一些报纸再度宜传有关使用竹筋混凝土的消息。五十年代,我们曾在某宿舍工程中使用竹筋混凝土预制楼板,至今已27年,尚有三千余平方米继续正常使用。但是从历年抽换残板的实物解剖和对正常使用的板的工作情况分析,甚感对竹筋混凝土前途及其施工工艺有探讨的必要,否则可能造成严重后果。一、竹筋混凝土预制板施工工艺该宿舍工程采用预制混凝土小梁(小梁     

竹筋陶粒混凝土的黏结性能

通过拉拔试验研究了竹筋陶粒混凝土的黏结性能,探讨了陶粒混凝土强度等级、竹筋类型、竹筋黏结长度、竹筋边长和竹筋刻痕间距对竹筋陶粒混凝土黏结强度的影响.结果表明:无刻痕竹筋陶粒混凝土的黏结破坏形式主要为拔出破坏,而带刻痕重组材竹筋陶粒混凝土的黏结破坏形式则是肋间混凝土被剪坏;同等条件下,重组材竹筋陶粒混凝土极限黏结强度高于层积材竹筋陶粒混凝土,但低于塑料筋陶粒混凝土;当竹筋刻痕间距为15 mm时,带刻痕重组材竹筋陶粒混凝土的极限黏结强度最高.另外,根据试验结果拟合出了重组材竹筋与陶粒混凝土的锚固长度计算公式,该公式可指导工程应用.     

复合墙板用竹基纤维复合材料筋与混凝土的锚固性能试验研究

竹基纤维复合材料筋(简称"竹筋")用作三明治式混凝土复合墙板的连接键,可实现节能和节材,而竹筋与混凝土的锚固性能则是影响其应用的关键。通过拉拔试验研究了筋材截面、黏结长度、混凝土强度与类别、养护龄期对竹筋与混凝土锚固性能的影响。试验结果表明:试件典型破坏形式有"竹筋"断裂和"竹筋"拔出两种;黏结长度和混凝土强度对锚固性能影响较明显;普通混凝土与"竹筋"的锚固性能在极限黏结强度和龄期稳定性方面优于陶粒混凝土。最后,拟合出"竹筋"黏结强度和锚固长度的计算式,其计算结果与试验数据吻合较好。     

竹筋混凝土梁构件力学性能研究

基于钢筋混凝土结构理论,对竹筋混凝土梁的力学性能进行研究,提出了竹筋混凝土梁的计算方法。对竹筋混凝土梁的配筋、受弯和受剪承载力进行了计算,验算了挠度,并与钢筋混凝土梁进行了对比,为竹筋混凝土构件应用于结构次要部位的可行性提供参考。     

改性竹筋混凝土受弯构件力学性能试验研究

针对竹筋混凝土结构存在的问题,提出了多种对竹筋的改性方法。在此基础上,对12根采用不同配筋和不同改性方法的受弯构件(11根竹筋混凝土梁和1根钢筋混凝土梁)进行了试验研究,分析了不同改性方法和不同配筋率竹筋混凝土受弯构件的力学性能、破坏形态及其影响因素。研究结果表明:竹筋能有效提高混凝土受弯构件的承载能力;经过适当方法改性后的竹筋能确保竹筋和混凝土之间的有效粘结,其正截面强度计算可以采用平截面假定;竹筋混凝土受弯构件的破坏均为脆性破坏,其破坏形态与其截面配筋率有关。     

环保型竹材应用前景广阔

从傣族的竹楼到福建、贵州的竹屋,中国古代已将竹子应用到建筑中。 6O年代我国对竹筋混凝土作了大量研究。由于竹子抗拉强度大,在钢材缺乏的年代,在大体积混凝土工程中,竹筋混凝土用于楼板、水坝、以竹代钢起到了积极作用。     

竹筋-陶粒混凝土复合板的热工性能研究

经对150 mm厚竹筋-陶粒混凝土复合板进行热工试验及计算分析,得出竹筋-陶粒混凝土复合板的传热系数K=0.625W/(m2·K),热惰性指标D=8.610;并采用ABAQUS有限元分析软件对竹筋-陶粒混凝土复合板的热工性能进行模拟,进一步研究竹筋-陶粒混凝土复合板的传热特点,分析结果显示,有限元分析结果与试验结果吻合较好.本模型作为竹筋-陶粒混凝土复合板热工计算的依据,其热流的传递主要通过斜向竹筋.     

预制竹筋多孔混凝土板的变形特性分析

采用加分配梁的四分点集中力加载方式研究加入不同配筋率的竹筋多孔混凝土的变形特性。试验表明竹筋能显著改善预制板的抗弯性能,随着竹筋配筋率的增加,预制板的跨中挠度会逐渐减少。通过荷载-挠度曲线,发现未开裂前的竹筋预制板呈线性弹性状态,且开裂后还能承受一定的荷载。竹筋对多孔混凝土有很好的增强增韧作用,预制竹筋多孔混凝土板可以更好、更稳定的在边坡防护中进行工程应用。     

钢筋、FRP筋、竹筋与混凝土粘结性能的研究

不同性质的材料,共同工作的前提是具有良好的粘结强度。粘结性能的优良直接影响了结构的耐久性及安全性。为促进混凝土结构的发展,分析了钢筋、锈蚀钢筋、FRP筋和竹筋与混凝土的粘结机理及影响粘结强度的因素。     

非顺筋裂缝对混凝土结构耐久性影响的调查分析

混凝土结构在建筑工程中广泛应用,而裂缝是混凝土的常见病和多发病,亦是导致混凝土结构耐久性降低的主要因素之一。本文通过对混凝土非顺筋裂缝的产生过程及类别特征进行了分析,并对浙江宁波地区部分建筑物进行了实地调研,对建筑物中存在的主要非顺筋裂缝进行了分析讨论,论述了混凝土非顺筋裂缝对结构耐久性的影响。     

粘钢技术在混凝土结构加固中的应用

通过对框架结构标准厂房进行加固分析,探讨了框架混凝土结构加固改造过程中所涉及的粘钢技术,研究了粘钢加固的设计与构造,总结了进行混凝土结构粘钢施工技术要求与检测方法.     

竹芯竹筋混凝土板抗弯性能试验研究

随着全球资源日益紧缺,环境日益恶劣,人们对建筑材料、环境保护提出了更高的要求。而毛竹属于可再生资源、经济且环保,将毛竹代替钢筋运用于混凝土楼板,不仅减去了钢筋繁琐的加工工序,而且提高了板的空心率,从而达到减轻自重的目的。为研究竹芯竹筋混凝土板中的受力性能,对3块配筋率不同的竹筋板进行均布荷载下的抗弯试验性能及相关材料力学性能试验。通过试验现象及数据对比分析,可知:毛竹抗拉破坏无屈服点,属于脆性材料;板破坏时,其跨中挠度可以达到以上,延性很好;竹筋板受弯过程,呈两阶段特征,即开裂前弹性阶段和开裂后带裂l0/25缝工作直至破坏;并结合试验挠度、应变、裂缝、承载力计算结果,提出了竹芯竹筋混凝土板设计的相关构造措施及建议。     

新旧规范混凝土框架结构计算分析与配筋对比

《建筑抗震设计规范》(GB 50011-2010)、《混凝土结构设计规范》(GB 50010-2010)、《高层建筑混凝土结构技术规程》(JGJ 3-2010)已相继颁布,新规范结合最新的科研成果及震害经验对旧规范中的条文进行修订,规范条文变化对结构整体计算指标及配筋产生多大影响是广大设计人员最为关心的问题。本文采用新旧规范SATWE软件对某框架结构工程算例进行了计算与比较,给出按新旧规范计算的结构整体指标和构件配筋的差异,从梁刚度增大系数取值方法、扭转位移比计算方法及楼梯的考虑对结构总体指标变化的主要原因进行了分析说明,从高强钢筋的应用、抗震等级、柱内力调整、梁斜截面抗剪承载力计算公式变化、正常使用极限状态验算等方面对配筋变化的主要原因进行了分析,供设计人员参考。     

谈现代建筑物的加固技术

从混凝土结构、砌体结构加固及钢结构加固三方面 ,介绍了现代建筑物的具体加固方法 ,以充分利用原有建筑进行加固、改造 ,满足现在的使用要求     

某混凝土柱-钢屋架单层工业厂房的鉴定与加固

介绍了某混凝土柱-钢屋架单层工业厂房的检测鉴定与加固,该厂房建于80年代末期,设计图纸已遗失.根据此类建筑的特点,对钢屋架进行了几何形式、截面尺寸、整体构造、挠度、材质、焊接质量、锈蚀等多方面的检测,发现了混凝土柱、钢屋架、填充墙各自存在的问题,并有针对性地进行了加固设计.我国目前仍有大量的同类厂房,当发现问题或需要进行改造时,本文可作为此类工程的参考.     

Rehabilitation of RC frame joints using local steel bracing

Reinforced concrete (RC) structural frames that were built prior to the 1970s generally do not meet current design code requirements and may behave in a non-ductile manner. The lateral load carrying capacity of these structures is often insufficient due to non-ductile reinforcement detailing, which includes insufficient or no beam-column joint transverse reinforcement and inadequate anchorage for the beam's bottom reinforcement. Experience shows that such frames are prone to earthquake damage and often suffer shear and bond slip non-ductile modes of failure. Recent earthquakes have demonstrated that the beam-column joint safety is an important factor in keeping the integrity of the entire structure. Concentric steel bracing systems have been used for the rehabilitation of non-ductile RC buildings in a number of countries. However, the application of eccentric (local) steel bracing in the rehabilitation of RC structures still lags behind due to the limited research and information on the design, modelling and behaviour of such a combined concrete-steel system. In this paper a new beam-column joint rehabilitation technique using local steel brace members is proposed. Two full-scale specimens representing a standard joint and a rehabilitated joint were made and tested under reversed cyclic load. Their behaviour was compared to that of a non-rehabilitated specimen. It is shown that the rehabilitation technique was successful in enhancing the overall performance of the deficient joint and upgrading it towards a close to current standard performance.     

Influence of chloride corrosion on the effective mechanical properties of steel reinforcement

This paper presents a methodology to develop advanced reduction factors for the effective mechanical properties of corroded steel reinforcement of reinforced concrete (RC) members. The reduction factors (mainly developed for bare steel reinforcement) reported in the literature scatter over a large range. In this regard, critical questions arise, such as the reliability and accuracy of the reduction factors of bare steel bars to evaluate residual capacity of corroded RC structure. This paper will provide answers to these questions based on reviewing past studies and the results observed from experimental inspection of corroded steel reinforcement carried out in this research. The results show using the reduction factors of bare steel bars to estimate residual capacity of corroded RC structures is not safe because they are significantly lower than the reduction that happens in real corroded RC columns.     

房屋建筑物加固技术概述

从直接加固和间接加固的角度分析了砌体结构和混凝土结构的加固技术，并列举了一些构造性加固措施和配套使用技术，阐述了钢结构的主要加固方法，从而对房屋建筑物加固技术进行了较系统的总结。     

Structural performance and economics of tall high strength RC buildings in seismic regions

For a multitude of economic and societal considerations, high rise structures are on the increase. This in turn promotes the use of high strength materials to reduce column size and construction times. Whereas design guidance and engineering understanding of high strength RC structures under static loading is well‐developed, little work has been undertaken on the economics of whole buildings and their performance under earthquake loading. In this paper, 10 buildings of 24 stories are designed and detailed according to modern seismic codes. The buildings are all nominally equivalent, using a stiffness equivalence criterion and its derivatives. The cost of construction is compared in terms of steel, concrete and formwork. The static inelastic response of the buildings is also assessed, followed by a full nonlinear dynamic analysis of all buildings using three earthquake records at the design acceleration and twice the design value. Comprehensive assessment of the static and dynamic results is undertaken. It is concluded that the cost increase is mainly due to the steel, whilst significant member reductions may be availed of by using high strength concrete. The behaviour of high strength concrete structures is not inferior to that of normal strength materials. Indeed, it is observed that lower levels of overstrength can be achieved in high strength materials than in their normal strength counterparts, mainly due to the over‐reinforcement of the latter to resist vertical forces. Recommendations on the use of equivalent cracked stiffness for period calculation in design, and also effective periods for use in displacement‐based design, are given. Copyright © 1999 John Wiley & Sons, Ltd.