Bar fracture modeling in progressive collapse analysis of reinforced concrete structures

Reliable evaluation of progressive collapse resistance of structures requires substantiated methods and techniques for analyzing the response of critical elements subjected to large deformations. Steel bar fracture is a significant event that can lead to progressive collapse of reinforced concrete (RC) structures. Given the sudden discontinuity associated with bar fracture, modeling of such an event in a continuum domain analysis is challenging. In this paper a method is proposed for finite element modeling and analysis of RC elements that accounts for bar fracture. It is demonstrated that such a modeling technique is capable of developing catenary action. Analytical results based on the proposed method show good agreement with experimental data. The underlying cause for a drop in beam vertical resisting force following the peak force is identified and explained.     

钢筋混凝土框架抗倒塌与抗震设计的对比分析

以一栋六层框架结构为例,对其抗倒塌设计与抗震设计的结果进行了分析,研究结果表明,抗倒塌设计不同于抗震设计,并提出抗倒塌设计的一些措施,为将来工程抗倒塌设计和相关方面的设计提供了参考依据。     

Toward an economic design of reinforced concrete structures against progressive collapse

A three-dimensional discrete crack model based on the Applied Element Method is used to perform economic design for reinforced concrete structures against progressive collapse. The model adopts fully nonlinear path-dependent constitutive models for concrete and reinforcing bars. The model applies a dynamic solver in which post-failure behavior, element separation, falling and collision are predicted. First, the model is used to study the behavior of multi-story reinforced concrete buildings designed in a traditional manner according to the ACI 318-08 and subjected to accidental removal of one or two central columns at the ground level. In an iterative way, the model is then used to investigate a safe design against progressive collapse for such extreme loading case. Based on the analytical results of the AEM, it can be concluded that the collapse of only one column would not lead to any progressive collapse of the studied reinforced concrete structure. However, the collapse of more than one column may lead to a progressive collapse of a considerable part of it. It is concluded also that the AEM could be successfully used as an analytical tool to suggest economical designs that are safe against progressive collapse of reinforced concrete structures.     

钢筋混凝土多层框架结构抗连续倒塌分析

在国内外关于结构抗连续性倒塌的研究现状及主要成果基础上,总结了结构抗连续性倒塌设计方法,运用PKPM软件作为计算手段,采用拆除构件法对钢筋混凝土框架结构进行抗连续性倒塌能力研究.     

钢筋混凝土楼面施工工艺总结

钢筋砼楼面施工各环节采取合理有效的施工措施,才能最大限度地避免工程质量缺陷。     

The influence of infilled panels in retrofitting interventions of existing reinforced concrete buildings: a case study

During the seismic events occurred in the last decades, the existing reinforced concrete (RC) building stock has often exhibited a significant brittle collapse of joints and secondary elements such as infill walls. A quite common strategy, in the attempt of mitigating this vulnerability, is the generalised implementation of strengthening interventions on the structural elements, even in the absence of a complete seismic assessment procedure. This paper presents some considerations about the effects induced by strengthening interventions involving the tying of the infill panels to the RC frame. Within this context, an appraisal of the actual displacement capacity and the possible alteration induced on the global collapse mechanism is provided. The analyses and discussion of results are presented with reference to an actual case study concerning a school building, which was part of a wide vulnerability assessment investigation performed in the Province of Foggia, Italy. In particular, seismic analyses performed using nonlinear static analysis procedures on the strengthened configuration and on the original structure are critically compared and discussed.     

An improved tie force method for progressive collapse resistance design of reinforced concrete frame structures

Progressive collapse of structures refers to local damage due to occasional and abnormal loads, which in turn leads to the development of a chain reaction mechanism and progressive and catastrophic failure. The tie force (TF) method is one of the major design techniques for resisting progressive collapse, whereby a statically indeterminate structure is designed through a locally simplified determinate structure by assumed failure mode. The method is also adopted by the BS8110-1:1997, Eurocode 1, and DoD 2005. Due to the overly simplified analytical model used in the current practical codes, it is necessary to further investigate the reliability of the code predictions. In this research, a numerical study on two reinforced concrete (RC) frame structures demonstrates that the current TF method is inadequate in increasing the progressive collapse resistance. In view of this, the fundamental principles inherent in the current TF method are examined in some detail. It is found that the current method fails to consider such important factors as load redistribution in three dimensions, dynamic effect, and internal force correction. As such, an improved TF method is proposed in this study. The applicability and reliability of the proposed method is verified through numerical design examples.     

大面积钢筋混凝土地面施工

由于大面积钢筋混凝土地面具有结构牢固、平整光洁和便于清洁的优点，在一般公众场所，从20世纪90年代起就取代了水泥砂浆地面、水磨石地面以及地板砖地面。从原材料的选用，混凝土配合比及水灰比的确定，坍落度和温度的控制、搅拌、运输、浇筑，直到平整度控制、压实磨光、养护、表面硬化剂处理各道工序均作了详细的阐述。     

Progressive collapse of multi-storey buildings due to failed floor impact

This paper proposes a new design-oriented methodology for progressive collapse assessment of floor systems within multi-storey buildings subject to impact from an above failed floor. The conceptual basis of the proposed framework is that the ability of the lower floor for arresting the falling floor depends on the amount of kinetic energy transmitted from the upper floor during impact. Three principal independent stages are employed in the proposed framework, including: (a) determination of the nonlinear static response of the impacted floor system, (b) dynamic assessment using a simplified energy balance approach, and (c) ductility assessment at the maximum level of dynamic deformation attained upon impact. In order to calibrate the proposed method, the part of the kinetic energy of the impacting floor that is transferred to the impacted floor is first theoretically determined for the two extreme impact possibilities, namely fully rigid and fully plastic impact. Moreover, a series of numerical studies is carried out to further refine the accuracy of this new approach with respect to different impact scenarios, whilst the effects of detailed joint modelling and redundancy are also investigated. The application of the proposed methodology is demonstrated by means of a case study, which considers the impact response of a floor plate within a typical multi-storey steel-framed composite building. Several possibilities regarding the location of the impacted floor plate, the nature of the impact event and the intensity of the gravity loads carried by the falling floor are examined. The application study illustrates the extremely onerous conditions imposed on the impacted floor resulting in an increased vulnerability to progressive collapse for structures of this type. Importantly, the likelihood of shear failure modes in addition to inadequate ductility supply under combined bending/axial actions is identified, thus establishing the need for further research work on the dynamic shear capacity of various connection types subject to extreme events.     

谈型钢混凝土在大跨度建筑中的应用

通过在苏州市体育中心健身馆工程结构设计中采用了型钢混凝土组合结构处理大跨度结构,提供了对该类结构的计算思路,并采取了相应的构造措施,取得了较好效果,有助于促进型钢混凝土在大跨度建筑中的推广应用。     

日本既有钢筋混凝土建筑抗震鉴定方法

日本是个地震频发国家,其抗震设计概念发展迅速。每当建筑规范修订后要执行更严格的标准时,按照旧规范设计的既有建筑,需要通过三级抗震鉴定方法,用以发现哪部分建筑物最有可能遭受破坏。在这种筛选方法中,低等级鉴定方法简单,但结果过于保守;而高等级鉴定方法则需通过更复杂的计算分析,才能得到较为可靠的结果。介绍了三级抗震鉴定方法的具体计算过程。并以一学校建筑为工程实例,进行了第一级和第二级的抗震鉴定分析,最终算得结构基本抗震性能指数E0,然后得到结构抗震性能指标Is,与结构抗震安全指标Is0作比较,从而确定结构是否抗震安全。还简单介绍了日本常见抗震加固方法,供国内抗震加固借鉴。     

浅谈现浇钢筋混凝土楼板的裂缝控制

针对现浇钢筋混凝土楼板极易出现裂缝的问题,结合GB50011-2001建筑抗震设计规范对产生裂缝的各种因素进行了分析,提出了在设计、施工、材料等方面进行裂缝控制的建议和方法,以指导实践。     

钢筋混凝土楼盖设计教学中的若干问题

钢筋混凝土楼盖设计是混凝土结构设计课程中的一个重要教学内容,从教学的角度出发,查阅了大量的资料和教材,阐述了相关概念及知识点,旨在提高课堂教学质量,为学生学习和掌握结构设计方法打下了坚实的理论基础。     

钢筋混凝土双向密肋夹芯保温叠合板研究

钢筋混凝土双向密肋夹芯保温叠合板由预制预应力混凝土底板、保温隔热夹芯和现浇混凝土面层组成.分析了预应力混凝土底板在施工阶段和使用阶段的受力状态,提出了钢筋混凝土双向密肋夹芯保温叠合板的设计计算方法,并对其施工工艺及质量检验提出了要求.     

钢筋混凝土框架结构抗震与抗连续倒塌的比较

从钢筋混凝土结构受力机制和倒塌破坏准则两方面,对抗震与抗连续倒塌的区别进行了分析与比较,结果表明：抗倒塌不同于抗震,结构抗震设计的有益作用并不能取代抗倒塌设计。     

Deterministic seismic design procedures for reinforced concrete buildings

A brief review is given of a deterministic design philosophy with respect to earthquake resisting ductile structures for reinforced concrete buildings. This was developed recently mainly in New Zealand. In this approach a preferred hierarchy in the development of energy dissipating mechanisms is postulated. Some applications of ‘capacity design procedures’ relevant to beams, columns and shear walls, are outlined. The paramount importance of quantifiable good detailing is emphasized and the relevance of this with respect to shear effects in plastic hinges, the confinement of compressed concrete, and bond between reinforcement and concrete are examined. These aspects of the specific seismic environment are also utilized to show fundamental differences in structural behaviour when effects of gravity loads or seismic displacements are compared.     

现浇钢筋混凝土空心板在实际工程中的应用

介绍了现浇钢筋混凝土空心板的设计方法，阐述了在工程施工中应采取的一些措施及注意事项，指出了现浇钢筋混凝土空心板的新发展方向，具有广阔的推广应用前景。     

钢筋混凝土楼盖体系的发展综述

对钢筋混凝土楼盖的分类及相应的结构构造、分析方法进行了较全面的综合阐述,并对近些年新出现的楼盖体系进行了介绍,对各种新型楼盖的应用研究状况进行了简要的叙述。     

现浇钢筋混凝土空心楼板施工技术

结合工程实例,阐述了现浇无梁空心楼板工程施工的工艺原理、施工技术要点以及质量保证措施,实践证明,与有梁预制空心楼板相比,其综合效益明显,以期推广现浇钢筋混凝土空心楼板的应用。