Seismic damage and performance of Palazzo Centi after L’Aquila earthquake: A paradigmatic case study of effectiveness of mechanical steel ties

This paper concerns the seismic response of Palazzo Centi after the 2009 L’Aquila earthquake. Built in the second half of XVIII century, Palazzo Centi is a three-storied building characterized by a rectangular plan with a central court. The vertical structural system is made of masonry walls arranged in plan to form a regular mesh.After the 2009 L’Aquila earthquake the building showed a widespread damage occurred in the vertical masonry structures with more intensity at upper storeys; there were also damages to non-structural parts: light masonry and fake vaults. The building case study is a paradigmatic example because during the 2009 earthquake, differently from other historical masonry buildings, it responded “reasonably” well in the main structural parts. The seismic behaviour was analyzed thoroughly in order to investigate the effectiveness of the, initially unknown, recent retrofit interventions carried out in 2003. These mechanical interventions proved to be the reason of the good seismic behaviour of the building and that “saved” it from more serious damages.On the basis of the data acquired by the authors during the post-earthquake reconnaissance activities and from the structural analyzes results, in conclusion, the case study of Palazzo Centi demonstrated to represent a clear example of the effectiveness of the traditional techniques in designing and retrofitting of masonry buildings.     

浅述国内外拆除爆破现状

综述了国内外拆除爆破发展和研究现状,并提出今后发展趋势和免于解决的问题。     

Discontinuous modelling of masonry bridges

 Computational modelling frameworks for masonry bridges range from highly simplified methods to complex nonlinear finite element or discrete elements. In majority of cases the macro level nonlinear finite element models¹ and homogenisation techniques are adopted. Attention has also been given to assessment methodologies (discrete element method, rigid block spring method, lattice modelling, discontinuous deformation analysis, combined discrete/finite elements), which deal more directly with the discontinuous nature of structural masonry in a simplified micro modeling manner. These methods model an inherently discontinuous medium, but are also applied to problems where the transition from a continuum to discontinuum is important. Principal computational issue is the treatment of large number of distinct interacting domains, where the contact conditions are continuously updated and enforced as the solution progresses. Modelling of masonry arches requires a consideration of deformable multi-bodies and their contact nonlinearity, which is here realised in the context of the discontinuous deformation analysis, based on an assumed deformation field within distinct domains of arbitrary shapes with a rigorous imposition of contact constraints. Dedicated to the memory of Prof. Mike Crisfield, for his cheerfulness and cooperation as a colleague and friend over many years.     

动力荷载下传统风格建筑双梁-柱节点抗震性能试验研究

为研究传统风格建筑混凝土双梁-柱节点的破坏特征及抗震性能,进行了2个节点试件的动力循环加载试验,包括一个典型传统风格建筑混凝土双梁-柱节点和一个单梁-柱节点.观察了节点试件的受力过程及破坏特征,研究了试件的荷载-位移滞回曲线、骨架曲线、承载能力、刚度及承载力退化、延性和耗能能力,并对其破坏模式进行了分析.研究结果表明:...     

建筑物细部定向爆破拆除技术浅析

在建筑物拆除爆破工程中,常常采用爆破切口的前后高差、不同区域延期起爆等技术措施确保建筑物整体定向倒塌,但是当后排立柱离保护物很近或是单排(棵)立柱定向爆破时对定向的精度要求更高,这时还必须在重点部位立柱内再次采用细部定向爆破拆除技术,即只进行局部爆破以形成定向铰支,并预开隔离缝,严格控制立柱在爆破后产生后坐危害,通过工程实践,爆破效果很好,其施工技术和参数选取可供同类工程借鉴.     

梁的蠕变脆断弯曲损伤Norton分析和预测

提出了纯弯曲梁的蠕变脆断损伤失效分析方法。与Kachanov的材料受载横截面减少 定义拉伸损伤变量类似,以梁的弯曲惯性矩减少定义弯曲损伤变量。为了讨论问题的广泛性, 应力和应交关系采用Norton非线性关系。推导了梁的弯曲蠕变脆断损伤基本方程,其中的材 料常数可由Kachanov拉伸损伤模型的材料常数确定。并且提出了便于工程应用的蠕变失效预 测方程。     

纯弯曲梁的应力损伤失效分析和预测

本文提出了梁的弯曲应力损伤失效分析方法,推导了梁弯曲应力损伤基本方程,与Ｋａｃｈａｎｏｖ的材料受载横截面减少定义拉伸损伤变量类似,以梁的弯曲惯性矩减少定义弯曲损伤变量。并且弯曲损伤模型的材料常数可由Ｋａｃｈａｎｏｖ拉伸损伤模型的材料常数确定。并且对应力损伤材料提出了便于工程应用的失效预测方程。     

考虑微观界面的2D编织SiC/SiC复合材料宏-细-微多尺度渐进损伤失效分析

该文将微观界面组分纳入宏-细-微三个尺度的多尺度渐进损伤失效分析中.对细、微观单胞模型施加周期性边界条件获取放大因子并采用k-means聚类方法进行缩聚;通过缩聚的放大因子求解宏观模型对应的细、微观组分应力并进行损伤失效判定;计算宏观模型退化后的弹性参数用于后续计算;针对2D编织SiC/SiC复合材料开展了渐近损伤失效...     

近邻软磁层偏置磁阻磁头结构参数设计的数学模型

概述了软磁层偏置磁阻磁头的工作原理和特点 ,采用传输线模型对其工作点的选取和结构参数进行了初步设计 ,与实验结果符合较好     

型钢高强高性能混凝土框架柱地震损伤分析

为了研究地震作用下型钢高强高性能混凝土构件的损伤,总结和分析了已有地震损伤模型存在的不足,基于低周反复荷载作用下型钢高强高性能混凝土框架柱的损伤试验研究结果,对框架柱的地震损伤特性进行了分析。通过合理地考虑循环次数对构件极限抵御能力（极限耗能和变形能力）的影响以及加载路径对损伤的影响,建立了能够全面反映水平地震作用下构件力学特性变化的基于变形和能量组合的非线性双参数损伤模型。对损伤模型中相应的参数进行了讨论和分析,并给出了其具体定义和表达式。结合试验结果,对损伤模型的有效性进行了验证。研究结果表明,该模型能够较好地描述型钢高强高性能混凝土框架柱的地震损伤演化过程与程度,且理论上更为合理。研究结果为该类结构构件的地震损伤评估以及基于损伤的抗震设计方法的建立提供了理论依据。     

A non-linear masonry infill macro-model to represent the global behaviour of buildings under cyclic loading

The presence of masonry infill walls in RC buildings is very common. However, and even today, in the design of new buildings and in the assessment of existing ones, these infill walls are usually considered as non-structural elements and their influence in the structural response is generally ignored. For horizontal loading, infill panels can drastically modify the response, attracting forces to parts of the structure that have not been designed to resist them. This paper presents an improved non-linear numerical simulation model for the influence of the masonry infill walls in the seismic behavior of structure. The model is implemented in the PORANL program. After the implementation and calibration of the proposed masonry model, a series of non-linear dynamic analyses of a building representative of Modern Architecture in Europe were carried out. The main objective was to investigate the behavior of this type of building, and any weakness under seismic loading. The building geometry and the dimensions of the RC elements and infill walls were set in the original project, and confirmed in the technical visits. The building under study has nine storeys and the structure is mainly composed of 12 plane frames oriented in the transversal direction. The building was analyzed with a simplified plane model, for each direction, and the existing infill panels were looked at in accordance with their dimensions and location. The earthquake action adopted in this study was simulated through three series of artificially generated earthquakes, for a medium/high seismic risk scenario in Europe.     

砌体加层隔震体系下部结构刚度退化后的抗震性能试验研究

研究砌体加层隔震结构体系下部结构出现损伤后的抗震性能,重点关注隔震层上部、下部结构频率比变化对下部结构响应的影响。采用随机振动理论推导加层隔震体系与加层非隔震体系下部结构加速度响应均方值比,给出了下部结构加速度响应均方值比随频率比的变化规律,分析表明对于加层隔震结构,出现损伤前隔震效果明显,但随着下部结构刚度的不断退化,加层隔震体系下部结构的地震响应会超过加层非隔震结构体系。对加层隔震和加层非隔震结构进行了振动台试验研究,对比试验模型损伤前后各楼层加速度反应,分析其损伤前后减震效果的变化,试验结果表明,初始加层隔震模型地震响应明显小于加层非隔震模型,但随着加层隔震结构下部砌体的不断损伤,加层隔震体系的减震效果逐渐降低,下部结构甚至出现了加速度反应被放大的不利现象,试验现象和数据与理论分析结果吻合良好。在加层隔震结构的分析和设计中必须考虑下部结构出现损伤后对结构的不利影响。     

古建筑的爆破安全允许振动限值研究

古建筑由于建筑结构和材料与现代建筑不同,而且历时漫长可能遭受到自然和人为的破坏,因此在保护此类建筑不受爆破振动破坏时,其安全允许振动限值应经论证选取。本文结合一起为保护国家级文物(六胜塔)进行的爆破振动监测,通过脉动测试和试爆测试,分析古塔结构反应,确定古塔的安全允许振速,更科学地控制爆破施工对古建筑的振动影响。     

Simultaneous doping of aluminum and fluorine on zinc oxide nanopowder using a low-cost soft chemical route

Simultaneous doping of aluminum (Al) and fluorine (F) on ZnO nanopowder was successfully achieved by a soft chemical method. The strong X-ray diffraction peaks revealed the high crystallinity of the synthesized nanopowder and the XRD profiles showed that the material has hexagonal wurtzite structure. EDAX results confirmed the presence of Al and F and from the quantitative analysis it was observed that there was a systematic increase in both dopants in the final product as they were included in the starting solution. The SEM images showed that the ZnO:Al:F powders have nanorod structure with hexagonal cross section. The simultaneous doping enhanced the carrier concentration of the ZnO nanopowders indicated by the higher IR reflectivity.     

斜向撞击方柱下的车辆简化数值模型研究

精确模拟车辆撞击建筑物的受力和变形需建立精细的数值模型并消耗大量的计算时间。但建筑结构防撞设计只针对被撞结构,合理地简化车辆模型能够在保证计算精度的同时提高计算效率。该文首先基于能量守恒原理建立了45°斜向撞击方柱的车辆简化数值模型,并在此基础上分析了撞击方向对柱变形和损伤的影响。分析表明：简化车辆模型能够准确模拟车辆斜向撞击方柱时的撞击力、撞击冲量、柱变形和材料应变响应,同时有效地提高了计算效率;相比正面（90°）撞击,斜向（45°）撞击时车辆变形耗能较小,造成柱损伤和变形更大。     

A failure analysis methodology for revealing esd damage to integrated circuits

A range of chemical and physical techniques is required in order to identify the failure sites and failure machanisms of ICs subjected to ESD transients. The damage features of ESD failures from the field are shown to be similar to those produced by simulated human-body-model testing. A curve tracer technique can be used to predict the location of an ESD failure site in the input or output circuit of an IC. Junction shorts induced by ESD transients form as a result of a combination of heating at the site of second breakdown, together with the heat generated by the discharge current in the discharge path. The ESD sensitivity of a given input or output circuit is dependent on the spacing between the input contact window. and the contact window of the nearest diffusion-to-Vss metallization.     

Automatic modeling method for regional seismic damage assessment of school buildings in Taiwan

This study proposes a new method for regional seismic damage assessment. Automatic modeling is applied to construct models of school buildings from a property database and component models. The capacity curves of school buildings are obtained through numerical simulation of nonlinear structure analysis instead of deriving the capacity curves by substituting parameters derived from a commonly adopted statistical regression approach into a formula. With professionally pre-set settings, detailed regional seismic damage assessment can be performed using a large number of numerical models generated in a short time. The accuracy and reliability of the proposed method is validated by comparing the base shear – roof displacement curve with data from experimental results and ETABS analysis conducted by the National Center for Research on Earthquake Engineering, as well as data obtained using existing damage assessment methods. Reconnaissance report data on school buildings affected in the Chi-Chi Earthquake is also used for further verification. The proposed regional seismic damage assessment method makes structural analysis on individual structures possible to provide a more accurate and detailed damage assessment.     

复合材料层板开孔拉伸损伤分析

针对纤维增强复合材料层板开孔拉伸,将复合材料层板的失效分为层内失效和层间失效,建立了复合材料层板开孔拉伸损伤分析模型。该模型基于逐渐损伤分析,对不同复合材料开孔层板进行了失效预测,并与文献试验结果进行了对比,破坏强度和失效模式均与文献试验结果非常吻合。结果表明本文中所建立的层板开孔拉伸损伤分析模型能够模拟含孔层合板拉伸过程中的损伤起始、损伤扩展和最终破坏模式,并最终预测含孔层合板拉伸失效模式和破坏强度。