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1.
The seismic behavior of unreinforced masonry buildings is typically characterized by premature brittle collapse mechanisms that can cause serious consequences for the protection of human lives and for the preservation of historical and cultural heritage. Structural health monitoring can be a powerful tool enabling a quick post-earthquake assessment of the structure's performance, but its applications are still scarce as a consequence of the severe limitations affecting off-the-shelf sensing technologies, in terms of local nature of the measurements, costs, as well as long-term behavior, installation, and maintenance. To overcome some of these limitations, the authors have recently proposed a new sensing technology, called “smart brick,” that is a durable clay brick doped with stainless steel microfibers, working as a smart strain sensor for masonry buildings. This paper presents the first full-scale application of smart bricks, used for detecting and localizing progressive earthquake-induced damage in an unreinforced masonry building subjected to shaking table tests. Smart bricks are employed to detect changes in load paths on masonry walls, comparing strain measurements acquired after each step of the seismic sequence with those referring to the undamaged structure. Experimental results are interpreted using a 3D finite element model built to reproduce the shaking table tests. Overall, the results demonstrate that the smart bricks can effectively reveal local permanent changes in structural conditions following a progressive damage, therefore being apt for earthquake-induced damage detection and localization.  相似文献   

2.
This paper presents the results of an experimental investigation carried out to investigate the seismic performance of a two storey brick masonry house with one room in each floor. A half‐scale building constructed using single wythe clay brick masonry laid in cement sand mortar and a conventional timber floor and timber roof clad with clay tiles was tested under earthquake ground motions on a shaking table, first in the longitudinal direction and then in the transverse direction. In each direction, the building was subjected to different ground motions with gradually increasing intensity. Dynamic properties of the system were assessed through white‐noise tests after each ground motion. The building suffered increasing levels of damage as the excitations became more severe. The damage ranged from cracking to global/local rocking of different piers and partial out‐of‐plane failure of the walls. Nevertheless, the building did not collapse under base excitations with peak ground acceleration up to 0.8g. General behaviour of the tested building model during the tests is discussed, and fragility curves are developed for unreinforced masonry buildings based on the experimental results. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

3.
The seismic stability of the facade brick-masonry walls of the machinery building of the Beauharnois powerhouse near Montreal, Quebec, Canada were investigated numerically by use of non-linear models and applying experimental methods on site and on the IZIIS’ seismic shake-table. The dynamic properties of the machinery building were obtained by ambient vibration measurements. Based on these results, a model of a representative part of the building, consisting of steel frames and brick masonry wall, was designed and constructed to the reduced scale at the IZIIS’ Dynamic Testing Laboratory and then tested on the two-component shake-table. The geometry of the original structure was completely scaled to 1/3, consisting of many realistically simulated details such us: brick layers, steel columns, openings, window frames, steel connectors between brick layers, number of layers, brick dimensions, etc. The material used for the model was: original steel for the frame structure and bricks of reduced mechanical properties for the masonry wall, close to the similitude requirements according to the Backingham’s theorem, valuable for adequate artificial—mass simulation model as well as true replica simulation model. More than 50 seismic tests were performed considering the design earthquake Nahanni NWT, H1, with a time scaling factor of 31/2, and acceleration scaling factor 1, according to the model design rules. The intensity of the applied input earthquake excitation was from 0.05 to 1.2 g. The design peak acceleration of Nahanni earthquake was 0.2 g. The cracks development was stated at 0.7 g input acceleration. These were concentrated around the openings. No collapse happened even under the strongest earthquake input. The numerical part of this paper deals with formulation/application of the critical plane approach to seismic analysis of masonry structures. Starting with the constituents, i.e. mortar and bricks, the macroscopic strength properties of masonry were established based on numerical homogenization. Generally, based on all the performed experimental tests, considering some simplifications and assumptions in the constructing details, as well as in the design of the model, the global conclusion is that the existing wall is very well incorporated in the steel structure of the powerhouse. The complementary stiffness of the steel frame and the brick masonry wall produces interactive deformation of the system. Only local cracking and relative displacement between the wall and the steel frames could be expected in the case of a strong earthquake.  相似文献   

4.
村镇隔震砌体结构振动台试验方案设计研究   总被引：1，自引：1，他引：0  
为使铅芯橡胶支座隔震技术应用于村镇砌体结构,将隔震层设置于地坪以上,本文给出了隔震构造的具体做法。选取典型村镇2层未设构造柱的砖砌体结构房屋为试验原型,按1:2缩尺,设计有隔震层和无隔震层的振动台对比试验。首先采用反应谱分析方法,对隔震和非隔震结构分别选取三条地震波,然后通过数值分析,研究隔震和非隔震结构在输入不同地震波时的地震反应规律,根据数值模拟的分析结果设计结构振动台试验中的传感器布置和加载方案。本文设计的砌体隔震振动台试验方案已试验成功,可为振动台试验设计和研究提供参考。  相似文献   

5.
提出了带竖向构造钢筋再生混凝土砖砌体结构,进行了2个两层再生混凝土砖砌体房屋结构1/2缩尺模型的模拟地震振动台试验研究,2个结构模型的墙体厚度均为120 mm,一层设有门洞和窗洞,二层设有窗洞。2个模型中,1个为带竖向构造钢筋再生混凝土砖砌体房屋,1个为普通无竖向构造钢筋再生混凝土砖砌体房屋。试验中输入El Centro地震动,测试分析了台面加速度反应、一层和二层顶板加速度反应、结构层间位移反应以及各阶段结构损伤与破坏特征等。研究表明:带竖向构造钢筋再生混凝土砖砌体房屋比普通再生混凝土砖砌体房屋的破坏程度轻,墙体裂缝位置相对错动小,抗震性能显著提高;带竖向构造钢筋再生混凝土砖砌体房屋可用于地震区村镇建筑。  相似文献   

6.
The paper is devoted to the investigation of seismic response of the masonry structure and describes experiences with modelling of boundary conditions during the test of large heavy model on 6DOF shaking table. The main aim of the research was how to increase dynamic resistance capacity of old masonry buildings including the medium and strong seismic effects. The results of theoretical and numerical analyses are compared including initial forecasting calculations made before any test started. The emphasis is given to the boundary conditions reached during the excitation of the large masonry model via shaking table. Strengthening and retrofitting procedures and their effects are discussed when special fibre mortar is used for repair and strengthening of masonry parts of structure.  相似文献   

7.
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8.
This paper discusses on the shaking table test results of two 1:4 scale model of two-story masonry structure typically used in constructing low-rise residential buildings. This test is performed to provide a better understanding of the seismic behavior of the PP-band (polypropylene band) mesh retrofitted adobe masonry house. The test structure is subjected to a series of different levels of harmonic motion that applied along the longitudinal direction. The results of the shaking table tests on building models show that the PP-band retrofitting technique can enhance the safety of masonry buildings, even during severe ground motion.  相似文献   

9.
江苏高邮、宝应MS4.9级地震现场震害调查与破坏原因研究   总被引：1，自引：1，他引：0  
江苏高邮、宝应Ms4．9级地震在极震区造成了数10间农村民居不同程度和不同方式的破坏,出现人员伤亡。震后对地震灾害现场进行震害调查与破坏原因研究,典型的震害特征包括砖砌体、砖木和砖混结构房屋局部倾倒、墙体贯通开裂、房顶瓦片掀翻和烟囱倒塌等。农村民居遭到破坏的主要因素包括：选址不当、施工质量较差、砂浆强度不够、缺少圈梁和构造柱等。同时,分析了竖向地震作用和鞭梢效应等地震效应,讨论了砖砌体和砖混结构抗震设计的加固方法和改善抗震性能的构造措施等,为农村民居的抗震设防和减轻震害损失等提供参考。  相似文献   

10.
Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant human casualties and economic losses.To maintain their integrity,several methods have been developed to retrofit existing masonry buildings,such as the constructional RC frame which has been extensively used in China.In this study,a new method using precast steel reinforced concrete(PSRC)panels is developed.To demonstrate its effectiveness,numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting,retrofitted with a constructional RC frame,and retrofitted with external PSRC walls(PSRCW).Sophisticated finite element models(FEM)were developed and nonlinear time history analyses were carried out.The results show that the existing masonry building is severely damaged under occasional earthquakes,and totally collapsed under rare earthquakes.Both retrofitting techniques improve the seismic performance of existing masonry buildings.However,it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame,while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes.The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.  相似文献   

11.
A seismic assessment of two multi-tier pagodas by numerical analysis is presented herein.The Changu Narayan temple and the Kumbeshwar temple in Nepal are used as the case studies.Both pagodas are built of brick masonry in earthen mortar,with timber columns and crossbeams.The Changu Narayan temple is a two-tier pagoda,and was seriously damaged during the 2015 Gorkha earthquake.The Kumbeshwar temple is a five-tier pagoda,and its top-tier collapsed due to the Gorkha earthquake.A seismic assessment was carried out using finite element(FE)analysis.The FE models were prepared,and dynamic identification tests and penetrometer tests were conducted.Pushover analysis and nonlinear dynamic analysis were performed as part of the seismic assessment.The main shock of the 2015 Gorkha earthquake was considered as the input accelerograms.The behavior between the two pagodas was compared with the collapse mechanisms and damage patterns observed in the actual structures.The comparison suggested common structural features of multi-tier pagodas.This study is dedicated to providing a better understanding of the seismic behavior of multi-tier pagoda-type structures and provides suggestions for their effective analysis.  相似文献   

12.
The efficiency of improving the seismic resistance of old masonry buildings by means of seismic isolation and confining the structure with CFRP laminate strips has been investigated. Five models of a simple two-story brick masonry building with wooden floors without wall ties have been tested on the shaking table. The control model has been built directly on the foundation slab. The second model has been separated from it by a damp-proof course in the form of a PVC sheet placed in the bed-joint between the second and the third course, whereas the third model has been isolated by rubber isolators placed between the foundation slab and structural walls. Models four and five have been confined with CFRP laminate strips, simulating the wall ties placed horizontally and vertically at floor levels and corners of the building, respectively. One of the CFRP strengthened models has been placed on seismic isolators. Tests have shown that a simple PVC sheet damp-proof course cannot be considered as seismic isolator unless adequately designed. Tests have also shown that the isolators alone did not prevent the separation of the walls. However, both models confined with CFRP strips exhibited significantly improved seismic behavior. The models did not collapse even when subjected to significantly stronger shaking table motion than that resisted by the control model without wall ties.  相似文献   

13.
Damage or collapse of buildings vulnerable to seismic forces may cause human casualties, and seismic upgrading of such structures is a practical solution to this deficiency. The study presented here proposes a simple approach to prevent structural collapse by separating the superstructure from its foundation to let the superstructure slide during extreme ground shaking. The sliding mechanism contributes to cap the horizontal force exerted on the superstructure. In such approach, the key is to maintain the friction force between the superstructure and the foundation sufficiently low and stable. This research proposes to realize a controlled sliding mechanism, which acts as a structural fuse, by means of carbon powder lubrication at the bases of the structure's columns. The fundamental behaviour of the proposed structural system, named the base shear capping building, is investigated by shaking table tests and numerical simulation. Both experimental and numerical results showed that graphite lubrication is an efficient and robust lubrication material, maintaining the friction coefficient between the steel column bases and mortar foundation at around 0.16. The sliding at the bases significantly reduced the acceleration transmitted to the superstructure, keeping the base shear coefficient not greater than about 0.40. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

14.
Throughout history, dry-stone masonry structures have been strengthened with different types of metal connectors in order to increase their resistance which enabled their survival, especially in the seismically active area. One such example is the ancient Protiron monument placed in the Peristyle square of the Diocletian's Palace in Split, Croatia. The Protiron was built at the turn of the 3rd century as a stone masonry structure with dowels embedded between its base, columns, capitals and broad gable. The stone blocks in the broad gable were connected by metal clamps during restoration at the beginning of the 20th century. In order to study the seismic performance of the strengthened stone masonry structures, an experimental investigation of seismic behaviour of a physical model of the Protiron was performed on the shaking table. The model was designed as a true replica model in a length scale of 1:4 and exposed to representative earthquake with increasing intensities up to collapse. The tests provided a clear insight into system behaviour, damage mechanism and failure under intensive seismic load, especially into the efficiency of connecting elements, which had a special role in increasing seismic resistance and protection of the structure from collapse. Additionally, this experiment provided valuable data for verification and calibration of numerical models for strengthened stone masonry structures.  相似文献   

15.
Two models of masonry infilled reinforced concrete frame buildings were tested at the shaking table. Models were built in the reduced scale 1:4 using the materials produced in accordance to modelling demands of true replica modelling technique. The first model represented a one‐storey box‐like building and the second one the two‐stories building with plan shaped in the form of a letter H. Models were shaken with the series of horizontal sine dwell motions with gradually increasing amplitude. Masonry infills of tested models were constructed of relatively strong bricks laid in weak mortar. Therefore, typical cracks developed and propagated along mortar beds without cracking of bricks or crushing of infill corners. Data collected from tests will be used in future evaluation, verification and development of computational models for prediction of in‐plane and out‐of‐plane behaviour of masonry infills. The responses of tested models can be well compared with global behaviour of real structures using the modelling rules. The similarity of local behaviour of structural elements, e.g. reinforced concrete joints, is less reliable due to limitations in modelling of steel reinforcement properties. The model responses showed that buildings designed according to Eurocodes are able to sustain relatively high dynamic excitations due to a significant level of structural overstrength. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

16.
为弥补试验的不足,对试验室里难以实现的情况进行研究,如大比例甚至足尺模型的动力试验,利用大型有限元软件MSC.MARC对钢筋-沥青复合隔震层建立了非线性有限元模型。利用钢筋非线性子程序UBEAM和非线性弹簧子程序USPRNG,分别模拟了钢筋和砖墩-上梁之间相互作用关系的非线性情况,引入了沥青油膏的温度影响系数。为验证该模型,在钢筋沥青隔震层试件振动台试验的基础上,对振动台试验中各试件的模态进行了计算、对各工况进行了三维有限元时程分析,并将分析结果与试验结果对比,计算结果与试验结果吻合较好,验证了该模型的准确性和合理性。最后利用该模型,建立了不同高度的砌体结构有限元模型,设计并建立了相应的墙下条形隔震层模型,对钢筋沥青复合隔震层在不同高度的砌体结构中的动力性能和隔震效果进行了数值模拟,并对计算结果进行了归纳和分析,得出了一系列有用的结论。  相似文献   

17.
The intrinsic vulnerability of masonry structures to seismic events makes structural health monitoring of the utmost importance for the conservation of the built heritage. The development of piezoresistive bricks, also termed smart bricks, is an innovative technology recently proposed by the authors for the monitoring of such structures. Smart bricks exhibit measurable variations in their electrical properties when subjected to external loads or, alternatively, strain self-sensing capabilities. Therefore, the deployment of a network of smart bricks into a masonry structure confers self-diagnostic properties to the host structure. In this light, this paper presents a theoretical investigation on the application of smart bricks to full-scale masonry structures for seismic assessment. This includes the study of the convenience of providing electrical isolation conditions to the sensors, as well as the effectiveness of smart bricks when installed into either new constructions or in pre-existing structures. Secondly, numerical results are presented on the seismic analysis of a three-dimensional masonry building equipped with a network of smart bricks. Finally, in order to map the strain field throughout the structure exploiting the outputs of a limited number of sensors, an interpolation-based strain reconstruction approach is proposed.  相似文献   

18.
梁斌  张海  姚新强  高武平  陈贺 《地震工程学报》2020,42(4):856-861,947
砖砌体结构是农村传统农居建筑的主要结构形式,如何精确评价其抗震能力具有重要的研究意义。目前既有传统农居中,20世纪80、90年代砖砌体结构仍是其重要的组成部分。为研究既有传统砖砌体结构的抗剪性能,首先对水泥砂浆、白灰砂浆、炉渣砂浆、黄泥砂浆4种典型砂浆开展抗压强度试验;然后对4种典型砂浆砌筑的砌体进行沿通缝抗剪强度试验,通过与传统老旧红砖砌体抗剪强度的平均值和公式值进行对比,对砌体抗剪强度计算公式进行修正后得到修正公式;最后对比修正值、标准值和设计值,对传统农居进行准确的砖砌体抗剪强度评估。本项研究主要为传统农居砖砌体结构的抗震性能评估、抗震加固以及抗震设计提供技术支持与科学依据。  相似文献   

19.
The evaluation of the out‐of‐plane behaviour of unreinforced walls is one of the most debated topics in the seismic assessment of existing masonry buildings. The discontinuous nature of masonry and its interaction with the remainder of the building make the dynamic modelling of out‐of‐plane response troublesome. In this paper, the results of a shaking table laboratory campaign on a tuff masonry, natural scale, U‐shaped assemblage (façade adjacent to transverse walls) are presented. The tests, excited by scaled natural accelerograms, replicate the behaviour of external walls in existing masonry buildings, from the beginning of rocking motion to overturning. Two approaches have been developed for modelling the out‐of‐plane seismic behaviour: the discrete element method and an SDOF analytic model. Both approaches are shown to be capable of reproducing the experimental behaviour in terms of maximum rotation and time history dynamic response. Finally, test results and numerical time history simulations have been compared with the Italian seismic code assessment procedures. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

20.
An innovative solution for the seismic protection of existing masonry structures is proposed and investigated through shake table tests on a natural scale wall assemblage. After a former test series carried out without reinforcement, the specimen was retrofitted using Steel Reinforced Grout. The strengthening system comprises horizontal strips of ultra‐high strength steel cords, externally bonded to the masonry with hydraulic lime mortar, and connectors to transversal walls, applied within the thickness of the plaster layer. In order to assess the seismic performance of the retrofitted wall, natural accelerograms were applied with increasing intensity up to failure. Test results provide a deep understanding of the effectiveness of mortar‐based composites for improving the out‐of‐plane seismic capacity of masonry walls, in comparison with traditional reinforcements with steel tie‐bars. The structural implications of the proposed solution in terms of dynamic properties and damage development under earthquake loads are also discussed.Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

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