基坑排桩对建筑抗震性的影响分析

以往对建筑抗震性影响因素的研究仅限于施工材料、技术手段等外部条件,忽略了基坑土体安全系数、基坑状态对建筑抗震性的影响,一定程度上削弱了建筑的抗震性能。本文从基坑排桩角度对建筑抗震性的影响展开分析,通过有限元强度折减法获取土体的安全系数与基坑状态的判断标准,在该标准下基于土体安全系数采用有限元强度折减法计算公式,获取各个土层计算参数。基于该参数使用ABAQUS有限元软件构建基坑排桩有限元分析模型(土体和桩体分别采用莫尔-库仑弹塑性模型和二维弹性模型)。实验采用所提分析方法,从基坑排桩排距、刚度两方面对建筑抗震性能进行分析。实验结果表明,当基坑排桩排距进行适当取值时,建筑抗震性越好;双排桩的刚度越大,建筑抗震性越好,且随着刚度的增加建筑抗震性能趋于平稳。

建筑物抗震性无线检测系统的设计

介绍了一种基于无线传感器网络技术的建筑物抗震性检测系统。首先,提出了以无线通信震动传感器形成一种可扩展的无线传感器网络的系统结构。然后,介绍在该系统中采用的无线震动传感器节点以及检测基站设备的设计。在本系统中,节点和基站设备所使用的近距离通信标准为802.15.4/ZigBee标准。

浅谈建筑结构的抗震性

抗震性是衡量建筑结构稳定、安全性的重要指标,在地震频发的今天,如何提高建筑的抗震性也是人们关注的重点问题之一。本文首先通过对不同结构的抗震性进行了讨论,然后,针对与人们密切相关的房屋建筑中的砌体结构进行了分析,分别从震害方式、抗震设计中存在的问题对砌体结构建筑进行了介绍,文中最后给出的抗震措施,对砌体结构的设计有所帮助。

基于最小二乘支持向量机算法的高层建筑结构的强震抗毁性估计模型

采用现有的估计模型对混凝土建筑结构的抗毁性进行估计时,存在估计精度低、耗时长等问题。为此,提出一种基于最小二乘支持向量机的强震作用下混凝土高层建筑结构的抗毁性估计模型。该模型采用最小二乘支持向量机对混凝土结构强震损伤程度相关数据的训练样本进行训练,创建混凝土结构抗毁性估计模型;为了减少可能存在的模型误差,采用KLASSO调参模型对结构抗毁性估计模型中的参数进行调节和优化,得出可靠、稳定的强震作用下混凝土高层建筑结构抗毁性估计模型。仿真实验证明,该模型估计精度相对较高,可节省估计用时,为更好地提升建筑行业的安全检测工作效率提供很好的依据。

Eurocode8、CECS 160:2004与GB50011—2010中考虑土-结构相互作用效应的比较

我国新版《建筑抗震设计规范》(GB 50011—2010)于2010年12月1日起正式实施;从考虑土-结构相互作用效应方面,我国抗震规范与欧洲抗震设计规范(Eurocode8)2004版和我国建筑工程抗震性态设计通则(CECS 160:2004)进行了比较,旨在为从事工程抗震的设计和研究人员提供一定参考和借鉴。

Anti-seismic behavior of HRB400 reinforced steel bars

The properties of anti-seismic HRB400 steel bars with 25 mm diameter were systematically investigated. The results showed that the properties of the HRB400 reinforced steel bars had been greatly enhanced comparing with HRB335 steel bars, i.e. coordination of strength and ductility, strain-aging sensibility, low temperature impact toughness, weld ability and high strain low cycle fatigue. The ductile-brittle transit temperatures of hot-rolled and strain-aged steel bars were evaluated as –17 °C and ?8 °C respectively, and the low temperature impact toughness of HRB400 steel bars remains to be improved. Transmission electron microscopy (TEM) and electron diffraction showed little vanadium existed in ferrite as VN, most of which existed in pearlite as alloy cementite which resulted in the declination of impact toughness. Methods were suggested to improve the anti- seismic properties of steel bars.

Experimental Study on Seismic Performance of Tall Building with Steel Transfer Trusses Located at a Higher Level

Based on a shaking table experiment of 1 :25 scale frame-shearwall structure model with steel transfer trusses,the dynamic characteristics,seismic responses in elastic and elastic-plastic phases with de- structive forms of the structure were studied.It was observed that cracks were developed with earthquake wave acceleration increasing,but no severe crack was developed in the structure during the experiment.In the seismic responses caused by artificial wave,site wave and E1 Centro wave,that caused by the artificial wave is the most intense one.Displacement angle between steel transfer trusses is large,which means the transfer stories might be weak.However,the seismic performance of the steel transfer trusses is good and the overall structure can satisfy seismic fortification requirements in the region of intensity 6.

Seismic Safety of RC Framed Buildings Designed According to Modern Codes

In order to ensure that a structure does not collapse when subjected to the action of strong ground motions, modern codes include prescriptions in order to guarantee the ductile behavior of the elements and of the whole structure. Obviously, it would be of special importance for the designer to know during the design process the extent of damage that the structure will suffer under the seismic action specified by the design spectrum and also the probability of occurrence of different states of behavior. The incremental nonlinear static analysis procedure used in this paper allows formulating a new, simplified, seismic damage index and damage thresholds associated with five limit states. The seismic behavior of a set of regular reinforced concrete buildings designed according to the EC-2/EC-8 prescriptions for a high seismic hazard level is then studied using the proposed damage index and damage states. Fragility curves and damage probability matrices corresponding to the performance point are calculated for the studied buildings. The obtained results show that the collapse damage state is not reached in the buildings designed according to the prescriptions of EC-2/EC-8 and also that the damage does not exceed the irreparable damage limit state.

Comparison of North American Seismic Screening Methods Applied to School Buildings

An ongoing project at McGill University is aimed at developing an adapted seismic screening method for schools in the province of Qu6bec, Canada. As part of this project the ＂FEMA 154 Rapid Visual Screening of Buildings for Potential Seismic Hazard＂ and the ＂NRC92 Manual for Screening of Buildings for Seismic Investigation＂ were used to assess 102 school buildings located in the city of Montr6al. Results for both methods are in reasonable agreement, with 65% of the buildings requiring a detailed evaluation according to FEMAI54 and 50% according to NRC92. Findings highlighted the particular characteristics of educational facilities： they are low rise buildings with high incidence of structural irregularities. Accounting for them in the screening phase is essential, and is better achieved by NRC92. However, this method is largely based on expert opinion, which makes it difficult to update, while FEMA154 uses a rational methodology for calculating vulnerability scores based on the capacity spectrum approach. The FEMA154 analytical procedure allows updating and adapting the method to its use outside its intended scope.

The Role of Architectural Considerations in Seismic Performance of Buildings： A Case Study in Iran

Experience from recent earthquakes such as Gilan, Zanjan, Bam and Lorestan earthquakes in Iran indicated that the constructed buildings are vulnerable against earthquake. Vulnerability of these structures is due to various reasons such as designing without considering seismic regulations, problems of regulations （design goals）, implementation problems, changing of the building occupancy class, increasing the weight of building stories, adding new stories to the building and changing in architecture of building without considering structural system. So the main objective of this research is to examine the features of building configuration and their effects as for the damages to buildings in past earthquakes. For this purpose, initially four occurred earthquakes in Iran are selected as case study. Then three types of buildings （steel structure, concrete structure and masonry buildings） are analyzed with details. Results showed that the most of damages are occurred in the old steel structures and masonry buildings which their ages are more than 25 years. The study showed that most of the buildings in the study area are steel structure and masonry buildings while concrete structures are infrequent which most of them had no or slight damages. Therefore, the importance and need to enhance the performance of available buildings against earthquake forces by rehabilitating methods would be more important than before. Also results indicated that the decisions related to architectural plan which have significant effect on seismic performance of buildings, can be divided into three categories： configuration of building, restrictive formal architectural plan and dangerous structural components, as these categories are not obstacle of each other, it is possible that each category has an influential effect on others. So organizing the design decisions in this way is very important so as to manage their effects and interdependencies.

Research on Seismic Behavior of Sloping Field Building Structure

The paper set up 3D solid overall superstructure model of Foundation and Box foundation on Rock Slope Subgrade base using the ABAQUS, and the establish the infinite element boundary, superstructure displacement of Box foundation and foundation at Rock Slope Subgrade was studied by inputting different direction of earthquake response. The results show that, for the mountain frame structure, influence on the horizontal displacement of the vertical under the action of alone big earthquake, and vertical seismic action on horizontal displacement effect is smaller by mutual function of horizontal and vertical seismic, basically is same as response under the action of horizontal earthquake alone; for step shaped box foundation, the change trend of mutual function of horizontal and vertical earthquake was the complete opposite of the maximum story drift each layer under the one-way horizontal earthquake, which indicate the presence of vertical earthquake wave effect on the box foundation displacement cannot be ignored.

Seismic Vulnerability of Building Construction Site

Building construction site plays an important role in the economic aspect of a region. So any disruption due to hazard event like earthquake can cause several direct and indirect damages. Direct damages can lead to the loss of equipments and qualified persons. Indirect damages can lead to inflation and loss of purchasing power. To deal with that situation, parameters that govern the vulnerability of building construction site have been identified. Using a MCDM （multiple criteria decision making） method, the priority order of these parameters has been set. Then a PVI （partial vulnerability index） and a GVI （global vulnerability index） are proposed. These indexes allow the classification of building construction sites according to their intrinsic vulnerability and seismic vulnerability respectively that is through the use of a given classification. Several Algerian building construction sites belonging to different seismic zones were considered in order to show the applicability of the method.

Seismic Performance of Dry-Friction Devices in Shear-Frame Buildings

In recent years the application of friction-based passive energy dissipation devices have been proven very effective in reducing structural response to earthquake excitations and also implemented for a large number of buildings. Their design heavily relies on numerical simulations to model the influence of the energy dissipation devices. The modeling of friction forces must be accurate for realistic simulation of the influence of these devices. In state-of-the-practice, the hysteretic behavior of friction devices has been typically modeled with Coulomb friction having a constant coefficient of friction. However, the basic laws for typical sliding materials and experimental investigations show non-linear relationship between friction and sliding velocity, which includes stiction and Stribeck effect. The influence of stiction and Stribeck effect may be significant and can not be ignored in simulating the dynamic responses of structures with friction-based energy dissipation devices. In this paper the optimal performance of dry friction device in shear-frame buildings when subjected to earthquake ground motions has been investigated. The focus of this paper is on the optimal minimization of response of the shear-frame building. Since buildings with friction devices behave in a highly nonlinear manner, nonlinear response-history analysis considering comprehensive sliding friction models has been carried out. The performance has also been evaluated using the various response measures： the maximum absolute acceleration, the maximum base shear, and the maximum inter-story drift. Different performance indices have been used to quantify the influence of the device properties.

Experimental Research on Seismic Performance of Storey-Adding Frame Structures

The seismic behaviors of an integral concreting frame, a light steel storey-adding frame and a storeyadding frame strengthened with carbon fiber reinforced polymer(CFRP)were investigated under low-cycle and repeated load(scale 1∶3). The failure characteristics, hysteretic behavior, rigidity degeneracy, deflection ductility and energy-dissipation capacity of the three specimens were compared. The test results reveal that chemicallybonded rebar technique can meet the requirements of storey-adding engineering. The carrying capacity, the deflection ductility, the energy-dissipating capacity and seismic performance of the light steel storey-adding frame are higher than those of the integral concreting frame, and they are the highest in the storey-adding frame strengthened with CFRP.

Evaluation of the Policies for Seismic Retrofit of Buildings

The Japanese government has established a law to Hanshin-Awaji Earthquake in 1995. This paper evaluates the incentives of the policies related to the law. The data shows achieved in 2018 if the current trends of improvement will supports the school retrofit works that are carried out by the promote seismic retrofitting of buildings immediately after the Great effectiveness, efficiency, administrative feasibility and technological that the policy target of seismic safety of existing buildings will be be continued. In the field of school buildings, national government local governments, using the guideline for school retrofit. However, there are still significant issues to make all buildings safe. One of the key challenges is how to persuade the elderly who would not invest their money to improve their old houses. Another challenge is to make owners understand the importance and have priority in improving the seismic safety of buildings. Currently many efforts are taken by the local governments, such as holding seminars for local communities, preparing financial support schemes, providing consultancy for seismic assessment and making earthquake hazard maps. This paper also provides comments on the improvement of the current policies for promoting seismic retrofit based on some international experiences in retrofit of buildings.

含剧烈地震动作用不同埋深砂土液化判别统一公式

震害调查和工程实践均表明,发展含剧烈地震动作用及深埋砂层下合理的液化判别方法为现代城市和重大工程抗震设防所必须。收集整理近期大地震液化新数据,剖析现有代表性液化判别方法,提出基于标准贯入试验的砂土液化判别统一模型和公式,以适于含剧烈地震动作用下不同埋深砂层的液化判别。所提出的双曲线型液化判别模型,对不同深度砂层具有一致的统一表达,符合液化临界线基本特征,且能够做到深、浅砂层和高、低地震动强度作用同时兼顾,较我国规范现有模型明显合理,较国际上基于CSR理论、沿深度分四段表达的NCEER模型明显先进。新公式通过了PGA<0.9 g作用下液化砂层埋深30 m内大量实测液化数据的检验,克服了我国规范砂层埋深超过10 m时严重保守的弊端,弥补了我国规范PGA>0.4 g和砂层埋深20 m以下液化判别方法的空白,也消除了国际上NCEER方法中砂层埋深超过10 m后液化临界线出现回弯的不合理现象以及很强和剧烈地震动(0.25 g<PGA<0.9 g)作用下较为保守的缺点。提出的公式已被具有样板规范性质的《建筑工程抗震性态设计通则》修订版采纳,可为相关规范修订及工程应用提供指导与技术支持。