Synthesis of accelerograms compatible with the Chinese GB 50011-2001 design spectrum via harmonic wavelets: artifi cial and historic records

A versatile approach is employed to generate artificial accelerograms which satisfy the compatibility criteria prescribed by the Chinese aseismic code provisions GB 50011-2001. In particular, a frequency dependent peak factor derived by means of appropriate Monte Carlo analyses is introduced to relate the GB 50011-2001 design spectrum to a parametrically defined evolutionary power spectrum （EPS）. Special attention is given to the definition of the frequency content of the EPS in order to accommodate the mathematical form of the aforementioned design spectrum. Further, a one-to-one relationship is established between the parameter controlling the time-varying intensity of the EPS and the effective strong ground motion duration. Subsequently, an efficient auto-regressive moving-average （ARMA） filtering technique is utilized to generate ensembles of non-stationary artificial accelerograms whose average response spectrum is in a close agreement with the considered design spectrum. Furthermore, a harmonic wavelet based iterative scheme is adopted to modify these artificial signals so that a close matching of the signals＇ response spectra with the GB 50011-2001 design spectrum is achieved on an individual basis. This is also done for field recorded accelerograms pertaining to the May, 2008 Wenchuan seismic event. In the process, zero-phase high-pass filtering is performed to accomplish proper baseline correction of the acquired spectrum compatible artificial and field accelerograms. Numerical results are given in a tabulated format to expedite their use in practice.

Response spectrum of seismic design code for zones lack of near-fault strong earthquake records

It was shown from the study on the recently near-fault earthquake ground motions that the near-fault effects were seldom considered in the existing Chinese seismic code. Referring to the UBC97 design concept for near-fault factors, based on the collected world-widely free-site records of near-fault earthquakes ground motions classified by earthquake magnitude and site condition, the attenuation relationship expressions of the acceleration spectrum demand at the key points within the long period and moderate period were established in term of the earthquake magnitude and the site condition. Furthermore, the near-fault factors＇ expressions about the earthquake magnitude and the fault distance were deduced for the area lack of near-fault strong earthquake records. Based on the current Chinese Building Seismic Design Code, the near-fault effect factors and the modified design spectral curves, which were valuable for the seismic design, were proposed to analyze the seismic response of structures.

Seismic design or retrofit of buildings with metallic structural fuses by the damage-reduction spectrum

Recently, the structural fuse has become an important issue in the field of earthquake engineering. Due to the trilinearity of the pushover curve of buildings with metallic structural fuses, the mechanism of the structural fuse is investigated through the ductility equation of a single-degree-of-freedom system, and the corresponding damage-reduction spectrum is proposed to design and retrofit buildings. Furthermore, the controlling parameters, the stiffness ratio between the main frame and structural fuse and the ductility factor of the main frame, are parametrically studied, and it is shown that the structural fuse concept can be achieved by specific combinations of the controlling parameters based on the proposed damage-reduction spectrum. Finally, a design example and a retrofit example, variations of real engineering projects after the 2008 Wenchuan earthquake, are provided to demonstrate the effectiveness of the proposed design procedures using buckling restrained braces as the structural fuses.

Characteristic Period Value of the Seismic Design Response Spectrum of UHV Electrical Equipment

Characteristic period is an important parameter of the seismic design response spectrum.There is important theoretical significance and engineering application value to the study of the characteristic period of seismic design response spectrum of ultra high voltage(UHV)electrical equipment.In this paper,1448 horizontal earthquake records within the world scope including the United States and Japan for Site Class Ⅲ were analyzed.Results show that both magnitude and epicentral distance have great influence on the characteristic period.About80% of characteristic periods of strong earthquake records are about 0.9s.Statistical analysis was conducted on the seismic hazard assessment results of 312 projects of China in recent years,and it is found that about 70% of characteristic periods are about 0.9s.Combined with the related code comparison and analysis,it is suggested that the characteristic period of the seismic design response spectrum of UHV electrical equipment should select 0.9s in order to effectively guarantee the seismic safety of UHV electrical equipment.

Designing of Acousto-optic Spectrum Analyzer

The structure of the acousto-optic spectrum analyzer was investigated including the RF amplifying circuit, the optical structures and the postprocessing circuit, and the design idea of the module was applied to design the spectrum analyzer. The modularization spectrum analyzer takes on the performance stabilization and higher reliability, and according to different demands, the different modules can be used. The spectrum analyzer had such performances as the detecting frequency precision of 1 MHz, the detecting frequency error of 0.58 MHz, detecting responsivity of 90 dBm and bandwidth of 50 MHz.

Newmark design spectra considering earthquake magnitudes and site categories

Newmark design spectra have been implemented in many building codes, especially in building codes for critical structures. Previous studies show that Newmark design spectra exhibit lower amplitudes at high frequencies and larger amplitudes at low frequencies in comparison with spectra developed by statistical methods. To resolve this problem, this study considers three suites of ground motions recorded at three types of sites. Using these ground motions, influences of the shear-wave velocity, earthquake magnitudes, source-to-site distances on the ratios of ground motion parameters are studied, and spectrum amplification factors are statistically calculated. Spectral bounds for combinations of three site categories and two cases of earthquake magnitudes are estimated. Site design spectrum coefficients for the three site categories considering earthquake magnitudes are established. The problems of Newmark design spectra could be resolved by using the site design spectrum coefficients to modify the spectral values of Newmark design spectra in the acceleration sensitive, velocity sensitive, and displacement sensitive regions.

基于航空高光谱和伽马能谱的铀矿勘查集成软件开发与应用

航空高光谱和航空伽马能谱是当前铀矿勘查领域两类重要的数据源,由于其异构且海量的特性,使数据的处理难度大,处理效率低,协同应用效果不足。在这种情况下开发一款面向航空高光谱和伽马能谱的铀矿勘查集成软件显得尤为重要。文章根据航空高光谱和航空伽马能谱数据的类型及处理方法,开展了针对两种数据应用的集成软件系统的设计。研究引入虚拟总线结构,实现了对不同数据处理模块的调用,并以Visual Basic为主要开发语言,对前台主系统进行搭建。最终利用搭建好的系统,以银根地区的航空高光谱和伽马能谱数据为数据源,完成软件的应用测试。测试结果发现,利用GS融合算法可以较好地保留地表纹理信息,同时丰富图像颜色,从而为铀矿赋矿围岩岩性的准确识别与划分提供参考。

匹配不同目标谱对RC框架结构易损性和抗倒塌能力的影响

选取合适的目标谱进行地震动记录的选择与调整是结构易损性分析的基础。首先,基于条件均值谱不同的参数设定,选取3组地震动记录;其次,运用谱匹配方法分别对设计谱和条件均值谱进行匹配。输入匹配前后共9组地震动记录对5层钢筋混凝土框架结构进行多重地震动强度水平的增量动力分析,提取工程需求参数如最大层间位移角和最大残余层间位移角,进而分析谱匹配效果的偏差指标以及不同损伤状态下的易损性分析和结构抗倒塌安全储备系数(CMR)。分析结果表明:谱匹配方法可以有效减小结构易损性的离散性;地震动记录的选择与谱匹配的目标谱相同时,各损伤状态下50%超越概率对应的S_(a)(T_(1),5%)值和CMR都未发生明显偏差;而当地震动记录的选择与谱匹配的目标谱不同时,各损伤状态下50%超越概率对应的S_(a)(T 1,5%)值和CMR作为两个指标可能会得到不同的偏差结果。

Design spectra including effect of rupture directivity in near-fault region

In order to propose a seismic design spectrum that includes the effect of rupture directivity in the near-fault region, this study investigates the application of equivalent pulses to the parameter attenuation relationships developed for near-fault, forward-directivity motions. Near-fault ground motions are represented by equivalent pulses with different waveforms defined by a small number of parameters （peak acceleration, A, and velocity V; and pulse period, Tv）. Dimensionless ratios between these parameters （e.g., ATv/V, VTv/D） and response spectral shapes and amplitudes are examined for different pulses to gain insight on their dependence on basic pulse waveforms. Ratios of ATv/V, VTv/D, and the ratio of pulse period to the period for peak spectral velocity （Tv-p） are utilized to quantify the difference between rock and soil sites for near-fault forward-directivity ground motions. The ATv/Vratio of recorded near-fault motions is substantially larger for rock sites than that for soil sites, while Tvp/Tv ratios are smaller at rock sites than at soil sites. Furthermore, using simple pulses and available predictive relationships for the pulse parameters, a preliminary model for the design acceleration response spectra for the near-fault region that includes the dependence on magnitude, rupture distance, and local site conditions are developed.

Consecutive combined response spectrum

Appropriate estimates of earthquake response spectrum are essential for design of new structures, or seismic safety evaluation of existing structures. This paper presents an alternative procedure to construct design spectrum from a combined normalized response spectrum （NRSc） which is obtained from pseudo-velocity spectrum with the ordinate scaled by different peak ground amplitudes （PGA, PGV, PGD） in different period regions. And a consecutive function./（/） used to normalize the ordinates is defined. Based on a comprehensive study of 220 strong ground motions recorded during recent eleven large worldwide earthquakes, the features of the NRSc are discussed and compared with the traditional normalized acceleration, velocity and displacement response spectra （NRSA, NRSv, NRSD）. And the relationships between ground amplitudes are evaluated by using a weighted mean method instead of the arithmetic mean. Then the NRSc is used to define the design spectrum with given peak ground amplitudes. At last, the smooth spectrum is compared with those derived by the former approaches, and the accuracy of the proposed spectrum is tested through an analysis of the dispersion of ground motion response spectra.

拟合楼层反应谱的三向地震动时程生成方法研究

为获得满足规范要求的拟合楼层反应谱的三向地震动时程,采用六阶常微分方程的本征函数为基函数,分解并重构天然地震动时程;通过构建影响矩阵,迭代计算逐步调整本征函数的幅值系数,最终实现预设拟合精度;引入正交化方法保证三向地震动时程两两之间的统计独立性,并通过两组算例提供验证。研究结果表明,迭代所得时程反应谱与目标楼层反应谱的拟合精度较高,迭代过程中时程反应谱均匀一致地向目标谱逼近,迭代过程收敛,所得三向地震动时程均无零飘现象,满足规范要求。

中国与伊朗抗震规范地震作用对比研究

介绍了伊朗抗震规范的抗震设防目标与方法、场地类型、地震风险分区、设计反应谱以及基底剪力的计算,并与《建筑抗震设计规范》相关内容进行了对比。结果表明,伊朗规范根据结构重要性对建筑有选择性地做“两水准”抗震设防;基于平均剪切波速伊朗规范中的Ⅰ类场地近似于中国规范的Ⅰ0场地,其余各类场地之间无直接对应关系;伊朗规范设计反应谱动力系数随场地类型与地震风险分区变化,在低地震风险区的软弱场地上动力系数峰值高达3.25;伊朗规范地震作用基于“中震”计算,经结构性能系数折减后的基底剪力:高延性混凝土框架的基底剪力比中国规范小,低延性混凝土框架的基底剪力比中国规范大得多,中延性混凝土框架的基底剪力与中国规范的大小比较结果在不同场地不同周期段表现不同。

与桥梁抗震规范设计反应谱一致的地震动合成

工程上在对结构进行动力响应分析时,大多是在实测强震数据库中筛选出与规范设计反应谱相一致的实测强震记录作为地震动输入依据,然而,实测强震记录数量有限,需要系统地处理才可投入工程应用,且在对大型工程结构进行动力反应分析时无法体现地震动的空间变异性,因此,本文以《公路桥梁抗震设计规范》(JTG/T 2231-01-2020)中的设计反应谱为例,详细梳理了地震动向量过程的本征正交分解方法(POD)和复相干函数模型,并将反应谱转化功率谱法和调幅功率谱迭代法相结合,基于降维模拟方法,在概率层面上高效地生成了与设计反应谱相一致且具有空间变异性和非平稳性的人工地震动向量过程。数值算例表明,根据目标反应谱转化为调幅功率谱后,再根据功率谱迭代法迭代一次生成的地震动样本与目标反应谱对应良好,同时,降维方法生成的地震动样本具有显著的非平稳性和空间变异性,且统计特征与目标值对应良好。可以认为,本文为桥梁结构在地震作用下的地震激励输入提供了新的途径。

广东某装配式市政桥梁减隔震设计分析

文章运用多振型反应谱分析和时程分析两种方法,对广东某装配式市政桥梁减隔震设计进行了深入研究。研究发现,设置减隔震支座能有效延长桥梁自振周期、增大阻尼,进而减轻地震对桥梁的影响。相比普通板式橡胶支座,减隔震支座能降低地震水平力,削减幅度为21%~27%。两种分析方法各有特点,计算结果略有差异,但均表明减隔震设计在降低桥墩内力和主梁与非连续墩相对位移方面具有显著效果。此外,桥梁减隔震设计应特别注意上部结构顺桥向和横桥向的位移需求,高度重视伸缩缝规格选择、抗震挡块设计和抗震构造措施设计,文章结论可为同类型桥梁的抗震设计提供有益参考。

采煤机扭矩轴的设计及载荷谱作用分析

对MG500/670-BD采煤机进行了扭矩轴设计,通过理论分析确定了扭矩轴的材料、外形尺寸及卸荷槽形式,最终设计了所需扭矩轴。模拟扭矩轴实际应用情况进行了载荷谱加载,结果表明,扭矩轴最小疲劳安全系数为3.43,最小静态安全系数为2.02,满足使用要求。在极限载荷作用下静态安全系数为1.01,为许用静态安全系数的0.84倍,且在U形槽处最大应力超出了材料的剪切应力,出现了破断现象。

游憩机会谱理论在南京市绿博园公园中的应用研究

城市公园面临着游憩环境恶化、活动与游憩空间供给脱节、游憩体验质量下降等诸多问题。游憩机会谱理论作为发展较成熟且应用广泛的理论,有助于探究环境资源、游憩活动与公园管理之间的内在规律,对于提高游客游憩体验质量、建立公园可持续发展模式等具有重要意义。本研究以南京市绿博园公园为研究对象,采用文献研究、实地调研、问卷调查和多元统计分析等方法,对公园游憩环境和游客行为进行调查与分析,构建绿博园游憩环境指标因子体系,划分游憩机会类型并制定量化标准,构建游憩机会评分模型,构建了绿博园游憩机会谱。最后,根据游憩机会的评分结果对绿博园目前存在的问题提出了优化策略。

基于D-最优混料设计优选益气固表速溶散处方及评价

目的综合中药粉体改性技术、矫味技术和原料药前处理技术制备益气固表速溶散,并进行处方优选及评价,解决儿童给药困难的问题。方法在单因素实验的基础上,以流出速度、休止角、吸湿率、粒径分布宽度为评价指标,采用D-最优混料设计优选益气固表速溶散的最佳处方,并通过物理指纹图谱、粉体学性质、口感评价和红外光谱等方法对益气固表速溶散及传统散剂进行评价。结果益气固表速溶散的最佳处方为药辅比5∶1,混料蔗糖-饴糖-柠檬酸比12∶12∶1;3批样品物理指纹图谱相似度均大于0.997,表明3批速溶散的物理质量一致;速溶散和传统散之间的相似度仅为0.129,表明其粉体学性质差异较大,其物理属性有所差异;益气固表速溶散与普通散的粉体学性质及口感存在差异,且速溶散优于传统散;两种散剂的红外光谱基本一致,表明其化学成分结构未发生明显变化。结论益气固表速溶散研制开发能更好地提高儿童用药依从性,为中医临床提供“良药可口”的新选择。

印度及美国规范地震参数转换在水泥工程中的应用

介绍了印度规范和美国规范地震参数转化方法,以水泥生产线余热发电项目水泵房框架结构为例,对比了印度规范IS 1893(Part 4):2005和美国规范ASCE/SEI 7-10中的结构重要性系数、场地分类、反应谱修正系数、最大地震反应谱加速度系数等重要地震参数的转换,并结合工程项目实例,比较了印度规范和美国规范的地震反应谱曲线拟合程度和水平地震力计算结果,验证了地震参数转化的正确性。地震参数转化结果表明,印度规范和美国规范的地震反应谱曲线基本拟合,水平地震力计算值基本相近。

Statistical Analysis on the Corner Period of Site-Related Design Spectra

According to the results of site seismic hazard analysis accomplished in the past decades, 96 site-related design spectra are selected as samples in this study. The result shows that the value of the corner period (T g) of the design spectrum in GBJ11-89 (China Seismic Building Code, issued in 1989) is lower than the value obtained by site seismic hazard analysis. The same situation exists when we compare the design spectra of the Codes to the spectra according to the earthquake records. The value in current seismic design code, GBJ50011-2001 issued in 2001, is greater than that in GBJ11-89, but still less than the value obtained by site seismic hazard analysis. If we accept the value got by site seismic hazard analysis, we have a suspicion that 2/3 of buildings built according to GBJ11-89 will not be safe when an earthquake with 2% probability of exceedance in 50 years occurs.

A Comparison of Saudi Building Code with 1997 UBC for Provisions of Modal Response Spectrum Analysis Using a Real Building

The study uses an actual building to compare the modal response spectrum analysis results of Saudi Building Code (SBC) and the 1997 Uniform Building Code (UBC) used in Saudi Arabia before the introduction of SBC. A sample of four buildings with reported analysis of comparison between IBC and UBC is taken for confirming the comparison. Eight sample places from SBC map for Saudi Arabia together with two sample places of high seismic activity in USA were taken for the comparisons. The study used software package ETABS in this study for modeling and analysis. The results are dissimilar from the comparisons reported for test places of USA. It is concluded that at most places SBC base shear is higher for both ELFP and MRSA. However, the results cannot be generalized and considered always right. The same is factual for overturning moments. Consequently, we cannot report that SBC is more conservative than UBC for all scenarios.