足尺钢框架振动台试验及动力弹塑性数值模拟

本文通过有限元分析程序OpenSees对一足尺四层钢框架结构进行静力及动力弹塑性分析,结构构件采用自由度较少的纤维模型模拟。在振动台试验之前,预测足尺钢框架结构连续在小震、中震及大震作用下的响应,将预测分析结果与振动台试验结果进行对比,结果显示该数值模拟方法能很好地反映结构的弹塑性行为及破坏机制,准确预测结构的地震响应及大震下结构倒塌时间。这进一步说明基于纤维模型的整体结构弹塑性分析方法,由于自由度数少,适用于整体结构抗震分析。     

Investigation of ‘equal displacement’ rule for bridges subjected to differential support motions

The ‘equal displacement’ rule is employed in seismic design practice to predict inelastic displacements from analyses of the corresponding linear elastic structural models. The accuracy and limitations of this rule have been investigated for ordinary structures but not for bridges subjected to spatially varying ground motions. The present study investigates this rule for moderate levels of inelastic behavior for four highway bridges in California accounting for the effects of spatial variability of the support motions due to incoherence, wave passage and differential site response. The bridge models vary significantly as to their fundamental periods and their overall configurations. Statistical analyses of pier‐drift responses are performed using as input simulated arrays of nonstationary ground motions in accordance with prescribed coherency models. It is found that the ‘equal displacement’ rule is fairly accurate for cases when the fundamental period of the bridge is longer than the transition period between the acceleration‐controlled and velocity‐controlled ranges of the response spectrum. Otherwise, the rule is non‐conservative for cases with large ductility factors and conservative for cases with small ductility factors. Wave passage and incoherence tend to reduce ratios of mean peak inelastic to elastic pier drifts, whereas incorporation of the differential site‐response effect by locating piers on softer soils tends to increase the same ratios. Mild or moderate positive correlation between these ratios and ductility demands is observed in most cases. Effects of spatial variability are more pronounced for longer and stiffer bridges. Copyright © 2013 John Wiley & Sons, Ltd.     

Development of duration‐dependent damage‐based inelastic response spectra

A simple relationship is proposed in this paper to construct damage‐based inelastic response spectra including the effect of ground motion duration that it can be used for damage control in seismic design of structures. This relation is established for three groups of ground motions with short‐duration, moderate‐duration, and long‐duration ranges. To develop the model, the duration effect is included in the cyclic ductility of structures by an energy‐based method, and then strength reduction factors are computed based on this modified ductility (named ). The strength reduction factors were calculated for 44 stiffness‐degrading oscillators having vibration periods between 0.05 and 4.0 s, four ultimate ductility capacities, and five damage levels subjected to 296 earthquake records. The results showed that ductility capacity, damage level, and ground motion duration are effective parameters in the energy dissipation of structures, which affect the spectra. The values of short‐period oscillators (e.g., low‐rise structures) under short‐duration records are generally greater than those under moderate‐duration and long‐duration records. Residual analysis has been made in terms of magnitude and distance to examine the validity of the proposed simple expression. Finally, the introduced spectra were compared with three previously published proposals. Copyright © 2016 John Wiley & Sons, Ltd.     

Higher modes in simplified inelastic seismic analysis of single column bent viaducts

The influence of the higher modes and their consideration in the pushover analysis of reinforced concrete single column bent viaducts with different degree of irregularity is discussed. Typical multimode pushover‐based methods (modal pushover analysis, modal adaptive non‐linear static procedure and incremental response spectrum analysis) are addressed and compared with a single mode procedure (N2) and inelastic time history analysis. If in the transverse direction the substructure of the viaduct is flexible in comparison with the superstructure, the influence of higher modes is small (the structure is regular) and single mode procedure works well. This typically occurs when the columns are high or considerably damaged. Conversely, for the analysis of irregular structures having short and slightly damaged columns, the multimode methods are needed. In most cases, all the analysed multimode pushover‐based methods have given the results comparable with time history analysis, with the exception of cases where torsional sensitivity is varying during the response. All the methods have limitations (discussed in detail in the paper), which should be fully recognized by the user. Copyright © 2005 John Wiley & Sons, Ltd.     

Systematic development of a new hysteretic damper based on torsional yielding: part II—experimental phase

This paper reports on experimental studies carried out on a 200 kN, 120 mm‐capacity prototype of the newly developed multidirectional torsional hysteretic damper for seismic protection of structures. The main goal of the experiments is to test the validity of the theory developed in a companion paper and to evaluate the low‐cycle fatigue performance of the energy dissipaters of the damper. Because the design and configuration of the damper allow easy replacement of the energy dissipaters, four sets of energy dissipaters were produced out of S355J2 + N, C45 (two sets), and 42CrMo4 + QT steel grades. Force–displacement response of the multidirectional torsional hysteretic damper is studied through fully reversed cyclic quasi‐static displacement‐controlled tests that were carried out in compliance with EN 15129. Following the verification tests, with the aim of studying fatigue and fracture behavior of the cylindrical energy dissipaters of the device, certain numbers of them were subjected to further cyclic tests up to failure, and observations on their fatigue/fracture behavior are reported. The experimental verification test results proved the validity of the developed theory and component design assumptions presented in a companion paper. Furthermore, the energy dissipaters exhibited excellent torsional low‐cycle fatigue performance with number of cycles to failure reaching 118 at a maximum shear strain of 8% for S355J2 + N steel grade. Copyright © 2015 John Wiley & Sons, Ltd.     

Probabilistic estimation of inelastic displacement demands in soil–structure interaction systems on cohesive soils

Inelastic displacement ratios (IDRs) of nonlinear soil–structure interaction (SSI) systems located at sites with cohesive soils are investigated in this study. To capture the effects of inelastic cyclic behavior of the supporting soil, the Beam on Nonlinear Winkler Foundation (BNWF) model is used. The superstructure is modeled using an inelastic single-degree-of-freedom (SDOF) system model. Nonlinear SSI systems representing various combinations of unconfined compressive strengths and shear wave velocities are considered in the analysis. A set of strong ground motions recorded at sites with soft to stiff soils is used for considering the record-to-record variability of IDRs. It is observed that IDRs for nonlinear SSI systems are sensitive to the strength and the stiffness properties of both the soil and the structure. For the case of SSI systems on the top of cohesive soils, the compressive strength of the soil has a significant impact on the IDRs, which cannot be captured by considering only the shear wave velocity of the soil. Based on the results of nonlinear time-history analysis, a new equation is proposed for estimating the mean and the dispersion of IDRs of SSI systems depending on the characteristic properties of the supporting soil, dimensions of the foundation, and properties of the superstructure. A probabilistic framework is presented for the performance-based seismic design of SSI systems located at sites with cohesive soils.     

Evaluation of site‐dependent constant‐damage design spectra for reinforced concrete structures

An investigation on the validity of the conventional design approach known as constant displacement ductility is carried out. The hysteretic behaviour described by the Modified Takeda model is taken to represent the characteristics of reinforced concrete structural systems. The results presented in the form of seismic damage spectra indicate that the conventional design approach may not be valid because cumulative damage is excessively high. The inelastic design spectra based on the constant‐damage concept are proposed in terms of simplified expressions. The expressions are derived from constant‐damage design spectra computed by non‐linear response analysis for SDOF systems subjected to ground motions recorded on rock sites, alluvium deposits, and soft‐soil sites. The proposed expressions, which are dependent on the local soil conditions, are functions of target seismic damage, displacement ductility ratio and period of vibration. The seismic damage of structures that have been designed based on this new design approach is also checked by a design‐and‐evaluation approach. The results are found to be satisfactory. Copyright © 2004 John Wiley & Sons, Ltd.     

Seismic behaviour of asymmetric buildings with supplemental damping

This paper investigates the response of asymmetric‐plan buildings with supplemental viscous damping to harmonic ground motion using modal analysis techniques. It is shown that most modal parameters, except dynamic amplification factors (DAFs), are affected very little by the plan‐wise distribution of supplemental damping in the practical range of system parameters. Plan‐wise distribution of supplemental damping significantly influences the DAFs, which, in turn, influence the modal deformations. These trends are directly related to the apparent modal damping ratios; the first modal damping ratio increases while the second decreases as CSD moves from right to left of the system plan, and their values increase with larger plan‐wise spread of the supplemental damping. The largest reduction in the flexible edge deformation occurs when damping in the first mode is maximized by distributing the supplemental damping such that the damping eccentricity takes on the largest value with algebraic sign opposite to the structural eccentricity. Copyright © 2000 John Wiley & Sons, Ltd.     

游走脾的诊治进展

游走脾（WS）,又称异位脾。1677年由荷兰医生Johannes von home在尸检中首次发现,是一种因脾脏的活动度增大,所引起的急或慢性疾病。当游走脾发生脾蒂扭转时,称为脾扭转（ST）。脾扭转发生几率较小,只占WS的20％,但危险性极大,严重者可致脾梗死甚或危及生命。本病为罕见病,全球仅报告500例。ST伴胰尾扭转在我国还没有病例报道,为提高对该病的认识,现将我院收治的1例患者予以报道。

     

Effects of structural walls on the elastic–plastic earthquake responses of frame–wall buildings

Effects of structural walls on the elastic–plastic earthquake response of short- to medium-height reinforced concrete buildings were investigated. The analytical model consists of independent lumped mass systems representing walls and frames connected at each floor. The wall structure undergoes flexural as well as shear deformation and fails in shear at relatively small story drifts, the frames deforming only in shear. As a measure of structural damage, the ductility factor responses of frame structures were calculated for different combinations of base shear coefficients for the frames and walls. In buildings with relatively weak frames, the installation of structural walls did not improve the large plastic response of the frames up to the point where the walls were unfailed in shear and the ductility factors of the frame structure were suddenly reduced to a very small number. For relatively strong frames, however, the response displacements decreased gradually as the number of walls increased, whether or not the walls failed. Empirical formulas for the required base shear coefficients of the walls and frames which gave a target ductility factor response also were derived for two particular groups of accelerograms. These equations should be of practical use in designing frame-wall type buildings and in retrofitting damaged buildings. Copyright © 1999 John Wiley & Sons, Ltd.