bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic soil pressures on rigid vertical walls
Authors: Veletsos A. S. , Younan A. H. 
Published: April 2007

AbstractA critical evaluation is made of dynamic pressures and the associated forces induced by ground shaking on a rigid, straight, vertical wall retaining a semi‐infinite, uniform viscoelastic layer of constant thickness. The effects of both harmonic and earthquake‐induced excitations are examined. Simple approximate expressions for the responses of the system are developed, and comprehensive numerical data are presented which elucidate the effects and relative importance of the various parameters involved. These solutions are then compared with those obtained by the use of a simple model previously proposed by Scott, and the accuracy of this model is assessed. Finally, two versions of an alternative model are proposed which approximate better the action of the system. In the first, the properties of the model are defined by frequency‐dependent parameters, whereas in the second, which is particularly helpful in analyses of transient response, they are represented by frequency‐independent, constant parameters.
Consistent inelastic design spectra: Hysteretic and input energy
Authors: Fajfar Peter , Vidic Tomaž 
Published: April 2007

AbstractThis is the second of two companion papers on inelastic design spectra (for strength, displacement, hysteretic and input energy) for systems with a prescribed ductility factor. All the spectra are consistent (interrelated and based on the same assumptions). This paper deals with two quantities related to cumulative damage: hysteretic and input energy. The input data for the procedure are the characteristics of the expected ground motion in terms of a smooth elastic pseudo‐acceleration spectrum and the time integral of the square of the ground acceleration ∫a2 dt. Simple, approximate expressions for two dimensionless parameters (the parameter γ and the hysteretic to input energy ratio EHEI) have been proposed. The parameter 7, which controls the reduction of the deformation capacity of structures due to low‐cycle fatigue, depends on the natural period of the system, the prescribed ductility factor, the hysteretic behaviour and the ground motion characteristics. The ratio EH/EI is influenced by damping, the ductility factor and the hysteretic behaviour. Very good approximations to the inelastic spectra for hysteretic and input energy can be derived from the elastic spectrum using the spectra for the reduction factor R, proposed in the companion paper, and the proposed values for γ and EH/EI
Non‐linear soil response in ground motions
Authors: Wen Kuo‐Liang 
Published: April 2007

AbstractFrom both theoretical and empirical studies, we know that a soft soil layer will amplify seismic waves of certain frequencies and cause damage to structures, depending on the physical properties and the thickness of the layer. Most developed cities are situated on a plane or a basin with soft geological strata. Thus, understanding the characteristics of soft soil response to seismic loading is important. Seismologists and engineers are interested in questions of linear versus non‐linear soil response and isotropy versus anisotropy as a soil property. The records of the downhole accelerographs of an array in Lotung provide an opportunity to study these problems. The results show that the soil response in Lotung does not have an anisotropy effect, and significant non‐linear soil response occurred during the strong ground motions in which peak ground acceleration values at ground surface are larger than 150 gal.
Structural control considering soil–structure interaction effects
Authors: Smith H. Allison , Wu Wen‐Hwa , Borja Ronaldo I. 
Published: April 2007

AbstractA discussion of the effects of Soil‐Structure Interaction (SSI) on the formulation of active structural control algorithms is presented. Two approaches for incorporating SSI effects in linear optimal control theory are developed: one which performs the control analysis on a structure with a fixed base and then considers the effects of SSI on the controlled structural response; and another which performs the control analysis using a structural equation of motion reformulated to include SSI effects. The two control formulations are studied and compared using a single‐degree‐of‐freedom structure supported through a rigid foundation resting on a linear, elastic half‐space. Results show that control effectiveness is affected by the approach used in formulating the equations of motion of the interacting system.
A measure of the capacity of earthquake ground motions to damage structures
Authors: Rodriguez Mario 
Published: April 2007

AbstractEven though a number of parameters have been proposed in the literature for measuring the capacity of earthquake ground motions to damage structures, most of them are not consistent with building damage observed during earthquakes. In this study, a parameter for measuring seismic damage capacity is proposed. It uses the energy dissipated by a structure in inelastic deformations and a structural overall drift, and it is evaluated for three typical ground motions recorded in severe earthquakes. By using this parameter, consistent results with building damage observed in these earthquakes are obtained, which indicate the importance of displacement control for minimizing seismic damage.
Pseudodynamic testing of strain‐softening systems with adaptive time steps
Authors: Bursi Oreste S. , Shing Pui‐Shum B. , Radakovic‐Guzina Zorica 
Published: April 2007

AbstractA structure may exhibit a severe strain‐softening behaviour when subjected to strong earthquake excitation. Pseudodynamic testing of such structures using an implicit time‐integration algorithm may be conceived of as a problem, since the Newton‐type iterations, which are often required when structural non‐linearity develops, may not converge under these circumstances. An unconditionally stable implicit time‐integration algorithm implemented with Newton‐type iterations is analysed to provide an insight into this problem. A simple convergence condition is derived to detect possible divergence. The condition is shown to be a sufficient criterion for convergence for general multiple‐degree‐of‐freedom structures, and it is used later on to develop an adaptive time‐stepping strategy to avoid divergence under severe strain‐softening conditions. The implementation of this technique for pseudodynamic testing is presented. As demonstrated by numerical examples, the algorithm proves to be effective and reliable.
An inelastic substructure technique for the pseudodynamic test method
Authors: Schneider Stephen P. , Roeder Charles W. 
Published: April 2007

AbstractAn inelastic substructure technique for the pseudodynamic test method is described. This technique requires testing of only a critical component of a multi‐degree‐of‐freedom structure, while the remaining portion is modelled using standard inelastic analytical procedures. This is an economical method to investigate the seismic behaviour of a structure, provided a critical subassembly is found. This paper describes the development of a substructure algorithm which is verified with a numerically simulated test. The method was used to evaluate the seismic performance of moment‐resisting steel frames. Modelling for an eight‐storey, three‐bay frame is discussed, and the boundary conditions between the analytical portion and the experimental component are evaluated. The results indicate that the selection of the critical subassembly was adequate and that the pseudodynamic response was significantly dependent on the behaviour of this experimental component. Furthermore, experimental results suggest that this information would have been difficult to obtain from quasi‐static testing or from standard inelastic dynamic analysis. Therefore, this substructure pseudodynamic technique was an economical tool to investigate the seismic behaviour of ductile frames.
Seismic energy dissipation for cable‐stayed bridges using passive devices
Authors: Ali Hosam‐Eddin M. , Abdel‐Ghaffar Ahmed M. 
Published: April 2007

AbstractThis study assesses analytically the effectiveness, feasibility and limitations of elastic and hysteretic damping augmentation devices, such as elastomeric and lead–rubber bearings, with respect to the dynamic and seismic performance of cable‐stayed bridges. This type of bridge, which has relatively greater flexibility, is more susceptible to undesirable vibrations due to service and environmental loadings than are conventional bridges. Therefore, damping is a very important property. Supplementary damping devices based on the plastic deformation of lead and steel are proposed at critical zones, such as the deck–abutment and deck–tower connections, to concentrate hysteretic behaviour in these specially designed energy absorbers. Inelastic behaviour in primary structural elements of the bridge can therefore be avoided, assuring the serviceability of these cable‐supported bridges. Analytically, three‐dimensional modelling is developed for the bridge and the damping devices, including the bridge geometrical large‐displacement non‐linearity and the local material and geometric non‐linearities of the energy dissipation devices. The effects of various modelling and design parameters of the bridge response are also studied, including the properties, modelling accuracy and location of the devices along the bridge superstructure.It is shown that an optimum model of the seismic performance of the bridges with these passive control devices can be obtained by balancing the reduction in forces along the bridge against tolerable displacements. Appropriate locations and hysteretic energy dissipation properties of the devices can achieve a significant reduction in seismic‐induced forces, as compared to the case with no dampers added, and relatively better control of displacements. In addition, proper selection of the location of the passive control systems can help redistribute forces along the structure which may provide solutions for retrofitting some existing bridges. However, caution should be exercised in simulating the device response for a reliable bridge structural performance. Moreover, while seismic response of the bridge can be significantly improved with added dampers, their degree of effectiveness also depends on the energy absorption characteristics of the dampers.
2‐D transient soil–surface foundation interaction and wave propagation by time domain BEM
Authors: Takemiya Hirokazu , Fei Guan , Sukeyasu Yoshiki 
Published: April 2007

AbstractThis paper shows an effective implementation of the half‐plane Green function for surface strip impulses (Lamb's problem), which was previously developed in a closed form by the authors, into the time‐domain boundary element method for the analysis of related initial boundary value problems. The time‐stepping algorithm utilizing Heaviside step function makes the solution process free from the Rayleigh wave front singularity. Illustrative analyses performed include that: First, the response due to an impulsive uniform strip loading is dealt with in order to check the accuracy of the present solution and to interpret the associated wave motion in the medium. Second, a rigid massless strip surface foundation is analysed when subjected to various impulsive loadings in vertical, horizontal and rotational directions to observe which wave is most concerned with the respective foundation motion. The field response is also of interest with respect to distance attenuation. Third, the dynamic cross‐interaction between active and passive foundations through soil is investigated when multiple strip foundations are placed separately on a half‐space with a certain distance.
An approach to the seismic design of steel structures based on cumulative damage criteria
Authors: Ballio Giulio , Castiglioni Carlo A. 
Published: April 2007

AbstractThe applicability of Miner's rule to the assessment of cumulative damage of structural details in steel structures under seismic loading is discussed and validated both numerically and experimentally. Starting from this consideration, a seismic design method is proposed that, based on linear elastic dynamic analyses, takes into account a more precise description of the structural behaviour.The proposed method also leads to the identification of a methodology for the assessment of the q‐factor, based on a comparison of the cumulative damage during an earthquake, estimated by means of dynamic linear and non‐linear analyses. This methodology is discussed with reference to columns of single‐storey buildings, and compared to other methods for the assessment of the q‐factor based on the ductility factor theory.
Prediction of earthquake energy input from smoothed fourier amplitude spectrum
Authors: Kuwamura Hitoshi , Kirino Yasunori , Akiyama Hiroshi 
Published: April 2007

AbstractThis paper attempts to show analytically that the energy‐input spectra of damped SDOF systems and undamped MDOF systems excited by an earthquake motion can be predicted by smoothing the Fourier amplitude spectrum of the base acceleration. The spectral window for smoothing in the frequency domain for a damped SDOF system is identical with the probability density function of the time‐variant or instantaneous vibration frequency resulting from non‐linear hysteresis. The spectral window for an undamped MDOF system is identical with the set of squared participation factors associated with vibration modes. It was found that the increase in damping factor and the increase in participation of higher modes provide wider spectral windows, resulting in more flattened or unaltered energy‐input spectra due to enhanced smoothing effects.
Prediction of the seismic capacity of RC structural walls by non‐parametric multidimensional regression
Authors: Peruš Iztok , Fajfar Peter , Grabec Igor 
Published: April 2007

AbstractThe use of a non‐parametric multidimensional regression is suggested for the prediction of the seismic capacity of reinforced concrete structural walls. This capacity is expressed in terms of the shear strength, drift, ductility and failure mode of the walls. For the application of the method a data base is needed which contains data on the results of tests performed on the structural elements under consideration. The data base used in the study was compiled from the available literature, and includes data from laboratory tests carried out on 262 structural walls. The method was validated by comparing the predicted and test results. A comparison with some available closed‐form empirical predictions has been made. The results show that the accuracy of the predictions obtained by the proposed method is, on average, higher than that provided by existing formulae.The proposed method has several advantages when compared to closed‐form empirical expressions based on standard linear regression: (1) The relationship between the input and output variables is not selected a priori by a prediction law. (2) It takes into account the currently available data base, which can be updated when new information becomes available. (3) An arbitrary number of input and output variables can be taken into account using the same data base. (4) The method can be applied directly to similar problems in structural and earthquake engineering, wherever a suitable data base is available.
Seismic response statistics of SDOF system to exponentially modulated coloured input: An explicit solution
Authors: Fu Gongkang 
Published: April 2007

AbstractFor single‐degree‐of‐freedom systems, this paper presents an explicit solution of response statistics to earthquake excitation modelled by modulated filtered white noise. The modulation is described by the sum of exponentially decaying functions, accounting for non‐stationarity of strong ground motion. The solution was obtained by analysis in the time domain using the state‐space approach and impulse responses. This solution is reducible to several known solutions for simpler cases. Also, it may be used to develop probabilistic seismic response spectra for design and retrofit of structures, such as highway bridges.
Base uplifting analysis of flexibly supported liquid‐storage tanks
Authors: Malhotra Praveen K. 
Published: April 2007

AbstractAn approximate method is presented for the analysis of earthquake induced uplifting in base plates of unanchored liquid‐storage tanks that are supported directly on flexible soil foundations. The method takes due account of the non‐linearities arising from the continuous variation of base contact area, membrane action and plastic yielding in the base plate. First, an ‘exact’ solution is presented for a uniformly loaded flexibly supported prismatic beam, uplifted by a concentrated force applied at one end. A series of such beams are later used in an approximate model of the base plate. The method is highly efficient and believed to be accurate for the level of uplifts encountered in practice. The results are presented for a range of foundation stiffness, representing loose sandy soils to rigid concrete mat. It is shown that, for the same overturning base moment, the flexibly supported tanks, in comparison with the rigidly supported tanks, experience significantly smaller axial compressive stress, but larger base uplift, foundation penetration, plastic rotation at plate boundary and hoop compressive stress in the tank wall.
Experimental study of base isolation by free rolling rods
Authors: Lin Tsung‐Wu , Chern Ching‐Churn , Hone Chao‐Chi 
Published: April 2007

AbstractExperimental and analytical studies of base isolation by free rolling rods under basement are described in this paper. The tests of the system, a one‐storey, 326‐kg structure mounted on a set of free rolling rods, is carried out on a 3m × 3m shaking‐table. The dynamic behaviour of the isolated structure is studied and used to verify the analytical results. In the isolation system, the coefficient of kinetic rolling friction, measured at different angular velocities, ranges from 0·0007 to 0·0016. The coefficients are reduced by decreasing the angular velocities. Two earthquakes, a short‐period and a long‐period motion in Taiwan, are utilized as the input signals. The accelerations experienced by the superstructure are decreased by factors of 56 and 60 in comparison with the fixed‐base condition for the two input earthquakes. Also, for each test, the peak relative‐to‐ground displacement of the basement is nearly equal to the peak ground displacement, and the permanent displacement of the basement is present after the end of the earthquake. Finally, tests of the system with a recentring‐force device is undertaken, where a soft spring added to the basement reduces efficiently the permanent displacement. Comparisons show a good agreement between experimental and theoretical results.
Composition of the leaf, flower and fruit volatile oils of Pittosporum tobira (Thunb.) W. T. Aiton grown in three locations in Portugal
Authors: Rodrigues Frederico S. L. M. , Antunes Luisa C. S. , Figueiredo A. Cristina , Costa Monya M. , Pereira João D. Silva , Colaço Renato D. Reis , Miranda Hélder H. S. , Barroso José G. , Pedro Luis G. , Scheffer Johannes J. C. 
Published: April 2007

AbstractThe yields of the essential oils isolated from the aerial parts of Pittosporum tobira grown in three different locations in Lisbon, Portugal, were determined by hydrodistillation; the chemical composition of the volatile oils, isolated by distillation–extraction, was analysed by GC and GC–MS. In the oils of the three aerial parts studied (leaves, flowers and fruits), in total 49 compounds were identified. The oil samples from the different aerial parts of P. tobira were isolated in yields of <0.05–0.17% by volume/fresh weight (v/f.w.). n‐Nonane was the most abundant component of all samples (26–68%) and myrcene (2–24%) was the second most abundant. There were no major differences between the oil compositions for the three collection sites or for the distinct aerial parts. Despite variations in the relative amounts of the main components of the oils isolated from both the leaves and fruits, over time, no main dissimilarities were detected between the collective and individual samples, or between the different collection sites. Copyright © 2007 John Wiley & Sons, Ltd.
Depression and chronic medical illnesses in Asian older adults: the role of subjective health and functional status
Authors: Niti Matthew , Ng Tze‐Pin , Kua Ee Heok , Ho Roger Chun Man , Tan Chay Hoon 
Published: April 2007

AbstractObjectiveDepression in elderly is reportedly associated with a number of specific chronic illnesses. Whether each of these co‐morbid associations results uniquely from disease‐specific psychobiological responses or is mediated by non‐specific factors like subjective health and functional status is unclear.MethodAnalysis of data of 2,611 community‐dwelling Chinese aged 55 and older, including depressive symptoms defined by Geriatric Depression Scale score ≥ 5 and self‐reports of specific chronic illnesses.ResultsThe prevalence of depressive symptoms was 13.3%, lower in those without chronic illness (7.5%), and higher in those with illnesses (13.2–24.2%). Crude Odds Ratios (OR) were significantly elevated for hypertension, eye disorders, diabetes, arthritis, ischemic heart disease, asthma/COPD, stroke, osteoporosis, heart failure, thyroid problem, and gastric problem. In multivariable analyses, only asthma/COPD [OR:2.85, 95% Confidence Intervals (CI): 1.36, 5.98], gastric problem (OR:2.64, 95% CI: 1.11, 6.29), arthritis (OR:1.87, 95% CI: 1.02, 3.42) and heart failure (OR:2.11, 95% CI: 0.98, 4.58) remained independently associated with depressive symptoms, after adjusting for comorbidities, subjective health and functional status, cognitive functioning, smoking, alcohol, psychosocial and demographic variables.ConclusionMost comorbid associations of depressive symptoms with specific chronic illnesses are explained by accompanying poor self‐reported health and functional status, but some illnesses probably have a direct psychobiological basis. Copyright © 2007 John Wiley & Sons, Ltd.
Prospective randomized clinical trial of the effect of needle size on pain, sample adequacy and accuracy in head and neck fine‐needle aspiration cytology
Authors: Brennan Peter A. , Mackenzie Neil , Oeppen Rachel S. , Kulamarva Gautham , Thomas Gareth J. , Spedding Anne V. 
Published: April 2007

AbstractBackground:Fine‐needle aspiration cytology (FNAC) is useful in the diagnosis of many conditions of the head and neck. No reported studies have investigated the optimal needle gauge in the head and neck region.Methods:This was a prospective randomized trial of 100 patients who required FNAC performed with either a 21G or 23G needle. Discomfort was scored by patients using a visual analogue scale. Sample accuracy was assessed in patients who subsequently had excision biopsy.Results:FNAC performed with a 23G needle was less painful (mean ± SE, 1.6 ± 1.01) than FNAC with a 21G needle (3.3 ± 1.94; p < .001). There was no difference in sample adequacy between the 2 needle sizes (p = .59). The sensitivities and specificities of both needles were similar.Conclusion:Head and neck FNAC should routinely be performed with a 23G needle, resulting in less patient discomfort, and giving sample adequacy comparable to a conventional 21G needle. © 2007 Wiley Periodicals, Inc. Head Neck, 2007