Nonlinear Site Response During the 7 September 1999 Athens, Greece, Earthquake (M\u3csub\u3eW\u3c/sub\u3e 5.6)

The largest available strong-motion recording (PGA=0.35g), least affected by topography, structural response and/or soil-structure interaction, is investigated for possible nonlinear site response during the M, 5.9 Athens earthquake of 7 September 1999. Smoothed horizontal-to-vertical spectral ratios (HVSR) are calculated in subsequent overlapping 3.5-s windows, thus covering a wide range of excitation levels. Mean HVSR curves are computed for a so-called “weak-“ and “strong-“ motion range (mean horizontal ground acceleration in window, MGA\u3c=10.2 cm/s/s and \u3e=20.5 cm/s/s). The two curves have similar shape, with the “strong” curve visibly shifted toward lower frequencies relative to the “weak” one; the dominant site resonance occurs at 4.0 Hz (0.25 s) and 4.7 Hz (0.21 s), respectively. Linear correlation analysis shows that the resonance frequency, f0, and MGA are significantly correlated (t=-0.661). We attribute this behaviour to the degradation of the sediment shear modulus (nonlinearity). Our results, combined with indications that sediment sites in the near-fault area were exposed to ground shaking well above PGA=0.35 g during the earthquake of 7 September 1999, imply that these sites exhibited considerable nonlinear response

Influence de la taille des grains et de l’altération des roches sur les mesures de l’atténuation des ondes ultrasonores en laboratoire

On présente une méthode de mesure en laboratoire, sur éprouvette de roche « sèche », de l'atténuation des ondes longitudinales. La mesure s'effectue par transmission, à l'aide de transducteurs piézo-électriques ; le signal reçu est étudié soit dans sa forme temporelle, soit après transformée de Fourier (en particulier la méthode du rapport de spectres est utilisée). On étudie l'atténuation sur deux séries de roches :

Variation of p-multipliers for pile groups in clayey soils

A common approach to assess the diverse response of the piles forming a pile group is the p-multipliers method. Although several studies have been occupied with the estimation of p-multipliers, usually assigned for pile group rows, they lead to values corresponding to specific soil conditions and pile group configuration. The aim of this study is to evaluate the variation of the aforementioned factors and for this purpose the results of a parametric three-dimensional nonlinear numerical analysis were used. The influence of the number of piles, the spacing, the soil shear strength and the deflection level on p-multiplier values is discussed and compared with values proposed by other researchers. © 2012 American Society of Civil Engineers

Design of reinforced embankments: Limit equilibrium and numerical methods

The aim of this paper is a comparative study of a reinforced embankment using two different design approaches. The first methodology is based on the limit equilibrium approach and the fundamental aspect of achieving equilibrium of forces and/or moments along predefined failure surfaces. The approach is widely used due to its simplicity and leads to an adequate and safe design, considered in many codes, by providing a global safety factor. However, it lacks the ability of predicting the kinematic field and the level of stresses, while a main shortcoming is the incapacity of materials to vary their ultimate strength in relation with the stress path. In the second approach, the powerful tool of numerical analysis is applied, providing the ability of modeling the mechanisms developed and allowing for shear strength variation with regard to stress and displacement field. In addition to estimating the safety factor, numerical analysis provides both displacement and stress field, indicating the areas where failure is to initiate and progress. Several numerical analyses under static and seismic loading have been carried out in order to assess the effect of both the multi-stage modeling and the creep action on the response of a reinforced embankment. Quantitative and qualitative comparison of the results arising from the aforementioned approaches is made and the main advantages and drawbacks are discussed

Analysis and design of reinforced embankments: Methodology, implementation and impact of critical parameters

This paper outlines the basic principles of analysis and design of reinforced embankments, according to the 'Design & Construction Guidelines' of the U.S. Department of Transportation, which are based on limit equilibrium principles. In addition, a case study of a high reinforced embankment with gabion's facing is presented, with reference to the parameters of design, the stages of analysis and design process, technical specifications and structural details of the project

Could the postoperative residual of urine predict the outcome of TVTOmidurethral sling procedure in female patients?

Objective: To assess if the amount of postoperative postvoid residual of urine that is within the normal range (less than 100 mls) could predict the outcome of TVTO (Tension –free vaginal tape obturator) procedure. Study design: Second Department of Obstetrics and Gynecology, Aretaieio Hospital, University of Athens, Greece. Patients that had been submitted to TVTO procedure between 2013 and 2017 were reviewed and outcome was assessed.The follow up assessment included cough stress test, the Patient Satisfaction Questionnaire (PSQ), the Urinary Distress Inventory-6 (UDI-6) and the Patient Global Impression of Improvement (PGI-I) questionnaire. Results: The mean follow-up was 3.7 years (+1.35 years). Forty eight patients (40.3%) had only a TVTO procedure. Forty three patients (36.1%) had a TVTO procedure combined with anterior colporrhaphy. Twenty eight patients (23.6%) underwent a TVTO procedure and anterior colporrhaphy and posterior colpoperineorrhaphy. According to cough stress test 88% patients (105/119) were cured having a negative cough stress test. Using logistic regression analysis it was found that patient's age (p = 0.78), postoperative postvoid residual of urine (= 0.24) or day of catheter removal (p = 0.22) had no statistically significant correlation with the medium term outcome of TVTO procedure. Also, regression analysis shows that patients’ Body Mass Index (BMI) has negative correlation to the postoperative outcome. Conclusion(s): PVR < 50 mls appears to be related with successful medium term outcome after TVTO procedure. Also, patients’ (BMI) has negative correlation to the postoperative outcome. © 2019 Elsevier B.V