169,794 research outputs found
Field Tests on Micropiles Under Dynamic Lateral Loading
No full textAbstractMicropiles are increasingly used as foundation support of new buildings in seismic areas as well as for the seismic retrofitting of structures that have experienced seismic damage. Hence, it is essential to enhance the knowledge of the dynamic behavior of micropiles under horizontal loading. In the present paper, first steps of an extensive experimental study carried out on two vertical micropiles in alluvial silty soil are reported. One of the vertical micropiles is injected throughout valves a-manchèttes placed along the steel core of the shaft, while the other one is simply grouted. In particular, experimental results of ambient vibration tests and impact load tests are reported and a comparison between the behavior of the vertical injected and non-injected micropiles is provided. Experimental data of impact load tests are also compared with results obtained from an analytical model
Serum Malondialdehyde Levels in Hypertensive Patients: A Non-invasive Marker of Oxidative Stress. A Systematic Review and Meta-analysis.
No full textIntroduction: Previous analyses have reported a higher malondialdehyde (MDA) serum level in hypertensive patients (HTs) compared to normotensive subjects (NTs).
Aim: We performed a systematic review and meta-analysis of these studies to offer a comprehensive information on this issue.
Methods: The PubMed, EMBASE and Web of Science databases were analysed to locate English-language articles published from January 1, 2000 up to January 1 2021. Studies were identified using the following MeSH terms: "Malondialdehyde" AND "Arterial hypertension". The difference of MDA serum levels between HTs and NTs was expressed as standardized mean difference (SMD) with 95% CI using a random-effect model.
Results: A total of of 4102 patients (2158 HTs and 1944 NTs, mean age 52.7 and 48.0 years, respectively) were included in 17 studies. Pooled mean MDA serum levels in HTs and NTs were 4.91 [standard error (SE): 0.34, 95% CI 4.23-5.59)] and 3.43 [SE 0.15, 95% CI 3.18-3.78] nmol/L, respectively. The SMD between HTs and NTs was 3.23 nmol/L (95% CI 2.54-3.92; Z-score for overall effect: 9.17, p < 0.0001, I2 = 98.6%). Egger's test resulted significant at p = 0.009 while Begg's test was not, p = 0.11. Subsequent adjustment via the trim-and-fill method did not predict a new model (studies trimmed = 0). Meta-regression analysis found no correlations either between SMD and age (p = 0.95) or BMI (p = 0.96) but a significant one considering the latitude of the study site as moderator variable (p = 0.001).
Conclusions: Among patients with HTs, serum MDA appears to have the greatest potential as non-invasive biomarkers of oxidative stress and endothelial dysfunction (ED)
The effect of tie beams on the kinematic response and impedence functions of monopile foundations
No full textThe paper focuses on the effect of tie beams on the kinematic response and impedance functions of monopile foundations. Considering a foundation system of a regular framed structure, constituted by monopiles connected with tie beams, a representative portion of the foundation is isolated by suitably modelling its boundary conditions, and kinematic Soil-Structure Interaction analyses are performed exploiting the numerical formulation proposed by Dezi et al. (2009) for the soil-pile system modelling. The model assumes a linear behaviour for the pile and is able to include the soil non linearity in a linear equivalent manner; this allows formulating the problem in the frequency domain where elastodynamic Green’s functions are used to account for the soil-pile interaction and for both the hysteretic and radiation damping. Tie beams are included into the formulation and the problem is solved by means of the finite element approach. A non dimensional parametric investigation is performed by varying the main geometrical and mechanical parameters affecting the whole system response. Results are presented in terms of impedance functions and kinematic response parameters, focusing on the effects of the foundation tie beams on the system response
Full scale experimental assessment of the dynamic horizontal behavior of micropiles in alluvial silty soils
No full textThe paper deals with an extensive experimental campaign of dynamic tests performed on full-scale vertical injected and not injected micropiles embedded in alluvial soils. The experimentation includes ambient vibration and impact load tests to investigate the dynamic behaviour of the soil-micropile system in very small and small-medium strain ranges, as well as snap back tests to investigate the evolution of the post-elastic response of the system. Micropiles are instrumented with strain gauges along the shaft, accelerometers and displacement transducers at the head. Modalities and results of the different performed tests are presented, focusing on the role of high pressure injections on the dynamic behaviour of the system, on the development of non-linear soil-pile phenomena, and, finally, on the evaluation of effectiveness of the different testing procedures to capture the dynamic response of soil-micropile systems. Ambient vibration test revealed to be a versatile method to identify the dynamic properties of soil-micropile systems, although it requires demanding post-processing techniques of data. Impact load test is faster to perform and easier to post process. Free vibration test proved to be relatively simple to perform and able to catch the
dynamic non-linear behaviour of soil-micropile systems
Full-scale experimental assessment of the dynamic horizontal behavior of micropiles in alluvial silty soils.
No full textThe effect of tie beams on the kinematic response and impedance functions of monopile foundations
No full textUso e Costo della risorsa infermieristica nei DRGs
No full textStudio multicentrico per la comparazione dei costi connessi allo stesso DRG tra diversi ospedali. L'analisi riguarda anche le specifiche attività prodotte dall'infermiere e osservate con rilevazione analitica sul campo. Prima pubblicazione sintetica di un ampio studi
Micropile foundation subjected to dynamic lateral loading
No full textThanks to their ease of installation, even in access-restricted spaces, micropiles are increasingly adopted for the seismic rehabilitation of existing structures. Moreover, both vertical and inclined micropiles are often used as foundation system for new constructions, ground improvements and many other applications. In order to deepen the knowledge of the dynamic behavior of those systems under horizontal loading, an extensive experimental study was carried out in an alluvial silty soil deposit on two single vertical micropiles and on a group of four inclined micropiles connected at the head by a concrete cap. Several testing procedures are exploited, in order to investigate the dynamic behavior of micropiles under different loading conditions and increasing force level, with special attention on the role of execution techniques and foundation configuration
Seismic Response of Bridges Accounting for Soil-Structure Interaction effects and the Non-Synchronous Ground Motion due to 1D and 2D site analysis.
No full textThis work focuses on the effects of soil-structure interaction and the spatial variability of seismic motion due to site effects on the seismic response of a multi-span viaduct on pile foundations. In particular, site effects induced in a soft clay deposit by an inclined bedrock layout are evaluated through different models, characterised by an increasing level of accuracy, which allows determining the free-field motion that is adopted to perform soilstructure interaction analyses in the frame of the substructure approach. The seismic input is represented at the outcropping bedrock by a set of suitably selected and scaled real accelerograms. After a brief presentation of the adopted numerical procedure, analyses results are presented focusing on both site and structural response. Amplifications effects obtained from simplified linear equivalent 1D and nonlinear 2D site response models are compared, discussing the applicability of the simplified approach. Structural responses, obtained by considering the non-synchronous motion resulting from the local stratigraphic conditions, in conjunction with soil-structure interaction effects, are shown in terms of piers displacement and ductility demands. Furthermore, the role of soil structure interaction is clarified comparing results with those obtained from fixed base bridge models, proving that its contribution is more significant if the simplified model for site response is adopted
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