micropile foundation subjected to dynamic lateral loading

Abstract Thanks 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

Global matrix 4.0 physical activity report card grades for children and adolescents : results and analyses from 57 countries

Background: The Global Matrix 4.0 on physical activity (PA) for children and adolescents was developed to achieve a comprehensive understanding of the global variation in children’s and adolescents’ (5–17 y) PA, related measures, and key sources of influence. The objectives of this article were (1) to summarize the findings from the Global Matrix 4.0 Report Cards, (2) to compare indicators across countries, and (3) to explore trends related to the Human Development Index and geo-cultural regions. Methods: A total of 57 Report Card teams followed a harmonized process to grade the 10 common PA indicators. An online survey was conducted to collect Report Card Leaders’ top 3 priorities for each PA indicator and their opinions on how the COVID-19 pandemic impacted child and adolescent PA indicators in their country. Results: Overall Physical Activity was the indicator with the lowest global average grade (D), while School and Community and Environment were the indicators with the highest global average grade (C+). An overview of the global situation in terms of surveillance and prevalence is provided for all 10 common PA indicators, followed by priorities and examples to support the development of strategies and policies internationally. Conclusions: The Global Matrix 4.0 represents the largest compilation of children’s and adolescents’ PA indicators to date. While variation in data sources informing the grades across countries was observed, this initiative highlighted low PA levels in children and adolescents globally. Measures to contain the COVID-19 pandemic, local/international conflicts, climate change, and economic change threaten to worsen this situation

Global Matrix 4.0 Physical Activity Report Card Grades for Children and Adolescents: Results and Analyses From 57 Countries

Background: The Global Matrix 4.0 on physical activity (PA) for children and adolescents was developed to achieve a comprehensive understanding of the global variation in children’s and adolescents’ (5–17 y) PA, related measures, and key sources of influence. The objectives of this article were (1) to summarize the findings from the Global Matrix 4.0 Report Cards, (2) to compare indicators across countries, and (3) to explore trends related to the Human Development Index and geo-cultural regions. Methods: A total of 57 Report Card teams followed a harmonized process to grade the 10 common PA indicators. An online survey was conducted to collect Report Card Leaders’ top 3 priorities for each PA indicator and their opinions on how the COVID-19 pandemic impacted child and adolescent PA indicators in their country. Results: Overall Physical Activity was the indicator with the lowest global average grade (D), while School and Community and Environment were the indicators with the highest global average grade (C+). An overview of the global situation in terms of surveillance and prevalence is provided for all 10 common PA indicators, followed by priorities and examples to support the development of strategies and policies internationally. Conclusions: The Global Matrix 4.0 represents the largest compilation of children’s and adolescents’ PA indicators to date. While variation in data sources informing the grades across countries was observed, this initiative highlighted low PA levels in children and adolescents globally. Measures to contain the COVID-19 pandemic, local/international conflicts, climate change, and economic change threaten to worsen this situation

Prove in vera grandezza e analisi numeriche di pali con forzante orizzontale impulsiva

Sommario This paper presents the results of lateral impact load field tests carried out on three steel pipe piles at the tourist port of La Spezia, Italy. The piles are vibro-driven into marine soft clay, with a L-shaped plan layout, kept free at the head. Two test campaigns are carried out, the first 1 week and the second 10 weeks after vibrodriving of the piles. The dynamic behaviour of the complex soilwaterpile system at very small strain is discussed. In particular, the response of the single pile and the mutual interaction between loaded and receiver piles are presented. The variation in dynamic behaviour of the whole system in time (for the two campaigns), due to reconsolidation of the soil close to the pile subsequent to the vibrodriving, is observed. The experimental data are compared with the results obtained from a 3-D finite element models of the whole soilwaterpile system considering both a solid and a shell model for the piles and linear behaviour for the soil

Full-scale pile subjected to different lateral dynamic loadings

This paper presents some results of dynamic lateral loading tests on a near-shore steel pipe pile vibrodriven into soft marine clay. Two typologies of tests are carried out on a free head pile: impact load tests and free vibration tests at different load levels. The aim of this experimentation is to investigate the dynamic soil-water-pile system interaction and determine the dynamic characteristics of the whole system by means of two different typologies of test and for different levels of the dynamic input. The obtained results show the complex dynamic behaviour of the vibrating soil water pile system in terms of natural frequencies and damping ratios. The values obtained from the two test typologies are compared and the variations with the level of the input force, due to the nonlinear behaviour of the system, are discussed

Experimental and numerical modal analysis of a historical masonry bridge

This paper presents the experimental test campaign and the calibration of the finite element model of a historical masonry bridge almost completely built with travertine blocks. The bridge has undergone very complex vicissitudes related mainly to exceptional river floods; it was partially rebuilt twice and other strengthening works were carried out over the time. To determine the mechanical characteristics of the materials, a campaign of experimental tests was planned encompassing onsite measurements of stresses and modulus of elasticity as well as laboratory measurements on specimens taken from the structures. Vibration tests were also carried out to evaluate the modal properties of the bridge. The acquired experimental data were used to calibrate a refined 3D model that has been developed also including the soil deposit. A very good consistency was achieved between experimental and theoretical behaviors

Dynamic tests on an existing r.c. school building retrofitted with external steel "dissipative towers

This paper deals with the dynamic tests carried out on a school building (four story reinforced concrete frame) seismically retrofitted with an innovative system that uses external steel dissipative towers. Before the retrofitting, ambient vibration tests were carried out with the aim of evaluating the actual linear dynamic of the building including the contribution of non-structural components (e.g. external and internal walls). Modal parameters determined by means of experimental tests are crucial for the final design of the retrofitting system allowing the calibration of a predicting f.e. model. Three low noise servo-accelerometers per floor were opportunely positioned at each floor to monitor its rigid motion. The modal parameters are identified with the Enhanced Frequency Domain Decomposition technique obtaining the natural frequencies, mode shapes and damping ratios. After the building retrofitting, snap-back tests at different load levels were performed in order to evaluate the dynamic characteristics of the new structural system. The load was applied in a quasi-static manner by means of two Dywidag bars 47 anchored at the last floor and connected to a steel triangular truss pulled by two hydraulic jacks; the instantaneous release was obtained by cutting a dog-bone shaped steel plate with a blowtorch. In addition to the accelerometers, displacement transducers were positioned at the base of the steel towers, close to the viscous dampers, to measure the motion of the two towers. The natural frequencies and the damping ratios of the retrofitted building are estimated from the time histories of accelerations (free decay functions) by means of the crossing time and the logarithmic decrement techniques, respectively. The adopted experimental methodology adopted has revealed to be effective for the dynamic characterization, both at very low strain and at higher strain level, of a low-rise reinforced concrete frame building in service, which is characterized by a high overall stiffness due to the contribution of the non-structural components