Statistical physics and epidemic inference: methods and applications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Dissipative steel exoskeletons for the seismic control of reinforced concrete framed buildings

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Effects of the long‐term behaviour of isolation devices on the seismic response of base‐isolated buildings

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Magnetic damped links to reduce internal seismic pounding in base-isolated buildings

AbstractA limited gap between closely spaced structural parts may induce internal pounding in seismically isolated structures, because of notable displacement at the level of the isolation system under severe earthquakes. A gap between a fixed-base elevator shaft and the surrounding building is presented here with reference to a reinforced concrete building located in the Sicilian town of Augusta. The building, comprising a basement and three storeys above the ground level, is seismically isolated at the top of rigid columns in the basement with a hybrid isolation system including elastomeric and sliding bearings, while a steel framed elevator shaft crosses the isolation level. Despite the gap, internal pounding may occur at all levels of the superstructure when the elevator with maximum load stops at the upper floors. To reduce structural pounding effects, a magnetic damped link (MDL) between adjacent corners of the elevator and the surrounding building is proposed. This is obtained as an in parallel combination of an eddy current damped link (ECDL) and an elastic helicoidal spring, and occupies less space than traditional passive dampers and transmits considerably less forces compared to a rigid link configuration. Specifically, an ECDL consists of an outer cylindrical copper tube, as conductor, and an inner tube, equipped with an array of axially magnetized and ring-shaped permanent magnets separated by iron pole pieces, as mover. The relative motion between conductor and magnets, during seismic loading, induces an eddy current producing electromagnetic damping. Given that viscoelastic linear behaviour can be hypothesized for the MDL, a simplified iterative design procedure of the ECDL is proposed, with optimization of the thickness and radius of the magnets, thereby enhancing magnetic flux and energy dissipation. The directionality of the near-fault ground motions is investigated through nonlinear seismic analysis, comparing no connection with four configurations of the interconnection: i.e., flexible and rigid elastic links, viscous and magnetic damped links

Nonlinear modelling of the in-plane-out-of-plane interaction in the seismic analysis of masonry infills in r.c. framed buildings

Abstract A five-element macro-model, with four diagonal out-of-plane (OP) nonlinear beams and one horizontal in-plane (IP) nonlinear truss, takes into account the OP and IP failure modes occurring, in the event of seismic loading, for masonry infills (MIs) inserted in reinforced concrete (r.c.) framed buildings. Pivot hysteretic models predict the nonlinear IP and OP force-displacement laws of the infill panel, based on geometrical rules defining loading and unloading branches. Firstly, a calibration of the proposed IP-OP interaction model of MIs is carried out considering full-scale experimental results of traditional masonry typologies. To evaluate the interaction, the numerical results of simultaneous IP and OP cyclic tests on MIs at the top, intermediate and lowest levels of an existing six-storey r.c. framed building are presented, assuming different displacement histories: i) OP loading faster than IP, at the sixth storey; ii) equal IP and OP loading, at the third storey; iii) IP loading faster than OP, at the first storey

In-plane and out-of-plane seismic damage of masonry infills in existing r.c. structures: the case study of De Gasperi-Battaglia school in Norcia

AbstractA significant correlation between the in-plane (IP) and out-of-plane (OOP) damage propagation of masonry infills (MIs) is frequently observed after strong earthquakes, posing a serious problem as regards vulnerability of public buildings such as schools. The present work is aimed at identifying the effects of different IP and OOP modelling assumptions of MIs on their seismic damage. To this end, the state secondary school De Gasperi-Battaglia in Norcia (Italy), object of monitoring by the Department of Civil Protection since 2000, is investigated for the heterogeneity of infill typologies. The school is composed of a basement and three storeys above ground level, with a reinforced concrete (r.c.) framed structure having a long-shaped rectangular plan. Two typologies can be identified in terms of transverse layout of MIs: (i) double-leaf interior partitions, made of hollow clay bricks; (ii) double-leaf exterior infill walls, constituted by facade solid bricks paired with hollow clay bricks. In addition, partial height infills in the longitudinal direction, due to classroom windows, make the columns susceptible to short column effects. MIs are represented by a five-element macro-model predicting both in-plane (IP) and out-of-plane (OOP) behaviour through a horizontal nonlinear truss and four diagonal nonlinear beam elements, respectively. Stiffness and strength values in the OOP direction are also reduced considering the evolution of the IP damage. Three assumptions are investigated for the behaviour of structural MIs: i.e. elastic both IP and OOP; inelastic IP and elastic OOP; inelastic both IP and OOP. Bare and infilled test structures are subjected to biaxial spectrum-compatible accelerograms, to evaluate the IP and OOP damage levels and effectiveness of the OOP simplified verification proposed by seismic codes

Effects of nonlinear modelling of the base-isolation system on the seismic analysis of r.c. buildings

Abstract Long-duration and high-amplitude horizontal velocity pulses are expected at sites located near an active fault; these are able to generate notable displacement at the level of the isolation system and pounding effects between closely spaced structural parts (e.g. in the case of an insufficient seismic gap between the elevator and building). A base-isolated commercial building, recently built in the Sicilian town of Augusta, designed in line with the former Italian seismic code, is considered as test structure. In particular, an r.c. framed structure with rectangular plan, composed of a basement and three storeys above ground level, is seismically isolated with a hybrid system including sixteen high-damping-rubber bearings (HDRBs) and twenty steel-PTFE low friction flat sliding bearings (LFSBs). An elevator shaft with steel framed structure crossing the isolation level is also placed in non symmetrical way along the longitudinal axis. A computer code for the nonlinear seismic analysis of base-isolated r.c. framed structures is improved by adding advanced nonlinear models of HDRBs and LFSBs. Finally, nonlinear dynamic analysis of the Augusta building is carried out with reference to near-fault earthquakes selected from the Pacific Earthquake Engineering Research center database and scaled in line with the design hypotheses adopted

Office High Rise Building- Fire Protection and Life Safety Analysis

This project developed the traditional prescriptive-based design analysis of the fire protection features of an existing office high rise building in the city of Sao Paulo, in Brazil. The analysis was then complemented by performance-based analysis of the building. The building is a high rise office located in a metropolitan area, provided also with underground car parking garages and a small theater. The fire protection analysis was conducted based on the local Sao Paulo state fire codes, mainly the Sao Paulo State enactment (Decreto Nº56.819/2011) and Sao Paulo Fire Department Technical Instructions; and, in addition to the local codes, the analysis was also conducted in accordance with internationally recognized codes, primarily the International Building Code (IBC 2012) and NFPA standards. The local codes requirements were compared with the international codes requirements in each section, with the objective of providing an overview of the main differences and possible opportunities for improvement or further studies. The main differences between the codes were observed in the construction features to avoid vertical fire spread, egress design, standpipe design and overall reliability and maintenance requirements for fire protection systems. A detailed discussion is presented in Section 5 Conclusion. The design of the building has been evaluated based on prescriptive requirements for construction fire resistance and compartmentation, fire detection and alarms, automatic and manual fire suppression systems, smoke management systems and egress arrangement and capacity. A performance based design was developed for six selected fire scenarios, being three fire scenarios for existing office floors of different arrangements, one for existing theater building and two proposed improvement scenarios for a specific office floor with customized internal layout. Fire scenario simulations were developed in Pyrosim to evaluate the ASET (Available Safe Egress Time) calculations and Pathfinder was used to determine the RSET (Required Safe Egress Time). A successful scenario was determined by the ASET being greater than RSET with an appropriate margin of safety, so that all occupants will reach a safe area before the environment becomes untenable. The main conclusions and recommendations are presented in Section 5 Conclusion. The building is mostly compliant with the local regulations with a few recommendations being presented. In addition, comments were made for it to be safer and, where possible for an existing building, compliant with the reference international regulations. The most important recommendations refer to the egress features (remoteness and common paths of travel), considering that there is the possibility that the two existing exits in the office floors are blocked by one fire scenario in the exit hallway. In addition to that, it is possible that the unique door leading to the hallway from either the west or east open office areas of the building is blocked by one fire. Special attention should be given to office floor layouts that are modified by tenants, where make-up air or smoke extraction flows, as well as egress paths may be different from original design. The performance based design conclusions will show this same risk when applied to the office floors, reinforcing the recommendations provided for the prescriptive based design

Mitigation of Seismic Pounding between Adjacent Buildings by means of Isolation and Supplemental Dissipation at the Base

Double concave surface slider (DCSS) is considered as an effective solution for baseisolation of existing structures located in a near-fault site, because of its capacity to notably increase horizontal displacements that can be accommodated in comparison to a single concave surface slider (SCSS) of identical in-plan dimensions. However, unexpected torsional pounding of in-plan irregular adjacent structures may be induced by variability of friction force and lateral stiffness of SCSS and DCSS, depending on the axial load and friction coefficient changes during an earthquake. Effectiveness of supplemental viscous damping at the base is studied in this work with the aim to analyse its effectiveness for limiting base displacement, so avoiding too large seismic gap requirement. Structural pounding between fixed-base and baseisolated L-shaped buildings, placed adjacent to form Tand C-shaped plans, is analysed. A simulated design of the original reinforced concrete (RC) fixed-base framed structure is preliminarily carried out in accordance to a former Italian code, for a medium-risk seismic zone. Then, seismic retrofitting with SCSSs is carried out, in order to attain performance levels imposed by the current Italian code in a high-risk seismic zone, while DCSSs have radius of curvature equal to half the SCSSs and the same friction coefficient. The insertion of additional fluid viscous dampers (FVD) at the base is examined, following damping distribution inversely proportional to the distance between the stiffness centre of the base-isolation system and the plane frame where each FVD is placed. Nonlinear modelling of SCSSs and DCSSs considers variable axial load combined with friction coefficient at breakaway and stick-slip and as function of the sliding velocity, axial pressure and rising temperature at the sliding interface. Attention is focused on the pulse-type nature of near-fault earthquakes generally observed in the velocity time-histories but largely overlooked in the acceleration ones. Automated classification algorithms using wavelet analysis are adopted to compile three datasets of seismic input rotated in the range 0°-360°, with a constant step of 15°. Distinction is made between no-pulse and velocity-pulse, the latter further categorised into non-acceleration and acceleration-pulses

Evaluation of the accuracy of a patient-specific instrumentation

Patient-specific instruments (PSI) has been introduced with the aim to reduce the overall costs of the implants, minimizing the size and number of instruments required, and also reducing surgery time. The aim of this study was to perform a review of the current literature, as well as to report about our personal experience, to assess reliability and accuracy of patient specific instrument system in total knee arthroplasty (TKA). A literature review was conducted of PSI system reviewing articles related to coronal alignment, clinical knee and function scores, cost, patient satisfaction and complications. Studies have reported incidences of coronal alignment ≥3° from neutral in TKAs performed with patient-specific cutting guides ranging from 6% to 31%. PSI seem not to be able to result in the same degree of accuracy as for the CAS system, while comparing well with standard manual technique with respect to component positioning and overall lower axis, in particular in the sagittal plane. In cases in which custom-made cutting jigs were used, we recommend performing an accurate control of the alignment before and after any cuts and in any further step of the procedure, in order to avoid possible outliers