Enhanced Seismic Retrofit of a Reinforced Concrete Building of Architectural Interest

Modern heritage buildings designed in the 1950s and 1960s often feature poor seismic performance capacities and may require significant retrofit interventions. A representative case study in Florence, i.e., the edifice housing the Automobile Club Headquarters, is examined here. The building was designed in 1959 with an articulated reinforced concrete structure and presents some enterprising solutions for the time, including suspended floors accommodating large glazed curtain wall façades in the main halls. The original design documentation was collected with accurate record research and checked with detailed on-site surveys. Based on the information gained on the structural system by this preliminary investigation, a time-history assessment analysis was carried out. Remarkable strength deficiencies in most members and severe pounding conditions between the two constituting wings, which are separated by a narrow technical gap, were found. As a result, a base isolation retrofit hypothesis is proposed in order to improve the seismic response capacities of the building without altering its elegant architectural appearance, being characterized by large free internal spaces and well-balanced proportions of the main structural members. A substantial performance improvement is obtained thanks to this rehabilitation strategy, as assessed by the achievement of non-pounding response conditions and safe stress states for all members up to the maximum considered normative earthquake level. Furthermore, the very low peak inter-storey drifts evaluated in retrofitted conditions help in preventing damage to the glazed façades and the remaining drift-sensitive non-structural components.

Neonatal brain ultrasound training for beginners: Could a head phantom be useful?

Background The traditional method of teaching the technique of neonatal brain ultrasonography is based upon the interaction between the practitioner and the neonate under the supervision of a tutor. This approach has disadvantages in that it may result in a longer imaging examination and the patient may become agitated. As demand for ultrasound services escalates and departments get busier, this often means that the trainee and supervisor are under pressure to work rapidly. Such environments are common but not conducive to the development of adequate skills and competencies. A neonatal head phantom used as part of a dedicated study day could help the beginner to learn basic elements of the ultrasound examination within a safe stress-free environment. It offers the opportunity to repeat the examination as often as the trainee wishes without time pressures and the distraction of a moving and potentially very sick baby. Aim The aim of this study is to evaluate the efficacy of a commercial phantom as a means for the practitioner to acquire the fundamental principles of neonatal brain ultrasound. Method A total of 17 participants attending a one day neonatal ultrasound course aimed at beginners were invited to complete a short two-part questionnaire that assessed their perceived improvement in scanning ability before and after using a commercially available head phantom. Results Of the 14 returned questionnaires, the overall perceived understanding, ability and confidence improved and anxiety levels about the procedure fell. The median pre-training score was 9.0 compared with the median post-training score of 12.0 (P = 0.005, Wilcoxon signed-rank test). At least 79% (up to 86%) of participants valued their experience with the phantom and would recommend the course to colleagues. Furthermore, about two-thirds reported that they would like to have additional practise with the phantom. Preliminary data from this study suggest that beginners found the head phantom useful for mastering some of the early skills required for neonatal brain ultrasound examinations, which in turn improved their confidence and reduced anxiety.

Extended Fatigue Life by Shot Peening Process via Shakedown Analysis

The goal of this work was to quantify the improvement in the fatigue limit of solid structures which have undergone shot peening (SP) by small rigid particles. The work was based on Melan’s shakedown theorem for estimating the allowable safe stress amplitude (in a lower bound sense) of structures that otherwise might fail during fatigue loading by plastic strain accumulation (ratcheting). Aided by geometrical simplification (mainly by assuming that the residual craters of the peened surfaces are shallow and flat), the benefit of SP to increase fatigue limits of structures subjected to fluctuating loads was quantified and compared to experiments. As a by-product, the long-time accepted empirical formulas for decreasing fatigue limits due to an increase of the loading mean tensile stress (Gerber, 1874, Z Bayer Arch Ingenieur-Vereins, 6, pp. 101–110; Goodman, 1899, Mechanics Applied to Engineering, Longmans, Green, London) have received a theoretical justification from shakedown analysis. The suggested empiricism-free solution traces well Gerber and Goodman’s empirical formulas in the positive mean stress regime of the applied load. It has a notable advantage that it also smoothly extends to the negative mean-stress regime (akin to the superimposed residual compressive stresses in a thin layer generated by the SP process) not covered hitherto by formulas. This shakedown analysis manifests the merit of shot peening processes by showing specifically the existence of larger range of fatigue-safe stress amplitudes (or equivalently, exhibiting a prolonged fatigue life) before disruption by ratcheting. Various fatigue experiments which were found in the open literature, are in a satisfactory agreement with the theoretical analysis.

A Quick Computation of Factor of Safety for Biaxial Stress States

Determination of overall factor of safety of a design involves repeated calculation of factor of safety at critical points in the design. For a given stress state at a point, the factor of safety is calculated by first finding the principal stresses and then comparing them with the maximum safe stress that can be applied without causing failure of the material according to an appropriate failure theory. In this paper, we suggest quick and ready-to-use expressions and graphs for calculating factor of safety for biaxial stress states for a number of commonly-used failure theories. These graphs can be directly used as design charts for computing factor of safety in engineering design activities.

The Sonic Pathfinder: A New Electronic Travel Aid

The development of a new electronic travel aid is described. The aim has been to produce an aid that gives the user useful information for safe, stress-free travel rather than to provide an electronic surrogate for vision.