Dynamic behaviour and seismic response of structures isolated with low shape factor bearings

This study investigates the mechanical behaviour of laminated elastomeric bearings with a low shape factor (LSF) and the dynamic response of structures mounted on them. Axial loads have a significant influence on the mechanical behaviour of the LSF bearings. Most of the existing theories and mechanical models for laminated bearings cannot be employed for LSF bearings because they disregard the important effects of axial shortening and bulging of the rubber layers on the horizontal bearing stiffness. In this study, a simplified model originally developed for slender rubber blocks is employed for describing the mechanical behaviour of LSF bearings, and validated against the experimental results on low-damping LSF bearings manufactured and tested at Tun Abdul Razak Research Center (TARRC). The proposed model is then used to simulate the seismic response of a structural prototype mounted on the low-damping LSF bearings and tested at University of Naples Federico II on a shaking table under horizontal seismic input. Further analyses are carried out to evaluate how the bearing shape factor affects the dynamic and seismic response of the prototype. The study provides some useful insight into the complex mechanical behaviour of LSF bearings and of structures mounted on them

An unusual presentation of multiple cavitated lung metastases from colon carcinoma

<p>Abstract</p> <p>Background</p> <p>Consolidation with or without ground-glass opacity is the typical radiologic finding of lung metastases of adenocarcinoma from the gastrointestinal tract. Lung excavated metastases from gastrointestinal carcinoma are very rare.</p> <p>Case presentation</p> <p>The authors describe an unusual presentation of multiple cavitated lung metastases from colon adenocarcinoma and discuss the outcome of a patient. The absence both of symptoms and other disease localizations, the investigations related to different diagnostic hypotheses and the empirical treatments caused a delay in correct diagnosis. Only a transparietal biopsy revealed the neoplastic origin of nodules.</p> <p>Conclusions</p> <p>This report demonstrates that although lung excavated metastases are described in literature, initial failure to reach a diagnosis is common. We would like to alert clinicians and radiologists to the possibility of unusual atypical features of pulmonary metastases from colon adenocarcinoma.</p

Clinical Outcomes of Patients With Metastatic Urothelial Carcinoma After Progression to Immune Checkpoint Inhibitors: A Retrospective Analysis by the Meet-Uro Group (Meet-URO 1 Study)

Background: Immune checkpoint inhibitors (ICIs) are currently the standard of care for metastatic urothelial cancer (mUC) after the failure of previous platinum-based chemotherapy. The choice of further therapy after ICI progression is a new challenge, and scarce data support it. We aimed to examine the outcomes of mUC patients after progression to ICI, especially when receiving chemotherapy. Methods: Data were retrospectively collected from clinical records of mUC patients whose disease progressed to anti-programmed death 1 (PD-1)or programmed death ligand 1 (PD-L1) therapy at 14 Italian centers. Patients were grouped according to ICI therapy setting into SALVAGE (ie, ICI delivered ⩾ second-line therapy after platinum-based chemotherapy) and NAÏVE (ie, first-line therapy) groups. Progression-free survival (PFS) and overall survival (OS) rates were calculated using the Kaplan-Meier method and compared among subgroups. Cox regression assessed the effect of treatments after progression to ICI on OS. Objective response rate (ORR) was calculated as the sum of partial and complete radiologic responses. Results: The study population consisted of 201 mUC patients who progressed after ICI: 59 in the NAÏVE cohort and 142 in the SALVAGE cohort. Overall, 52 patients received chemotherapy after ICI progression (25.9%), 20 (9.9%) received ICI beyond progression, 115 (57.2%) received best supportive care only, and 14 (7.0%) received investigational drugs. Objective response rate to chemotherapy in the post-ICI setting was 23.1% (28.0% in the NAÏVE group and 18.5% in the SALVAGE group). Median PFS and OS to chemotherapy after ICI-PD was 5 months (95% confidence interval [CI]: 3-11) and 13 months (95% CI: 7-NA) for the NAÏVE group; 3 months (95% CI: 2-NA) and 9 months (95% CI: 6-NA) for the SALVAGE group, respectively. Overall survival from ICI initiation was 17 months for patients receiving chemotherapy (hazard ratio [HR] = 0.09, p &lt; 0.001), versus 8 months for patients receiving ICI beyond progression (HR = 0.13, p &lt; 0.001), and 2 months for patients who did not receive further active treatment (p &lt; 0.001). Conclusions: Chemotherapy administered after ICI progression for mUC patients is advisable irrespective of the treatment line

A focus on the new italian guidelines for safety assessment of existing bridges (Key-note lecture)

New Italian guidelines for safety assessment of existing bridges were recently approved. This achievement was reached after the increasing number of casualites which clearly demonstrated the need for an in deep consideration of existing bridges. Actually, most of italian bridges already spent around 50 years of their service life and may require extraordinary repairs to achieve satisfactory safety levels according to latest code provisions. The guidelines represent an unprecedented document in the international context: they provide with additional analysis cases with different traffic loads and partial safety factors to be adopted in order to establish the bridge safety class at ultimate limit state. After introducing the main scope of the work, a preliminary case-study bridge with relative outcomes is proposed

An experimental study on a novel reclaimed rubber compound for fiber-reinforced seismic isolators

Classical rubber seismic isolators reinforced with steel shims are generally large, heavy, and expensive so rarely used for housing buildings. In the last few years, different technologies have been investigated and fiber reinforced elastomeric isolators (FREIs) demonstrated to be a promising option. Only by properly combining a lower cost of raw materials including the manufacturing process and an easier installation process can result in a cost-effective solution. In the present study, novel reclaimed-rubber FREIs reinforced with low cost fabrics were designed and manufactured. A reclaimed compound (RC) has been developed resulting in mechanical properties not significantly different from virgin rubber. Mechanical characterization of the RC showed a typical response of soft compound even if with lower tensile deformation capacity. RC adhesion with polyester and nylon fabrics was investigated in order to prevent debonding between different layers. In this regard recycled-rubber FREIs with polyester and nylon fabrics were manufactured and tested in unbonded configuration. The devices showed promising performance and paved the way for the development of low-cost and environmental-friendly seismic isolators for housing buildings

On the response of fiber reinforced elastomeric isolators (FREIs) under bidirectional shear loads

Fiber Reinforced Elastomeric Isolators (FREIs) have been proposed as an alternative to Steel Reinforced Elastomeric Isolators (SREIs) and several studies have highlighted the advantages of this technology over conventional devices. When FREIs are unbonded to the top and bottom substructure, the bearings exhibit softening under imposed lateral deformations with or without instability depending on the aspect ratio of the device. Research studies available in literature have focused on the response of rectangular bearings when loaded in shear along their base. Very little is known on the lateral response of these devices under bidirectional shear loading. This study aims to assess the response of rectangular FREIs under combined axial and bidirectional shear loads and to show the effects of (i) the secondary shape factor of the bearing, of (ii) the axial pressure, of (iii) the horizontal loading direction on the stability of these devices. As result of a large set of analyses, stability domains have been derived which take into account all of the variables listed above. Based on the results of this work, simple to use design considerations can be derived. Results of this study contribute towards the real implementation of this technology particularly in developing regions of the world

Seismic fragility of base-isolated single-storey unreinforced masonry buildings equipped with classical and recycled rubber bearings in Himalayan regions

Unreinforced masonry (URM) buildings are one of the most common constructions all around the world, but they are significantly prone to structural damage in case of earthquake. Due to the high vulnerability of URM buildings to seismic loading, a quantitative risk assessment along with identification of additional protection measures has become necessary. Even though base isolation is a suitable seismic protection option, its conventional cost may prevent a wide implementation in developing countries. In this context, this study presents a comparative seismic fragility analysis of a single-storey URM building before and after base isolation using both classical laminated rubber bearings (LRBs) and recycled-rubber fibre-reinforced elastomeric isolators (RR-FREIs). The main aim of the study is to assess the effectiveness of RR-FREIs as alternative to LRBs for seismic vulnerability reduction of low-resistance URM buildings located in Himalayan regions. Fragility analysis accounted for uncertainties associated with both material properties and earthquake records. The Latin hypercube sampling (LHS) technique was used to reduce the computational work while maintaining acceptable accuracy. The building response was obtained using nonlinear layered shell element models, through nonlinear time history analysis of fixed-base (FB) building models and fast nonlinear analysis of base-isolated (BI) building models. Fragility curves show a significant reduction in the vulnerability of BI buildings in comparison to their FB counterpart, as well as a satisfactory performance of RR-FREIs in comparison with LRBs. A parametric study is also discussed to identify the influence of different intensity measures, fragility analysis method, and variability in isolator properties

Stability analysis of unbonded fiber reinforced isolators of square shape

Fiber-reinforced elastomeric isolators (FREIs) are generally installed in unbonded configurations. Because of the simultaneous application of axial loads and large lateral deformations, instability of these bearings is a major concern. This paper shows the results of a large series of 3D finite element analyses (FEAs) on square-shaped FREIs. The analyses aimed at obtaining easy to use design charts where the stability limits of these devices can be rapidly determined. The output of the analyses is compared to analytical results available in literature and the limitations of well-known closed form solutions are discussed

Tuning the lateral response of unbonded fiber reinforced elastomeric isolators (U-FREIS): Experimental - Numerical findings

Fiber-reinforced elastomeric isolators (FREIs) are elastomeric devices which have been introduced as a low-cost alternative to the well-known steel-reinforced elastomeric isolators (SREIs). As common in rubber-based devices, the application of FREIs to lightweight structures is challenging: when the mass is limited, the resulting slender bearings tend to become unstable under large horizontal displacements. On the basis of numerical and experimental findings, this research work aims to demonstrate a simple to implement and low-cost approach to extend the application of FREIs to lightweight structures. The technique here discussed allows (i) to reduce the horizontal stiffness of FREIs, (ii) to increase the stability range of the bearings, and (iii) to obtain a desired hardening response for large lateral deformations, with no instability