Effects of vertical ground motions on the dynamic response of URM structures: Comparative shake‐table tests

AbstractThis paper discusses the results of an experimental study aimed at evaluating the influence of the vertical ground motion component on the seismic performance of unreinforced brick‐masonry buildings. The research was motivated by post‐earthquake observations of significant structural damage in the vicinity of the fault, where horizontal and vertical ground motions are often strong and synchronized. Vertical accelerations can fluctuate gravity loads, which control the in‐plane lateral load capacity of masonry piers and affect the out‐of‐plane overturning stability of thin walls. Such phenomena seem not to be sufficiently explained in existing literature, while experimental evidence is undoubtedly missing. Here, the damage potential of vertical accelerations was investigated through a series of multidirectional shake‐table tests on full‐scale structures under simulated near‐source ground motions of increasing intensity. The experiments comprised three nominally identical building specimens subjected to the principal horizontal component alone, the horizontal component combined with the vertical one, and the full three‐component ground motion. The buildings included structural/nonstructural elements (e.g., gables, chimneys, and parapets) sensitive to gravity load variations due to their low axial loads. Two different sets of three‐component earthquake records were employed to assess the effects of both tectonic and induced seismicity scenarios. Overall, the vertical earthquake motion did not cause appreciable differences in the behavior of the buildings. Any influence on the strength and peak response of structural/nonstructural walls was marginal and non‐systematic. Data and observations from these experiments add substantially to our understanding of the vertical acceleration effects on masonry structures

Full‐scale shake‐table tests on two unreinforced masonry cavity‐wall buildings: effect of an innovative timber retrofit

AbstractTwo full-scale building specimens were tested on the shake-table at the EUCENTRE Foundation laboratories in Pavia (Italy), to assess the effectiveness of an innovative timber retrofit solution, within a comprehensive research campaign on the seismic vulnerability of existing Dutch unreinforced masonry structures. The buildings represented the end-unit of a two-storey terraced house typical of the North-Eastern Netherlands, a region affected by induced seismicity over the last few decades. This building typology is particularly vulnerable to earthquake excitation due to lack of seismic details and irregular distribution of large openings in masonry walls. Both specimens were built with the same geometry. Their structural system consisted of cavity walls, with interior load-bearing calcium-silicate leaf and exterior clay veneer, and included a first-floor reinforced concrete slab, a second-floor timber framing, and a roof timber structure supported by masonry gables. A timber retrofit was designed and installed inside the second specimen, providing an innovative sustainable, light-weight, reversible, and cost-effective technique, which could be extensively applied to actual buildings. Timber frames were connected to the interior surface of the masonry walls and completed by oriented strands boards nailed to them. The second-floor timber diaphragm was stiffened and strengthened by a layer of oriented-strand boards, nailed to the existing joists and to additional blocking elements through the existing planks. These interventions resulted also in improved wall-to-diaphragm connections with the inner leaf at both floors, while steel ties were added between the cavity-wall leaves. The application of the retrofit system favored a global response of the building with increased lateral capacities of the masonry walls. This paper describes in detail the bare and retrofitted specimens, compares the experimental results obtained through similar incremental dynamic shake-table test protocols up to near-collapse conditions, and identifies damage states and damage limits associated with displacements and deformations

Displacement Demand for Nonlinear Static Analyses of Masonry Structures: Critical Review and Improved Formulations

This paper discusses different formulations for calculating earthquake-induced displacement demands to be associated with nonlinear static analysis procedures for the assessment of masonry structures. Focus is placed on systems with fundamental periods between 0.1 and 0.5 s, for which the inelastic displacement amplification is usually more pronounced. The accuracy of the predictive equations is assessed based on the results from nonlinear time-history analyses, carried out on single-degree-of-freedom oscillators with hysteretic force–displacement relationships representative of masonry structures. First, the study demonstrates some limitations of two established approaches based on the equivalent linearization concept: the capacity spectrum method of the Dutch guidelines NPR 9998-18, and its version outlined in FEMA 440, both of which overpredict maximum displacements. Two codified formulations relying on inelastic displacement spectra are also evaluated, namely the N2 method of Eurocode 8 and the displacement coefficient method of ASCE 41-17: the former proves to be significantly unconservative, while the latter is affected by excessive dispersion. A non-iterative procedure, using an equivalent linear system with calibrated optimal stiffness and equivalent viscous damping, is then proposed to overcome some of the problems identified earlier. A recently developed modified N2 formulation is shown to improve accuracy while limiting the dispersion of the predictions

A masonry catalogue for the Groningen region

Human induced seismicity has become an uprising problem in the Groningen region of The Netherlands, in which the vast majority of buildings are non-seismically engineered unreinforced masonry houses. In order to accurately assess the seismic vulnerability of these buildings, a characterization of the constitutive masonry is required. In 2015, as a part of a larger project, a campaign on the material characterization of existing buildings was performed, including laboratory and in-situ testing of the masonry walls. The campaign constitutes the germ for the creation of a regional material properties database. 16 buildings were tested in total, comprising residential structures and schools, dating from the early ‘20s to 2005. The constitutive walls included both clay and calcium silicate brick masonry of various qualities and conditions. The in-situ testing included non-destructive tests such as rebound hammer and sonic tests, and semidestructive test, i.e. flat jack and shove test. Samples were carefully taken to the laboratory, where the destructive campaign took place, including compressive, flexural, shear and bond wrench tests. Despite of the limited number of sampled buildings, the campaign provided a better insight of the researched material. The available data suggests that the use of sub-typologies (e.g. depending of the masonry quality or condition) could reduce the dispersion on the results. A first attempt of correlation between in-situ and laboratory tests is proposed, which could benefit from further calibration. In this paper, the material characterization campaign is described, and the main outcomes are discussed

Can a Gleason 6 or Less Microfocus of Prostate Cancer

Prostate cancer (PC) remains a cause of death worldwide. Here we investigate whether a single microfocus of PC at the biopsy (graded as Gleason 6 or less, ≤5% occupancy) and the PSA <10 ng/mL can define the archetype of low-risk prostate disease. 4500 consecutive patients were enrolled. Among them, 134 patients with a single micro-focus of PC were followed up, and the parameters influencing the biochemical relapse (BR) were analysed. Out of 134 patients, 94 had clinically significant disease, specifically in 74.26% of the patients with PSA <10 ng/mL. Positive surgical margins and the extracapsular invasion were found in 29.1% and 51.4% patients, respectively. BR was observed in 29.6% of the patients. Cox regression evidenced a correlation between the BR and Gleason grade at the retropubic radical prostatectomy (RRP), capsular invasion, and the presence of positive surgical margins. Multivariate regression analysis showed a statistically significant correlation between the presence of surgical margins at the RRP and BR. Considering a single micro-focus of PC at the biopsy and PSA serum level <10 ng/mL, clinically significant disease was found in 74.26% patients and only positive surgical margins are useful for predicting the BR

Disease-specific and general health-related quality of life in newly diagnosed prostate cancer patients: The Pros-IT CNR study

Background: The National Research Council (CNR) prostate cancer monitoring project in Italy (Pros-IT CNR) is an observational, prospective, ongoing, multicentre study aiming to monitor a sample of Italian males diagnosed as new cases of prostate cancer. The present study aims to present data on the quality of life at time prostate cancer is diagnosed. Methods: One thousand seven hundred five patients were enrolled. Quality of life is evaluated at the time cancer was diagnosed and at subsequent assessments via the Italian version of the University of California Los Angeles-Prostate Cancer Index (UCLA-PCI) and the Short Form Health Survey (SF-12). Results: At diagnosis, lower scores on the physical component of the SF-12 were associated to older ages, obesity and the presence of 3+ moderate/severe comorbidities. Lower scores on the mental component were associated to younger ages, the presence of 3+ moderate/severe comorbidities and a T-score higher than one. Urinary and bowel functions according to UCLA-PCI were generally good. Almost 5% of the sample reported using at least one safety pad daily to control urinary loss; less than 3% reported moderate/severe problems attributable to bowel functions, and sexual function was a moderate/severe problem for 26.7%. Diabetes, 3+ moderate/severe comorbidities, T2 or T3-T4 categories and a Gleason score of eight or more were significantly associated with lower sexual function scores at diagnosis. Conclusions: Data collected by the Pros-IT CNR study have clarified the baseline status of newly diagnosed prostate cancer patients. A comprehensive assessment of quality of life will allow to objectively evaluate outcomes of different profile of care

Seismic bridge response modification due to degradation of viscous dampers performance

The goal of this thesis is to analyze the variation of a seismic response of a bridge in case of degradation of installed viscous fluid damper. The study was conducted with nonlinear time-history analyses of a detailed three- dimensional FE model of the Vincent Thomas Bridge, provided by Caltrans. Three different type of excitations were used (two white noises and a real measured earthquake). Such numerical model, including cables, suspenders, suspended structure, towers, cable bents and anchorages, reflects the state of the structure after the last retrofit phase, when dampers and fuses were installed and towers were stiffened. A preliminary validation of the numerical model of the bridge, aimed to ensuring the reliability of the FE model, has been carried out by comparing the numerical response with recorded signals. The degraded performance of the dampers was simulated through the use of gap, spring and viscous elements and validated against experimental results of real devices. The parametric study was intended to investigate the effects of progressive degradation of the energy dissipators on the bridge structural performance, both under service load conditions and seismic excitations. Results indicated a significant level of relative displacement experienced by the devices during daily loading conditions, potentially resulting in a premature degradation due to wear of the internal components of the units. For this reason an alternative device was proposed at least in conceptual terms, in order to decompose the dampers during service loading and to engage then only in case of seismic event. A solution to the early degradation of the damper devices has been propose

Experimental campaign on double-leaf stone masonry specimens at the University of Pavia and EUCENTRE Pavia

Seismic response of unreinforced masonry (URM) structures is influenced by the behaviour of spandrel elements, as also demonstrated by numerical simulations and post-earthquake observation. Until recently, the understanding of the seismic behaviour of these structural components was not supported by adequate experimental tests. Only in the last few years some experimental programs have been performed with the purpose of studying the in-plane cyclic behaviour of masonry spandrel beams, made of clay bricks or perforated blocks. The experimental study presented in this work aims at investigating the seismic behaviour of stone masonry spandrels, both in the presence or in the absence of a horizontal tensile resistant element. For this reason, an experimental apparatus was designed in order to test full-scale masonry spandrel specimens. The test setup allows one to investigate the behaviour of spandrels reproducing realistic boundary conditions in the element; in particular, attention was paid to the connection between spandrel and piers. Cyclic quasi-static tests were performed on four specimens in EUCENTRE Lab, University of Pavia, Italy. The specimens were made of double-leaf stone masonry with 2 different geometries and different horizontal force and timber lintel configurations. The deformation field of the masonry was monitored also by high precision infrared camera able to position a series of passive markers glued on the specimen