Fatigue assessment and deterioration effects on masonry elements: A review of numerical models and their application to a case study

Safety assessment with respect to seismic and vertical loads of existing and very old masonry structures is currently a central topic for the scientific engineering community. In particular, there are many ancient bridges still in service that are subjected to higher and more frequent cyclic loads. For these structures, it is important to determine the actual fatigue strength, rather than the ultimate carrying capacity. In this way the remaining service life, with possible traffic load limitations, may be estimated. This paper reports an updated review of the state-of-the art on recently published fatigue models that account for deterioration effects under cyclic loads. In addition, results related to fatigue performance of a bridge are shown and comments are provided. The numerical comparisons among existing fatigue models reveal that the application of the available fatigue models is particularly problematic for ancient masonry elements, where appropriate stress-life curves are required

Fatigue behaviour and residual service life of existing masonry arch bridges

The conservation and safety assessment of old masonry arch bridges represent nowadays a research field of considerable interest. Most of them are testimonies of the past with a significant historical and cultural value, and represent nowadays a large part of the transport infrastructures serving strategic link for roads and railways networks. In many cases their masonry primary elements are already deteriorated due to weather conditions and to the effects of cyclic traffic loads that are increased in both the frequency and the intensity with respect to the past. Even if the ultimate load is not reached, the cumulated damage along with the localised deterioration can reach levels not acceptable leading the entire structure out of service. This paper is addressed to the fatigue assessment of old masonry arch bridges with particular attention to the residual service life evaluation of the arch elements. Unlike of metals and metallic structures, little informations are available to date on the fatigue behaviour of masonry elements, also confirmed by the fact that there are no specific guidelines for assessing the fatigue limit and the residual life. The paper at first shows a critical review of the damage models for the fatigue performance assessment of masonry arch bridges. Then, an application to a case study is presented, where also the influence of intradosal C-FRP reinforcement on the residual service life and the ultimate capacity is discussed

Fatigue Assessment and Deterioration Effects on Masonry Elements: A Review of Numerical Models and Their Application to a Case Study

Safety assessment with respect to seismic and vertical loads of existing and very old masonry structures is currently a central topic of engineering scientific community. In particular, there are many ancient bridges still in service subjected, respect to the past, to higher and more frequent cyclic loads. For these structures it is really important to determine, rather than the ultimate carrying capacity, the actual fatigue strength. In this way the remaining service life, with also possible traffic load limitations, may be estimated. This paper reports an updated review of state of the art about the recent fatigue models published in the literature, taking also into account deterioration effects under cyclic loads. In addition, some results related to the fatigue performance of a case study are shown and commented. The numerical comparisons reveal that the application of the available fatigue model is particular problematic in the case of ancient masonry elements, where appropriate stress-life curves are required

Fibrinogen: a novel predictor of responsiveness in metastatic melanoma patients treated with bio-chemotherapy: IMI (italian melanoma inter-group) trial

PURPOSE: To evaluate a panel of pretreatment clinical and laboratory parameters in metastatic melanoma (MM) in order to verify their impact on response and survival in a single prospective multi-institutional phase III study comparing out-patient chemotherapy (CT) vs bioCT. METHODS: A total of 176 patients were randomised to receive CT (cisplatin, dacarbazine, optional carmustine) or bioCT (the same CT followed by subcutaneous IL-2 plus intramuscular α-IFN-2b). Pretreatment total leucocytes, lymphocytes, eosinophyls, C-reactive protein (CRP), lactate dehydrogenase (LDH), erytrosedimentation rate (ESR), and fibrinogen were analyzed. Some clinical parameters (performance status, age, sex, and disease site) were also considered. As we found a positive trend for bio-CT with no statistical significance in OR (25.3% vs 20.2%) and OS (11 Mo vs 9.5 Mo), all analyses are stratified by treatment arm. RESULTS: In univariate analysis, higher value of lymphocytes percentage (P < .0001), lower value of total leucocytes (P=.005), CRP (P=.003), LHD (P < .0001), ESR (P < .027), fibrinogen (P < .0001), and no liver disease were strongly related to a better survival. In a multivariate analysis, using the Cox proportional hazards model, only fibrinogen (P=.004), LDH (P=.009) and liver disease (P=.04) were found to have an independent role on clinical outcome in metastatic melanoma patients. CONCLUSION: Liver disease and higher LDH and fibrinogen levels had an important impact on survival in MM patients. In particular, fibrinogen has been recently reconsidered both for its determinant role in the host hemostatic system, and for its capability to provide protection against NK and LAK-cell-induced lysis. These observations could have some important implications for therapeutic approaches, in particular when immunological strategies are used

Fatigue behavior of ancient masonry arch bridges: residual service life evaluation using stress-life curves method

The conservation and safety assessment of old masonry arch bridges represent nowadays a research field of considerable interest. Most of them are testimonies of the past with a significant historical and cultural value, and represent nowadays, a large part of the transport infrastructures serving strategic link for roads and railways networks. In many cases, their masonry primary elements are already deteriorated due to weather conditions and to the effects of cyclic traffic loads that are increased in both the frequency and the intensity with respect to the past. Even if the ultimate load is not reached, the cumulated damage along with the localised deterioration can reach levels not acceptable, leading to the out of service of the entire structure. In this paper, different models are applied in according to the stress-life curve method for estimating the fatigue strength and residual service life of a case study, an Italian ancient multi-span masonry arch bridge still in service

Stress-Life Curves Method for Fatigue Assessment of Ancient Brick Arch Bridges

Estimating the saftey of an ancient masonry arch bridge is a legitimate, but very interesting, structural engineering challenge. This is due to the fact that most of these bridges are still in service and suffer from higher and more frequent cyclic loads, a problem not encountered in the past. Therefore, for these structures it is important to know the actual fatigue strength rather than the ultimate carrying capacity in order to provide useful indications on the remaining service life with also possible traffic load limitations. In this article, different models are applied according to the stress-life curve method for estimating the fatigue strength of a case study: an ancient multi-span masonry arch bridge still in service. The obtained results highlight that, unlike steel elements, current design codes do not provide any relevant indication as to the fatigue strength assessment of existing masonry membratures. Moreover, appropriate stress-life curves are needed for evaluating the actual capacity and residual service life of low-strength masonry elements under cycling loads

Seismic performance evaluation of multi-span existing masonry arch bridge

Existing old masonry arch bridges represent an architectural and cultural heritage of inestimable value, assuming nowadays an important strategic role since most of them are still in service and link roads of primary importance for vehicular traffic. They were mostly built in the last century without considering any horizontal action, and nowadays are serving roads characterized by a transit loads certainly heavier and more frequent than the ones of past. Moreover, very often due to absence of maintenance and to weathering conditions, the elements deteriorate more and more with a consequent loss of integrity and reduction of their carrying capacity. In this paper the seismic assessment of an old multi span masonry arch bridge still in service is illustrated. Pushover analyses are performed with the aim to investigate the numerical model sensitivity and the influence on the global nonlinear response of the bridge components

Seismic assessment of old existing masonry arch bridges: an application to a case study

Masonry arch bridges are widely spread in Europe and they still serve nowadays many roads characterized by an important vehicular traffic. Moreover, most of them result inadequate since they have been designed mainly for vertical traffic loads by neglecting the lateral earthquake action. For this reason the seismic assessment of old masonry arch bridges becomes a complex matter of structural engineering in conjunction with the fact that, very often, the materials deteriorate and worn away because of cyclic vertical loads and weathering conditions. This paper presents the seismic assessment of an Italian multispan masonry arch bridge built before the Second World War. The bridge is actually in service and crosses the " Cavone River " (in the Southern Italy), from which takes the name. A series of nonlinear analyses are performed in order to investigate the nonlinear response of the bridge and for evaluating its seismic performance

Fatigue assessment of old existing masonry arch bridges: critical review of research and application to a case study

The conservation of old masonry arch bridges is nowadays a very interesting engineering challenge since mostly of them are still in service and are subjected, differently from the past, to higher and more frequent traffic loads. Therefore, it is very important to properly predict the actual behavior under cyclic loadings taking into account the fatigue strength of the masonry and its resistance degradation due to repeated loads. In this paper modeling criteria and assessment procedures of masonry arch bridges are being critically reviewed. A particular attention is given to the fatigue behavior under cyclic loads and to residual life evaluation. The paper concludes with some numerical investigations on an existing multi-span Italian masonry bridge with backfill above the arches in order to assess the fatigue bridge capacity

A study of local collapse mechanisms of an ancient church in Matera

The conservation and protection of the Italian architectural heritage is a current and particularly interesting theme for the scientific community. A part of this historical heritage is represented by worship places made traditionally with masonry systems that result, nowadays, still open to the public. In this work, particular attention is paid to the churches typology found within the “Sassi” UNESCO site of Matera. They are very often built with calcarenite masonry, a local rock also frequently named “tuff”, and show a high degree of seismic vulnerability also facilitated by many factors such as, for example, the material inhomogeneity, the low connections among the structural elements in conjunction with an inadequate maintenance status. In this paper the most vulnerable local collapse mechanisms of an ancient masonry church are at first individuated and, then, analytically evaluated. Two different approaches are followed: by using the classical kinematic linear analysis, and by simulating the nonlinear response of these macro-elements by the means of nonlinear pushover analyses. Moreover, in the paper some comparisons among the obtained results are shown