This paper investigates the potential of combined proton-photon therapy schemes in radiation oncology, with a special emphasis on fractionation. Several combined modality models, with and without fractionation, are discussed, and conditions under which combined modality treatments are of added value are demonstrated analytically and numerically. The combined modality optimal fractionation problem with multiple normal tissues is formulated based on the biologically effective dose (BED) model and tested on real patient data. Results indicate that for several patients a combined modality treatment gives better results in terms of biological dose (up to14.8% improvement) than single modality proton treatments. For several other patients, a combined modality treatment is found that offers an alternative to the optimal single modality proton treatment, being only marginally worse but using signifcantly fewer proton fractions, putting less pressure on the limited availability of proton slots. Overall, these results indicate that combined modality treatments can be a viable option, which is expected to become more important as proton therapy centers are spreading but the proton therapy price tag remains high.

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In recent years induced seismicity in the north of the Netherlands has considerably increased. The built environment in the region mainly consists of unreinforced masonry (URM) buildings. Those buildings were not designed for seismic loads and have specific characteristics, that limit their seismic performance. In early 2017 a quasi-static cyclic pushover test on a calcium silicate element assemblage was carried out at Delft University of Technology. The assembled structure is representative of a typical terraced house built after the 1980’s in the Netherlands. The test was selected for a blind prediction contest, with the aim of (i) sharing the knowledge between consultant companies, (ii) improving the understanding of the structural behaviour of a typical URM structure, and (iii) contributing to the development of the Dutch guidelines for the seismic assessment of existing buildings. Nine engineering consultants working for the seismic assessment of the Groningen building stock participated to the contest. The predictions were characterised by different modelling methodologies, from analytical computations to equivalent-frame based or full finite element analyses. The paper presents an analysis of the submitted predictions, in an anonymous format, and trends related to the adopted analysis methodology are identified. On average, the predictions can provide a good estimate of the experimental outcomes, but a large scatter between the predicted results is observed. Finally, the received predictions have been used to assess the seismic vulnerability of the tested structure according to the recent Dutch seismic guidelines and with different assessment procedures: the assessments based on the numerical analyses were overall consistent to that based on the experimental outcomes.@en