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The staircase method is traditionally employed to estimate the endurance limit, requiring to test of a relatively large number of specimens at several load levels to obtain a reliable dataset, making this procedure time-consuming and expensive. A rapid method, based on thermography is alternatively employed to estimate the endurance limit, intended as the fatigue strength at 1 or 2 million cycles. The procedure results in a relation between the stabilized temperature as a function of the maximum applied stress or amplitude and involves manual processing of the data to determine the endurance limit. The present paper presents a statistical model based on the Maximum Likelihood Method to estimate the endurance limit by the aforementioned thermographic method, which is automatic, and does not involve manual manipulation of the dataset., Paper 41

Background and aim of the work: The incidence of long bone non-unions has been estimated to range between 5-10%. Nonunion of fracture is a delayed complication of fracture. A large bone resection, associated with Ilizarov’s osteo-distraction technique, is commonly used in these cases. The war experience was very important for dealing with these injuries. The purpose of this study is to report whether the use of Platelet Rich of Plasma(PRP) or Hyperbric Oxygen Therapy(HOT) as an adjuvant to the osteogenic distraction of Ilizarov with respect to the classical method has advantages. Methods: From 183 tibial non union, we enrolled 50 patients suffering by Type B according ASAMI non union classification. We divided the patients into two groups. The first group was a retrospective group of patient treated by Ilizarov Tecnique plus PRP. Instead the second group, patients were treated by Ilizarov Tecnique associated with HOT. The chosen criteria to evaluate the two groups during the clinical and radiological follow-up were: the complication after the surgery in the two groups; the duration of surgery; the objective quality Bone results and functional results were evaluated according to ASAMI classification while the subjective quality of life correlated with Ilizarov frame function by the Short Form 12 Health Survey (SF-12); The correlation between bone regenerate/bone healing and X-rays. The evaluation endpoint was set at 12 months from the remotion of Ilizarov’s frame for both groups. Results: In comparing the complications of the two populations, there were a significant statistically difference(p0.05. The average Time for remove Ilizarov’s Frame in months was 15.37(±7.34; range 9–32) in PRP while in HOT was15.22(± 7.83; range 9–31), p>0.05. Conclusions: From our study we can conclude that the association of HOT and PRP with the Ilizarov technique does not improve the functional outcomes but allows a more rapid healing of the regenerated bone and therefore an early removal of the device and a corresponding improvement in the quality of life. (www.actabiomedica.it)

Aim Periprosthetic fracture after knee arthroplasty occurs more frequently in the supracondylar area of femur, especially after low energy trauma associated with torsional or compressive forces. Several techniques have been described for the treatment of displaced fractures. The aim of this study is the evaluation of the outcomes and bone healing of periprosthetic femoral fractures managed by standard plate fixation compared to plating with bone grafting. Methods Thirty-six periprosthetic fractures around the knee were selected. Eighteen patients underwent standard plate and screws fixation while other eighteen were treated by plating associate with a cortical strut. Knee Society Score (KSS) and Short Form 12 (SF12) with the UNION SCORE (RUS) were used for the evaluation of results. Results After a minimum follow-up of 12 months, the results showed a statistically significant difference in SF-12, KSS, and RUS in favour of plating associated to bone graft with respect to the plating alone; four cases of non-union were recorded in the group of patients treated by standard plating. Conclusions Our experience once again demonstrated that plating and bone grafting may ensure a mechanical and biological support for the healing of periprosthetic fracture of the knee more than simple plating.

Damping is an important parameter in the calculation of vibrations in high-rise buildings. This research presents a verification study of the Energy Flow Analysis as identification tool for damping in high rise buildings. The study investigates the magnitude of the error that can be expected with some of the assumptions and simplifications made to accommodate for the lack of information typically present in in-situ measurements. To eliminate experiment-related uncertainties, the study is performed in a controlled FEM environment. From the study it can be concluded that with a small number of monitor positions the damping prediction of the soil with the EFA is quite accurate in case of a well-known load on the high-rise building.

Hot-driven rivets were used for the construction of steel structures up until bolted and welded joints replaced them. In shear riveted connections, the applied load is transmitted by frictional and/or shear forces, depending on the magnitude of the clamping force. The clamping force, i.e. the normal force in the rivet, is correlated with fatigue life because the load transfer mechanism strongly influences the local stress distribution around the hole of the rivet. The variation in clamping force is partially responsible for the large scatter of the fatigue resistance of riveted connections when compared to the plain material. The present work shows the results of dedicated laboratory work aimed to measure the clamping force in rivets installed on a Dutch bridge, the Botlekbrug. A comparison is made with the test data present by others.

Two basic procedures are currently available to determine the critical condition of a flawed structure, at which unstable crack extension may occur. The first method based on elastic-plastic fracture mechanics is accurate but requires a time consuming elastic-plastic finite element analysis. The second method estimates the critical condition with an interaction diagram between linear elastic fracture mechanics describing brittle fracture, and a limit load analysis of the net section, i.e. the unflawed ligament. This method is simpler to use but has a lower level of accuracy. The current paper provides a third option, consisting of a constraint-modified failure assessment procedure. It uses a linear elastic solution for evaluating brittle fracture and a simplified elastic-plastic analysis for evaluating plastic collapse. This third option provides good agreement with three considered tests.

Adequacy of the Eurocode’s partial factor for fatigue design of steel joints in railway bridges is investigated in this study. The main uncertain parameters on the load side of the limit state function are studied and their influences on the reliability index are investigated through a sensitivity analysis.

Demountable connectors have been rarely applied in steel-FRP hybrid structures due to the lack of research, which could prove their reliable structural performance. In typical applications, e.g. in multi-girder hybrid decks, the connectors are not only subjected to longitudinal shear forces, but also to substantial tensile forces originated from the uneven load distribution between the girders. Therefore, the aim of this study is to investigate the feasibility of three types of bolted connectors in steel-FRP hybrid structures by examining their shear and tensile resistance. To that end, push-out and pull-out tests were conducted to determine respectively, the shear and tensile strengths of the connectors. The suitability of the connectors in typical multi-girder hybrid steel-FRP deck applications is concluded from the test results.

Reliability analysis is a crucial phase in assessing the safety status of new and existing structures. One of its applications is to predict the fatigue life of fatigue prone details. Two models are used to formulate the fatigue limit state: S-N curves in combination with Palmgren-Miner damage accumulation rule and linear elastic fracture mechanics using fatigue crack growth rate curves. Within each model, choices must be made on the values of the variables and these choices are sometimes different in different standards. This study investigates the consistency between the standards by determining the failure probability of the different models and values for a transverse butt weld joint under Variable Amplitude Loading. Partial factors required for the design are then derived as a function of the required reliability for each model and associated values. The influence of the uncertainties related to each involved variable is evaluated by performing a sensitivity analysis.

Fatigue – crack initiation and growth due to repetitive loading – is one of the main failure modes of steel bridges. To ensure the bridge safety during its lifetime, partial factors should be used on both load effects and material resistance to keep the probability of failure less than its target value, set by considering failure consequences. The current standards suggest two design methodologies. First, by using partial factors to prevent failure probability to reach its target value at the end of the life, which results in an expensive design. Second, using smaller partial factors and letting the failure probability get close to its target value but prevent failure by performing regular inspection and damage repair. While in the first method it is possible to use not large enough partial factors, in the second one, the lack of knowledge in (long) crack behavior, critical crack length and inspection interval are the main issues. The goal of this research is to solve these issues to assure fatigue safety in an economical way by making the best use of inspection techniques. Therefore, a sound physical and probabilistic approach will be followed considering the stochastic nature of involved parameters. Several possible inspection categories will be defined and for each one of them, an optimal partial factor will be set and required inspection interval and procedure will be regulated.