One of the main problems of the damages of rail tracks which is caused by track settlement is Unsupported sleeper. Due to this defect the underlying area of sleeper is not supported on the ballast and causes the sleeper displacement to increase. The increase creates vibration in the track and vehicle components and causes problems on their performance. Hence, in this study the investigation of rail displacement in tracks with Unsupported sleeper has been dealt with. Three dimensional modeling of the vehicle and ballasted track has been carried out using ANSYS and SIMPACK programs. To use this software, the modeling of a flexible track in the vehicle multibody model is possible. Ballasted track which is formed from components as rail, sleeper and ballast, has been considered to be flexible. In simulating the vehicle all of its main components have been considered and damping and stiffness values of bogie suspension systems have been considered to be nonlinear. The results obtained from numerical simulation have good agreement with field test results. The results show that the speed of the vehicle on the track displacement with less than four Unsupported sleepers has no effect, but by increasing the number of Unsupported sleepers, the effect of increasing velocity would be considerable.

The phenomenon of Unsupported sleepers is considered one of the most critical factors affecting the dynamic performance of ballasted railway tracks. Disrupting the contact between the sleeper and the ballast leads to increased deflection, stress concentration, and reduced track stability. This study aims to numerically analyze and simulate the dynamic effects of Unsupported sleepers, focusing on their numbers and layout patterns in the ballasted railway tracks. For this purpose, a three-layer mechanical model consisting of rail, sleeper, and ballast was developed in MATLAB, and its results were compared with an equivalent finite element model created in ABAQUS. The MATLAB model employs mass, stiffness, and damping matrices along with a time-dependent moving load to evaluate the system's response under various Unsupported sleeper conditions. In the ABAQUS model, sleepers and ballast were modeled as concentrated masses, with their interactions represented via equivalent spring-damper systems; loading was applied incrementally along the train path. The results indicate that increasing the number of Unsupported sleepers—particularly in sequential arrangements—significantly amplifies rail deflection and mid-span stress, with the most critical response observed in the case of three-consecutive-Unsupported-sleepers. These findings indicate the necessity of continuous monitoring and preventive maintenance of Unsupported zones to ensure track safety and extend structural service life.

The track stiffness experienced by a train will vary along the track. Sometimes the stiffness variation may be very large within a short distance. One example is when an Unsupported sleeper is hanging in the rail. Track stiffness is then, locally at that sleeper, very low. At insulated joints the bending stiffness of the rail has a discontinuity implying a discontinuity also of the track stiffness. A third example of an abrupt change of track stiffness is the transition from an embankment to a bridge. At switches both mass and stiffness change rapidly. The variations of track stiffness will induce variations in the wheel/rail contact force. This will intensify track degradation such as increased wear, fatigue, track settlement due to permanent deformation of the ballast and the substructure, and so on. As soon as the track geometry starts to deteriorate, the variations of the wheel/rail interaction forces will increase, and the track deterioration rate increases. In the work reported here the possibility to smooth out track stiffness variations is discussed. It is demonstrated that by modifying the stiffness variations along the track, for example by use of grouting or under-sleeper pads, the variations of the wheel/rail contact force may be considerably reduced.

Background and Aim: Fiber-reinforced composite (FRC) restoration is a relatively new method used to enhance the durability of composite restorations. This study measured the fracture resistance of Unsupported enamel in composite restorations reinforced with fiber ribbon in comparison with conventional composite restorations.    Materials and Methods: In this in vitro study, 30 freshly extracted sound premolars were randomly divided into three groups (n=10): (I) control group: intact teeth, (II) mesio-occluso-distal (MOD) preparation followed by restoration with Filtek P60 composite, and (III) deep MOD preparation and cusp reduction, followed by reinforcement with Interlig fiber ribbon, and subsequent restoration and cusp coverage with Filtek P60 composite. The teeth were stored in saline for one week. Next, their fracture resistance was measured by a universal testing machine. The load at fracture was recorded in Newtons (N). One-way ANOVA followed by the Tamhane post-hoc test was used to compare the groups (alpha=0.05).    Results: Fracture resistance of enamel in both experimental groups was significantly reduced compared to intact teeth (P<0.05). Fracture resistance of enamel in FRC restorations was significantly higher compared to the conventional composite restorations (P<0.05). Conclusion: FRC restorations significantly increased the fracture resistance of Unsupported enamel compared to the conventional composite restorations under in vitro settings.

Identifying the contribution of each part of the railway to total lateral resistance is considered the most important issue in choosing type of sleeper for providing lateral stability of ballasted railway track. On the other hand, identifying the percentage of effect of each part can help to present new methods for increasing lateral resistance of ballasted railway track. Methodology of this study was based on experimental work in the laboratory. In this paper, the contribution of each part of the sleeper comprised of base, crib and shoulder was determined in the total lateral resistance by STPT tests. In all of the measurements, the greatest value of lateral resistance was related to the area under the sleeper (base zone) and its corresponding valuesin concrete, steel and wood sleepers were 62%, 56% and 51%, respectively. The contributions of shoulder and crib area to the lateral resistance were28% and 9% for concrete sleeper, 27% and 22% for wooden sleeper and 18% and 26% for steel sleeper, respectively.

In this paper, stress analyses in concrete sleeper has investigated by using results of the tests which have been done in main line of railway track. In these tests, special concrete sleeper (B70) installed in railway track. Five load cells fixed inside of the sleeper during constructing of that. After replacing this special sleeper with ordinary sleeper, and tamping in railway track, a train with certain axle load passed through that point of track. Forces on sleeper are analyzed (output of measurement). The results show that B70 concrete sleepers are designed well for tamped and no tamped cases. In the both cases, the stresses in sleeper cross sections are in allowed range. Also, the results show that the track without DTS operation (after replacing of the sleeper) decreases share of sleeper bearing and increases forces on adjacent sleepers. These forces together with dynamic effect of rail-sleeper interaction will accelerate sleeper's deterioration. This means that after replacing failured sleepers, the sufficient length of track must be operated by DTS and Tamping machines.