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- Author or Editor: Zoltan Orban x
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Masonry arch bridges are the oldest bridge structures; thousands of them are still in operation despite the change in the loads carried by them since their construction. Many of them belong to our historical heritage, therefore their management require careful consideration.Assessment of masonry arches is necessary for a several reasons. Arch bridges deteriorate with time, and accordingly their capacity to carry load also declines. To maintain the safety of their operation it is thus necessary to confirm that their load carrying capacity is sufficient for the current and foreseeable applied loads without accelerated deterioration, and therefore that arches remain serviceable.A methodology is proposed in the paper for the assessment and lifetime expectancy of masonry arch bridges with the adaptation of advanced tools for structural analysis and testing.
The paper presents a case study that summarizes the monitoring results of a steel bridge strengthening project where a damaged structural element was temporary strengthened with fiber reinforced plastic sheet. The evolution of damage and the effects of strengthening were monitored with a computerized 24-channel displacement measuring system during normal traffic operation. The results of the monitoring project confirmed the efficiency of the proposed strengthening solution by comparing displacement results prior and after the strengthening intervention, and highlighted the need for applying a system that is capable to follow fatigue damage evolution.
The paper presents methods of inspection of masonry arch railway bridges. Results of a test program are demonstrated where the efficiency of various non-destructive testing methods for the inspection of arches was studied. It is shown that non-destructive investigation can provide valuable information regarding the condition of the bridge and help establishing basic input parameters for structural analysis and condition assessment.
The paper presents an approximation method for the assessment of the load carrying capacity of masonry arch railway bridges. The method is a simple semi-empirical tool for the initial level assessment that is considered to serve as a first sieve and provides conservative values for the load-carrying capacity and permissible axle load of single-span arches.
The proposed method is based on results obtained by the RING 2.0 masonry arch bridge analysis software. The method uses a closed mathematical formula to calculate the carrying capacity and its input parameters can easily be determined by simple site inspections or using data from bridge files.
The study demonstrates and evaluates an approach in the structural analysis phase when assessing reinforced concrete slabs.
Due to different values of a parameter in the tests’ results, 10 models was crated for the first case study and 4 models for the second one.
In order to compare the results in terms of the flexural bearing capacity, the slabs were analyzed by using elastic finite element analysis and yield-line analysis.
Comparing the results shows that minor modification in the parameters associated with bearing capacity and the boundary conditions can affect the adequacy factor considerably, while the parameters those relate to boundary conditions affect the distribution of the yield lines.
Avoiding the formation of shrinkage cracks is one of the most important tasks in construction of concrete industrial floors. Cracks appear on the surface of floors when the nonlinear processes in the structure lead to internal stresses that exceed the actual tensile strength of the concrete. The tensile stresses developed depend on the constrained deformation of the floor during shrinkage and the elastic modulus of the material of the concrete slab. However, on the top surface of the floor, the tensile stresses can be increased, if the shrinkage deformations are constrained by the uneven evaporation and the generated friction between the sub-base and the floor. The value of friction coefficient is depended primarily on the surface roughness of the subbase and the type of polyethylene foil used between the sub-base and the concrete slab. The paper presents the results of experimental investigations on the friction coefficient and the effects of its value on the cracking process of industrial concrete floor slabs.
Concrete indeterminate flexural members represented by continuous beams reinforced with both fiber-reinforced polymers and steel bars in a way that allows for moment redistribution at failure are analyzed. The efficiency of introducing steel bars in the critical sections where plastic hinges are likely to form is evaluated in terms of reliability. Monte Carlo simulation and the concept of comparative reliability are both employed. Ultimately, the effect of different design parameters on the strength reduction factor is evaluated.
Concrete-filled steel tube columns are widely used in civil engineering structures due to their excellent ductility, energy absorption capacity, ultimate load-bearing capacity, and seismic behavior. In this paper, a numerical study modeling of eight lightweight concrete and conventional concrete filled steel tubes was carried out using ABAQUS software, and the lateral load-carrying capacity of square and circular steel tubes under cyclic load was compared. The quarter and one-third height of the tubes was filled with concrete with respect to the pier's height, to improve the base performance of the piers. The results show that the capacity of steel tubes filled with lightweight concrete increased by 40%–70% regarding energy absorption. The square tubes showed better performance than the circular tubes in terms of yielding load, yielding displacement, and energy dissipation.
Diagnostics is an important and challenging task of the structural analysis and condition assessment of historic masonry structures. However the interpretation of the results of the measurements, especially for buildings made from brick and stone, is to be more subjective than that for concrete structures. Therefore improvement of the reliability of the used techniques and finding better correlations between the test results and the mechanical properties of masonry has proven to be of great importance.
While several diagnostic procedures are commonly used in practice to test mechanical properties of masonry, e.g. Schmidt hammer test, analysis of drilled samples, penetration tests, etc. the results of these methods are considered reliable under laboratory conditions, several additional factors have to be taken into account in case of an in-situ application of these methods, that may largely affect the obtained results and conclusions. The results of the diagnostic procedures therefore need to be interpreted with a view to these environmental factors.
The paper focuses on the practical use of several test methods for historic masonries via a real case study. The presented case study attempts to demonstrate benefits from the combined application of Pendulum Schmidt Hammer, moisture meter and scanning electron microscopy.
Steel fibers recovered from recycled tires were considered for use as reinforcement in concrete to improve the tensile properties of concrete as well as being an economically viable and environmentally friendly alternative. This paper investigates the effect of purified and non-purified recycled tire steel fiber in concrete with a constant fiber proportion of 30 kg m−3 to determine properties in fresh and hardened concrete. The results indicate that concrete with purified tire fibers have better tensile properties than those with non-purified tire fibers. Density, strength, and toughness significantly increase but workability tends to decrease when using recycled tire steel fiber as reinforcement in concrete.