Current Issue : October-December Volume : 2021 Issue Number : 4 Articles : 5 Articles
Bridge designs are becoming slender and lighter, making wind dynamic effects even more important than wind static effects. Some types of bridges show especially vulnerable situations during construction stages, when the structure is lighter or does not have its final stiffness. The aim of this document is to assess the dynamic wind loading on simple girder bridges during their construction phases. The studied section is formed by two steel beams supporting a concrete slab, but the analysis was made when the concrete slab has not been built yet. Several CFD simulations were made to find the aerodynamic parameters depending on the section’s dimensions. Three construction stages were analyzed: when only one beam is placed, when both beams are in their final locations but they are not connected yet, and when both beams are joined by the bracing. The results showed that vortex shedding effects are stronger in the along-wind direction due to the low horizontal bending stiffness of the beams and their large area perpendicular to the flow. Increasing beams’ distance is a good solution to reduce wind effects. However, closing the section with light plates was more effective, decreasing the frequency of vortex shedding and its effects....
Arches are employed for bridges. This particular type of structures, characterized by a very old use tradition, is nowadays, widely exploited because of its strength, resilience, cost-effectiveness and charm. In recent years, a more conscious design approach that focuses on a more proper use of the building materials combined with the increasing of the computational capability of the modern computers, has led the research in the civil engineering field to the study of optimization algorithms applications aimed at the definition of the best design parameters. In this paper, a differential formulation and a MATLAB code for the calculation of the internal stresses in the arch structure are proposed. Then, the application of a machine learning algorithm, the genetic algorithm, for the calculation of the geometrical parameters, that allows to minimize the quantity of material that constitute the arch structures, is implemented. In this phase, the method used to calculate the stresses has been considered as a constraint function to reduce the range of the solutions to the only ones able to bear the design loads with the smallest volume. In particular, some case studies with different cross-sections are reported to prove the validity of the method and to compare the obtained results in terms of optimization effectiveness....
The Building Information Modeling (BIM) methodology considers the representation of the building as a virtual BIM model and its main concept is to centralize all the information generated throughout the development of the project. Structural design involves a set of tasks, namely, structure definition, structural analyses, and after the generation of drawings and technical documentation. In all processes, it is required confidence in data transferred between the BIM systems used, and to support this, a high level of interoperability is claimed. The present study aims to evaluate the degree of interoperability between the BIM-based platforms, ArchiCAD (Graphisoft), Revit (Autodesk), and ETABS (CSI). Two-way data flows between these systems were explored using distinct transfer strategies: add-in applications; Industry Foundation Classes (IFC) standard data format. The research made allows identifying the most appropriate procedure to be adopted by structural engineers, given the interoperability limitations verified, enabling the establishment of a practical guide of sequential procedures on the development of structural designs using BIM tools....
.e post-disaster emergency rescue and loss evaluation hinges on the timeliness and accuracy of safety assessment of building structures in quake-hit regions. At present, the damage identification of quake-hit buildings in China is mainly conducted based on the experience of the experts. Such an assessment method will inevitably lead to the differences in identification results because each expert has his/her own subjective understanding of the degree of structural damage. In order to solve this problem, the low cyclic loading test of 7 specimens of shear wall is conducted and the hysteretic curves of seven shear walls are drawn. .e failure modes and seismic performance of members under different design parameters (axial compression ratio of shear wall, shear span ratio, form of edge member, reinforcement ratio, stirrup ratio of coupling beam, and span height ratio) are compared. By recording the damage images taken at the controlled displacement under each level of load, the corresponding damage indexes are calculated, and the correspondence between the typical component damages and the damage indexes is discovered. After that, the images are compiled into an atlas. .e authors calculate the damage index of the overall structure based on the damage indexes of the components and carries out damage identification of RC shear wall structure with the said damage index....
Natural vibration characteristics serve as one of the crucial references for bridge monitoring. However, temperature-induced changes in the natural vibration characteristics of bridge structures may exceed the impact of structural damage, thus causing some interference in damage identification. This study analyzed the influence of temperature on the natural vibration characteristics of simply supported beams, which is the most widely used bridge structure. The theoretical formula for the variation of the natural frequency of simply supported beams with temperature was proposed. The elastic modulus of simply supported beams in the range of 40 C to 60 C was acquired by means of the falling ball test and the theoretical formula and was compared with the elastic modulus obtained by the three-point bending test at room temperature (20 C). In addition, the Midas/Civil finiteelement simulation was carried out for the natural frequency of simply supported beams at different temperatures. The results showed that temperature was the main factor causing the variation of the natural frequency of simply supported beams. The linear negative correlation between the natural frequency of simply supported beams and their temperature were observed. The natural frequency of simply supported beams decreased by 0.148% for every 1 C increase. This research contributed to the further understanding of the natural vibration characteristics of simply supported beams under the influence of temperature so as to provide references for natural frequency monitoring and damage identification of beam bridges....
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