The structural deformed shape (SDS) is considered an important factor for evaluating structural conditions owing to its direct relationship with structural stiffness. Recently, an SDS estimation method based on displacement data from a limited number of data points was developed. Although the method showed good performance with a sufficient number of measured data points, application of the SDS estimation method for on-site structures has been quite limited because collecting sufficient displacement data measured from a Global Navigation Satellite System (GNSS) can be quite expensive. Thus, the development of an affordable SDS estimation method with a certain level of accuracy is essential for field application of the SDS estimation technique. This paper proposes an improved SDS estimation method using displacement data combined with additional slope and strain data that can improve the accuracy of the SDS estimation method and reduce the required number of GNSSs. The estimation algorithm was established based on shape superposition with various combined response data (displacement, slope, and strain) and the least-squares method. The proposed SDS estimation method was verified using a finite element method model. In the validation process, three important issues that may affect the estimation accuracy were analyzed: effect of shape function type, sensor placement method, and effectiveness of using multi-response data. Then, the improved SDS estimation method developed in this study was compared with existing SDS estimation methods from the literature. Consequently, it was found that the proposed method can reduce the number of displacement data required to estimate rational SDS by using additional slope and strain data. It is expected that cost-effective structural health monitoring (SHM) can be established using the proposed estimation method.
To enhance structural performance of concrete and reduce its self-weight, ultra-high-performance concrete (UHPC) with superior structural performance has been developed. As UHPC members with 180 MPa or above of the compressive strength can be designed, a rational assessment of thin-walled UHPC structural member may be required to prevent unexpected buckling failure that has not been considered while designing conventional concrete members. In this study, theoretical local buckling behavior of the thin-walled UHPC flanges was investigated using geometrical and material nonlinear analysis with imperfections (GMNIA). For the failure criteria of UHPC, a concrete damaged plasticity (CDP) model was applied to the analysis. Additionally, an elastic-perfectly plastic material model for steel materials was considered as a reference to establish differences in local buckling behavior between the UHPC and steel flanges. Finite element approaches were compared and verified based on test data in the literature. Finally, this study offers several important findings on theoretical local buckling and local bending behavior of UHPC flanges. The inelastic local buckling behavior of UHPC flanges was mainly affected by crack propagation due to its low tensile strength. Based on this study, possibility of the local buckling of UHPC flanges was discussed.
Ultra-high-performance fibre-reinforced concrete (UHPFRC) is a relatively newly developed construction material that not only has high compressive strength (greater than 150 MPa), but also high tensile strength (10–20 MPa). The use of UHPFRC enables the design of slender structural members; hence, instability could become a major governing failure mode. However, the estimation of buckling strength for a concrete structure is not easy, owing to its material characteristics. In this paper, the lateral torsional bucking behaviour and strength of ultra-high-performance concrete I-beams are discussed. A methodology is introduced to obtain the effective moment of inertia of UHPFRC I-beams, considering tensile cracks. By using the effective moment of inertia, the linear elastic buckling strength can be calculated. In addition, the inelastic lateral torsional buckling behaviour is investigated through finite-element analysis. A generalised buckling strength curve with a slenderness parameter is discussed. As a result, the limitations for classification of compact and non-compact members are defined, and lateral torsional buckling strength equations are suggested for a simply supported UHPFRC I-girder subjected to centre point loading. Several experimental studies were also conducted, and the results are applied to verify the final results.
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