Search

Rolling friction pairs in the tower saddle of suspension bridges could significantly reduce the horizontal load that is transferred to the tower. To investigate the dependence of the rolling friction coefficient (μ) of a rolling friction pair on the normal load (fn) and the cylinder radius (R), an experiment was conducted where a sandwich-like mechanism measured μ. Based on the μ–fn–R relationship, a numerical model, which used one-dimensional (1D) Gaussian random nonplanar surface representation, was proposed in this research to calculate the overall rolling friction coefficient (μT) of a multiroller plate system. The experimental results showed that the dependence of μ on fn and R could be divided into three stages: (1) roughness; (2) elastic; and (3) inelastic. In addition, μ was proportional to fn/R in the elastic stage. The proposed numerical model could accurately calculate μT for a multiroller plate system. The μT rose with increasing surface nonplanarity and slightly increased with the number of rollers (N). This clarified that the μ–fn–R relationship and proposed numerical model could help to quickly determine the size of the rollers and the flatness of plates during design and reduce the scale of the experiments required. [ABSTRACT FROM AUTHOR]

Four shear-critical RC shear walls were tested under a tension-bending-shear load to replicate seismic behavior of the bottom shear wall in high-rise buildings. The axial tension ratio ranged from 0 to 0.5 and the aspect ratio was 1.06. The shear compression failure mode was observed for each specimen, characterized by the formation of an inclined crack at 45° and direct strut action. The shear displacement was a dominant deformation component throughout the loading history. When the axial tension force increased from 0 to 1,293 kN, the ultimate drift ratio increased from 0.90% to 2.38%, while shear capacity linearly decreased from 1,507 to 895 kN. The load–displacement curve showed a significant pinching effect and strength degradation effect. In addition, this paper reports an innovative experimental method to obtain shear resistance of transverse reinforcement (Vs) based on the plasticity theory and strain measuring result. Test results using this method show that not all horizontal distributed rebar yield simultaneously at the ultimate capacity. The US code-specified shear strength contribution of horizontal distributed rebar was found to be unsafe for each test specimen. Finally, a database of RC shear walls subject to combined tension-bending-shear load was established to evaluate shear strength formulas in design codes. The comparison showed the Chinese code predicted spuriously higher tension-shear capacity, while the US code predicted conservative capacity. Based on the developed database, a simplified design formula is proposed with adequate safety concerns and accuracy. [ABSTRACT FROM AUTHOR]

The multiscale modeling method is newly introduced to the research on cable anchorage systems for self-anchored suspension bridges with steel box girders to improve the reliability of the conventional modeling methods. Two kinds of boundary conditions (BCs), the hard BCs and flexible BCs, are defined and illustrated. The strategy of the modeling method of the cable anchorage system for multiscale analysis is then introduced. Based on the proposed strategy, a multiscale model of the cable anchorage system is developed for the Taohuayu Bridge, which is the largest self-anchored suspension bridge in the world. For comparison, a scale model test is carried out, and two elaborate finite-element (FE) models, including a traditional scale model and a full-scale model, are established according to the traditional scale modeling method and full-scale modeling method. For further validation, a full-scale whole-bridge elaborate FE model is established, determined as the full-scale G model. In the test, a complex stress distribution of the anchor structure is newly observed. Intensive comparison study of various models demonstrates that the fuzzy region exists in the test model, scale model, and full-scale model, caused by the use of the assumption of hard BCs and the Saint-Venant principle. The fuzzy region cannot be quantitatively determined, leading to unreliable analysis results and a large amount of trial-and-error work. In the multiscale model, the complex BCs of the cable anchorage system are accurately simulated by the flexible BCs, and the influence of the fuzzy region is eliminated. The results of the multiscale model matches well with the full-scale G model. It is concluded that the multiscale modeling method is the most suitable modeling method to simulate the mechanical behaviors of the cable anchorage system of self-anchored bridges with steel box girders, reliably and efficiently. [ABSTRACT FROM AUTHOR]

This paper presents finite-element analysis (FEA) and experimental study on the seismic behavior of joints between steel K-style outrigger truss and concrete core in tall buildings. Two new joint types with different details, including the joints with outside steel plates and encased steel plates, were conceived and intensively compared. Elaborate FEA models of the joints were developed, and a preliminary finite-element study was first conducted to evaluate the failure modes and hysteretic behavior of the joints to support the preparation of the laboratory test program. Then two specimens with different joint details were tested under cyclic loads. Several indexes that could reflect the seismic performance of the joints, such as the strength degradation, the rigidity degradation, the ductility, and the energy dissipation capacity, were analyzed. The mechanism of the joints was also revealed based on the stress distributions obtained by further FEA and test results, and a simplified FEA model was finally proposed for a more general purpose in routine design practice, and could provide a powerful tool for future research in design methods of the joints. The FEA and experimental results indicated that the joints exhibited favorable seismic performance which could transfer the loads reliably, and the joint with outside steel plates was better than that with encased steel plates, with more construction convenience, higher buckling load, and less concrete cracks. [ABSTRACT FROM AUTHOR]