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This study investigates the seismic behavior of long-span prestressed concrete box-girder bridges subjected to long-duration (LD) ground motions and spectrally equivalent near-fault (NF) and far-fault (FF) short-duration ground motions. For this purpose, the Kömürhan and Gülburnu Highway Bridges built with the balanced cantilever method using prestressed concrete box-girder were selected. This paper consists of two main sections. First, ambient vibration tests were conducted to identify the modal parameters of the bridges and calibrate the finite element models. Second, using three ground motion sets consisting of 42 acceleration records applied to the orthogonal and vertical directions of the bridges, the structural responses were evaluated and compared. In order to determine the type of ground motion that is critical for this type of bridge, these sets consist of 14 long-duration ground motions, 14 spectrally equivalent near-fault short-duration ground records, and 14 spectrally equivalent far-fault short-duration records. The comparison parameters considered for this study were displacements and internal forces in the piers and decks. The results strive to highlight the extent to which the duration and characteristics of the ground motion sets affect the structural behavior. Results indicate that the mean deck displacements of selected bridges obtained from FF short-duration records were nearly 10.70% and 7.44% less than those obtained from the LD and NF short-duration ground motions. These trends were also observed in the bridge piers. Moreover, increases of up to 17.54% and 26.65% in the mean shear forces of the piers under LD and NF short-duration ground motions were observed compared to those determined from the FF short-duration counterparts. Similar trends were observed in the bending moment values. It was also observed that far-fault short-duration records may have substantial consequences on such structures. [ABSTRACT FROM AUTHOR]

Bond slip in RC beam–column joints may affect the seismic response or performance assessment of structures considerably. Explicit macroscopic models that satisfy the joint kinematics can be incorporated within a frame model to numerically account for the effect of bond slip. Seismic performance assessment of buildings generally rules out the explicit modeling owing to the associated computational cost. Simplified implicit models are instead preferred owing to the ease of implementation in a commercial finite element (FE) provided the model parameters are calibrated experimentally. Extrapolation of the calibration is generally not valid in other cases with different geometry, sizes and even loading protocols. Most commercial software do not offer the features to explicitly modeling the bond slip. Numerical modeling of bond slip is proposed in this paper that can be conveniently implemented in a commercial software such as Seismostruct. Unlike the prior art, the slip parameter can be extracted using a semiempirical approach preceded by the generation of a numerical database. The proposed framework is also validated against the experimental results of one exterior and one interior beam–column joints. Sample illustration on an example building designed against the same seismic hazard level but following the recommendations per IS 13920, ACI 318 and EC8 is considered for monotonic (without bond slip) and cyclic (with bond slip) pushover analyses. Consideration of bond slip initiates early yielding and results in reduction of secant stiffness at the onset of yielding. The extent of influence depends on the compliance of design standards. For example, relatively higher percentage of reinforcement when designed per IS 13920 (as compared to ACI 318 and EC8) leads to a somewhat lower slip parameter resulting in lesser yield displacement and reduction of secant stiffness at the onset of yielding. [ABSTRACT FROM AUTHOR]

To investigate the effectiveness of viscous damper on seismic control of single-tower cable-stayed bridges subjected to near-field ground motions, a 1/20-scale full cable-stayed bridge model was designed, constructed and tested on shake tables. A typical far-field ground motion and a near-field one were used to excite the bridge model from low to high intensity. The seismic responses of the bridge model with and without viscous dampers were analyzed and compared. Both numerical and test results revealed that viscous dampers are quite effective in controlling deck displacement of cable-stayed bridges subjected to near-field ground motions. However, due to near-field effects, viscous damper dissipated most energy through one large hysteresis loop, extensively increasing the deformation and damping force demand of the damper. Further study based on numerical analysis reveals that to optimize deck displacement of cable-stayed bridges during an earthquake, a viscous damper with relatively larger damping coefficient should be introduced under near-field ground motions than far-field ones. [ABSTRACT FROM AUTHOR]

In this paper, a novel central buckle composed of buckling-restrained braces (BRBs) is developed for long-span suspension bridges, and its preliminary design procedure is presented. Seismic performance of suspension bridges equipped with BRB central buckles is investigated and compared with those with conventional central buckles (e.g. rigid or flexible central buckles). Furthermore, the effect of BRB yield force, as well as the effectiveness of BRB central buckles combined with viscous dampers, is evaluated using parametric analyses. The results indicate that the BRB central buckle is more effective than other central buckles in reducing both the longitudinal girder displacements and force demands on towers during an earthquake. Furthermore, the combination of BRB central buckles and viscous dampers is a superior option for mitigating the seismic response of long-span suspension bridges. [ABSTRACT FROM AUTHOR]

The common characteristic of self-centering (SC) post-tensioned (PT) connections is the gap opening and closing at the beam-column interface, which often face the problem of deformation incompatibility with floor system and cause severe damage of floor slab. To address this drawback of PT frame expansion, an innovative friction-damped SC coupled-beams (CBs) that incorporate PT strands to provide a SC capacity along with friction devices (FDs) to dissipate energy is presented. The global mechanics of this system are briefly explained. An individual FD is tested to investigate the wear resistant properties and friction coefficients of friction materials for the energy dissipation system of SC-CBs. Detailed three-dimensional finite element models (FEMs) of a single-story single-bay frame using SC-CBs are developed with consideration of different FDs installation positions. Analytical results indicate that SC-CBs can sustain large lateral deformations without structural damage under cyclic loading. Then, simplified computational models are validated based on the solid models and applied in nonlinear dynamic analysis of a five-story MRFs using SC-CBs. The frame using SC-CBs minimizes the residual drift and displays good energy dissipation capacity under both the design basis and maximum considerable levels of seismic loading. [ABSTRACT FROM AUTHOR]

Roller bearings of curved viaducts generate large displacements which lead to damage of bearings or pounding damage at expansion joints between adjacent superstructures. In this study, dispersed steel stoppers are installed near each roller bearing to reduce seismic damage due to large displacements of roller bearings. The concentrated pounding phenomenon between adjacent superstructures can be transferred to the dispersed steel stoppers. Shock absorber devices (SADs) are also installed at each steel stopper to mitigate pounding forces. The effectiveness of SAD stiffness on reducing viaduct damage is analyzed. The pounding forces at steel stopper, displacements on the top of piers, displacements of superstructures, curvatures at pier bases, and the relationships of bending moment and curvature are studied accordingly. The application of SADs with high stiffness can mitigate viaduct damage in earthquakes. [ABSTRACT FROM AUTHOR]