Narrow Results

In this study, the authors investigated the behavior of the proposed bolt-assembled precast panel building (BPPB) system under the simulated seismic loading through a large experimental campaign. A pseudo-static test was carried out on a two-story half-scale building specimen constructed by many individual precast components which were properly joined together with bolted connections. The results show that the building specimen had the good seismic performance with high bearing capacity, comparable energy dissipation capacity and perfect structural integrity. The crack pattern and failure mode of the building specimen are different from those of traditional cast-in-situ concrete structures and equivalent cast-in-situ precast concrete structures. The final damage was concentrated in the bolted joint zones, a shear failure occurred in the edge of concrete panel near the bolt holes. It results in that the traditional design approaches of concrete shear wall cannot be applied to this new system. Therefore, the design philosophy and design formulas were proposed for the bolt-connected precast concrete panels to ensure the ductility of the panels and further improving the seismic performance of the BPPB system. The design theory of the bolt-connected precast concrete panels was validated by the successful prediction of the building specimen’s flexural capacity.

The buckling-restrained braces (BRBs) are widely applied in reinforced concrete frames (RCFs) to improve their performance under seismic loading. A procedure for designing such structures based on stiffness ratios was developed. The stiffness ratio was assumed to decrease gradually from the bottom story to the roof. The intermediate stiffness ratios were defined by linear interpolation. A step-by-step design procedure was presented. Three structures with 5, 10, and 15 stories were designed using the procedure and considering three seismic intensity levels. Linear time analysis showed that the stiffness ratio reduced along structural height had no significant effect on the inter-story drift ratio (IDR) of low-rise structures. The nonlinear time history analysis was performed to assess the structural seismic performance. On the basis of the analytical results in terms of the elastic and inelastic IDRs, reinforcements, hysteretic energy ratios of BRBs and structural damage, recommended range of stiffness ratios are proposed for various structures and design seismic intensities.

The safety of railway vehicles running on bridges needs to be evaluated in the seismic design of bridges. This study examined the spectral intensity calculated from the lateral vibration of the bridge deck during earthquakes, a Japanese code-based index to measure bridge vibration’s strength. In addition, the effect of the torsion of the bridge deck on vehicle derailment is investigated using a nonlinear vehicle–track–bridge model. The bridge deck torsion increases the derailment risk, especially for bridges with a low natural frequency. The reason lies in that the lateral and torsional deck motions are highly correlated for bridges with lower frequency. Based on this observation, a code-type formula was proposed to evaluate the vehicle running safety including both lateral and torsional motions of the bridge deck. The accuracy of the proposed formula was demonstrated by comparison with vehicle–track–bridge simulation excited by ground motion records. The new procedure overcomes the non-conservative assessment of derailment caused by ignoring bridge torsion.

This paper investigates the effect of the horizontal and vertical components of ground motions (HGM and VGM, respectively) on the seismic response of Reinforced Concrete (RC) buildings designed to modern capacity design principles and located in the vicinity of active faults. Fiber-based analytical models are used to monitor the global and local response of twelve reference structures, including verifying the response modification factor and tracing the member shear supply-demand response using a ductility- and axial force-sensitive shear strength approach. The simulation models are subjected to near-field earthquake records with increasing severity up to collapse, including and excluding VGM. The results indicate that the lower the contribution of horizontal seismic forces to the seismic response, the higher is the significance of VGM. The fluctuation of axial forces in vertical structural members significantly increases when including VGM. This not only has direct consequences on tension and compression response but also has impact on shear capacity. The diverse range of buildings and performance criteria and large number of incremental dynamic analyses confirm the importance of including VGM in seismic design and assessment of contemporary RC buildings, and hence cast doubts on the reliability of pre-code structures located in the vicinity of active faults.

This paper deals with the dynamics of a single-degree-of-freedom elastoplastic oscillator. The model adopted herein is useful for understanding the dynamic behavior of civil engineering structures, such as steel structures, especially when plastic inelasticity is of concern. Using appropriate internal variables, the dynamic hysteretic system can be written as a singular autonomous system. The free vibration of such a nonlinear system reduces to periodic motion. The harmonic forced oscillator can exhibit periodic or quasi-periodic behaviors. A bifurcation diagram is numerically computed, which indicates that periodic elastoplastic limit cycles exist for some ranges of structural parameters. The bifurcation boundary separates the shakedown from other alternating plasticity phenomena.