Earthquake Engineering and Engineering Vibration最新文献

This research is concentrated on the longitudinal vibration of a tapered pipe pile considering the vertical support of the surrounding soil and construction disturbance. First, the the pile–soil system is partitioned into finite segments in the vertical direction and the Voigt model is applied to simulate the vertical support of the surrounding soil acting on the pile segment. The surrounding soil is divided into finite ring-shaped zones in the radial direction to consider the construction disturbance. Then, the shear complex stiffness at the the pile–soil interface is derived by solving the dynamic equilibrium equation for the soil from the outermost to innermost zone. The displacement impedance at the top of an arbitrary pile segment is obtained by solving the dynamic equilibrium equation for the pile and is combined with the vertical support of the surrounding soil to derive the displacement impedance at the bottom of the upper adjacent segment. Further, the displacement impedance at the pile head is obtained based on the impedance function transfer technique. Finally, the reliability of the proposed solution is verified, followed by a sensitivity analysis concerning the coupling effect of the pile parameters, construction disturbance and the vertical support of the surrounding soil on the displacement impedance of the pile.

This paper presents a new finite element model updating method for estimating structural parameters and detecting structural damage location and severity based on the structural responses (output-only data). The method uses the sensitivity relation of transmissibility data through a least-squares algorithm and appropriate normalization of the extracted equations. The proposed transmissibility-based sensitivity equation produces a more significant number of equations than the sensitivity equations based on the frequency response function (FRF), which can estimate the structural parameters with higher accuracy. The abilities of the proposed method are assessed by using numerical data of a two-story two-bay frame model and a plate structure model. In evaluating different damage cases, the number, location, and stiffness reduction of the damaged elements and the severity of the simulated damage have been accurately identified. The reliability and stability of the presented method against measurement and modeling errors are examined using error-contaminated data. The parameter estimation results prove the method’s capabilities as an accurate model updating algorithm.

The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the event. An attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators with 5% initial damping, directly in terms of easily available seismological, site, and model parameters. None of the available models for the bilinear and pinching oscillators are useful when design spectra for a seismic hazard at a site are not available. The statistical estimates of a residual displacement spectrum are proposed in terms of earthquake magnitude, epicentral distance, site geology parameter, and three model parameters for a given set of ductility demand and a hysteretic energy capacity coefficient in the case of bilinear and pinching models, as well as for a given set of pinching parameters for displacement and strength at the breakpoint in the case of pinching model alone. The proposed scaling model is applicable to horizontal ground motions in the western U.S. for earthquake magnitudes less than 7 or epicentral distances greater than 20 km.

Abstract

Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete (RC) structures. Limited research has been performed to investigate the life-cycle cost (LCC) of coastal bridge piers with nonuniform corrosion using different materials. In this study, a reliability-based design optimization (RBDO) procedure is improved for the design of coastal bridge piers using six groups of commonly used materials, i.e., normal performance concrete (NPC) with black steel (BS) rebar, high strength steel (HSS) rebar, epoxy coated (EC) rebar, and stainless steel (SS) rebar (named NPC-BS, NPC-HSS, NPC-EC, and NPC-SS, respectively), NPC with BS with silane soakage on the pier surface (named NPC-Silane), and high-performance concrete (HPC) with BS rebar (named HPC-BS). First, the RBDO procedure is improved for the design optimization of coastal bridge piers, and a bridge is selected to illustrate the procedure. Then, reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances. Next, the repair time of the pier is predicted based on the time-dependent reliability indices. Finally, the time-dependent LCCs for the pier are obtained for the selection of the optimal design.

Abstract

Frame and rocking wall (FRW) structures have excellent resilient performance during earthquakes. However, the concrete at interfacial corners of rocking walls (RWs) is easily crushed due to local extreme compression during the rocking process. An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage, enhancing its earthquake resilient performance (ERP). The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall (SCRW) by two post-tensioned unbonded prestressed tendons. Moreover, two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance. Two SCRW specimens and one monolithic reinforced concrete (RC) shear wall (SW) were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW, focusing on studying the effect of the curved interface on the SCRW. The key resilient performance of rocking effects, failure modes, and hysteretic properties of the SCRW were explored. The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation, avoiding damage within the SCRW. The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation, and the resilient performance of the SCRW is better than that of monolithic SW. In addition, the curved interface of the SCRW makes the rocking center change and move inward, partially relieving the stress concentration and crush of concrete. The rocking range of the rocking center is about 41.4% of the width of the SCRW.

Abstract

At present, there is not much research on mid-story isolated structures in mountainous areas. In this study, a model of a mid-story isolated structure considering soil-structure interaction (SSI) in mountainous areas is established along with a model that does not consider SSI. Eight long-period earthquake waves and two ordinary earthquake waves are selected as inputs for the dynamic time history analysis of the structure. The results show that the seismic response of a mid-story isolated structure considering SSI in mountainous areas can be amplified when compared with a structure that does not consider SSI. The structure response under long-period earthquakes is larger than that of ordinary earthquakes. The structure response under far-field harmonic-like earthquakes is larger than that of near-fault pulse-type earthquakes. The structure response under near-fault pulse-type earthquakes is larger than that of far-field non-harmonic earthquakes. When subjected to long-period earthquakes, the displacement of the isolated bearings exceeded the limit value, which led to instability and overturning of the structure. The structure with dampers in the isolated story could adequately control the nonlinear response of the structure, effectively reduce the displacement of the isolated bearings, and provide a convenient, efficient and economic method not only for new construction but also to retrofit existing structures.

Abstract

As an important part of nonstructural components, the seismic response of indoor water supply pipes deserves much attention. This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete (RC) frame structure. Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance. Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions. A seismic fragility study of displacement demand is conducted based on numerical simulation. The acceleration response and displacement response of different combinations are compared. The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes.

Abstract

Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions. Due to the unique marine depositional environment of coral sandy soils, the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities. This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades. The focus of coverage includes the contractive-dilative behavior, the pattern of excess pore-water pressure (EPWP) generation and the liquefaction mechanism and liquefaction resistance, the small-strain shear modulus and strain-dependent shear modulus and damping, the cyclic softening feature, and the anisotropic characteristics of undrained responses of saturated coral sandy soils. In particular, the advances made in the past decades are reviewed from the following aspects: (1) the characterization of factors that impact the mechanism and patterns of EPWP build-up; (2) the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient; (3) the establishment of the invariable form of strain-based, stress-based, or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction; (4) the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus; and (5) the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics. Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.