Earthquake Engineering & Structural Dynamics最新文献

In conventional steel building construction, the slabs are rigidly connected to the beams by steel-headed stud anchors. This study explores a novel sliding slab system where the slabs are allowed to slide with respect to the steel frame by adding low-friction Teflon pads and a horizontal all-steel sandwiched buckling-restrained brace (H-SBRB) to enhance the seismic response of the building system. In this work, the effectiveness of this system in enhancing the seismic response is evaluated by constructing and validating a numerical model of a full-scale three-story steel dual-frame building equipped with a buckling restrained braced frame (BRBF). The frame specimen was subjected to strong ground motions simulated using a shaking table at the National Center for Research on Earthquake Engineering in Tainan, Taiwan. A component test of the Teflon was conducted, where the frictional behavior displayed a velocity-dependence, and the results were integrated into the analytical model. The model showed a good correlation with the test results, particularly in drift response, slab response, floor acceleration, and overall sliding response. Two H-SBRB design forces, referred to as Design 1 and Design 2, were presented, and the slab sliding response was obtained by conducting nonlinear response history analyses. Design 1 reduced the floor accelerations by 19%, the interstory drifts by 15%, and the total base shear by 13% compared to a building model with rigidly-connected slabs. In Design 2, the H-SBRB design force was reduced, leading to a reduction in floor acceleration by 31% and interstory drift by 34%.

This paper presents an experimental study that examined the role of the slab continuity and framing action on the overall hysteretic behavior of a composite-steel moment resisting frame (MRF) up until incipient collapse using advanced instrumentation. The test frame was subjected to three loading phases including asymmetric cyclic lateral loading representative of ratcheting prior to earthquake-induced collapse. It is shown that the presence of partially restrained transverse beams as part of the floor system results into additional overstrength at the beam-to-column joints due to the development of transverse compressive strains at the slab surface. The primary deteriorating mechanisms of the test frame were local buckling at the bottom flanges of the composite-steel beams followed by concrete crushing at the slab at a lateral drift demand of 3%–4%. Additional instabilities within the dissipative zones of the beams featured the crack initiation and propagation. However, the axial restraint provided by the slab and the framing action led to the stabilization of the crack growth and the local buckling straightening at the bottom flange of the beams even at lateral drift demands higher than 10% rad. This is due to the development of a compressive axial force that passed through the slab and reached up to about 35% of the axial resistance of the bare steel beam at incipient collapse. It is shown that this force prevents the beam axial shortening within the dissipative zones of the test frame, which contradicts the results from conventional beam-to-column connection tests with simplified boundary conditions. The experimental results suggest that controlled slip in the ductile shear studs in shallow composite-steel beams act as a capping mechanism of the additional strain demands that may arise due to the potential overstrength on the concrete compressive strength from its assumed characteristic value, the slab confinement, and the presence of the transverse beams. Composite-steel beams under hogging bending were able to sustain about 50% of their peak flexural resistance even at chord rotations exceeding 15% rad due to the stabilization of the local buckling length within the dissipative zone. On the other hand, composite-steel beams under sagging bending attained a zero flexural resistance at the same rotational demands while not achieving a complete separation due to the developed cracks. Measurements from a digital image correlation system suggest that the strut inclination at the interior joint was about 30% higher than that suggested by current standards due to the slab continuity.

In recent years, cylindrical structures free to rock have been exploited in practical engineering. However, their seismic response in three dimensions (3D), greatly sensitive to the parameters that define it, is difficult and time-consuming to predict. To this end, this study focuses on developing a rocking spectrum, an efficient graphical tool linking seismic rocking response to structural parameters, for seismic response prediction and performance-based seismic design of cylindrical structures. The development of the rocking spectrum is based on the numerical rocking response of 2500 idealized rigid cylinders excited by 100 sets of synthetic bidirectional pulse-like ground motions. The minimum Redundancy Maximum Relevance (mRMR) algorithm is first employed to reveal that the rocking response is more related to ground acceleration, ground velocity, and ground displacement when the response is small (close to uplift), intermediate, and large (close to overturning), respectively. Following these relations, the support vector machine (SVM) algorithm is employed to develop the rocking spectrum. The obtained rocking spectrum can reliably predict the rocking response of cylinders subjected to the synthetic pulse-like ground motions. The applicability of the spectrum is also discussed for as-recorded pulse-like ground motions.

Cultural heritage preservation requires a deeper understanding of their seismic response and imposes the use of effective strengthening methods. Fibre-reinforced polymers (FRP) have emerged as an effective solution for strengthening masonry structural elements. The decision over the optimal configuration for a FRP-based strengthening is a trade-off between different objective functions such as strength, inelastic stiffness and cost. Although some studies have explored design alternatives and topology optimisation, experimental investigation remains limited, especially regarding the evaluation of seismic response. This study investigates the seismic capacity of unstrengthened and strengthened mortared–masonry arches through tilting table experiments and numerical simulations. The optimal strengthening arrangement is obtained through topology optimisation, and experimental results demonstrate its performance. A three-dimensional numerical model, following a macro-modelling approach through the so-called concrete damage plasticity material model, is adopted. Numerical results are validated with existing literature and experimental data. A parametric study is conducted for full-scale arches to evaluate the effect of dimensions and the embrace angle of masonry arches. The study reveals that the numerical model successfully replicates masonry arches' nonlinear behaviour and hinge mechanism. In addition, both experimental and numerical results highlight the effectiveness of optimised strengthening placement achieved through topology optimisation.

In the realm of earthquake engineering, response spectra play a crucial role in characterizing the effects of site dynamic characteristics under seismic activity. Consequently, accurately predicting seismic response spectra is of paramount importance. We have developed a physics-guided bidirectional long short-term memory neural network model (Phy-BiLSTM) that is proficient in predicting site seismic response based on bedrock records. The core principle of the Phy-BiLSTM is to improve the alignment between the solution space and the ground truth by integrating physics knowledge obtained from the physical model. The model introduced in this study utilized the 5%-damped response spectra, which were derived from strong ground motion records collected at the KiK-net downhole array. The results substantiate the performance enhancement of Phy-BiLSTM in comparison to the data-driven BiLSTM model. Furthermore, we conduct a comparative analysis of the Phy-BiLSTM model against traditional methods (EQ, SBSR) as well as other neural network architectures (CNN and LSTM). The result highlights the advantages of Phy-BiLSTM in accurately predicting the site seismic response.

CFST (concrete-filled steel tube) combines the advantages of steel and concrete, and has multiple advantages such as high bearing capacity, good ductility and excellent seismic performance. BRB (buckling-restrained brace) effectively enhances the seismic performance of buildings by providing excellent energy dissipation capacity and ductility. In order to study the failure mechanism and seismic performance of prefabricated CFST composite frames with BRBs, two specimens were tested under cyclic loading. The test parameters included the column cross-section type and the end plate type. In this study, the failure mode, hysteretic curve, strength degradation, stiffness degradation, ductility, and energy dissipation capacity of the structure are analyzed in detail. The test result showed that the assembly CFST composite frame with BRBs improves structural response and can be used in cooperative work. Finally, the concrete filled steel tube composite frame with BRB was analyzed using OpenSees software. It showed good safety and can be applied and popularized in high-rise composite structure buildings. The results showed that the numerical model is in good agreement with the experimental results, and the error is less than 13%. They exhibited good safety, so that they can be applied and promoted in high-rise composite structure buildings.

This study presents a comprehensive statistical analysis of the efficacy of pendulum tuned mass dampers (PTMD) in mitigating the overturning risk of rigid blocks subjected to artificial seismic loads. The block is modeled as a rigid parallelepiped undergoing rocking motion, with the PTMD characterized by its mass, length, and viscous damping properties, mounted on top of the block. The analysis includes the derivation of the differential equations of motion for the coupled system, which are numerically integrated. The seismic accelerograms are synthetically generated as realizations of a stationary random process characterized in the frequency domain by its power spectral density (PSD). Second-order white-noise filters are used for sample generation. A Monte Carlo simulation is performed to conduct a parametric analysis, determining the sensitivity of the PTMD parameters to seismic intensity and block slenderness. The results indicate that the efficacy of the PTMD in reducing overturning risk strongly depends on the block's slenderness and the intensity of ground motion. The TMD demonstrates robust performance for moderate ground motion and block slenderness. Although the design parameters do not exhibit systematic trends with respect to mass ratio of PTMD and block due to the inherent nonlinearity of the coupled system, stabilizing, and optimal parameter ranges can still be identified to minimize the overturning risk. Significant reduction of overturning risk can be achieved with respect to the block without PTMD.

The seismic ground movements may lead to significant bending, tensile, and compressive strains to the buried steel pipelines. This study concerns the dynamic behavior of the buried pipeline at its yielding state to offer preliminary design criteria in the geohazard region. An analytical scheme is proposed to assess the responses of the pipelines under a normal fault or a strike-slip fault. A piecewise function is assumed to describe the deformed S-shaped pipeline under the seismic fault. Then, the explicit strain and displacement are obtained by considering the asymmetry of curvature and pipeline-soil interaction. Moreover, the deformed length and yield displacement are predicted explicitly based on the first yielding theory of the classical beam for both asymmetric and symmetric cases. In addition, the proposed analytical results, characterized by the deformed shape and the yield displacement, are verified efficiently by developing a three-dimensional (3D) finite element model (FEM) in the present study, as well as other predictions elsewhere. It is found that the present study offers a good reference for strength evaluation and failure analysis of pipelines subjected to a normal fault or a strike-slip fault.