On the Seismic Response of Irregular Concrete Building with Shark Dampers Considering SSI Effects

Seismic Performance of a Curved Continuous Rigid-Frame Composite Girder Bridge Under Ground Motions

To investigate the seismic performance and damage evolution of a curved continuous rigid-frame composite girder bridge under near-fault velocity pulse-like ground motions, a refined three-dimensional full-bridge finite element model was established, incorporating pile–soil interaction, expansion joint pounding, shear key damage, and nonlinear hysteretic behavior of high damping rubber bearings (HDRBs). Nonlinear time-history analyses were conducted under E1 and E2 seismic levels using near-field pulse records (short, moderate, and long periods), a near-field non-pulse record, and a far-field record. The fiber section capacity-to-demand ratio method was adopted to assess pier damage. Results show that near-field pulse-like motions govern the structural response, with long-pulse records producing the most unfavorable displacements and internal forces. Under E2, HDRBs exhibit significant yielding and hysteretic energy dissipation, effectively protecting the piers but imposing greater deformation demands on expansion joints and unseating preventers. Continuous girder piers display a transverse frame effect and a longitudinal S-shaped moment distribution with a secondary peak at the upper-middle portion due to higher modes. Rigid-frame hollow thin-walled piers exhibit S-shaped internal force distributions associated with abrupt section changes, and the tallest pier reaches a capacity-to-demand ratio of 0.82, indicating moderate yielding. The vertical seismic component amplifies transverse bending–torsion responses of curved girders through spatial coupling. The findings provide a scientific basis for ductility design and damping detailing of similar complex curved bridges.

Seismic Response and Fragility of Rectangular RC Hollow Tall Piers Under Near-Fault Ground Motions Considering Flexure–Shear Interaction

Rectangular reinforced concrete (RC) hollow bridge piers may exhibit significant shear participation after flexural cracking and yielding, whereas their seismic responses are commonly evaluated using flexure-dominated numerical models. This study investigates the effects of axial–flexure–shear interactions on the cyclic response and seismic fragility of rectangular RC hollow bridge piers. Cyclic loading tests on seven one-eighth-scale specimens were analyzed to characterize the effects of the shear-span ratio and reinforcement configuration. The experimental results were then used to assess a conventional flexure model and an axial–flexure–shear interaction model, denoted as AFSI–MBTEM. Full-scale piers with heights of 16, 24, and 32 m were subsequently analyzed under cyclic loading and representative near-fault ground motions. Finally, 7200 nonlinear time-history analyses were conducted using 80 records divided into non-pulse and short-, medium-, and long-period pulse-like groups, while seismic fragility curves were developed using displacement ductility as the demand parameter. The tests indicated flexure-dominated but distinctly shear-sensitive behavior, particularly for specimens with low shear-span ratios. Compared with the flexure model, AFSI–MBTEM reproduced pinching, post-peak deterioration, and hysteretic energy more accurately, reducing the mean absolute error in hysteretic energy from 23.57% to 13.29%. For the full-scale piers, model differences generally decreased as the pier height and shear-span ratio increased together, although the effects on large-deformation stability and seismic response remained configuration- and ground-motion-dependent. AFSI–MBTEM predicted higher fragility in 46 of the 48 height–motion–damage-state comparisons. At the upper analyzed intensity of PGA = 1.5 g, it also produced higher DS4 exceedance probabilities in the examined critical cases. Within the investigated section configurations, axial-load ratios, and coupled height–shear-span cases, the results indicate that neglecting axial–flexure–shear interactions may lead to nonconservative fragility estimates, particularly for configurations with greater shear participation.

An investigation on soil–structure interaction effects on linear seismic responses of tall tubular frames with damped outriggers

Seismic Response Evaluation of Irregular Reinforced Concrete Buildings Using an Integrated IAF–NRI–ISS Framework

Structural irregularities can alter seismic deformation and internal force requirements, but comparisons of different types of irregularities using a single set of response measures remain limited. This research introduces a response-index framework for comparing seismic performance of irregular reinforced concrete (RC) buildings. Nine ten-storey RC models, one regular reference and eight with irregularities such as mass, re-entrant corners, vertical stiffness, and geometric irregularities, were evaluated through Response Spectrum Analysis. Six response parameters—roof displacement, maximum storey drift, drift ratio, base shear, column axial force, and column bending moment—were assessed using the Irregularity Amplification Factor (IAF), Normalized Response Index (NRI), Deformation–Force indices (DI–FI), and Irregularity Severity Score (ISS). The framework integrates response amplification, normalization, behavioral classification, and overall ranking within a unified reference-based process. The vertical stiffness model S-2 achieved the highest ISS (1.461), primarily due to a bending moment of 404.57 kip-ft, followed by S-1 (ISS = 1.285). Sensitivity analysis showed that S-2 consistently remained the top-ranked option, except when the bending moment was excluded. The framework provides a concise basis for identifying dominant response mechanisms and comparing the rankings of irregular configurations, thereby aiding seismic assessment and informing design decisions for RC buildings.

Seismic Performance Evaluation of a Building Incorporating Different Lateral Load Resisting Systems

Earthquakes produce significant lateral forces on structures, which may lead to excessive displacement, structural instability, and collapse if proper seismic resistant measures are not adopted. The present study focuses on the comparative seismic performance evaluation of a G+11 reinforced cement concrete (RCC) building incorporated with different vibration control system using ETABS 20. The building was analyzed for Seismic Zone V using the Response Spectrum Analysis (RSA) method in accordance with the provisions of IS 1893 (Part 1): 2016. Six structural models were considered in the study, namely bare frame structure, fluid viscous damper model, friction damper model, X-bracing model, shear wall model, and lead rubber bearing (LRB) base isolated model. The seismic performance of each model was evaluated based on parameters such as maximum storey displacement, storey drift and storey shear. The results obtained from the analysis indicate that the Shear Wall model provides the most effective reduction in displacement and drift due to its Enhanced stiffness, although the shear wall and bracing systems significantly improve structural stiffness but attract higher seismic forces hence greater base shear than bare frame model. The fluid viscous damper and friction damper showed overall good seismic performance by reducing the overall displacement, drift and storey shear without attracting higher seismic forces. The base isolated model increases the displacement due to increased flexibility in the structure but reduces drift and force transmission into the structure. The study concludes that vibration control systems considerably enhance the seismic performance of RCC structures and assist in improving structural safety in earthquake-prone regions.

Incremental Dynamic Analysis of Bridge Column Seismic Vulnerability Considering Soil-Structure Interaction Effects

This study evaluates the influence of Soil–Structure Interaction (SSI) on the seismic vulnerability of a Department of Public Works and Highways–derived reinforced-concrete bridge column subjected to near-fault ground motions. Nonlinear fiber-based models were developed for fixed-base, stiff-soil, and soft-soil support conditions. Ten horizontal records from spatially separated stations during the 1995 Kobe earthquake were applied through Incremental Dynamic Analysis using Peak Ground Acceleration as the intensity measure and maximum column drift ratio as the damage measure. Lognormal fragility curves were developed for drift limits of 0.5%, 0.7%, 1.5%, 2.5%, and 5.0%. Foundation flexibility increased the first lateral period from 0.2183 s for the fixed-base model to 0.3486 s and 0.4416 s for the stiff- and soft-soil models, respectively. At the 0.5% drift limit, the median PGA capacities were 0.3435 g, 0.3998 g, and 0.3704 g for the fixed-base, stiff-soil, and soft-soil conditions. At the 5.0% limit, the corresponding medians were 1.6240 g, 1.6745 g, and 1.5125 g. The results show that SSI effects are damage-state-dependent: soft-soil flexibility delayed lower drift-limit exceedance but increased extensive-damage and collapse vulnerability. The findings provide a controlled component-level assessment of foundation-flexibility effects for a Philippine bridge-column prototype. The fragilities remain conditional on the Kobe record set, PGA-based scaling, and linearized foundation springs.