Reinforced concrete frames with masonry infill walls form the main lateral force-resisting system in a large number of buildings across the world. Furthermore, the geometrical and material parameters of the frame and infill and their interaction affect the lateral force-displacement response of infill wall RC frames. This interaction is affected by the gap between columns and masonry infill. Although limited numerical and experimental research has been done to determine the behavior of the buildings incorporating a masonry wall and an RC frame, little research has been done on the effects of the gap distance between them. However, a systematic investigation into the interaction between the infill wall and the column is more important than ever. Therefore, the current study aims to examine the response of the interaction between the RC frame and the infill walls. A finite element model of a masonry-infilled RC frame was developed with and without gaps, and the influence of column–infill gap distances on the lateral force-displacement response was investigated. The cases studied have been categorized into four modeling types, bare frame model [BF], infill wall model with full contact model [INFC], infill wall with a gap [ING] model, and infill wall with rubber isolator [INRI]. The measured responses include lateral displacement, story drift, story shear force, and overturning moment over building height. Only the effect of lateral load in-planes with constraints in the other directions is investigated in this study. In conclusion, the rubber isolator has the potential to significantly reduce the intensity of earthquake damage; in other words, rubber isolation contributes to improving the structural behavior against seismic loading.

Adjacent irregular buildings with insufficient separation are vulnerable to seismic pounding, particularly when plan asymmetry and soil flexibility modify their dynamic response. This study investigates the influence of horizontal plan layout on the seismic response and pounding behavior of adjacent irregular steel buildings considering soil–structure interaction. Six adjacent L-shaped building configurations with identical structural properties but different plan arrangements were modeled in SeismoStruct. Nonlinear time-history analyses were performed using nine real earthquake records with different intensity, duration, and frequency characteristics. Pounding was represented through nonlinear gap elements, while soil flexibility was simulated using an equivalent spring–dashpot soil–structure interaction model. The response was evaluated in terms of natural frequencies, roof displacement histories, torsional rotations, relative gap response, storey drifts, shear forces and bending moments. The results show that plan layout strongly affects global response and pounding potential. Layouts with less favorable mass and stiffness distribution produced larger roof displacements, amplified torsional rotations and higher relative gap demands. Layouts 1 and 6 generally exhibited the most critical responses, whereas Layouts 3 and 4 showed comparatively more stable behavior. The findings indicate that pounding risk is governed not only by translational displacement but also by asynchronous torsional response.

This study investigates the response of a circular tunnel embedded in saturated potentially liquefiable ground under moving train loading, with particular focus on the effect of an annular rubber-soil mixture cushion placed around the tunnel lining. A three-dimensional finite element model was developed in OpenSees using coupled solid-fluid soil elements and shell elements for the tunnel lining. Two configurations were analysed under identical soil, boundary, and loading conditions. The first configuration represents the reference tunnel without the cushion, while the second represents the tunnel surrounded by the rubber-soil mixture cushion. The results show that the cushion substantially modifies the tunnel-soil interaction mechanism. The peak lining internal force decreased by approximately 62%, and the force distribution along the lining became more uniform. However, this structural benefit was accompanied by larger tunnel movement and surface settlement. The train-induced invert displacement increased from 15.7 to 56.8 mm, while the maximum surface settlement increased from 19.7 to 25.5 mm. The additional movement was mainly associated with rigid-body settlement, since tunnel distortion remained nearly unchanged. The excess pore pressure ratio remained close to 0.08, indicating that liquefaction was not triggered under the moving train load considered. The cushion also reduced the computed high-frequency acceleration amplitudes by 49% at the tunnel invert and by 65% at both the ground surface and the liquefiable zone. A functionality-based interpretation showed that the structural comparative functionality indicator (CFI) increased from 0.50 to 0.81, whereas the settlement-based serviceability CFI decreased from 0.91 to 0.68. The findings indicate that an annular rubber-soil mixture cushion acts primarily as a lining protection and response filtering measure rather than as a settlement control measure.

The MitraClip device has emerged as an effective treatment option for patients with mitral regurgitation. However, implementing a MitraClip alters the mitral valve structure and left ventricular flow dynamics. In this study, we experimentally investigate the effects of the MitraClip and the resulting twin pulsed jets on flow dynamics within the left ventricle. A custom-made left heart pulse duplicator was utilized, considering three different configurations: (1) a healthy mitral valve; (2) a regurgitant mitral valve; and (3) a repaired mitral valve with a MitraClip device. The flow field within the left ventricle was examined using time-resolved particle image velocimetry across different planes. Of particular interest was the analysis of flow structures, viscous energy dissipation and the accumulation of viscous shear stresses in the left ventricle. The results indicate that mitral valve regurgitation increases both viscous energy dissipation and the accumulation of viscous shear stresses in the left ventricle along with a 45% increase in peak velocity compared to the case with a normal mitral valve. Moreover, while mitral valve repair with a MitraClip alters the flow dynamics in the left ventricle, generating twin pulsed jets, it effectively reduces viscous energy dissipation (by 25 and 36% in the lateral and side planes, respectively) and shear stress accumulation compared to the regurgitant valve. However, these improvements do not fully restore the levels observed in a healthy mitral valve. MitraClip mitigates the adverse effects of mitral regurgitation by restoring key hemodynamic parameters closer to healthy levels, highlighting its potential as a promising treatment.

Aortic regurgitation (AR) alters normal blood flow patterns in the left ventricle (LV), affecting diastolic filling dynamics, and is commonly quantified by the regurgitant fraction (RF). However, conventional diagnostic methods have notable limitations, prompting growing interest in four-dimensional flow magnetic resonance imaging (4D-flow MRI) as a tool for quantitatively assessing AR severity. In parallel, viscous energy dissipation (VED), which captures the energy loss caused by viscous forces within blood flow, provides additional important insight into the hemodynamic burden imposed on the LV by valvular dysfunction. This study aims to investigate the potential correlation between RF and VED in patients with AR, hypothesizing that higher RF values are associated with increased VED, thereby reflecting greater hemodynamic compromise. This pilot study included 10 patients with diagnosed AR and 9 healthy controls, all of whom underwent standardized cardiac MRI, including 4D-flow MRI. Volumetric blood flow and VED were assessed using validated post-processing techniques. Statistical analyses were conducted to evaluate group differences and explore the correlation between RF and VED. In healthy controls, LV flow exhibited a typical pattern during diastole and systole, forming a vortex during filling. Severe AR patients displayed disrupted LV flow, with regurgitant jets altering the flow dynamics. Quantitatively, integrated kinetic energy (iKE), vorticity (iVRT), and VED (iVED) were significantly elevated in AR patients compared to controls: iKE (0.003 ± 0.002 J vs. 0.001 ± 0.0004 J, p = 0.019), iVRT (0.304 ± 0.0738 s−1 vs 0.251 ± 0.0466 s−1, p = 0.077), and iVED (0.434 ± 0.307 mW vs. 0.166 ± 0.055 mW, p = 0.020). An increase was observed in patients with severe AR compared to controls, iKE rose to (0.005 J vs. 0.001 J), iVRT (0.335 s−1 vs. 0.233 s−1), and iVED (0.792 mW vs. 0.174 mW). All three parameters positively correlated with RF: iVRT (R2 = 0.175, p = 0.1263; Spearman R = 0.486), iVED (R2 = 0.628, p = 0.0038; Spearman R = 0.597), and iKE (R2 = 0.601, p = 0.0051; Spearman R = 0.616), indicating that increasing regurgitation severity is associated with greater intraventricular energy and flow disruption. This study quantifies the impact of AR on LV flow dynamics and demonstrates elevated VED in patients with AR. The observed correlation underscores the potential of VED as a complementary metric to RF in evaluating the hemodynamic impact of valvular regurgitation. Further studies with larger cohorts are needed to validate these findings and explore their clinical implications.