Seismic Performance Of Structures Research Articles

Seismic performance of pentagonal type aluminum alloy suspen-dome structure with large opening

Prestressing technology is an effective way to enhance the mechanical properties of space structures. In view of this, a new pentagonal type aluminum alloy suspen-dome structure with large opening is proposed in this paper by introducing the lower cable support system into the aluminium alloy single-layer reticulated shell structure. The seismic performance of this new structure is investigated using time-procedure analysis. Firstly, the effects of rise-span ratio, thickness-span ratio, prestressing level, horizontal radius factor for lower chord nodes and roof loading on the free vibration characteristics of the structure with different supporting stiffness are investigated. The distributions of internal forces and displacements of members of overall structure considering lower support and roof structure only are analyzed. Subsequently, the dynamic response of the structure under seismic combinations of different dimensions and directions is investigated, and reasonable combinations that should be considered for simplified analyses are derived. Furthermore, seismic internal force coefficients are introduced to assess the degree of seismic effects on various types of members. On this basis, parametric analysis of the seismic performance of the structural performance is conducted and quantitative assessment of the sensitivity of the parameters is carried out. Additionally, the free vibration characteristics and dynamic performance of steel and aluminium suspen-dome are compared. The results show that considering the supporting structure weakens the structural stiffness while increasing the structural dynamic response; reasonable values of key parameters in the seismic design of the structure are obtained; and the rise-span ratio and thickness-span ratio are important influencing factors of the seismic performance of the structure. Besides, the internal forces of members in aluminium alloy suspen-dome are less affected by seismic effects than those in steel suspen-dome, and the new structure has good seismic performance.

Cyclic seismic pushover testing of a multi-story underground station

The experimental approach is crucial for investigating the seismic performance and damage process of underground structures. Considering the shortcomings of the 1-g, centrifuge shaking table and monotonic displacement pushover tests, a large-scale cyclic displacement pushover test method is proposed based on the soil-underground structure dynamic interaction and seismic performance quantification system. Taking a two-story three-span subway station structure as the prototype, the cyclic displacement pushover test device was designed for a 1/7-scale multi-story subway station based on the seismic response characteristics of underground structures. The corresponding numerical simulations and experiments were conducted. Typical numerical results (including the seismic damage process, capacity curves of the structural columns, and strain response) and test results (the macroscopic phenomenon of structural damage development, strain response, and deformation response) are interpreted. The results show that the proposed cyclic displacement pushover test is better than the monotonic displacement pushover test, the damage process of the tested station structure conforms to the description of the inter-story drift ratio (IDR) quantification system of seismic performance. Meanwhile, the column has greater strain amplitudes than other components, and the column strain curves reach their peaks before other components. Furthermore, the tested station structure has a similar damage pattern to the Daikai subway station. The reliability and feasibility of the proposed cyclic displacement pushover test method are verified.

Shaking table tests and seismic performance assessment of a vertical mixed concrete/steel structure with large cantilevers

A series of shaking table tests were carried out on a vertical mixed concrete/steel structure with large cantilevers spanning 12 m. Structural seismic performance in terms of damping ratio, vertical response of the cantilever segment, lateral acceleration and deformation responses, and seismic failure mechanism of the specimen were analyzed through test data. Moreover, a further assessment of the specimen's seismic performance was performed through seismic fragility curves of the upper and lower structures, respectively, resulting from the shaking table test outcomes. It was found that the structure shows satisfactory seismic performance. After being subjected to the input motion with a PGA of 1.8g, cracks in the specimen are mainly observed on the floor of the upper structure, and the natural frequency decreases by 14 % compared to the initial state. And the fragility analysis results demonstrate a lower probability of significant structural damage or collapse. In addition, differences in material and structural form between the upper and lower structures lead to significant variations in seismic performance in the height direction. Deformation and damage occur mainly in the upper steel structure. The failure of the structure is mainly due to the loss of lateral resistance of the upper steel structure. The damage to the cantilever portion of the transfer story occurred in the steel trusses at the lower chord level. The diagonal trusses used for the transition story can provide adequate vertical stiffness and strength. Significant amplification of the cantilever segment on the vertical acceleration response spectrum is observed over the period range of 0–0.2 s.

Experimental and numerical investigation of a steel yielding arc and ring damper

The use of yield steel dampers in structures improves seismic resilience by efficiently absorbing energy, reducing the impact of seismic forces, and enhancing overall safety and stability. This paper introduces Arc and Ring Dampers (ARDs), a replaceable structural fuse system with the goal of improving seismic performance of structures against earthquakes. The ARD configuration consists of a central ring surrounded by four arcs. For the first time, an experimental study is carried out on full-scale damper specimens to determine seismic performance and failure mechanisms under cyclic loading. Nonlinear finite element method (FEM) analysis is employed for numerical validation and parametric exploration, taking into account variables such as arc and ring thickness, ring and arc radius, and stiffener width. According to the results, by carefully selecting and designing the geometric characteristics of this damper, it would offer a remarkably efficient energy absorption capacity and a significant load-bearing ability, resulting in a 36 % increase in its equivalent damping ratio. This study also describes these geometric features in detail, including the arcs' and ring's width-to-thickness ratios. Furthermore, this damper maintains structural stiffness without degradation under cyclic loading conditions, showing good ductility up to a value of 5.5. The theoretical predictions here are in good agreement with the experimental outcomes.

Hidden structural information reconstruction and seismic response analysis of high‐rise residential shear wall buildings with limited structural data

AbstractThe high‐rise residential shear wall structure is a crucial component of urban building clusters, while the limited availability of detailed structural information becomes a critical bottleneck in improving the accuracy of seismic performance assessment for high‐rise residential shear wall buildings in urban areas. Based on easily obtainable yet limited structural data at the urban scale, this paper proposes a method to address the shortcomings of existing research on reconstructing hidden structural information and enhance the accuracy of structural seismic performance assessment. It includes a physics‐constrained generative adversarial network module and a fuzzy inference system module to reconstruct the spatial arrangement of shear walls, and material strength grades within buildings, respectively. Validated against two actual buildings, the method outperforms the widely used simplified analysis method at the urban scale, achieving 85.9% accuracy in predicting damage states across various floors.

Mechanical performance study of PVA fiber-reinforced seawater and sea sand cement-based composite materials

Due to the swift progress in the construction sector, there is a global concern about the potential scarcity of river sand and freshwater resources. The development of new construction materials is considered an inevitable trend for industry growth. PVA fibers, known for their strong corrosion resistance, cost-effectiveness, and high toughness, have the potential to enhance the corrosion resistance and seismic performance of structures in marine environments. However, their mechanical properties and durability in the seawater and sea sand environment are not well understood. Therefore, the investigation of the impact of seawater and sea sand on the mechanical properties and durability of PVA fiber-reinforced cement composites is considered crucial. A mechanical performance analysis of PVA fiber-reinforced seawater and sea sand fiber cement composites was conducted in this study. PVA fiber volume fractions of 0%, 0.75%, and 1.5%, cement composite matrix strength grades of C30 and C50, and curing periods of 28 days, 90 days, and 180 days were examined, investigating their influence on the bending toughness of PVA fiber-reinforced seawater and sea sand cement composites. Specific conclusions include the addition of fibers increased the peak bending load, had a less corrosive effect in seawater, and improved the flexural toughness of the material. The most significant improvement was observed at 1.5% fiber content, where the load-deflection curve was fuller and the energy absorption capacity of the material increased by 33–109%, maintaining good bending toughness. Furthermore, higher fiber contents are required for high-strength cementitious composites to improve flexural toughness and durability. The formulation of calculation formulas for predicting bending strength and corresponding deflection, which fit well with the experimental results; and the development of a calculation model for the bending toughness index of PVA fiber-reinforced seawater and sea sand cement composites, providing an effective prediction of material bending toughness.

Seismic Assessment of an Old Historical Unreinforced Masonry Power House Building

Abstract Design of unreinforced masonry buildings is a major concern in seismically active zones in Nepal. The ChandraJyoti Jalvidhyut Power House, a historical landmark in Nepal, represents the nation’s pioneering effort in hydropower generation and signifies its rich cultural heritage. This study comprehensively assesses the structural assessment and seismic performance deficiencies of the ChandraJyoti Jalvidhyut Power House. Material tests on bricks with the individual properties and behaviour of construction materials were done. Utilizing a finite element model in DIANA software V 10.5, the structure’s response under pushover loading conditions is simulated, providing insights into its structural behaviour. Additionally, fragility curves are developed to correlate earthquake intensity with the probability of damage, offering essential information for preservation strategies and seismic risk mitigation. The compressive strength test of bricks, with a value of 9.6 MPa, falls short of the 10 MPa minimum requirement specified by NBC 203:2015, indicating insufficient load-bearing capacity. The building’s pushover analysis shows that the longitudinal direction experiences higher lateral forces (base shear of 945.87 kN) and greater drift ratios exceeding 0.4%, which increases the likelihood of cracks compared to the transverse direction (base shear of 826.77 kN). The analysis also highlights significant nonlinear behavior in both directions, with maximum roof displacements of 35.18 mm (transverse) and 34.4 mm (longitudinal), reflecting the impact of structural irregularities.

Development of the compound intensity measure and seismic performance assessment for aqueduct structures considering fluid-structure interaction

The primary motivation of this investigation is to develop the compound ground motion intensity measure (IM) for the seismic performance assessment of aqueduct structures. To achieve this goal, taking the typical aqueduct structure in Southwestern China as a case study, a three-dimensional finite element model of aqueduct-water-foundation fully coupling system is established. Moreover, for the seismic hazard, a total of 300 as-recorded ground motions based on the design response spectrum are selected from PEER-NGA strong ground motion database, including near-field non-pulse (NFNP), near-field pulse-type (NFP) and far-field (FF). Then, the nonlinear correlation between single IMs is considered by Copula function, the compound IM is proposed that can comprehensively characterize the seismic performance of the aqueduct structure. Based on evaluation criteria, the applicability of the proposed compound IM is compared and verified. Finally, the conditional probability function and the unconditional probabilistic seismic risk analysis is employed to evaluate the seismic performance of aqueduct structures. It can be concluded that the compound IM considers the acceleration, velocity and displacement factors, which improves the correlation, efficiency and proficiency of probabilistic seismic demand analysis. Furthermore, the compound IM can help to improve the accuracy of the structural seismic performance assessment and reduce the uncertainty of structural response estimation. In summary, the findings of this study highlight the significance of proposing the compound IM and developing fragility curves when evaluating the seismic performance of aqueduct structures.

Study on Multi-Index Evaluation Technology of Seismic Performance of Green Ecological Building Structure

Traditional evaluation methods based on static elastic-plastic analysis usually produce results with low fitting degree compared with actual data. In this paper, a new seismic performance evaluation method is proposed. Firstly, several evaluation indexes of green ecological building structure are calculated. Subsequently, a cumulative damage model is established based on fatigue life curve and Miner criterion, which allows to determine the total dissipated strain energy and damage index. In order to verify the effectiveness of this method, it is compared with the traditional static elastic-plastic analysis method through experimental tests. The results show that compared with the traditional method of 50% to 60%, the proposed method achieves a significantly higher fitting degree with the actual data, ranging from 70% to 92%. This emphasizes the superiority and reliability of the proposed method in evaluating the seismic performance of green ecological building structures, and provides insights for safer and more flexible building practices.

Unlocking Resilience: Examining the Influence of Fluid Viscous Dampers on Seismic Performance of Reinforced-concrete Structures in Earthquake-prone Regions

Unlocking Resilience: Examining the Influence of Fluid Viscous Dampers on Seismic Performance of Reinforced-concrete Structures in Earthquake-prone Regions

Non-linear response of confined concrete beam-column structures under horizontal loading

In this study, a behavior law for confined concrete is considered with the introduction of transverse reinforcement to increase the compressive strength of concrete, using the model of Mander et al. This model integrates the confinement effects provided by transverse reinforcement, enhancing the load-bearing capacity of concrete under compressive stress. A pushover analysis is carried out on a full-scale, four- levels structure, using the N2 method. This advanced technique combines non-linear static analysis with inelastic response spectra. Using this approach, the structure's seismic performance can be estimated, accounting for its ductility and the non-linear effects at each loading stage. The inelastic response spectra are adjusted using reduction factors based on the structure's capacity to dissipate seismic energy through inelastic deformations. By varying the confinement rate of the concrete sections, different performance points of the structure can be obtained. The confinement ratio is a crucial parameter influencing the ductility and strength of confined concrete. Closer spacing of transverse reinforcement increases the confinement ratio, which improves the concrete's deformation capacity and ultimate strength. The results show the effect of the behavior law used to consider concrete confinement on the performance points of the structure. In particular, it is observed that increasing the confinement leads to significant gains in the strength and ductility of the structure. These results highlight the importance of optimally using transverse reinforcement to design structures that ensure their performance and safety under seismic loads.

Selection of 110 kV Prefabricated Steel Substations Considering Seismic Vulnerability in China

Prefabricated modular substations are expected to become the mainstream construction type for substations in China. However, there is a lack of scientific basis for structural selection and seismic performance evaluation. Taking a 110 kV substation as an example, this study compares the construction cost of cast-in situ reinforced concrete (RC) substations and prefabricated steel (PS) ones. Two types of PS structures are considered: one with H-section steel columns and the other with box-section steel columns. A seismic vulnerability analysis is performed to compare the probability distribution of various damage states of substation building structures under different seismic damage levels. Results indicate that the construction cost of PS structures is approximately 27.9% higher than that of cast-in situ concrete. When using H-section steel columns, there is a significant difference in the flexural stiffness in two horizontal directions, resulting in reduced seismic performance in the weak-axis direction. The construction cost of using box-section steel columns is slightly higher than that of the H-section steel case, but its seismic performance is significantly improved. Although the probability of slight and moderate damage states for the box-section steel column scheme is generally higher than that of the cast-in situ RC scheme, the probability of collapse is reduced. Thus, box-section steel columns are recommended for prefabricated modular substation building structures.

Seismic performance of underground subway station structure near the strike-slip fault by the developed hybrid IBE-FEM method

To investigate the influence of strike-slip faults on the seismic responses of underground structures, based on the single-layer potential theory of the boundary element concept and the fault-site-underground structure coupling mechanisms, we proposed a hybrid indirect boundary element-finite element numerical method (IBE-FEM) to simulate efficiently the seismic response of the entire process from the near seismogenic-fault to the underground structure. Initially, based on the kinematic finite-fault model, the seismic wavefield of an overlying soft-soil sedimentary-layer site subjected to strike-slip faults with source parameters, such as rupture velocity, dip-angle, and upper-boundary burial depth, was solved using the indirect boundary element method (IBE). Subsequently, the accuracy of the IBE-FEM in predicting the site seismic wavefield was verified. On this basis, the influence laws of the source parameters and the fault-site coupling effects on the seismic performance of the structure were preliminarily investigated by establishing a numerical model of the nonlinear dynamic interaction system of a soil-underground structure. The results showed that the seismic responses of the underground structure located in the footwall far-fault region were more strongly affected by variations in the rupture velocity. The lateral deformation of the structure under the rupture velocity condition of bedrock shear-wave velocity (vs) was dramatically increased compared to sub-vs, and the lowest amplification is 59 %. Furthermore, the hanging wall and seismic damage concentration effects significantly impacted the structure located in a strike-slip fault site with a shallow-burial. This study provides a reliable and efficient analytical method for the seismic design of underground structures in complex near-fault regions.

Assessing Ground Motion Intensity Measures and Structural Damage Measures in Underground Structures: A Finite Element Analysis of the Daikai Subway Station

Research on the characterization of ground motion intensity and damage of underground structures is limited, while reasonable selection of ground motion intensity measures and structural damage measures is a crucial prerequisite for structural seismic performance evaluation. In this study, a two-dimensional finite element model of soil and structures was established based on the Daikai subway station in Japan. Through incremental dynamic analysis, 32 ground motion intensity measures and seven structural damage measures were comprehensively evaluated from seven properties, including efficiency, practicality, proficiency, scaling robustness, relativity, hazard computability, and sufficiency. According to the analysis results, the purpose and significance of each property during measure optimization were hierarchically sorted out. The results show that peak ground acceleration, acceleration spectrum intensity, and sustained maximum acceleration are recommended as ground motion intensity measures, while maximum inter-story drift ratio, column end displacement angle, and two-parameter measures are recommended as the structural damage measures for seismic performance evaluation of the shallow-buried subway station. Furthermore, measure optimization approaches are proposed as follows: the basic selection of IMs should satisfy scaling robustness, hazard computability, and sufficiency to site condition; the optimal selection of IMs is suggested to be evaluated mainly through efficiency, practicality and proficiency, and verified through relativity and relative sufficiency between IMs. The optimal selection of DM is suggested to be evaluated through four properties, including efficiency, practicality, proficiency, and relativity.

Study on Seismic Performance of RC Frame Structures Considering the Effect of Infilled Walls

This paper studies the impact of half-height infilled walls on the failure modes of frame columns through quasi-static tests of both frame models and half-height infilled wall frame models. Based on the experimental results, a seismic analysis model of reinforced concrete (RC) frame structures is established, and parametric studies are carried out to analyze the effects of masonry materials and masonry heights on the seismic performance of structures. The results show that the load-bearing capacity and stiffness of the structure are improved, while the ductility of the structure is reduced because of the existence of infilled walls. As the height of infilled walls increases, there is a notable decrease in the free height of frame columns. At a wall-to-column height ratio of 0.2, the masonry walls exert a negligible effect on the frame structure’s seismic performance. In contrast, at a ratio of 0.6, there is a transition in column failure modes from bending to shearing. When evaluated at consistent masonry heights, aerated concrete block-infilled walls demonstrate the least impact on the seismic performance of RC frame structures. Thus, in the absence of additional structural enhancements, the use of aerated concrete blocks is recommended to mitigate the negative implications of infilled walls on the seismic integrity of RC frames.

Parametric optimization scheme of energy dissipation and shock absorption for prefabricated concrete frame

The prefabricated concrete frame structure system has advantages such as short construction period and good seismic performance, but its deformation and energy dissipation capacity are poor under earthquake action, making it prone to damage. By improving the analysis and simulation functions of existing finite element analysis for prefabricated structures, the engineering applicability of the analysis algorithm has been improved. Then, a finite element model has been established for collaborative optimization, and a parameterized optimization scheme that meets the seismic reduction requirements has been obtained. The results show that the optimization method proposed in the study has a better effect in seeking the minimum cost, and meets the design requirements of the specification. The optimization scheme of prefabricated concrete frames designed by the research institute based on finite element analysis can efficiently optimize various parameters, greatly improving the structure energy dissipation and seismic performance.

Energy-based seismic design method for seismically isolated structures with friction pendulum systems

Friction pendulum systems (FPSs) serve as effective isolators that can help ensure adequate seismic performance of structures against significant aftershocks. A commonly used method for FPS design is the equivalent static analysis method outlined in ASCE 7-22. However, this method risks underestimating the seismic performance of FPSs due to its inability to account for energy dissipation from multiple hysteresis loops exceeding two cycles. Moreover, it is not well-suited for designing FPSs with conical friction surfaces, which exhibit nonlinear elastic behavior and hysteresis. A straightforward solution to address these issues is to apply an energy-based seismic design method. In this study, we propose and analytically validate one such method tailored for seismically isolated structures employing FPSs. Our analysis considers FPSs with both spherical (ISF) and conical (ICF) friction surfaces. For ISFs, the design follows the energy-based seismic design method proposed by Akiyama, whereas, for ICFs, it is based on the energy input to the device and its geometric approximation to an ISF. The conclusions of this study are summarized as follows: (1) the proposed energy-based design method effectively predicts the maximum FPS deformation, facilitating a rough estimation of FPS size; (2) because the design assumes symmetrical seismic response of the isolation layer in both the positive and negative directions and the friction surfaces of the ISF and ICF are geometrically similar, in the proposed method, the maximum deformation of an isolation layer with a natural period greater than 2 s depends solely on the friction coefficient, regardless of the friction surface type; (3) to satisfy the relevant conditions, the appropriate FPS design range is determined through nonlinear analysis. The results of this study demonstrate that the proposed energy-based seismic design method provides a reliable and effective means of designing FPSs for enhanced seismic performance.

Beneficial and detrimental impacts of soil-structure interaction on seismic response of high-rise buildings

In the traditional design method, structures are usually assumed as rigid base structures without considering soil-structure interaction (SSI). However, whether the effect of SSI on the seismic performance of structures is beneficial or detrimental is far from consensus among researchers. Moreover, previous literature mostly concentrated on the seismic behaviour of mid-rise buildings and moment-resisting frames. Therefore, it is in real need to comprehensively investigate the seismic response of tall buildings considering SSI. In this study, a soil-foundation-structure model developed in finite element software and verified by shaking table tests is used to critically explore the effects of SSI on high-rise buildings with a series of superstructure and substructure parameters. The beneficial and detrimental impacts of SSI are identified and discussed. Numerical simulation results indicate the rise in the stiffness of subsoil can dramatically amplify the base shear of structures. As the foundation rotation increases, inter-storey drifts are increased, and base shears are reduced. In general, SSI amplifies the inter-storey drifts showing detrimental effects of SSI. However, as for the base shear, SSI exerts detrimental effects on most piled foundation cases as well as classical compensated foundation structures resting on Ce soil, whereas, for compensated foundation structures resting on soil types De and Ee, effects of SSI are beneficial since the base shear is reduced. Moreover, regarding buildings with different structural systems and foundation types, minimum base shear ratios considering the SSI reduction effect are presented.

Environmental impact of the vibration generated by the underwater shaking table of the National Facility for Earthquake Engineering Simulation (NFEES)

Earthquake simulation shaking tables serve as the valuable tools for investigating the seismic performance of structures, yet they can generate excessive vibrations in surrounding environments during operation. The National Facility for Earthquake Engineering Simulation (NFEES) in China, which is currently in the commissioning phase, will be the world's largest earthquake simulation research facility. Its experimental center consists of a 16 m × 16 m shaking table and two 6 m × 6 m underwater shaking tables (one movable). This study aims to investigate the environmental impact of the vibration generated by the fixed underwater shaking table. Initially, the vibrations of the surrounding ground, shaking table foundations, and adjacent simulation center are tested using the sinusoidal full-load and full-acceleration excitations generated by the shaking table. Upon analyzing the test results, it is observed that the peak ground acceleration (PGA) in the short side direction of foundation attenuates rapidly for high-frequency loading, with a maximum acceleration attenuation up to 55.95 % at distances of 0 m–20 m. The maximum acceleration of the foundation occurs at the edge of the shaking table and significant differences in acceleration are observed at various points across the foundation. The VLZmax of the simulation center is 66.85 dB, which is lower than the limit requirements of the Chinese standard GB55016. Subsequently, an overall finite element model of the surrounding soil-shaking table foundations-adjacent simulation center is established. Following the validation of the numerical model, the vibration isolation efficiency of the adjacent river course and the foundation isolation joint that separates the large shaking table foundation from the underwater shaking table foundation are assessed. Compared to the test results, numerical results show relatively minor discrepancies in the peak acceleration of the ground and the foundation, with maximum errors of 24.59 % and 21.11 %, respectively. The river course and the foundation isolation joint demonstrate better vibration isolation performance for short-wavelength waves, with a maximum vibration isolation efficiency reaching 64.71 % and 63.56 %, respectively.

Structural and non‐structural numerical blind prediction of shaking table experimental tests on fixed‐base and base‐isolated hospitals

AbstractBase‐isolated hospitals are frequently preferred to fixed‐base ones because of their improved seismic structural performance. Despite this, the question remains open on the advisability of using this modern seismic protection technology in preference to other conventional solutions, on the grounds of a holistic approach based on limiting non‐structural damage as well as continuity of service to the community in the aftermath of an earthquake. Two full‐scale four‐storey (fixed‐base) and three‐storey (base‐isolated) hospital buildings have been recently built and subjected to three‐dimensional shaking table tests at the National Research Institute for Earth Science and Disaster Prevention (Japan), with particular attention to evaluating and classifying functionality of non‐structural components and vital medical equipment. A two‐phase experimental campaign was carried out considering two earthquakes scaled at different intensity levels and applied along the horizontal and vertical directions. The current study aims to provide results of a numerical structural and non‐structural blind prediction of these hospital settings. A homemade numerical code is developed to account for lumped plasticity modelling of steel frame members and variability of the friction coefficient of spherical sliding bearings. Moreover, three non‐structural components are modelled in the fixed‐base structure: that is, elastic single degree of freedom systems representing two tanks filled with sand at the top floor; elastic beam elements for piping at the third floor; five‐element macro‐model for the in‐plane‐out‐of‐plane nonlinear response of partition walls at the first floor. The identification of predominant vibration periods of the fixed‐base structure is carried out using a homemade numerical code based on the continuous wavelet transforms in combination with the complex Morlet wavelet. Finally, the sliding and rocking motion of three items of medical equipment (i.e., incubator at third floor, dialysis machine at second floor and surgical bed at first floor) are analysed by means of a homemade numerical code, considering acceleration time histories of selected structural nodes of the fixed‐base structure.