Inter-story Drift Research Articles

Comprehensive evaluation of seismic fragility in base isolated buildings enhanced with supplemental dampers considering pounding phenomenon

Base isolation is a proven technology effective in minimizing earthquake-induced damage to both the structural and non-structural elements (especially freestanding contents) of buildings. Nevertheless, it has been shown that allowing the flexible isolation layer to endure substantial demand displacements might subject the isolated structure to failure. This vulnerability arises from potential superstructure yielding due to increased deformations and reduced stiffness, such as those occurring through pounding against a moat wall during intense earthquakes. One alternative to controlling these large deformations is to use supplementary dampers at the isolation plane of the building, creating a hybrid base isolation system (HIS), which adds damping to the isolation system. In this research, the seismic performance of base isolated structures with lead-rubber bearing (LRB) are studied in conjunction with linear viscous dampers (LVD). Due to this aim, a base-isolated steel frame with 2 story X-type braces and a surrounding moat wall is modeled with two various configurations: LRB, and LRB with LVD. Fragility curves are developed for an ensemble of near-field (NF) pulse-like ground motions and for the maximum inter-story drift ratio (MIDR) as an engineering demand parameter (EDP). The incremental dynamic analysis (IDA) is conducted to calculate the damage probability of the structure by assuming different threshold values for damage states. It was found that adding viscous dampers to the isolation system balanced the behavior of the structure under near field pulse-type records; resulting in reduced isolation displacement while its adverse effects are insignificant and can be ignored. Moreover, the median spectral acceleration, namely the spectral acceleration associated to a probability of exceedance (POE) equal to 50 %, at the specific limit state, in the hybrid base isolation system is higher compared to the conventional one.

Cyclic moment-rotation model for bolted double-angle connections with composite floor systems

This paper presents a simplified moment-rotation model for cyclic response of bolted double-angle beam-to-column connections in composite steel frames with concrete on metal decking floors. The proposed model employs mechanics-based equations to determine model parameters, along with empirical observations from previous studies and data from recent large-scale multi-bay frame experiments. Several design variables and construction details, such as orientation of the metal decking, concrete reinforcement layout, and deck splicing details around the connection, were considered in the proposed model. Comparisons between the connection model and experimental results showed reasonable agreement in moment-resisting capacity up to 8% interstory drift. Notably, the proposed model adequately simulated varying responses based on connection details not captured by existing moment-rotation models. Analyses of 2- and 4-story frames using the proposed model showed up to 1.3 times higher ductility and 47% lower initial rotational stiffness compared to those using the existing ASCE 41 connection models with strengths of 20% and 35% of the plastic moment capacity of the girder. These results indicate the potential overestimation of stiffness and moment-resisting capacity, and the underestimation of ductility when using existing moment-rotation models due to insufficient modeling parameters to represent actual behavior. Therefore, the proposed model demonstrates its applicability in incorporating various design variables and construction details of bolted double-angle connections with composite concrete on metal deck floors. This model can be used to account for the non-negligible strength and stiffness of bolted double-angle connections in steel gravity framing under seismic loads.

A self-centering multilevel rocking wall-frame system for mitigating seismic damage in precast concrete buildings

In order to improve seismic resilience and reparability of precast concrete buildings, different forms of rocking wall building systems have been proposed in recent decades. The base-rocking single wall-panel system incurs limited damage under lateral loading, but it experiences high floor acceleration and storey forces for mid- and high-rise buildings due to the effect of higher vibration modes. A multiple-rocking wall system has been proposed to reduce the effect of higher modes in storey forces, but this system leads to larger drifts, thereby increasing the damage to drift-sensitive non-structural elements. To overcome these limitations, the present study proposes a Self-centering Multilevel Rocking Wall-frame (SMRW) system that simultaneously reduces all forms of seismic demands. The SMRW system consists of multiple small rocking wall units, semi-rigid horizontal precast concrete panels and post-tensioned base-rocking boundary columns at each floor level. To enhance the energy dissipation capacity of the proposed system, external tension-compression yield steel dampers are provided across each rocking interface. Superior seismic behaviour of the proposed SMRW system is validated by comparing the seismic performance of 3, 9, 15 and 21-storey building models with the proposed SMRW system together with the base-rocking, multiple-rocking and conventional cantilever structural wall systems. For this purpose, nonlinear static and dynamic (time-history) numerical analyses are conducted on the building models using finite-element and fiber-element modelling, which are validated using experimental results. As the numerical results demonstrate, the proposed SMRW system, while being a low-damage system, can simultaneously mitigate the inter-storey drift, floor acceleration and storey forces/moments compared to other systems. Therefore, the proposed SMRW system can significantly reduce seismic damage to a building’s structural and non-structural elements, and can offer a truly low-damage option for mid and high-rise buildings in seismic regions.

Seismic Performance Assessment of Steel Buildings Equipped with a New Semi-active Displacement-Dependent Viscous Damper

This paper investigates numerically the seismic behavior of multi-degree-of-freedom (MDOF) systems with novel 2–4 direction and displacement-dependent (2–4DDD) and 2–4 Displacement-Velocity- (2–4DVD) Semi-Active (SA) controls. This study builds upon the novel SA 2–4DDD control system, in which the damper forces are controlled by inter-story drifts. For the first time, this paper investigates numerically the behavior of an MDOF system with 2–4DDD controls. A 3-story steel frame is modeled in OpenSees and then subjected to real earthquake records. The frame is modeled considering three control systems: (i) conventional passive nonlinear viscous dampers (NVDs), (ii) SA 2–4DDD dampers, and (iii) a new 2–4DVD SA damper. Parametric studies are conducted to determine the optimal parameters of 2–4DVD control in the designed frames. New design methodologies for MDOF systems with 2–4DVD and 2–4DDD controls are also proposed. The results are discussed in terms of inter-story drift, base shear force, acceleration, dissipated energy and required damper force. Results from Nonlinear Time History Analyses show that, compared to a frame with traditional NVDs, the inter-story drifts and base shear of the frame with 2–4DVD control are up to 72% and 32% lower, respectively. 2–4DVD control also reduces damping forces and acceleration by up to 60% and 87%, respectively, compared to 2–4DDD control. It is also shown that the 2–4DDD control was not stable in high-frequency earthquake records. Conversely, the new 2–4DVD control leads to smoother damping force changes between quadrants for the case study investigated in this paper. This study contributes toward the development of new seismic retrofitting dampers for nonlinear MDOF systems.

Overturning Resistance of Structure Base-Isolated by Laminated Rubber Bearing Considering Pounding Against the Moat Wall

The overturning resistance of structures base-isolated using laminated rubber bearings (LRBs) is crucial to the stability of the structure due to the poor tensile performance of LRBs. Pounding occurs between the structure and moat wall, which can result in a reduction of the overturning resistance of the structure. This study aims to investigate the overturning resistance of a structure base-isolated by LRBs considering pounding against the moat wall based on numerical simulations. The influence of the gap size, pounding stiffness, and the horizontal stiffness of the isolation storey on the overturning resistance of the isolated structure was evaluated through parameter studies. The results indicate that poundings between the structure and moat wall result in short but large pounding forces. Pounding forces would amplify acceleration, inter-storey drifts of the isolated structure, and significantly increase the risk of overturning of the isolated structure. Increasing the gap ratio can improve the seismic performance of the structure. Larger pounding stiffness leads to greater pounding forces generated by the structure, and the risk of overturning of the structure increases. The coefficient of overturning resistance initially decreases, and then increases, as the stiffness of the isolation storey increases.

Impact of irregular masonry infill walls on the seismic response of reinforced concrete frame buildings using linear dynamic analysis

This paper aimed to investigate the seismic response of reinforced concrete (RC) frame buildings using linear dynamic analysis. The study focused on the effects of irregular distributions of masonry infill walls both in elevation (soft story at different levels) and in horizontal (plan) distribution on seismic behavior. Seventeen models were analyzed, including infill frame models with soft stories, models with infill panels only in certain bays, and bare frame models. All models were analyzed using the linear response spectrum (RS) dynamic analysis method. Structural design typically focuses on peak response values, and response spectrum analysis examines the structure's behavior and performance through these peak values. The analysis results indicate that masonry infill walls significantly affect the building's fundamental time period, base shear, story shear, and inter-story drift.

Seismic Isolators Layout Optimization Using Genetic Algorithm Within the Pymoo Framework

In most previous studies, seismic base isolation system optimization has mainly focused on determining isolation layer parameters. However, the subsequent steps of isolator device selection and positioning can significantly impact overall system performance. To address these shortcomings, we propose an alternative optimization approach demonstrated through two models: regular and irregular 8-storey reinforced concrete structures. This approach utilizes the Pymoo framework and commercially available isolators to find optimal isolator layout configurations in two steps. First, using the equivalent lateral force (ELF) procedure, an initial population of seismic isolators meeting shear strain, base shear coefficient, and buckling requirements was randomly selected from suppliers' elastomeric bearing catalogs. Second, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was used to improve the seismic response of the models under the fast nonlinear analysis (FNA) method by minimizing peak roof acceleration, inter-story drift ratio, displacement of the isolated base layer, as well as maximizing the fundamental period. The results underscore the effectiveness of this approach in improving seismic response. Compared to fixed-base structures, the optimal solutions achieved more than double the fundamental period, reduced peak roof acceleration by over 70%, and diminished base shear force by approximately 50%. This methodology can serve as a reference for future research across various structure types, including hybrid isolation systems and steel structures. Doi: 10.28991/CEJ-2024-010-08-07 Full Text: PDF

Conceptual study of an innovative friction damper for the seismic retrofit of precast RC structures with poor connections

Precast RC structures have been widely used in industrial and commercial buildings since the 60 s in the most developed areas. However, during those decades of economic growth, most buildings were constructed without seismic design criteria, accounting for gravity loads only. For this reason, this structural typology often faces a significant seismic risk in earthquake-prone areas due to the lack of effective connection between structural elements. As a result, the seismic retrofit of precast RC structures is essential to prolong their service life and mitigate seismic losses. The present work shows the conceptualisation study of an innovative seismic protection device called Bidirectional Rotational Friction Damper (BRFD) for precast RC structures that behave simultaneously as a beam-to-column joint and damper. This device unifies the concepts of rotational friction dampers and a movable plate system, producing a damping effect along two main directions. Furthermore, the device's ability to dissipate energy through friction enables it to remain undamaged during multiple seismic events while maintaining its damping capacity. After defining a simplified analytical model, to evaluate the influence of the BRFD on a structure's behaviour during a seismic event, a case study was conducted on a single-story, single-bay precast reinforced concrete structure made of plane parallel frames, i.e. that lacks secondary frames. Quasi-static and nonlinear time history analyses were performed to evaluate the BRFD efficacy in reducing seismic forces and displacements, and an importance analysis was carried out using a multi-criteria decision-making (MCDM) approach to identify the optimal configuration of the BRFD for the case study. The main results highlight that introducing the BRFD positively influences the dynamic performance of the structure, producing a significant reduction of interstorey drift and total base shear and preventing structural and non-structural damage.

Influence of Ground Motion Non-Gaussianity on Seismic Performance of Buildings

The non-Gaussian feature of seismic ground motion has been reported in some works. However, there remains a lack of research on the influence of the ground motion non-Gaussianity on the seismic performance of buildings, which motivates this study. By employing a non-Gaussian non-stationary random process simulation method previously proposed by the authors, 40,000 ground motion acceleration signals are efficiently generated, including 20,000 Gaussian and 20,000 non-Gaussian records. As computational examples, a four-story frame building and a three-tower super-tall building are selected. The generated acceleration signals serve as external excitations for the two buildings, allowing for a comparison of the differences in seismic structural responses caused by the Gaussian and non-Gaussian earthquake groups. Probability analysis is performed using top-layer displacement and maximum inter-story drift ratio as damage indicators. The results show that the structural responses induced by both Gaussian and non-Gaussian earthquake groups have identical first- and second-order moments but different higher-order moments. The responses from non-Gaussian earthquakes display distinct non-Gaussian traits, with their distribution of extreme values exhibiting a longer tail compared to the Gaussian counterparts. This leads to a notably larger value of non-Gaussian responses under high crossing probabilities, with an amplification that can surpass 18%.

Comparative analysis of seismic isolation effects under three-way seismic actions for suspension core-tube structure and frame core-tube structure

In this paper, the suspension core-tube structure and frame core-tube structure are taken as the research objects, and the modal analysis of them and their basic seismic isolation structures are carried out firstly to explore the self-vibration characteristics and seismic isolation effect of the structures. Secondly, the nonlinear time-history analysis of the four structures under the action of rare earthquakes in the X, Y, and Z directions is carried out, and their inter-story drift angles, inter-story shear forces, base shear forces, maximum accelerations at the apex of the core-tube, and cantilever beam stresses are analyzed comparatively. Finally, the displacements and loads of the energy dissipators, the maximum horizontal displacements and tensile and compressive stresses of the seismic isolation bearings are analyzed to evaluate the performance of both of them under rare earthquakes. The results show that the suspension core-tube structure and the frame core-tube structure with base seismic isolation bearings can provide good control of their inter-story drift angles and internal forces, etc. The suspension core-tube structure is superior to the frame core-tube structure in controlling the maximum acceleration at the apex of the core tube response.

Experimental investigation of the infill response under the inter-story drift level for different opening location

This paper investigates the response of infilled frames associated with inter-story drift ratio considering the central and eccentric window opening under the in-plane force. The behavior of the structure was studied by experimental and numerical approach. Experimental results show that the lateral load capacity in eccentric window frame (EW) is 1.17 times of central window frame (CW due to interruption of diagonal loaded action by the central opening. The elastic condition of CW frame and EW frame is obtained at lateral drift of 0.2% and 0.4% respectively. As a result of weak mortar interaction, the diagonal action of crack distribution emerges along the corner of the panel in testing A numerical simulation was performed and validated with experimental results. As the comparison of results, the elastic limit points coincide between the two approaches of numerical and experimental. However, the slightly difference occurs at the peak point. The similarity can be seen in the range of 80% to 100% in the value of peak load and displacement at peak load. The numerical investigation revealed that the highest stress distribution occurred along the diagonal axis, aligning with the results of the experimental investigation.

Seismic performance assessment of a base-isolated hospital building subjected to February 6, 2023, Kahramanmaraş, Türkiye earthquakes (Mw 7.7 Pazarcık and Mw 7.6 Elbistan) and seismic fragility analysis considering different construction stages

The construction period of large structures such as hospitals can be prolonged due to complex construction processes. The behavior of frictional pendulum systems (FPSs) is strongly influenced by the seismic weight of the superstructure and the corresponding coefficient of friction. Therefore, the effects of the isolator behavior, which varies throughout the construction stages (CSs), on structural responses should be evaluated. Existing literature lacks adequate investigation into the behavior of isolated structures subjected to earthquakes during CSs. To address this gap, this paper investigates the structural performance of a base-isolated hospital building equipped with FPSs that experienced residual displacements during the February 6, 2023, Kahramanmaraş, Türkiye earthquakes (Mw 7.7 Pazarcık and Mw 7.6 Elbistan). At the time of the earthquakes, the building was still under construction (65–70 % complete). In addition to the hospital building under consideration, there were three more hospital buildings equipped with FPSs under construction during the 2023 Kahramanmaraş-Türkiye earthquakes in Türkiye. The seismic behavior and residual displacements of the structure during this CS were evaluated and numeric results were validated with real data measured in the field. Moreover, fragility analyses were performed for different CSs of the hospital building to reveal the probabilities of damage for base-isolated buildings exposed to earthquakes at various CSs. For fragility assessment, damage states (slight, moderate, extensive, collapse) were defined and four damage measures were chosen. Thus, the extent to which construction stages affected which types of damage was determined. A total of 1296 nonlinear time-history analysis were conducted to obtain fragility curves for all CSs and damage measures considering lower bound, nominal, and upper bound values of isolators. Selected isolated hospital building showed vulnerability in maximum top floor acceleration (MTFA) and maximum isolator displacement (MID) damage measures, but resilience in maximum roof drift ratio (MRDR) and maximum inter-story drift ratio (MIDR) damage measures. For the design basis earthquake (DBE) level, the probability of reaching the extensive damage state was 5.25 % for the MID, 11.39 % for MTFA, and 0 % for MIDR and MRDR. Similarly, for the maximum considered earthquake (MCE) level, these values were determined as 34.09 % for MID, 43.42 % for MTFA, and 0 % for MIDR and MRDR. The analysis revealed that while the probability of damage to the base isolation system was not related to CSs, residual displacements increased as construction progressed. Collapse thresholds for MIDR and MRDR demand exceptionally severe seismic events. As construction progresses, probabilities of exceeding damage states increase for MIDR and MRDR, indicating heightened vulnerability.

Experimental and analytical studies on the influence of rocking ground motions on the frame structure

The characteristics of rocking ground motions and their influence on structural response are rarely considered. This study scrutinizes the structural response solely under the influence of rocking components, utilizing data derived from shaking table tests. Notably, a robust correlation is lacking among the peak parameters of rotational components. The maximum rocking response of each floor is similar to the input peak values of the rocking components. The interstory drift and base force of the structure are closely related to the rotational angle of the rotational components. The mentioned responses are mainly controlled by the structure's 1st mode(X-axis), positively correlated with the wavelet amplitude corresponding to the structure's first mode frequency. The structural acceleration response is closely related to the rotational acceleration of the rocking components. The proportion of higher order modes in acceleration response is usually large. Lower floor acceleration responses are greatly influenced by the high-frequency components of the rocking components, while upper floor acceleration responses are more affected by the low-frequency components.

Influence of Repeated Earthquake events on Structural Response of Multi‐storeyed RC buildings

Over the past decade, reinforced concrete (RC) multi-storeyed buildings have become more prevalent in urban environments. In addition, it has been well established in literature, that collapse of several RC buildings and resulting causalities, thereof are mainly attributed to the repeated nature of occurrence of earthquakes, more often leading to collapse. However, most existing design codes consider only a scenario earthquake characterized by the response spectrum specified by local codes of practice. This consideration do not address the repetitive nature of earthquakes, leading to inadequate estimation of design earthquake force. Hence, the present investigation focusses on proposing a probabilistic model to logically address the number of earthquake sequences to be considered at a chosen location. In addition, to ascertain attainment of collapse state of code designed 3D RC buildings, under a pattern of earthquake sequences (with simultaneous bi-directional ground motion data), a simple and computationally less intensive NLTHA (Nonlinear Time History Analysis) approach has been considered. Moreover, this approach captures the effect of sequential earthquakes and provides a quick rational decision on the structural behaviour, necessary for further analysis. Hence, eliminating the need to resort always for complex IDA (Incremental Dynamic Analysis) approaches to illustrate the structural behaviour. Moreover, the structural behaviour of RC buildings are represented in terms of base shear experienced and their corresponding response parameters (Horizontal displacement, Inter-story drift ratio (IDR), etc.,). The outcome of the results clearly contemplates the accumulation of damages in terms of response parameters, emphasizing the need for consideration of repeated earthquake sequences in seismic analysis.

Seismic Fragility Analysis of a Multi-Tower Super High-Rise Building Under Near-Fault Ground Motions

ABSTRACT Earthquake damage to engineering structures often occur in near-fault areas. Near-fault ground motion is characterized by high-energy velocity pulses, long action period, and strong destructiveness. This paper forces on the seismic analysis of a multi-tower super high-rise building that subjected to near-fault ground motions. The interactions between each tower makes the internal forces and dynamic responses much complex and totally different from single-tower super high-rise buildings. However, currently, multi-tower buildings in China are usually regarded as multiple single-tower buildings, and then separately designed based on the relevant provisions in seismic code for single-tower buildings. The mutual influence between the towers is almost not taken into account. Seismic response history analysis was carried on a three-tower super high-rise building using finite element method. Various near-fault and far-fault ground motions and high-energy velocity pulses were used as inputs. Through calculation of inter-story drift ratio and maximum displacement, the quantitative seismic fragility analysis was conducted for the main tower and sub-tower structures. The results show that the responses from near-fault ground motions to the structure are much greater than those from far-fault ground motions. The damage probabilities of various damage levels for near-fault ground motions are 12.5% higher than far-fault ground motions averagely. A further analysis reveals that the velocity pulses are the main factor causing structural damage in near-fault ground motions.

Seismic Isolation Layout Optimized of Mid-Rise Reinforced Concrete Building Frame Structure

Seismic isolation technology plays a crucial role in enhancing earthquake resistance and mitigating disasters for building structures. In this study, the ETABS analysis software V21.0.1 is utilized to establish a numerical model of a six-story steel reinforced concrete frame structure. Both the time-history analysis method and response spectrum method are employed to calculate the seismic response of the model under earthquake actions. The placement of an isolation layer on the foundation and from the first to fifth floor is considered, with separate calculations conducted for each scenario. Subsequently, a comprehensive comparison and analysis of the dynamic response characteristics among different design schemes are performed. The results demonstrate that the most favorable isolation effect is achieved when the isolation layer is implemented on the foundation or first floor. Compared to non-isolated structures, the natural period of the structure can be extended by 2.2 times and 2 times under the base isolation and first-floor top isolation schemes, respectively. The damping coefficients can reach 0.35 and 0.36, respectively, while the inter-story drift angles can be reduced by 66% and 67%, respectively.

Interpretable machine learning models for displacement demand prediction in reinforced concrete buildings under pulse-like earthquakes

This work proposes a novel procedure to guide the development of machine learning models for estimating the seismic demand in existing reinforced concrete (RC) buildings. The proposed approach is organized across two scales. A large-scale (nonparametric) machine learning model is first obtained by means of Gaussian Process Regression (GPR) using all candidate building attributes and intensity measures. SHapley Additive exPlanations (SHAP) values are utilized to facilitate its interpretation and to assist the rational selection of a small subset of intensity measures, which is finally employed to develop a (symbolic) reduced-scale machine learning model by means of Genetic Programming (GP). Simplified models of archetype buildings are adopted to develop machine learning techniques at both scales, in such a way to alleviate the simulation time for preparing large datasets. Refined models representative of actual buildings are instead considered for the unbiased final assessment.The proposed approach is applied to develop predictive machine learning models for the maximum inter-storey drift in bare frames, pilotis frames and frames with infills under pulse-like seismic ground motions. Consequently, the critical examination of the SHAP values revealed the most significant intensity measures and unfolded interesting patterns depending on the occupancy rate of the infills. Moreover, the final assessment demonstrates that this approach allows the management of a non-homogeneous building stock consisting of very diverse structural systems (i.e., spanning from existing buildings designed against gravity loads only to buildings that comply with outdated seismic codes) while providing satisfactory predictions of the seismic demand with minimum computational effort.

Seismic response of irregular RC buildings designed for gravity and seismic loads

Irregular reinforced concrete framed buildings are peculiar and their seismic response is difficult to predict using simplified approaches. The irregularity in structural configuration is characterized by cross-sectional area reduction of the columns along the height, in-elevation and in-plan irregular distribution of the masses, complex floor geometry or floor geometry variation along the height. This study analyses the seismic response of several four-storey buildings with different types of irregularities, namely in-elevation floor height and floor geometry variation. Additionally, responses of both seismically designed and gravity load designed structures are compared for each geometry considered. A numerical model accounting for non-linear flexural and shear response of the structure is developed, aimed at conducting non-linear incremental dynamic analyses. The results are discussed in terms of inter-storey drift, floor acceleration profiles, fragility functions and floor response spectra. A significant influence of the irregularity on floor accelerations and displacements was observed, as well as on the spectral acceleration at collapse, mainly caused by mass and stiffness variation along the height. On the other hand, no significant influence was detected on failure modes.

A Review paper Advancements in Shear Wall Design for Seismic Resistance in Residential Buildings: A Comprehensive Review

This comprehensive review synthesizes diverse studies, providing valuable insights into the advancements, challenges, and future directions in shear wall design for seismic resistance in multi-story residential buildings. It serves as a reference for researchers, engineers, and practitioners seeking a deeper understanding of shear wall dynamics in the context of structural stability and seismic resilience. Shear walls are a prevalent feature in multi-story constructions as they effectively counteract horizontal forces and offer substantial rigidity and durability within the same plane. This unique quality allows them to carry both significant horizontal loads and provide support for vertical or gravitational loads, thereby presenting a valuable asset in the realm of structural engineering applications. The location and arrangement of shear walls in a building are important factors in their effectiveness in resisting seismic loads. Studies have shown that shear walls arranged in the form of a core at the center of the building are the most effective in reducing top-story displacement during earthquakes. Corrugated steel plate shear walls (CPSW) have been introduced as an alternative to flat steel plate shear walls (FPSW) due to their advantages in terms of stiffness, strength, and ductility. Double layer corrugated steel plate shear walls (DCPSW) have been found to have the highest inelastic deformations, which can be considered an advantage over CPSWs. End shear walls in tall buildings have been shown to decrease maximum inter-story drift and improve seismic performance. Keywords: Shear walls, multi-story residential buildings, lateral support, seismic performance, structural integrity, retrofitting, literature review

Study on seismic performance of SRC frame-bent structures in CAP1400 nuclear power plants

With the conventional island turbine plant project of a CAP1400 nuclear power plant (NPP) as the research background, this paper proposed to apply steel reinforced concrete (SRC) frame-bent structure system to the main building of the NPP. Substructures comprising three frames and two spans from the prototype structure were identified for testing, and a test model was constructed at a scale ratio of 1/7 to test the dynamic and pseudo-dynamic characteristics of the substructures. On the basis of the test results, the structure was further verified using the finite element analysis method. The results showed that the first three modes of substructure were respectively lateral translation with torsion, longitudinal translation with torsion and torsion; The ratio between the third-order and first-order mode cycles was 0.72, indicating that the torsional stiffness of the structure was relatively small and the torsional effect was obvious. When the maximum acceleration peak was 2200 gal, the maximum inter-story drift ratio of the model structure reached 1/31. Ultimately, when the structure was finally destroyed, the concrete at the bottom of each SRC column was crushed and peeled off.