Interstorey Drift Ratio Research Articles

Experimental and numerical simulation of seismic behavior of reinforced concrete frames infilled with refractory straw blocks

Recent earthquakes have highlighted the vulnerability of infilled reinforced concrete structures due to the insufficient consideration of infill masonry walls' contribution to strength and stiffness. This study presents a novel refractory straw block (RSB) designed to address these challenges and improve the seismic performance of reinforced concrete (RC) frames. Unlike traditional infills, RSB is characterized by low-elastic-modulus, low-density, and high-ductility. Quasi-static tests were performed on three types of frames: unfilled, infilled hollow grouted bricks (HGB), and infilled RSBs. Failure model, stiffness, and load-displacement response of three specimens were investigated and analyzed. The results indicate that RSBs as infill material does not alter the failure mode and constitutive relationship of bare frame, while HGBs leads to shear failure. The peak load for the specimen IF-HGB was 69.3 kN at 1.1 % drift, compared to 38.8 kN at 2.4 % drift for the specimen IF-RSB, and 36.4 kN at 2.0 % drift for the specimen BF. The strengths of specimens IF-HGB and IF-RSB were 1.90 and 1.07 times that of specimen BF, respectively. The stiffness of specimen IF-HGB was 3.7 times that of the other specimens, but its allowable displacement was only 61 % of theirs. Dynamic time-history analyses were also performed on structures with no longitudinal infill (BF), with RSBs (SBF), and with fired bricks (FBF). At the design level of rare events (magnitude 8, PGA 400 gal), severe damage occurred, but collapse was limited. When the PGA increased further, the collapse probability of model FBF rose rapidly, whereas the collapse probabilities of models SBF and BF remained low and similar. Accounting for the confining effect of walls, model FBF showed a higher probability of severe damage than models SBF and BF, particularly under minor earthquakes. The maximum inter-storey drift ratio of the model SBF and FBF were respectively 1.2 times and 1.7 times that of the model BF, which shows that straw blocks as infill can greatly avoid the effect of infill on the seismic behavior of the structure. The study also emphasized the often-overlooked confining effect of masonry on columns, which can lead to unrealistic damage assessments and seismic shear force distributions.

Study on seismic performance of prestressed fabricated reinforced concrete frame structure assembled by steel sleeves

This paper introduces a novel type of prestressed fabricated reinforced concrete frame (PSFRC frame) structure, which utilizes steel sleeves for assembly. The PSFRC frame incorporates prestressed tendons, stiffened steel sleeves, and high-strength bolts, resulting in improved bearing capacity and assembly efficiency. To assess the seismic performance of the PSFRC frame joint, experimental tests were conducted on one reinforced concrete (RC) joint and two PSFRC frame joints under cyclic loading. Hysteresis analysis and elastic-plastic time-history analysis were also performed using a finite element model. The experimental results showed that the PSFRC edge joint reached a peak load of 89.30 kN, while the PSFRC middle joint exhibited a capacity of 169.95 kN, which was 58.87 % higher than that of the cast-in-place specimen XJ (107.87 kN). The hysteresis curves of the PSFRC joints demonstrated significant fullness, with the equivalent damping coefficient of the PSFRC joint being increased by 11.56 % compared to the RC joint. Additionally, a simulation method using ABAQUS software was proposed to investigate the seismic response of the integral structure of the PSFRC frame. Finite element models for both PSFRC and RC frames were established, and their seismic performance was analyzed under cyclic loading and the El Centro seismic wave. Various parameters including peak loading capacity, stiffness degradation, peak acceleration value, inter-storey drift ratio, and concrete damage value were considered. The finite element analysis results revealed that the load-carrying capacity of the PSFRC frame (435.33 kN) was approximately 30 % higher than that of the RC frame (386.48 kN). Furthermore, at the peak acceleration of 600 gal, the maximum inter-storey drift ratio of the first floor for the PSFRC frame was 1/58, which was below the limit value of 1/50. The plastic hinge position at the beam end of the PSFRC frame was further from the core area, aligning with seismic design objectives. This research provides valuable insights into the design of fabricated building structures and methods for analyzing seismic performance.

RC wall building structures: Comparison of first and second generation Eurocode 8 seismic design and detailing strategies

This study provides a thorough comparative analysis of structural design strategies across different ductility classes and seismic action levels, as outlined in Eurocode 8 provisions. The analysis is carried out for 5- and 10-storey building examples. The research highlights key findings regarding base shear demand, storey displacements, sensitivity coefficients, and other crucial structural performance parameters. Those findings indicate that while buildings designed for DCM and DC3 ductility classes generally exhibit similar base shear values and roof displacements, exceptions arise, particularly in the lower-storey buildings where DC2 demonstrates significantly lower roof displacements. The influence of strut inclination on design bending moments is also noted, underscoring its significance in structural behaviour. Moreover, the study delves into interstorey drift ratio (IDR) demands from analysis, revealing consistent displacement patterns across various structures with notable implications for deflection and stability. Additionally, insights into chord rotation control, sensitivity coefficients, and reinforcement quantities shed light on their behaviour under diverse seismic conditions, aiding in optimising structural design strategies.

Investigating seismic performance of SMRF buildings under subshear and supershear rupture conditions: Assessment of storey-level internal damage

The source effect of earthquake ruptures causes spatial-temporal variability in ground motion characteristics in the vicinity of a fault. This research employs a dynamic rupture-based method with SPECFEM3D to simulate two rupture types: subshear and supershear. While the former depends on the rupture length of the fault, the latter depends on the rupture velocity. Synthetic earthquake ground motion data are generated across the entire domain, encompassing both near-fault and far-fault locations. Ground motions exhibit multidimensionality, with subshear effects evident in the fault normal component and supershear effects distinctly reflected in the fault parallel component. These ground motions have been employed to excite low (S1L), mid (S1M), and high-rise (S1H) steel special moment resisting frame (SMRF) buildings modelled using the modified Ibarra-Medina-Krawinkler (IMK) analogy. Understanding the far-field effects of supershear earthquakes and the near-field effects of directivity in subshear earthquakes on the structural response of SMRF buildings has been aided by several engineering demand parameters (EDPs), including floor acceleration, interstorey-drift ratio, and roof drift ratio.

Inerter-based tuned mass dampers for response control of multi-degree-of-freedom structures subjected to wind and earthquake excitations

The present work explores the utilization of the tuned mass damper-inerter (TMDI) in controlling the structural response subjected to wind and earthquake excitations. An example of a 25-storey reinforced concrete building is taken up. The equations of motion of the structure-TMDI combined system are established by assuming the building behaves as a shear-building with multiple degrees of freedom. These equations are solved using Newmark’s time integration method. The objective functions are the wind- and earthquake-induced structural response quantities, such as the maximum inter-storey drift ratio (MIDR) and peak floor acceleration (PFA). The prime contribution of this study is the inclusion of statistical measures such as the mean, 85th, and 95th percentiles for these quantities. A genetic algorithm-based multi-objective optimization is performed to estimate the optimum TMDI parameters. Based on the outcomes of this study, it can be recommended that the TMDI be optimized to perform well under the 95th percentile for MIDR and PFA in effectively reducing the peak structural responses. Frequency domain analysis results demonstrate TMDI’s multiple-mode controlling capability. The energy comparison plots of the uncontrolled and controlled structures prove the effectiveness of the optimum TMDI in providing enough damping and ensuring structural stability.

Cyclic response of innovative modular joints for modular buildings under bidirectional loading

Based on their dual functions of loading-bearing and energy-dissipating, modular loading-bearing and energy-dissipating joints (MVJ) was used to vertically connect modules, particularly high-rise modular building applications. Fully bolted MVJs can be assembly and disassembly rapidly, and the modules can be recycled after disassembly. Quasi-static tests were conducted on two full-scale space specimens to evaluate seismic resistance properties of the MVJs. Owing to the critical function of MVJs in the buildings, the constant axial loading on the modular column and the vertical displacement on both double beams were implemented simultaneously to simulate the worst loading condition. Owing to the characteristics of double beams under vertical forces, and the requirements of simulation of boundary conditions, a double-beam hinged loading device was proposed. The experimental results demonstrate that the proposed MVJs exhibited great moment capacity. Accordingly, the ratios of the tested average ultimate moment capacity Mu to the designed ultimate moment capacity of double beams MP,beam were 0.828 for S1 and 0.995 for S2. Diagonal cracks occurred on the ends of MVC web for both S1 and S2, indicating that the proposed MVJs were crucial in both loading-bearing and energy-dissipating; the MVC web was used to dissipate energy. Because of the insufficient weld strength between the column and the ceiling beam, as well as the bidirectional cyclic displacement observed at both ends of double beams, the error in the average ultimate moment capacity between the tested and the predicted result is 17.08 %. Analysis conducted on the ductility factor and inter-storey drift ratio demonstrated the feasibility of implementing MVJs in seismic regions.

Fires Following Earthquake Fragility Functions for Protected Steel Braced Frames

The paper describes the outcomes of the analysis of a steel braced frame protected with spray-applied fire resistive material and subjected to fires following earthquake (FFE). Nonlinear time-history analyses were performed in order to evaluate the seismic response. Then, the post-earthquake fire ignitions within selected compartments were considered based on the damage suffered by the structure, which was estimated according to the inter-storey drift ratio and floor acceleration. Natural fire curves were determined by means of zone models. Thus, compartmentation and opening characteristics were included in the analysis. Finally, thermomechanical analyses were completed and failure criteria based on the column and beam displacement and rate of displacement were investigated. The results of the probabilistic analyses were used to produce fragility functions to evaluate the probability of exceeding a limit state conditioned on an intensity measure in the context of FFE.

Post-earthquake fire performance of a steel moment-resisting frame

The effects of earthquakes and fires are typically analyzed separately in structural design. However, historical events highlight that fires following earthquake (FFE) can cause significantly more damage than an earthquake alone. The 1906 San Francisco earthquake exemplifies this, with fires destroying 80% of the city. Other major FFE events include Tokyo (1923), Kobe (1995), and Tohoku (2011) earthquakes. Earthquakes can damage infrastructure, leading to potential ignitions and structural fire performance deterioration. This paper focuses on the post-earthquake fire performance of a four-story five-bay steel frame using a probabilistic FFE framework to develop FFE fragility functions and consider uncertainties in the ground motions, compartmentation measures, fire development, and material properties. Damage to structural and non-structural components is considered. In this respect, the probabilistic FFE framework generates the fire scenarios based on seismic response. The seismic response is assessed through nonlinear time-history analyses. Then, post-earthquake fire ignitions in specific compartments are assessed based on the structural damage, determined by inter-storey drift ratio (IDR) and peak floor acceleration (PFA). Compartmentation and opening characteristics as well as the potential for fire spread are considered based on seismic damage in windows, doors, and partition walls following seismic fragility functions found in the literature. Finally, thermomechanical analyses are performed, and failure criteria based on displacement and displacement rate are applied to the beams and columns. The results of the probabilistic analyses were used to produce fragility functions to evaluate the probability of exceeding a limit state conditioned on an intensity measure in the context of FFE. A higher probability of exceeding the collapse limit state with shorter times to collapse was observed when the structure was subjected to higher values of spectral acceleration.

Beam-column joint modeling effects on the seismic response of a non-ductile reinforced concrete building

Seismic performance evaluation of existing reinforced concrete buildings requires numerical approaches that reflect the damage modes that may arise from deficiencies in beam-column joints. In this study, the seismic performance of an existing reinforced concrete building with four stories was investigated by applying elastic and deformable beam-column joint models. The deformable beam-column joint model was verified using an exterior non-ductile beam-column joint test. The model included a rotational spring located at the joint with two connected nodes in a zero-length with rigid elements in the vicinity of frame elements. Moment- rotation relationships represent the joint behavior, and they were defined based on shear stresses and strains. After effective modeling of beam-column joints, it was aimed to obtain the cyclic behavior of the building model using non-linear time history analysis. For this purpose, scaled earthquake records were applied to the three-dimensional numerical model, and the results were compared in terms of inter-storey drift ratios, column and beam chord rotations, and base shear. It was determined that the exterior beam-column joints reached their strength and deformation capacity, while the beam and columns remained below their section deformation limits according to the Turkish Earthquake Code.

Design and optimization of roof-top fire water tanks as compliant deep tank dampers-inerter for seismic protection of multi-storeyed buildings

Water tanks are installed on the roofs of high-rise buildings for services and to fight fire outbreaks. These tanks are often considered unsuitable for design as tuned liquid dampers (TLDs) and have higher depth ratios than that required in conventional TLDs due to practical constraints in dimensioning the tank as per the tuning requirement. The present work aims at alleviating these hindrances and utilizing deep water storage tanks as effective passive damping devices for the host building. In this paper, a water storage tank for firefighting, situated on the roof of a building, is designed as a compliant deep tank damper inerter (CDTDI) in controlling the response of the host building subjected to seismic excitations. The tank is flexibly connected to the building through spring and damping elements to act as a compliant damper system. Further, the tuning effect, mass, and damping enhancement potential of an inerter element are employed to improve the volumetric efficiency of the compliant damper system. Two example buildings, 10- and 20-storey, are taken up and modeled as multi-degree-of-freedom (MDOF) systems whose masses are lumped at storey levels. The coupled dynamic equations of motion of the CDTDI-MDOF structural system are formed and solved in the time domain using the Newmark-β method. An external excitation-dependent, multi-objective Grey Wolf optimization is performed to estimate the optimum CDTDI parameters by subjecting the buildings to 100 recorded seismic ground excitations. The average values of the peak roof displacement, the maximum inter-storey drift ratio, and the peak floor acceleration are considered objective functions of the optimization. The results reveal the proficiency of the CDTDI in controlling the multiple modes of the structure. Further, the optimally designed CDTDI provides significant damping and stability to the structure, which is evident from the energy plots.

Utilising Artificial Neural Networks for Assessing Seismic Demands of Buckling Restrained Braces Due to Pulse-like Motions

Buckling restrained brace frames (BRBFs) exhibit exceptional lateral stiffness, load-bearing capacity, and energy dissipation properties, rendering them a highly promising choice for regions susceptible to seismic activity. The precise and expeditious prediction of seismic demands on BRBFs is a crucial and challenging task. In this paper, the potential of artificial neural networks (ANNs) to predict the seismic demands of BRBFs is explored. The study presents the characteristics and modelling of prototype BRBFs with different numbers of stories and material properties, utilising the OpenSees software (Version 2.5.0) for numerical simulations. The seismic performance of the BRBFs is evaluated using 91 near-fault pulse-like ground motions, and the maximum inter-storey drift ratio (MIDR) and global drift ratio (GDR) are recorded as a measure of seismic demand. ANNs are then trained to predict the MIDR and GDR of the selected prototypes. The model’s performance is assessed by analysing the residuals and error metrics and then comparing the trend of the results with the real dataset. Feature selection is utilised to decrease the complexity of the problem, with spectral acceleration at the fundamental period (T) of the structure (Sa), peak ground acceleration (PGA), peak ground velocity (PGV), and T being the primary factors impacting seismic demand estimation. The findings demonstrate the effectiveness of the proposed ANN approach in accurately predicting the seismic demands of BRBFs.

Inelastic response spectra for an integrated displacement and energy-based seismic design (DEBD) of structures

The severe socio-economic impact of recent earthquakes has further highlighted the crucial need for a paradigm shift in performance-based design criteria and objectives towards a low-damage design philosophy, in order to reduce losses in terms of human lives, repair/reconstruction costs, and recovery time (deaths, dollars and downtime). Currently, displacement-based parameters are typically adopted to design/assess the seismic performance of the structures, by limiting the maximum displacement or the maximum interstorey drift ratio (IDR) reached by the structure under different earthquake intensities. However and arguably, displacement-based quantities are characterized by inherent weaknesses, since, for instance, they are not cumulated parameters, thus not able to capture directly the effects of multiple cycles, deterioration and damage cumulation. Therefore, in the last decades, energy-based approaches were investigated and developed in order to establish alternative engineering demand parameters for the assessment of post-event damage through a dynamic energy balance. Towards the main goal of developing an integrated Displacement and Energy-Based Design/assessment procedure (DEBD) for actual use in practice, this research work proposes an innovative approach based on the use of inelastic spectra correlating the energy components with the corresponding maximum displacement response parameters of the structure. In practical terms, the proposal is to further integrate and develop the well-known Direct Displacement-Based Design, by directly adopting the hysteretic energy as an additional design parameter. The energy inelastic spectra are developed through an extensive parametric analysis of Single-Degree-of-Freedom (SDoF) systems, with different nonlinear hysteretic models. In such an approach, the maximum seismic energy demand imparted to a structure can be directly predicted and controlled, whilst distinguishing the various components of the energy balance, including the hysteretic one. The effects of near-field and far-field earthquakes are also investigated. Results show that in the first case the seismic demand is concentrated in the peak of a few large cycles that absorb the demand energy induced by the high component in peak ground velocity in the second case the higher equivalent number of plastic cycles tends to become critical for structures with inadequate structural details and prone to suffer by cumulative cycles and overall plastic fatigue mechanisms.

Seismic performance of self-centering braced rocking frame with novel self-centering friction dampers characterized by low-secondary stiffness

Research has demonstrated that self-centering energy dissipation dampers (SCEDs) are effective devices for reducing the residual deformation of structures after a strong earthquake. However, the equivalent damping ratio of SCEDs is relatively lower than that of conventional dampers such as viscous dampers, BRBs, or friction dampers. According to displacement spectrums, the lower damping ratio could result in a lower natural period and higher equivalent stiffness of structures for a given displacement target, and thus the structures could attract more earthquake action to the structures. To alleviate the problem, a novel self-centering damper composed of elastic post-buckling plates and adjustable friction devices (PBSCFD) was proposed and used as the self-centering braces for a self-centering braced rocking frame (SBRF) structure for example. First, the theoretical force-displacement relationship of the PBSCFD was derived based on its configuration and work principle, and then a scaled PBSCFD was manufactured and tested to investigate its mechanical properties and verify the theoretical constitutive model. Subsequently, the SBRF structure with PBSCFDs was designed by the direct displacement-based seismic design method (DDBD), and its seismic performance was examined by elastic–plastic time-history analysis. Finally, the effects of the secondary stiffness ratio of the self-centering braces on seismic mitigation of the SBRF structure were investigated. The results show that PBSCFDs is characterized by classic self-centering behavior with low secondary stiffness, which can be designed to obtain significant control effects on the base/interstorey shear and interstorey drift ratio of the SBRF structure under rare and extremely rare earthquake compared to the conventional SCEDs with significant secondary stiffness.

Assessment of seismic inelastic displacement profiles of steel MRFs by means of modal behavior factors

A new method for the estimation of inelastic displacements of steel moment resisting frames (MRFs) under strong seismic ground motions is presented. The method comes as an extension of previous work of the authors from reinforced concrete to steel MRFs. Key-elements of the present method are the modal behavior (strength reduction) factors, accounting for the first four modes of significance. These factors are expressed in terms of natural period, interstorey drift ratio and/or plastic rotation, soil type and performance level. These factors are multiplied by the corresponding elastic modal displacements to generate the inelastic modal displacement profile. Eventually, the inelastic displacements can be calculated after combining the modal responses through any combination rule (e.g. SRSS). The results of the presented method are compared with that of the well-known equal displacement rule and three others and attested through nonlinear time history analyses.

Development of a novel fire following earthquake probabilistic framework applied to a steel braced frame

This paper describes a novel probabilistic fire following earthquake (FFE) framework to develop FFE fragility functions for steel braced frames. In particular, an 8-storey steel braced frame, located in a high seismic area, was used to demonstrate the framework. An algorithm was formulated to generate fire scenarios based on seismic damage. Damage caused by the earthquake was expressed in terms of inter-storey drift ratio (IDR) and peak floor acceleration (PFA). Damage was captured in structural and non-structural components, such as glazing and partition walls. In particular, floors with IDR and PFA that exceeded pre-defined thresholds were considered to experience ignition after an earthquake. More than 1100 nonlinear FFE analyses were performed by randomly generating values of window widths, fire load densities, earthquake intensities, and yield strength of steel at ambient and at high temperatures. Historic ground motions and natural fire curves were employed to characterize the hazards. Thermomechanical analyses were completed and failure criteria based on displacement and displacement rate were applied to the girders (primary beams) and columns. The results of simulations were processed to generate FFE fragility curves and surfaces for girder and column failures with respect to the time to failure in the FFE scenario and grouped based on spectral acceleration intervals. The results showed that the girder always failed first given the low structural redundancy due to the end conditions. Moreover, the higher the spectral acceleration, the more uniform the damage across the structure with a lower time to reach failure. It was finally found that the fire load density did not have a significant effect on the probability of failure for the case study under consideration.

Seismic Performance of Vertical Irregular Steel Frame Structure under Mainshock-Aftershock

Abstract: The majority of the structures are involved with architectural importance and it is highly impossible to achieve uniform structural properties in all directions. Hence earthquake resistant design codes considered it as irregular frames based on relative difference in the story properties. In many cases these irregularities are responsible for structural collapse of buildings under earthquake ground motions. The seismic response of buildings with irregular distribution of stiffness along the height may be differentfrom that ofregular building. Also, past earthquakes showed that structure may be subjected to sequence of ground motions but current codes do not have guidelines for such cases. It is considered that aftershock do not cause any more damage to damaged structure by the preceding mainshock ground motion. In this study steel moment resisting frame buildings are evaluated to understand the seismic response of vertical stiffness irregular frames subjected to mainshock-aftershock ground motions. The 9-story steel moment resisting frame building situated in Los Angeles is used in this study was originally developed as part of the SAC steel project. In this study soft and stiff storey case was considered at three different locations along the height, i.e., at bottom storey, mid-height storey and top storey. The single modification factor is used for irregularity. For comparison purpose dynamic properties of regular and irregular frames are kept same. Two sets of 6 records were selected representing a seismic hazard level of 2% and 10% probability of exceedance in 50 years respectively as mainshock. Two sets of 30 mainshockaftershock ground motion are considered for the study. These ground motions were developed using randomized approach. A non-linear time history analysis of regular and irregular building is carried out separately under mainshock and mainshockaftershock. The effect of building irregularity was studied for single storey modification at bottom storey, mid-storey and top storey with comparison to regular building. The comparison of a regular and irregular building is carried out in terms of maximum roof displacement and interstorey drift ratio. Also, comparison of frames under mainshock and mainshock-aftershock is done.

Behaviour and design of coupled steel-concrete composite wall-frame structures

This paper explores the lateral load-carrying behaviour of coupled steel-concrete composite (SCC) wall-frame structures, which comprise concrete-filled steel tubular (CFST) columns, composite beams and composite walls. Both experimental and numerical studies were conducted. The experimental programme includes one single-storey bare frame structure and three single-storey coupled SCC wall-frame structures. The experimental results showed that applying the composite wall can significantly increase the lateral load-carrying capacity of the entire structure. It was also evident that increasing the wall width and lowering the structural height can effectively enhance the lateral load-carrying capacity. The modelling approaches in ABAQUS and OpenSees were proposed to conduct the finite element (FE) analysis. In particular, ABAQUS was used to build single-storey coupled SCC wall-frame structures to assess the effects of several parameters, such as beam stiffness, the thickness of steel tubes and wall faceplates, wall width, concrete grade, steel grade and axial load ratio. It was found that increasing the thickness of steel tubes and wall faceplates as well as wall width can effectively increase the lateral performance of the structure but increasing the steel beam stiffness only results in limited improvement. Increasing the steel grade can improve the lateral performance of the structure much more significantly than the concrete grade. When the axial load ratio reaches 0.6, the lateral strength of the structure is greatly reduced owing to the P-Δ effect. Moreover, one multi-storey bare frame structure and three multi-storey coupled SCC wall-frame structures were constructed in OpenSees as a case study. The multi-storey coupled SCC wall-frame structures display extraordinary lateral load-carrying capacity by analysing the curves of base shear force versus roof drift ratio. Besides that, instead of the nominal inter-storey drift ratio, the destructive inter-storey drift ratio together with the roof drift ratio are recommended to assess the multi-storey coupled SCC wall-frame structures in order to avoid overconservative design.

System-level analysis of a self-centring moment-resisting frame under post-earthquake fire

Post-earthquake fire is a multi-hazard combination with cascading effects, of which catastrophic consequences are not only caused by the earthquake but exacerbated by the triggered fire. Only a few studies focused on the system-level structural analysis in earthquake-fire sequence, mostly on the conventional moment-resisting frame. Despite the self-centring system being a novel structure with excellent seismic performance, its post-earthquake fire response is still unclear due to limited research. Accordingly, this study aims to investigate the system-level behaviour of a self-centring system under post-earthquake fire. A numerical model of the six-storey prototype frame is established, and a two-stage bilinear material model is proposed to reflect the combined effects of pre-induced damage and temperature on material properties. A total of 11 ground motions (DBE and MCE levels) followed by 3 fires on different storeys compose the post-earthquake fire scenarios. A welded moment-resisting frame with reduced beam sections (WR-MRF) is selected for comparison, with the DBE response designed the same as the self-centring frame (SC-MRF). Results show that the SC-MRF exhibits smaller responses to the preceding earthquake and subsequent fire than the WR-MRF. Post-earthquake fire mainly affects two inter-storey drift ratios in each scenario, while it has a negligible effect on others which remain unchanged from the residual status after the earthquake. An obvious increase in structural responses can be found from fire-only (FO) to post-MCE fire (P-MCE-F) scenarios, and deformation is slightly larger in multi-floor fires than in single-floor ones. The findings unveil the post-earthquake fire responses of a seismic-resilient system with self-centring mechanism and provide a comparative assessment against the conventional structure. The methodology, including the proposed material model, can be further extended for analysis on other systems to understand and enhance the comprehensive performance in earthquake-fire sequence.

Mechanical model and seismic performance of frames with a self-centring connection

The desired structural performance of a novel self-centring pinned beam–column connection with friction dampers (SC-PC-FD) has been reported. An accurate mechanical model of the SC-PC-FD connection is required for easy modelling of frames with these connections using common commercial structural analysis and design software. This paper presents a simple mechanical model for a SC-PC-FD connection. The accuracy of the model was verified using results from experimental and numerical studies on two-strand and four-strand SC-PC-FD connections. Moreover, the seismic performance of frames with SC-PC-FD connections was evaluated using incremental dynamic analysis and compared with that of moment-resisting frames. For this purpose, one-, three- and five-storey building models with moment connections and SC-PC-FD connections were designed. The two-dimensional frames were subjected to far-field, pulse near-field and no-pulse near-field earthquake records and the collapse margin ratios (CMRs) and fragility curves of the models were obtained. The developed component-based mechanical model accurately predicted the monotonic and cyclic behaviour of the SC-PC-FD connection. With the novel SC-PC-FD system, the maximum residual interstorey drift ratio and the number of developed plastic hinges at the main members of the self-centring models were reduced significantly, while the CMRs were increased.

Experimental verification for a mechanics‐based digital cloning method predicting structural performance and damage

AbstractThis paper introduces a novel digital twin modelling framework combining accurate structural health monitoring (SHM) results delivered by hysteresis loop analysis (HLA) with the basis function modelling to predict structural damage and responses of earthquake‐affected structures under future seismic events. The measured data sets of a 12‐storey 1/10 scale reinforced concrete (RC) structure shaken by three damaging base excitations (Events 1, 2 and 3) using a shake table has been employed to validate the performance of the introduced predictive framework. The results show that the digital twin created under the first base excitation (Event 1) predicts the inter‐storey displacement responses of the test structure due to the second and third excitations (Events 2 and 3) with an average correlation coefficient of ∼0.88 and ∼0.94, respectively. The inter‐storey drift ratio (IDR) values predicted by the digital twin also result in the same seismic performance delivered by the measured values, making the introduced framework a promising tool for assessing structural collapse and subsequent financial risk using incremental dynamic analysis (IDA). Moreover, the maximum difference of 5% between the identified and predicted stiffness values illustrates the robust and accurate performance of the proposed framework in diagnosing structural damage in highly nonlinear and damaged structures.