Maximum Drift Ratio Research Articles

Simplified calculation models for evaluating the post-earthquake axial load-carrying capacity of RC bridge piers

This study aims to develop simplified calculation models of the post-earthquake axial load-carrying capacity of reinforced concrete columns to determine the post-earthquake traffic flow capacity of the bridges for the evaluation and design process. To this end, the maximum and residual drift ratios are first determined as the engineering demand parameters for the simplified calculation model for the evaluation and design process, respectively. Then, the optimal models describing the relationships between the maximum/residual drift ratio and the post-earthquake axial load-carrying capacity are selected. The analysis results show the normal cumulative model in the coordinate system of ln(x)-y is the optimal relationship model. On this basis, the effects of high-sensitivity parameters (i.e. the axial compressive ratio and shear span ratio) on the post-earthquake axial load-carrying capacity are investigated. Results indicate that the axial compressive ratio negatively affects, while the shear span ratio positively affects the post-earthquake axial load-carrying capacity. Finally, the simplified calculation models of the post-earthquake axial load-carrying capacity are developed from the optimal model and the effects of the high-sensitivity parameters, and with validated high accuracy. The simplified calculation models provide engineers and policymakers with a tool to predict the post-earthquake traffic flow capacity of bridges.

Seismic performance of Li-Tie type brick masonry infilled wooden frames considering joint damage: Degradation mechanism and hysteretic model

This paper investigated the influence of the damage to column-foot (C-F) joints and the gaps of mortise-tenon (M-T) joints on the seismic behavior of Li-Tie style timber frames with masonry-infilled wall. Five full-scale Li-Tie type brick masonry-infilled timber frames, two without the joint damage, two with the damage to C-F, and one with the gaps of M-T joints, were cyclically tested. The failure modes, mechanical and deformation mechanisms were revealed. The second-order effect, strength degradation law, and the changing laws of the equivalent viscous damping coefficient and strain of the specimens were analyzed. The results showed that when the maximum inter-layer drift ratio was less than 2.4 %, the second-order effect of Li-Tie type timber structure with the masonry infill can be ignored. The masonry infilled timber frames considering the joint deterioration suffered a large strength degradation degree, and a more significant loss of the peak load and ductility. The equivalent viscous damping coefficient of the masonry infilled timber frame considering C-F damage increased by up to 24.67 %, while that of the one including the gaps of M-T joint decreased by 6.67 %. The C-F damage led to an increase in the strain at the beam end, the damage to M-T joint resulted in an decrease in the strain at the beam end. However, the damage to C-F and the gaps in M-T joint had little influence on the strain distribution in the C-F area. Based on the hysteretic, stiffness and strength degradation characteristics, and tests results of the specimens, the new tri-linear hysteretic models of Li-Tie type brick masonry infilled wooden frames with and without the joint damage were established and verified. Good agreement between the model predictions and test results was observed.

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.

Accuracy and uncertainty of predicted maximum and residual displacements of RC bridge columns under earthquake excitations

Fundamental to the performance-based seismic design is the accuracy of predicted responses under earthquake excitations. This study evaluates the accuracy and uncertainty of predicted maximum and residual displacements of concrete bridge columns subjected to different types of ground motions. A series of nonlinear time-history analyses considering a wide range of element formulations and model parameter combinations was performed to reproduce measured responses from previous shake table tests. Variations in element formulation had little influence on the accuracy and uncertainty of predicted maximum displacements. The gradient inelastic force-based element, however, predicted bar tensile strain profiles across the plastic hinge with higher resolution, but at a higher computational cost than displacement-based and beam with hinges elements. Models with tangent stiffness-based Rayleigh damping produced the most accurate predictions of the maximum drift ratios with an RMSE of 0.011, indicating that the maximum displacement (or drift ratio) can be predicted with reasonable accuracy. Residual displacements, on the other hand, were predicted with unreasonable levels of error and uncertainty. A data-driven model was thus proposed to correct predicted residual displacement. Following correction, the RMSE of the predicted residual drift ratios was reduced by 43 % to 0.006.

Cyclic performance of RC frame joints with drilled openings

The construction industry commonly employs reinforced concrete (RC) beams with utility pipe openings to facilitate the passage of pipes through structures. These openings can be made through pre-construction or post-construction processes. Pre-construction openings in RC members are included in the design, and in most cases, designers include reinforcements around the opening to deal with the stress concentration and failure mechanism caused by the presence of the opening. However, post-construction or drilled openings are added after the structure is built, potentially disrupting established load paths, and developing stress concentrations that are not anticipated by the designer. In this study, three-dimensional nonlinear numerical finite element models (FEM) models were developed and validated according to four sets of experimental data. These models formed the basis for a parametric study exploring different design parameters. Parameters such as the width and depth of the specimen and the size of the opening were investigated. The results suggest that the presence of the opening leads to a brittle behavior and a sudden drop in the strength and stiffness of the specimen after the ultimate load. Increasing the depth of the beam results in more brittle behavior in specimens with openings and decreased the drift ratio where the specimen failed by up to 75%. However, increasing the width of the specimen increases the ductility of these specimens. Finally, opening size was found to lead the specimen to behave more brittle in all cases, and decrease the maximum drift ratio from 5% to 1.5%, and decrease the load capacity in 1.5% drift ratio by up to 61%. This study will help engineers and designers to understand the effect of beam-column joints with post-construction openings under cyclic loading, whether these openings are intentional or by human error.

Advanced tree-based machine learning methods for predicting the seismic response of regular and irregular RC frames

In this study, predicting the maximum drift ratio (MDR) for two types of structures: 8-story regular (R8) and vertically irregular (IR8) reinforced concrete (RC) frames are focused. To accomplish this, advanced tree-based machine learning (ML) methods, namely Random Forest (RF), eXtreme Gradient Boosting (XGBoost), and Stochastic Gradient Boosting (SGB) are utilized. 2300 ground motion (GM) records, includes twenty-one input parameters and their nonlinear time history analyses results are considered as a dataset. The performance of the RF, XGBoost, and SGB models was examined considering the impact of the data pre-processing issue to test whether the use of data pre-processing approaches in model development could improve the prediction performance of the advanced ML models. Various data pre-processing techniques, including outlier detection using boxplot, missing data imputation using RF, data transformation using log transformation, and feature selection using Hill Climbing are employed as part of ML pipeline. The models' performance is evaluated using six different well-established statistical evaluation metrics. Subsequently, the results are systematically compared to identify the most effective prediction model. Our findings highlight the substantial impact of data pre-processing on the performance of ML models when predicting seismic responses, specifically the MDR of RC frames. Notably, RF consistently outperformed other ML models for both R8 and IR8 structures in the case of the simple ML pipeline strategy and data pre-processing approach. The RF model achieved R2 scores of R2 = 0.87 and R2 = 0.91 on the test data before implementing data pre-processing for R8 and IR8, respectively. After data pre-processing, R2 scores showed an improvement of 12% and 6.22% in the cases of R8 and IR8. In contrast, the performance scores of SGB consistently fell behind those of RF and XGBoost models.

Seismic performance assessment of RC bridge piers with variable hysteresis performance dampers

A novel variable hysteresis performance damper (VHD)—multi-stage slip friction damper is developed and applied to implement multi-level seismic resistance of structures. Different from the conventional slip friction dampers, which feature only a single type of slip friction surface, this innovative damper incorporates two types: a flat slip surface and a wedge slip surface. The quasi-static cyclic loading tests of the VHD were carried out to investigate its variable hysteresis performance. The test results revealed that the developed damper presented excellent adaptive performance, and its hysteresis behavior changed from a complete rectangle with efficient energy dissipation to a flag-shaped curve with exceptional self-centering capacity as deformation increases. Subsequently, the developed VHD with unique adaptive performance was applied in RC bridge piers (BP) to improve the seismic performance. Nonlinear time history and fragility analysis methods were employed to assess the seismic performance of the RC bridge piers with VHDs (BP-VHD) in deterministic and probabilistic manners, considering maximum and residual deformations as performance indicators. For comparison, seismic responses of RC bridge piers with traditional buckling restrained braces (BRBs) and self-centering energy dissipation braces (SCEBs) were also presented. The analysis and comparison results demonstrate that the developed VHD is as effective as BRB in reducing maximum deformation at small PGAs, meanwhile, it can effectively reduce the residual deformation of the structure to allowable values when the PGA is large. Furthermore, the failure probability of BP-VHDs is lower compared to piers with BRBs and SCEBs, particularly concerning maximum and residual drift ratios as performance indicators. The application of the VHD can effectively achieve the goal of multi-level seismic resistance for RC bridge piers.

Maximum Drift Demands of Earthquake Damaged Reinforced Concrete Columns Based on Residual Flexure Cracks

Assessment of existing reinforced concrete (RC) structures after an earthquake is a challenging task that must somehow relate qualitative and quantitative observations in the plastic hinge regions and the associated residual deformation capacity of damaged structures. Having an estimate available for the remaining drift capacity will result in more economical and informed decisions regarding demolition or strengthening options. This study aims to develop a practical methodology to estimate the maximum drift demand of an RC column based on the residual crack width. For this purpose, fiber-based frame elements are used to model the RC column considering appropriately concrete behavior in compression and tension stiffening effects. Afterwards, the accuracy and reliability of the proposed methodology are demonstrated by validating the computational approach with two cyclic experimental results from literature and new test data for a one-bay one-story RC frame conducted within the course of this study. A comprehensive parametric study is performed for RC columns with different axial loads, longitudinal and transverse reinforcement ratios, and ground motions to exhibit the stochastic behavior. The study identifies the axial load ratio as the predominant parameter. Key findings include strong correlations between maximum drift ratios and total residual crack widths, as well as maximum compressive strains, with regression analysis yielding equations for accurate drift ratio estimation. Simple predictive models are proposed to estimate the maximum deformation demands based on observed residual crack widths. Residual cracking exceeding 5 mm poses significant risk for the columns with axial load ratios above 0.4, with 90% probability of exceedance 2% drift ratio.

Experimental study on seismic performance of stainless steel full-scale frames: Global response

This paper presents an experimental study of the seismic performance of austenitic stainless steel full-scale frames using the pseudo-static test method. The bottom single-span, two-storey substructure of the designed prototype frame was chosen as the test frame. Two full-scale frames were tested, one with a bolt-welded joint and the other with an extended end-plate joint. This paper is the first of two accompanying papers to this experimental study and focuses on the specimen design, testing details and global response of the stainless steel frame under cyclic loading. The test results were utilized to analyse the global response of the frames, encompassing failure mode, bearing capacity, deformation capacity, energy dissipation capacity, the overstrength factor, ductility factor and seismic response modification factor. The experimental findings suggest that the stainless steel frames with two joint types demonstrate consistent ability to dissipate energy during cyclic loading. The structure also performs well in terms of deformation, with uniform inter-storey deformation and no soft-storey detected. The maximum storey drift ratio of the frame is 7%. Prior to reaching a storey drift ratio of 2%, the frames with both joint types exhibit similar cumulative plastic deformation, stiffness degradation, and cumulative energy dissipation.

Progressive collapse behaviour of earthquake-damaged interior precast concrete joints with headed bars and plastic hinge relocation

This study investigated progressive collapse behaviour of earthquake-damaged interior precast concrete (PC) joints with headed bars. The main objective was to quantify the impact of slight and moderate earthquake damage on their residual collapse resistance. The research began with a numerical investigation to understand the interaction between a 2D frame’s global response to seismic loading and its local response during a threat-independent progressive collapse event. Additionally, a separate set of numerical studies examined interior PC joints under cyclic loading to determine maximum drift ratio demands, yielding 2.5% for slightly and 3.5% for moderately damaged joints. Subsequently, an experimental programme under quasi-static loading conditions was conducted on five interior PC joints under cyclic loading, followed by progressive collapse resistance tests. Test results indicated that damaged joints exhibited flexural and catenary action during progressive collapse, but compressive arch action could not be mobilised due to residual cracks from the initial cyclic loading phase. Comparing damaged joints to fully intact ones from a companion study revealed deterioration in stiffness and deformation capacity during a subsequent progressive collapse, with degree of severity proportional to the extent of damage sustained in the cyclic loading phase. Relative to the intact joints without being subjected to cyclic loading, moderately damaged specimens exhibited a degradation of 63% in stiffness and 38% in deformation capacity, compared to slightly damaged specimens, which showed reductions of 38% in stiffness and 28% in deformation capacity. In contrast, strain hardening of steel bars in both slightly and moderately damaged specimens led to slightly greater collapse resistance than the intact joints. Additionally, failure mode shifted from ductile fracture to premature pull-through failure of headed bars in moderately damaged specimens. In this regard, in post-earthquake progressive collapse assessment, it is recommended to use maximum crack width thresholds of 0.2 to 1.0 mm for slight damage and 1.0 to 2.0 mm for moderate damage.

Strengthening damaged columns on the soft first story of reinforced concrete building using ultra-high-strength fiber-reinforced concrete panels

In this study, ultra-high-strength fiber-reinforced concrete (UFC) panels were used as a quick and effective measure for seismic strengthening of damaged reinforced concrete (RC) columns. Four 1/3-scale specimens, which replicated RC columns of the soft-first-story of a 10-story condominium building that was heavily damaged in the 2016 Kumamoto Earthquake, were constructed and tested. The specimens were strengthened using UFC panels after being preloaded to the drift ratio, at which the maximum load capacity of the target column was measured, and then subjected to the main loading until the ultimate state was reached. The UFC panels were installed on the two faces of the column in a direction parallel to the assumed loading direction. Two of the specimens had a UFC or RC wing wall attached to one side of the column, which was also aligned with the assumed loading direction. During the preloading and main loading, the specimens were subjected to a cyclic lateral load and varying axial load that simulated an earthquake load. The proposed method improved the maximum strength and ultimate drift ratio, and helped restore the initial stiffness of specimens with UFC panels and a wing wall to that of a column specimen during preloading. The test results of a previous study, wherein the target column, loading method, and strengthening method were the same but the specimens were not damaged before strengthening, were compared to study the impact of the damage on the RC column before strengthening.

Weak axis low-damage performance of seismic resilient rocking steel column base with friction connection

Rocking column bases with friction connections are a critical technology employed in the low-damage design of steel structures. In this study, cyclic loading tests were conducted along the weak axis of the column, incorporating INITIAL, AFTERSHOCK, and REPAIR cases, with a maximum drift ratio of 3%. In the AFTERSHOCK case, both the sliding and maximum moments at the column base exhibited a significant decrease of 67% and 16%, respectively. To address the decrease in sliding strength attributed to the loss of bolt tension, Belleville Springs (BeSs) were employed, and the bolts were maintained within the elastic range. The results demonstrate that the hysteretic curves of the column base almost perfectly align in all three cases, revealing a strength loss of less than 2% and a significant enhancement in seismic resilience. This low-damage column base proves well-suited for deployment in regions with high seismic risk, especially for buildings subjected to continuous seismic excitation. A finite element analysis (FEA) model was developed to quantitatively evaluate the damage, sliding, bolt tension loss, and energy dissipation performance of the column base. Finally, a simplified flag-shaped analytical model was proposed to guide the design of such low-damage column bases, providing a basis for their integration into overall structural analyses.

Seismic evaluation of historical Pertev Pasha Mansion under February 6 Kahramanmaraş (Pazarcık) Earthquake (Mw 7.7)

Historical masonry structures with aesthetic aspects play an important role in cultural heritage. However, such structures are vulnerable to seismic effects. Therefore, periodic maintenance and structural evaluations are required for these structures. In this study, a historical masonry building called the Pertev Pasha Mansion, located in Trabzon, Turkey, was selected for the evaluation. The building was demolished in the last few years and has been planned to be rebuilt in its original form. In the study, the finite element model of the building was created based on reconstruction drawings. Modal analysis was performed to obtain the frequencies and mode shapes of the building. Finally, seismic analyses were conducted based on the February 6 Kahramanmaraş earthquakes for two different acceleration records that were collected from different stations, one near the epicenter (Pazarcık station) of the earthquake and the other near the building (Ortahisar station). From the results of the modal analysis, the frequency and mode shapes of the structure were obtained. The displacement and stress results were obtained from the seismic analysis and presented with contour diagrams. At the end of the study, a general evaluation considering the novel Turkish guidelines for historic structures was conducted. According to the results of the seismic analysis performed using the Pazarcık station data, the drift ratio values of the structure exceeded 0.7%, which corresponds to the Collapse Prevention (CP) performance level. However, according to the seismic analysis results obtained using Ortahisar station data, the maximum drift ratio of the structure was 0.001%, corresponding to the Limited Damage (LD) performance level. Consequently, if the building had been built close to the center of the earthquake, it was likely to collapse, but it was estimated that it would have received limited damage because its current location was far from the center of the earthquake.

Comparative experimental study on shaking table test of small radius curved bridge considering different connection types between pier and beam

During the Great Wenchuan Ms 8.0 earthquake, many small-radius curved bridges suffered varying degrees of damage, including Baihua Bridge, Huilan Overpass, and Xiaohuangou Bridge. To understand the damage mechanism, shaking table tests were conducted on two scaled bridge models with different middle pier connection types. In one model, the middle pier and beam were cast monolithically together (CM bridge), while the other had a fixed support installed at the pier-beam connection (FS bridge). Both bridges were subjected to two earthquake ground motions. Visually, damage differed considerably between the bridges. The CM bridge exhibited many horizontal and circumferential cracks at the top and bottom. Meanwhile, the FS bridge concrete was crushed at the top of the middle pier, which must be paid attention to. Amplification factors, maximum drift ratios, residual drift, planar rotation angles, and bearing slip were analyzed for both bridges. For both structures, amplification factors in the X and Y directions decreased with stronger ground motions, while those in the Z direction showed an opposite trend; meanwhile, maximum drift ratios, residual drift, rotation angles, and bearing slip all increased with stronger motions. The acceleration amplification factors of the CM bridge increased with greater ground motion, rising rapidly. The CM bridge saw a maximum drift ratio of 7.07 versus 3.16 for the FS bridge. The trend for the CM bridge was a gradual increase, while the FS bridge had a sudden increase after the maximum drift ratio reached 1.61%. The CM bridge planar rotation angle rose gradually to 0.23°, while the FS bridge angle increased much faster, reaching 0.54° or 2.35 times that of the CM bridge. The FS bridge concrete splitting failure demonstrated vulnerability to seismic events exceeding the design level and the structural measures in this region should be enhanced in the design.

Seismic mitigation of continuous girder bridges equipped with U-shaped stainless steel dampers under near-fault earthquake excitations

Bridges that are close to seismic faults may suffer from severe damages under earthquake excitations. To enhance the seismic performance of continuous girder bridges, this paper presents a combined energy dissipation system (CEDS), incorporating isolation bearings and U-shaped stainless steel dampers. The U-shaped stainless steel dampers are equipped between every two bearings, and the top and bottom ends of dampers are fully fixed with the girders and the bent caps, respectively. Considering the strained conditions under seismic loadings, the mechanical property of U-shaped stainless steel dampers is numerically investigated with the loading directions of 0, 45, and 90 degrees. The hysteretic behavior of U-shaped stainless steel elements affected by the geometric parameters, i.e., the width, the thickness, the radius of arc segment, and the length of straight section, are further investigated. After that, a continuous girder bridge is adopted to verify the feasibility of the combined energy dissipation system, and two groups of U-shaped stainless steel dampers are designed for continuous piers and transition piers, respectively. The results turn out that the U-shaped stainless steel element shows excellent energy dissipation capacity. The maximum relative displacement between the girders and bent caps of piers can be effectively reduced by adopting the CEDS, which prevents the girders falling from supporting seats, and it is more effective in the longitudinal direction of bridges with the seismic reduction rate of 20–70%. Though the installation of U-shaped stainless steel dampers enhances the constrict of the top of piers, the maximum drift ratio increases in an acceptable range.

Experimental-analytical investigation of accelerated bridge construction concrete columns with self-centering Fe-SMA bars subjected to near-fault ground motions

Excessive seismic damage and residual deformation in bridge piers can result in time-consuming post-earthquake repair and replacement, which will adversely affect the recovery and seismic resilience of the transportation infrastructure. Seismic damage or permanent deformation in bridges can be minimized using advanced materials and novel technologies, of which shape memory alloy (SMA) has gained substantial momentum. The goal of this study is to investigate the feasibility of using unbonded iron-based shape memory alloy (Fe-SMA) bars as self-centering elements in accelerated bridge construction (ABC) piers to reduce residual seismic deformation. Shake table testing is performed on a one-third-scale bridge column specimen subjected to near-fault ground motions. A numerical model of the test specimen is developed in OpenSees, and the “pre-test” analysis results are compared with the experimental measurements. Acceptable correlations are observed between the simulated and measured residual drifts, accelerations, forces, and hysteretic responses. Furthermore, the test results are compared to that of a similar conventional cast-in-place RC column without self-centering elements. The maximum residual drift ratio in the tested Fe-SMA column specimen is found to be much smaller than the conventional column specimen highlighting the potential benefits of the proposed design.

Inerter location effect on the generalized tuned mass damper inerter control

This paper investigates the inerter location effect on the generalized tuned mass damper inerter (TMDI) control, in which the end of the inerter is located at any position of the primary structure. A good understanding of the inerter location effect can help us achieve an optimal generalized TMDI control. Two mass ratios weighting the mass amplification effect and negative stiffness effect are defined to understand the inerter location effect. Based on the two mass ratios, the relationship between the TMD and generalized TMDI is established, the analytical solution of the optimal tuning frequency is derived, and a high-accuracy prediction equation judging whether the generalized TMDI performs better than the TMD is proposed. Finally, numerical analyses on a 76-story high building equipped with TMD and generalized TMDI are performed. The results show that the the generalized TMDI in fact is a large mass ratio TMD with a frequency-dependent stiffness, the generalized TMDI with larger inertance and smaller physical mass has more inerter location choices, and the damping ratio of the primary structure has no influence on the critical inerter location. The generalized TMDI considering the inerter location effect has better control effect than the TMD in suppressing both the wind-induced vibration and earthquake-induced vibration. The mean reduction ratios of peak floor accelerations for the TMD and TMDI controls are 60.53% and 54.5% under the wind-induced force excitation, and those of maximum floor drift ratios for the TMD and TMDI controls are 94.32%, 87.56% under the earthquake excitation.

Experimental and Numerical Investigation on the Behavior of a New Replaceable Steel Device Used in Self-Centering Prefabricated Shear Wall

An experimental and numerical investigation on the behavior of a new replaceable steel device (RSD), is presented in this paper. The RSD consists of a steel pipe with two circular steel plates that close the ends of the tube, four stiffeners, and an added damping and stiffness (ADAS)-type steel plate that functions as a fuse element. This RSD is characterized by its compressive strength, which is much higher than its tensile strength and is compatible with the rocking behavior of a self-centering prefabricated shear wall (SCPSW), and also by its ability to dissipate energy. Three-dimensional finite element analyses were carried out to investigate the behavior and performance of the RSD, both individually and in the case where they were installed at the bottom of the toe and heel of a SCPSW. The results show that the RSD has stable behavior and is compatible with the gap opening in the corner of the SCPSW. The combined specimen of SCPSW and RSD (SCPSWR) remains stable under cyclic loading, with a maximum drift ratio of 3.98%, demonstrating that the RSD could be a viable candidate for practical use in seismic-prone areas. The behavior of the RSD was assessed by conducting two sets of cyclic tests, which provided good agreement with the numerical results. The results indicate that the RSD’s performance is influenced by the plastic behavior of the fuse element, plastic buckling of the disks, and pipe deformation. If the RSD is damaged, it can be easily replaced, because fabrication and installation of the proposed RSD is easy and cost-effective.

Seismic behavior of RC columns under high active confinement force

AbstractThis paper details the invention of a tensioning and anchoring device based on the “wedge‐cutting effect” that can tension and anchor multi‐layer carbon fiber reinforced polymer (CFRP) fabric. To achieve a high active confinement effect on an RC column, the device is characterized by its capability to lift the applied prestress to the greatest extent and minimize prestress loss. All eight RC columns with identical structural dimensions were designed and fabricated, including three unstrengthened and five strengthened columns. The seismic performance test and finite element simulation were conducted under a low cyclic reciprocating load. The test parameters include active confinement force and axial compression ratio, with active confinement force varying as a function of the number of layers of CFRP fabric. The results indicate that the seismic performance of RC columns with high active confinement can be significantly improved. Under a high axial compression ratio, the maximum displacement ductility coefficient and ultimate drift ratio of specimens strengthened with four layers of prestressed CFRP fabrics can increase by 87% and 152%, respectively, while the energy consumption can increase by 4.3 times. Additionally, the ultimate horizontal bearing capacity can be raised by 41%. The seismic performance of strengthened columns increases with the increase of active confinement, particularly under high axial compression. The finite element model is in good accord with the experiment. With an increase in active confinement force, the properties of confined concrete and CFRP are utilized to a greater extent, and more energy is dissipated by the opening and closing of numerous micro cracks.

Seismic Upgrading of Existing Steel Buildings Built on Soft Soil Using Passive Damping Systems

In regions prone to seismic activity, buildings constructed on soft soil pose a significant concern due to their inferior seismic performance. This situation often results in considerable structural damage, substantial economic loss, and increased risk to human life. To address this problem, this study focuses on the seismic retrofitting of steel moment-resisting frames using friction and metal-yielding dampers, taking into account the soil-structure interaction. The effectiveness of these retrofit methods was examined through a comprehensive non-linear time history analysis of three prototype structures subjected to a series of intense seismic events. The soil behavior was simulated using a non-linear Bouc-Wen hysteresis model. Various parameters, including lateral displacement, maximum drift ratio, the pattern of plastic hinge formation, base shear distribution, and dissipated hysteretic energy, were used to compare the performance of the two retrofit strategies. The findings from the non-linear analyses revealed that both retrofit methods markedly enhanced the safety and serviceability of the deficient buildings. The retrofitted structures exhibited notable reductions in residual displacements and inter-story drift compared to the original frame structures. In the original frame, primary structural elements absorbed a significant amount of the seismic input energy through deformation. However, in the retrofitted frames, dampers dissipated up to 90% of the total input energy. Additionally, integrating dampers into the original frames effectively transferred the non-linear response of the structural elements to the dampers.