Maximum Residual Drift Research Articles

Experimental study on hysteretic performance of self-centring energy dissipation beam-to-column connections equipped with SMA plates

Shape memory alloys (SMAs) exhibit excellent superelasticity. Using SMA members together with other energy dissipation members can help balance the self-centring and energy dissipation capacities of structures to achieve a better seismic performance. A novel type of self-centring energy dissipation beam-to-column connection equipped with SMA plate was proposed. The quasi-static tests were conducted and the hysteretic performance of the connections was evaluated. The results show that the bending strength and stiffness of the specimens equipped with a two-layer SMA connecting plate were larger than those of the specimens equipped with a one-layer SMA plate. The connections showed a good self-centring performance, and the maximum residual drift angle was only 0.35% when unloading from 4% drift angle. The SMA-Q160/ALA connection could recover 79.2% of the loading angle at most. Moreover, a SMA-Q160/ALA parallel system configuration could significantly improve the energy dissipation capacity of beam-to-column connections. The total energy dissipation and equivalent viscous damping coefficient were larger than those of the connections equipped with only SMA plate.

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.

Parametric study on a resilient hybrid steel-shape memory alloy yielding damper

A critical factor obstructing structural resilience is residual deformation after a damaging event. The search for a solution for removing residual deformation has led to the consideration of Shape Memory Alloys (SMAs) that can undergo large deformations and return to their original undeformed shape. This study focuses on an innovative hybrid yielding steel-SMA damper that uses monofilament wire loops. Because of numerous design parameters that affect the performance of this hybrid damper, this research aims to carry out a parametric study to optimize the damper’s performance. The study was conducted at the device level as well as a structural level. At the device level, the key design parameters, including SMA to steel ratio, max imposed strain, and the length of the elements, were evaluated. At the same time, the damper’s effect on the seismic performance of low, mid, and high-rise structures was investigated at the structural-level study. In the end, the results showed that using the damper in strong ground motions successfully reduced the maximum residual drift up to 71%, 97%, and 92% for low, mid, and high-rise structures, respectively. Therefore, it was concluded that the damper could add the self-centering ability to hysteretic dampers while maintaining satisfactory energy dissipation performance. Furthermore, some of the advantages claimed by the developers, including versatility in design and performance, adequate load resistance, and stable behavior, were also confirmed in this study.

Experimental study of precast self-centering concrete shear walls with external friction dampers

Self-centering walls perform relatively well in reducing structural damage and residual deformation owing to the joint rocking mechanism. Nevertheless, drawbacks of the self-centering walls were limited robustness and redundancy, thus sufficient dissipating capacity is essential for improving stiffness, reducing seismic response, and controlling structural collapse. Among all these dampers used in self-centering systems in previous studies, slip-friction dampers are highly preferred because of their simplicity, perfect rigid-plastic hysteresis characteristic, large stroke, and stable dissipating capacity. After the earthquake ceases, friction force can be eliminated by loosening the tightening bolts to help facilitate post-earthquake recovery, and it is convenient to be replaced or repaired. In the present study, experiments of asymmetric friction dampers with brass-steel interfaces were conducted. To obtain the optimal characteristics for stable dissipating, different configurations of slip-friction dampers were designed and tested. The friction dampers were further installed vertically at the base rocking joint of the self-centering shear walls, and the performance of the walls was studied under horizontal quasi-static cyclic loading. Application of the friction dampers significantly increases the energy dissipating capacity and the post-yield stiffness. The energy dissipating ratio improved up to 81.2% compared to rocking walls with no additional damping. Damage was limited to the brass shims in friction dampers, while wall specimens were able to exhibit up to 3.0% horizontal drift without cracks, degradation, and significant concrete damage at the boundary elements. An average maximum residual drift of both positive and negative directions observed at the end of the test was 0.415% at 3.0% horizontal drift, that major structural realignment is not required, and repair of the structure is practically feasible.

Seismic design and performance of a steel frame-shear plate shear wall with self-centering energy dissipation braces structure

The steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) is a new seismic lateral resistant component. This paper outlines the performance requirements of the steel frame-shear plate shear wall with self-centering energy dissipation braces (SF-SCSPSW) structure and presents a direct displacement-based seismic design method for the structure. A combined strip model of the SPSW-SCEDB that considers the effect of the bolted connection on the wall plate is established. The comparison of the simulated and experimental results shows that the model can accurately predict the strength and hysteretic behavior under cyclic loading. The 8- and 15-story prototype buildings were designed using the presented method. The results of nonlinear dynamic analysis showed that larger inter-story deformations occurred on the lower floors, and the inter-story ratios gradually decreased with an increase in the number of floors. The maximum inter-story drift ratio (1.73%) of the 8-story structure under mega earthquakes and the maximum residual drift ratio (0.018%) of the 15-story structure under large earthquakes were less than the limit values (2% and 0.5%). Local yielding occurred between the brace connection and the column under mega earthquakes, but the columns remained in an elastic state. The seismic responses of the SPSW-SCEDBs in the two structures met the performance requirements of being elastic and suffering light and moderate and serious damage under frequent, medium, large, and mega earthquakes, respectively. The effectiveness of the proposed design method was verified.

Cyclic response of a self-centering RC wall with tension-compression-coupled disc spring devices

A strong self-centering ability and robust ductility have previously been observed in the pseudo-static cyclic loading test conducted on a self-centering shear wall (SCSW) with disc spring devices (DSD). However, the bearing capacity and initial stiffness of the wall are reduced by 34.18% and 53.72% respectively compared with the conventional reinforced concrete wall. Therefore, this paper develops a tension–compression-coupled DSD (TCCDSD) to enhance the bearing capacity of the SCSW. The static cyclic responses of the TCCDSD and the SCSW-TCCDSD are investigated through numerical models. TCCDSD exhibits high first and soft second stiffness values during loading, as well as an asymmetric flag-shaped cyclic response. The mechanical model proposed in the paper demonstrates a high accuracy. Compared with the previous SCSW-DSD, the bearing capacity and initial stiffness of the SCSW-TCCDSD increase by 18.12% and 43.53%, respectively, yet the maximum residual drift ratio only increases by 0.044%. Parametric analysis reveals that increasing the first tensile stiffness or the first compressive stiffness of the TCCDSD can enhance the initial stiffness of the wall. Increasing the second compressive stiffness of the TCCDSD can reduce the residual drift of the SCSW, while a higher second tensile stiffness will result in an obvious residual drift. Moreover, a steel plate reinforcer (SPR) is designed to control the damage of the wall. Despite the reduction damage of the region covered by the SPR, severe shear deformation is concentrated on the interface between the wall and foundation as the SPR is not embedded into the foundation.

Seismic performance of bridge with unbonded posttensioned self-centering segmented concrete-filled steel-tube columns: An underwater shaking table test

As one of the prefabricated structures, precast segmented bridges can be used to shorten construction time, reduce traffic delays, improve quality control, and minimize environmental impact. Despite the numerous advantages of segmented pre-fabricated rapid assembly technology, it is not widely used in high seismic hazard zones nor applied to complex water-abundant situations because of the lack of knowledge on its seismic performance. Through experimental and numerical studies, researchers have studied the seismic performance of such type of column under quasi-static testing. The behaviors of the column or bridge under desired strong ground motions (GMs) have been rarely investigated. This paper presents the major findings of an underwater shaking table testing program conducted on a 1/4 scaled single-span bridge with novel self-centering segmented concrete-filled steel tube columns. This study focuses on the performance of the bridge subjected to different GMs under 4 water conditions, which are with water at a height of 1.2 m, 1.5 m, 1.8 m, and without water. The bridge model incorporated two post-tensioned precast self-centering segmented concrete-filled steel tube (PSCFST) single columns with fixed and sliding supports connected to a single span steel box-girder superstructure. The internal unbonded PT tendons are installed at the center of the segment section, and external energy dissipation (ED) bars are installed on the outside of the bottom segment. The bridge model was then subjected to a sequence of natural and artificial GMs with different amplitudes. The well-designed PSCFST bridge demonstrated a desirable seismic performance, and no significant damage was observed. Concerning the overall response of the structure, the maximum drift ratio reached 2.14%. Moreover, a maximum residual drift of 0.09% was observed after the tests, which indicates that the test model demonstrated a desirable self-centering capability after a sequence of GMs. The cumulative energy dissipation and equivalent viscous damping ratio of the bridge were calculated. A comparison is made for the seismic performance of the bridge especially in terms of the displacement and acceleration of the whole structure under the cases of with and without water.

Energy distribution in RC shear wall-frame structures subject to repeated earthquakes

Repeated earthquakes are possible events in seismic zones. The aftershocks can grow so large that they can be regarded as design-level earthquakes. These can affect the nonlinear behavior of structures. Different studies indicated that the destructions caused by earthquakes were highly influenced by the seismic energy induced to the structure during the earthquake. This study investigated the seismic behavior of RC shear wall-frame structures and the structural response and energy distribution in these structures subject to single and sequence of natural records. To this end, 10-, 15-, and 20-story structures were assessed for the selected structural system. Previous studies assessed the displacement, maximum drift, maximum residual drift, and energy distribution in structures. Therefore, this research aimed to study the records of the repeated sequences and their energy concepts. The results of analyses revealed that repeated earthquakes led to increase in seismic requirements of RC shear wall-frame structure, but it did not cause structural collapse. In addition, the presence of the second record reduced the residual structural displacement in some cases. Nevertheless, the effect of repeated earthquakes should be taken into consideration in the assessment of the reliability of structures. Other results on energy distribution indicate that an increase in the structure height will possibly increase the contribution of α[M] and decrease the contribution of β[K] in dissipation of input energy.

Validation of a steel dual-core self-centering brace (DC-SCB) for seismic resistance: from brace member to one-story one-bay braced frame tests

A steel dual-core self-centering brace (DC-SCB) is an innovative structural member that provides both energy dissipation and self-centering properties to structures, reducing maximum and residual drifts of structures in earthquakes. The axial deformation capacity of the DC-SCB is doubled by a parallel arrangement of two inner cores, one outer box and two sets of tensioning elements. This paper presents cyclic test results of a DC-SCB component and a fullscale one-story, one-bay steel frame with a DC-SCB. The DC-SCB that was near 8 m-long was tested to evaluate its cyclic behavior and durability. The DC-SCB performed well under a total of three increasing cyclic loading tests and 60 lowcycle fatigue loading tests without failure. The maximum axial load of the DC-SCB was near 1700 kN at an interstory drift of 2.5%. Moreover, a three-story dual-core self-centering braced frame (DC-SCBF) with a single-diagonal DC-SCB was designed and its first-story, one-bay DC-SCBF subassembly specimen was tested in multiple earthquake-type loadings. The one-story, one-bay subassembly frame specimen performed well up to an interstory drift of 2% with yielding at the column base and local buckling in the steel beam; no damage of the DC-SCB was found after all tests. The maximum residual drift of the DC-SCBF caused by beam local buckling was 0.5% in 2.0% drift cycles.

Significance of residual drifts in building earthquake loss estimation

SUMMARYThe influence of residual interstorey drifts on economic losses in building resulting from earthquakes is examined. Current building‐specific loss estimation methodologies that estimate economic losses based on peak response quantities such as peak interstorey drift ratios or peak floor accelerations are extended to explicitly account for residual interstorey drifts. The new approach incorporates the influence of residual drifts by accounting for the possibility of having to demolish a building as a result of excessive residual interstorey drifts, where the probability of demolition is computed as a function of the maximum residual drift in the building. The proposed approach is illustrated by estimating direct economic seismic losses in four reinforced concrete moment‐resisting frame buildings in Los Angeles, California. Two buildings have nonductile detailing representative of pre‐1970s building codes, whereas the other two buildings have ductile requirements satisfying current seismic building codes in the U.S. Results indicate that economic losses at intermediate levels of ground motion intensity are often dominated by losses due to residual interstorey drifts. This is particularly true in the case of ductile buildings in which neglecting losses from residual drifts can lead to significant underestimations of economic losses. Copyright © 2012 John Wiley & Sons, Ltd.

Probabilistic estimation of residual drift demands for seismic assessment of multi-story framed buildings

This paper presents the implementation of a probabilistic approach to estimate residual drift demands (e.g. residual roof, residual drift at specific stories, and maximum residual drift over all stories) during the seismic performance-based assessment of existing multi-story buildings. The approach combines residual drift demand fragility curves obtained from an inelastic intensity measure, incorporates explicitly the aleatory uncertainty (i.e. record-to-record variability) inherent in the estimation of residual drift demands at the end of the seismic excitation, with maximum inelastic displacement seismic hazard curves to obtain site-building-specific residual drift demand hazard curves which express the mean annual frequency of exceeding residual drift demands. Recognizing the evolution of central tendency and dispersion of residual drift demands with changes in the ground motion intensity, this procedure makes use of functional models that capture that variation. It is shown that the relationship between transient (maximum) and residual (permanent) drift demands depends on the mean annual frequency of exceedance and the building’s number of stories for a similar lateral load resisting system.