Conventional Moment-resisting Frames Research Articles

Design procedure of a shear fuse system for steel moment-resisting frames

In steel moment-resisting frames (MRFs), seismic energy is generally dissipated through the formation of flexural plastic hinges at beam ends. In ensuring such a mechanism, current code provisions limit the utilization of beams with small span-to-length ratios in MRFs. This study presents the design procedure of a novel shear fuse system that integrates replaceable shear links with non-prismatic beams to enhance the performance and repairability of MRFs with small beam span-to-length ratios. The proposed design strategically weakens the beam at its midspan by incorporating a replaceable link, prioritizing shear yielding in the link over flexural yielding in the beam outside the link, thus ensuring adequate frame ductility and protecting the critical beam-to-column connections. It can function as an efficient replaceable shear fuse system, as the damaged fuse can be substituted with a new one following a severe earthquake. In fulfilling the study’s purpose, first, several formulas are developed to provide a comprehensive design procedure. Next, example design calculations are presented for an MRF with a small beam span-to-depth ratio. Ultimately, a numerical investigation is provided to examine the proposed system’s performance compared to conventional MRFs. The results indicate that the proposed shear fuse system provides a more consistent cyclic behavior than the conventional prismatic beam design, exhibiting stable strain-hardening behavior up to the 5 % story drift ratio without noticeable strength degradation. It appropriately shifts the plastic hinges away from the beam-to-column connections while increasing the frame’s overall ductility with 1.14 times greater energy dissipation in the final loading cycles.

Experimental Study and Seismic Design of Swing Story-Lateral Force Resisting Structural System

A seismic vibration control system, consisting of a swing story substructure, a lateral force resisting substructure and connecting dampers, is recently proposed. The analytical model and optimization method based on the stability maximization and H2 criteria have been established. In this paper, excellent vibration control effects of the proposed system are verified through the small-scale shaking table tests on a two-story model. Experimental results demonstrate the accuracy of the analytical model and the validity of the vibration control strategy. Through numerical analyses of benchmark structures, the input energy of the optimally designed system is remarkably mitigated, and favorable vibration control effects for reducing both inter-story drifts and absolute floor accelerations under earthquake ground motions are verified by comparing with conventional moment-resisting frame structures. In addition, significant control effects can be achieved when the optimal stiffness is greater than the critical buckling stiffness. A seismic design flow chart of the intensity-reduced design method is proposed based on the numerical analyses and the Chinese Seismic Design Code of Buildings. The results indicate that the seismic intensity-reduced design for the proposed system is feasible.

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.

Residual drift risk of self-centering steel MRFs with novel steel column bases in near-fault regions

This paper evaluates the potential of novel steel column bases to reduce the residual drift risk of steel buildings located at near-fault regions when installed to post-tensioned self-centering moment-resisting frames (SC-MRFs). To this end, a prototype steel building is designed that consists of either conventional moment-resisting frames (MRFs) or SC-MRFs or SC-MRFs equipped with the novel steel column base (SC-MRF-CBs). The MRFs and SC-MRFs are used as benchmark frames. The frames are modelled in OpenSees where material and geometrical non-linearities are considered along with stiffness and strength degradation. A set of 91 near-fault ground motions with different pulse periods is used to perform incremental dynamic analysis (IDA), in which each ground motion is scaled appropriately until different residual storey drift limits are exceeded. The probability of exceedance of these limits is then computed as a function of the ground motion intensity and the period of the velocity pulse. Finally, the results of IDA are combined with probabilistic seismic hazard analysis models that account for near-fault directivity to evaluate and compare the residual drift risk of the frames used in this study. Results show that the predicted residual drift performance of the frames is influenced by the pulse period of the near-fault ground motions. The use of the novel steel column base significantly reduces the residual drift risk of the frames and the SC-MRF-CB exhibits the best residual drift performance. Finally, the paper highlights the effectiveness of combining post-tensioned beam-column connections with the novel steel column base, by showing that the SC-MRF-CB improves the residual drift performance of the MRF and SC-MRF by 80% and 50%, respectively.

Development of a corrugated web shear link for steel moment-resisting frames

Seismic codes set a minimum beam span-to-depth ratio for steel moment-resisting frames (MRFs) to ensure the formation of sufficiently long flexural plastic hinges at the beam ends. This requirement restricts the application of deep beams in framed-tube structures. To resolve this problem, this paper proposes using a replaceable corrugated web shear link at the beam mid-span. The proposed link is designed to ensure shear yielding in the link and prevent the formation of flexural plastic hinges at the beam ends. Given the use of a corrugated web in the proposed link, it eliminates the need for intermediate web stiffeners, which not only makes the link less expensive to build but also reduces the possibility of web fracture due to low-cycle fatigue by reducing the amount of welding involved in the construction process. The proposed design also makes it possible to replace the links damaged by strong ground motions, which improves the resiliency of the structure. The seismic performance of the proposed link was studied by experimentally-validated finite element modeling and analysis. For this purpose, single story-single bay MRFs with different span-to-depth ratios with and without the proposed system were modeled and analyzed under cyclic loading. In the numerical models, the corrugated webs of shear links were constructed with trapezoidal, zigzag, and curved geometries with different numbers of half-waves and corrugation angles. The results showed that the proposed system has lower strength degradation, more ductile behavior, and higher deformation and energy dissipation capacities than conventional MRFs.

Development, seismic performance and collapse evaluation of steel moment-resisting knee braced frame

This paper introduces and assesses the seismic and collapse behavior of a new lateral load-resisting system referred to as steel Moment-Resisting Knee Braced Frame (MKF). A design method following the Performance Based Plastic Design (PBPD) procedure is proposed to analyze the structure and size the structural members. A prototype frame part of an office building located in Vancouver, British Columbia, Canada is then selected to demonstrate the design method and evaluate the performance of the proposed system. The prototype MKF is also designed using the conventional elastic approach in accordance with the National Building Code (NBC) of Canada. The seismic performance and collapse response of the proposed system are examined using the nonlinear static analysis, nonlinear response history analysis (NLRHA) and incremental dynamic analysis (IDA) performed on the prototype five-story MKF under potential sources of seismicity in the west coast of Canada including shallow crustal, subduction interface and subduction intraslab events. Fragility curves are finally developed using results of the IDA to obtain the collapse probability of the system. The results of the analyses are compared to those obtained from a steel Moment-Resisting Frame (MRF) counterpart designed in accordance with the PBPD and elastic approaches. Findings of the study show that the proposed steel MKF can efficiently satisfy the code-specified story drift limit and manifest the yielding mechanism assumed in design. The MKF designed according to the PBPD approach offers the lightest structure among all frames studied and yields a collapse probability lower than that of the MKF designed as per the elastic design method. The proposed system can be used in seismic design of steel multi-story buildings as an alternative to conventional steel MRFs.

Local buckling behaviour of high-strength steel tubular columns subjected to one-sided cyclic loading and implications in seismic design of steel MRFs

After yielding, steel structures progressively exhibit an asymmetrical hysteretic behaviour under earthquakes biased in one direction (ratcheting effect). This response may be favourable to structural components because of the absence of symmetrical cyclic loading reversals. To evaluate the inelastic behaviour of components to asymmetrical cyclic loading, this study develops a set of one-sided cyclic loading histories for columns on the basis of a parametric study on the asymmetrical hysteretic behaviour of steel moment-resisting-frames (MRFs). Experimental and computational results indicate that steel tubular columns subjected to one-sided cyclic loading may exhibit 15%–71% higher ductility compared with that under symmetrical cyclic loading showing adequate resistance to local buckling initiation and sufficient ductility afterwards. These reduced ductility demands may permit the use of high-strength steels in energy dissipative zones, such as high yield-to-tensile strength ratio (Y/T) steels, resulting in reduced material consumption and more economical seismic design of buildings. The above findings are utilized in the seismic design of a MRF employing high Y/T steel, which enjoys almost the same lateral strength as a corresponding conventional steel MRF but nearly 25% smaller cross-sectional area in columns. Nonlinear time-history analyses revealed that the high Y/T MRF behaved elastically under frequent events, whilst the ground floor columns of the conventional MRF yielded. Under rare seismic events, the average story drift ductility demand for the high Y/T MRF was only 1.77, while for the conventional MRF was 2.57. The former MRF successfully resisted the earthquake loads without experiencing local buckling in columns.

Experimental investigation of moment resisting frames with perforated shear link

This paper focuses on the application of a new shear link in moment-resisting frames by perforating the web at the mid-span of the beam. Typically, in moment-resisting frames the plastic hinges are formed at the end of the beams adjacent to the beam-column connections. Seismic codes specify a minimum length for the beams that are part of the moment-resisting frames to ensure those beams are flexure-critical, and their plastic hinges are formed at their ends. The use of shear fuse in the mid-span of seismic beams enables the designers to violate the minimum span-to-depth ratio requirement and facilitates the replacement of the damaged parts of the perforated web moment resisting frames subjected to strong ground motions. In this study, a new shear link is proposed in the mid-span of the beam through perforating the web, resulting in a different plastic mechanism in structural beams. Two single-bay perforated web moment resisting frames with a beam span-to-depth ratio less than that required by seismic code provisions are tested. The specimens are subjected to a displacement-controlled cyclic loading. The test results are compared with those of a conventional moment-resisting frame with identical material and geometrical properties. Based on the test results, the new proposed perforated web moment resisting frames provides sufficient strength and stiffness with stable cyclic hysteresis loops. Besides, this frame is proposed in the rehabilitation of existing buildings for its ease of construction and providing shear fuse in the middle of the beam.

Mitigating seismic response of RC moment resisting frames using steel energy-dissipative columns

A novel system of steel Energy-Dissipative Columns (EDCs) is proposed to mitigate seismic responses of reinforced concrete Moment Resisting Frames (MRFs). The EDC-MF dual system aims to not only dissipate seismic energy by replaceable steel strip dampers in EDCs but mitigate inter-story drift concentration to avoid soft/weak-story failure of conventional MRFs. A simplified numerical model of EDC-MF dual system is established by using lumped mass shear model for MRFs and finite element model for EDCs. Parametric studies are conducted to investigate the effect of storey number, stiffness ratio, soft story factor and seismic intensity factor on the mitigation efficiency of EDCs. The results show that the lateral stiffness ratio of EDC to MRF, the story irregularity factor of MRFs, and the ratio of story shear capacity of EDC-MF systems to seismic base shear are the most important parameters. It is found that both the maximum inter-story drift and the inter-story drift concentration can be effectively mitigated due to the presence of EDCs, compared to traditional MRFs. The mitigation efficiency of EDCs increases with increasing lateral stiffness ratio and story irregularity factor under various ground motion intensities. A rational range of lateral stiffness ratios of 0.02–0.2 is recommended for the seismic design of EDC-MF dual systems.

Experimental testing and numerical modelling of a heavy timber moment‐resisting frame with ductile steel links

SummaryThis paper presents the development, experimental testing, and numerical modelling of a new hybrid timber‐steel moment‐resisting connection that is designed to improve the seismic performance of mid‐rise heavy timber moment‐resisting frames (MRF). The connection detail incorporates specially designed replaceable steel links fastened to timber beams and columns using self‐tapping screws. Performance of the connection is verified through experimental testing of four 2/3 scale beam‐column connections. All 4 connection specimens met the acceptance criteria specified in the AISC 341‐10 provisions for steel moment frames and exhibit high strength, ductility, and energy dissipation capacity up to storey drifts exceeding 4%. All of the timber members and self‐tapping screw connections achieved their design objective, remaining entirely elastic throughout all tests and avoiding brittle modes of failure. To assess the global seismic performance of the newly developed connection in a mid‐rise building, a hybrid timber‐steel building using the proposed moment‐resisting connection is designed and modelled in OpenSees. To compare the seismic performance of the hybrid MRF with a conventional steel MRF, a prototype steel‐only building is also designed and modelled in OpenSees. The building models are subject to a suite of ground motions at design basis earthquake and maximum credible earthquake hazard levels using non‐linear time history analysis. Analytical results show that drifts and accelerations of the hybrid building are similar to a conventional steel building while the foundation forces are significantly reduced for the hybrid structure because of its lower seismic weight. The results of the experimental program and numerical analysis demonstrate the seismic performance of the proposed connection and the ability of the hybrid building to achieve comparable seismic performance to a conventional steel MRF.

11.16: Seismic performance evaluation of MRFS with dissipative continuous columns

ABSTRACTThe Dissipative Continuous Column (DCC) concept is proposed as a gravity load and seismic energy dissipating dual‐functional structural component. The proposed DCC is made up of two closely spaced continuous columns which are interconnected with replaceable steel strip dampers (RSSDs) over the height. It works in a way similar to pin supported coupled shear walls, but minimizes the construction invasive and ensure rapid return to occupancy after severe earthquakes. The innovative moment resisting frame (MRF) system with DCCs can also mitigate the inter‐storey drift concentration and reduce the soft storey failure risk significantly due to the contribution of large flexure stiffness of the DCCs. Based on the experimental test results, a simplified analysis model of the DCCs is developed for the design and seismic performance evaluation of the MRFs system with DCCs. The simplified analysis model consists of dual column and multiple zerolength equivalent elasto‐plastic springs with rigid end. Numerical models of a 4‐story conventional steel MRF and a 4‐story steel MRF with DCCs were set up using the proposed simplified model. Nonlinear Dynamic Time History Analysis were undertaken, and the results showed that the MRFs with DCCs can reduce the economic loss by limiting the structural damage in the replaceable steel strip dampers and mitigating both the maximum inter‐story drift ratio and drift concentrations.

03.09: Performance assessment and design methodology of free from damage moment resisting frames

ABSTRACTThe seismic design strategy implemented in current codes is based on the capacity design principle that allows the formation of plastic hinges into predefined parts of the structure. Therefore, significant damage is expected at ultimate limit state, to which high repair costs are associated.Recently, new design strategies have been proposed in order to avoid the damage of the structure. The most of them are grouped into two categories, namely i) using special damping devices introduced in the structure as additional resisting element; ii) changing the dissipation mechanism of the structure by means of friction‐based dissipative joints. The second possibility is really promising and effective because it guarantees low forces transferred to the foundations and no architectural interference, if adopted for moment‐resisting frames (MRFs).The novelty of free from damage joints lays in the fact that the energy is dissipated by friction at the interface between plates in contact instead of the classical plastic deformation energy dissipation mechanism.The performance of MRFs equipped with free from damage joints differs from that of conventional MRFs. This implies the need to update the current EC8 rules to free from damage MRFs. Therefore, in this paper new design criteria have been proposed. The effectiveness of the new rules has been verified by means of a comprehensive set of numerical analyses, by comparing the seismic performance of two sets of frames having geometrical configurations that are typical for current European practice: a set of traditional MRF structures (EC8 compliant) and another set of MRFs equipped with friction joints.

Seismic performance assessment of steel moment-resisting frames equipped with linear and nonlinear fluid viscous dampers with the same damping ratio

This manuscript presents a comparative study between the seismic collapse performances of steel moment-resisting frames (MRFs) with the same additional damping ratio while equipped with linear and nonlinear viscous dampers. Three steel moment-resisting frames of 6, 8 and 12 stories were designed based on ASCE 7–10 with and without dampers. The characteristics of the linear (α=1) and nonlinear (α=0.5) dampers were then assigned while assuming equal damping ratios (20% for the models of 6 and 8 stories, and 25% for the model of 12 stories). The sophisticated nonlinear model of the structures was then developed in Opensees considering both cyclic strength and stiffness deterioration with lumped plasticity as well as the linear and nonlinear dashpot for dampers while nonlinear geometry was included in all the models. The collapse probability was calculated using well-known incremental dynamic analysis (IDA) under far-field records. The paper demonstrates that the use of damper improves the performance of the steel MRFs and reduces the collapse probability in comparison with the conventional steel MRFs. Moreover, it was observed that steel MRFs with linear dampers have better collapse performance than steel MRFs with nonlinear dampers for the same damping ratio.

Probabilistic economic seismic loss estimation in steel buildings using post‐tensioned moment‐resisting frames and viscous dampers

SummaryThe potential of post‐tensioned self‐centering moment‐resisting frames (SC‐MRFs) and viscous dampers to reduce the economic seismic losses in steel buildings is evaluated. The evaluation is based on a prototype steel building designed using four different seismic‐resistant frames: (i) conventional moment resisting frames (MRFs); (ii) MRFs with viscous dampers; (iii) SC‐MRFs; or (iv) SC‐MRFs with viscous dampers. All frames are designed according to Eurocode 8 and have the same column/beam cross sections and similar periods of vibration. Viscous dampers are designed to reduce the peak story drift under the design basis earthquake (DBE) from 1.8% to 1.2%. Losses are estimated by developing vulnerability functions according to the FEMA P‐58 methodology, which considers uncertainties in earthquake ground motion, structural response, and repair costs. Both the probability of collapse and the probability of demolition because of excessive residual story drifts are taken into account. Incremental dynamic analyses are conducted using models capable to simulate all limit states up to collapse. A parametric study on the effect of the residual story drift threshold beyond which is less expensive to rebuild a structure than to repair is also conducted. It is shown that viscous dampers are more effective than post‐tensioning for seismic intensities equal or lower than the maximum considered earthquake (MCE). Post‐tensioning is effective in reducing repair costs only for seismic intensities higher than the DBE. The paper also highlights the effectiveness of combining post‐tensioning and supplemental viscous damping by showing that the SC‐MRF with viscous dampers achieves significant repair cost reductions compared to the conventional MRF. Copyright © 2016 John Wiley & Sons, Ltd.

Development of structural shear fuse in moment resisting frames

Codes require that the span-to-depth ratio of the beams in moment resisting frames (MRF) should be limited to guarantee the development of plastic hinges with a sufficient length at beam ends. This requirement limits the application of MRFs mostly in framed-tube structures. In the current design procedure of steel MRFs, the strength and stiffness design of the structure are coupled often leading to overdesigned structures and foundations. To overcome the abovementioned limits, in this paper a new replaceable shear structural fuse is introduced for MRFs. The fuse is a shear link designed as a sacrificial component by weakening the shear strength of a segment at the middle of the beam to dissipate the seismic energy by shear yielding with stable hysteretic behavior. The monotonic and cyclic behavior of a single span-single story MRF with various beam span-to-depth ratios equipped with the proposed shear fuse is investigated through finite element modeling, verified using experimental data. The performance of the proposed system is compared with the conventional MRFs with flexural plastic hinges at reduced beam sections. In general, the shear yielding of the link is shown to be a great replacement for flexural hinges in MRFs, especially with low beam span-to-depth ratios.

Seismic performance and probabilistic collapse resistance assessment of steel moment resisting frames with fluid viscous dampers

SUMMARYThis paper evaluates the seismic resistance of steel moment resisting frames (MRFs) with supplemental fluid viscous dampers against collapse. A simplified design procedure is used to design four different steel MRFs with fluid viscous dampers where the strength of the steel MRF and supplemental damping are varied. The combined systems are designed to achieve performance that is similar to or higher than that of conventional steel MRFs designed according to current seismic design codes. Based on the results of nonlinear time history analyses and incremental dynamic analyses, statistics of structural and non‐structural response as well as probabilities of collapse of the steel MRFs with dampers are determined and compared with those of conventional steel MRFs. The analytical frame models used in this study are reliably capable to simulate global frame collapse by considering full geometric nonlinearities as well as the cyclic strength and stiffness deterioration in the plastic hinge regions of structural steel members. The results show that, with the aid of supplemental damping, the performance of a steel MRF with reduced design base shear can be improved and become similar to that of a conventional steel MRF with full design base shear. Incremental dynamic analyses show that supplemental damping reduces the probability of collapse of a steel MRF with a given strength. However, the paper highlights that a design base shear equal to 75% of the minimum design base shear along with supplemental damping to control story drift at 2% (i.e., design drift of a conventional steel MRF) would not guarantee a higher collapse resistance than that of a conventional MRF. At 75% design base shear, a tighter design drift (e.g., 1.5% as shown in this study) is needed to guarantee a higher collapse resistance than that of a conventional MRF. Copyright © 2014 John Wiley & Sons, Ltd.

Seismic design, modelling and assessment of self-centering steel frames using post-tensioned connections with web hourglass shape pins

A new self-centering steel post-tensioned connection using web hourglass shape pins (WHPs) has been recently developed and experimentally validated. The connection isolates inelastic deformations in WHPs, avoids damage in other connection parts as well as in beams and columns, and eliminates residual drifts. WHPs do not interfere with the composite slab and can be very easily replaced without bolting or welding, and so, the connection enables non-disruptive repair and rapid return to building occupancy in the aftermath of a strong earthquake. This paper presents a simplified nonlinear model for the connection and the associated beams and columns that consists of nonlinear beam-column elements, and hysteretic and contact zero-length spring elements appropriately placed in the beam-column interface. The model was calibrated against experimental results and found to accurately simulate the connection behaviour. A prototype building was selected and designed as a conventional steel moment-resisting frame (MRF) according to Eurocode 8 or as a self-centering steel MRF (SC-MRF) using the connection with WHPs. Seismic analyses results show that the conventional MRF and the SC-MRF have comparable peak storey drifts, and highlight the inherent potential of the SC-MRF to eliminate damage in beams and residual drifts. The paper also shows that repair of damage in the conventional MRF will be costly and disruptive after the design basis earthquake, and, not financially viable after the maximum considered earthquake due to large residual drifts

Seismic design and evaluation of steel moment‐resisting frames with compressed elastomer dampers

SUMMARYThis paper evaluates the hysteretic behavior of an innovative compressed elastomer structural damper and its applicability to seismic‐resistant design of steel moment‐resisting frames (MRFs). The damper is constructed by precompressing a high‐damping elastomeric material into steel tubes. This innovative construction results in viscous‐like damping under small strains and friction‐like damping under large strains. A rate‐dependent hysteretic model for the compressed elastomer damper, formed from a parallel combination of a modified Bouc–Wen model and a non‐linear dashpot is presented. The model is calibrated using test data obtained under sinusoidal loading at different amplitudes and frequencies. This model is incorporated in the OpenSees [17] computer program for use in seismic response analyses of steel MRF buildings with compressed elastomer dampers. A simplified design procedure was used to design seven different systems of steel MRFs combined with compressed elastomer dampers in which the properties of the MRFs and dampers were varied. The combined systems are designed to achieve performance, which is similar to or better than the performance of conventional steel MRFs designed according to current seismic codes. Based on the results of nonlinear seismic response analyses, under both the design basis earthquake and the maximum considered earthquake, target properties for a new generation of compressed elastomer dampers are defined. Copyright © 2011 John Wiley & Sons, Ltd.

Development of floor slab for steel post-tensioned self-centering moment frames

A floor slab constructed in conventional moment-resisting frames (MRFs) limits opening of gaps at the beam-to-column interfaces, causing losses of self-centering capability and preventing its use in steel post-tensioned (PT) moment frames. This work presents two novel slab schemes to reduce the restraints on the seismic responses of a PT frame. The first scheme uses a slab in typical MRFs with a modification so that near the connection, the metal deck is discontinuous and the longitudinal bar in the deck is debonded from concrete to minimize slab restraints. The second scheme uses truss elements to connect the slab and beams in only one bay (rigid bay) of the PT frame for transferring inertial forces from the floor to the frame. The sliding device is provided at one end of floor beams transverse to the PT frame, where sliding of the slab is expected. The cyclic behaviors of the bare connection and the connection with the first slab scheme are also evaluated by testing four connections. Additionally, how the rigid bay affects the cyclic behavior of the frame, distribution of column shear, beam axial force variation, and gap opening response near the beam-to-column interface is evaluated by conducting frame subassembly tests. The test results demonstrate that (1) the PT frame with any of two slab schemes develops large deformation capacities with small residual deformations, and (2) the column shear and beam axial force can be estimated based on the proposed method.

Experimental evaluation of the seismic performance of steel MRFs with compressed elastomer dampers using large-scale real-time hybrid simulation

Real-time hybrid simulation combines experimental testing and numerical simulation, and thus is a viable experimental technique for evaluating the effectiveness of supplemental damping devices for seismic hazard mitigation. This paper presents an experimental program based on the use of the real-time hybrid simulation method to verify the performance-based seismic design of a two story, four-bay steel moment resisting frame (MRF) equipped with compressed elastomer dampers. The laboratory specimens, referred to as experimental substructures, are two individual compressed elastomer dampers with the remainder of the building modeled as an analytical substructure. The proposed experimental technique enables an ensemble of ground motions to be applied to the building, resulting in various levels of damage, without the need to repair the experimental substructures, since the damage will be within the analytical substructure. Statistical experimental response results incorporating the ground motion variability show that a steel MRF with compressed elastomer dampers can be designed to perform better than conventional steel special moment resisting frames (SMRFs), even when the MRF with dampers is significantly lighter in weight than the conventional MRF.