Performance Of Steel Moment Frames Research Articles

Seismic Behavior Improvement of Rigid Steel Frame Braced with Cable and Optimal Rotational Friction Damper

The research focused on enhancing the seismic performance of steel moment frames using cable braces and a central friction damper. By optimizing the design and pretensioning force of the cable braces, this study aimed to improve the energy absorption and overall behavior of the frames under cyclic earthquake loads. A quasi-cyclic loading test was developed through FE simulations using ABAQUS software, version 2023. To verify the modeling, an experimental test was compared with the numerical modeling, and the numerical results confirmed the accuracy of the experimental data. Results made by modeling in ABAQUS software (version 2023) include the impact of pretensioning force on stiffness and energy absorption, the relationship between pretensioning force and force required to move the target, the increase in absorbed energy with pretension force up to 25%, and the superior seismic performance of frames with rotational friction dampers. This study also highlighted the benefits of using cable braces with a friction damper regarding the symmetry of hysteresis diagrams, cyclic performance, and energy absorption capacity. The amount of pretensioning of the cables affects the energy dissipation capacity. As the pretensioning of the cables increases, the energy dissipation capacity initially increases. However, further increases in pretensioning lead to decreased energy dissipation capacity beyond a certain point. When the percentage of cable brace pretension increases from 2% to 25%, the energy dissipation capacity is enhanced by 2%, and when in the 25–30% range, it stabilizes at around 35%. Energy dissipation capacity decreases for pretensions of more than 30%.

Database of tall pre-Northridge steel moment frames for earthquake performance evaluations

This article describes a detailed database of tall steel moment frame buildings that are representative of the construction practices in San Francisco prior to the 1994 Northridge earthquake. The database contains design details that affect the structural performance of steel moment frames, including frame geometry, member cross-section sizes, and gravity system characteristics. This database also captures irregularities that might impact seismic response, such as podiums, setbacks, mass concentrations (mechanical, electrical, and plumbing (MEP) floors), interrupted column lines, and atriums. The database includes information on 89 moment frame buildings, 14 of which were built before 1960 and are constructed with riveted connections, while the remaining 75 have welded flange connections like those that suffered brittle fracture during the 1994 Northridge earthquake. The buildings are further distinguished between space frame, perimeter frame, and partial space frame systems. For about half (41/89) of the buildings in the database, section sizes of representative structural members were collected, which enabled the evaluation of the seismic design, elastic, and inelastic response using computational workflows. The design diagnostics indicate that most of the buildings meet the minimum seismic strength and strong-column weak-beam requirements of modern building codes, even though they were not necessarily designed with this intent. On the contrary, about one-third of the buildings do not meet the seismic design drift limit of current codes, and about half of them have weak beam-column panel zones. This database, associated structural analysis models, and processing scripts are published at DesignSafe https://doi.org/10.17603/ds2-wjad-r340 to facilitate collaboration and continued development of open-source data for high-resolution simulations to inform risk mitigation strategies on a regional scale.

Seismic Performance of Steel Moment Frame with Side-Plate Connections Combined with Friction Dampers

With the gradual change in the design method of structures from resistance-based methods to performance-based methods, existing common building frames do not respond to the criteria of these methods, and if these frames are designed with new performance criteria, the design will be uneconomical. The basic problem of the existing types of frames is the imbalance between hardness and plasticity in them. A structure must have sufficient hardness in order not to be displaced in an earthquake, and it must have high ductility in order to dissipate the energy of the earthquake well. In this article, the purpose of the structure's performance in the combination of friction dampers and side-pleat joints in the steel structure of the bending frame is according to the constraints in solving the problem such as architectural, executive and design limitations and considering the uncertainties inherent in the system. This problem is solved in such a way that all three conditions are estimated, and for this purpose, three structures, 6, 10, 15 stories, have been modeled in three dimensions and have been analyzed under time history analysis. In examining the arrangement of dampers in the frames, the amount of energy in the 3x3 structures in the second frame is more than the first frame, which has increased by about 15%. But in 5x5 structures, the amount of energy when the frame damper is 3 is more than other frames. In these structures, when the damper is in the third frame, the energy of the structure has increased by about 10% compared to other states. Also, the effect of side plate connection in increasing the hardness is also important. that the above connection will reduce displacement by creating hardness at the connection point, and as a result, it will absorb more energy.

Study of the seismic behavior of rigid and semi-rigid steel moment-resisting frames

Steel moment resisting frames are prevalent seismic force resisting systems that are used extensively in high seismic regions worldwide. New design procedures suggested by codes have resulted in extensive use of semi-rigid connections in moment resisting frames. These connections have some degree of flexibility. This study focuses on seismic performance of steel moment-resisting frames with different degrees of moment connection rigidities. Three moment frames (5, 10 and 15 stories), each with different levels of connection rigidities (full, 80%, 70% and 60% rigidities) are analyzed under the 22 far-field ground motions presented in FEMA P695. Detailed modal analysis, non-linear static (pushover) analysis and incremental dynamic analysis (IDA) were conducted. Results reveal that semi-rigid frames have lower base shears and higher structural deformations, but higher energy absorption capability. Lastly, detailed performance analysis was conducted. The results show that probability of exceeding the fully operational performance level is higher in semi-rigid frames as compared to rigid connections. The inclusion for the rigidity in the beam-column can have an impact on the performance of steel moment frames which cannot be ignored during the design and retrofit of steel moment-resisting frames.

The Effect of Post-Earthquake Fire on the Performance of Steel Moment Frames Subjected to Different Ground Motion Intensities

The Effect of Post-Earthquake Fire on the Performance of Steel Moment Frames Subjected to Different Ground Motion Intensities

Cyclic performance of steel moment frames with prefabricated RC and ECC wall panels

This paper presents an experimental and numerical study on the cyclic performance of steel moment frames with prefabricated wall panels. Two types of prefabricated wall panels are included in the test program, namely the reinforced concrete (RC) panel and the engineered cementitious composites (ECC) panel. Three full-scale frame specimens, with dimensions of up to 4,350 × 4,200 mm, are tested under cyclic loading to reveal the failure pattern, the hysteretic behaviour, the bearing capacity, and the stiffness degradation when working with different types of wall panels. The experimental results demonstrate that, compared to an RC wall panel, an ECC wall panel significantly improves the bearing capacity and the stiffness of a steel moment frame. Additionally, the steel frame-ECC wall panel specimen exhibits gradual reduction in bearing behaviour at the post-peak stage due to the ductile ECC material. A detailed finite element modeling (FEM) is established and validated by the test results. The laws of the internal force distribution are proposed for the steel frame-wall panel members, which indicate that the ECC wall panel works effectively at relatively larger drift ratios and exhibits superior synergistic characteristic with the steel moment frame.

Seismic performance of steel moment frames considering the effects of column-base hysteretic behavior and gravity framing system

This paper presents a parametric study conducted on five Steel Moment Frames (SMFs) varying in height (2-, 4-, 8-, 12-, and 20- story) to assess the interactive effect of the column base hysteretic behavior, continuous gravity columns and partially restrained gravity beam-column connections in their seismic performance. The frame response is examined through sophisticated Nonlinear Time History (NTH) and Nonlinear Static Pushover (NSP) analyses conducted as per FEMAp695 methodology. For each SMF, a range of base connection strengths (and their corresponding rotational stiffnesses) accompanied by different levels of gravity columns rigidity and gravity connection strengths are assigned, resulting in a total of 80 model simulations. Two collapse/failure limit states are formulated for the assessment 1) sidesway collapse defined as per FEMAp695; and 2) column-base connection failure, defined as base rotations exceeding a 0.05 rad threshold. Results from the simulations indicate that the gravity framing system profoundly affects the behavior of the SMFs analyzed by reducing their probability of collapse. In this manner, the seismic demands for the design of column-base connections can be reduced safely, incorporating their high deformation capacity as part of the energy dissipative mechanisms. Potential design implications are discussed, and limitations, as well as lines for future research, are outlined.

Seismic Performance Evaluation of Steel Moment-Resisting Frames Designed According to 3rd and 4th Editions of 2800 Seismic Code

Current design codes have prepared linear analysis methods instead of nonlinear ones in order to reduce time, cost and other factors such as less need of these methods for expert knowledge. In linear analysis method, elastic strength demand of structure is decreased by applying a response modification factor called behavior factor (R) and by considering the design code regulations, structure members will be permitted to experience nonlinear response (in the time of middle-to-severe earthquakes). Because of different assumptions for linear (force-based method that has deficiencies) and nonlinear methods and whereas seismic stability or instability is not merely related to the strength of structure, rather it depends largely on the capability of structure to resist drifts, seismic performance evaluation of structures designed by linear procedure appears to be necessary using standards for evaluation. In this research, seismic performance of steel moment frames once designed based on 3rd edition of 2800-Iranian seismic code and allowable stress design (ASD) method and another time based on new ones, the 4th edition of 2800 seismic code and load and resistance factor design (LRFD) method, are compared with each other through nonlinear pushover and time-history analyses according to ASCE/SEI 41–13. Results showed positive change of design codes procedure with respect to alteration of design method in both types of ductile design, intermediate and special. Since mean of overstrength values and mean of ductility values have increased a little, mean of behavior factor values has become closer to the recommended values of the new seismic code. Also, a small number of structures met total collapse during nonlinear time-history analyses.

Seismic Performance of Steel Moment Frames Containing Concentric Bracing Equipped with Shape Memory Alloys

Background: A building’s stability is a critical design element that structural engineers must understand. And, utilization of Shape Memory Alloys (SMAs) in steel structures can importantly diminish seismic residual deformations, which will facilitate postseismic retrofitting. Objective: The aim of the present study was to evaluate the seismic behavior of 7-story and 15-story steel frames with moment frame system having chevron concentric brace equipped with Shape Memory Alloys (SMAs). Braces containing various amount of alloy (including 20%, 40%, 60%, 80% and 100%) applied to study SMAs effect on structural performance. Relatively persistent displacement of the structure as well as its relative maximum displacement under the earthquake imposing on frame models were investigated using non-linear dynamic analysis by OpenSees finite element software. The earthquakes were in near- fault nine accelerographs, which involved various maximum accelerations. Results: Results indicated a reduction in relatively persistent displacement using 20% SMAs in braces. Addition more amount of alloy resulted in less relative displacement as compared to steel one braces. Conclusion: Applying SMAs brace showed a reduction in persistent structural displacement in any types of frames. Furthermore, adding more than 20% SMAs to the brace, resulted in a decrease in structural displacement.

Evaluation of Progressive Collapse Resistance of Steel Moment Frames Designed with Different Connection Details Using Energy-Based Approximate Analysis

This study evaluates the progressive collapse resistance performance of steel moment frames, individually designed with different connection details. Welded unreinforced flange-bolted web (WUF-B) and reduced beam section (RBS) connections are selected and applied to ordinary moment frames designed as per the Korean Building Code (KBC) 2016. The 3-D steel frame systems are modeled using reduced models of 1-D and 2-D elements for beams, columns, connections, and composite slabs. Comparisons between the analyzed results of the reduced models and the experimental results are presented to verify the applicability of the models. Nonlinear static analyses of two prototype buildings with different connection details are conducted using the reduced models, and an energy-based approximate analysis is used to account for the dynamic effects associated with sudden column loss. The assessment on the structures was based on structural robustness and sensitivity methods using the alternative path method suggested in General Services Administration (GSA) 2003, in which column removal scenarios were performed and the bearing capacity of the initial structure with an undamaged column was calculated under gravity loads. According to the analytical results, the two prototype buildings satisfied the chord rotation criterion of GSA 2003. These results were expected since the composite slabs designed to withstand more than 3.3 times the required capacity had a significant effect on the stiffness of the entire structure. The RBS connections were found to be 14% less sensitive to progressive collapse compared to the WUF-B ones.

Probabilistic Seismic Assessment of SMFs with Drilled Flange Connections Subjected to Near-Field Ground Motions

This paper aims to probabilistically evaluate the influences of drilled flange (DF) connection on seismic performance of steel moment frames (SMFs) incorporating near-field ground motions. Meanwhile, reduce beam section (RBS) connection as a prequalified connection and pre-Northridge welded unreinforced flange (WUF) connection were compared with DF connection. To model accurately the components of RBS and WUF connections and panel zone in SMFs, the proposed models of former researches were utilized. However, to simulate all DF connections the hinge properties were extracted from experimentally validated finite element models. Two sample low- and high-rise buildings were designed based on valid codes and simulated by OpenSees platform in order to study the nonlinear performance of aforementioned connections. Incremental dynamic analysis process was carried out to assess comprehensively the effect of DF connection on structural response and probability of structural instability for various intensity of seismic loads. Then, the seismic risk for Collapse Prevention and immediate occupancy limit states were calculated by fragility analysis. Also, seismic demand hazard curves for the sample buildings were extracted. The results of this study indicated that DF connections provided acceptable seismic performance as well as RBS connections in low- and high-rise buildings.

Column splice fracture effects on the seismic performance of steel moment frames

The influence of welded column splice fracture on the seismic response of steel moment frames is examined. The study is motivated by pre-Northridge moment frames with welded column splices with crack-like flaws that are highly vulnerable to fracture. Costly retrofit strategies to repair these splices are usually intentioned to preclude splice fracture, without an explicit examination of its effects on global response. This study simulates post-fracture response of splices through a new material model, which is informed by fracture-mechanics based estimates of splice strength, and reproduces phenomena such as gapping and re-seating that occurs in the splices after fracture. Nonlinear response history simulations (incorporating this model) are used to examine the response of 4- and 20-story moment frames. The simulations, using 100 ground motions, and reflecting key aspects of nonlinear response are conducted within a Performance Based Earthquake Engineering (PBEE) framework, to examine global and local structural response in a probabilistic sense. The simulations indicate that neither the collapse potential nor building deformations are significantly affected by splice fracture when compared to benchmark simulations without fracture. This is attributed to a combination of phenomena; these include the mobilization of building rocking due to splice fracture, and the tendency of fractures to cascade upwards through individual columns rather than across a story. The results suggest that splice fracture may not necessarily trigger structural collapse, and retrofit strategies that consider global, rather than local response may be more cost effective. Limitations of the study are outlined.

Applications of vertical steel pipe dampers for seismic response reduction of steel moment frames

A newly developed vertical steel pipe damper is introduced to improve the seismic performance of steel moment frames. The damper exhibits large lateral stiffness and excellent capability to dissipate energy due to earthquakes. It provides a reliable, compact, inexpensive, and replaceable damper. Improved performance of the structure is verified analitically using a four-story steel moment frame equipped with steel pipe dampers. Vertical steel pipe dampers are placed between any two points where large relative motion exists during earthquake excitation. A nonlinear dynamic analysis of the structure using PERFORM-3D software demonstrated the significant benefit of equipping the structure with steel pipe dampers. All structural components, except the steel pipe dampers, remain elastic during earthquake excitation. Structures properly designed with vertical steel pipe dampers will only require minimum post-earthquake inspection and limited damage. Some practical issues associated with the application of vertical steel pipe dampers to building structure for seismic response reduction are presented in this paper.

A superelastic viscous damper for enhanced seismic performance of steel moment frames

This study proposes a hybrid passive control device and investigates its performance in improving response of steel frame structures subjected to multi-level seismic hazards. The proposed superelastic viscous damper (SVD) relies on shape memory alloy (SMA) cables for re-centering capability and employs a viscoelastic (VE) damper that consists of two layers of a high damped (HD) blended butyl elastomer compound to augment its energy dissipation capacity. First, experimental tests are conducted to characterize behavior of SMA cables and VE damper and to assess the influence of various parameters such as displacement amplitude and loading frequency on their mechanical response. Then, an analytical model of a six-story steel special moment frame building with the installed SVDs is developed to determine the dynamic response of the structure. Nonlinear response history analyses are conducted to evaluate the behavior of controlled and uncontrolled buildings under 44 ground motion records. Results shows that SVDs can effectively mitigate dynamic response of steel frame structures at different seismic hazard levels and enhance their post-earthquake functionality.

The beneficial effects of beam web opening in seismic behavior of steel moment frames

Implementation of openings in beams web has been introduced as an innovative method for improving seismic performance of steel moment frames. In this paper, several steel moment frames have been studied in order to evaluate the effect of openings in beams web. The beam sections with web opening have been modeled as a simplified super-element to be used in designing frames and to determine opening configurations. Finite element models of designed frames were generated and nonlinear static pushover analysis was conducted. The efficient location for openings along the beam length was discovered and the effects of beams with web openings on local and global behavioral characteristics of frames were discussed. Base on the results, seismic performance of steel moment frames was improved by creating openings in beams web, in terms of reduction in stress level of frame sensitive areas such as beam to column connections and panel zones.

Seismic performance of steel moment frames with reduced beam sections

This paper presents an investigation on the seismic performance of steel moment-resisting frames with reduced beam sections (RBS), and addresses the design issues related to the RBS frames. Nonlinear static and time history analyses of eight frames (three- and ten-story steel moment frames with different RBS configurations are conducted. The 1940 Imperial Valley (El Centro station, 0.32 g PGA) and the 1994 Northridge (Newhall station, 0.59 g PGA) ground motions factored to 0.3 g and 0.6 g are used in the time-history analyses. Global and local performances of the frames are discussed in terms of plastic deformation, inelastic drift ratio, as well as strength demand. The quantitative indices, such as flange reducing rate and location of the RBS, are recommended for seismic design practice.