Steel Moment Resisting Frame Structures Research Articles

Seismic behavior and life-cycle cost effectiveness of steel moment resisting frame structures with self-centering friction-viscous dampers

The self-centering friction-viscous damper (SCFVD) is a novel self-centering system that utilizes preloaded ring springs to offer self-centering and friction-based energy dissipation capacity, while a viscous damper provides viscous-based energy dissipation capacity. This study is to study the seismic behavior of steel moment-resisting frames (MRFs) with SCFVDs, considering cost effectiveness. The mechanical model of the SCFVD is first presented and validated through pseudo-static tests on a full-scale specimen. Simulation models of 3-story, 9-story, and 20-story steel MRFs with SCFVDs and viscous dampers are then built, and numerical analysis under 40 earthquake records is conducted on them to compare and evaluate the structural peak dynamic response and energy dissipation from an economic perspective. The results show that the SCFVD's hysteretic response can be reliably predicted by the mechanical model. When compared to the uncontrolled steel-MRFs and the steel-MRFs with FVDs, the SCFVD can significantly mitigate structural peak and residual drift, especially under high-intensity earthquakes, but may aggravate structural peak acceleration. Besides, the SCFVD can mitigate the structural hysteretic energy dissipation and damage to the 3-story and 9-story steel MRFs. The cost/average reduction ratio of peak drift for the steel-MRFs with SCFVDs is reduced by 6.3% when compared to that for the steel-MRFs with FVDs.

Ideal-Pulse-Based Strong-Motion Duration for Multi-Pulse Near-Fault Records

ABSTRACT Serious damage to near-fault structures is caused mainly by velocity pulses in a ground motion, hence, the necessity to develop a pulse-related definition of strong-motion duration to adequately describe the intensity of near-fault ground motion. For a multipulse record, an ideal-pulse-based strong-motion duration, which is defined as the time interval between the beginning of the first pulse and the end of the last pulse in an ideal-pulse signal, is proposed. This strong-motion duration corresponds with the time interval of the occurrence of strong vibrations and energy accumulations in the original record. For near-fault records, pulselike characteristics can be completely presented within this duration. Meanwhile, the ideal-pulse-based strong-motion duration shows good performance in the estimation of structural responses. The elastic and inelastic displacement spectra of the original records agree well with those of the records shortened according to the proposed duration. The validity of applying the proposed duration to structural analysis is further verified by the nonlinear time history analyses of 3-, 9-, and 20-story steel moment-resisting frame structures. The proposed strong-motion duration accurately estimates nonlinear structural responses. It is proven that the ideal-pulse-based strong-motion duration can adequately describe the intensity of near-fault ground motions, both from the perspective of the energy accumulation process in a ground-motion record and that of the structural analyses subjected to these ground motions.

Seismic Fragility Assessment of SMRFs Equipped with TMD Considering Cyclic Deterioration of Members and Nonlinear Geometry

This paper presents seismic fragility curves to assess the effect of far-field ground motions on the behavior of high-rise steel moment resisting frame (SMRF) structures equipped with Tuned Mass Damper, considering the cyclic deterioration of members and P-Delta effect in the nonlinear region. For this purpose, three 8-, 20-, and 30-story SMRF structures are selected, 44 earthquake record sets are extracted from the FEMA P-695, Incremental Dynamic Analysis (IDA) is operated, and four structural damage states are considered through the framework of HAZUS, including slight, moderate, extensive, and complete. Maximum structural inter-story drift and floor acceleration are employed to quantify the damage states, and spectral acceleration is used as the intensity measure. Results show that the Tuned Mass Damper can reduce the probability of damage under earthquake excitation in all damage states for both structural and non-structural elements. The decline varies from 4.0% to 20.0%, depending on the ground motion intensity level, based on engineering demand parameters. Moreover, it is clear that nonlinear properties and component deterioration under cyclic excitation can affect structural response in all damage states, which concerns the obtained curves.

Reliability Assessment Methodology of Blast Protective Steel Moment Resisting Frame Using NiTi SMA-based Connection

This paper proposes a methodology framework for the reliability assessment of smart steel Moment Resisting Frame structures (MRFs) equipped with Nickle Titanium Shape Memory Alloy (NiTi SMA) connections subjected to blast loading. The reliability assessment framework is formulated based on a two-step approach algorithm. In the 1st Step, the Monte Carlo Latin Hypercube Sampling Strategy simulation (MC-LHS) is adapted to generate the uncertain parameters sample points. Considering the numerical simulations, the 2nd Step employs simplified performance functions and the generated random outcomes from the 1st Step. The proposed reliability approach is verified against direct Monte Carlo Simulation (MCS) and First-Order Reliability Method (FORM). The performance functions are columns’ axial force and bending moments, rotation capacity at the connections, and Inter-Story Drift Ratio (ISDR). Throughout the development of the reliability assessment, the probabilistic models are parametrized on geometrical properties, material properties, vertical loads, model errors, and charge weights. The developed reliability framework is applied to a prototype 4-story smart MRF. The structural safety level is obtained in terms of the Reliability Index (β). The results show that the reliability framework provides an accurate and efficient structural collapse prediction of the MRFs equipped with NiTi SMA-based connections. Finally, sensitivity analysis is performed to indicate the sensitivity of building collapse to blast wave characteristics, material strength, vertical gravity loads, and column profile dimensions. The sensitivity analysis results also confirm the efficiency of the proposed reliability framework in observing the highly sensitive parameters, which is explosive charge weight.

P-Delta effects on nonlinear dynamic response of steel moment-resisting frame structures subjected to near-fault pulse-like ground motions

The objective of this study is to explore the P-Delta effects on the steel moment-resisting frame structures (MRFs) subjected to the near-fault ground motions with large, medium, and small pulse periods. The 3-, 9-, and 20-story MRFs designed for the American SAC Phase II Steel Project are used as benchmark models. Three near-fault and one far-field ground motion groups, each with 11 different records, are selected for the nonlinear time-history analysis. The P-Delta effects are quantified based on peak inter-story drift ratio (PIDR) demands. When the near-fault ground motions act on the structures, even if the structures have the low height and the earthquake is weak, the P-Delta effects could not be ignored. The nonlinear response of the group with Tp near to T1 is the largest, but the largest P-Delta effects appear in the group with TP slightly larger than T1. P-Delta effects do not influence the prediction of the weakest floor and the PIDR demands due to the ground motions which can trigger higher-mode effects. However, for long-period buildings, P-Delta effects can sharply increase the components’ distortion at the low half of the structure and even change the structural collapse direction, although P-Delta effects would decrease the demands at the middle stories. The panel zones are significantly important components for the seismic performance of MRFs and not only the weakest floor but also all the floors at the low half of the building are worthy of attention in the seismic design of MRFs.

Blast Performance of Steel Frames Equipped with NiTi SMA Bolts: Design Procedure and Numerical Evaluation

This study evaluated the performance of smart steel moment-resisting frame structures (MRFs) equipped with nickle titanium shape-memory alloy (NiTi SMA) connection systems subjected to blast overpressure. A total of five NiTi SMA–based connections were designed conforming to current European standards, and their numerical models were developed. To study the effect of number of parameters, e.g., section profiles, bolt diameter, and bolt preload, a parametric study has been conducted on NiTi SMA–based connections. The numerical models were validated against experimental data, and key design procedures have been proposed. A simplified Kingery blast calculation framework was adapted to determine the blast reflected overpressure profile. The strength of the NiTi SMA bolts and steel components were adjusted due to a high strain rate of blast loading. Four MRFs equipped with a NiTi SMA–based connection were designed with different heights. Global-level transient analyses were performed on the MRFs subjected to blast overpressure. The results showed that in addition to relatively large maximum interstory drift ratio, the NiTi SMA–based connections significantly reduced the residual interstory drift ratio compared with the steel bolted connection system counterpart. The results also revealed that the proposed key design procedures are essential to emphasize the role of NiTi SMA bolts.

P-Delta Effects on Nonlinear Seismic Behavior of Steel Moment-Resisting Frame Structures Subjected to Near-Fault and Far-Fault Ground Motions

This paper presents a comparison of P-Delta effects on the nonlinear seismic behavior of the steel moment-resisting frame structures (MRFs) subjected to near-fault and far-fault ground motions. The 3-, 9- and 20-story MRFs designed for the American SAC Phase II Steel Project are used as benchmark models. The 40 near-fault ground motions with large velocity pulses, as well as ten typical far-fault ground motions, are selected and scaled for the nonlinear time-history analysis. The P-Delta effect is quantified based on peak inter-story drift ratio (PIDR) demands. The displacement demands of the whole structure and the distortion of the structural components are compared and analyzed. It was found that, at each floor, the P-Delta effect under near-fault ground motions is more significant than that under the far-fault ground motions. The P-Delta effect under near-fault ground motions also increases more rapidly with decreasing structure height even for low-rise structures or low earthquake intensity. It was also found that the P-Delta effect cause the PIDR demands to increase by 10% for all three structures subjected to far-fault ground motions. In contrast, considering the P-Delta effect, the PIDR demands rapidly increase by 45% for the high-rise building subjected to near-fault ground motions. Note that the increasing PIDR demands occur at the weakest floor and with the stronger earthquake intensity. However, the P-Delta effect does not change the location of the weakest floor and the yield sequence of components. The seismic behaviors under far-fault and near-fault ground motions are significantly different, because near-fault ground motions not only have velocity pulse but also possibly trigger structural higher vibration modes. In addition, the P-Delta effect may change the distortion direction of the components so that the prediction of the structural collapse direction may be affected. In addition, it was found that if the structure’s period is near the pulse period, the P-Delta effect becomes more significant with the increase of earthquake intensity, and accordingly, it should not be ignored. Moreover, the P-Delta effect cannot be neglected either for the structures susceptible to near-fault ground motions, even if those structures are not tall or the earthquake intensity is not strong.

Seismic acceleration demand and fragility assessment of storage tanks installed in industrial steel moment-resisting frame structures

Recent seismic events highlighted the importance of non-structural elements in seismic assessment and performance-based earthquake engineering. When referring to industrial facilities, storage tanks represent one of the most critical components for the continuous functionality of industrial and building plants after seismic events. At the same time, the dispersion of dangerous or inflammable materials, due to their collapse, could become a safety issue in terms of both human life and environmental impact. This study focuses on the seismic performance assessment of a liquid-storage tank installed in an industrial steel moment-resisting frame building. The performance is assessed in terms of fragility curves, that are provided for the meaningful limit states that affect the liquid-storage tank and considering several intensity measures. The results related to the structural performance are also discussed in detail in terms of fragility functions and floor response. The assessment is performed through nonlinear dynamic analyses using two different modelling approaches to evaluate the structural and non-structural performance. The first modelling approach explicitly accounts for the tank-structure interaction, while in the second one the tank is only modelled considering its seismic mass. The results show the importance of the modelling assumptions to accurately estimate the seismic demand on liquid-storage tanks and corresponding fragility, which is calculated in terms of different intensity measures (IM): average ground spectral acceleration, peak floor acceleration, and floor spectral accelerations. Peak floor acceleration, drift profiles, and absolute acceleration and relative displacement floor response spectra are instead scrutinised for what concerns demand. The comparison with the code formulations available in the literature for estimating the seismic demand to non-structural elements pointed out their inaccuracy for the analysed liquid-storage tank and the need for further efforts to develop more accurate procedures. Furthermore, the outcomes indicate that the IM adopted for secondary components, i.e. peak floor acceleration, may not always be the optimal one hence additional attention should also be paid to the definition of updated fragility curves for non-structural elements, identifying and adopting more suitable IMs.

Seismic retrofit of steel frame structures

Abstract:Moment resisting frames are considered as an effective seismic force resisting system that is used for steel structures. Some of these structures that were built in high seismic hazard zones were designed according to old strength-based design codes. Currently, these structures do not meet the requirements of the new seismic codes. Therefore, the seismic retrofit of these structures is mandatory and cannot be overlooked. Steel braces and concrete-steel composite elements are common solutions for enhancing the seismic behavior of existing steel frame structures. This paper presents a numerical study that evaluates different possible techniques for the seismic retrofit of existing steel moment-resisting frame structures. The study investigates the performance of three multi-story buildings with different heights that are located in a high seismic hazard zone. Three retrofit techniques were introduced including; 1) X-Steel braces, 2) buckling restrained composite braces, and 3) composite concrete-steel plate shear walls. The seismic performance enhancement of the studied structures was evaluated in terms of the structure’s fundamental period, maximum inter-story drift and maximum base shear-to-weight ratios. Moreover, the cost of retrofitting material was estimated for each technique and they were compared to select the retrofit technique with the least constitutive material cost.

Weighted and Unweighted Scaling Methods for Ground Motion Selection in Time-history Analysis of Structures

ABSTRACT A weighted scaling method (WSM) is developed for the selection and modification of structure-specific earthquake records in time-history analysis. The matching errors and scaling factors are calculated by weighted least-squares method to match with target spectrum. The weight factors are determined by the modal-mass participation factors. The 3-, 9-, and 20-story steel moment-resisting frame structures are used as examples. Their mean structural responses were calculated by the WSM and the unweighted scaling method (USM). WSM is as accurate as USM for estimating mean structural responses, but WSM has a better capacity for reducing the variability of structural responses.

Comparison of Scaling Ground Motions Using Arithmetic with Logarithm Values for Spectral Matching Procedure

In recent studies, spectral matching is the most commonly proposed method for selecting earthquake records for time-history analysis of structures. However, until now, there have been no serious investigations of the effects of coordinate values on the scaling of ground motions. This paper investigated the influence of using arithmetic and logarithmic values of response spectra in spectral matching procedures (i.e., ASM and LSM methods) on the results of nonlinear structural time-history analysis. Steel moment resisting frame structures of the 3-, 9-, and 20-stories, which represent low-, medium-, and high-rise buildings, respectively, were used as examples. Structural benchmark responses were determined by calculating the arithmetic mean and median of peak interstory drift ratio (PIDR) demands based on the three record sets developed by the American SAC Steel Project. The three record sets represent seismic hazard levels with 50%, 10%, and 2% probabilities exceeded in 50 years, and their average acceleration spectra were also taken as the target spectrum. Moreover, another 40 record components for selection were scaled both by ASM and LSM methods. The seven components whose spectra were best compatible with the target spectra were selected for the structural time-history analysis. The scale factors obtained by the LSM method are nearly larger than that of the ASM method, and their ranking and selection of records are different. The estimation accuracies of structural mean (median) responses by both methods can be controlled within an engineering acceptable range (±20%), but the LSM method may cause larger structural responses than the ASM method. The LSM method has a better capacity for reducing the variability of structural responses than the ASM method, and this advantage is more significant for longer-period structures (e.g., 20-story structure) with more severe nonlinear responses.

Earthquake loss assessment of steel moment-resisting frames designed according to Eurocode 8

Current design and assessment guidelines define several seismic performance levels, aiming to ensure that structures exhibit adequate behaviour at different seismic intensity levels. Typically, the acceptance criteria at different performance levels are met by ensuring that local deformation demands are lower than pre-defined capacities. Despite the proven effectiveness of such an approach, it provides an ambiguous measure of the performance of the building, which, in most cases, is neither meaningful nor appropriate for building owners, stakeholders or decision-makers. The main objective of the research presented in this paper is to evaluate the expected direct economic seismic losses of steel moment-resisting frame structures designed according to Eurocode 8 (EC8). A set of 120 archetype buildings, representative of the current building stock in Portugal, were designed according to Part 1 of EC8 using three different behaviour factors, q: a) code-prescribed upper bound limits for medium and high ductility classes; b) behaviour factor defined according to an Improved Force-Based Design (IFBD) procedure. The PEER-PBEE methodology with the improvements proposed by Ramirez and Miranda [1] was employed for the estimation of expected seismic losses evaluated for the seismic intensity levels considered in Part 3 of EC8. The results obtained indicate that the buildings designed in accordance with EC8 comply with the non-collapse criteria. However, the level of damage could imply significant repair costs. Importantly, the results also highlight that a rational selection of the behaviour factor can result in a reduction of steel weight but still ensuring acceptable levels of expected annual losses.

Seismic Fragility Assessment of Steel SMRF Structures under Various Types of Near and Far Fault Ground Motions

In this paper, the seismic collapse probability of special steel moment-resisting frame (SSMRF) structures, designed to 4th edition of Iranian seismic design code, under near fault pulse-like and far fault ordinary ground motions is evaluated through fragility analysis. For this purpose, five sample frames with 3 to 15 stories are designed and imposed to the ground motion excitations with different characteristics. Fragility curves are derived for the sample frames using the results of incremental dynamic analyses. Three sets of near fault ground motion records with different range of pulse period and one set of far fault ordinary records are used in dynamic analyses. Each record set involves ten acceleration time histories on soil type III. Based on the obtained results, it was found that pulse-like motions with medium- and long-period pulses are significantly more destructive than other types of ground motions. Fragility analysis reveals that the average collapse probability for the case study frames under the far and near fault ground motions at the intensity of 0.35g equals to 4.3% and 10.3%, respectively. These values are 15.9%and 38.6%, for PGA of 0.53g. It is also found that the increase in the height, leads to increase in higher modes effect to transfer drift demands toward upper stories.

Displacement profile for displacement based seismic design of concentric braced frames

The direct displacement based design (DDBD) procedure is well developed and used for designing reinforced concrete and steel moment resisting frame structures, wall structures and bridges. However, a limited number of studies is available on designing steel concentric braced frame (CBF) structures using DDBD approach. Moreover, those studies use the design displacement profile proposed for the reinforced concrete moment resisting frame structures by Priestley et al. (2007). Furthermore, Wijesundara et al. (2018) have highlighted that higher interstorey drifts can be observed in CBFs during the inelastic response due to the effects of higher mode amplifications. Therefore, the main objective of this study is to propose a new design displacement profile that is capable of predicting the effects of higher mode amplifications on the displacement profile for designing steel CBFs.In this regard, an attempt is made to develop a design displacement profile based on the median maximum storey displacements obtained from the nonlinear time-history analysis for a set of real ground accelerations. For this purpose, twelve different steel CBF structures with varying brace configuration, braces slenderness over the height of building, and different heights are selected. Nonlinear timehistory analyses are performed for the 3-D nonlinear finite element models of the selected frames using OpenSEES software. The developed models are capable of simulating the out-of-plane buckling. The models are subjected to a set of 30 real ground motion records with varying levels of spectral acceleration at the first modal period of the structures. The maximum storey displacement at each storey levels is recorded for all the ground motion records. On the basis of the observed storey displacement and interstorey drift, the appropriate design displacement profile for CBFs is proposed. The proposed equations show a high correlation with the observed behaviour of the suggested CBFs.

Seismic Response and Damage of Reduced-Strength Steel MRF Structures with Nonlinear Viscous Dampers

AbstractAn experimental investigation of the seismic response and damage of steel moment resisting frame (MRF) building structures with nonlinear viscous dampers was conducted using ground motions ...

Predicting the Weight of the Steel Moment-Resisting Frame Structures Using Artificial Neural Networks

To estimate the cost of a building prior to the detail design phase, engineers and project managers need suitable tools and guidelines. Steel is an important construction material that is used in high volumes in buildings and has a significant role in the total cost of projects. In this paper, the application of the artificial neural network (ANN) method to predict the quantity of steel used in the steel moment-resisting frame (MRF) structures is presented. First, more than 1100 steel MRF structures were designed applying the changes in the influenced parameters, then these models were transferred to the ANN, and finally, the results of the performed parametric study were analyzed. The obtained results demonstrate that by using the proposed ANN method, the weights of the structures can be estimated with an acceptable accuracy prior to the starting of the design process. Based on the performed parametric study, several sets of required inputs in terms of the parameters of the story height, the span length, the number of stories, the seismicity rate of the construction site, ductility, the class of soil site and column cross section type influenced on the weight per unit area of the structure are submitted.

Seismic Performance of Steel MRF Structures with Nonlinear Viscous Dampers from Real-Time Hybrid Simulations

Real-time hybrid earthquake simulations (RTHS) were performed on steel moment-resisting frame (MRF) structures with nonlinear viscous dampers. The test structures for the RTHS contain a moment-resisting frame (MRF), a frame with nonlinear viscous dampers (DBF), and a gravity load system with associated seismic mass and gravity loads. The MRFs have reduced beam section beam-to-column connections and are designed for 100%, 75%, and 60%, respectively, of the base shear strength required by ASCE 7-10. RTHS were performed to evaluate the seismic performance of these MRF structures. Two phases of RTHS were conducted: (Phase-1) the DBF is the experimental substructure in the laboratory; and (Phase-2) the DBF with the MRF is the experimental substructure. Results from the two phases of RTHS are evaluated. The evaluation shows that the RTHS provide a realistic and accurate simulation of the seismic response of the test structures. The evaluation also shows that steel MRF structures designed with reduced strength and with nonlinear viscous dampers can have excellent seismic performance.

Accounting for the Flexibility of Beam-Column Joints within New Zealand Steel Moment-Resisting Frame Structures

In New Zealand there currently appears to be no simplified, effective method of analysing the rotational stiffness of beam-column joints in steel moment resisting frame structures. Many practicing engineers use simplified design tables to detail beam-column joints for strength requirements, without accounting for the flexibility of joints. This tends to underestimate the flexibility of structures and hence the drifts they undergo in wind and earthquake events. To permit improved consideration of beam-column joint stiffness in a simplified manner, this work adapts the European component method to develop a series of tables that practitioners could look up to quickly identify beam-column joint stiffness values. The potential use for such stiffness values is highlighted by examining the impact of joint flexibility on the drifts expected in a 4-storey steel MRF subject to 1 in 500 year return period earthquake loading.

Seismic Simulation of U.S. and Japanese Type Steel Moment-Resisting Frame Structures Using Practical FEM Macro Models

Building structures around the world have been designed using various framing methods. In Japan, the two-way moment-resisting frame structure, which is designed as a 3D seismic frame with beams connected to the columns, with moment connections in both directions, is traditionally constructed. In contrast, in the United States and many other countries in high seismic regions, the one-way moment-resisting frame structure, which is designed as separate seismic and gravity frame structure with only a few expensive moment connections in seismic frames, is typically constructed. Structures with these different framing systems are likely to exhibit different seismic response and collapse mechanism when subjected to large earthquake excitation. However, the simulation up to complete collapse has almost not been conducted and safety margin to complete collapse of these different framing systems has not been sufficiently understood. In this study, seismic simulation of U.S. and Japanese type three-story steel moment-resisting frame structures is conducted using general-purpose finite element analysis program. Practical macro models used for the simulation are based on beam and shell elements. It is found that composite effects of floor slab accelerate column yielding in both U.S. and Japanese type steel frame structures and drift concentration may occur at relatively small ground motion level and eventually result in complete collapse.

11.14: Seismic performance of high‐strength‐steel frame with buckling hinge beams in energy dissipation bays

ABSTRACTAlthough steel moment resisting frame (MRF) systems had long been recognized as effective seismic resistant structures, recent earthquake events and seismic loss estimations indicated that uniform damages of structural members and significant residual deformations would be expected after even a moderate earthquake event for steel MRF systems designed following the conventional ductility‐based design philosophy, and this incompleteness produced the impetus for overhaul of design methodologies and developing innovative systems. With the goal of enhancing the seismic performance of steel MRF structures in low‐to‐moderate seismic regions, this research explored the seismic behavior of high‐strength‐steel (HSS) frame with energy dissipation bays (EDBs) equipped with buckling hinge beams, denoted as the HSSF‐BHEDB system. In particular, the HSS frame is composed of steel with the nominal yield strength higher than 460 MPa, and the buckling hinge beams in the EDBs are constructed with cross‐sections classified as Class 3 or Class 4 by Eurocode 3. The motive of the novel design concept was to improve the structural nonlinearity of steel MRF systems with encouraging damage evolution mode and controllable residual deformations under earthquakes, and the limited energy dissipation of both the buckling hinge beams composed of slender cross‐sections and HSS members can provide a solution for structures in low‐to‐moderate seismic regions. In this work, the design concept and the rationale of the HSSF‐BHEDB were explored in detail. Then, a large‐scale quasi‐static test of a structure was conducted to provide experimental evidence and assess the feasibility of the design concept, and the behavior of the specimen from inception of yielding to failure was completely investigated. The test results showed that the system was characterized by the damage‐control behavior that diverted inelastic damages in the buckling hinge beams of the energy dissipation bay (EDB) in a wide deformation range. In the stage where the HSS frame initiated inelasticity and the energy dissipation of buckling hinge beams deteriorated, a ductile manner was still achieved. In addition, the controllable residual deformations of the specimen highlighted the satisfactory recentering behavior of the HSSF‐BHEDB structure. Lastly, the applicability of the bilinear hysteretic model of significant post‐yielding stiffness ratio and trilinear hysteretic model for featuring the hysteretic behavior of the HSSF‐BHEDB system in different yielding stages were validated by the test results.