Steel Moment Resisting Frame Buildings Research Articles

Effectiveness of repairing yielding anchor rods in exposed column bases in steel structures

AbstractOne of the features of Japanese structural steel design is an economical design option for yielding exposed column bases before first‐story columns, namely weak‐base/strong‐column design, which is unlike the strict capacity design for column bases. This study aims to develop a repair methodology that identifies damage states of the yielding column bases and anchor rods, and selects appropriate repair/retrofit methods. As a standard repair method for damaged exposed‐type column bases, the applicability and effectiveness of the re‐tightening process of anchor rods need to be examined. This study first reviews the literature on standard retrofit techniques for column bases and required deformation capacity of ductile anchor rods. The threaded anchor rod deformation capacity with different steel grades and screw threads commonly used were tested to clarify the required ductility. To clarify the reparability of exposed column bases, numerical models of four‐ and six‐story steel moment resisting frame buildings were developed and validated by shaking table test results. The results show that this simple repair method was proven to be effective through the test program and numerical analysis and it's not always applicable for standard anchor rods assumed for pin or fixed column bases designed to remain elastic. Finlly, a repair methodology and flow chart that identifies the damage states of anchor rods and selects appropriate repair/retrofit methods for the exposed steel column base was suggested and applied to the simulation results.

Meta databases of steel frame buildings for surrogate modelling and machine learning-based feature importance analysis

Traditionally, nonlinear time history analysis (NLTHA) is used to assess the performance of structures under future hazards which is necessary to develop effective disaster risk management strategies. However, this method is computationally intensive and not suitable for analyzing a large number of structures on a city-wide scale. Surrogate models offer an efficient and reliable alternative and facilitate evaluating the performance of multiple structures under different hazard scenarios. However, creating a comprehensive database for surrogate modelling at the city level presents challenges. To overcome this, the present study proposes meta databases and a general framework for surrogate modelling of steel structures. The dataset includes 30,000 steel moment-resisting frame buildings, representing low-rise, mid-rise and high-rise buildings, with criteria for connections, beams, and columns. Pushover analysis is performed and structural parameters are extracted, and finally, incorporating two different machine learning algorithms, random forest and Shapley additive explanations, sensitivity and explainability analyses of the structural parameters are performed to identify the most significant factors in designing steel moment resisting frames. The framework and databases can be used as a validated source of surrogate modelling of steel frame structures in order for disaster risk management.

Seismic risk-based optimization of tension-only shape-memory alloy device for steel moment-resisting frames

This study introduces the seismic risk-based design of SMA devices for steel moment-resisting frame buildings. The investigation begins with the numerical representation of the device which includes SMA wires exhibiting super-elastic stress–strain response, along with steel components. The model is then compared against an actual test result. Accordingly, several four-story steel-frame buildings are numerically characterized, all designed to withstand similar seismic loads. This includes a control frame building (Bare-SMF), a frame building with SMA devices using a traditional design approach (SMA-D), and a frame with buckling restrained braces (BRB-D) for comparison. As the traditional design method relies on the first modal shape and static loads, the pushover analysis results for all structures possessed similar amount of strength and deformation capacity. However, the nonlinear time history analysis revealed inconsistencies in the responses of the retrofitted buildings (SMA-D and BRB-D) when compared to Bare-SMF. To address this issue, a seismic risk-based design approach that combines nonlinear time history analysis on a steel moment-resisting frame and the particle swarm optimization algorithm is employed. By using this approach, the SMA brace quantities were determined such that the cost of SMA devices can be minimized while the life-cycle probability of collapse and demolition is smaller than that of Bare-SMF. As a result of the risk-based design approach, three brace quantities are determined according to a decision maker’s attitude against the seismic risk. As a result, the cost of SMA devices could be reduced by more than 40% while maintaining a significant reduction in the life-cycle probability of collapse and demolition.

Optimum seismic design of frame structures with and without metallic yielding dampers considering life-cycle cost

This paper investigates the optimal design of steel moment-resisting frame (MRF) buildings, with and without metallic yielding dampers, using a life-cycle cost (LCC)-based optimal design process. The aim is to minimize the LCC as the design criterion, which includes construction cost and the loss of lifetime seismic consequences. The study employs the endurance time (ET) method for structural response analysis and the FEMA P-58 procedure for seismic loss assessment. Four design approaches are examined: (1) typical code-based design of an existing MRF without damper, (2) optimal LCC-based design of a new MRF without damper, (3) optimal LCC-based design of an existing MRF equipped with damper, and (4) optimal LCC-based design of a new MRF equipped with damper. In the third scenario, only the damper properties are optimized, whereas in the fourth scenario, both the frame and damper properties are optimized together. The main contribution of this study is the simultaneous comparison of the design outcomes from the four aforementioned design approaches. The results indicate that LCC-based re-designed structures can effectively reduce costs compared to code-based designs. The best results were achieved by incorporating metallic dampers. Moreover, incorporating dampers also reduced the construction cost for the LCC-based re-designed cases. Based on the results, when dealing with similar scenarios, adding dampers to an existing frame can be sufficient, eliminating the need to redesign both the damper and frame together.

Seismic Performance of Vertical Irregular Steel Frame Structure under Mainshock-Aftershock

Abstract: The majority of the structures are involved with architectural importance and it is highly impossible to achieve uniform structural properties in all directions. Hence earthquake resistant design codes considered it as irregular frames based on relative difference in the story properties. In many cases these irregularities are responsible for structural collapse of buildings under earthquake ground motions. The seismic response of buildings with irregular distribution of stiffness along the height may be differentfrom that ofregular building. Also, past earthquakes showed that structure may be subjected to sequence of ground motions but current codes do not have guidelines for such cases. It is considered that aftershock do not cause any more damage to damaged structure by the preceding mainshock ground motion. In this study steel moment resisting frame buildings are evaluated to understand the seismic response of vertical stiffness irregular frames subjected to mainshock-aftershock ground motions. The 9-story steel moment resisting frame building situated in Los Angeles is used in this study was originally developed as part of the SAC steel project. In this study soft and stiff storey case was considered at three different locations along the height, i.e., at bottom storey, mid-height storey and top storey. The single modification factor is used for irregularity. For comparison purpose dynamic properties of regular and irregular frames are kept same. Two sets of 6 records were selected representing a seismic hazard level of 2% and 10% probability of exceedance in 50 years respectively as mainshock. Two sets of 30 mainshockaftershock ground motion are considered for the study. These ground motions were developed using randomized approach. A non-linear time history analysis of regular and irregular building is carried out separately under mainshock and mainshockaftershock. The effect of building irregularity was studied for single storey modification at bottom storey, mid-storey and top storey with comparison to regular building. The comparison of a regular and irregular building is carried out in terms of maximum roof displacement and interstorey drift ratio. Also, comparison of frames under mainshock and mainshock-aftershock is done.

The effectiveness of using the simple adaptive control method on the structural response complexity of high-rise and low-rise buildings

This paper presents an investigation of the effectiveness of the Simple Adaptive Control Method (SACM) in mitigating the dynamic response of steel moment-resisting frame buildings. The study aims to evaluate the performance of SACM in reducing the complexity of structural responses, which is measured by the Shannon entropy. Two building types, a 3-story and a 20-story, equipped with MR dampers installed at each story, are considered in this study and subjected to different earthquake loads. The Shannon entropy of acceleration, velocity, and displacement of each story is calculated for both controlled and uncontrolled responses. Results show that SACM is an effective control method in reducing the complexity of structural responses, which suggests its potential for practical applications in Structural Control and Health Monitoring.

Fragility framework for corroded steel moment-resisting frame buildings subjected to mainshock-aftershock sequences

This study proposes a framework for the seismic fragility assessment of steel moment-resisting frames exposed to different rates of corrosion and subjected to real mainshock-aftershock (MS-AS) sequences. The inherent uncertainties in the structural characteristics may significantly affect the structural performance. Thus, in addition to the demand parameters, the framework considers randomness in the capacity parameters using the Latin hypercube sampling. Three frames are modeled in OpenSees and then subjected to nine real as-recorded MS-AS sequences to illustrate the application of the framework. Four limit states are defined based on the maximum interstory drift ratio and the multiple stripe analysis is chosen for the fragility assessment. The presented framework allows for the plot of the fragility surfaces for each corrosion level conditioned on both the mainshock and the aftershock intensity. The results indicate that corrosion and aftershock may significantly affect the seismic fragility especially for the extreme limit states.

A novel design criterion for I-shape beams of steel MRF buildings in subduction-zone earthquake-prone areas

This paper highlights the difference in the seismic response of 5-storey, 10-storey, and 15-storey steel moment resisting frame (MRF) buildings of various span lengths (6 m, 7.5 m, 9 m), located on Site class C in Vancouver, B.C., Canada, resulted under the mega-thrust subduction zone ground motions against crustal ground motions (GMs). To emphasize on the impact of GM duration on the seismic response of buildings, seven spectrally equivalent short and long duration record pair sets were selected from ground motion databases and employed in analyses. Numerical models that account for P-Δ effects and strength and stiffness degradation of steel MRF beams were used. Detailed nonlinear dynamic analyses were conducted to assess the collapse safety according to FEMA P695 (2009) methodology. The results indicated high probability of buildings’ collapse under the long duration subduction GM suite, with a 38% average reduction in the median collapse capacity. Moreover, tall MRF buildings designed according to the current building code and steel design standard did not satisfy the collapse safety criteria when subjected to subduction GMs characterized by significant duration t5-95 > 60 s, while the middle-rise buildings showed borderline pass. To overcome this drawback, a novel design criterion for I-shape MRF beams is proposed; hence, selecting MRF beam sections of Class 1 that are able to achieve aggregated fatigue coefficient greater than the proposed limit value, the occurrence of low cycle fatigue of plastic hinge region of MRF beams is delayed and the collapse safety criterium is achieved.

Seismic Assessment and Retrofit of Pre-Northridge High Rise Steel Moment Resisting Frame Buildings with Bilinear Oil Dampers

This paper presents quantitative information on the effectiveness of seismic retrofit solutions using bilinear oil dampers for seismically deficient existing tall steel buildings. For this purpose, a benchmark 40-story steel space moment-resisting frame building is studied that represents 1970s design practice in North America. Rigorous seismic performance assessment based on ASCE 41 recommendations reveals a high collapse risk for the existing building. The local engineering demand parameters are comprehensively assessed to quantify the impact of seismic retrofit on steel columns and column splices, which are particularly vulnerable due to the time of construction. Multiple retrofit schemes are explored with numerous damping levels and vertical damping distribution methods. The dampers are designed via a recently developed multi-degree-of-freedom performance curves method. A new balanced vertical damping method is proposed to account for the effects of frame inelasticity. This strongly depends on the supplemental damping level, and it determines the effectiveness of the employed vertical damping distribution method. The results indicate that the proposed retrofit strategies can minimize the collapse risk of the tall building. It is shown that the balanced vertical damping distribution method provides the most uniform drift distribution along the building height. Despite the reduction in story drift ratios, the axial force demand in exterior columns remains relatively high in the bottom stories regardless of the seismic retrofit solution. On the other hand, bilinear oil dampers produce relative constant forces despite exhibiting higher velocity demands than expected.

A numerical investigation of new types of bolted joints for cold-formed steel moment-resisting frame buildings

Thin-walled cold-formed steel (CFS) structures have seen an increasing application in low-to multi-story buildings. However, the immature investigation of the seismic performance of the new types of CFS joints has limited the application of CFS structures in seismic regions. This paper presents numerical investigations of the seismic performance of two types of beam-to-column CFS joints, which were proposed to be used to connect CFS members in T-, L- and cruciform joints for multi-story framed buildings. Experimental and numerical studies of the seismic performance of an additional type of gusset-place joints are also reported. As the gusset-plate joints have been well-studied by previous researchers, they are used as benchmark cases in this research. The FE models, which are set up using the commercially available software ABAQUS, are validated against test results. Good agreements between the FE modelling results and the tests are achieved. Parametric studies are carried out to investigate the factors that influence the seismic performance of the proposed CFS joints. The investigated factors include the initial stiffness, the load-bearing capacity and the ductility of the joints. Comparisons of the seismic performance are carried out between the proposed two types of joints and the gusset plate joint. Recommendations are made for the improvement of the seismic performance of the proposed joints. The results show that the initial stiffness of the proposed joints lies between 1 and 4 times EI/l. As Eurocode 3 Part 1–8 defined joints to be rigid if the stiffness is no smaller than 25 EI/l, the joints to be pinned if the stiffness is no larger than 0.5 EI/l, and the joints are semi-rigid if the stiffness is between 25 EI/l and 0.5 EI/l, the proposed joints designed in this paper can be classified within the semi-rigid classification. By changing the thickness of the components, the ductility of the proposed joints can be significantly improved. Considering the different bearing capacities of the two types of joints, it is recommended that the two joints connect the main beam and the secondary beam respectively.

Effect of interior gravity framing system and composite floor slab action on the lifetime seismic risk assessment of steel frame buildings subjected to mainshock–aftershock sequence

The structural analysis practices of steel moment-resisting frame buildings often neglect the participation of the interior gravity frames and composite floor slab action in their lateral strength and stiffness. In addition, the effects of aftershocks are frequently omitted in steel frame buildings’ seismic performance evaluations. This study investigates the effects of structural modeling assumptions and the incorporation of aftershocks on the seismic vulnerability and time-dependent lifetime seismic risk for a group of steel moment-resisting frame buildings. Three ductile steel moment-resisting frame buildings of four, eight, and twelve stories are examined in this study. The results indicate that the seismic performance of steel special moment-resisting frame buildings is substantially underestimated when based on structural models that ignore additional sources of lateral stiffness and strength owing to the interior gravity frame system and the composite floor slab action. In addition, when ignoring aftershocks from the seismic performance assessment, the possibility of catastrophic failure could be underestimated by a factor of 11 at the end of an assumed 50-year lifetime for the steel frame buildings, underscoring the need to account for aftershock effects in evaluating the collapse safety of the selected buildings.

Low-rise steel moment frames with energy-dissipating exterior walls: Computer modelling and seismic performance assessment

This research focused on a new type of energy-dissipating exterior wall system for enhancing the seismic performance of low-rise steel moment-resisting frame (MRF) buildings. The computer model for the energy-dissipating exterior wall system was developed based on simple elements and existing material models. Adequacy of the computer model was confirmed by the published test results. To address how the exterior wall system would affect seismic performance of low-rise steel MRF buildings, a representative 2-story MRF demonstration building was selected. The exterior wall system was introduced in the demonstration building for rehabilitation purpose. Computer models for the original and rehabilitated systems were developed. Based on the results from computer simulations of the original and rehabilitated systems, it was found that the energy-dissipating exterior wall system can reduce both transient and residual inter-story drift angle responses in the demonstration building. Moreover, based on the analysis results, a useful criterion denoted as the equal-energy rule was established for future design of the exterior wall system to achieve the intended transient inter-story drift angle responses allowed by a certain performance objective in low-rise steel MRF buildings.

Effects of demand parameters in the performance-based multi-objective optimum design of steel moment frame buildings

This paper investigates the effects of various demand parameters involved in the optimal performance-based design of steel moment frame buildings. These parameters include the peak values of story drift ratio, floor velocity, floor acceleration, and residual drift ratio. The performance-based design is performed to minimize two conflicting objectives, including the initial construction cost and the expected annual repair cost of the building under the design constraints. FEMA P-58 is utilized as a comprehensive and popular methodology for seismic risk assessment and building loss estimation in this paper. It evaluates the building performance in a probabilistic manner in terms of several metrics such as repair cost, repair time, carbon emissions, embodied energy, injuries, and fatalities. The Monte Carlo analysis is used to consider various uncertainties affecting seismic performance. A set of three steel moment-resisting frame (MRF) buildings representative of low-to mid-rise frames are selected as a case study in this research. The results of this study indicate that the story drift ratio has a major role in the performance-based optimal design of steel MRFs. Accordingly, despite increasing the two parameters of floor acceleration and floor velocity due to increasing the initial cost of structural moment frames, the annual repair cost of the building decreases when the story drift ratio decreases.

Retrofit of existing steel structures against progressive collapse through roof-truss

The paper presents the results of a comprehensive study on the evaluation of the effectiveness of a retrofit strategy of existing steel buildings against progressive collapse. In this respect, it investigates the performance and the design of a retrofit solution to increase the robustness of steel Moment Resisting Frame buildings. A truss steel system added at the building's rooftop level (i.e., ‘roof-truss’), and intended to define an alternative load path, was investigated as a retrofit solution. The numerical model key components, including the plastic hinges and the beam-column connections, were validated against available experimental results. The validated models were then used to study the robustness of the structure under column loss scenarios by means of non-linear static and dynamic analyses performed in OpenSees. The simulations allowed for the identification of possible failure modes and alternative load paths together with the definition of the Dynamic Increase Factor (DIF). In this regard, it is shown that column buckling is critical for the selected case study. Moreover, the outcomes showed how the proposed retrofit solution allows the definition of effective alternative load paths when subjected to column loss scenarios and informs on the critical details that should be checked by employing this retrofit system.

Multi-objective optimal design of steel MRF buildings based on life-cycle cost using a swift algorithm

This paper proposed a swift multi-objective optimization algorithm for the performance-based design of steel moment-resisting frame (MRF) buildings considering life-cycle cost (LCC). Two components of the life-cycle cost, including the initial construction cost and the lifetime seismic damage cost of the building, are considered as two separate objectives of the optimization problem and are minimized simultaneously using the proposed algorithm. The proposed algorithm called Multi-objective Uniform Damage Optimization (MUDO) is an adaptive method that utilizes the concept of uniform damage (deformation) theory. MUDO leads to design alternatives for the building that are optimal (minimum) for both mentioned objectives. These alternatives, called Pareto optimal designs, allow decision-makers to choose the optimal investment option according to the project goals and by the trade-off between optimization objectives. The proposed algorithm is used to optimize three steel MRF buildings with 3, 6, and 9 stories. The lifetime seismic damage cost is calculated by assessing seismic losses at several ground motion intensities and using a probabilistic approach presented in HAZUS. A Monte Carlo analysis is used in this research to account for inherent uncertainties in structural response. The results demonstrate that MUDO can find competitive Pareto optimal designs in a much shorter time compared to a well-known metaheuristic algorithm called non-dominated sorting genetic algorithm II (NSGA-II).

Lifetime risk-based seismic performance assessment of buildings equipped with supplemental damping and base isolation systems under probable mainshock-aftershock scenarios

This research attempts to investigate the efficacy of different passive vibration control systems, from both technical and economic points of view, to mitigate the lifetime seismic risk of typical buildings under probable mainshock-aftershocks sequences via a novel probabilistic framework. In this regard, three separate common building models are considered, including 5-, 10-, and 15-story intermediate steel moment-resisting frame buildings. These models are designed optimally with/without passive vibration control systems, including hysteretic damping, linear viscous damping, and base isolation systems as independent alternatives. Next, for the hazard modeling, all active faults located in the greater Tehran area are taken into account to simulate the earthquake scenario. Afterward, probable earthquake scenarios during the 50 years of buildings’ life-spans are generated randomly, including the events, as well as their corresponding synthetic stochastic accelerograms. In the next step, responses of buildings and their cumulative losses are calculated under the whole scenarios considering various damage types such as structural, non-structural, and content-related. In the end, by using the Monte-Carlo simulation method, the seismic risk of different building alternatives is estimated. Interestingly, the application of each of the considered vibration control devices leads to a significant reduction in lifetime losses (both physical and economic). It is revealed that the viscous damper has the highest efficacy among different systems. Importantly, by neglecting aftershocks' effects, the estimated lifetime risk will be underestimated by about 27 to 57% below the expected value. Finally, among the active faults in the greater area of Tehran, the North Tehran, Kahrizak, and Mosha faults have the highest contribution in the estimated lifetime risk of buildings.

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.

Behaviour of Multi-storeyed Steel Building with Steel Plate Shear Wall

The present study describes the analysis and design of high-rise steel building frame with and without Steel plate shear wall (SPSW). Further it is compared with moment resisting steel framed building and X-Braced steel framed building. For present work Response Spectrum Analysis is carried out for steel moment resisting frame building having G+19 storey situated in zone III. Modeling is done by using strip modeling. The analysis of steel plate shear wall and the building are carried out using software SAP2000 V15. The main parameter considered in this project is to compare the seismic performance of buildings i.e. lateral deflection. The models are analyzed by Response Spectrum analysis as per IS 1893:2002 and design has been carried out by using IS 800-2007.

Single and multi-objective optimization of steel moment-resisting frame buildings under vehicle impact using evolutionary algorithms

Single and multi-objective optimization of steel moment-resisting frame buildings under vehicle impact using evolutionary algorithms

Incorporation of post-earthquake fire (PEF) and subsequent aftershock for performance analysis of steel buildings

The advancements in analysis and design approaches considering the seismic loads have helped safeguard buildings against structural failure and collapse. However, design objectives should also consider the associated effects and performance evaluation incorporating the sequential effects. Improving the performance of buildings at both the asset and community levels is now of major interest in the field of structural engineering. This research addresses the advancement toward this goal by incorporating post-earthquake fire and aftershock to multi-hazard design methodology. A set of mid-rise buildings – 3-, 9-, and 20-story moment resisting steel frames, characteristic of those found in rapidly growing metropolitan areas of US, are selected for the study considering the relative vulnerability to post-earthquake fire. The analyses of the responses are based on advanced finite element simulation methods/techniques and corresponding approaches. ABAQUS/CAE is primarily employed for the simulation and analysis. The effects of fire are thoroughly studied from the literature and considered explicitly, and the analysis is performed for a complete cycle of main shock (full-intensity) –fire- aftershock (reduced intensity) earthquake. The research commences with the investigation of the effects of modeling approach-- using beam element and using solid element with slab, on Post Earthquake Fire (PEF) study of a single room model. At the end of a complete sequence, the model developed using 3D solid elements are found to underestimate the stiffness loss by around 15% compared to those developed using 2D beam elements. The behaviors of selected steel moment resisting frame buildings then simulated with PEF are investigated to quantify the overall performance behavior of the building system. Inter-story Drift Ratio (IDR) and Stiffness Degradation over the complete sequence of events are chosen as the damage measures. The same approach is applied to a real building in California and the performance behavior is studied. All the building systems studied show the significant damages and change in behavior after incorporating the fire and aftershock. In all building sets, the stiffness loss (global) due to mainshock alone (2% to 10% in the cases studied) is very less as compared to the stiffness loss due to fire alone (6% to 15%) and aftershock (10% to 25%) alone.