Steel Frame Structure Research Articles

Progressive collapse mechanisms of multi-story steel-framed modular structures under module removal scenarios

Due to different assembly requirements and novel integration strategies, the modular structures may have undesirable loading mechanisms and distinct structural behaviors. However, there are limited data on the progressive collapse performances of modular structures, which impedes their industrial applications. This study numerically investigates the structural robustness of multi-story steel-framed modular structures against progressive collapse by using pushdown analysis. A six-story structure with five modules per floor is designed and established. The applied load, failure process and load redistribution mechanisms are studied under module removal scenarios. Parametric analyses are also conducted to investigate influences of cross-sectional dimensions of frame members, number of stories and bays, arrangements of bracings, and module removal scenarios on the robustness of the modular structures. The results show that the prototype modular structure designed with Hong Kong design code can withstand collapse under module removal scenarios. The load redistribution mechanisms among columns are significantly influenced by the overturning action and bracing effects. The ceiling beam in the lower module and the floor beam in the upper module form a double beam system. The column section, beam section, arrangement of bracings and number of stories significantly influence the robustness of the modular structure. Finally, a design method based on buckling load equation for columns is proposed to estimate the progressive collapse resisting capacity of modular structures with good accuracy and efficiency.

Numerical Prediction Method for Vibration Characteristics of Steel-Framed Autoclaved Lightweight Aerated Concrete Floor Structures

The prediction of floor vibration is of great importance from the viewpoint of accurate prediction of a room’s sound environment. Despite the advantage of low cost, because the density and elasticity of autoclaved lightweight aerated concrete (ALC) panels are much lower than those of reinforced-concrete panels, ALC floor structures suffer from weak sound insulation and require better sound insulation design. However, there have been not yet been any studies of sound insulation improvement of steel-framed ALC floor structures, and it is novel to clarify how the floor-impact-sound characteristics are affected by the panel size and beam structure. In this paper, a finite element analysis was applied to the vibration simulation of an ALC floor structure on a steel-framed structure. The validity of the proposed method was firstly confirmed by comparison with measurement results. Furthermore, by using the validated simulation method, the effect of the arrangement of ALC panels and their supporting steel-framed structure on the vibration characteristics of the whole structure was investigated. It was found that the vibration performance was improved when the number of beams was increased and adjacent ALC floor panels were bonded to each other.

Shaking table test on seismic response of a planar irregular structure with differential settlements of foundation

The differential settlement of the foundation not only causes the degradation of the static performance of structures, but also affects the seismic performance. To investigate the seismic response of a planar irregular steel frame structure under differential settlement of foundation, we proposed a method to mimic multi-point differential settlement of foundations of scaled models steel frame structures. Four columns in the settlement location are adjusted downward to the set settlement distance, and then, the columns are fixed with nuts to achieve the effect of settlement in one location. Then a shaking table test was carried out on a scaled-down building model to analyze the dynamic responses of the structure. Eight seismic waves and three ground shaking intensities were set to represent frequent, moderate, and rare earthquakes. The seismic response, location changes, and torsion of the irregular planar structure were analyzed via shaking table tests under different seismic waves with frequent, moderate, and rare earthquake excitation, as well as changing parameters such as settlement location and settlement depth. The results show that compared with other locations, when a differential settlement of the foundation occurs in the corner location of the structure plane, the structure is more likely to be torsional and more prone to seismic damage. For the same seismic intensity and settlement depth, the settlement location at the corner of the structure face exhibited the greatest seismic response to the structure. In contrast, the settlement located near the center of the structure face had the least effect on the seismic response of the structure. The proposed method enables a fast and efficient way to understand the dynamic response of the structures with differential settlement of foundations, which will further benefit the development and optimization of the seismic strengthening scheme for these structures.

Reformative Effects of Intumescent Coating on the Structural Characteristics of Cold-Formed Steel.

Intumescent fire-resistive coatings are a more recent type of passive fireproofing thin film that swells many times its initial applied thickness, generating an insulating char that functions as a thermal barrier between the fire and structural steel. It keeps the heat of steel members from reaching critical levels and aids in the structural integrity during a fire. They are architects and designers' favorite choice for passive fire protection of load-bearing steel frame structures because of their aesthetic look, versatility, rapidity of application, and ease of inspection and maintenance. In this study, axial tensile, thermal conductivity, and hardness tests have been performed on S235 cold-formed steel specimens that were exposed to increasing temperature periods. The mechanical behavior of coated and uncoated specimens was investigated over the modulus of elasticity, yield strength/strain, and ultimate strength/strain values for all temperatures. As a result of the research, gradually increasing changes were observed in the mechanical properties of coated and uncoated specimens at increasing temperature levels, compared to each other. However, performance increment on the coated specimens was limited in terms of strength and strain characteristics than expected. Two essential reasons for this conclusion are that the specimens were exposed to heat for a long time after reaching the target temperature and also that the wall thickness of the specimens was thinner with respect to the usual application method of the protective coating. In order to examine the structural properties of the test specimens after elevated temperature effects, thermal conductivity measurement was also performed. Temperature difference between coated and uncoated surfaces provided a benefit in the range of 29-56% due to the coating. Lastly, microstructure imaging techniques demonstrated grain coarsening and no crack development with the increase in temperature.

Seismic performance evaluation of Y-shaped eccentric brace–high-strength steel frame structure based on remote collaborative hybrid test

A remote collaborative hybrid test (RCHT) system based on the OpenFresco platform was established. The seismic performance of the Y-shaped eccentric brace–high-strength steel frame (YEB–HSSF) structure was evaluated via the RCHT loading of a multistory and multi span YEB–HSSF model with two test substructures at different locations. The test phenomena and results showed that the maximum inter-story drift angles of the RCHT model were 0.0018 and 0.0077 rad under frequent-intensity and rare-intensity earthquakes, respectively, which satisfies the requirements of GB 50011-2010. Under the action of a rare intensity earthquake, the webs of the test substructure links preferentially entered the yield state with shear deformation, whereas the other members remained in the elastic state; this conforms with the design concept of damage-controllable structures. Finally, a finite-element pure numerical model corresponding to the RCHT model was established to further evaluate the seismic performance of YEB-HSSF structure. The results showed that the base shear distribution ratio resisted by the HSSF part in the global model tended to increase with increasing peak ground acceleration. Under the action of a rare 9 intensity earthquake, the shear links were close to the ultimate bearing capacity, and the shear distribution ratio resisted by the HSSF part exceeded 40%. This indicates that the YEB-HSSF structure satisfies the design requirements for dual systems based on GB 50011-2010.

A Combined Machine Learning and Model Updating Method for Autonomous Monitoring of Bolted Connections in Steel Frame Structures Using Vibration Data

This research paper presents a novel structural health monitoring strategy based on a hybrid machine learning and finite element model updating method for the health monitoring of bolted connections in steel planer frame structures using vibration data. Towards this, a support vector machine model is trained with the discriminative features obtained from time history data, and those features are used to distinguish between damaged and undamaged joints. An FE model of the planer frame is considered where the fixity factor (FF) of a joint is modeled with rational springs and the FF of the spring is assumed as the severity level of loosening bolts. The Cat Swarm Optimization technique is further applied to update the FE model to calculate the fixity factors of damaged joints. Initially, the method is applied to a laboratory-based experimental model of a single-story planer frame structure and later extended to a pseudo-numerical four-story planer frame structure. The results show that the method successfully localizes the damaged joints and estimates their fixity factors.

Location of semi-rigid connections effect on the seismic performance of steel frame structures

In design steel frames, combining semi-rigid and rigid connections can result in better structural performance, particularly in seismic locations. In this study, the effects of semi-rigid beam-to-column connections located on the seismic performance of steel frame structures are investigated. The analysis uses six and twelve-story moment resisting steel frames (MRSF) with rigid, semi-rigid, and dual beam-column connections. These frames are designed according to the Egyptian design codes. Drain-2Dx computer program and seven earthquake ground motions are used in the non-linear dynamic analysis. The rotational stiffness of beam-to-column connections is indicated through the end fixity factors with a value equal to 0.6. The performances of these frames are evaluated through the roof drift ratio (RDR), the maximum story drift ratios (SDR), and the maximum column axial compression force (MACF). The results indicated that the quantities of fundamental periods, roof drift ratio, the story drift ratio, and the column axial compression force are related to stiffness, rigidity, and the number of semi-rigid connections in steel frames.

Novel joint for improving the collapse resistance of steel frame structures in column-loss scenarios

In this study, to improve the collapse resistance of steel frame structures, corrugated steel plates are welded between the inner side of the flange of the I-shaped beams and the column to form novel steel frame joints with corrugated plates (reinforced joints). Collapse resistance tests of the novel reinforced joints under welded and bolt-welded connections are conducted. After a finite element model is validated, the effects of the circular arc length, thickness, and central angle of the corrugated plates on the collapse resistance of the novel reinforced joints are analyzed, and design recommendations are proposed. Results show that the failure modes of the tested specimens are the fracture failure of the beam flange outside the reinforced area and the sequential fracture of the tension flange of the joint region and corrugated plate. Compared with the original specimens, the bearing capacities and ductility of the reinforced specimens are significantly improved. A partial or complete out-shift plastic zone can be realized in the novel reinforced joints. The novel reinforced joints can effectively improve the collapse resistance of steel frame structures under welded and bolt-welded connections without affecting their seismic behavior. The corrugated plate even provides an additional resistance reserve for steel frame structures.

An output‐only structural condition assessment method for civil structures by the stochastic gradient descent method

The interesting to assess the condition of a structure with structural health monitoring data has gained many attentions. Most of the existing methods require the measurement at the force location. This paper presents a novel output-only condition assessment method that does not require measurement at the force location. The unknown structural damage indices and input force can be identified with the stochastic gradient descent method. The dynamic acceleration response sensitivities with respect to the unknown structural damage indices and input force are derived analytically. Both unknown damage indices and unknown input force can be identified by minimizing the discrepancy between the measured and calculated vibration data. Numerical studies on a two-dimensional truss and seven-floor frame and experimental studies on a steel frame structure are presented to verify the accuracy and efficiency of the proposed method. Results demonstrate that the damage severity, location, and unknown input force can be identified. Also, the measurement at the force location is not required. Furthermore, when 20% measurement noise is considered, the identified error is less than 5%.

A Two-Stage Structural Damage Detection Method Based on 1D-CNN and SVM

Deep learning has been applied to structural damage detection and achieved great success in recent years, such as the popular structural damage detection methods based on structural vibration response and convolutional neural networks (CNN). However, due to the limited number of vibration response samples that can be acquired in practice for damage detection, the CNN-based models may not be fully trained; thus, their performance for identifying different damage severity as well as the damage locations may be reduced. To solve this issue, in this paper, we follow the strategy of "divide-and-conquer" and propose a two-stage structural damage detection method. Specifically, in the first stage, a 1D-CNN model is constructed to extract the damage features automatically and identify the damage locations. In the second stage, a support vector machine (SVM) model and wavelet packet decomposition technique are combined to further quantify the damage. Experiments are conducted on an eight-level steel frame structure, and the accuracy of the experimental results is greater than 99%, which demonstrates the superiority of the proposed method compared to the state-of-the-art approaches.

3D Simulation of Battery Fire on a Large Steel Frame Structure due to Depleted Battery Piles

Lithium ion batteries (LIB) can rupture and result in thermal runaway and battery fires. In the process of transporting lithium ion batteries using trains, the massive collection of batteries can cause train fire and pose significant danger to the public. This is especially critical when the fire occurs amid a heavily populated metropolitan environment. This paper reports the 3D analysis of a warehouse with possible train fire due to LIB rupture and the fire propagation at a rail yard. Six critical fire cases with the battery train in close vicinity to the warehouse were considered. The six fire cases are the worst-case scenarios of a Monte Carlo simulation of different fire cases that may occur to an actual steel storage facility at the Capital Railyard, Raleigh, North Carolina. A 3D finite element (FE) frame model was constructed for the steel warehouse and the most critical fire cases were simulated. The results indicated that several structural components of the warehouse would experience large stresses and deflections during the simulated battery fires and resulting in instability to the structure. Specifically, members of the roof frame represent the most critical elements and that the members can result in large deformations as early as 4 minutes after the fire starts. Furthermore, effective utilization of fire protection can delay somewhat the fire effects and extend time to failure to 45 minutes and in one of the simulated cases, prevent structural instability. Thus, fire from LIB waste transport using train is a very realistic problem due to the thermal runaway, and the analysis performed in current study can be used as a preventive investigation technique for buildings that may be exposed to the train fire risk.

Experimental Evaluation of Theoretical Impact Models for Seismic Pounding

ABSTRACT One of the identified consequences of the aftermath of strong quakes is that structural pounding may trigger substantial damage including the collapse of colliding structures. This situation is attributed to inadequate distance between the adjacent structures. In order to address this concern, various numerical and experimental studies were conducted simulating earthquake induced pounding using different models of impact force. In this study, shaking table tests were conducted to assess the impact of seismic pounding between steel frame structures under near-field and far-field earthquakes. Five theoretical pounding force models, namely: linear spring, linear viscoelastic, Hertz, non-linear viscoelastic and Hertzdamp models were employed to replicate the pounding force. Various components of the theoretical models such as contact element stiffness, coefficient of restitution and impact damping ratio were calculated using the experimental results. Comparing the results of the Experimental Impact force time history with the prediction outcomes showed that the models over-predicted the pounding response. However, the prediction outcomes were congruent with the experimental results. Lastly, the linear viscoelastic model generated the least variance and most accurate predicted results compared to the other models. Hence, it can be inferred from the data that among other models, linear viscoelastic is the most accurate model to be used for the testing of pounding response.

Effect of damping model and inelastic deformation on the prediction of vertical seismic acceleration demand on steel frames

This study addresses the modeling of different energy dissipation mechanisms for numerical prediction of the vertical acceleration demand in regular moment-resisting steel frame structures. One of the issues discussed is the consideration of viscous damping in the structural model. It is shown that well-established Rayleigh-damping may highly overestimate the damping of the vertical modes, resulting in much too low vertical acceleration response predictions. A study with different damping models provides an appropriate damping modeling strategy that leads to reasonable predictions of both horizontal and vertical frame acceleration demands. Another open question is the effect of inelastic material behavior on the vertical acceleration demand on the considered regular structures. The results of a shell model of a frame structure exposed to high intensity ground motion excitation demonstrate that inelastic material behavior has virtually no impact on the vertical acceleration demand, while structural inelasticity leaves the horizontal acceleration response significantly smaller compared to the elastic demand. This leads to the conclusion that common frame models that capture the inelastic horizontal response but behave elastic in the vertical direction are suitable for the computation of both the horizontal and vertical acceleration demand.

Study on anti-progressive collapse performance of assembled steel frame joints with Z-type cantilever beam splices

A new type of joint with Z-type cantilever beam splices was proposed for assembled steel frame structures in this study. The basic specimen was designed based on the theory of bolt sliding energy dissipation, and three groups of specimens were obtained by changing key parameters. That is, there is no section weakening (Z-BASE), flange weakening of cantilever beam near column (Z-RBS), flange weakening of steel beam near splicing (Z-SRBS), and flange and web weakening of steel beam near splicing (Z-RBS-RWS). The effects of reducing beam section and beam web on the anti-progressive collapse performance of assembled steel frame joints with Z-type cantilever beam splices were studied. The test results were described in detail in general behavior, failure modes, deflection shapes, limit displacements, and resistance mechanisms. According to the test results, specimen Z-RBS had the best anti-progressive collapse performance, and its ultimate load and initial failure displacement were 116% and 114% higher than specimen Z-BASE, respectively. In addition, specimens Z-SRBS and Z-RBS-RWS also had better anti-progressive collapse performance than specimen Z-BASE. Moreover, the validity of the results was verified and study parameters were analyzed using ABAQUS. The assembled steel frame joints with Z-type cantilever beam splices had better anti-progressive collapse performance than ordinary cantilever beam assembled steel frame joints. And the bearing capacity and ductility of the structure were improved by increasing the distance from the cantilever beam splices to the failed middle column, a, and reducing the aperture of the bolt on the cantilever beam splices, b. However, reducing the number of bolts on the cantilever beam splices, c, exhibited the opposite influence. Based on the above comparisons, the proposed design details of assembled steel frame joints with Z-type cantilever beam splices are given.

Selection of Ground Motion Intensity Measures in Fragility Analysis of a Mega-Scale Steel Frame Structure at Separate Limit States: A Case Study

Selecting an appropriate ground motion intensity measure (IM) to estimate the aleatory uncertainty produced by ground motion variability is the first and crucial step in fragility analysis. The choice of IM is influenced not only by the structural system type itself but also by the limit state of the structural damage. In this study, an investigation of the selection of IM in fragility analysis with respect to different limit states is developed for a 48-story mega-scale steel frame structure with buckling restrained braces. A comparative study of the efficiency of 27 IMs is conducted at four structural damage limit states, i.e., negligible, light, moderate, and severe, through the lognormal standard deviation estimated in fragility equations. In addition, for the purpose of considering the influence of different earthquake characteristics, two completely different sets of ground motions are selected, namely near-field pulse-like and far-field earthquakes. The research shows that the ground motion characteristics and structural damage limit states have nonnegligible effects on the flexibility of intensity measures. For combination-type IMs, the number of combined terms and the combined power index have a significant impact on their performance; thus, an optimized dual-parameter combination-type intensity measure is recommended.

Experimental Dynamic Response of a Multi-Story Frame Structure Equipped with Non-Conventional TMD Implemented via Inter-Story Isolation

A shaking table experiment conducted on a multi-degrees-of-freedom frame structure equipped with a non-conventional tuned mass damper (TMD) is presented. The non-conventional TMD is characterized by a high mass ratio, without adding further structural masses, and is realized via inter-story isolation. The structure top story mass of a four-story steel frame structure is isolated and converted into tuned mass, connecting to the substructure with two high damping rubber bearings placed in series. Aspects related to the dynamic structural response as well as the seismic effectiveness assessment of a non-conventional TMD are addressed. Three structural configurations are tested: the reference four-story structure, the three-story intermediate structure, and the three-story structure equipped with a non-conventional TMD. The input motion conditions considered are: white noise, sine sweep, and natural earthquakes. Through experiments, structural identification is carried out and different dynamic behaviors emerge for the configurations tested. The nonlinear effects provoked on the structure by the adopted isolators are investigated, showing high dissipative capabilities in a wide range of amplitudes of the excitation. It is demonstrated that a non-conventional TMD is a smart control strategy useful for enhancing structural vibration mitigation.

Optimum sizing design of steel frame structures through maximum energy dissipation of friction dampers under seismic excitations

This paper focuses on optimum sizing design of steel frame structures equipped with friction dampers (FDs) in order to prevent the vulnerable effect of an earthquake. The fundamental concept is to maximize the energy dissipation of implemented FDs under different seismic excitations. The FDs utilized as passive energy dissipation devices in a steel structure increase the energy dissipation capacity of the structure by decreasing the seismic demand during an earthquake. In this context, the Pall friction dampers (PFDs) are implemented as diagonal damped brace members in investigated structures. Three different earthquake records (Kobe, Kocaeli-Duzce, Erzincan) are utilized to acquire nonlinear dynamic responses of the steel frame structures through time-history analyses. The open application programming interface (OAPI) functions are used to integrate a finite element modelling based structural analysis program, SAP2000, with a design optimization algorithm encoded in MATLAB for achieving the exact structural behaviours by synchronously data transferring. As an optimizer, one of the recent nature-inspired metaheuristic techniques, so-called Grey Wolf (GW) algorithm is used. Initially, under effect of seismic excitations, the steel frame structures are optimally sized for attaining minimum design weights without implementing the PFD elements by subjecting only strength, displacement, drift, and geometric structural design constraints taken from AISC-LRFD practice code provisions. Afterward, in order for optimally modelling the PFD elements, the frames are equipped with PFDs to calculate optimum yield strengths that is defined as slip load of a PFD. To do so, the GW algorithm ensures the maximizing of the dissipated energy and controls the yield strengths between the stories since the shear force due to the earthquake increases towards the base of the structure. Eventually, the provisions-based sizing design optimizations of the steel frame structures equipped with optimally modelled PFD elements are conducted under seismic excitations for conclusive evaluations.

Robustness of Steel Frame Structures Equipped with FREEDAM Dissipative Joints

AbstractIn the framework of a recent RFCS project, innovative joint solutions named FREEDAM were developed with the objective of proposing beam‐to‐column joints able to dissipate the seismic energy with limited or even no damages. The efficiency of the proposed solutions was validated through experimental, numerical, and analytical investigations on moment resisting frames (MRFs) and dual concentrically braced frames (D‐CBFs). However, according to modern design codes, including the Eurocodes, structures subjected to accidental events such as impact, explosion, or loss of a bearing element should not undergo damages disproportionate to the initiating cause. Accordingly, to validate the proposed solutions, it was also required to demonstrate the ability of structures equipped with FREEDAM joints to exhibit an appropriate level of robustness in case of such accidental events. This paper presents the robustness assessment performed on 20 MRFs and D‐CBFs. The loss of a supporting column was considered in full agreement with the Eurocode requirements. Analytical and numerical studies are conducted to demonstrate how the request for robustness influences the design of the joints which were initially tailored for seismic performances.

Design of Earthquake Resistant Structure Using Cabkoma Strands: A Review

Abstract: Earthquakes are the indication for transformation of earth internal surface. The Indian subcontinent has suffered some of the greatest earthquakes in the world. Many research studies have been focusing on decreasing the impact of seismic waves on structures. For this initially there were many passive techniques introduced to reduce the damage caused due to earthquakes which are based on decreasing the lateral loads on structures. But since the late twentieth century the focus has shifted to introduce active earthquake techniques which are meant to absorb the seismic waves or do not let the waves propagate through the building. Though it is not possible to prevent an earthquake, the least that can be achieved in reducing the damage is to make the buildings earthquake resistant with the advancements in earthquake resistant techniques. The major goal of this dissertation is to use CABKOMA strands to create a novel earthquake-resistant technology. In this study, CABKOMA strands are used to examine the seismic response of ordinary moment resisting steel framed structures of high rise, mid-rise, and low rise analyzed with and without strands to determine the workability of cabkoma strands. To determine how well the intended structures function against earthquake motions, a comparative examination is done between them. Additionally, this work shows a comparative analysis of the seismic behavior of high-rise, mid-rise, and low-rise steel structures designed utilizing CABKOMA strands with the seismic behavior of high-rise steel structures designed using bracings an existing earthquake technique, by varying the arrangement of strands at the corner, Centre, and both centre and edge of the structures. Eventually, this work presents cabkoma strand optimization for effective strand utilization by varying strand to strand spacing from 0.5m to 1m while maintaining the same strand positioning.

Acoustic Emission-based Damage Detection and Classification in Steel Frame Structure Using Wavelet Transform and Random Forest

This research proposes a unique approach for detecting damage locations and identifying damage kinds. This method is beneficial for discovering and categorizing internal structural faults that vision-based approaches cannot locate. Construction-related vibrations in a steel frame structure can be used as a source for acoustic emission. Sensor devices detect the stress waves produced by structure collapse, and spectrum analysis using wavelet transform of such data is valuable in pinpointing the location of the damage. The col-lected characteristics from these signals are input into the most effective RF (Random Forest) classifier, which are used to categories damage types like cracks and bolt loosening. When compared to previous damage localization approaches, the findings show that the proposed strategy is more efficient and has a higher classification accuracy.