Seismic Performance Of Steel Frames Research Articles

Experimental Investigation on the Evaluation of the Seismic Performance of Steel Frame with and without Sustainable STRP Bearings Subjected to Cyclic Loading

Experimental Investigation on the Evaluation of the Seismic Performance of Steel Frame with and without Sustainable STRP Bearings Subjected to Cyclic Loading

Seismic fragility assessment of the innovative and optimal box-shaped dampers in steel frame structures

Box-shaped dampers (BSDs) are newly introduced, innovative, and low-cost metallic dampers installed along the diagonal members of the frames. Dissipating the input energy by continuously forming plastic hinges, BSDs prove to possess the potential to serve as a fuse during earthquakes. Nonetheless, little literature exists on the seismic response of the BSD-equipped steel frames. Hence, this study aims to evaluate the seismic performance of steel frames equipped with BSDs. First, the failure mechanism and shape effects of these dampers were investigated using non-linear finite element analysis (FEA) in ABAQUS. Using the results obtained from the FEA, the incremental dynamic analysis (IDA) is utilized to determine the vulnerability of BSD-equipped frames during earthquakes. In this regard, IDA analysis was performed on 5- and 10-story steel frames equipped with BSDs, and the fragility curves of the frames were extracted, followed by calculating the structures' collapse margin ratio (CMR). Furthermore, the obtained results were compared to that of traditional X-braced frames. The results revealed that the BSD-equipped frames display better performance compared to that of the X-braced frames, indicating that these dampers can replace the conventional bracing systems for structural strengthening.

Seismic behavior of steel frames with H-shaped damper

This paper investigates the effect of dampers on the seismic performance of steel frames with unequal depth beam-column (UDBC) joints. First of all, the finite element (FE) models of the UDBC joint and steel frame were regenerated by ABAQUS and verified by experimental results. Secondly, the design method for three H-shaped dampers with different web perforation forms (vertical, elliptical, and diamond) was provided. Finally, five steel frames were built using ABAQUS, and pushover analysis and dynamic time-history analysis were performed on them. The results indicated that dampers could decrease the maximum vertex displacement and inter-story shift angle of steel frames with UDBC joints under three seismic waves by 4.47% to 17.17% and 7.71% to 23.88%. The effect of H-shaped dampers was similar to that of T-shaped connectors. Under the action of the Kobe wave and the Qian'an wave, the H-shaped damper exhibited more excellent seismic performance. Compared with frames with T-shaped connectors, the maximum vertex displacement and the maximum inter-story shift angle of frames with H-shaped dampers decreased by 3.44% to 12.39% and 9.55% to 16.15%. The web perforation form of H-shaped dampers somewhat affected the seismic behavior of steel frame structures. Among them, diamond dampers could minimize structural deformation.

Experimental study on the seismic performance of non-compact H-section steel frames

In order to assess the seismic performance of steel frame systems with non-compact members, cyclic tests were conducted on three full-scale frames incorporating beams and columns of varying plate width-thickness ratios. The seismic performance of these specimens, including failure modes, hysteresis curves, load-bearing capacities, ductility, and energy dissipation capabilities was thoroughly examined. The test results indicated that the dominating failure mode observed in all the specimens was the local buckling deformation occurring at the beam end and column bottom zones, and the occurrence of the first concentrated local failure would lead to the ultimate load-bearing state of the frames. Moreover, the occurrence sequence and development degree of the buckling deformations had a significant effect on the seismic performance of the frames. These findings suggest that reasonable combinations of beam and column sections should be carefully considered to retain rational balance between load-bearing capacity, ductility and energy dissipation capabilities for non-compact frames.

Investigation of effective parameters on seismic performance of steel frames with CFST columns

The seismic performance of steel frames with composite columns is evaluated by the seismic performance factors. Despite the essentiality of appropriate coefficient values, there are limitations in the building code regarding seismic performance factors of composite structures. These values have been presented in the regulations based on engineering judgment and comparison with similar steel and concrete structures. However, limited research exists on the determination of seismic performance factors for composite structures, where these coefficients are affected by numerous parameters. This article aims to cover the existing gaps and examine the parameters that have received inadequate attention in regulations and articles, despite their significance in the seismic design of composite structures. The present study conducts a nonlinear static pushover analysis of steel structures with concrete-filled tubular steel columns (CFST) to investigate the influential parameters in seismic performance factors. The variables studied in this research encompass the height of the structure, soil type, lateral force-resisting system, and structural irregularity. The findings demonstrate that changes in structural height influence the value of the response modification factor in all examined soil types for IMFs and SMFs. Also, the response modification factors provided in ASCE 7 prove to be conservative for the studied lateral force-resisting systems excluding SMFs in composite structures. In addition, the seismic performance of the studied models has dropped due to the geometric irregularity of the plan and the irregularity of non-parallel systems. Besides, the response modification factor values for composite structures surpass those specified for similar steel structures, while Eurocode 8 and ASCE 7 consider these values to be equal and similar to steel structures, respectively.

Effects of beam-column connection rigidities and soil-structure interaction on seismic performance of steel frames

Structures can be exposed to non-linear deformations under earthquake effects. However, linear methods are mostly preferred for designs because of their simplicity and facility. The inelastic behavior of the structure is approximately taken into account by using some coefficients. However, it is possible to make more realistic and economical designs by using methods that consider the inelastic behavior of the structure. In this context, the displacement-based design method is becoming increasingly popular. This study evaluates the seismic performance of steel frames resting on elastic foundations with different beam-column joint stiffnesses using the static pushover analysis method. Static pushover curves, plastic deformations, performance points, and base shear forces were compared. The results show that the base condition greatly affects the seismic performance of the building.

Improving the Seismic Performance of Steel Frames under Mainshock–Aftershock Using Post-Tensioned Connections

In this study, the seismic responses of moment-resisting steel frames (MRSFs) with welded and post-tensioned connections under 28 artificial seismic sequences (mainshock–aftershock) are compared. For this aim, the mainshock are scaled at different ground motion intensity levels as a function of the spectral pseudo-acceleration corresponding to the fundamental period of vibration of the structure Sa(T1), whereas different intensity levels of the aftershocks are used for a percentage of the peak maximum acceleration of the mainshock. The seismic performance comparison of both structural systems is computed for the maximum, residual inter-story drift and hysteretic energy demands. The results show that post-tensioned frames significantly reduce the structural demands, especially in the case of residual inter-story drifts and hysteretic energy in comparison with moment-resisting steel frames with welded connections. The reductions in the structural response tend to be larger as the intensity of the aftershock tends to increase. Therefore, it is concluded that the use of post-tensioned connections is a great alternative to mitigate the seismic response of buildings subjected to seismic sequences.

Seismic performance of steel frame equipped with structural fuse

Seismic performance of steel frame equipped with structural fuse

Finite element analyses on hysteretic behavior of steel frames infilled with AAC masonry wall with circular-arc openings

ABSTRACT The steel frame infilled with the autoclaved lightweight aerated concrete (AAC) masonry wall is widely applied in buildings. However, earthquake damage investigation has revealed that infill walls have a significant influence on the mechanical behaviors of the frame structure. In this paper, a new type of AAC masonry wall with circular-arc openings at the corners was proposed based on the principle that setting openings at the corners of the infill wall would weaken the tension (compression) band, so as to reduce the unfavorable interaction between the steel frame and the infill walls. Additionally, the seismic performance of steel frames infilled with AAC masonry walls with circular-arc openings at the corners under low cycle loading was investigated through finite element (FE) method simulations on 11 specimens. The results demonstrated that the circular-arc openings are effective in delaying the cracking of the AAC wall and weakening the additional stiffness of the AAC masonry wall for the steel frame.

Numerical Study of Hybrid Steel Frames under Far-field Earthquakes

The 1994 Northridge and 1995 Kobe earthquakes have shown the susceptibility of severe damage of welded moment-resisting frames, especially at the beam to column connections subjected to severe earthquake ground-motions. Since then, an alternative of welded connections called bolted or semi-rigid connections is considered for designing or retrofitting of steel moment frames. From the last few years, the semi-rigid connections combined with rigid connections, termed as hybrid frames have become a promising approach to design the steel frames for enhanced seismic performance. In the present paper, a numerical study is carried out to investigate the seismic performance of the hybrid steel frames. For this purpose, a ten-story high-rise rigid steel frame is analyzed and designed for seismic requirements as per Indian Standards. The rigid connections of frames are replaced by semi-rigid connections with a moderate degree of semi-rigidity. The six different patterns (locations of semi-rigid connections) of hybrid frames are considered here to compare the seismic responses with those obtained from the rigid connected steel frame. The nonlinear time-history analyses are executed using the SAP2000 software at two scaled PGA level in compliance with design basis earthquake and maximum considered earthquake. An ensemble of five time-histories of far-field earthquakes is considered for the numerical study. A wide range of seismic response parameters, namely, the maximum value of base shear, top-story displacement, inter-story drift ratio, the total number of plastic hinges is extracted for the suggestion of a suitable pattern for hybrid frames. The major findings from the present numerical study show that the pattern and number of semi-rigid connections in the hybrid frame considerably affect the seismic performance of steel frames. It is also observed from the seismic responses that the hybrid frames are better than the rigid frame at high PGA levels.

Experimental study on the seismic performance of steel frames with infill ALC wall panels

To explore the seismic performance of H-shaped steel frames with infill precast autoclaved lightweight concrete (ALC) wall panels, the horizontal low-cyclic loading tests were conducted under vertical load. The influence of the connector style, the arrangement, and the integrity of the wall panels on the seismic performance of the structure were analyzed depending on four specimens of H-shaped steel frames with ALC wall panels and one hollow H-shaped steel frame. The failure mode, bearing capacity, rigidity and strength degradation, and energy dissipation performance were compared and discussed. The results showed that the steel frame with infill wall panels had better ductility and energy-dissipating capacity than the hollow frame. The infill ALC wall panels greatly enhanced the seismic performance of the frames and had a significant influence on the bearing capacity, stiffness, energy dissipation capacity, and ductility performance of the specimens. The maximum ductility factors and total energy dissipation of the steel frame with ordinary infill wall panels were 1.58 times and 2.27 times larger than those of the hollow frame. Due to cooperation with the steel frame, the panels delayed the buckling and in-plane deformation of the frame. The sliding connector improved the bearing capacity, displacement ductility, and energy dissipation of the overall structure compared with the hooking connector. Moreover, the bearing capacity of the frames with the reinforced wall panels was improved further. Additionally, the equivalent compression bar model was developed to estimate the bearing capacity of the steel frames with the infill ALC wall panels. The experimental conclusions and the proposed analytical model improve the practical design of the steel frames with the infill ALC wall panels in high-rise buildings.

Experimental and parametric study of a novel braced system to improve seismic performance

Concentrically braced frames have high stiffness, but show poor ductility in terms of the buckling of compressive member. Using the yielding dampers, of which the knee-joints are a part, can improve the seismic performance of steel frames. The bracing components in this system disperse energy by adhering to the knee joint and then yielding. The role of the bracing members is to provide rigidity, while the function of the knee member is to produce ductility similar to a yielding damper. These steel dampers are inactive and installed at the connection of brace to the frame. We obtained new results by combining Y-shaped braces with knee members. In this regard, three proposed bracing frame specimens were experimentally tested at the structural laboratory. Furthermore, all of the three laboratory specimens were modeled and validated in ABAQUS finite element software, and the results confirm the optimal performance of this seismic system along with energy absorption and appropriate behavior in the stability of this design. Moreover, it shows a good capacity for energy dissipation and the knee element starts the energy absorption process faster at lower frame displacements. It increases the durability of structure against lateral loads and less force is applied to the main elements of the structure. Using a knee bracing system can be a good alternative to the brace system in terms of its ease of replacement. Reasonable agreement with the experimental results is observed. The behavior of deformation-force hysteresis curves gives good results that, the experimental and parametric experiments showed that this system will have a lot of force adjustment.

Application of self-centring hybrid rocking columns in steel frames

This study proposed a novel rocking component, namely self-centring hybrid rocking columns (SCR). Cyclic loading tests are conducted on a substructure consisting of the SCR and a frame beam-to-SCR connection to investigate its hysteretic performance. A numerical model of the SCR substructure is built and validated against the test results. Finally, the seismic performance of steel frames equipped with the SCR is demonstrated through the nonlinear time history analysis. It shows that the proposed self-centring hybrid rocking column has acceptable lateral resisting, energy dissipation and self-centring capability. The simplified numerical model of the SCR can reasonably well capture the hysteretic behaviour of the SCR substructure no matter with or without the steel damper and tension braces. The system-level analysis of steel frames with the SCRs verifies the effectiveness of the proposed SCR in mitigating maximum and residual drift responses of steel frames under earthquakes. After equipping the SCRs, the inter-storey drift concentration is also mitigated under earthquakes.

Seismic behavior of hollow-core infilled steel frames; an experimental and numerical study

This study describes an experimental program designed to investigate the influence of the presence and orientation of hollow-core wall panels as well as beam to column connection rigidity on the seismic performance of steel frames infilled with hollow-core wall units. For this purpose, four half-scale, single-story, and single-bay specimens, including three infilled steel frames and one bare moment frame, were subjected to cyclic lateral loading. The bare steel frame and two infill specimens had rigid connections, while the last one had pinned connections. One of rigid connections specimen was constructed with hollow-core wall panels placed vertically, whereas the other was fabricated with wall panels with the horizontal core. The experimental results indicated that the vertical placement of hollow-core wall units controlled structural damage and improved the seismic performance through the rocking mechanism within the steel frame. In addition, the strength, stiffness, and energy dissipation capacity of the infilled pinned connections frame were less than those in rigid connections specimen. In another part of this study, a parametric study was conducted with finite element method using ABAQUS software. The parametric nonlinear analyses study revealed that the infilled frames with hollow-core wall panels placed vertically had less initial stiffness and more strength than those with horizontal core panels. On the other hand, the initial stiffness and strength of the infilled steel frame, bare steel frame, and infill contribution were reduced by the decrease in the rigidity of the steel frame connections, regardless of infill aspect ratio and the relative stiffness of the hollow-core panels to the surrounding steel frame.

Numerical Investigation of the Seismic Performance of Steel Frames with Energy-Dissipating Composite Walls.

To improve the seismic performance of steel frame buildings in rural areas, an energy-dissipating composite wall (EDCW) assembled from concrete-filled steel tubular columns and concrete sheet walls was designed. Cyclic loading tests were simulated using the finite element method (FEM) to analyse the seismic performance of the EDCW. The reliability of numerical modelling and analysis was verified by comparing the hysteretic curves obtained by the finite element model with those obtained by previous experiments. The EDCW was designed for installation in a two-storey steel frame, and the FEM was used to determine the seismic performance of the steel frame, including the deformation and failure characteristics, hysteresis curves, and skeleton curves. The numerical simulation results showed that the EDCW dissipated most of the seismic energy and thus substantially improved the seismic performance of the frame. The seismic performances of 16 frames were compared to investigate the effects of the span ratio of the steel frame to the EDCW, the installation location of the EDCW, and the stiffness of the steel frame on the seismic performance of the frame.

Seismic performance of steel frame with replaceable low yield point steel connection components and the effect of structural fuses

In the context of high quality development of construction industry and the construction of resilient city, an innovative ductile and dissipative steel frame system with replaceable low yield point steel (LYP) components was proposed. By means of superposition of prefabrication function, damage control function and post-earthquake replaceable function, this quality solution was provided for satisfying the two-stage resilient design target of “the damage is controllable to achieve structural safety subjected to the earthquake excitation, and the structural function is restorable after earthquake with lower cost”. This multi-functional system relied on common connection methods (bolted connections with cover plates, T-stubs, or angle steels) and was easy to process and construct without additional complicated dissipative elements. Six numerical models of steel frames with different connection configurations were generated, namely five bolted three-storey steel frame structures with LYP connection components and a welded three-storey steel frame structure with reduced beam section. The static elastic-plastic analysis and nonlinear dynamic history analysis were carried out to explore the seismic performance of the overall structures and to verify the effect of structural fuses. The analysis results demonstrated that the steel frames with replaceable LYP connection components had good load-carrying capacity, desirable deformation capacity and dissipation capacity, meanwhile, the well-designed replaceable LYP connection components were able to concentrate plasticity and damage, to give full play to the role of structural fuses. The strategies of widening beam flanges at the root of beam and reducing the design resistance capacity coefficient were effective to improve the structural fuse effect. The desirable fuse effect can be realized with smaller required weakening degree in the case of widening beam flange.

Shaking Table Test for Evaluating the Seismic Performance of Steel Frame Retrofitted by Buckling-Restrained Braces

To investigate the seismic performance of buckling-restrained braces under the earthquake action, the shaking table test with a two-story 1/4 scale model is carried out for the ordinary pure steel frame and the buckling-restrained bracing steel frame with low-yield-point steel as the core plate. The failure modes, dynamic characteristics, acceleration response, interstory drift ratio, strain, shear force, and other mechanical properties of those two comparative structures subjected to different levels of seismic waves are mainly evaluated by the experiment. The test results show that under the action of seismic waves with different intensities, the apparent observations of damage occur in the pure frame structure, while no obvious or serious damage in the steel members of BRB structure is observed. With the increase in loading peak acceleration for the earthquake waves, the natural frequency of both structures gradually decreases and the damping ratio gradually increases. At the end of the test, the stiffness degradation rate of the pure frame structure is 11.2%, while that of the buckling-restrained bracing steel frame structure is only 5.4%. The acceleration response of the buckling-restrained bracing steel frame is smaller than that of the pure steel frame, and the acceleration amplification factor at the second story is larger than that at the first story for both structures. The average interstory drift ratios are, respectively, 1/847 and 1/238 for the pure steel frame under the frequent earthquake and rare earthquake and are 1/3000 and 1/314 for the buckling-restrained bracing steel frame, which reveals that the reduction rate of lateral displacement reaches a maximum of 71.71% after the installation of buckling-restrained brace in the pure steel frame. The strain values at each measuring point of the structural beam and column gradually increase with the increase of the peak seismic acceleration, but the strain values of the pure steel frame are significantly larger than those of the buckling-restrained bracing steel frame, which indicates that the buckling-restrained brace as the first seismic line of defense in the structure can dramatically protect the significant structural members. The maximum shear force at each floor of the structure decreases with the increase in height, and the shear response of the pure frame is apparently higher than that of the buckling-restrained bracing structure.

Seismic Fragility Curves for Performance of Semi-rigid Connections of Steel Frames

A steel frame with a semi-rigid connection is one of the most widely used structural systems in modern construction. These systems are cheap to make, require less time to construct and offer the highest quality and reliable construction quality without the need for highly skilled workers. However, these systems show greater natural periods compared to their perfectly rigid frame counterparts. This causes the building to attract low loads during earthquakes. In this research study, the seismic performance of steel frames with semi-rigid joints is evaluated. Three connections with capacities of 50, 70 and 100% of the beam’s plastic moment are studied and examined. The seismic performance of these frames is determined by a non-linear static pushover analysis and an incremental dynamic analysis leading finally to the fragility curves which are developed. The results show that a decrease in the connection capacity increases the probability of reaching or exceeding a particular damage limit state in the frames is found. Doi: 10.28991/cej-2021-03091714 Full Text: PDF

Study on seismic performance of prefabricated self-centering beam to column rotation friction energy dissipation connection

Under severe earthquakes, a significant number of unexpected plastic hinges and brittle failure were found in conventional rigid beam to column welded connections of steel frames. To improve the seismic performance of steel frames, an innovative prefabricated self-centering beam to column (SCBC) connection was proposed and experimentally validated in this paper. The SCBC connection consisted of disc springs at the bottom flange of beam and a rotation friction hinge (RFH) at the beam end. The bottom disc springs could not contact with slab systems and provided restoring moment, whereas the RFH was designed to dissipate seismic energy. Firstly, its configuration form and design methodology were introduced. Then cyclic tests of a 1/4 scale SCBC connection specimen was carried out and the responses of the SCBC connection was compared to that of the RFH. Finally, the restoring force model of the SCBC connection was established through theoretical analysis. The experimental and analytical results demonstrated full flag-shaped hysteretic curves of the SCBC connection under cyclic loadings, verifying the desirable energy dissipation capacity and reliable self-centering capability of the SCBC connection. The calculation results based on the restoring force model were in good agreement with the test results, showing that the proposed restoring force model could reasonably predict the hysteretic behavior of the SCBC connection.

Performance of self-centering devices containing superelastic SMA bars and their application via finite element analysis

This paper aimed to use finite-element analysis to evaluate the seismic performance of self-centering devices, containing superelastic shape memory alloy (SMA) bars and their application. It should be noted that the devices could perform bending behaviors combining with tensions or compression. Cyclic performance of the devices under pulling and pushing actions have been modelled and verified by previous experimental results. Then, parametric studies were conducted to investigate the effect of design parameters on the stiffness of the self-centering devices containing SMA bars. An application of the device to a steel frame was proposed and modelled. Results shown that the increasement of diameters and number of SMA bars have positive effects while the increase of bars length and moment arms have negative effects on the effective stiffness of the devices. Besides, with the same area, the use of SMA bars in the rectangular shape gives higher effective stiffness than the use of those in the circular shape. However, with the same moment of inertia, the former gives lower effective stiffness than the latter. The hysteretic responses of a steel frame equipped with SMA devices showed perfect self-centering capacity with symmetric behavior. The devices are effective to enhance the seismic performance of steel frames.