Bare Steel Frames Research Articles

Seismic performance of frame with middle partially encased composite brace and steel-hollow core partially encased composite spliced frame beam

Steel-hollow core partially encased composite spliced frame beam (SHSFB) and middle partially encased composite brace (MPECB) demonstrate the potential to economize on steel consumption while exhibiting superior performance. To investigate the seismic performance of frames with SHSFBs and MPECBs, horizontal low-cyclic loading tests were conducted on four frame specimens, involving two two-story frames with no brace and two multi-story X-braced frames. Numerical simulations were performed using the “Open System for Earthquake Engineering Simulation” (OpenSees). The results indicate that the novel composite frames exhibit commendable seismic performance and energy dissipation capacity. The unbraced frame with SHSFBs has deformation capacity and mechanical properties comparable to bare steel frame. In contrast to the frame specimen equipped with bare steel braces featuring a 6 mm flange thickness, the specimen utilizing MPECBs with 4 mm flange thickness exhibits only a slight reduction of 3.60 % in maximum bearing capacity and 2.68 % in initial lateral stiffness. Significantly, each SHSFB and MPECB component reduces steel consumption by 16.71 % and 24.79 %, respectively, compared to bare steel components. Therefore, while ensuring adequate mechanical properties, frame structures equipped with SHSFBs and MPECBs will require less steel. Based on both experimental and simulation results, the formulas for predicting the ultimate bearing capacity and initial lateral stiffness of the novel composite frame were proposed, and the structural design for the multi-story X-braced frame was analyzed, offering valuable insights for practical engineering applications.

Experimental and analytical studies of infill wall with sliding joints considering a door opening

AbstractSemi‐rigid steel frame stands out due to its remarkable deformation capability under seismic loading, while the introduction of partitioned walls would disturb the expected seismic behavior of the infilled steel frames. Furthermore, the presence of door openings might exacerbate these negative effects. To mitigate the detrimental multiple‐diagonal strut effect of traditional infill walls around the door opening, an innovative low‐damage wall panels system: prefabricated infill wall panels with a door opening and sliding joints are presented for semi‐rigid steel frames. For testifying the effectiveness of the proposed structure, a quasi‐static test was carried out on three half‐scaled steel frames: a bare frame, a frame infilled with conventional wall panels with a door opening, and a frame infilled with the novel wall panel system with a door opening. Experimental results reveal that the developed innovative wall panels with a door opening could avoid unfavorable crack developments and opening deformation around the door area. It is mainly attributed to the releasement of the adverse multiple‐diagonal strut mechanism of traditional wall panels with door openings. Thus, the presented infilled frame showcases seismic performance similar to the bare steel frame, while having a higher energy dissipation capacity. Moreover, the developed analytical prediction method based on the superposition principle could accurately estimate the lateral load‐carrying capacity of the structures. Due to negligible deformation of the both bottom infill wall panel and the door opening, the innovative infill wall only contributes about 10% lateral load‐carrying capability to the infilled frame.

Experimental study on seismic performance of frame with steel-hollow core partially encased composite spliced beam

This paper conducted design and experimental study on frame specimen equipped with steel-HPEC (Hollow-core partially encased composite) spliced beams (SHS beam in short). SHS beams are comprised of two bare steel beams and an HPEC beam with thinner flange plates, present similar deformation and bearing capacity to traditional I-shaped steel structure, in addition to the benefits of good lateral stiffness and steel saving. Lateral low-cyclic loading tests were conducted on a bare steel frame and a frame with SHS beams to investigate their failure modes, seismic performance, and evaluate the feasibility of implementing SHS beams in frame structures. The frame specimen with SHS beams exhibited similar failure modes as those observed in steel frame specimen. Due to the higher stiffness of SHS beams, which effectively limited out-of-plane deformation in frame, SHS beam frame presented higher initial lateral stiffness, ultimate bearing capacity and energy dissipation capacity when contrast with bare steel frame. For calculations, SHS beams could be construed as stepped beams with variable rigidity. Finally, the calculation methods and formulas for initial lateral stiffness and ultimate bearing capacity of both the frames with SHS beams and bare steel frames were proposed, and the calculated results agreed well with the experimental values.

Seismic behavior of hinged steel frames with masonry infill walls

Historic buildings are important parts of our cultural heritage and contribute to the social and economic of communities. Hinged steel frames with masonry infill walls were extensively used in conserved historical buildings built in the early 20th century in Shanghai, China. Those historical buildings are characterized by low strength in materials and the seismic actions were not properly considered in designs. Therefore, a better insight into their seismic performance assessment is necessary for both structural rehabilitation and maintenance of historic architectural features. This paper describes an experimental and numerical investigation on seismic behavior of hinged steel frames, with a special focus on the effect of masonry infill walls. Shaking table tests were conducted on two 1:4 scaled three-story, two-bay hinged steel frame model structures, i.e., a bare steel frame (Model M1) and a steel frame with masonry infill walls (Model M2). Three seismic records, i.e., Shanghai artificial signal (SHW-II, which was specified for the type IV soft base conditions in Shanghai), El Centro signal (obtained from the Imperial Valley earthquake in 1940) and Pasadena signal (obtained from the Kern County earthquake in 1952) were selected. The failure modes, dynamic characteristics, acceleration, inter-story shear forces as well as inter-story drifts of the two model structures were measured and compared. Three-dimensional finite element (FE) models of hinged steel frames with and without masonry infill walls were established. Effects of the stiffness of beam-column joints and the distribution of infill walls were also investigated. Results indicated that masonry infill walls altered the distribution of lateral force and increased the stiffness of the frame, leading to a noticeable reduction of structural deformation. The effect of infill walls was related to the ratio of stiffness of the walls to that of surrounding frames. In addition, a soft-story mechanism could occur in the case of partially infilled frames.

A Comparative Study on Different Types of Passive Energy Dissipating Devices

Earthquake induced structural vibrations causes fatigue and reduction of performance of the tall steel framed structures. One of the effective ways for improving the seismic performance of a structure is the use of bracings, dampers and isolators. These devices change the stiffness and damping of the structures thereby reducing the seismic vibrations to a great extent. The main objective of this study is to compare the different types of passive energy dissipating devices in a 3 bay 10 storey steel frame building for better seismic response. The frame was modelled in SAP2000® and some of their responses to earthquake such as base shear, maximum joint displacement, inter storey drift were determined and compare during non-linear dynamic time history analysis in SAP2000®.The passive energy dissipating devices used in this study are diagonal bracing, v bracing, cross bracing, rubber base isolator and friction damper. At first a single storied shear frame model was tested in shake table and results obtained from SAP 2000® were compared. The close proximity validated the procedure. It is observed that addition of dampers to the system increases the stiffness to the frame. When compared, displacement for steel frame with dampers is reduced by 80% and that with different bracing systems are reduced up to 78% as compared to bare steel frame. For base isolators, base shear decreases up to 63.33% but an increase in the maximum joint displacement was observed. The comparison of performances of all types of dissipating mechanisms has been presented in the study.

Seismic responses of infill walls with sliding joints and openings in semi-rigid steel frame

Forming door and window openings in partition infill walls is a frequent activity in engineering practices, while the complexity of the mechanical behavior of such infill systems with openings due to the destructive damage to the infill walls has not been thoroughly considered. To protect the vulnerable door and window openings and mitigate the detrimental multiple diagonal struts effect of infill around the opening, the paper presents two novel precast infill walls with sliding joints and door and window openings for semi-rigid steel frames. The quasi-static cyclic tests are performed on three specimens: a reference bare steel frame and two infilled steel frames with door or window opening. Test results confirm that the developed infill systems effectively prevent potential cracking or deformation of the openings and release the adverse multiple diagonal struts effect of infill with a door or window opening. Because of the working mechanism of the developed infills, the two infilled steel frames behave with similar seismic responses to the bare steel frame, while the novel infills are significantly undamaged and no detectable opening deformation is observed even at the inter-story drift ratio of 3.33%. Furthermore, both experimental and numerical responses of the developed innovative infill systems confirm the effectiveness of the infill systems without any additional fixtures to protect the fragile door and window openings.

Structural Behavior of steel frame Infilled with Ferrocement Precast Panel S ubjected to Lateral Load

Background: When a severe earthquake ground motion hits the structure even if it doesn’t collapse it may undergoes inelastic deformations. Steel structure infilled with precast panels becomes less efficient when subjected to large lateral loads like strong wind and earthquake. Hence assessment of actual performance of steel frames provided with infills in the event of earthquake is essential. Methods: In the current study, a prototype model of steel frame size 4m x4m bay & 4m height with G+2 story is scaled down and subjected to lateral seismic load by conducting shake table test to assess modal frequencies, the same structure is modelled in Hypermesh and analyzed in Nastran, ETABS software. The results obtained are validated for a 16X16m bay of 4m height commercial complex of G+9 Multi-storeyed structure infilled with Ferrocement Precast panels analysed in ETABS software for base shear, response spectrum and pushover analysis to assess the performance of the structure. Findings: The frequency from modal analysis was found to be 45.21 Hz, for G+2 storied model in ETABS, values obtained for frequency, base shear, performance point of the structure are in appreciable. Novelty: As per the traditional earthquake design methods, structures are designed for less forces than maximum considered for earthquake. The overall performance of the structure is found to be safe even infilled with Ferrocement precast panels. Advantages: Ferrocement panels as infills has benefit as they are slender from structural point of view. Compared with steel bare frame dynamic behavior of bare steel frame which is infilled with Ferrocement precast panel subjected to lateral loads is high that helps in assessing the damage in the event of an earthquake in critical zone V. Keywords: Infill; Ferrocement precast panels; Pushover Analysis; Performance point; Response spectrum

Behavior of Steel frame subjected to lateral load

Background: A steel frame system becomes structurally less efficient when subjected to large lateral loads such as a strong wind, earthquake. Many research efforts have been made to develop more efficient structural systems with better resistance against strong lateral loads. Methods: An attempt is made in this direction by both analytical and experimental studies. A bare steel framed model of size 4m x4m is chosen for G+2 storey with columns of height 4m. The particular frame is scaled down to 1:11 scale to perform shake table test for seismic zone-V in terms of modal frequencies. Same frame is modelled in Hypermesh software & analysis is done in Nastran and ETABS software’s. The results obtained can be applied to 16 X 16m G+9 Multi-storeyed commercial complex structure and analysed in ETABS software for Base shear, response spectrum and pushover analysis to assess the performance of the structure. Findings: Prototype of G+2 storey scaled down model, ETABS and Nastran analysed models showed approximately same values of modal frequencies 10- 12% which is an allowable percentage. Novelty: The results obtained shows that the base shear, performance point of the structural system and in terms of model frequencies are with in safer limits. The overall performance of the structure was found to be safe between operational to collapse stage. Advantages: The present work gives the dynamic behavior of bare steel frame subjected to lateral loads which helps in assessing the damage causing due to earthquake can be pretended to prevent the loss of life. Keywords: Bare steel frame; Shake table; Base Shear; Response spectrum; Modal frequencies

Numerical evaluation on collapse-resistant performance of steel-braced concentric frames

Steel-braced concentric frames (SBCFs) are a popular form of structure and has been widely employed in seismic regions owing to their high strength and elastic stiffness; however, the effects of key parameters on the collapse behavior of SBCFs are unclear due to insufficient investigations, which should be further explored in column removal scenarios. To this end, numerical models were employed to explore the key parameters affecting the collapse behavior of SBCFs in this study. The numerical models of steel frames with or without braces were validated based on previous experimental results. According to the refined model, the effects of brace members of various types and with different slenderness ratios on the collapse behavior were illustrated. The results showed that an X brace type with smaller slenderness ratio is the most appropriate for enhancing robustness against progressive collapse. Thereafter, full-scale numerical models were established to investigate the effect of the column removal position, and the results showed that the frame relied purely on flexural action in a side column loss. Moreover, the effect of the position of horizontal brace layers on the collapse behavior was investigated in the middle and side column removal scenarios. To gain deeper insight into the load-resisting mechanisms, the specific contributions to the total resistance of different mechanisms in different stories, bare steel frames and braces, and tensile and compressive braces were separated. Finally, a strategy for the robustness enhancement of high-rise steel frames was empirically proposed, and it was suggested that the provision of a brace layer for approximately every 10 stories would be effective for the anti-collapse design of high-rise buildings.

Behaviour of thin flush end-plate connections in a 3D bare steel frame under fire loading: experimental study

PurposeThe paper aims to report a fire test conducted on a three-dimensional frame in order to investigate the behaviour of bare steel flush end-plate connections with relatively low thickness at elevated temperatures.Design/methodology/approachA half-scale model was fabricated and exposed to modified (scaled) ISO 834 heating curve using a semi-open furnace. The maximum temperature inside the furnace reached 1,026 °C.FindingsThe rotations of connections are reported and compared with those of a previous study on an exactly the same model with thick end-plates. Various modes of failure such as local buckling of the beams flanges and lateral-torsional buckling of beams were observed during the test. Finally, the structure collapsed after 29 min of heating due to the fracture of weld between one of the beams and one of its attached end-plates whilst the other beam had undergone a maximum deflection of 35 cm (≈ 1/6 span length). Other observed failure modes included bolt fracture, bolt thread stripping and large inelastic deformation of the end-plates.Originality/valueAlthough the adoption of thin end-plates increased the rotational capacity of the connections, it did not improve the robustness of the structure under fire conditions.

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.

Cyclic behavior of semi-rigid steel frame infilled with damping wall panels

Semi-rigid connected steel frame is characterized by excellent displacement ductility and energy dissipation capacity, while detrimental infill-frame interaction from the traditional infill would be a key role in seismic behaviors for such steel frames and may damage both infill and steel frame. In this study, the solution to partition the infill with low-strength mortar sliding joints and uncouple the infill from the surrounding frame by flexible connections for the semi-rigid steel frames is presented. Three specimens designed in this context were examined experimentally and numerically. The test results show that the frame with low-strength sliding joints and flexible connections behaves similarly to the bare steel frame, and improves the energy dissipation capacity by about 19.83%. Unlike the semi-rigid steel frame with traditional infill, significant crack of the infill or local stress concentration on the columns is undetected even at a drift ratio of 3.33% in the proposed infilled steel frame. Parametric analysis results confirm that the friction factor of the low-strength sliding joints is the key parameter to improve the lateral bearing capacity of the infill system.

Ductile connection to improve the fire performance of bare-steel and composite frames

PurposeIn order to improve the robustness of bare-steel and composite structures in fire, a novel axially and rotationally ductile connection has been proposed in this paper.Design/methodology/approachThe component-based models of the bare-steel ductile connection and composite ductile connection have been proposed and incorporated into the software Vulcan to facilitate global frame analysis for performance-based structural fire engineering design. These component-based models are validated against detailed Abaqus FE models and experiments. A series of 2-D bare-steel frame models and 3-D composite frame models with ductile connections, idealised rigid and pinned connections, have been created using Vulcan to compare the fire performance of ductile connection with other connection types in bare-steel and composite structures.FindingsThe comparison results show that the proposed ductile connection can provide excellent ductility to accommodate the axial deformation of connected beam under fire conditions, thus reducing the axial forces generated in the connection and potentially preventing the premature brittle failure of the connection.Originality/valueCompared with conventional connection types, the proposed ductile connection exhibits considerable deformability, and can potentially enhance the robustness of structures in fire.

Experimental and numerical study on seismic performance of semi-rigid steel frame infilled with prefabricated damping wall panels

This study proposes an innovative prefabricated damping wall panels infill for semi-rigid connected steel frame to release adverse infill-frame interaction. The comparative experimental studies of three specimens under quasi-static cyclic test are designed and performed, one of which is a bare semi-rigid steel frame, one is a common infill semi-rigid steel frame, and the other is a prefabricated damping wall panels infill semi-rigid steel frame. Experimental results show that the severe crack development and obvious out-of-plane displacement appear on the common infill, showing its detrimental infill-frame interaction. However, the developed infill system can considerably release adverse infill-frame interaction and provide adequate out-of-plane resistance, so that the novel infill is significantly undamaged and no visible out-of-plane displacement is observed in each wall panel as interstory drift up to 3.33%. Additionally, the developed infill system performs similar seismic responses with the bare frame, in terms of hysteretic response, loading capacity degradation, and displacement ductility. Moreover, the novel infill can improve about 23.3% additional energy dissipation capacity of the steel frame, and release the stress of the columns. Furthermore, the experimental and numerical results are in good agreement. The hysteretic responses and deformation modes of the presented novel system in the experiment are well-matched with the numerical simulation results, which validates the rationality and accuracy of the pseudo-static test and feasibility of the novel infill system to release adverse infill-frame interaction. The numerical results of the rigid steel frame further confirm the effectiveness of the proposed damping wall panels for both semi-rigid steel frames and rigid steel frames. As a result, it can be proved in this study that the innovative infill system can release adverse infill-frame interaction to perform as a bare steel frame with better energy dissipation capacity.

STUDY ON SEISMIC BEHAVIOR OF STEEL FRAME WITH ENERGY DISSIPATING CLADDING PANEL CONNECTIONS

An energy dissipating cladding panel connecting method for steel frames was proposed. In order to study the effect of this new kind of connecting method on the seismic behavior of the main structure, quasi-static cyclic tests were carried out on two steel frames with X- or U-shaped steel dampers as the energy dissipating connections and one bare steel frame counterpart. The quasi-static cyclic tests of the two kinds of dampers were carried out as well. The test results indicated that local buckling occurred on the X-shaped dampers during the fatigue loading stage, and the final failure was governed by the fracture of the core board; the U-shaped dampers only presented slight cracks in the fatigue loading stage and showed better fatigue performance; the hysteresis loops of the two kinds of dampers were plump and showed hardening stages, and the X-shaped damper showed a more obvious hardening effect owing to the membrane effect of the core board; the failure modes of the three steel frames were similar, and the damage mechanism of the steel frame was not altered by the cladding panels; cracks occurred on the cladding panel of GKJ-1 in the final loading stage due to the membrane effect of the X-shaped dampers, and the final failure mode of the specimen was governed by the broken of the connecting bolt between the cladding panel and the beam; no damage was observed in the U-shaped dampers and cladding panel of GKJ-2; the cladding panels with energy dissipating connections could increase the stiffness, strength and hysteresis energy of the steel frame.

Mechanical Behavior of CCA Wall Infilled Steel Frames with Preset Vertical Slits

In view of the unfavorable interaction between the steel frame and cellulose fiber cement sheets autoclaved (CCA) wall, preset vertical slits are adopted on the wallboard. Four 1:2-scale, single-bay, and single-storey steel frames, one bare steel frame, one CCA wall infilled steel frame without any measures, and two CCA wall infilled steel frames with different patterns of a slit, were tested under low cyclic load. The failure mode and additional stiffness of the CCA wall were obtained from the test. Besides, the effects of the vertical slits on hysteretic performance, bearing capacity, and the stiffness degradation of specimens were also studied. It was found that the preset vertical slits were effective in delaying the cracking of the CCA wall, and in reducing the additional stiffness of the CCA wall for the steel frame structures. To further study the failure characteristics of CCA wall, the finite element models of the CCA wall infilled steel frames were established and verified against the test results. The findings in this paper will have a certain reference value for the future research and engineering applications of similar steel frames with infill walls.

Seismic performance of semi-rigid steel frame infilled with prefabricated damping wall panels

In this research, two innovative semi-rigid steel frames infilled with prefabricated damping wall panels in different types of connection are proposed. Working principles and main features of the developed infill system with both uncoupling mechanism and sliding joints are defined. A quasi-static test was conducted to explore the seismic response of the two systems, as compared with a bare steel frame. Test results confirm that the detrimental infill-frame interaction is prevented by the proposed wall panels. Both specimens infilled with prefabricated damping wall panels characterize a considerably large deformation capacity up to 3.33% drift, while significant crack or corner crushing in the wall panels is not observed, contributed to the configurations of the prefabricated damping wall panels. The infilled steel frames have stable seismic behavior similar to the bare steel frame without infill, indicating that the prefabricated damping wall panels can be designated as an additional safety stock with damping for the steel frame rather than the major component of strength, stiffness, and brittleness. Specifically, thanks to satisfactory energy dissipation capacity of the damping layers, dissipated energy of steel frame infilled with the prefabricated damping wall panels is about 23.3% larger than the bare steel frame after yielding. Moreover, it would be a more effective and controllable configuration that the lateral displacement of the upper wall panel is directly enforced by the top beam.

An improved cable-cylinder bracing system with quarter-ring yielding devices for seismic retrofit of steel moment frames

This study proposes an innovative hybrid lateral load-resisting system, termed the ring-cable-cylinder bracing system, aimed at improving the energy dissipation capacity and ductility of the previously introduced cable-cylinder bracing (which offers relatively the same level of seismic energy dissipation and ductility as the original bare steel frame), and minimizing the damage to the beam-to-column connections via utilizing quarter-ring curved yielding devices. First, the proposed bracing system and its working mechanism are introduced. A mathematical procedure based on the theorem of the least work and the method of virtual work is then presented to derive highly-accurate, practical, and easy-to-use equations for calculating the thickness of the utilized quarter-ring yielding devices. The design requirements for these curved devices, based on the characteristics of the frame in which they are utilized, are also discussed exhaustively. In the next step, the presented formulae’s accuracy and usability are comprehensively investigated by conducting a finite element parametric study. The results show that the proposed system can provide an extra source of energy dissipation and ductility. It was also observed that the new system leads to an increase in both initial stiffness and ultimate strength and limits the pinching phenomena in the hysteretic cycles.

Seismic demands of bare and base-isolated steel frames for real against simulated records of a past earthquake

A challenging task in earthquake engineering is investigation of engineering demand parameters under regional records of large earthquakes due to inherently low frequency of these events. Use of simulated records in such cases is a recent alternative. Ground motion simulations were traditionally performed to model physical processes in earthquake occurrences. Nowadays, simulations are also used for engineering purposes. However, detailed assessment of simulated records against real data including their effect on structural response is necessary. The aim herein is to explore how alternative simulation methods differ in terms of engineering demand parameters for multi-degree-of-freedom models and to find out their efficiency in design and assessment of base isolated structures. For this purpose, bare and base-isolated models of a 6-story steel moment-resisting frame are considered. Force-based, displacement-based and energy-based demands are evaluated due to real and simulated records of 2009 L′Aquila (Italy) event (Mw = 6.3). Ground motion simulation approaches include stochastic finite-fault method and hybrid integral-composite techniques. Analyses show that when seismological misfits between the real and simulated records are smaller, closer matches between their engineering demand parameters are observed. Finally, numerical results reveal that simulated motions validated against real data provide alternative sets particularly for regions with sparse observed records.

Seismic behaviour of masonry infilled hinged steel frames with openings: experimental and numerical studies

This study describes an experimental and numerical investigation on the seismic behaviour of masonry infilled hinged steel frames with openings. Experimental tests of six half-scaled, single-storey and single-bay specimens including one bare hinged steel frame, one solid infilled hinged steel frame, and four masonry infilled hinged steel frames with different opening sizes were carried out under lateral cyclic loading. The cracking patterns, failure modes, hysteretic behaviour, characteristic loads and displacements, stiffness degradation and equivalent viscous damping ratios of these specimens were compared. Furthermore, detailed three-dimensional finite element (FE) models of test specimens were developed in the commercially available FE code ABAQUS, and a series of nonlinear pushover analyses were performed. In particular, the lateral load–displacement relationships of test specimens were numerically simulated and validated against the experimental results. In addition, the mechanical behaviour of infilled walls under lateral loading was investigated.