Multi-story Steel Frames Research Articles

Study on Reinforcement Method and after-Reinforcement Performance of Beam-Column Joints in an in-Service Multi-Story Steel Frame

Study on Reinforcement Method and after-Reinforcement Performance of Beam-Column Joints in an in-Service Multi-Story Steel Frame

Energy-Based Design of Buckling-Restrained Steel Braced Frames for Concurrent Occurrences of Earthquake and Wind

This paper describes the development of a dual hazard spectrum for use in the dynamic analysis of steel frames subject to the combined effects of earthquakes and wind. The proposed spectrum is obtained by combining the power spectra of earthquakes and wind using the square root of the sum of squares (SRSS) combination method. An equivalent time excitation function is then computed using an inverse fast Fourier transform (IFFT) and serves as input for the dynamic analysis. Using time-history analysis on the OpenSees platform, the dynamic responses expressed in terms of peak and residual inter-story and roof drifts for two multistory steel frames located in two US cities (Los Angeles and Charleston) are obtained to demonstrate that designing these buildings based on just one hazard may not be adequate. For frames that are considered under-designed, an energy-based design procedure that uses buckling-restrained braces (BRBs) to dissipate the excess energy imparted to these frames is proposed so they will satisfy the FEMA 356 recommended drift limits for the performance levels of immediate occupancy and life safety.

A two-level performance-based plastic design method for multi-story steel frames with double-yielding systems

The performance-based seismic design (PBSD) is usually conducted under design basis earthquakes (DBE), and then, the performance of the designed structures is examined under maximum considered earthquakes (MCE). As a result, it is challenging to simultaneously satisfy the performance targets associated with the DBE and MCE levels. To this end, this study proposes a two-level performance-based plastic design (PBPD) method. The fused steel frames exhibiting trilinear capacity curves are selected as the example structures. The peak interstory drift ratios under the DBE and MCE levels are defined as the performance targets and they are explicitly utilized at the beginning of the design procedure. The expressions of two energy modification factors are first obtained by establishing energy balance equations for single-degree-of-freedom (SDOF) systems under the DBE and MCE levels, respectively. Nonlinear time history analyses (NLTHA) for SDOF systems with various trilinear capacity curves are conducted to derive necessary design parameters. The versatility and flexibility of this design method are achieved by enabling both the primary and secondary yielding systems to yield under the DBE level. To demonstrate and validate the proposed design method, a six-story benchmark steel frame equipped with idealized metallic yielding damping braces is selected and designed with two sets of performance targets. The nonlinear static and NLTHA results proved that the designed structures can simultaneously meet the prescribed performance targets under both DBE and MCE levels.

Behavior of a Multi-Story Steel Structure with Eccentric X-Brace

Eccentrically Braced Frames (EBFs) outperform moment-resisting frames in seismically active regions because of their strength, stiffness, energy dissipation, and ductility. Conventional bracing systems, such as X, Y, V, or K types, are utilized to enhance structural integrity. This study employs computational modelling to analyze multi-story steel buildings featuring an eccentric X-brace system. In this investigation, 120 multi-story steel frame buildings were selected. These multi-story structures comprise six-, nine-, and twelve-story geometries. ETABS built a full-scale FE model of multi-story structures. The study's parametric variables are the X-brace eccentricity, steel X-brace section size, and X-braced placement. Steel X-braces may have an eccentricity of 500, 1000, or 1500 millimeters. The ETABS model was validated when its findings matched experimental data. According to the data, the eccentric X-brace increases top-story displacement more for 6-story multi-story structures than for 9- and 12-story ones. Eccentric X-braces reduced lateral stiffness, allowing more significant floor movement. Eccentric and diagonal braces offer less lateral rigidity than concentrically braced frames due to their flexibility. Eccentricity reduces stiffness, even if the X-braced component has a larger cross-section. EBFs may migrate horizontally. Since the EBF absorbs more energy, changing the X-brace section size and eccentricity affects its ductility.

Research on the influence of panel zone on dynamic damage of multi-story steel structure

As the most important component of steel structure, the panel zone has done a lot of research. In this article, the influence of the thickness of the panel zone on the performance of the multi-story steel frame is studied through the dynamic elastic-plastic time-history analysis of the panel zone models with different thickness. Then the appropriate thickness of the panel zone is summarised. The research conclusions are as follows: The displacement of each story is uniform and the displacement of the first story decreases after considering the influence of panel zone. While the residual deformation increases. When the thickness of panel zone is increased by three or four times, the residual deformation decreases significantly. The inter-layer displacement, plastic deformation energy, velocity conversion, maximum ductility ratio and maximum cumulative ductility ratio are closer to those of the frame model which is not consider the influence of panel zone when the panel zone is increased by three times. It concluded that the influence of panel zone should be considered, and the thickness of panel zone needs to be thickened by three or four times according to the model in this article.

An Adaptive Section Discretization Scheme for the Nonlinear Dynamic Analysis of Steel Frames

The paper presents an adaptive section discretization scheme for the inelastic response analysis of structural members with cross sections that can be decomposed into rectangular and circular subdomains. Each subdomain can consist of a different material. As long as the largest strain in a subdomain does not exceed the specified trigger strain values, the subdomain contribution to the section response is determined by the numerically exact cubature rule for the subdomain. Once the largest strain reaches the trigger value for a subdomain, it is discretized with a fiber mesh and the numerical evaluation of its contribution to the section response is determined with the midpoint integration rule. The fiber mesh with the midpoint integration rule remains in effect for the activated subdomain until the end of the response history. The paper applies the adaptive discretization scheme to the thin-walled sections common in metallic structures and investigates the effect of different trigger strain values on the accuracy and computational efficiency of the inelastic response analysis of wide-flange steel sections and multistory steel frames under static and dynamic excitations.

Infuence of inverted-v-braced system on the stability and strength of multi-story steel frames

Population growth in urban centers, together with the lack of physical space, has led to the construction of increasingly tall and slender buildings. Multiple-story structures present substantial challenges to civil engineering because they have specific requirements for their design, construction, and use. The increased number of foors leads to more lateral displacements resulting from horizontal actions. Under these conditions, to ensure system stability, structural bracing components are commonly adopted. In addition, along with the use of more resistant materials and new construction techniques, it is necessary to improve the methodologies adopted in the structural analysis to offer professionals in the area the conditions to undertake safer and more economical projects with better speed and efficiency. Thus, in this study, numerical analyses were applied to steel planar reticulated structures to evaluate their stability and strength when inserting bracing systems. The study compared the arrangement of the bars and analyzed the influence of the parameters of the bracing systems, such as the properties of the cross-section and the position of the inverted-V-braced system. The MASTAN2 program was used to perform nonlinear static assessments using reticulated finite elements that considered both geometrical and physical nonlinearities. It was observed that the inverted-V-braced system had a substantial impact on all of the structures that were analyzed, providing increased stiffiness and, as a result, significantly reducing the frame’s lateral displacement.

Seismic performance of a narrow flange H-beam-to-column full-bolt end-plate weak-axis connection

This study proposes a full-bolted end-plate weak-axis connection T-shape joint based on a narrow flange H-beam-to-column section. A quasi-static test was conducted to solve the problems of large steel cross-section and high steel utilization, as well as the decline in space utilization and aesthetics caused by convex beam-to-column components in low-rise and multi-story steel frame residential buildings. The failure mode, hysteresis curve, and bearing capacity of the specimens were discussed and investigated. The test results show that the stiffness of the joints of the specimens are relatively high, the failure mode is the beam hinge failure mechanism, the hysteresis curves of the joints are full fusiform, and the seismic performance is good. An experimental numerical model was established using the ABAQUS software to determine the factors that affect the performance of the joint. The effects of skin thickness, bolt diameter, beam end-plate thickness, stiffener thickness and rid slope on the seismic performance of the T-shape joint were analyzed. The numerical simulation results indicate that when the thickness of the skin plate increases, the energy dissipation capacity of the joint significantly increases, whereas the ductility decreases. a moment–rotation formula that can be used as a reference in the control design of the key parameters of the joint was obtained, which is useful in practical engineering applications.

Optimum design of nonlinear semi-rigid steel frame based on performance-price ratio via genetic algorithm

In this study, a two-stage structural optimization method is presented for multistory steel frames with semi-rigid connections. Based on the traditional optimization result in the first stage, the performance-price ratio (PPR) is introduced in the second stage to provide an idea to modify the unreasonable structural design that might occur in the price (or weight) only oriented optimization of first stage. The efficient advanced analysis (EAA) method accounting for the flexibility of beam-to-column connections, second-order effect, initial imperfection and plasticity development in members is applied in structural calculation, which is also used to acquire the ultimate capacity of structures. All schemes satisfying traditional optimization constraints in a simple design problem were obtained by exhaustive search. The price-performance relation of schemes showed that the structural ultimate capacity depends only on the rationality of members’ combination and has low correlation with the total cost. Design examples showed that the two-stage optimization considering PPR enables much more robust structural design at a slightly higher cost than the traditional optimum one.

Seismic performance of a steel frame structure with dissipative cladding connections

In this study, a dissipative connection system for multistory steel frame structures is proposed, in which two bearing connectors are located at the top and a metal yielding dissipative connector (i.e., tapered connector) is located at the bottom of a large panel. Quasi-static test was conducted to investigate the performance of individual connectors first. Then two steel subassemblies, one having a steel frame with a large cladding panel and the other as its counterpart, a bare frame, were prefabricated and tested under quasi-static loading. Effect of the cladding panel and the proposed connections on the seismic performance of the steel frame was evaluated. It was indicated that the damage of the tapered connector was caused by the rupture of one energy dissipation plate during the fatigue loading and the hysteresis behavior of the connector was affected by the membrane effect. The proposed energy dissipation connector can improve the strength, stiffness, especially the energy dissipation capacity of the subassembly. However, the failure of both subassemblies was mainly caused by the yielding of the column foot and buckling of the beam end, therefore the cladding panel did not change the damage pattern of the steel frame. Three-dimensional (3D) finite element (FE) analysis was conducted to reproduce the tests of the connectors and the subassemblies, facilitating a better understanding of the working mechanism of the system.

Seismic performance analysis of multi-story steel frames equipped with FeSMA BRBs

Buckling-restrained braces (BRBs) have been widely used in seismic prone areas around the world. However, one major problem associated with the steel BRB frames is the excessive residual deformation under strong earthquakes, mainly due to the low post-yield stiffness ratio of the steel BRBs. Recently, the community has fabricated the iron-based shape memory alloy (FeSMA) BRBs, which exhibited full hysteresis with high post-yield stiffness ratios, but the seismic behavior of the FeSMA BRB frames still remains unknown. As such, this paper conducts seismic performance analysis of multi-story steel frames equipped with the FeSMA BRBs, through a comparison with those equipped with conventional steel BRBs. Incremental dynamic analysis (IDA) is further conducted to establish the probability seismic demand models. Based on the IDA data, bivariate fragility analysis is conducted to quantify the probability of exceedance, conditioned on various limitations of the maximum and residual interstory drift ratios. According to current analysis, it indicates that both the maximum interstory drift ratios and the maximum floor accelerations are comparable between these two types of BRB frames. The major advantage of the FeSMA BRBs over the steel BRBs is that the former can better control residual interstory drift ratios.

Effect of member grouping and pool size of discrete cross-sections on the optimal design of a large-scale 3D steel frame

This paper examines the effect of member grouping and selected pool size of discrete cross-sections on the optimal design of a large-scale steel frame structure. Member grouping is commonly applied to structural optimization problems to significantly reduce the solution space of candidate designs and improve the efficiency and robustness of the search to achieve near-optimum solutions. At the same time, discrete sets of cross-sectional steel shapes (profile lists) assigned to a particular member group are often limited to a subset of cross-sections to further limit the search space and ensure practicality in the final design. However, for large-scale structural systems (e.g., tall buildings), limiting the number of member groups coupled with the exclusion of lighter cross-sectional shapes may significantly impact the quality of the optimal solution (i.e., weight of the frame). This work presents a case study of a large-scale three-dimensional (3D) steel frame to evaluate the sensitivity of the optimal design to practical combinations of member groups and steel profile lists used in multi-story steel frames. A recently developed metaheuristic search algorithm was applied to the steel frame and independent optimization experiments were performed for 16 unique member grouping and profile list combinations (cases) to quantify their influence on the variability and quality of the optimal design. Results reveal a 33% difference in the optimal (final) weight between member group and profile list combinations producing the smallest and largest solution spaces. Yet, the lightest design (corresponding to the largest solution space) produced a greater number of unique steel shapes and required significantly higher computational cost.

Collapse resistance of multi-storey steel frame structures: Evaluation method based on member resistance

As the interaction of structural members and the type of beam-to-column connections significantly influence the collapse resistance of steel frame structures, there are limitations in using the existing theoretical models to calculate the resistance of multi-story steel frame structures with different structural parameters. The collapse resistance of multi-storey frame structures can be calculated using member resistance based on determining the inter-story constraints and the law of mutual influence of inter-story internal forces. In this paper, the resistance of structural members during the small and large deformation stage is discussed based on the coupling relationship between the bending moment and axial force developed in members. The theoretical analysis showed that the evolution of internal force multi-storey frames was reflected in the inter-story differences of flexural resistance and axial forces in the small and large deformation stages, respectively. Thus, a resistance calculation method suitable for steel frame structures with different connections was proposed based on member resistance. Finally, the rationality of the theoretical method was verified through a multi-scale model. The theoretical calculations showed a significant agreement with the numerical results.

Energetic investigation of in elevation upsurge and uneven harden construction with unusual stimulating structure

To unravel real-world difficulties and to understand physical physiognomies of loams and building overwhelming BRB also lacking BRB enterprises, 12 mockups remained advanced exploiting dissimilar procedures of invigorating and mud categories. It embraces X stimulating, V stimulating, Y healthy, and cold lacking BRB, as sound as three categories of loam: gravel, buildup, and mud, every of which will sustenance four facsimiles, for a over-all of 12 reproductions. Houses with a depth of 21 pulses and seismic neighborhood 4 be necessary been well-thought-out. The upheaval load combination will be based on multi-story steel frames with and without BRBs. It is premeditated expending and rectilinear self-motivated breakdown. The outcomes illustration how countless appearances of the building, such as division dislocation, section sense, section laboriousness, too section crop, transformation in rejoinder to seismic excitation and seismic armies. Bestowing to the encounters, story dislodgment, story drift, and story laboriousness all vary histrionically the minute the mud type fluctuates, and unalike forms of BRB help pointedly to weather fiddling. As a result, soil structure interface in amalgamation with X BRB requirement be ideal over seismic excitation.

Seismic performance assessment of multi-story steel frames with curved dampers and semi-rigid connections

Curved steel damper is an innovative energy dissipation device for seismic application. The performance of the curved steel damper has been well studied and experimentally tested. In addition, the behavior of one story curved damper semi-rigid frame (CDSRMF) has been studied extensively. In this study, the seismic performance of multi-story (3 story, 6 story and 9 story) CDSRMFs are extensively examined using nonlinear static (pushover analysis) and nonlinear dynamic analysis. The results show that the addition of the curved damper has significantly improved the stiffness, strengths and energy dissipation of the CDSRMFs. The formation and distribution of plastic hinges in CDSRMFs show that the significant part of nonlinear deformations is concentrated in curved damper elements instead of the primary elements. The curved damper can be used as a robust structural fuse which can be efficiently inspected and replaced as needed. The results demonstrate that multistory CDSRMF can be used as a reliable and resilient seismic force resisting systems.

Seismic Design Load for Multi-Story Steel Frames Composed of Expanded Sections

The steel frames, which are composed of expanded-section columns and beams, have bigger moment-resisting capacity and better structural stability. So that they are broadly applied in multi-story structures in low to medium seismic zones. However, the section is likely to local buckling due to its expanded sections, which decreases the structure ductility. To support its application, how to determine the horizontal seismic design load is studied here.

Seismic resistance estimation of multi-story steel frames under ductility level earthquake impact by nonlinear static method

The article proposes a technique for taking into account the higher vibration modes under seismic resistance estimation of multi-story steel frames by nonlinear static method. The characteristic point search has also been improved. As part of the study, the proposed method was verified by time history analysis. Proposed technique allows one to significantly reduce the calculation time, while excluding the deficit of seismic resistance.

Experimental and numerical study on the cyclic behavior of link-beam shear-panel connected to frame beams

This paper presents experimental and numerical studies on the use of shear panel, used as a lateral load resisting system in multi-story steel frames and is designed based on the link beam approach. The purpose of this study was to achieve a reliable lateral load-resisting system that eliminates the problem of using large columns in the steel shear wall systems and changed the shape of hysteresis loops from an S-shape to a Spindle-shape. To examine the purposed device, four ½-scale one-story specimens (three with the shear panel and one bare frame) with frame-beam-only-connected shear panels were tested under cyclic lateral load. Two boxes were used to attach the shear panel to the frame beams in two specimens to shorten the length of the shear panel and approximate its behavior to that of shear-link-beam and to make the system repairable. Based on the experimental and numerical results, the shape of the hysteresis loops of the proposed system are spindle-shape, and pinching did not occur in this system. In Specimens S1, S2 and S3 frame members (beams and columns) remain elastic during cyclic loading and the primaryenergy- dissipationelement is yielding of link-beam shear-panel. All the specimens exhibited satisfactory energy dissipation. The observed predominant failure modes include i: yielding of the shear panel at mid span, ii: cracks occur in welded connection, and iii: tearing in plates connecting frame beams to columns. The results of the finite element analysis were in good agreement with the experimental results. Analytical results showed that maximum strength and the energy dissipation capacity is much better for shear panels with lower height-to-thickness ratio and large span-to-height ratio.

Numerical studies on full-scale steel columns under complex seismic loading

Numerical analyses using the finite element software Opensees are conducted to examine the ultimate seismic behavior of Wide-Flange steel columns used in multi-story steel frames. An OpenSees fatigue model was adopted to consider the effect of local buckling and cyclic strength degradation. The numerical model is validated with the experimental results from seven full-scale column specimens tested by the authors in an earlier study utilizing the Multiple Usage Structural Testing System (MUST). The comparisons of results include hysteretic behavior which is obtained through three cyclic tests on steel columns with two different axial load levels, and time history behaviors of four additional columns tested by pseudo-dynamic hybrid simulation with both horizontal and vertical seismic excitations. A series of parametric studies on axial load, height or width to thickness ratio of web and flange, aspect ratio of cross section, and section forms are also carried out.

Nonlinear Seismic Response of Multistory Steel Frames with Self-Centering Tension-Only Braces

The self-centering tension-only brace (SC-TOB) is a new and innovative bracing system that provides both a flag-shaped recentering hysteresis and load mitigation to structures. This paper presents an extensive investigation of the nonlinear seismic response of multistory steel frames built with SC-TOBs to internal force, drift, and energy dissipation. Pushover analysis subjected to two lateral load distributions and nonlinear dynamic analysis under ground motion ensembles corresponding to four hazard levels were conducted. The SC-TOBs can be designed to serve as conventional tension-only braces (TOBs) only providing lateral stiffness during minor earthquakes, to function with energy dissipation as intensity increases, and to fully recenter a structure even after severe earthquakes. The findings show that with an increase in the earthquake intensity, both the force response and drift response of the SC-TOB frames (SC-TOBFs) increased; however, the force distribution and drift distribution shapes of the SC-TOBFs remained almost constant. The SC-TOBFs generally experienced more energy dissipation in the lower parts of the building, while the upper stories dissipated almost no energy under certain load conditions, suggesting that the bracings on those stories could be replaced by conventional TOBs for economy. It is demonstrated that the SC-TOBs have immense potential to effectively improve seismic resilience to structures such that rehabilitation costs and operational disruptions after earthquakes are minimized.