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In this study, the structural details of a hinge connection for steel girder segments were developed to improve the process of rapid and easy construction. In the connector developed in this study (referred to as the "speedBridge" hereafter), the compression load exerted on the upper flange is resisted by two bearing blocks in contact with each other, and the tensile force on the bottom flange is resisted by the hinge structure installed at the lower part of the steel girder. The structural behavior of the developed connection was investigated experimentally. It was shown that the developed connection details could develop an excellent connection plastic rotation of 5% rad without fracture. The test specimen developed initial stiffness in accordance with elementary beam theory for a supported beam. The maximum load reached 110% of the plastic moment of the beam. Finite element analysis was conducted to comprehend the load transfer path, and the results demonstrated that the hinge connection exhibited sufficient stiffness and strength, exceeding the bending capacity of the beam under tension without any signs of the failure modes considered in the design procedure. [ABSTRACT FROM AUTHOR]

In this study, the structural details of a hinge connection for steel girder segments were developed to improve the process of rapid and easy construction. In the connector developed in this study (referred to as the “speedBridge” hereafter), the compression load exerted on the upper flange is resisted by two bearing blocks in contact with each other, and the tensile force on the bottom flange is resisted by the hinge structure installed at the lower part of the steel girder. The structural behavior of the developed connection was investigated experimentally. It was shown that the developed connection details could develop an excellent connection plastic rotation of 5% rad without fracture. The test specimen developed initial stiffness in accordance with elementary beam theory for a supported beam. The maximum load reached 110% of the plastic moment of the beam. Finite element analysis was conducted to comprehend the load transfer path, and the results demonstrated that the hinge connection exhibited sufficient stiffness and strength, exceeding the bending capacity of the beam under tension without any signs of the failure modes considered in the design procedure.

This paper focuses on investigating the structural behavior of members and connections that are part of moment frames under the combined effect of bending moment and thermally induced axial force during a compartment-fire event. The finite-element analysis method was employed to conduct this study using models benchmarked against experimental data from several past studies while utilizing temperature-dependent material models. A numerical parametric study on typical floor beams with slender elements for compression were conducted under combined bending and axial loading to develop interaction-capacity curves at temperatures representing fire events. The results were compared against the member-strength equations provided in the AISC Specification. The analysis results demonstrated that the AISC beam-column strength equations including the combined effects of axial-load and bending moment provided reasonable estimates for member-slenderness ratios greater than 60, but overestimated the strength of beams with slender elements for low member-slenderness ratios. Combined-load-strength studies were also conducted on a typical connection used in moment frames. The moment-connection behavior was governed by failure modes exhibited at the ends of floor beams. Therefore, the interaction equations available for beam columns resulted in conservative estimates and are recommended for calculating moment-connection capacity during compartment-fire scenarios. [ABSTRACT FROM AUTHOR]

Loading protocols simulate local earthquakes are usually used to evaluate structural components' strength and deformation capacities. First, the present research proposes a loading protocol that accurately simulates the local seismic demand based on far-field conditions, while being also consistent with the region's structural design and construction conditions. The proposed loading protocol can be applied to the steel structure's bending components, particularly the steel moment connections in general and experimental terms. Moreover, the proposed loading protocol presents the guidelines for evaluating the moment connections' performance at the target, qualifying, and collapse control levels. Similar specimens of welded unreinforced flange-welded web (WUF-W) steel moment connections in box-columns were subjected to the proposed and SAC loading protocols in the laboratory; and the results were analysed. Based on the experimental and finite element studies performed in this research and matching and controlling the proposed loading protocol's presented conditions and regulations, the damage parameters and the seismic demand resulting from both loading protocols were evaluated and compared. The experimental and finite element of the WUF-W connections have well satisfied the target value level; and the qualifying condition of the proposed and SAC loading protocols and the control conditions of the collapse threshold provided in the proposed loading protocol was well satisfied the experimental specimen. [ABSTRACT FROM AUTHOR]

Engineering designs that ensure the safety of residents while ensuring economic issues is the same as modern seismic design with the advantage of ductility, the structure is designed so that its final elastic force is proportional to creating a crack in the structure. In steel flexural frames, joints with the reduced cross-sectional area have been extensively tested and have acceptable performance under different cycle loads. One of the weaknesses of the last research was the lack of attention to reducing costs. Also, we can conclude that most of the research has been done on a specific type or most of them have been trial and error, they have only evaluated the results and have not tried to achieve the best and most optimal dimensions of these connections. In this study, the analysis of several connections in different types has been done and the analyzes have been optimized. Also, it has been tried to model Reduced Beam Section (RBS) connections using ABAQUS software by dynamic analysis and numerical methods, finally, after analyzing the desired connections, the output of the performed analyzes is transferred to MATLAB using a genetic algorithm. Finally, the optimized models are first reviewed in terms of maintaining stability and then compared with other RBS models that are not optimized. After that comparisons have been done with other optimized algorithms, and the results obtained from modelling and analysis are presented. The energy entering the structures has always been considered by the building engineering community due to lateral forces such as earthquakes. [ABSTRACT FROM AUTHOR]

Four Q690 high-strength steel beam-to-column moment connections, which use welded joints between beam and column flanges as well as a bolted beam web to the column flange, were tested under cyclic loading. The effects of beam-to-column welding details and panel zone strength were studied. Two pairs of welded flange details were incorporated, including the Chinese code-specified complete-joint-penetration (CJP) welded connections with backing plates where the bottom backing plate is reinforced by a fillet weld, and enhanced CJP welded connections with backing plates removed, weld roots backgouged, and further reinforced by fillet welds. Three panel zone thicknesses were designed to characterize strong, intermediate and weak panel zones, respectively. The test results show that backing plates should be removed in these moment connections to prevent brittle weld fracture, but still rendering only limited plastic hinge rotations in the order of 0.01–0.02 rad in the beam end before ductile fracture of the beam flange. The panel zone, however, survived even after a plastic shear rotation of 0.03 rad, demonstrating much higher plastic deformation capacity than the beam plastic hinge. This suggests that ductility can be exploited in 690 MPa high-strength steel panel zones, but not reliably in 690 MPa steel beams. • Q690 high-strength steel welded flange-bolted web connections were tested. • Backing plates should be removed to prevent brittle weld fracture. • Q690 steel beam ends developed very limited plastic rotations. • Q690 steel panel zones could sustain plastic rotations above 0.03 rad. [ABSTRACT FROM AUTHOR]

Built-up box columns are more frequently used in earthquake-prone regions such as Japan and Iran. As the installation process of continuity plates and welding inspection are difficult, expensive, and time-consuming, this study was aimed at experimentally and numerically investigating continuity plate elimination from built-up box columns with regard to the seismic design specifications of special and intermediate moment resisting frames. Results of an experimental study of three full-scale rigid connections between I-beam and box-column subjected to cyclic loading were used for comparison and verification of numerical results. Experimental study showed that samples reached story drift angle of 0.06 radians before experiencing the permissible strength degradation. Therefore, the tested connections satisfied the criterion for special moment resisting frame (SMRF) in AISC. Based on observations of crack initiation and propagation in the experimental study, a rupture index (RI) was employed to investigate the effects of different complete joint penetration (CJP) groove welding methods used in the experimental study on connection ductility as well as to identify the regions prone to crack initiation and propagation. Both the numerical and experimental results showed the superiority of using back plate in CJP welding. [ABSTRACT FROM AUTHOR]

Double‐I sections are widely used as columns in moment‐resisting frames. The conventional welded moment connection between I‐beam and double‐I built‐up column behaves in a partially restrained manner and does not provide the strength and ductility required in special moment frames. In this paper, a modification method is proposed to improve the behavioural characteristics of conventional moment connections. The modification involves replacing the continuous cover plate with two alternative plates having increased width and thickness at the location of the beam flange‐plates. The behaviour of the proposed connection was investigated in detail both experimentally, by means of two full‐scale specimens, and analytically, by means of eight finite element models. Based on the results obtained, in beams with a modified connection most of the plasticity develops remote from the column cover plate, and the panel zone remains in an elastic state. Accordingly, the deformation of the modified connection is reduced significantly and its stiffness is increased to the level required for a fully restrained connection. The hysteresis curves of the modified connection are also stable during large inelastic deformations with no substantial pinching. The modified connection provides the strength and ductility required in special moment frames. [ABSTRACT FROM AUTHOR]

For seismic design of steel special moment frames (SMFs) the current seismic provisions require the use of continuity plates when either the proportion between the beam flange width and column flange thickness is not met or a strength limit state is not satisfied. The provisions require that the weldments between these continuity plates and the column flanges be a complete joint penetration (CJP) groove weld. Full-scale testing of 10 moment frame connections was performed to investigate the design of continuity plates using fillet welds instead of CJP welds. Six of these frames were one-sided connections using the prequalified reduced beam section (RBS) connection. The remaining four were two-sided connections using the prequalified welded unreinforced flange-welded web (WUF-W) connection. While violating the current continuity plate requirements, all 10 connections surpassed the 0.04-rad story drift criterion required by the provisions for SMF connections. The testing has demonstrated that (1) the criteria governing when to use a continuity plate may be relaxed for RBS connections, (2) fillet welds sized to develop the tensile strength of the continuity plate may be used to fasten the continuity plate to the column flange, (3) the required continuity plate thickness may be determined based on a plastic interaction equation, and (4) the width-to-thickness ratio of continuity plates should be limited to prevent instability. It was also found that sizing the doubler plate welds for the shear flow determined from their elastic shear stiffness, as opposed to developing the shear strength of the doubler plate as required on the provisions, was adequate to fasten an elastic doubler plate to a column. [ABSTRACT FROM AUTHOR]

Hollow structural sections (HSSs) are highly efficient in resisting compression, torsion, and bending. Their high torsional rigidity generally eliminates lateral-torsional buckling (LTB), which in turn eliminates the need for lateral bracing in flexural members. As a result, their plastic rotational capacity is mainly governed by flange local buckling (FLB) and web local buckling (WLB). Moment-resisting connections for single-HSS flexural members can be complicated. This study investigates the behavior of double-HSS flexural members under large displacement reversals. The study configuration consists of a double-HSS beam connected to a column through a center gusset plate secured by flare-bevel groove welds. The advantages of the proposed double-HSS moment connection are: (1) compared to a single-HSS, it effectively reduces the width-thickness ratios (b/t) of the flanges by using a double-HSS, thereby considerably increasing the member's compactness and ductility; (2) it provides simple and practical connection details between the beam and column; and (3) it eliminates the need for lateral bracing. In addition, on-site welding can be eliminated by using shop-welded double-HSS beam-column stubs spliced by a bolted end connection. Experimental tests indicate that the proposed double-HSS moment connections showed a stable response up to a story drift angle of approximately 0.07 rad for the HSS sizes tested. Nonlinear finite-element analyses, including fracture behavior via the extended finite-element method (XFEM), were used to simulate test results, and finite-element analysis (FEA) was used to formulate the design procedure for the center gusset plate and welds connecting the double-HSS beam and column flange. [ABSTRACT FROM AUTHOR]

A new seismic resilient steel moment connection with top shear tabs and bottom replaceable metallic fuse is proposed. The shear tabs are realized by a combination of shear angles, with or without shear plates or splice plates, while a buckling-restrained plate (BRP) is employed as the fuse. Both the shear tabs and BRP are placed at a splice location which represents the beam inflection point under gravity load. Analytical models were developed to determine the stiffness, strength, and deformation of the proposed connection, as well as a trilinear moment-rotation relationship at the spliced section. In this way, a coordinated seismic design procedure to achieve structural serviceability and resilience in steel moment frames with the proposed connection was derived based on the equal-stiffness and zero-moment strategies. Cyclic loading tests of full-scale beam-to-column subassemblies equipped with the proposed connection were conducted. Three resilient connections with different shear tabs (bolted/welded shear angles above/below the beam top flanges) were examined and compared with a conventional fully welded connection. The test results validated the concept and confirmed success of the analytical and design methods to ensure sufficient lateral stiffness and concentrate plastic damage into the BRP. Moreover, the resilient connections with bolted or welded shear angles above the beam top flanges exhibited about 11–18% higher moment resistance at 4% drift and 20% more energy dissipation, and thus are recommended over that with welded shear angles beneath the beam top flanges. • A new seismic resilient connection with top shear tabs and bottom fuse is proposed. • The shear tabs comprise a pair of angles with or without shear or splice plates. • A buckling-restrained plate is employed as the replaceable metallic fuse. • A coordinated seismic design procedure was derived for this connection. • Analytical and experimental study was conducted to validate the concept and design. [ABSTRACT FROM AUTHOR]

The moment beam-to-column connections include those connections that can transfer the moment between the beam and the column. Bolted unstiffened and stiffened extended end-plate moment connections are from this category. This type of connection, which was investigated after severe damage to connections in the Northridge earthquake, Due to proper behavior under cyclic loading, was introduced as one of the pre-qualified connections of the AISC code and subsequently by the Iranian Code. Since low cyclic fatigue is another cause of failure in connections under the Northridge earthquake, it is necessary to study the fatigue behavior of this type of connection under the effect of low cycle fatigue. So far little studies have been done on the effect of low cycle fatigue on various types of connections, including end plate connections. In the present study, the S-N fatigue chart (Effective stress to the number of load cycles) that was used to estimate the effect of high cycle fatigue was developed to the low fatigue region for the end plate connections. Then, with using the S-N chart, the effect of low cycle fatigue on a 12-story structure under the influence of various earthquake records was studied to investigate the effect of low-cycle fatigue on structures with end plate moment connections. The analysis of steel structures showed that in end plate moment connections at the plastic hinge position, the effect of the cumulative cyclic fatigue before the plasticization of the connection under severe earthquakes is influential. Since the effects of fatigue are cumulative, it will be significant and destructive for end plate connections of buildings that have experienced several medium and large earthquakes.

This paper evaluates the effect of slot existence with limited length between flanges and web junction of I-shaped beams at the region of moment connections on vertical force and shear stress distribution in beam flanges and web at connection section in comparison with classical theory of stress distribution. The main purpose of this research is to evaluate the efficiency of the slot in connections such as slotted web beam to column connection in modern age. The issue of the slot has many benefits but very little studies have been done on it. Accordingly, one hundred and twenty models with two moment connections under the concentrated static load in mid span have been made for doing parametric study in ANSYS Workbench finite element software. The linear static analysis was done on all constructed models. Variable parameters in these models for parametric study include slot length between flange and web junction in connection region (from 0 to 190 mm), beam length, beam section height and Poisson’s ratio of beam material. In all models the amount of shear stress in section height over the section vertical axis in connection region and also the devoted contribution from force which goes to flanges and web under the concentrated load on mid span have been calculated. Performed studies have shown that vertical shear stress distribution in beam to column connection section with moment connection differs a lot from what is stated in mechanics of materials equations. Practically the available equations in regulations which state that web receives the entire vertical shear and ignore the contribution of flanges are not reliable. In addition, studies have shown that the slot existence in junction of web and flanges in connection section with limited length can has great effect on the quality of vertical shear stress distribution over the section of connection and also the slot existence has great effect on the reduction of shear stress in flanges and increase in shear stress in web according to classical theory. As a total result, nowadays slotted web beam to column connection can be used as a fantastic and simple idea to improve modern connections behavior.

Beams are genarally used to face bendind force and columns are used to face axial load. as the seismic load comes parallely with respect to earth surface. so the column faces the load pependicularly which is very risky for the column. after that load gets distributed to all the beams. for this reason columns must be strong to make the structure more earth quake resistant.Generally column failure is reason of soft story and collapse of structure Also, because of the axial load yield of columns in shear and moment forces cause loss of strength more than beams and other elements. Structural design codes have a requirement for strength column and weak beam in all joints of special moment connection. In this research strength column and weak beam in prequalified moment connection like reduced beam section (RBS), cover plate connection (WFP) and the welded unreinforced flange-welded web (WUF-W) connection in intermediate moment frames studied. Results shown that ignore strung column and weak beam requirements effect function of the connection and cues to plastic hinge formed in a column. This is effect reduce energy abortion, stiffness and bearing capacity of connections. so as a result it was suggested that for better perfomance prequalified welded connections in intermediate steel moment frame controlled strong columns weak beams requirements.

The strength and deformation capacity of structural elements are influenced by their cumulative damages received through load cycles. Loading protocols would provide the estimation of the structural components' capacities and a proper simulation of the seismic reality, which are used to assess the performance of connections. Given the widespread application of I-beam to box-column moment connections, the seismic performance of moment connections in the box-columns should be thoroughly investigated. However, most regulation details for the qualification of moment connections are presented for the H-shaped columns. Accordingly, in this study, 12 prequalified types of RBS and WUF-W moment connections in the box-columns are selected and analyzed under different cyclic loading scenarios. Therefore, the seismic behavior of such moment connections is studied for the drift qualifying criteria and collapse threshold when they are subjected to the SAC and ATC-24 loading protocols. Besides, energy dissipation, demand, loading protocols' impact, and their influences are examined. [ABSTRACT FROM AUTHOR]

Today, for the moment frame structures, seismic provisions of the structural engineering design codes depend on the inelastic deformation as well as inelastic capacity of the connections. A cyclic loading protocol is normally exercised for measuring such capability. This paper investigates the deformation capacity of steel moment resisting frame’s connections subjected to different loading protocols. To evaluate the performance of the connections subjected to various cyclic loads, behavior of three types of connections is studied. Behavior and capacity of each connection are assessed subjected to different loading protocols; namely ATC, FEMA and SAC. The results from this research indicate that the ATC and FEMA loading make greater demands on the connections; while SAC basic loading shows a better agreement with the target values of the loading protocol. A loading protocol has been developed taking some criteria into account in order to match the target values presented in SAC study for steel moment connection’s bam to column sub-assemblies. Then the connections were subjected once again to the proposed loading protocol and results compared to those of other loading protocols. The results reveal that the connections subjected to the proposed loading protocol provide greater deformation and strength capacity. Also, lower equivalent plastic strain and lower dissipated energy were observed when the connection is subjected to the proposed loading protocol.

Floor vibration due to human activities (walking, running, etc.) and operating machines generally makes inconveniences for residents. The natural vibration frequency of beams is determined as the main source and also the controlling parameter of such the phenomenon. Many studies have been conducted on determining the natural frequency of beams in recent years; however, the proposed formulations in many of them are not very practical for vibration control of tall building floors. In this paper, the finite element method (FEM), nonlinear (NL) dynamic analyses, and artificial intelligence (AI) techniques were adopted to constitute the simple frequency equations of the fixed ends and cantilever steel beams for controlling the floor vibration. The input data required for training the AI-based model are simulated in a NL FE platform considering various cases of the steel moment connections. The analysis outcome of several hundred beams with different properties indicated that the calculated vibration frequency values of the fixed ends and cantilever beams were respectively 2.07 and 0.33 times larger than the frequency value of the simply supported beams with similar conditions. To this, the implemented soft computing technique was determined as an effective approach to improve the computational efficiency of the NL-FE simulations. [ABSTRACT FROM AUTHOR]

• The through-beam and through-bar details at the interior beam-column connection for thin-walled CFT columns are proposed. • Cyclic loading tests for proposed details are performed to investigate their seismic performances. • Load-carrying capacity, failure modes, ductility, and joint shear capacity of each specimen is investigated. • Modified plastic stress distribution method are made based test observation. • Design and detailing considerations of the proposed details are given. In this study, the results of the cyclic loading tests of four interior connection specimens made of concrete-filled thin-walled tube column and U-section beam are presented. Through-beams and through-bars passing through the column were used as the connection details. The tests showed that both slip significantly occurred during cyclic loading and thus the strength, ductility, and energy dissipation capacity of the specimens were significantly affected by the connection details. The web plates of the beam U-section, which were welded to the thin column tube wall, did not fully contribute to the connection strength, due to out-of-plane deformation and premature weld fracture of the tube wall plates. Based on the test results, a modified plastic stress distribution method to estimate the connection strength was suggested. In addition, design and detailing considerations of the proposed through-beam and through-bar connection details are given. [ABSTRACT FROM AUTHOR]

Highlights • Developed a moment connection for a progressive collapse resistant precast frame. • Experimental destructive testing was performed to obtain moment-rotation behavior. • 2 configurations were tested: higher strength with lower ductility and vice versa. • Experimental results were input into a system-level computational model. • Models show that both tested connections prevent collapse for a column removal. Abstract This paper documents the experimental development of a new spandrel-to-column moment connection detail for progressive collapse resistance in precast concrete building frames. This study focuses on a 10-story prototype precast concrete frame building with perimeter special moment frames (SMF) that are subjected to a ground-floor column removal. The experimental subassembly represents a spandrel-to-column connection on the perimeter SMF near the middle of the building face (i.e. not at the corners). The connection is non-emulative and utilizes unbonded high-strength steel post-tensioning (PT) bars which pass through ducts in the column and are anchored to the spandrels via bearing plates. The proposed design strives for construction simplicity, avoids field welding and/or grouting, and maximizes ductility by allowing the high strength steel bars to act as structural "fuses" when yielding. A full-scale quasi-static pushdown test is performed on two variants of the proposed connection: one with higher moment-rotation capacity and limited ductility, and another with lower capacity and higher ductility. The results show that the connection can reliably achieve its design yield capacity, performs well under service level demands, and can achieve moderate-to-high ductility. The experimental results are then applied to a system-level computational model of the prototype building frame under a column removal scenario. The results of a nonlinear dynamic analysis demonstrate that the system can arrest progressive collapse in the event of a single column loss scenario when either variant of the proposed connection is considered. [ABSTRACT FROM AUTHOR]

Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations of joints with bidirectional effects and variable axial loads were studied using the finite element method (FEM) in ANSYS v17.2 software. The results obtained showed a ductile behavior when cyclic loads are applied. No evidence of brittle failure mechanisms in the studied joint configurations was observed, in line with the design philosophy established in current seismic provisions. However, beams connected to the column minor axis reached a partially restrained behavior. Joints with four beams connected to the column exhibited a partially restrained behavior for all axial load levels. An equivalent force displacement method was used to compare the hysteretic response of 2D and 3D joints, obtaining higher deformations in 3D joints with respect to 2D joints with a similar number of connected beams. Consequently, design procedures are not capable of capturing the 3D deformation phenomenon.

A seismic performance evaluation of selective storage racks subjected to Chilean Earthquakes was conducted using nonlinear pushover and nonlinear dynamic time-history analyses. Nine seismic records with two horizontal components and magnitude Mw > 7.7 were applied to numerical models of prototype rack structures. The prototype racks were designed considering two types of soil and two aspect ratios. The inelastic behavior of beam connections was included in the models. The results showed a predominantly elastic behavior, mainly in the cross-aisle direction, in comparison to the down-aisle direction. The inelastic action was concentrated in pallet beams and up-rigths. Higher values of base shear were reached, due to elevated rigidity in rack configurations, and an acceptable performance was obtained. A response reduction factor was reported in both directions, reaching values larger than the limit imposed by the Chilean standard. However, values below this limit were obtained in the cross-aisle direction, in some cases. Finally, in all cases, the calculated response modification factor is highly influenced by the overstrength obtained from seismic design.

A novel blind bolt, named Slip-Critical Blind Bolt (SCBB), was recently invented at Tongji University to be used as slip-critical high strength bolt for moment connections with handy installation from outside of tubular column. This paper applied SCBBs in extended endplate connections to cold-formed Square Hollow Section (SHS) columns, and investigated this application in the beam-to-column assembly against progressive collapse. The performance of SCBBs at connection regions was evaluated in four full-scale specimens with different configurations. Four distinct failure modes were identified, including fracture at beam section, pull-out of bolts from column wall, plastic deformation of endplates and welded bottom flange fracture forcing the reinforcing component to work. Throughout the damage evolution, the SCBBs performed satisfactorily by clamping the connected plates firmly without slip occurring at the plate interface, showing a good mechanical property as being slip-critical high strength bolts. Under the progressive collapse scenario, SCBBs maintained the integrity of the blind bolted connection, thus facilitated the assembly to effectively develop the catenary mechanism which provided significant vertical resistance under large deflection. The considerable potential of SCBB to be applied into the blind bolted moment connections against progressive collapse and its effectiveness were further verified by comparison between the test specimens and other published moment-resisting beam-to-column assemblies. [ABSTRACT FROM AUTHOR]

Prequalification of the Double Split Tee (DST) connection has been conducted using hot-rolled shapes, whose availability is still limited in several countries. In addition, the range of available T web and flange thicknesses is narrow for these shapes. Thus, the use of built-up T-stubs on the DST connection seems to be a promising alternative, considering that they offer more freedom of sizing and allow a better use of the material. The experimental research reported here aimed to validate the use of built-up tees instead of hot rolled tees in DST moment connections. Four beam-to-column full-scale double built-up T (DBT) moment connections were subjected to cyclic loading following the prescribed loading history in AISC seismic provisions. The parameters varied among the specimens were the T flange thickness, the type of weld between the T flange and the stem (fillet weld or full penetration groove weld), and the column web thickness, in order to observe the most significant limit states of the connection, namely development of plastic hinges in beams, panel zone plastification, and T flange prying. The results indicate that the connection can sustain 4% drift without strength degradation, whether it is designed for T flange prying or beam hinging. In the case of the former, only limited permanent deformation of the flange is observed, while for the latter significant plastic deformation of the beam can be achieved with little or no damage of the T. The type of weld used has no significant effect on the connection performance. [ABSTRACT FROM AUTHOR]

This paper proposed a precast concrete-based dry mechanical joint for fully-restrained moment connections which can be used to connect reinforced concrete precast columns. In the proposed connections, a pair of steel plates is provided and connected by high-strength bolts to transfer axial loads and moments. One plate is installed at the bottom of upper columns, and another one is placed on the top of lower columns. The stiffness of the column plates is determined to enable axial loads and the moment to be transferred at joints, providing a fully-restrained moment connection between columns. The structural behavior of the moment connections was evaluated through experimental and analytical investigations. Through extensive experimental investigations, columns jointed with plates capable of sufficient stiffness and strength demonstrated structural behavior similar to those of conventional columns. The plate deformations which fail to transfer the moment were not prevented with columns jointed by plates incapable of providing sufficient stiffness and strength. A good match in terms of the load-displacement relationship and plate deformation was also demonstrated between the finite element analysis based prediction and the test data for all specimens. The introduced connections will contribute to modular offsite construction for buildings and heavy industrial plants. [ABSTRACT FROM AUTHOR]

Following the loss of an inner column, a moment resisting frame initially carries the upper load by the flexural mechanism with potential contribution from the catenary mechanism as the beams connected to the failed column deflect. The effective utilization of the catenary mechanism depends on the behaviour of the beam-to-column connections in the affected span. Previous studies have demonstrated that the types and details of the moment connections determine their behaviour, especially the failure mode, in the column removal scenario. Two typical failure modes, the beam-end continuous failure and the beam-end interrupted failure, have been studied in the literature. A third failure mode, identified as the column-wall failure, is investigated in this paper through a full-scale laboratory test and finite element (FE) simulations of an I beam-square hollow section column connection with inner diaphragms inside the column. The present experimental observation and FE analysis indicate that a column-wall failure starts with the separation between the bottom inner diaphragm and the column’s inside wall, before fracture takes place in the column wall near the two ends of beam’s bottom flange. The crack extends inwards along the bottom flange and finally upwards, at which point the flexural mechanism is fully replaced by the catenary mechanism. The column-wall failure mode is more desirable than the beam-end (or beam-section) continuous failure mode under the column removal scenario due to the former’s ability to develop an effective catenary mechanism to bridge over the member failure of the column itself. In fact, the column-wall failure mode appeared to develop a more effective catenary mechanism than even the beam-end interrupted failure mode, although further research is required to ascertain the relative merits between the two modes and associated connection methods. [ABSTRACT FROM AUTHOR]

This paper proposes dry mechanical beam-column joints for fully restrained moment connections of concrete components. This novel joint can be used for reinforced concrete precast frames and steel-concrete composite precast frames. The new dry mechanical joint consists of extended steel plates with bolts designed to transfer tension and compression forces, providing fully restrained moment connections at the beam-column joint. The extended end plate with bolts introduced for column-beam joint assembly was originally used in the steel moment frame, as introduced in AISC 358. This study developed similar but unique mechanical joint details for concrete frames in order to provide fully restrained moment connections for both steel-concrete composite precast frames and reinforced concrete precast frames. Experimental and analytical investigations were performed to verify the structural behavior of fully restrained moment connections for concrete components in order to identify the parameters that influence the structural behavior of dry mechanical moment concrete connections. These connections are expected to be used in modular offsite construction for buildings and heavy industrial plants. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Box-columns are frequently used in moment resisting frames due to the numerous advantages they offer. Accordingly, bolted extended end-plate moment connections are widely used in steel structures due to their advantages such as easy fabrication and fast erection. However, some problems such as inaccessibility to the inside of box-columns for assembling the continuity plates as well as fastening the bolts prevent the wide applications of these connections to connect I-beams to box-columns. The present study aims to solve these problems by proposing two new connection configurations. In these connection models, a short stub beam is used to connect I-beams to box-columns by bolted end plate connection. These connection models have different force transfer mechanisms so that the use of continuity plates should be necessary for the first model while it can be omitted in the second model. The behavior of these connection models is investigated under cyclic loading by using finite element method. To validate modeling techniques used in this study including the mesh and element types, material properties and contact elements, the numerical results of an end-plate connection model are compared with experimental data. Then, for each connection model, eight specimens including four-bolt unstiffened and eight-bolt stiffened extended end-plate connections are analyzed under cyclic loading. All the specimens studied in this program were shown to undergo the 0.05 rad total story drift with the AISC seismic provision requirements being satisfied. [ABSTRACT FROM AUTHOR]

The welded unreinforced flange-welded web (WUF-W) moment connection is one of seven prequalified connections for the special moment frames (SMF) specified in AISC 358-10. Previous studies reported that some WUF-W connections with a steep access hole slope failed before completing a loading cycle of 4% drift ratio. For investigating in detail the effect of access hole geometry including access hole slopes on the connection behavior, experimental tests require excessive costs and efforts because there are the large number of combinations of configuration parameters for access hole geometry. In this study, the cyclic behavior of WUF-W connections is evaluated using three-dimensional nonlinear finite element (FE) analyses with an adequate solid element and failure index. Based on the results of FEA, the effect of configuration parameters on the connection behavior is investigated. [ABSTRACT FROM AUTHOR]

A discussion of several approaches to predicting the flexural strength of beams with holes in the tension flanges is presented. Experimental data pertinent to the discussion is then presented, summarized and analyzed. It is observed that although provisions in the AISC 360-16 specification predict a net section fracture of the tension flanges in a number of the experiments, many of those beams were able to achieve their full plastic moment prior to failure. Two alternative models are proposed as improvements to the provisions in AISC 360-16; the merits and limitations of those models are discussed. [ABSTRACT FROM AUTHOR]

The beam-to-column connections of special composite moment frames (C-SMFs) serving as the primary seismic force resisting system (SFRS) of a building structure are required to meet the performance criteria specified in the 2010 AISC Seismic Provisions. Chapter K of the Seismic Provisions states that experimental results should be used to provide evidence that the specific beam-to-column connection satisfies the requirements for strength and story-drift angle. This paper focuses on the split-tee connection for C-SMFs with wide flange (WF) beams and rectangular concrete-filled tube (CFT) columns. The paper provides a general description of the split-tee connection identifying its key features and components. This is followed by discussion of expected behavior in the elastic and inelastic ranges of cyclic loading. This discussion is based on prior research and large-scale testing, and it focuses on the various limit states controlling the strength and deformation capacity of the connection. The paper includes the complete design procedure for split-tee connections along with a detailed design example. The information presented in this paper can be used to create a body of evidence to apply for prequalification of similar split-tee connections in C-SMFs. [ABSTRACT FROM AUTHOR]

Energy is dissipated by yielding at beam ends in steel moment resisting frames subjected to earthquakes. In addition, the column panel zone can be proportioned to participate in energy dissipation. AISC360, Eurocode 3, and FEMA-355D specifications have different philosophies for the design of panel zones which lead to different amounts of deformation demands. This paper presents a numerical study undertaken to quantify the deformation demands in panel zones proportioned according to different specifications. Pursuant to this goal, the panel zone design requirements of three specifications were compared first to identify differences and similarities. A parametric study was conducted by considering the beam depth, axial load level on columns, thickness of panel zone, and seismic hazard as the prime variables. Archetypes were analyzed by employing three-dimensional explicit nonlinear finite element time history analyses. The analysis results revealed that designs according to AISC360 and Eurocode 3 resulted in significant amounts of yielding of the panel zone while the designs according to FEMA 355D resulted in minimal amount of yielding. The panel zone deformation demands were quantified and an equation used to estimate the deformation levels was developed herein. [ABSTRACT FROM AUTHOR]

Three full-scale specimens were tested to evaluate the cyclic performance of rehabilitated pre-Northridge steel beam-to-column moment connections. A Kaiser bolted bracket (KBB) was used on the beam bottom flange for all specimens, but different rehabilitation schemes (another KBB, a notch-tough beam flange replacement weld, or a double-tee welded bracket) were used to strengthen the top flange. All specimens were able to sustain an interstory drift angle of 0.04 radian, with large inelastic deformations in the panel zone. Two specimens experienced fracture at the replacement complete-joint-penetration (CJP) welds, mainly due to the large shear deformation in the panel zone. Because it may not be economically feasible to mitigate weak panel zones in seismic rehabilitation, an analytical model was developed to predict the panel zone deformation capacity and the associated strength. In this model, it was postulated that the ultimate panel zone deformation capacity corresponded to that when each column flange was fully yielded and excessive kinking would cause fracture of the beam flange CJP welds. This postulation was verified by the test data of two specimens that experienced weld fracture due to excessive panel zone deformation. It was shown that the deformation capacity is a function of db/tcf (beam depth-to-column flange thickness ratio). The effect of column axial load was also studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rotational stiffness of two closely spaced connections (a compound connection) is the same as a single connection. [•] Application in column–beam and splice connections opens new design frontiers in structural timber design. [•] This reinforced timber connection behaves isotropic, i.e. no angle to grain dependency. [Copyright &y& Elsevier]

Highlights: [•] The behaviour of the RBS moment connection subjected to cyclic loading is examined. [•] Endplate bolted moment connection in European profiles is applied. [•] Experimental and FEM analysis conducted for two specimens. [•] M–φ diagrams from experimental and FEM analysis are compared. [•] The RBS performance is excellent when the plastic hinge is formed at the RBS area. [Copyright &y& Elsevier]

A self-stressed steel fiber reinforced concrete (SS-SFRC) moment connection is proposed to strengthen multi-span simply-supported T-section reinforced concrete (RC) girders. In the proposed moment connection technique, old concrete needs to be removed from adjacent girder ends and negative moment reinforcement is placed into cast-in-place SS-SFRC to develop continuity over the interior support. Two series of tests consisting of 15 girder specimens were conducted to investigate the reliability of the proposed SS-SFRC moment connection. An analytical model is presented to predict the load-carrying capacity of the resulting continuous composite girders. Test results show that SS-SFRC is excellent in preventing concrete cracking at the interior support. Both the load-carrying capacity and the serviceability of the strengthened girders are significantly improved. The analytical model is demonstrated to predict the load-carrying capacity of the resulting continuous composited girders with an acceptable degree of accuracy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rotational stiffness of two closely spaced connections (a compound connection) is the same as a single connection. [•] Application in column-beam and splice connections opens new design frontiers in structural timber design. [•] This reinforced timber connection behaves isotropic, i.e. no angle to grain dependency. [Copyright &y& Elsevier]

Abstract: This work elucidates experimentally and numerically the behavior of steel beam-to-column moment connections proposed by widening and tapering the portion of beam flanges to increase the ductility and strength of the connection used in moment-resisting frames. Effectiveness of the tapered beam flange and the extent to which geometrical variables of the tapered beam flange affects the connection behavior were examined, based on a parametric study using finite element analysis. Additionally, seven full-scale specimens were tested to clarify their cyclic performance. All of the proposed tapered beam flange specimens, using either the column-tree full welded connection or the web-bolted flange-welded connection, achieved satisfactory ductile behavior by forming a plastic hinge in the beam section away from the column face. Extensive yielding, which occurred in the tapered zone of the beam section, resulted in stable energy dissipation. Based on the parametric study and experimental results, we recommend design parameters and a related procedure for practical design applications. [Copyright &y& Elsevier]

Abstract: This paper presents numerical studies on the cyclic behavior of connection between I-beam and a built-up box column. The connection utilized the flange plates to connect the beam flanges to the column flange. The flange plates were groove welded to column flange and fillet welded to the beam top and bottom flanges. In order to upgrade the connection, vertical top and bottom rib plates were groove welded to the column flange and fillet welded to the beam flange plates. The effect of the vertical rib plate''s geometry and position on the behavior of moment connections was investigated. Nonlinear finite element analyses using ABAQUS program were performed to investigate the cyclic behavior of welded flange plate connections. The results showed that vertical rib plate''s reinforcement can significantly improve the behavior of the connection. [Copyright &y& Elsevier]

Abstract: Steel moment resisting frames are widely employed in regions of high seismic risk to resist seismic forces. Comparisons among different analytical investigations show that geometric characteristics of connection parts have great influences on connection''s behavior. In order to evaluate this issue, a special connection is detailed that consists of a top and a bottom flange plate which is fillet welded to beam flange and groove welded to column flange. This connection is considered as an exterior connection. Beam is the most important part of connection, so we focused on varying the depth of the beam. Considering that, this parameter isn’t independent in rolled shape profiles, i.e. when beam depth increases, the thickness of flange and web will increase at the same time, we cannot examine the effect of beam depth alone. Therefore, we have used the plate girder instead to consider beam depth separately. All of models are designed according to AISC 360-05 provisions. Three-dimensional nonlinear finite element analyses of the connections were carried out. The results show, when beam depth increases, strength increases too, but stiffness and ductility decrease significantly. On the other hand, fracture potential of connection changes significantly. [Copyright &y& Elsevier]

Abstract: Double-I built-up columns are used extensively in low and medium rise steel structures. When I beam is connected to double-I built-up columns, through the column cover plate, the load transfer at the joint becomes a disturbing problem. To retrofit the connection, a new geometry is considered. In this method the each flange of the beam is connected to the column by a trapezoidal stiffeners plate. A series of five non-linear three-dimensional finite element models were developed using ABAQUS program to study the behavior of the retrofitted connection under cyclic loadings. The outcomes of numerical investigations indicate that the proposed retrofitting method is a proper choice for “special moment frames (SMF)” and the retrofitted models have sufficient strength and ductility. It reduces also the risk of brittle fracture of the full penetration groove weld. [Copyright &y& Elsevier]

Abstract: This paper presents the results of an experimental programme for a new blind bolted connection to unfilled hollow section (HS) columns under static loading. In this connection, channels with side plates connect beam flanges to the side face of HS columns. This is a simple alternative connection to typical face connections, i.e. the extended endplate connection or the T-stub connection (with T-stubs connecting the top and bottom flanges of the beam to the face of the column). The channel side plate connection was found to be much stiffer than a typical face connection and has the potential to achieve a rigid connection status for braced frames according to the EC3 classifications. Comparison of the test results and three dimensional finite element (FE) modelling indicates that the FE analyses can be used to predict the connection behaviour with sufficient accuracy. The preliminary investigation for the channel side plate connection shows promising results and forms the basis for the development of other blind bolted side connections for applications in the low rise construction industry. [Copyright &y& Elsevier]

Abstract: This paper presents the results of an experimental and analytical study into a new bolted moment connection between unfilled hollow section columns and open section beams, referred to herein as the extended T-stub connection with back face support. The connection is comprised of T-stubs connecting the top and bottom flanges of the beam to the face of the column and channels connecting the T-stubs to a backplate at the back face of the hollow section column. The addition of the channels to a standard T-stub connection helps to distribute the beam flange tension load to the back face of the hollow section column thus reducing demand on the flexible column face which often will compromise the stiffness of the connection. The extended T-stub connection with back face support was found to be comparable to a previously tested side connection and is much stiffer than a typical face connection. Comparison of the test results and three dimensional finite element () model indicates that analysis can be used to predict the connection behaviour with sufficient accuracy. The experimental results and analytical sensitivity analysis demonstrate that this new connection can offer a robust and reliable moment connection for application in the low rise construction industry. [Copyright &y& Elsevier]

Abstract: A post-tensioned negative moment connection technique is proposed to strengthen old multiple span simply-supported T-section reinforced concrete (RC) girders. In this technique, old concrete is removed from girder ends and flanges, a diaphragm is placed between the two adjacent girder ends over the interior support and negative moment steel strands are installed in new cast-in-place concrete and post-tensioned to make continuity. A total of six two-span simply-supported T-section RC girders were cast and five of them strengthened using the provision of the proposed post-tensioned negative moment connections. Both laboratory tests and nonlinear finite element (FE) analysis were conducted to investigate the structural performance of the strengthened RC girders. The moment redistribution in the strengthened continuous RC girders was also measured and is discussed. It is shown that the proposed post-tensioned moment connection technique can reliably transfer the negative moment over the support and markedly increase member stiffness and the load-carrying capacity of existing multiple span simply-supported RC girders. The validity of the FE analysis was also demonstrated through comparisons with experimental results. [Copyright &y& Elsevier]