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In practical applications, steel single angles are often subjected to eccentric loading when connected to a gusset plate through one leg only, resulting in complex compression behaviour. This behaviour has not been as extensively studied as that of concentrically loaded members. Various international codes of practice offer differed approaches for designing these elements. The literature indicates that the Indian Standard Code IS 800–2007 accurately predicts the axial capacity of eccentrically loaded single angle columns. However, a recent amendment to IS 800 in 2024 introduced modified design provisions. This study is the first to explore the implications of these latest design provisions by comparing them with earlier provisions and experimental strengths reported in the literature. Initially, the design strengths as per the previous and latest design provisions for various Indian Standard Angles (ISA) were presented and compared accounting for varying slenderness ratio, plate slenderness ratio (b/t), and different types of end connections and restraints. The findings reveal that the latest design provisions generally result in much higher design strengths compared to the earlier provisions, with a maximum increase of 104.84%. Upon noticing the significant variation, this study is further extended to compare with the reported data available in the literature. The nominal strengths calculated using the latest provisions were often higher than the strengths reported in the literature considered in this study, indicating potential unsafe design. [ABSTRACT FROM AUTHOR]

To study the mechanical performance of bolted connections with different structural forms of reinforced rings, based on the results of monotonic loading tests on two bolted connections between a concrete-filled steel tubular column and a steel beam with an outer reinforcing ring, this article uses ABAQUS v.2020 software to establish a three-dimensional refined finite element analysis model of such connections using appropriate constitutive models for concrete and steel. Subsequently, the effect of the dimensions of the steel beam, reinforcing ring, and cover plate on the load-bearing properties and the failure mechanism of the connections is investigated, and the numerical model is consistent with the verification test results. Then, the numerical simulations comparing bolted exterior reinforced rings under seven different construction measures (i.e., number of bolts, stiffeners) based on a conventional welded exterior reinforced rings with rigid connections (i.e., CGJ) are standardized. The research results indicate that when four rows of bolts are introduced on exterior reinforced rings, the web of steel beam is welded with stiffeners, and the top and bottom reinforced rings are also added with stiffeners; this bolted connection with an external reinforcing ring (i.e., GZ-7) can achieve the rigidity and load-bearing capacity of a fully welded external reinforcing ring rigid connection. At the same time, the reinforcing ring plate is bolted to the flange of the steel beam, and the force transmission path at the connection is changed to avoid the brittle fracture easily caused by the welded flange joints. It is also in line with the development trend of sustainable construction of "assembly" and "disassembly". [ABSTRACT FROM AUTHOR]

The first wall (FW) of a blanket or divertor faces high temperature plasma. Thus, the FW needs to withstand extremely high heat fluxes. Periodic plasma pulses bring some reliability challenges to FW structures. The FW is composed of tiles, heat sink and a bolt with different connection between the tile and the heat sink. In this study, the performances of two connection forms for the tile and the heat sink were investigated. The FLUENT software was used to evaluate the heat transfer performances for the two types structure. Elastic-plastic analysis was subsequently adopted to estimate the structural properties based on the thermal hydraulic results. At the same time, the thermal and structural results under a transient high thermal load (2 MW/m2) were also analyzed. Finally, structural fatigue analysis under a cyclic thermal load with 0.5 MW/m2 was also performed. The results indicated that there was a large discrepancy in the tile results for the two connections, while the differences in the heat sink result were not significant. The advantages and disadvantages of two connections also be discussed at last.

The brittle behavior traditional directly welded connections of steel beams to concrete-filled steel tube columns is caused primarily by excessive out-of-plane deformation of the tube walls at the level of the beam tension flange. To address this issue, this study proposes a reference connection that involves fillet welding a built-up steel beam directly to the corner of a diamond-shaped concrete-filled steel tube (DCFST) column. Two options are suggested for enhancing the seismic performance of the reference connection: a predrilled hole with a 12-mm diameter at the midwidth of each beam flange, or a rib stiffener reinforcement on the outside of each beam flange. The two proposed specimens and a traditional directly welded connection were subassembled and investigated experimentally. The results showed that the reference DCFST connection significantly improved the seismic response of the directly welded connection in terms of initial stiffness, strength, ductility, and energy-dissipating capacity. Specifically, the initial stiffness and strength capacity increased by over 150% compared with that of the traditional connection counterpart. Furthermore, the rib stiffeners contributed to further enhancement of the seismic response by shifting the beam plastic hinge away from the column face. Overall, these findings suggest that the use of DCFST connections is reliable for composite moment-resisting frames (C-MRFs), and the proposed enhancements can improve the seismic performance of these connections significantly. [ABSTRACT FROM AUTHOR]

Steel structural members in different application areas may be subjected to localized flame impingement instead of flashover scenario due to several reasons. Though extensive research has been performed to study component level systems in conventional fires (ISO 834, ASTM E119, other parametric fire curve), the behavior of beam column rigid connection in localized fire is still not investigated in details. To understand the behavior of beam-column connection under localized fires, the present paper deals with a detailed numerical investigation of the behavior of a moment resisting frame (MRF) assembly with fully welded beam column connection in terms of connection rotation and forces under different positions of localized fire source underneath the exposed beam. For fire scenarios where the frame survived during the entire duration of fire, the post fire rotation of the connection located at far end from the fire source was found to be higher than the near end. Secondly, for cases where the frame failed, it was observed that for identical strength of weld and base material, failure is likely to initiate at the weld line connecting the bottom flange of the beam located at far end from the fire source. Finally parametric studies were performed with different weld sizes and it was concluded that size of weld has significant effect on increasing the joint survival time for MRF exposed to localized fire. [ABSTRACT FROM AUTHOR]

Recently, studies have been carried out to apply lean duplex stainless steels, with less than 1.5% nickel, which provides higher material strength and lower cost compared with austenitic stainless steel for building structures. This study compared with existing experimental and finite element analysis results on the structural behaviours of cold-formed lean duplex stainless steel welded connections with different tensile strength (tensile strength-to-yield stress ratio) and plate thickness despite identical steel grade. The main variables are plate thickness and weld lengths. The material tensile strength of a 3.0 mm thick plate was 22% lower than that of a 1.5 mm thick plate. All specimens showed block shear facture in the base metal. Block shear strengths predicted by current design codes and the proposed equations from previous studies were compared with test strengths. KDS 41 31 00-19/AISC2016 and EC3 design specifications underestimated block shear capacity by on average 24%, 43%, respectively for 1.5 mm and 3.0 mm thick specimens, and equations suggested in previous studies of stainless steel welded connections did not sufficiently account for the influence of stress triaxiality by material property and plate thickness difference on the block shear strength of lean duplex stainless steel specimens. Therefore, thickness-dependent modified strength equations were recommended based on experimental and numerical studies of lean duplex stainless steel welded connections and comparison of carbon steel and other stainless steel connections. [ABSTRACT FROM AUTHOR]

Cyclic loading tests on two groups of welded flange‐bolted web connections employing 690 MPa high‐strength steels were conducted to quantify their plastic deformation and energy dissipation capacities under seismic loading conditions. The Q355 and Q690 beams in the two groups of specimens were designed with Class 1 and Class 3 cross‐sections, respectively; however, the Q690 columns in each group were designed nearly identical except for the thickness of their webs, which varied in order to identify the effect of shear panel strength on the connection seismic performance. Different beam‐to‐column flange welding types in each group were also considered. It was found that welding without backing bars should be used between Q690 beams and columns to accommodate some plastic rotation in the order of 0.01 rad in the beams, while a plastic shear distortion as high as 0.04 rad could be developed in Q690 web panels. This evidenced that those Q690 joint components could still sustain appreciable plastic deformations. In particular, Q690 web panels could be even qualified as high‐ductility class (DCH) in Eurocode 8. [ABSTRACT FROM AUTHOR]

Block shear rupture is a potential failure mode in welded steel gusset plates. The research on this failure mode in welded connections is scarce, and in available few studies, only concentric loading condition has been considered. Nevertheless, gusset plates are often loaded eccentrically, either in-plane or out-of-plane, depending on the connection. This paper examines the block shear failure in welded gusset plates under eccentric loading. First, an advanced nonlinear finite element model with ductile fracture prediction capability was developed and verified in detail against the authors' experiment. Then, a comprehensive parametric study consisting of 260 connections was performed. Based on the results, the eccentricity of the applied load made the tensile and shear stress distributions on the failure planes uneven. The ratio of the eccentricity to the connection length was the main parameter that affected block shear strength under eccentric loads. In out-of-plane eccentric cases, gusset plate thickness was also a significant factor. Moreover, the findings implied that current block shear strength equations suggested for welded gusset plates did not take into account load eccentricity-induced effects and overestimates the connection capacity. Accordingly, modified design equations are proposed that predict the block shear strength under eccentric loading with greater accuracy. [ABSTRACT FROM AUTHOR]

The non-uniform stress distribution that occurs in a tension member adjacent to a connection, in which all elements of the cross section are not directly connected, is commonly referred to as the shear lag effect. This effect reduces the design strength of the member because the entire cross section is not fully effective at the critical section location. This phenomenon has long been taken into account in various structural codes, however the rules of the codes used are somewhat conservative and it seems that they need to be reviewed. In this research, a series of steel box section connected through two wings and plate sections were studied through finite element method using ABAQUS software, and the ultimate member capacity was obtained. It can be seen that in this regard the relationship between the rules is somewhat conservative and optimized relationships have been proposed to address this issue. Parameters used include connection length, axial force eccentricity, and weld size. The results show that the length of the connection, the gusset plate thickness and also the eccentricity have a significant influence on the shear latency coefficient.

To study the mechanical performance of bolted connections with different structural forms of reinforced rings, based on the results of monotonic loading tests on two bolted connections between a concrete-filled steel tubular column and a steel beam with an outer reinforcing ring, this article uses ABAQUS v.2020 software to establish a three-dimensional refined finite element analysis model of such connections using appropriate constitutive models for concrete and steel. Subsequently, the effect of the dimensions of the steel beam, reinforcing ring, and cover plate on the load-bearing properties and the failure mechanism of the connections is investigated, and the numerical model is consistent with the verification test results. Then, the numerical simulations comparing bolted exterior reinforced rings under seven different construction measures (i.e., number of bolts, stiffeners) based on a conventional welded exterior reinforced rings with rigid connections (i.e., CGJ) are standardized. The research results indicate that when four rows of bolts are introduced on exterior reinforced rings, the web of steel beam is welded with stiffeners, and the top and bottom reinforced rings are also added with stiffeners; this bolted connection with an external reinforcing ring (i.e., GZ-7) can achieve the rigidity and load-bearing capacity of a fully welded external reinforcing ring rigid connection. At the same time, the reinforcing ring plate is bolted to the flange of the steel beam, and the force transmission path at the connection is changed to avoid the brittle fracture easily caused by the welded flange joints. It is also in line with the development trend of sustainable construction of “assembly” and “disassembly”.

The non-uniform stress distribution that occurs in a tension member adjacent to a connection, in which all elements of the cross section are not directly connected, is commonly referred to as the shear lag effect. This effect reduces the design strength of the member because the entire cross section is not fully effective at the critical section location. This phenomenon has long been taken into account in various structural codes, however the rules of the codes used are somewhat conservative and it seems that they need to be reviewed. In this research, a series of steel box section connected through two wings and plate sections were studied through finite element method using ABAQUS software, and the ultimate member capacity was obtained. It can be seen that in this regard the relationship between the rules is somewhat conservative and optimized relationships have been proposed to address this issue. Parameters used include connection length, axial force eccentricity, and weld size. The results show that the length of the connection, the gusset plate thickness and also the eccentricity have a significant influence on the shear latency coefficient. [ABSTRACT FROM AUTHOR]

Effective design concepts for welded mixed connections in steel structures Mixed connections made of normal strength and high strength steels enable optimal material use to the forces acting on them. This leads to ecological and economic advantages through reduced material consumption and smaller weld geometries. Normative rules for butt‐welded mixed connections of normal strength and high strength steels do not exist, therefore a design approach for such connections is to be developed in the research project "Effective design concepts for mixed connections in steel structures". In addition, the design concepts already developed for butt‐welds and fillet‐welds are being extended up to S960, in order to integrate the results into the new version of EN 1993‐1‐12. For this purpose, extensive experimental investigations of the load‐carrying capacity are carried out by varying the base material, welding consumable, heat input, plate thickness and weld geometry. With the results obtained and further accompanying investigations, the influences of the varying parameters on the load‐carrying capacity of the welded connections will be identified. First results of that project are reported in the following. [ABSTRACT FROM AUTHOR]

Earthquake-induced uplifting/settlement at the base of liquid-storage tanks causes yielding in the bottom plate. Limited amount of yielding is a source of deformability and damping in tanks, but excessive yielding during repeated cycles can rupture the bottom plate and cause the liquid to leak from the tank. This study is conducted to experimentally determine the amount of plastic yielding that can be allowed in the bottom plate during the expected number of load cycles. Four test specimens for this study were obtained from a tank that was demolished after 66 years of service. A novel test protocol is developed for engineers to account for the large number of load cycles expected during a magnitude M 9 earthquake in the region of interest. From the results of cyclic tests, it is determined that (1) the bottom plate can sustain 20 cycles of ±0.335 rad (±19°) plastic rotation without rupture; and (2) the plastic moment capacity of the bottom plate increases by 32% due to strain hardening. These results are significant in performance-based seismic design and evaluation of liquid-storage tanks. [ABSTRACT FROM AUTHOR]

The beam-column connections are known as a fundamental component in steel moment-resisting frames. The present investigation studies the progressive collapse behavior of four various welded types of beam-column connections including, welded unreinforced flange-welded web moment (WUF-W), reduced beam section (RBS), welded flange plate (WFP), and welded flange-weld web connection with internal diaphragms (I-W). The nonlinear analysis with suitable finite element modeling has been generated to assess the connection's performance under a column removal scenario. The load–displacement curves, fracture modes, Von-Mises stresses, and other comparable theoretical results were described. The results are verified with existing experimental data. The results of the analyses showed that the studied models' overall failure occurs in the beam-column connection regions in the large rotation under the catenary action mode. The plastic strain accumulation occurred around the access hole, and the failure was initiated from these areas. Each of the investigated connections showed sufficient strength under column removal scenario. WFP connections demonstrated the best performance due to the top and bottom plates' presence and the keep away of critical stresses from the connection area. The RBS connections exhibited the weakest behavior due to absorbing excessive stresses and fast fracture and tolerating minimum vertical loads. Also, it is observed that in the designing of buildings exposed to the phenomenon of progressive collapse, the considerable axial load generated in the connections area should be considered in the design phase. [ABSTRACT FROM AUTHOR]

The typical failure of a welded single angle tension member is a gross section failure. The rupture strength of the single angle tension member is affected by the effect of shear lag. Full-scale tests on twenty-seven single angle specimens reported in this paper. Four different angle sections with four different section types were used in the test. The test parameter includes the steel's grade, length of the connection, the eccentricity of the connection, and balanced and unbalanced weld arrangement. Twenty-three specimens failed by fracture of the gross section area, one failed in mixed mode (angle tear and the weld failure), and the remaining three failed in the weld. To interpret the experimental results, finite element analysis was performed on the specimen's model. The finite element model well represents the welded single-angle tension member's behaviour, and finite element results show exemplary test results. The ultimate strengths of the test specimens were also evaluated by using the current design standards (IS 800, AISC, CSA, AS 4100, and EC-3), the (1− x̅/L) rule, and Kulak and Wu's equation. In general, IS 800 provides a good prediction of test results, AISC and AS 4100 provide a slightly conservative forecast; however, CSA and EC-3 provide a slightly un-conservative prediction. For a balanced weld arrangement, the specimen's ultimate strength increased with an increase in connection length; however, an increase in connection length does not increase the specimen's ultimate strength for an unbalanced weld arrangement. The angle specimen's efficiency decreased significantly with an increase in eccentricity. The rupture strength predicted by assuming the ultimate strength of the connected leg and the strength contributed by the outstanding leg at the critical section shows a good prediction of the strength over the (1− x̅/L) rule. [ABSTRACT FROM AUTHOR]

In Ecuador, the use of square tubular steel connections has been increased in houses and shopping centers. However, there is no regulation that explains the connection’s behavior. In this research, the experimental behavior of this connection was evaluated. Because of this, tests were carried out where the elastoplastic behavior of welded joints with square steel tubes conformed by G profiles of 60x30x2 and 80x40x3 mm, subjected to monotonic load, were analyzed. Each test consisted of imposing progressive load on the upper connection of the frame, in order to measure the displacements and distortion of the geometry of the beam-column connection elements of the lower connection. The results show that the experimental collapse load in frames 1, 2 and 3 (connection without reinforcement) decreased 12.82 % in comparison to the theoretical value, meanwhile, the collapse for frames 4, 5 and 6 (reinforced connection) increased by 14.96 %. The reinforcement was made up of plates installed in the column of the lower connection. With this, the failure due to local buckling has been avoided and the formation of plastic hinges in the beam of the welded joint has been guaranteed, thus fulfilling the criterion of weak beam-strong column. [ABSTRACT FROM AUTHOR]

The development of a bonded glass-steel element that is capable to i) transfer out-of-plane loads due to wind loads in transverse direction, ii) in-plane shear loads, due to wind in longitudinal direction and iii) in-plane compression due to self-weight implies that the structural continuous adhesive glass-metal connection becomes an integral part of the entire bonded glass-steel unit. The frame members are restrained by the joint-glass system due to the glass bonded to the steel frame. To assess the capability of continuous adhesive glass-steel connections to transfer the abovementioned loads, research is indispensable. The available knowledge on the capacity of glass panes used as structural bracing element in steel frames is limited. This paper reports about the structural performance of welded steel corners, both not bonded and bonded with glass panes, to assess the in-plane load-bearing capacity of these connections. In a first experimental phase tests on welded steel corners with different configurations are conducted, whilst during the second phase specimens bonded with glass panes on both sides are tested. Numerical models are developed and validated based on the experimental results, which are then used for parametric studies. As such, the rotational stiffness of semi-rigid welded steel corner configurations and the additional stiffness obtained by bonded glass panes can be determined. The results demonstrated that the specimens with adhesively bonded glass panes on both sides using the structural silicones Sikasil® SG-500 and DowSil™ 993, and the hybrid polymer adhesive Soudaseal 2 K, significantly increased the initial rotational stiffness of the welded steel corners. Specimens bonded with the hybrid polymer adhesive behave significantly stiffer than specimens bonded with the structural silicones. Parametric studies on validated finite element models reveal that the effect of the glass thickness is important for low values of the adhesive thickness. The width-to-thickness ratio of the adhesive layer largely influences the value of the rotational stiffness of the connection. The generated data by the numerical models can now be implemented in analytical models for the calculation of steel structures with semi-rigid joints. • Continuous adhesive glass-metal connections using three adhesives are investigated. • The rotational in-plane stiffness is experimentally determined for (un)bonded specimens. • Analytical analyses allowed the validation of the experimental results. • Finite element models were validated and used for parametric studies. • The results can be used for the calculation of (bonded) steel structures with semi-rigid joints. [ABSTRACT FROM AUTHOR]

● The welded flexural connection in CFS beams is introduced and its seismic behavior is studied for the first time through a comprehensive numerical modeling. ● Weld material and CFS beam finite element models are developed based on the available test data to be later used in calibrated models. ● Distribution of stress along the longitudinal flare-bevel groove welds obtained from the nonlinear analysis is compared with the theoretical values, and three general stress distributions patterns are distinguished. ● CFS moment frames (six in number) with the welded connections are built and subjected to column axial compression and cyclic lateral drift to identify their modes of failure and ductility. ● A seismic modification coefficient, R, equal to 3.8 is estimated and proposed. The Cold-Formed Steel (CFS) construction in seismic regions requires carefully selecting and designing an approved seismic-force resisting system. Among the available seismically-resistant structural systems, the bolted CFS moment frames have recently gained some attention. However, given the currently existing design issues associated with the bolted connections in CFS moment frames, this paper seeks to conduct a numerical investigation into the potential substitution of bolt fasteners with the weld materials in CFS frames. The objective is to explore the possibility of including the welded connection as an alternative to bolted connections in subsequent editions of the ASCE 7 code. To this end, finite element models, consisting of two built-up CFS beams and twenty-three flare-bevel-groove and fillet weld specimens, are initially validated against the cyclically and monotonically loaded tests with data available in the relevant literature. Subsequently, the verified weld and CFS beam models are incorporated in the simulation of thirty-four CFS beam-to-column welded moment connections, each differing in beam dimension, weld length and size, and gusset plate thickness. The built-up beams comprise back-to-back and lip-to-lip double C-section profiles. Stress variations along the weld lines, derived initially from nonlinear finite element analyses and then computed from the theoretical elastic analysis, are compared to establish a basis for categorizing stress distribution patterns in the longitudinal welds. Finally, six CFS frames assembled with the welded moment connection and subjected to a combined column axial compression and cyclic lateral drift are examined, resulting in an estimated seismic modification coefficient, R, equal to 3.8. Overall, the welded moment connections demonstrate a stable seismic response with an average ductility ratio, μ , of 2.7. The dominant failure mode is a locally developed ductile fracture in the two end segments of the longitudinal welds, identified as critical regions. [ABSTRACT FROM AUTHOR]

After failure of a column in structure by an abnormal loading, undesirable performance and damage of connections of the beams connected to the top of this column, can lead to the local failure of floor and in turn result in progressive collapse in the structure. Accordingly, the best method for rehabilitation of the structure against this incident is the strengthening of the connections. The strength and flexibility of the connections during the large rotations result in spreading the axial forces in beams and forming the catenary action. This action can greatly prevent structural failure due to the column removal. In this paper, the performance of prevalent bolted and welded top and seat angle steel connections is evaluated numerically. All parts of the connections are modeled in finite element software. The modeled structure is analyzed nonlinearly under the vertical displacement in the location of removed column, and its results have been verified with experimental results. In addition, the behavior, failure modes, how the catenary action develops and the effects of different parameters on connection behavior are investigated. The results indicated that bolted connections have better performance than welded connections.Also, in welded connections, increasing the thickness of the angles and increasing the length of the connected angle leg to column, improve the catenary action and the resistance of the connections against progressive collapse. But adding the stiffener plate in the middle of the seat angle does not increase the connection capacity in all cases.

The block shear equations specified in the current AISC specification for structural steel buildings and North American cold-formed steel design specifications are based on research results of carbon steel bolted connections. These equations were found to be inapplicable for the welded connections in the literature. This issue is primarily associated with the use of the incorrect assumption on block shear failure mechanism. The present paper examines the accuracy of various block shear equations available in the design specifications and in the literature. The paper also examines the shear hardening capacity and the level of tensile stress over the critical net area with the results of finite element analysis, in which the fracture simulation is considered. It shows that the block shear capacities of lean duplex stainless steel welded connections can be predicted accurately using tensile stress equal to 1.25Fu, as proposed in the literature. [ABSTRACT FROM AUTHOR]

The rate of applying cruciform columns with bolted connection in double-directed Moment resisting frames and tubular systems has positive trend because of their architectural advantages. Construction of doubler plate for shear strengthening panel zone and continuity plate, with regard to special moment resisting frame requirement, needs convenient detail which is presented in this research. There was no applicable information in this research filed, so new constructional details involving of inclined plates and vertical angles were presented in order to strengthen the panel zone. Furthermore, the different welding configurations were studied. For this reason, 16 nonlinear numerical models were simulated to study different constructional detail of panel zone. In present research, steel material and weld behavior were evaluated by fracture indexes of material. Results show the performance of panel zone will be improved by using proposed constructional details.

This contribution explores how design changes can affect resistance of rail wagon seat-to-frame connections at impact test and proposes alternative way to construct such connections. Results were due to a nature of presented problem obtained by computer modelling using MSC Nastran with explicit finite element method solution invoked. Physical tests were also conducted and comparison with numerical results is presented.

The block shear equations specified in the current AISC specification for structural steel buildings and North American cold-formed steel design specifications are based on research results of carbon steel bolted connections. These equations were found to be inapplicable for the welded connections in the literature. This issue is primarily associated with the use of the incorrect assumption on block shear failure mechanism. The present paper examines the accuracy of various block shear equations available in the design specifications and in the literature. The paper also examines the shear hardening capacity and the level of tensile stress over the critical net area with the results of finite element analysis, in which the fracture simulation is considered. It shows that the block shear capacities of lean duplex stainless steel welded connections can be predicted accurately using tensile stress equal to 1.25Fu, as proposed in the literature.

The aim of this study is to determine the effect of depth of fusion on the behavior of tempered martensite and thermomechanically rolled steel welded joints. To obtain the effect of depth of fusion on the stress and displacements, three different welded sample welded to each other by metal active gas welding method applied in PB position were prepared in accordance with the related standard. According to the welding procedure specification EN ISO 15614-1 which clarifies how samples should be welded, different current, voltage, travel speed and wire feed speed were selected for each sample. After the welding process, welded samples were subjected to visual and magnetic testing to evaluate quality of the weld seams. After the non-destructive tests, samples were cut into small pieces to measure the depth of fusion and three samples having different depth of fusion were obtained. The finite element models of these samples were created in ANSYS to evaluate the stresses and displacements of samples. The models of samples were subjected to the loads which range from 1000N to 45000N and the results were obtained under lineer-static analysis. The results of finite element analyses of samples such as stresses and displacements are compared with each other in terms of depth of fusion for each sample. It is seen that depth of fusion has remarkable effect on the behavior of welded joints. [ABSTRACT FROM AUTHOR]

In this paper, the block shear fracture behavior of base metal in austenitic stainless steel (STS304, corresponds to ASTM 304 type) fillet-welded connection has been investigated through experimental and numerical methods. Even though the block shear fracture strength of welded connection thanks to stress triaxiality effect differs from those of bolted connection under monotonic tension, block shear strength equations of welded connection with base metal fracture in the design codes are identical to those of bolted connection. Main variables are weld method (TIG and Arc welding) and weld length (transverse and longitudinal to the direction of loading). It is found from study results that welding method did not affect the strength of welded connection. Block shear strengths by current codes (KBC2016, AISC2016 and EC3 1–3) and other researchers' proposed equations were compared with those of experimental results and finite element analysis results. Finite element analysis (FEA) model was developed based on previously test data. Also, parametric study for investigating the weld length effect on strength has been performed with the developed finite element analysis procedures. Consequently, condition of weld length and end distance perpendicular to the direction of applied force for fracture mode transition boundary from tensile fracture to block shear fracture in welded connection was investigated. In addition, block shear strength equation with modified tensile stress and shear stress factors of base metal fracture in austenitic stainless steel (STS304) welded connection is suggested considering stress triaxiality. • Finite element analysis of stainless steel welded connections was conducted. • Strength and fracture mode by analysis agreed with those of test results. • Specimens failed by block shear fracture of base metal. • Condition of fracture transition according to variables were investigated. • Effective tensile and shear stress factors were suggested. [ABSTRACT FROM AUTHOR]

Development of a modified design resistance function for welded connections of high strength steel In various research projects, a design resistance function modified for high strength steel could be developed for fillet welds with same base metal by Rasche [1]. In the frame of another research project [2] the applicability of this modified design resistance function could be confirmed for mixed connections with fillet welds with base metal of normal and high strength steels. The results of these research on a design model for the determination of the load carrying capacity of welded connections made of high strength steel has been presented as an amendment to the European code committee SC3 and is meanwhile accepted for incorporation in the future version of prEN 1993‐1‐8 [3]. For butt welds of high strength steel it could be observed that the failure may occur in the weld or in the heat affected zone though the verification is usually done at the member section. Therefore, an adapted design model for butt welds with high strength steel is also planned to be developed. [ABSTRACT FROM AUTHOR]

Load carrying capacity of fillet welds with mild carbon and high strength steel. The requirement towards slender and more filigree constructions with high loadings consistently leads to the application of high strength steels. Decisive for the application of high strength steels is, aside of the question of stability and for bridges and similar structures fatigue, mainly the type of joints and connections. In the course of previous research projects, a for high strength steel modified design resistance function could be developed for fillet welds with same base metal by Rasche. The objective of the project was the review of the modified design resistance function for determining the carrying capacity of mixed connections with fillet welds of normal and high strength steels in order to improve the normative carrying capacity of fillet welds for mixed connections in the currently used steel standards. The results will be summarized and will be derived as a proposal for the future code development. [ABSTRACT FROM AUTHOR]

The fatigue cracking at transverse diaphragm cutouts and rib-to-diaphragm connections is one of the primary ways in which orthotropic steel decks (OSDs) are damaged. In this study, the fatigue damage mechanism of the cutouts and rib-to-diaphragm connections was investigated through a full-scale model experiment and numerical simulations. The applicability and accuracy of different fatigue evaluation methods for the cutouts and rib-to-diaphragm connections were compared. Furthermore, the fatigue behavior of the novel rib-to-diaphragm connection was evaluated, and its optimized structure was suggested based on parametric analysis. The results show that a complex stress distribution dominated by in-plane stresses was observed at the rib-to-diaphragm connection under wheel loading. The cracking of the weld toe at the transverse diaphragm side was found to be the dominant failure mode. The hot spot stress method has a higher prediction accuracy than the critical distance theory for predicting the fatigue life of the cutouts. For the longitudinal rib-to-transverse diaphragm connection, the hot spot stress method could be used to predict the fatigue life of U-rib side weld toes based on fatigue grade FAT 90, and the equivalent structural stress method provided a reasonable prediction of the fatigue life for all fatigue failure modes. Last but not least, a novel rib-to-diaphragm connection structure that can effectively improve fatigue performance was suggested, and its fatigue life was evidenced to be greater than 50 million cycles after geometrical parameter optimization. • The fatigue failure modes of rib-to-diaphragm connections was studied through full-scale model tests and numerical simulation. • The applicability of different fatigue evaluation methods for fatigue performance of diaphragm cutouts and welded connections were discussed. • The equivalent structural stress method was proven effective for fatigue assessment of rib-to-diaphragm connections. • A novel rib-to-diaphragm connection structure was recommended, which can effectively improve its fatigue performance. [ABSTRACT FROM AUTHOR]

In order to evaluate the seismic behavior of prefabricated panel structures by dry connectors (PPSDC) , two one-half scale two-story models were constructed and subjected to a series of quasi-static; tests. The joints of the two models were connected by bolted and welded connections, respectively. This paper presents the results from the tests, with focuses on the force transfer mechanism, the failure mode, the hysteretic behavior, the skeleton curves and their characteristic parameters, and the strains in the reinforcing steel bars. Based on the test results, the concept of ductile failure mode of the PPSDC is proposed together with the design principles for ductile joints in such structures. The test results show that the integrity and utmost bearing capacity of PPSDC are good, but the failure mode and characteristics of the PPSDC are obviously different from cast-in-situ structures and other prefabricated concrete structures. The punch-shear damage of concrete and anchor damage of built-in fitting are the main reasons for the failure of the two PPDSC models, respectively. In order to ensure the ductility and the deformation capacity of the PPSDC, the ductile design principles of 4 strong anchorage, strong peripheral and weak steel plate’ should be followed in the design stage, in which the connected steel plates are regarded as a main weakest component dissipating energy and the failure of different parts in the dry connectors could be controlled. [ABSTRACT FROM AUTHOR]

The paper shows that the main factors that lead to the fracture of the holder of elevating-and-traversing stand body is the load with alternating signs, the magnitude of which increases by 23% after stand modernization; as well as long service life of elevating-and-traversing stand structure. Alternating load increment apparently provokes the nucleation and growth of fatigue cracks, specific surfaces of which are found in the holder fracture. Among the adverse factors the changes of initial microstructure in the form of rough Widmanstätten structure should be mentioned, which usually has poor crack resistance under the application of cyclic load. The presence of these changes is likely due to the metal recrystallization process in the heat-affected zone of the welded joint of eyelet with the holder ring. In order to prevent similar incidents in future it is necessary to perform check calculation to verify the low-cycle fatigue of its components, taking into account the structural, technological and operational factors. [ABSTRACT FROM AUTHOR]

This paper presents two simplified procedures for the calculation of the Effective Notch Stress (ENS) on non-overlapping circular hollow section (CHS) K-joints. The proposed procedures aim to alleviate the modeling challenges associated with the traditional ENS calculation on joints with complex geometry, such as the CHS joints. The first procedure is an extension of the recently proposed extrapolation method, similar to the extrapolation in the widely-used Structural Hot-Spot Stress (SHSS) approach. The second procedure provides ENS estimations based on the parametric relationship between the ENS and SHSS. Through an extensive numerical study, this investigation develops parametric equations supporting each procedure, covering practical geometric range for CHS K-joints under balanced brace axial load. Both simplified procedures demonstrate close agreement with the traditional ENS calculation and provide reasonable fatigue life assessments with a substantial number of experimental data, based on the S-N framework. [ABSTRACT FROM AUTHOR]

A common structural steel connection design problem is to size a fillet-welded plate boundary for an eccentric shear and/or normal force. Three common design models for dealing with the design of the fillet-welded plate boundary are reviewed, and a new model is presented. The new model is derived to produce designs similar to the instantaneous center of rotation method; however, the model offers an explicit solution by assuming a stress distribution on the boundary that designers can easily confirm or modify in daily practice. [ABSTRACT FROM AUTHOR]

This paper presents an extrapolation method to determine the effective notch stress (ENS) on the weld toes of welded circular hollow section (CHS) X-joints in-line with the extrapolation method to determine the structural hot-spot stress in existing design guidelines. This investigation verifies and extends the recently proposed ENS extrapolation scheme to CHS X-joints, which elevates significantly the difficulty in generating a weld toe radius along the brace-to-chord intersection as required in existing guidelines. An extensive numerical study then investigates the ENS extrapolation for CHS X-joints under three loading conditions, namely, the brace axial load, the brace in-plane bending load, and the brace out-of-plane bending load. The numerical study derives a set of recommended extrapolation parameters that ensures accurate ENS estimation for each loading condition. This paper demonstrates that the proposed extrapolation method for the CHS X-joints yields good agreement with the standard ENS calculation procedure described in the International Institute of Welding (IIW) guideline. [ABSTRACT FROM AUTHOR]

Seismic performance of beam-to-column connections used in the middle-low rise buildings was investigated through the cyclic loading test. Four joint specimens were prepared in accordance with the variables of material and connection type. In two cases of welded connection, the brittle fracture in weld did not occur but cracked at heat-affected zone (HAZ) and/or near weld access hole. In the connections with extended end-plate, punching failure followed by end-plate failure occurred at the flange of column around bolt head. The moment capacities based on failure modes were calculated and compared with the test results. The connections were classified as rigid, semi-rigid, flexible in terms of bending stiffness and strength. [ABSTRACT FROM AUTHOR]

Orthotropic decks were applied to the long span bridges after World War II due to several advantages, such as light weight, high strength, few deck joints, durability, rapid construction, life-cycle economy. The fatigue problem of orthotropic decks was realized twenty years ago since fatigue failure was found. In the past two decades large amount of studies and investigations were carried out and fruitful achievements were obtained. It was found that most of the fatigue cracks were occurred at the welded connection details, such as rib-to-deck plate, rib-to-diaphragm, and rib-to-diaphragm-to-deck plate (RDDP). These connections are sensitive to fatigue cracking due to high concentrated stress and residual stress at welded connections. In this paper practical fatigue failure cases at the welded connections, ease to occur fatigue cracking, are presented, and analyzed through a numerical modeling of orthotropic deck via FE (finite element) software. Furthermore, the improvement technologies of fatigue are also discussed. The results of the analysis can be contributed to the evaluation of the fatigue design for the orthotropic deck.

A series of in-plane shear tests were carried out on twenty-one steel roof deck diaphragms. This test program was initiated and designed to evaluate the seismic inelastic response of steel roof decks with different thicknesses and different types of deck-to-frame connections: nails and arc spot welds. Self-drilled screws were used for sheet side lap fasteners in all specimens. The tests included monotonic, quasi-static reversed cyclic inelastic deformation, and seismic motions. Shear performance and failure mode of the steel decks for both types of deck-to-frame connections were investigated. Lateral resistance and elastic stiffness of steel decks with different panel thicknesses and connector types were determined and compared with those available in the Diaphragm Design Manual. Testing of all specimens confirmed that the inelastic deformation of a deck is mainly concentrated on the edge of the diaphragms parallel to the lateral loading. The cyclic tests showed a pinched hysteretic behavior for all the specimens. Nail specimens sustained large inelastic deformation cycles with progressive strength degradation. In contrast, weld specimens showed very significant deterioration and very rapid strength reduction after the peak load was reached. These tests confirm that the response modification factor for structural systems built with steel decks with nail–screw connectors should be greater than the current value in the building codes. [ABSTRACT FROM AUTHOR]

Die Sichtprüfung von Schweißnähten ist die einfachste und am häufigsten durchgeführte Art der Schweißnahtprüfung. Neben laufenden Soll-Kontrollen durch das Schweißpersonal während der Fertigung ist für alle Ausführungsklassen abschließend eine vollumfängliche Sichtprüfung nach EN 1990-2 [1] durchzuführen. Dabei können direkte und indirekte Prüfmethoden angewendet werden, zu denen auch die Geometrieerfassung durch Laserscanning zu zählen ist. In diesem zweiten Teil des Beitrages wird die Anwendung eines mobilen Laserscansystems für den klassifizierenden Vergleich zur rein rechnerischen Ermittlung der Ermüdungsfestigkeit erläutert (Teil 1 s. Stahlbau, H. 5, S. 336-343). Assessment of welds based on 3D laser scanning. Practical application of a mobile laser scan system for the surface assessment of welds - Part 2. The visual examination of welds is a simple and frequently used method for weld inspections. Besides the comparison between a target and performance state executed by the technical staff during the production process, a final visual inspection of the welds for all execution classes is demanded by EN 1990-2 [1]. According to this standard, direct or indirect methods can be applied. An example for an indirect method is the scanning of the real geometry of the weld using laser scan technology. In this second part of this article the application of a mobile laser scan system is used as a base to quantify and compare the fatigue limits of scanned specimens with numerical methods only. [ABSTRACT FROM AUTHOR]

Extreme events such as earthquake and fire can cause severe damage to building structures. The possible coupling of various extremes such as earthquake followed by fire is more destructive. It is necessary to capture the behavior of building structures subjected to the post-earthquake fire (PEF) for safety reasons. This study aims to investigate the behavior of unstiffened welded steel connections subjected to the PEF scenario. Experimental tests were carried out on two groups of steel I-beam to hollow column connections with different column wall thicknesses under ISO fire including 4 connections with the same specifications within each group in which 3 connections were tested under the coupling of cyclic loading and subsequent fire while 1 connection was only subjected to fire. All undamaged and pre-damaged connections were tested in a gas furnace under the given constant static load which was about 30% of the ultimate monotonic loading strength of the connections. The furnace temperature, temperature distribution and the deflection of the beam were measured during the fire tests. It was found that the load-carrying capacity of the welded connections decreases significantly with the increase of the pre-damage level. Preliminary finite element modeling was carried out for a heat transfer analysis on the basis of uniform fire exposure as well, which showed nonuniform temperature distribution of the connections. [ABSTRACT FROM AUTHOR]

• An innovative connection for beam to unfilled and CFT circular columns is proposed. • Three full-scale planar moment connections are tested under lateral cyclic loading. • The force transferring mechanisms in the connection and panel zone is investigated. • The specimens sustained rotations more than 6% story drift without any damage. • Specimens tolerated stipulated drift by AISC 341–16 for special moment connections. This research presents a specific configuration for the fully restrained connections between I-shaped beams and concrete filled and unfilled circular columns. In the proposed connection, there is a vertical plate which passes through the aligned slots in the connection zone. The through-plat connection provides a new reliable path to transfer the in-plane forces from the beam to the circular column. The performance of the through-plate connection is experimentally evaluated and, the interior planar connections are tested under lateral cyclic loading. Specimens are consisted of two concrete-filled columns and one unfiled circular column. Herein, the fabrication process and analysis of the proposed connection are presented. The experimental full-scale tests are carried out to understand the mechanisms of the force transferring from the beam to the circular column, and also the shear transferring in the panel zone region. The failure modes, hysteretic performance, strength, initial stiffness, ductility and panel zone behavior of the through-plate connection are evaluated. It is shown that the through-plate connection is a suitable configuration for seismic applications with large deformation demands. The specimens have sustained rotations more than 6% story drift with no damage in the column and the connection components. The results of the experimental program reveal the adequacy of the proposed connection as a special moment connection according to the AISI/AISC341-16 seismic provisions. [ABSTRACT FROM AUTHOR]

This paper presents an approach to integrate a lower-bound material J – R curve into the load–deformation relationship for circular hollow section joints. The lower-bound J – R curve derives from a regression analysis of the experimental data for a wide range of structural steels reported in the literature and follows a linear relationship up to a maximum crack extension of 2.0 mm. The deterioration in the joint strength caused by ductile tearing adheres to a reduction factor based on the crack area. The J – R curve modified load–deformation responses compare closely with reported experimental results for both welded tubular joints and large-scale tubular frames. [ABSTRACT FROM AUTHOR]