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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]

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”.

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]

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]

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]

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]

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]

During the welding process, the microstructure of the base material changes locally that leads to altering mechanical properties in the weld and the neighboring areas, Heat Affected Zone (HAZ). The constitution of the HAZs also varies spatially as a result of different temperature gradients during heating and cooling cycles. Consequently, the macroscopic material behavior of the HAZ also varies spatially as well and therefore the determination of the mechanical behavior of the welded connection is very challenging. In this study, a hierarchical multiscale approach is presented and applied in order to characterize the material behavior of the Heat Affected Zone (HAZ) in welded connections. First, the metallurgical constituents in particular areas of HAZ have been identified experimentally. Next, several representative volume elements (RVEs) have been constructed using microscopic images. Then employing the computational homogenization methods, the stress–strain curves representing the macroscopic material behavior in respective points of the HAZ have been calculated. Meanwhile, some miniature tensile tests have been performed to experimentally identify the stress–strain behavior in the HAZ. Finally, the numerically calculated stress–strain curves are compared with the measured experimental data and they show a good agreement. The comparison of the results depicts that the proposed multiscale approach is suitable for the characterization of the material properties in welded connections or in general for materials with specially varying microstructures. [ABSTRACT FROM AUTHOR]

Earthquake causes wide and severe damage to building structures, due to not just the great ground motion but also secondary actions, such as impact, blast or fire, occurring after earthquake. The extreme combined loading scenario should be considered for safety of buildings and lives. Taking fire for example, the combined load can be considered as an event in which the structures are first partially damaged under an earthquake and then attacked by fire. In order to investigate the post-earthquake loading scenario, it is important to assess the partial damage caused by earthquake on different components of structures. The behavior of welded steel I-beam to hollow square tubular columns is investigated herein. A detailed experimental study is presented in which two groups of unstiffened welded steel connections, with the same configurations, subjected to static and cyclic loading are considered. The flexibility and strength of the connections are measured, while the damage phenomena and failure modes are explored during the tests. The connection damage is found to be a cumulative fracture developing process which leads to significant gradual degradation of the mechanical properties of the connection. The quantificational evaluations of the cyclic loading induced damage are also carried out to investigate the connection damage level according to different loading intensities. A finite element modeling numerical study is also carried out to validate the experimental results and a good agreement is achieved. The test results and FE modeling provide a benchmark data for the unstiffened welded connections and can be used for further investigations of the connections subjected to combined actions such as post-earthquake fire. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an experimental investigation about the shear lag effects of tension steel members with welded connections. In total twenty tests were conducted, including twelve on single angles and eight on single tees. Various weld arrangements were considered as test parameters for the angle specimens which were connected by their short legs. For the tees, the influences of weld length and flange-to-web width ratio were studied. The test results showed that, the test efficiency, which is defined as the ratio of the ultimate capacity to the calculated tensile capacity of the gross section, can be increased when a balanced weld arrangement instead of an unbalanced one was employed for the angle specimens. For the tee specimens, the test efficiency was not sensitive to the weld length. In addition, increasing the flange-to-web width ratio could increase the test efficiency of the tees, although the improvement was not significant. Subsequently, design specifications for shear lag were examined, and the test-to-predicted ratios were presented. For more extensive comparisons, the ratios from an earlier investigation undertaken by the authors and co-workers and those from other researchers were also included for discussion. Finally, with the available database, reliability studies were undertaken to examine the resistance factors used in the current codes for predicting the ultimate tensile capacity of single angles and tee sections, and accordingly, new design recommendations are proposed. [Copyright &y& Elsevier]

In order to investigate the cyclic responses of high strength structural steel and welded effect on base metal under large inelastic strains induced by earthquakes, 27 coupons of Q460C steel and welded connection were tested subjected to monotonic and cyclic loading with various patterns. The typical behaviors were compared and discussed including monotonic properties, hysteretic behaviors, failure modes and cyclic constitutive characteristics. The monotonic and cyclic behaviors of steels with different yield strengths were also compared. Base on the test results, parameters of this high strength steel material and welded connection for a cyclic model combining isotropic and kinematic hardening were calibrated, which can be incorporated into numerical models of structures in ABAQUS. In addition, the parameters of a constitutive model for beam element analysis were also established and the model was further formulated into numerical analysis as a user defined material in ABAQUS. The analysis results revealed that the cyclic accumulation significantly affected the ductility of steel material and welded connection, comparing with monotonic behaviors. The welded connection coupons displayed greater levels of cyclic hardening than all the base metals, however, welding process made undesirable impacts on ductility of steel structures. [ABSTRACT FROM AUTHOR]

Im Stahlbau gibt es einen Trend zu zunehmend schlankeren und leichten Konstruktionen aus Baustählen mit höherer Festigkeit (Streckgrenze ReH > 355 N/mm2). In den letzten Jahren wurden hierzu moderne Stähle entwickelt, die neben einer hohen Festigkeit gute Schweißeigenschaften und eine hohe Zähigkeit besitzen. Trotz der guten Schweißeigenschaften ist die normative Tragfähigkeit insbesondere von Kehlnahtverbindungen dieser Stähle gering. In diesem Beitrag werden experimentelle und numerische Untersuchungen zur Tragfähigkeit von Kehlnahtverbindungen höherfester Baustähle vorgestellt. Als Ergebnis wird die Tragfähigkeit dieser Kehlnahtverbindungen bestimmt und ein erweitertes Bemessungsmodell zur Bestimmung der Tragfähigkeit von Kehlnahtverbindungen höherfester Baustähle S460 und S690 unter Berücksichtigung des Schweißzusatzwerkstoffs vorgestellt. Load bearing capacity of fillet welded connections of high strength steel. In recent years a trend towards an increasing number of slim and lightweight steel constructions using high-strength steels can be observed (yield strength ReH > 355 N/mm2). Therefore, modern high-strength steels have been developed, which comprise aside a high strength, good welding characteristics and a high ductility. Despite the good welding characteristics there is a low normative load-bearing capacity of fillet welded joints of high-strength steels. In this article experimental and numerical investigations on the load-bearing capacity of fillet welds are presented. As a result the load bearing capacity of these fillet welded connections is determined. An expanded design model for high-strength steels S460 and S690 is presented, which considers both, the strength of the base and the filler metal. [ABSTRACT FROM AUTHOR]

Abstract: Major earthquakes in urban areas have often been followed by significant fires that cause extensive damage to property. Therefore, a seismic-induced fire is a scenario that should be addressed properly in performance-based engineering. In this paper, numerical and experimental results of welded steel–concrete composite full-strength beam-to-column joints under post-earthquake fires are described. This was part of a European project aimed at developing fundamental data and prequalification design guidelines of ductile and fire-resistant composite beam-to-column joints with concrete-filled tubes. In detail, seismic and fire analyses were used to design moment-resisting frames endowed with the proposed joint typology. A total of six specimens were designed and subjected to both monotonic and cyclic lateral loads. The specimens were subassemblages of beam-to-column joints, and performed well. Since the scope of the project was to promote joint typologies able to survive a seismic-induced fire, some specimens were pre-damaged before being subjected to fire loadings by imposing monotonic loads equivalent to damage levels induced by seismic loadings. Thus, after fire testing, valuable information about the performance of the proposed joint typology was obtained, and the adequacy of the concurrent seismic and fire design was demonstrated. [Copyright &y& Elsevier]

This paper presents an overview of the development of fatigue design provisions and detailing for steel bridge structures. The historical performance of welded steel bridges in the USA is reviewed with focus on fatigue cracking at cover plate and similar attachment details, as well as distortion induced cracking at web gaps. The role of materials including modern high performance steels (HPS) is reviewed. Variable amplitude loading is also examined and compared with current design of steel bridges for fatigue resistance. Also examined are methods to improve and retrofit fatigue sensitive details, including modern post-weld enhancement by ultrasonic impact treatment (UIT). Orthotropic steel decks are reviewed based on the results of two full-scale prototype laboratory fatigue tests which identified the complex behaviour that occurs at fatigue sensitive details and were verified by field measurements on field installations. The merits of thin epoxy concrete wearing surfaces is examined in terms of the critical role the deck plate thickness has on the epoxy concrete fatigue resistance and durability. The orthotropic deck is the only bridge deck system likely to provide a 100 year life when the deck plate thickness equals or exceeds 16 mm. [ABSTRACT FROM AUTHOR]

T-joint connections are used extensively in industry as parts of machine components and structures. The T-joint connection is typically constructed through the welding of its tubular members, with significant stress and strain concentrations occurring at the toe of the weld under loadings. In this paper, a welded T-joint connection of square hollow-section (SHS) tubes subjected to a multi-axial state of stress is examined both numerically and experimentally. The hot spot strains and stresses in the connection are determined through a detailed finite element (FE) analysis of the joint. The weld geometry is accurately modelled using FE. To model the weld, several full-scale welded T-joints were cut at the connection to obtain the size and depth of penetration of the weld. For the experimental study, a test rig with a hydraulic actuator capable of applying both static and cyclic loadings is designed and used. Strain gauges are installed at several locations on the joint to validate the FE model. The verified FE model is then used to study the through-the-thickness stress distributions of the tubes. It is shown that the membrane stresses which occur at the mid-surface of the tubes remain similar regardless of the weld geometry. The weld geometry only affects the bending stresses. It is also shown that the stress concentrations are highly localized at the vicinity of the weld toe. At a distance of about half of the weld thickness from the weld toe, the effect of the weld geometry on the bending stresses becomes insignificant as well. To reduce the stress concentrations at the T-joint, plate reinforcements are used in a number of different arrangements and dimensions to increase the load-carrying capacity of the connection. [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. [ABSTRACT FROM AUTHOR]

The existing fatigue design S–N curve for SHS-to-plate T-joints under in-plane bending is given in the Canadian Standard, CAN/CSA-S16.1-M89, in terms of the classification method. That S–N curve is however based on the class of longitudinally loaded plates with welded non-load carrying attachments, which are different from the SHS-to-plate T-joints. The increased use of welded thin-walled (t<4 mm) tubular joints in the road transport and agricultural industry for applications such as lighting poles, traffic sign supports, truck trailers, swing ploughs, haymakers and linkage graders, means that there is a need to develop fatigue design curves for tubular joints where the tube wall thickness is less than 4 mm. This paper aims to determine fatigue design curves for SHS-to-plate T-joints where the thin-walled tubes have a thickness of less than 4 mm. Tube-to-plate T-joints, made up by welding a square hollow section tube to a plate, are tested under fatigue loading. Constant stress-amplitude cyclic loading is applied to these connections as in-plane bending load. Stress concentration factors (SCFs) have been determined from strain distributions obtained using strain gauge measurements. Analysis of the fatigue test data using least squares method is carried out to determine the design curves of the tube-to-plate T-joints under in-plane bending, for both the classification method and the hot spot stress method. A class of 44 is recommended for the classification method. An Sr.hs–N curve is proposed, with a recommended SCF of 2.0 for the hot spot stress method. [Copyright &y& Elsevier]