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In the study, based on the non-linear calculation methods used to determine the seismic performance of structures in TBSC 2018, the stress-strain, moment-curvature, displacement capacity, plastic rotation limits, and deformation-based damage limit values of the reinforced concrete circular cross-section columns were calculated and compared according to different design parameters. The studied effects of the design parameters on the non-linear relation of reinforced concrete columns were also evaluated in terms of strength, curvature, and displacement ductility of the sections. All design parameters affecting the non-linear behavior and deformation limits of the reinforced concrete circular cross-section columns were taken into account. Deformation demands for reinforced concrete structural members are essential for detecting element damage. Based on TBSC (2018), non-linear relationships of reinforced concrete columns were obtained in order to calculate plastic hinge properties and deformation limits. For the Limited Damage, Controlled Damage, and Collapse Prevention performance levels defined for the structural elements in TBSC 2018, plastic rotation and deformation limit values were obtained according to the characteristic values calculated from the non-linear analyzes of reinforced concrete circular columns. For column models, damage limits and damage zones calculated based on TBSC 2018 were shown on the visually obtained moment-curvature relationships. Depending on the upper deformation limit values derived, cross-sectional deformation damage levels were determined and evaluated using the moment-curvature relationships. The variation of the nonlinear behavior of column models by design parameters and deformation-based damage limits were examined both analytically and visually. The deformation limits remain in a safer direction as a result of increasing longitudinal and spiral reinforcement ratios for the reinforced concrete circular columns. [ABSTRACT FROM AUTHOR]

• Strain limit is investigated to consider the fracture in the tubular joints. • Tensile loaded longitudinal plate to high strength tubular X joints are tested. • Fine meshing is required to achieve the convergence of strain in the FE analysis. • The proposed 2.5 % strain limit facilitates economical design for flexible joints. • Whereas, it becomes more stringent for joints susceptible to early rupture. Applying high strength steels to tubular joints can increase the propensity to fracture failure due to their lower ductility. However, to simulate the fracture behavior in the finite element (FE) analysis, sophisticated material damage model with rigorous fracture criteria should be incorporated. Recently, the latest draft of ISO 14346 has advocated the use of 5 % strain limit in FE analysis of tubular joints. The strain limit concept has been further developed by the authors' previous work, for its use as a practical alternative to the complicated material damage model. Specifically, a lowered limit of 2.5 % was recommended for longitudinal plate to circular hollow section (CHS) joints subjected to in-plane bending. This study extends the strain limit investigation to longitudinal plate to tubular X joints subjected to tensile loads. An experimental program is first presented which included both CHS and rectangular hollow section (RHS) chord members fabricated from two high strength steels with nominal yield stresses of 460 MPa and 700 MPa. Based on test-validated supplemental numerical analyses, it is suggested that the joint load corresponding to 2.5 % strain limit can be taken as the load-bearing capacity to suppress occurrence of a fracture failure for the tubular joint configurations considered in this study. [ABSTRACT FROM AUTHOR]

To build the design method of new energy-saving block & invisible multi-ribbed frame composite walls developed by our research team, taking window and door openings of various dimensions as the parameters of the experimental study, six 1/2 scaled energy-saving block & invisible multi-ribbed frame composite wall specimens were made. The cyclic loading tests on specimens were performed. The failure characteristic, hysteretic behavior, ductility, energy dissipation capacity and stiffness degradation were investigated. The test results show that as window and door openings increase, integrity of the wall weaken, causing bearing capacity of the wall to decline, degrading the stiffness more slowly after yield, the limit displacement to be bigger, ductility to be good, energy dissipation capacity increased. The above results indicated that to rigid walls, when the bearing capacity does not decrease obviously, with appropriated opening, the seismic behavior of the wall can be greatly improved. Based on the analysis and comparison of test data, deformation limit of the wall under different performance objectives are determined, which provides the basis for the establishment of design method of the wall. [ABSTRACT FROM AUTHOR]

This article proposes a new approach to define serviceability deformation limits for the structural design of segmental tunnels built in soft soil. In modern design codes, the structural design of segmental tunnels has been established considering only the ultimate strength of linings; therefore, the used limits for tunnel deformation and distortion were determined empirically. A parametric analysis was performed by means of finite element models in MIDAS FEA© software. The main variables were the diameter of the tunnel, number of segment joints, soil pressure distribution and slenderness ratio. In order to establish the deformation limits, a serviceability limit state was defined. The new approach for defining serviceability limit considered the deformations, crack width and segment joint behavior. The serviceability limits were compared with the deformation limits commonly used in practice. The results indicated that the serviceability limits of segmental tunnels depend on two parameters: slenderness ratio (modified up to 97%) and soil pressure distribution (modified up to 164%). Thus, empirical recommendations are not suitable for every case. The application of serviceability limits showed differences higher than 60%, in contrast with the traditional recommendations for deformation. This can influence the structural design of segmental tunnels, built in soft soils. [ABSTRACT FROM AUTHOR]

This study aims to investigate the strength reduction effect of chord axial stresses on the static strength of cracked tubular T/Y-joints under out-of-plane or in-plane bending moment using finite element analyses. The cracked tubular T/Y-joints contain a semi-elliptical surface crack at the weld toe of the chord. The benchmark analysis compares the numerically computed load–deformation response of a cracked X-joint fabricated from high-strength steel reported in a recent experimental study. This investigation quantifies the strength reduction caused by the chord axial stresses using the chord stress function Qcf. The parametric study covers the effect caused by the variation in both the local crack geometries, that is, the crack area and the global joint dimensions on the computed chord stress function. Finally, we give recommendations to calculate the strength reduction of the investigated cracked joints due to the chord axial stresses. [ABSTRACT FROM AUTHOR]

The paper studies numerically the behaviour of a beam-to-column joint between a hat-shaped steel beam (WQ-beam) and a concrete-filled composite column in a slim floor steel-concrete composite frame. 3D continuum elements are used in the discretization of the joint with contact surfaces between the components. Both material and geometrical nonlinearities are included. The computational results are verified by comparing them to experimental results. The verified model is applied to study the development of the load-transfer mechanisms in the joint. The load carrying capacity of the joint is categorized on the base of five parameters: the flange width, the web height, the wall thickness and the corners of the console, and the gap between the WQ-beam endplate and the column face. In addition, a criterion to evaluate the limit load of the joint is proposed. The design capacity of the joints from the proposed criterion is compared with the values calculated according to both other criteria and design code. It can be concluded that the proposed criterion is suitable for estimating the resistance of the studied joint. [ABSTRACT FROM AUTHOR]

The deformation of fluid particles is usually directly related to various Lagrangian phenomena in fluids. We show typical analytical expressions under external strain rate fields by defining the deformation limit for small fluid particles, aiming at providing analytical tools for supporting future investigations on the Lagrangian phenomena in fluids. In particular, when particles are driven by a constant strain rate which is greater or equal to the rotation rate, the orientation of fluid elements aligns with strain tensor in short times and then decouples with them in long times, while the fluid particles are flattened in most cases, which are similar to previous observations in turbulent flows. This supports the simplifications in previous Lagrangian models (e.g., Fang et al., 2015 [20] ), where the strain rates were assumed to be locally homogeneous. [ABSTRACT FROM AUTHOR]

Steel reinforced concrete (SRC) columns are widely used in high-rise buildings of earthquake prone regions. Fewer studies have been carried out on the estimation method of deformation capacity for flexural-controlled SRC columns, which is vital for the seismic evaluation. In the paper, 110 SRC columns with a failure dominated by flexural effect were collected from literatures to establish a test database firstly. The data of yield rotation and ultimate rotation of column specimens were extracted from the backbone curves. Then, an analytical method to predict the yield rotation was developed based on the classical model for flexural-dominated RC columns, showing a reasonable accuracy. The influences of shear-span ratio, axial load, steel shape ratio, transverse reinforcement, total longitudinal bar ratio and concrete compressive strength on the ultimate rotation were discussed with the test results of database specimens. Based on the parameter study, an empirical equation, related to shear-span ratio, axial compression ratio and concrete compression strength, was proposed via the regression analysis. In addition, the machine-learning methods, including the artificial neural network and support vector machine, were adopted to evaluate the accuracy of proposed empirical equation further. Finally, some useful recommendations were provided for the seismic evaluation of SRC columns. • 110 specimens were collected to establish a test database, which is a valuable source for the seismic evaluation of flexural-dominated SRC columns. • The theoretical model and empirical expression were provided respectively to predict the yield and ultimate rotation, showing an acceptable accuracy. • The limit values of rotation of SRC columns for a quick evaluation were proposed. [ABSTRACT FROM AUTHOR]

This study reports a deformation limit for the initiation of ductile fracture failure in fatigue-cracked circular hollow section (CHS) X- and K-joints subjected to brace axial tension. The proposed approach sets the deformation limit as the numerically computed crack driving force in a fatigue crack at the hot-spot location in the tubular joint reaches the material fracture toughness measured from standard fracture specimens. The calibration of the numerical procedure predicates on reported numerical computations on the crack driving force and previously published verification study against large-scale CHS X-joints with fatigue generated surface cracks. The development of the deformation limit includes a normalization procedure, which covers a wide range of the geometric parameters and material toughness levels. The lower-bound deformation limits thus developed follow a linear relationship with respect to the crack-depth ratio for both X- and K-joints. Comparison of the predicated deformation limit against experimental on cracked tubular X- and K-joints demonstrates the conservative nature of the proposed deformation limit. The proposed deformation limit, when extrapolated to a zero crack depth, provides an estimate on the deformation limits for intact X- and K-joints under brace axial loads. [ABSTRACT FROM AUTHOR]

In this study, existing deformation limits are first re-examined to investigate if they can be rationally extended to high strength steel circular hollow section (CHS) joints that are subjected to in-plane bending (IPB) moment. It is pointed out that existing deformation limits, which have been developed and validated primarily for mild steel joints, need to be modified when high strength steels are involved. By noting that the ductility of IPB-loaded joints can be significantly reduced with the use of high strength steel, a new deformation limit is proposed which allows less deformation to less ductile high strength steel joints. The deformation limit, proposed in terms of joint rotation angle, is validated both numerically and experimentally. In addition, a recently proposed strain limit criterion is also discussed. To provide a guide for obtaining converged strain from finite element (FE) analysis, mesh sensitivity study is comprehensively conducted. It is shown that the element size required for the convergence of strain is substantially smaller than that required for obtaining satisfactory global response such as joint load-deformation relationship. By applying a systematic FE modeling strategy, numerical investigation is made to check the feasibility of the 5% strain limit criterion which has recently been advocated by the revised draft of ISO 14346. While the limiting principal strain of 5% is shown to be reasonable for CHS-to-CHS joints loaded by IPB, for longitudinal branch plate-to-CHS joints, a lower limiting strain appears more appropriate. • Proposed a new deformation limit criterion for high strength steel circular hollow section (CHS) joints that are subjected to in-plane bending (IPB). • Examined the feasibility of the 5% strain limit which has recently been advocated by several researchers. • Proposed to modify the limiting principal strain for IPB-loaded longitudinal plate-to-CHS joints. • Validated newly suggested deformation and strain limits using experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a study on the behaviour of welded "T" joints between RHS sections under brace axial loading. A finite element model was developed to investigate the influence of some geometrical variables on the joint's response. The brace load (always in tension) was incremented up to joint failure, while the chord was kept unloaded. In the companion paper (part II) a complementary study including chord axial loading is presented. The force-displacement curves corresponding to the different geometries are analyzed and compared, focusing on the failure loads and elastic stiffness. Different failure criteria are discussed and applied to the present curves and a comparison of the numerical results with the Eurocode 3 provisions is presented and discussed. [ABSTRACT FROM AUTHOR]

This paper deals with the behaviour of welded "T" joints between RHS sections submitted to tension brace loading combined with chord axial loading. In the companion paper (part I) a finite element model and a study without axial load in the chord, focusing on the joint behaviour as a function of the significant geometrical variables, were presented. In this part II paper, tension loading on the brace is incremented up to the joint failure, but is combined with different chord load levels in tension or compression, that are kept constant for each case. The same geometries and geometric variables as in the companion paper are used, and therefore the influence of these features together with the chord load level (in tension or compression) on the connection's response is evaluated. The force-displacement curves from the different geometries and chord load levels are analysed and compared, with a special attention on the influence of the chord load on the joint resistance and stiffness. Finally, a comparison of the numerical results with the Eurocode 3 (2005) and the newer ISO 14346 (2013) provisions is presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper concerns about deformation limits of circular corrugated unidirectional reinforced composites for bending dominated applications. Hence, a two-dimensional analytical stress function approach is used which takes through-thickness normal stresses into account. Hereby, the possible failure modes, namely fibre fracture and layer delamination, of unidirectional laminated circular corrugated sheets are predicted. Additionally, the accurate representative bending stiffness in corrugated-direction is extracted by using an energy approach. The influence of corrugation geometric parameters on deformation limits and stiffness is experimentally as well as theoretically investigated. For this reason, large curvature validation experiments of four different corrugation types are conducted by means of a specially constructed bending device. Finally, bending charts are provided facilitating the choice of an appropriate corrugation geometry during a preliminary design phase. [Copyright &y& Elsevier]

Die Bemessung von geschweißten Kreishohlprofil (KHP)-Fachwerkknoten mit Knotenblechen unter Zugbeanspruchung ist in DIN EN 1993-1-8: 2010-12 geregelt. Im Rahmen einer Diplomarbeit wurde der Einfluss maßgebender geometrischer Parameter auf die Tragfähigkeit dieses Knotentyps experimentell und numerisch untersucht. Die Ergebnisse bestätigen zum einen erwartungsgemäß die Normnachweise, zum anderen werden der Gültigkeitsbereich der Bemessungsformeln sowie die zugrundeliegenden Versagensmechanismen veranschaulicht. Design of plate to circular hollow section joints under tensile loads. The design of welded plate to circular hollow section (CHS)-joints under tension is standardised according to DIN EN 1993-1-8: 2010-12. By means of experimental and numerical investigations the influence of the most important parameters on the bearing capacity of this type of joint was investigated within the framework of a diploma thesis. The findings of these investigations confirm the existing design recommendations and illustrate the range of validity and occurring failure mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Concrete filled steel tubular (CFST) members are subjected to local bearing forces in a large number of truss and lattice structures. Previous research has focused on rectangular CFST members under such loading condition. There is a lack of understanding on circular CFST members subjected to local bearing force. This paper intends to fill the knowledge gap in this area. A series of tests were conducted on circular CFST, unfilled circular hollow section (CHS) steel tube and plain concrete specimens loaded with local bearing force. The load was applied either perpendicularly to the member or at an angle of 45°. A deformation limit was adopted to define the ultimate strength of the specimen since the load verse deformation curve exhibits a ductile behavior. The effects of important parameters were investigated based on the test results. Finally, design formulae were developed to predict the ultimate strength of circular CFST members under local bearing forces. [Copyright &y& Elsevier]

Abstract: This work determines the maximal possible deformations of a corrugated sheet where the corrugation pattern consists of two circular segments. The influence of the lay-up of cross-ply laminates and the influence of the geometry is investigated. The calculations are based on considerations of layerwise strains that are calculated with the help of an analytical singly-curved shell model. For the evaluation of the influence of geometric nonlinearities according finite element simulations are performed and compared to the linear strain limit calculations. The influence of scalable geometry parameters is also investigated. [Copyright &y& Elsevier]

Welded thin-walled T-joints made up of circular hollow section (CHS) braces and square hollow section (SHS) chords were tested under static in-plane bending load. The hollow sections are cold-formed and have thicknesses less than 4 mm. The CHS-SHS T-joints are used in building the undercarriages and structural supports of equipment and structural systems used in the road transport and agricultural industries. Failure in the CHS-SHS T-joints was observed to occur as a result of chord-face yielding. Chord cracking was also observed after large deformations, resulting in a peak load being attained in these joints. There is no design formula in the existing CIDECT design guides, IIW static recommendation and Eurocode 3 for CHS-SHS T-joints under in-plane bending. In this paper, load versus chord flange indentation graphs, for the CHS-SHS T-joints are used to determine the deformation limit that defines the ultimate strength of the joints. The deformed shape of the chord observed from experimental tests is used to create a yield line model. The weld size and the rounded corners of the SHS chord are considered in the model. A formula is derived, for the ultimate strength of the CHS brace and SHS chord vierendeel connections based on a plastic mechanism analysis using yield line theory. There is a reasonably good agreement between the ultimate strength predicted using this formula and that determined experimentally. [Copyright &y& Elsevier]

This paper presents a new approach in the definition of joint strength for thick-walled circular hollow section (CHS) X-joint subjected to brace axial loading. This is based on the plastic load approach for limit analysis of pressure vessel components proposed by Gerdeen. A consistent coefficient λ associated with the plastic load approach has been determined, and the corresponding joint strength for X-joint under brace axial loads is found to correlate closely with the results obtained using Lu’s deformation limit. The strength prediction for thick-walled CHS X-joint using the present approach is found to be in good agreement with design recommendations by ISO and CIDECT for joints with chord radius-to-thickness ratio γ>7. For X-joints with γ<7, significant difference in results is observed especially with the ISO recommendation for joints with brace–chord diameter ratio β≥0.7. [Copyright &y& Elsevier]

Summary: L‐shaped reinforced concrete (RC) shear walls have been studied over the years due to their importance in tall buildings. However, few investigations focus on the progression of damage with increasing deformation, especially on the deformation limits for different performance levels. Hence, an experiment was conducted on 12 L‐shaped RC shear walls subjected to axial and cyclic lateral loadings. The variables were shear span ratio, axial load ratio, and longitudinal boundary element reinforcement ratio. The seismic performances were analyzed and discussed in terms of crack pattern, failure mode, hysteretic response, backbone envelope, and ductility factor. On the basis of the three key performance state points on the backbone envelope, a method was proposed to assess the seismic performances of L‐shaped RC shear walls using six distinct performance levels. These performance levels were provided with relevant deformation limits and proved to be in good agreement with six significative damage states. Further, comparative analysis showed that the deformation limits derived from experiments were significantly underestimated by current codes and methods available in literature, because these prediction models were mainly developed for rectangular shear walls. Considering the contribution of flange, a modification of Cui's method yields good estimations of deformation limits for L‐shaped RC shear walls. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a study on the behaviour of welded "T" joints between RHS sections under brace axial loading. A finite element model was developed to investigate the influence of some geometrical variables on the joint's response. The brace load (always in tension) was incremented up to joint failure, while the chord was kept unloaded. In the companion paper (part II) a complementary study including chord axial loading is presented. The force-displacement curves corresponding to the different geometries are analyzed and compared, focusing on the failure loads and elastic stiffness. Different failure criteria are discussed and applied to the present curves and a comparison of the numerical results with the Eurocode 3 provisions is presented and discussed.

Abstract This paper deals with the behaviour of welded "T" joints between RHS sections submitted to tension brace loading combined with chord axial loading. In the companion paper (part I) a finite element model and a study without axial load in the chord, focusing on the joint behaviour as a function of the significant geometrical variables, were presented. In this part II paper, tension loading on the brace is incremented up to the joint failure, but is combined with different chord load levels in tension or compression, that are kept constant for each case. The same geometries and geometric variables as in the companion paper are used, and therefore the influence of these features together with the chord load level (in tension or compression) on the connection's response is evaluated. The force-displacement curves from the different geometries and chord load levels are analysed and compared, with a special attention on the influence of the chord load on the joint resistance and stiffness. Finally, a comparison of the numerical results with the (Eurocode 3, 2005) and the newer (ISO 14346, 2013) provisions is presented and discussed.