Strong Axis Research Articles

Parameter priority of stub and slender rectangular CFDST columns subjected to eccentric loading

AbstractThis paper evaluates the behavior and ultimate load that previously identified parameters have on stub and long slender rectangular concrete‐filled double skin tubular (CFDST) columns subjected to eccentric loading. The investigation was performed using FE models that were calibrated and validated to eccentrically loaded experimental responses. A parametric investigation was thereafter conducted on seven parameters to establish the parameter priority on stub and long slender rectangular CFDST columns subjected to eccentric loading. The strong and weak axis minimally affects the parameter priority for a particular slenderness ratio. The investigation revealed that the parameter priority is different for stub and long slender columns. For load eccentricity, lateral curvature, steel strength, outer tube thickness, concrete strength, fixity, and inner tube thickness affect the ultimate load by 60.2%, 14.0%, 8.1%, 8.0%, 4.3%, 3.4%, and 2.1%, respectively, when compared to all parameters. For long slender columns, the load eccentricity, fixity, outer tube thickness steel strength, lateral curvature, concrete strength, and inner tube thickness affect the ultimate load by 70.7%, 10.6%, 6.2% 5.9%, 2.4%, 2.3%, and 2.0%, respectively, when compared to all parameters.

Probabilistic modelling of steel column response to far-field detonations

Due to the deficiency of current design guidelines for blast loadings on steel structures, this research develops probabilistic models for steel wide-flange columns under axial and far-field blast loading on both their weak and strong axes. A total of 160 finite element (FE) simulations were conducted using ANSYS LS-DYNA, with columns subjected to different Axial Load Ratios (ALRs) and blast impulses. Validation against two experimental tests showed a strong correlation in displacement plots, with a material model accounting for strain rate effects. Probabilistic models for predicting maximum displacement and residual axial capacity were formulated using Bayesian inference and posterior statistics. These models were developed by incorporating dimensionless physics-based explanatory functions. The slenderness ratio of the column was identified as the most influential. The models account for uncertainties such as material and geometric properties, as well as strain rate effects. Graphical plots between the ALR and Damage Index (DI) were examined to assess the column's damage level. Furthermore, the probability of failure (fragility) of four columns for similar blast impulse was assessed w.r.t DI. These models along with ALR vs DI plots will be useful tools to know the level of building occupancy and retrofitting options.

Mechanical performance and analytical model of BC joint with assembly error and load-carrying capacity of its single-layer dome based on numerical analysis

The mechanical performance of prefabricated single-layer dome is significantly affected by assembly errors of BC joint, which are inevitable in practical engineering due to manufacture and installation, etc. In this study, mechanical performance of BC joint with assembly error is comprehensively investigated. Finite element model of bolt-column (BC) joint is firstly established and validated based on previous research. Then bending behaviors about the strong axis and mechanical performance of BC joint with assembly error under eccentric force are comprehensively investigated. Moment-rotation curves, load-displacement curves and failure modes of the joint under other static loading conditions are also obtained. Subsequently, an analytical model for the strong axis moment-rotation curves of BC joints with assembly error is proposed. Ultimately, load-carrying capacity and failure mode of the imperfect semi-rigid single-layer dome are determined. A comprehensive investigation is conducted on the mechanical behaviors of dome that incorporates assembly error of BC joints. The research demonstrates that (I) there are two stages, slip stage and contact stage, appearing in the strong axis bending moment-rotation curves; (II) under eccentric force, joint with assembly error demonstrates two different mechanical behaviors as eccentric distance increasing, that is small eccentric behavior and large eccentric behavior; (III) the static force performance of BC joint shows significant sensibility to assembly error, except for axial tension performance; (IV) the proposed analytical model can accurately capture the characteristics of strong axis moment-rotation curve; (V) assembly error has a non-negligible effect on the mechanical performance of single-layer dome; (VI) single kind of joint stiffness affects the limit load of dome little. However, the coupling effect of all kinds of stiffness can not be neglected.

Analisis Pengaruh Penempatan Shearwall Pada Gedung Hotel Shafira

Hotel Shafira is a flat-shaped building with 10 floors, 12 meters wide and 72 meters long. These structures are prone to significant horizontal irregularities, reducing the overall efficiency of the building. The irregularity is partly due to the uneven distribution of the mass, as seen from the difference in the span of the portal between the back and front of the building which produces large cavities. Analysis with the ETABS program revealed that the eccentricity between the center of self and the center of mass reached 5 meters in the direction of the strong axis. This study overcomes the uneven load distribution by repositioning the shearwall through a trial and error approach, reducing eccentricity from 4 meters to 1.3 meters. This change not only increases the building's capacity, but also reduces the need for reclamation by 13.9% and shows the results of the pushover analysis in the Immediate Occupancy category. The placement of shearwalls has a significant influence on the capacity and stability of the building structure.

Design Aid for Selection of H-Piles

This paper presents design aids for the selection of HP sections for driven piles according to the American Institute of Steel Construction Specification 360-22 “Specification of Structural Steel Buildings.” Graphical aids for the design selection of W-shapes have been provided by Keil (2000), Hosur and Augustine (2007), and Sa’Adat and Banan (2014). However, to date there are no aids available for the design of H-Piles. This work seeks to eliminate that gap by providing the data necessary to create interaction diagrams for combined stresses including compression, bending, and tension in both the strong and weak axes for 50 ksi grade steel HP sections.

Specialized Pulmonary Vascular Cells in Development and Disease.

Endothelial cells (ECs) develop organ-specific gene expression and function in response to signals from the surrounding tissue. In turn, ECs can affect organ development and morphogenesis and promote or hinder disease response. In the lung, ECs play an essential role in gas exchange with the external environment, requiring both a close physical connection and a strong axis of communication with alveolar epithelial cells. A complete picture of the composition of the pulmonary endothelium is therefore critical for a full understanding of development, maintenance, and repair of the gas exchange interface. Defining the factors that control lung-specific EC specification, establish EC heterogeneity within the lung, and promote the differing contributions of EC subtypes to development, health, and disease will facilitate the development of much-needed regenerative therapies. This includes targeting therapeutics directly to ECs, developing pluripotent or primary cell-derived ECs to replace damaged or diseased vasculature, and vascularizing engineered tissues for transplant.

Frictional Axial Resistance of Clamped Split Pocket Mechanism Steel Structural Joint: An Experimental Study

The Clamped Split Pocket Mechanism (CSPM) prefabricated joint system was developed for a single-story steel instant house, designed to be compact and rapidly constructed without modifying the end of the beam and column element member. The CSPM bolted joint system was proposed as an optimal solution for post-disaster housing, especially after earthquakes. Despite its potential, the frictional tensile resistance behavior of the CSPM bolted joint system has not been previously studied, necessitating experimental investigation. This study examined the frictional tensile resistance behavior of the CSPM joint system by monitoring the effective friction coefficient under axial tension force. The experiments considered both the strong and weak axes of the joint and utilized two configuration types of specimens (L and T) with varying bolt pretensions of 2.5, 5, 7.5, and 10 kN. Results indicated that the effective friction coefficient of the CSPM bolted joint system ranged from 0.19 to 0.26, correlated to bolt pretension. Increased bolt pretension resulted in larger surface deformation of the split pocket, triggering a not uniform frictional tensile resistance across the steel surfaces of the split pocket joint. From this study, the achieved effective friction coefficients could guide the design of minimum pretension forces for clamps in prefabricated steel instant houses. Doi: 10.28991/CEJ-2024-010-09-07 Full Text: PDF

Effect of joint behaviors on the load-carrying capacity of single-layer reticulated dome

The majority of previous studies have primarily focused on the impact of nodal deviation or joint’s strong axis bending stiffness of semi-rigid single-layer reticulated shell, ignoring the effect of other kinds of joint stiffness and its interaction with joint size and nodal deviation. Therefore, the single-layer reticulated dome considering all kinds of joint stiffness and joint size is established initially. Subsequently, a comprehensive investigation is conducted to analyze the effect of all types of joint stiffness of improved bolt-column (IBC) joints, as well as joint size and nodl deviation, on the load-carrying capacity of dome. Finally, the coupling effect among these factors on the mechanical performance of dome is also determined. The main conclusions obtained are presented as follows: (I) the axial stiffness of the IBC joint significantly influences the load-carrying capacity of single-layer reticulated dome, resulting in an average decline ratio of 27 %; however, the other types of joint stiffness have a negligible impact, with an average effect of only 1 %. Moreover, the limit load of the dome considering practical stiffness of IBC joint can achieve the 61 % of that of rigid dome; (II) rigidly joined domes with nodal deviations of S/300, S/600, S/900, S/1200 and S/1500 exhibit decline ratios of 0.57, 0.47, 0.41, 0.37 and 0.34, respectively, in load-carrying capacity compared to perfect domes. Moreover, when considering the coupling effect of joint stiffness, joint size and nodal deviation on the load-carrying capacity of the domes, these nodal deviations affect the capacity by 0.65, 0.57, 0.52, 0.49 and 0.46.

Local–overall buckling behavior of corroded intermediate compression-bending H-section steel columns

The primary aim of this paper is to assess the impact of corrosion damage on intermediate H-section steel columns subjected to combined compression and bending about the strong axis. The study conducted a comprehensive investigation into the corrosion-induced transition in the buckling behavior of steel columns through experimental and numerical analyses. Six H-section Q355 steel intermediate columns were designed, with five undergoing an artificial spray-accelerated corrosion process. The three-dimensional scanning technology was employed to quantify the general corrosion and corrosion pits. Eccentric compression tests were carried out on intermediate H-section steel columns to investigate the effect of the different corrosion levels on the failure mode and load-displacement curves, as well as to determine local buckling load based on the load-strain curves. The test results showed that the corrosion characteristic parameters of each cross-section of the steel column exhibited irregularity and variation in all locations, reflecting the heterogeneity of corrosion. The density of corrosion pits exhibited a decreasing trend with increased corrosion duration. Corrosion remarkably reduced both the ultimate carrying capacity and local buckling capacity, with the most severely corroded specimen exhibiting an average cross-sectional area loss rate of 37 %, resulting in a 43 % and 51 % reduction in ultimate load and buckling load compared to the uncorroded specimen. Furthermore, the corrosion features substantially influenced the failure mode, resulting in a transition from overall buckling to local buckling or local-global interaction buckling. A numerical methodology was developed to incorporate the actual surface morphology of corrosion, and the reliability of the modeling method was validated through comparison with experimental results, further revealing the failure mechanism of corroded intermediate H-section steel columns under compression and bending about the strong axis.

К вопросу расчета ИОЛ у пациентов с витреоретинальной патологией

Purpose. To estimate the probability of a change in the calculated IOL after microinvasive vitrectomy 25G in patients with operated macular rupture. Methods. A retrospective analysis of patients operated on for a macular rupture with a diameter from 400 microns to 1000 microns was performed. The exclusion criteria were: the axial length of the eye is less than 22.0 mm and more than 26.0 mm, recurrence of previously operated macular ruptures, the presence of concomitant ocular pathology that can affect the final postoperative result (macular degeneration, glaucoma, diabetic and postocclusive retinopathy), the presence of previously performed surgical interventions on the retina. The study involved 64 eyes, of which 34,37 % (22 eyes) with a native lens; 14,06 % (9 eyes) with artifacia before vitrectomy; 6,25 % (4 eyes) vitrectomy with cataract phacoemulsification and IOL implantation and 45,31 % (29 eyes) cataract phacoemulsification with IOL implantation was performed within 4–9 months after primary vitrectomy. These patients were the study group. The comparison parameters are best corrected visual acuity, K1, K2, Ave. K1, Ave. K2, Axis, Ave. K2-K1, axial length of the eye, Ave. axial length of the eye, as well as calculated models of IOL and implantable after vitreoretinal surgery. Results. The change in the optical strength of the IOL occurred in 44,82 %. The change in the IOL model is 37,93 %. The change in the optical strength and model of the IOL is 20,68 %. The change in the optical strength of the previous IOL model is 24,1%. The change in the strong axis of more than 20 ° with the previous IOL parameters is 13,79 %. Only in 27,58 % there were no changes in the calculation of IOL. Conclusion. An individual approach to the calculation and selection of intraocular lenses in patients with vitreoretinal pathology allows implantation of all types of IOLs with maximum patient satisfaction with the functional result. Keywords: biometric indicators, IOL, vitrectomy, cataract, phacoemulsification, keratometry

Simulating the hysteretic behaviour of thin-walled H-Section steel members using the geometrically exact beam theory

Based on Gonçalves's geometrically exact beam theory considering cross-section deformation, the warping and distortional deformation of thin-walled members are described in this paper by means of a combination of section deformation modes. By integrating with the J2 elastic‒plasticity theory for the steel, a numerical model is established for the hysteretic behaviour of thin-walled steel members. Four classes of H-section members are selected on account of the design codes, and the influence of section warping and distortion deformation modes on the calculation of the hysteretic behaviour of components with different section types is analysed. The crucial aspect lies in the bending hysteresis behaviour around the strong and weak axes of the cross-section for H-beam steel members subjected to typical thin-walled members with relatively large widths and thicknesses. Test results on the hysteretic behaviour of H-section steel members are compared with those calculated from the proposed model in terms of the hysteric behaviour of components, strength degradation, energy-dissipating capacity, etc. These findings validate the correctness and feasibility of the established non-linear analysis model for thin-walled members.

Effect of joint stiffness on the load-carrying capacity of single-layer cylindrical reticulated shell with improved bolt-column (IBC) joint

To enlarge the application of single-layer reticulated shells, this study proposes an innovative semi-rigid joint based on the original bolt-column (OBC) joint, referred to as the improved bolt-column (IBC) joint. The mechanical behavior of the IBC joint under the pure load and the coupling effect of bending and axial force is investigated using numerical tests. Then, the practical analytical model of IBC joint is developed based on a three-parameters power model and component method. Subsequently, a mechanical model considering joint stiffness is developed to establish semi-rigidly connected single-layer cylindrical reticulated shell. A total of 456 numerical models of shells are conducted to examine the impact of different kinds of joint stiffness on the load-carrying capacity of shells systematically. The results demonstrate that (i) weak axis bending stiffness and axial stiffness significantly affect the load-carrying capacity of shells by approximately 19 % and 14 % on average respectively; (ii) strong axis bending stiffness and torsional stiffness have relatively minor effects on the critical load of shells, with average decline ratios of only 5 % and 6 % respectively; (iii) out-of-plane shear stiffness and in-plane shear stiffness exhibit negligible impacts on the load-carrying capacity of shells, with an average effect not exceeding 1 %. Finally, the findings of numerical simulation considering all stiffness of IBC joint reveal insights into both varying laws of load-carrying capacity and failure modes for shells. It is observed that the mean critical load can reach up to 59 % of the one of rigidly-connected shells, which is significantly higher than those observed in shells with pinned joints.

Wire texture C-axis distribution of strontium ferrite/PA-12 extruded filament

The magnetic anisotropy of strontium ferrite (SF)/PA12 filament, a popular hard magnetic ferrimagnetic composites that is used for 3D-printing of permanent magnets, is studied by vibrating sample magnetometry. The studied filaments have a composition of SF/PA-12 thermoplastic composite with a 40% wt. ratio of SF. SF particles are non-spherical platelets with an average diameter of 1.3 um and a diameter to thickness ratio of 3. Filaments are produced by a twin-screw extruder and have a diameter of 1.5 mm. SEM images show that the SF particles are homogeneously distributed through the filament. VSM measurements on different parts of the filaments show that the outer part of the cylindrical filament has a higher anisotropy, and the core is mostly isotropic. This conclusion is consistent with computational work by others which suggest that particle alignment predominantly takes place near the walls of the extruder die where shear flow is maximum. Additional hysteresis curve measurement of the outer cylindrical part of the filament parallel to the r and ϕ directions indicates that the squareness of the hysteresis curve (S) is larger in the r-direction. This indicates that the outer surface of the filament has a strong easy axis in the r-direction. We conclude that the SF platelets line up parallel to the walls of the extrusion die.

Lateral Cyclic Behavior of SRC-RC Hybrid Columns Bending around Strong and Weak Axes: Effects of Embedment Lengths

Lateral Cyclic Behavior of SRC-RC Hybrid Columns Bending around Strong and Weak Axes: Effects of Embedment Lengths

Global and Local Geometrical Imperfections of Pultruded GFRP Profiles Based on a Modal Approach

The ultimate capacity of pultruded glass fibre reinforced polymer (pGFRP) profiles depends significantly on geometrical imperfections (GIs), given their sensitivity to buckling phenomena arising from both thin walls and low elastic moduli. However, GIs are not yet comprehensively addressed in design guidance. This paper proposes a new approach to characterize the initial GIs of pGFRP profiles based on a modal approach. Given the lack of comprehensive knowledge in this area, this study presents a highly accurate and robust methodology to measure GIs and dimensional deviations (DDs) in pGFRP profiles using a 3D contact coordinate measurement machine (CMM). The modal approach encompasses the measurement of dimensional parameters and a point cloud transformation that enables the assessment of GIs associated with pure buckling modes of pGFRP profiles. This procedure allows the quantification of three types of global GIs associated to (i) minor-axis (weak axis), (ii) major-axis (strong axis) bending, and (iii) twist. Additionally, the procedure also includes the assessment of local GIs, considering the wall (plate-like) imperfections. The separation of GIs into these four types (shape and amplitude) is of major relevance as its paves the way to the development of analytical design formulas for the strength prediction of pGFRP members. The approach described in this paper also serves two important purposes: (i) the statistical analysis of DDs and GIs of pGFRP members, and (ii) the identification of distinct shapes and amplitudes of GIs that form the basis for reliable design considerations of pGFRP members.

Elliptical concrete-filled FRP tubes with an embedded H-shaped steel under axial compression and cyclic lateral loading: Experimental study and modelling

Concrete-filled FRP tubes (CFFTs) have found increasing applications due to their superior ductility and remarkable corrosion resistance. In published literature, circular CFFTs and rectangular CFFTs have been investigated extensively, while there are relatively few studies on elliptical CFFTs. There is no research about elliptical CFFTs with an embedded H-shaped steel (i.e., HS-ECFFTs) under axial compression and cyclic lateral loading. Against this background, this paper investigated the seismic behaviour of HS-ECFFTs experimentally and numerically. Test results indicated that: (1) all HS-ECFFTs performed well with remarkable energy dissipation ability; (2) due to the effective FRP confinement, the local buckling of the H-shaped steel was prohibited; (3) the elliptical aspect ratio had limited influences on the ductility, the stiffness degradation and the energy dissipation; (4) the FRP thickness, after a certain threshold, showed beneficial but limited influences on the peak load, the stiffness degradation and the energy dissipation; (5) the HS-ECFFT specimen performed much better in terms of the peak load, the ductility, the stiffness degradation and the energy dissipation when it was bending around the strong axis. The proposed numerical model established on the OpenSees platform could generate reasonably accurate numerical results for all HS-ECFFTs.

Experimental and numerical investigation into hysteretic performance of orthogonal double corrugated steel plate shear wall

The orthogonal double corrugated steel plate shear wall (ODC-SPSW) is comprised of two identical corrugated plates that are arranged orthogonally and interconnected through high-strength bolts located at the valleys of the corrugations. Due to the strong axis of one corrugated plate coinciding with the weak axis of the other corrugated plate, the flexural rigidity of each plate can be significantly enhanced in its weak axis, thereby improving its shear resistance. The ODC-SPSW has itself boundary elements in two side and connected only with frame beams at its top and bottom, leading to conveniently moving within the frame. This paper presents experimental and numerical analyses of the shear resistance and the hysteretic performance of ODC-SPSW. Two experimental specimens subjected to cyclic loading were tested, and accordingly finite element (FE) simulations were conducted, both reaching an excellent agreement. Firstly, the test results of two ODC-SPSW specimens under cyclic loading are reported and analyzed. Second, FE models are established to simulate the hysteretic energy-dissipation performance of the test specimens. The numerical results from FE Model agree well with the test results, thus validating the FE models. Moreover, a parametric study was conducted using the validated FE model through changing various geometrical parameters, such as aspect ratio, bolt number and arrangement, corrugation depth, corrugated steel plate thickness, boundary element dimensions of the ODC-SPSWs. It is found that these parameters affect significantly the ultimate shear resistance and hysteretic energy-dissipation capacity of the ODC-SPSW. The numerical result obtained indicated the dimensions of the boundary elements have little effect on the shear resistance and hysteresis performance of the ODC-SPSWs. Finally, some design recommendations are concluded which can provide valuable references for the practical design of ODC-SPSWs.

Structural damage assessment of reinforced concrete buildings in Adıyaman after Kahramanmaraş (Türkiye) Earthquakes on 6 February 2023

Two destructive earthquakes (Mw: 7.7 and Mw: 7.6) occurred in Kahramanmaraş, Türkiye, on February 6, 2023. The epicenters of these two earthquakes were very close to each other (approximately 90 km apart), and both took place on the same day. The first earthquake occured at 04:17 local time with a magnitude of 7.7 and a depth of 8.6 km, while the second earthquake occurred at 13:24 local time with a magnitude of 7.6 and a depth of 7.0 km. These two earthquakes caused extensive damage, particularly in 11 provinces, with Adıyaman being one of the hardest-hit areas. Most buildings in Adıyaman were severely affected or collapsed as a result of the earthquakes. Reports indicate that over 35,000 buildings collapsed in the aftermath. Furthermore, between February 6, 2023, and May 6, 2023, more than 30,000 aftershocks, ranging in magnitude from 0.2 to 6.6, were recorded. In this study, earthquake damages in reinforced concrete buildings in Adıyaman province were evaluated. The causes of damages in reinforced concrete buildings were evaluated in terms of material quality, design of building and reinforcement details. Field observations are also provided, along with accompanying pictures. The earthquake regulations in Türkiye, established in 1975, 1998, 2007, and 2018, which apply to a significant portion of the country's buildings, are discussed. An evaluation was conducted to assess whether the damaged buildings complied with the earthquake regulations in Türkiye. Field observations revealed that the earthquake regulations, particularly in relation to reinforcement details, were overlooked. In addition, designers should avoid design mistakes such as to make discontinuous of frames, to place most of vertical element strong axis in one direction, insufficient support condition of stairs and adjacent building effects.

Flexural resistance of 3D cut welded joints between SHS columns and through I‐beams

AbstractSteel structures can be designed according to different framing methods depending on the location of Moment‐Resisting‐Frames (MRFs). In Europe and the United States, one‐way MRFs are widely exploited due to their ability to clearly identify the seismic and gravity frames and limit the use of expensive joints only in MRFs. Furthermore, this is the most appropriate solution if double‐tee columns are adopted since they can provide high strength and stiffness only in the plane orthogonal to their strong axis. Instead, two‐way MRFs are commonly used in Japan; this solution creates 3D seismic structures and requires the selection of columns able to provide enough strength and stiffness along both their axes. This is the reason why tubular columns are usually used in Japan. Nevertheless, the main drawback of this practice is the need to manufacture complex beam‐to‐column connections.In this framework, the recent introduction of 3D Laser Cutting Technology (3D‐LCT) in Civil Engineering provides a way to reduce this complexity. It allows manufacturing quickly 3D cutting shapes with high precision, optimising the welding quantity and costs. Moreover, all the operations are programmed and fully realised by the machine, avoiding any intervention of operators, eliminating human errors, increasing the quality level and saving time. An example of this simplification is given by connections between Square‐Hollow‐Section columns and passing‐through double‐tee beams. Nevertheless, the novelty of this solution represents a limit to its application in practice because no design equations are currently included in common standards.To fill this knowledge gap, this paper investigates the flexural behaviour of SHS columns to passing‐through double‐tee beam connections according to the component method approach. In particular, the study has been carried out through numerical and analytical activities devoted to providing design formulations.

On the Capacity of Beams with U Cross Section Subjected to Bending and Torsion

AbstractBeams with singly symmetric U cross sections are often subjected to bending about the strong axis and simultaneously to scheduled torsion, since the shear center is outside the section geometry. The member capacity of such sections, which is strongly influenced by effects of lateral torsional buckling, can therefore hardly be represented with the common design regulations based on reduction factors χLT of EN 1993‐1‐1. However, numerical approaches allow analyzing deeply the structural behavior of corresponding beams. In the present study, different numerical finite element simulations (GMNIA) including simplified numerical models based on the plastic zones theory are incorporated to determine member capacities and to derive corresponding reduction factors for simplified verifications. As the load‐bearing capacity of members susceptible to stability is strongly influenced by imperfections, the straightness according to manufacturing tolerances as well as approaches for the acquisition of structural imperfections (residual stresses) are considered in the numerical analyses. The investigations are carried out for selected structural systems with different sets of parameters, such as for the member lengths and cross section types. Concluding, a capacity curve is derived and compared to different reduction factors χLT specified in EN 1993‐1‐1.