• Steel and Composite Structures
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• v.38 no.5
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• pp.547-562
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• 2021

This paper aims to explore the mechanical behavior and moment-rotation model of blind bolted joints between concrete-filled double skin steel tubular columns and steel-concrete composite beams. For this type of joint, the inner tube and sandwiched concrete were additionally identified as basic components compared with CFST blind bolted joint. A modified moment-rotation model for this type of connection was developed, of which the compatibility condition and mechanical equilibrium were employed to determine the internal forces of basic components and neutral axis. Following this, load transfer mechanism among the inner tube, sandwiched concrete and outer tube was discussed to assert the action area of the components. Subsequently, assembly processes of basic coefficients in terms of their stiffness and resistances based on the component method by simplifying them as assemblages of springs in series or in parallel. Finally, an experimental investigation on four substructure joints with CFDST columns for validation purposes was carried out to capture the connection details. The predicted results derived from the mechanical models coincided well with the experimental results. It is demonstrated that the proposed mechanical model is capable of evaluating the complete moment-rotation relationships of blind bolted CFDST column composite connections.

• Journal of Korea Foresty Energy
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• v.18 no.2
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• pp.84-91
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• 1999

The objective of this study was to present creep and the effects of mechano-sorptive deflection of drift pin moment resisting joint between LVL members under changing relative humidity (RH) conditions. The LVL members with steel gusset were jointed by a square pattern of eight injected drift pin. Three diameter drift pins were used to test specimens (6mm, 10mm, and 16mm). The creep test was conducted under two constant loading conditions : one at 30 kgf(840 kgf-cm) and the other at 60 kgf(1680 kgf-cm). The experiment was conducted in an open shed outside. (1)The total rotation creep model of moment resisting joing can be expressed as the sum of the creep of controlled environment (3-parameter model), dimensional change and mechano-sorptive deflection resulting from the variable environment. (2)Mechanosorptive rotation creep is recoverable as moisture content increases during adsorption. Least squares method for linear regression analysis was performed using mechano-sorptive rotation creep as the dependent variable and moisture content as the independent variable. The slope of low moment specimens are compared with those of high moment. This means that low moment condition is more easily affected by changes in humidity than high moment conditions. (3)Although creep deflection is higher for small diameter drift pin than for large diameter drift pin, the shape of creep deflection curves for all specimens is similar.

• Structural Engineering and Mechanics
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• v.12 no.2
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• pp.201-214
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• 2001

Four finite element (FE) models are examined to find the one that best estimates moment-rotation characteristics of top- and seat-angle with double web-angle connections. To efficiently simulate the real behavior of connections, finite element analyses are performed with following considerations: 1) all components of connection (beam, column, angles and bolts) are discretized by eight-node solid elements; 2) shapes of bolt shank, head, and nut are precisely taken into account in modeling; and 3) contact surface algorithm is applied as boundary condition. To improve accuracy in predicting moment-rotation behavior of a connection, bolt pretension is introduced before the corresponding connection moment being surcharged. The experimental results are used to investigate the applicability of FE method and to check the performance of three-parameter power model by making comparison among their moment-rotation behaviors and by assessment of deformation and stress distribution patterns at the final stage of loading. This research exposes two important features: (1) the FE method has tremendous potential for connection modeling for both monotonic and cyclic loading; and (2) the power model is able to predict moment-rotation characteristics of semi-rigid connections with acceptable accuracy.

• Journal of the Korean Data and Information Science Society
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• v.10 no.1
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• pp.19-27
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• 1999

An orientation-shift model for unit random vectors in $R^3$ is defined. The Euler angles are introduced to parametrize orientation-shifts and their moment estimators are found. Through the analytic perturbation method, the asymptotic distributions of the estimators are obtained.

• Steel and Composite Structures
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• v.20 no.3
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• pp.469-486
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• 2016

Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics ($M-{\phi}$ relationship), or at least three basic joint properties, namely the moment resistance $M_R$, the rotational stiffness $S_j$ and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance $M_R$, initial stiffness $S_{j.ini}$ and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.

• International Journal of High-Rise Buildings
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• v.4 no.1
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• pp.45-55
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• 2015

The rotation capacity of the moment connections could significantly influence on the seismic performance of steel moment resisting frames. Current seismic provisions require that beam-to-column connections in Intermediate Moment Frames (IMF) should have a drift capacity as large as 0.02 radian. The objective of this study was to evaluate the effect of the rotation capacity of moment connections on the seismic performance of high-rise IMFs. For this purpose, thirty- and forty-story high-rise IMFs were designed according to the current seismic design provisions. The seismic performance of designed model frames was evaluated according to FEMA P695. This study showed that the forty-story IMF satisfied the seismic performance objective specified in FEMA P695 when the rotation capacity of the connections was larger than 0.02. However, thirty-story IMFs satisfied the performance objective when the connection rotation capacity is larger than 0.03.

• Steel and Composite Structures
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• v.41 no.6
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• pp.831-850
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• 2021

Surface subsidence caused by mining subsidence has an impact on neighboring structures and utilities. In other words, subsurface voids created by mining or tunneling activities induce soil movement, exposing buildings to physical and/or functional destruction. Soil-structure is evaluated employing probability distribution laws to account for their uncertainty and complexity to estimate structural vulnerability. In this study, to investigate the displacement field and surface settlement profile caused by mining subsidence, on the basis of a Winklersoil model, analytical equations for the moment-rotation response ofsoil during mining induced ground movements are developed. To define the full static moment-rotation response, an equation for the uplift-yield state is constructed and integrated with equations for the uplift- and yield-only conditions. The constructed model's findings reveal that the inverse of the factor of safety (x) has a considerable influence on the moment-rotation curve. The maximal moment-rotation response of the footing is defined by X = 0:6. Despite the use of Winkler model, the computed moment-rotation response results derived from the literature were analyzed through the ELM-SVM hybrid of Extreme Learning Machine (ELM) and Support Vector Machine (SVM). Also, Monte Carlo simulations are used to apply continuous random parameters to assess the transmission of ground motions to structures. Following the findings of RMSE and R2, the results show that the choice of probabilistic laws of input parameters has a substantial impact on the outcome of analysis performed.

• Steel and Composite Structures
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• v.29 no.6
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• pp.717-734
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• 2018

This paper presents the flexural performance of steel beam-to-column joints composed of hollow structural section beams and columns. A finite element (FE) model was developed incorporating geometrical and material nonlinearities to evaluate the behaviour of joints subjected to bending moments. The numerical outcomes were validated with experimental results and compared with EN1993-1-8. The demountability of the structure was discussed based on the tested specimen. A parametric analysis was carried out to investigate the effects of steel yield strength, end-plate thickness, beam thickness, column wall thickness, bolt diameter, number of bolts and location. Consequently, an analytical model was derived based on the component method to predict the moment-rotation relationships for the sub-assemblies with extended end-plates. The accuracy of the proposed model was calibrated by the experimental and numerical results. It is found that the FE model is fairly reliable to predict the initial stiffness and moment capacity of the joints, while EN1993-1-8 overestimates the initial stiffness extensively. The beam-to-column joints are shown to be demountable and reusable with a moment up to 53% of the ultimate moment capacity. The end-plate thickness and column wall thickness have a significant influence on the joint behaviour, and the layout of double bolt-rows in tension is recommended for joints with extended end-plates. The derived analytical model is capable of predicting the moment-rotation relationship of the structure.

• Journal of Korean Society of Steel Construction
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• v.8 no.3 s.28
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• pp.127-137
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• 1996

Connections as basic elements and an integrated part of a steel frame has an effect on the frame's performance. Conventional analysis and design techniques are based on either idealized fixed or pinned conditions. In fact, the use of rigid or pinned connection model in steel frame analysis serves the purpose of simplifying the analysis and design processes, but all connections used in current pratice possess stiffness and transfer moment which fall between the extreme cases of fully rigid and ideally pinned. To predict the behavior of the semi-rigid steel frames, it is necessary to predict the moment-rotation behavior of the beam-to-column connections. In this research, prediction equation for moment-rotation behavior of the beam-to-column connection is suggested and the effect of design parameters has investigated. Prediction model, in a nondimensional form shows the moment-rotation characteristic for connections. It is composed of the curve fitting power function using standardization constant K and 4 parameter $KM_o$, ${\theta}_0$, b, n based on the pretest result about moment-rotation behavior of connection.

• Journal of Astronomy and Space Sciences
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• v.39 no.2
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• pp.59-65
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• 2022

In this paper we propose a new perspective for explaining galaxy rotation curves. We conjecture that there is a gravitational moment of inertia which, together with gravitational mass, contributes to the gravitational potential. We substantiate a formula for the potential created by the moment of inertia. We validate our model by computing orbital rotation velocities for several galaxies and showing that computed rotation velocities correspond to the observed ones. Our proposed approach is capable of accounting for constant gas velocities outside of a galactic disc without relying on the dark matter hypothesis. Furthermore, it addresses several problems faced by the application of the dark matter hypothesis, e.g., the absence of inward collapse of dark matter into a galaxy, the spherical distribution of dark matter around galaxies, and absence of traces of the effect of dark matter in two ultra-diffuse galaxies, NGC 1052-DF2, and NGC 1052-DF4.