Member Length Research Articles

Performance of Impulse Response Testing on Prismatic Members with Intermediate Joints

Nondestructive Testing (NDT) methods have extensively been used to assess the conditions of civil infrastructure in the recent decades. Among various NDT techniques, Impulse Response (IR) has a vast application due to its simplicity and low cost. However, factors such as reflections from changes in impedance along the investigated members can adversely influence the success of the method. Numerous numerical and experimental studies have already been performed to evaluate the effect of change in mechanical impedances such as bulging, necking and similar anomalies. In this study, the effect of the presence of joints connecting the investigated members to other members, as another source of impedance change, is demonstrated. A three-story steel-concrete composite column of a building was selected for testing and IR tests were conducted. The obtained mobility graphs were clear, and the height of the column was easily measured with an acceptable error. The results of this study show that although the joints located between the top and bottom of the tested member are sources of change in mechanical impedance, they do not result in concealing the resonant frequencies from the wave reflected from the bottom of the member. Thus, IR method seems to be applicable in determining the length of prismatic members with intermediate joints such as piles of unknown bridge foundations with bracing and columns of buried buildings.

A compound strip method for static and buckling analyses of thin-walled members with transverse stiffeners

The objective of this study is to propose and develop a Compound Strip Method (CSM) for static and buckling analyses of thin-walled members with transverse stiffeners. Traditionally thin-walled members are analyzed as prismatic members using computationally efficient methods such as the popular Finite Strip Method (FSM) — spline or semi-analytical. However, with structural systems getting more complicated and also for seeking better performance, transverse components that render the members no longer prismatic are possible, such as spaced transverse stiffeners along the member length. Existing FSM cannot take into account the stiffeners’ effect in the present form. Hence, this study presents a new compound strip method (CSM) based on the spline FSM for static and buckling analyses of thin-walled members with transverse stiffeners. The transverse stiffeners are modeled with shell element formulation by considering in-plane deformation. Transverse stiffeners can be placed flexibly along the member length in the proposed CSM. The developed CSM is then used to analyze plates and thin-walled members with transverse stiffeners. The accuracy of the method is validated with shell finite element solutions through static and buckling analyses of those members. Meanwhile, the impact of transverse stiffeners on the members’ buckling modes is also revealed by the analyses.

Geometric Design-based Dimensional Synthesis of a Novel Metamorphic Multi-fingered Hand with Maximal Workspace

Current research on robotic dexterous hands mainly focuses on designing new finger and palm structures, as well as developing smarter control algorithms. Although the dimensional synthesis of dexterous hands with traditional rigid palms has been carried out, research on the dimensional synthesis of dexterous hands with metamorphic palms remains insufficient. This study investigated the dimensional synthesis of a palm of a novel metamorphic multi-fingered hand, and explored the geometric design for maximizing the precision manipulation workspace. Different indexes were used to value the workspace of the metamorphic hand, and the best proportions between the five links of the palm to obtain the optimal workspace of the metamorphic hand were explored. Based on the fixed total length of the palm member, four nondimensional design parameters that determine the size of the palm were introduced; through the discretization method, the influence of the four design parameters on the workspace of the metamorphic hand with full-actuated fingers and under-actuated fingers was analyzed. Based on the analysis of the metamorphic multi-fingered hand, the symmetrical structure of the palm was designed, resulting in the largest workspace of the multi-fingered hand, and proved that the metamorphic palm has a massive upgrade for the workspace of underactuated fingers. This research contributed to the dimensional synthesis of metamorphic dexterous hands, with practical significance for the design and optimization of novel metamorphic hands.

Junctural Alignment in Kyoto Japanese Compound Nouns

Descriptively, in Tokyo Japanese compound words whose second member measures up to four moras in length, compound accent is placed on the syllable immediately preceding or following the boundary, or "juncture," between compound members. The length of the second member of the compound determines which of the two possible syllables is accented. Kubozono (1995) proposes an analysis with a constraint which requires that compound accent be aligned with the juncture. However, Ito and Mester (2018) account for compound accent location without reference to the juncture.Kyoto Japanese compound accent placement is similar to that of Tokyo Japanese (Nakai 2002) with a crucial difference: compound accent is placed on the mora, not the syllable, immediately preceding or following the juncture. This results in a discrepancy in which compound accent is placed on the first mora of a heavy syllable in some cases and on the second mora of a heavy syllable in other cases. I demonstrate that this discrepancy makes alignment to the juncture indispensable for Kyoto Japanese and that general left and right alignment constraints relativized to three levels of recursive word (maximal, minimal, any) cannot by themselves place compound accent in the correct location in all cases.

Research on Reinforcement Technology of Grid Bars with Oversized Slenderness Ratio

The stiffness of axially loaded members is usually measured by slenderness ratio, which is the ratio of the calculated length of the member to the minimum turning radius of the member section. If the slenderness ratio is too large, the component is easy to produce bending deformation in the process of use. Under the action of dynamic load, it will produce large amplitude vibration, and it is easy to produce bending deformation in the process of transportation and installation. Therefore, the slenderness ratio of the component should be controlled in the design to make it not exceed the allowable slenderness ratio specified in the specification. Aiming at the problem that the slenderness ratio of space truss exceeds the limit, this paper puts forward the method of reducing the calculated length of members by adding supporting members or auxiliary members, so as to reduce the slenderness ratio of members, and studies the influence of increasing supporting members on the bearing capacity, deformation and seismic performance of space truss, so as to provide theoretical basis and guidance for the implementation of the reinforcement method.

Optimal Shape Adjustment of Large High-Precision Cable Network Structures

Traditional shape adjustment methods for large high-precision cable network structures usually use many actuators and are only applicable to predictable shape distortions. To this end, a new method, namely, the minimum residual nodal displacement method, for optimal shape adjustment of large high-precision cable network structures is developed. The new shape adjustment method can significantly reduce shape distortion of a cable network structure by automatically placing a small number of actuators at optimal locations. This new method is applicable to cable network structures under both predictable and unpredictable shape distortions, and can determine the minimum number of actuators needed to satisfy prescribed design requirement for surface accuracy. In this method, a simple linear relationship between nodal displacements, external loads, and undeformed member lengths of a cable network structure is established, and residual nodal displacement of the structure is minimized. The effectiveness of this new method is proved in numerical simulation results, where a planar cable network structure and a reconfigurable deployable mesh reflector are investigated.

Design Procedure and Ultimate Capacity of New Turnbuckle for Measuring Tensile Force

A turnbuckle is a device that is installed between tension wires or rods for the purpose of adjusting the tensile force and length of tension members. Tensile force can be adjusted by rotating the body of turnbuckle but the conventional turnbuckle is incapable of measuring tensile force without specific measurement equipment such as a load cell, accelerometer and data logger, etc. New turnbuckles have therefore been developed for adjustment and easy measurement of tensile force. In previous works, the newly developed turnbuckles have been tested and analyzed in order to establish their size, shape and measurable load capacity. The present study addresses the design process and ultimate capacities of new turnbuckles having measurable load capacities of 100, 200 and 300 kN. The ultimate load capacities are obtained via experimental investigation. For each turnbuckle the ultimate loads and the first yield loads are about 5 times and 1.5 times the service load, respectively.

A simplified method for calculating non-uniform temperature distributions in thin-walled steel members protected by intumescent coatings under localized fires

This paper presents a method to calculate the non-uniform temperature field of steel members protected by intumescent coatings under localized fires. In this proposed method, the steel member is divided into a number of segments along the length according to the localized fire temperature field, and each segment divided into plate elements with different surrounding fire temperatures. The temperature of each plate element is assumed uniform and is calculated by the lumped mass equation with the thermal conductivity of intumescent coatings approximated using a three-stage thermal conductivity model. Heat conduction between different steel plate elements is ignored. Comparisons of steel temperature results between measured results and the proposed simplified temperature calculation method show very good agreement in temperature distributions along the steel member length, in the cross-section and detailed temperature–time relations at critical and high temperature locations, with differences in calculated and measured average temperatures in different segments being less than 7.2 %. Comparisons of load carrying capacities of axially-loaded steel members using measured temperature distributions and calculated temperature distributions show small (<6%) differences.

Experimental and numerical investigations of circular recycled aggregate concrete-filled stainless steel tube columns

This paper reports a comprehensive experimental and numerical study of the flexural buckling behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube columns. The experimental programme, adopting four series of column specimens designed with various stainless steel tube sizes, recycled coarse aggregate replacement ratios and member lengths, included material tests on both recycled aggregate concretes and stainless steel tubes, initial global geometric imperfection measurements and pin-ended column tests. The obtained experimental results, including the failure loads, load–mid-height lateral deflection curves and flexural buckling failure modes, were reported in detail. The effects of the stainless steel tube size, recycled coarse aggregate replacement ratio and member length on the flexural buckling resistances of the column specimens were examined. The lateral deflection distributions along the column specimen lengths and the development of the longitudinal strains of the outer stainless steel tubes were discussed. The experimental programme was supplemented by a numerical modelling programme, in which finite element models were developed and validated against the test results and then used for conducting parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. Given that there have been no existing design codes for recycled aggregate concrete–stainless steel composite structures, the relevant codified design rules for circular natural aggregate concrete-filled carbon steel tube columns failing by flexural buckling, as used in Europe, Australia/New Zealand and America, were assessed for their applicability to circular recycled aggregate concrete-filled stainless steel tube columns, based on the test and numerical data. The assessment results revealed that the design rules, as given in the Australian/New Zealand standard and American specification, result in unsafe flexural buckling resistance predictions when used for circular recycled aggregate concrete-filled stainless steel tube columns, while the Eurocode design rules lead to more safe and accurate flexural buckling resistance predictions.

Stochastic Approach on Safe Designing of Double Layer Grid Space Structure against Member Length Imperfections

The imperfections in Double Layer Grid Space Structure (DLGSS) threaten the safety of designs. The imperfections in the member length of DLGSS may result from human-based causes such as manual cuts, tolerance sensitivity in CNC cuttings and variation in temperature. Therefore, analyzing the impacts of imperfections is vital to ensure the safety of DLGSS systems. Thus, a safe design of DLGSS against member length imperfections is the main focus of this paper. A novel and practical safe design approach, which considers member length imperfections, has been proposed based on linear elastic and probabilistic analyses methods. The impacts of member length imperfections on the DLGSS behavior were also evaluated in detail. Variation in positions of imperfect members, initial size of length imperfections (longer or shorter than the ideal size) and number of imperfect members were selected as the parameters to be analyzed. A 3D computer program, which considers the initial length imperfections of members, has been codded to analyze the space trusses. The impact of imperfection on a space structure was investigated by repeating the simulations for stochastic dispersion of imperfect member position and initial member length imperfection. The results revealed that initial length imperfection might have a considerable impact on the DLGSS behavior. The DLGSS systems can safely be designed by employing the proposed design approach to overcome the defined imperfections.

Global Sensitivity Analysis of Quantiles: New Importance Measure Based on Superquantiles and Subquantiles

The article introduces quantile deviation l as a new sensitivity measure based on the difference between superquantile and subquantile. New global sensitivity indices based on the square of l are presented. The proposed sensitivity indices are compared with quantile-oriented sensitivity indices subordinated to contrasts and classical Sobol sensitivity indices. The comparison is performed in a case study using a non-linear mathematical function, the output of which represents the elastic resistance of a slender steel member under compression. The steel member has random imperfections that reduce its load-carrying capacity. The member length is a deterministic parameter that significantly changes the sensitivity of the output resistance to the random effects of input imperfections. The comparison of the results of three types of global sensitivity analyses shows the rationality of the new quantile-oriented sensitivity indices, which have good properties similar to classical Sobol indices. Sensitivity indices subordinated to contrasts are the least comprehensible because they exhibit the strongest interaction effects between inputs. However, using total indices, all three types of sensitivity analyses lead to approximately the same conclusions. The similarity of the results of two quantile-oriented and Sobol sensitivity analysis confirms that Sobol sensitivity analysis is empathetic to the structural reliability and that the variance is one of the important characteristics significantly influencing the low quantile of resistance.

Laboratory testing and numerical modelling of pin-ended hot-rolled stainless steel angle section columns failing by flexural-torsional buckling

The flexural-torsional buckling behaviour and resistances of pin-ended hot-rolled stainless steel angle section columns have been studied in the present paper, based on laboratory testing and numerical modelling. The testing programme adopted four hot-rolled stainless steel angle sections and included initial global and torsional geometric imperfection measurements and twelve pin-ended column tests. The key obtained test results, including the failure loads and deformations at the failure loads, the load–mid-height lateral deflection curves and failure modes, were fully reported and discussed. Strong interaction between flexural-torsional buckling about the major principal axis and flexural buckling about the minor principal axis was observed for each pin-ended hot-rolled stainless steel angle section column specimen during and upon testing. The testing programme was followed by a numerical modelling programme; finite element models were developed and validated against the test results, and afterwards used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. On the basis of the experimentally and numerically obtained data, the accuracy of the codified design methods, as adopted in Europe, America and Australia/New Zealand, and a recently proposed DSM-based design approach for pin-ended hot-rolled stainless steel angle section columns susceptible to flexural-torsional buckling, were evaluated. Overall, it may be concluded that (i) all the three considered design codes result in conservative flexural-torsional buckling resistance predictions, (ii) the current European code leads to more accurate resistance predictions for pin-ended columns with non-slender hot-rolled stainless steel angle sections, but a lower degree of design accuracy for pin-ended columns with slender hot-rolled stainless steel angle sections, in comparison with the American specification and Australian/New Zealand standard, and (iii) the DSM-based design approach yields substantially improved resistance predictions, due to the rational consideration of the length-dependent characteristic of flexural-torsional buckling and the interaction of flexural-torsional buckling with minor-axis flexural buckling, but with many predictions lying on the unsafe side.

Elastic local buckling of three-flanged cross-sections

In current structural steel design specifications, the local buckling of cross-sections is typically treated on an element-by-element basis, with the boundary conditions along the adjoined longitudinal edges of the individual plates assumed to be simply-supported. In reality, cross-sections buckle locally as a whole and the individual plate elements interact. As a result, the boundary conditions along the adjoined longitudinal edges of the critical isolated plate (i.e. that with the lowest elastic local buckling stress) lie between lower and upper bounds of simply-supported and fixed, respectively. Based on this concept, explicit formulae to predict the elastic local buckling stress of full cross-sections of common profiles, including I-sections, have recently been developed (Gardner et al., 2019) [1]. In the present paper, the formulae for single I-sections set out in Gardner et al. (2019) [1] are extended to cover the case of three-flanged cross-sections that arise in longitudinally-stiffened plate girders and in the haunch and apex regions of portal frames. The geometry and loading of the studied cross-sections are assumed to remain constant along the member length, i.e. the influence of tapering and moment gradients on local buckling are not considered herein, but has been evaluated in parallel work (Quan et al., 2020) [2]. The proposed formulae are calibrated against results from finite strip analysis performed using CUFSM v4.05 (Li and Schafer, 2010) [3] on a range of three-flanged sections, and provide predictions of elastic local buckling stresses that are typically within 5% of the numerically obtained values.

Hybrid finite element formulation for geometrically nonlinear buckling analysis of truss with initial length imperfection

This paper presents a novel hybrid FEM-based approach for nonlinear buckling analysis of truss with initial length imperfection. The contribution deals with establishing two types of truss finite element (perfection and imperfection element) considering large displacement based on displacement formulation and mixed formulation. Therefore, the hybrid global equation system is developed by assembling perfection and imperfection truss elements. The incremental-iterative algorithm based on the arc-length method is used to establish calculation programs for solving geometrically nonlinear buckling analysis of truss with initial length imperfection. Using a written calculation program, the numerical test is presented to investigate the equilibrium path for plan truss with initial member length imperfection.

Efficient Pointing Accuracy Analysis Using Support Vector Machine for Highly Precise Space Truss Structure Due to Clearance Uncertainty

This research proposes an efficient pointing accuracy analysis method applying a support vector machine (SVM), one of machine learning methods, to reduce computational cost sufficiently for a highly precise space truss consisting of multiple-stage structures with uncertainties of member lengths and the node clearances. The SVM is applied to classify the nodal position definiteness of the truss structure in terms of the uncertain variables to avoid useless pointing accuracy analysis for the instable structures. For an efficient classification, the nodal position definiteness for a larger-stage truss is estimated from learning results for a fewer-stage truss. Through numerical examples, the nodal position definiteness for 20- or 30-stage truss is demonstrated to be efficiently classified by the learning results for only 3-stage truss structure. Then, the pointing accuracy evaluated as the direction angle distribution is confirmed to be identical to the result by Monte Carlo simulation.

Effect of Member Length Uncertainty and Backlash on Deformation Accuracy for a High-Precision Space Truss Structure

Effect of Member Length Uncertainty and Backlash on Deformation Accuracy for a High-Precision Space Truss Structure

Cold-formed high strength steel tubular beam-columns

High strength steel is used more often in a variety of civil engineering applications due to its high strength-to-weight ratio and cost effectiveness. This paper presents the experimental investigation on cold-formed high strength carbon steel tubular members subjected to combined compression and bending. The nominal 0.2% proof stresses of the test specimens were 700 and 900 MPa. The test specimens consisted of square hollow sections (SHS), rectangular hollow sections (RHS) and circular hollow sections (CHS). The material properties, global geometric imperfections of the specimens were measured. The behaviour of the beam-column members was investigated through testing 32 specimens which had a nominal member length of 1480 mm. The second order effects were also considered by measuring the mid-height deflections for all specimens. The compression and bending capacities, load-deformation histories and failure modes of the test specimens were also reported. The test results were compared with the values predicted from the American, Australian and European standards. Improved design recommendation is provided for cold-formed high strength steel tubular beam-columns. Based on the experimental results, finite element modelling methodology is also proposed.

Design of structural stainless steel members by second order inelastic analysis with CSM strain limits

System-level advanced analysis is now a viable tool for widespread use in structural design. By directly capturing frame and member level instability effects, plasticity, initial geometric imperfections and residual stresses in the analysis, the need for subsequent individual member checks can be eliminated. The analysis of structural members and frames is typically carried out using beam elements, which are unable to capture the effects of local buckling. However, local buckling dictates the strength and ductility of cross-sections and the extent to which plastic redistribution of forces and moments can be exploited; it cannot therefore be disregarded. A proposal is made herein, in which strain limits, defined by the continuous strength method, are applied to simulate local buckling in beam element models, thereby controlling the degree to which spread of plasticity, force and moment redistribution and strain hardening can be utilised in the design of structural elements and systems. Strains are averaged over a defined distance along the member length to reflect the fact that local buckling requires a finite length over which to develop and to allow for local moment gradient effects. Design is based directly on the application of strain limits to all cross-sections in the structure. The accuracy of the proposed method for the design of stainless steel members is assessed through comparisons with benchmark shell finite element results; both I-section and hollow section members are considered. Comparisons against current design methods confirm the significant benefits of applying the proposed approach in terms of both the accuracy and the consistency of the resistance predictions. The reliability of the design approach is demonstrated through statistical analyses performed in accordance with EN 1990. Application of the proposed method is particularly appropriate for stainless steel structures due to the high material value and the complexities presented by the nonlinear material stress–strain response for traditional design treatments. The proposed method is due to be included in the two major international stainless steel design standards EN 1993-1-4 and AISC 370.

Diversity in Public Library Boards: Perspectives of Board Members

&#x0D; &#x0D; &#x0D; The initial aim of this study was to learn if there was any diversity in ethnicity, sexual orientation, gender, or disability among public library board members. Through participant interviews, this study reports on member perceptions of diversity in the areas of member recruitment, qualifications, training, and length of term. Board members from four public libraries in Alberta and Saskatchewan were interviewed and the results were analyzed through the framework of critical race theory (CRT). Findings suggest that library boards lack diversity, particularly in finding, recruiting, and training members who are truly representative of their community. Cultural sensitivity and cross-cultural training are important for board members to connect with their communities. &#x0D; &#x0D; &#x0D;

Axial compression capacity of steel circular tube with large initial curvature: Column curve and application in structural assessment

From the inspection of existing steel bar structures (composed of members subjected to pure axial force), some axially compressed steel circular tubes (SCT) exhibit large bending under axial compression. This is induced by the large initial curvatures of the SCTs. To assess the structural safety in these cases, a process is proposed in this paper. The process involves three steps: (1) determine the initial member curvature (without load) from the inspected member curvature (under load), (2) estimate the axial compression capacity of the SCTs with large initial curvatures, and (3) conduct structural assessment considering the effect of large member curvatures. To address step (1), an iterative procedure is proposed. The assumed initial member curvature is modified in the iteration to approximate its actual value. The effectiveness of the procedure was validated via a space truss example. To address step (2), a column curve that incorporates the large initial curvature of axially compressed SCTs is derived. The column curve was developed based on the extreme-fibre-yielding criterion and calibrated using 4800 data points obtained from the FEA. Generally, the buckling factor decreases by approximately 25% as the amplitude of the initial curvature varies from l/1000 to l/100 (l is the member length). As an illustration, the iterative procedure proposed in step (1) and the column curve derived in step (2) are adopted for assessing the safety of an existing steel latticed roof. According to the result, there could be a 20% underestimation of the design stress ratio of SCT members if the large member curvatures are ignored.