Member Length Research Articles

구조부재의 형상과 위치에 대한 IFC 상호운용성 개선

본 연구는 보, 기둥, 벽체, 슬래브 등 구조부재의 형상과 위치를 서로 다른 방식으로 표현하여 발생하는 문제점을 해결하여 IFC의 상호운용성을 개선하기 위한 것으로서, IFC에서 부재의 길이, 부재 단면의 높이, 두께, 부재의 기준위치, 편심 등을 명확하게 나타낼 수 있는 부재의 형상과 위치 표현 방법을 제시하였다. 이 과정에서 엔지니어가 구조부재의 형상과 위치를 인식하고 취급하는 방식을 기준으로 하였다. 그리고 간단한 구조물에 대해서 본 연구에서 제시한 방법에 따라 IFC 파일을 작성하고, 이로부터 엔지니어가 인식하고 취급하는 방식에 맞추어 보 단면의 치수, 부재의 길이, 기준위치, 편심을 표현할 수 있음을 구체적으로 확인하였다. 이상의 결과를 고려하면, 본 연구에서 제시한 방법이 여러 응용소프트웨어에서 보, 기둥, 벽체, 슬래브의 형상과 위치 등 기본적인 자료를 IFC 기반으로 보다 신뢰도 높고 완전하게 교환하는 데에 활용될 수 있을 것으로 기대된다. 【The purpose of this study is to improve the interoperability of IFC for the basic data such as the size of member section, length, thickness, reference location, and eccentricity of the structural members. For this, the method to represent the basic data of structural member is proposed. In the proposed method, the most important criteria is the way that engineers recognize and treat the basic data of structural members. Then, in this study, an IFC file is generated based on the proposed method for a simple RC building composed of members and it is examined that the correct basic data can be derived from the IFC file in the way that engineers do in practice. From the results of the examination, the proposed method is expected to improve the interoperability of IFC for the basic data.】

Structural health and dynamic behavior of residential buildings: field challenges in the rehab of damaged reinforced concrete

Reinforced concrete buildings require special consideration under dynamic excitations due to their anisotropic material properties. Strain compatibility equations are used in concrete analysis and design with assumptions about the stress and strain field across member section and member length. However, these assumptions fall short of describing real life behavior when concrete elements deteriorate, age or undergo cyclic loading. This paper addresses the structural health of reinforced concrete buildings and proposes an analytical model to account for concrete damage through loss of bond. The proposed model relates steel loading that causes bond distress to design parameters such as development length and bar properties, and therefore could be complemented by field measurement. The paper proposes a diagnosis method and discusses the sustainability of the structure by assisting in a simplistic decision rule as to whether to perform minor fixes, major rehabilitation, or disposal. Emphasis is placed on the difference between reversible and irreversible effects of cyclic loading on structural behaviour, and draws a distinction between damage to the girder and damage to the column in the overall structural system. The model is compared to empirical results to address field challenges faced when the structure is subjected to severe conditions in its ambient environment, or to unusual loading. Deterioration in concrete causes alteration in its composite behavior with the reinforcing steel. This affects the fundamental period of the structure, and its response to seismic loading.

The Effective using of Higher Strength Structural Steels in Compression Members

The continuous effort to achieve more efficiency of steel structures results to decrease their weight. Generally, it is accepted that the weight decreasing of steel structures could be achieved mainly by their geometrical and material optimization, using the thin- walled cross-sections and the higher strength steels. The results of numerical analysis of middle and higher strength structural steels using in compression members are presented in the paper. The homogeneous I cross-sections of the members with web slenderness βw = 40, 48, 60, 80, 120; member length L = 3,0; 4,0; 5,0; 6,0 m and structural steels S235, S275, S355, S420 and S460 were assumed. The full theoretical plastic load Npl, local post-critical load Nul and global buckling load Nuy and Nuz for all considered members by the European standards EN 1993-1-1 and EN 1993-1-5 for the design of steel structures were calculated. It is known that these standards have been transformed into national standards of all CEN countries which are generally used from 2010. The effective applying of the higher strength steels on the compressed members taking in consideration their shaping and material optimization is presented in this paper. The obtained numerical results are compared and analysed by choosing technical parameters.

An advanced analysis method for three-dimensional steel frames with semi-rigid connections

This paper presents an advanced analysis method for three-dimensional semi-rigid steel frames accounting for three main nonlinear sources. The second-order effects are considered by the use of stability functions obtained from the solution of beam–columns under axial force and bending moments at two ends. The spread of plasticity over the cross section and along the member length is captured by monitoring the uniaxial stress–strain relation of each fiber on selected sections. The nonlinear semi-rigid beam-to-column connection is simulated by a 3D multi-spring element. The generalized displacement control method is applied to solve the nonlinear equilibrium equations in an incremental-iterative scheme. The nonlinear load–displacement responses and ultimate load results compare well with those of previous studies. It is concluded that using only one element per member with monitoring the end sections accurately likely predict the nonlinear responses of three-dimensional semi-rigid steel frames.

Global instability of elliptical hollow section beam-columns under compression and biaxial bending

The global instability of elliptical hollow section members under combined compression plus biaxial bending is studied in this paper by means of laboratory testing and numerical simulations. A total of 9 beam-column tests were carried out under different combinations of compression and bending about both principal axes. The material properties of the tested sections were determined by means of tensile coupon tests. All tested elliptical hollow sections were EHS 150×75×5, and three nominal member lengths of 1 m, 2 m and 3 m were considered. Graphs of applied load versus mid-span bending moment, based on theoretical first and second order elastic considerations and the experimental second order inelastic response, are presented and described. Numerical models were initially validated against the experimental data using measured material and geometric properties, including imperfections. The models were subsequently employed in parametric studies to assess the influence of member slenderness and cross-sectional aspect ratio on the structural response. Finally, based on the experimental and numerical findings, design rules for hot-finished EHS beam-columns were assessed and statistically verified.

Matching floral and pollinator traits through guild convergence and pollinator ecotype formation.

Pollinator landscapes, as determined by pollinator morphology/behaviour, can vary inter- or intraspecifically, imposing divergent selective pressures and leading to geographically divergent floral ecotypes. Assemblages of plants pollinated by the same pollinator (pollinator guilds) should exhibit convergence of floral traits because they are exposed to similar selective pressures. Both convergence and the formation of pollination ecotypes should lead to matching of traits among plants and their pollinators. We examined 17 floral guild members pollinated in all or part of their range by Prosoeca longipennis, a long-proboscid fly with geographic variation in tongue length. Attractive floral traits such as colour, and nectar properties were recorded in populations across the range of each species. The length of floral reproductive parts, a mechanical fit trait, was recorded in each population to assess possible correlation with the mouthparts of the local pollinator. A multiple regression analysis was used to determine whether pollinators or abiotic factors provided the best explanation for variation in floral traits, and pollinator shifts were recorded in extralimital guild member populations. Nine of the 17 species were visited by alternative pollinator species in other parts of their ranges, and these displayed differences in mechanical fit and attractive traits, suggesting putative pollination ecotypes. Plants pollinated by P. longipennis were similar in colour throughout the pollinator range. Tube length of floral guild members co-varied with the proboscis length of P. longipennis. Pollinator shifts have resulted in geographically divergent pollinator ecotypes across the ranges of several guild members. However, within sites, unrelated plants pollinated by P. longipennis are similar in the length of their floral parts, most probably as a result of convergent evolution in response to pollinator morphology. Both of these lines of evidence suggest that pollinators play an important role in selecting for certain floral traits.

Probabilistic characterisation of the length effect for parallel to the grain tensile strength of Central European spruce

The paper presents a probabilistic model characterising tensile strength parallel to grain of Central European spruce boards without longitudinal joints. The effect of length of members on strength is considered explicitly by considering a member by a serial arrangement of weak sections triggered by major knots of knot clusters. In order to demonstrate the applicability of the proposed model the model parameters are calibrated based on the analysis of three samples of spruce of Switzerland (Mischler-Schrepfer, 2000 [25]) and Austria (Schickhofer and Augustin, 2001 [28]), in total 460 boards tested in full size. This model might serve as basis for studies concerning the length effect of boards relevant for solid timber structures as well as basis for judging the length effect of finger jointed construction timber and glulam, and as starting point for modelling the process of proof loading.

Influence of stirrup spacing on shear resistance of reinforced concrete beams

This study investigates the behaviour of, and evaluates the benefit accruing to, shear critical reinforced concrete beams, when provided with vertical stirrups spaced at decreasing intervals along the axis of the beam, but with the same amount of web reinforcement per unit beam length. Tests are carried out on three reinforced concrete beams, identical in geometry, flexural reinforcing, amount of web reinforcement per unit span length, material properties and test details. The only varable is vertical stirrup leg spacing along the span. The beams are loaded at half point on a simple span of 2500 mm and all fail in shear. Experimental results demonstrate that, as stirrup spacing decreases, there is a strength gain at ultimate. Besides increased carrying capacity, closer spacing of shear reinforcement results in more beneficial deformational characteristics. Transverse deflections and crack widths decrease as stirrup spacing decreases. The test results establish the desirability of using stirrup reinforcement in practice at as close an interval as possible, along the member length, keeping the amount of web reinforcement per unit length unaltered. This beneficial aspect of using closer stirrup leg spacing than the maximum permitted by codes is not found in the available national building codes for structural concrete.

Buckling of elliptical hollow section members under combined compression and uniaxial bending

Experimental and numerical investigations into the behaviour of elliptical hollow section beam-columns under axial compression and uniaxial bending have been performed and described in this paper. A large-scale experimental programme, comprising a total of 10 tensile coupon tests and 24 beam-column tests, was carried out. The beam-column tests included 6 pure compression tests, 3 buckling about the major axis and 3 about the minor axis, and 18 eccentric compression tests, 9 inducing compression plus bending about the major axis and 9 inducing compression plus bending about the minor axis. All tested elliptical hollow sections were EHS 150×75×5, and three member lengths of 1m, 2m and 3m were considered. The test results have been supplemented by numerically generated results based on validated FE models to assess the influence of member slenderness and cross-sectional aspect ratio. On the basis of the experimental and numerical findings, design rules covering instabilities in hot-finished EHS beam-columns have been assessed and verified by statistical analysis. The limiting length concept has also been extended to EHS beam-columns.

철근콘크리트 기둥의 축방향 변형률 평가

소성힌지 구역의 축방향변형률의 예측은 지진하중을 받는 철근콘크리트 기둥의 합리적인 연성 평가를 위하여 필요한 항목이다. 축방향변형률은 콘크리트의 유효압축강도를 저하시키고 층간 변위를 크게 할 수 있다. 기존 연구는 주로 소성힌지가 발생하는 보의 축방향변형률 예측에 국한되었지만 횡력을 받는 구조물에서는 저층부 기둥도 소성힌지가 발생한다. 이 논문에서는 기둥 부재에 작용하는 축력의 크기에 따라 변화하는 축방향변형률을 예측할 수 있는 모델과 평가식이 제안되었다. 단면 해석법을 이용하여 하중이력에 따른 축방향변형률의 변화와 철근의 변형률 변화를 고찰한 후, 해석과 실험 결과를 근거로 축방향변형률 예측 모델을 제안하였다. 제안된 모델은 부재 축방향변형률을 3가지 경로(재하, 재하 후 반대하중이 하중이 가해지는 구간, 동일한 부재 회전각에서 반복하중을 받을 구간)로 구분하였다. 이 연구에서 제안된 기둥 부재의 축방향변형률의 계산식은 축력비가 다른 철근콘크리트 기둥의 실제 축방향변형률을 추적하였고, 축력비의 영향을 반영하였다.

Discussion of “Second-Order Analysis of Plane Frames with One Element per Member” by Richard J. Balling and Jesse W. Lyon

The authors presented an analytical model that, as indicated by thetitle, can be used to determine the second-order response of planeframes with one element per member. The authors stated that “Acorotational element is developed directly from the governingsecond-orderdifferentialequationsofbeamtheory.Thecorotationalelement includes not only the effect of axial force on the bendingmoment (P-delta effect) but also the additional axial strain causedby end rotations. Hinged and semirigid end conditions are also in-cludedsothatplastichingescouldbeconsidered.Theresultinglocalelementtangentstiffnessmatrixiscomparedtotraditionallocalele-ment elastic and geometric stiffness matrices. The method is imple-mented and executed on two example problems in which only oneelement per member is used. Results compare favorably to thosefromanonlinearcommercialprograminwhichseveralelementspermemberareused.Athirdexampleproblemincludesbothgeometricandmaterial nonlinearitytodevelopapushovercurve.”Finally,theauthors concluded that “The elastic and first geometric stiffnessmatrices degenerate to traditional elastic and geometric stiffnessmatrices if the initial member length L

Optimum Unbraced Length Ratios of Slender Steel Sections

To get minimum weight design of steel structures, selection of suitable steel section for design of a steel member is always been a point of great interest from a designer's point of view. Because of thin flanges and webs slender sections are lighter as compared to compact and non-compact sections. Aim of this research study is to determine the optimum unbraced length of slender steel sections under bending and compression effects. Required objectives are achieved by selecting a wide range of steel sections having non compact to slender webs and flanges. After making a careful selection of different steel sections, each steel section is analyzed under compression and bending for a given unbraced length of steel member and optimum values of flange and web slenderness are determined. Same procedure is repeated for all selected steel sections for different unbraced length ratios. Results have determined the optimum values of flange and web slenderness which can lead towards the minimum weight and cost of steel structures.

Ultimate capacity of battened columns composed of four equal slender angles

Cold-formed steel structural members play a great role in modern steel structures due to their high strength and light weight. The behavior and strength of battened column members composed of slender angle sections are mainly governed by local buckling of angle legs or torsional buckling of the angle between batten plates. Moreover, local buckling depends on the interaction between the width–thickness ratio of angle leg, overall slenderness ratio of angle between batten plates and overall slenderness of column. Theoretical study has been carried out by a nonlinear material and geometrical finite element model. Numerous cases of slender battened column sections having different width–thickness angle leg ratios, overall slenderness ratios between batten plates and overall slenderness ratios are chosen in this study. Complete ultimate strength curves are drawn and different failure modes are studied by taking different member lengths, which produce local or torsional buckling of single angles between batten plates or overall buckling of the member. Empirical equations for the effect of shear deformation factor and the ultimate axial load capacities of members formed of battened slender angle sections are proposed. Strengths of axially loaded battened members predicted using finite element as well as the proposed empirical equations is compared with the design strengths obtained using North American and European codes. It is concluded that the design strengths predicted by North American and European codes are generally conservative, and these design rules have been shown to be reliable using reliability analysis.

Pullout resistance of bearing reinforcement embedded in coarse-grained soils

The bearing reinforcement was developed as a cost-effective earth reinforcement. It is composed of a longitudinal member and transverse members. The longitudinal member is made of a steel deformed bar and the transverse members are a set of equal angles. The present article studies the influence of soil properties (friction angle, grain size and gradation) and dimension and spacing of the transverse members on the pullout mechanism of the bearing reinforcement. The total pullout resistance is the sum of the pullout friction and the pullout bearing resistance. The tan δ/tan ϕ ratio, where δ is the friction angle between soils and the longitudinal member and ϕ is the internal friction angle of soil, is greater than unity because of the roughness and rigidity of the steel deformed bar. The bearing failure mechanism of a single transverse member is dependent upon the B/D50 value, where B is the leg length of the transverse member and D50 is the average grain size of the soil. The transverse member interference is dependent upon the ratio of spacing between transverse members and the leg length of transverse members, S/B. Based on a critical analysis of the test results, the pullout resistance equations of the bearing reinforcement with different dimensions and spacing between transverse members embedded in different coarse-grained soils are introduced and verified. These equations were developed based on a limit equilibrium analysis, which is a simple rational method for analyzing the internal stability of bearing reinforcement earth walls.

4변형 인자에 의한 고강도콘크리트의 내화성능 평가

A numerical model considering the internal vaporization and the creep effect, in the form of a analytical program, for tracing the behavior of high strength concrete(HSC) members exposed to fire is presented. The two stages, i.e., spalling procedure and fire resistance time, associated with the thermal, moisture flow, creep and structural analysis, for the prediction of fire resistance behavior are explained. The use of the analytical program for tracing the response of HSC member from the initial pre-loading stage to collapse, due to fire, is demonstrated. Moisture evaporates, when concrete is exposed to fire, not only at concrete surface but also at inside the concrete to adjust the equilibrium and transfer properties of moisture. Finite element method is employed to facilitate the moisture diffusion analysis for any position of member, so that the prediction method of the moisture distribution inside the concrete members at fire is developed. The validity of the numerical model used in this program is established by comparing the predictions from this program with results from others fire resistance tests. The analytical program can be used to predict the fire resistance of HSC members for any value of the significant parameters, such as load, sectional dimensions, member length, and concrete strength.

Evaluate the capability and accuracy of response-2000 program in prediction of the shear capacities of reinforced and prestressed concrete members

The program Response-2000 developed at the University of Toronto by Evan C. Bentz (1) was used in this research to obtain shear strength predictions. This program allows users to analyze beams and columns subjected to moment, shear, and axial loads comprising virtually any type of beam geometry, material types, and material properties. The fundamental theory supporting the program is the Modified Compression Field Theory (MCFT).Member response analysis and sectional analysis were both used in Response-2000 to predict the behavior of the beams. Member response calculates the full member behavior including the deflection and curvature along the member length, as well as predicted failure modes. The analysis was performed by specifying the length subjected to shear and any constant moment region. Response-2000 provided a very good prediction of experimental behavior when compared to a database of 534 beams tested in shear. These include prestressed and reinforced sections, very large footing-like sections, sections made with very high strength concrete and elements with unusual geometry. All are predicted well. The results include that Response-2000 can predict the failure shear with an average experimental over predicted shear ratio of 1.05 with a coefficient of variation of 12%. This compares favorably to the ACI 318-08 [2] Code prediction ratios that have an average of 1.20 and a coefficient of variation of 32%.

Elastic buckling of cold-formed channel sections in shear

The paper studies and provides solutions to the elastic buckling of whole channel sections including flanges and lips where the sections are loaded in pure shear parallel with the web. The elastic buckling analyses of thin-walled channel sections in pure shear have been implemented by means of the Spline Finite Strip Method (SFSM) to determine the elastic buckling loads (Vcr) of the sections. The shear buckling coefficients (kv) of the web for design of a section are back-calculated from the shear buckling loads. The main variables are the flange widths, member lengths and lip sizes. The boundary conditions at two end sections are simply supported. The results of the analyses plotted in the format of interaction charts are given as design guidelines for designers to predict the elastic buckling shear coefficient (kv) without using the Spline Finite Strip Method (SFSM) software. Typical buckling modes at different flange widths, member lengths and lip sizes are also included in this paper. The modes include local web and flange buckling, section distortional buckling and section twisting.

Efficient combination of a TCUD method and an initial force method for determining initial shapes of cable-supported bridges

The TCUD method (Kim and Lee, 2001) can provides the reasonable initial shape of cable-supported bridges under full dead load by including the unstrained lengths of the cable members as unknowns and introducing additional constraint conditions equal to the total number of the cable members. However, the axial deformations in the girder and main tower members are not avoidable which result in some difference from a target configuration when long-span cable-supported bridges are considered. In this study, an effective method to be able to eliminate those axial deformations as well as to preserve merits of the TCUD method is newly proposed. For this purpose, the TCUD method and the initial force method with successive substitution are reviewed based on an elastic catenary cable element, respectively, and a new algorithm combining two methods efficiently is presented. In addition, a truss-cable element for modeling hangers and a beam-column element for the girder and main tower members are supplementarily developed, respectively. The proposed method is applied for two suspension bridges and a cable-stayed bridge to demonstrate its accuracy and effectiveness.

The South Australian Legislative Council: Possibilities for Reform

This paper seeks to enter the current debate over the future of the South Australian Legislative Council by critiquing recent reform proposals and then outlining some modest suggestions for reform. The paper contends that a number of recent reform proposals are explicitly partisan and seek to enlarge the role of large parties and majority government. On the contrary others would ban political parties. The paper contends that whilst the Legislative Council exhibits many of the characteristics of an effective and useful upper house, reform of four areas would enable its review function to be improved. These areas include: the size of the Council; the term lengths of members; the method for resolving deadlocks; and the method for replacing retiring members. The paper then critically examines the proposal to ban political parties; and argues instead that instituting the Robson Rotation system would promote freedom of association and freedom of choice by voters.

A Method of Determing Dynamic Stability Critical Length of Construction Member

Based on the theory of elastic stability of structure,the calculating formula for dynamic stability critical length of construction member being in lateral resonance under the axial dynamic load is derived in this paper. The influence of different parameters, such as end conditions; rod size; damp force and excitation frequency, natural frequency, rod material, on dynamic stability critical length of rod is analyzed. The paper puts forward some related measures for reducing vibration of rod, and may provide reference values for the design and analysis of engineering.