Study on critical buckling load calculation method of piles considering passive and active earth pressure

Yong-hui Chen,Long Chen,Kai Xu,Lin Liu,Charles W.W. Ng 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.3

Different types of long slender pile shall buckle with weak soil and liquefied stratum surrounded. Different from considering single side earth pressure, it was suggested that the lateral earth pressure can be divided into two categories while buckling: the earth pressure that prevent and promotes the lateral movement. Active and passive earth pressure calculation model was proposed supposing earth pressure changed linearly with displacement considering overlying load, shaft resistance, earth pressure at both sides of the pile. Critical buckling load calculation method was proposed based on the principle of minimum potential energy quoting the earth pressure calculation model. The calculation result was contrasted with the field test result of small diameter TC pile (Plastic Tube Cast-in-place pile). The fix form could be fixed-hinged in the actual calculation assuring the accuracy and certain safety factor. The contributions of pile fix form depend on the pile length for the same geological conditions. There exists critical friction value in specific geological conditions that the side friction has larger impact on the critical buckling load while it is less than the value and has less impact with larger value. The buckling load was not simply changed linearly with friction. The buckling load decreases with increased limit active displacement and the load tend to be constant with larger active displacement value; the critical buckling load will be the same for different fix form for the small values.

Study on critical buckling load calculation method of piles considering passive and active earth pressure

Chen, Yong-Hui,Chen, Long,Xu, Kai,Liu, Lin,Ng, Charles W.W. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.3

Different types of long slender pile shall buckle with weak soil and liquefied stratum surrounded. Different from considering single side earth pressure, it was suggested that the lateral earth pressure can be divided into two categories while buckling: the earth pressure that prevent and promotes the lateral movement. Active and passive earth pressure calculation model was proposed supposing earth pressure changed linearly with displacement considering overlying load, shaft resistance, earth pressure at both sides of the pile. Critical buckling load calculation method was proposed based on the principle of minimum potential energy quoting the earth pressure calculation model. The calculation result was contrasted with the field test result of small diameter TC pile (Plastic Tube Cast-in-place pile). The fix form could be fixed-hinged in the actual calculation assuring the accuracy and certain safety factor. The contributions of pile fix form depend on the pile length for the same geological conditions. There exists critical friction value in specific geological conditions that the side friction has larger impact on the critical buckling load while it is less than the value and has less impact with larger value. The buckling load was not simply changed linearly with friction. The buckling load decreases with increased limit active displacement and the load tend to be constant with larger active displacement value; the critical buckling load will be the same for different fix form for the small values.

Buckling of axial compressed cylindrical shells with stepwise variable thickness

Fan, H.G.,Chen, Z.P.,Feng, W.Z.,Zhou, F.,Shen, X.L.,Cao, G.W. Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1

This paper focuses on an analytical research on the critical buckling load of cylindrical shells with stepwise variable wall thickness under axial compression. An arctan function is established to describe the thickness variation along the axial direction of this kind of cylindrical shells accurately. By using the methods of separation of variables, small parameter perturbation and Fourier series expansion, analytical formulas of the critical buckling load of cylindrical shells with arbitrary axisymmetric thickness variation under axial compression are derived. The analysis is based on the thin shell theory. Analytic results show that the critical buckling load of the uniform shell with constant thickness obtained from this paper is identical with the classical solution. Two important cases of thickness variation pattern are also investigated with these analytical formulas and the results coincide well with those obtained from other authors. The cylindrical shells with stepwise variable wall thickness, which are widely used in actual engineering, are studied by this method and the analytical formulas of critical buckling load under axial compression are obtained. Furthermore, an example is presented to illustrate the effects of each strake's length and thickness on the critical buckling load.

Buckling of axial compressed cylindrical shells with stepwise variable thickness

H.G. Fan,Z.P. Chen,W.Z. Feng,F. Zhou,X.L. Shen,G.W. Cao 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.1

This paper focuses on an analytical research on the critical buckling load of cylindrical shells with stepwise variable wall thickness under axial compression. An arctan function is established to describe the thickness variation along the axial direction of this kind of cylindrical shells accurately. By using the methods of separation of variables, small parameter perturbation and Fourier series expansion, analytical formulas of the critical buckling load of cylindrical shells with arbitrary axisymmetric thickness variation under axial compression are derived. The analysis is based on the thin shell theory. Analytic results show that the critical buckling load of the uniform shell with constant thickness obtained from this paper is identical with the classical solution. Two important cases of thickness variation pattern are also investigated with these analytical formulas and the results coincide well with those obtained from other authors. The cylindrical shells with stepwise variable wall thickness, which are widely used in actual engineering, are studied by this method and the analytical formulas of critical buckling load under axial compression are obtained. Furthermore, an example is presented to illustrate the effects of each strake’s length and thickness on the critical buckling load.

Analysis of buckling load of glass fiber/epoxy-reinforced plywood and its temperature dependence

Choi, Sung Woong,Li, Meixian,Lee, Woo Il,Kim, Han Sang SAGE Publications 2014 Journal of composite materials Vol.48 No.18

<P>There has been an increase in the use of fiber-reinforced composite materials in many areas. In particular, glass-fiber-reinforced composites have gained in popularity owing to their low cost, high-strength properties, durability, ease of repair, and being simple to form. This paper analyzes the buckling load for the glass-fiber-reinforced plywood specifically used for the liquid natural gas cargo tank and carriers, especially the No 96 cargo containment system insulation box. The buckling load of the plywood reinforced with glass fiber composite on both outer surfaces was estimated with various composite thicknesses and compared with the buckling load of unreinforced plywood. The buckling load was also evaluated at various temperatures to verify the temperature dependence of the buckling load. A much higher buckling load for the glass fiber/epoxy-reinforced plywood was obtained as the number of glass fiber/epoxy prepreg composite was increased. However, the rate of increase in the buckling load decreased as the temperature decreased and as the number of glass fiber/epoxy prepreg composite increased.</P>

Time-dependent analysis of slender, tapered reinforced concrete columns

Alexandre de Macêdo Wahrhaftig 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.2

This study analyzed stresses in concrete and its reinforcement, computing the additional loading transferred by concrete creep. The loading varied from zero, structure exclusively under its self-weight, up to the critical buckling load. The studied structure was a real, tapered, reinforced concrete pole. As concrete is a composite material, homogenizing techniques were used in the calculations. Due to the static indetermination for determining the normal forces acting on concrete and reinforcement, equations that considered the balance of forces and compatibility of displacement on cross-sections were employed. In the mathematical solution used to define the critical buckling load, all the elements of the structural dynamics present in the system were considered, including the column self-weight. The structural imperfections were linearized using the geometric stiffness, the proprieties of the concrete were considered according to the guidelines of the American Concrete Institute (ACI 209R), and the ground was modeled as a set of distributed springs along the foundation length. Critical buckling loads were computed at different time intervals after the structure was loaded. Finite element method results were also obtained for comparison. For an interval of 5000 days, the modulus of elasticity and critical buckling load reduced by 36% and 27%, respectively, compared to an interval of zero days. During this time interval, stress on the reinforcement steel reached within 5% of the steel yield strength. The computed strains in that interval stayed below the normative limit.

Load-carrying capacities and failure modes of scaffold-shoring systems, Part II: An analytical model and its closed-form solution

Huang, Y.L.,Kao, Y.G.,Rosowsky, D.V. Techno-Press 2000 Structural Engineering and Mechanics, An Int'l Jou Vol.10 No.1

Critical loads and load-carrying capacities for steel scaffolds used as shoring systems were compared using computational and experimental methods in Part I of this paper. In that paper, a simple 2-D model was established for use in evaluating the structural behavior of scaffold-shoring systems. This 2-D model was derived using an incremental finite element analysis (FEA) of a typical complete scaffold-shoring system. Although the simplified model is only two-dimensional, it predicts the critical loads and failure modes of the complete system. The objective of this paper is to present a closed-form solution to the 2-D model. To simplify the analysis, a simpler model was first established to replace the 2-D model. Then, a closed-form solution for the critical loads and failure modes based on this simplified model were derived using a bifurcation (eigenvalue) approach to the elastic-buckling problem. In this closed-form equation, the critical loads are shown to be function of the number of stories, material properties, and section properties of the scaffolds. The critical loads and failure modes obtained from the analytical (closed-form) solution were compared with the results from the 2-D model. The comparisons show that the critical loads from the analytical solution (simplified model) closely match the results from the more complex model, and that the predicted failure modes are nearly identical.

Buckling of Orthotropic Plates under Various Inplane Loads

Inho Hwang,Jong Seh Lee 대한토목학회 2006 KSCE journal of civil engineering Vol.10 No.5

When a laminated composite plate is subjected to a compressive edge force lying in the plane of the plate, failure can occur by buckling at a stress below the strength of the material. Critical buckling loads of orthotropic plates are usually calculated using the analytical solutions which are based on the assumption of uniform end loads, despite the fact that real structures are subjected to various non-uniform inplane loads. This paper examines the buckling behavior of the orthotropic plates under non-uniform inplane loads with different boundary conditions (all edges simply supported, two loaded edges clamped and others simply supported, and all edges clamped) using the finite element method (FEM). Numerical results show that the existing formulas for buckling load based on the uniform load assumption leads to overestimation of buckling loads.

Stability of unbraced frames under non-proportional loading

Xu, L.,Liu, Y.,Chen, J. Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.11 No.1

This paper discusses the elastic stability of unbraced frames under non-proportional loading based on the concept of storey-based buckling. Unlike the case of proportional loading, in which the load pattern is predefined, load patterns for non-proportional loading are unknown, and there may be various load patterns that will correspond to different critical buckling loads of the frame. The problem of determining elastic critical loads of unbraced frames under non-proportional loading is expressed as the minimization and maximization problem with subject to stability constraints and is solved by a linear programming method. The minimum and maximum loads represent the lower and upper bounds of critical loads for unbraced frames and provide realistic estimation of stability capacities of the frame under extreme load cases. The proposed approach of evaluating the stability of unbraced frames under non-proportional loading has taken into account the variability of magnitudes and patterns of loads, therefore, it is recommended for the design practice.

맥놀이하중을 받는 공간구조물의 동적좌굴과 임계하중

하준홍(Ha, Jun-Hong),손수덕(Shon, Su-Deok),이승재(Lee, Seung-Jae) 대한건축학회 2016 大韓建築學會論文集 : 構造系 Vol.32 No.7

In this study, the dynamic unstable phenomenon and critical load variation of the spatial truss under the beating-wave load were researched. For this purpose, a non-linear governing equation of a shallow spatial truss was derived. In addition, a dynamic analysis and a characteristic analysis of the buckling phenomenon were conducted using the numerical method. The analysis model was selected considering the number of free nodes and the rise-span ratio, and the response to the periodic parameter that determines the period of the beating function was analyzed. To compare the results, a analysis for the step load and sinusoidal—wave load were also conducted. Resonance was observed in the analysis results for both the sinusoidal-wave load and the beating-wave load. The patterns of critical load level were similar in the area lower than the natural frequency, but they were different in the area above it. Furthermore, the critical level of the beating-wave load changed more sensitively than the sinusoidal-wave load did and was much lower than the step load.