Bending Failure Mode and Prediction Method of the Compressive Strain Capacity of A Submarine Pipeline with Dent Defects

A dent is a common type of defects for submarine pipeline.For submarine pipelines,high hydrostatic pressure and internal pressure are the main loads.Once pipelines bend due to complex subsea conditions,the compression strain capacity may be exceeded.Research into the local buckling failure and accurate prediction of the compressive strain capacity are important.A finite element model of a pipeline with a dent is established.Local buckling failure under a bending moment is investigated,and the compressive strain capacity is calculated.The effects of different parameters on pipeline local buckling are analyzed.The results show that the dent depth,external pressure and internal pressure lead to different local buckling failure modes of the pipeline.A higher internal pressure indicates a larger compressive strain capacity,and the opposite is true for external pressure.When the ratio of external pressure to collapse pressure of intact pipeline is greater than 0.1,the deeper the dent,the greater the compressive strain capacity of the pipeline.And as the ratio is less than 0.1,the opposite is true.On the basis of these results,a regression equation for predicting the compressive strain capacity of a dented submarine pipeline is proposed,which can be referred to during the integrity assessment of a submarine pipeline.

FATIGUE LIFE PREDICTION OF RC BEAMS STRENGTHENED WITH PRESTRESSED CFRP UNDER CYCLIC BENDING LOADS

The application of prestressed carbon reinforced polymer （prestressed CFRP） in reinforced concrete （RC） members can improve the mechanical properties of strengthened structures and strengthening efficiency. This paper proposed a semi-empirical prediction fornmla of fatigue lives of the RC beams strengthened with prestressed CFRP under bending loads. The formula is established based on the fatigue life prediction method of RC beams and fatigue experimental data of non-prestressed CFRP reinforced beams done before. Fatigue effect coefficient of the formula was confirmed by the fatigue experiments of the RC beams strengthened with prestressed carbon fiber laminate （prestressed CFL） under cyclic bending loads. Fatigue lives of the strengthened beams predicted using the formula agreed well with the experimental data.

Behavior of Reinforced Concrete Columns under Combined Axial Load and Bending in Accordance with a Nonlinear Numerical Model

A nonlinear numerical model was developed to analyze reinforced concrete columns under combined axial load and bending up to failure. Results of reinforced concrete columns under eccentric compression tested to failure are presented and compared to results from a numerical nonlinear model. The tests involved 10 columns with cross-section of 250 mm × 120 mm, geometrical reinforcement ratio of 1.57% and concrete with compression strength around 40 MPa, with 3,000 mm in length. The main variable was the load eccentricity in the direction of the smaller dimension of cross-section. Experimental results of ultimate load and of the evolution of transverse displacements and concrete strains are compared with the numerical results. The estimated results obtained by the numerical model are close to the experimental ones, being suitable for use in verification of elements under combined axial load and bending.

GENERAL SOLUTION OF THE OVERALL BENDING OF FLEXIBLE CIRCULAR RING SHELLS WITH MODERATELY SLENDER RATIO AND APPLICATIONS TO THE BELLOWS (Ⅰ)-GOVERNING EQUATION AND GENERAL SOLUTION

The overall bending of circular ring shells subjected to bending moments and lateral forces is discussed. The derivation of the equations was based upon the theory of flexible shells generalized by E.L. Axelrad and the assumption of the moderately slender ratio less than 1/3 (i.e., ratio between curvature radius of the meridian and distance from the meridional curvature center to the axis of revolution). The present general solution is an analytical one convergent in the whole domain of the shell and with the necessary integral constants for the boundary value problems. It can be used to calculate the stresses and displacements of the related bellows. The whole work is arranged into four parts: (Ⅰ) Governing equation and general solution; (Ⅱ) Calculation for Omega_shaped bellows; (Ⅲ) Calculation for C_shaped bellows; (Ⅳ) Calculation for U_shaped bellows. This paper is the first part.

THE CRACK TIP FIELDS OF ORTHOTROPIC COMPOSITE PLATE UNDER BENDING

In this paper, mechanics analysis for crack tip fields of linear elastic orthotropic composite plate under symmetric bending load was done. By using a complex variable method, the equations for bending moment, twisting moment, stress, strain and displacement fields near crack tip are derived.

Segmental Bridges under Combined Torsion, Bending and Shear

Segmental bridges with unbonded prestressed tendons have some advantages, such as the weather independence and the corrosion protection of prestressing tendons. This paper analyzed the behavior of a prestressed segmental bridge with unbonded tendons under combined loading of torsion, bending and shear. According to the experiment research, a modified skew bending model was developed to calculate the bearing capacity of segmental bridges subjected to combined bending, shear and torsion. The finite element method was used to investigate the deflection behaviors of such structure, also to check the theoretical model. The theoretical and FEM research results were compared favorably with the test results from Technical University of Braunschweig, Germany. Finally, suggestion for the design and construction of segmental bridges with external prestressing was made.

BENDING OF CORNER-SUPPORTED RECTANGULAR PLATE UNDER CONCENTRATED LOAD

In this paper the solution for the bending of corner-supported rectangular plate under concentrated load at any point (α/2, η) of the middle line of the plate is given by means of a conception called modified simply supported edges and the method of superposition. Some numerical example is presented. The solution obtained by this method checks very nicely with what was obtained by G.T. Shih[3] by means of spline finite element method when η=d/2. This shows that this method of solution is satisfactory.

Fatigue crack growth behavior of a 170 mm diameter stainless steel straight pipe subjected to combined torsion and bending load

In a nuclear powerplant,the rotary equipment,such as a pump directly fitted with hanger in the piping system,experiences torsional and bending loads.Higher crack growth rate occurs because of this torsional load in addition to the bending load.Hence,it is necessary to study the fatigue behavior of piping components under the influence of combined torsional and bending load.In this study,experimental fatigue life evaluation was conducted on a notched stainless steel SA312 Type 304LN straight pipe having an outer diameter of 170 mm.The experimental crack depth was measured using alternating current potential drop technique.The fatigue life of the stainless steel straight pipe was predicted using experiments,Delale and Erdogan method,and area-averaged root mean square-stress intensity factor approach at the deepest and surface points of the notch.Afterward,the fatigue crack growth and crack pattern were discussed.As a result,fatigue crack growth predicted using analytical methods are in good agreement with experimental results.

Location estimating of load for bending beam

We propose a method by which location of load for bending beam can be approxi- mately retrieved by matching the measured and theoretically forecasted displacement distribu- tion. To show the method validity, a principal experiment is performed.