Accurate SIF Analysis of a Partially Cylindrical Side Crack Opened by Far-Field Tension

In recent years, due to a remarkable progress of qualified mesh generation algorithms combinedwith computational image processing technologies, a complex shaped 3D crack analysis has been carried out more and more easily by finite element method. Generally speaking, in order to assess thereliability of numerical solution, existence of a closed-form solution or a practically exact numericalsolution is important and thank-worthy. In contrast with 2D problems, however, there are very fewnumber of closed form solutions regarding to 3D crack problems. In the present analysis, we examineda highly accurate body force method (BFM) analysis for a partially cylindrical 3D surface crackin which a suitable basic density function can be supposed reasonably by taking account the crackgeometry. The present SIF solution could be used effectively for the purpose of benchmark the finiteelement solution for general non-planar crack problems.

Sound Radiation Response of a Rectangular Plate Having a Side Crack of Arbitrary Length, Orientation, and Position

Here, sound radiation characteristics of a rectangular plate having a side crack of different crack lengths, orientations, and positions are studied considering clamped boundary conditions. First, a free and forced vibration response analysis of a cracked plate is done using the Ritz method. Orthogonal polynomials are used for faster convergence and some corner functions are used to generate the effect of a crack. Radiated sound power and radiation efficiency of the cracked plate are computed by the quadruple integration. A convergence test of radiation efficiency is carried out to fix the number of polynomials and corner functions in the analysis. It is found that the radiation efficiency and radiated sound power computed by the Ritz method are close to the same obtained from the boundary element method (BEM). The natural frequencies computed using the Ritz method are also found to be close to that obtained from the finite element method (FEM). The radiation efficiency curves of different modes are shown for a change in crack length, orientation and position. Finally, the variations of normalized sound power are shown to be due to a change in the crack parameters.

Cracking Mechanism and Strengthen Method of Reinforced Concrete Hammerhead Piers

This paper indicates cracking mechanism and strengthening method of reinfoced concrete hammerhead piers. A field investigation phase has been undertaken in conjunction with analytical studies to model the cracking process. It is shown that the front cracks in the pier cap developed because the bending tensile stress far exceeds the tensile strength, while the side crack caused by none bursting reinforcement. Based on the analysis results, an internally prestressing approach is provided, and the retrofitting effect is verified by finite element analysis. Strengthening with internally prestressed tendons of bridge pier cap is proven to be a reliable and relatively easy-to-install technique.

Experimental Study on the Effect of Joint Spacing on Fragmentation Modes and Penetration Rate under TBM Disc Cutters

Joint spacing is one of the significant factors affecting the rock fragmentation by TBM cutters. Based on laboratory test, the effect of joint spacing on the fragmentation modes and penetration under TBM disc cutters is studied. In the test, two kinds of concrete with different strengths are adopted to simulate rock sample. The joint spacing varies from 50mm, 80mm, 200mm and the intact samples are also tested for comparison. Firstly, four kinds of fragmentation modes for single-set jointed rock are found: (1) the crack initiates from the joint plane and propagates to free surface, to form fragmentation chipping. (2) The side crack and median crack initiate beneath the crushed zone and propagate to joint plane to produce chipping. (3) In the rock block indirectly indented by cutter, the crack initiates from the joint plane and propagates to adjacent joint plane to produce chipping. (4) Normal fragmentation mode. Basically, the first two kinds are generally for jointed rock, while the other two kinds are respectively for the jointed rock with small and large joint spacing. Secondly, from the viewpoint of the fragmentation modes, the effect of joint spacing on tunnel face stability is investigated and then compared with field data of Jinping II Hydropower Station. Finally, it is shown that highest penetration rate can be achieved with the joint spacing of 50-80mm, and moreover, joint spacing gives more notable effect on fragmentation of the rock with higher strength.

Study of Vibration Characteristics of Cantilever Rectangular Plate with Side Crack

In this paper, the vibration characteristics of the cantilever rectangular plate with side crack are studied in the way of analysis, which including natural frequency and mode shape. The influences of different parameters of crack, such as the locations and lengths of crack, to the vibration characteristics of the cantilever rectangular plate are investigated. The modal function of the crack plate consists two parts, which are (1) the modal function of intact cantilever rectangular plate from beam functions combination method and (2) corner functions presenting the discontinuity of displacement and slope along the crack. The natural frequencies and modal shapes can be obtained when taking the modal function into the method of Ritz. At last, the effects of the crack location and crack length on the vibration characteristics are investigated, and it could provide the theoretical basis for engineering application and the relevant study.