Influence of the Cross–Sectional Shape and Corner Radius on the Compressive Behaviour of Concrete Columns Confined by FRP and Stirrups

Axial compression tests were carried out on 72 FRP (fiber reinforced polymer)–stirrup composite−confined concrete columns. Stirrups ensure the residual bearing capacity and ductility after the FRP fractures. To reduce the effect of stress concentration at the corners of the confined square−section concrete columns and improve the restraint effect, an FRP–stirrup composite−confined concrete structure with rounded corners is proposed. Different corner radii of the stirrup and outer FRP were designed, and the corner radius of the stirrup was adjusted accurately to meet the designed corner radius of the outer FRP. The cross−section of the specimens gradually changed from square to circular as the corner radius increased. The influence of the cross−sectional shape and corner radius on the compressive behaviour of FRP–stirrup composite−confined concrete was analysed. An increase in the corner radius can cause the strain distribution of the FRP to be more uniform and strengthen the restraint effect. The larger the corner radius of the specimen, the better the improvement of mechanical properties. The strength of the circular section specimen was greatly improved. In addition, the test parameters also included the FRP layers, FRP types and stirrup spacing. With the same corner radius, increasing the number of FRP layers or densifying the stirrup spacing effectively improved the mechanical properties of the specimens. Finally, a database of FRP–stirrup composite−confined concrete column test results with different corner radii was established. The general calculation models were proposed, respectively, for the peak points, ultimate points and stress–strain models that are applicable to FRP−, stirrup− and FRP–stirrup−confined concrete columns with different cross−sectional shapes under axial compression.

An Analytical Elastic Solution for Right-Angle Trapezoidal Opening in Steeply Inclined Coal Seam

In the process of underground mining, steeply inclined rocks or coal seams are often encountered, forming the openings of right-angle trapezoid. According to the geological conditions of a mining project in China, an analytical elastic solution of stress and displacement around right-angle trapezoidal opening in a homogeneous, isotropic, and linear elastic geomaterial is presented, which is based on the evaluation of the conformal mapping representation by an appropriate numerical calculation and the complex potential functions. The different results from other shaped openings are shown as follows. In a right-angle trapezoidal opening, the maximum displacements of roof falling occur on the low side, while the most horizontal displacements on the low side are around the roof and the most horizontal displacements on the high side are around the middle of the high side in this opening. These results are also compared with the numerical calculations in FLAC software, illustrating that the solution may be easily applied to rock mechanics or rock engineering for understanding the deformation of floor heave and roof falling down. The solution is also suitable for optimum design of bolt supporting in a right-angle trapezoidal opening, which is different from the traditional concept of symmetrical bolt supporting. Finally, a methodology is proposed for the estimation of conformal mapping coefficients for a given cross-sectional shape of an opening without symmetrical axis.

Cross-sectional shape evolution of GaN nanowires during molecular beam epitaxy growth on Si(111)

We study the cross-sectional shapes of GaN nanowires (NWs) by transmission electron microscopy. The shape is examined at different heights of long NWs, as well as at the same height...

Stimulated Brillouin scattering in a sub-wavelength anisotropic waveguide with slightly-misaligned material and structural axes: Misalignment-sensitive behaviors and underlying physics

The stimulated Brillouin scatterings (SBSs) in the sub-wavelength rutile waveguides with slightly misaligned material and structural axes are numerically studied. The misalignment is introduced between the extraordinary material axis and longitudinal axis of the waveguide only. Four nanowire waveguides with different cross-sectional geometries are considered. They consist of a circular waveguide, two elliptical waveguides with different cross-sectional orientation angles, and a trapezoidal waveguide with a completely unsymmetrical cross-sectional shape. As reported earlier, the resonant peaks emerging rapidly in response to the introduced small misalignment angle can also be observed in the calculated Brillouin gain spectra of the considered waveguides. But these misalignment-sensitive resonant peaks further exhibit some extraordinary behaviors, which may not be intuitively understandable. For instance, despite a plausible absence of symmetry breaking, many misalignment-sensitive resonant peaks can still be observed in the forward SBS gain spectrum of the trapezoidal waveguide. Based on the symmetry properties of the considered waveguides, the physics underlying the observed extraordinary phenomena are revealed. The obtained results highlight the effectiveness of introducing symmetry breakings for activating/harnessing opto-mechanical couplings in photonic-phononic micro structures, which would enable us to gain some deeper insights into the sub-wavelength opto-mechanics in anisotropic media.

Analysis of Residual Ridge Morphology in a Group of Edentulous Patients Seeking NHS Dental Implant Provision—A Retrospective Observational Lateral Cephalometric Study

A convenience sample of 154 edentulous patients referred for implant provision at a Regional National Health Service Dental Hospital in the North West of England were identified. The cephalometric radiographs that were taken as part of the patient baseline investigation were assessed. Digital tracing was used to measure the anterior maxillary and mandibular bone height and ridge angle with respect to the maxillary and mandibular planes. The mean height of the bone in the maxilla was found to be 14 mm, and the mean ridge angle for the anterior maxillary residual ridge is 104°. The mean height of bone in the mandible was 18 mm, while the mean ridge angle for the anterior mandibular residual ridge was 77°. Using the Cawood and Howell classification demonstrated that class VI mandibles were the most common. The cross-sectional shape of the mandible varied, with the triangular shape most common. Although there was adequate bone stock for implant placement in these cases, the mandibular residual ridge resorption presents a lingual inclination to the residual bone. The limited residual ridge position and inclination would dictate that conventional implant placement could be challenging.

Discrete sizing, cross-sectional shape, topology optimization, and material selection of a framed automotive body

This study proposed a discrete structural optimization method for a framed automotive body. Up to four types of discrete design variables are considered simultaneously, that is, the sizing, cross-sectional shape, topology, and material variables. Firstly, to solve the nonconvex and nonlinear optimization problem, the original non-dominated sorting genetic algorithm, the third version (NSGA-III), is adapted. An improved extreme points identification scheme and a new mutation operator are proposed to stabilize the normalization of the population and accommodate the manufacturing constraints, respectively. Two test problems demonstrate that the modified NSGA-III can handle continuous and discontinuous multiple objective optimization. Subsequently, the classical 10-bar truss is used to illustrate the proposed method. A weight reduction of 4.5 kg is achieved as compared to previous optimal designs in the literature. Finally, a framed automotive body is optimized for maximizing the first order natural frequency and minimizing the total mass, the maximum stresses and the maximum displacements in different load cases and the manufacturing cost. The results obtained by different optimization procedures are presented and discussed. The results demonstrate the feasibility and effectiveness of the proposed method. A weight reduction of 17.59% is achieved while other structural performances satisfy the design requirements.

Optimization and Experimental Study of the Subsea Retractable Connector Rubber Packer based on Mooney-Rivlin Constitutive Model

The sealing performance of the rubber packer is of vital importance for the subsea retractable connector, and the cross-sectional shape of the rubber packer is one of the most important factors affecting it. The compression distance of the rubber packer is increased by 19.54% utilizing the established two-dimensional numerical model. In addition, a new parameter called the anti-shoulder extrusion variable was defined in this paper. Shoulder extrusion will not occur when using this variable as a constraint during simulation. In general, the upper end and the lower end of a rubber packer are subject to different constraints, and the structural parameters of the rubber packer affect each other in terms of sealing performance. Therefore, the importance and originality of this study are exploring the optimization of the thickness and chamfer angles of the upper and lower ends of the rubber packer by use of a combination of the response surface optimization method and the multi-objective genetic algorithm, taking the thickness and chamfer angles of the upper and lower ends as design variables, and the stress on the inner side of the casing wall and the axial force of the compressed rubber packer as optimization objectives. Besides that, the anti-shoulder extrusion variables are also introduced as constraints to prevent shoulder extrusion. Ultimately, the cross-sectional shape of the rubber packer with a smaller-thickness and larger-angle upper end, and a larger-thickness and smaller-angle lower end can be obtained. The result to emerge from the test in this paper is that the pipe pressure that can be sealed by the optimized rubber packer structure is 25.61% higher than that before optimization. The anti-shoulder extrusion variable and the asymmetric cross-sectional shape of the rubber packer proposed in this paper shed new light on the finite element simulation of rubber and the research on similar seals.

Research on Optimization of Cross-sectional shape for Aircraft Door Rubber Seal

Rubber seals are widely used in aircraft door structures, which play important roles on sealing, sound insulation and heat preservation. Aircraft door rubber seals are critical to the normal flight of the aircraft and the safety of the passengers. In this paper, a finite element model of rubber seals for aircraft door with different cross-sections is established. The deformation and stress distribution of the seals under the action of concentrated force and compressive displacement are analyzed, and the calculation results of seals with different cross-sections are compared. The optimal structural form of the cross-sectional shape of the seal is obtained. The research results are of great significance to improve the safety and durability of seals and enhance the sealing performance.