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Strengthening concrete structures with ultra-high performance concrete (UHPC) can both improve the bearing capacity of the original normal concrete (NC) structure and prolong the service life of the structure due to the high strength and durability of UHPC. The key to the synergistic work of the UHPC-strengthened layer and the original NC structures lies in the reliable bonding of their interfaces. In this research study, the shear performance of the UHPC–NC interface was investigated by the direct shear (push-out test) test method. The effects of different interface preparation methods (smoothing, chiseling, and planting straight and hooked rebars) and different aspect ratios of planted rebars on the failure mode and shear performance of the pushed-out specimens were studied. Seven groups of push-out specimens were tested. The results show that the interface preparation method can significantly affect the failure mode of the UHPC–NC interface, which is specifically divided into interface failure, planted rebar pull-out, and NC shear failure. The critical aspect ratio for the pull-out or anchorage of planted rebars in UHPC is around 2. The interface shear strength of straight-planted rebar interface preparation is significantly improved compared with that of the chiseled and smoothened interfaces, and as the embedding length of the planted rebar becomes longer, it first increases greatly and then tends to be stable when the rebar planted in UHPC is fully anchored. The shear stiffness of UHPC–NC increases with the increase of the aspect ratio of planted rebars. A design recommendation based on the experimental results is proposed. This research study supplements the theoretical basis of the interface design of UHPC-strengthened NC structures.

Dynamic response for a series of cylindrical shells filled with water were discussed previously, which indicated that the limit buckling load of the cylindrical shells was greatly improved by the presence of water. To obtain a good protective structure, a double layered liquid-filled hemispherical shell structure is designed. Three kinds of structures (single layered empty hemispherical shell, double layered empty hemispherical shells, and single layered liquid-filled hemispherical shell) are compared with the double layered liquid-filled hemispherical shells. The collapse behavior of four kinds of hemispherical shell structures and their deformation modes under drop hammer impact are presented to investigate the effects of inner water on the response of the liquid-filled hemispherical shells. Test results show that the effects of inner water mainly include "distributing loadings" and "ironing effect". Double layered liquid-filled hemispherical shells have the highest bearing capacity among all four kinds of structures. Three-dimensional numerical simulations of all the tested specimens were carried out using ANSYS and LS-DYNA. Under same impact condition, the effective protection space of empty hemispherical shells is very small due to its larger vertex displacement. In terms of generalized specific energy absorption (η) of structures with same vertex displacement, liquid-filled hemispherical shells are better than empty shells. For liquid-filled shells, η of double layered shells is smaller than single layered shell, but single layered shell has no inner space. Parameter analysis indicates that only the outer thickness has a significant effect on the impact force. Increasing the outer thickness and ensuring a reasonable distance between the inner and outer shell can improve the crashworthiness of double layered liquid-filled shells and protect the internal objects.

This paper carried out burst tests on the carbon and polyvinyl alcohol (PVA) fiber high-strength concrete specimens to investigate the effects of fiber type, fiber content, water content, heating rate and test specimen size on the burst, and the whole burst process of fiber-high concrete was photographed and recorded. The results indicated that fiber addition will improve the high temperature burst behavior of the high-strength concrete, and the performance of PVA is greatly different from that of carbon fiber. The water content and heating rate have little influence on the burst of the PVA test specimen, but they will greatly affect the carbon fiber test specimen. The size of the test specimen has a great influence on the burst. For the PVA concrete test specimen, the large size test specimen bursts on the surface, as for the carbon fiber test specimen, the large size test specimen delays the initial burst time, but the burst becomes fiercer.

Taking stress wave propagation into account, the governing equations of composite bar with the clamped-fixed boundary conditions considering FSDT (first order shear deformation theory) are derived on the basis of Reddy’ theory and solved by the variable-separated method. The analytic expression of the critical buckling load is obtained basing on the characteristics of homogeneous linear equations having nonzero-solution. The results of the theoretical study and the numerical calculation indicate that FSDT has influence on dynamic buckling of composite bar, and the critical buckling load is small when FSDT is considered. They also show that the magnitude of effect taken by FSDT is small when the layer angle is big.

Taking into account the effects of stress wave and the moment of inertia, the governing equations of composite laminated plate under the axial step load are derived by using Hamilton principle. Based on Variable Separation Method, the analytical expression of the critical dynamic buckling load for symmetry composite laminated plates with one edge fixed and three edges simply-supported can be deduced by considering the characteristics of the buckling solution, and the buckling mode is also acquired. Using MATLAB software, the relationship between the critical load and length can be obtained. The influences of different layer parameters and the order of the mode on the dynamic buckling are discussed.

Considering the effect of stress wave, the dynamic buckling of circular cylindrical shells under an axial step load is discussed using the classical shell theories and the state-space technique in the paper. Based on the Hamilton’s principle, the dynamic buckling governing equations of shells are derived and solved with the Rayleigh-Ritz method. If the linear homogeneous equations have a non-trivial solution, the determinant of the coefficient matrix must be equal to zero, so the expression of the critical load on the dynamic buckling is got. The relationship between the critical load and length is obtained by using MATLAB software. The influences of boundary conditions, thickness, the number of circumferential waves and the number of axial waves on the dynamic buckling loads are discussed based on numerical computation.

Computer simulation on the dynamic buckling of different forms of initial-defect and different boundary conditions plates under axial impact load was carried out by using ABAQUS /Standard.The strain-time history curve of the symmetric point of upper and lower surface is give,they are coincidence before the buckling and suddenly separate when the buckling occur which is called be bifurcation,and the critical buckling time is also acquired. The results indicate that the influence of different initial-defect locations and amplitudes on the dynamic buckling is very great.

The computer simulation of the dynamic buckling on the cylindrical shell subjected to pulse load was carried out by ABAQUS/Expliect. The value of the rectangle and triangle pulse load is the same and the shape is different, and they are applied on the impact end of the cyclindrical shell. The influence of the load amplitude, the shape of load and the effect of the stress wave on the critical buckling time of cylindrical shell were discussed. The radial displacement curve was obtained which indicates that stress wave propagate along the length of the cylindrical shells, and the curve of strain time history is also acquired which is used to judge bifurcation and give the critical time.

The compressive strength of two kinds of lightweight concrete was studied. The results show that the incorporation of EPS can improve the plastic deformation ability of concrete. The effect of EPS on the compressive strength of concrete depends on the amount and particle size of EPS foam. The incorporation of manufactured sand can improve the compressive strength of EPS concrete. The effect of the amount of manufactured sand on the compressive strength of EPS concrete depends on the amount of EPS in concrete.

Dynamic buckling of bars under step load was studied by considering the stress wave effect. Straight bars without axial inertia were taken as an example when deformation was small. The buckling solution satisfying the boundary conditions was given by the semi-analytic method. The buckling solution was substituted to the dynamic buckling governing equations. The unified expression of dynamic buckling critical load was obtained by discussing the character of the solution. The dynamic buckling critical load was obtained by calculating the value of when the stress wave propagated to the critical length . The value of dynamic buckling load was 2.5 times the one’s of static buckling load with corresponding equivalent length.

The thermal property of closed-cell aluminum foam is studied numerically and the effects of the distribution of the circular pore on the thermal property are studied theoretically. When the convection and radiation are ignored, the effects of porosity, cell size, and distribution forms of pore on the apparent thermal conductivity are investigated. Moreover, the effects of air in the pore on the thermal property are analyzed as well. Simulation results show that apparent thermal conductivity linearly increases with the increase of porosity, while the cell size and the distribution have negligible effects on the thermal property. By comparison, thermal conductivity of air has slight effect on thermal property of foamed aluminum in the context of small size pore.

The dynamic response of fluid-filled hemispherical shell in mass impact is studied by experiment using DHR9401. Combining the time history of impact force with experimental observation of the deformation process, it can be seen that the dynamic response can be divided into four stages: the flattening around the impact point, the forming and expanding outward of shell plastic hinge, the plastic edge region flatten by the punch, and elastic recovery. The experimental results show that: Because the shell filled with liquid, the local impact load that the shell suffered is translated into area load and loads on the inner shell uniformly, so that it has a high carrying capacity. Numerical simulation is used to study the time history of energy absorption of different shell structures. The result shows that the crashworthiness of sandwich fluid-filled shell is improved greatly. Under the certain impact energy, deformation of its inner shell is very small, which can provide effective security space.

In this paper, the differential equations of the steel rope shock absorber are established under the basic excitation, using the Fourier series expansion method and the Harmonic balance method, the corresponding frequency response equations are derived, then their numerical solutions is got, and the influence of the mass, damping, stiffness, and hysteretic force on the frequency response characteristic is analyzed under the basic excitation. It can be drawn by analyzing and comparing. Under the basic excitation, with the basic simplified mass increasing, the natural frequency will decrease, while the resonance amplitude will increase. With the steel rope damping, stiffness and the foundation damping increasing, the natural frequency will not change significantly, while the resonance amplitude will decrease. With the foundation stiffness increasing, the natural frequency and the resonance amplitude will increase significantly. The equipment mass and steel rope hysteretic force have no significant effect on the frequency response characteristics.

Sandwich cellular structure, associated with more excellent mechanical properties and physical characteristic, such as, panel ductility and high core compressibility, is widely used in aerospace, transportation, military equipment and civil infrastructure. Due to the special compression properties of functional graded cores, the graded sandwich structure presented more excellent impact resistance than the ungraded sandwich. This article presents the results of experimental, numerical investigation into the failure mode and dynamic plastic response of layered graded sandwich plate with layered honeycomb cores to air blast loading. The core arrangements (different core density) effects on the structure’s deformation behavior, energy absorption and impact resistance were mainly discussed. Three typical failure modes can be observed, that was, local deformation, global bending and penetration failure. Under specific loading conditions, the graded sandwich had more excellent impact resistant and energy absorption ratio, especially for the density-decreased core arrangement sandwich.

Computer simulation of cylindrical shell subject to lateral impact by rigid projectile is carried out. The effects of three kinds of typical rigid projectiles, geometric parameters of cylindrical shell and constraint conditions on critical speed are analyzed. The results indicate that the shape of projectile and size of cylindrical shell have a great influence on penetration, and the tapered projectile has a minimum critical speed. The influence of constraint conditions on penetration has a great relationship with thickness of cylindrical shells; energy distribution varies with different thickness of cylindrical shells.

For rebuilding an ancient tower at province Gansu, the structure of dislocation steel joints was used make the tower having filtering contraction shape. For this kind of dislocation steel joints structure, there are no relevant calculation regulations in the Code for design of steel structures in China. To investigate the mechanical characteristics of the joints and ensure the safety of the joints and the whole structure under the applied and seismic load, the computer simulation research on the dislocation steel joint was carried out according to the design requirement. Under the extensive analysis the comprehensive understanding of the mechanical characteristics of the dislocation steel joints was obtained and the reference basis for design was provided.

The buckling of no-way double-layer portal frame that column is fixed is simulated by using ANSYS. Through analyzing the portal frame subjected to different loads on the roof of the structure that are uniform load, trapezoidal load and triangular load, the critical buckling load of the double-layer portal frame and buckling mode are obtained. The regular between the critical buckling load and the form of the load on the roof can be acquired by the analysis of the results, which can be used as a reference for engineering application.

The dynamic buckling of composite bars subject to axial rigid body impact are simulated using the finite-element software ABAQUS6.8. The critical velocity and the bifurcate time are obtained by stain-time curve and effects of fiber angle and impact velocity on dynamic buckling behavior of composite bars are also investigated. The results indicate that the ply angle and impact velocity have an influence on dynamic buckling of composite bars.

Compressive buckling of laminate plates with a delamination are simulated using ABAQUS 6.8 software. Effects of sizes, positions, asymmetric and shapes of delamination on the compressive buckling are investigated without the consideration of delamination growth and contact. The results indicate the sizes, positions, asymmetric and shapes of delamination have an important influence on compressive buckling.

Chaotic motion of symmetric laminated composite arch with two hinge supports under transverse periodic excitation was investigated. The nonlinear dynamic equations of the arch are changed into the square-order and cubic nonlinear differential dynamic system by Galerkin method, and its homoclinic orbit parameter equations are also acquired. The critical conditions of horseshoe-type chaos are obtained by using Melnikov function. The influence of loading frequency on chaotic region are analysed by numerical calculation. The motion behaviors of system are described through the bifurcation diagrams, the time-history curve, phase portrait and Poincaré map. The results are given as follows. The influence of loading frequency on chaotic region are significant. When the height of arch reach some value, the system can occur horseshoe-type chaos. The system of symmetric laminated composite arch under transverse periodic excitation may occur steady motion and chaotic motion.

Taking into account the nonlinear constitutive relationship and transverse Poisson effects, the propagation characteristic of nonlinear wave for one-dimension elastic thin rod is studied. With the help of Mathematic, two traveling wave solutions for this nonlinear wave equation are obtained by sine-cosine function method, which include the shock wave solution and the solitary wave solution. The necessary condition of these solutions is given also.

Some experimental results of the free-free tubes laterally impacted by the missile were given and the finite element program LS-DYNA was used to simulate this dynamic response process. The instantaneous deformation of the circular shell given by experiments and computer simulation were compared and discussed. It can be seen that when the impact occur the local dents firstly appear at the beginning of impact. With time increase, the depth of the dents increase, the scope of the deformation of the tube wall is enlarged; the total stiffness of the cross-section of the tube is weaken and decreases at the impact point, the beam-like bending deformation take place and the rigid-body translations occur. Through the computer simulation the exchanged energy between the missile and the tube were acquired. The impact energy of the missile is transferred to internal energy and kinetic energy of the tube. The ratio of the internal energy with the kinetic energy of the tube is great for the weakness rigidity of the tube wall, which is opposite to that of a free-free beam. This research made us deeply understand the character of the response when studying the elastic-plastic behavior of the free circular shell under intense dynamic loading.

Based on the theory of thermo-elasticity mechanics, the finite element numerical simulation models have been established for the package bulging process. The mechanism of the interfacial void evolution is postulated. By taking the interface strength as function of process (moisture and temperature), it shows that the critical stress that results in the unstable void growth and delamination at the interface is significantly reduced and becomes comparable to the magnitude of the vapor pressure. The simulation result can make us understand the mechanism of the void-growth at the interface framework and provide data base for improving reliability of package and optimum design

Objectives: We examined the prevalence and risk factors of migraine among the She population. The prevalence of migraine among She Chinese in Fujian province is high. Methods: This study is a cross-sectional survey. Subjects completed a questionnaire that collected demographic and clinical data related to migraine. Physical examination and clinical laboratory tests were performed. Data were analyzed by regression analysis. Results: Of the 5519 subjects enrolled, 2377 were male (43·1%) and 3142 female (56·9%). Of these, 581 (10·53%) experienced migraine annually, including 6·18% of males and 13·82% of females. Highest prevalence rate was among those aged 40–49 years (11·28%). The 141 (24·3%) subjects who had migraine with aura had higher incidence of family history of headache than those without aura (38·5% vs 19·9%, P < 0·0001). Conclusion: Female gender and insomnia are possible risk factors for migraine in the She population.

To solve the problem that nano-hydroxyapatite (nHA) crystals aggregation and non-uniformly distribution in nano-hydroxyapatite/chitosan (CS) composite microspheres, nHA/CS microspheres were prepared through in situ biomimetic method in water-in-oil (W/O) emulsions. The physical and chemical properties of the composite microspheres were investigated by scanning electronic microscopy (SEM), X-ray energy-dispersive spectroscope (EDS), X-ray diffraction (XRD), fourier transform infrared spectroscope (FTIR) and laser particle size analyzer. The results indicate that the composite microspheres are spherical with average size of 8.62 μm and disperse uniformly. Moreover, the nHA crystals are dispersed uniformly within composite microspheres and bonded with CS matrix. The composite microspheres have great potential in bone tissue engineering and drug delivery system.