Impact of Earthquake Action on the Design and Sizing of Jointed Masonry Structures in South Kivu, DRC

This article deals with the investigation of the effects of seismic impacts on the design and dimensioning of structures in South Kivu. The starting point is the observation of an ambivalence that can be observed in the province, namely the non-consideration of seismic action in the study of structures by both professionals and researchers. The main objective of the study is to show the importance of dynamic analysis of structures in South Kivu. It adopts a meta-analytical approach referring to previous researches on South Kivu and proposes an efficient and optimal method. To arrive at the results, we use Eurocode 7 and 8. In addition, we conducted static analysis using the Coulomb method and dynamic analysis using the Mononobe-Okabe method and compared the results. At Nyabibwe, the results showed that we have a deviation of 24.47% for slip stability, 12.038% for overturning stability and 9.677% for stability against punching through a weight wall.

Microwave-induced thermoacoustic imaging of joints

Due to the complexity of joint structures and the diversity of disorders in the joints,the diagnosis of joint diseases is challenging.Current clinical diagnostic techniques for evaluating joint diseases,such as arthritis,have strengths and weaknesses.New imaging techniques need to be developed for the diagnosis or auxiliary diagnosis of arthritis.As an emerging nonintrusive low-cost imaging method,microwave-induced thermoacoustic imaging(TAI)can present tissue morphology while providing the tissue microwave energy absorption density distribution related to dielectric properties.TAI is currently in development to potentially visualize joint anatomic structures and to detect arthritis.Here,we offer a mini review to summarize the status of research on TAI of joints and present an outlook to the future development of TAI in the detection of joint diseases.

Nonlinear Modeling and Identification of Structural Joint by Response Control Vibration Test

Components of mechanical product are assembled by structural joints,such as bolting,riveting,welding,etc.Structural joints introduce nonlinearity to some engineering structures,and the nonlinearity need to be modeled precisely.To meet serious quality requirements,it is necessary to detect and identify nonlinearity of mechanical products for structural optimization.Modal test to acquire a dynamic response has been applied for decades,which provides reliable results for finite element(FE)model updating.Here response control vibration test for identification of nonlinearity is presented.A nonlinear system can be regarded as linearity for particular steady state response,and classical linear analysis tool is applicable to extract modal data for particular response.First,its applicability is illustrated by some numerical simulations.Subsequently,it is implemented on experimental setup with structural joints by shaking table.The stiffness and damping function dependent of relative displacement are fitted to describe its inherent nonlinearity.The spring and damping forces are identified by harmonic balance method(HBM)to predict output response.Based on the identified results,the procedure is recommended that it allows a reliable measurement of nonlinearity with a certain accuracy.

Theory of Degrees of Freedom for Parallel Mechanisms with Three Spherical Joints and Its Applications

The analysis of degrees of freedom（DOF） of a moving platform is the fundamental problem in kinematics of parallel mechanism. However, many problems should be considered to correctly perform the DOF calculation by using the traditional DOF criterion, and it is difficult to find a DOF criterion suitable for all kinds of mechanisms. A rule that can be used to determine the position and orientation of the moving platform is presented. Based on the proposed rule, a new form of DOF criterion is proposed, which is suitable for a class of parallel mechanisms with three spherical joints attached to the moving platform. The basic types of generalized limb structures are given based on the possible dimension of achieving the center of spherical joint attached to the moving platform, and the general steps of analyzing the DOF are presented. This proposed formula simplifies the DOF analysis of parallel mechanisms with spherical joints attached to the moving platform, and plays an important role in structural synthesis of such parallel mechanisms.

Test analysis of detection of damage to a complicated spatial model structure

A two-stage damage detection approach is proposed and experimentally demonstrated on a complicated spatial model structure with a limited number of measurements. In the experiment,five known damage patterns,including 3 brace damage cases and 2 joint damage cases,were simulated by removing braces and weakening beam鈥揷olumn connections in the structure. The limited acceleration response data generated by hammer impact were used for system identification,and modal parameters were extracted by using the eigensystem realization algorithm. In the first stage,the possible damaged locations are determined by using the damage index and the characteristics of the analytical model itself,and the extent of damage for those substructures identified at stage I is estimated in the second stage by using a second-order eigen-sensitivity approximation method. The main contribution of this paper is to test the two-stage method by using the real dynamic data of a complicated spatial model structure with limited sensors. The analysis results indicate that the two-stage approach is ableto detect the location of both damage cases,only the severity of brace damage cases can be assessed,and the reasonable analytical model is critical for successful damage detection.

Regression Formulations for the Stress at Hot Spot of Multiplanar Tubular DT Joints

Stress concentration analysis of multiplanar tubular DT joints plays an important role in the fatigue design of offshore platforms. A semi-analytic method for stress analysis under the condition of any loads is briefly introduced in the paper. Nineteen multiplanar tubular DT joints with one of two braces of the same dimension subjected to axial loads and out- of- plane bending moments are computed for parametric stress analysis by using the present method. The influence of geometrical parameters on the stresses of multiplanar tubular DT joints is discussed and compared with corresponding uniplanar T joints. The regression formulae for the stress at hot spot of multiplanar DT joints are found by modification of SCF of corresponding uniplanar T joints. The parametric formulae for the maximum stress by superposition. Finally, the influences of stiffening effect and load-interaction effect on the maximum stress of DT joints are discussed.

Structural Analysis of Platforms with the Effect of Joint Flexibility

A modified space beam element is presented in this paper to consider the local joint flexibility of T, Y tubular joints subjected to axial forces and in-plane bending moments for analysis of platforms. Two numerical examples are shown to verify the efficiency and validity of the method presented here.

Seawater Corrosion Fatigue of Welded Joints Under Random Variable Amplitude Loading

Offshore platforms are always subjected to wave action which is random variable amplitude cyclic loading. In order to simulate the stressing condition at the 'hot spot' of the tubular joints and the marine environment, random variable amplitude fatigue tests have been carried out on welded plate joints in sea water. The tests have been conducted under the conditions of loading frequency of 0.2 Hz/, stress ratio of -1, seawater temperature of about 20°C and cathodic protection with the potential about -850 mV, SCE. The test results have been compared with the seawater corrosion fatigue life under constant amplitude loading. Miner's linear cumulative damage summation rule has been used to predict the corrosion fatigue life under variable amplitude loading. The predicted life is in good agreement with the test data.

Electrochemical cutting of mortise-tenon joint structure by rotary tube electrode with helically distributed jet-flow holes

In aero-engines,mortise-tenon joint structures are often used to connect the blades to the turbine disk.The disadvantages associated with conventional manufacturing techniques mean that a low-cost,high-efficiency,and high-quality nickel-based mortise–tenon joint structure is an urgent requirement in the field of aviation engineering.Electrochemical cutting is a potential machining method for manufacturing these parts,as there is no tool degradation in the cutting process and high-quality surfaces can be obtained.To realize the electrochemical cutting of a mortise-tenon joint structure,a method using a tube electrode with helically distributed jet-flow holes on the side-wall is proposed.During feeding,the tube electrode rotates along its central axis.Flow field simulations show that the rotational speed of the tube electrode determines the direct spraying time of the high-speed electrolyte ejected from the jet-flow holes to the machining area,while the electrolyte pressure determines the flow rate of the electrolyte and the velocity of the electrolyte ejected from the jet-flow holes.The machining results using the proposed method are verified experimentally,and the machining parameters are optimized.Finally,mortise and tenon samples are successfully machined using 20 mm thick Inconel 718 alloy with a feeding rate of 5μm/s.

Stiffeners layout design of thin-walled structures with constraints on multi-fastener joint loads

The purpose of this paper is to present an extended topology optimization method for the stiffeners layout design of aircraft assembled structures. Multi-fastener joint loads and manufacturing constraints are considered simultaneously. On one hand, the joint loads are calculated and constrained within a limited value to avoid the failure of fasteners. On the other hand, the manufacturing constraints of the material distribution in the machining directions of stiffeners are implemented by an improved piecewise interpolation based on a beveled cut-surface. It is proven that the objective function is strictly continuous and differentiable with respect to the piecewise interpolation. The effects of the extended method with two different constraints are highlighted by typical numerical examples. Compared with the standard topology optimization, the final designs have clearly shown the layout of stiffeners and the joint loads have been perfectly constrained to a satisfying level.

New filler metal systems for the brazing of titanium alloys

It＇ s well known welding takes the leading role in development of titanium structures. However, in number of cases technological processes of brazing are more appropriate and, sometimes, being the single possible, in particular, during production of multilayer thin-wall structures. It should be noted that brazing filler metals of Ti-Cu-Ni, Ti-Zr-Cu-Ni, Zr-Ti-Ni and Cu-Zr-Ti systems in a form of plastic foils, as well as in powder form are mainly used in world practice for brazing of titanium alloys. Present work provides the results of complex investigations of brazing filler metals of Ti-Zr-Fe, Ti-Zr-Mn and Ti-Zr-Co systems using differential thermal analysis, light and scanning microscopy, X-ray microspectrum analysis. Data on melting ranges of pilot alloys were obtained, and liquidas su^Caces of given systems using simplex-lattice method were build. Brazing filler metals covering brazing temperature range of current structural titanium materials based on solid solutions as well as intermetallics were proposed. Structure, chemical inhomogeniety and strength characteristics of brazed joints were studied. It is determined that brazing of solid solution based alloys （OT4, VT6 ） using indicated brazing fiUer metals ensures strength characteristics of joints, which are not inferior to that obtained with application of known brazing filler metals even if they are received at lower brazing temperature.

Choosing Your China Structure:Joint Ventures

Forming a joint venture (JV) in China can be a successful endeavor as long as each side’s goals, contributions and responsibilities are mutual and understood. Unfortunately, this is not always the case,

Analytical algorithms of compressive bending capacity of bolted circumferential joint in metro shield tunnels

The integrity and bearing capacity of segment joints in shield tunnels are associated closely with the mechanical properties of the joints.This study focuses on the mechanical characteristics and mechanism of a bolted circumferential joint during the entire bearing process.Simplified analytical algorithms for four stress stages are established to describe the bearing behaviors of the joint under a compressive bending load.A height adjustment coefficient,α,for the outer concrete compression zone is introduced into a simplified analytical model.Factors affectingαare determined,and the degree of influence of these factors is investigated via orthogonal numerical simulations.The numerical results show thatαcan be specified as approximately 0.2 for most metro shield tunnels in China.Subsequently,a case study is performed to verify the rationality of the simplified theoretical analysis for the segment joint via numerical simulations and experiments.Using the proposed simplified analytical algorithms,a parametric investigation is conducted to discuss the factors affecting the ultimate compressive bending capacity of the joint.The method for optimizing the joint flexural stiffness is clarified.The results of this study can provide a theoretical basis for optimizing the design and prediciting the damage of bolted segment joints in shield tunnels.

Evaluation of tensile properties of a compositemetal joint with a novel metal insert design by experimental and numerical methods

Composite-metal joints with a metal insert are one kind of connecting structure.In this paper,tensile experimental tests were carried out to investigate tensile properties of a compositemetal joint with a novel metal insert design.Finite element models of the joint were established,and strain distribution and tensile strength were analyzed.The numerical results are in good agreement with the experimental results.Results show that the joint failure is dominated by shear properties of the resin layer.Increasing the resin layer thickness in a certain range will improve the tensile strength of the joint,while increasing the radius of the fillet on the ending side of the metal insert will decrease the joint strength.Increasing the resin layer plasticity will improve the joint strength.The effect of the embedded depth of the metal insert can be ignored.

Joint Venture Structuring in Restricted Industries

When investing in China’s restricted in- dustries, it is essential to have a joint venture (JV) partner. Often the maximum percent- age of equity allowed in foreign ownership can only be 50 percent. So what options are available to the foreign investor to mitigate the risk of not owning, on paper, a