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The cast-steel joint is often used in a tree-like column structure to achieve smooth transition. Its performance is critical to ensure the whole structural safety. In this paper, the load bearing behavior of a cast-steel joint with three branches is investigated. First, a finite element model of the test joint was established by SolidWorks and analyzed by ANSYS considering the geometric and material nonlinearity. Then, the calculation formula for load-carrying capacity of the cast-steel joint with branches was deduced by the method of regression analysis, which is used for estimating the geometric parameters and load-carrying capacity at the stage of preliminary design of the cast-steel joint. Comparison analysis shows that there is a good agreement between the experimental result, the FEM result, and the prediction result from formula.

Coalbed methane can be detected employing the amplitudevariation-with-offset technique. However, there are two issues in applying this technique to a coalbed: strong azimuthal anisotropy resulting from high-density fractures, and the seismic response being composed of many or several individual reflections within the coalbed. To overcome these difficulties, we present an exact solution for reflections in extensive dilatancy anisotropy media. First, we build a three-layer model and simulate the wave propagation in this model. Then we derive an exact P- and converted S-wave reflection coefficient equation based on boundary conditions. Finally, substituting given model parameters into the exact equation, we obtain the variation in the reflection coefficient with incidence angle. The results show that the fracture factors, wavelet frequency and thickness of the coalbed have different effects on the reflection coefficient. Furthermore, we create a synthetic seismogram by forward calculation, and the result fits well with results of the exact equation.

The tree-like structure is a branch of space bionic structures,belonging to the Bionic Architectural Structures. Cast-steel joints with branches are the keys to build the tree-like structures.They are used widely,and the most common joints in our projects are cast-steel joints with two、three and four branches. The cast-steel joints with two branches are planar,while the joints with three and four branches are spatial.Until now,the basic theoretical researches about the cast-steel joints with branches are also relatively scarce.This paper did researches about mechanical properties, calculation methods and structural optimization of the cast-steel joints with three branches deeply and systematically. The result shows that the bending moment has a big influence on the value of the max stress. And the three main failure modes of the cast-steel joint with three branches are yield of the main tubular along the axial direction, local buckling at the connection of the main tubular and branches, and the tearing out of the branches.

For considering the losses of pre-stress in suspend-dome structures, an improved rigid cable method was proposed. The main character of this method is the temperature stress is applied to corresponding element to compensate the loss of pre-stress. The relationship between temperature and pre-stress loss is deduced, which can give the definite num of temperature needed to add on the corresponding elements. An example and engineering application are discussed. Results show that the improved rigid cable method is effective and applicable.

Basing on the practical engineering of elliptic paraboloid roof structural design in Qinyang Stadium, four structural schemes such as suspend-dome, single-layer latticed shell, double-layer latticed shell and rigid suspend-dome, are calculated and designed respectively. After satisfying the requirements of strength, stiffness and stability, the quantity of steel is compared. The advantages and disadvantages on mechanical performance, construction and cost of four schemes are discussed. Results of comparison provide the accordance for the final decision of structural schemes of Qinyang Stadium and can be referenced by other similar practical engineers.

This paper, based on the practical engineering of the steel structure of Henan Shangpin food Co. LTD, introduces the design of a light-weight steel structure with three-span gabled frames, and discusses the solution of the large suspended loads. By taking the steel quantity as the target, the depth calculations and statistical analysis of the reasonable value of the column spacing were carried out. The results show that the large suspended loads should be imposed in the form of live load. When the column spacing is about 8m, the steel quantity is the lowest.

The design and analysis of the suspended lattice shell located in Zhejiang province of China is introduced, and some key problems are discussed in this paper. Especially, tensile cable is a key element in large span suspended structures. And the construction of tensile cable is the key technology problem as the tensile force of tensile cable is very sensitive to the construction precision. The tension slacken analysis method is used to obtain the control stress and complete the work with only one time tensile construction. Results of the engineering show that the construction process is simple and the construction scheme is economic.

The ultimate bearing capacity of the single-layer cylinder latticed shell structure, calculated without considering the single-member instability(P-δ effect), was not consistent to the actual value of ultimate bearing capacity in practice. The ultimate bearing capacity of the single-layer cylinder latticed shell structure was studied in detail by proposing a method of multi-element simulation, considering the member instability. The value of the ultimate bearing capacity decreased by 1.2% after considering the member instability taking a single-layer latticed shell structure with a 40m span as example. The analysis results show that the value of ultimate bearing capacity is tiny affected for the single-layer cylinder latticed shell structure with a small span and high rise-span ratio

The design and analysis of the large span steel latticed shell structure in site of Yuyao TianLuoshan is introduced, and some key problems are dwelled on in this paper. By the geometrical nonlinear finite element method, the nonlinear stability analysis is carried out. The buckling modal and the whole course of instability are shown by two analysis method, the eigen-buckling analysis and the geometrical nonlinear finite element method. The influence of spring support to the stability of the structure is analyzed. It is shown that the structure has good wind-resisting capacity, which is fit to the circumstance near sea with lots of typhoon. Large compressive membrane stresses arise in the structure under the condition of temperature rise, leading to a significant reduction in the stability load-carrying capacity of the structure.

The ultimate bearing capacity of the single-layer latticed shell structure, calculated without considering the single-member instability(P-δ effect), was not consistent to the actual value of ultimate bearing capacity in practice. It was studied in detail that the ultimate bearing capacity of the single-layer latticed shell structure considering the member instability by proposing a method of multi-element simulation. The value of the ultimate bearing capacity decreased by 15.6% after considering the member instability taking a single-layer latticed shell structure with a 40m span as example. The analysis results show that the value of ultimate bearing capacity is significantly affected for the single-layer latticed shell structure with a small span and high rise-span ratio

How to judge the dynamic instability of trusses is an important problem. It is found that stress rate of a truss has the catastrophic characters when trusses are out of stability. According to the relationship of the total strain energy and the stress rate, the principle of stress rate is proposed , that the dynamic instability was made in structures if the stress rate was suddenly changed to a relative very great value. Some examples, such as a dome shell, a three-bar spatial frame, a plane truss, and so on, are discussed. The results showed that it was effective to judge the instability of truss structures by using the tress rate criterion. By comparison of the stress rate criterion with the displacement criterion it can be obtained that the result of displacement criterion was comparatively obvious in the global instability while the result of stress rate criterion was more ocular in judging the local instability in truss structures.

Aiming at the dynamic stability of the K8 single-layer latticed shell structures, it was carried out the dynamic stability analysis based on the finite element method(FEM) in this paper. The dynamic responses of the structure are calculated using the FEM and the B-R rule is applied to determine the dynamic instability critical loads. Results show that the dynamic instability is prone to take place in the K8 single-layer latticed shell structures under the severe seismic load and the dynamic instability critical seismic wave peak value is about 0.7g. The location of instability starts from the intersection between the third circular members and the radial members, then it spreads abroad until the structure collapses.

Studies on the static stability and the ultimate bearing capacity of vierendeel latticed shells have been carried out. The buckling modal and the whole course of instability are shown using the Finite Element Method. The ultimate bearing capacity is compared with that of the single-layer latticed shell structure. The results show that the ultimate bearing capacity of the vierendeel latticed shells is 2.87 times more than that of the single-layer lattice shell in the condition of consuming the same steel. The vierendeel latticed shell structure not only has the advantages of concision and transparency like the single layer latticed shell structure, but also has the stability and carrying capacity like double-layer latticed shell structure.

Aiming at failure mechanisms and judgment criterion of progressive collapse for space trusses, the responses and the failure mechanisms of diagonal square pyramid space trusses, leaning laid pyramid space trusses and orthogonal square pyramid space trusses with circumferential simple supports under different seismic waves were analyzed in this paper. The results show that space trusses have a good performance of earthquake resistance, but progressive collapse occurs easily. Based on the failure mechanisms of space truss, a judgment criterion of space truss is proposed under strong earthquakes, according to the characteristics of energy, displacements and plastic levels of members. The judgment criterion is expressed by judgment coefficient J. When J>6, space trusses tend to be ductile failure, however, When J> 6, space trusses tend to be progressive collapse.

First-principles calculations of the second-order optical response functions and the dielectric functions of urea [CO(NH(2))(2)] and some of its derivatives such as monomethylurea (H(2)NCONHCH(3), MMU), and N,N'-dimethylurea (H(3)CHNCONHCH(3), DMU) crystals are performed. On the basis of the density functional theory (DFT) in the local-density approximation (LDA), the highly accurate full-potential projected augmented wave (FP-PAW) method was used to obtain the electronic structure. Over a wide frequency range (0.0-10.0 eV), the dielectric constants and second-harmonic generation (SHG) susceptibilities of the urea crystal family have been obtained, and the results are in good agreement with the experimental values. The origin of the linear and nonlinear optical (NLO) properties of the urea crystal family has been analyzed by coupling the calculated electronic structure and optical spectrum. The prominent spectra of χ((2)) are successfully correlated with the dielectric function ε(ω) in terms of single-photon and double-photon resonances. The virtual electron (VE) and virtual hole (VH) processes have also been performed for the urea crystal family. From the research into the electron deformation density, crystal configuration, substitutional group, and so forth, it is found that the origin of the SHG of the urea crystal family is the charge transfer due to the strong "(̀)push-pull" effect along the hydrogen bond, which favors a head-to-tail arrangement of the molecules and enhances the SHG response. The electron-donating substitutional group supplies more electrons to the electron-accepting group, and helps to form large dipoles in molecules. The influence on the NLO properties of the local symmetry of the substitutional group is also discussed in detail.

This paper deals with the issues involved during the design of a complex roof structure in the grand theater located at the city of Hangzhou, China. The complexity comes from the structural being of three reasons: long-span, complex structure and special figuration. To study the roof structure completely, researches on the mechanical properties of the structure are carried out in the paper. The nonlinear finite element method is used to analyze the geometrical nonlinear stability. Buckling and post-buckling analyses are performed to determine the load-carrying capacity of the perfect and imperfect roof structure. Meanwhile, the critical loads of the structure with different parameters are also discussed in this paper. It is shown that the effect of supporting stiffness originated from foundations and concrete structures to improve the critical load is evident. The buckling of the structure is a global collapse. With the temperature rises, the limited load-carrying capacity of the structure decreases obviously.

The minimum weight design method of large-span statically determinate trusses satisfying the displacement constraint is studied. The displacement calculation formula is provided, and the critical condition of minimum weight design satisfying the condition of allowed displacement is educed using Cauchy inequality. The distribution coefficient, which is used to obtain the minimum weight design, is defined and the coefficient distribution method is proposed. An engineering example is analyzed using the coefficient distribution method above, and the compared results are discussed. Study results show that the proposed method, coefficient distribution method, is correct，reliable and effective.