Abstract:Based on the wind tunnel testing of a low-rise building, the wind pressure characteristics of the low-rise building with holes of different sizes and shapes on its roof corner were analyzed. The superimposition of internal and external pressures makes the emergence of large positive pressure on the roof. The internal pressure shows an overall uniform distribution. With the opening area becoming smaller, the internal pressure gets stronger. The probability density function of the internal pressure is closer to the Gaussian distribution, and when compared with external pressure, the non-Gaussian characteristic of net pressure is weakened. The internal pressure also exhibits a strong correlation in frequency domain. There appear two humps in the internal pressure spectrum corresponding to Helmholtz frequency and vortex shedding frequency, and the peak of the vortex shedding frequency is offset for the case of net pressure. Furthermore, the internal pressure characteristics indirectly show that the length of the front edge enhances the development of the conical vortices and the conical vortices appearing in pairs do not become the strongest simultaneously.

Abstract:Based on the classified site criterion in current seismic design code of building (GB 50011-2010) and quantitative classification scheme of near-fault ground motions proposed by Baker, the sites of 746 accelerograms from the strong-motion databank of some countries were classified as four site classes, and the 746 accelerograms were classified as far-field, near-fault and near-fault pulse-type ground motion accelerograms. Using the selected accelerograms, the empirical equations of near-fault pulse-type ground motion corresponding to four kinds of sites were presented for the inelastic displacement ratio spectra of constant ductility and constant yielding strength. The effects of site condition and different ground motion parameters on inelastic displacement ratio spectra were also evaluated. It is concluded that the influences of near-fault pulse-type ground motion on displacement ratio spectra of constant ductility and constant yielding strength are significant at periods ［0.3 s,5 s］ and periods ［0.5 s,3 s］ respectively, and site condition can control the period ranges of the above significant effect. PGV／PGA can provide the largest influence on displacement ratio spectra for near-field ground motions.

Abstract:To address the dynamical instability of single-layer latticed shells under earthquake excitation, proceeding from the damage accumulative effect of steel material, the constructive relationship between strain and damage was first set up on the basis of the theory of both plastic strain and energy dissipation. Then, the criterion for dynamic stability by means of B-R kinetic criterion in combination with plastic strain energy density was put forward. The method of incremental dynamic analysis was used to study the dynamic stability of a Kiewitt-8 type single-layer latticed shell under earthquake excitation when considering the damage accumulation effect. Finally, some conclusions are obtained that strain-damage constitutive mode can reflect the features of structural failure and greatly affect the structure, which may be helpful in engineering repair and the estimation of seismic capacity.

Abstract:Five precast concrete specimens with steel cable connections were tested statically. These specimens include three wall-wall specimens and two floor-floor specimens. Then the existing methods were used to calculate the shearing resistance of the connections. The results show that the shear capacity of the seam is mainly composed of shear friction of the steel cable in tension and the dowel action of the steel cable. The specimens exhibit excellent ductility. Based on the test results, in-depth analyses were conducted to study the behavior and the failure mechanism of the connection with steel cable. Using rational assumptions, we proposed a trilinear model to predict the shear behavior of the steel cable connection. The results of the trilinear model are in good agreement with those obtained in the test, which provide useful reference to the design and construction of total precast concrete structures with steel cable connections.

Abstract:A comparative analysis between Rayleigh damping model and Caughey damping model was first conducted, and then, by ANSYS secondary developing based on APDL programming language, the Caughey damping model was successfully applied to the random seismic response analysis of complex high-rise building structure. An actual complex high-rise building structure was selected as the research object. By using the combination method of field vibration test and numerical simulation, the influence of different damping models on the random seismic response of complex high-rise building was analyzed, and the applicability and effectiveness of the two damping models were also discussed. The results have indicated that the curve shape of Rayleigh damping model is closely related to the control frequencies, the calculated damping ratio is lower than the actual test damping ratio between two control frequencies, and it is contrary among other frequency ranges. The Caughey damping model can more accurately meet the actual damping in a wider frequency range.

Abstract:A practical design method was proposed for the reliability-based wind resistant optimization of transmission line towers. Firstly, the failure modes and their key elements were identified, and their safety margin equations were established. Second, the failure modes with a reliability index of less than the target reliability index were optimized by strengthening its key element. Lastly, the system reliability index was calculated, and the failure mode with the least reliability index would be optimized if the system reliability index was less than the target reliability. An optimization example of a tower under several wind speeds was given and the results show: 1) there were key elements in the whole failure path, and the structure would be well strengthened if the key element was strengthened;2) it was a method in which the weak points were eliminated directly to strengthen the whole structure and it was very effective; 3) as the wind speed increased, it would be less effective; and 4) the method was simple and its results were reasonable.

Abstract:The bonding behavior of CFRP-Concrete Interface is a key performance of concrete structure strengthened with CFRP plate, and it has a critical effect on the mechanical behavior and the failure mode of the strengthened structure. This paper adopted double-shear tests on 4 concrete components strengthened with CFRP plate to investigate the mechanical behavior and the failure mode of the specimens with different bond length and to analyze the influence of different bond lengths on the ultimate capacity and the distribution of the bonding stress. According to the test results, the distribution of the CFRP strain along the bond length shows an exponential decreasing law, and the stress near the loading position is much greater than the other end. The orthotropic spring elements were adopted to simulate the adhesive layer with ANSYS software, and the finite element model of the specimen was established. The local bond slip curve obtained from the test was used as the F-d curve of spring elements. The FEA results agree with the experimental ones, confirming the correctness of the FEM. Based on the bond slip curves obtained from the test, some bond-slip constitutive relationships were fitted according to several classic bond-slip constitutive relations. The test and FEA results show that the CFRP plate has begun peeling from the concrete surface when the tensile stress applied to CFRP reaches 24% of the tensile strength of the material. To ensure the full utilization of CFRP strength, the anchorage for CFRP plate should be adopted.

Abstract:Based on the experimental research on the shear test behavior of two general beams and two overhanging RC beams strengthened with PVA-ECC, the regulations for the change of the mode of diagonal cracks, failure, deflection and strain have been analyzed in the experiment. The results show that this reinforced method can increase the crack-resisiting capacity and impove the shear stiffness and the load-bearing capacity of the beam. According to the test results, the computational formula of the shear load capacity of overhanging RC beams strengthened with PVA-ECC was established. The calculated results fit well with the experimental results, thus providing a theoretical reference for practical engineering designs.

Abstract:This paper summarized the current research status of double-steel-layer-concrete composite shear walls. Then, it presented a brief introduction to the experiments of double-steel-layer-concrete composite shear wall. Based on the experimental study of double-steel-layer- concrete composite shear wall, the hysteretic behavior of the wall was analyzed and the finite element model with initial imperfections was established. Compared with the experimental results, the FEM model was verified to be efficient. Through numerical analysis, the influence of several parameters, including the high aspect ratio, the width-to-thickness ratio and the axial compression ratio, on the hysteretic behavior of the wall was explored. The numerical results have shown that all the 3 parameters have effects on the mechanical performance of the wall, the axial compression ratio is the most important factor for the loading capacity of the wall and the high aspect ratio and width-to-thickness ratio are the most important factors for the initial stiffness of the wall.

Abstract:Based on the nonlinear temperature field theory, the temperature program of reinforced concrete member was developed. By analyzing the mechanical behavior of different temperature-stress specimens, the transient strain importance was discussed, and the transient strain model under the biaxial stress state as well as transient modulus was proposed. According to the flat shell theory and thermal elastic-plastic constitutive model, the finite element model of reinforced concrete two-way slab was established to simulate the fire behavior of the three slabs. In addition, the effect of transient strain and thermal strain on the fire behavior of the slab was studied. The results have shown that the predictions agree well with the test results, and the transient strain model is verified. The parametric study indicates that the transient strain and thermal strain have an important influence on the fire behavior of the slab.

Abstract:The effect of excavation-related unloading on the underlying soil will reduce the ultimate pile shaft resistance. In this study, Mindlin's stress solution was used to allow for the variation of vertical effective stresses induced by excavation around a single pile. The ultimate resistances of the pile shaft before and after the excavation were calculated. The results of theoretical calculation were compared with others through a case study. Furthermore, the variations of reduction factors for shaft resistance with excavation depth, excavation length, ratio of length to width and pile length were analyzed. The results showed that reduction factors for shaft resistance decreased firstly and then increased with the increase of excavation depth, and it decreased first and then tended to be stable with the increase of excavation length and ratio of length to width. With the increase of pile length, the reduction factors for shaft resistance increased.

Abstract:Based on the elastic theory of settlement analysis, a finite element method was employed to investigate the influence of inclined bedrock on foundation settlements under non uniformly distributed load in terms of two key variables: the depth width ratio and the bedrock inclination. The first variable refers to the ratio between the depth from the compressible soil to the bedrock and the width of the foundation, while the second assumes the dip perpendicular to the direction of the strip foundation. According to the numerical results, the design charts of settlement influencing factors and differential settlement influencing factors under different load conditions were given to help practice application. Besides, parameter analysis of the influence of calculating parameters on settlements and the position variation of the largest settlement with the change of the depth width ratio and the bedrock inclination were given.Morover, a design example was presented to illustrate the use of the design charts.

Abstract:In order to solve the settlement calculation problem of saturated soft soil under different stress levels, the low stress component of the Nishihara model was analyzed and improved after considering the rheological properties. Through the Laplace transform and its inverse transform, a one-dimensional consolidation analytical solution was obtained under instantaneous loading condition. Based on the solution, the unified analytical solution was obtained in the method of integral under multilevel loading conditions. And the analytical solution was used in the settlement calculation for the test section of Dongting Lake Area soft soil embankment. It has been shown that the calculated settlement values of the analytical solutions under different stress levels have different change laws, which is in agreement with those of the field tests. At the early stage of consolidation, the calculated consolidation settlement rates are much lower than that of the elastic model under the same conditions. Therefore, when calculating the settlement of soft foundation, it is necessary to consider the influence of different stress levels on the settlement of soft foundation, and to consider lag effect caused by soft soil creep.

Abstract:The circular foundation is one of the most widely used foundation types. However, little emphasis has been placed on the research of the bearing capacity for circular shallow foundations than strip footings. To solve this problem, an upper-bound solution of the bearing capacity of circular shallow foundations was presented on the basis of the limit analysis by building a multi-block discrete model and taking soil weight, cohesion, and overload into account. Then, the present solutions have proved more accurate through comparisons with measured values found in references and calculation results using other methods. Additionally, analyses of the ground slide surface were carried out, which show that the scope of the slide surface searched is smaller than that of the classical logarithmic spiral surface, due to the weight of the soil. The scope of the slide surface increases with the increase of internal friction angle and embedded depth, but decreases with the increase of the unit weight of soil.

Abstract:Based on the minimum thermal resistance theory and homogenization method, the effective thermal conductivity of hollow beads insulating mortar was estimated. With ANSYS imitating the heat transmission of the 2D unit model of hollow beads insulating mortar, we can find it will bring about calculation errors by considering the extreme cases of the transverse thermal resistance of resistance network. Compared with the effective thermal conductivity of 3D unit cell model calculated by ANSYS with three kinds of theoretical calculating value, it is more accurate than the effective thermal conductivity of unit calculated by the model of effective thermal resistance average. A model was built by assuming transverse thermal resistance infinitesimal and infinite. Final laboratory finding also confirms this conclusion. With only 0.2% deviation between the experiment values and the calculation of theoretical model, it is feasible to estimate the effective thermal conductivity of hollow bead insulating mortar.

Abstract:A beam-rail-pier 3D finite element model was built by adopting the mechanism of ideal elastic-plastic ballast resistance under the background of a 156m long-span simply supported steel truss bridge on Huangling-Hancheng-Houma Railway line. The purpose was to study the distribution of longitudinal force due to temperature variations, bridge deflection, braking force and the breaking force of long rail in steel truss bridges. The influences of design parameters on longitudinal forces, such as the bearing arrangements of adjacent simply supported bridges, pier longitudinal stiffness and the arrangement of small resistance fasteners, were also discussed. It has been shown that the longitudinal force due to temperature variations plays a major role. Secondly, the bearing of adjacent simply supported bridge should be in the same direction as the steel truss bridge. Thirdly, the longitudinal force due to temperature variations and structural deflection increases and the braking force decreases as the pier longitudinal stiffness increases. Finally, the small resistance fasteners have a good effect on the longitudinal force due to temperature variations, which can reduce the force by 36% after being installed.

Abstract:In order to describe the crack development of epoxy asphalt concrete (EAC) from the three-dimensional (3D) scale perspective, a 3D virtual specimen of EAC with the heterogeneous (coarse aggregates, asphalt mastic and air voids) and multilayer (aggregate gradation) morphological features was first reconstructed by using the Fish language provided in the discrete element software PFC3D. Secondly, the corresponding micromechanical models describing the interaction of micro-scale components of the virtual specimen were assigned. Finally, a single-edge notched beam virtual three-point bending test was implemented by using the discrete element method (DEM). The progressive development of microcrack trajectories was tracked and visualized, and the simulation results were compared with the surface crack development of specimens captured in a digital camera method. The results have indicated that the macro fracture responses of virtual test show generally good agreement with the experiment results, and the virtual test presents better stability than the laboratory test. Additionally, the three-dimensional DEM developed is capable of simulating the initiation and propagation of cracks during the bending fracture of EAC, thus improving the two-dimensional (2D) method. Furthermore, it has been found that the method based on the DEM program, which is used to illustrate the development of 3D cracks, can be used as a supplemental tool to investigate the fracture behavior of EAC.

Abstract:In order to study the fracture behavior of asphalt concrete under pure modeⅠand mixed-modeⅠ-Ⅱ, an Extended Finite Element Method (XFEM) was employed to simulate the fracture process of single-edge notched beam specimen (SEB). Based on the comparison of numerical results and experimental records, it can be concluded that XFEM can serve as an efficient tool for the simulation of crack path and calculating mechanical response. Moreover, the fracture of SEB can be divided into four stages. The beam has already been under damage accumulation stage when the load reaches the peak value and crack initiates after the peak load. Fracture behavior can be considered as a process in which tensile stress decreases in the damaged zone and increases in the undamaged zone. Meanwhile, the length of the damaged zone is increasing. The critical offset coefficient obtained through numerical analysis is 0.45~0.51, which shows good agreement with the test result. Unloading behavior occurs near the mid-span section when offset coefficient is equal to 0.45, which inhibits the damage growth and the initiation of secondary cracks.

Abstract:The value relevance of accounting earnings between ST companies and non-ST companies is asymmetric.Book value and operating cash flows are main factors which have great influence on earnings value. This paper uses the relevant data of China′s A-share market between 2009 and 2011，and finds out that the accounting earnings of ST companies is far weaker than that of non-ST companies according to earning capitalization model. This paper introduces book net assets，operating cash flow and interaction effects of book net assets and operating cash flow，and finds out that (1) book net asset has value relevance, (2) the operating cash flow of ST companies has significant negative correlation and (3) accounting earnings, book net asset and operating cash flow have significant interaction effects.