Advanced Materials Research Vols. 243-249

Abstract: Fiber reinforced polymer (FRP) is a new kind of material for structural engineering in recent year. The partial inferiority of the bond and mechanical properties for FRP bars, however, leads to wider cracks compared with those of steel-reinforced concrete structures. Therefore, current design methods for predicting crack widths developed in concrete structures reinforced with steel bars at service load may not be used for concrete structures reinforced with FRP bars. This paper presents an analytical formula that calculates the maximum crack with in FRP- reinforced concrete beam, taking into account both the bond and the mechanical properties of FRP bars. The experimental results compared well with those proposed by the model.

Abstract: The insurance is the valid means which transfers engineering risk, but applied very limited in our country. The present condition of the construction engineering insurance and the factors restraining its wide application are investigated. The investigation results indicated that the main factors restricting the development of construction engineering are various. The knowledge to insurance is not enough, or the fluke mind is existing. The contractor is inactive to insure. The owner regards the insurance as compulsive request of the government and the bank and has to fulfill it.

Abstract: The curved box-girders of Hefei Xinqiao International Airport Terminal were taken as a background of this article. Aiming at the type of the cross section, thickness of the steel plates and curvature of the beam axis, parametric analysis was carried out to evaluate the ultimate bearing capacity of this kind of curved box-girder. Using the finite element analysis software ANSYS, the effects of former three parameters was calculated. From the results, it could be found out that the ultimate bearing capacity increases as the section aspect ratio grows, and it increases linearly as the thickness of the flange and web plate grows. In addition, the ultimate bearing capacity increased and decreased with the increment of the curvature of the beam axis R. The finite element results provided a theoretical basis for experimental research and analysis of the local models provided reasonable suggestions for design as well.

Abstract: The frequency of ground records on liquefied and non-liquefied sites is different. The calculation method of frequency decreasing rate is given here and the division line between liquefied and non-liquefied sites is proposed. To analyze the time-frequency curves of acceleration, the zero-crossing method is employed. The soft sites and ordinary non-liquefied sites are included in non-liquefied sites. The results show: (1) The concept and calculation method of frequency decreasing ratio, which is proposed in this paper, can describe the characteristics and regulations of time-frequency on liquefied and non-liquefied sites; (2) Before peak ground acceleration (PGA), the difference of the average frequencies of acceleration on liquefied and non-liquefied sites is not obvious and the average frequency of acceleration on soft sites is smaller than that either on liquefied or non-liquefied sites; (3) After PGA, the average frequency of acceleration on ordinary non-liquefied sites is the highest in the three types of sites, that of soft sites is the middle and that of liquefied sites is the smallest; (4) If the absolute change of the time-frequency is used as the criteria, it will be confused between soft sites and liquefied sites; (5) The threshold value of frequency decreasing ratio is 0.5 between liquefied and non-liquefied sites, which can judge the liquefied sites, non-liquefied sites and soft sites correctly.

Abstract: Conservatories at gardens by the bay in Singapore consist of Cool Dry and Cool Moist, which are intended for the display of plants that typically thrive separately in cool dry and cool moist climates. The envelope itself consists of a grid shell-arch steel structure with a double glazed skin that sits directly on the grid shell, and the arches are the main load-bearing components. This paper analyzed the stability of one single arch whose span is the longest one in the corresponding structure, including buckling analyses and non-linear full range analyses. It also carried out stability analyses on some arch segments. The results showed that the stability bearing capacity of single arches met requirements, while some arch segments didn’t. After using the stiffening ribs, the local stability reached its requirements.

Abstract: A mathematical model to simulate the natural dam break process and to forecast the flood hydrograph in the breach is developed in this paper. The breach is assumed trapezoidal, coupling with the bottom width and side slope angle keeping constants during the overall process of dam breach. Simulation of dam breach evolution is based on the conservation of mass of reservoir capacity and sediment transport capacity. Particularly, broad-crest weir relation is utilized to simulate the outflow in the breach, and an empirical equation is used to compute the rate of erosion in the breached section. Because of the implicit form of these equations, an iterative solution is proposed with convergence achieved in a few iterations. The model can be used by engineers or decision makers for a wide range of applications including risk assessment of natural dams, flood routing forecasting in the downstream reach as well as floodplain inundation mapping .

Abstract: By the combination of POD method and mode superposition method, the eigenvector similarity factor is introduced on the representation of the similarity between the load spacial distribution and the structural mode. Meanwhile, the eigenvalue got from the wind pressure field decomposition indicates the relative ratio of the energy associated with the corresponding load spacial distribution to the total of the wind load energy. It is proved that the eigenvector similarity factor and the eigenvalues are two of most important factors when measuring the relative significance of each modal response. So the quick estimates of the modal responses are provided, which predominates in picking structural modes to obtain wind-induced dynamic response of long-span roof structure with frequency-domain method. Then, by arranging the estimative response of each mode in reduced-order and truncating higher modes to expedite computations, the accurate wind-induced response is calculated by ACQC method, which has taken into account the partial correlation of wind loads and the quad-spectra (imaginary parts of XPSD) of the generalized wind loads. Finally, utilizing the rigid model wind tunnel test data of some large railway station platform, the effectiveness of the scheme proposed is verified.

Abstract: The result of low cycle reversed loading indicates that，hysteresis loops of out stiffener ring joint performs good plumpness and stability, meanwhile, bulge is observed in the joint region. In order to explain this phenomenon, nonlinear simulation analysis is applied on stiffener ring joint under low cycle reversed loading. The analysis includes hysteretic energy dissipation index of joint, deformation and plasticity development at connection area. The analysis observes that:(1) hysteresis loops of the joint is stable, with the dissipation coefficients all above 2.0,which is in accordance with the criterion of good plasticity; (2) the size of web welding line openings is too large so that hysteresis loops of the connection do not coincide, thus the size of the openings must be controlled in a certain range; (3)obvious deformation is observed in the column wall of the connection region with a similar pattern as the hysteresis loops, which manifests the principle that the hysteresis loop is mainly contributed by the column wall deformation rather than beam end plastic deformation; (4)in the initial stage of low cycle reversed loading, plastic zonal area runs through the annular plate and the plasticity occurs in the beam after a fairly long period. Under reversed loading, as significant deformation occurs in the connection area and plastic zonal area runs through the ring plate, it is concluded that stiffener ring joint does not comply with the principle of “strong joint”.

Abstract: The failure of the reinforced concrete (RC) column on the ground floor may result in progressive collapse of the whole building. In the paper, the finite element program LS-DYNA is used to simulate the dynamic response of RC column with different constraints subjected to blast pressure. A three dimensional solid model is established for the RC column. A brittle damage model is applied to simulate the concrete. The lateral displacement and failure mode of RC column with different scaled distances are investigated and discussed. It can be found that the pressure nephogram and x-direction displacement of fixed end column under different scaled distance have the obvious symmetry. Moreover, both the maximum pressure and x-direction displacement of one end fixed and one end simply supported column are bigger than fixed end column with the same scaled distance.

Abstract: The past study indicates that, when the space joint of concentric annular-stiffer is loaded, stress concentration may generate at corner. The destruction usually concentrates in the joint region, and then cannot generate “strong joint”. To change this unfavorable characteristic, the reduced beam section connection is adopted. Through oriented reducing beam section, the plastic region is formed, which can achieve the aim of “weak beam, strong joint”. After the simulation and analysis to space joints on outer concentric annular-stiffer which are processed by reduced beam section, the loading conditions of the joints are obviously improved in the following aspects: (1) the stress distribution on annular plate is smoothed obviously, the degree of stress concentration on corner is significantly decreased; (2) to assure plastic hinge firstly appear on the beam end but not the ring surface, we can change the size of ring plate, length of beam and the flange weaken degree; (3)the joint stiffness does not decrease during the stage of elastic loading; (4)under repeated loading, the joint region has little change and the plastic expansion on the ring surface is not obvious. Above all, reducing beam section can improve the mechanical properties of CFST-steel beam space joints with outer concentric annular-stiffer, thus the “strong joint” requirement could be fulfilled.