Applied Mechanics and Materials Vols. 275-277

Abstract: Confinement by fiber reinforced polymer (FRP) wraps can significantly enhance strength and ductility of concrete. Although various models exist for envelope curves of concrete confined by transverse reinforcement and FRP, only a few simple models represent the hysteretic behavior of the confined concrete; therefore, development of stress–strain model of unloading and reloading paths for confined concrete is needed. In this paper, an experimental and numerical investigation for describing the cyclic stress–strain behavior of lateral ties and FRP confined polyolefin fibre reinforced concrete (FRPCFRC) prisms under repeated axial compressive loading is presented. The study focuses on the effect of repeated unloading and reloading cycles on confined concrete prisms. The combined effect of spacing of lateral ties, FRP wraps and volume fraction of polyolefin fibres was studied both experimentally and numerically from the point of deformability characteristics of concrete under repeated loading as loading, unloading and reloading.The envelope curve is derived from the results of uniaxial, monotonic, compression loading tests on specimens. It explicitly accounts for the effects of lateral tie spacing of 145mm spacing and 75mm spacing, single layer of woven roving(GFRP) and polyolefin fibres of volume fractions 0.7% and 1.2% on concrete prisms of size 150 ×150 ×300 mm were investigated. The behaviour was also simulated in finite element numerical model in ANSYS software, with a view to analyzing FRPCFRC prisms under repeated loading. This analysis accounts for energy dissipation through hysteretic behavior, stiffness degradation as damage progresses, and degree of confinement. It was observed from hysteretic behavior that for increased confinement by FRP wraps and addition of polyolefin fibres the degradation of strength and stiffness reduces significantly.

Abstract: Currently it is still a lack of reliable evidences on the evaluation of the bearing capacity of foundation in highway construction of Shanxi Province. Mainly reason is that the method widely used to determine in bearing capacity of loess foundation in building structures is not completely suitable to length and wide range of highway subgrade project. Because Shanxi loess region terrain is very complex, the capacity of Q3 loess-like silt in Yuncheng of Shanxi is collected and analyzed, based on statistics of a large number of bearing capacity from site loading tect. A linear regression relationship is established between loess foundation bearing capacities and water content, liquid limit, void ratio. Another linear regression relationship is established between saturation and liquid limit void ratio . Meanwhile, it compares these two sets of linear regression relationship with the measured bearing capacity and the carrying capacity by specification. Applied result show that the relative errors of the bearing capacities computed by the formulas are less than 10%, compared with other standard methods to determine the loess bearing capacity. It is significantly improvement for meeting the requirements of the highway construction.

Abstract: The Hong Run petrochemical oil depot is located in a saline area in the north of Weifang.This area is severe cold in winter and has large temperature span throughout a year. Due to the area's rigorous environmental conditions, concrete with 50 years durability and strength grade of C40 was fabricated with the ordinary Portland cement, high performance superfine mineral powder and high performance pumping agent. Tests using the onsite concrete samples show that concrete mechanical properties meet the design requirements. After 300 freezing and thawing cycles including accelerated freezing thawing method and single-side freezing thawing method, the quality loss rate and relative dynamic modulus both comply with the design requirements. This suggests that the sample concrete has excellent frost resistance ability.

Abstract: Considering the hooping effect between steel tube and core concrete, established a small-deformation elastic analysis theory for the concrete-filled rectangle steel tube (CFRST) member, founded the elastic constitutive relations of CFRST, and accomplished the semi-analytical and semi-numerical solution of the composite elastic modulus. Research shows: composite elastic modulus of CFRST is higher than conversion elastic modulus without considering the hooping effect. Within certain value range of parameters, composite elastic modulus is 1.36% - 15.3% higher than conversion elastic modulus. Further more, as the steel ratio increases, the composite elastic modulus increases significantly, but the sensitivity of the composite elastic modulus to the strength of concrete is small.

Abstract: The seismic response of slope supported by composite soil nailing is analyzed by using finite element software ADNIA, in which the EL-Centro wave is selected as input earthquake wave.The analytical contents include the displacement and acceleration of supporting slope, as well as the time history responses of the axial forces of anchors. In the establishment of finite element model, the interaction between soil body and supporting structure is considered. The elastic-plastic M-C model with nonlinear static and dynamic behavior is used to simulate the soil body, and the dual linear strengthen model is adopted to simulate the supporting structure, then the interaction between soil body and supporting structure is simulated with contact element. The results show that the composite soil nailing slope supporting structure has better seismic performance than the general soil nailing slope supporting structure. The maximum horizontal displacement of the latter occurs at the slope top, but that of the former occurs at the slope upper. Especially after the imposition of the prestress, the slope displacement under earthquake reduces significantly, and the axial forces of anchors under earthquake enlarge significantly. Moreover, the axial forces of anchors reach maximum values near the slipping surface. The displacement and the acceleration of slope increase along the slope height. The conclusions obtained provide basis for the seismic design of permanent supporting slope and reference for similar projects.

Abstract: Owing to strong nonlinearity of shotcrete and difficulty of determining the equivalent material properties of steel-shotcrete composites for numerical analysis, methods are required to estimate nonlinear behavior of steel-shotcrete composite in the computational aspect efficiently. In this study, the behavior of steel-shotcrete composites, main primary supports in the NATM tunnel, are estimated by finite element method using the fiber beam-column element. The numerical results are compared with results of uniaxial and flexural test. Results of comparison show that finite element analysis of using fiber beam-column element can be an efficient tool of estimating the steel-shotcrete composite as the primary support in the NATM tunnel.

Abstract: This paper develops a new advanced strength model for circular columns retrofitted with fiber reinforced polymer (FRP) based on a newly collected test database which is so far the most updated and comprehensive one and has contained more than 800 axial compression test results of FRP confined circular concrete columns. This paper first reviews some existing design-oriented strength models and then provides an in-depth comparison between experimental test results and models predictions. The comparison results indicated that more or less deficiency exists when these models were extended to predict the confined strengths of a much larger amount of columns than that when they were derived, directly resulting in deteriorations of the prediction accuracy. These conclusions exactly reflect the necessity and significance of developing a new advanced confinement strength model in the paper.

Abstract: Rubber bearings are widely used in bridge structures. The aqueduct structures are water bridges, so rubber bearings are often set at the end of the aqueducts. Rubber bearing cannot solve the problems such as temperature stress and supporting inhomogeneous settlement, but also play role of isolation damping. This paper mainly studies on the effects of the water-depth with changing rubber bearing on the seismic performance of the aqueduct-water coupling structure by numerical analysis.

Abstract: A series Anti-slipping tests on steel pipe joints with swivel coupler were carried out in this paper. Sixteen specimens after turnover loaded, were tested to investigate the influence of variations in the Fastener tightening torque (Tr, from 20 to 40N•m), fastener turnover frequency (N, from 10 to 50) and turnover loading amplitude (△P, from 4.0 to 8.0kN) on the anti-slipping performance of steel pipe joints with swivel coupler. The experimental results showed that, the anti-slipping ultimate strength and stiffness of specimens were increased first and then decreased with increasing Tr or N, and decreased with increasing △P. The swivel coupler turnover should not exceed the number of 20, and the force of diagonal bracing bearing should less than 6 kN.

Abstract: As a specific example，this paper introduces the whole arrangement of the spillway of Zuocun reservoir，and explains a specific course of spillway design for small-scale reservoir danger control and reinforcement project from three aspects, the calculation of discharge capacity、water surface profile of chute and hydraulic calculation of stilling pool. The project can provide a reference for similar engineering.