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Precast, prestressed hollow-core (PHC) slabs are widely used in floor and roof decks because of their economic benefits. Because no shear reinforcement can be provided because of fabrication restraints, designers have to opt for deeper profile or filling PHC slab cores with concrete when the load demand exceeds the limited concrete shear capacity of PHC slabs. This research project is exploring an innovative technique for strengthening the web-shear capacity of PHC slabs by bonding external fiber-reinforced polymer (FRP) sheets along the internal perimeter of the slab voids. Experimental testing and numerical simulation on full-scale single web, I-shaped beam specimens cut out longitudinally from full-width hollow-core slabs have been performed during the first phase of this research to investigate the feasibility and effectiveness of this new technique. The influence of several design parameters, including the length and the width of the strengthened zone, the thickness of applied FRP sheets, and...

Prismatic members subjected to internal axial loads exist widely in engineering applications. Because the effects of internal loads and end loads on stability are quite different, the traditional effective length method is not applicable. Engineers require an efficient and convenient method for solving the stability problem of such members. A two-bar model is proposed to illustrate the concept that the effect of compressive axial loads on the stability of sway-inhibited columns can be understood as a negative lateral stiffness. After obtaining the expression of negative lateral stiffness, a relationship between end loads and internal loads can be established so that the internal loads can be considered equivalent to end loads. Then, the column subjected to internal loads can be analyzed as a normal column (without internal axial loads), and the critical buckling load can be obtained easily with the Euler formula. Eigenvalue buckling analyses were performed to examine the proposed method, and the c...

Because loess underground erosion is one of the major engineering geological problems in loess areas of China, foundation loess of the Zichang-Yongping section of West-East Gas Pipelines is taken as the research object. The soil-water characteristic curve (SWCC) and hydraulic conductivity function (HCF) of samples have been obtained by laboratory tests, and on this basis, seepage field numerical simulations of loess foundation with and without the pipelines have been processed by the finite-element method. Critical groundwater seepage velocity of underground erosion and the relationship between groundwater seepage velocity and underground erosion velocity have been tested by self-made instruments. Results of tests and numerical simulation indicate that the pipelines not only change the original seepage field of a loess foundation, but also accelerate the underground erosion of a loess foundation. Loess on the top and upstream groundwater side of pipelines will be eroded first, finally causing the failure of foundation and the exposure of pipelines. The combination of soil solidified material and revegetation is suggested as an effective and durable solution to deal with the underground erosion problem of loess pipeline foundations.