Browsing by Subject "shear"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Shear Capacity of High-Strength Concrete Prestressed Girders
    (Minnesota Department of Transportation, 1998-05) Cumming, David A.; French, Catherine E.; Shield, Carol K.
    As part of a project at the University of Minnesota to investigate the application of high-strength concrete in prestressed girders, four shear tests were performed on high-strength concrete prestressed girders. Originally constructed in August 1993, the girders, Minnesota Department of Transportation (Mn/DOT) 45M sections were 45 inches deep. Each girder utilized 46 0.6-inch diameter prestressing strands on 2-inch centers. The girders were designed assuming a 28-day compressive strength of 10,500 psi. Later, a 4-foot-wide and 9-inch-thick composite concrete deck was added to each girder using unshored construction techniques. The shear test results were compared with predicted results from ACI 318-95 Simplified Method, ACI 318-95 Detailed Method (AASHTO 1989), Modified ACI 318-95 Procedure, Modified Compression Field Theory (AASHTO LRFD 1994), Modified Truss Theory, Truss Theory, Horizontal Shear Design (AASHTO 1989), and Shear Friction (AASHTO LRFD 1994). The calculated shear capacities were in all cases conservative compared to the actual shear capacity.
  • Thumbnail Image
    Item
    Shear Distribution in Prestressed Concrete Girder Bridges
    (2015-10) Dymond, Benjamin
    As shear requirements for prestressed concrete girders have changed, some structures designed using older specifications do not rate well with current methods. However, signs of shear distress have not been observed in these bridge girders and they are often deemed to be in good condition. The primary objective of this research program was to investigate the accuracy of existing shear distribution factors, which are used to estimate bridge system live load effects on individual girders, and provide recommendations on shear distribution to be used in Minnesota with three components: a full-scale laboratory bridge subjected to elastic and inelastic behavior, field testing of bridges, and a numerical parametric study. Results from the components were integrated to develop recommendations for rating prestressed concrete girder bridges. Laboratory bridge inelastic testing indicated shear force redistribution after cracking and before ultimate failure. Use of elastic distribution factors is conservative for shear distribution at ultimate capacity. Elastic laboratory testing was used to validate the finite element modeling technique and study the behavior of a traffic barrier and end diaphragm, which affected shear distribution. Ignoring the effects of the barrier was conservative and ignoring the effects of the end diaphragm was slightly inaccurate by 4 to 6 percent but was warranted for simplicity. Parametric study results indicated that a ratio of longitudinal stiffness to transverse stiffness could be used as a screening tool. If the stiffness ratio was less than 1.5, shear demand from a simple, conservative grillage analysis may be more accurate than shear demand from AASHTO distribution factor methods. Grillage analysis shear demand results due to permit trucks may also be more accurate, regardless of the screening tool ratio.
  • Thumbnail Image
    Item
    Variation In Web-Shear Capacity of Hollow-Core Slabs With Filled Cores
    (2020-06) Asperheim, Scott
    The web-shear capacity of hollow-core slabs both with and without concrete or grout core-fill material, as well as slabs that were cast with a solid extruded core (i.e., with one of the voids omitted), was experimentally investigated using two different hollow-core slab geometries to evaluate how the fill material affected the shear capacity. The shear demand at failure was compared to five different methods of predicting the shear capacity of hollow-core slabs: ACI 318 (2014), the AASHTO (2017) sectional design model, a method proposed by Lin Yang (1994), the EN 1168 (2011) general method, and the EN 1168 (2011) simplified method. Additionally, a web-shear capacity prediction method was proposed based on the ACI-ASCE Committee 326 (1962) report on shear and diagonal tension.