Browsing by Author "Hube, M. A."

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    Comparison of 3D stress-strain concrete models
    (2021) Llera Martin, Juan Carlos de la; Chacón, Matías F.; Hube, M. A.; Celentano, Diego J.
    The inelastic response of reinforced concrete buildings is strongly sensitive to the material stress-strain constitutive model adopted for concrete. This paper is a first step on an ongoing work to do a complete benchmark analysis of available concrete models. Consequently, this article quantifies the differences in the response of three well-known 3D stress-strain continuum concrete models: (i) the Hyperbolic Drucker-Prager (DPH) plastic model; (ii) the UNIlateral (UNI) damage model; and (iii) the Faría-Oliver-Cervera (FOC) plastic-damage model. Consistent algorithms in terms of the updated stresses and the tangent stiffness tensor for all these models were implemented in the ANSYS software using user-material FORTRAN routines adapted to solid-type finite elements. Models results were validated using a set of experimental benchmark tests subjected to uniaxial and biaxial stress states under monotonic and cyclic loading. Moreover, the unilateral (crack opening-and-closure) effect was compared among these models. A set of ten response parameters were compared relative to the experimental tests, e.g., the peak stress, the unloading stiffness at each loading cycle, and the total dissipated energy. Results show that the dissipated energy and the unloading stiffness in the last loading cycle, for all tests, leads to the largest errors.
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    Experimental Evaluation of In-Span Hinge Details in Reinforced Concrete Box Girder Bridges
    (NATL ACAD SCIENCES, 2010) Hube, M. A.; Mosalam, K. M.
    During the past three decades, considerable research efforts have sought to improve the seismic design of California highway bridges. However, the in-span hinge (ISH) regions of concrete box girders have not been studied adequately. ISHs are classified as disturbed regions caused by the concentrated bearing loads and the possible existence of utility and maintenance openings, which induce a complicated three-dimensional stress state. Nevertheless, ISHs are commonly designed as two-dimensional short cantilevers following standard procedures. These designs typically lead to congested reinforcement causing constructability concerns from practical and economical aspects. The behavior and the strength of ISHs were assessed with five one-third scale specimens that were tested at the University of California, Berkeley. The first two specimens represent the as-built conditions of typical ISHs of California box girder bridges. These specimens were detailed identically, hut with one, utility openings were considered to study their influence on the behavior and strength of ISHs. The typical ISH characteristics were obtained from a survey of eight projects in California. The other three specimens represent new ISH designs, aimed at reducing the steel congestion and improving the structural performance of ISHs. Findings from the experimental results revealed that as-built ISHs fail with a combination of three failure modes: (a) beam shear, (b) two-dimensional strut and tie, and (c) punching shear. On the basis of the observed failure modes, it was concluded that the current ISH design could he optimized to reduce steel congestion and improve constructability.