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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    Effect of lateral stiffness on expected economic losses in reinforced concrete shear wall buildings
    (2023) Cando, M. A.; Hube, M. A.; Parra, P. F.; Arteta, C. A.
    This research paper evaluates the effect of lateral stiffness on expected economic losses in reinforced concrete shear wall buildings designed following current Chilean standards, including DS60 and DS61. Economic losses were evaluated for a group of four 20-story archetype buildings located in Santiago, Chile. The methodology developed by the Pacific Earthquake Engineering Research Center was considered to estimate economic losses. The expected annual loss (EAL) and the present value (PV) of the losses in 50 years were used as measures of economic loss. A probabilistic seismic hazard analysis, which considered the seismicity of central Chile, was performed to estimate both metrics. The results show that when the lateral stiffness of the building increases, the EAL also increases. This implies that stiffer buildings are more vulnerable from an economic point of view. This counter-intuitive finding results from the higher seismic hazard of stiffer buildings and the minimum design base shear required by DS61 that governed the design of the studied buildings. Additionally, it was found that the EAL and the PV of losses in 50 years for the four archetypes do not exceed 0.3% and 7.8% of the total construction cost of the buildings, respectively. These monetary losses are relatively low, which is consistent with the outstanding seismic performance of reinforced concrete shear wall buildings.
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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.
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    Seismic response of reinforced concrete wall buildings with nonlinear coupling slabs
    (2021) Ramos, L.; Hube, M. A.
    Reinforced concrete (RC) structural walls are widely used in high-rise buildings as the lateral force resisting system because of their inherent economy, stiffness, and strength. The floor plan configuration of residential buildings in Chile consists mainly in assemblies of large longitudinal walls and shorter transverse walls coupled by floor slabs. The coupling effect of the slabs has affected the response and the observed damage of RC buildings in recent earthquakes. The main objective of this article is to assess the seismic response of a RC structural wall building with coupling slabs. Additionally, the effect of the amount of slab reinforcement on the seismic response of the building is evaluated. To achieve the proposed objectives, seven three-dimensional models of a case study building were developed using shell-type elements in DIANA. The first four models aim to evaluate the effect of using elastic slabs with reduced (i.e. cracked) moment of inertia. The last three models consider nonlinear behavior for both walls and slabs. The response of the building was estimated using nonlinear static analysis and the seismic performance is evaluated from the results of roof displacement and shear, moment, and axial forces of the walls. Additionally, the seismic performance is evaluated from the strain demands of concrete and steel in both walls and slabs. Relevant conclusions about the building behavior, slab demands, and failure mode are drawn.