The increasing need to reduce damage and downtime in modern buildings has led to the development of a low-damage design philosophy, where the earthquake loads can be resisted with damage confined to easily replaceable components. Post-tensioned (PT) concrete walls have emerged as a popular lowdamage structural system that have been implemented in a range of buildings. In order to provide essential evidence to support the development of lowdamage concrete structures, a system-level shake-table test was conducted on a two-storey low-damage concrete wall building implementing state-of-art design concepts. The test building included PT rocking walls that provide the primary lateral-load resistance in both directions, a frame that utilized slotted beam connections, and a range of alternative energy dissipation devices that were installed at wall base or/and beam-column joints. The building was subjected to 39 tests with a range of intensity ground motions, incorporating both unidirectional and bidirectional ground motions on the structure with different combinations of wall strength and energy dissipating devices. The building performed exceptionally well during the intense series of tests, confirming the suitability of both the design methods and the connection detailing implemented. The building achieved an immediate occupancy performance objective even when subjected to maximum considered earthquake hazard shaking. The building exhibited only minor damage at the conclusion of testing, with distributed cracking in the floors and cosmetic spalling in the wall toes that did not compromise structural capacity or integrity and could be easily repaired with minimal disruption.The test has provided a rich dataset that is available for further analysis of the building response and validation of design methods and numerical models.
Summary To support the development of low‐damage concrete structures, a system‐level shake‐table test of a two‐story concrete wall building implementing state‐of‐the‐art design concepts was conducted using the multi‐functional shake‐table array at Tongji University as part of an international collaborative project. The test building was designed with a perimeter frame and exterior post‐tensioned concrete walls in both directions. Different floor systems and wall‐to‐floor connections were incorporated in the test building to compare a number of design concepts and construction details. A range of energy dissipation devices were installed at the wall base and/or slotted‐beam joints of the test building. To simulate the test building response during the shake‐table tests, numerical models of the test building in both the longitudinal and transverse directions were established in OpenSees. Because the test building utilized flexible and isolated wall‐to‐floor connections that specifically reduced potential wall‐to‐floor interaction, planar frame numerical models were selected to represent the test building in each direction of loading. In the models, fiber hinge elements were used to simulate the unbonded post‐tensioned walls and a modified multi‐truss spring method was adopted to simulate the slotted‐beam joints with and without dampers. Inelastic time‐history analyses of the numerical models were conducted considering three earthquake intensities and comparisons of the test and simulation responses of the building are presented. The simulation results showed that the analytical model established in this study could reasonably predict both the global and local responses of the test building under different shaking intensities.
Steel-microfiber-reinforced concrete has been proven to be an effective type of hybrid fiber-reinforced concrete (HyFRC). The microfiber used in these concretes generally include microfilament steel (MS) fibers and synthetic fibers, such as polypropylene (PP), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN) fibers. This study aims to obtain the optimal type of steel-microfiber HyFRC, with low fiber content, which can be easily used in engineering projects without special fabrication procedures, thus achieving the concept of sustainability. Four types of HyFRC that blend steel (S) fiber with MS, PP, PVA and PAN were studied. These HyFRC were compared through a systematic experimental campaign in which the fiber dispersion, mixture workability, and concrete mechanical properties were investigated. The experimental results of the fiber dispersion and mixture workability indicate the following qualitative relationship: MS > PVA ≈ PP > PAN. For the mechanical properties of the concretes, the S-MS, and S-PVA HyFRCs generate an overall higher enhancing effect than those of the S-PP and S-PAN HyFRCs and show a positive hybridization effect for most properties. The S-MS HyFRC is superior in strength, and the S-PVA HyFRC has a significantly improved toughness. Because PVA has relatively good dispersion and workability properties, and toughness is the most important and effective mechanical property in the fiber-reinforced concrete, this study recommends that the S-PVA HyFRC is the optimal type of steel-microfiber HyFRC.
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