Journal Articles
2024
Distributed real-time hybrid simulation method for dynamic response evaluation of floating wind turbines
Abstract
Limited land and near coast spaces led to the development of floating wind turbine (FWT) farms in unlimited space of deep water with steady winds. Experimental evaluation of dynamic responses of FWT is essential to ensure its safe operation. However, due to laboratory limitations and scaling issues, realistic FWT responses are difficult to be replicated on scaled-down test specimens. To facilitate larger-scale testing of FWT and apply realistic wind and wave loads, distributed real-time hybrid simulation (dRTHS) method is proposed which combines the testing of FWT substructures at geographically distributed laboratories using wind tunnels and wave tanks. In this research, dRTHS experimental method for FWT is developed and its feasibility is verified through a series of virtual dRTHS (vdRTHS) and proof-of-the-concept partial dRTHS tests. The equation of motion of a prototype FWT structure under coupled aerodynamic and hydrodynamic loads was partitioned to represent the wind turbine tower and platform substructures, based on which substructural formulation was derived. During the vdRTHS, two distributed real-time controllers were used to simulate the physical testing of the two substructures tested in the wind tunnel and water tank, respectively, with interfacing data being transferred in real-time through a network. FWT responses from vdRTHS match well with those obtained from numerical simulations of the whole FWT model and the substructured models, demonstrating that the feasibility of the proposed dRTHS method. In addition, the substructuring approach, the vdRTHS testing platform, and the method to overcome network communication delay are effective in the vdRTHS resulting in reliable FWT dy namic responses under coupled loading conditions. Furthermore, the proposed dRTHS concept was verified through a partial distributed physical tests during which the wind turbine substructure was tested physically, while the platform substructure and the hydrodynamic loads were simulated numerically.
Authors: Hezha Lutfalla Sadraddin, Dr. Xiaoyun Shao
2023
Experimental Investigation of Lateral Behavior of Light-Frame Shear Walls Applied with Elastomeric Adhesive
Abstract
The seismic design of light-frame wood buildings requires adequate lateral strength and stiffness without inversely compromising the energy dissipation performance, mainly attributable to the connections. The impact of elastomeric adhesives on the seismic performance of light-frame shear walls (LFSW) was examined experimentally. Eleven LFSW specimens subjected to monotonic and cyclic loading tests represented four configurations of sheathing-to-framing connections. The reference configuration used standard nailing in the connections, while the other three configurations added elastomeric adhesives. The adhesives adopted are the conventional polyurethane-based and two silyl-modified polyether-based (SMP) adhesives of different mechanical properties. Experimental results of force-displacement relationships and performance characteristics were evaluated, including strength, stiffness, energy dissipation, and ductility. The failure modes, sheathing deformation, and hold-down and anchor bolt forces were monitored to explain the quantified performance reasonably. Calculated values from the tests were compared with their counterparts in the design provisions, including shear wall deflection and allowable story drift. It is noted that the adhesive configurations doubled the wall strength and increased stiffness by half compared with the reference configuration. Of all the configurations, the most energy dissipation was achieved when using the SMP adhesive of high-elongation and the least using conventional adhesive. The superior elongation capability of the SMP adhesives indicates a synergistic effect with nails allowing more deflection of sheathing from framing and more energy dissipation than conventional adhesives of inherently limited elongation.
Authors: Dr. Bilal Alhawamdeh, Dr. Xiaoyun Shao, Dr. David M. Salazar
2020
Fatigue performance of wood frame roof-to-wall connections with elastomeric adhesives under uplift cyclic loading
Abstract
Roof-to-wall-connection (RTWC) is critical in the loading path of wood-frame residential buildings, whose fatigue performance under varying wind loading is investigated in this paper. To get an insight on the wind-induced fatigue behavior at low to moderate hourly mean wind speeds and to demonstrate the effects of adhesives on the fatigue performance of RTWC, two types of fatigue experiments, namely the constant and the varying amplitude loading tests, were conducted on three RTWC configurations with and without elastomeric construction adhesives. Based on the constant amplitude loading test results, fatigue life prediction models were developed, and the reduction in the static load capacity due to cyclic loadings were estimated. Adhesives are shown to increase the endurance limit of the RTWCs, which is desirable to enhance the life-cycle performance of wood buildings. The varying amplitude loading test results indicate that buildings in non hurricane regions are vulnerable to fatigue damage at a low-level mean wind speed. It may induce loadings above the endurance limit of the RTWCs. On the other hand, the linear Miner’s cumulative fatigue damage model can be reasonably used to predict fatigue damage of the RTWCs when subject to multi-amplitude wind loadings. Toenailed connections generally fail in a less ductile manner at a certain number of load cycles with no warnings compared to the connections with adhesives that fail in a more ductile manner. The testing results presented herein provide essential data on the hysteresis behavior and failure modes of RTWCs to facilitate future implementation of adhesives in wood constructions.
Authors: Dr. Bilal Alhawamdeh, Dr. Xiaoyun Shao
Uplift Capacity of Light-Frame Rafter to Top Plates Connections Applied with Elastomeric Construction Adhesives
Abstract
The effects of the application of elastomeric construction adhesives on the wind uplift resistance of light-frame wood connections were investigated and are presented in this paper. Previous research has revealed that proper roof-to-wall connections play a critical role in mitigating structural damage during severe winds by providing a continuous load transfer path from the roof down to the foundation. Monotonic uplift tests of 30 rafter-to-top-plates connections of six configurations were conducted. Two specimen groups, standard ring shank nails alone and strengthened with hurricane ties, were constructed with and without elastomeric adhesive application, and their wind uplift resistances were compared to explore the effectiveness of the two adh sives (i.e., polyurethane and polyether) when applied to the roof connections. Experimental results show that the addition of adhesives allowed both groups to resist higher uplift loads (approximately 200%–460%) and dissipate considerably more energy (approximately 200%–750%). Replacing hurricane ties with the adhesives approximately doubles the uplift capacity but reduces the energy dissipation by nearly half owing to reduced deformation capacity. Failure modes were also examined to provide reasonable explanations for the observed performance of the connections.
Authors: Dr. Bilal Alhawamdeh, Dr. Xiaoyun Shao