S. F. Fathizadeh

Bio: S. F. Fathizadeh is an academic researcher from Shiraz University. The author has contributed to research in topics: Damper & Truss. The author has an hindex of 4, co-authored 5 publications receiving 24 citations.

Development of a novel cost-effective toggle-brace-curveddamper (TBCD) for mid-rise steel structures using multi-objective NSGA II optimization technique

Abstract: Curve-shaped laser-cut steel plate dampers named curved damper have been recently introduced, and their performance has been experimentally investigated through cyclic loading tests. Using the same concept, this study aims to propose a novel cost-effective toggle brace–curved damper (TBCD) system, which combines the toggle braces and curved dampers to provide a practical passive control device. The seismic performance of three-, six-, and nine-story steel moment–resisting structures utilized with TBCD is analyzed using nonlinear time history analysis (NTHA). For better comparison, the TBCD system is optimized using the multi-objective nondominated sorting genetic algorithm (NSGA-II). The seismic performance of the proposed system is then compared against the optimized viscous dampers (VDs), viscoelastic dampers (VEDs), and buckling-restrained braces (BRBs). The results of the optimization process show that the TBCD has comparable performance to the other passive control devices presented, while it leads to more cost-effective design solutions by reducing the constructional, installation, life cycle maintenance and repair cost, and downtime. Hence, the proposed TBCD system can be considered as an efficient alternative to conventional seismic force–resisting systems for both newly built structures and the seismic retrofitting of existing structures.

Considering soil–structure interaction effects on performance-based design optimization of moment-resisting steel frames by an engineered cluster-based genetic algorithm

Abstract: An engineered cluster-based genetic algorithm (ECGA) has been used for performance-based design optimization of two dimensional moment-resisting steel frames (MRSF) considering effects of the soil-...

Multi-level performance-based design optimisation of steel frames with nonlinear viscous dampers

Abstract: This paper presents a practical multi-level performance-based optimisation method of nonlinear viscous dampers (NVDs) for seismic retrofit of existing substandard steel frames. A Maxwell model is adopted to simulate the behaviour of the combined damper-supporting brace system, with a fractional power-law force–velocity relationship for the NVDs, while a distributed-plasticity fibre-based section approach is used to model the beam-column members thus incorporating the nonlinearity of the parent steel frame in the design process. The optimum height-wise distribution of the damping coefficients of NVDs satisfying given performance requirements is identified via a uniform damage distribution (UDD) design philosophy. The efficiency of the proposed multi-level performance-based design optimisation is illustrated through nonlinear time-history analysis of 3-, 7- and 12-storey steel frames under both artificial and natural spectrum-compatible earthquakes. Sensitivity analysis is performed to investigate the effects of initial height-wise damping distribution, convergence factor and uncertainty in design ground-motion prediction on the optimisation strategy. The efficiency of the final optimum design solution is also investigated by using drift-based, velocity-based, and energy-based UDD approaches to identify the most efficient performance index parameter for optimisation purposes. It is found that regardless of the selected performance parameter, the optimum damping distribution identified by the proposed methodology leads to frames exhibiting lower maximum inter-storey drift, local damage (maximum plastic rotation) and global damage index compared to an equal-cost uniform damping distribution. However, using drift-based UDD approach generally results in a better seismic performance. It is shown that the proposed UDD optimisation method can be efficiently used to satisfy multiple performance objectives at different intensity levels of the earthquake excitation, in line with performance-based design recommendations of current seismic codes. The proposed method is easy to implement for practical design purposes and represents a simple yet efficient tool for optimum seismic retrofit of steel frames with NVDs.

Experimental and numerical investigations of a new hysteretic damper for seismic resilient steel moment connections

Abstract: In this study, a novel hysteretic damper is proposed for beam-column steel connections to dissipate seismic energy. The proposed system is classified as a low-damage device and the energy dissipation in the connection is provided through the bending deformations in hourglass shape steel pins inside the hysteretic damper. At the first stage, full-scale experimental prototypes have been fabricated and tested in the dynamic testing laboratory. In the next stage, micro- and macro-modelings of the proposed device calibrated through the experimental testing have been investigated using ABAQUS and OpenSees platforms, respectively. Both experimental and finite element simulations indicated that the proposed damper has a high capacity of energy dissipation without a significant decline in the resistance through loading cycles. Applying this damper to the connection helps all structural members including beams and columns to maintain in the elastic region, and will improve the ductility and seismic resilience of the whole building structure. The proposed damper has the easiness of fabrication, installation, and replacement.