E. Noroozinejad Farsangi

Bio: E. Noroozinejad Farsangi is an academic researcher from Graduate University of Advanced Technology. The author has contributed to research in topics: Damper & Seismic analysis. The author has an hindex of 3, co-authored 10 publications receiving 30 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.

Assessment of Structure-Specific Fragility Curves for Soft Storey Buildings Implementing IDA and SPO Approaches

Abstract: Soft storey building is popular due to the functional and aesthetic purpose, despite its weakness in resisting seismic excitation. Nonlinear Static (Pushover) Analysis (POA) is a time saving and simple assessment procedure prosposed in Eurocode 8 (EC8). However, its reliability in designing structure still remains a question. At the first stage, seismic performance of several building models using POA in EC8 is assessed. Later on, empirical accuracy of fragility curves generated by POA (using SPO2FRAG software) is studied and verified through Incremental Dynamic Analysis (IDA) results. Four models of regular and soft storey frame of 5- and 11-storey varying heights were designed according to Eurocode 2 (EC2) and (EC8). The simulation is performed in a NL platform to carry out POA and IDA. Capacity curve obtained is served as main input in SPO2FRAG software to generate fragility curve. Then, IDA is performed to generate IDA and fragility curves. Peak ground acceleration, PGA was converted into corresponding Sa(T1) using design spectrum from EC8. Performance levels of Life Safety (LS) and Near Collapse (NC) proposed by Vision-2000 have been the main interest in this study. Results shown that the base shear calculated by using Lateral Force Method in EC8 is adequate. Fragility curve generated by SPO2FRAG, has good comformity with IDA-based fragility estimation for regular 5-storey model; however, some deviation is observed for soft storey model (5-storey). All 11-storey frames shown unsatisfactory match of fragility curves from what was generated by SPO2FRAG, compared to IDA results.

The Self-Organizing Map

Abstract: An overview of the self-organizing map algorithm, on which the papers in this issue are based, is presented in this article.

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.

Admixtures to concrete

Abstract: In 1971 the Danish Concrete Association established a working group on admixtures for concrete. The work in this group was terminated in the spring of 1973 by a report of 120 pages and with 75 references. The report is based on extensive literature research covering the four main groups of admixtures: concrete accelerators, retarders, plasticizers and air-entraining admixtures. The main theme of the report concerns various theories forwarded by researchers as to why admixtures behave as they do and the correlations between molecular structure of an admixture and the effect obtained in a concrete mixture. In order to make the report useful in practical concrete work, the various other aspects of use of admixtures also had to be included. /TRRL/

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.

Fragility-based analysis of the influence of effective stiffness of reinforced concrete members in shear wall buildings

Abstract: When modeling RC shear wall buildings for seismic analysis there is little consensus in the literature on the appropriate value of the wall effective shear stiffness (GAeff) and the slab effective bending stiffness (EIeff). A probabilistic analysis based on fragility curves is a robust technique to assess the influence of these parameters on the expected seismic performance, but such studies are scarce because they require computationally expensive analysis such as Incremental Dynamic Analysis (IDA). In this paper, fragility curves are developed following the recently introduced SPO2FRAG procedure, a simplified methodology that does not require IDA but the computationally more affordable incremental static (pushover) analysis. The fragility curves provided by SPO2FRAG are used to evaluate the influence of the values of GAeff and EIeff on the analytical seismic response of full 3D nonlinear models of two actual (and representative) residential wall buildings of 17 and 26 stories located in Santiago (Chile). The accuracy of SPO2FRAG is also evaluated through comparisons with empirical fragilities.