Validation of Fiber-Based Distributed Plasticity Approach for Steel Bracing Models

Nonlinear analysis approach is not anymore limited only to research purposes, but becoming more popular as a tool that can be used during design, thanks to the increased efficiency of computer software and hardware. An accurately calibrated numerical model may simulate the behaviour of buildings in a quite realistic way, which helps designers understand better the performance of their structures. However, the feasibility of the nonlinear analysis approach is limited by the complexity of the numerical model, and the aim of any researcher or engineer is to obtain the most useful information in a reasonable amount of time. This study focuses on the validation of a simplified numerical modelling approach to simulate the nonlinear behaviour of steel bracings. The paper presents a comparison between two different modelling approaches; a refined finite element model using volumetric elements, and fiber-based model using beam elements with distributed plasticity. The numerical models calibrated with the experimental result from existing literature, reproduce the behaviour of cold formed square, and hot rolled open section steel elements under inelastic cyclic loading. The hysteresis loops obtained from two models show that the accuracy obtained by simpler fiber-element formulation is quite close to the more refined volumetric model. Finally, in order to assess the accuracy of the fiber-based modelling approach to estimate the nonlinear cyclic response of full-scale braced frame configurations, two real scale frames are analysed, and the results are compared with the results of the experiments performed on the test frames. In terms of computation time and accuracy, distributed plasticity model is much more efficient, and can be a good option to perform nonlinear analysis of multi-level buildings, which would be quite cumbersome with volumetric modelling approach. This study has been realized thanks to the research fund received from European commission with the contract MEAKADO RFSR-CT-2013-00022

VALIDATION OF FIBER-BASED DISTRIBUTED PLASTICITY APPROACH FOR STEEL BRACING MODELS

Nonlinear analysis approach is not anymore limited only to research purposes, but becoming more popular as a tool that can be used during design, thanks to the increased efficiency of computer software and hardware. An accurately calibrated numerical model may simulate the behaviour of buildings in a quite realistic way, which helps designers understand better the performance of their structures. However, the feasibility of the nonlinear analysis approach is limited by the complexity of the numerical model, and the aim of any researcher or engineer is to obtain the most useful information in a reasonable amount of time. This study focuses on the validation of a simplified numerical modelling approach to simulate the nonlinear behaviour of steel bracings. The paper presents a comparison between two different modelling approaches; a refined finite element model using volumetric elements, and fiber-based model using beam elements with distributed plasticity. The numerical models calibrated with the experimental result from existing literature, reproduce the behaviour of cold formed square, and hot rolled open section steel elements under inelastic cyclic loading. The hysteresis loops obtained from two models show that the accuracy obtained by simpler fiber-element formulation is quite close to the more refined volumetric model. Finally, in order to assess the accuracy of the fiber-based modelling approach to estimate the nonlinear cyclic response of full-scale braced frame configurations, two real scale frames are analysed, and the results are compared with the results of the experiments performed on the test frames. In terms of computation time and accuracy, distributed plasticity model is much more efficient, and can be a good option to perform nonlinear analysis of multi-level buildings, which would be quite cumbersome with volumetric modelling approach. This study has been realized thanks to the research fund received from European commission with the contract MEAKADO RFSR-CT-2013-00022

Three dimensional nonlinear dynamic modeling of a vertically isolated ancient statue displayed in a base isolated museum building

This research concerns with the question of how the seismic isolation methods can be applied efficiently to protect the ancient statues under both horizontal and vertical strong earthquake excitations. The results are achieved by carrying out nonlinear dynamical analyses under three dimensional earthquake ground motion data on a generic ancient statue model, considering that it is displayed in a non isolated and a horizontally isolated building. The model is developed with 8-node cubic finite elements, and placed on a rigid platform, which is modelled as an area element of rectangular shape. The isolation devices are modelled as non linear spring elements for the horizontal seismic isolation, and gap elements (compression only) for the vertical seismic isolation

How does conceptual design impact the cost and carbon footprint of structures?

Making sustainable conceptual design decisions is the key to reduce the environmental impact of the con- struction industry. Such early decisions, which must be given in a short timeframe, have the largest impact on a project's quality, cost and embodied carbon. This study showed how much the conceptual design decisions affect the cost and carbon footprint of a building's structure using our Non-dominated Sorted Genetic Algorithm II tool. First, we tested the tool's reliability by comparing its solutions with three case studies from literature. Then, we showed that by quickly examining various conceptual design solutions on a Pareto graph (which spotlights cost and CO2-optimized options), more sustainable design alternatives can be identified. Then, using the tool, we analyzed 36 building configurations, providing a spectrum of embodied carbon emissions (including the life cycle assessment steps A1, A2, A3, A4, A5, C2, C3, C4) ranging between 60 and 360 kgCO2e/m2. By comparing 25 material types from 15 databases (EPDs and ICE), we concluded that the geometry decisions (span length, height and shape) have the largest influence, material type (steel, timber, reinforced concrete), recycling and reuse of steel are crucial, and the embodied carbon calculations are highly sensitive to the supplier data and location. Overall, this study showed that architects and engineers possess the ability to significantly reduce the embodied carbon of structural systems by selecting the appropriate materials and structural system at the conceptual design stage

Growth and feed utilization of goldfish (Carassius auratus) fed graded levels of brewers yeast (Saccharomyces cerevisiae)

In this study, a feeding trial was conducted to examine the potential of replacing fish meal with brewers yeast in practical diet of goldfish (Carassius auratus). Five isoproteic (37% CP) and isocaloric (3350 kcal/kg) diets were formulated to contain graded levels of brewers yeast. Fish meal protein was replaced by 0%, 15%, 25%, 35%, and 45% of yeast. Each diet was randomly allocated to triplicate groups of 20 fish (initial average weight of 0.56 g fish^-1) in glass aquarium (65L). Fish were fed three times per day to apparent satiation for 84 days. At the end of the experiment, weight gain, specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), condition factor (CF), survival rate (SR), hepatosomatic indices (HSI) and body composition of goldfish fry were determined. According to the results, weight gain, SGR, FCR and PER of fish fed the diet including yeast replaced 35% of the fish meal were better than those of fish fed the other diets. There were no significant differences in SR and HSI values among fish fed diets (p>0.05). However, CF among fish fed the experimental diets was significantly different (p>0.05). Whole body composition was similar among fish fed different diets. The optimal replacement level of fishmeal protein by brewers yeast was determined by second-order polynomial regression to be (y= 2, 2237- 0,0004x^2 + 0,0279x; R² = 0,9977) 34.875%, on the basis of SGR