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"performance-based design"
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A Prediction Model for the Calculation of Effective Stiffness Ratios of Reinforced Concrete Columns
Nonlinear dynamic analyses of reinforced concrete (RC) frame buildings require the use of effective stiffness of members to capture the effect of cracked section stiffness. In the design codes and practices, the effective stiffness of RC sections is given as an empirical fraction of the gross stiffness. However, a more precise estimation of the effective stiffness is important as it affects the distribution of forces and various demands and response parameters in nonlinear dynamic analyses. In this study, an evolutionary computation method called gene expression programming (GEP) was used to predict the effective stiffness ratios of RC columns. Constitutive relationships were obtained by correlating the effective stiffness ratio with the four mechanical and geometrical parameters. The model was developed using a database of 226 samples of nonlinear dynamic analysis results collected from another study by the author. Subsequent parametric and sensitivity analyses were performed and the trends of the results were confirmed. The results indicate that the GEP model provides precise estimations of the effective stiffness ratios of the RC frames.
Journal Article
A methodology for the integrated seismic design of nonlinear buildings with supplemental damping
Summary Designing structures to behave nonlinearly (elastically or inelastically) under strong seismic events has been long recognized to help reducing the seismic forces acting on them. Nonetheless, nonlinear structures often experience larger displacements than their linear counterparts. The concept of allowing nonlinear behavior in structures while capping forces at lower levels and adding viscous damping has been shown to be able to lead to good designs in terms of both levels of seismic forces and peak deformations. This paper presents an approach for the design of nonlinear (elastic or inelastic) structures equipped with viscous dampers that would produce desired levels of inter‐story drifts while reducing seismic forces as well. To attain a nonlinear elastic behavior, use could also be made by the negative stiffness device introduced by others. As inter‐story drifts are reduced to desired levels, the methodology could naturally be used as part of the performance‐based design framework. The values of capping forces and damping coefficients serve as design variables. The capping forces are the yield forces in yielding members and the maximum forces in nonlinear elastic members. The procedure relies on analysis tools only, hence, could be easily incorporated into the practical design process. Copyright © 2014 John Wiley & Sons, Ltd.
Journal Article
The CAED Framework for the Development of Performance-Based Design at the Wildland–Urban Interface
The hazard posed by wildland–urban-interface (WUI) fires is recognized by the international fire research community and features as one of nine research need priority threads in the Society of Fire Protection Engineers (SFPE) Research Roadmap. We posit that the first step in the journey to enhancing fire safety engineering at the WUI is to develop a common understanding between developers, engineers, planners, and regulators of the development scope, wildfire problem, technical design solutions, and verification methods to be used. In order to define a fire safety engineering consultation process appropriate for the wildfire context, this paper aims to translate well-established and evidence-based performance-based design (PBD) consultation frameworks and approaches from traditional fire safety engineering to the wildfire context. First, we review international English-language fire safety engineering frameworks that have been developed for the urban context. Next, we distil the results into a streamlined framework, which we call the “CAED Framework”. Finally, we apply and discuss the contextualization of the CAED Framework to the WUI context through a comparative case study of urban and WUI development. In doing so we seek to provide a structure for the development of standardized PBD within the WUI context across jurisdictions internationally, as well as to embed best practices into the emerging field of performance-based wildfire engineering.
Journal Article
Computational workflow for resilient architectures
The paper shows the results of an applied research aimed at developing an operative methodology and its corresponding computational workflow for the design of resilient architectures able to responsively react to the variation of the environmental conditions. The proposed methodology consists in a form-searching process built-up by a series of consequential and interrelated phases aimed at reducing the energy needs of the building and improving indoor and outdoor comfort conditions. The analysis of the processes, above defining the limits and potentials of the chosen design approach, opens the debate on parametric tools that allow to systematically explore the space o design possibilities.
Journal Article
Treasures gutted by fire. Fire safety design awareness as a consequence of historic building accidents and disasters
Many of the emblematic buildings of historical importance that have been constructed throughout human history still survive today. However, a significant number has been destroyed by fire. Despite the impact this loss has on cultural heritage, important lessons can also be learnt, enhancing our understanding on how fires develop in historical structures and why they occur in the first place. A review of the existing fire design approaches, in conjunction with the heritage building values and fundamental conservation principles, initiates a dialogue in terms of acceptable interventions and fire protection solutions. The aim of this study is to provide contemporary scientists, conservation professionals and building owners with an insight of how building physics affect the fire performance of historic structures, highlight common risks following a thorough literature review and discuss the role of the fire and conservation engineer.
Journal Article
Performance Simulation Integrated in Parametric 3D Modeling as a Method for Early Stage Design Optimization—A Review
During the last decades, standards on building construction have risen sharply to integrate new, ambitious demands regarding energy efficiency, as well as thermal and optical comfort in the design procedure. Building simulation software assists in the accurate calculation of a hypothetical or existing building’s performance on several aspects; but they are, in their vast majority, assessment-oriented, rather than focused on dynamically supporting the decision-making procedure. During the last two decades, a clear shift of design professionals and academia towards addressing performance issues from the conceptual stages of a building’s design is observed. In this review, the methodology of performance-driven design optimization using computational/parametric design and optimization is presented, and the core literature available on the topic is reviewed in order to identify the current status, different approaches, obstacles, and areas of future research on the subject. The review findings confirm that there is enormous potential for the design of better-performing buildings using this technique, but there are still many obstacles to overcome and areas for future research.
Journal Article
Multi-level performance-based design optimisation of steel frames with nonlinear viscous dampers
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.
Journal Article
Performance-Based Seismic Design and Parametric Assessment of Linked Column Frame System
Linked column frame system, as a new seismic load-resisting system, has a proper seismic behavior in various performance objectives due to ductile behavior of replaceable link beams. Thus, returning to occupancy after moderate earthquake is rapid and low-cost. Performance-based seismic design methods should be used for this system in order to have proper seismic behavior. In this study, by using performance-based plastic design method, a highly accurate and simple design procedure is proposed for this system. 9 prototype structures with 3, 6 or 9 stories and with 3, 4 or 5 bays are selected for parametric design and assessment. For assessment of the designed structures, nonlinear static and dynamic analyses with models according to experimental test results of the members and recommended ground motion records of FEMA P695 are used. According to analyses results, the designed structures in three hazard levels meet the performance objectives.
Journal Article
Performance-based control co-design of building structures with controlled rocking steel braced frames via neural dynamic model
Controlled rocking steel braced frames (CRSBFs) are modern systems for resilient building structures known for their effective energy dissipation and self-centering features. In a CRSBF, post-tensioned (PT) strands and shear fuses are the distinct features providing the self-centering and energy dissipation mechanisms. As a relatively new structural system, there is a need to study this system’s optimal design. Control co-design has gained interest in recent years as a class of integrated engineering system design methods as an alternative to the traditional approach of optimizing the structural design and sequentially optimizing the control system’s design. It considers the direct relationship between physical and control system design decisions to discover non-obvious design solutions that enable new performance and functionality levels. This paper proposes a performance-based control co-design methodology for building structures integrating CRSBFs that concurrently minimizes the mainframe weight and determines the CRSBF design parameters subject to design code requirements as the optimization constraints. The patented neural dynamic model of Adeli and Park is used in this research to solve the nonlinear optimization problem. The seismic performance evaluation of the proposed methodology includes a shear frame and a nonlinear 6-story 3D building structure. The 6-story building model consists of 282 nodes with 1,692 degrees of freedom. A total of 610 frame elements, 8 PT strands with nonlinear material, and 32 nonlinear links are determined without requiring high-performance computing. Results show that the energy dissipation mechanism effectively reduces the seismic demand in structural members. The proposed performance-based control co-design methodology can lead to 21% reduction in the total weight of the 6-story frame structure.
Journal Article