Life-Cycle Cost Model and Design Optimization of Base-Isolated Building Structures

Design of economic structures adequately resistant to withstand during their service life, without catastrophic failures, all possible loading conditions and to absorb the induced seismic energy in a controlled fashion, has been the subject of intensive research so far. Modern buildings usually contain extremely sensitive and costly equipment that are vital in business, commerce, education and/or health care. The building contents frequently are more valuable than the buildings them-selves. Furthermore, hospitals, communication and emergency centres, police and fire stations must be operational when needed most: immediately after an earthquake. Conventional con-struction can cause very high floor accelerations in stiff buildings and large interstorey drifts in flexible structures. These two factors cause difficulties in insuring the safety of both building and its contents. For this reason base-isolated structures are considered as an efficient alternative design practice to the conventional fixed-base one. In this study a systematic assessment of op-timized fixed and base-isolated reinforced concrete buildings is presented in terms of their initial and total cost taking into account the life-cycle cost of the structures

High Performance Optimization Computing Platform

Structural optimization over the past decades matured from an academic theoretical field, to an important tool in the design procedure in various engineering disciplines. Some commercial software applications provide some suites with optimization solutions, but they are focused mostly in the aeronautics, automotive and aerospace industry. High Performance Optimization Computing Platform (HP-OCP) is a software developed by the ISAAR-NTUA and provides a holistic optimization approach for civil engineering structures. More precisely, HPOCP is a computational suite that has the ability to integrate with several structural analysis and design software and provide optimization solutions. Structural optimization is mainly divided in three groups, sizing (or parametric), shape and topology optimization. All of them are integrated in HP-OCP and the appropriate algorithms are provided in each category. Considering size and shape optimization, the parametric optimization module is developed, in which the design variables of the mathematical formulation can be the dimension of the section properties, the quality of the material, the coordinates of the nodes etc. In this module plenty of derivativebased and derivative-free algorithms are provided like the Projected Quasi-Newton, Constrained Optimization by Linear Approximation, Latin Hypercube Sampling etc. [1]. Considering the topology optimization module [2], the SIMP method is applied and the mathematical algorithms that are implemented are the Optimality Criteria and Method of Moving Asymptotes. HP-OCP was developed in C# programming language, making it a powerful suite that can be integrated with any commercial software that provide Application Programming Interface, batch analysis via XML files or any other type of data exchange format. In the current work the integration of HP-OCP with the SAP2000, ETABS and SCIA Engineering software is presented. Several examples considering parametric and topology optimization problems are examined. Remarkable cost reduction is succeeded in real-world structures, validating in this way the usefulness of HP-OCP not only in the research field but also in applied civil engineering problems

Parallel Computing in HP-OCP

The most computationally demanding part of structural design optimization is the solution of the FE equations and design of the structural model. Therefore, there is a need for the implementation of strategies that can reduce the computational cost of each iteration and thus manage to achieve the same optimized result with considerable reduction in the optimization time. High Performance Optimization Computing Platform (HP-OCP) is an optimization software developed in C# programming language by ISAAR-NTUA and OptiStructre Ltd. [1] which provides a holistic optimization approach for civil engineering structures. It combines powerful derivative-based and derivative-free optimization algorithms like the Projected Quasi-Newton (PQN), Constrained Optimization by Linear Approximation (COBYLA), Latin Hypercube (LH), Differential Evolution etc. [2] integrated with different structural analysis software's like SAP2000, ETABS & SCIA Engineer utilizing their abilities in finite element analysis and most importantly different design codes into the optimization procedure. To deal with the computational demand deriving from this coupling of optimization algorithms and commercial structural analysis software's parallel computational procedures have been implemented to HP-OCP. These procedures were tested in real world civil engineering problems and produced very good results. Parallel strategies are implemented both at the level of the optimization algorithm, by exploiting the natural parallelization features of the evolutionary algorithms, as well as at the level of the repeated structural analysis problems that are required by the optimization algorithm. The numerical tests presented demonstrate the computational advantages of the proposed parallel strategies, which become more pronounced in large-scale optimization problems.

Innovative Computational Techniques for Multi Criteria Decision Making, in the Context of Cultural Heritage Structures’ Fire Protection: Case Studies

Fire protection for cultural heritage structures is a challenging engineering task that could benefit from the use of specialized computational tools relying on a performance-based design (PBD) concept rather than on prescriptive-based fire protection codes. In the first part of the present study, the theoretical basis of the proposed computational selection and resource (S and R) allocation model is discussed, related to the assessment of the fire safety index (FSI) and the authenticity preservation index (API). Furthermore, two different multi criteria optimization approaches are proposed to generate optimized fire protection upgrading designs, incorporating the nondominated sorting evolution strategies II (NSES-II) algorithm and the analytic target cascading (ATC) method. In this second part of the present work, the proposed S and R allocation model is implemented in two test cases; Villa Bianca, a famous mansion in Thessaloniki, Greece, and the Monastery of Simonos Petra located in Mount Athos, Greece. Several cases are examined regarding the targeted FSI or API values, taking also into account budget restrictions. In cases where the preservation of the authenticity is considered as an objective within the design process, the need to implement more sophisticated and customized fire protection measures can lead to a significant increase up to almost 200% regarding the total cost, subject to the pursued safety level. Detailed results obtained for each case study are presented and discussed comparatively, demonstrating the efficiency of the proposed S and R allocation model in a wide range of scenarios, as well as its possible utility in multiple applications, facilitating the fire protection design process. Finally, a comparison between the two multi criteria optimization approaches incorporated in the study is also presented and discussed

Innovative Computational Techniques for Multi Criteria Decision Making, in the Context of Cultural Heritage Structures’ Fire Protection: Case Studies

Fire protection for cultural heritage structures is a challenging engineering task that could benefit from the use of specialized computational tools relying on a performance-based design (PBD) concept rather than on prescriptive-based fire protection codes. In the first part of the present study, the theoretical basis of the proposed computational selection and resource (S and R) allocation model is discussed, related to the assessment of the fire safety index (FSI) and the authenticity preservation index (API). Furthermore, two different multi criteria optimization approaches are proposed to generate optimized fire protection upgrading designs, incorporating the nondominated sorting evolution strategies II (NSES-II) algorithm and the analytic target cascading (ATC) method. In this second part of the present work, the proposed S and R allocation model is implemented in two test cases; Villa Bianca, a famous mansion in Thessaloniki, Greece, and the Monastery of Simonos Petra located in Mount Athos, Greece. Several cases are examined regarding the targeted FSI or API values, taking also into account budget restrictions. In cases where the preservation of the authenticity is considered as an objective within the design process, the need to implement more sophisticated and customized fire protection measures can lead to a significant increase up to almost 200% regarding the total cost, subject to the pursued safety level. Detailed results obtained for each case study are presented and discussed comparatively, demonstrating the efficiency of the proposed S and R allocation model in a wide range of scenarios, as well as its possible utility in multiple applications, facilitating the fire protection design process. Finally, a comparison between the two multi criteria optimization approaches incorporated in the study is also presented and discussed

Innovative Computational Techniques for Multi-Criteria Decision Making, in the Context of Cultural Heritage Structures’ Fire Protection: Theory

The preservation of cultural heritage structures includes, among others, an efficient fire protection design process. This engineering design process frequently generates critical decision making issues related to conflicts that involve the buildings’ authenticity preservation, the implementation of special fire protection measures and addressing the particular needs of such structures. However, conventional approaches based on prescriptive regulations are often problematic in such cases; on the contrary, Performance-Based (PB) approaches could successfully deal with such structures to deliver designs that satisfy an acceptable fire safety level, and at the same time minimize the cost and any interventions on the building’s appearance, to the extent that authenticity is a key demand. Thus, in this study the upgrade of the fire safety level of cultural heritage structures is expressed as a Multi-Criteria Decision Making (MCDM) problem. Accordingly, the Analytic Hierarchy Process (AHP) is incorporated into a new fire protection Selection and Resource (S&R) allocation model, aiming to assess both fire safety and authenticity preservation levels with reference to the protection measures selected. Furthermore, in this study two different multi-criteria optimization approaches are applied to generate optimized solutions of the fire safety upgrading scheme. In this first part of the study, the theoretical basis of the proposed S&R allocation model that relies on a MCDM problem and how to deal with is discussed, while in the second part the implementation of the proposed model is presented for two real-world test cases. More specifically, in this study the theoretical part of the multi-objective and the multi-disciplinary problems (belonging to the MCDM type of problems) is provided with respect to the problems’ description and the methods adopted for solving the corresponding problems