Chara Ch. Mitropoulou

Life-cycle cost assessment of optimally designed reinforced concrete buildings under seismic actions

Life-cycle cost analysis (LCCA) is an assessment tool for studying the performance of systems in many fields of engineering. In earthquake engineering LCCA demands the calculation of the cost components that are related to the performance of the structure in multiple earthquake hazard levels. Incremental static and dynamic analyses are two procedures that can be used for estimating the seismic capacity of a structural system and can therefore be incorporated into the LCCA methodology. In this work the effect of the analysis procedure, the number of seismic records imposed, the performance criterion used and the structural type (regular or irregular) is investigated, on the life-cycle cost analysis of 3D reinforced concrete structures. Furthermore, the influence of uncertainties on the seismic response of structural systems and their impact on LCCA is examined. The uncertainty on the material properties, the cross-section dimensions and the record-incident angle is taking into account with the incorporation of the Latin hypercube sampling method into the incremental dynamic analysis procedure. In addition, the LCCA methodology is used as an assessment tool for the designs obtained by means of prescriptive and performance-based optimum design methodologies. The first one is obtained from a single-objective optimization problem, where the initial construction cost was the objective to be minimized, while the second one as a two-objective optimization problem where the life-cycle cost was the additional objective also to be minimized.

Numerical calibration of damage indices

In this study a numerical calibration procedure is proposed; while its application in some of the most widely accepted damage indices (DIs) used for quantifying the extent of damage in reinforced concrete structures is presented. In particular, without loss of generality of the applicability of the proposed procedure, the Park and Ang local damage index, its modified variant presented by Kunnath, Reinhorn and Lobo; the Chung, Meyer and Shinozuka local damage index; along with the maximum and final softening damage indices proposed by DiPasquale and Cakmak, are calibrated on the basis of the width of crack openings. The estimation of the crack width is performed by means of detailed modelling with hexahedral finite elements for the concrete and rod elements for the steel reinforcement; while due to the computing demands the databank of values for the damage indices under investigation is defined based on coarse models with beam-column elements. These two steps of the proposed procedure are based on the incremental dynamic analysis. Next, the statistical characteristics of the DIs are computed by means of horizontal statistics in conjunction with the maximum likelihood function method and an optimization algorithm.

The effect of uncertainties in seismic loss estimation of steel and reinforced concrete composite buildings

The objective of this work is to study the influence of various sources of uncertainties on the seismic response of structural systems. For this purpose, four test examples are considered, in particular two steel and two steel–concrete composite buildings. In order to study the impact of uncertainty on this type of structure, life-cycle cost analysis is performed for each structure, which is a measure of the damage cost due to future earthquakes that will occur during the design life of a structure. The calculation of the life-cycle cost of structural systems requires the calculation of the structural capacity in multiple earthquake hazard levels. Multicomponent incremental dynamic analysis (MIDA) is considered as one of the most efficient procedures for estimating the seismic capacity of 3D structural systems; therefore, in this work, MIDA is incorporated into the seismic loss estimation procedure. In order to take into account uncertainty on the mass, the material properties, the damping and the record-incident angle, the Latin hypercube sampling method is integrated into the MIDA framework.

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.

Evolution Strategies-Based Metaheuristics in Structural Design Optimization

During the last three decades, there has been a growing interest in problem-solving systems based on algorithms that rely on analogies to natural processes. Nature-inspired optimization techniques have been proven to be quantitatively appealing, since they have been proved to be robust and efficient even for the most complex problems examined. These methods, also known as metaheuristics, are used for combinatorial optimization problems. The objective of this study is to assess the performance of metaheuristic optimization when implemented for the design of three-dimensional steel structures having single or multiple objectives. Almost every real-world problem involves simultaneous optimization of several incommensurable and often competing objectives, which constitutes a multiobjective optimization problem. In multiobjective optimization problems, the optimal solution is not unique as in single-objective optimization problems. Structural optimization problems are formulated as sizing design optimization, where the cross-sectional dimensions of the structural elements constitute the sizing design variables. In particular, this chapter is concerned with the structural optimization of skeletal truss structures under static loading conditions with single and multiple objectives. Combinatorial optimization methods and in particular algorithms based on evolution strategies are implemented for the solution of both type of problems.

Structural Seismic Design Optimization and Earthquake Engineering: Formulations and Applications

Structural Seismic Design Optimization and Earthquake Structural Seismic Design Optimization and Earthquake Engineering: Formulations and Applications focuses on the research around earthquake engineering, in particular, the field of implementation of optimization algorithms in earthquake engineering problems. Topics discussed within this book include, but are not limited to, simulation issues for

Design Optimization of Active and Passive Structural Control Systems

Improving structural seismic response using dampers became a widely used method in the recent decades. Various devices were developed for seismic protection of structures and appropriate methods were proposed for effective design of control systems. An actual problem is how many dampers should be used as is their optimal location for yielding the desired structural response with minimum cost. A method for finding effective dampers’ placement and using amplifiers for dampers connection was recently proposed in the literature. The current study presents analyses of the amplification and placement of active controlled devices on the efficiency of a control system. A model of a twenty-story structure with active control systems including different dampers configurations is simulated. The response of the structure to natural earthquake excitations is also reported. The results of this study show a method of selecting proper configuration of active devices allowing cost effective control. DOI: 10.4018/978-1-4666-2029-2.ch010

Advances in Life Cycle Cost Analysis of Structures

Life cycle cost assessment (LCCA) of structural systems refers to an evaluation procedure in which all costs arising from owing, operating, maintaining and ultimately disposing are considered. LCCA is considered as a very significant assessment tool in the field of the seismic behaviour of structures. In this chapter two test cases are examined where the application of LCCA plays significant role for the extraction of important conclusions. In the first case LCCA is implemented for the assessment of the European seismic design codes and in particular EC2 and EC8 with respect to the recommended behaviour factor q. The assessment is performed on a multi-storey RC building which was optimally designed. In the second test case, 3D RC buildings are assessed with reference to life cycle cost calculated based on multicomponent incremental dynamic analysis and the significance of considering randomness on both record and incident angle is demonstrated.

Damage Index-Based Lower Bound Structural Design

The scope of the work is to detect the most appropriate damage index, able to provide a reliable description of the structural damage level. This damage index is used to formulate a performance-based design framework to be used as a design tool for achieving safer and more economic designs. This objective is achieved by comparing alternative structural systems that comply with the design demands in the most cost-efficient approach, i.e. those requiring less material volume for concrete and steel reinforcement. In this direction, design optimization problems for structural systems are defined for each damage index under consideration and the structural optimization problems at hand are solved by means of a popular metaheuristic search algorithm.

Structural Optimization: An Assessment Approach of Design Procedures Against Earthquake Hazard

The objective of this work is to assess seismic design procedures with reference to optimally design of 3D reinforced concrete structures. For this purpose four optimization problems are formulated corresponding to different values of the behaviour factor q. The optimization problems are formulated as sizing optimization problems where the size and steel reinforcement of the beams and the columns are considered as design variables, while the initial cost is the objective function to be minimized. Furthermore, life-cycle cost analysis is an assessment tool for the performance of systems; and has been used in many fields of science and engineering. In this chapter the influence of the analysis procedure, the number of seismic records imposed and the performance criterion used on the life-cycle cost analysis procedure is also investigated. In particular the nonlinear static and the multiple stripe incremental dynamic analysis are applied while the maximum inter-storey drift and the maximum floor acceleration are adopted as the performance criteria calculated in multiple hazard levels that are required for the life-cycle cost analysis. In the test example considered, the life-cycle cost was calculated taking into consideration the damage repair cost, the loss of contents cost due to structural damage that is quantified by the maximum inter-storey drift and the floor acceleration, the loss of rental cost, the income loss cost, the cost of injuries and the cost of human fatality.