Life-Cycle-Kosten-basiertes Design von Wind erregten hohen Gebäuden

In this thesis a practical design tool based on Life-Cycle Cost Analysis (LCCA) is proposed for wind-sensitive structures. A cost-based approach can broaden the perspective of managers and stakeholders in order to choose the best design solution on the basis of the monetary losses expected during the structure lifetime. In this context, an automated and computationally efficient procedure named Life-Cycle Cost Wind Design (LCCWD) is developed for the design of tall structures. All the key aspects related to wind engineering are considered: the characterization of the wind load and of the aerodynamic structural response uncertainty, the probabilistic analysis of non-structural damages, the choice of an effective control system considering technical and economic aspects. The efficiency of the LCCWD approach is demonstrated by making use of a case study of a 180-m high tall building, for which wind tunnel load data are available. The control system consists in a bidirectional TMD, located at the top floor of the building. The structural analysis is carried out in the frequency domain and considers power-law function mode shapes and torsional response. Costs related to both drift-sensitive and acceleration-sensitive non-structural components are evaluated and the beneficial contribution of the TMD in reducing both types of damage is assessed in a Life-Cycle Cost perspective. The main results of the numerical application consist in: 1) to establish the best orientation of the building for the specific geographic area; 2) to determine most appropriate types of nonstructural elements by comparing different cost-based solutions; 3) to provide indications about the possible use of the interior spaces within the height of the building in relation to the distribution of nonstructural components; 4) to estimate the time, called Break-Even Time (BET), after which the initial costs associated with the installation of the control system are recovered, with a consequent significant lifetime costs reduction. The LCCWD is effective and easily adaptable to real applications in order to choose the best cost-based design solution on the basis of different alternatives that will simultaneously meet the need of customers and designers. With the LCCWD it is possible to accept or reject design alternatives and select 'optimal' and technically valid systems or decide for a particular structural control device that meets specific cost-based technical performance.In dieser Arbeit wird ein praktisches Design-Tool basierend auf Lebenszykluskostenanalyse (LCCA) für windempfindliche Strukturen vorgeschlagen.Ein kostenbasierter Ansatz kann die Perspektive von Managern und Stakeholdern erweitern, um die beste Designlösung auf der Grundlage der monetären Verluste auszuwählen, die während der Strukturlebensdauer erwartet werden. In diesem Zusammenhang wird ein automatisiertes und rechnerisch effizientes Verfahren namens Life-Cycle-Cost-Wind-Design (LCCWD) für das Design von Hochbauten entwickelt.Alle wichtigen Aspekte der Windtechnik werden berücksichtigt: die Charakterisierung der Windlast und der strukturellen Antwortunsicherheit, die probabilistische Analyse von nichttragenden Schäden, die Wahl eines effektiven Kontrollsystems unter Berücksichtigung technischer und wirtschaftlicher Aspekte. Die Effizienz des LCCWD-Ansatzes zeigt eine Fallstudie eines 180 m hohen Gebäudes, für das Windlastdaten zur Verfügung stehen. Das Kontrollsystem besteht aus einem bidirektionalen TMD, das sich im obersten Stockwerk des Gebäudes befindet. Die Strukturanalyse wird im Frequenzbereich durchgeführt und berücksichtigt Power-law-Funktionsformen und Torsionsverhalten. Kosten in Bezug auf driftsensitive und beschleunigungssensitive nicht-strukturelle Komponenten werden bewertet und der nutzbringende Beitrag der TMD zur Reduzierung beider Arten von Schäden wird in einer Lebenszykluskostenperspektive bewertet. Die Hauptergebnisse bestehen darin: 1) die beste Orientierung des Gebäudes für das spezifische geografische Gebiet zu ermitteln;2) Ermittlung der am besten geeigneten Arten von nichtstrukturellen Elementen durch Vergleich verschiedener kostenbasierter Lösungen; 3) Hinweise auf die mögliche Nutzung der Innenräume in Bezug auf die Verteilung von nichttragenden Bauteilen geben; 4) um die Zeit zu schätzen, Break-Even-Time (BET) genannt, nach der die anfänglichen Kosten im Zusammenhang mit der Installation des Steuersystems zurückgewonnen werden. Der LCCWD ist effektiv und leicht an reale Fälle anpassbar, um die beste kostenbasierte Designlösung auf der Basis verschiedener Alternativen auszuwählen, die gleichzeitig die Bedürfnisse von Kunden und Designern erfüllen. Mit dem LCCWD ist es möglich, Designalternativen zu akzeptieren oder abzulehnen und "optimale" und technisch gültige Systeme auszuwählen oder sich für ein bestimmtes Struktursteuergerät zu entscheiden, das eine spezifische kostenbasierte technische Leistung erfüllt

Life-cycle cost analysis of bridges subjected to fatigue damage

AbstractLife-cycle cost analysis (LCCA) is a decision-making tool particularly useful for the design of bridges as it predicts lifetime expenses and supports the inspections management and the maintenance activities. LCCA allows to consider uncertainties on loads, resistances, degradation and on the numerical modelling and structural response analysis. It also permits to consider different limit states and different types of damage in a unified framework. Among the types of damages that can occur to steel and steel-concrete composite bridges, fatigue is one of the most dangerous ones, as it may lead to sudden and fragile rupture, even at operational traffic levels. In this context, the present paper proposes a framework for LCCA based on the use of the Pacific Earthquake Engineering Research (PEER) equation which is for the first time utilized for fragility and cost analysis of bridges subjected to fatigue, highlighting the possibility of treating the problem of fatigue damage estimation with an approach similar to the one currently adopted for damage induced by other hazards, like earthquake and wind. To this aim, a damage index computed through the Palmgren-Miner's rule is adopted as engineering demand parameter. The framework is applied to a composite steel-reinforced concrete multi-span roadway bridge by evaluating the fatigue limit state from different traffic load models, i.e. a Technical Code-based model and a model based on results of Weigh in Motion monitoring system. The evolution over time of the probability of failure and the life-cycle costs due to fatigue damage induced by heavy traffic loads are investigated for different probability distributions of the engineering demand parameter and for different fragility models. The comparison between the fatigue failure probabilities and the life-cycle costs obtained with the two traffic models, encourages the adoption of traffic monitoring systems for a correct damage estimation

active control of art objects subjected to seismic excitation

Abstract The problem of the protection of statues and works of art is important in earthquake-prone regions. Among mitigation techniques, the base isolation demonstrates to be one of the most effective, as it creates a disconnection between the artwork and the floor that avoids the seismic acceleration transmission. Although passive base isolation systems, if well designed for a specific location and a specific piece of art, are efficient in protecting the artifact, they are not immediately adaptable for different artworks, different locations within the building and different seismic hazard conditions. For these reasons, in the present paper it is exploited the possibility of using a base active control strategy in which a force provided by an actuator counterbalances the seismic acceleration. The base active and passive control solutions are compared considering different seismic intensities and different characteristics of the artwork. Results demonstrate the robustness and adaptability of active control for the seismic protection of works of art

An Automated Procedure for Assessing Local Reliability Index and Life-Cycle Cost of Alternative Girder Bridge Design Solutions

Stakeholders of civil infrastructures have to usually choose among several design alternatives in order to select a final design representing the best trade-off between safety and economy, in a life-cycle perspective. In this framework, the paper proposes an automated procedure for the estimation of life-cycle repair costs of different bridge design solutions. The procedure provides the levels of safety locally guaranteed by the selected design solution and the related total life-cycle cost. The method is based on the finite element modeling of the bridge and uses design traffic models as suggested by international technical standards. Both the global behavior and the transversal cross section of the bridge are analyzed in order to provide local reliability indexes. Several parameters involved in the design, such as geometry and loads and materials' characteristics, are considered as uncertain. Degradation models are adopted for steel carpentry and rebars. The application of the procedure to a road bridge case study shows its potential in providing local safety levels for different limit states over the entire lifetime of the bridge and the life-cycle cost of the infrastructure, highlighting the importance of the local character of the life-cycle cost analysis

CALIBRATION OF NUMERICAL MODELS TO SUPPORT SHM: THE CONSOLI PALACE OF GUBBIO, ITALY

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TOWARDS THE DEVELOPMENT OF A COMPREHENSIVE FRAMEWORK FOR LIFE CYCLE COST ANALYSIS OF BRIDGES SUBJECTED TO MULTIPLE HAZARDS

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FRAGILITY ASSESSMENT OF WIND-EXCITED VIDEO SCREEN ROOMS IN HIGH-RISE BUILDINGS

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