Finite element model updating of a tied-arch bridge using Douglas-Reid method and Rosenbrock optimization algorithm

Abstract Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element (FE) model updating method is often applied. This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas-Reid method in combination with Rosenbrock optimization algorithm. Based on original drawings and topographie survey, a FE model of the investigated bridge is created. Eight global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Then, eight structural parameters are selected for FE model updating procedure through sensitivity analysis. Finally, the optimal structural parameters are identified using Rosenbrock optimization algorithm. Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies, they may not be the optimal variables which minimize the differences between numerical and experimental modal data. However, a satisfied agreement between them is still presented. Hence, FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures

Time-dependent analysis of precast segmental bridges

Prestressed segmentally constructed balanced cantilever bridges are often subjectedto larger deflections than those predicted by calculations, especially for long-termeffects. In this paper, the case of modular balanced cantilever bridges, which areprestressed segmental bridges obtained through a repetition of the same doublecantilever, is investigated. The considered bridges are two typical cases of modular balanced cantilever both subjected to large deformations during their lifetime. In this case, due to the unusual employed static scheme, creep deflections indefinitely evolve over time particularly at the end of the cantilevers and in correspondence of the central joint. These remarkable deflections cause discomfort for vehicular traffic and in certain cases can lead to the bridge collapse. Important extraordinary maintenance interventions were necessary to restore the viability of the bridges and to replace the viaduct design configuration. To this aim, the static schemes of the structures were varied, introducing new constraints, new tendons and carbon fiber reinforcements. In the present work, time analysis was performed to compare the time-dependent behavior of the bridge according to two different creep models, the CEB-FIP Model Code 2010 and the RILEM Model B3, with the real time dependent behavior of the bridge observed during its lifetime. The two different employed models exhibit different behaviors in terms of displacements and bending moments acting on the bridge. Interesting considerations are made on their reliability in simulating the long-term creep effects that evolve indefinitely over time. Moreover, retrofitting techniques have been proposed and modeled to predict their effectiveness in reducing time-dependent deflections

Development of corrosion hazard maps for reinforced concrete bridges

Infrastructures in coastal areas are often prone to several hazards, and thus the elaboration of effective risk management plans in such zones are possible if all relevant threats are considered and analyzed. In this context, the assessment of the corrosion hazard attributable to airborne chlorides is of utmost importance since the resulting deterioration phenomena can heavily jeopardize both reliability and resilience of the infrastructures. Therefore, this contribution aims at proposing the preliminary version of a possible framework for the elaboration of corrosion hazard maps at regional scale for coastal areas, with focus on reinforced concrete bridges. The proposed approach encompasses three main steps. First, the relevant stock of infrastructures vulnerable to chloride-induced corrosion is identified and quantified. This requires the collection of relevant features, such as construction type, position, and age. Environmental conditions are examined next, including data about sea waves and salinity, wind, temperature, humidity, rainfall, and chloride deposition rate. Finally, the corrosion hazard is estimated in probabilistic sense. The proposed methodology is presented together with the preliminary results obtained from a relevant case study

Shell-supported footbridges

Architects and engineers have been always attracted by concrete shell structures due to their high efficiency and plastic shapes. In this paper the possibility to use concrete shells to support footbridges is explored. Starting from Musmeci’s fundamental research and work in shell bridge design, the use of numerical form-finding methods is analysed. The form-finding of a shell-supported footbridge shaped following Musmeci’s work is first introduced. Coupling Musmeci’s and Nervi’s experiences, an easy construction method using a stay-in-place ferrocement formwork is proposed. Moreover, the advantage of inserting holes in the shell through topology optimization to remove less exploited concrete has been considered. Curved shell-supported footbridges have been also studied, and the possibility of supporting the deck with the shell top edge, that is along a single curve only, has been investigated. The form-finding of curved shell-supported footbridges has been performed using a Particle-Spring System and Thrust Network Analysis. Finally, the form-finding of curved shell-supported footbridges subjected to both vertical and horizontal forces (i.e. earthquake action) has been implemented

Solar Radiation Parameters for Assessing Temperature Distributions on Bridge Cross-Sections

Solar radiation is one of the most important factors influencing the temperature distribution on bridge girder cross-sections. The bridge temperature distribution can be estimated using estimation models that incorporate solar radiation data; however, such data could be cost- or time-prohibitive to obtain. A review of literature was carried out on estimation models for solar radiation parameters, including the global solar radiation, beam solar radiation and diffuse solar radiation. Solar radiation data from eight cities in Fujian Province in southeastern China were obtained on site. Solar radiation models applicable to Fujian, China were proposed and verified using the measured data. The linear Ångström–Page model (based on sunshine duration) can be used to estimate the daily global solar radiation. The Collares-Pereira and Rabl model and the Hottel model can be used to estimate the hourly global solar radiation and the beam solar radiation, respectively. Three bridges were chosen as case study, for which the temperature distribution on girder cross-sections were monitored on site. Finite element models (FEM) of cross-sections of bridge girders were implemented using the Midas program. The temperature–time curves obtained from FEM showed very close agreement with the measured values for summertime. Ignoring the solar radiation effect would result in lower and delayed temperature peaks. However, the influence of solar radiation on the temperature distribution in winter is negligible

Seismic behavior of a low-rise horizontal cylindrical tank

Abstract Cylindrical storage tanks are widely used for various types of liquids, including hazardous contents, thus requiring suitable and careful design for seismic actions. The study herein presented deals with the dynamic analysis of a ground-based horizontal cylindrical tank containing butane and with its safety verification. The analyses are based on a detailed finite element (FE) model; a simplified one-degree-of-freedom idealization is also set up and used for verification of the FE results. Particular attention is paid to sloshing and asynchronous seismic input effects. Sloshing effects are investigated according to the current literature state of the art. An efficient methodology based on an "impulsive-convective" decomposition of the container-fluid motion is adopted for the calculation of the seismic force. The effects of asynchronous ground motion are studied by suitable pseudo-static analyses. Comparison between seismic action effects, obtained with and without consideration of sloshing and asynchronous seismic input, shows a rather important influence of these conditions on the final results

OPTIMUM DESIGN OF A HYBRID ISOLATION DEVICE FOR SERVER RACKS USING CONSTRAINED DIFFERENTIAL EVOLUTION ALGORITHM

Nonstructural elements and contents often constitute a large fraction of the economic investment in ordinary buildings. In case of seismic events, damage to nonstructural elements not only contributes to the overall direct material costs but can also significantly impact the indirect costs. The latter are especially affected by earthquake-induced damage if production and business flows depend on proper functioning of such nonstructural components, since consequent downtime costs turn out to be very high. Within this framework, server racks' performance under seismic loading is of interest in the present work. The economic relevance of these nonstructural components requires the implementation of proper design solutions so that their performance under earthquakes can fulfill specific requirements. In this perspective, including isolation devices between server racks and building floors is deemed effective for enhancing the stability of the protected equipment, preserving the computer components' integrity and, minimizing downtime losses. Hence, the present work is meant to optimize a hybrid isolation system for server racks. Specifically, the hybrid isolation device designed for such application combines at least two elastomeric isolators and three sliders, and it is intended for the seismic protection of server racks characterized by different configurations. The objective function is formulated to minimize the accelerations transmitted to server racks and manufacturing cost

Analysis of the Joint Effects of Thermal Stresses and Corrosion on Integral Abutment Bridges

The corrosion of reinforced concrete structures in coastal areas turns out to be very severe and can extend significantly in windy zones. Additionally, frequent temperature changes and, above all, exposure to extreme temperatures might induce wider cracks and micro‐cracks in concrete structures which, in turn, might accelerate the diffusion of corrosive agents. Motivated by this evidence, the present study aims at verifying the sensitivity of integral abutment bridges to the combined effect of thermal stresses and corrosion. Preliminary results show that a high thermal stress may amplify the negative effects of corrosion but also that the bridge used for the case study is more sensitive to thermal stresses than to corrosion

Effects of Near-Fault Ground Motions on Civil Infrastructure

Near-fault earthquakes (NFEs), characterized by high peak ground velocity (PGV) and long period pulses, show different properties from far-field ones. The input motions from NFEs are usually composed of a small number of sinusoidal large waves in addition to significant vertical components. These specific characteristics of NFEs strongly influence the seismic response of civil infrastructure and may reduce the effectiveness of the adopted protection devices

Nonlinear static analysis by finite elements of a Fujian Hakka Tulou

Hakka Tulous are massive circular earth constructions of the Fujian Province, China, included in the UNESCO World Heritage list. They are subjected to earthquakes of medium magnitude, but their response to the seismic action is not yet investigated in depth. The seismic response of Fujian Tulous was herein investigated through pushover analysis modelling the Tulou structure by finite elements. Although the Tulou is a big construction with a circular earth wall of about fifty meters in diameter, a micromechanical approach was used to model the earth nonlinear behaviour. Even if no binder is added to the earthen material, the Concrete Damaged Plasticity model can be adopted and has shown to be effective in modelling its nonlinear behaviour, as well as the nonlinear response of the Tulou earth wall. Performing pushover analysis of a big earth structure using a micromechanical approach seems to give reliable results, that must be proved by future research