Optimal control of the heave motion of marine cable subsea-unit systems

One of the key problems associated with subsea operations involving tethered subsea units is the motions of support vessels on the ocean surface which can be transmitted to the subsea unit through the cable and increase the tension. In this paper, a theoretical approach for heave compensation is developed. After proper modelling of each element of the system, which includes the cable/subsea-unit, the onboard winch, control theory is applied to design an optimal control law. Numerical simulations are carried out, and it is found that the proposed active control scheme appears to be a promising solution to the problem of heave compensation

FEM-based numerical strategy for analysis of composite modular floor prototype for emergency housing applications

The paper presents the numerical modelling of a temporary residential floor prototype composed of three jointed composite floor sandwich panels made of glass fiber reinforced polymer (GFRP) skins, a polyurethane foam core (PU) and pultruded U-shaped GFRP profiles working as ribs. Panels are supported on a GFRP pultruded frame structure. A 3D nonlinear finite element model is developed considering geometrical and material nonlinearities and adherent surfaces interaction. The model is coherently validated with experimental results, showing its capability to capture the mechanical performance of a single panel (which includes the possibility of local instability on the GFRP skin), two and three panels working together, and the whole prototype. A series of parametric studies are then conducted using the numerical model developed. Those studies aim to (i) assess the influence that ribs on the panel stiffness and on the shear stresses distribution through the sandwich panel’s components, (ii) the flexibility of the designed connections between jointed panels and frame structure, and (iii) the influence of geometry in the modular housing.This work is part of the research project ClickHouse – Development of a prefabricated emergency house prototype made of composites materials, involving the company ALTO – Perfis Pultrudidos, Lda., CERis/Instituto Superior Técnico and ISISE/University of Minho, supported by FEDER funds through the Operational Program for Competitiveness Factors – COMPETE and the Portuguese National Agency of Innovation (ADI) – project no. 38967. Special thanks are given to company ALTO – Perfis Pultrudidos, Lda., who manufactured all the elements (GFRP profiles and sandwich panels) involved in the research. The numerical model was performed in collaboration with the Department of Construction Engineering of the Universitat Politècnica de València

Bridge expansion joint in road transition curve: effects assessment on heavy vehicles

Properly-designed road surfaces provide a durable surface on which traffic can pass smoothly and safely. In fact, the main causes that determine the structural decay of the pavement and its parts are the traffic loads. These repeated actions can create undesirable unevennesses on the road surface, which induce vertical accelerations on vehicles, up to hindering contact between pavement and tire, with dangerous consequences on traffic safety. The dynamic actions transmitted by the vehicles depend on these irregularities: often, a bridge expansion joint (BEJ), introducing a necessary discontinuity between different materials, determines from the beginning a geometric irregularity in the running surface. Besides, some structural conditions could emphasize the problem (e.g., local cracking due to the settlement of the subgrade near the abutment or the discontinuity of stiffness due to the presence of different materials). When the BEJ is located in a transition curve, an inevitable vertical irregularity between road and joint can reach values of some centimeters, with serious consequences for the road safety. This paper deals with the analysis of a case study of a BEJ. Several test surveys were performed in order to fully characterize the effects on both vehicles and pavement. The three-dimensional representation of the pavement surface and the acceleration measurements on a heavy test vehicle were performed to analyze the joint behavior under traffic. Finally, a finite element model was implemented to evaluate the stress contribution on vehicle components induced by the vertical irregularities

Vibration characteristics of a suspension footbridge

Author's manuscript version. The final published version is available via doi:10.1006/jsvi.1996.0789. Copyright © 1997 Academic Press. All rights reserved.A suspension footbridge located in a tourist attraction in Singapore has a suspended span of 35 m and was designed for static pedestrian and wind loads. In common with other bridges of this type, it is a light, efficient structure and has a lively dynamic performance. Distributed parameter and finite element models were used to understand the vertical plane behaviour of the bridge and a prototype dynamic test using impact excitation was conducted to check the models and investigate the dynamic response. The first two vertical vibration modes were found to occur at the same frequency, 2 Hz, as the average pedestrian footfall. Response to pedestrians was simulated using linear and non-linear models of a moving excitation source. © 1997 Academic Press Limited

Performance and study of variousbridge girders

According to various research papersthe design and analysis of various girders for steel and concrete by using v software STAAD Pro. And finite element method. In this project  theto check the analysis of bridge by using software. Hence, in this project determine the static analysis of T, I and Box girder. In these three girders which can be determine which is effective and economical to bridges.Both models are subjected to I.R.C. Loadings to produce maximum bending moment

A flexible method to evolve collisional systems and their tidal debris in external potentials

We introduce a numerical method to integrate tidal effects on collisional systems, using any definition of the external potential as a function of space and time. Rather than using a linearisation of the tidal field, this new method follows a differential technique to numerically evaluate the tidal acceleration and its time derivative. Theses are then used to integrate the motions of the components of the collisional systems, like stars in star clusters, using a predictor-corrector scheme. The versatility of this approach allows the study of star clusters, including their tidal tails, in complex, multi-components, time-evolving external potentials. The method is implemented in the code nbody6 (Aarseth 2003).Comment: MNRAS accepted. Code available here: http://personal.ph.surrey.ac.uk/~fr0005/nbody6tt.ph

Static, dynamic and creep behaviour of a full-scale GFRP-SFRSCC hybrid footbridge

A three-year research project (Pontalumis) was carried out for the development of an innovative simply supported hybrid footbridge, with 11 m of length and 2 m of width. The footbridge is composed of two pultruded I-shaped glass fibre reinforced polymer (GFRP) girders (400×200(×15) mm2) bonded and bolted to a 37.5 mm thick deck in steel fibre reinforced self-compacting concrete (SFRSCC). The present paper describes the material/structural concept of this footbridge, its design and construction process, and summarizes the response of the prototype when submitted to static short and long-term load tests, and dynamic load tests. The prototype was simple and fast to execute, presenting a reduced dead-weight of only about 3 tonf. The static and dynamic behaviour of the prototype as well as its long-term deflection fulfil standards’ requirements for footbridge structures and are in good agreement with conventional analytical and numerical design tools.AD

Mechanical Behavior of Concrete Materials and Structures: Experimental Evidence and Analytical Models

This reprint contains 15 papers published in the Special Issue entitled "Mechanical Behavior of Concrete Materials and Structures: Experimental Evidence and Analytical Models”. Dealing with the broad spectrum of the mechanical behavior of concrete materials and structures, the reprint includes experimental findings and numerical analyses using both conventional and advanced methodologies. This book presents contributions in the field of not only ordinary and prestressed concretes, but also special concretes, including high-strength, recycled, and fiber-reinforced concretes, for both structural and non-structural applications, and for the development of related numerical/analytical predictive models