Climent Molins | Universitat Politecnica de Catalunya (original) (raw)

Papers by Climent Molins

Revista IBRACON de Estruturas e Materiais, Feb 1, 2012

This paper is part of an extensive work about the technological development, experimental analysi... more This paper is part of an extensive work about the technological development, experimental analysis and numerical modeling of steel fibre reinforced concrete pipes. The first part ("Steel fibre reinforced concrete pipes. Part 1: technological analysis of the mechanical behavior") dealt with the technological development of the experimental campaign, the test procedure and the discussion of the structural behavior obtained for each of the dosages of fibre used. This second part deals with the aspects of numerical modeling. In this respect, a numerical model called MAP, which simulates the behavior of fibre reinforced concrete pipes with medium-low range diameters, is introduced. The bases of the numerical model are also mentioned. Subsequently, the experimental results are contrasted with those produced by the numerical model, obtaining excellent correlations. It was possible to conclude that the numerical model is a useful tool for the design of this type of pipes, which represents an important step forward to establish the structural fibres as reinforcement for concrete pipes. Finally, the design for the optimal amount of fibres for a pipe with a diameter of 400 mm is presented as an illustrating example with strategic interest.

Advanced Materials Research, Oct 1, 2010

A method for non-linear dynamic analysis of wall masonry structures is presented. The method take... more A method for non-linear dynamic analysis of wall masonry structures is presented. The method takes advantage of a Generalized Matrix Formulation (GMF) for the serviceability and ultimate analysis of structures composed of arches and/or masonry walls, in which open and solid walls are described as equivalent frame systems. This formulation has been complemented with a cyclic constitutive model and an algorithm for the integration of the equation of motion, resulting in a numerically efficient method for non-linear analysis in time domain of complex masonry systems.

A recent survey showed that 40% of existing rail network bridges in Europe are masonry arches. M... more A recent survey showed that 40% of existing rail network bridges in Europe are masonry arches. More than 60% of those bridges are over 100 years old and still carry ever increasing levels of loading and increasing volumes of traffic. Due to the constantly increasing weight of rail traffic there is increasing demand for better understanding of their life expectancy and fatigue limits. It is imperative that the bridge stock is not adversely affected by these changes in the loading regime and that appropriate assessment, modelling, repair and strengthening techniques are available. This background document is an attempt to address and solve the above questions.To this end, the document is divided in the following parts: D4.7.1 Structural assessment of masonry arch bridges D4.7.2 Numerical analyses of load distribution and deflections in railway bridge transitionzones due to passing trains D4.7.3 Methods of analysis of damaged masonry arch bridges D4.7.4 Potentiality of probabilistic methods in the assessment of masonry archesEC Sixth Framework ProgramSustainable Bridges – Assessment for Future Traffic Demands and Longer LivesTIP3-CT-2003-001653</p

Construction and Building Materials, 2021

Experts responsible for the safety evaluation of unique masonry heritage structures usually need ... more Experts responsible for the safety evaluation of unique masonry heritage structures usually need to weigh information from various diagnosis activities before deciding the best course of action for preservation. Typical sources of valuable information are historical and in-situ surveys and inspections, minor and non-destructive testing, structural health monitoring, and structural analysis, among others. Due to the complexity of the problem and singular aspects of monuments, these decisions are challenging and often made solely on the basis of expert judgement. A systematic risk assessment procedure is proposed involving the computation of two indices to facilitate the decision-making process: an index related to the estimated risk of damage, and another to the uncertainty behind this estimation. Results from applying the procedure to several case studies are provided to demonstrate its usefulness.

Structural Control and Health Monitoring, 2020

Funding information Ajuntament de Sant Cugat through a project aimed at monitoring the Monastery ... more Funding information Ajuntament de Sant Cugat through a project aimed at monitoring the Monastery of Sant Cugat, ref. num. C-10764. Ministry of Education, Culture and Sports of the Spanish Government through a project aimed at studying the structural condition of Mallorca Cathedral, ref. num. 2/131400106ca-5/030300592 EF. AGAUR agency of the Generalitat de Catalunya and European Social Fund, through a predoctoral grant awarded to the corresponding author. Ministry of Science, Innovation and Universities of the Spanish Government and European Regional Development Fund through the SEVERUS project, ref. num. RTI2018-099589-B-100. Summary Masonry heritage structures are often affected by slow irreversible deterioration mechanisms that can jeopardise structural stability in the foreseeable future. Static structural health monitoring (SHM), aimed at the continuous measurement of key slow-varying parameters, has the potential to identify such mechanisms at a very early stage. This can greatly facilitate the implementation of adequate preventive and remedial measures which can be critical to ensure that such structures are preserved for generations to come. However, since monitored parameters usually experience reversible seasonal variations of the same order of magnitude as changes caused by active mechanisms, identification of the latter is often a difficult task. This paper presents a fully integrated automated data analysis procedure for complete static SHM systems utilising dynamic linear regression models to filter out the effects caused by environmental variations. The method does not only produce estimated evolution rates but also classifies monitored responses in pre-defined evolution states. The procedure has successfully been used to identify vulnerable areas in two important medieval heritage structures in Spain, namely the cathedral of Mallorca and the church of the monastery of Sant Cugat.

Construction and Building Materials, 2020

In recent years in Chile, the use of fiber reinforced shotcrete (FRS) has been widely extended in... more In recent years in Chile, the use of fiber reinforced shotcrete (FRS) has been widely extended in underground works, particularly in tunnels for roads, mines and hydroelectric projects. In these projects, the design of the supports is mainly based on the modified Q-Barton method, which relates the rock mass quality to the minimum energy absorption capacity of the FRS, which is determined by the square panel test, with panels filled during spraying. However, to obtain these specimens, complex procedures must be followed both on-site and, in the laboratory, and the results obtained present a large scatter. To improve the execution control of the FRS lining of tunnels, an empirical correlation has been developed between the square panel test of a synthetic-fiber reinforced concrete and the double-punch Barcelona test of cylinders, at laboratory level.

Structural Analysis of Historical Constructions, 2016

Masonry structures, usually being composed of a repeating geometric pattern, lend themselves well... more Masonry structures, usually being composed of a repeating geometric pattern, lend themselves well to analysis using periodic unit cells. Based on stress and strain equilibriums and rational assumptions concerning the interaction of the components of the cell, one may propose micro-mechanical models using simple analytical expressions which simulate well the behavior of masonry. Models describing the nonlinear behavior of masonry constituent materials may be implemented in such models and used to simulate the failure modes anticipated to arise in the composite. In this way, the nonlinear behavior of masonry composites may be derived, as defined by the interaction of its two main material phas-es: units and mortar. Taking advantage of the low computational cost of models based on analytical expres-sions, which is only a fraction of those based on finite element simulations, wide and in-depth parametric analyses can be performed with ease. In this paper, a model for the nonlinear behavior of masonry is presented and used in a parametric study, investigating the influence of various material properties on its compressive strength. The results indicate a strong dependence of the compressive strength of masonry on material parameters that are difficult to measure accurately or are often ignored, particularly in existing and historic masonry structures.

Tunnelling and Underground Space Technology, 2016

This paper presents research results regarding the distribution of steel fibers in concrete used ... more This paper presents research results regarding the distribution of steel fibers in concrete used to build precast tunnel segments for Line 9 of the Barcelona Metro. The fiber distribution was studied using the actual fiber contents obtained by means of crushed cores drilled from different points of three full-scale tunnel lining segments. A statistical analysis determined that the fiber content in the ends of segments tend to be greater than in the central zone. In addition, cores with a diameter of 150 mm were found to have a lower scatter in the fiber content than smaller diameter specimens. Finally, based on probabilistic approaches, a minimum of 11 cores is proposed to control the fiber content in FRC segments.

12th International Conference on Structural Analysis of Historical Constructions, 2021

The church of the monastery of Sant Cugat close to Barcelona is a medieval construction character... more The church of the monastery of Sant Cugat close to Barcelona is a medieval construction characterized by a complex structural behaviour stemming from the interaction among various structural elements built over different periods. Despite having survived for several centuries, such structures are often affected by slow irreversible deterioration mechanisms that can jeopardise their stability in the future. In order to identify such mechanisms at an early stage, and to better understand the cause of visible pathologies, a static structural health monitoring (SHM) system was installed in the church since 2017. Although this monitoring strategy, aimed at the continuous measurement of key slow-varying parameters, has been used successfully in the past to facilitate the diagnosis of this structural typology, the interpretation of data collected by such systems remains a challenging task. One of the main reasons for this is the fact that many monitored damage and deformation features are s...

The purpose of this document is to define the basis for the analysis and design of the FOWT confi... more The purpose of this document is to define the basis for the analysis and design of the FOWT configurations to be developed during this project. The basis shall define the framework for covering the design of both floater types (spar and semis-submersible) and all their subsystems

The EU Horizon 2020 project COREWIND has developed two floating platforms for the new Internation... more The EU Horizon 2020 project COREWIND has developed two floating platforms for the new International Energy Agency (IEA) Wind 15 MW reference model. One design-"WindCrete"-is a spar floater, and the other-"Activefloat"-is a semi-submersible floater. In this work the design of the floaters is introduced with their aero-hydro-servo-elastic numerical models, and the responses of both floaters in both static and dynamic simulations are verified against the operational and survival design limits. The static displacements and natural frequencies are simulated and discussed. Additionally, the effects of the mean wave drift forces, and difference second order wave forces on the systems' responses are presented. The increase in the turbine's power capacity to 15MW in IEA Wind model, leads to an increase in inertial forces and aerodynamic thrust force when compared to similar floating platforms coupled to the Danish Technical University (DTU) 10MW reference model. The goal of this work is to investigate the floaters responses at different load cases. The results in this paper suggest that at mild wave loads the motion responses of the 15MW Floating Offshore Wind Turbines (FOWT) are dominated by low frequency forces. Therefore, motions are dominated by the wind forces, and second order wave forces rather than the first order wave forces. After verifying and understanding the models' responses, the two 15MW FOWT reference numerical models are publicly available to be used in the research and development of floating wind energy. 1 Introduction Floating Offshore Wind Turbines (FOWTs) will play a key role in the transition towards renewable and sustainable energy systems. In Europe, 80% of the offshore wind energy resources lies in deep water regions (Hundleby and Freeman, 2017). Going into deeper water sites opens the door for bigger turbines with higher energy capacities, and so there is a need of new concept models that can be used for academic research and innovation in the field of FOWTs. Specifically, there is a need for aero-servo-hydro-elastic models of the coupled floater and wind turbine. COREWIND (COst REduction and increase performance of floating WIND technology) is a Horizon 2020 project aiming to decrease the Levelised Cost Of Energy (LCOE) of FOWTs by 15%, through the optimization of the mooring lines and the power cable. Two FOWTs conceptual designs will be used to validate the innovations presented in COREWIND for mooring 1

Preliminary studies of a concept consisting of a monolithic concrete SPAR platform were presented... more Preliminary studies of a concept consisting of a monolithic concrete SPAR platform were presented in 2014. The studies were performed in the framework of the AFOSP KIC-InnoEnergy project (Alternative Floating Platform Designs for Offshore Wind Towers using Low Cost Materials) showing significant costs reduction. The experimental phase of the project was developed during 2014. The experiments comprised a set of hydrodynamic tests performed in the CIEM wave flume facility at the Universitat Politecnica de Catalunya (UPC), with a 1:100 scale model assuming Froude similitude. The complete experimental campaign included free decay tests, a set of 22 regular wave trains of different periods to determine the RAO’s and another set of 21 regular and irregular wave trains in conjunction with a mechanical wind device, simulating the mean thrust force exerted by the wind turbine. To adjust the weight of the whole system, a set of adjustable weights inside de scale model were designed assuring s...

Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2020, 2020

Static structural health monitoring (SHM), aimed at the continuous measurement of slow-varying pa... more Static structural health monitoring (SHM), aimed at the continuous measurement of slow-varying parameters over a long period, has been proved to be a powerful tool to support the diagnosis of masonry heritage structures. In such applications, the initial interpretation task involves the identification of evolutionary conditions from recorded data. However, this can be difficult since monitored features are influenced by environmental changes. In addition, many masonry heritage structures are characterised by a complex structural behaviour stemming from the interaction among different elements, making the task of interpreting SHM data for diagnosis very challenging. One such structure is the church of the monastery of Sant Cugat close to Barcelona, built mostly between the 12th and 15th centuries. Certain key structural parameters of the church have been monitored since 2017 with the aim of understanding the cause of visible pathologies and identifying any active deterioration mechanisms that could pose a threat to the structural integrity of the church in the future. This paper presents the application of an automated data analysis methodology to this problem. The method uses dynamic regression models to filter out components related to reversible seasonal fluctuations from measurements and automatically classifies monitored parameters into evolutionary states based on predicted evolution rates and dispersion metrics from the filtering procedure. A tool is presented which allows analysis results to be updated as new data is received. Finally, results from the proposed methodology are used for the diagnosis of the structure and their usefulness in a broader decision-making framework is discussed.

Journal of Offshore Mechanics and Arctic Engineering, 2020

The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (... more The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (OC5) project is validation of aero-hydro-servo-elastic simulation tools for offshore wind turbines (OWTs) through comparison of simulated results to the response data of physical systems. Phase III of the OC5 project validates OWT models against the measurements recorded on a Senvion 5M wind turbine supported by the OWEC Quattropod from the alpha ventus offshore wind farm. The following operating conditions of the wind turbine were chosen for the validation: (1) idling below the cut-in wind speed, (2) rotor-nacelle assembly (RNA) rotation maneuver below the cut-in wind speed, (3) power production below and above the rated wind speed, and (4) shutdown. A number of validation load cases were defined based on these operating conditions. The following measurements were used for validation: (1) strains and accelerations recorded on the support structure and (2) pitch, yaw, and azimuth angles,...

Construction and Building Materials, 2019

When subjected to dynamic loading, materials can exhibit a mechanical behaviour quite different f... more When subjected to dynamic loading, materials can exhibit a mechanical behaviour quite different from its static counterpart. The evaluation of dynamic properties is thus very useful in the assessment of existing masonry structures. This paper presents results of an experimental campaign to determine both the dynamic Young's modulus and the shear modulus of brick masonry constituents through two non-destructive testing methods. Following a discussion on the reliability of the methods, a robust procedure is described and tested on a variety of samples. The results show that the techniques can be successfully applied to provide reliable estimates of the dynamic elastic properties of brick masonry constituents.

Construction and Building Materials, 2018

The use of fiber reinforced concretes (FRC) as a substitute for reinforcement meshes, particularl... more The use of fiber reinforced concretes (FRC) as a substitute for reinforcement meshes, particularly in the construction of tunnels, frequently faces quality control problems because the specifications and acceptability criteria are based on parameters obtained from the flexion test of standard EN-14651, which is very difficult to perform at works. Considering the advantages presented by the Barcelona test, in this paper, equivalences are established between both tests, which allow estimating the FRC toughness and residual strengths. The predictions of these properties obtained using the Barcelona tests results present a maximum difference of less than 20%.