Pere Roca

Numerical treatment of prestressing tendons in the nonlinear analysis of prestressed concrete structures

Abstract A formulation for the nonlinear material and geometric, instantaneous and long-term analysis of prestressed concrete structures is described, where the treatment of prestressing is achieved as a further extension of existing numerical models for reinforced concrete structures. Both the geometric and mechanical aspects of prestressing are treated in a consistent way with respect to the displacement formulation of the finite element method which is usually adopted for such analyses. A brief review of some common treatments for many of the existing numerical models for reinforced concrete beams, slabs and shells is made as well as the description of both the theoretical and computational features that are proposed for their extension to include prestressing. Special focus is given to such aspects as the geometric description of the layout of the tendons, force losses, prestress equivalent forces, prestress strain increments under external loads, the contribution of the prestressing to the global stiffness, and the stress relaxation of steel.

Nonlinear geometric and material analysis of prestressed concrete general shell structures

Abstract In a previous paper [Comput. Struct. 46, 905–916 (1993)], a general formulation was presented for the nonlinear material and geometric, instantaneous and long-term nonlinear analysis of prestressed concrete structures. Such a formulation is based on a discrete treatment of the prestressing tendons where both the prestress geometric and mechanic effects are introduced consistently with the displacement formulation of the finite element method. In the present paper the application of this formulation to the nonlinear analysis of prestressed concrete shells of general geometry is discussed. Special concern is devoted to the definition of the space curved shell and tendon geometries, which potentially require large amounts of data preparation. In order to minimize this requirement, a set of automatic procedures have been adopted which, using an analytical description as data, generate a complete work interpolation for both the shell middle surface and the tendon axial curves. Finally, three numerical examples are presented through which, by comparison with existing experimental results, the efficiency and the reliability of the method are shown.

FLEXIBILITY-BASED LINEAR DYNAMIC ANALYSIS OF COMPLEX STRUCTURES WITH CURVED-3D MEMBERS

A flexibility-based formulation of a new mass matrix for the dynamic analysis of spatial frames consisting of curved elements with variable cross-sections is presented. The main characteristic of such formulations is the exact equilibrium of forces at any interior point, with no additional hypotheses about the distribution of displacements, strains or stresses. Accordingly, the derived element mass matrix takes into account the exact stiffness and mass distribution throughout each element. In validation tests, results obtained with this method are compared with those obtained by other numerical or analytical formulations, showing the accuracy of the proposed method. The comparison of experimental results for a multispan arch bridge subjected to a dynamic load with those achieved by means of the proposed method are finally included to illustrate its efficiency in the treatment of complex structures.

Comparison of seismic analysis methods applied to a historical church struck by 2009 L’Aquila earthquake

This paper presents the seismic assessment of a historical church by means of different analysis methods. The church of San Marco, seriously damaged by 2009 L’Aquila earthquake, Italy, is chosen as case-study. The analysis tools adopted and compared are linear and non-linear kinematic analysis, FEM pushover analysis and FEM nonlinear dynamic analysis. The different methods are evaluated regarding their ability to predict the damage and collapse mechanisms actually caused by the earthquake. The accelerograms of the main shock of the 6th April 2009 L’Aquila earthquake are considered for nonlinear dynamic analysis. The influence of relevant construction features, as original disconnection between parts or RC additions, is analysed into detail. Limit analysis is carried out to understand some of the critical collapse mechanisms which are not clearly revealed by FE analysis. The comparison of the analysis methods indicates advantages and limitations of each approach.

Viscoelasticity and Damage Model for Creep Behavior of Historical Masonry Structures

This paper presents a continuum model for the simulation of the viscous effects and the long-term damage ac- cumulation in masonry structures. The rheological model is based on a generalized Maxwell chain representation with a constitutive law utilizing a limited number of internal variables. Thanks to its computational efficiency, this approach is suitable for the analysis of large and complex structures. In the paper, the viscous and damage models are presented and their coupling is discussed. The FE simulation of the construction process of the representative bay of Mallorca Cathedral is presented, together with the analysis of the long-term effects. The parameters of the model are tentatively calibrated on the basis of the time-dependent viscous deformations detected during the cathedral monitoring. detailed. The application of the model to the numerical study of a representative bay of Mallorca Cathedral is discussed. The procedure to identify the parameters that define the vis- cous and damage model, starting from the experimental monitoring activity, is also described. The parameters of the model have been calibrated using a 5-year monitoring pe- riod. In spite of it, the study has mostly a tentative character given the important uncertainties and difficulties involved. One of the main difficulties is found in the estimation of the initial deformation of the structure after construction. In the present study, an attempt towards an estimation of this de- formation is carried out through a sequential analysis involv- ing two construction phases suggested by the historical re- search carried out on the building. The structure shows significant deformation which, ac- cording to previous studies (12), can be related with the combined effects of construction process undergoing delicate intermediate stages, long-term deformation and geometric non-linearity. The research presented aim to explore the vi- ability of a numerical simulation of deformation and damage taking into account these combined effects.

Capacity of Shear Walls by Simple Equilibrium Models

A novel method is presented for the determination of the ultimate capacity of masonry solid shear walls based on simple models resulting from equilibrium considerations. Some basic principles determining the acceptability of the models are firstly stated. Based on these rules, specific models are proposed for solid shear walls subjected to either distributed or concentrated loading. The performance of the models and their applicability for the estimation of the ultimate capacity is shown by comparison with experimental results and advanced numerical simulation.

Mechanical Characterization of Historical Masonry by Core Drilling and Testing of Cylindrical Samples

ABSTRACT This article presents an experimental study aimed at the characterization of the mechanical behavior of existing masonry. The research proposes a methodology based on the in situ core drilling of existing masonry members, made of clay brick and low-strength lime mortar. The obtained cylindrical samples, with different diameters, are tested in the laboratory to derive the compression and frictional response of the composite material and the components (units, mortar). This article addresses the main issues related to the extraction of cylindrical specimens: the testing and the interpretation of results. The proposed minor destructive technique is suitable for existing masonry structures and especially for those of the built cultural heritage, since a direct estimation of the mechanical parameters can be obtained without damaging excessively the historical structure.

Review of Different Pushover Analysis Methods Applied to Masonry Buildings and Comparison with Nonlinear Dynamic Analysis

This article presents the comparison among different nonlinear seismic analysis methods applied to masonry buildings, i.e., pushover analyses with invariant lateral force distributions, adaptive pushover analysis and nonlinear dynamic analysis. The study focuses on the influence of lateral force distribution on the results of the pushover analysis. Two simple benchmark case studies are considered for the purpose of the research, i.e., a four-wall masonry building prototype without floor rigid diaphragms and a two-wall system with a cross-vault. The comparative study offers a useful review of pushover analysis methods for masonry structures and shows advantages and possible limitations of each approach.

Analysis of the Effect of Provisional Ties on the Construction and Current Deformation of Mallorca Cathedral

ABSTRACT This article presents the analysis of the structure of Mallorca Cathedral taking into account the influence on the structural behavior of auxiliary iron ties used during the construction process. Recent studies (Roca et al. 2012, 2013) presented some hypotheses about the construction process of the cathedral. This article complements the previous results by considering the use of auxiliary ties as temporary stabilizing device during the construction. Evidence of the use of ties during the construction has been recognized after a comprehensive survey. The study of the role of such ties and the effect of their later removal are studied by a FE analysis carried out on a representative bay of the structure. The study includes a time-dependent FE analysis after the removal of the ties to assess the long-term structural behavior. The results of the numerical analysis are compared with the deformation trends identified by means of a recent monitoring campaign.

Hole Drilling Technique for On-Site Stress Measurements of Masonry Piers: Analysis of the Santa Maria del Mar Cathedral in Barcelona, Spain

AbstractThe construction of the Santa Maria del Mar cathedral dates back to 1329. The cathedral represents an excellent example of the Gothic style in Catalonia. Because of the observed damage on the piers of the main nave, special attention was focused on determining the piers’ stress states. During a research campaign, the resulting stresses are determined numerically as well as experimentally based on a minimally destructive technique called the hole drilling technique. The technique allows determination of the principal stresses and their direction in stone masonry. The experimental results are compared with the outcome of a comparative numerical analysis. The quality of the experimental technique and the usefulness of the on-site methodology in the framework of cultural heritage sites are presented and discussed. The aim of the paper is the final corroboration of the applicability of the hole drilling technique in masonry structures. The technique has been previously checked in the Altes Museum (Berl...