Showing papers by "Katrin Beyer published in 2017"
TL;DR: In this paper, the drift capacity of masonry walls is evaluated at six different limit states that characterise the response from the onset of cracking to the collapse of the wall, and analytical expressions that estimate the ultimate drift capacity are proposed.
Abstract: This paper summarises 123 existing quasi-static shear–compression tests on stone masonry walls and evaluates the results to provide the input required for the displacement-based assessment of stone masonry buildings. Based on the collected data, existing criteria for estimating lateral strength and stiffness of stone masonry walls are reviewed and improvements proposed. The drift capacity of stone masonry walls is evaluated at six different limit states that characterise the response from the onset of cracking to the collapse of the wall. To provide input data for probabilistic assessments of stone masonry buildings, not only median values but also the corresponding coefficients of variation are determined. In addition, analytical expressions that estimate the ultimate drift capacity either as a function of masonry typology and failure mode or as a function of masonry typology, shear span and axial load ratio are proposed. The paper provides also estimates of the uncertainty related to the natural variability of stone masonry by analysing repeated tests and investigates the effect of mortar injections and the effect of the loading history (monotonic vs cyclic) on stiffness, strength and drift capacities. The data set is made publicly available.
87 citations
TL;DR: In this paper, the authors describe an experimental campaign on five thin T-shaped reinforced concrete walls (DOI: 10.6084/m9.3490754.v2).
Abstract: The present data paper describes an experimental campaign on five thin T-shaped reinforced concrete walls (DOI: 10.6084/m9.figshare.3490754.v2), which includes: details on the test units, materials...
51 citations
TL;DR: In this paper, a detailed micro-modeling method using extrinsic cohesive elements is proposed to simulate the force-deformation behavior of stone masonry panels, where a new node-to-node algorithm is implemented in a finite element library with a parallel framework.
35 citations
TL;DR: In this paper, the authors present numerical simulations of modern unreinforced clay block masonry walls that are subjected to different loading protocols and show that the force capacity is not very sensitive to the loading protocol.
29 citations
TL;DR: In this paper, an analytical model was proposed to compute the monotonic force displacement response of in-plane loaded unreinforced brick masonry walls accounting for walls failing in shear or flexure.
Abstract: This article introduces an analytical model to compute the monotonic force–displacement response of in-plane loaded unreinforced brick masonry walls accounting for walls failing in shear or flexure. The masonry wall is modelled as elastic in compression with zero tensile strength using a Timoshenko beam element. Its cross-section properties (moment of inertia and area) are continuously updated to capture the non-linearity that results from flexural and shear cracking. For this purpose, diagonal cracking of shear critical walls is represented by one Critical Diagonal Crack. The ultimate drift capacity of the wall is determined based on an approach evaluating a plastic zone at the wall toe. Validation against results of cyclic full-scale tests of unreinforced masonry walls made with vertically perforated clay units shows that the presented formulation is capable of accurately predicting the effective stiffness, the maximum strength and the ultimate drift capacity of the wall. It outperforms current empirical code equations with regard to stiffness and ultimate drift capacity estimates and yields similar results concerning strength prediction.
21 citations
TL;DR: In this article, an analytical model describing the flexural response of vertically spanning out-of-plane loaded unreinforced masonry walls is presented, based on the second-order Euler-Bernoulli beam theory.
Abstract: Summary
An analytical model describing the flexural response of vertically spanning out-of-plane loaded unreinforced masonry walls is presented in this paper. The model is based on the second-order Euler-Bernoulli beam theory and captures important characteristics of the out-of-plane response of masonry walls that have been observed in experimental tests and from numerical studies but for which an analytical solution was still lacking: the onset and the evolution of cracking, the peak strength of the out-of-plane loaded walls, and the softening of the response due to P−Δ effects. The model is validated against experimental results, and the comparison shows that the model captures both the prepeak and postpeak response of the walls. From the analytical model of the force-displacement curve, a formula for the maximum out-of-plane strength of the walls is derived, which can be directly applied in engineering practice.
20 citations
TL;DR: In this article, the authors present a database of 16 wall tests with lap splices and a corresponding reference wall with continuous reinforcement, including the description of a new test on a wall with lap-splice.
Abstract: Recent postearthquake missions have shown that reinforced concrete (RC) wall buildings can experience critical damage owing to lap splices, which led to a recent surge in experimental tests of walls with such constructional details. Most of the 16 wall tests described in the literature thus far were carried out in the last six years. This paper presents a database with these wall tests, including the description of a new test on a wall with lap splices and a corresponding reference wall with continuous reinforcement. They complement the existing tests by investigating a spliced member with a shear span ratio smaller than two, which is the smallest among them. The objective of this database is to collect information not just on the force capacity but mainly on the deformation capacity of lap splices in reinforced concrete walls. It is shown that (1) well-confined lap splices relocate the plastic hinge above the lap splice, (2) lap splices with adequate lengths but insufficiently confined attain the peak force but their deformation capacity is significantly reduced, and (3) short and not well-confined lap splices fail before reaching the strength capacity. The analysis of the test results, which are used in the companion paper for the finite element analysis of walls with lap splices, indicates in particular that the confining reinforcement ratio and the ratio of shear span to lap splice length influence the lap splice strain capacity.
17 citations
TL;DR: In this article, an equivalent uniaxial steel stress-strain law is proposed that represents the monotonic envelope of the cyclic response of spliced rebars in reinforced concrete (RC) walls up to the onset of strength degradation.
Abstract: Spliced longitudinal reinforcement may result in a reduction of both strength and displacement capacity of reinforced concrete (RC) members. This applies in particular when lap splices are located in regions where inelastic deformations concentrate, such as the plastic zone at the base of RC walls. This paper introduces a simple numerical model suitable for engineering practice to simulate the force-displacement response of RC walls with lap splices. Based on experimental data from 16 test units, an equivalent uniaxial steel stress-strain law is proposed that represents the monotonic envelope of the cyclic response of spliced rebars in RC walls up to the onset of strength degradation. It allows for modeling lap splice response with finite element (FE) models while avoiding the use of complex interface bond-slip elements. A new semi-empirical expression for the strain at the onset of strength degradation is derived, which expresses the strain capacity of the lap splice as a function of the confining reinforcement ratio and the ratio of lap splice length to shear span of the wall. The proposed equivalent constitutive law was included in shell element models to predict the force-displacement response of the test unit set of RC walls. Results demonstrated the ability of this approach to adequately capture the peak strength and displacement capacity of the spliced units.
14 citations
TL;DR: In this article, a displacement-based finite element is proposed to evaluate limit state demands for performance-based analysis of reinforced concrete (RC) structures, in which axial equilibrium is strictly verified along the element length.
Abstract: Distributed plasticity beam elements are commonly used to evaluate limit state demands for performance based analysis of reinforced concrete (RC) structures. Strain limits are often preferred to drift limits since they directly relate to damage and are therefore less dependent on member geometry and boundary conditions. However, predicting accurately strain demands still represents a major simulation challenge. Tension shift effects, which induce a linear curvature profile in the plastic hinge region of RC columns and walls, are one of the main causes for the mismatch between experimental and numerical estimates of local level quantities obtained through force-based formulations. Classical displacement-based approaches are instead suitable to simulate such linear curvature profile. Unfortunately, they verify equilibrium only on an average sense due to the wrong assumption on the axial displacement field, leading to poor deformation and force predictions. This paper presents a displacement-based element in which axial equilibrium is strictly verified along the element length. The assumed transversal displacement field ensures a linear curvature profile, connecting accurately global displacement and local strain demands. The proposed finite element is validated against two sets of quasi-static cyclic tests on RC bridge piers and walls. The results show that curvature and strain profiles for increasing ductility demands are significantly improved when axially equilibrated rather than classical displacement-based or force-based elements are used to model the structural members.
9 citations
01 Jan 2017
TL;DR: In this paper, a shell model with truss elements was used to simulate the response of the tested specimens to out-of-plane failure of a thin reinforced concrete wall, and good estimates of the critical tensile strain that leads to instability as well as the displacement in cycles prior to failure were obtained.
Abstract: Construction of multi-storey reinforced concrete (RC) wall buildings in areas of moderate to high seismicity has become a common practice in several Latin-American countries such as Colombia, Peru, Ecuador and Mexico. The large material cost has led to the common practice of designing walls with only one layer of reinforcement and very low thickness. The earthquakes in Chile (2010) and New Zealand (2011) have shown that such design approach can induce out-of-plane failure of the walls under seismic action. In order to study the influence of different parameters on the out-of-plane response of thin members, an experimental campaign on RC columns was recently carried out at Ecole Polytechnique Federale de Lausanne. These columns, axially loaded in cyclic tension-compression, represent the boundary element regions of RC walls, which correspond to the parts of the wall mainly involved in the instability mechanism. This paper illustrates the application of a shell model with truss elements to simulate the response of the tested specimens. The accuracy of the numerical model is assessed by comparison against the experimental results. It is shown that good estimates of the critical tensile strain that leads to out-of-plane instability as well as the out-of-plane displacement in cycles prior to failure are obtained. The failure mode is adequately simulated and also local behaviour is consistently reproduced. Therefore, the application of similar models to assess the vulnerability of thin RC walls to out-of-plane instability appears to be a relatively simple and robust numerical tool for engineering practice.
6 citations
01 Jan 2017
TL;DR: In this article, Reinforced concrete walls and thin walls are constructed with reinforced concrete and reinforced concrete materials, respectively, in the context of thin-wall construction and reinforcement of reinforced concrete walls.
Abstract: Keywords: Reinforced concrete walls ; Thin walls Reference EPFL-CONF-224470 Record created on 2017-01-17, modified on 2017-01-17
01 Jan 2017
TL;DR: In this paper, a quasi-static cyclic test was performed on reinforced concrete walls in order to evaluate bi-directional loading in a bi-layer reinforced concrete wall with bi-dimensional load balancing.
Abstract: Keywords: reinforced concrete walls ; quasi-static cyclic tests ; bi-directional loading Reference EPFL-CONF-224465 Record created on 2017-01-17, modified on 2017-01-17
01 Jan 2017
TL;DR: In this paper, a collaborative project between the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland and the Universidad del Valle, the EIA University, and the University of Medellin in Colombia, equivalent reinforced concrete columns with a single vertical reinforcement layer are tested at EPFL in order to investigate the effect of loading history, reinforcement ratio and eccentricity of the longitudinal rebars with regard to the element axis ration the out-of-plane response.
Abstract: Over the last few years the increasing demand of housing for low income population in Colombia and several neighboring countries, associated to the significant increase of cost of land, has prompted construction companies to build medium to high rise reinforced concrete (RC) wall buildings. Most of these new residential buildings are constructed with walls that have thicknesses as low as 80 mm and are only lightly reinforced. The recent earthquakes in Chile (2010) and New Zealand (2011) have caused significant damage to some of the RC walls, some of which tended to buckle out-of-plane. In Colombia the wall thicknesses are significantly thinner than in Chile or New Zealand and is therefore is to be feared that these buildings may present the same out-of-plane failure mode during a future earthquake. Furthermore, many of the walls have only a single vertical reinforcement layer, which could increase the out-of-plane instability, as it will be shown in this paper. Although recent experimental tests have shown that wall out-of-plane deformations can extend throughout a relatively large part of the wall length, the boundary regions are the critical zones that control the development of associated failure modes. For thin walls behaving predominantly in flexure those boundary regions are subjected to mainly axial strains, and hence testing equivalent RC columns under cyclic axial tension and compression provides direct insights into the influence of the parameters triggering wall instability and possible out-of-plane failure. Within a collaborative project between the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland and the Universidad del Valle, the EIA University, and the University of Medellin in Colombia, equivalent RC columns with a single vertical reinforcement layer are tested at EPFL in order to investigate the effect of loading history, reinforcement ratio and eccentricity of the longitudinal rebars with regard to the element axis ration the out-of-plane response. The paper presents the details of this recent experimental campaign, describing the geometry and the reinforcement layout of the specimens, the test setup, the extensive instrumentation used, and the results obtained from the first tests. The experimental findings allowed to draw initial conclusions on the development of the out-of-plane instability, on the particularities of single layer reinforcement members and on the development of out-of-plane failures.
01 Jan 2017
TL;DR: In this article, Reinforced concrete walls are modeled as nonlinear nonlinear models for nonlinear modeling with reinforcement reinforced concrete walls and nonlinear modelling with nonlinear reinforcement reinforcement techniques.
Abstract: Keywords: Reinforced concrete walls ; Nonlinear modelling Reference EPFL-CONF-224468 Record created on 2017-01-17, modified on 2017-01-17
01 Jan 2017
TL;DR: In this article, a force-based beam element was used to interact with unreinforced masonry for shear-flexure interaction in an unstructured masonry construction.
Abstract: Keywords: Unreinforced masonry ; Force-based beam element ; Shear-flexure interaction Reference EPFL-CONF-224472 Record created on 2017-01-17, modified on 2017-01-18
01 Jan 2017
TL;DR: In this paper, an enhanced displacement-based element strictly verifying axial equilibrium is proposed to ensure the axial force to remain constant within the element while maintaining the linearity of the curvature profile.
Abstract: Engineers and researchers often use nonlinear beam-column elements to simulate the response of reinforced concrete structures. Namely, distributed plasticity elements are arguably the most attractive due to the good compromise between accuracy and computational time. Formulation wise, three types of distributed plasticity beam elements can be distinguished: displacement-based, force-based and mixed formulations. The simplicity of numerical implementation renders the first class of elements particularly appealing from a practical point of view despite the fact that the classically employed shape functions yield exact solutions only for linear elastic problems and nodal loads. As a consequence, when material or geometrical nonlinearities are involved, equilibrium within the element is not strictly satisfied. Recent experimental tests on the inelastic behavior of bridge piers have shown that the curvature profile above the base section of a fixed structural member is different from the one simulated by a plane-section force-based beam formulation, which satisfies exact equilibrium and considers only the effect of the moment gradient. These tests confirmed in particular that the tension shift effects due to inclined cracks in concrete members are responsible for a curvature distribution that evolves in a bilinear shape along the member height during the inelastic phase of the response. This paper presents an enhanced displacement-based element strictly verifying axial equilibrium which ensures the axial force to remain constant within the element while maintaining the linearity of the curvature profile. This yields in two advantages over the classical displacement-based element: First, it yields a better prediction of the moment capacity as the axial force verifies equilibrium exactly, which is not the case in classical displacement-based elements where only an average equilibrium is guaranteed. Second, the combination between the axial force equilibrium and the linear curvature profile can be used to simulate the effects of tension shift in RC elements, both at the global and local level. The new element is first applied to an example column to illustrate its main features, and then used to simulate the response of a reinforced concrete bridge pier that was tested under cyclic loading. By comparing numerical to experimental results, it is shown that the proposed element predicts satisfactorily the global force-displacement response. Additionally, when compared to simulations using classical displacement-based or force-based beam elements, a greater accuracy can be obtained for the prediction of the evolution of curvatures and rebar strains over the height of the bridge pier for increasing ductility demands. The improved predictions come at the cost of a more involved state determination with respect to the classical displacement-based formulation.
01 Jan 2017
TL;DR: In this article, Reinforced concrete walls and plan-asymmetric buildings are constructed with reinforced concrete walls with torsion reference EPFL-CONF-224467 Record created on 2017-01-17, modified on 2017 -01-23
Abstract: Keywords: Reinforced concrete walls ; Plan-asymmetric buildings ; Torsion Reference EPFL-CONF-224467 Record created on 2017-01-17, modified on 2017-01-23
DOI•
21 Sep 2017
TL;DR: In this article, a Forschungs-and Weiterbildungsprojekt, das gemeinsam von EPFL and der Universitat Pavia ausgefuhrt wird, vorgestellt.
Abstract: Im Jahr 1356 wurde Basel von einem Erdbeben mit einer geschatzten Magnitude von 6.6 er-schuttert. Wahrend dieses Erdbebens und des nachfolgenden Feuers wurden grosse Teile von Basel zerstort. Ein solches Ereignis kann jederzeit wieder auftreten. Um vorbereitet zu sein, ist es wichtig, das erwartete Erdbebenverhalten der bestehenden Gebaude zu ermitteln. Der Cha-rakter des Stadtzentrums von Basel ist stark von historischen Natursteinmauerwerksgebauden aus verschiedenen Epochen gepragt. Natursteinmauerwerksgebauden gehoren zu den am starks-ten gefahrdeten Strukturen unter Erdbebenanregung. Gleichzeitig gehoren sie zum Schweizer Kulturerbe und das nicht nur hinsichtlich ihres Aussehens sondern auch hinsichtlich der Bau-substanz als solche. In diesem Beitrag wird ein Forschungs- und Weiterbildungsprojekt, das gemeinsam von EPFL und der Universitat Pavia ausgefuhrt wird, vorgestellt. Das Projekt hat zum einen zum Ziel rea-listischer Modelle fur das Erdbebenverhalten von Natursteinmauerwerksgebauden zu entwi-ckeln und damit die Gebaude zu identifizieren, die keine Intervention benotigen. Zum anderen sollen Verstarkungsmassnahmen entwickelt werden, die reversibel und so wenig invasive wie moglich sind und daher auch fur Kulturguter geeignet sind. Die Forschungsresultate werden in parallel laufenden Weiterbildungskursen direkt in die Ingenieurpraxis vermittelt. In diesem Bei-trag wird das Forschungsprojekt vorgestellt und es werden erste Ergebnisse beschrieben.
01 Jan 2017
TL;DR: In this article, the axially equilibrated displacement-based beam element is implemented in the OpenSees finite element software for nonlinear static and dynamic analysis of RC bridge piers.
Abstract: Experimental tests on the inelastic behavior of RC bridge piers have shown that, due to tension shift effects, the curvature profile above the base section of the structural member differs from the one that would develop according to a force-based or a classical displacement-based beam formulation with plane section hypothesis. Due to the inclined cracks in concrete members, it was found that the curvature distribution evolves in a bilinear shape along the member height during the inelastic phase of the response, and that the length of plastification increases with increasing ductility demands. Recently, it was shown that axially equilibrated displacement-based elements can more effectively predict the local-level response of RC members. The process of imposing the equilibrium of the axial forces along the element length allows the beam element to improve the simulation of both curvature and strain profiles. The finite element was originally implemented in the authors’ structural analysis software SAGRES, which was developed for nonlinear static analysis and is not freely available to the engineering community. This paper presents the validation of the implemented axially equilibrated displacement-based element in the open source finite element software OpenSees and provides some application examples of both nonlinear static and dynamic analyses. The results are compared against classical approaches (force-based and displacement-based), pinpointing the advantages of the axially equilibrated displacement-based beam element.
01 Jan 2017
TL;DR: In this paper, the authors investigated the validity and accuracy of a displacement-based approach for out-of-plane loaded unreinforced masonry walls against the results of numerical simulations.
Abstract: The assessment of the out-of-plane stability of unreinforced masonry walls is a key element in the seismic assessment of existing buildings. This paper investigates the validity and accuracy of a displacement-based approach for out-of-plane loaded unreinforced masonry walls against the results of numerical simulations. A discrete element model of a vertically-spanning masonry wall that is able to represent the peak strength, joint crack-initiation up to the complete joint detachment and rocking of the wall is first validated and next benchmarked against several configurations. Results from static pushover analyses are presented in view of the displacement-based assessment procedure. The displacement-based procedure is next tested against non-linear time-history dynamic analyses. Its applicability to different wall configurations is discussed.
01 Jan 2017
TL;DR: In this paper, unreinforced masonry and URM walls were used for drift capacity estimation in an unstructured masonry building with drift capacity of 1.5m.
Abstract: Keywords: Unreinforced masonry ; URM walls ; Drift capacity Reference EPFL-CONF-224473 Record created on 2017-01-17, modified on 2017-01-18
01 Jan 2017
TL;DR: In this article, Reinforced concrete slabs are reinforced with reinforced concrete blocks and a slab-column connection is used to achieve cyclic behavior in the context of slabs.
Abstract: Keywords: Reinforced concrete slabs ; Cyclic behaviour ; Slab-column connection Reference EPFL-CONF-224466 Record created on 2017-01-17, modified on 2017-01-17