In the pursuit of introducing bacteria-based self-healing mortar for masonry repair, this study examined the potential of incorporating a poly-lactic acid (PLA) agent—already established in concrete repair—into cement-lime mortars, typical of historical constructions. Testing prisms constructed with varying lime/cement ratios revealed decreased flexural and compressive strength in high-cement-concentration mortars upon the addition of the agent; for mortars with high lime concentration, however, the agent led to an increase in both strengths. Furthermore, the agent's potential to self-repair was confirmed by allowing the remaining portions of tested samples to heal under humid conditions. Irrespective of mortar composition, cracks were resealed thus confirming the aesthetic, and potentially watertightness, restoration.@en

Cracks represent a prevalent form of damage in masonry structures, posing not only aesthetic concerns but also compromising structural durability; therefore, they are undesirable and need to be repaired. The repointing technique is traditionally implemented in this context, especially in historical masonry. However, this method fails to provide a long-term solution, leaving structures vulnerable to future damage. The paper investigates the applicability of a bio-based self-healing mortar to enable autonomous repair of masonry. This innovative mortar, developed to repair concrete structures, was implemented to explore the capacity of couplets to recover their original bond capacity and aesthetic aspect after multiple damaging events. Specimens built with calciumsilicate and clay bricks were subjected to subsequent cracking cycles using a crack-mouth-opening -displacement controlled bond-wrench test. Experimental results showed that self-repair, in terms of bond restoration and aesthetic filling of cracks, occurs even after multiple cracking cycles when the bio-based mortar is used with both types of bricks, optimizing the autogenous healing (intrinsic) of cement-based mortars. The effectiveness varied also according to the types of brick and healing environment used, e.g. under humid conditions (RH ~ 95%), 50% vs 80% of the original capacity was regained in fully separated couplets made respectively with clay and calcium-silicate bricks.@en

This paper presents the results of an experimental campaign carried out to characterise the mechanical properties of multi-wythe masonry infrastructure in the city of Amsterdam. Samples were extracted from a 1.2 m thick bridge’s pillar constructed in 1882. For the characterisation of shear and compressive properties of masonry, tests on cores with a 100 mm diameter were performed at the Stevinlaboratorium of Delft University of Technology. Samples were extracted along different locations in the wall thickness to evaluate the effect of exposure to environment conditions. Overall, the study provides a first insight on the mechanical properties of multi-wythe masonry city infrastructure and knowledge regarding the sampling and testing strategy for these structures. In turn, this will increase the knowledge on multi-wythe masonry, which is limited in literature, and will support the assessment of many infrastructures in typical Dutch canal cities.

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Canals delimited by masonry quay walls are integral elements of many cities in the Netherlands. Historically built to enable the efficient transportation of goods, today such infrastructure also gives the cities their historical and monumental character. In recent years, many quay walls in the Netherlands have shown substantial deformation and damage, and in few cases even collapse. Historical quay walls, which are constructed in thick multi-wythe unreinforced brick masonry and are supported on a system of timber piles, nowadays sustain traffic loads larger than the one they were designed for. Instances of collapse and severe damage has given rise to a need for research assessing the safety of these structures, which are not appropriately covered by any normative or standardised guidelines. This paper presents a novel methodology to numerically assess the performance of masonry walls in historical quays under the dynamic effect of traffic loads. Application of the proposed methodology to a case study in Amsterdam, the Netherlands, is presented.@en

Innovative solutions for seismic-retrofitting existing structures are currently required, as often traditional strategies are expensive, non-reversible, highly invasive, and/or fail to address both serviceability and ultimate limit states together. The present paper describes a preliminary experimental campaign performed at TU Delft to investigate an innovative structural glass window for strengthening masonry buildings. To this purpose, a prototype composed of a timber frame, a semi-rigid adhesive, and a 20 mm thick structural glazing layer was designed. The prototype aimed to improve the structure’s behavior against minor but more frequent service vibrations (SLS), as well as against ultimate ones (ULS). Specifically, an increase in the structure’s in-plane capacity and stiffness was targeted to reduce cracking at low drifts/displacements, while at larger drifts, the adhesive’s tearing and timber crushing were used to activate damping. To evaluate the prototype’s performance, a quasi-static, cyclic, in-plane test on a strengthened full-scale wall was performed and compared with available data on a similar, yet unstrengthened, wall. Although the benefits were not pronounced in terms of cracking and energy dissipation, the implementation of the proposed strategy provided an increase in terms of initial stiffness (18%), force capacity (8%, 36%), and ductility (220%, 135%). This outcome provides the ground for numerical studies that will help better delineate the proposed strategy and improve the current design.@en

Cracks are one of the most common expressions of damage in masonry structures. Aside from aesthetic issues, they can compromise the overall behaviour of the structure; therefore, they are undesirable and need to be repaired. The repointing technique is traditionally implemented in this context, especially in historical masonry. Nevertheless, future damage is not prevented and may arise again, thus requiring renewed repointing interventions. The paper describes a preliminary study conducted at Delft University of Technology to investigate the applicability of the innovative self-healing technology to enable an automatic repair of masonry cracks. A bacteria-based self-healing mortar, developed to repair existing concrete structures, was implemented to explore the capacity of couplets to recover their original strength and aesthetic aspect after multiple damaging events. Specimens built with calcium-silicate and clay bricks were subjected to subsequent cracking cycles using a crack-mouth-opening-displacement controlled bond-wrench test. Experimental results showed that self-repair, in terms of strength restoration and aesthetic filling of cracks, occurs even after multiple cracking cycles when the self-healing mortar is used with both types of bricks, optimizing the autogenous healing of cement-based mortars. In this context, the healing effectiveness tended to decrease as the crack width and the number of cycles increased. The effectiveness varied also according to the types of brick and healing environment used, e.g. under humid conditions (RH ~ 95%), 50% vs 80% of the original capacity was regained in fully separated couplets made respectively with clay and calcium-silicate bricks. This outcome provides the ground to delineate the remaining testing campaign.

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Bed joint reinforced repointing is a retrofitting technique for unreinforced masonry structures that is commonly applied in the Netherlands to repair settlement-induced damage. Using this technique, the bed joints of masonry walls are reinforced with steel rebars that are embedded in a high strength repair mortar. Due to the increase of induced seismic events in the northern part of the Netherlands, an experimental study was carried out at Delft University of Technology to investigate the performance of this retrofitting technique for combined settlement and seismic loading. This paper aims to simulate the experimental results, with a focus on the comparison of different finite element modelling approaches for studying both un-strengthened and strengthened full-scale tested walls. To that end, three different models are investigated – comprising both macro (continuum) and simplified and detailed micro (brick-to-brick) modelling approaches. The bricks and mortar joints are modelled as one homogenous continuum in the macro model, whereas in the two brick-to-brick models these structural components are modelled separately, with the detailed model including interface elements to simulate the brick–mortar bonds. Nonlinear pushover analyses are subsequently carried out using all three modelling approaches, for both monotonic and cyclic loading cases. Based on these analyses, the detailed brick-to-brick model was found unsuitable to simulate the strengthened wall because cracks in the model mainly occur in the form of opening of the brick–mortar bond interfaces, while smeared cracking in the plane stress elements of the mortar joints is very limited. Similarly, the continuum damage model was found to be inaccurate when pre-existing damage in the experiment needed to be taken into account. The continuum damage model also showed lower axial stresses in the rebars, compared with the simplified brick-to-brick model, as the former does not allow for the direct assignment of material properties for the high strength repair mortar in the strengthened joints.

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The brick-to-mortar bond often represents the weakest link leading to cracking and failure of masonry structures. For this reason, the in-situ characterization of masonry’s flexural bond behaviour (here defined as flexural bond strength and flexural bond fracture energy), is essential for the assessment of existing buildings. Among masonry bond properties, the flexural bond strength is commonly determined on-site, given the minimal invasiveness of the so-called bond wrench test. However, often the reliability of the results is questioned inputting their large variability to the operator. The present study discharges this assumption by comparing the accuracy of various testing set-ups (manually-operated vs computer-controlled set-ups). Additionally, the influence of the specimen’s type (with/without head joints and couplets vs wallet) on the flexural bond strength assessment is studied providing preliminary correlation factors that can be of help for the in-situ measurement on single-wythe masonry. In addition, to obtain a complete description of the bond behaviour, a new test set-up able to determine the post-peak response is presented. Considerations regarding the dissipated bond fracture energy and its relation to the tensile fracture energy are provided with the support of literature data.

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The present work aims at providing insights on the material characterization of multi-wythe masonry infrastructure, in particular exploring a through-thickness effect of mechanical properties and benchmarking the core testing as an efficient slightly-destructive testing method. An experimental campaign was carried out to characterize shear, compressive and bond properties of a 1.2-m thick bridge's pillar constructed in 1882 in the city of Amsterdam (the Netherlands). Both cores and rectangular samples (e.g. prisms, triplets, couplets) were extracted across different locations in the wall thickness to evaluate the effect of exposure to environment conditions and to verify the capability of core testing methods. Results show that the masonry close to the water side (external) showed higher values of elastic modulus and lower values of flexural bond properties with respect to masonry inside the pillar. As for the capability of core testing on multi-wythe masonry, generally cores would present similar compressive/shear properties compared with rectangular samples. Besides, bond patterns and dimensions of cores showed negligible effect on compressive properties; However, this needs to be extensively verified by considering other masonry typologies. Overall, the study provides a first insight on the mechanical properties of multi-wythe masonry urban infrastructure and knowledge regarding the sampling and testing strategy for these structures. In turn, this will increase the knowledge on multi-wythe masonry, which is limited in literature, and will support the assessment of many infrastructure in typical Dutch canal cities by providing input for calculation methods.

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Perforated unreinforced masonry (URM) walls in out-of-plane (OOP) two-way bending are commonly encountered in natural hazard investigations. However, related research is rather limited. This study focuses on the influence of openings on the two-way bending capacity of URM walls. An experimental database about the perforated URM walls in OOP two-way bending was created. A brief review of the experimental results show that the arrangement of the opening area can significantly affect the two-way bending capacity of walls (defined as the peak pressure on the wall net area): when the opening area is non-covered and non-loaded, the two-way bending capacity of the perforated wall is higher than that of its solid counterpart; when the opening area is covered with timber or glass plates loaded as the rest of the wall, the two-way bending capacity of the perforated wall is lower than that of the corresponding solid wall. These observations from the experiments were confirmed by an analytical estimation using the Yield Line Method (YLM). Next, to study the influence of openings on the two-way bending capacity, a numerical study has been carried out by employing the 3D simplified brick-to-brick modelling approach. The results of calibration and validation show that this modelling approach can precisely predict the two-way bending capacity and crack patterns. By applying the validated numerical models, the influence of the arrangement for the opening area from the experimental results and YLM evaluation was confirmed. Further, a parametric study focusing mainly on cases with the opening area non-covered and non-loaded was conducted. The influence of the geometric parameters of openings, namely, the opening size, shape and position was investigated on walls with different aspect ratios. Results show that the two-way bending capacity increases as the opening size or aspect ratio (height to width) increase, but it is insensitive to the opening position. Eventually, based on the numerical results, analytical equations were proposed to account for the influence of the considered parameters on the two-way bending capacity. A comparison with the Australian Standard (AS3700) indicates that the proposed equations incorporate more opening parameters such as opening shape.

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To date, several different structural representations of masonry are available for use in the numerical and analytical assessment methods, each calling for a distinct level of refinement regarding the material input. To determine material properties, in terms of strength, stiffness, and toughness under compression, bending, and shear loading, extensive experimental research is necessary. To minimise the burden associated with performing complex and invasive experimental studies, this paper investigated the possible correlations between different material properties, particularly toughness, which received limited attention in past research. The correlation study was mainly conducted on the rich database established from tests on laboratory-made as well as specimens extracted from unreinforced masonry structures built between 1910 and 2010 in the Netherlands. Considering the outcomes of the correlation study, this paper puts forward recommendations to indirectly derive elastic and toughness properties as a function of strength properties. In this way, a complete picture of material properties can be obtained, while minimising the number of experiments and the extent of their invasiveness.

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Accurate assessment of the overall mechanical behavior of masonry, composed of bricks and mortar joints, remains challenging due to its inhomogeneous and orthotropic nature. In this study, the feasibility of various mean-field homogenization schemes for the three-dimensional orthotropic elastic properties of masonry is comprehensively investigated. Three kinds of masonry patterns are considered, including the stack bonded pattern, the running bonded pattern and the double-leaf Flemish bonded pattern that has received limited attention so far. Special attention is paid to the homogenization schemes which have not been applied to the masonry case, such as Lielens’ interpolative double inclusions (D-I) and the interaction direct derivative (IDD) schemes. After a comparison between the well-known mean-field homogenization schemes, an improved micro-mechanical model is proposed by combining the advantages of the IDD and D-I models. The validation of the proposed model is conducted through a comparison against experimental data from literature and numerical results obtained via finite element analyses (FEA). The results show that the proposed model can accurately evaluate the orthotropic elastic properties of the three masonry typologies for a wide range of stiffness ratios between brick and mortar, ranging from 1 to 1000. The proposed model also shows better performance than the classical schemes especially when the stiffness ratios between brick and mortar are higher than 10, which is of major importance for the application of mean-field homogenization based multiscale methods to the nonlinear analysis of masonry. Furthermore, the presented homogenization method can be of interest for other anisotropic materials, e.g., laminate materials.

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The shove test (ASTM Standard C1531) is an experimental technique aimed at studying the shear-sliding behavior of brick masonry. It can be executed according to various testing methods that differ in the way the vertical compression load is applied and in the way bricks and/or joints are locally removed for inserting jacks. One of the most critical aspects is the correct evaluation of the compressive stress state on the sliding brick. The objective of the present paper is to investigate the capability of the shove test in determining the shear strength parameters of brick masonries and to highlight the main advantages and disadvantages of the various testing methods. To this aim, nonlinear numerical simulations of the shove test were performed by adopting a brick-to-brick modeling strategy. The 2D numerical model was calibrated and validated through comparisons with experimental results of triplet tests and shove tests. The numerical analyses allowed to understand the influence the different testing methods and the masonry mechanical properties, such as dilatancy, may have on the test results. Based on the numerical outcomes, correction factors were calibrated for the proper evaluation of the compressive stress state on the sliding brick. Improvements with regards to the experimental procedures, i.e. additional test phases and measurements, were also proposed to enhance the results interpretation.

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Out-of-plane (OOP) failure of unreinforced masonry (URM) walls in two-way bending was widely observed after natural hazards such as earthquakes. Of various crucial factors influencing the force capacity of URM walls in OOP two-way bending (force capacity being defined as the wall peak force in terms of pressure), the pre-compression and aspect ratio (defined as the wall height to length with the height kept constant) have not been sufficiently studied. To better understand their influence, an extensive numerical study was conducted by employing a detailed 3D brick-to-brick modelling method. First, a set of monotonic quasi-static tests on full-scale walls was taken as references for calibration and validation. The numerical results matched well with the experimental results in terms of initial stiffness, force capacity and crack pattern. Afterwards, the validated model was adopted to carry out a parametric study. Results show that the force capacity of the URM walls in OOP two-way bending is exponentially related to the aspect ratio and linearly related to the pre-compression. Besides, the influence of the pre-compression and aspect ratio on the force capacity can be interdependent. Additionally, when the pre-compression is relatively low, a wall does not crack in a localized manner into several rigid plane plates at the force capacity. Instead, the deformed shape of the wall approximates a curved surface, indicating distributed rather than localized cracking at force capacity. Furthermore, the force capacity is much higher than the residual force when the rigid-plates crack pattern is formed in the post-peak stage. The parametric study also shows that torsional failure of bed joints is the predominant failure mechanism for URM walls in OOP two-way bending, and its contribution to the force capacity generally increases as the pre-compression or aspect ratio increases. Finally, the numerical results were compared with the predictions by three major analytical formulations, namely Eurocode 6, Australian Standard for Masonry Structures (AS 3700) and Willis et al. (2006). As a result, the relations between the force capacity and the aspect ratio or pre-compression derived from the numerical models could not be accurately predicted by the analytical formulations. Based on previous results, recommendations on improving the analytical formulations were proposed.

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In dit rapport is via een forensic engineering aanpak een eerste analyse gegeven (rapid assessment, RA) van het bezwijken van de Grimburgwal (GBW) op 1 september 2020. Het doel van het onderzoek is om te achterhalen welke lessen zijn te leren van het bezwijken van de Grimburgwal voor de overige kades in Amsterdam. De volgende onderzoeksvragen zijn in dit onderzoek beantwoord op basis van de in dit rapport gepresenteerde informatie en analyses. Hierbij dient te worden aangegeven dat veel duidelijk is geworden maar dat ook nog gegevens ontbreken. Verder zijn alleen analyses uitgevoerd die in deze fase van Rapid Assessment konden worden uitgevoerd. Op basis hiervan is de beantwoording van de onderzoeksvragen als volgt: Beantwoording vraag 1: Welke faalmechanisme(n) hebben significant bijgedragen aan het bezwijken van de Grimburgwal? De Grimburgwal kade is in september 2020 in verschillende fasen bezweken. Als eerste was er sprake van een horizontale vervorming van de kade en enige dagen voor bezwijken zijn gaten in het straatwerk aangetroffen. De kade is daarna via een verticale vervorming losgeraakt en uit het vlak richting de gracht gevallen. Hierbij is een sectie van circa 25 m geheel onder water verdwenen. Het bezwijken is aan het oostelijke deel begonnen. Het westelijke deel is als gevolg daarvan meegetrokken en gekanteld. Als belangrijkste faalmechanisme is opgetreden een horizontale buigvervorming van de houten paalfundering gevolgd door het breken van de houten palen. De vervorming is het gevolg van een lokaal diepere bodemligging van de gracht. Deze verklaring berust op de verwachting dat er in elk geval onder een gedeelte van de kade slechts twee palenrijen achter elkaar aanwezig waren dan wel effectief functioneerden. Dit is conform het bestek, de duikinspectie en is tevens aannemelijk gezien de zeer korte afstand van de kade tot het pand BG2. Door bestaande scheurvorming was de mogelijkheid tot herverdeling van de krachten langs de kade in langsrichting verminderd, waardoor de sterkere delen (met wèl drie palenrijen) niet meer in staat waren de belasting over te nemen. De analyses zijn uitgevoerd met als aanname een ongedegradeerde houtsterkte. De sterkte van het hout was nog niet vastgesteld bij publicatie van dit rapport. Beantwoording vraag 2: Wat zijn de onderliggende oorzaken van deze mechanismen? De oorzaak van de diepere bodemligging is in dit onderzoek niet onderzocht. Naar alle waarschijnlijkheid is het draaien van boten een logische oorzaak hiervoor, omdat de instorting precies nabij het draaipunt voor brug 201 heeft plaatsgevonden. Het is waargenomen dat de diepte van de gracht in de richting van de brug toeneemt en daarna weer afneemt. De herhaaldelijke aanvaringen hebben de kade verzwakt, wat mogelijk verklaart waarom deze precies op de plaats van de schade als eerste is gescheurd. Tevens is dit het smalste deel van de kade, met mogelijk slechts twee palenrijen. Er lijkt geen sprake van belangrijke mate van aantasting van het hout (op basis van inspecties). De trigger (het laatste duwtje) voor de instorting is waarschijnlijk het vernieuwen van het straatwerk geweest van (eerst mei en later) augustus 2020. Het straatwerk zorgt voor een extra belasting op de kade. Dit straatwerk was nodig als gevolg van de reeds opgetreden kadevervorming. De bijdrage van de rondwaterstroming en eventuele droogte/regen is niet bekend, doch kan een rol hebben gespeeld in combinatie met de al opgetreden vervorming en ontstane lekweg van achter de kade richting de gracht voor de vorming van de gaten in het straatwerk. De gebroken hemelwaterafvoer is zeer waarschijnlijk een gevolg en geen oorzaak van de instorting. Beantwoording vraag 3: Op welke manier zijn de resultaten van dit onderzoek in te zetten voor beoordeling van de veiligheid en het nemen van maatregelen voor de overige kademuren in Amsterdam? Uit deze Rapid Assessment is gebleken dat de geometrie van de kade een belangrijke bijdrage heeft gespeeld in de gevoeligheid van de kade voor ontgronding/verdieping van de gracht. Door de combinatie van een kade die mogelijk op twee palen en zeker deels op drie palen rust is een uitspraak over de representativiteit van deze kade niet met volledige zekerheid te doen. De kade had volgens afdeling monumenten van Amsterdam (MenA) sowieso een wat afwijkende opbouw en een kade(deel) met twee palen is zelfs sterk afwijkend van het gebruikelijke areaal. Op basis van de bij vraag 1 en 2 beschreven mechanismen en oorzaken die ook voor de kade met drie palen gelden, kan desondanks worden gesteld dat maatregelen die voor de Grimburgwal worden aanbevolen ook voor overige kades van toepassing zijn. Uit deze Rapid Assessment is gebleken dat de geometrie van de kade een belangrijke bijdrage heeft gespeeld in de gevoeligheid van de kade voor ontgronding/verdieping van de gracht. Hieruit volgen de volgende mogelijke maatregelen/vervolgacties: - Controle of er (meer) kades met korte kespen / vloerconstructies zijn en slechts twee palenrijen. Deze zijn kwetsbaarder dan de constructies met meer rijen palen. Deze kades kunnen met voorrang worden getoetst en zonodig versterkt. - Uitvoeren van een controle op de waterdiepte en ontgrondingen, vooral op routes van scheepvaart en bij kades met twee of drie palenrijen. Er kunnen dan maatregelen genomen worden bij een te grote waterdiepte/ontgronding. - Locaties met aanvaarschades met voorrang te onderzoeken. - Systematisch aandacht te besteden aan zettingen achter de kades en problemen met leidingen of riolering, omdat dit kan duiden op het horizontaal vervormen van de kade, al dan niet door een diepere bodemligging. Er kan bijvoorbeeld een registratie/meldingssysteem gebruikt worden voor het optreden van verzakkingen aan de kades/het straatwerk. Als er een opdracht tot herstraten wordt gegeven dient altijd EERST een analyse van de oorzaak van de verzakking te worden gemaakt die het gedrag van de kade meeneemt. Dit kan ook voorkomen dat herstraatwerk tot vergroting van de belasting op de kade leidt. - Uitvoeren van metingen (liefst horizontaal aan de kades maar ook verticaal) om de relatie van de vervorming met mogelijk falen te onderzoeken (numeriek of experimenteel). Analyse van de zakkingen van de kades met Insarmetingen kan helpen om andere “hotspots” in kaart te brengen. Door middel van nadere analyses dient te worden vastgesteld welke grenswaarden een indicatie voor falen geven. Het effect van droogte op de zakkingen in de stad dient hierbij mede te worden onderzocht. In het onderzoek van de GBW is gebleken dat er veel factoren mogelijk een bijdrage hebben geleverd aan het falen. Enkele daarvan konden niet worden uitgesloten maar zijn ook niet bevestigd. Dit geeft wel aan dat bepaalde zaken nog nader onderzocht kunnen worden. Aan de GBW was een oude kade aanwezig die de huidige kade kruiste nabij de locatie van bezwijken. Ook voor andere kades zijn dergelijke vervangingen gangbaar geweest. De exacte samenstelling van de kade op het punt van bezwijken (met twee of drie palen) is ook niet geheel zeker, ondanks diverse inspanningen hier duidelijkheid over te krijgen. Nader onderzoek naar de (invloed van de) opbouw van bestaande kades, zowel archeologisch als modelmatig wordt sterk aanbevolen. Om voor de Grimburgwal de relatieve invloed van de verschillende factoren nog specifieker te onderscheiden zouden de volgende activiteiten kunnen worden uitgevoerd: - Onderzoek op houten samples uit de restanten om deze te drogen en te wegen en tevens trekproeven te doen om de buigtreksterkte sterkteklasse vast te stellen. Ook de mechanische eigenschappen van de paal-kesp verbinding kan worden onderzocht. - Onderzoek naar de exacte opbouw van de fundering in de bezweken en aanpalende gedeeltes. - (na bovenstaande) Niet lineair eindig elementen model in 3D van de gehele kade voor het analyseren van de geschetste bezwijkmechanismen uit de RA en daarna variëren met verschillende scenario’s zoals andere geometrieën Het is in dit onderzoek goed mogelijk gebleken met verschillende ekenmethoden een indruk te krijgen van de stabiliteit van de kade. Doorontwikkeling en validatie van modellen voor gecombineerde berekening van de gehele constructie (vloer, metselwerk, palen) is nodig, omdat deze gecombineerde modellen geen gemeengoed zijn. @en

Bed joint reinforced repointing is a strengthening method often used in the Netherlands to counteract settlement damage. This strengthening technique consists of cutting a slot in the mortar joint and installing twisted steel bars embedded in a high-strength repair mortar. Due to the increase in seismic activities, triggered by gas extraction in the region of Groningen (northern part of the Netherlands), it is of interest to investigate whether this strengthening technique is efficient against seismic load. In order to characterize the performance of the bed joint reinforced repointing using twisted steel bars, an experimental campaign was conducted at Delft University of Technology. A quasi-static cyclic in-plane test on a full-scale wall was performed; similar tests on unstrengthened specimens were available from a previous experimental campaign [1][2] and were used for comparison. Moreover, small scale pull-out tests were performed to study the interaction between the steel bars and the repair mortar. By comparing the response of unstrengthened and strengthened masonry specimens, it is observed that the use of bed joint reinforced repointing can provide an increase in terms of ductility and displacement capacity, but not in terms of force capacity. Regarding the serviceability limit state, a reduction in crack width and an increase of load at onset of cracking were observed. The preliminary information obtained for the presented case study provides the ground for futher research as well as benchmark for numerical modelling.@en

Masonry panels consisting of piers and spandrels in buildings are vulnerable to in-plane actions caused by seismicity and soil subsidence. Tectonic seismicity is a safety hazard for masonry structures, whereas low-magnitude induced seismicity can be detrimental to their durability due to the accumulation of light damage. This is particularly true in the case of unreinforced masonry. Therefore, the development of models for the accurate prediction of both damage initiation and force capacity for masonry elements and structures is necessary. In this study, a method was developed based on analytical modeling for the prediction of the damage initiation mode and capacity of stand-alone masonry piers; the model was then expanded through a modular approach to masonry walls with asymmetric openings. The models account for all potential damage and failure modes for in-plane loaded walls. The stand-alone piers model is applicable to all types of masonry construction. The model for walls with openings can be applied as is to simple buildings but can also be extended to more complex structures with simple modifications. Model results were compared with numerous experimental cases and exhibited very good accuracy.

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Due to the increase of induced seismic activities in the Groningen area (north part of the Netherlands), the assessment of low-rise residential buildings with slender façade piers became of relevance. In this framework, the in-plane response of slender walls made of calcium silicate (CS) brick and element masonry is investigated in this paper. In-plane tests on full-scale masonry walls are presented along with a summary of an extensive material testing campaign. Despite the slenderness of the walls, uncommon for earthquake prone regions, the walls show a high ductility and displacement capacity typical of walls failing in rocking. Nevertheless, the finally brittle failure of CS element masonry walls is unfavourable with respect to the more gradual softening failure behaviour of CS brick masonry wall. This brittle failure may be related to the large size of the elements, 40 times bigger than the bricks, which promoted the faster development of splitting cracks in the units.

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The effect of mortar and brick properties on the growth of ivy-leaved toadflax (Cymbalaria muralis) and yellow corydalis (Pseudofumaria lutea) has been investigated in laboratory. Different mortar compositions were designed and tested in combination with two different bricks. Highly porous bricks and mortars showed good bioreceptivity; mortars with lime-trass and, in lower extent, those with natural hydraulic lime binder, gave the best results in terms of bioreceptivity. The addition of vermiculite to the mortar was beneficial for plant growth. The brick-mortar combinations most favourable for plant growth were those with estimated low compressive and flexural bond strength values. Proposals are advanced for obtaining a compromise between mechanical strength and bioreceptivity.

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