Rubble Masonry Research Articles

Grociana piccola: a rare example of Republican military fortifications in Italy

AbstractRecent investigations at Grociana piccola, a site in northeastern Italy consisting of two sub-rectangular fortifications, offer the rare opportunity to investigate Early Roman military architecture outside the Iberian peninsula. Excavations have revealed an inner rubble masonry rampart dated to the 2nd c. BCE by associated pottery, mainly amphora remains. This date suggests that the fortification was in use during the first Roman conquest and/or later campaigns of the 2nd c. BCE, providing one of the earliest and smallest examples of a military fort. The fort's ramparts were built using the same building technique as much larger 2nd-c. BCE military camps. Another trench uncovered the northeastern corner of the outer rampart and a probable tower or artillery platform which can be connected to a temporary camp built during the mid-1st c. BCE.

Study on ecological adaptability construction characteristics of residential buildings in Kangba area, Tibet, China.

Located in the southwest of the Qinghai-Tibet Plateau, Tibet is characterized by high cold, high radiation, and large differences in temperature between day and night. Tibetan residential buildings are famous for adapting to the harsh ecological environment and maintaining durability. Based on the residential buildings in Tibet, this paper extracts the technical process and color decoration culture in the construction process in order to adapt to the harsh natural environment. This paper first analyzed the four ecological construction modes of Tibetan residential buildings, analyzed the interior layout characteristics and cultural customs connotation, and introduced the architectural decoration characteristics and decorative color painting. The results show that the ramming type of adobe mainly includes the selection of building foundation, wall laying, floor and roof construction and so on, and its insulation effect is better. The rubble masonry type mainly adopts irregular gneiss, supplemented by clay, which has strong compressive capacity. Logs dry type using log masonry, heat preservation. and shock resistance is better. Concrete-infilled wall frame is composed of horizontal and vertical load-bearing system, which has stronger seismic performance. Tibetan residential buildings generally have two or three floors. The first floor is the enclosure and sundry room, the second floor is the rest place, and the third floor is the Sutra hall and sun terrace. The overall outdoor color of Kangba Tibetan buildings is mainly red and black, while the indoor color is mainly blue and red, with wood carvings and furniture. The layout of Tibetan villages can be divided into centripetal layout and scattered layout. Tibetan residential buildings provide a new sustainable development direction for the current global urbanization process at the expense of the ecological environment. It can alleviate the crisis of global resource shortage, climate warming, and biodiversity degradation.

Assessing the life cycle study of alternative earth-retaining walls from an environmental and economic viewpoint.

This research aims to assess the sustainability of the most common earth-retaining walls (Gravity Walls and Cantilever Walls) in terms of environmental impacts, economic issues, and their combination. Gravity walls observed in this study consist of Gabion Wall, Crib Wall, and Rubble Masonry Wall, while Cantilever Walls include Reinforced Concrete Wall. Six different criteria were taken into account, including global warming potential, fossil depletion potential, eutrophication potential, acidification potential, human toxicity potential, and cost. To achieve the aim of this study, life cycle assessments, life cycle costs, and multi-criteria decision-making methods were implemented. The results showed that the most environmental-friendly option among all alternatives was the Gabion Wall, followed by the Rubble Masonry Wall. However, in terms of economic aspects, the Cantilever Concrete Wall was the best option, costing about 17% less than the Gabion Wall. On the other hand, the results of multi-criteria decision-making showed that the Gabion Wall was the most sustainable choice. This study addressed the research gap by carrying out a sustainability assessment of different retaining walls while considering cost and environmental impacts at the same time.

Mechanical characterization of historical rubble stone masonry and its correlation with the masonry quality assessment

The paper presents a study on the mechanical characterization of eight rubble stone masonry walls from different structures of a Portuguese monument and on the assessment of their quality using the Masonry Quality Index (MQI) and the Italian Building Code Commentary (IBCC 2019). Rebound hammer tests were used to evaluate the quality of stone units and mortar joints, and flat-jack tests to assess the mechanical properties of masonry walls. The results allowed to propose new quantitative criteria to rate the quality of mortars and stones in MQI and to support the decision of applying the multiplication factor concerning the quality of mortars in IBCC 2019 methodology.Image processing was used to quantify several features of masonry walls and introduce new quantitative criteria on MQI. The results identified the amount of mortar, the mortar quality, the shape features of stone units and the horizontal alignment of joints as key parameters in the mechanical resistance of rubble masonry made of irregular hard stone and lime-based mortars. The mechanical properties obtained by IBCC 2019, MQI and double flat-jacks tests showed good correlations, highlighting the advantages that come from the quality assessment of masonry to estimate masonry mechanical properties.

Pull-out behavior of twisted steel connectors employed in masonry: The influence of the substrate

It is well known that multi-leaf walls, cavity walls as well as rubble masonry are prone to brittle collapse mechanism due to weak transverse connections. Twisted steel bars are widely used to strengthen such kind of masonry buildings, in particular to improve the transverse connection between different structural elements.Due to the shape of the twisted bar, the connector works as a self-threading screw, anchoring to the substrate material without any binder. The effectiveness of such technique mainly relies on the bond between the bar and the substrate, which relies on mechanical interlocking and friction mechanisms.In this paper, an experimental study on the pull-out behavior of twisted steel connectors inserted in units of different materials (bricks and stones) that can be commonly found in existing masonry buildings is presented. Mechanical and microstructural characterization of the substrate materials was conducted to investigate the influence of some key parameters (compressive strength, tensile strength, elastic modulus as well as abrasion resistance) on the pull-off load of the connector. To get a preliminary insight on the structural behavior of such connectors in presence of different loading regimes, the bars were also subjected to two cycles of unloading/reloading. Additionally, a 3D scanner was employed to geometrically characterize the inner surface of the hole left by the bar after its extraction. Results showed that among the different mechanical and microstructural parameters investigated, the substrate compressive strength plays a key role in the pull-out behavior of the connectors.

Applying multi-criteria decision-making on alternatives for earth-retaining walls: LCA, LCC, and S-LCA

The aim of this research is to assess the sustainability performance of different concrete and stone walls being used in residential buildings in Malaysia in terms of environmental issues, economic concerns, and social aspects. The concrete walls consist of crib wall (CW), cantilever reinforced concrete wall (CRCW), and keystone wall (KW), while stone walls include gabion wall (GW) and rubble masonry wall (RMW). Four different assessment criteria such as global warming potential (GWP), ozone layer depletion (OLD), cost present value (CPV), and social impacts (SI) were considered. In this study, life cycle assessment (LCA) was conducted to evaluate the considered walls based on individual criteria of GWP and OLD, while life cycle cost (LCC) and social life cycle assessment (S-LCA) were performed based on CPV and SI, respectively. In S-LCA, three main social indicators such as workers, local community, and society were taken into account. Then, a multi-criteria decision-analysis (MCDA) approach is implemented to assess and prioritize alternative walls, which is resulted from LCA, LCC, and S-LCA, by considering combination of abovementioned criteria. The primary results of LCA for GWP criterion shows that the GW and RMW are the best options with respective emissions of 12784 KG CO2eq and 20020 KG CO2eq. On the other hand, the result for OLD indicates that the best alternatives are GW and RMW with respective emissions of 178.99 CFC-11 eq and 224.88 CFC-11 eq. The results of LCC declare that RCW is the best option by 595600 MYR which is 14% less than the second-best option (RMW). The S-LCA results show that the CW is the best option with 10% better than the second option (KW). The MCDA results revealed that the sustainability performance of the GW was the highest among alternatives followed by RWW, RCW, KW, and CW. The presented approach in this research has been successfully applied on a case study. It provides valuable insight on the assessment of earth-retaining systems assisting decision makers in prioritizing and selecting the most sustainable retaining walls to be used in residential buildings in Malaysia and other countries with similar climate conditions.

Three-dimensional discrete element modelling of rubble masonry structures from dense point clouds

This paper presents a framework for the three-dimensional structural analysis of full scale, geometrically complex rubble masonry structures from point clouds generated from Structure-from-Motion photogrammetry or terrestrial laser scanning. According to the method, a point-based voxelization algorithm was adopted, whereby a dense point cloud was down-sampled into equidistant points, bypassing the need for conventional intensive processes, such as watertight mesh conversion, to obtain the geometric model of the rubble masonry for structural analysis. The geometry of the rubble masonry structure was represented by a sum of hexahedral rigid blocks (voxels). The proposed “point cloud to structural analysis” framework was implemented to assess the structural stability of the southwest leaning tower of Caerphilly Castle in Wales, UK. Simulations were performed with the three- dimensional computational software 3DEC, based on the Discrete Element Method (DEM) of analysis. Each voxel of the rubble masonry was represented as a rigid, distinct block while mortar joints were modelled as zero thickness interfaces which can open and close depending on the magnitude and direction of the stresses applied to them. The potential of the automated procedure herein proposed has been demonstrated to quantitatively assess the three-dimensional mechanical behaviour rubble masonry structures and provide valuable information to asset owners in relation to the structural health condition of assets in their care.

3D homogenized limit analysis of non-periodic multi-leaf masonry walls

This paper presents a 3D model aiming at investigating the out-of-plane collapse behavior of multi-leaf non-periodic masonry walls. These structural elements are widely employed in several constructions that are part of the European architectural heritage, but have been seldom addressed in the available literature due to their natural complexity and uniqueness. Specifically, the model here proposed allows a quick assessment of the out-of-plane collapse behavior of multi-leaf walls through the extraction of out-of-plane homogenized failure surfaces, acting as macroscopic failure criteria in bending and torsion. These failure surfaces are obtained after solving a standard-form linear programming problem written into a MATLAB script, which expresses a limit analysis problem pairing the well-established upper bound theorem and a homogenization approach. A twofold numerical application is performed by investigating a rubble masonry three-leaf wall and a quasi-regular three-leaf wall; in the latter case study, the influence of the rate of transversal interconnection between the outer wythes of the wall is also investigated. The results show that the presence of two different masonry bonds in the outer wythes entails some changes in the out-of-plane collapse behavior of the two case studies: namely, the out-of-plane response of the wall both under flexural and torsional actions is increased for the rubble masonry three-leaf wall, whereas it is decreased for the quasi-regular three-leaf wall. Moreover, in the latter case it is once more confirmed that a good transversal interconnection between the outer wythes - usually brought by the presence of transversal bricks – has beneficial effects on its out-of-plane collapse behavior, which are displayed both by the out-of-plane homogenized failure surfaces and deformed shapes at collapse.

The renewal of the bearing capacity of rubble masonry by the composite solution

The possibility of the involving nanotubes as modifiers of the structure of the composite solutions to ensure the safety and durability of the rubble foundation is considered. The greater efficiency of injection can be achieved by integration the composite solutions into the foundation body. The various compounds are integrated into the composite’s composition, in particular nano-additives in order to modify the structure of the cement stone, increase the strength properties, increase its crack resistance, change the dynamic viscosity. The strength indicators of the produced composition with the involved boehmite were measured according to GOST methods, and ultrasound analysis was performed. The bentonite clay in a composite solution increases its plasticity and viscosity, maintains resistance to the delamination. The oxides in clay are the basis for hydraulic binders and have a chemical affinity with cement. It was found that most of the particles in P2T2A bentonite don’t exceed 10 microns. The addition of the boehmite to the composite system can lead to more dense packing of a cement stone. It’s achieved by filling the voids formed during the formation of a cement stone. The composite solution modified by the boehmite has increased the strength and continuity of the structure.

CHARACTERIZATION OF HISTORICAL MASONRY MORTAR FROM SITES DAMAGED DURING THE CENTRAL ITALY 2016-2017 SEISMIC SEQUENCE: THE CASE STUDY OF ARQUATA DEL TRONTO

Mortar quality is a fundamental parameter to take into account when studying the structural behavior of masonry, especially under seismic actions. Separation between the leaves of rubble masonry can occur, inducing the partial or total collapse of the construction. A good quality mortar is essential to delay/prevent the separation of leaves, but often, especially in ancient building with a cultural value, mortars have low binder capabilities. The paper presents an experimental investigation on mortar specimens taken from buildings of a little municipality in Marche region, Arquata del Tronto, heavily damaged by recent earthquakes in Central Italy (2016-2017). Both diagnostic techniques as X-Ray diffraction, Fourier-Transform infrared spectroscopy and calcimetry, and mechanical test as compression tests were carried out in order to correlate the obtained values with the performance of the original masonry.

Automatic segmentation of 3D point clouds of rubble masonry walls, and its application to building surveying, repair and maintenance

Abstract Changing climatic conditions are contributing to faster deterioration of building fabric. Increasing number of heavy rainfall events can particularly affect historic and Cultural Heritage (CH) buildings. These evolving and uncertain circumstances demand more frequent survey of building fabric to ensure satisfactory repair and maintenance. However, traditional fabric surveys have been shown to lack efficiency, accuracy and objectivity, hindering essential repair operations. The recent development of reality capture technologies, together with the development of algorithms to effectively process the acquired data, offers the promise of transformation of surveying methods. This paper presents an original algorithm for automatic segmentation of individual masonry units and mortar regions in digitised rubble stone constructions, using geometrical and colour data acquired by Terrestrial Laser Scanning (TLS) devices. The algorithm is based on the 2D Continuous Wavelet Transform (CWT), and uniquely it does not require the wall to be flat or plumb. This characteristic is important because historic structures, in particular, commonly present non-negligible levels of bow, waviness and out-of-verticality. The method is validated through experiments undertaken using data from two relevant and highly significant Scottish CH buildings. The value of such segmentation to building surveying and maintenance regimes is also further demonstrated with application in automated and accurate measurement of mortar recess and pinning. Overall, the results demonstrate the value of the automatic segmentation of masonry units towards more comprehensive and accurate surveys.

Push-over analysis of a rubble full-scale masonry wall reinforced with stainless steel ribbons

Many strengthening techniques for masonry structures were thoroughly investigated in several researches. The in plane shear behaviour of an ancient full-scale masonry wall, characterized by an opening that is strengthened by the lintel in the arch form, retrofitted with an innovative system constituted by three-dimensional pre-tensioned stainless steel ribbons, was previously tested. In this paper the double flat-jack test results were analyzed and design of the retrofitting system was detailed. The collapse mechanisms in terms of flexural bending and shear, both sliding and diagonal tension, as function of the compression stress level were taken into account. The arrangement of the ribbons was established on the base of an equivalent frame model of the masonry wall, investigating the flexural and shear strength of each element (piers and spandrel). Moreover, the numerical results of the response behaviour modelling of the unreinforced and reinforced masonry wall were presented. The analytical modelling of the wall was accomplished suitably applying the methods of the disturbed stress field model, successfully used for reinforced concrete elements. The numerical results provided a good prediction of the response behaviour of the wall, both in terms of load–displacement curve and crack pattern at failure.

Structural window frame for in-plane seismic strengthening of masonry wall buildings

ABSTRACT This article describes the initial development stages of a structural window frame system for the in-plane seismic strengthening of load-bearing masonry wall buildings. The solution implemented ultimately aims to stiffen (and strengthen) the opening such that the wall would behave as if there were no opening. This is achieved by installing a structural steel window frame composed of a profile forming a closed ring inside the opening, properly tied to the surrounding masonry wall. The strengthening concept was validated by means of a series of tests in which two approximately 1:2 geometric scale physical specimens with a similar central opening were cyclically tested to failure. One of these specimens (UMW) was unreinforced whereas the other (RMW) had a UPN profile internal ring tied at the corners and at mid-length and mid-height of the opening by means of threaded rods with chemical anchors. The material of these walls was common rubble masonry with lime-based mortar and render. The experimental results show that the strengthening technique leads to a significant increase in strength and in-plane deformation capacity, as well as in terms of cumulative dissipated energy at collapse. Nonlinear numerical specimens of the tested walls were also developed and calibrated.

Determining strength of rubble masonry of bridges’ supports being in operation

The purpose of this article is to create a methodology for determining the design strength of rubble masonry of bridge supports meeting the modern safety requirements for transport structures. The article contains data on the use of the rubble masonry in solid supports of railway bridges. Development of methodology of determining the permissible stresses on the rubble masonry, and the practice of applying the design strength of the rubble masonry in regulatory documents are considered. Analysis of the research works is carried out, according to which the design strength of the rubble masonry of solid supports is determined when calculating the load-bearing capacity. The experimental data of European scientists in the field of determining the strength characteristics of stone masonries are considered. A domestic method for determining the design values of strength characteristics for building materials used in transport construction is presented. The main deficiencies of the existing method for determining the design strength of rubble masonry are defined and suggestions are made for its clarification. The article concludes with the formulation of tasks required to be solved for clarification of strength characteristics of the operated railway supports made of rubble masonry.

Rubble masonry response under cyclic actions: experimental tests and theoretical models

The presented research investigates the problem of assessing the seismic resistance of rubble masonry walls to normal lateral forces. Published research on this topic is sparse and reliable data on existing rubble masonry are still lacking. In particular, further studies are required when disconnected rubble walls are rocking out-of-plane with fully cracked sections. This subject was addressed by on-site experimental tests of full-scale elements. The selected case studies are located in Italy, in regions prone to earthquakes, which were sites of devastating seismic sequences in the past. Numerical predictions of the overturning forces and displacements required to cause failures of isolated walls are compared with the results of the quasi-static experiments using force-equilibrium formulations. An improvement in the existing procedures to evaluate masonry vulnerability under seismic loads is presented along with recommendations for the selection of an appropriate level of degradation, especially for rubble works.

Rubble masonry response under cyclic actions: experimental tests and theoretical models

Rubble masonry response under cyclic actions: experimental tests and theoretical models

Discrete element modeling of masonry structures: Validation and application

The failure mechanism and maximum collapse load of masonry structures may change significantly under static and dynamic excitations depending on their internal arrangement and material properties. Hence, it is important to understand correctly the nonlinear behavior of masonry structures in order to adequately assess their safety and propose efficient strengthening measures, especially for historical constructions. The discrete element method (DEM) can play an important role in these studies. This paper discusses possible collapse mechanisms and provides a set of parametric analyses by considering the influence of material properties and cross section morphologies on the out of plane strength of masonry walls. Detailed modeling of masonry structures may affect their mechanical strength and displacement capacity. In particular, the structural behavior of stacked and rubble masonry walls, portal frames, simple combinations of masonry piers and arches, and a real structure is discussed using DEM. It is further demonstrated that this structural analysis tool allows obtaining excellent results in the description of the nonlinear behavior of masonry structures.

Mechanical Characterization of Masonry Walls With Flat-Jack Tests

The results from an experimental campaign on old masonry buildings from Lisbon are presented and discussed. The tests aim at the evaluation of the masonry deformability properties in compression and the shear strength parameters based on flat-jack testing technique. Tests were carried out in both internal brick masonry walls and external rubble limestone masonry walls. The evaluation of the shear parameters was done according to a new testing technique—shear tests onmasonry walls with flat-jacks—involvingmore than one masonry unit. One of the goals is the calibration and development of this testing technique and to show its first application to the test of rubble stone masonry walls. For that, the experimental technique is fully explained in this paper, and the results of some in situ tests are used to discuss the calibration procedure. Because of the characteristics of the walls, in particular, the great heterogeneity and thickness of the external masonry walls, the application of the flat-jack testing technique involved some uncertainties that are described and debated in this work.

Investigation on the 2010 Schola Armaturarum collapse in Pompeii

The headquarters building of a military association named Schola Armaturarum and located in the archaeological site of Pompeii, Italy, suddenly collapsed on November 6, 2010. The structure was almost totally made of rubble masonry walls, some of which having important frescoes, and was partially reconstructed after the Second World War with a new roof composed of reinforced concrete ring beams and one-way joists. As the collapse induced a dramatic loss to the worldwide cultural heritage, the author was appointed by Judicial Authority to investigate the causes and responsibilities of that accident. This paper describes the phases of the investigation, providing detailed information on the structural configuration after collapse and the most probable sequence of damage. The discussion is supported by photos, drawings, and data from site surveys. The main goal of this paper is to shed some light on what happened in Pompeii and to present procedures and techniques used during the investigation.

Connection systems between composite sandwich floor panels and load-bearing walls for building rehabilitation

The use of advanced composites for building rehabilitation presents several advantages when compared with traditional construction materials. When degraded building floors need to be replaced, composite sandwich panels are a potentially interesting solution, namely for buildings with load-bearing rubble masonry walls. In this paper, connection systems between composite sandwich floors and load-bearing walls are proposed, and their behaviour under vertical loading is investigated. The systems comprise steel angles anchored to the walls, serving as main supports of the sandwich panels, which are then adhesively bonded and/or bolted to the angles. These connection systems are experimentally assessed using sandwich panels made of glass-fibre reinforced polymer (GFRP) face sheets and cores of either polyurethane (PUR) foam or balsa wood, by means of flexural tests on cantilevers, which are also simulated using non-linear finite element models. The structural response of the connection systems is determined, including the rotational stiffness conferred to the floors, the strength and the failure modes. Moment–rotation relationships are obtained for the connection systems and sandwich panel types considered, which provide a wide range of rotational stiffness values, from 60 to 10,856kNm/rad per unit width (m). These are then used to analytically estimate the short-term mid-span deflections of floors with semi-rigid connections and spans ranging between 2m and 5m. It is shown that some of the proposed connections allow significant floor stiffness increases compared with simply supported conditions, with reductions in total mid-span deflection of up to 65% being achieved for a span of 4m. The results obtained for the proposed connections highlight (i) their potential benefits for fulfilling serviceability limit states and (ii) the importance of considering an adequate structural model when designing sandwich floor panels.