Soil settlements are one of the causes of damage to historic masonry buildings, together with mechanical properties deterioration and environmental actions. The size of the settlements is often unknown, as most often measurements in time are not available. The crack pattern provides information on the members where settlements occur, and monitoring can measure the rate in time. The aim of the paper is structural analysis for the assessment of the piers and foundations and decision making for strengthening works. A case study of the arched bays on the interior walls of a historic church is chosen. A limit analysis model with rigid blocks and interfaces is set up; this includes as variables the masonry strength properties for shear friction and cohesion. Numerical crack predictions are compared to crack pattern surveys, to find the material properties with the effects closest to the observations. The results of the model are then compared to a nonlinear finite element model, as a verification of the results of the simplified rigid block analysis. The limit analysis model is used in addition to generate results on pillar reactions in relation to different settlement patterns. Finally, a machine learning algorithm is used to establish a relation amongst these quantities, to be used in the design of foundation strengthening.

A comparison between limit analysis and a nonlinear finite element approach is proposed to assess the stability of masonry arches subjected to both vertical and horizontal loads. The limit analysis code discretizes the arch by means of infinitely resistant voussoirs and mortar joints reduced to interfaces. It is based on the lower bound theorem and is mathematically formulated using linear programming, where the objective function to maximize is the collapse multiplier, equality constraints are represented by equilibrium equations and inequalities rely on the material admissibility imposed on mortar joints. The finite element-based method discretizes the arch in a heterogeneous fashion, where voussoirs are meshed with classic four-node elastic elements in plane strain and joints are modelled by means of orthotropic shell elements coupled with elastic perfectly fragile cutoff bars. In this way the nonlinearities are handled adopting the simplest finite element available in any commercial software, and in particular the cutoff bars are displayed perpendicular with respect to the joint allowing the failure of the structure in mode I. To benchmark the proposed models, an arch of the main nave of the San Bassiano Church (Pizzighettone, northern Italy) is analyzed. After a deep analysis of the results obtained in terms of failure mechanism and global behavior, the efficacy and the robustness of both approaches proposed are assessed.

Construction, damage and conservation are intertwined in the life of Milan Cathedral. The evolution of the structural system and the restorations carried out throughout the centuries are described with a particular focus on the case study of the tiburio, with the supporting pillars; these underwent dramatic damage in the XX century, close to collapse, followed by repair and strengthening interventions and the rebirth of the Cathedral. This same part of the monument is currently the object of the latest ongoing restoration interventions, related to service state conditions. The organization of the Veneranda Fabbrica del Duomo di Milano is outlined by the worksite management. The inspection and maintenance are set in relation to the technical activities of other institutions. The aim of all operations for the preservation of the structural safety and cultural identity of the monument up to the present day, is discussed. A discussion is provided for monumental heritage buildings, encompassing structural assessment, reliability evaluation, damage survey, maintenance and repair operations, in relation to the underlying social values.

Within the scope of capacity assessment of corroded structures, Model Code 2020 provides a model for the evaluation of shear resistance of corroded reinforced concrete (RC) members. The verification of these provisions is carried out here against a database selected from laboratory tests on slender beams with shear failure. The corrosion in the tests includes both localized and generalized attacks. Most tests used accelerated corrosion; the model results are also compared to those obtained for the very few natural corrosion tests available. The formulation is discussed and the application shown. The results show a varying performance, depending on the corrosion attack. The causes of these results are discussed. The application of the model for in situ conditions is discussed. Conclusions are drawn on the applications and needed future research.

This paper presents the RecycleSlab research project, where a largescale experimental test is being prepared. The specimen is a two-story building with flat slabs with drop panels, cast with concrete made with coarse recycled concrete aggregates (CRCAC), and will be tested under combined gravity and lateral loads. In this paper, the test setup is described in terms of structural design, test protocol, specimen dimensions and materials characterization. In addition, the research project will explore the effectiveness of innovative digital surveying techniques for the assessment of seismic damage in flat slab structures. For that purpose, the specimen will be measured in 3D before and after testing using laser scan technology with the aim of creating digital models. The testing of the fullscale two-story flat slab structure will be carried out at the ELSA laboratory of the European Commission's Joint Research Centre.

Jacques Heyman’s 1966 article “The Stone Skeleton” has been influential in the assessment of masonry arches in general, including masonry bridges and gothic architecture. Heyman’s article relies on limiting assumptions about arch behavior, and concludes that an arch can be declared stable based on the location of a statically admissible thrust line within the arch. In the following commentary, we assess the validity of the assumptions made by Heyman and the uses that have been made of his application of the lower bound theorem of plasticity. We conclude that Heyman’s methods have enduring value, but that the user needs to recognize the limitations of the assumptions made and the limits on the validity of conclusions imposed by these assumptions.

Masonry polygonal domes are parts of several historic monuments and masonry buildings. The analysis of polygonal domes with a static approach is here presented, considering the structure made of vault cells and ribs. The vaults are portions of a cylindrical surface with single curvature in the meridian direction, and translation of the generatrix curve in the direction of the cylinder axis. The system is divided into rigid elements with interfaces. The first part of the work regards the geometry of the rigid elements, in particular the angles that characterize the shape of these. Then the equilibrium equations applied to every element are presented, with a procedure to calculate the membrane response for the self-weight in a non-redundant system, under symmetry conditions. The sum of the solution for the vaults is combined with effects of the weight of ribs and radial walls. The use of the equilibrium solution for pointed domes, domes with a lantern and oculus or additional load to the dome self-weight is shown. A limit analysis static approach is formulated calculating the maximum load relative to the equilibrium of the rigid elements considering the interfaces tensile strength and limited cohesion and friction for the shear resistance.

This paper presents a state-of-art regarding the punching of flat slabs made with coarse recycled concrete aggregate concrete (CRCAC). Punching shear is a phenomenon that occurs in reinforced concrete slabs when concentrated loads are applied near a column or other support. It refers to the failure mechanism where the concrete reaches shear failure at a critical section around the column. CRCAC is a structural material that conforms with circular economy concepts, but its design for punching using current formulae may be unsafe due to the lower strength of the concrete that can be caused by the shape or the surface cleanness of the recycled aggregates when compared with the natural ones. The results highlight the need for further research on this area, since the available experimental results are few and mainly from tests with thin slab specimens. Since the punching phenomenon is dependent on the scale effect, it is mandatory to have more results for slabs with representative thickness. The applicability of the models for punching resistance in EC2, ACI318-19, and the upcoming second generation of EC2 was also investigated. These codes can produce safe estimates for CRCAC slabs. However, it was found that the second generation of EC2 is less conservative than the other models.

The life of Milan Cathedral is described with the evolution of the structural system and the restorations carried out throughout the centuries. The organization of the Veneranda Fabbrica del Duomo di Milano is outlined, with the latest restoration interventions. The case study of the construction and restorations of the Tiburio with its supporting pillars is analyzed, from the initial design to the dramatic damage in the 20th century. The rebirth of the Cathedral was the fruit of restorations preserving the structural identity of the monument up to the present. The conclusions address the study of damage and maintenance and repair operations of monumental heritage buildings within a life cycle perspective, in relation to the underlying societal values.

Strengthening of flat slab-column connections to resist imposed lateral drifts is often required for older reinforced concrete structures in which the flat slabs were typically designed to resist gravity load only or have been designed for less stringent requirements. The complex stress state around the columns means that strong experimental evidence is required for the repair and strengthening techniques to be adopted with confidence in practice. Although a significant amount of research has been devoted to strengthening of slab-column connections, a series of limitations still remain. A thorough literature review revealed that only relatively thin and isolated specimens have been tested under seismic-type loading and realistic strengthening scenarios. To overcome these limitations, a full-scale two-story flat slab building specimen was tested at the European Commission's Joint Research Centre - ELSA Laboratory in Ispra, Italy. This paper describes and analyzes the results obtained from the last of a series of phases, on repaired and strengthened internal and external slab-column connections using post-installed bolts. Compared with previous tests, the full-scale building specimen has a thicker slab (200 mm), realistic slab continuity conditions and the connections were strengthened after they suffered damage from gravity loading and previous lateral loading phases. The results show that post-installed bolts are efficient even under the described conditions (i.e. damaged and repaired specimens with realistic thickness), and punching shear failure was prevented in the strengthened connections.

As an outcome of a recent European research project, the modelling of the response of flat slab structures for seismic and cyclic loading was the object of a blind competition. No other blind tests are available in the literature on this topic. The test results concern a full-scale, two-storey, three-by two bay reinforced concrete flat slab frame. The seismic tests were carried out using a hybrid pseudo-dynamic test up to the ULS design excitation. The cyclic test reached a drift capacity of 2.5% and 6% in two concatenated tests. A synthesis of the models of three participants is provided, with one 3D NLFE (Nonlinear finite element) models and two slab and frame models. The CSCT (Critical Shear Crack Theory) model included in the fib MC2010 was adopted in the two latter to predict punching failure. The results are presented and discussed. Conclusions are drawn on research developments and practical approaches.

Frequently observed damage in historic masonry vaults has always given rise to concerns on their stabil-ity. The effect of present damage on masonry vaults structural response should be taken into considera-tion during structural analysis as it clearly affects its behavior.The aim is to propose a method to study the safety of vaults, setting up a finite element model with a limited number of discontinuities, based on the consideration of the vault construction and damage observation.A case study from Milan cathedral is adopted where damage is documented. A complex damage mechanism characterized by sliding of voussoirs and detachment of the rib from the web was docu-mented in the 1960s. The results show the possibility to analyze the evolution of the observed mecha-nism and to evaluate numerically its safety in function of the documented settlements.Technical applications of the present work include interpretations of the causes of observed damage, estimation of the level of settlements based on observed damage, and numerical evaluation of the safety of the current mechanical state.(c) 2023 Consiglio Nazionale delle Ricerche (CNR). Published by Elsevier Masson SAS. All rights reserved.

An experimental campaign carried out on prestressed bridge beams corroded in a marine environment is analyzed in order to understand the failure modes related to the deterioration phenomena and setup models for capacity assessment. Three main failures modes were identified: shear in the web, shear failure in corroded zones with prestress loss and flexural failure for corroded strands in tension; this last mode becomes dominant for increasing corrosion. A truss model was used for flexure and shear resistance, considering the presence of both bottom pretensioned strands breaks and a draped post‐tensioned tendon cuts. The development of new anchorage at the sides of the damaged zones of the strands was modeled. Corrosion effects are modeled reducing the reinforcement cross‐section and bond, and modifying the prestressing distribution and the truss angle for shear. The accuracy of the model predictions relies on the corroded cross section loss input. In the light of the comparison of test and models results a methodology setup in the literature is here extended with scenarios considering higher levels of corrosion damage.

Extending the life of historic masonry bridges frequently requires strengthening of arches showing damage or limited load bearing capacity. The "Reinforced Arch Method" (RAM) uses a cable on the extrados and/or the intrados, prestressing the blocks. A recent application is the xv century bridge (Ponte Antico) in Omegna (Verbania, IT) along a route of an historic quarrying district. Originally formed of two stone arches, today a damaged structure with one arch remains after a 20th century collapse. The structure is modelled numerically and assessed in the present condition and with the strengthening by four extrados cables, comparing the results of a linear elastic finite element model and limit state verifications, and static limit analyses with optimization of the thrust line and limit load. The strengthening and the intervention proposed for the collapsed arch are discussed, in relation to their new life as a footbridge on a touristic route.

A model based on the kinematic approach of limit analysis is here described and applied to analyze barrel arch bridges up to collapse. The approach extends concepts of the Discontinuity Layout Optimization (DLO), formulated by Smith and Gilbert (2007), applied for two-dimensional geotechnical, slabs and arch bridges to the three dimensional geometry and structural response of a cylindrical shell. This is done by describing the barrel structure with nodes connected to each other by the possible fracture lines and imposing compatibility and associated flow rules for rotation, sliding and twist. The simplified model of a bridge is formulated according to the component structural analysis proposed by the Italian CNR DT213/215. Experiments on masonry barrels up to collapse are considered as benchmark for the application of the model, including straight and skew barrels.