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

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

Regeneration and Structural Strengthening of the Fortress of Arnara,Latium, Italy

The fortress of Arnara is a small castle in a high seismic hazard zone in Latium, Italy, which represents a landmark for the local population. It was chosen as a case study, being a perfect example of Middle Age fortress, well preserved during the centuries despite some strong earthquakes damaged it in the past. The project presented here is a significant example of how the interest of a community to regenerate an ancient structure for its re-use can pave the way to a complete structural strengthening, which includes anti-seismic concepts aiming at retrofitting the ancient fortress walls. The overall project joins architectural and structural solutions. The architectural solution aims at a functional reconfiguration of the spaces, so to attract the locals to reuse it, while at the same time highlighting some valuable architectural features of the fortress. The structural solution aims at improving the seismic resistance of the masonry walls with a structural intervention that is respectful and integrates with the existing forms. This was achieved by means of a tenso-structure that has the two-fold role of reconnecting the different portions of the structures and of endowing it with a distinctive architectural sign. This project demonstrates that rediscovery of architectural heritage can also be pursued by proposing a new use for these structures, following an appropriate regeneration strategy that must take into account the cultural features of the territory, being at the same time respectful of the past history of the buildings.     

Seismic vulnerability assessment of historic centers: description of a predictive method and application to the case study of scanno (Abruzzi,Italy)

ABSTRACT

In this article, a predictive model for the seismic vulnerability assessment of old Italian historic centers is presented through its direct application to a meaningful case study, the historic center of Scanno, in Abruzzi, Italy.

The proposed method is calibrated on the basis of the observations carried out on similar historic centers hit by the 2009 L’Aquila earthquake and is applied in order to provide likely damage scenarios by means of fragility curves. The method is based on the evaluation of a limited number of structural and typological parameters that can be obtained by simple and rapid inspections on buildings. In addition, it is conceived in order to provide useful information on the most effective anti-seismic strategies to be implemented on urban scale for pursuing a global mitigation of the seismic risk and for the application of suitable risk reduction policies.

The final aim of the article is to give an applicative vision of the method, by providing instructions on how to judge the features of the buildings that are influential on their seismic behavior, as well as by showing the potentiality of the method itself in providing likely damage scenarios, also with the support of GIS-based representations.     

Shaking table tests on a stone masonry building: modeling and identification of dynamic properties including soil-foundation-structure interaction

This article presents the identification of dynamic properties of a stone masonry building, followed by numerical simulation of its dynamic response accounting for soil-foundation-structure interaction. The first part regards numerical simulations of the earthquake response of a two-story building prototype with timber floors, made of three-leaf stone masonry without laces. This 1:2 scale prototype was tested on a shaking table in its as-built state and after strengthening, at the National Technical University of Athens. Afterward, the building prototype was modeled with flat shell elements and equivalent frames (common frames and macro-elements), for an investigation of its linear and nonlinear seismic response, assuming base fixity. Numerical results were compared to the experimental ones, which yielded conclusions on the considerations of each employed modeling strategy, as well as its efficiency and applicability. The second part considers the effect of soil-structure interaction using appropriately modified foundation stiffness values to account for the foundation soil flexibility. Comparison of the numerical results with and without SSI effects showed how the flexibility of the soil-foundation system and the soil-structure interaction modified the system’s modal characteristics and response within the elastic range, in terms of both seismic loads and deformations, and produced conclusions about its consequences on the overall structural stability.     

Application of Shape Memory Alloys in Historical Constructions

A device prototype, based on the superelastic properties of Shape Memory Alloys (SMAs), is proposed to enhance the thermal and seismic behavior of steel tie-rods. First, the thermal behavior of steel tie-rods with and without SMAs is presented based on the results of extensive experimental tests in thermal room. Next, the seismic performances of the proposed SMA system are discussed based on the results of a series of shaking table tests on a 1:4-scale timber roof truss model. In this article, the functioning principles of the proposed SMA-based device prototype are illustrated and the main aspects related to its implementation in practice are discussed in detail. Finally, a recent example of application of the proposed technology to a historic single-aisle church, realized in the 13th century in Brindisi (southern Italy), and equipped with inadequate and deteriorated steel tied rods, is shown.     

A Comparative Study on the Compressive Strength of Bricks from Different Historical Periods

The aim of this article is to present the results of compressive strength tests for bricks from different historical periods. The studies were conducted on hand-molded and mechanically formed bricks. The bricks that were used for the studies came from historical structures from the center of the royal city of Crakow. Compressive strength was determined on rectangular prisms and on cylinders cut out from bricks in various directions—anisotropy and shape effects were then analyzed.

?The basic aim of the conducted studies was to estimate the possibility of carrying out the strength tests on relatively small samples and re-calculating these results on normalized brick strength determined according to EN772–1. Based on the tests results, a range of correlation coefficient values for cylinder samples with diameters of 30 mm and 50 mm was given. It was indicated that for the tested historical bricks characterized by significant material non-homogeneity within the element and sensitivity to damages while cutting out the samples, correlation coefficients are higher than for bricks used contemporarily.

?The results of these studies are presented alongside the findings from existing studies on the compressive strength of bricks.     

Performance of Wall to Diaphragm Anchors for Use in Seismic Upgrade of Heritage Masonry Buildings

Performance of wall to diaphragm (WD) anchors in heritage unreinforced masonry (URM) buildings during the recent New Zealand earthquake series is commented on, detailing typical failure modes. Current building code provisions for the design of masonry anchors are discussed and overview of an associated experimental program investigating the effectiveness of a relatively new type of retrofit WD anchors is presented. A total of 40 anchors were tested for pull out capacity (POC), of which 30 were installed in salvaged heritage material assemblages and 10 were tested in-situ at a heritage URM building. The POC of anchors ranged from 13.01 kN to 23.12 kN when installed in a heritage URM wall and between 9.54 kN and 12.16 kN when driven from side into two consecutive floor joists of a heritage timber diaphragm. Investigated also were the effects of embedment length, installation quality, anchor location, condition of masonry, and condition of substrate materials on anchor performance.     

Material Characterization and Micro-Modeling of a Historic Brick Masonry Pillar

A masonry pillar composed of solid clay bricks, cement mortar and infill is extracted from a historical structure and tested in concentric compression. It is subjected to cyclic and monotonic loads up to compressive failure.

In parallel, samples are extracted from the pillar and are subjected to destructive tests. Non-destructive tests are performed on the pillar, as well. The properties of the constituent materials are critically examined and their role in the maximum load reached and the failure mode obtained are discussed.

Finally, a finite element micro-model of the pillar is used for the simulation of the pillar test. The influence of the existing damage on the pillar is investigated using the model, resulting in a fair approximation of the global Young’s modulus, maximum load and the failure mode.

Highlights

●?A brick masonry pillar extracted from a historical building is tested in compression.

●?Material samples extracted from the pillar are characterized by mechanical tests.

●?A finite element micro-model of the pillar is used for the simulation of the compressive test.

●?The effect of damage on the compressive strength of the pillar is numerically investigated.     

The Groin Vaults of St. John Hospital in Jerusalem: An Experimental Analysis on a Scale Model

The St. John Hospital is part of a larger complex of buildings known as the Hospitallers Quarter, located south of the Holy Sepulchre in Jerusalem. At present, the hospital looks like an irregular volume both in height and in plan; it is covered by ten groin vaults resting on very stocky pillars. Each vault is formed by intersecting double curvature surfaces. In order to verify the effectiveness of continuous carbon fiber reinforced polymer sheets reinforcement, bonded at the extrados of vaults, laboratory tests were carried out on a 1:5 scale model, built with materials and construction techniques similar to those of the real building. Experimental tests were performed on the unstrengthened and strengthened vault. The experimental results shown that the strengthening system is able to increase the collapse load of the vault, without substantial variation of the initial stiffness.     

Analytical Investigations of Traditional Masonry Mortars from Ancient City Walls Built during Ming and Qing Dynasties in China

With the development of China’s economy, the protection and conservation of ancient buildings were put on the agenda. However, the current understandings on Chinese traditional mortars are limited and rarely reported in the literature. In this article, the authors investigate seven ancient city wall sites built during the Ming and Qing dynasties (1368–1841 AD) in situ, and subsequently the laboratory analysis were carried out on the collected mortar samples. The characterizations of mortar samples were performed using digital microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), simultaneous thermal analysis (TG-DSC), as well as wet chemical analysis. The analytical results show that pure lime mortar was widely used in construction during the Ming and Qing dynasties, and it was also a common practice adding sticky rice soup into slaked lime to form sticky-rice lime mortar during preparations. This organic-inorganic composite material could effectively improve mechanical strength of the lime mortar. Moreover, it was first found that the sticky-rice lime mortar sample from Kaifeng ancient city wall contained very fine quartz aggregates, with an approximate binder/aggregate ratio of 1:1. The appearance of this type of mortar probably indicates a great development of Chinese traditional mortars during the mid-19th century.