Abstract: This work presents the investigation of the efficiency of different prestressing devices as a rehabilitation measure for the seismic risk mitigation of historical masonry towers. As a first phase, the seismic vulnerability of theoretical masonry towers was assessed by means of numerical models validated with information from the literature, observed damage and behavior of these structures due to passed earthquakes (crack pattern and failure mechanisms), and mainly taking into account the engineering experience. Afterwards, the validated models were rehabilitated with different prestressing devices; analyzing the results and concluding which device or the combination of them improved in a better way the seismic performance of the masonry towers. Finally, the methodology will be applied in two historical masonry towers located in seismic areas; the medieval tower “Torre Grossa” of San Gimignano, Italy, and one of the bell towers of the Cathedral of Colima, Mexico.
Abstract: This paper aims to present the design, strengthening and testing of full scale masonry walls and arches. The preservation of our cultural heritage is a really important topic. Majority of masonry structures are deteriorated because of ageing effects, load increments, movements at their foundations, etc. Because of this, retrofitting is needed. In order to afford this problem, a compatible and minimally invasive strengthening technique based on Textile Reinforced Mortar (TRM) is developed. The experimental campaign consists of the characterisation of the constitutive materials of the stone structures and the strengthening textile and mortar (TRM has been characterised by pure tensile tests). Furthermore, the influence of the different arrangements of the masonry and mortar type has been analysed by testing 24 masonry prisms. Finally, 12 full-scale stone arches have been erected, strengthened and tested. The purpose is to compare the mechanical behaviour up to failure of both unstrengthened and strengthened structures. During the tests the effectiveness of the technique has been proved being the ultimate load up to 21 times higher.
Abstract: Industrial masonry chimneys usually are considered as historical heritage since they remind the industrial revolution that took placed by the XIX century, shaping a particular landscape in many cities, what led many Town Halls to protect them as cultural heritage. In this work an assessment of the seismic vulnerability is performed to check the structural integrity according to a return period of 500 years. Detailed geometrical investigations took place and dynamic tests performed with the goal to obtain natural frequencies and structural damping using four seismic accelerometers at different heights and orientations. From the experimental results a numerical model has been calibrated adjusting numerical frequencies to match those experimentally obtained. Artificial accelerograms were generated specialized for the city of Valencia and the crack pattern was obtained corresponding to a return period of 500 years. After these analyses the model of the chimney was strengthened using strips of FRP and the calculations repeated to obtain the reinforced achieved regarding seismic vulnerability. Conclusions related to these calculations are outlined.
Abstract: For at least five hundred years, the majestic grange of St. Anne in Montauro (CZ) has been overlooking the wonderful gulf of Squillace, placed at the core of Calabrian Ionic Coast. Masonry ramparts size (more than 7 metres high and 1,60 wide at the basis) together with the massive presence of four angular towers immediately hit even an inattentive beholder. Unfortunately, the predominant presence of grange results damaged by a clearly visible crack outline, which turned a great part of surrounding wall into a perpendicular heap of huge masonry portions. They appear disconnected and sheer, so that some panel systems are already collapsed on the north-east side of the building, included many internal constructions such as the church. The serious damage is not only due to repeated seismic events of high magnitude, that systematically run over this zone of Calabria. This article will describe in detail the methodologies and techniques of its making safe, considering the seismic and geological risk of the zone.
Abstract: Worldwide, hurricanes or tropical cyclones cause immense damage and loss of life, yet we do not have a clear set of guidelines for improving the survivability of heritage structures. This paper synthesizes lessons learned in practice regarding appropriate assessment with discussion of vulnerability indicators, wind and storm surge forces and retrofit approaches
Abstract: Hasankeyf historic settlement area is one the most important sites in southeastern Anatolia which dates back to the 15th century. Zeynelbey Tomb is a distinct cylindrical structure has a height of 9.6 m and with double domes extending to an overall height of 16.5m; however, the outer dome suffers from multiple and large vertical tension cracks threatening the overall structural stability and safety of the structure. A preliminary visual inspection and structural evaluation using analytical modeling was carried out. The tension zones developing at the outer dome was determined using analytical simulations and causes of vertical tension cracks were elaborated. A general remedy of strengthening was developed to surround the dome using vertical ribs and horizontal post tensioning strands that are placed in three vertical layers. The deterministic analytical simulations using the horizontal post-tensioning have allowed finding the necessary amount of tension force in each horizontal strand to diminish the tensile stresses inside the dome and put the structure in a stable compression state. This paper describes the steps carried out for the assessment, evaluation, and retrofit studies, which might set an example to similar historic structures with comparable structural problems in the dome.
Abstract: The Trigonio tower, constructed in the 15th century for fortification reasons, is part of the city walls of the old town of Thessaloniki. The tower is a cylindrical masonry building and has been considered as part of the cultural heritage of humanity by the UNESCO World Heritage Committee. Today it presents some major damage to its load bearing system, including intense cracking, moisture damage and disintegration of mortar, bricks and stones. An extensive research study for the evaluation of the tower’s bearing capacity, as well as for the suggestion of efficient strengthening interventions was held, in order to effectively prolong its expected lifetime. To this purpose, refined analytical models of 3D finite elements have been formed and used for the estimation of the elastic and inelastic tower’s response to gravity and seismic loads. Results’ evaluation of several static and dynamic analyses showed that the tower’s stability is not at risk under the action of gravity loads in general, but it’s bearing capacity under strong seismic excitations is questionable, thus becoming obvious the necessity of strengthening interventions. An invertible intervention of strengthening the tower with proper sets of external pre-stressed steel rings was also examined. Linear (elastic) analyses showed that they cannot sufficiently evaluate the effectiveness of this strengthening process. Inelastic analyses, using material laws of Drucker-Prager’s type, showed that the use of prestressed steel rings can significantly reduce the plastic strains’ appearance and therefore the cracking in the masonry walls of the monument.
Abstract: The netlike cracks along the rebars at the bottom of concrete slabs as well as the circular cracks around the columns and beams were found in an underground park, which is a cast-in-site concrete frame. The building was about 300 m away from the sea.
The influencial factors which can cause rust of the rebars, such as concrete carbonization, chloride ion (Cl-1) content, and design & construction measures, were analyzed respectively. The in-site inspections and X-spectrum analysis of concrete specimens drilled from the R.C. members were conducted. The concrete carbonization depth and the concrete protection layer were also collected.
In order to find out the main influence factor, steps were carried out as following: at first, according to comparison with the data of calculation and inspection results, the formula for the partial carbonization depth was modified to be used at high humidity environment. Then, the weight ratio of Cl-1 in the drilled R.C. members was 0.02%~0.07% and was lower than the required index 0.1% set by department of construction of Shandong province (DBJ14-S6-2005). The thickness of the concrete protection layer was measured and found to be thinner than the standard set by DBJ14-S6-2005, so as the main reason was identified at last.
To ensure the safety and durability of the building, strengthening measures were brought forward with consideration of the results from both the theoretical calculation and the inspections. The rusted concrete protectionion layer was removed and the anti-rust reagent was brushed when the rusted rebar was cleansed by special machine which can meet the durability requirements. The carbonic fibres reinforcement polymers were stuck on the new concrete protection layer which can provided the bearing capacity. The measures can be a good reference for the same project.
Abstract: This paper presents the structural analysis and constructional method for the stabilization and strengthening of the foundation of the two entrance gates in Holy Shrine of Imam Reza (PBUH). The holy shrine of Imam Reza (PBUH) is a great complex in the city of Mashhad in Iran. It was founded nearly 1000 years ago and has developed and become extensive through the times. There are several entrances and wide courts around the oldest section in the centre of the complex. Recently, the extension scopes of this complex, required excavation and construction in the basements near the two main gates, called Saat and Naghareh Khaneh Edifice. These activities, near the 400 years old edifices, needed special mobilization, like, monitoring the historical buildings and strengthening their foundations. A deep study was performed, which pursued two purposes. The first purpose was to strengthen the foundation of the buildings and the second was to make a tunnel through the foundation of the buildings because of some operational benefits for the client. At the first glance these two purposes, seemed contradictory, but finally, a new structural system for the foundation were designed and built, which was able to carry the superstructure loads to the ground while a wide tunnel was constructed as well. Special scheduled sequences of construction were prepared, which was flexible and sufficiently reliable so as to overcome any undesirable circumstances and obstacles. Monitoring the buildings behaviour during the constructional phase was conducted to assist the execution directions. This project was carried out successfully and it is in use.
Abstract: Designed by architect C. L. Engel (1778 – 1840), the Naval Barracks facility was originally built in the 1820´s for the Russian Navy and also served as a shipyard. The building of national heritage is a prime example of neo-classical architecture in Helsinki. Strengthening and underpinning work for this structure was realised from 1985 to 1988. It was a part of the larger renovation project, where the building was made suitable for the Ministry for Foreign Affairs of Finland. The purpose of underpinning was to realise a new basement in its eastern part as well as to lower the basement floor level in other sectors. The ground engineering duties covered geotechnical and structural designs of temporary and permanent structures from the basement up to the ground floor.