In the proposed modelling approach each stone block is modelled as a discrete element which is discretized by triangular finite elements. Material non-linearity including fracture and fragmentation of discrete elements as well as cyclic behaviour during dynamic load are considered through contact elements which rate analysis for stone masonry pdf implemented within a finite element mesh.
The numerical analysis based on experimental test data has been carried out to simulate the main features of dry stone structures. DEM method for realistic modelling of the response of dry stone masonry structures. Material non-linearity are considered through contact elements. Model is capable of predicting behaviour of these structures under seismic loads. The model provides a realistic prediction of the collapse load. Check if you have access through your login credentials or your institution.
German masons repointing a wall in 1948. Traditionally, the first mortar was made with lime and sand, which would make lime putty. Starting in the early 20th century, however, masons started using Portland Cement, a strong, fast drying cement, not purely on its own though. Masonry cement made its appearance in the 1930s, which is a combination of Portland cement and ground limestone. The purpose of Wikipedia is to present facts, not to train. Before starting any actual work, building owners examine the masonry units, mortar, and the techniques used in the original construction. They try to identify the true problem they are facing and find out what were the causes of the deterioration or cracks.
If there are cracks or problems in the actual bricks or stone masonry there could be a larger problem that also needs to be addressed. If there is a larger issue, repointing may cause further damage. If a historic structure needs repointing, building owners usually hire an architectural historian or conservator to help pinpoint the issues. If the crack is smaller than 2mm and not causing any major defects, than it is better to leave it and not repoint. It is common to see cracking along old repairs because of the shrinkage of hard mortar and the seasonal flexing along the joint. Examining the structure before working will also help establish the strength and permeability of the original mortar in order to match the new.
It helps to establish what the original components of the old mortar are in order to find the best match. It is essential that the mortar used for repointing have similar performance characteristics to the original mortar used in a building. The mortar must have greater vapor permeability and softer compressive strength than the original mortar. Rather than the mortar relieving the stress, the masonry units will, which will cause further damage to the masonry unit, such as cracking or spalling. This is when the face or outer section of a masonry unit breaks away from the rest of the unit. This will be more expensive and strenuous to fix.
There are two common methods of analyzing mortar. The first is called “wet chemical. This is when a sample of the mortar is crushed and mixed with a dilute acid. The mortar will be broken down, and the type of mortar and sand used will be determined by the color and the texture. Another form of “wet chemical” analysis is the same process but the carbon dioxide gas that is given off by the digestion will be collected and the type of mortar will be determined by its volume. The amounts of each component will also be determined. The second method to analyzing mortar is “instrumental.
This is when thin slices of mortar are examined by a transmitted light microscope. This process can provide more information than “wet-chemical” examination. Other examples of “instrumental analysis are scanning electron microscopy, X-ray diffraction, and atomic absorption spectroscopy. Analysis is not solely based on lab work, however. There are important performances of mortar that can not be determined in a lab: original water content, rate of curing, weather conditions during original construction, method of mixing and placing the mortar, and cleanliness of sand. It is important to also match the color of the mortar. However, in the past lime mortar tended to be mixed on site with whatever sand was locally available.