Construction Technologies and Architecture Vol. 3

Abstract: This paper deals with the chemical analysis of the coating on building materials which were used for construction of Mánes bridge in Prague. It is a historical bridge which is more than a hundred years old. Using the method of infrared spectroscopy, we can determine the organic and inorganic compounds in coatings, adhesives, grout, and polymer materials. The organic compounds are added into the concrete and other building materials due to improvement of physical and mechanical properties such as compressive strength, tensile strength, modulus of elasticity or water absorption. The building materials can be covered with the coating for protection against mechanical damage. The chemical analysis of the building material is important to know before reconstruction and remediation of the historical buildings. As a result, the infrared spectrum of the coating was measured and it was determined that the coating was on the acrylate base.

Abstract: Rehabilitation of a historic farmstead originated from 17-18^th century is focused on the strengthening and preservation of structures including masonry vaults in existing agricultural buildings and underground corridor near Prague. For specification of the actual strength of masonry and also for the determination of material characteristics, the physically-chemical analysis of mortar was prepared. The estimation of actual masonry strength makes it easier to rebuilt two masonry vaults and also to strengthen existing historical corridor which leaded in the past to the ruins of castle. Principles of ISO 13822 for the assessment of existing structures and CSN 73 0038 is applied for the verification of the reliability level of historical masonry vaults which represent an important aspect of the culture of its period and could be considered to have some heritage value.

Abstract: The humidity of historical constructions can be considered as a global problem causing either partial or complete destruction of the affected buildings. Therefore, it is necessary to solve this problem by certain interventions to reduce or completely remove humidity from these structures in order to preserve the historical and cultural heritage of the nation. This paper will describe a summary of previous theoretical and practical knowledge of the issue. This part will be followed by research dealing with the effectiveness of non-invasive methods of combating humidity in buildings carried out in situ, specifically the technology of wireless dehumidification known as the magnetokinetic method. The paper will describe two historical objects, investigated in situ, where these technologies were applied several years ago. As these technologies are highly questioned by the professional public, this research is expected to help demonstrate the effectiveness of this technology on the basis of real values obtained directly from practice.

Abstract: The article deals with church microclimate monitoring and describes microclimatic changes within one year. The monitoring period was the year 2020. Based on the results of long-term monitoring and taking into account the temperature of the inner surface temperature of masonry was executed simulation in 2D software to analyze surface temperature according to the agency of moisture on the surface of the perimeter wall. Attention was targeted to the determination of the period to the occurrence of adverse events (condensation of water vapor and occurrence of mild).

Abstract: Testing methods used for assessment of buildings considered as a cultural heritage are focused mainly on non-destructive testing methods. Old buildings are usually sensitive to destructive in-situ testing, and a variety of non-destructive techniques (NDT) are frequently used. One of the most commonly used sensors are accelerometers, which can measure vibrations of different part of structures. These can be used in either continuous monitoring or in short-time assessment. Impact-Echo is a well-known method which can locate defects, caverns, or damaged parts not only in industry-level structures, but also in preservation of cultural heritage. This type of measurement requires attaching a sensor to the surface of the observed element. This is in most cases done by adhesives which can damage the more porous structures. In this paper a comparison of two different sensor types in testing of reference concrete elements is presented: contact piezoceramic accelerometer; non-contact MEMS type microphone. Signals recorded by each sensor type are assessed by the statistical method of feature extraction.

Abstract: This paper deals with the issue of detection of internal defects and failures of concrete structures with emphasis on the use of non-destructive methods. All parts of the structure that reduce its service life or bearing capacity can be considered as internal defects and failures. These are, for example, gravel nests, cracks, delamination, caverns etc. Due to the prevalence of concrete structures, the development of this part of diagnostics is very important both for the safety of their users and to reduce the economic costs of their future repairs.

Abstract: Electrical conductive composite materials are nowadays widely used in many industrial applications include building materials. One of the possible applications is as a resistance probe. Those probes were designed to monitor internal structural changes of building materials built into construction and to predict their durability, over-load, or defects. Mostly used composite materials are silicate or biopolymer-based with carbon-based filler. This article is dedicated to the study of the microstructure of silicate-based electrically conductive composites with graphite-based fillers. The microstructural shape of fillers was chosen concerning preserving as high conductivity as possible. Furthermore, the effect of moisture on the electrically conductive properties of the silicate composite was monitored.

Abstract: This article deals with defects in solid fired bricks caused by repeated freezing and defrosting. Defects can be divided into surface (visible) such as cracks or chips of the test element. The second type of defects are those in the internal structure (invisible on the surface). The defects in the internal structure can be the easiest detected by non-destructive methods such as the resonant pulse method or the ultrasonic pulse method. This article deals with the possibility of detecting defects in the internal structure of solid fired bricks and their relation to surface defects. The test elements were repeatedly frozen and defrosted, and after a certain number of cycles, changes in the internal structure were monitored by the resonance method and by the ultrasonic method. The variable for monitoring the failure of the internal structure is the relative dynamic modulus of elasticity (RDM).

Abstract: Many existing steel railway bridges, often recognized and protected for their heritage value, are exposed to degradation and increasing traffic loads and their reliability needs to be assessed. The key question is whether a particular bridge can be preserved, or needs to be strengthened or replaced. The main aspect in decision-making is specification of the target reliability. Development and wider use of the adjusted partial factor method seem to be reasonable to find the balance between demands on the input information, computational complexity, and improvements in reliability assessment. Adjusted partial factors are based on the relevant statistical parameters for basic variables and a selected target reliability index. In this contribution, the effect of the target reliability on updated partial factors are demonstrated. The case study illustrates that the target reliability levels recommended in various documents for new and existing structures are inconsistent in terms of the values and criteria according to which these values are to be selected. Consequently, the values of the partial factors for assessment may be significantly dissimilar.