New approach using direct crack width calculations of the minimum reinforcement in tensile RC elements is presented. Verification involves checking whether the provided reinforcement ensures that the crack width that may result from the thermal-shrinkage effects does not exceed the limit value. The Eurocode provisions were enriched with addendums derived from the German national annex. Three levels of accuracy of the analysis were defined - the higher the level applied, the more significant reduction in the amount of reinforcement required can be achieved. A methodology of determining the minimum reinforcement for crack width control on the example of a RC retaining wall is presented. In the analysis the influence of residual and restraint stresses caused by hydration heat release and shrinkage was considered.

In 1875 a steel railway bridge was built in northern Warsaw. It had seven spans of 66.22 m and two spans of 15.24 m. In 1908 the second railway bridge was built downstream of the older one. The spacing of supports and spans were the same as in the older bridge. During World War I, both bridges were blown up and then rebuilt, first temporarily and then permanently. Again both were blown up in 1944. In 1945, a temporary crossing was built. In 1947 a permanent bridge was rebuilt, partially replacing rivets with welding. On the pillars of the older bridge, the Gdański Bridge was built (not in this study). In 1963 welded connections were strengthened, in 1980 the structure of the northern track was replaced. In 2016, the northern track was renovated. The replacement of the structure of the southern track is ongoing since 2018.

The road network development programme, as well as planning and design of transport systems of cities and agglomerations require complex analyses and traffic forecasts. It particularly applies to higher-class roads (motorways and expressways), which in urban areas, support different types of traffic. Usually there is a conflict between the needs of long-distance traffic, in the interest of which higher-class roads run through undeveloped areas, and the needs of bringing such road closer to potential destinations, cities [1]. By recognising the importance of this problem it is necessary to develop the research and methodology of traffic analysis, especially trip models. The current experience shows that agglomeration models are usually simplified in comparison to large city models, what results from misunderstanding of the significance of these movements for the entire model functioning, or the lack of input data. The article presents the INMOP 3 research project results, within the framework of which it was attempted to increase the accuracy of traffic generation in agglomeration model owing to the use of BigData – the mobile operator’s data on SIM card movements in the Warsaw agglomeration.

This paper describes a fiber-based model proposed for computing the nonlinear longitudinal shear distribution in composite steel-concrete beams. The presented method incorporates the accurate stress-strain relationship with strain softening for concrete and bi-linear constitutive relation for structural steel, both in agreement with Eurocodes, however any one-dimensional constitutive relation can be used. The numerical solution for a simply supported beams loaded with the uniform load, concentrated force and both was presented. The results indicate that the highest value of the shear flow for a beam under an uniform load is at the ends and in the one third of the span length and for the point load, the maximum shear is in the proximity of the concentrated force.

The aim of the article is to analyze existing foreign experiences presented in the literature in the field of estimating demolition waste and their applicability in Poland condition. Using the case study method for more than a dozen objects, the authors prove the necessity to verify the suitability of the proposed models in relation to regional conditions (e.g. climatic conditions, local technologies, etc.). The amount of concrete waste from demolition of objects made in the analyzed technology is characterized by a low coefficient of variation, especially in the case of public facilities and is only 10%. However, in the case of residential buildings, the volatility was 16,7%. The calculated average index of concrete waste was compared with the two literature models. The results obtained differ from the values obtained from the models. Based on an analysis of the advantages and disadvantages of the selected models and their assumptions, a proposal has been formulated for the development of an effective tool for estimating demolition waste taking into account regional specific conditions together with the concept of sustainable construction. The focus was on waste from demolition of concrete objects.

The paper describes the recent developments of Hybrid Fibre-Reinforced Polymer (HFRP) and nano-Hybrid Fibre-Reinforced Polymer (nHFRP) bars. Hybridization of less expensive basalt fibres with carbon fibres leads to more sustainable alternative to Basalt-FRP (BFRP) bars and more economically-efficient alternative to Carbon-FRP (CFRP) bars. The New-Developed HFRP bars were subjected to tensile axial loading to investigate its structural behaviour. The effect of hybridization on tensile properties of HFRP bars was verified experimentally by comparing the results of tensile test of HFRP bars with non-hybrid BFRP bars. It is worth to mention that the difference in obtained strength characteristics between analytical and numerical considerations was very small, however the obtained results were much higher than results obtained experimentally. Authors suggested that lower results obtained experimentally can be explained by imperfect interphase development and therefore attempted to improve the chemical cohesion between constituents by adding nanosilica particles to matrix consistency.

The impact of a moving load speed on the dynamic overload of beams, assuming that the track of the load has no unevenness, is examined. First the problem of a visco-elastic beam on a Winkler foundation subjected to a force moving at a constant speed will be solved. Using the Bubnov-Galerkin method, the deflections of the beam, and then the bending moments and shear forces will be determined. The solution of the problem will be obtained both for the case of a forced vibration and the case of a free vibration after the moving force has left the beam. Using these solutions, dynamic amplification factors will be determined for the deflections, bending moments, and shear forces, which are different for the two cases.

The magnitude of the amplification factors increases and decreases alternately as a function of the speed. In the case of a single force on a beam, the dynamic overloads are limited, and do not exceed 60%. There is no resonance phenomenon in the beam subjected to the single moving force. The dynamic amplification factors determined in this way can be used as correction coefficients when designing engineering structures subjected to moving loads by static methods.

The article highlights the fact that numerous key decisions in temporary construction organisations are made as a result of informal, non-contractual relationships between organisation members that are not a result of formal organisational structures. These hidden relationships can be visualised in the form of social networks and Social Network Analysis methods (SNA) can be used to perform their structural analysis. In latest studies on self-organising networks in the construction sector, researchers have mostly focused on the design phase of large construction projects, e.g. infrastructural ones. Meanwhile, there exists a need for similar research to focus on temporary organisations created for the purpose of performing construction work. The authors took up this subject and examined a self-organising network of communication between the participants of the construction of a multi-family residential complex located in Katowice, Poland. The structural analysis of this network facilitated its in-depth understanding and identifying certain flaws and dysfunctions concerning individual participants of this project, which became a basis for further discussion. At the same time, the authors highlighted the benefits of managing such a self-organising network in the context of the effective achievement of project goals.

The aim of the paper is to present the possibilities and limitations of using the Digital Image Correlation systems. In order to assess the measurement inaccuracies the measuring volume 1250 × 1100 mm was analysed using two cameras with sensor resolution 6 megapixels. It was stated very good accuracy of the line segment length change. It causes that observation of crack widths can be considered as precisely. Some practical information concern how determine the compatibility between crack width measured traditionally and by using DIC are given. In the second part of the paper the results of the tests concerning capacity of interface between two concrete casting at the same time were presented. Use of the optical measurement system Aramis enables the analysis of the deformation, determination of failure mode of the tested specimens and limit displacement between edges of the interface.

A great number of non-functional child care facilities for children up to the age of three have been created in Poland to this day. This state of affairs may be the consequence of the low level of knowledge in this field, as well as few available studies on topics associated with nursery facilities, which may familiarise readers with the legal aspects, administrative procedures, or examples of good functional and material solutions of such units. What is more, there is also little information about the needs and preferences of people directly related to the topic. The aim of the article is to analyse the expectations and preferences of nursery facilities’ users in terms of the functional and material solutions. Based on a survey conducted among the nurseries’ employees and parents placing their children in the care of such institutions, a number of guidelines has been defined, allowing for the design of an optimal nursery facility that would meet the market’s expectations.

An attempt was made in the present work to study the compressive strength and microstructure of geopolymer containing high calcium fly ash (HCFA) and silica fume. Concentration of sodium hydroxide solution 8M, 10M, 12M & 14M, liquid to binder ratio 0.5 and sodium hydroxide to sodium silicate ratio 2.5 were selected for the mixes. Geopolymer mortar test results indicated that the mix with 40% silica fume by the weight of HCFA yielded higher compressive strength under ambient curing. The XRD pattern typically shows the major portion of amorphous phase of geopolymer. The existence of C-A-S-H gel, N-A-S-H gel and hydroxysodalite gel products were observed through SEM which developed dense microstructure and thus enhanced strength of HCFA and silica fume geopolymer.

Robotic total stations are a group of surveying instruments that can be used to measure moving prisms. These devices can generate significant errors during kinematic surveys. This is due to the different speeds of the total station’s measurement subsystems, which results in the observations of the point location being performed in different places of the space. Total stations which are several years old may generate errors of up to a few dozen centimeters. More modern designs, with much lower delays of the mechanical and electronic subsystems, theoretically allow to significantly reduce the values of the errors. This study involved the performance of kinematic tests on the modern robotic total station Leica MS50 in order to determine the values of measurement errors, and also to define the possibility of using them for the above-mentioned applications.

The paper presents the example of performance-based analysis for the existing large-space steel structure raised in 1980s. Hall is used as a paper products warehouse. Advanced mechanical simulations are performed using Safir software. Factors that impact the final fire resistance of the structure are discussed. Local and global imperfections and possible ways of structure modelling are taken into account. For selected cases advanced fire scenario that considers both localised fire and possibility of further ignition of stored goods is prepared using Fire Dynamics Simulation software. The results obtained indicate that added imperfections have little impact on the fire resistance of the structure and older-type steel hall roof without any fire protection could survive 30 minutes of fire. Main failure modes and values of structure's deflections are also presented. Finally, performed simulations show that even for large-space structure the flashover is possible in some special cases.

A group of old apartment houses with the age over 100 years (that is those carried out before the First World War) takes an important place in polish building resources. Technical maintenance of apartment houses, traditional methods erected, is nowadays and will be a valid problem in the nearest future. The results of the work refer to the general population, estimated for 600 objects, that is about 20% of municipal downtown apartment houses in Wrocław.

The purpose of the research was to identify an influence of widely considered maintenance of apartment houses on a degree and intensity of their elements’ deterioration. The goal of the work has been fulfilled by symptoms’ analysis of declining of inspected elements’ exploitation values, that is identification of mechanics of their defects arising.

The range of the work has required creation of original qualitative model of pinpointed defects and its transfer into quantitative one. It has made possible to analyse the reason - effect phenomena „defect - technical wear” relevant to the most important elements of Wroclaw downtown district’s apartment houses. The research procedure has been conducted in accordance of fuzzy sets theory which made possible to describe qualitative model of pinpointed defects and its transfer into a quantitative one.

Key messages from the IPCC Special Report on Global Warming of 1.5°C.

The transition to a zero-carbon economy is the inclusive growth story of the twenty-first century. It needs to be managed with effective and cohesive policies, whilst recognizing that sustainable development, inclusive growth and climate action are interwoven and mutually supportive.

Prof. Tandong Yao and Prof. Fahu Chen describe our growing understanding of climate change impacts in the “Pan-Third Pole” region, discussing both coping strategies and research initiatives focusing on the region.

Air quality and climate change, as two crucial environmental emergencies confronting our societies, are still generally viewed as separate problems requiring different research and policy frameworks. However, they should rightfully be viewed as two sides of the same coin. What we truly need to seek, therefore, are “win-win” solutions.

A Declaration of the Joint Symposium on Climate Change “Safeguarding Our Climate, Advancing Our Society” 10 December 2018.

The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics.

Journal Metrics: JCR Impact Factor 2018: 1.361, 5 Year Impact Factor: 1.323, SCImago Journal Rank (SJR) 2017: 0.319, Source Normalized Impact per Paper (SNIP) 2017: 1.005, CiteScore 2017: 1.27, The Polish Ministry of Science and Higher Education 2017: 25 points.

Abbreviations/Acronym: Journal citation: Bull. Pol. Ac.: Tech., ISO: Bull. Pol. Acad. Sci.-Tech. Sci., JCR Abbrev: B POL ACAD SCI-TECH Acronym in the Editorial System: BPASTS.

Dr. Franck Courchamp of France’s National Center for Scientific Research (CNRS) explains why a reduction in meat consumption would be good for everyone, lists the catastrophic consequences of biological invasions, and suggests what could be done to protect giraffes.

Prof. Mario Molina, a Nobel Prize winner, talks about his experience in making the harmful effects of chlorofluorocarbons (CFCs) known to scientists, the general public, manufacturers and politicians.

Any effective response to ecological crisis calls for collaboration of all parties involved.

We talk to the pioneering climate-change researcher Prof. Hans Joachim Schellnhuber about the role of decency in fighting climate change, and why excellent climate science requires freedom and trust.