Fast Construction Research Articles

Review of experimental investigations on seismic performance of precast segmental bridge columns in seismic regions

Due to the fast construction and low interference, precast segmental bridge columns have gained increasing attention for use in non-seismic regions. However, their applications in seismic areas remain scarce due to their ambiguous dynamic performance. To estimate the seismic performance of PSBCs, existing quasi-static cyclic tests and shaking table tests are gathered and reviewed in this study. According to the structural details and material property at the joints, the PSBCs are categorized as 11 types based on the connection type, namely grouted splice sleeve couplers (GSSCs), grouted corrugated duct connections (GCDCs), wet joint connections (WJCs), mechanical bar splice connections, socket connections (SCs), unbonded post-tensioned tendon connections (UPTCs), partial precast columns (PPCs), hybrid connections (HCs), high-strength steel bars (HSBs), high-performance concrete (HPC), and external dissipators (EXDs). Based on the experimental results, the failure reason of each connection types are discussed and the effective structural details are suggested. And also, the PSBCs are divided into those with ductile and resilient connections according to the damage levels, residual drift ratios, displacement ductility coefficients, equivalent viscous damping ratios and effective stiffness parameters. With the achievements in this research, the application of PSBCs is expected to be promoted in medium-to-high seismic regions.

Precast concrete wall-raft connectors for increasing the lateral load capacity: An experimental and analytical approach

Precast structural walls and rafts commonly resist lateral load in structures owing to improved traits and faster construction. The behavior of five different types of precast reinforced concrete structural wall and raft connection systems is evaluated in this study. In all five configurations, the cyclic load is applied in the wall systems to observe the lateral load-carrying capacity and hysteretic characteristics. The damage and failure patterns were assessed. To confirm and contrast the behavior of the proposed precast structural wall and raft connection systems with the experimental findings, FEM analysis was used. Only shear and flexural cracks were observed. The specimen with 12 mm dia rods has the maximum load carrying capacity of 10.23 kN in the negative cycle, which is 57% more than the specimen without grouting and connector. The suggested connection can improve the resistance behavior in all key directions by absorbing more energy than precast walls under dynamic load.

Hybrid Beam-Column Connection of Precast Concrete Structures: A Review

The use of precast concrete materials as structural elements has become common practice. Precast concrete material offers various advantages over cast in place concrete, including energy-saving, pollution reduction, increased labor productivity, high material durability, reduced formwork and scaffolding usage, faster construction, and the ability to carry out construction in any weather conditions. However, there are some disadvantages in assembling precast elements, particularly in connection areas, which serve as the main structure of a building. Several studies have been conducted to develop connection types for precast concrete. Some of these include dry connections and wet connections, each with their own advantages and disadvantages. To mitigate the weakness of both connection types, many studies are currently focusing on developing a combination of dry and wet connections known as Hybrid Connections. Various developments have been made in the Hybrid connection system.

СОВРЕМЕННЫЕ ТЕНДЕНЦИИ ПОВЫШЕНИЯ КАЧЕСТВА ТРУДОВЫХ РЕСУРСОВ (НА ПРИМЕРЕ СТРОИТЕЛЬНОЙ ОТРАСЛИ)

This article is devoted to modern trends in improving the quality of labor resources (using the example of the construction industry). The relevance of the research topic is due to statistics showing a significant increase in construction over the past year. In addition, the relevance of the issue under consideration is determined by the fact that modern construction companies operate in the context of the introduction of modern technologies, new materials and digital solutions, leading to rapid changes in the labor market. In the article, the author studied the specific features of the construction industry, considered an algorithm for assessing human resources in the construction industry, analyzed the consequences of the transition of the construction industry to digital technologies; the set of professions required in the conditions of digital transformation in construction is outlined, the directions of work with labor resources in the conditions of the transition to digitalization are determined, the possibilities of the digital duplication system for improving the quality of labor in the construction industry are revealed. In the article, the researcher paid special attention to the need to retrain personnel of construction companies in the context of the transition to digital transformation. Moreover, this must be done at all levels, starting with line workers and engineers (work managers, foremen, etc.) at construction sites and ending with the management team of companies, because the work order cannot be changed if even one link continues to work as before technical mode. The author concluded that rapid expansion and increasing construction rates highlight the critical importance of maintaining quality standards. Education and training of the workforce, as well as external control, are necessary to ensure fast and high-quality construction in today’s digital transformation environment.

Neural networks for a quick access to a digital twin of scanning physical property measurements

A simple and fast construction of neural networks is shown to be useful for augmenting physical-property experimental data.

Simplified seismic vulnerability analysis of historic residential buildings with fragility curves

In the disciplines dealing with the preservation of the built heritage, the assessment of the seismic vulnerability plays a decisive role. A high number of numerical models have been developed to simulate the behaviour of different building typologies subjected to seismic action, but requiring a in-depth knowledge of the object of study they are not suitable for urban scale analysis. The widespread historical built heritage in Italy, as in many other countries, requires the definition of rapid and reliable assessment procedures that allows a large-scale evaluation of the vulnerability of historical buildings before a seismic event. This analysis should be based on existing databases, such as the Reluis-Cartis database, without necessarily proceeding at this stage with detailed investigations of each individual building. Based on state-of-the-art procedures, a methodology is proposed for the fast construction of the fragility curves starting from information available on the Reluis-Cartis database. The curves define the relationship between the probability of reaching a safety factor or a vulnerability index in function of the seismic acceleration PGA. The methodology allows to understand the probability of loss of the structural safety in function of a given PGA. The developed methodology is applied here in two cases: (a) a small historic building hit by several earthquakes in order to calibrate the methodology and (b) to a set of historic building of the same typology in a historic center never hit by earthquakes in order to assess the level of the probability of loss of the structural safety given the code defined PGA, as well as to draw conclusions on prioritizing intervention strategies at the urban scale.

NPA Cells in the Marine Environment

Novel Polymeric Alloy (NPA) cells are a cellular confinement system with the engineering properties required by international standards for long-term confinement in demanding infrastructure projects. Three-dimensional NPA cells are used as a cover protection system against channel, stream and shoreline erosion caused by flowing water and tractive forces. NPA cells enhance the performance of conventional erosion control materials and dissipate energy from flood, current and wave action for hydraulic and marine structures and are a best available technique for canals, channels, drainage, shorelines, riverbanks, sea-walls, dams and port infrastructure. Soft or hard armor is used to optimize the erosion protection for natural or man-made channels, hydraulic structures and barriers. The surface treatment is dependent upon the geometry, hydraulic, site and environmental conditions along the water course, as well as optimization and cost-efficiencies. For example, sand infill is used for beachfront erosion control, vegetation for riverbank protection, gravel in sites subject to moderate flow velocities and concrete hard-armor in high velocity channels and walls subject to wave action. Reinforcement of load support structures in port applications can use sand, granular or recycled materials. Whereas the suitability of a cellular confinement system is directly dependent on the key attributes of the cell as well as its geometry, cells made of Novel Polymeric Alloy (NPA) have measurable higher tensile strength, resistance to deformation and environmental durability to hydraulic forces and thermal cycling over the project lifespan than conventional HDPE-based soft-cells. This includes high resistance to photochemical degradation – leaching of additives, oxidation and UV light – to preserve confinement for the lifespan of the project. Concrete solutions in non-erodible canals and walls are particularly advantageous with NPA cells. While the cellular mattress eliminates form work for fast construction, NPA cells add high tensile strength to the concrete. The creates a strong yet flexible mattress, which absorbs hydraulic forces and ground movement and resists cracking of the concrete for improved surface durability. Additionally, the high reinforcement factor of the NPA system also enables a reduction in concrete thickness to improve cost-effectiveness and sustainability. These properties also make NPA cells suitable to load support pavements used in marine ports, wharfs, terminals and container yards situated on soft, compressible and saturated soils, using sand for structural infill with no loss in structural stability.

Research on the Influence of Design Parameters on the Seismic Capacity of High Rise Prefabricated Structure Buildings

Building industrialization and resilience are the goals and trends of structural engineering development. Prestressed assembly design and construction is an effective way to achieve this goal. The birth of prefabricated buildings has met people's demand for diversified buildings from many angles. At the same time, prefabricated buildings have also broken the limitations of long construction time and low efficiency of traditional buildings, and gained broader development prospects in construction work. Compared with cast-in-place concrete structure, prestressed prefabricated concrete structure has the advantages of good performance, small residual deformation after earthquake, full use of high-strength materials to reduce self-weight, industrial production and fast construction speed. Each part of the prefabricated building can be disassembled and assembled. When designing the structure, it is necessary to consider the characteristics of the structural system, and set up the connection mode reasonably during assembly to ensure the stability of the structure. This paper expounds the influence of design parameters on the seismic capacity of high-rise assembled structure buildings, and puts forward the seismic design strategy of high-rise assembled structure buildings.

Cultural identity in the architecture of individual dwelling in the conditions of industrialization

The development of fast construction methods that allow to speed up and cheapen the procedure of housing construction will form conditions for simplifying mortgage programs by financial institutions. Despite the positive aspects of industrialization, this process is characterized by signs of depersonalization and loss of regional authenticity in architecture. This leads to the erosion of national mentality and loss of cultural identity. The search for signs of cultural identity of the Russian individual dwelling is based on the volumetric and spatial analysis of the architecture of the traditional Russian dwelling house of the North-Western regions of the Russian Federation. Since this area corresponds to the third and fourth climatic zone, in which most of the territory of the Russian Federation is located. As a result of the analysis, the characteristic planning features of individual residential houses formed under the influence of natural and climatic conditions of the region are determined and the stable, not changing in time signs of identity are revealed. As a result of the study, the parameters of the optimal percentage ratio of warm and cold zones in the volume of the house for the formation of a sustainably developing system of national housing, and the stylistic and typological characteristics formed on their basis.

Improvement on manufacturing processing time of AAC Block

Autoclaved aerated concrete (AAC) was invented in 1920s. AAC is composed of lime, cement, sand, fly ash and aluminum powder, which is the component that plays an important role in creating air voids, an essential factor of the AAC. The production process of the AAC block comprises of stages such as: mixing, casting, cutting, autoclaving, etc. All of the stages are conducted in an eco-friendly manner. The AAC is also called the future of construction materials because of its light weight feature when compared to red bricks along with excellent sound/heat insulation. AAC Blocks will help to reduce the use of cement, sand together with steel and other materials in the construction work. AAC Blocks can be used for both interior and exterior construction. In many construction projects, the AAC block is a more expensive choice than the red brick but the AAC blocks are more often used due to its cheap total construction value. Application of AAC block is very wide such as in industrial constructions, commercial buildings, offices, schools in rural areas, especially in fast construction of houses. The AAC blocks use cement mortar to bond and require a thinner layer than red bricks. Although the bond layer is very thin at only a few millimeters, the strength of the bond is very strong in both cases of load bearing and non-load bearing walls. The AAC Block has many more advantages when compared to other brick types in the construction market, however, the manufacturing process still needs improving to compete with itself in the future. AAC is a kind of cast concrete. The manufacturing process consists of: First, the sand, cement, lime, water, aluminum powder with a reasonable ratio is mixed well until the mixture is slurry. Secondly, the mixture is poured into the mold and left in the mold for a few hours. Thirdly, a transportation device helps to unmold and move the products to the cutting area. At the cutting area, the mixture is cut into blocks and proceeds to the autoclave under heat and pressure for 10 hours. There are many approaches to decrease the manufacturing time of AAC blocks. The main focus of the previous approaches is the forming of air voids when casting. In the traditional method, the aluminum powder will react with calcium hydroxide and water to create hydrogen gas which results in the creation of foam within the concrete. This method takes a long period of time for the reaction to complete. To reduce the time needed, some researchers use air or different reaction methods to create the foam. In this paper, a new approach will be introduced. The reduction of time will be focused on the waiting time before the cutting by measuring the time needed for the material to reach the suitable hardness. Among the 4 stages in producing AAC blocks, the paper will focus on improvement the process of molding and unmolding to reduce the amount of time and also keeping the quality suitable. The paper also presents the method to measure the hardness of the mixture of lime, sand, etc. before cutting.

Characteristics and Application of Modular Integrated Construction

The modular buildings technology is a new type of construction technology, and it is officially called modular integrated construction. It is a new type of construction technology, this system treats each room as a separate module, all prefabricated in the factory. After the factory production, the rooms are transported to the site and assembled into the whole building through reliable connection. This paper discusses the advantages and disadvantages of modular building technology, and describes the development prospect in future. Compared to the traditional way of building, modular buildings have fast construction speed, environmentally friendly construction process, high construction quality and broad development prospects. At the same time, it has some aspects that are not mature at this stage, like the incomplete production chain and low freedom caused by high-degreed standardization. Modular buildings have been applied in many field, and it can be used in cooperation with existing computer technology like building information model. The main development direction of modular architecture in the future is digitalization, intelligence and integration.

Research on Construction Safety Risk of Prefabricated Construction Project

With the development of the construction industry and the vigorous promotion of national policies, prefabricated buildings have developed rapidly. Compared with traditional buildings, prefabricated buildings have the characteristics of fast construction, low cost and low pollution. The construction of prefabricated buildings has higher requirements for constructors and is more difficult to obtain professional skills. In particular, safety accidents are prone to occur during the hoisting of prefabricated components, resulting in casualties and economic losses. The safety risk in the construction of prefabricated buildings has become an urgent problem to be solved. This paper focuses on the safety risk analysis from the four aspects of manufacturing, transportation, storage and on-site assembly of prefabricated components in the construction process of prefabricated buildings, and gives the corresponding safety risk prevention measures.

Seismic Analysis of Flat Slab Buildings on Hilly Ground

In India, hilly region especially northern part is more seismically active region. Flat Slab systems are widely popular in multi-storey buildings. Flat slab building has more advantages than a regular building like fast construction, free design space, reduced floor to floor height and economical. Flat slab buildings are also being built in high seismicity region. Buildings on hilly ground are vulnerable due to their vertical and horizontal irregularity and they undergo high shear and torsion during the earthquake. Further due to short column and soft storey on uphill side has higher lateral forces that are cause to failure of buildings. In this paper, an attempt has been made to assess the seismic behavior of flat slab resting on hilly slope with soft storey and set back configuration. The methodologies have been adopted are linear dynamic analysis i.e. response spectrum analysis. Building is analyzed and designed by Etabs software. Maximum displacement, maximum inter-storey drift and storey shear are determined as response quantities. It is observed from the study that for flat slab buildings on hill slopes the storey shear is very high in the bottom columns at higher ground level, therefore extra care should be taken to design these columns for earthquake load.

Review on comparative study of diverse wall materials for affordable housing

Modular Construction is a boon to the construction industry. Rapid construction methods are now evolving by the day. It is imperative to access these techniques on the basis of sustainability parameters. The advanced construction management concept such as fast track construction is being implemented in real estate industry with special focus on lean management. Ferro-cement panels, gypsum sheets, etc. are some of the precast members in construction which reduce the scheduled duration of the convectional project. It also significantly decreases the dead load of the structure. India’s focus on Sustainable Development goals has also conceptualized affordable housing as one of the methods to achieve it. The alternative for the conventional method of building houses is the use of ferrocement as it is cost effective. As the cost of constructing houses will reduce, the poor people living in slums area will afford to live in a hygienic place. This paper tries to analyze the two trending panel techniques namely: Gypsum & Ferro-cement on various technical aspects and the implication on affordable housing. Also, on conclusive note, the results of comparison are mentioned.

MASS HOUSING IN UKRAINE IN THE SECOND HALF OF THE 20TH CENTURY

The housing issue is rightly considered one of the most acute problems of humankind. It is generated by social causes and has a social meaning. The housing issue cannot be solved with purely technical, architectural or artistic approaches. Rather, it also depends significantly on economic, political and environmental circumstances. At different times, the nature of the living environment was formed under the influence of social order, the level of development of productive forces, household and economic systems, and other factors. In the second half of the 20th century, following standard designs, Ukrainian cities mostly consisted of four- and five-story residential buildings in new residential areas. As a result, the living environment of many cities in the country acquired a common and rather modest appearance, dominated by concrete construction. At that time, this was the most effective way of mass housing construction. New technologies and design solutions were used. Such housing was cheap and purposefully met the social standards at the time. In addition, for the owners of such housing, it meant a new higher level of comfort. This publication focusses on housing construction in the second half of the 20th century in Ukraine after 1956. It is important to identify the quality of such housing and its compliance with modern requirements. Methods of systematization of historiographical materials, comparative and historical analysis, and field surveys were used to achieve the aim. Among the main achievements are the comfortable density of residential areas and fast construction times. The disadvantages of this period’s mass housing construction are related to missing maintenance, ongoing destruction, often complex ownership situations and the challenge to adapt each building to current needs and regulations.

Cost Effectiveness and Quality Adequacy in Construction Project

This article looked at the challenges of defining quality in the construction business, the potential benefits of executing quality, and the roadblocks to using quality in development. We use information gathered during contractor interviews as well as information from questionnaire surveys. Clients want better service quality, faster construction, and technological advancements. It's no coincidence that the building industry has turned to manufacturing as a source of inspiration and innovation. Total Quality Management (TQM Generation and Re-engineering) and other fabrication-based methodologies are being encouraged and integrated into the development process. Because of its excellence, it has made more progress than any other benefit industry. However, because of the requirement for standardization and the multiple stakeholders involved, implementing TQM standards in development is particularly difficult.

Research on the Fast Construction Method of Basic Geographic Framework of 3D Smart Community

In order to promote the reform and innovation of social governance system, create "community brain" and build digital twin community in digital space, the hierarchical and household-level three-dimensional basic geographic framework plays the role of data base. Based on the key technologies such as deep learning change monitoring, batch building and rendering of hierarchical household 3D models on the Web side, and multi-source address matching, this paper explores and realizes the technical route of quickly building hierarchical household-level 3D basic geographic framework of 3D smart communities. Through the technique of dynamic rendering monomer, a three-dimensional model visualization platform of oblique photography is built, which effectively integrates various government resources of people, houses, things and things, and realizes socialization, intelligence and specialization of social governance and convenience services.

Implications of Siesmic Detailing on the Fire Performance of Post-Tensioned Timber Frames

Post-Tensioned Timber (PTT) frames have significant advantages over traditional timber frame systems especially where a low damage design and fast construction are desired. New Zealand practitioners designing timber structures for fire are accustomed to applying ambient design methods to an element cross-section reduced by a char depth based on a duration of Standard Fire exposure following NZS 3603 or AS/NZS 1720.4. The behaviour of PTT frames in fire remains a concern because this approach does not account for the actual mechanics of PTT connection and frame response under natural fires that will occur in the structure. This paper examines the individual and interdependent response of PTT connection components (tendon, dissipater, fasteners, etc) to fire. It is shown that the ambient analysis tool for PTT connections, the Modified Monolithic Beam Analogy, cannot be applied to the fire case by only using char reduced cross-sections of timber elements. This approach of combining ambient methodologies with reduced cross-sections does not account for the specific connection detailing, which result in unique damage in fire that may govern the structural response. The responses of two seismically detailed PTT connections are predicted using this approach and compared to a first principles assessment of connection behaviour to demonstrate that failure will occur earlier than otherwise predicted. Numerical thermal analyses of these two connections also qualitatively corroborate the damage that occurs. This investigation establishes that additional studies are required to understand the complex behaviour of these connections when exposed to fire before a design methodology can be developed.

Block Polarization HARQ for Polar-Coded Modulation

In this paper, we propose a block polarization (BP) scheme as a framework to study polar-coded hybrid automatic repeat request (Polar-HARQ) under bit-interleaved polar-coded modulation (BIPCM). The BP scheme of BIPCM can combine multiple independent polar subcodes to form a longer polar code under the block polarization between polar subcodes. The BP scheme of HARQ further carries out block polarization based on the BP scheme of BIPCM, which can combine multiple transmitted BP schemes of BIPCM together to form a longer polar code. When the underlying channels are non-uniform, such as the polarization effect of high-order modulation will lead to non-uniform reliabilities, it is not suitable to use the fixed sequence (e.g., the polarization weight (PW) sequence or Polar sequence in the 5G standard) to construct polar codes. The underlying channels on each polar subcode have uniform reliability by dividing different blocks according to the reliabilities of the underlying channel. Based on this characteristic of BP scheme, we propose a rate-allocation (RA) method to study fast code construction of BP scheme. The key idea of the proposed RA method is finding out the equivalent channel whose average symmetric capacity equals the target transmission rate. The allocated rates are computed according to the symmetric capacities of split channels under the block polarization between polar subcodes. Then the ranking of bit indices within each polar subcode can be obtained by fixed sequence. In this way, the RA code construction is concise and robust for diverse configurations which are the desired features for practical implementation. Simulation results show that the proposed BP scheme under RA construction can achieve almost identical performance as the Gaussian approximation construction with much lower complexity.

Fault detection and analysis for wheelset bearings via improved explicit shift-invariant dictionary learning

The wheelset bearing is an indispensable part of the high-speed train, and monitoring its service performance is a concern of many researchers. Effective extraction of those impulse signals induced by the defects on the bearing elements is the key to fault detection and behaviour analysis. However, the presence of considerable noise and irrelevant components brings difficulties to extracting the wheelset bearing fault impulse signals from the measured vibration signals. This paper proposes an improved explicit shift-invariant dictionary learning (IE-SIDL) method to address this issue. Based on the shift-invariant characteristics of the wheelset bearing fault impulse signal in the time-domain, the circulant matrix is used to construct a shift-invariant dictionary and explicitly characterize the fault impulses at any time. To improve the efficiency of dictionary learning, a method of three flips is introduced to realize fast dictionary construction, and the frequency-domain reconstruction property of the circulant matrix is employed to quickly update the dictionary. Besides, an indicator-guided subspace pursuit (SP) method based on the sparsity of envelope spectrum (SES) is adopted for the sparse coding to improve sparse solution accuracy and adaptation. The effectiveness of the IE-SIDL method is proved through the simulated and experimental signals. The results demonstrate that the improved dictionary learning method has an excellent capacity in extracting fault impulse signal of the wheelset bearings, and the good time- and frequency-domain characteristics of the processed signals facilitate fault detection and behaviour analysis.