Low-cost Construction Research Articles

Experimental evaluation on dynamic performance of medium–low-speed maglev vehicle running on low-positioned subgrade

ABSTRACT As a novel urban rail transit system with relatively low construction costs, medium–low-speed maglev transportation is currently experiencing rapid development in China. However, there have been rare studies on the experiments of medium–low-speed maglev vehicle passing curves and low-positioned subgrade. Therefore, this paper systematically conducts on-site dynamic tests on the Qingyuan Maglev Tourism Line. The experiment provides a detailed analysis of the dynamic characteristics of the vehicle system and subgrade under varying speeds up to 132 km/h. The study explores the impacts of operating speed, track layout, and type of girder structure. The results indicate that a significant increase in operating speed and the application of emergency braking intensify the dynamic response of the vehicle system. When passing through the R700m curve and low-positioned subgrade sections at different speeds, the primary vibration frequency of the sprung structure is below 2.5 hz, while the unsprung structure shows a wide frequency distribution. The peak frequencies of the vibration for the low-positioned subgrade are mainly distributed in the 60–140 hz range, and the vibration response of the girder remains at a low level. The Sperling index values, levitation gap, and lateral offset of the levitation electromagnet of the testing vehicle do not exceed 2.5, 4 mm, and 10 mm, respectively, indicating excellent ride comfort and stable levitation performance. The results of this test study provide a reliable assessment of the safety of the vehicle and subgrade system and would help precise modelling of vehicle and subgrade system in the future.

Experimental investigation on wind loads and wind-induced responses of large-span flexible photovoltaic support structure

Flexible photovoltaic (PV) support structure offers benefits such as low construction costs, large span length, high clearance, and high adaptability to complex terrains. However, due to the high flexibility and low damping of the cable system, wind load becomes the primary control factor for structural safety and the key consideration in the design. In this study, a 45 m span flexible PV support structure with 3 spans and 12 rows was designed. The wind loads on PV panels were obtained by wind tunnel tests on a rigid model and the wind-induced responses were investigated by wind tunnel tests on an aeroelastic model. The shielding effects and tilt angle of PV modules on the wind load and wind-induced vibration of the flexible PV support were studied. The experimental results show that in the rigid model wind tunnel test, the wind pressure on the surface of PV modules exhibits a gradient distribution along the direction of wind flow, with symmetric distribution along the mid span. With the increase in the tilt angle of the PV module, the shielding effect becomes significant and the most pronounced shielding effect on the mean wind pressure coefficient occurs in the second row of the windward zone. In aeroelastic model wind tunnel tests, the mean vertical displacement of the flexible PV support structure increases with the increase of wind speed and tilt angle of PV modules. Due to the wind-resistant anchor cables set in both the windward and leeward zones, the vibration amplitude near the edge rows is significantly smaller than that of the middle rows when the structure is subjected to wind suction. When the flexible PV support structure is subjected to wind pressure, the maximum mean vertical displacement occurs in the first rows at high wind speeds. The shielding effect has a noticeable impact on the wind-induced response of the leeward zone at α = 20° under wind pressure, resulting in the decrease of amplitude vibration by approximately 53 %. The wind vibration coefficients in different zones under the wind pressure or wind suction are mostly between 2.0 and 2.15. Compared with the experimental results, the current Chinese national standards are relatively conservative in the equivalent static wind loads of flexible PV support structure.

Oxidation and ablation resistance of (TiZrHf)C medium-entropy ceramic coating on C/C composite constructed in-situ at low temperature down to 900°C

The low-cost construction of ultra-high temperature high/medium-entropy ceramic coatings is pivotal for advancing their engineering applications. The study successfully prepared (TiZrHf)C medium-entropy ceramic coatings on C/C composite surfaces using an in-situ molten salt disproportionation reaction at temperatures as low as 900°C. The (TiZrHf)C coatings, approximately 20 μm thick, showed uniform distribution of Ti, Zr, and Hf, typical of medium-entropy ceramics. The process entails Hf reducing Zr⁴⁺ and Ti⁴⁺ to divalent states, which then disproportionate and react with carbon to form the coatings. High-temperature oxidation tests revealed larger oxide grain sizes and dense boundaries in coatings with higher Ti content, indicating superior oxidation resistance. Additionally, ablation tests demonstrated that a suitable amount of liquid-phase TiO₂ formed on the composite surface improves ablation resistance by stabilizing the oxide layer. This cost-effective, highly designable method promotes medium/high-entropy ultra-high temperature ceramics' engineering application.

Low cost Non freeze-drying construction strategy of cellulose aerogels for efficient solar desalination

Aerogel-like materials with three-dimensional pore structures show great potential in the field of efficient solar-driven interfacial evaporation by virtue of their fast water transport as well as efficient energy confinement properties. However, the preparation of aerogels is currently limited by high-cost strategies such as freeze drying or supercritical drying. Here, we present a foam template-assisted (FTA) strategy for atmospheric pressure drying of cellulose nanofiber (CNF) aerogels. Building a robust CNF network is the key to resisting surface tension during water evaporation and achieving drying in ambient environments, which is achieved through cleverly designed ionic cross-linking with the help of FTA. Cellulose aerogel (CA) constructed using the FTA strategy exhibit lightweight (9 mg cm−3) and porous properties (porosity: > 99 %). The tannic-coated CA (TCA) was achieved by further polymerizing tannic acid on the CA surface, which has excellent photothermal conversion capability. Meanwhile, TCA achieved an impressive evaporation rate of 3.58 kg m-2h−1 and an energy efficiency of 97.2 % at 1sun radiation by virtue of its excellent energy confinement and water management capabilities. This strategy provides a promising solution for the low-cost construction of aerogels as well as for the realization of efficient solar-driven interfacial evaporators.

Experimental void fraction measurement approach of small channel two-phase flow

This investigation presents a novel experimental approach for assessing void fraction parameters in two-phase flows within microchannels. The study critiques the conventional impedance methods that utilize alternating current (AC) for void fraction measurements, highlighting the inherent drawbacks such as ground capacitance interference and non-uniform current distribution. To circumvent these issues, the research introduces the use of direct current (DC), which ensures a homogeneous distribution across the conductor's cross-section, as a more reliable alternative. Termed the "Direct Impedance Method," this technique employs DC to enhance the accuracy of void fraction measurements. The study explores various geometric configurations of full-ring and half-ring electrodes, both vertical and horizontal, within a microchannel of 500 μm diameter. An empirical formula is derived to calculate the void fraction from the electrical data obtained. High-speed imaging at 4000 frames per second supplements the method by providing visual confirmation of the flow patterns. The comparative analysis of the direct impedance method and image processing using the homogeneous theoretical model reveals a deviation of approximately 2 %–10 % for the slug and annular flow pattern. In contrast, the deviation is more for the bubble pattern. The results affirm that the Direct Impedance Method is a cost-effective and reasonably precise technique for small-channel applications. Its accuracy is inversely proportional to the channel diameter, rendering it unsuitable for channels larger than 2 mm. The method's low construction cost further enhances its practical appeal.

Experimental Research on Dynamic Mechanical Properties of High-Density Foamed Concrete.

Foamed concrete is increasingly utilized in protection engineering because it offers a high energy absorption ratio and a relatively low construction cost. To investigate the dynamic properties of foamed concrete, a series of dynamic compression tests are carried out on high-density foamed concrete with densities of 800 kg/m3, 1000 kg/m3, and 1100 kg/m3 under a strain rate range of 59.05 s-1~302.17 s-1 by using a Φ-100 mm split Hopkinson pressure bar (SHPB) device. The effects of strain rate on the stress-strain relationship, dynamic compressive strength, and dynamic increase factor of foamed concrete are discussed in detail. The results show that the dynamic mechanical characteristics of foamed concrete with different densities exhibit a significant strain rate enhancement effect. Additionally, the energy absorption characteristics of foamed concrete are investigated, demonstrating that it can effectively prevent the transmission of incident energy and that its energy absorption efficiency declines as the strain rate increases. A high-speed camera was also employed to capture the failure process of foamed concrete. The results exhibit that fracture production and development induce the failure of foamed concrete, the failure process of foamed concrete advances as the strain rate increases, and the failure mode becomes increasingly severe.

A box quadrat for standardised sampling of Orthoptera in open habitats: Design, handling, applications and baseline data

Globally, insects are declining at an alarming rate. Therefore, there is an urgent need for standardised monitoring methods to detect changes in insect populations at an early stage. Box quadrat sampling enables highly precise assessments of Orthoptera community composition within a specific area. However, a detailed design of a box quadrat that guarantees an easy workflow, precise descriptions of its handling and a compilation of baseline data for future comparisons have yet been lacking. Based on thirty years of our own experience in box quadrat sampling, we present here: (i) the detailed design of a box quadrat, (ii) its standardised handling in the field (including a video as a supplement), (iii) its applications and (iv) Orthoptera species richness and abundance baseline data for open habitats. The low construction costs (∼300 €) and simple design allow for a wide distribution of this type of box quadrat in future. Moreover, due to the plug system and the light aluminium construction, the quadrat can easily be transported, assembled, handled and dismantled by one person. For comparisons of Orthoptera species richness, abundance and community composition between habitats, we recommend using a quadrat of 2 m² size and 0.8 m height and a minimum sampling area of 20 m² per plot (10 touchdowns per plot). For long-term monitoring or when species are sampled that generally occur in low density, a sampling area of 30 m² (15 replicates) is suggested. By contrast, for the surveys of tiny species (e.g., groundhoppers) and developmental stages (nymphs), smaller box quadrats can also be used and the sampled area per plot can be below 20 m². Box quadrat sampling is less dependent on favourable weather conditions and vegetation structure than many other insect survey techniques. Overall, it allows rapid and highly precise assessments of Orthoptera community composition.

Color Catcher Sheets for the Construction of Low-Cost, Planar Optical Sensors

Color Catcher Sheets for the Construction of Low-Cost, Planar Optical Sensors

Optimization of Embodied Energy and Construction Cost of Low-Income Housing in Urban India

India is the most populous country in the world, having a population of 1.42 billion in 2022. It is urbanizing rapidly, with the present urbanization level at about 35%, which is expected to reach about 40% by 2030. There was an estimated demand of 11.22 million homes in urban India in 2017, of which 95% was in the affordable housing sector. This demand is expected to increase with the current urbanization trends. The Indian government is promoting the construction of millions of affordable houses under its ambitious Prime Minister’s Housing Program. These houses are planned, designed, and constructed using local materials and techniques, considering local climatic, geological, hazard, and socio-economic conditions. We examined the 30 most commonly applied housing typologies to determine which typologies and materials have minimum embodied energy and construction costs. The results indicate that load-bearing housing construction of up to three stories, with a plinth–carpet area ratio of 1.31, constructed with any of the blocks-based masonry techniques, has the lowest embodied energy and construction cost, and houses with a plinth–carpet area ratio of 1.51 have the highest. Further, houses constructed with Hollow CC block masonry have the lowest embodied energy, and HF Fly Ash block-based masonry has the lowest construction cost.

On the Univariate Vector-Valued Rational Interpolation and Recovery Problems

In this paper, we consider a novel vector-valued rational interpolation algorithm and its application. Compared to the classic vector-valued rational interpolation algorithm, the proposed algorithm relaxes the constraint that the denominators of components of the interpolation function must be identical. Furthermore, this algorithm can be applied to construct the vector-valued interpolation function component-wise, with the help of the common divisors among the denominators of components. Through experimental comparisons with the classic vector-valued rational interpolation algorithm, it is found that the proposed algorithm exhibits low construction cost, low degree of the interpolation function, and high approximation accuracy.

Feasibility of managing and organizing the problem of informal settlements a field study on informal areas in Najaf Governorate

The research aims to study the problem of informal housing in Najaf Governorate, present strategic scenarios to solve the problem, as well as choosing the low-cost construction strategy as an approved strategy in the research. The study included (9) areas in which informal housing units spread, namely (Al-Radhwiya, Al-Rahma neighborhood, Al-Najaf Sea depression, Al-Shawafi area, behind Al-Quds neighborhood, Al-Jadidah II slums, Al-Jadidah III slums, Tabuk neighborhood, Al-Barakiyah), affiliated to the Najaf Governorate Municipality Directorate. The researchers used the descriptive analysis method based on structured personal interviews in informal areas to identify the problem, in addition to using financial tools by calculating costs (fixed capital, working capital) and revenues to solve the problem by submitting a proposal to establish a low-cost residential complex. The study reached several conclusions, the most important of which is that efforts and procedures can be organized to reach a radical solution by choosing the optimal and fastest scenario, which is building low-cost housing units, and benefiting from the areas on which slums were built. The study recommended a set of recommendations, the most important of which is forming a government working group from the departments concerned with urban planning, the municipality, the Investment Authority, and departments related to infrastructure, to prepare a technical study and an action plan to establish a package of projects distributed across the governorate's areas. These projects are granted to the best investors in establishing low-cost housing units, and forming a subcommittee to evaluate the lands and re-use them in an optimal manner. In a way that achieves benefit for the city, whether by converting them into green spaces, parks, or investment projects that enhance commercial activity in the city.

Perceptions, Tensions, and Contradictions in Timber Construction: Insights from End-Users in a Chilean Forest City

The study addresses the underutilisation of wood in construction in Chile, particularly given the country’s robust forestry sector. The research investigates perceptions, tensions, and contradictions among end-users regarding timber construction in Valdivia, a city with a mixed forestry industry. Methods included a comprehensive survey of 96 households across various socioeconomic clusters, utilising descriptive and exploratory statistical analyses. Key findings reveal persistent negative perceptions about wood’s durability, fire resistance, and maintenance costs. However, positive aspects, such as lower construction costs and adequate thermal comfort, were also noted. Surprisingly, concerns were raised about wood’s environmental impact, including deforestation and its role in combating climate change, contrasting with the material’s known ecological benefits. The study concludes that these perceptions are deeply influenced by ideological and sociopolitical factors, suggesting that mere marketing strategies may not suffice to alter public opinion. Instead, a collaborative effort involving public policy, industry advancements, and transparent scientific communication is essential to promote the benefits of timber construction and address the entrenched biases.

EXPERIMENTAL EVALUATION OF EXPANSIVE SOIL STABILIZED WITH WHEAT HUSK ASH AND SISAL FIBER

Everything starts with soil. Being a civil engineer, we are aware of how essential soil is to construction, as everything is dependent on it. Before building any kind of structure on top of soil, we examine the soil's characteristics and behavior to determine its strength and ability to support the weight of the structure to be built on top of it. In this study work, we used agricultural waste materials, such as wheat husk ash (WHA), as a stabilized material in soil at different percentages of 5%, 10%, and 15% to perform various tests on the soil to determine its qualities or strength. Sisal fibers are inexpensive, readily available locally, and environmentally benign, making them an excellent choice for enhancing soil properties. The stabilizing effect of sisal fiber on soil characteristics has been experimentally investigated in this work. In light of this, an experimental study is carried out using pricey, locally accessible soil that has been blended with various percentages of sisal fiber. In the CBR mold and UCS sampler, soil samples are prepared at their maximum dry density (MDD) matching to their optimum moisture content (OMC) both with and without Sisal Fiber and WHA. In the laboratory, CBR and UCS tests are carried out in accordance with the proportion of Sisal Fiber by dry weight of soil, which is determined to be 1%, 1.5%, or 2%. According to test results, the amount of sisal fiber in the soil increases with its saturated CBR and UCS value. When wheat husk ash and sisal fiber are added, the CBR of the mix increases and the pavement thickness decreases, resulting in lower construction costs and ultimately, more economical highway building. Key Words: Compaction test, CBR, UCS, WHA, Sisal Fiber

Experimental study on the pullout behavior of steel rebars in masonry shotcreted layer

Unreinforced masonry (URM) buildings are quite popular worldwide due to their low construction costs, despite being susceptible to significant damage even from moderate earthquakes. In many cases, reconstruction may not be the most viable option due to financial and time constraints. Among the available retrofit solutions, steel-reinforced shotcrete (SRS) proves to be a cost-effective, straightforward, yet effective method for repair/retrofitting. This paper presents the results of an experimental study aimed at evaluating the effects of various construction conditions on the rebar pullout resistance of steel-reinforced shotcrete used as a retrofit method for URM walls. To achieve this, a total of 46 full-scale URM specimens were manufactured and tested, each consisting of a one-sided 50 mm-thick shotcrete layer with a single 8 mm steel rebar. The variables examined included the condition of the URM surface before the shotcrete application (wet/dry, with/without finishing including plaster/scratched plaster/oil paint), the condition of the rebar surface (rusty/clean), the type of rebar (plain/ribbed), rebar cover in the shotcrete layer (20/25/30 mm), and the URM substrate temperature before application of shotcrete (20 °C/-16 °C). The results indicate that there is an increase in pullout resistance of the specimens under the following conditions: when the wall's finishing is removed, the wall's surface is wetted before shotcrete application, ribbed steel rebar is utilized, and the temperature of URM before shotcrete application is 20 °C, there is an increase in pullout resistance of the specimens by 58 %, 56 %, 32 %, and 13 %, respectively. Additionally, when the steel rebar cover is sufficient, ribbed steel rebar is utilized, and this rebar is rusted, there is an increase in pullout resistance of the specimens by 55 %, 10 %, and 6 %, respectively.

Simulation of flow characteristics in open channels with inflatable dam

Abstract Inflatable dams are structure cylindrical inflatable and deflated bile structures made of rubberized material placed on top of a rigid base and inflatable by air, water, or a combination of both. The present paper aims to measure the water surface elevation, and depth of flow in Shatt Al Ibrahim and comparison with design depth and study the flow state according to design discharge and also according to scarce discharge. The study effect of the height of the dam filled with water on upstream and downstream water depth and analyzed numerically by using HEC-RAS program one–one-dimensional flow in two states, steady flow and unsteady flow under different variables such as changing of discharge. Good results were obtained in two flow states. The results show that the proper solution for maintaining the required water levels is to construct inflatable dams, due to lower construction and maintenance costs, easy and simple of operation, simple and easy to inflate and deflate quickly to prevent upstream flooding. The results of the current study indicated an increase in the water surface height (WS) and water depth (Wd) across the channel after the implementation of inflatable dams compared to natural conditions. Specifically, the data indicate a significant increase in (WS) and (Wd) at “station 52”, where (WS) increased by 0.45 m with a 0.5 m dam and 1.43 m with a 1.5 m dam compared to the basic scenario. This confirms the adaptability of inflatable dams in adapting water levels to real-time requirements, underscoring their potential as a cost-effective solution to mitigate upstream floods and improve water resource management practices.

Seasonal large-scale thermal energy storage in an evolving district heating system – Long-term modeling of interconnected supply and demand

Given the strong seasonal nature of heating demands, peak heat is important during colder seasons. Instead of peak heat plants, seasonal large-scale thermal energy storage (TES) could be utilized. These can be charged during warmer seasons and discharged when required, decreasing the need for peak heat plants. Systems modelling studies on seasonal TES are lacking. Thus, a long-term local energy system model is applied under different scenarios to investigate the potential roles of seasonal TES in an evolving heating system. The results show that seasonal TES is economically viable for: all future electricity price cases for low TES construction costs, corresponding to repurposing of underground oil storages, and for most electricity price cases for mid- and high construction costs, corresponding to new underground excavations. Seasonal TES mainly decrease the investments in and usage of electric boilers or biogas boilers, while increase the utilization of heat pumps. Other technologies may be affected depending on the future trajectory of electricity price developments. The size of the TES is between 3 and 7% of the annual district heating heat demand, depending on construction cost and electricity price development. The expansion of district heating into new housing is mostly unaffected by the availability of TES.

Probabilistic evaluation of spectral acceleration demands on light secondary systems supported by partially self-centering structures

Partially self-centering structures are promising seismic resilient structural systems by reducing residual inter-story drifts with low initial construction costs. Comprehensive studies focused on structural design and performance evaluation, but no research was conducted to investigate the design of nonstructural components in partially self-centering structures. This research focuses on developing the probabilistic spectral acceleration demands for the nonstructural design in partial self-centering structures. 320 near-fault recorded ground motions were adopted for considering the uncertainties of seismic excitations. The spectral accelerations of the light nonstructural component were obtained through comprehensive dynamic analyses. The logarithmic normal distribution can be used for describing the probabilistic distribution of floor spectra for partially self-centering structures under earthquakes, validating through the Anderson-Darling test. The influences of design parameters (including structural period, hysteretic parameters, structural damping, the ratio of the structural period to the nonstructural period, and nonstructural damping) on the probabilistic distribution of floor spectra were investigated through parametric dynamic analysis results. Artificial neural network (ANN) models were developed for predicting the probabilistic floor spectra for partially self-centering structures. The analysis results indicate that ANN models can achieve excellent accuracy with a coefficient of determination larger than 0.99. Comparative analysis results reveal that the ASCE method may underestimate the acceleration demand of light secondary systems supported by partially self-centering structures. The developed ANN models were interpreted using the shapely additive explanations. It has been found that the fundamental periods of the main structure and nonstructural components and the response modification factor show significant effects on the median and deviation of the probabilistic floor spectra for partially self-centering structures. The software FloorSpecPS was established to predict the probabilistic floor spectra for partially self-centering structures using the developed ANN models in practical application.

Barriers and Enablers for Green Concrete Adoption: A Scientometric Aided Literature Review Approach

Green concrete is a concept of concrete that uses waste materials to reduce its environmental impact and has various benefits for the environment, economy, and society, such as lower construction cost, less landfill waste, new waste markets, and better quality of life. This study aims to investigate and analyze the barriers and enablers for green concrete development and implementation, based on a mixed-method approach that combines a scientometric analysis and a literature review. The Scopus database was explored first and then these data were used to investigate and capture six categories of barriers and enablers: awareness, technical, economic and market, implementation, support/promotion, and social. Results reveal that the technical and operational aspects are the main challenges for green concrete, while the awareness and social acceptance are not major issues. The current study surpasses the mere popularization of green concrete. Instead, it delves into its multifaceted dimensions, that is, technical, economic, social, and institutional. By meticulously analyzing a diverse group of research articles, key challenges and opportunities associated with green concrete are pinpointed. The findings not only deepen our understanding of the barriers impeding the widespread adoption of green concrete, but also shed light on potential solutions. In summary, this work bridges theory and practice, providing invaluable insights for future researchers, practitioners, and policymakers in the sustainable construction domain.

Performance-based assessment of the novel prefabricated CFST bridge pier by numerical approach

This study aims to profoundly investigate the seismic performance and application prospect of the typical continuous beam bridge with the novel prefabricated concrete-filled steel tubular (CFST) piers, with advantages in simple on-site assembly, convenient transportation of prefabricated components, good seismic performance, and low construction cost. According to two prototype continuous beam bridges respectively equipped with low and tall typical reinforced concrete (RC) piers, 7 bridge cases with prefabricated CFST piers featuring various configurations of the tie beams are designed. Three-dimensional numerical models of these bridge cases are established and verified with the previous experimental studies, and numerical simulations of all the bridge cases are conducted to assess and compare the seismic responses and fragility curves. The results show that the bridges with prefabricated CFST piers exhibit a reduction in top pier transversal displacement and maximum curvature along the pier height, which are 43 % and 138 % lower than those of the prototype RC piers, respectively. Besides, the bridges with prefabricated CFST piers generally present lower probabilities of being damaged compared to those of the prototype bridges with RC piers.

Differentiation of aging properties in different circumferential layers of the polyethylene pipeline

Abstract Polyethylene (PE) pipelines have been widely used as a substitute for steel pipelines in urban natural gas transportation around the world, due to their corrosion resistance, low cost, and good construction performance. As a kind of non-metallic material, PE pipelines age while being used. Currently, the aging status of PE pipelines is not clear and a reliable method to evaluate the aging life of them is necessary to be deeply explored. Due to the different contact with oxygen while using, the aging conditions of the outer, middle, and inner layers are also various. According to the research in this work, the aged PE80 pipelines in accelerated aging experiments were divided into three layers including outer, middle, and inner layers. The aging performance of the three layers has great differences. A comprehensive method for the aging properties of PE80 pipelines should be established while evaluating PE pipelines in service.