Carbon dioxide (CO2) emissions is a major greenhouse gas that causes global warming. Many researchers in the fields of architecture, engineering, and construction try to measured CO2 emissions during ...a building's lifecycle. However, research on the CO2 emissions during construction stage are less studied than those during other stages because they are considered to be lower than the emissions from the building's materials' production or operational stage. In addition, research has been hindered by a complicated calculation process and a lack of data, and thus few methods are available for forecasting construction-stage carbon emissions, especially at the early design stage. In order to estimate the environmental effects of the emissions from the vast number of construction activities, this study applies a random forest (RF) based predictive method to predict construction-stage carbon emissions. The RF-based model uses data from 38 buildings in the Pearl River Delta region of China for the initial training set to find the relation between construction-stage carbon emissions and design parameters. Compared with the multilinear regression method, the RF-based model has a higher coefficient of determination and lower mean square error. The model developed in this study facilitates the prediction of construction-stage carbon emissions at the early design stage of a building. This opens up novel opportunities to reduce carbon emissions from buildings, which had previously been possible only at the latter stages of a building's life cycle. It will also help policymakers account for the probable distribution and amount of CO2 emissions in a city when multiple construction projects are proceeding simultaneously, so that measures can be implemented to avoid excessive emissions.
•A random forest-based model is developed for the prediction of construction-stage carbon emissions at the early design stage.•The relationships between design parameters and predicted construction-stage carbon emissions are quantitatively determined.•The building's foundation area, underground area, and height are found to have the greatest effect on its construction-stage carbon emissions.•The random forest-based model facilitates the prediction of construction-stage carbon emissions at the early design stage of a building project.
Construction of bridges by the cantilever method needs to consider the accidental release of the formwork traveller (ARFT) in the design phase. Often this phase is a critical situation that current ...regulations treat as a static analysis amplified by a dynamic factor due to the difficulty in setting up a model able to simulate the complex interaction between the formwork and the structure in the time domain during the accidental release. To overcome the simplistic approach of the regulations and to avoid the complexity of detailed ARFT modelling, in this research the release of the formwork is modelled as a simple force-time function applied to the bridge. This function has an equivalent effect on the structure as the accidental release, and it has been tuned using experimental tests on a 1:100 scale aeroelastic model of the cable-stayed Bioceanic Bridge. To test the applicability of the proposed time-function the Chilina continuous beam Bridge was also analysed. The article shows that the simplified procedure in the regulations can sometimes underestimate and overestimate dynamic amplification and, thus, a methodology is proposed to carry out the specific dynamic calculation that the regulations suggest for those cases where it is necessary.
•Experimental tests on the scale model of the cable-stayed bridge.•Comparison with finite element model results.•Evaluation of the dynamic amplification factor in regulations.•Proposal of force functions for the numerical dynamic study.•Comparison of results between kinds of formwork travellers.
The construction process of self-anchored suspension (SAS) bridges undergoes frequent system transformations and loadings, accompanied by complex strong geometric and contact nonlinear behaviours. ...The accurate state assessment of such a process generally requires the nonlinear finite element analysis (FEA) to perform a stage-by-stage forward, cumulative calculation based on the principle of incremental superposition. This sort of calculation means that the structural equilibrium of any intermediate state of the process, referred to as a construction stage, must be accumulated from its previous construction loading history, which is susceptible to computational effort and divergence limitations. This paper overcomes these limitations by proposing a direct and fast method that is independent of the cumulative calculation in the analysis of any specified construction stage, in favour of the construction optimization design and uncertainty analysis. The unstrained assembly formats for the typical construction process of SAS bridges are established, and the elements with constant physical quantities as the characteristic parameters are used to describe the various structures, boundaries, loads and their changes during the construction. On this basis, an interactive analysis framework integrating the numerical iteration with the FEA is established to achieve an accurate equilibrium for the construction stages. An enhanced interval-genetic algorithm (IGA) is employed as the optimization engine to smoothly accelerate global convergence. The proposed framework is applied to an SAS bridge under construction, and the validity and performance of this approach are demonstrated by considering the in-field test data.
•An interactive CP-IS framework integrating the numerical iteration with the FEA.•Unstrained assembly format established for self-anchored suspension bridges.•Strong global optimisation ability of the framework achieved by the IGA algorithm.•The framework is applied to the construction practice of the Weihe River Bridge.
For improving the dynamic management performance of construction cost, the dynamic control model of cost of construction based on fuzzy neural network is studied. Consider the effect of resource ...allocation, construction progress and construction quality on the cost of project in construction stage, and build the cost control index for the project in stage of construction. The fuzzy logic model is used in selecting the main cost related indicators from project cost control index system at the construction stage as input neurons of the BP NN, and the BP neural network is employed to output the results of prediction of cost at the construction stage. The project cost prediction results are set as the data basis for the dynamic control of the project cost, determine the most optimistic cost, the most probable cost and the most pessimistic cost of project cost in stage of construction through key chain method, and set buffers to realize dynamic control of project cost in stages of construction. The evaluation results prove that the developed method will be able to accurately predict the project cost in stages of construction, and the cost saved in the construction phase of the project is more than 300000 yuan.
Many tank structures may not be stable during the construction phase, and this may lead to their becoming vulnerable to buckling under environmental loading conditions such as wind. Installing ...intermediate ring stiffeners of the proper size at the mid-height of the cylindrical shell may be the most effective way to stabilize these structures, especially under the effects of wind action. In the study, analytical and numerical studies were conducted to identify the required strength and stiffness for the intermediate ring stiffener. First, a new cylindrical shell-to- intermediate ring stiffness ratio was derived by considering curved beam and shell membrane theories. For strength criteria, the tributary height and the effect of shell- ring interaction on the internal forces and moments were examined by making use of Linear Analysis (LA) and Geometrically Nonlinear Analysis (GNA). The stress resultants developed in the intermediate ring stiffener were identified so that they could be used as strength criteria. For stiffness criteria, by considering the changes in the buckling resistance based on the developed stiffness ratio, an expression to compute the minumum intermediate ring stiffness was determined. In addition, Geometrically Nonlinear Analysis including Imperfections (GNIA) was also performed to examine the effect of the geometric imperfections on buckling strength of the steel tank with an intermediate ring stiffener, taking different imperfection amplitudes into account. The developed design equations in simple algebraic form can be utilized for the structural stability of cylindrical steel tanks during erection.
•The tanks may collapse under environmental effects such as wind before the roof is installed.•The weakness of the shell part of the structures during construction phase was addressed.•Effect of reinforcing steel tanks with ring stiffeners on wind buckling was studied.•A new stiffness ratio of cylindrical shell to intermediate ring stiffener was developed.•A novel stiffness criterion is proposed by taking into account the buckling strength of CS
To provide industry practitioners with a better understanding of the health impacts of occupational noise generated during construction activities, this paper applies measurement schemes to collect ...noise exposure samples of workers employed in 10 different trades and develops a health damage assessment model to quantify noise exposure level into hearing impairments suffered by field workers in units of “USD”. On-site measurements were conducted at two representative ongoing building projects in Beijing during 2013, and 270 valid noise exposure samples covering 10 trades were acquired. With these data, the occupational noise exposure indicator LEX, 8h was calculated and compared with the threshold limit of 85 dBA stipulated by China's authority. Then, a comparative analysis of noise exposure levels was conducted between two projects and among trades. Furthermore, a health damage assessment model was established to evaluate the real health impacts of construction noise in one of the sampling projects. The results demonstrate that workers in the construction industry suffer severe occupational health damage as a result of construction noise in China. Specifically, 94% of the total health damage occurred during the superstructure construction stage. Roofbolter operators, air duct workers, formwork fixers and concreters suffered from substantial harm in terms of per capita daily damage values. The occupational noise exposure measurement and health damage assessment based on practical project samples indicate that the proposed sampling schemes perform well and that the established health assessment model can effectively quantify health damage suffered by workers due to construction noise, thereby demonstrating its potential as a tool for establishing health subsidy standards for various trades.
•On-site noise exposure data of different construction workers were collected.•Occupational noise exposure law of measured trades was analyzed.•A noise-induced health damage assessment model was developed.•94% of the total health damage occurred in superstructure construction.•Formwork fixers were most impaired trade.
Due to the rapid development of the construction industry, large construction projects consume a significant amount of energy, and emit large amounts of carbon dioxide into the atmosphere, which has ...received extensive attention from the society. According to statistics, 30% of the energy losses and 40% of the solid wastes of the construction industry are generated during the construction phase. In addition, 40% of the solid waste generated by the construction industry is generated during the construction phase. Therefore, it is an important large potential research value in the construction stage emission reduction. As a result, this study aims to investigate precast concrete pile products and their carbon footprint at the construction stage based on the life cycle assessment (LCA) method. Based on the Intergovernmental Panel on Climate Change (IPCC), the Chinese Life Cycle Database (CLCD) databases, a database of mechanical equipment carbon emission factors was compiled. The carbon footprint of precast concrete piles was divided into three sources: material transportation, construction equipment, and office area. The carbon footprint calculation model of precast concrete pile during the construction stage was established. Lastly, a detailed case study was conducted to verify the empirical findings. Pile foundation area, pile foundation cost, and pile foundation number were analyzed as independent variables, through SPSS(Statistical Product and Service Solutions) software for regression analysis. Based on research result, the carbon emissions of construction machinery reached 73% of the total carbon emissions during the construction of precast concrete piles, and the carbon emissions of pile drivers are more than half of the carbon emissions of construction machinery. And there is a strong linear relationship between the area of pile foundation, the cost of pile foundation and the number of pile foundation and the total carbon emission during the construction of precast concrete piles.
This study contributes to the body of knowledge by providing the carbon footprint calculation and establishing the trend of carbon emissions for precast concrete pile construction. In addition to that, the findings of this study can be used to improve construction management plans and select energy-saving technologies. The results can also provide a theoretical support for the formulation of regulations and emission reduction policies based on building energy conservation and carbon emission reduction.
This study examines the differential impact of HSR station and airport on local debt risk during the construction and operation stage. Based on the data of China's prefecture-level cities from 2010 ...to 2019, Feasible Generalized Least Square (FGLS) model results show that HSR station under construction reduces local debt risk by attracting extra-municipal capital inflows. However, the more HSR stations and airports are opened, the more local governments invest in other infrastructure, leading to increased local debt risk. By dynamic test, it is found that the longer the opening time, the greater the difference between the positive impact of HSR stations and airports on debt risk. Further synergies suggest that both local governments and investors have high expectations for urban development driven by HSR stations rather than airports, and the presence of HSR station amplifies the positive external effects of the airport construction. These findings not only deepen the understanding of the risk impact of HSR station and airport, but also provide enlightenment for countries to develop HSR station and airport through debt.
•We test diverse impacts of HSR station and airport on local debt risk.•HSR station reduces the local debt risk during construction stage.•The opening of HSR and airport increases the local debt risk.•Government and investors have higher expectations for HSR-led urban development.
•The collapse mechanisms of a post-tensioned reinforced concrete (RC) truss bridge occurred during its construction has been analyzed.•Several numerical analyses have been carried out in order to ...reproduce the bridge failure.•Construction stage analysis has been performed in order to reproduce the bridge construction phases.•The results obtained have been compared to the crack patterns observed in the bridge before and after the collapse finding an excellent match.
On March 2018 a post-tensioned reinforced concrete (RC) truss bridge, built inside a North American university campus using the Accelerated Bridge Construction (ABC) method, collapsed during the construction phase, while the bars of a diagonal member were being re-tensioned. This process was not part of the scheduled construction phases, but it was decided by the designers after having observed several cracks in the structural nodes.
This paper aims to analyse the final design of the bridge useful to determine the hypothetical causes of the collapse. Several numerical analyses have been performed to reproduce the behaviour of the different structural elements during the construction phases. In particular, construction stage analyses have been carried out to obtain the internal actions acting on the structural elements and on the nodes during the different construction steps and in order to analyse in detail the critical phases where the occurrence of the collapse has been hypothesized. The collapse mechanism is identified in the shear failure of a node of the concrete truss during the re-tensioning of a diagonal element. In fact, the reapplication of the post-tension had increased the axial force of the diagonal and consequently the shear action on the node. Moreover, the results obtained have shown that the bridge has never been in safe conditions, mainly because the interface surface of the cold joints had not undergone any type of work and remained smooth.
•Tests carried out on asphalt specimens drilled out of a dam core.•Triaxial compression tests conducted at different temperatures and axial strain rates.•Triaxial creep tests conducted at different ...temperatures.•Discussion of stress-strain behavior of asphalt core during dam construction.
The stress-strain behavior of asphalt concrete strongly depends on temperature and strain rate. The asphalt concrete in a dam core is placed and compacted at high temperature, and the temperature reduces slowly inside the embankment dam during construction. Embankment dams are constructed layer by layer, and it is typical to spend one to three years to complete a 100–150 m high structure. This paper investigates the stress-strain-strength behavior of the asphalt concrete by conducting triaxial compression tests at different temperatures in the range 5–60 °C, at different axial strain rates in the range 1%/min to 0.00025%/min, and by performing triaxial creep tests. The tests are carried out on asphalt specimens drilled out of a compacted dam core.
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