Current Issue : April - June Volume : 2021 Issue Number : 2 Articles : 5 Articles
One of the major challenges of constructing any high rise building for civil engineers is to make it earthquake resistant. This resistance largely depends on the building’s shape and structural system. A comparative study has been done in this paper about the seismic behavior and response of buildings having a regular plan and plan irregularity (re-entrant corners). The 5 building models considered in this study are 15 stories each, the same area and identical weight. Among the 5 building models, 2 are with a regular plan (square, rectangle) and the other 3 building models are with plan irregularity (re-entrant corners). All of them are modeled using ETABS 2015 program for Dhaka, Bangladesh (seismic zone 2). Static loads, wind loads and seismic loads are considered for each model and dynamic response under Bangladesh National Building Code (BNBC) 2006 response spectrum has been meticulously analyzed. A comparison for story displacement, base shear, story drift and time period has been established and explored for dynamic response spectrum among the models. The results show that buildings with irregularity have a greater value of time period, drift and displacement and hereby are more susceptible to damage during an earthquake or disaster....
Expanded clay concrete (ECC) is a promising structural material for buildings due to its light weight and heat- and sound-insulating properties. Adding basalt fibers (BFs) in ECC reduces its brittleness and enhances its mechanical properties. The heat treatment (HT) of BF-reinforced ECC can significantly accelerate the strength growth during cast-in-situ construction, which allows the reduction of the turnover of the formwork and the construction period, as well as leading to lower construction costs. This paper presents an HT technology for load-bearing structures, containing a BF-reinforced ECC mix and using infrared rays for cast-in-situ construction. The issue of the strength growth of BF-reinforced ECC during HT has been studied. Microsilica and fly ash were added to the ECC mix to obtain a compressive strength of more than 20 MPa. Four different mixes of ECC with chopped BFs in the ratios of 1:0, 1:0.0045, 1:0.009 and 1:0.012 by weight of cement were studied. Test specimens were heated by infrared rays for 7, 9, 11, 13, 16 and 24 h. Then, the heat-treated specimens were tested for compressive strength after 0.5, 4, 12 and 24 h cooling periods. The analysis and evaluation of the experimental data were carried out based on probability theory and mathematical statistics. Mathematical models are proposed for forecasting the strength growth of BF-reinforced ECC during cast-in-situ construction....
The scientific and effective prediction of the water consumption of construction engineering is of great significance to the management of construction costs. To address the large water consumption and high uncertainty of water demand in project construction, a prediction model based on the back propagation (BP) neural network improved by particle swarm optimization (PSO) was proposed in the present work. To reduce the complexity of redundant input variables, this model determined the main influencing factors of water demand by grey relational analysis. The BP neural network optimized by PSO was used to obtain the predicted value of the output interval, which effectively solved the shortcomings of the BP neural network model, including its slow convergence speed and easy to fall into local optimum problems. In addition, the water consumption interval data of the Taiyangchen Project located in Xinyang, Henan Province, China, were simulated. According to the results of the case study, there were four main factors that affected the construction water consumption of the Taiyangchen Project, namely, the intraday amount of pouring concrete, the intraday weather, the number of workers, and the intraday amount of wood used. The predicted data were basically consistent with the actual data, the relative error was less than 5%, and the average error was only 2.66%. However, the errors of the BP neural network model, the BP neural network improved by genetic algorithm, and the pluralistic return were larger. Three conventional error analysis tools in machine learning (the coefficient of determination, the root mean squared error, and the mean absolute error) also highlight the feasibility and advancement of the proposed method....
The construction risk of deep foundation pit (DFP) engineering is high, and accidents occur frequently. It is necessary to evaluate the risk of deep foundation pits before construction. At present, although there are many risk assessment methods, there is not one with strong applicability and high accuracy. Based on expert scoring, this paper analyses the risk from two aspects (the severity of consequences and the probability of occurrence), divides the severity of the consequences into five indexes, calculates the risk by using the analytic hierarchy process (AHP), and sets the expert weight index so that the subjective expert scoring result can obtain the best possible objective calculation result. In addition, this paper uses the membership function from fuzzy mathematics to establish the level of risk and optimize the evaluation criteria of risk events. An engineering example is introduced, and the result of the risk assessment shows that the evaluation result R (risk value) obtained by the optimized risk assessment method in this paper is 7.9 and that the level of risk is grade III. The risk assessment method proposed in this paper has strong applicability and can obtain more accurate evaluation results. This method can provide a reference for the risk assessment of deep foundation pit engineering....
The bond-slip effect has a great influence on the seismic performance of reinforced concrete structures and ignoring it will overestimate the seismic performance of the structures. Based on the low-cyclic reversed loading experiment of a reinforced concrete column, this paper uses OpenSees to establish a nonlinear finite element model considering bond-slip and verify its correctness. In this paper, a multispan continuous girder bridge with varying pier heights is taken as an example. Considering the effect of the bond-slip behavior of steel bars, a refined finite element model based on the OpenSees platform is established to do the numerical simulation analysis. 10 seismic waves are selected from the Pacific Earthquake Engineering Research Center (PEER) according to the site condition and modulate the amplitude to 150waves.This paper uses the incremental dynamic analysis (IDA) and the second-order reliability method to analyze the seismic fragility of bridge components and systems, respectively. Results show that the exceeding probability increases obviously when considering bondslip, and with the increase of seismic spectral acceleration, the influence of bond-slip on the exceeding probability of components also increases; when bond-slip is considered, the difference of system fragility between the upper and lower limits under four damage states is greater than that without bond-slip....
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