Current Issue : April - June Volume : 2021 Issue Number : 2 Articles : 5 Articles
In the shaking table test of large cassette structure, story drift is an essential set of experimental data.Thetraditional method of displacement measurement is limited to problems such as necessary full contact with the structure model for installation of sensors, large work of installation, and easily interfered by environment. The noncontact displacement measurement method, such as optical measuring technology, can solve the above problems and serve as an effective supplementary method for traditional displacement measuring in the shaking table test. This paper proposed a vison-based displacement measuring method. Predesigned artificial targets which act as sensors are installed on each floor of the cassette structure model. A high-speed industrial camera is used to acquire the series of the images of the artificial targets on the structure model during the shaking table test. A Python-OpenCV-based structural calculation program combining computer vision and machine vision is developed to extract and calculate the displacement of the artificial targets from the series of the images acquired. The proposed method is applied in a shaking table test of a reduced-scale fifteen-floor reinforced concrete cassette structure model, in which the laser displacement meter and the seismic geophone are also applied as a comparison.Theexperimental results acquired by the proposed method are compared with the results acquired by the laser displacement meter and the seismic geophone. The average error of the story drift obtained by the proposed vision-based measurement method is within 5% and is in good agreement with the laser displacement meter and the seismic geophone, which confirms the effectiveness of the proposed method....
Rockfall occurs on the excavation of the slope of highway resulting from excavated rock pieces. In order to solve the problem of rockfall protection during the disturbance of high slope secondary excavation, rockfall analysis program RocFall was used to perform inverse calculation for rockfall path of excavation disturbed rock. Based on a case study of a reconstruction and expansion project, two rockfall movement models were proposed under excavation disturbance. Moreover, the safety of protective structures under five protection schemes and different initial rockfall movement points is evaluated according to the rockfall interceptions rate. The evaluation results were further verified by long-term field observation. The results show that the protective structure at the slope top has a better interception effect to rockfall. It was difficult to intercept the splash stone, which threats to the traffic safety of the existing roads. According to different construction points of mechanical excavation and the interception rate of splash stone by the protective structure, the forbidden region and safety region of mechanical excavation were proposed....
The construction industry in Senegal is experiencing an upsurge in the development of residential housing units and administrative buildings within the new Diamniadio municipality, an area located just about 35 km from the capital city of Dakar. Laboratory oedometer or expansive-index tests, however, show poor density and compromised shear strength in the soil samples within the area -posing serious construction problems due to significant volume changes (swellings) that occur when subjected to moisture, thus, bringing into question the structural performance integrity of the soil, and the financial implications of substitute soil types used to compensate for its poor tensile strength. By way, the companies collect the soil of this location (Diamniadio) and throw it to make pile or micro-pile (pious) for their structures. This article demonstrates how we can value the soil of Diamniadio and the Typha Australis in residential building with a reasonable cost. Typha Australis is a plant generally luxuriant within the northern and central belts of Senegal but also known for its negative ecological impacts on the agricultural production of rice. The valorisation of the soil of Diamniadio will pass by the ability to increase its stability or to decrease its shrinkage/swelling rate. When we achieve it, the soil associate with Typha Australis will be used for small bricks which can be useful for partition wall and so the soil will not be ever thrown as a non-useful material. Tests results of soil specimens extracted from the site show a shrinkage rate of 29.19% with estimated cracking depths of 3.5 cm. But by adding gradually Typha Australis, the shrinkage rate will pass from 29.19% to 5.13% with the material treats with 10% by mass of Typha Australis. Moreover, the crackings in the cylindrical specimen disappear. That shows the increase of the stability; thus the composition will be used for building bricks. However, the densities will also be affected by the presence of Typha Australis. The density is decreased from 2032.28 Kg/m3 for the soil without Typha Australis to 937 Kg/m3 for the one with 10% of Typha Australis....
With the advantages of fast construction speed and small disturbance to stratum, shield tunneling is becoming the preferred construction scheme for metro construction. However, if the disturbance of stratum cannot be clearly understood, it will affect the safety of adjacent underground structures and aboveground buildings. Based on the construction of the interval tunnel between Shizishan station and Chuanshi station of Chengdu metro line 7 project, this paper proposed a simplified calculation method to analyze the impact of shield excavation on adjacent pile foundation. A two-stage method of modified Peck formula and Winkler elastic foundation model was used to investigate the additional displacement and internal force of pile. A three-dimensional numerical model validated with the field test data was performed to compare with the theoretical results. The impact factors and their impact degree were discussed. The results show that the additional displacement and internal force are at a reasonable and acceptable level. The permanent pile foundation should adopt the small diameter pile as far as possible. When the small diameter pile foundation cannot meet the stress requirements, the design scheme of the pile group should be adopted. The area around shield tunnel is divided into strong impact area of pile foundation (S ≤ 0.75 D), slight impact area (0.75D≤ S ≤ 1.5 D), and no impact area (S > 1.5 D). The pile researched in this paper (S 0.83 D) is in the slight impact area....
This paper discusses the origins of torsion and its effect on the response of structures with a focus on the contribution of experimental data. The fact that torsion increases the stresses in structures, augmenting strain and damage during earthquakes, was confirmed in the 1960s. Over the years, the torsional response of structures has mainly been analysed through numerical studies, because few buildings are equipped with translational sensors, and even fewer are equipped with rotational sensors. This is likely to change as building instrumentation becomes more widespread and new generations of rotational sensors are developed. Therefore, this paper focusses on a number of scientific questions concerning the rotational response of structures during earthquakes and the contribution of experimental data to the understanding of this phenomenon....
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