Airblast evolution initiated by Wangjiayan landslides in the M_(s)8.0 Wenchuan earthquake and its destructive capacity analysis

Airblasts,as one common phenomenon accompanied by rapid movements of landslides or rock/snow avalanches,commonly result in catastrophic damages and are attracting more and more scientific attention.To quantitatively analyze the intensity of airblast initiated by landslides,the Wangjiayan landslide,occurred in the Wenchuan earthquake,is selected here with the landslide propagation and airblast evolution being studied using FLUENT by introducing the Voellmy rheological law.The results reveal that:(1)For the Wangjiayan landslide,its whole travelling duration is only 12 s with its maximum velocity reaching 36 m/s at t=10 s;(2)corresponding to the landslide propagation,the maximum velocity,28 m/s,of the airblast initiated by the landslide also appears at t=10 s with its maximum pressure reaching594.8 Pa,which is equivalent to violent storm;(3)under the attack of airblast,the load suffered by buildings in the airblast zone increases to 1300 Pa at t=9.4 s and sharply decreased to-7000 Pa as the rapid decrease of the velocity of the sliding mass at t=10 s,which is seriously unfavorable for buildings and might be the key reason for the destructive collapse of buildings in the airblast zone of the Wangjiayan landslide.

Influence of soil——structure interaction on seismic collapse resistance of super-tall buildings

Numerous field tests indicate that the soilestructure interaction （SSI） has a significant impact on thedynamic characteristics of super-tall buildings, which may lead to unexpected structural seismic responsesand/or failure. Taking the Shanghai Tower with a total height of 632 m as the research object, thesubstructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower. Therefined finite element （FE） model of the superstructure of Shanghai Tower and the simplified analyticalmodel of the foundation and adjacent soil are established. Subsequently, the collapse process of ShanghaiTower taking into account the SSI is predicted, as well as its final collapse mechanism. The influences ofthe SSI on the collapse resistance capacity and failure sequences are discussed. The results indicate that,when considering the SSI, the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved, with a corresponding decrease of the seismic demand.In addition, the SSI has some impact on the failure sequences of Shanghai Tower subjected to extremeearthquakes, but a negligible impact on the final failure modes. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Preliminary investigation of building damage in Hatay under February 6,2023 Turkey earthquakes

On February 6,2023,an M_(w)7.8 earthquake hit the south of Kahramanmaras prefecture,Turkey,followed by another M_(w)7.5 earthquake after nine hours in the middle region of the Kahramanmaras prefecture.More than 84,000 buildings collapsed or were severely damaged,and more than 50,000 lives were lost in Turkey and Syria.Some of the authors,as members of Chinese rescue team,entered Antakya,Hatay prefecture,and investigated the damaged buildings.This paper first summarizes the damage patterns of buildings and provides three reasons for the massive number of collapsed buildings;i.e.,the lack of seismic measures for better ductility,site effects such as liquefaction and surface rupture,and pronounced low-frequency components of the ground motions.Next,the seismic responses of two typical buildings are calculated based on the geometric data estimated by visual inspection.The results imply that the resonance of the whole structure and the poorer ductility of key members resulted in the collapse of buildings.Finally,some conclusions are drawn.Note that although a large number of buildings were seriously damaged to collapse,the majority of buildings in the areas of extreme shaking were lightly or moderately damaged,which implies that well designed and constructed buildings were able to survive and protect human lives even in over-design earthquakes.

A Study of Underpinning Methods Used in the Construction Industry in Nigeria

Foundation and retaining wall failures account for the highest case of structural failures.This is a report on a study of underpinning methods used in the construction industry in Nigeria.In view of underpinning,just like most engineering decisions,there is no unique solution,the research investigated technique of remedying foundation defects and whether there are innovations as regards to the underpinning methods used in Nigeria.To achieve the desired objective structured questionnaire,oral interviews and case study of an ongoing underpinning work were carried out.Result shows that differential settlement with a mean of 2.28 is the most frequent cause of foundation failure.While the continuous strip and reinforced mat with mean of 2.7 and 2.67 respectively,are most frequently used underpinning methods in Nigerian construction industry.Also 81.3%of the respondents agree that underpinning methods adopted are suitable and effective.Professionals in Nigeria have devised unique method of underpinning.It was recommended that proper and adequate site investigation should be carried out.Heavy penalties and sanctions should be meted on those construction firms that employ quack professionals.

Mechanical Characteristics Test of Concrete Steel Bars Available in Côte d’Ivoire

Buildings collapse has now become a recurrent phenomenon in Côte d’Ivoire. Therefore, this study was conducted to find out the reasons for these disasters, and check in particular to the extent, and concrete steel bars produced in Côte d’Ivoire and used in buildings’ structures are involved. Samples having 6, 8, 10 and 12 mm in diameter steel taken from the five (5) major manufacturers or suppliers of the Ivorian market were subjected to physical, chemical and mechanical tests to determine their performance. A comparison of these results with the NF EN 10080 and NF A35 080-1 standards made it possible to calculate the probability to have out-of-standard products in a structure. Pieces having 60 cm were cut from three bars of the same thickness and then subjected to tests. These are the chemical test by optical emission spectrometer, physical tests by caliper measurements of diameter, height of bolts and ribs and calculation of linear mass, and tensile tests with the help of hydraulic press. These tests made it possible to determine the characteristics of the steel bars. Then, these characteristics were compared with standards NF EN 10080 and NF A35 080-1, in order to judge their conformity for construction. Finally, the likelihood of having non-standard steel bars in a structure is calculated. These tests indicate that the relative surfaces of the bolts of the various bars HA6, HA8, HA10 and HA12 vary from 0.146 to 0.323 respectively;0.120 to 0.312;0.101 to 0, 297 and 0.142 to 0.482. Likewise, their calculated linear masses of these bars are respectively between 28.3 mm2 and 222 g/m;50.3 mm2 and 395 g/m;78.5 mm2 and 617 g/m;and 113 mm2 and 888 g/m. In addition, their yield strengths and elongations at break vary from 344 MPa to 582 MPa and from 0.2% to 15% respectively. According to analysis of these results, 100% of steel bars would lead to a steel-concrete adhesion that complies with standard requirements and 100% have a linear mass or density lower than the standard. Similarly, on the mechanical aspect, 70% of steel bars have a yield strength lower than 400 MPa and 95% have an inappropriate ductility. Non-compliance with cross-sections, inadequate performance and non-compliance with the chemical composition of steel bars expose buildings to low durability and even sudden collapse of their structural elements. Concrete steel bars contribute a great deal to failures found in buildings.