The Specific Characteristics of Shock and Blast Impacts on Construction Sites

Author(s):  
A.A. Komarov ◽  

The practices of hazardous and unique facilities’ construction imply that specific attention is paid to the issues of safety. Threats associated with crash impacts caused by moving cars or planes are considered. To ensure safety of these construction sites it is required to know the potential dynamic loads and their destructive capacity. This article considers the methodology of reducing dynamic loads associated with impacts caused by moving collapsing solids and blast loads to equivalent static loads. It is demonstrated that practically used methods of reduction of dynamic loads to static loads are based in schematization only of the positive phase of a dynamic load in a triangle forms are not always correct and true. The historical roots of this approach which is not correct nowadays are shown; such approach considered a detonation explosion as a source of dynamic load, including TNT and even a nuclear weapon. Application of the existing practices of reduction of dynamic load to static load for accidental explosions in the atmosphere that occur in deflagration mode with a significant vacuumization phase may cause crucial distortion of predicted loads for the construction sites. This circumstance may become a matter of specific importance at calculations of potential hazard of impacts and explosions in unique units — for instance, in the nuclear plants. The article considers a situation with a plane crash, the building structure load parameters generated at the impact caused by a plane impact and the following deflagration explosion of fuel vapors are determined.

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3761 ◽  
Author(s):  
Kong ◽  
Jiang ◽  
Jiang ◽  
Wu ◽  
Chen ◽  
...  

Microseismic events commonly occur during the excavation of long wall panels and often cause rock-burst accidents when the roadway is influenced by dynamic loads. In this paper, the Fast Lagrangian Analysis of Continua in 3-Dimensions (FLAC3D) software is used to study the deformation and rock-burst potential of roadways under different dynamic and static loads. The results show that the larger the dynamic load is, the greater the increase in the deformation of the roadway under the same static loading conditions. A roadway under a high static load is more susceptible to deformation and instability when affected by dynamic loads. Under different static loading conditions, the dynamic responses of the roadway abutment stress distribution are different. When the roadway is shallow buried and the dynamic load is small, the stress and elastic energy density of the coal body in the area of the peak abutment stress after the dynamic load are greater than the static calculations. The dynamic load provides energy storage for the coal body in the area of the peak abutment stress. When the roadway is deep, a small dynamic load can still cause the stress in the coal body and the elastic energy density to decrease in the area of the peak abutment stress, and a rock-burst is more likely to occur in a deep mine roadway with a combination of a high static load and a weak dynamic load. When the dynamic load is large, the peak abutment stress decreases greatly after the dynamic loading, and under the same dynamic loading conditions, the greater the depth the roadway is, the greater the elastic energy released by the dynamic load. Control measures are discussed for different dynamic and static load sources of rock-burst accidents. The results provide a reference for the control of rock-burst disasters under dynamic loads.


Author(s):  
L. T. M. Trang ◽  
H. Nouri

<p>The dynamic model construction of transmission network components that include generator buses, load buses and power branches, within MATLABSimulink environment is presented. The degree of frequency deviation of buses when the power of motor loads and static loads vary, is studied. Furthermore, the influence of motor loads with different inertia constants are considered in the control technique of load frequency using a PID controller. The results show that the frequency oscillation of the dynamic load is greater than the frequency oscillation of static load. Also the speed of frequency control of the dynamic load is greater than the speed of the frequency control of the static load and the inertia constants of the dynamic load has significant influence on the frequency control characteristics.</p>


2020 ◽  
Vol 2020 (12) ◽  
pp. 19-30
Author(s):  
Aleksandr Medvedskiy ◽  
Mihail Martirosov ◽  
Anton Homchenko ◽  
Darina Dedova

The purpose of this work is to investigate the impact of the inner defects of elliptical stratification type upon behavior of the rectangular carbon plastic plate at the impact of static and dynamic loads. The investigation methods: the problem is solved in a numerical way with the aid of a finite ele-ment method (FEM) in the LS-DYNA software com-plex (Livermore Software Technology Corp.). The investigation results: the distribution of stresses in plate layers under the impact of static and dynamic loads is obtained. The distribution of destruc-tion indices with the use of different destruction criteria for unidirectional composites (on the basis of carbon band) is defined. Conclusions: the impact of defects of the type of specified shape stratification, dimensions, amount and places of location with regard to the plate under consideration under the action of compressive static load does not practically tell. Under the action of the compressive dynamic load there is observed a noticeable impact of inner defects upon rectangular plate behavior.


2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lyu Pengfei ◽  
Bao Xinyang ◽  
Lyu Gang ◽  
Chen Xuehua

To effectively monitor and control the severe mining-induced rockburst in deep fault area, the fault activation law and the mechanical essence of rockburst induced by crossing fault mining were studied through theoretical analysis, microseismic monitoring, field investigation, and other methods; numerical simulation was employed to verify the obtained fault activation law and the mechanical nature. First, the distribution of microseismic sources at different mining locations and the fault activation degree were analyzed. According to the microseismic frequency and the characteristics of the energy stage, the fault activation degree was divided into three stages: fault stress transfer, fault pillar stress behavior, and fault structure activation. It was determined that the impact disaster risk was the strongest in the stage of the fault pillar stress behavior. Based on the periodic appearance law of microseisms in fault area, three types of conceptual models of fault-type rockburst were proposed, and the rockburst carrier system model of “roof-coal seam-floor” in the fault area was established. The mechanical essence of fault-type rockburst was obtained as follows: under the action of fault structure, the static load of the fault coal pillar was increased and superimposed with the active dynamic load of the fault, leading to high-strength impact disaster. Finally, the prevention and treatment concepts of fault-type rockburst were proposed. The monitoring and prevention measures of fault-type rockburst were taken from two aspects: the monitoring and characterization of fault rockburst and weakening control of the high static load of the fault coal pillar and dynamic load of fault activation. The proposed concepts and technical measures have been verified in the working face 14310 of Dongtan Coal Mine with sound results. The research results have a guiding significance for the prevention and control of rockburst in a similar mining face under crossing fault mining.


2021 ◽  
Author(s):  
Turky Sami Jeddawi

An experimental investigation has been conducted to determine the deformation and failure characteristic of slab under static and dynamic loads. Two identical reinforced concrete (RC) of dimensions 1950 x 1950 x 100 mm are tested under same boundary conditions. All top and bottom reinforcement are 10 M doubly plates reinforcement with total 1.0 % steel ratio. The static load is applied at the midpoint of the slab by using load cell 400 x 400 mm with a capacity of 250 kN. The static load increment used in this investigation is 5 kN. The dynamic load is applied at the midpoint of the slab by using a drop-weight of 475 kg from a height of 4.15 m generating an impact energy of 19.24 kJ with impact velocity of 9 m/s. The experimental results revealed that the absorption energy of the impact loading is about 1.4 times the static loading. The maximum deflection is found to be slightly higher for impact loading.


Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 851
Author(s):  
Siqi Li ◽  
Shenglei Tian ◽  
Wei Li ◽  
Xin Ling ◽  
Marcin Kapitaniak ◽  
...  

In order to study the deformation displacement and the stress field of brittle rocks under harmonic dynamic loading, a series of systematic numerical simulations are conducted in this paper. A 3D uniaxial compression simulation is carried out to calibrate and determine the property parameters of sandstone and a model of the cylindrical indenter intruding the rock is proposed to analyze the process of elastic deformation. Four main parameters are taken into account, namely the position on the rock, the frequency and the amplitude of dynamic load, the type of indenter and the loading conditions (static and static-dynamic). Based on the analysis undertaken, it can be concluded that both of the deformation displacement and stress field of the rock change in a harmonic manner under the static-dynamic loads. The frequency and the amplitude of harmonic dynamic load determine the period and the magnitude of the rock response, respectively. In addition, the existence of harmonic dynamic load can aggravate the fatigue damage of the rock and allow a reduction in static load. Our investigations confirm that the static-dynamic loads are more conducive to rock fracture than static load.


1987 ◽  
Vol 109 (4) ◽  
pp. 416-421 ◽  
Author(s):  
Kosuke Nagaya

This paper discusses the dynamic behavior of a flexible multiple disk clutch subjected to dynamic loads. The expressions for obtaining the dynamic response and the transmission torque of the clutch have been derived from the equation of motion of a circular plate by applying the Laplace transform procedure. The results for the clutch subjected to a static load have also been obtained. The comparison between both static and dynamic results has been made to clarify the effect of the impact of the load on the behavior of the clutch.


1997 ◽  
Vol 4 (1) ◽  
pp. 39-50
Author(s):  
Michael A. Stewart ◽  
David J. MacKenzie ◽  
Robin K. Mackenzie

When impact sound tests are carried out in new and refurbished flats there is not normally a load on the floor. When the flat is occupied however, loading due to furniture, appliances, people etc, will occur which compresses the resilient layer if a floating floor construction has been used. The effect this has on impact sound insulation is considered in this paper. Impact sound transmission through a chipboard floating floor on battens supported on a concrete floor has been measured when static loads were placed on the chipboard – the loads were in the range 20 kg/m3 to 160 kg/m2. Three different resilient layers under the battens were tested: 25 mm mineral wool quilt, resilient battens and resilient battens on 13 mm mineral wool quilt. The weighted standardised impact sound pressure level (L'nTw) increased by 0.5 dB to 5 dB with the larger increases for the greater loads. Further measurements were made after the floating floors had been left under a static load of 200 kg/m2 for six months: there was an additional increase in L'nTw of 1.5 dB. Finally, measurements were compared with floors where the resilient layers had been soaked to simulate water leakage from baths, pipes etc; there was no significant difference in results.


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