Destruction Of Building Structures Research Articles

Novel meter-scale seismic metamaterial with low-frequency wide bandgap for Lamb waves

Seismic metamaterials (SMs) have attracted the attention of many researchers in the field of damping and elastic wave isolation because of their bandgap properties, i.e., attenuating elastic waves in the range of bandgaps. However, the dimension of these SMs often reaches the 10-meter scale, which impedes practical engineering application. To break through this bottleneck and achieve a smaller scale, a meter-scale novel SM composed of steel and rubber is proposed for attenuating ultra-low frequency seismic Lamb waves. Firstly, the finite element method is used to analyze the band structure of SMs and calculate the bandgaps. To explain the mechanism of bandgap, the vibration modes of the waves at the bandgap boundary frequency are further analyzed. Subsequently, the transmission spectrum of Lamb waves incidents on the finite SMs system is analyzed to prove the authenticity of the bandgaps. Finally, parameter analyses including the geometric variables, material properties, equivalent mass density, and structural matrix forms with identical equivalent mass density are investigated numerically. The results show that Lamb waves in the range of 0–20 Hz are significantly attenuated by SMs, and the aforementioned parameters are significant factors affecting the bandgap properties and transmission properties. The proposed SM has a smaller size while maintaining some wide bandgaps at 0–20 Hz for ultra-low frequencies. It is worth noting that the 2 Hz seismic peak spectrum causing the destruction of building structures is covered effectively.

К вопросу о дифференциации режимов дефлаграционного горения и взрыва

This work raises the issues of feasibility of developing a conceptual approach to the detailed differentiation of combustion modes. Its goal is to try to characterize the modes of combustion for gas-, vapor- and dust-air mixtures as an explosion or deflagration (clap), calculated dependences, allowing to identify an explosion and a higher deflagration (clap) in accordance with the fire and explosion hazard indicators and criteria that characterize their consequences. Although these processes are close to each other, they run at different speeds, are implemented at different pressures and are characterized by certain, different level of injury to people, the level of damage and (or) destruction of building structures, i.e., the consequences of an accident. This paper defines the indicators and criteria that allow to identify the combustion mode as a deflagration (clap) or as an explosion of flammable gas-, vapor-, and dust-air mixtures based on the fire and explosion hazard indicators of mixtures determined by calculation and data describing their consequences. Definitions (terms) and criteria are proposed that allow to identify the concepts as an explosion and as an increased deflagration (clap). Increased deflagration (clap) — ignition and subsequent combustion of combustible gas-, vapor-, dust-air mixtures with an apparent speed from 10 to 60 m/s without the formation of a shock wave, with a pressure increase of no more than 5 kPa and not accompanied by damage and destruction of load-bearing structures.

APPLICATION OF THE METHOD OF DIMENSIONAL CHARACTERISTICS TO THE CALCULATION OF THE HUMIDITY MODE OF MULTI-LAYERED ENCLOSING BUILDING STRUCTURES

The implementation of the energy saving program in construction, adopted in the Russian Federation, has led to a signifi cant change in the design decisions of building envelopes. To achieve the normative values of heat transfer resistance, various facade systems are currently widely used for insulation of external walls using polymeric materials as heaters, which have low values of the coeffi cient of thermal conductivity with a relatively high value of the coeffi cient of vapor permeability. Therefore, when choosing a textured layer of facade systems, it is necessary to take into account the value of its resistance to diff usion of water vapor in order to avoid the accumulation of moisture in the outer walls. The problem associated with the possible accumulation of moisture is especially relevant when designing both three-layer exterior walls and walls with internal insulation. To eliminate the formation of molds on the inner surfaces of the enclosing structures, leading to dangerous diseases of skin and respiratory tract organs, as well as the destruction of building structures, it is necessary to accurately calculate the humidity mode of the enclosing structures in order to protect them from overmoistening. The article presents a methodology for determining the position of the plane of possible condensation in multilayer enclosing structures, based on the use of the dimensionless characteristics method.

Revealing patterns of the effective mechanical characteristics of cellular sheet polycarbonate for explosion venting panels

Explosive concentrations of various substances can accumulate inside industrial premises. In the presence of a sufficient amount of oxygen and an ignition source, such a situation could lead to explosion that may result in the destruction of building structures and the building in general. Strengthening the stability of supporting structures is aimed at protecting industrial premises against possible destruction by explosion indoors. One of the effective ways to protect construction structures against the excessive pressure of explosion is to use explosion venting panels. In order to solve practical tasks on protecting industrial premises and structures against explosion, one must be able to choose both the area and parameters for explosion venting panels. In addition, in order to reduce the related loads to safe quantities, it is necessary to properly calculate the bearing structures in terms of dynamic stability while maintaining their carrying capacity. The set task to ensure protection against explosion by applying explosion venting panels with flexible elements can be solved through integrated accounting for mechanical properties of cellular polycarbonate sheets. We have performed experimental research into performance of the inertia-free explosion venting panels with flexible enclosing elements exposed to dynamic loads under conditions of explosion. Based on the obtained results, the effective rigidity and critical displacement of cellular polycarbonate sheets of flexible elements have been determined. It has been established that for cellular polycarbonate sheets with a thickness of 4‒8 mm effective rigidity ranges within 301–215 N·m; the critical displacement of edges in this case is 2.9–9.8 mm. A mathematical model has been proposed that takes into consideration the influence of geometric dimensions and the critical value of deflection in a polycarbonate sheet as the flexible element of fencing on the operational conditions for explosion venting panels

Geodesic methods for modeling and protection of megalopolis objects

This article presents new techniques for the use of geodetic instruments when performing work on monitoring deformation processes and protecting monuments of cultural heritage. The prevention of dangerous deformations and destruction of building structures is an extremely important task, the solution of which ensures the preservation of all construction costs. For this reason, an increased attention was given to the development of early detection methods of possible structural damage to structural elements. There are many different methods for detecting displacement. Nevertheless, little work has been devoted to the development of real time observation methods. In addition to the existing methods, a permanently operating observation station is considered. The new method is based on: 1-The use of robotic motorized total station; 2- A preliminary calculation of the measurement accuracy. The actual results of the observations are given. Besides, the technique of preserving monuments of cultural heritage, including the creation of their models based on laser scanning and survey with unmanned aerial vehicles, is shown.

РЕКОНСТРУКЦИЯ ТРУБОПРОВОДОВ С ИСПОЛЬЗОВАНИЕМ ПОЛИМЕРБЕТОНА

Accidents on sewers accompanied by the destruction of building structures have been a most serious problem not only for the water industry but also for the entire city. In the world the damage from the deterioration of reinforced concrete sewer tunnels and in-line structures due to corrosion is estimated at billions of euros per year. A way out of the current situation with corrosion in sewers can be timely and prompt repair and rehabilitation using protective coatings applied by trenchless methods. One of the methods of sewer rehabilitation is lining the internal walls of the sewers with plate composite materials (blocks) or continuous protective coatings where polymer concrete can be used. Polymer concrete comprises a thermosetting organic binder (usually epoxy resin) and a large amount of dispersed filler (talc, aerosil, crushed quartz, basalt, granite chips, etc.). The special composition of filler materials and advanced production technologies ensures the high qualities of polymer concrete. An assessment of the technical and economic indicators of the reconstruction of existing sewers and canals using polymer concrete blocks is given. Through a realistic example it is shown that the most effective option of the reconstruction of a sewer canal while ensuring environmental safety is lining with polymer concrete blocks (segments).

Analysis of causes of combustible mixture explosions inside production floor areas

The work provides a cause analysis for major industrial explosions and a review of the causes of combustive air-gas mixture generation in a production environment. It has been established that during operation of explosive production facilities, it is process equipment that, as a rule, creates explosive environment inside the floor area. A qualitative method for determination of a potential accident has been reviewed. Analysis of the nature of explosion effect on building structures and equipment has shown that exposions characterised by absence of equipment and building structure disintegration normally have a localized character. It has been identified that during explosions inside process equipment, the largest structural damage occurs in spots hit by equipment debris. Complete destruction of building structures and equipment is caused by explosions inside equipment containing large quantities of combustible products. It has been identified that most explosions are accompanied by partial or total destruction of building structures and equipment. Therefore, measures taken to protect equipment and buildings from explosion effects lack efficiency.

General observations of effects of the 30th September 2009 Padang earthquake, Indonesia

The Mw 7.5 Padang earthquake struck at 17:16 local time on 30th September 2009 with an epicentre offshore about 60 km west-northwest of Padang, capital of West Sumatra Province. More than 1,100 people were killed, and over 2,900 injured. The earthquake caused significant damage to public buildings and offices as well as to about 140,000 houses. It affected 250,000 families through the total or partial loss of their homes and livelihoods. More than half the earthquake fatalities occurred when several villages inland from Pariaman were buried by landslides. However, the damage and destruction of building structures was a major cause behind human and property losses. In addition to landslides, the earthquake triggered extensive liquefaction and lateral spreading in the region. A ten-member team from New Zealand visited the area under the auspices of NZAid and New Zealand Society for Earthquake Engineering to undertake building safety evaluations. The team spent most of their time in Padang city and other nearby earthquake-affected areas. This paper presents their observations and explores causes behind the damage and destruction of buildings by the moderate to strong earthquake shaking.

The purpose and effects of earthquake codes

abstract When large earthquakes occur and there is significant damage and destruction of building structures, an almost universal response is the demand for better (and usually bigger) building codes. This paper examines the effects of this public outcry for protection with respect to the economic consequences, the actual process of seismic code formulation, and the technical adequacy of our present knowledge and design procedures. Some general directions are suggested such that new codes can be: better understood with respect to their intended design objectives; economically feasible; and practically enforceable.