Protection Systems For Structures Research Articles

Methods of calculation and engineering protection of critical infrastructure objects and other strategic facilities against long-range projectiles

Relevance. One of the key areas of russia's military operations against Ukraine is the destruction of critical infrastructure objects (CIO) of strategic importance. The main types of enemy means for air strikes on CIO are air-launched, ground-launched and water-launched missiles, as well as barrage munitions. The vast majority of the CIO were built in Ukraine above ground, without any engineering structural protection systems to counter air threats, explosions or other impacts related to military operations. The importance of developing the most effective methods of engineering structural protection of the CIO from various types of projectiles as soon as possible was demonstrated by the experience of Ukraine's war with russia, in particular, the analysis of the significant impact of damage to the CIO in the energy sector. At present, Ukraine has a certain lack of regulatory data for designing reliable protective structures for CIO. The aim of this work is to develop a regulatory base for making calculations for the possible impact of various types of forceful effects from air strikes, terrorist attacks, etc. when designing the CIO and other strategic facilities. Currently, the issue of organising the defence of critical infrastructure and other strategic objects is being systematically addressed on the basis of the "Country-Fortress" principle, which provides for the organisation of echeloned air defence combined with comprehensive civil and engineering defence measures. In addition, it is necessary to provide for the reliable protection of existing facilities, taking into account the hazards and threats of today. The process of reducing the risks of damage to the CIO involves identifying threats, their comprehensive assessment, developing measures to reduce threats and their prompt implementation, followed by an assessment of the measures effectiveness. Results. The presented methods of risk assessment of critical infrastructure damage, methods of their engineering and analytical calculations and methods of engineering structural protection against ammunition of various types allow developing an effective integrated system of protection of strategically important objects. The article deals with both the protection of existing facilities and the design of new ones, taking into account the requirements for engineering protection and civil defence.

Principle and Method for Determining the Calendar Safety Life of Aircraft Structural Protection Systems

The calendar safety life of the surface protection system in aircraft structures is the time limit for it to be used without functional failure at a certain level of reliability and confidence. The reliability of such protection systems and the operational safety and economy of the structure are closely related. This paper firstly establishes two methods for determining the calendar safety life of aircraft structural protection systems under a single service environment and in multiple service environments. A method for determining the reliability of the calendar safety life of the aircraft structural protection system was proposed, and an expression of the relationship between the maintenance costs for the aircraft fleet and the reliability of the calendar safety life of the aircraft structural protection system based on the relationship between the amount of corrosion damage to the structural substrate and the corrosion time and the expression of the calendar safety life of the protection system was established. Finally, taking a hypothetical aircraft fuselage wall plate connection structure as an example, an alternating corrosion fatigue test with protection system specimens was carried out. The process for determining the calendar safety life of the structural protection system and its reliability are given. This method is important to ensure the safety of aircraft structures, improve the efficiency of use, and reduce maintenance costs. Generally speaking, the reliability of the calendar safety life of the structure is 99.9%, and after the analysis in this paper, the reliability of the structural protection system is about 70%.

Numerical Modeling of Roadway Embankment Construction Over Existing Sewers

Abstract This article presents a case study of the influence of a roadway embankment on existing sewers with a diameter or width in the range of 3.3 to 4.3 m using numerical modeling. The proposed embankment would be constructed directly above the existing sewers, which would induce an additional load on the sewers. Traditional analysis methods cannot account for the soil–structure interaction and the benefit of the lateral supporting characteristics of the soils. In order to evaluate the loading of the proposed embankment on the existing sewers, a soil–structure interaction analysis using a two-dimensional finite element analysis was performed for various loading cases. The sensitivity of soil parameters was also studied in the analysis. From the analysis, the loads on the sewers, including axial force, bending moment and shear force, were obtained, and then the structural capacity of the existing sewers was checked. Lightweight sand fill or expanded polystyrene (EPS) geofoam was considered to reduce the additional vertical and horizontal loads on the sewers. The EPS geofoam or a structural protection system consisting of a concrete slab supported by concrete piles was proposed to eliminate any incremental vertical and horizontal loads on the sewers. Findings from the analysis concluded that the lightweight sand fill was the most economical material for reducing the additional loads on the sewers, EPS geofoam was the most suitable material to eliminate incremental loading on the sewers for a lower embankment, and the structural protection system was necessary to eliminate the incremental loads on the sewers for a higher embankment.

Seismic response of friction damped and base-isolated frames considering serviceability limit state

ABSTRACT The present study evaluates the seismic performance of steel moment resisting frames (MRFs) upgraded with different structural protective systems. For this, three 5 storey steel MRFs (Ordinary moment frame (OMF), intermediate moment frame (IMF) and special moment frame (SMF)) and two 10 storey MRFs (IMF and SMF) were studied. As structural protective systems, friction dampers (FDs), base isolation with lead rubber bearings (LRBs), and a combination of them were considered. The structures were modeled using a finite element program and evaluated by the nonlinear time history analyses. In the nonlinear time history analyses, seven natural accelerograms, namely, 1976 Gazli, 1978 Tabas, 1986 San Salvador, 1987 Superstition Hills, 1992 Cape Mendocino, 1994 Northridge and 1999 Chi-Chi were taken into account. Roof drift, roof absolute acceleration, relative displacement, interstorey drift ratio, base shear, top storey moment, and hysteretic curve were employed to compare the elastic and inelastic responses of all frames. The results clearly highlighted that the application of FDs with LRB had remarkable improvement in the earthquake performance of the case study frames reducing the local/global damages in the main structural systems and satisfied the serviceability (i.e., fully operational, FO and operational, OP) limit states as well.

Discrete-continual mathematical models in solving vibration protection problems of building structures

The paper outlines the method of forming mathematical models for the dynamic interaction of the vibroactive technological equipment with load-bearing structures of industrial structures on the basis of discrete-continual approximations previously developed by the author. Ways of implementing methods in the formation of vibration protection systems of structures are provided in the paper. The features of systems’ functioning and their sensitivity to fluctuating vibration frequency processes are also described.

Self-centering and damping capabilities of a tension-compression device equipped with superelastic NiTi wires

The hysteretic damping capacity and high recoverable strains characterizing the superelastic response of shape memory alloys (SMA) make these materials attractive for protection systems of structures subjected to dynamic loads. A successful implementation however is conditioned by functional fatigue exhibited by the SMA when subjected to cyclic loading. The residual deformation upon cycling and the efficiency in material usage are the two most restrictive issues in this sense. In this paper, a device equipped with superelastic NiTi SMA wires and capable of supporting external tension compression loads with optimized properties is presented. It is shown how the introduction of the wires’ pre-straining allows for the absorption of deleterious residual deformation without affecting the self-centering capabilities upon unloading, in contrast with what occurs for pre-strained tendons. These features were experimentally verified in an in-scale prototype composed of two 1.2 mm diameter superelastic NiTi SMA wires. In order to numerically assess the dynamic response of a simple structure subjected to seismic excitations, a multilinear superelasticity model for the NiTi wires was developed.

Artificial Neural Networks for Predicting the Response of Structural Systems with Viscoelastic Dampers

Abstract: Passive energy dissipation systems have been identified as one of the modern structural protective systems against seismic disturbances. Research and development activities are on globally to develop appropriate design procedures and suitable technology for application in the field. Structural systems with energy‐dissipating devices call for rigorous nonlinear analysis, which is a complex one and the results are highly sensitive to the type of input motion and component behavior assumed in the analysis. The Federal Emergency Management Agency 273 (FEMA 273) (1997) has suggested simplified procedures for replacing the original nonlinear system by an equivalent linear system. Recently, artificial intelligence (AI) techniques based on artificial neural networks (ANN) have been profitably used for solving complex problems of an iterative nature. Combining the equivalent model with an appropriate AI technique would help one to quickly predict the dynamic response of such yielding systems. This article highlights the feed forward back‐propagation neural network using the Levenberg–Marquardt algorithm for predicting the response quantity of systems with energy‐dissipating devices. The neural network is trained to reflect the nonlinear relationship of strength, stiffness, and damping existing in the system. The methodology developed is illustrated and validated with a chosen example from the FEMA 274 and is found to predict well the average peak displacement, base shear, and roof displacement. Based on these, the sensitivity studies have been carried out and the influence of each parameter on the results have been brought out. It may be noted that sensitivity details and the influence of each parameter do not show up in the regular time‐series analysis. The main advantage of the methodology and the network developed is in quick preliminary decision on the amount and the number of dampers required to reduce peak displacement for a new design as well as for retrofitting.

Performance assessment of lightning shielding systems Part I. Developmental analysis

This paper describes the analytical basis and development of a computer program for the performance assessment of lightning shielding systems (PALSS). The program is specifically written for a PC-AT for the convenience of engineers and designers whose design methods are now tending towards the use of software in workstations. The program is written in C language, is very user friendly and is enhanced with illustrative graphics. The analytical method used is based on a three-dimensional implementation of the electrogeometric model of the lightning stroke and shielding system configuration together with the structures that are required to be protected. A Monte Carlo technique is used to manipulate the statistical distributions of the lightning stroke parameters to yield a quantitative assessment. Examples of the use and usefulness of such a program are included. It is envisaged that the design of lightning protection systems for structures will be able to rely on such statistically based methods which can now be so easily and conveniently used.

Analysis and design of protection systems for structures against direct lighting strokes. Part 1: Theory

In the paper, a new method for the analysis and design of lightning protection systems for constructions and buildings against direct strokes is presented. while the theory of the method is discussed in the paper, its applications are presented in a companion paper with the same heading: ‘Part 2: Applications’. The theory is based on the study of the critical field strength values in nonuniform fields, and its applications to an electromagnetics model of the lightning stroke. The main goal of the paper is to give the electrical engineer a tool for the determination of the parts of the structure and its vicinity, which are exposed to lightning strokes. The probability of strokes which may hit the structure is valuable information in the design of a reliable lightning protection system.