فصلنامه پدافند غیرعامل
سال پنجم شماره 4 (پیاپی 20، زمستان 1393)

One of the passive defense approaches is about reinforcing buildings against blast loads. Walls as parts of buildings are not excluded in this regard. In recent years، using FRP fiber as an appropriate solution to improve the system behavior of lateral resistance and maintaining the existing masonry walls safety has been under scrutiny and various factors affect the quality of this kind of reinforcement. This article deals with the study of the effects of geometrical features and the method of FRP layers arrangement on reinforcing walls with masonry materials. Several unarmed and reinforced masonry walls which differ from one another in number، thickness، width and the method ofFRP layers arrangement، under blast loading with measured distanceof Z=6 (m/kg(1/3) have been modelled and analyzed using AUTODYN. The results of the study of various arrangement of the fiber show that reinforcement using FRP sheet in way that covers the wall surface completely is the most reliable method and parametric study of the wall surface with definite and armed with the fiber in the form of a sheet under blast loads indicate that the wall destruction threshold has reduced from Z=9 (m/kg(1/3)) in an unarmed status to Z=4 (m/kg(1/3)) to a reinforced status.

Today increasingbuilding density to respond to population growth is inevitable. In the meantime; urban development leads to the increase of natural hazards too and in regard to Iran being situated on the one of the two seismic belts of the earth، the need to plan and design in accordance with the principles of urban passive defense in the course of constructionis strongly felt. In this regard، this studydeals with a descriptive􀀅analytical method and aims to reduce the vulnerability ofcities against natural hazards، particularly earthquakes، and it attempts to determine the maximum building densitybased on passive defense principles. Required information has been obtained from documents، journals and related books. In this paper، after examining the documents and information، a method for determining the maximum building density with anapproach to reduce vulnerability against earthquakehas been provided and by using that، the densitypatternwithin the limits of the study in Shahroud city has also been calculated. Accordingly، in compliance with proposed method، in the first step it must be specified that considering ahypotheticalearthquake، with the condition of maintaining the minimum required space in the streets for assistance، the remaining space of street for the buildup of building debris، what the maximum of destruction capacity for what the height of a building is. The next step، having obtained the building height، with the assumption of the height of each floor and the building occupation rate، the maximum density and the number of floors of the building can be calculated.

Analysis of the structures subjected to the explosion is one of the most important topics that have attracted researchers'' attention. The governing differential equation of beam-columns in dynamic form is a 4th order partial differential equation (PDE) and its analytical solution is very difficult if not impossible. In this paper، a method for solving 4th order PDE of beam-columns subjected to blast loading has been developed. Also the static analysis، in which dynamic effects of the explosion are ignored، has been considered. A numerical example is presented to illustrate efficiency of the proposed method and bothstatic and dynamic results are compared، as well. The results of this study show that ignoring the dynamic effects for beam-columns subjected to blast loading can lead to incorrect results. Also it is concluded that axial force effect can considerably increase deflection of beam-columns subjected to blast loading.

Key infrastructures especially electrical power systems، from their inception to the present، have been an integral part of life in human society; therefore، have great potential to put at risk by threatfactors; for this reason، the security of their systems is tied to the national security of the overall community and trying to maintain this securityis of utmost importance to senior managers and decision makers. The factors threatening power systems include natural and human disasters. The main purpose of this paper will be modeling and simulating power systems based on passive defense against electromagnetic threats، and studying measures to enhance safety and security strategies against these types of threats. Threat detectionby determining their occurrence scenarios in which they provide guidelines to protect against interference or degradation in the power system to maintain business processes، assets and related resources is necessary. In this paper،the purpose ofpower system is a high voltage substation with a control room and the threats to that are High Altitude EMP (HEMP) and High Power EMP (HPEM). Since the major components of the power system in this paper، includeelectronic cabinets، control racks and concrete structures are for a high voltage substation، and therefore; the Shielding Effectiveness (SE) in each of them will be examined using simulation. The resultsshow thatwiderectangular windows mounted in the said chambers structures and racks havethe lowest and the circular windows have the highestelectromagnetic shielding. Simulation results for substations structure show that the concrete structures have almost no protection against threats، but when used in reinforced concrete structure، the parameter SE at low frequencies will be improved. A review of the protective measures، based on the results of previous studies and conducted simulations، constitute provisions of the final section of this paper.

Water has always been emphasized as fundamental human needs. Today، the supply and distribution of drinking water are considered as one of the most fundamental responsibilities of governments􀀪 Most experts believe that the third world war will be for water، therefore; water supply and maintaining the infrastructure are of utmost importance. Most water supplies will be provided from groundwater sources such as wells and surface water such as rivers. Water storage tanks including air and ground water are the main components of the system. Water plants are considered the basic infrastructures of any country which have always been noticed and threatened by enemies in various forms. In this study، threats to these infrastructures are identified and scored according to the different conditions so that each area can be protected due to possible threats. Moreover، in this study the country is divided into two regions، border and central، and cities into two groups، big and small. After the preparation and completion of questionnaires based on threats by experts and professors in this field and analyzing the results، it was indicated that the necessary arrangements with the threats in each area are different from those of other areas. For example، in border cities، water supply infrastructure should not be as superficial and observable and if implemented، must be fully camouflaged but this infrastructure can be used in central towns.

Irrevocable energy absorbers are used to absorb kinetic energy resulting from impacts. This energy is used to dominate plastic deformity in the absorber. In this article، we first introducesquare column and tube energy absorbers and then two methods are explained to improvethe energy absorption of square column absorbers and two other methods for that of tube absorbers، as well. As it is evident، the best yield mode to have the highest energy absorption is the advancing axial symmetric curvature mode. Therefore; energy absorption tools should be designed in a manner so as to yieldin this mode. In the first method، pyramidal patterns on absorption walls are used for square column absorption which causes axial symmetric yield modeand in the second method، bow initiators in tube corners are used to prevent position curvature while slant loading. Regarding the tube absorber، at first، using a metal ring which is placed and compressed above the tube، the absorption of this absorber is improved and in the second method، by creating wide grooves on the thick wall tube، we can witness advancing curvature in this absorber. Utilizing the presented patterns in this article، the capacity of energy absorption in these absorbers are found to have improved.

Passive defense is defined as measures that do not need to make use of weapons and could reduce financial damage and casualties or mitigate their effects. Passive defense includes cover، dispersion، redundancy and displacement، deception، warning، reinforcements and safe structures. One of the passive defense measures is reinforcement by armors that can defend vehicles against attack، through increasing the resistance and efficiency of armored vehicles in the future battlefields. Nano Armors، are materials whose structure is either made in nano or nanoparticles are used in their structure. Using nanotechnology would enhance armor efficiency against high speed projectiles. In this Article، the desired impact of nanotechnology for armors reinforcement including body armors and armored vehicles are investigated.