en Offshore Structure مقاله پژوهشي Research Paper <div style="text-align: justify;">Oil, gas, and petrochemical facilities are strategic industry facilities, and their passive defense issues are of high priority in every country. Explosions due to sabotage or‌‌ aerial bombardments are of the most important factors in considering issues related to passive defense in the abovementioned facilities. In this study, the effect of blast loading on pressure vessels is investigated. The research issue is the study on the interaction between factors that affect on responses of pressure vessels under blast loading. For this purpose, the response surface method and central composite method were used for design numerical tests. Four factors were selected, type of pressure vessel (vertical or horizontal), the thickness of vessel body, the yield strength of steel vessel, and the amount of explosive material. Two responses were studied, the maximum displacement of pressure vessels and the residual displacement of pressure vessels. The result shows that the quadratic equation is the best model to provide equations. Then for two responses according to the four factors presented equations. These equations are simple and practical for engineers and researchers. The result shows that for both of the selected responses, in the stronger explosion, the role of body thickness and type of steel is the same but in the weaker explosion, the role of yield strength increased. In addition, it was found that role of the amount of explosive material is more than another parameter. And the interaction of material explosive by other parameters in vertical type is more than horizontal pressure vessels.</div> ,Pressure Vessel,Oil and Gas Facilities,HE Explosion,RMS method,Passive Defense 41 52 http://ijmt.ir/browse.php?a_code=A-10-1757-1&slc_lang=en&sid=1 Hamed Khalilpour s.hamed.khalilpour@gmail.com 10031947532846003865 10031947532846003865 No University of Qom University Ruhollah Amirabadi r.amirabadi@qom.ac.ir 10031947532846003866 10031947532846003866 Yes University of Qom University Mahdi Adjami adjami@shahroodut.ac.ir 10031947532846003867 10031947532846003867 No Shahrood University of Technology