Nuclear newer plant structures, systems and I components may be subject to a variety of impulsive loads caused by accidental explosions and or high energy pipe ruptures. Examples of such loads are jet impingement, reactor vessel sub-compartment pressurization, pipe whip restraint reaction and blast pressure. Various US NRC Regulatory Guides and Standard Review Plans specify required loads and provide acceptable methods for structural design. The design of concrete structures, subject to impulse and impact loads is governed by the ACI-349 Code. Acceptable analysis techniques vary from simplified quasi-static methods for single degree of freedom systems, to detailed computer analysis techniques accounting for material and geometric non-linearities. This paper reviews briefly the impulsive loads and the procedures for analyzing a n d designing structures found in nuclear facilities.

This paper is concerned with the description and explanation of Hardened Cement Paste (HCP) response to dynamic (explosive) loading. An experimental testing technique had been developed to study the dynamic cracking of HCP samples, using cylindrical explosive microcharges. Following the initiation of the microcharge, radial cracks propagate and measurements of their growth may be conducted. Procedures to predefine the crack path have been investigated, like preparation of linear grooves along the sample. Predefining the crack path enabled relatively simple measurements of its propagation velocity. The dynamic crack propagation velocity was found to be relatively low, within the range of 70-200 m/sec. (about an order of magnitude lower than the theoretical value). The dynamic HCP failure process was found to be usually of multicrack type. Studies of michrocharge initiation near a samples boundary provided insight into the development of scabbing cracks and of their interaction with the radial cracks propagating towards the boundary. It has been found that that crack interaction is strongly dependent on the relationship between the stress wave velocity and the crack propagation velocity.

The 15 papers in this Symposium Publication describe a range of applications for this seemingly narrow area of structural engineering: design to resist or discourage terrorism against civilian and governmental buildings, design to eliminate or minimize destruction from industrial accidents, and design to protect military facilities. To assist the reader in focusing on a particular level of interest, the papers have been grouped into three sections. Section One, Design Aspects, relates directly to the design process. Section Two, Current Procedures and Recent Developments, provides an overall viewpoint. Section Three, Theoretical Developments, focuses on research issues. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP175

This paper investigates the use of structural damping in blast response calculations. In recently published literature, there are many examples of structural damping being used in computational models with little or no experimental or theoretical justification. The use of even small amounts of damping in computational models involving nonlinear plastic response can significantly influence the response calculations. For example, for a given blast loading, a reinforced concrete slab with only 48 kPa maximum capacity and 25 percent of critical damping (a value typically recommended) will deflect the same as (i.e., provide the same level of protection as) a slab with 690 kPa maximum capacity and no damping. Clearly a fictitious damping term that provides as much as 93 percent of the resistance is problematic. Structural damping during plastic response cannot be clearly defined or verified experimentally. Therefore, the use of damping in plastic response calculations should be avoided.

Hardening structures against weapons effects has been, until recently, of concern almost exclusively of the military. However, with the increase of terrorist activities directed against civilian targets, there is a growing interest in applying these principles to the design of non-military structures. A design approach is presented for civilian structures subject to an external explosion. The issues addressed are threat assessment, countermeasures, weapons effects, analytical techniques, and optimization techniques used. Introduction In military terminology, terrorism is considered low-grade warfare. As such, many of the principles used to design military targets are applicable to the protective design of civilian targets subject to terrorist attack. However, the objectives of design are different for civilian targets. For military facilities the primary objective is to maintain function after attack. ‘Function’ refers to essential activities such as launching a missile or maintaining communications or intelligence. For civilian facilities the primary objective is to save lives while preserving the non-military character of the facility; maintaining function becomes a secondary issue. Because of this difference, protective design principles need to be reevaluated. In this paper the fundamental principles of military facility design are used to develop a rational approach to the design of new civilian structures. These ideas are also applicable to the retrofit of existing structures. This paper is partially based on work done for the Foreign Buildings Office of the US Department of State in developing engineering guidelines for protecting US embassies abroad. Threat and Countermeasures There are many possible threats to be considered in the design of civilian structures (Fig. 1). Some threats are excluded, such as aerial attack or nuclear attack because they are impractical to design for. Other threats are not