International Concrete Abstracts Portal

A micromechanical damage model for concrete capable of taking into account the effect of highly time-varying load (time-varying stress) is outlined here. Giving primary consideration to concrete-type material, it is shown how an existing self-consistent rate-insensitive model can be modified and extended to induce rate dependency of concrete with pre-existing damage (cracks). The variations of several fracture mechanics parameters of concrete, viz., stress intensity factors, fracture toughnesses, etc., under the influence of high loading rates are investigated; the role of inertia of the material is explained and quantified. The process of crack evolution including crack kinking and nucleation under tensile and compressive stress-field has been thoroughly considered along with all possible situations that may arise. The resulting rate-sensitive model has been codified for high-speed computer and a few experiments have been replicated to validate it.

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

The number of blast resistant facilities planned, designed, and constructed recently in petrochemical plants points to an increased interest in this specialized type of design. This paper deals with the numerous decisions to be made in designing blast resistant buildings. First, the need for a blast resistant design must be evaluated. Then, design objectives and relative cost must be balanced to produce an optimal design. Design practices must be established as there are various company, military, and professional publications available. Detailing practices also require careful consideration as there are differences in the implementation of shear reinforcing, precast elements, penetrations, and exterior doors. Several actions would greatly benefit the design of petrochemical blast facilities. A clear definition from government and insurance sources is needed on what facilities need to be protected from explosions. Improvements are needed in the evaluation of blast loads within petrochemical facilities. A consensus on engineering calculations and construction details would help unify design approaches.

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 discusses the historical development of design criteria for blast resistant buildings in the petrochemical industry, including static vs. dynamic design requirements for control rooms, and TNT equivalence vs. VCE models for quantifying blast loads. Existing industry guidelines for the siting and design of plant buildings are reviewed. A methodology and examples are presented for the categorization, design and structural evaluation of building components for blast resistance