Dynamic Response And Damage Assessment Of Reinforced Concrete Slabs Subjected To Blast Loading

In the modern society, more and more explosive terror attacks and explosive accidentshave happended around the world. These explosions not only inflict heavy casualties andproperty loss, but also cause serious damage even disastrous collapse to neighboring buildings.The research for blast resistant capacity of structures is far from sufficient in China, so it isnecessary to carry out overall research on it. During explosions, reinforced concrete (RC)slabs with large a surface area for the pressure to act on and a comparably small thickness, arevulnerable to widespread damage More seriously, RC slabs failure may cause the loss oflateral support capacity for major members of columns and beams, even may lead to theprogressive collapse of RC frame. This dissertation integrates theoretical analysis andnumerical simulation method to study dynamic response and damage assessment of RC slabssubjected to blast loading, and this research also has important theoretical significance andpractical value. Main research and conclusions can be obtained as follows:(1) RC slabs are reduced to one-degree systems to study dynamic response theoretically.Based on reasonable assumptions, combined with severe plastic deformation properties ofconcrete slabs, a theoretical formula for limit deformation of concrete slabs with largedeformation is established by means of using the law of conservation of energy andLagrange’s equations. Base on the principles of equal deflections and equal energy, the RCslab element is represented by an equivalent one-degree system through conversion factors.Then the maximum displacement of key point of a RC slab is calculated by single degrees offreedom system dynamic analysis. The formula and theoretical analysis are verified bycompared with some numerical results(2) Using a explicit dynamic finite element analysis program, LS-DYNA, a finiteelement model method of RC slabs with simply supported on four sides is developed forsimulating dynamic response and damage assement, then is discussed and verified throughcorrelated experimental studies. Development change processes for various parameters ofdynamic response of RC slabs are revealed. Under different conditions, several parameters were simulated to get the effects on dynamic response and explosion resistance. The majorinfluential parameters were screened out to provide some theories and suggestions ondetermining reasonable parameters in blast-resistance design and blast resistant measures.(3) Damage assessment parameters and criteria for RC slabs are discussed. Apressure-impluse damage criterion for RC slabs is defined based on the support rotation, and anumerical method to generate pressure-impulse diagrams is established. Pressure-impulsediagrams and curves fitting formulas for RC slabs are established, and compared withpressure-impulse diagrams from equivalent one-degree system approach. Under differentdamage levels, the effects of key parameters on pressure-impulse diagrams are discussed.Pressure-impulse diagrams established in this dissertation can reflect the actual materialproperties and dynamic response more effectively, and can carry out accurate damageassessments for RC slabs under different blast loads.(4) Based on an equivalent one-degree system method, a blast-resistant design for RCslabs structural elements is carried out. Blast resistant measures for new and exsiting RC slabsare put forward. It is found that blast resistance of a new RC slab can be improved by meansof enhancing concrete strength, increasing thickness, decreasing span-thickness ratio,increasing reinforcement ratio, two-way double layers of reinforcement layout, andstrengthening supports for slabs. For exsiting RC slabs, forming composite protectivestructure with multilevels and various methods is an effective blast-resistant improvementmeasure.