Prefabricated High-Strength Headed Steel Reinforcement with High-Strength Concrete for Accelerated Construction of Shear Walls in Nuclear Structures

<p>This dissertation investigates the use of high-strength headed steel reinforcement (HSR), high-strength concrete (HSC), and prefabricated reinforcing bar (rebar) assemblies to accelerate the construction of squat (height-to-length ratio < 2.0) reinforced concrete nuclear shear walls in non-containment, safety-related concrete nuclear structures. The primary goal of using HSR and HSC is to significantly reduce the required reinforcement amounts as compared with state-of-practice walls (using normal-strength materials) with the same dimensions. </p><p>From an industry survey and full-scale laboratory evaluation, it was found that prefabricated rebar assemblies can reduce on-site construction times of nuclear walls by 70-80% and that the bars engaged in assembly movement are most susceptible to spacing changes exceeding construction tolerances. </p><p>Two experimental programs were conducted to investigate the effects of HSC and HSR on the monotonic and reversed-cyclic lateral load behavior of squat shear walls. These specimens were based on prototype nuclear wall designs from available U.S. Nuclear Regulatory Commission design control documents. These experiments demonstrated that: 1) HSR and HSC perform best when combined, providing improved lateral strength and deformation capacity; 2) using HSR with HSC, a wall with significantly reduced provided reinforcement (less than half) can achieve similar peak lateral strength as a state-of-practice wall; 3) state-of-practice methods are effective for the design of reduced volumes of HSR as trim reinforcement around wall web penetrations; 4) squat rectangular walls with increased normalized base moment-to-shear ratio can be susceptible to flexure failure, contrary to current code commentaries; and 5) intersecting end walls can significantly increase the flexural stiffness and flexural strength of squat walls and should be more accurately incorporated in design. </p><p>Closed-form design methods from building codes and literature were evaluated through comparisons with the experimental measurements, resulting in recommendations for accurate and conservative design calculations of lateral stiffness, diagonal-cracking strength, and peak strength of squat walls with HSC and HSR. Additionally, nonlinear finite-element numerical models for the lateral load analysis of squat walls with HSC and HSR were developed. Recommendations were made for models that can accurately: 1) simulate reversed-cyclic wall lateral load behavior; and 2) predict wall peak lateral strength using simpler monotonic pushover analyses.</p>