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Three-dimensional (3-D) nonlinear site response analyses are conducted using finite element models of actual soil profiles from ten nuclear power plant (NPP) sites in the United States to investiga...

The U.S. Nuclear Regulatory Commission’s functional containment concept provides advanced nuclear power plant designers with more flexibility in terms of the civil/structural design if the appropri...

Seismic soil-structure interaction (SSI) analysis of nuclear facilities is an important consideration during design and retrofit. SSI tools used in the nuclear industry are currently based on an equivalent linear (EL) approach. Procedures for developing input ground motion for EL approaches are well established. However, the procedures for establishing input ground motion for nonlinear soil-structure interaction (NLSSI) analysis of nuclear facilities are not well established. A collaborative research group at Idaho National Laboratory has recently developed analytical methods and numerical tools for using NLSSI analysis for nuclear facility seismic calculations. NLSSI analysis for a nuclear facility allows for calculation of seismic wave motion through a near-field soil domain using either (a) vertically propagating shear and compressive waves, which is the current industry practice, or (b) a three-dimensional nonvertical wave field. This technical note presents an iterative procedure for establis...

Seismic analysis and risk assessment of safety-critical infrastructure like hospitals, nuclear power plants, dams, and facilities handling radioactive materials involve computationally intensive nu...

This paper focuses on the direct shear behavior of rebar-coupler anchor systems, and their use for anchorage of steel-plate composite (SC) walls to the concrete basemat of safety-related nuclear facilities. Large-scale rebar-coupler anchor specimens were tested under direct shear loading until failure. The results included the applied load-slip displacement responses of the specimens, the direct shear strength, and the observed failure mode. The American Concrete Institute (ACI) 349 code equation for calculating the direct shear strength of embedded anchors was compared with the direct shear strengths from the tests. The code equation underestimated the direct shear strength of the anchor system, because shear failure was assumed to occur in the rebars, whereas experimental observations indicated that shear fracture failure occurred in the couplers rather than the rebars. The design equation was updated to utilize the net shear area of the couplers instead of the rebars, after which the direct shear strengths from the tests could be calculated with reasonable accuracy. The experimental results were also used to propose an empirical model for the shear force vs. slip displacement response of rebar-coupler anchor systems.

A finite element model is developed in LS-DYNA to simulate the nonlinear cyclic response of flexure-critical steel-plate concrete (SC) composite shear walls. The developed finite element model is validated using data from tests of four large-scale SC wall piers with an aspect ratio (height-to-length) of 1.0. Each SC wall was constructed with steel faceplates, infill concrete, steel studs and tie rods, and a steel baseplate that was post-tensioned to a reinforced concrete foundation. Steel studs tied the faceplates to the infill concrete and the infill concrete to the baseplate. Damage to the SC walls included cracking and crushing of the infill concrete and yielding, outward buckling and tearing of the steel faceplates. The finite element predictions include global force–displacement responses, equivalent viscous damping ratio, damage to the steel faceplates and infill concrete, strain and stress distributions in the steel faceplates, and estimates of the contribution of the steel faceplates and infill concrete to the lateral resistance of the walls. The DYNA-predicted responses are in good agreement with the measured responses. The impacts of interface friction between the steel faceplates and the infill concrete, and of the distribution of shear studs on the baseplate, to the global response of the SC walls are investigated using the validated DYNA model.

This paper focuses on the in-plane behavior, analysis, and design of steel-plate composite (SC) wall piers without boundary elements. A series of SC wall pier specimens with aspect ratios (wall height-to-length ratios, h/lw) ranging from 0.6 to 1.0 were tested under cyclic loading until failure. The results include the lateral load-displacement (V-Δ) responses of the specimens along with observations of steel plate local buckling and concrete crushing. Detailed 3D finite element models of the SC wall specimens were developed and benchmarked using the experimental results. The models explicitly accounted for the effects of geometric nonlinearity and material inelasticity including steel local buckling, concrete crushing, and tension fracture. The benchmarked models were used to conduct parametric studies. The parameters included were the wall aspect ratio (h/lw), reinforcement ratio (ρ), and wall thickness (T). The experimental results and parametric studies indicated that the lateral load capacity...

An experimental study investigated the behavior of large-scale steel-plate composite (SC) walls subjected to cyclic lateral loading. The testing program involved four rectangular SC wall specimens with an aspect ratio (height-to-length) of 1.0. The specimens were anchored to a concrete basemat with a pretensioned bolted connection that was designed to be stronger than the walls. The design parameters considered in the investigation were wall thickness, reinforcement ratio, stud spacing, and tie bar spacing. The pretest analyses, global force-displacement responses, contributions of the steel faceplates and infill concrete to the lateral resistance, load transfer between the faceplates and infill concrete, and damage to the face plates and infill, are documented. The four SC walls failed in a flexural mode characterized by tensile cracking of the concrete, tensile yielding of the steel plates, crushing of concrete at the toes of the wall, outward local buckling of the steel faceplates, and fracture...

Steel plate composite (SC) wall piers are composed of two steel plates on both sides of a concrete infill. Composite action between the steel plates and concrete infill is achieved using shear connectors and tie bars. The tie bars also provide structural integrity by connecting the two steel plates together. SC wall piers do not have any flange walls, cross walls, or boundary elements. Their seismic response and lateral load capacity are governed by the in-plane flexural behavior and capacity of the SC wall cross-section at the base of the wall. The lateral load capacity is reached due to flexural failure in terms of: (i) concrete crushing of the concrete infill in compression, (ii) local buckling of the steel faceplates in compression, and (iii) rupture of the steel faceplates in tension. SC wall piers are composite alternatives to conventional reinforced concrete (RC) shear walls where the steel rebar curtains are replaced by steel faceplates on the exterior surfaces of the concrete walls. This approach expedites construction by eliminating the need for additional formwork and staging of concrete casting. This approach can also provide structural efficiency if the SC wall crosssection is detailed appropriately with adequate shear connectors and tie bars. These elements provide composite action and also restrain the steel faceplates from buckling prematurely (before yielding). Local buckling typically occurs between the base of the steel plates and the first row of shear connectors or ties, which makes this spacing important detailing criterion for SC wall piers. This paper will summarize the results from cyclic in-plane shear tests conducted on SC wall piers. Some of the cyclic lateral load-drift ratio responses are presented along with the typical hysteresis behavior and story drift capacity. Design equations for predicting the lateral load capacity of SC wall piers without boundary elements are compared with the test results.

Steel-plate composite (SC) walls are composed of steel faceplates, infill concrete, shear studs bonding the faceplate to the infill, and tie rods linking the faceplates. In new build nuclear power plants, elastic response is sought of SC walls in design basis earthquake shaking and numerical and experimental studies on SC walls have focused primarily on response to design basis loadings. The inelastic response of SC walls for beyond design basis earthquake shaking has yet to be explored and characterized. The experimental and numerical response of four SC walls subjected to cyclic in-plane loading is summarized in this paper. The walls have an aspect ratio of 1.0 and are flexure-critical. A number of design parameters are investigated, including infill concrete thickness, reinforcement ratio, stud spacing, and tie bar spacing. Numerical models of these walls are constructed using the general-purpose finite element code LS-DYNA. The numerical analyses, and key experimental results are presented.

Pseudodynamic testing was employed to observe the seismic performance of two retrofit methods on two-story, three-bay frame structures. The test frames had hollow clay tile (HCT) infill in the central bay and incorporated the seismic deficiencies of Turkish con- struction practice, such as use of plain reinforcing bars, low-strength concrete, and insufficient confining steel. Two noninvasive and occupant-friendly retrofit schemes suggested in the Turkish Earthquake Code, namely, use of fiber-reinforced polymers (FRPs) and precast concrete panels integrated on the HCT infill, were employed. The specimens were subjected to three different scale levels of ground motion from the 1999 Duzce earthquake. The control specimen experienced severe damage at the 100% scale level and reached the collapse stage due to the loss of integrity of the infill wall and significant damage on the boundary columns. The retrofitted test structures were able to survive the highest level 140% Duzce ground motion. Test results confirmed the success of the two previously developed retrofit methods for simulated earthquake loads. DOI: 10.1061/(ASCE)ST.1943-541X.0000434. © 2012 American Society of Civil Engineers. CE Database subject headings: Pseudodynamic method; Seismic effects; Rehabilitation. Author keywords: Pseudodynamic method; Seismic effects; Rehabilitation.

A two-story, three-bay RC frame with code incompliant seismic design and detailing is tested using continuous pseudodynamic test method for three scale levels of Duzce ground motion. The ground motion produced minimum, signifi- cant, and severe damage states on the test structure. Diagonal cracking of the infill wall, column damage in the form of cover spalling and rebar buckling, and complete disintegration of the infill wall were the important observed damage events for the three scale levels, respectively. Nonlinear time history analyses were able to estimate the story displacement response with reasonable accuracy. The importance of element removal for near collapse damage state is unfolded. Tracing the local engineering demand parameters such as strains and curvature was found to be extremely difficult. (DOI: 10.1193/1.3609876)

The accuracy of estimating the performance levels of a deficient RC frame using linear elastic and nonlinear dynamic analysis is evaluated in this study. This was achieved by comparing the response of a structure tested with pseudo-dynamic testing and estimated by the linear elastic assessment procedures along with nonlinear dynamic analysis. The test structure (three bay-two storey planar frame) is a ½ scale reinforced concrete frame having masonry infill walls in the central span. The test frame contains a number of structural deficiencies such as low concrete compressive strength (7MPa), lack of transverse reinforcement detailing at potential plastic hinge regions and beam-column joints. Tests were conducted for the NS component of 7.14 magnitudes 1999 Duzce Earthquake for three different scale levels. Test results indicated that drift deformation demands estimated using nonlinear dynamic analysis were within 15% of those observed in the tests. On the other hand, damage estimations of TEC and FEMA 356 were found to be conservative resulting in retrofit decisions. It was also observed that although nonlinear dynamic analysis provided reasonable estimations for inter-storey displacements, local demand parameters such as column curvature demands were estimated with less accuracy.