Editor’s Note

Kunnath et al. develop a “Nonlinear Uniaxial Material Model for Reinforcing Steel Bars” to advance nonlinear analysis of reinforced concrete (RC) structures based on fiber-based discretization of the member cross sections, since the accuracy of a fiber-section model is almost entirely dependent on the ability of constitutive material models to represent the overall inelastic behavior of the member. First, a base material model to describe the primary cyclic stress-strain relationship of reinforcing steel is developed. Using available concepts to simulate bar buckling, low-cycle fatigue fracture, and cyclic degradation, a generic phenomenological material model is developed and implemented in an open-source computational platform. The effectiveness of the new reinforcing bar model is validated through comparison with available experimental data.

In “Anchorage of Longitudinal Column Reinforcement in Bridge Monolithic Connections,” Timosidis and Pantazopoulou propose an analytical method for the definition of the strain distribution along the anchorage of the column longitudinal reinforcement inside a bridge connection. The anchorage capacity of the main column reinforcement is considered to be affected by two independent mechanisms. The capacity of the first mechanism depends on the average bond stress along the elastic part of the anchorage, while that of the second mechanism depends on the coefficient of friction arising between main column bars and transverse reinforcement that encloses and restrains the anchorage. The proposed model is used to compute the joint shear response of selected bridge connection specimens for which data for strain distribution along anchorages are available, and the calculated values are shown to correlate well with associated experimental data.

Wu et al. develop an “Analytical Method for Failure of Anchor-Grout-Concrete Anchorage due to Concrete Cone Failure and Interfacial Debonding” using deformation compatibility conditions at the anchor-grout and grout-concrete interfaces. Three different failure modes are considered, including concrete cone failure at the unloaded end without interfacial debonding, interfacial debonding plus concrete cone failure at the same height as the interfacial shear crack tip, and interfacial debonding plus concrete cone failure at the unloaded end. It is found that if the embedment length is relatively long, the concrete cone failure occurs locally, while if the concrete diameter is large enough, the failure mode is the interfacial debonding without concrete cone failure.

A numerical and experimental study to examine the “Behavior of Reinforced Concrete Box Culverts under High Embankments” is presented by Pimentel et al. A box culvert (BC) under a $9.5\text{-}\mathrm{m}$ -high embankment was instrumented and observed during the construction period. Numerical analyses are performed using a finite-element code capable of considering the construction sequence, the nonlinear behavior of the reinforced concrete structure, and the elastic-plastic behavior of the soil and the interfaces. Following validation of the model with observed behavior, a parametric study is carried out to identify the main parameters influencing the interaction mechanism and to evaluate the BC structural performance up to failure. It is concluded that the soil pressures and the nonlinear behavior of the BC are directly related and should be incorporated in the design process.

An “Experimental and Numerical Investigation of Corrosion-Induced Cover Cracking in Reinforced Concrete Structures” is carried out by Val et al. A comparison of finite-element simulations and recorded experimental data is used to estimate the amount of corrosion products penetrating into concrete pores and cracks. It was found that the amount of corrosion products penetrating into the concrete pores before crack initiation is larger than that obtained by other researchers. The paper also finds that corrosion products do not immediately fill corrosion-induced cracks in concrete after their initiation and that the thicker the concrete cover, the longer it will take to fully fill a crack.

A two-part paper investigating the performance of buildings with structural fuses is presented by Vargas and Bruneau. The “Analytical Response and Design of Buildings with Metallic Structural Fuses” is discussed in the first paper. It is proposed to concentrate damage on disposable and easy-to-repair structural elements called “structural fuses.” The proposed structural fuse design procedure is developed from a parametric study examining the nonlinear behavior of single-degree-of-freedom systems subjected to synthetic ground motions. The nonlinear dynamic response is presented in dimensionless charts normalized with respect to key parameters. The proposed design procedure is illustrated by an example using buckling-restrained braces (BRBs) as metallic structural fuses. This example forms the basis of the companion paper, “Experimental Response of Buildings Designed with Metallic Structure Fuses,” and serves as a proof of concept of the developed design procedure. This experimental project assessed the replaceability of BRBs designed as sacrificial and easy-to-repair members. The BRBs are connected to the frame model by a removable and eccentric gusset plate especially designed to prevent performance problems observed in other experimental research. A secondary objective of the test was to examine the use of seismic isolation devices to protect nonstructural components from severe floor vibrations in buildings designed per the structural fuse concept. The seismic isolation device consists of a bearing with a spherical ball rolling in conical steel plates and was installed on the top floor of the frame model. Experimental results indicate that the objectives of the structural fuse concept were successfully achieved with the beams and columns remaining elastic while the BRBs worked as metallic fuses and dissipated the seismically induced energy.

Kueht and Hueste evaluate the seismic provisions in building codes adopted in Memphis, Tennessee, and other Central United States cities in “Impact of Code Requirements in the Central United States: Seismic Performance Assessment of a Reinforced Concrete Building.” The investigation identifies potential deficiencies for a typical four-story reinforced concrete (RC) frame building designed for three sets of seismic provisions: the 2003 International Building Code (IBC), the 2003 IBC with local Memphis amendments, and the 1999 Standard Building Code (SBC). Special seismic detailing was required for the IBC and SBC designs, while the amended IBC design required only intermediate seismic detailing. Nonlinear simulations of the building model for two earthquake recurrence intervals (10% and 2% in $50\text{years}$ ) indicates that special seismic detailing can provide a significant improvement in the seismic performance of similar low- to mid-rise RC buildings in the Central United States. The performance of RC frames in the Central and Eastern United States (CEUS) is the subject of Celik and Ellingwood’s paper “Seismic Risk Assessment of Gravity Load Designed Reinforced Concrete Frames Subjected to Mid-America Ground Motions.” This study presents a set of probability-based tools for seismic vulnerability and risk assessment of such gravity load designed (GLD) RC frames, and uses these tools to evaluate the seismic vulnerability of RC frames that are representative of the building inventory in Memphis—the largest population center close to the New Madrid seismic zone. This evaluation indicates that the majority of existing GLD RC frames, such as those considered in this study, which are typical of design practices in the CEUS prior to 1990, would not meet the life safety and collapse prevention performance objectives that are found in recent building codes and guidelines for performance-based earthquake engineering.

A “Semiactive Viscous Tensile Bracing System” and an energy absorbing mechanism are proposed by Rahani et al. to improve the performance of conventional braces. The developed mechanism, which does not require an actuator and/or large power supply, is composed of a viscous damper, a length correction control system, and a normal wind bracing on each floor. The hysteretic response of the braces is almost similar to ductile tensile steel members. The structural behavior of the system is investigated through nonlinear dynamic simulations, and it is shown that the proposed system significantly improves the performance of conventional bracing systems by reducing drift demands and also minimizing permanent drift.

In “Wind-Induced Cladding and Structural Loads on a Low-Wood Building,” Zisis and Stathopoulos used a test building constructed in Fredericton, New Brunswick, and equipped with weather, pressure, and load monitoring instrumentation, to collect pressure, and force coefficient data. A 1:200-scale model was also fabricated and tested for a total of 15 angles of wind attack at the Building Aerodynamics Laboratory of Concordia University. Mean and peak local and area-averaged pressure coefficients were measured, and finite-element analysis via a 3D linear model was performed to compute force coefficients for the selected wind directions. Pressure distribution comparisons between the full-scale and the wind tunnel results showed generally good agreement. However, significant overestimation of the fluctuating dynamic component of the foundation force is apparent when this is derived from the fluctuating roof pressures, in comparison to the directly measured values in the field.

“Flexural Test of a Composite Beam Using Asymmetric Steel Section with Web Openings” by Ju et al. describes an experimental study of a new type of composite beam developed to reduce floor-to-floor height in buildings. Instead of using shear connectors, the longitudinal shear strength is obtained through the bond strength of the interface between concrete and steel and the bearing strength of the opened web area. The flexural behavior of the proposed beam was assessed using a simple beam test and compared with the performance of a slim floor beam and a bare steel beam. The proposed system showed satisfactory horizontal shear resistance and good composite behavior. The ultimate strength of the proposed system exceeded the design value and failed due to concrete crushing in the compression zone without bond or local failure in accordance with the design objective.