The evaluation of the mechanical properties of steel fiber-reinforced concrete (SFRC) with different types of fibers and dosages endorses new design recommendations for using several types of construction materials for structural elements. The double-punch test (DPT) offers procedural and economic advantages for evaluating the indirect tensile strength of the SFRC. The objective of this paper is to show and discuss the results of the mechanical characterization obtained experimentally for SFRC using the DPT, with different types of anchorage and fiber dosages. The variables of the study were the dosage of steel fibers (20, 40, and 60 kg/m3) and the number of hooks at the ends of the fiber (1, 1.5, and 2 hooks). The paper develops empirical models for predicting the tensile strength, residual strength, and toughness of SFRC subjected to the DPT without resorting to experimental tests. The models were developed considering the trends of 385 results: 108 from 40 DPTs measured in this study, and 277 from 23 DPTs available in the literature.

The load transfer within joints of reinforced concrete elements can strongly influence the behavior of the structure. Additionally, cracks play an important role—they develop due to bending-induced tensile stresses in concrete and meander along the starter bars anchored in joints. The performance of joints becomes even more relevant under seismic loading conditions, whereby the reinforcing bars are subjected to cyclic loading and, at the same time, cyclic opening and closing of the cracks intercepting the starter bars. Such load and crack cycling may significantly influence the load and displacement capacity of starter bar anchorages. Experimental tests were carried out to verify a generic bond model to describe the bond stress-slip relationship under these seismic conditions. This seismic bond model should allow the realistic numerical simulation of seismically loaded reinforced concrete structures even if joints are designed with starter bars shorter than the development length.

Concrete screw anchors can be susceptible to stress-induced hydrogen embrittlement cracking because they are case hardened and often coated. Hydrogen attack can result in decreased tensile ductility and decreased fracture stress at the root, which is where the threads meet the core. Currently, Acceptance Criteria 193 (AC 193) requires that two types of tests are conducted to qualify screw fasteners for stress-induced hydrogen embrittlement cracking under service conditions: 1) Method A, which is a test subjecting a concrete screw installed in concrete to a sustained tensile load while in an aggressive environment; and 2) Method B, which is a bending test on the threaded portion of the fastener while in an aggressive environment. This study examines Method A and Method B qualification test data obtained from three manufacturers for five different diameters and 11 different lengths. The comparison of the test results for the two methods shows that Method B is a redundant test, resulting in no additional safety or information beyond that gained from Method A.

Anchors used in seismic applications have to resist cyclically pulsating loads and cyclically opening and closing cracks which potentially intersect the anchor location. In reality, cyclic load and cyclic crack phenomena act on anchors simultaneously; however, seismic tests in laboratories are carried out with either one of the two parameters kept constant. To investigate the effect of simultaneous load and crack cycling on anchor behavior, experimental tests with synchronized load and crack cycling protocols on headed bolts cast in special concrete specimens were carried out. The test results demonstrate that the anchor displacement depends on the phasing of load and crack cycling, and justify the reduction of the constant anchor load during simulated cyclic crack tests to compensate for disregarded load cycling effects. The influence of various phase lags and different frequencies on the relative anchor displacement is described by an analytical model based on the integrated cumulative damage regime.

The anchorage of carbon fiber-reinforced polymer (CFRP) strips using CFRP anchors is gaining acceptance in strengthening applications of concrete members. CFRP anchors can fully develop the strength of CFRP strips when adequately detailed. However, parameters that influence the behavior and strength of CFRP strips and anchors are not well understood. In this study, 26 tests on concrete beams were conducted to study the influence of five key parameters on CFRP anchor effectiveness: 1) the width of the anchored CFRP strip; 2) the material ratio of CFRP anchor to CFRP strip; 3) the concrete strength; 4) the length/angle of anchor fan; and 5) the bond condition between a CFRP strip and concrete. Results indicate that narrow anchored CFRP strips developed higher stresses at fracture than wide strips and required smaller anchor material ratios to be fully developed. Test results provide valuable data for designing anchored CFRP strengthening systems.