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The Post-Tensioning Institute (PTI) announced that its cornerstone publication, the PTI Journal, received an honorable mention in the 2025 MarCom Awards, an award program that celebrates excellence in marketing and communication. The Journal was recognized in the Publication-Magazine-Association category for its excellent quality and content. The PTI Journal is a publication for the post-tensioning industry, delivering valuable insights and technical expertise to professionals worldwide. This recognition highlights PTI's successful collaboration with Advancing Organizational Excellence (AOE), which provides comprehensive support in content development, layout design, and meticulous editing to ensure each issue meets the highest standards.

This study experimentally investigates the effects of the unbonded post-tensioning on the response of reinforced concrete (RC) beams under impact loads. A total of ffteen specimens were cast and tested. All specimens had identical longitudinal reinforcement, but varying shear reinforcement ratios designed to be both flexuraland shear-defficient in static conditions according to the ACI code. In particular, thirteen unbonded post-tensioned (PT) beams were tested under drop weight impact applied at the midspan in simply supported conditions and compared with conventional type RC beams. The main variables investigated include increasing levels of PT force and the application of two different impact energies per each specimen type, shear- or flexural-defficient. The experimental results showed that the levels of PT force and shear reinforcements of the specimens played an important role in their overall behavior. With respect to benefcial design recommendations, relationships between the impact resistance and the static capacity are provided; a general increase in strength of around three times that of the static capacity is observed when impacted. Additionally, relationships between the ratio of the impact energy to static capacity are developed with regard to the maximum and residual member displacements. Keywords: dynamic response; failure mechanism; impact tests; reinforced concrete; unbonded post-tensioning.

This paper presents the behavior of six tests of planar prestressed concrete frames under the loss of a middle column. The six tests consist of two non-prestressed reinforced concrete (RC) specimens and four prestressed concrete (PC) specimens with bonded post-tensioning tendons (BPT). The structural response of the specimens with different flexural reinforcement ratio, span-depth ratio, and effective prestress level has been reported. In addition, the impact of parabolic BPT on the behavior of RC frames to resist progressive collapse is also evaluated. Experimental results indicated that the BPT cannot only increase the initial stiffness and yielding load of the RC counterparts, but also increase the ultimate load capacity in the catenary action stage. Moreover, it will impact the load-resisting mechanisms and the failure modes. Contrary to the commonly accepted sequential mobilization of compressive arch action and catenary action to resist progressive collapse of RC frames, no effective compressive arch action is developed in PC frames to mitigate progressive collapse risk. Based on experimental observations, it is found that higher effective prestress in BPT results in enhanced initial stiffness and yielding load but less deformation capacity and ultimate load capacity. It is also found that higher non-prestressed flexural tensile reinforcement ratio could improve the behavior of PC specimens to resist progressive collapse. Keywords: bonded; catenary action; compressive arch action; mechanism; post-tensioning tendon; prestressed concrete; progressive collapse.

An approach to improve the progressive collapse resistance of conventional reinforced concrete (RC) frame structures was put forth by using unbonded post-tensioning strand (UPS). Two UPSs with straight profiles were mounted at the bottom of the beam section. A static loading test was conducted on an unbonded prestressed RC (UPRC) beam-column subassemblage under a column removal scenario. The structural behaviors of the test specimen such as load-carrying capacity, failure mode, post-tensioning force of the UPSs, and reinforcing bar strain were captured. By analyzing the results of the tested substructure, it was found that the compressive arch action (CAA) and catenary action (CTA) were sequentially mobilized in the UPRC subassemblage to avert its progressive collapse. The presence of UPSs could significantly improve the load-carrying capacity of conventional RC structures to defend against progressive collapse. Moreover, a high-fidelity finite element (FE) model of the test specimen was built using the software ABAQUS. The FE model was validated by experimental results in terms of the variation of vertical load, horizontal reaction force, and post-tensioning force of the UPSs against middle joint displacement (MJD). Finally, a theoretical model was proposed to evaluate the anti-progressive collapse capacities of UPRC subassemblages. It was validated by the test results as well as the FE models of the UPRC subassemblages, which were calibrated using the available experimental data. Keywords: finite element (FE) model; progressive collapse performance; reinforced concrete (RC) frame structure; theoretical model; unbonded post-tensioning strand (UPS).

Remodeling aging structures is common to enhance their structural, economic, and functional performance. However, the exceeding of bearing capacity of existing piles caused by increased upper loads due to vertical expansion frequently hinders their revitalization. In this paper, a methodology is proposed to control the demand-to-capacity ratio of existing piles without retrofitting the foundation, which is often accompanied by technical limitations and safety issues. A total of 12 tests were performed on four full-scale specimens, with tendon shape, wall thickness, boundary condition, and construction sequence as variables. Factors affecting load-transfer performance were identified based on test results. The target load-transfer pattern implemented in accordance with the tendon shape was confirmed. To verify the validity of the method, tests using tendon shape and wall thickness as variables were compared with results from finite element analysis. Keywords: external post-tensioning; foundation retrofitting; load-transfer; remodeling; vertical expansion.

This paper presents experimental results on seismic behaviors of post-tensioned (PT) monolithic exterior beam-column connections. Lateral cyclic loading tests were carried out for six full-scale exterior beam-column joint subassemblies fabricated with normal- and high-strength materials. Despite substantial joint cover spalling, the normal-strength specimens exhibited satisfactory lateral strengths and hysteretic behaviors up to [+ or -]5% drift ratios by virtue of the confinement effect of post-tensioning. The high-strength PT specimens also showed stable hysteretic behaviors with significantly reduced joint damages. It was found that the post-tensioning can increase the joint shear strength by more than 60% in both types of specimens. Furthermore, the post-tensioning was effective in retaining the lateral stiffness of the beam-column joints under the repeated loads, especially in high-strength specimens, enabling them to maintain at least 90% of their first-cycle stiffnesses throughout the testing. Keywords: cyclic test; exterior beam-column connection; high-strength concrete (HSC); joint shear demand; joint shear strength; monolithic connection; tendons; unbonded post-tensioning.

The numerical simulation of concrete fracture is difficult because of the brittle, inelastic-nonlinear nature of concrete. In this study, notched plain and reinforced concrete beams were investigated numerically to study their flexural response using different crack simulation techniques in ABAQUS. The flexural response was expressed by hardening and softening regime, flexural capacity, failure ductility, damage initiation and propagation, fracture energy, crack path, and crack mouth opening displacement. The employed techniques were the contour integral technique (CIT), the extended finite element method (XFEM), and the virtual crack closure technique (VCCT). A parametric study regarding the initial notch-to-depth ratio (ao/D), the shear span-to-depth ratio (S.S/D), and external post-tensioning (EPT) were investigated. It was found that both XFEM and VCCT produced better results, but XFEM had better flexural simulation. Contrarily, the CIT models failed to express the softening behavior and to capture the crack path. Furthermore, the flexural capacity was increased after reducing the (ao/D) and after decreasing the S.S/D. Additionally, using EPT increased the flexural capacity, showed the ductile flexural response, and reduced the flexural softening. Moreover, using reinforcement led to more ductile behavior, controlled damage propagation, and a dramatic increase in the flexural capacity. Furthermore, CIT showed reliable results for reinforced concrete beams, unlike plain concrete beams.

To investigate the shear strength of a nuclear power plant containment structure, six small-scale specimens of reinforced- or post-tensioned cylindrical concrete walls were tested under cyclic lateral loading. Particularly, the present study focused on the effect of the magnitude of vertical and horizontal prestressing forces. Further, to investigate the effect of high-frequency earthquakes, high-rate loading as well as low-rate loading were considered. The test results showed that the shear strengths of reinforced concrete (RC) walls and prestressed concrete (PSC) wall without horizontal prestressing force were greater than the nominal shear strength specified in current design/evaluation methods. On the other hand, in the case of walls subjected to horizontal prestressing force, the shear strengths were decreased, due to early delamination of the cover concrete. Particularly, strength degradation was pronounced when full horizontal prestressing was applied. The effect of early delamination was further investigated through nonlinear finite element analysis.

This paper focused on flexural behavior of damaged partially prestressed concrete beams strengthened with external post-tensioned tendons. A total of six strengthened beams and two unstrengthened beams, serving as control specimens, were tested to failure. The test parameters were prestressing tendon types (steel and carbon fiber-reinforced polymer [CFRP]) and initial damage levels (undamaged, in-service damage, and over-loaded damage). The test results revealed that strengthening the beams with external tendons could successfully improve serviceability andultimate flexural capacity with good deformability. Additionally, the initial damage had slight effect on ultimate capacity and ductility, but it did affect the cracking and deflection behavior. The ductility of the strengthened beams using external CFRP tendons wascomparable to those using steel strands. Finally, the experimental results were compared to theoretical predictions obtained from several design approaches, indicating that the flexural capacity of the strengthened beams with initial damage can be analyzed in the same way as those without initial damage, whereas the effect of initial damage should be considered in calculating the deflection of the beams with overloaded initial damage. Keywords: carbon fiber-reinforced polymer (CFRP); external post-tensioning; initial damage; prestressed concrete beams; steel strands; strengthening.

A parametric study was performed to understand the behavior of unbonded post-tensioned concrete beams under low-velocity drop-weight impact. Nonlinear finite element dynamic analysis was used for the simulation of both shear- and flexural-critical members. The modeled design parameters incorporated various concrete strengths, spacing of transverse reinforcement, and increasing levels of post-tensioning force. All beams were simulated under impact at four levels of impacting velocity of the drop hammer. Results of the parametric study were used to identify critical design and loading conditions on the dynamic behavior of unbonded post-tensioned members. Post-tensioning was shown to be beneficial for both shear and flexural resistance against low-velocity impact, and a static shear-to-flexural capacity ratio of at least 5 was found to prevent large shear failure. Additionally, the study was useful at correlating prior experimental results on the behavior of unbonded post-tensioned members, as well as developing the relationship between the peak deformation and the impacting energy and static design capacity with conservativeness.