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The “Post-Tensioned Structural Concrete—Code Requirements and Commentary” (“Code”) provides minimum requirements for the materials, design, and detailing of post-tensioned concrete buildings and, where applicable, nonbuilding structures. This Code was developed by using a consensus process and addresses structural concrete members and systems that contain post-tensioned tendons. The Technical Advisory Board Code Task Group of the Post-Tensioning Institute was instrumental in the development of code provisions and commentary for this Code and whose efforts are gratefully acknowledged. Among the subjects covered are: design and construction for strength, serviceability, and durability; one-way slabs; two-way slabs; beams; post-tensioning anchorages; construction document information; and field inspection and testing. This Code adheres to the chapter and section numbering of ACI CODE-318-25 and either references or repeats applicable provisions from ACI CODE-318. Provisions that are identical to ACI CODE-318 and are repeated in this Code are denoted with an equal sign (“=”). Provisions that are applicable to post-tensioned concrete but are not repeated in the Code are denoted as “See ACI CODE-318.” The Code organization is such that all design and detailing requirements for structural systems or for individual members are presented in chapters devoted to those individual subjects, and the chapters are arranged in a manner that generally follows the process and chronology of design and construction. Information and procedures that are common to the design of multiple member types are located in utility chapters. Within chapters, the terms “out of scope” are used for numbered section headings from ACI CODE-318 that are not covered by this Code, while the term “intentionally left blank” is used as a place holder to maintain consistency with section numbering in situations where ACI CODE-318 includes a numbered provision that is not also in this Code. Uses of the Code include adoption by reference in a general building code, and earlier editions have been widely used in this manner. The Code is written in a format that allows such reference without change to its language. Therefore, background details or suggestions for carrying out the requirements or intent of the Code provisions cannot be included within the Code itself. The Commentary is provided for this purpose. Some considerations of the committee in developing the Code are discussed in the Commentary, with emphasis given to the explanation of new or revised provisions. The commentary also provides explanations regarding situations where use of ACI CODE-318 and this Code are used. For instance, design of cast-in-place, nonprestressed concrete members or structures requires the use of ACI CODE-318 alone. Design of post-tensioned concrete structures requires the use of this Code and ACI CODE-318. Design of precast, post-tensioned concrete structures requires the use of applicable provisions of this Code, ACI CODE-318, and ACI-PTI CODE-319. For provisions that specifically address precast concrete and are generally not within the scope of post-tensioning, this code references either ACI CODE-318 or ACI-PTI CODE-319, where applicable. Much of the research data referenced in preparing the Code is cited for the user desiring to study individual questions in greater detail. Other documents that provide suggestions for carrying out the requirements of the Code are also cited, including PTI design manuals, recommended practices, and reports. Keywords: anchorage; anchorage device; anchorage zone; beam-column frame; beams (supports); bonded tendon; combined stress; compressive strength; concrete; construction documents; continuity (structural); cover; deep beams; deflections; earthquake-resistant structures; elongation; flexural strength; floors; inspection; joints (junctions); loads (forces); modulus of elasticity; moments; post-tensioned concrete; prestressed concrete; prestressing steels; quality control; reinforcing steels; roofs; serviceability; shear strength; spans; splicing; strength analysis; stresses; stressing; structural analysis; structural design; structural integrity; structural walls; T-beams; torsion; unbonded tendon; walls.

“Low-Carbon Concrete—Code Requirements and Commentary” (“Code”) provides provisions for concrete where reduced global warming potential (GWP) is required. The Code was developed by a consensus process and addresses cast-in-place concrete with specified compressive strength greater than 17.2 MPa and less than or equal to 55.2 MPa. Precast concrete, tremie concrete, auger-cast concrete/grout, shotcrete, pavers, and masonry units are not included in the scope of the Code. This is the first edition of the Code and the scope is limited by the available benchmark data. Future editions of the Code will be broader in scope as data beyond strength benchmarks and for other types of concrete becomes available. The Code may be adopted as a stand-alone code or can be used in combination with a structural design code or low-carbon material code adopted by an authority having jurisdiction. The Code is in a format that allows reference to a set of chapters based on the structure type. Adoption would include all of Chapters 1 to 4, the applicable Chapter(s) of 5, 6, 7, and/or 8, plus Appendix A. This Code is written in a format that allows reference without change to its language. Therefore, background details or suggestions for carrying out the requirements or intent of the Code provisions cannot be included with the Code itself. The Commentary is provided for this purpose. Some considerations of the committee in developing the Code are discussed in the Commentary along with references for the user desiring to study individual questions in greater detail. Keywords: baseline; benchmark; bridge; building; compressive strength; concrete; cradle-to-gate; environmental product declaration (EPD); environment; global warming potential (GWP); hardscape; life cycle assessment (LCA); low-carbon concrete (LCC); low-embodied carbon concrete; pavement; performance requirement; residential; sustainability; sustainable; structure.

An approach to improve the progressive collapse resistance of conventional RC frame structure was put forth by using unbonded post-tensioning strand (UPS). Two UPSs with a straight profile are mounted at the bottom of the beam section. A static loading test was conducted on an unbonded prestressed RC (UPRC) beam-column sub-assemblage under a column removal scenario. The structural behaviors of the test specimen, such as the load-carrying capacity, failure mode, post-tensioning force of the UPSs, and rebar 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 sub-assemblage 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 by using the software ABAQUS. The FE model was validated by the 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 sub-assemblages. It was validated by the test result as well as by the FE Models of the UPRC sub-assemblages which were calibrated using the available experimental data.

In this study, the challenge of automating concrete crack image classification by developing a lightweight machine-learning model that balances accuracy with computational efficiency was addressed. Traditional deep learning models, while accurate, suffer from high computational demands, limiting their practicality in on-site applications. This study’s approach used the Random Forest (RF) classifier combined with a Histogram of Oriented Gradients (HOG) and Local Binary Patterns (LBP) for feature extraction, offering a more feasible alternative for real-time structural health monitoring. Comparative analysis with the Convolutional Neural Network (CNN) model highlights our model’s significantly reduced size and inference times, with only a marginal compromise in accuracy. The results demonstrated that the RF models, particularly RF with LBP, are well-suited for integration into resource-constrained environments, paving the way for their deployment in portable, on-site diagnostic systems in civil engineering. This study contributed a novel perspective to the field, emphasizing the importance of efficient machine learning solutions in practical applications of structural health monitoring.

This paper discusses the seismic performance of precast coupled structural walls with the influence of connections and their location. Full-scale quasi-static tests were conducted on the coupled structural walls by varying the number of connections. The test results show that the number of connections and their position along the height of the coupled wall significantly influence the lateral strength, stiffness, energy dissipation, and failure modes. Walls with two connections seem to improve the strength and hysteretic response, exhibiting superior cyclic performance. Increasing the number of connections improves the initial stiffness to a certain extent, but the designs are expensive. Walls with connections closer to lateral loading lines exhibit vulnerability, requiring design to optimize energy dissipation and crack control. Connections with over-strength may need to be avoided as they may not increase the energy dissipation under earthquake loading. The outcomes of the study help in designing precast systems with better seismic resilience, good ductility, and ease of replacement after an earthquake hits the system.