International Concrete Abstracts Portal

Slag-based zero-cement concrete (ZC) of high strength (60 MPa [8.70 ksi]) was developed as an eco-friendly construction material. In the present study, to investigate the structural behavior of precast columns using ZC, cyclic loading tests were performed for five column specimens with reinforcement details of ordinary moment frames. Longitudinal reinforcement was connected by sleeve splices at the precast column–footing joint. The test parameters included the concrete type (Portland cement-based normal concrete [NC] vs. ZC), construction method (monolithic vs. precast), longitudinal reinforcement ratio, and sleeve size. The test results showed that the structural performance (failure mode, strength, stiffness, energy dissipation, and deformation capacity) of the precast ZC columns was comparable to that of the monolithic NC and precast NC columns, and the tested strengths agreed with the nominal strengths calculated by ACI 318-19. These results indicate that current design codes for cementitious materials and sleeve splice of longitudinal reinforcement are applicable to the design of precast ZC columns.

This paper presents a novel framework of analysis to assess the resistance of existing reinforced concrete (RC) members experiencing spatial variability of crack patterns and spatial variability of concrete mechanical properties. The spatial variabilities are considered by using digital image processing (DIP) to map crack patterns onto three-dimensional nonlinear finite element (NFE) models where the concrete mechanical properties (compressive strength, tensile strength, damage, and modulus of elasticity) are spatially varied using random fields to form random NFE models (RNFE). The framework was developed and applied to assess a corroded RC beam (determine the distribution of the resistance) and column (determine the reliability of the column at the ultimate limit state). Research findings indicate improved accuracy in assessing the resistance of the corroded members up to 20%, and the adaptivity of the developed framework for performing reliability analysis of existing RC structures.

Two large-scale beam-column connections with beam longitudinal headed bars were tested to evaluate their susceptibility to breakout failures. The specimens were designed following the strength and transverse reinforcement detailing provisions in Chapter 15 of ACI 318-19. The variable investigated was the headed bar embedment length, which was determined based on either Chapter 25 of ACI 318-19 or recent research at the University of Kansas, the latter leading to a 22% shorter embedment length. Both specimens exhibited beam flexural yielding, but the specimen with shorter bar embedment length experienced significantly more connection damage followed by a concrete breakout failure. Based on the limited test results, it is recommended that nominal joint shear strength be calculated based on a joint effective depth equal to the headed bar embedment length and a shear stress of 1.0λ√(fc' ) (MPa) [12λ√(fc' ) (psi)]. A method for calculating headed bar group anchorage strength in exterior beam-column connections is proposed, which led to reasonable and conservative strength estimates in the test specimens.

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.