International Concrete Abstracts Portal

Design recommendations are presented for calculating the immediate deflection of cracked prestressed concrete members under service load. Inconsistency and sometimes confusion regarding the calculation of immediate deflection for the different approaches presently available highlight the need for a rational approach to computing deflection. The ACI 318-19 approach for reinforced (nonprestressed) concrete is broadened to include prestressed concrete. This involves the implementation of an effective moment of inertia taken together with an effective eccentricity of the prestressing steel used to define the effective curvature and/or camber from the prestressing force. Proposed revisions to ACI 318 are presented for prestressed Class T and Class C flexural members and clear steps are provided for calculating immediate deflection. The effectiveness of the new approach is validated against an extensive database of test results, showing reasonable accuracy and reliability in predicting deflections. The paper concludes with practical recommendations for implementation and a worked-out example to illustrate the proposed methodology. These findings aim to enhance the accuracy and consistency of deflection predictions in prestressed concrete design, contributing to better serviceability and performance of concrete structures.

This study investigates the impact of air-entraining admixtures (AEA) on mortar performance, focusing on fresh-state and hardened-state properties critical to durability and engineering applications. Ten distinct mortar mixtures were analyzed, following guidelines established by EFNARC (European Federation of National Associations Representing Producers and Applicators of Specialist Building Products for Concrete). AEAs were introduced at varying proportions (0.01–0.5% of cement weight) to evaluate their effects on intrinsic properties (density, void ratio, water absorption), rheological parameters (plastic viscosity, yield stress), and mechanical characteristics (compressive strength, ultrasonic velocity, modulus of elasticity).

Regression models were developed, yielding high predictive accuracy with R² values exceeding 0.98. Notably, ultrasonic velocity and modulus of elasticity demonstrated strong correlations with intrinsic properties across all curing ages. Similarly, compressive strength showed significant associations with rheological parameters, highlighting the influence of air content and flow behavior on structural performance. These findings offer precise quantitative models for predicting mortar behavior and optimizing formulations for enhanced performance.

Coastal reinforced concrete bridges are critical infrastructures, yet they face significant threats from corrosion due to saline environments and extreme loads like wave-induced forces and seismic events. This state-of-the-art review examines the resilience of corrosion-damaged RC bridges under such conditions. It compiles advanced methodologies and technological innovations to assess and enhance durability and safety. Key highlights include synthesizing loss estimation models with advanced reliability methods for a robust resilience assessment framework. Analyzing catastrophic bridge failures and environmental deterioration, the review underscores the urgent need for innovative materials and protective technologies. It emphasizes advanced analytical models like Performance-Based Earthquake Engineering (PBEE) and Incremental Dynamic Analysis (IDA) to evaluate combined impacts. The findings advocate for engineered cementitious composites (ECC) and advanced sensor systems for improved real-time monitoring and resilience. Future research should focus on developing comprehensive resilience models accounting for corrosion, seismic, and wave-induced loads to enhance infrastructure safety and sustainability.

This paper investigates the seismic performance of exterior beam-column joints in special moment frames (SMFs) with varying axial load ratios. Cyclic testing of four additional specimens with an axial load ratio of 0.45 is compared with four companion specimens at 0.10. Each specimen was designed and constructed with Gr.60 (420), Gr.80 (550), or Gr. 100 (690) reinforcement in accordance with ACI CODE-318 provisions for special moment frame joints, except for the provisions of joint shear and confinement. While ACI CODE-318 tightens confinement requirements for SMF columns and joints, especially under high axial loads, this study reveals that increasing the axial load ratio benefits joint behavior. The study also demonstrates the feasibility of using high-strength reinforcement in exterior beam-column joints of SMFs, provided that appropriate modifications are made. The findings in this study have influenced modifications from ACI CODE-318 to the Building Code Requirements for Concrete Structures in Taiwan.

The paper investigates the bond behavior between non-pretensioned indented steel wire and high-performance concrete (HPC) to study the effect of embedment length and concrete compressive strength on bonding performance with time. A total of 63 concrete specimens, cross section of 160 x 160 mm reinforced with indented steel wire of 7.5 mm diameter, were cast and tested under uniaxial load. The main test parameters included the embedment lengths: 40, 80, 120, 200, and 240 mm, and concrete compressive strengths: 40, 60, 72, and 88 MPa. The modified pullout test method developed at the Cracow University of Technology was used in the experimental investigation. The results show that the average maximum bond stress (16, 23, 26, and 32 MPa) is increased with an increase of concrete compressive strength (over time) and is decreased with longer development length of indented steel wire for the same concrete compressive strength. An increase of bond stress is slower than an increase of HPC compressive strength. Moreover, it was demonstrated that the maximum bond stress occurs at the slip of 2.8 mm, independently of concrete compressive strength ranging from 40 to 88 MPa. The average values of the adhesive bond of HPC to non-pretensioned indented steel wire range from 2.90 to 3.75 MPa. Finally, a verification of the fib Model Code 2010 concrete bond-slip model for HPC reinforced with non-pretensioned indented steel wires was conducted. It was determined that the model is not applicable to elements made of concrete with a strength of 60 MPa and above.