Time-dependent behaviour of circular steel tube confined reinforced concrete (STCRC) stub columns subjected to low axial load

Design Provisions for Shrinkage and Creep of ConcreteDesign Provisions for Shrinkage and Creep of ConcreteDesign Provisions for Shrinkage and Creep of Concrete

This paper reviews and extracts lessons from historic buildings, whose stability relies mainly on compression to resist gravity loads, that can inform the construction of affordable housing and shelters using 3D printed concrete without reinforcement and formwork. The first part consists of a literature survey of historic constructions with systems relying on compression considering four vectors of analysis: (1) form; (2) structural principle; (3) materials; and (4) construction process . The survey starts by identifying forms whose structural principle may be adequate for 3D printing of concrete applications. Then, historic structures displaying similar forms are analyzed in terms of structural behavior, the types of materials employed, and the construction process used to obtain foundations, walls, and roofs. A series of historically inspired shapes for printing is thus obtained from this survey. To address the printability of the structures identified after the survey, the second part of the paper provides a brief description of existing processes for construction scale printing considering material aspects, such as fresh state behavior, and printing system configurations. Addressing the fresh state properties of concrete is crucial as it determines whether the structure fails during printing. Finally, a set of strategies including potential toolpaths and intermediate states are defined to print the identified forms, considering issues concerning material requirements and printing process.

Learning from historical structures under compression for concrete 3D printing construction

In this paper, optimized shape functions have been used in Rayleigh method to determine the critical buckling load and the fundamental natural frequency of non-prismatic steel-reinforced slender concrete columns. A range of admissible shape functions describing the mode shape in buckling as well as for the fundamental natural frequency of the column are considered and then an optimization strategy is developed to arrive at the optimum shape function. The results obtained from the present method based on the implementation of Rayleigh method through the concept of generalized coordinates are verified and validated by the finite element method. The application of the theory is demonstrated by two illustrative examples, both of which are steel-reinforced concrete towers that are representative of practical structures. Of particular significance is the duality between the free vibration and buckling problems which is captured and fruitfully exploited in the analysis. The effect of an additional mass located at the top of the tower is included in the investigation. Additionally, the impact of the creep behavior of the towers on results due to continuing lapse of time is critically examined and assessed. Finally, significant conclusions are drawn following the discussion of results. 

Buckling and free vibration analysis of non-prismatic columns using optimized shape functions and Rayleigh method

In this paper, the flexural creep behavior of hooked-end steel fiber reinforced high-strength concrete was evaluated to investigate the steel fiber content influence on long-term behavior of flexural members. An experimental program consisted of nine prismatic beam specimens with dimensions of 150 × 150 × 600mm reinforced with different contents of steel fiber (0, 0.75 and 1.5% at the volume fraction). To introduce flexural creep loading to notched prismatic beam specimens, a four-point bending test setup was used. The sustained load with 40% of the flexural strength was applied by means of a lever system and controlled by a load cell for 90 days. During sustained loading, crack mouth opening displacement (CMOD) was monitored. Conventional flexural test after creep tests were carried out to evaluate the residual capacity of each specimen. Test results showed that steel fiber content has a significant effect on the flexural creep behavior of high-strength concrete and long-term flexural load with 40% of flexural strength doesn’t generate negative effects on the residual capacity of steel fiber reinforced high-strength concrete.

http://koreascience.kr:80/article/JAKO202015358834550.pdf

Effets of Steel Fiber Contents on Flexural Creep Behavior of High-Strength Concrete

Time-dependent strains in reinforced concrete (RC) members are usually estimated using approximate algebraic methods. This paper presents an exact method for estimating the time-dependent s...

Time-Dependent Strains in Axially Loaded Reinforced Concrete Columns

The test method of ASTM C512 (ASTM. 2015. Standard test method for creep of concrete in compression. ASTM C512/C512M. West Conshohocken, PA: ASTM) dictates the use of a spring-loaded creep ...

Analysis of the ASTM C512 Spring-Loaded CREEP Frame

https://google.iopscience.iop.org/article/10.1088/1757-899X/936/1/012053/pdf

Optimal Rate of Printing of 3D Printed Concrete Columns and Walls to Avoid Buckling

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Numerical Simulation of Nonlinear Behavior of Reinforced Concrete Beam-Slab Systems

https://google.iopscience.iop.org/article/10.1088/1757-899X/936/1/012023/pdf

M N Shariff

Papers

Time-Dependent Strains in Axially Loaded Reinforced Concrete Columns

Analysis of the ASTM C512 Spring-Loaded CREEP Frame

Optimal Rate of Printing of 3D Printed Concrete Columns and Walls to Avoid Buckling

Numerical Simulation of Nonlinear Behavior of Reinforced Concrete Beam-Slab Systems

A Software Tool to Estimate the Time-dependent Deformation in RC Walls and Columns