Improving the Numerical Modelling of In-Situ Rock Bolts Using Axial and Bending Strain Data from Instrumented Bolts

Numerical modelling has become an important tool in the underground rock bolt reinforcement designing process. Numerical modelling provides the advantage of easily and quickly simulating complex underground geometries and mechanisms with sensitivity analyses. However, a numerical model needs to be calibrated using mathematical solutions, lab testing or with actual in-situ observations and measurements (which is the preferred method) before its results can be quantitatively applied to reinforcement design. Instrumented rock bolts provide a useful data source for calibrating in-situ rock bolt models. In this work, procedures have been presented to identify and determine the orientation of structures in the rock mass based on the strains on the instrumented rock bolts. A method to calibrate the rock bolt model with in-situ data is also presented. The results of the presented procedures have been validated with laboratory tests and numerical modelling. The procedures have been applied to create and calibrate an in-situ rock bolt model in FLAC3D and the results are validated using in-situ data.

Combined Flexural and Shear Strengthening of RC T-Beams with FRP and TRM: Experimental Study and Parametric Finite Element Analyses

Due to inadequacies of reinforcement design in older structures and changes in building codes, but also the change of building use in existing structures, reinforced concrete (RC) beams often require upgrading during building renovation. The combined shear and flexural strengthening with composite materials, fibre-reinforced polymer sheets (FRP) and textile reinforced mortars (TRM), is assessed in this study. An experimental campaign on twelve half-scale retrofitted RC beams is presented, looking at various parameters of interest, including the effect of the steel reinforcement ratio on the retrofit effectiveness, the amount of composite material used for strengthening and the effect of the shear span, as well as the difference in effectiveness of FRP and TRM in strengthening RC beams. Significant effects on the shear capacity of composite retrofitted beams are observed for all studied parameters. The experimental study is used as a basis for developing a detailed finite element (FE) model for RC beams strengthened with FRP. The results of the FE model are compared to the experimental results and used to design a parametric study to further study the effect of the investigated parameters on the retrofit effectiveness.

Comparison reinforcement design shear wall modelling planar and assembly in elevator shaft

Shear walls modelling as planar or assembly have different assumption in behaviour that will give different responses in forces. Shear wall planar modelling as individual walls which each wall was modelled as a vertical beam. Shear Wall assembly modelling as a combined unit to be represented by one beam element. The application of shear wall assembly is placed in elevator shafts in buildings or stairwell. [1]. In ETABS program, there are two types modelling shear wall are planar walls and wall assemblies. The analysis is based on three types of design section that are Simplified Compression (C) and Tension (T), Uniform Reinforcing and General Reinforcing. The purpose of this study is comparing the planar walls Simplified C and T with planar walls Uniform Reinforcing and wall assemblies Uniform Reinforcing. The conclusion for longitudinal reinforcement are, first, planar walls Simplified C and T is 40 to 96 % larger than wall assemblies, except pier P6 is 28 % smaller, second, planar walls Uniform Reinforcing is larger than 7 to 33 % wall assemblies Uniform Reinforcing, except pier P6 is 39 % smaller, third, the planar walls Simplified C and T, planar walls Uniform Reinforcing transversal reinforcement are 1 to 8 % larger than wall assemblies Uniform Reinforcing, except pier P6 is 51 % smaller.

Reinforcement Design and Physical Testing of New and Old Cushion Cap of Existing Bridge

As an important part of bridge structure, pile cap plays an important role in its operation. There is a lack of sufficient research in the design and construction of the existing bridges, especially in the operation process of the river crossing bridge, there will be more security risks, so it is urgent to strengthen the bearing platform. Combined with the general design theory of bridge cap, considering the feasibility of construction and the difficulty of operation, the new and old caps are planted with steel bars to make them bear the common force. Aiming at the problem of insufficient bearing capacity, the cap reinforcement method is proposed, so as to improve the stability of the bridge. The research results can provide reference for similar bridge reinforcement projects in the future.

Volumetric Deformations and Crack Control in Reinforced Concrete Structures

Restraint temperature and shrinkage strains are one of the major reasons for cracking of reinforced concrete. Cracking of concrete reduces structural integrity, initiates or accelerates deterioration mechanisms, causes serviceability problems and may raise aesthetical concerns. Particularly for liquid retaining structures, cracks are vital for structural functionality. Measures must be take to prevent or control crack. In most cases, it may not be feasible to prevent crack formation, but crack width can be controlled by providing sufficient amount of reinforcement. Design guides provide limited information on adequate reinforcement design for temperature and shrinkage cracks in reinforced concrete structures. The Finite Element Method(FEM) was used in order to investigate the crack risk, magnitude of crack width, and adequate reinforcement ratio for controlling cracks within the design specifications. In order to find the thermal and shrinkage strains effect during early ages, computer simulations was performed for hardening concrete. Using the computer program ABAQUS/6.4, incremental numerical analysis technique was implemented that provided realistic simulation of stress/strain history. Considering an appropriate value for thermal and shrinkage strains, a parametric study was carried out to estimate the reinforcement ratio for fixed base walls. The crack width was estimated based on the calculated steel stress and the ACI 318-02 crack prediction equation. With consideration of ACI 350-01 specification for allowable crack width, the required amount of reinforcement ratio for various wall dimensions was recommended.

Volumetric Deformations and Crack Control in Reinforced Concrete Structures

Restraint temperature and shrinkage strains are one of the major reasons for cracking of reinforced concrete. Cracking of concrete reduces structural integrity, initiates or accelerates deterioration mechanisms, causes serviceability problems and may raise aesthetical concerns. Particularly for liquid retaining structures, cracks are vital for structural functionality. Measures must be take to prevent or control crack. In most cases, it may not be feasible to prevent crack formation, but crack width can be controlled by providing sufficient amount of reinforcement. Design guides provide limited information on adequate reinforcement design for temperature and shrinkage cracks in reinforced concrete structures. The Finite Element Method(FEM) was used in order to investigate the crack risk, magnitude of crack width, and adequate reinforcement ratio for controlling cracks within the design specifications. In order to find the thermal and shrinkage strains effect during early ages, computer simulations was performed for hardening concrete. Using the computer program ABAQUS/6.4, incremental numerical analysis technique was implemented that provided realistic simulation of stress/strain history. Considering an appropriate value for thermal and shrinkage strains, a parametric study was carried out to estimate the reinforcement ratio for fixed base walls. The crack width was estimated based on the calculated steel stress and the ACI 318-02 crack prediction equation. With consideration of ACI 350-01 specification for allowable crack width, the required amount of reinforcement ratio for various wall dimensions was recommended.