ACI 318-63 requires that the minimum ratio of longitudinal bars shall be at least 1.0%. Also, The vertical center-to-center spacing of the lateral ties shall be one of the smallest of: (1) 16 longitudinal bar diameters to restrain longitudinal bars from buckling, (2) 48 tie diameters to ensure sufficient tie area to restrain the lateral displacement of the reinforcing bars, and (3) the least lateral dimension of the column to develop the maximum strength of the concrete core. As shown in Fig. 1, The dimensions and steel reinforcement details of the columns involved in this experimental program were particularly selected to represent relatively older columns. In this experimental program, the longitudinal reinforcement ratio, ρl, was constant
However, the absence of plastic deformation does not mean that composites are brittle materials like monolithic ceramics. The heterogeneous nature of composites result in complex failure mechanisms which impart toughness. Fiber-reinforced materials have been found to produce durable, reliable structural components in countless applications. The unique characteristic of composite materials, especially anisotropy, require the use of special design
As the human body ages, it becomes more fragile. America’s infrastructure is nearly the same. With the everyday use of many large structures, such as bridges, buildings, and other large structures made of concrete and/or steel, many are beginning to wither away while the average American is unaware of these changes. In many projects around the world, there is a material that is being commonly used to strengthen structures known as Carbon Fibre Reinforced Polymer (CFRP). The types of structures that this material can help to strengthen includes, but is not limited to, reinforced concrete columns, bridge girders, steel structures, and cable
This report aims to describe the experiment performed to investigate the stiffness of a channel section, and in particular calculate the flexural rigidity (EI) of the beam by two different sets of calculations based on the results gained in the experiment. The EI of an object is used
The comparison of measurement and prediction of prestress losses in prestressed members is highly documented in literature. Hale et al. (2006) studied the prestress losses behavior of girders subjected to increased fiber stresses. They concluded that the previous AASHTO LRFD Specifications equations (2004) overestimated the prestress losses by roughly 50%. It was found that the NCHRP Report 496 (Tadros et al., 2003) equations predicted the losses to within an average of 6%. Currently, there have been quite a few investigations on empirical models for prestress losses for HSC. In a study conducted by Kowalsky et al. (2001) on several HPC bridge girders in North Carolina to determine the prestress losses of HPC girders. The researchers found shrinkage losses were a small component of the overall prestress losses and that the elastic shortening and creep losses were the main contributors. These larger than expected losses from elastic shortening and creep were because of a predicted modulus of elasticity that was higher than actual. The total prestress losses ranged from 12.9% to 19.1% of the initial jacking stress. In an investigation conducted by Tadros et al. (2003), seven full-scale bridge girders were instrumented in Washington, Texas, Nebraska and New Hampshire to determine the prestress losses of HPC girders. The total prestress losses measured were found to be lower than the AASHTO LRFD (1998) model. Modiﬁed expressions were proposed to AASHTO and later adopted in
Web members have a high strength-to-weight performance (Grogan, 2007). Prefabricated trusses allow for high strength members to be optimized by being placed only where they are needed to support a large chord or web force (Shepherd, 2006). Robustness is a structure’s ability to maintain a certain performance requirement. Kanno performed a plastic limit analysis on a truss, the conclusion was made that the worst case scenario was the minimization of the load under the absence of structural components (Kanno, 2012). The load is transmitted from the chords as axial forces to the webs (Wei, 2014).
Steel-reinforced concrete is a widely used structural material. The effectiveness of the steel reinforcement depends on the bond between the steel reinforcing bar and the concrete. Reinforced concrete is a composite material in which concrete 's relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength and ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars and is usually embedded passively in the concrete before it sets. Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and
The article “Reliability based design applied to retaining walls”, by Bak Kong Low seek to introduce a different approach on design procedures for retaining walls. It involves achieving a homogenous result as the Hasofer-Lind reliability index and first-order reliability method (FORM), using Microsoft Excel, in an intuitive expanding dispersion ellipsoid perspective. The method, claimed by the author, provides more straightforward computations and interpretations of the aforementioned reliability-based design procedures. It is emphasised that the article considered the methodology and concepts with respect to reliability based design, and not in its widest aspect (Low, 2005). Hence, the author illustrated the practical spreadsheet-automated reliability analysis through two cases. One is a simple retaining wall with two random variables and the other one is an anchored retaining wall with nine random variables. For the latter case, it was considered as correlated normal variates initially and correlated non-normals after that. The intuitive expanding dispersion ellipsoid perspective and the definition of reliability index were explained in the main body of the paper. Any limitations, correlations and uncertainties were discussed briefly as well.
It is well-known that many reinforced concrete columns including particularly those RC columns constructed prior to the 1970s have been reinforced with an inadequate amount of transverse steel reinforcement which provides inefficient confinement to the concrete core or lateral restrain to the longitudinal reinforcing bars. Since the FRP composites owe some of the extraordinary properties such as high strength-to-weight ratio and excellent corrosion resistance, the use of externally bonded FRP composites has significantly increased in the construction industry. As confinement jackets, using FRP techniques is nowadays become one of the most popularly innovative confining means for upgrading existing RC structures. Therefore, several experimental studies have been carried out to date, such as on retrofitting or strengthening those structures with FRP systems, for example. In case of rarely sever seismic loads, establishing an axial stress-strain model considering cyclic axial compressive load is, in turn, imperative for simulating FRP-confined RC columns subjected to earthquake loads and performing a proper seismic design of such FRP-jacketed RC Columns, which are typically subjected to both axial and lateral force Wang et al.(2012). A uniaxial stress-strain model can be developed from laboratory testing results on axially loaded concrete columns confined with fiber-reinforcement polymer (FRP) composites and can then be applied as the constitutive law for confined concrete
Abstract: Advancement in recent years on the efficiency of glass fiber-reinforced polymer (GFRP) in production and cost benefits have increased their use as alternative means to steel rebar in bridge deck bases. The purpose in applying rebar is to increase the tensile strength of concrete. Considering the versatility of bridges there are many factors that need to be analyzed when choosing whether to use steel rebar or GFRP material such as: cost, tensile strength, and weather resistance. Stress-strain graphs were calculated, graphed, and analyzed to determine the yield tensile strength and stiffness of steel rebar and GFRP. Data collected from alkaline bath tests were graphed and analyzed to determine the thermal and corrosion resistance of each material. Costs per square inch of each material were also compared as well as each materials quality and life expectancy. The results of the conducted test analysis found the GFRP to have greater thermal resistance, lower cost, and higher life expectancy than the steel rebar, however the steel rebar’s stiffness was found to be about six times larger than the GFRP’s. These results suggest that the advancements in GFRP can provide longer lasting bridge structures and will change the future of construction and restoration of bridges.
Increasingly, engineers are designing composite and mixed building systems of structural steel and reinforced concrete to produce more efficient structures than realized using either material alone. Recent literature has pointed out a need for greater understanding of the interaction of structural steel and reinforced concrete in such systems. In this paper, the behavior of composite beam-column connections is examined through results of an experimental research program where15 two-thirds scale joint specimens were tested under monotonic and cyclic loading.
For comparison, the shear results of BSM alone, which are influenced by F-T cycles are presented. Figures 3-13, 3-14 and 3-15 present shear stress-shear displacement curves of samples subjected to different numbers of F-T cycles and sheared at 150kPa, 250kPa and 350kPa vertical loads, respectively. If analysis the curves in Figures 3-6, 3-7 and Figures 3-13 to 3-15, it can be reveal that the shape of BSM sample sheared alone also have similar shape of shear stress-strain curves irrespective of the numbers of F-T cycles. Regardless the applied normal stresses, the highest stresses are all provided by the un-thermal treated samples, and the shear strengths start to drop when the samples were subjected to increasing number of F-T cycles.
Composition of fibres reinforced composite the fibres are important class of reinforcement, as they satisfy the desired conditions and transfer strength to the matrix constituent influencing and enhancing their properties as desire.
A Chakraborty et al  have studied the thermo-elastic behavior of functionally graded beam structures based on the first-order shear deformation theory and these properties are varying along its thickness. The governing differential equations are used to construct interpolating polynomials for the element formulation. To determine various stresses, both exponential and power-law variations of material property distribution are used. Thermal behaviors of functionally graded beam (FGB) by taking the distribution of material properties in exponential function were analyzed by GH Rahimi and AR Davoodinik . The steady state of heat conduction with exponentially and hyperbolic variations through the thickness were consider for the use of thermal loading. They found that thermal behavior of both isotropic beam and functionally graded beam depend up on the temperature distribution.
Introduction: It has been well established that drilling of FRP’s lead to drilling induced damage thus reducing component’s life and reliability. Thrust force induced in drilling of FRPs is one of the major reasons for drilling induced damage . Several studies have been made worldwide to critically review the delamination induced in drilling of FRPs. These research efforts clearly indicate direct relationship of damage induced with thrust force induced during drilling of FRPs [2-6]. Various mechanistic, mathematical and analytical models have been developed based on different reasoning,