External Confinement And Non Circular Sectional Shape

After creating a rough surface for the CFRP to grip on, an epoxy is put onto the concrete. Then, the sheet of CFRP is carefully placed upon the concrete. Finally, the CFRP is rolled into the epoxy until it is flush and there is no excess epoxy. With America’s infrastructure aging, a material that could strengthen these structures, such as CFRP, is not being used. These large structures are aging and are beginning to need repairs. Although it can be expensive at first, the United States should implement the use of CFRP to help strengthen the aging large structures that make up our nation because of its ability to increase strength, to improve durability, and to replace emissions that are harmful to the environment.

Proc., 7th Int. Conf. on Fracture Mechanics of Concrete and Concrete Structures. Korea Concrete Institute,

In 2005, H Azamirad et al published a paper “A criticism of Self-Compacting Concrete” which talks about the problems in using SCC such as segregation and roles of different materials which affect it. It talks about the economic problems too. Finally it says about some projects which are executed with SCC. This paper helped in identifying the disadvantages of using SCC.

Smith and Su (1997) carried out a numerical study to examine the overall and internal failure mechanisms of a soil-nailed wall during construction, under service and ultimate loading conditions. When the surcharge was applied, the horizontal displacement at the top half of the wall increased more rapidly. The increased settlement under surcharge concentrated in the loading zone and the largest settlement observed to appear at the front of surcharge location at collapse. Briaud and Lim (1999) conducted a numerical simulation to study the effect of various design decisions for tieback walls. In advance of doing parametric study, the numerical model was calibrated against an instrumented case history. The results provided some information on the impact of the following components on the wall behavior: Magnitude of the

up of one or more curved slabs or folded plates whose thicknesses are small compared to their other dimensions. Thin shells are characterized by their three-dimensional loadcarrying behavior, which is determined by the geometry of their forms, by the manner in which they are supported, and by the nature of the applied load.” Concrete shell structures are able to span large distances with a minimal amount of material. An arch, spanning tens of feet, can be mere inches thick. In maintaining

In the present paper, the addition of fly ash and an expansive agent to the concrete of or a thin layer of fly ash to the interface between steel tube and concrete to improve the compressive strength. More over This paper

Structural researchers have realized the beam-column joint’s effects and consequences on the stability and durability of structures since the last century. Many buildings were collapsed under exposure to earthquakes; in most cases the main reason for its collapse is the local failure in beam-column joints. Therefore, many attempts have been done by structural researchers all over the world to overcome these crises by improving the resistance capacity of joints. The amount of steel reinforcement both longitudinal or transverse direction, and distribution pattern of it have a significant effect on the behavior of joints.

Over the last two decades Fiber Reinforced Polymers have emerged as an attractive competitor to the more conventional civil engineering materials for the creation of new structures and the strengthening/rehabilitation of existing ones [1-book]. Therefore many related associations such as ACI committee provided practical design manuals for all aspects of application FRPs for strengthening structural elements. The comparison between experimental and analytical code based studies performs previously for shear strengthening of RC beam with FRP composites is not very promising. Specially for shear strengthening the use of additional principle in the actual shear design equations must be questioned.[] The large dispersion between the expected values of different models and experimental results is of real concern bearing in mind some of this semi-empirical models are applied to present design codes. [01-arc] Shear strengthening of RC members with FRP is actually a research problem have not been completely solved and is still under investigation; [2-ar] so that the trustworthiness of existing models to achieve reliable and safe codification needs to be evaluated. Many uncertainties and complicated problems have assessed so far for strengthening of RC beams with FRPs are: real effective strain of FRPs in shear strengthening [Chen & Teng 2003a], main failure modes recognized for each section configuration, most accurate evaluation model [03-arc], and interactions between the external

Pre-cast pre-stressed double-tee girders are considered as an essential element of modern infrastructure used to construct civil project worldwide. These girders can be found in under-strengthlevel because of the local damages and developed cracks as the result of collision due to transportation and mishandling. Therefore, it is very important to find out an efficient retrofitting technique in order to restore the lost capacity and/or even outperform it. The current paper presentsa field tests up to collapse forthree actual-size pre-cast pre-tensioned double-tee (DT) girders having different levels of damage retrofitted using Externally Bonded Carbon Fiber Reinforced Polymer (EB-CFRP) technique. The girder stems for two of them were strengthened in flexure using uni-directional U–shaped CFRP sheets, while all girders were shear-strengthened at the dapped-ends. Each girder was loaded incrementally up to collapse using concrete Jersey Barriers, at the meantime, the deflections of the girder and developed strains on both concrete surface and the CFRP sheets were recorded at each increment. Test results assured the adequacy of the adopted strengthening configurations from both ultimate capacity and ductility viewpoints. It addition, the flexural resistance showed reasonable results compared to the analytical design resistance recommended by ACI 440.2R-08.

So that a reliable model for the design of CFRP- confined rectangular concrete columns subjected

The tensile force transferred from the steel bar through the bond to the concrete is illustrated and compared for difference reinforcement ratio (ρ = 0. 5%, 0.89% and 1.12% for steel 12 mm, 16 mm and 18 mm) in figure (5.79) and table (5.17). Before first crack accured (Pre-cracking stage), the precentage of tensile force transferred from the steel bar to the concrete accounts is about 8%, 13% and 16%. Aftere first crack accured (cracking stage), the precentage of tensile force transferred from the steel bar to the concrete is about 53%, 60% and 72%. During Post-cracking stage almost all the tensile force is carried by the steel bar 82%, 89% and 90% for P-12- FEM, P-16-FEM and P-18-FEM respectivily.

The steel tube in a concrete filled tubular (CFT) column acts as both lateral and longitudinal reinforcement, and is thus subjected to hoop tension and biaxial stresses of longitudinal compression. At the same time, concrete is tri-axially stressed. Concrete filled tubular (CFT) column has become popular as structural-member in buildings due to their excellent performance for structural characteristics, which include high ductility, stiffness, and high strength. The advantages of the Concrete filled tubular (CFT) column over other composite members are that the filled-in concrete prolongs local buckling of the steel tube wall, the steel tube provides formwork for the concrete, the tube prevents excessive concrete spalling and composite columns add more stiffness to a frame compared to old-style steel frame construction. According to past study on the concentric compression behavior of Concrete filled tubular (CFT) columns, the ultimate axial strength of Concrete filled tubular (CFT) columns is largely affected by the thickness of the steel tube and the shape of its cross section Although confining effect in square columns show a small increase in axial strength due to triaxial-effects, although it has large wall thicknesses. On the other hand, the axial load and deformation behavior of columns is remarkably affected by the cross sectional shape, diameter/width-to thickness ratio (D/t) of the steel tube, and the strength of the filled concrete.

Abstract 1: A slowly growing number of studies have concentrated too much on investigating, but less on modelling the cyclic axial stress-strain response of concrete columns (RC) confined with fiber-reinforced polymer FRP sheets. Since the early 1990s, the largest amount of research, including both experimental and analytical studies, has been rising continuously, in contrast, on the monotonic axial stress-strain behavior of concrete columns externally jacketed with FRP composite wraps. However, most of the available literature on the behavior of FRP-confined RC columns has focused extensively on square and circular concrete columns that can be classified as small or medium-size. Also recently, a few experimental studies have been devoted to investigating the cyclic axial compression behavior of small-scale unreinforced (plain) rectangular concrete columns with smaller-cross sections. Therefore, a deep review indicates that there is a distinct lack of research on the axial stress-strain behavior of FRP-confined RC columns subjected to a cyclic axial compression loading. This is owing to the fact that the majority of the structural buildings columns (RC) are noncircular ,and it has been clearly demonstrated that the behavior of these columns mainly depends on several factors such as aspect ratio of cross-section,

The maintenance, restoration and development of structural components, is maybe one of the most typical problems in construction field applications. In addition, a huge number of structures developed in the past utilizing the ancient established design codes in various parts of the world are basically structurally hazardous as indicated to the recent time design codes on the other hand the retrofitting has become necessary due to the environmental degradation, heavier loading conditions and their life spans. Therefore, various strengthening techniques are being introduced, historically the structural components were repaired by post-tensioning or jacketing with new concrete in conjunction with a surface adhesive, since mid-1960’s steel

This chapter introduces the results of the nonlinear static and dynamic analyses for the existing and rehabilitated frames. The importance of accounting for the masonry infill in the analysis is also discussed. In this chapter, a comparative study was done on the performance of structures rehabilitated using different techniques, namely; (1) introducing a RC structural wall, (2) rehabilitating using X-steel bracings, (3) rehabilitating using FRP bracings, and (4) rehabilitating using FRP-confinements. The importance of accounting for the shear degradation in the model of columns and beams is also investigated. The analysis results are drawn in terms of maximum PGA or PGV resisted by the frames, maximum ID ratio capacity, maximum storey shear / Weight ratio, and maximum energy dissipated by the frames.