Job Thomas

Shear Strength of Prestressed Concrete T-Beams with Steel Fibers Over Partial/Full Depth

The test results of nine shear-critical partially prestressed concrete flanged beams with and without steel fibers are presented in this paper. T-beam specimens were cast with three grades of concrete: normal strength (35 MPa [5.07 ksi]), moderately high strength (65 MPa [9.42 ksi]), and high strength (85 MPa [12.32 ksi]). For each grade of concrete, three beams were cast: a control beam without fiber reinforcement, a beam with fiber reinforcement over the full depth of the cross section, and a beam with fiber reinforcement only in the web portion. Test results indicated that the provision of fiber reinforcement only in the web portion appreciably improved the shear-resisting capacity of the partially prestressed) beams. A model to predict the shear strength of prestressed and reinforced (nonprestressed) concrete beams has been proposed. The proposed model is expected to predict the test results of reinforced concrete beams having steel fibers over partial and full depth.

Crack Width in Partially Prestressed T-Beams Having Steel Fibers

A method to determine crack width in partially prestressed T-beams containing steel fibers can be useful in verifying serviceability limit states for these steel fiber reinforced concrete (SFRC) members in flexure. This article reports the experimental and analytical results of crack width and crack spacing at various loading stages of a study of 12 partially prestressed T-beams, with and without hooked end steel fibers, placed over the partial or full depth of the cross sections. The beams were cast and tested using three grades of concrete having compressive strengths of 35, 65, and 85 MPa (5.07, 9.42, and 12.32 ksi). The authors propose an analytical model to predict the crack width and spacing in these beams, taking into consideration the influence of bond slip of longitudinal reinforcement and the pullout of fibers aligned across the crack. The authors conclude that the width of the cracks that developed in beams having fiber reinforcement only in the web portion was observed to be close to that in beams having fiber reinforcement in the full section. This indicates that the presence of fibers in the tension zone (web portion) is an effective and economical way of controlling the crack width.

Flexure-Shear Analysis of Concrete Beam Reinforced with GFRP Bars

This paper gives the details of flexure-shear analysis of concrete beams reinforced with GFRP rebars. The influence of vertical reinforcement ratio, longitudinal reinforcement ratio and compressive strength of concrete on shear strength of GFRP reinforced concrete beam is studied. The critical value of shear span to depth ratio (a/d) at which the mode of failure changes from flexure to shear is studied. The failure load of the beam is predicted for various values of a/d ratio. The prediction show that the longitudinally FRP reinforced concrete beams having no stirrups fail in shear for a/d ratio less than 9.0. It is expected that the predicted data is useful for structural engineers to design the FRP reinforced concrete members.

Effect of Support Settlement on the Behaviour of Stone Masonry Arch Bridge

In this paper, the behaviour of an existing masonry stone arch bridge when subjected to foundation settlement is evaluated. The 13 Arch Bridge, also called Kannara Bridge situated in the Kollam–Shenkottai Railway line is considered for this study. This bridge is originally designed for Metre Gauge (MG) load and is now being upgraded for Broad Gauge (BG) load. CATIA V5 is used to model the bridge in its original form and strengthened form. Transient load analysis is carried out in ANSYS V15 to study the deformation of the bridge in different situations. The cases, namely, when the supports are intact and when the central support sinks with respect to the other supports were analysed for the original bridge and for the strengthened bridge. The middle support deflection and maximum principal stresses were determined. A parametric study on the influence of thickness of the concrete jacket on the deformation properties of the bridge was carried out. Three thicknesses for the concrete jacket, namely, 200, 450 and 600 mm, were considered. It is found that the provision of concrete jacket offers high resistance against deformation of the bridge due to settlement. The concrete jacket of 450 mm is suggested as a feasible solution to mitigate the settlement problems.

Green Rating Credits for Waste Utilization in Construction

Implementation of sustainable construction practices is the need of the hour, and this requires a paradigm shift in our concept of waste management. Waste materials arising from construction and demolition activities and industrial by-products can be utilized as value-added materials in building construction. The sustainability of building construction practices can be evaluated with the help of different green building assessment systems. This paper reviews the credits or scores assigned by green rating systems for the management and utilization of waste materials in construction. IGBC and GRIHA are the Indian green rating systems, and BREEAM, LEED, CASBEE, BEAM Plus, and Green Star are the foreign rating systems analyzed in this paper. It is recommended to incorporate credits in the Indian rating systems for the use of recycled or sustainable sourced aggregates in concrete and for the management of construction and demolition wastes.

Supplementary Cement Replacement Materials for Sustainable Concrete

Human willpower and advancements in technology have pushed the boundaries of concrete construction to its limits and this requires concrete of high performance which simultaneously satisfies the requirements of high strength and durability. It is ambitious to imagine the production of fully sustainable concrete as long as cement and natural aggregates are used. Wherever possible, suitable green practices can be adopted to reduce the environmental impacts of concrete production. This includes the introduction of suitable waste materials in the concrete production process. Supplementary cementing materials derived from industrial wastes can be used to partially replace cement in concrete. This not only facilitates effective waste utilisation, but also reduces the hefty carbon footprint associated with the production of cement and hence concrete. This chapter evaluates the technical feasibility of utilising supplementary cementing materials obtained from industrial wastes to replace the cement in concrete by evaluating the strength and durability characteristics of high-performance concrete. The test results indicated that replacement of cement with supplementary materials up to 10% can be recommended.

Influence of Soil-Structure Interaction on the Structural Performance of D-30 Transmission Line Tower

Electric power transmission is the second process in the delivery of electricity to consumers. Transmission line towers are used for supporting the extra-high-voltage electric lines. Steel towers are normally used for this purpose. Since transmission line towers are placed about 200–300 m apart, an optimum design of the structure may lead to a great savings in the material cost. In this study, the analysis of a transmission tower was carried out accounting for the soil-structure interaction. The deflection and maximum force in the member were evaluated by carrying out the finite element analysis. The vertical loads such as weight of tower structure, power conductor, ground wire, lineman with tools, insulator strings, and fittings were accounted for in this study. Unbalanced pull due to broken conductor, broken ground wire and load due to temperature variation are the longitudinal forces used in this analysis. Torsional load are due to the breakage of conductors and ground cable. Wind load on members and horizontal component of tension force on conductors and earth wires are considered as transverse force. Three cases such as tower alone, tower plus pile, and tower plus pile plus soil were analyzed using NISA software. The results indicated that the member forces reduce significantly when soil-structure interaction is accounted for in this analysis. Hence, economy can be achieved by considering soil-structure interaction in transmission line towers.