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This paper presents the investigation on built-up cold-formed steel column sections strengthened with carbon fibre-reinforced polymer (CFRP). Here, box-shaped column sections were fabricated by screwing together with individual channels. Behaviour of twelve plain and twelve CFRP-strengthened box sections was studied under axial compression. Three lengths of 300 mm, 500 mm and 700 mm with section thickness of 0.6 mm, 0.75 mm and 1 mm were studied in the investigation. The cold-formed steel design procedure suggested by North American specification AISI S100-16 and Euro code 3 (EC3) provisions was applied and compared with the experimental results, which were in good agreement. The results also indicate that the proposed strengthening technique is effective in repair and increasing the load-carrying capacity of cold-formed steel built-up box column.

This paper presents experimental findings of carbon fibre reinforced polymer (CFRP) strengthened cold-formed steel built-up channels subjected to axial load. In order to sensitively detect the buckling strengths and failure modes, twenty-four built-up columns were tested in which twelve columns were unadorned and another twelve columns were strengthened using CFRP sheets. The columns were tested for ultimate load, lateral displacement and failure modes. Tension coupon tests were conducted to determine the material properties of test specimens. The experimental results were compared with the design load calculated according to AISI S100-16 specification and are found to be in good agreement. It is established that the use of CFRP for strengthening increases the ultimate load and delays the buckling.

Objectives: Structural steel can be broadly classified into hot rolled steel and cold formed steel (CFS). CFS manufactured from roll forming or press braking operation. The main advantage of CFS sections are thin wall and light weight. These thin wall leads to buckling of structural member. This paper aims to study the capacity of Carbon Fibre Reinforced Polymer (CFRP) strengthened CFS channel beams, buckling behaviour, deflection and cost studies on CFRP strengthening. Methods/Statistical analysis: In this study three different length of CFS channel sections are selected for testing in which beams are tested for bending. All the beams were tested in plain section and CFRP strengthened series in universal testing machine. Findings: Experimental results shows the enhancement in capacity of beam due to CFRP strengthening. The local and distortional buckling modes were observed as failure modes. Experimental results were compared with maximum load resistance calculated by AISI specification which are in good agreement. Cost studies were compared on replacing a new member with CFRP strengthened channel member. Improvements/Applications: CFRP strengthening is suitable for enhancement of capacity of beams and repair. This CFRP strengthening technique can applied to reinforced concrete members, hot rolled steel, in filled steel tubes and bridges etc.

The problem of debonding failure is a fundamental issue in concrete structures that are externally strengthened with adhesively glued plates. Many standards and studies recommend using single-lap pull-out tests to measure the ultimate force that causes debonding failure. The pull-out test also allows defining and calibrating interface bond-slip relationships between concrete and the bonded plates to obtain the maximum interfacial bond strength. The aim of this research was to enhance bond strength in the presence of embedded shear connectors, which were fabricated at concrete–adhesive interface level to delay debonding of the externally bonded strips from the concrete surface. A new rational model was also proposed to predict the bond strength of adhesively glued plates-to-concrete joints in the presence of connectors. In the experimental programme, 60 concrete prisms with adhesive and steel bar connectors were fabricated. The specimens were divided into two main series of concrete prisms bonded with steel plates and CFRP strips using the new connectors. Different diameters of connectors were used with and without adhesive on the surfaces of concrete prisms to bond the strips for investigating the capacity of the new embedded connectors. The experimental results showed that the interfacial bond strength increased remarkably when these connectors were used. Moreover, it was found that increasing the connector’s diameter has a great effect on increasing the bond strength and uniformly distributes the interfacial shear stresses, leading to the minimisation of premature debonding failure of bonded plates. The results exhibited that the steel connectors are more effective at increasing the shear bond strength for all specimens adhesively glued with both CFRP strips and steel plates. Finally, the proposed bond strength model was satisfactorily verified through the experimental investigations.

Cold formed steel differ from hot rolled steel by its lesser thickness and weight. The cold formed steel applicable in roof purlin, pipe racks and wall panels etc. Due its lesser wall thickness the cold formed steel member subjected to buckling. The enhancement of load carrying capacity of the cold formed steel member can be achieved by external strengthening of CFRP. In this study cold formed channel members connected back to back to form I shaped cross section using screws. These built up beam members were 300mm, 400mm and 500mm in length with 100mm screw spacing and edge distance of 50mm were chosen for testing. CFRP fabric cut according to length, width of built up beams and wrapped outer surface of beam using epoxy resin. Experiments were carried out in two sets firstly plain built up beams and secondly CFRP wrapped beams. The test results shows that increased load carrying capacity and reduction in deflection due to CFRP strengthening. Experimental results were compared with AISI standards which are in good agreement. Experimental results shows that CFRP strengthening is economic and reliable.

Repair of reinforced concrete beam with externally bonded steel plate or fibre reinforced polymer (FRP) laminate is becoming both environmentally and economically preferable rather than replacement of deficient beam. The well known advantages of external reinforcement over other methods include; low cost, ease of maintenance and the ability to strengthen part of the structure while it is still in use. The disadvantage of this method, however, is the premature debonding of the externally bonded strips which is brittle and undesired mode of failure. It is also known that debonding of the externally bonded steel plates prevents the reinforced concrete (RC) beam from reaching its full strengthening capacity. The aim of this study was to increase the scientific understanding on the behaviour of damaged reinforced concrete beams strengthened and/or retrofitted for shear using vertical steel plate fixed with adhesive and steel connectors to eliminate or delay debonding failure. Four reinforced concrete beam specimens were prepared to investigate the effects of connectors in preventing or delaying premature debonding of shear strips to restore the capacities of fully damaged beams. Three damaged beams have been repaired and strengthened with steel plates and loaded monotonically up to the maximum load capacities in order to define load–deflection relationship. It is concluded that the repairing of severely shear-damaged RC beams with steel plates by using steel and adhesive connectors can fully restore the original shear capacities of the beams.

During the recent decades, Carbon Fiber-Reinforced Polymer (CFRP) composite materials have proven valuable properties and suitability to be used in the construction of new buildings and in upgrading the existing ones. The objective of this paper is to review the previous work in this area and compare it with the current experimental results to show the design equations for CFRP strengthened steel structural elements. Research findings have shown that CFRP sheets and strips are not only effective in restoring the lost capacity of a damaged steel section, but are also quite effective in strengthening of steel sections to resist higher loads, extend their fatigue life and reduce crack propagation.

Cold-formed steel members usually display local-global buckling interaction which strongly effects the structural strength of columns. Through strengthening web of the members this buckling can be controlled to some extent. In this investigation, Carbon Fibre Reinforced Polymers (CFRP) is used for strengthening cold formed steel channel member. This paper presents compression tests of cold-formed plain and CFRP strengthened steel channel section columns. This paper also proposes a design method based on Direct Strength Method provisions specified in American Iron and Steel Institute (AISI), for determining the axial compression strength. Results obtained from the proposed design method are compared with experimental test data and are found to be in good agreement.

Carbon fiber reinforced polymer (CFRP) composites are considered to have high performance and potential for use in strengthening , retrofitting and for the rehabilitation of structural sections. In this paper, design procedures are proposed for the axial load capacity of cold formed steel lipped channel columns strengthened with carbon fiber reinforced polymer (CFRP). For the purpose of validation, the results are based on the proposed design equation from the North American specification for the design of cold-formed steel structural members (AISI-2007) and Euro code for cold-formed members and sheeting (EC3-EN1993-1-3:2006) are compared against the experimental test data. The test results showed that the capacity of the columns are close to the theoretical values predicted by the AISI-2007 and EC 3 provisions. Some tested specimens showed reduced capacity and premature failure due to peeling and debonding of the CFRP from the steel. Various experimental investigations are suggested for future work to further validate and update the design equations. From the experimental studies, it has been observed that there is significant increase in strength due to CFRP strengthening.

This paper presents the results of a research project aimed at providing standard circular web openings to the popular precast pretensioned inverted T-beam. Opening size and placement and required materials strengths were investigated. In this paper the nonlinear analysis and design of simply supported pretensioned inverted T-beam with circular web openings are presented. Two design parameters are varied: opening location and number of openings. The results from nonlinear finite element analysis were substantiated by test results from five pretensioned inverted T-beams with web opening and one solid beam. Good agreement is shown between the theoretical and the experimental results. The test results obtained from this investigation show that the performance of the specimens with web openings is almost identical to that of the specimen without web openings. A simple design method for pretensioned inverted T-beam with circular web openings is proposed.

This paper presents the results of a research project aimed at providing standard circular web openings to the popular precast pretensioned inverted T-beam. The main advantage of these openings is that mechanical equipment can pass through the webs of inverted T-beams. Another advantage is a slight reduction in inverted T-beams weight that would improve the demand on the supporting frame both under gravity loading and seismic excitation. Opening size and placement and required materials strengths were investigated. Also, the effects of using straight tendons, rather than two-point depression and one-point depression, of the prestressing strands were investigated. In this paper the nonlinear analysis and design of simply supported pre-tensioned inverted T-beam with circular web openings are presented. Two design parameters are varied such as: opening location and numbers of openings. The results from a nonlinear finite element analysis are substantiated by test results from five pretensioned inverted T-beam with web opening and one solid beam. Good agreement is shown between the theoretical and the experimental results. The effect of openings on the behavior of such beams at different stages of loading is presented. The test results obtained from this investigation show that the performance of the specimens with web openings was almost identical to that of the specimen without web openings. A simple design method for estimating the cracking load for the different crack patterns is proposed. Based on these tests, design recommendations are made that will allow the addition of web openings to inverted T-beam with minimal additional calculation.

A precast, prestressed concrete girder with circular web openings allows building service systems (mechanical, electrical, communications, and plumbing) to cross the girder line within the member’s depth, reducing a building’s floor-to-floor height and the overall height of the structure. These height reductions have the potential to improve the competitiveness of total precast concrete structures versus other types of building systems. The experimental program reported in this paper tested five full-scale inverted-tee girders with circular web openings to failure, to evaluate the openings’ effect on girder behavior. The girders failed in a ductile manner due to diagonal cracking above the openings. The tested girders were designed using available recommendations in the existing literatures. It was observed that concrete fractured from tension zones around an opening, with cracks developing vetically towards the beam flanges. A beam would collapse when the cracks reached the flanges. In the present work, an analytical solution is developed for the load-deflection calculation of prestressed beam with web openings at any load stage. The solution assumes a trilinear deflection response characterized by the flexural cracking initiation, steel yielding, and ultimate capacity. Closed form expressions are presented for the case of simple beams subjected to four-points loading. These expressions are modified from present ACI code equations by incorporating appropriate laboratory determined coefficients in order to predict more precisely with some degree of conservativeness on flexural load-point deflection with any extent of uncracked, postcracked, and postyielded region along their spans. Accordingly, a simplified analysis procedure is developed by adopting a trilinear load-deflection response. The effectiveness of the simplified procedure is demonstrated by comparing its results to those of the analytical solution and the experimental values.

A precast, prestressed concrete girder with circular web openings allows building service systems (mechanical, electrical, communications, and plumbing) to cross the girder line within the member’s depth, reducing a building’s floor -to-floor height and the overall height of the structure. These height reductions have the potential to improve the competitiveness of total precast concrete structures versus other types of building systems. The experimental program reported in this paper tested three inverted -tee girders with circular web openings strengthened with GFRP to failure to evaluate the openings’ effect on girder behavior. The test girders were designed using available recommendations in the existing literature. Finite element is used to plot interaction diagram in estimating the cracking load for the different crack patterns was perform. Good agreement was shown between the interaction diagram and the experimental results.

This paper presents the results of a research project aimed at providing standard circular web openings to the popular precast pretensioned inverted T-beam. Opening diameter and placement and required materials strengths were investigated. In this paper, the non-linear analysis, interaction diagram and deflection response surface plot of simply supported pretensioned inverted T-beam with circular web openings are presented. Two design parameters are varied that is: opening location and numbers of openings. The results from non-linear finite element analysis were substantiated by test results from five pretensioned inverted T-beams with web opening and one solid beam. Good agreement is shown between the theoretical and the experimental results. The effect of openings on the behaviour of such beams at different stages of loading are presented. The test results obtained from this investigation show that the performance of the specimens with web openings was almost identical to that of the specimen without web openings. An algorithm which is written to plot interaction diagram for estimating the cracking load is proposed. Deflection response surface plots using general factorial design are also presented.

This initial study evaluated the physical properties, setting time, density and compressive strength of Calcium Carbide Kiln Dust (CCKD) as a potential cement alternative for mortar. CCKD is the by-product of Calcium Carbide (CC) production. This by-product leads to environmental pollutions as CCKD has no valuable and beneficial usage, hence it is disposed as landfills. This study explores the possibility of adding CCKD to mortar mixtures by replacing Ordinary Portland Cement (OPC). Six (6) mortar mixtures containing different CCKD replacements up to 40% by weight and one control mortar results are reported. The results indicated that there is a systematic increase in initial and final setting time with the decrease of density and mortar strength. The mixture compressive strength was lower than the control mortar at all ages. It can be concluded that CCKD mortar mixtures may be utilized to compensate setting rate of cement-based materials. However, more research and development, especially on optimum mix design, setting times, early strength, and durability of concrete should be carried out.