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International Concrete Abstracts Portal

Showing 1-5 of 1070 Abstracts search results

Document: 

SP-362_74

Date: 

June 18, 2024

Author(s):

Camille Martin--Cavaillé, Alexandra Bourdot, Olivier Rateau, Malo L’helguen, Nassim Sebaibi, and Rachid Bennacer

Publication:

Symposium Papers

Volume:

362

Abstract:

A possible way to reduce CO2 emissions linked to cementitious materials is to use alternative resources, particularly co-products from other industries. Oyster shell co-products are a calcareous resource produced by aquaculture currently available in coastal areas and must be valorized. The present study investigates the impact of crushed oyster shells used as aggregates in concrete on its mechanical behavior. Thus, concrete samples with 50% aggregates replaced by crushed oyster shells were formulated. Two different types of cement were used: CEMI for reference and low-carbon cement CEMIII-C. Mechanical strength and Young’s modulus were assessed at 28 days, and cracking under compression was followed by acoustic emission technique. Results show that oyster shell aggregates slightly reduce concrete's mechanical resistance but significantly decrease its Young’s modulus. However, cracking behavior under compression remains similar during compression loading.


Document: 

SP-360_24

Date: 

March 1, 2024

Author(s):

Maria Antonietta Aiello and Luciano Ombres

Publication:

Symposium Papers

Volume:

360

Abstract:

The issues related to deformability, strength and ductility of concrete elements reinforced with FRP (Fiber Reinforced Polymer) bars are critically analyzed and discussed in this paper. The analysis is conducted from an experimental point of view by means of bending tests on concrete beams reinforced with Carbon FRP (CFRP) bars with different amounts of reinforcement, and by an analytical approach aiming to evaluate the deflection and cracking phenomenon (number and width of cracks). The experimental results are compared with the analytical predictions and with predictions developed on the basis of the available codes (ACI, EC2, JSCE). The analysis of the results obtained confirms the most relevant issues of the mechanical behavior of FRP bar-reinforced beams, still worthy of research efforts; some technological and construction solutions that can provide significant improvements are also addressed.

DOI:

10.14359/51740636


Document: 

SP-360_33

Date: 

March 1, 2024

Author(s):

Wassim Nasreddine, Peter H. Bischoff, and Hani Nassif

Publication:

Symposium Papers

Volume:

360

Abstract:

The use of FRP tendons has become an attractive alternative to steel tendons in prestressed concrete structures to avoid strength and serviceability problems related to corrosion of steel. There is however a lack of knowledge in serviceability behavior related to deflection after cracking for beams prestressed with FRP tendons. Conventional approaches used to compute deflection of cracked members prestressed with steel is problematic at best, and the situation is exacerbated further with the use of FRP tendons having a lower modulus of elasticity than steel. Deflection of FRP reinforced (nonprestressed) concrete flexural members computed with Branson’s effective moment of inertia 𝐼􀀁 requires a correction factor (called a softening factor) that reduces the member stiffness sufficiently to provide reasonable estimates of post-cracking deflection. For FRP prestressed concrete however, this approach does not always work as expected and deflection can be either underestimated or overestimated significantly.

This study investigates the accuracy of different models proposed for estimating deflection of cracked FRP prestressed members using a database of 38 beams collected from the literature. All beams are fully prestressed. Results indicate that using Branson’s effective moment of inertia 𝐼􀀁 with a generic softening factor can produce reasonable estimates of deflection provided the 𝐼􀀁 response is shifted up to the decompression moment or adjusted with an effective prestress moment defined by an effective eccentricity of the prestress force. The former approach overpredicts deflection by 20% on average while the latter overpredicts deflection by not more than 5% based on the beams available for comparison. Assuming a bilinear moment deflection response overpredicts deflection by 12%, while an approach proposed by Bischoff (which also shifts the 𝐼􀀁 response upwards) overpredicts deflection by 23%. These last two approaches work reasonably well without the need for a correction factor.

DOI:

10.14359/51740645


Document: 

SP-360_18

Date: 

March 1, 2024

Author(s):

Mohamed Bouabidi, Slimane Metiche, Radhouane Masmoudi.

Publication:

Symposium Papers

Volume:

360

Abstract:

The current market of utility poles is growing rapidly. The dominant materials that are used for this purpose are generally wood, steel, concrete, and fiber-reinforced polymers (FRP). FRP poles are gaining wide acceptance for what they provide in terms of strength and durability, lack of maintenance and a high strength to weight ratio. Hybrid structures can combine the best properties of the materials used, where each part enhances the structure to provide a balanced structure. This study evaluates a hybrid structure composed of three main layers, an outer FRP shell, a hollow concrete core and an inner hollow steel tube, this whole system is to be utilized as a tapered utility pole. The outer FRP shell provides protection and enhances the strength of the pole, the concrete core provides stiffness, and the inner steel tube enhances the flexural performance while reducing the volume in consequence the weight of the structure compared to a fully filled pole. A new design for a 12-feet long hybrid FRP pole using finite element is presented in this paper. The design was based on a parametric study evaluating the effect of key-design parameters (i.e., the thickness of FRP, the volume and strength of the concrete, the thickness and diameter of the steel tube). Concrete strength affected the general performance of the pole, the decrease in concrete strength due to utilizing lightweight concrete was compensated with increasing the FRP pole thickness. For the same pole configuration, with incremental variation of the FRP thickness values from 3 mm to 7 mm up to the initial concrete cracking load, no significant variation of the pole top deflection was observed. However, at failure load the increase of FRP thickness from 3 mm to 7 mm decreased the ultimate tip deflection by 50%. New hybrid utility poles have the potential to be an interesting alternative solution to the conventional poles as they can provide better durability and mechanical performances.

DOI:

10.14359/51740630


Document: 

SP-360_23

Date: 

March 1, 2024

Author(s):

Raphael Kampmann, Tim Rauert, Niklas Pelka, und Bastian Franzenburg

Publication:

Symposium Papers

Volume:

360

Abstract:

Corrosion of reinforcement steel is a major issue for many structural concrete components, because it leads to strength reduction and may significantly reduce the service life. For this reason, fiber-reinforced polymer rebars (FRP rebars) have been developed, as they represent a viable alternative that may replace reinforcing steel for structures that are particularly susceptible to corrosion issues. However, structural design philosophies for these new materials are still in development and further research is needed to implement FRP rebars properly and safely in design codes but also to ensure that design calculations properly predict the actual behavior and performance of FRP reinforced structures.

This study was conducted to evaluate the strength and structural deformation behavior of flexural beams that were designed according to Eurocode 2 and, for comparison, according to different design methods pro-posed for FRP reinforced structures. With regard to the development of a uniform design concept for alternative reinforcement materials existing in Germany/Europe, different bending design concepts includ-ing the serviceability limit state were evaluated. In addition, the theoretically calculated and predicted strength/deformation were compared to the experimentally obtained measurements. A total of 15 flexu-ral beams, with ans overall length of 4.5 m (177 in.), a width of 200 mm (7.8 in.), and a height of 400 mm (15.8 in.), were cast; three of these beams (designed according to Eurocode 2) featured traditional steel rein-forcement, to serve as control group. The remaining 12 flexural beams were evenly allocated to capture the two alternative reinforcement materials, while generating three different reinforcement distribution patterns with comparable reinforcement ratios (equivalent cross-sectional areas). Thus, a total of six subgroups –three with GFRP and three with BFRP – each with two specimens, were analized. To test all beam in pure bending and to eliminate the influence from shear forces, two equally increasing loads were applied at the (longitudinal) third-points of the beams. Both deflections and loads were measured at several points to evaluate the structural performance of the FRP reinforced structural members.

The results showed that the deflection of the glass fiber reinforced bars at the design load capacity measured twice as much as the deflection of the control group. Almost three times as much deflection (at the same load) was observed for the concrete beams reinforced with basalt fiber rebars. In addition, it was observed that the concrete beams with glass and basalt fiber reinforcement bars showed a nearly elastic-elastic behavior up to the point of failure, whereas the steel-reinforced concrete beams showed an elastic-plastic behavior. However, the deformational behavior differed between the various beam types. While the prevailing equations properly captured the post-cracking performance of traditionally reinforced concrete beams, they do not adequately predict the deflections of FRP reinforced concrete beams. From the measurements and analyses, it was concluded that the serviceability limit state (SST) is more critical than the ultimate limit state (LTS) for the design of concrete flexural beams reinforced with FRP rebars.

DOI:

10.14359/51740635


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