Thin Concrete Panels Research Articles

Bond Performance of Reinforcing Bars in Thin Concrete Panels with the Presence of Innovative Void Formers Under Tensile Loading

Bond Performance of Reinforcing Bars in Thin Concrete Panels with the Presence of Innovative Void Formers Under Tensile Loading

Tensile performance of cast-in headed studs in thin concrete panels with void formers

In recent times, voided concrete slab or wall system has been increasingly popular due to material and cost savings benefits offered by such system. Fastenings are required to be attached to such systems either to connect to other concrete elements or fixtures. There has been limited published literature on the performance of fastenings in thin concrete shell elements due to presence of voids. The Concrete Capacity (CC) method is the state-of the-art prediction model for capacity of anchors in concrete widely adopted in design standards worldwide. The CC-method has been proven to be a robust model for predicting concrete cone capacity of cast-in and post-installed anchors with effective embedment depths, hef between 4 and 20 times diameter of anchors with a minimum hef of 40 mm in mature age concrete. In this study, over 200 headed studs are investigated experimentally in early age concrete whereby the hef for over half of the specimens is lesser than 40 mm. Further, the failure mode for the headed studs in the presence of plastic void former is expected to be a plug failure which prohibits the development of the full concrete cone. The purpose of this study is to examine the applicability of the CC-method for pull out performance of headed studs in the presence of void formers. A total of 228 headed anchors with varying effective embedment depths ranging from 19 mm to 61 mm were tested in thin concrete panels with varying thicknesses. Based on structural reliability analysis, a modification factor was proposed to the CC-method to safely predict the pull-out design capacity of headed studs in thin concrete panels with plastic void formers to maintain the same degree of safety as for typical headed stud applications within the scope of the CC-method.

Model for predicting the shear strength and strains of thin concrete panels retrofitted with CFRP

Carbon Fiber Reinforced Polymers (CFRP) can be an alternative material to retrofit thin and low-rise concrete walls. The literature review reports no predictive backbone models that include the deformation associated with the main limit states of concrete panels retrofitted with CFRP fabrics. This paper aims to describe a backbone model to predict the shear strength and strains associated with the peak shear strength (max) and the loss of lateral resistance (llr) limit states of thin concrete panels retrofitted with CFRP strips. A model to correlate the shear strength associated with the max and llr limit states between panels and walls was developed to extrapolate the response from panels to walls. The experimental program includes cyclic diagonal compression tests of 15 panels. The results obtained allowed analyzing the hysteresis curves, the shear strengths and strains, and the energy dissipation associated with the max and llr limit states in the panels. The response of specimens retrofitted with CFRP were compared with those retrofitted with conventional methods, and with specimens that comply the minimum web shear steel ratio. The response measured in the panels showed that the dissipated energy associated with the limit states depends on the volumetric ratio, the inclination, and the number of CFRP strips. Results also demonstrate that performance of panels retrofitted with CFRP strips outperforms that of panels with the minimum web shear steel ratio.

Development and Application of Precast Concrete Double Wall System to Improve Productivity of Retaining Wall Construction

The construction of most apartment underground parking lots utilizes reinforced concrete (RC) structures composed mainly of rebar work and formwork. RC structures lower construction efficiency and significantly delay the construction because they require a large number of temporary materials and wooden formwork. In this study, a precast concrete double wall (PCDW) system was developed to address the existing problems of RC structures and to improve the productivity of retaining wall construction. PCDW is a precast concrete (PC) wall in which two thin concrete panels are connected parallel to each other with truss-shaped reinforcement between them. PCDW can contribute to securing integrity, reducing the delay in construction, and improving quality. An overall process for the member design and construction stage of the PCDW system was proposed, and its improvement effects were examined regarding various aspects in comparison to the RC method.

Thermo-mechanical loading of GFRP reinforced thin concrete panels

The experimental investigation is focused on the thermo-mechanical behaviour of thin concrete panels reinforced with GFRP rebars. The considered thin panels (thickness of 4 cm) were exposed to increasing temperature and bending loading. These concrete elements are typical for low bearing function concrete layers in façade claddings. The influence of two aspects was studied: the concrete cover and the external surface of rebars. The heating condition was such that the temperature of the internal GFRP rebars reached about the transition temperature of the resins. This allowed to verify the variation of the deformability and the load carrying capacity of the panels with post-heating bending tests. As main outcome, the imposed temperature did not generate evident degradation of the GFRP reinforcement and of its adhesion to the concrete, while a reduction of the initial global stiffness was measured.

In-plane shear behaviour of thin low reinforced concrete panels for earthquake re-construction

Low reinforced thin concrete panels have been used for the re-construction of living buildings in the devastated zone of L’Aquila. A structural characterization of these types of panels is presented in this paper, paying particular attention to the fact that these panels are subjected mainly to shear forces. Refined compression-field theory (RCFT) has recently been proposed in order to better predict the behaviour of reinforced concrete members subjected to in-plane shear and axial stresses. This theory is based on continuum mechanics, i.e. satisfying compatibility, equilibrium and formulating the constitutive equations in terms of average (i.e. “smeared”) stresses and strains. The improvement of RCFT in comparison with the two most famous theories for reinforced concrete member subjected to shear [i.e. the modified compression-field theory (MCFT), and the rotating-angle softened-truss model (RA-STM)], deals with an embedded bar model based on the tension stiffening model in concrete. After an ad-hoc calibration procedure, the RCFT is employed in order to reproduce the envelope of the experimental load-deflection response of three full-scale thin low reinforced concrete panels subjected to cyclic loading. The predictions provided by RCFT are compared with the experimental data as well as with those provided by MCFT and RA-STM. This paper presents the necessary parameters for the design of thin low reinforced concrete panels using the RCFT. The preliminary numerical validations seem very promising. However, additional experimental data are required for calibrating and validating the parameters of the proposed RCFT theory.