This paper focuses on the analysis of non-linear forced vibrations of a sandwich beam with a viscoelastic core layer. The analytical formulation considers
Ultra-high performance concrete (UHPC), possessing excellent mechanical properties, can be used as an excellent material to repair or strengthen the reinforced concrete structural elements. However, the effectiveness of repairing and strengthening by applying the layers of UHPC on the surface of substrate concrete depends on whether the interface between overlay and substrate ensures adequate bonding performance over the entire life span under different loading and exposure conditions. This paper presents an experimental investigation on the effects of key factors on the interfacial bond strength between UHPC overlay and normal concrete substrate (NC). The different surface roughness of the NC substrate, curing conditions, exposure conditions, and test methods (slant shear, bi-surface shear, splitting tension, and third-point flexure), were considered as variable parameters affecting the bond behavior. The results showed that while the curing conditions have an insignificant effect on the bond behavior, the surface roughness of the NC substrate affected the bond strength significantly. The preparation of the substrate’s surface using the sandblasting technique achieved the highest bond strength determined using different bond tests, except the bi-surface shear test, which gave the highest bond strength for the surface prepared using drill holes, owing to the interlocking action of the UHPC that filled the holes drilled in the NC substrate. Furthermore, it was found that the highest reduction of the bond strength under the cyclic exposure conditions with the drill holes' specimens. Even though the bond strength of the UHPC-NC composites subjected to the cyclic exposure conditions got significantly deteriorated, all bond strength results met the acceptable limits for applications as a repairing/strengthening, as specified by different design codes. Finally, the comparison between experimental results and predictions using different existing code models (i.e., CEB-FIP 1990, Eurocode 2 2004, CAN CSA A23.3 2014, AASHTO LRFD 2014 and AFGC 2013) revealed that the AASHTO LRFD and AFGC predictions were substantially conservative.
This paper is intended to investigate the stress block for high strength concrete (HSC) using the finite element model (FEM) and analytical approach. New stress block parameters were proposed for HSC including the stress intensity factor (α1) and the depth factor (β1) based on basic equilibrium equations. A (3D) finite element modeling was developed for the columns made of HSC using the comprehensive code ABAQUS. The proposed stress parameters were validated against the experimental data found in the literature and FEM. Thereafter, the proposed stress block for HSC was used to generate interaction diagrams of rectangular and circular columns subjected to compression and uniaxial bending. The effects of the stress block parameters of HSC on the interaction diagrams were demonstrated. The results showed that a good agreement is obtained between the failure loads using the finite element model and the analytical approach using the proposed parameters, as well as the achievement of a close agreement with experimental observation. It is concluded that the use of proposed parameters resulted in a more conservative estimation of the failure load of columns. The effect of the stress depth factor is considered to be minor compared with the effect of the intensity factor.
The cast‐in C‐channel is a small anchoring steel piece used to post‐connect different types of elements in precast concrete members. The objective of this study was to investigate the ultimate capacity of cast‐in C‐channels under uniaxial tension and to compare its ultimate load capacity and failure modes with a three‐dimensional finite element (FE) simulation, and to develop a mechanistic solution for cast‐in C‐channels. Five samples were cast and tested in varying configurations to induce the different failure modes of the channels, focusing on the influence of the confinement of the host concrete as well as the effect of the studs. The results showed that flexure of the channel governed the capacity in both the experimental work as well as in FE. In addition, the results of having local lip yielding as another dominant failure mechanism were similar to that observed in the experimental work and the finite element method (FEM). The FEM predicted not only the failure modes as addressed in mechanistic formulations but also captured the diagonal cracking in the host concrete and relative slip of the embedded channel, both phenomena observed in the experimental work but not accounted explicitly in the current design formulations.
The construction and building materials sector are becoming increasingly concerned about sustainability and environmentally friendly materials/composites. One of these developed composites is called engineered cementitious composite (ECC), and it has the ability to reduce carbon and energy impacts on the environment in addition to its remarkable performance, such as control cracking and ultra-high ductility. Over the previous years, scientists have made coherent efforts and activities to create a greener ECC. These efforts can be mostly categorized by the utilization of more cost-effective and environmentally friendly binders, fillers, and fibers. This review focuses on the utilization of environmentally friendly binders called limestone calcined clay cement (LC3) as well as greener fibers in creating greener ECC. The fresh, mechanical, and sustainability performance of LC3-based ECC are comprehensively discussed in this study. Based on the existing studies, it is concluded that LC3-based ECC has a higher strain capacity and better self-healing capability. It reduces the carbon footprint and embodied energy compared to the OPC-based ECC. Overall, the review aims to promote the use of ECC-LC3 in construction projects and encourage further research in this area. Further research should focus on enhancing the long-term mechanical and durability performance of LC3-based ECC.
In this paper, experimental and numerical investigations into the performance of circular unfilled and concrete filled stainless steel tubular stub columns strengthened by carbon steel bars welded to the inner surface were presented. The carbon steel bars were fabricated to be a structural component of the stub column and directly participate in supporting the axial load. Ten stub columns of 141.3 mm outer diameter and 3.4 mm thickness were tested under axial compression load for different numbers and sizes of carbon steel bars. 3D finite element models (FEMs) were carried out for the strengthened stub columns by using finite element program ABAQUS and validated with the experimental results. The validated numerical work was utilized to carry out a parametric study to assess (i) the practical configuration of the carbon steel bars, (ii) the possible reduction of stainless steel thickness, which can be compensated for by the addition of carbon steel bars, (iii) the effect of the diameter to thickness ratio (D/t) on the stub column performance. The numerical work was further utilized to generate extensive data to validate the load carrying capacity predicted by the ACI and Eurocode4 codes and the continuous strength method (CSM). The experimental and numerical results demonstrated that this strengthening technique enhanced the axial load carrying capacity for unfilled and filled stainless steel stub columns. The results from the parametric study confirmed that (i) strengthening by two carbon steel bars is the most practical configuration to minimize the welding process, (ii) a substantial reduction in stainless steel thickness can be achieved by using carbon steel bars, (iii) the ultimate load carrying capacity is inversely proportional to the D/t ratio. CSM was the most accurate method for predicting the failure load of the strengthened stainless steel tube.
Waste materials may be used as raw materials for interlocking masonry products in order to contribute to sustainable development and environmental protection. Rubberized concrete Interlocking Brick (RCIB) was developed by volumetric replacement of 56% of the ordinary Portland cement with fly ash and 20% of the sand with crumb rubber (CR) to reduce the production cost of conventional concrete bricks (CCB) and restrict the depletion of natural resources and contributing to solving the environmental problems associated with the accumulation of scrap tires in landfills. The mechanical and sustainability evaluation of masonry prism made of the developed brick is the aim of this research. Consequently, compressive strength, failure mechanism, stress–strain behaviour, and energy absorption of grouted and ungrouted prisms made of RCIB were measured experimentally under axial compression load. The thermal resistance, fuel consumption, CO2 emission, and cost analysis of RCIBs were estimated. The findings reveal that grout had a significant impact on the compressive strength of rubberized concrete interlocking masonry prisms where the compressive strength of grouted and ungrouted prisms was 10.99 MPa and 5.83 MPa, respectively. Web splitting and vertical cracks were the common failure modes observed in both prisms. Moreover, the rubberized concrete interlocking masonry prisms revealed greater energy absorption as well as a gradual and ductile failure mechanism. The RCIB exhibited higher thermal resistance than CCB (increased from 0.106 to 0.171 m2 K/W) which could contribute to a 62% reduction in annual fuel consumption and CO2 emission. Further, more than 25% of the material cost could be saved.
This study investigates the mechanical performance of Super Fibre Warm Mix Asphalt (WMA) using Non-Destructive Testing (NDT) based on Resilient Modulus (MR). Four fibre types: commercial Dellanite Fibre (DF), waste Cellulose Fibre (CF), Wool Fibre (WF), and Jute Fibre (JF) were added at 0.3% by weight to Evotherm-modified bitumen, mixed at 130°C, and compacted at 115°C. MR testing was conducted at 25°C and 40°C to evaluate fatigue and rutting behaviour, respectively. At 25°C, DF and CF exhibited the highest MR values of 3830 MPa and 3774 MPa, indicating superior fatigue resistance. At 40°C, CF had the highest MR (1698 MPa), followed by DF (1647 MPa), showing better rutting resistance. JF consistently showed the lowest performance, with MR values of 1444 MPa (25°C) and 679 MPa (40°C). Statistical analysis confirmed significant differences among fibres (p < 0.001). The findings demonstrate that DF and CF substantially enhance WMA stiffness and temperature resilience.
No abstract is provided for this article.
This paper presents experimental and numerical investigations of cold-formed circular stainless steel tubular (HSST) stub columns strengthened externally using carbon fiber reinforced polymer (CFRP) wraps. For the experimental investigation, eleven stub columns were tested under axial compression loading. The experimental variables were the CFRP thickness (tf), the CFRP arrangement (fully or partial wrapping), and the diameter-to-thickness ratio of stainless steel tubes (D/ts). The ratio of the compressive strength of wrapped specimens to that of unwrapped specimens (strengthening ratio) was employed to assess the compressive behavior of CFRP-wrapped HSST columns. Three-dimensional finite element (FE) simulation was implemented using ABAQUS software and validated against the experimental results. A parametric study was performed on the validated FE models for further investigation. The experimental results indicated that the full CFRP wrapping reasonably enhanced the ultimate compressive strength of the columns. In contrast, the partial wrapping showed no improvement in the ultimate compressive strength. The FE parametric study results showed that the strengthening ratio (i) decreases with increasing the diameter of the tubes, (ii) decreases when the failure mode changes from outward to inward local buckling (iii) is affected by the strength of the CFRP and tube materials. Based on the parametric study results, a design model was proposed to predict the ultimate strength of axially loaded CFRP-wrapped HSST stub columns.
This work aims to investigate the wave propagation in an exponential-law-based functionally graded (FG) plate with micro-structural defects using a simple exponential-trigonometric quasi-3D HSDT that employs four variables only. In this study, the elastic properties varied across the plate's thickness using a function of volume fraction in the form of exponential power-law. Hamilton's principle is utilized to obtain the governing differential equations, and the analytical solution is processed using the Navier approach. A parametric investigation has been developed to explore the impacts of material exponent, porosity distribution, and plate thickness on the wave propagation of the exponentially graded material (EGM) varying plate. The results showed that the phase velocity in the plate decreases with increasing the percentage of porosity volume of the plate for a specific material power exponent. In contrast, the FG plate's porosity does not affect the primary frequency.
