Research on seismic performance of fibre reinforced high-strength concrete steel beam assembly joints

ABSTRACTIn this paper, the flexural performance of a new type of composite beam comprised of High Strength Steel (HSS) section encased by polyvinyl alcohol‐engineered cementitious composite (PVA‐ECC) and lightweight concrete (LWC) is studied. An experimental investigation on the flexural performance of HSS beams encased by different thickness of ECC is conducted and their performances are compared with bare HSS beam and normal strength concrete (NSC) encased HSS beam. Four‐point bending tests are carried out on simply supported beams including one bare HSS beam, one NSC encased HSS (NSC‐HSS) beam and two ECC‐LWC encased HSS (ECC‐HSS) beams. For ECC‐HSS beams, both top and bottom flanges of the HSS sections are encased with PVA‐ECC while the web was encased by LWC. The test results showed a significant improvement in load‐carrying capacity, ductility and failure modes for ECC‐HSS beams when comparing with bare HSS and NSC‐HSS beam.

Reinforced concrete structures are susceptible to steel corrosion in harsh environment and require frequent and expensive repair and maintenance to enhance the service life of these structures. FRP rebars offer a good alternative to steel rebars, provide similar strength and better durability against corrosion at a reasonable cost. Basalt fiber is a high-performance non-metallic fiber made from basalt rock melted at high temperature. BFRP rebars have been used in several structures recently. BFRP reinforced normal and high strength concrete beams have been investigated in this research. The BFRP reinforced concrete beams are designed to fail by concrete crushing rather than a brittle rebar failure (ACI-440). However, such design approach doesn’t fully utilize the tension capacity of FRP rebars. Therefore, increasing the concrete strength will harness more of the tension capacity of the FRP rebars. In this study, two high-strength concrete (HSC) beams and four normal concrete beams (with a replication) and different reinforcement ratios were cast and tested under four-point loading. The beam with the higher reinforcement ratio showed higher ductility while the beam with higher concrete strength showed higher overall capacity. FE simulation of the beams was carried out using ABAQUS software. Results of the simulations were in good agreement with the experimental results.

Research on seismic performance of fibre reinforced high-strength concrete steel beam assembly joints

Shear performance of prestressed ultra high strength concrete encased steel beams

High-strength steel beams with hexagonal web openings under impact load

A macroscopic finite element model is extended to account for fire induced spalling in high strength concrete (HSC) beams. The model is based on the principles of mechanics and thermodynamics and utilizes pore pressure calculations to predict fire induced spalling in concrete. For validating the model, spalling measurements were made by conducting fire resistance experiments on four normal strength and high strength concrete beams. Spalling predictions from the model are compared with the measured values of spalling at various stages of fire exposure. The validated model is applied to investigate the influence of fire scenario, concrete strength (permeability) and axial restraint on the fire induced spalling and fire response of RC beams. Results from the analysis show that fire scenario, and concrete permeability largely influence the extent of fire induced spalling in concrete beams. Further, it is also shown that the extent of spalling has significant influence on the fire resistance of RC beams.

Effects of stirrup, steel fiber, and beam size on shear behavior of high-strength concrete beams

The flexural responses of high‐strength fiber‐reinforced concrete (HSFRC) beams and high‐strength concrete (HSC) beams are compared in this study. A series of HSFRC and HSC beams were tested under pure flexural loading. The effects of the type of concrete, compressive strength of the concrete, and tensile rebar ratio on the flexural behavior of the concrete beams were investigated. The flexural behavior of the HSFRC and HSC beams including the induced crack and failure patterns, load and deflection capacity, crack stiffness, ductility index, and flexural toughness was compared. The crack stiffness of the HSC and HSFRC beams increased with the rebar ratio. For the same rebar ratios, the crack stiffness of the HSFRC beams was much greater than that of the HSC beams. The ductility index of the HSC beams decreased sharply with an increase in the rebar ratio, but the ductility index of the HSFRC beams did not show a clear decrease with increasing rebar ratio. The flexural toughness of the HSFRC beams was greater than that of the HSC beams at higher rebar ratios of 1.47% and 1.97%, indicating that the energy absorption of the HSFRC beams was greater than that of the HSC beams. Test results also indicated that HSFRC developed better and more consistent ductility with higher rebar ratio. In addition, the tested bending strength and sectional analysis results were compared.

The structural behavior and simplified thermal analysis of normal-strength and high-strength concrete beams under fire

The use of periodical elliptically-based web (EBW) openings in high strength steel (HSS) beams has been increasingly popular in recent years mainly because of the high strength-to-weight ratio and the reduction in the floor height as a result of allowing different utility services to pass through the web openings. However, these sections are susceptible to web-post buckling (WPB) failure mode and therefore it is imperative that an accurate design tool is made available for prediction of the web-post buckling capacity. Therefore, the present paper aims to implement the power of various machine learning (ML) methods for prediction of the WPB capacity in HSS beams with (EBW) openings and to assess the performance of existing analytical design model. For this purpose, a numerical model is developed and validated with the aim of conducting a total of 10,764 web-post finite element models, considering S460, S690 and S960 steel grades. This data is employed to train and validate different ML algorithms including Artificial Neural Networks (ANN), Support Vector Machine Regression (SVR) and Gene Expression Programming (GEP). Finally, the paper proposes new design models for WPB resistance prediction. The results are discussed in detail, and they are compared with the numerical models and the existing analytical design method. The proposed design models based on the machine learning predictions are shown to be powerful, reliable and efficient design tools for capacity predictions of the WPB resistance of HSS beams with periodical (EBW) openings.

Properties of high-strength steel fiber-reinforced concrete beams in bending

Shear behavior of high-strength concrete beams reinforced with carbon fiber-reinforced polymer bars

This paper reports experimental data on the behavior and shear strength of high-strength concrete slender beams reinforced with fiber-reinforced polymer (FRP) bars. Shear tests were conducted on six large-scale reinforced concrete beams without stirrups using high-strength concrete (f' c = 65 MPa) along with three beams using normal-strength concrete (f' c = 35 MPa). The beams measured 3250 mm long, 250 mm wide, and 400 mm deep, and were tested in four-point bending. The test variables were strength of concrete, and the reinforcement ratio and modulus of elasticity of the longitudinal reinforcing bars. Carbon and glass FRP bars and conventional steel bars were used as longitudinal reinforcement in this investigation. The experimental shear strengths of the FRP-reinforced concrete beams were compared to theoretical predictions provided by ACI 440.1R-03 and the modified form of this method proposed by the authors. The test results indicated that the high-strength concrete beams exhibited slightly lower relative shear strength compared to normal-strength concrete beams. In addition, the ACI 440.1R-03 design method provided very conservative predictions whereas the proposed modified equation gave better results.

To date, no studies have focused on high strength concrete (HSC) beams under pure torsion, even though HSC beams are more problematic than normal strength concrete beams and hollow beams are more problematic than plain beams as far as torsional ductility is concerned. This paper studies the ultimate behavior of HSC hollow beams with respect to their strength and ductility. Sixteen beams were tested. The hollow beams had a constant square cross section and were symmetrically reinforced. The variable parameters were the concrete?s compressive strength, from 46.2 to 96.7 MPa (from 6699 to 14,022 psi), and the total amount of torsional reinforcement, from 0.30 to 2.68%. The findings show that the torsional ductility is low and that the range of reinforcement ratio where ductility still occurs is very narrow. Different codes of practice were compared in the light of the experimental results, with the ACI Code appearing to be the most appropriate for predicting torsional strength and limiting torsion reinforcement. Some of the other codes were found to be excessively permissive and could lead to the acceptance of brittle beams or unsafe values of the predicted maximum torque.

Flexural behavior and bond coefficient of BFRP bar reinforced normal and high strength concrete beams