Abstract
Self-compacting concrete is widely used around the globe today due to its special and unique properties. This study examines the effect of natural and crushed gravel combinations in different percentages in short-and long-term properties of concrete. The best utilized sand had a fineness modulus of 2.7. In the mentioned mix designs, silica fume was used with 0 and 7% of the weight of the cement. In order to check the properties of fresh and hardened concrete, 9 and 5 test types were performed, respectively. The carried out tests were slump flow, V-funnel, J-ring, L-box, U-box and column segregation for fresh concrete, and compressive, tensile and flexural strengths for hardened concrete. A mix with only 100% natural gravel was considered as the control mix. According to the results, the control mix design and the one containing 100% crushed gravel with silica fume were the best in fresh and hardened concrete tests, respectively. Finally, using the optimization method, a mix design with 25% natural gravel, 75% crushed gravel and silica fume was introduced as the best mix in terms of the results of both fresh and hardened concrete tests.
Address
Moosa Mazloom1, Mohammad Ebrahim Charmsazi and
Mohammad Hosein Parhizkari: Department of Structural and Earthquake Engineering, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, I. R. Iran
Abstract
The elastic theory of beams is fundamental in engineering of design and structure. In this study, we construct Green's function for inhomogeneous fourth−order differential operators subjected to associated constraints that arises in dealing with dynamic problems in the Rayleigh beam. We obtain solutions for homogeneous and completely inhomogeneous beam problems using Green's function. This enables us to consider rotational influences in determining the eigenfrequency of beam vibrations. Additionally, we investigate the dynamic vibration model of inhomogeneous beams incorporating rotational effects. The eigenvalues of Rayleigh beams, including first−order correction terms, are also computed and displayed in tabular forms.
Abstract
This study aims to determine the characteristics of concrete as identified by Rebound Hammer and Ultrasonic Pulse Velocity (UPV) tests, focusing particularly on their efficacy in estimating compressive strength of concrete material. The study involved three concrete samples designed to achieve a target strength of 29 MPa, comprising normal concrete, instant concrete, and concrete with additives. These were cast into cube specimens measuring 150x150x150 mm. Compressive strength values were determined through both destructive and non-destructive testing on the cubic specimens. As a result, the non-destructive methods yielded varying outcomes for each correlation approach, influenced by the differing constituent materials in the tested concretes. However, normal concrete consistently showed the most reliable correlation, followed by concrete with additives, and lastly, instant concrete. The study found that combining Rebound Hammer and UPV tests enhances the prediction accuracy of compressive strength of concrete. This synergy was quantified through multivariate regression, considering UPV, rebound number, and actual compressive strength. The findings also suggest a more significant influence of the Rebound Hammer measurements on predicting compressive strength for BN and BA, whereas UPV and RN had a similar impact on predicting BI compressive strength.
Address
Yudhistira J.U. Mangasi, Nadhifah K. Kirana,Jessica Sjah and
Nuraziz Handika: Department of Civil Engineering, Faculty of Engineering, Universitas Indonesia,
Kampus UI Depok 16424, Indonesia
Eric Vincens: Univ Lyon, Ecole Centrale de Lyon, CNRS, ENTPE, LTDS, UMR5513, 69130 Ecully, France
Abstract
Masonry arch bridges as a vital infrastructure were not designed for seismic loads. Given that masonry arch bridges are made up of various components, their contribution under the seismic actions can be very undetermined and each of these structural components can play a different role in energy dissipation. Iran is known as a high-risk area in terms of seismic excitations and according to the seismic hazard zoning classification of Iran, most of these railway infrastructures are placed in the high and very high seismicity zones or constructed near the major faults. Besides, these ageing structures are deteriorated and thus in recent years, some of these bridges using various retrofitting approaches, including sprayed concrete technique are strengthened. Therefore, investigating the behavior of these restored structures with new characteristics is very significant. The aim of this study is to investigate the cyclic in-plane performance of masonry arch bridges retrofitted by sprayed concrete technique through the finite element simulation. So, by considering the fill-arch interaction, the nonlinear behavior of a bridge has been investigated. Finally, by extracting the hysteresis and enveloping curves of the retrofitted and non-retrofitted bridge, the effect of strengthening on energy absorption and degradation of material has been investigated.
Key Words
cyclic loading; energy absorption; finite element modeling; masonry arch bridges; retrofitting; sprayed concrete
Address
Mahdi Yazdani: Department of Civil Engineering, Faculty of Engineering, Arak University, Arak, Iran
Mehrdad Zirakbash: Faculty of Civil Engineering and Transportation, University of Isfahan, Isfahan, Iran
