Reinforced Concrete Buckling-Restrained Braced Frame with Structural Fuse Detailed for Seismic Loading

 Reinforced Concrete Buckling-Restrained Braced Frame with Structural Fuse Detailed for Seismic Loading

Abstract
Buckling-restrained braces (BRBs) increase the strength of a system while dissipating a significant amount of hysteretic energy. This research presents a concept for a lateral force-resisting system using a reinforced concrete buckling-restrained braced frame (RCBRB) as a structural fuse for the design of new buildings in seismic regions. Experimental and numerical analysis results are presented for a single-story subassembly. The experiment was performed on a reduced-scale prototype reinforced concrete (RC) frame designed and constructed with modern seismic details and supplemented with a BRB as a structural fuse to examine the structural performance of the RCBRB frame under quasi-static cyclic loads. The BRB fractured in tension at approximately 3.5% drift ratio with minor repairable damage observed in the RC frame members. A numerical analysis model was developed in OpenSees with various material types and elements to model the nonlinear behaviour of the proposed system compared with the numerical analysis model of the undamaged RC frame; the global and local experimental response of the RC frame and BRB was used to validate the numerical model. When compared to the numerical analysis results of the RC frame, the resulting RCBRB frame increased both the lateral load capacity and stiffness of the RC frame by approximately 250%. The resulting lateral force-resisting system would be capable of resisting strong earthquake ground motions that can yield or even fracture the BRB without damaging the RC frame beyond a state of repair. The BRB was attached to the RC frame utilizing steel embed plates cast into the concrete that were designed using the uniform force method. A numerical model was developed and validated using the experimental results and showed that the RCBRB frame more than doubled the lateral strength and nearly tripled the total hysteretic energy dissipation when compared to the numerical analysis model results of an undamaged RC frame alone.

Thanks too

Authors: Jake D. Dunn,
S.M.ASCE jacobddunn@gmail.com, and
Chris P. Pantelides,
F.ASCE https://lnkd.in/gbHuzmNs c.pantelides@utah.edu
AUTHOR AFFILIATIONS
Publication: Journal of Structural Engineering
Volume 151, Issue 2
https://lnkd.in/gfpxKKpb

 

Revisiting the Ambient and Postfire Strength of Channel-Type Shear Connectors

Abstract

The ability of steel-concrete composite floor systems to withstand loads relies on shear connectors, which prevent or limit slip between the two materials. This paper presents an experimentally validated numerical investigation along with parametric studies aimed at evaluating the behaviour of channel-type shear connectors in ambient and postfire conditions. A three-dimensional finite-element model of a push-out test was developed, which incorporated the nonlinear material properties of steel and concrete in ambient conditions as well as their thermomechanical properties to simulate heating and cooling and the effects of fire exposure. The model was validated using experimental data obtained by the authors and those from previous studies. Subsequently, a parametric study assessed the load-slip behaviour of the channel-type connectors assuming different compressive strengths of concrete, slab thicknesses, connector dimensions, and maximum temperatures experienced. The failure mode in ambient and postfire conditions was observed to be affected by the length, web thickness, and height of the channel, but not by its flange thickness. The numerical results, combined with an analytical investigation of failure mechanisms, were then used to develop an improved design equation for channel-type shear connectors, which performs noticeably better than current design provisions in comparison with experimental data.

Thanks to 

Authors: Erfan Maliji and Hossein Yousefpour https://orcid.org/0000-0001-5454-6584 hyousefpour@nit.ac.irAUTHOR AFFILIATIONS

Publication: Journal of Structural Engineering

Volume 151, Issue 2

https://doi.org/10.1061/JSENDH.STENG-14090

Virtual Constant Load Method for Moving Force Identification on Simply Supported Beam

 Virtual Constant Load Method for Moving Force Identification on Simply Supported Beam

Abstract
During the operation of a simply supported beam bridge, moving forces are a primary load on the bridge. Therefore, moving force identification (MFI) is essential for ensuring bridge safety. Nevertheless, current theories for identifying moving forces present shortcomings. To ascertain the force through the bridge beam response, it is essential to know the beam’s bending stiffness. Practical or laboratory measurements of this bending stiffness are difficult to record, limiting practical implementations of MFI theory. Therefore, a virtual constant load (VCL) method is developed to achieve MFI when the beam bending stiffness is unknown. The proposed method uses a vehicle with a known axle load to efficiently traverse a simply supported beam. Upon establishing a correlation between the dynamic responses and the MFI model under the influence of the known axle load, a correction coefficient is derived for characterizing the strain response of the MFI model. This coefficient includes bending stiffness information, eliminating the need to explicitly solve for the beam bending stiffness. The updated model effectively achieves force identification when the bridge bending stiffness is unknown. To validate this method, MFI was conducted using numerical and laboratory analyses. The results demonstrate that the proposed method can accurately identify moving forces acting on beams with unknown bending stiffness.

THANKS TO

Authors:
Hai-Chao Zhou zhouhc1712@163.com,
Hong-Nan Li, F.ASCE hnli@dlut.edu.cn,
Ting-Hua Yi, M.ASCE yth@dlut.edu.cn, and
Dong-Hui Yang, M.ASCE dhyang@dlut.edu.cn
AUTHOR AFFILIATIONS
Publication: Journal of Structural Engineering
Volume 151, Issue 2
https://lnkd.in/gAcVWFYM