Seismic Rehabilitation of Existing Buildings

Research and practice on progressive collapse and robustness of building structures in the 21st century

Experimental tests of different types of bolted steel beam–column joints under a central-column-removal scenario

The vulnerability of conventional RC structures to structural failure caused by the loss of corner columns has been emphasized over the past years. However, the lack of experimental tests has led to a gap in the knowledge for the design of RC building structures to mitigate the likelihood of progressive collapse caused by losing a ground corner column. Seven one-third scale RC beam-column substructures were tested to investigate their performance. The variables selected for the test specimens included beam transverse reinforcement ratios, type of design detailing (nonseismic or seismic), and beam span aspect ratios. Shear failure was observed to have occurred in the corner joint, and a plastic hinge was formed at the beam end near the fixed support in the nonseismic detailed specimens. However, plastic hinges were also formed in the beam end near to the corner joint for the seismically detailed specimen. Vierendeel action was identified as the major load redistribution mechanism before severe fail...

https://dr.ntu.edu.sg/bitstream/10356/95421/2/Performance%20of%20Three-Dimensional%20Reinforced%20Concrete%20Beam-Column%20Substructures%20under%20Loss%20of%20a%20Corner%20Column%20Scenario.pdf

Performance of Three-Dimensional Reinforced Concrete Beam-Column Substructures under Loss of a Corner Column Scenario

Experimental study on the progressive collapse performance of RC frames with infill walls

Dynamic performance of RC beam-column substructures under the scenario of the loss of a corner column—Experimental results

Experimental and analytical studies carried out on a RC moment-resisting frame after it is subjected to the loss of its ground-story exterior column is presented in this paper. Four full-scale interior beam-column subassemblages with varying degrees of nonseismic detailing were subjected to a monotonic loading regime to simulate the effects of redistributed gravity loads on the subassemblage after the loss of an exterior ground column. The variables in the test specimens include the beam longitudinal reinforcement ratios and the spacing of the transverse reinforcement within the beams, columns, and joints. The load-displacement relationships, crack development patterns, and failure mechanism obtained from the tests are also discussed. The finite-element models are validated by comparing the results with the experimentally obtained data. Parametric studies are then performed to study the influence factors, such as the beam transverse reinforcement ratio and the incorporation of an additional exteri...

Experimental and Analytical Assessment on RC Interior Beam-Column Subassemblages for Progressive Collapse

To prevent the casualties that can result from the collapse of earthquake-damaged structures, it is important that structures be rehabilitated as soon as possible. This paper proposes a rapid rehabilitation scheme for repairing moderately damaged reinforced concrete (RC) beam-wide column joints. Four nonseismically detailed interior beam-wide column joints were used as control specimens. All four subassemblages were subjected to similar cyclic lateral displacement to provide the equivalent of severe earthquake damage. The damaged control specimens were then repaired by filling their cracks with epoxy and externally bonding them with carbon-fiber-reinforced polymer (CFRP) sheets and glass-fiber-reinforced polymer (GFRP) sheets. These repaired specimens were then retested and their performance compared with that of the control specimens. This paper demonstrates that the repair of damaged RC beam-wide column joints by using FRP can restore the performance of damaged RC joints with relative ease, suggesting that the repair of beam-column joints is a cost-effective alternative to complete demolition and replacement DOI: 10.1061/(ASCE)CC.1943-5614.0000163. © 2011 American Society of Civil Engineers. CE Database subject headings: Beam columns; Joints; Rehabilitation; Seismic effects; Fiber reinforced polymer. Author keywords: Beam-wide column joints; Beam-wall joints; Repair; Rehabilitation; Seismic; Fiber-reinforced polymers.

Seismic Behavior of Reinforced Concrete Interior Beam-Wide Column Joints Repaired Using FRP

Two specimen series (limited seismic (LS) and nonseismic (NS)) were subjected to quasistatic loadings to evaluate the residual axial capacity of blast-damaged reinforced concrete (RC) columns. A validated numerical model was used to predict the residual lateral deflection of RC columns subjected to an explosive attack. Three hydraulic actuators were installed horizontally to reproduce the target residual lateral deflection as predicted through this numerical model. Another two hydraulic actuators were installed vertically to apply the axial load and measure the residual axial capacity of the damaged columns. The effects of parameters such as axial loading and the transverse reinforcement ratio are investigated through this study. The results obtained from the experimental study showed the improved performance that LS detailing provided to RC columns to resist blast or lateral loads. This subsequently led columns detailed with a higher transverse reinforcement ratio to have an increased residual axial capacity when laterally damaged, as compared with the NS detailed spec- imens. Axial load (service load) on the columns was also found to affect the residual deflection profile and residual axial capacity of the columns after the specified blast event. The validity range of a previously published function to determine blast-damaged residual axial capacity of RC columns is refined through the results obtained. DOI: 10.1061/(ASCE)CF.1943-5509.0000210. © 2012 American Society of Civil Engineers.

/pdf/residual-axial-capacity-of-reinforced-concrete-columns-with-unjnyaofdx.pdf

Residual axial capacity of reinforced concrete columns with simulated blast damage

In this paper, the effects of eccentricity on the effectiveness of carbon-fiber-reinforced polymer (CFRP) or glass-fiber-reinforced polymer (GFRP) in repairing the shear strength and ductility of nonseismically detailed beam-wide column joints have been evaluated. For this purpose, four (two concentric and two eccentric) full-scale nonseismically detailed interior beamwide column joints were used as control specimens. All four subassemblages were subjected to similar cyclic lateral displacement to provide the equivalent of severe earthquake damage. The damaged control specimens were then repaired by filling their cracks with epoxy and externally bonding them with CFRP sheets and GFRP sheets. These repaired specimens were then retested and their response histories were obtained. Hence, a total of eight specimens were tested: four control, and four repaired. The response histories of the control and repaired specimens were then compared. The results were compared through hysteretic loops, load-displacement envelopes, energy dissipation capacity, secant stiffness degradation, and shear strength and damage indices. Moreover, the effectiveness of the proposed repair schemes in repairing the eccentric and concentric joints was also compared. The present study demonstrates that proposed repair schemes can recover the performance of both damaged reinforced concrete (RC) concentric and eccentric beam-wide column joints effectively.

/pdf/effects-of-eccentricity-on-the-seismic-rehabilitation-1b8yweipa9.pdf

Qian Kai

Papers

Dynamic performance of RC beam-column substructures under the scenario of the loss of a corner column—Experimental results

Experimental and Analytical Assessment on RC Interior Beam-Column Subassemblages for Progressive Collapse

Seismic Behavior of Reinforced Concrete Interior Beam-Wide Column Joints Repaired Using FRP

Residual axial capacity of reinforced concrete columns with simulated blast damage

Effects of Eccentricity on the Seismic Rehabilitation Performance of Nonseismically Detailed Interior Beamwide Column Joints