scholarly journals Strengthening of Precast RC Frame to Mitigate Progressive Collapse by Externally Anchored Carbon Fiber Ropes

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1306
Author(s):  
Jianwu Pan ◽  
Xian Wang ◽  
Hao Dong
Keyword(s):  
Carbon Fiber ◽  
Load Capacity ◽  
Progressive Collapse ◽  
Analytical Models ◽  
Deformation Condition ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Catenary Action ◽  
Rc Frames ◽  
Collapse Failure

The robustness of precast reinforced concrete (RC) frames is relatively poor, while the precast RC frames are strengthened to mitigate progressive collapse, avoiding “strong beams and weak columns” and the anchorage failure of strengthening materials under large deformation condition are the key problems. Aiming to discuss these problems, this paper carried out an experimental research of strengthening on three half-scale assembled monolithic frame subassemblages to mitigate progressive collapse. One specimen was strengthened by implanting carbon fiber rope (CFR) with polymer into concrete, one specimen was strengthened by binding CFR with special knot, and the last one was not strengthened. The failure mode, collapse failure mechanism and strengthening effect of subassemblages were discussed. Analytical models of load capacity increment contributed by CFR and construction suggestions of precast RC frame to mitigate progressive collapse were proposed. The results indicated that none of the strengthened specimens had anchorage failure. The two strengthening methods significantly increased the load capacity of the subassemblages in the catenary action (CA) stage with little effect on the flexural action (FA) stage and compressive arch action (CAA) stage.

scholarly journals Strengthening of Precast RC Frame to Mitigate Progressive Collapse by Externally Bonded CFRP Sheets Anchored with HFRP Anchors

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Jianwu Pan ◽  
Xian Wang ◽  
Fang Wu
Keyword(s):  
Failure Modes ◽  
Progressive Collapse ◽  
Analytical Models ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Concrete Frames ◽  
Catenary Action ◽  
Cfrp Sheets ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer

Currently, the robustness of precast reinforced concrete frames is attracting wide attention. However, avoiding “strong beams and weak columns” during strengthening against progressive collapse is a key problem. To discuss this problem, an experimental study on two 1/2-scale precast frame subassemblages under a pushdown loading regime was carried out in this paper. One specimen was strengthened with carbon fibre-reinforced polymer (CFRP) sheets on the beam sides. The middle parts of the CFRP sheets were anchored with hybrid fibre-reinforced polymer (HFRP) anchors. Another specimen was not strengthened. The failure mechanisms, failure modes, and strengthening effect are discussed. The strengthening effect is very obvious in the early catenary action stage. No shearing failure develops on HFRP anchors, which proves that the anchoring method is effective. Based on the experimental results, analytical models and preventive strengthening design and construction measures to mitigate progressive collapse of the precast RC frame are proposed.

scholarly journals Effects of Corrosion on Compressive Arch Action and Catenary Action of RC Frames to Resist Progressive Collapse Based on Numerical Analysis

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2662
Author(s):  
Lu Zhang ◽  
Tingyu Wei ◽  
Hongyu Li ◽  
Jian Zeng ◽  
Xiaofang Deng
Keyword(s):  
Numerical Model ◽  
Mechanical Performance ◽  
Progressive Collapse ◽  
Significant Loss ◽  
Catenary Action ◽  
Rc Frames ◽  
Collapse Resistance ◽  
Arch Action ◽  
Rebar Corrosion ◽  
Modeling Strategy

Many negative factors can influence the progressive collapse resistance of reinforced concrete (RC) frame structures. One of the most important factors is the corrosion of rebar within the structure. With increasing severity of corrosion, the duration, robustness, and mechanical performance can be greatly impaired. One specific side effect of rebar corrosion is the significant loss of protection against progressive collapse. In order to quantify the effects of rebar corrosion on load-resisting mechanisms (compressive arch action (CAA) and tensile catenary action (TCA)) of RC frames, a series of numerical investigations were carried out in this paper. The previous experimental results reported in the literature provide a benchmark for progressive collapse behavior as a sound condition and validate the proposed numerical model. Furthermore, based on the verified numerical model, the CAA and TCA with increasing corrosion and an elapsed time from 0 to 70 years are investigated. Comparing with the conventional empirical model, the proposed numerical model has shown the ability and feasibility in predicting the collapse resistance capacity in structures with corroded rebar. Therefore, this numerical modeling strategy provides comprehensive insights into the change of load-resisting mechanisms in these structures, which can be beneficial for optimizing the design.

Improving the tie force method for progressive collapse design of RC frames

2018 ◽  
Vol 9 (4) ◽  
pp. 520-531 ◽  
Author(s):  
Arash Naji
Keyword(s):  
Design Methodology ◽  
Progressive Collapse ◽  
Limit State ◽  
Content Type ◽  
Catenary Action ◽  
Closed Form Solutions ◽  
Rc Frames ◽  
Orthogonal Beams ◽  
Similar Equation ◽  
Good Agreement

Purpose The purpose of this paper is to recover the deficiency of existing tie force (TF) methods by considering the decrease in section strength due to cracking and by selecting limit state of collapse according to section properties. Design/methodology/approach A substructure is selected by isolating the connected beams from the entire structure. For interior joints, the TFs in the orthogonal beams are obtained by catenary action. For corner joints, the TFs are assessed by beam action. For edge joints, however, the resistance is gained by greater of the resistance under catenary action for periphery beams and beam action for all the connecting beams in both directions. For catenary action, the TF capacities must satisfy Equation (20). On the other hand, for beam action, the TF must satisfy Equation (16), while R is calculated from Equation (17). In the case where the length of the connecting beams is similar, Equation (19) can be used. Findings Closed form solutions are available for TFs on both beam and catenary stages. Originality/value The proposed formulation makes designing more practical and convenient. However, the proposed formulation had good agreement with experimental results.

Lateral Load Behavior of an Open-Ground-Story RC Building with AAC Infills in Upper Stories

2016 ◽  
Vol 32 (3) ◽  
pp. 1653-1674 ◽  
Author(s):  
Supratik Bose ◽  
Durgesh C. Rai
Keyword(s):  
Brick Masonry ◽  
Hysteretic Behavior ◽  
Analytical Models ◽  
Rc Frame ◽  
Masonry Infills ◽  
Rc Frames ◽  
Open Ground ◽  
Strength And Stiffness ◽  
Infilled Rc Frames ◽  
Masonry Infilled Rc Frames

Autoclaved aerated concrete (AAC) masonry infills in upper stories can be beneficial for improving the seismic response of open-ground-story (OGS), reinforced concrete (RC)–frame buildings. Two reduced 1:2.5-scale models of single-story, single-bay RC frames with and without AAC infill masonry were tested for resistance properties and hysteretic behavior. Low strength and stiffness of AAC masonry, about half of the conventional brick masonry, led to improved load sharing between the infill and the frame, which helped an early development of frame yield mechanism for enhanced energy dissipation. Test results were used to evaluate the reliability of using existing strength and stiffness relations of conventional masonry infilled RC frames for AAC infilled frames. Analytical models were developed to predict the observed hysteretic behavior of tested specimens. Nonlinear analyses of a five-story, four-bay OGS-RC frame were performed for conventional brick masonry infills and relatively softer and weaker AAC infills in upper stories. The results indicated that the undesirable effect of weak/soft ground story mechanism of OGS-RC frames can be reduced to an acceptable level by using AAC infills in upper stories.

An RHT-Model-Based Equivalent Parameter Scheme for Blast Response Simulation of RC Frames

2021 ◽  
Author(s):  
Ziqi Tang ◽  
Shanglin Yang ◽  
Run Zhang ◽  
Xiaohu Yao
Keyword(s):  
Response Analysis ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Model Based ◽  
Rc Frames ◽  
Multiple Components ◽  
Equivalent Parameter ◽  
Blast Response ◽  
Constitutive Parameters ◽  
Parameter Scheme

In this paper, a novel equivalent parameter scheme based on the Riedel–Hiermaier–Thoma (RHT) model is proposed for blast response simulations of reinforced concrete (RC) frames. Considering the strengthening effect of longitudinal and stirrup reinforcements on concretes, constitutive parameters in the RHT model are modified to homogenize RC components based on reasonable simplifications and numerical tests. Numerical results of RC beams illustrate that this scheme significantly improves the computational efficiency and effectively predicts real explosion response behaviors with high accuracy. The scheme is then employed for the blast simulation of an RC frame with multiple components with results compared with those of real frame experiments to further demonstrate its reliability. Owing to its efficiency and accuracy, the present RHT-model-based equivalent parameter scheme can serve as a feasible tool to conduct blast response analysis of the RC frame and guide the corresponding anti-explosion designs.

Restoring Force Model of Joints of RC Frame Retrofitted by FRP

2012 ◽  
Vol 256-259 ◽  
pp. 693-696
Author(s):  
Peng Li ◽  
Ya Ping Peng ◽  
Er Lei Yao
Keyword(s):  
Seismic Performance ◽  
Seismic Retrofitting ◽  
Frame Structure ◽  
Force Model ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Restoring Force ◽  
Rc Frames ◽  
Restoring Force Model ◽  
Hysteretic Performance

In order to evaluate the seismic performance of reinforced concrete (RC) frames retrofitted by FRP, the experiment of RC frames retrofitted at joints by FRP was carried out. The enhancement in seismic performance of the retrofitted frames is evaluated in hysteretic performance, bearing capacity, stiffness degradation and energy dissipation. And the strengthening effect of the frame retrofitted by CFRP and C/GFRP was compared in the experiment. The restoring force model of RC frame joints retrofitted with FRP was proposed and ranges of the characteristic parameters were determined. The equation of restoring force model for joints strengthened by C/GFRP was suggested. The result show that seismic performance of RC frame retrofitted by FRP based on joints can be improved remarkably. The restoring force model which proposed can be used in seismic elasto-plastic analysis of RC frame structure retrofitted by FRP and practical engineering seismic retrofitting design by FRP.

Experimental Research on Seismic Behavior of Seismically Damaged RC Frame Column Strengthened with Sprayed Hybrid BF/CFRP

2014 ◽  
Vol 501-504 ◽  
pp. 1592-1599 ◽  
Author(s):  
Yu Jia Peng ◽  
Qian Gu ◽  
Rui Gao ◽  
Getahune Bitewlgn
Keyword(s):  
Energy Dissipation ◽  
Load Capacity ◽  
Experimental Program ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Cyclic Shear ◽  
Concrete Frame ◽  
Shear Loads ◽  
Seismic Behaviors ◽  
Frp Retrofit

This experimental program was designed for investigating the seismic behaviors and strengthening effect of pre-damaged RC frame columns retrofitted with sprayed BFRP and hybrid BF/CFRP. Four RC frame column specimens, among which one was unstrengthened and three was pre-damaged and strengthened with sprayed FRP, were tested under an incremental loading procedure of the pseudo-static, cyclic shear loads combined with constant gravity loads. The test results including the failure mode, ultimate bearing load capacity, load-displacement hysteresis curves and ductility of specimens were obtained and analyzed. It indicates that spraying hybrid BF/CFRP strengthening scheme can effectively improve the ductility and energy dissipation ability of pre-damaged concrete frame columns. Although the improvement of the peak loads and ultimate lateral deformation of damaged frame columns were not obvious compared with those of the reference column, but it should be pointed out that the strengthened columns were pre-damaged seriously with yielded steel bars and the recover of load bearing ability resulted from spraying FRP retrofit can not be neglected. It also shows that increasing the thickness of spraying overcoat can effectively improve the energy dissipation ability of damaged frame columns.

INCREASING ROBUSTNESS OF REINFORCED CONCRETE STRUCTURES UNDER COLUMN LOSS SCENARIO

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Said Elkholy ◽  
Bilal El-Ariss
Keyword(s):  
Reinforced Concrete ◽  
Simple Technique ◽  
Progressive Collapse ◽  
Element Analysis ◽  
Catenary Action ◽  
Rc Frames ◽  
Plane Frames ◽  
Nonlinear Static ◽  
Steel Cables ◽  
Push Down

This paper presents a simple technique to enhance robustness of reinforced concrete (RC) plane frames to progressive collapse under column loss scenario. The response of the enhanced/mitigated RC frames is analyzed using fiber force-based finite element analysis and applying displacement-controlled nonlinear static pushdown at the location of failed column. The technique involves addition of external unbounded steel cables to the continuous beam in each floor at anchorage and deviator locations. The cables transfer the loads above the failed column to the anchorages and deviators that are assumed to perform as rigid arms, which in turn redistribute the loads to adjacent columns. The numerical model computes the frame progressive collapse robustness using push-down analysis to simulate a column elimination and estimate the effects of cable catenary action on the frame. Two-dimensional RC frame of six stories and four bays was adopted in the study. The numerical results demonstrate the prospect of increasing robustness of RC frames to progressive collapse using presented technique.

A Hysteretic Model of Conventional Steel Braces and an Analysis of the Collapse Prevention Effect of Brace Strengthening

2012 ◽  
Vol 174-177 ◽  
pp. 3-10 ◽  
Author(s):  
Sheng Nan Huang ◽  
Xin Zheng Lu ◽  
Lie Ping Ye
Keyword(s):  
Dynamic Analysis ◽  
Incremental Dynamic Analysis ◽  
Hysteretic Behavior ◽  
Fragility Analysis ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Hysteretic Model ◽  
Collapse Prevention ◽  
Conventional Steel ◽  
Rc Frames

A hysteretic model of conventional steel braces consisting of 18 parameters is proposed. This model is able to simulate the hysteretic behavior of conventional steel braces accurately. The collapse-prevention strengthening effect with steel braces for a typical reinforced concrete (RC) frame that was close to the epicenter and collapsed during the Great Wenchuan Earthquake is discussed via push-over analysis and collapse fragility analysis based on incremental dynamic analysis. The result could be referred to for the seismic collapse prevention design of RC frames.

Sign in / Sign up

Export Citation Format

Share Document