Investigation on Strengthening Approaches Adopted for Poorly Detailed RC Corbels

Abstract

Poor detailing of the position of bearing pad over reinforced concrete (RC) corbel may lead to premature failure, which is undesired and structurally vulnerable. An appropriate retrofitting solution is necessary to ensure the functionality of such RC corbels. Considering the growing popularity of external carbon fiber-reinforced polymer (CFRP) in retrofitting, this research examines the effectiveness of an externally wrapped unidirectional CFRP sheet and compares its performance against traditional retrofitting methods. Moreover, it is intended to fulfill the lack of extensive research on external CFRP application for corbel strengthening. A total of eight medium-scale corbel specimens were tested on vertical load. Observed premature failure due to placing the bearing pad near the edge of corbel was verified and the effectiveness of the proposed structural strengthening solutions was studied. Experimental results show that although the loading capacity of the damaged corbel due to the poor detailing of bearing pad position could not be fully recovered, the external CFRP wrapping method demonstrated superior performance over RC jacketing and was able to prevent localized failure. Further study based on non-linear 3D finite element analysis (FEA) was carried out to identify the governing parameters of each retrofitting solution. Numerical studies suggested important parameters of various retrofitting alternatives for higher capacity assurance.

Reinforced Concrete Corbel Strengthened Using Carbon Fiber Reinforced Polymer (CFRP) Sheets

“…• appropriate anchorage of the reinforcement; • assurance of reinforcement yielding before concrete crushing by limiting the ratio of the tie reinforcement; • checking the strut stress or the equivalent shear stress at the loading bearing face in order to avoid brittle failure; and • consideration of horizontal forces in the design of corbels and the consequent unfavorable effect on the slope of the resultant F d (Figure 3). Figure 4 presents a typical damage that may appear at the uttermost face of a reinforced concrete corbel, according to Neupane et al [12]. The presence of cracks or concrete spalling in the nib of the corbel is probably due to the following conditions: inadequate dimensions or positioning of the load bearing plate, lack of complementary reinforcement in the bends of the main tie reinforcement, overloading during the use of the structure, or insufficient anchorage length.…”

“…The presence of cracks or concrete spalling in the nib of the corbel is probably due to the following conditions: inadequate dimensions or positioning of the load bearing plate, lack of complementary reinforcement in the bends of the main tie reinforcement, overloading during the use of the structure, or insufficient anchorage length. 4 presents a typical damage that may appear at the uttermost face of a reinforced concrete corbel, according to Neupane et al [12]. The presence of cracks or concrete spalling in the nib of the corbel is probably due to the following conditions: inadequate dimensions or positioning of the load bearing plate, lack of complementary reinforcement in the bends of the main tie reinforcement, overloading during the use of the structure, or insufficient anchorage length.…”

“…Also, the proposed solution, wrapping the corbel and the column with CFRP sheets, would be able to correct the issues related to the lack of vertical secondary reinforcement and the questionable utilization of vertical hooks for the main tie reinforcement. Laboratory researches (Neupane et al [12] and Ivanova et al [13]) have indicated that this kind of solution can increase the load capacity of corbels, especially in the elastic range, with an increase of about 20%. The steps of this rehabilitation are described in detail in the next section.…”

“…Spalled reinforced concrete corbel due to the inadequate position of the load bearing plate (Source: Neupane et al[12]). …”

A Review of Precast Concrete Beam‐to‐Column Connections Subjected to Severe Fire Conditions

“…Researchers have investigated the performance of half-grouted sleeve and welded connection at elevated temperatures [53,56,57], as shown in Table 4. However, thus far, no extensive study has been carried out on the fire behaviour of bearing pads, bolts, and welds [71][72][73][74][75].…”