Bearing capacity of damaged reinforced concrete beams strengthened with metal casing

Tatiana Lyashenko,Irina Karpiuk,Vasyl Karpiuk,Denis Danilenko,Anna Danilenko

doi:10.14311/ap.2021.61.0703

Abstract

Experimental data on the bearing capacity of damaged reinforced concrete beams with the dimensions of 2000×200×100 mm, reinforced with prestressed metal casings, are presented. Damaging in the form of through normal and crossing inclined cracks, as well as excessive vertical moving of the beam were obtained during previous tests for the effect of high-level transverse alternating loads.The authors of the article have developed a method and equipment for restoring and strengthening damaged reinforced concrete beams using a casing. Beams are manufactured and tested in accordance with the three-level design of an experiment.Previously damaged and reduced to the ultimate (pre-emergency) state, the beams were strengthened with the declared method and equipment, and then retested. New data on the bearing capacity of ordinary and damaged beams, as well as reinforced concrete elements strengthened with casings and tested for the action of transverse forces and bending moments were obtained. The research results are presented in the form of experimental-statistical dependences of the bearing capacity of the support areas, deformability and crack resistance of the investigated elements on the ratio of the most significant design factors and external factors. A comparative analysis of the influence of these factors on the main parameters of the bearing capacity of ordinary as well as previously damaged and then strengthened test beams is carried out.The possibility and appropriateness of using the proposed method of strengthening reinforced concrete beams damaged by through normal and cross-inclined force cracks in the conditions of an existing production has been experimentally proved.

Highlights

Every day, engineers are facing new problems related to the increased seismicity of buildings and structures’ siting, their physical wear and tear, changes of their functional purpose, increased load, etc. [1]
The design of such a reinforcement is controlled by the lack of a normative methodology and clear recommendations in the proprietary technologies, which adequately reflect the real stress-strain state of both the damaged structure and the reinforcement elements. This highlights the relevance of this work. It was experimentally established [7] that low-cycle transverse alternating and intermittent load of high levels does reduce the bearing capacity of prototypes to 20 % and their crack resistance, and significantly increases the width of the opening of normal cracks and, especially, oblique ones, the value of deflections up to 35 %, and change the nature of their destruction in comparison with a one-time static loading of proportionally increasing load
The test results of experimental reinforced concrete prototype-beams of the first (ASD) and second (A) series showed that their deformation, cracking and destruction occurred according to the rules of structural mechanics and were predictable

Summary

Introduction

Engineers are facing new problems related to the increased seismicity of buildings and structures’ siting, their physical wear and tear, changes of their functional purpose, increased load, etc. [1]. In the Odessa State Academy of Civil Engineering and Architecture, complex experimental studies of the bearing capacity of the bearing sections of reinforced concrete span structures under complex stress state are being carried out [7, 29,30,31] To achieve this goal, the authors of the article have created a method and equipment [32] to restore and strengthen a reinforced concrete beam in a predangerous state due to its division by through normal and cross-inclined cracks (Figure 1) into separate blocks connected with each other by longitudinal and transverse reinforcement under the action of alternating cyclic or high-level pulsating load, as well as strengthening of an ordinary span reinforced concrete structure that, being in a satisfactory technical condition, can reach the specified state under seismic effects. Monitoring the concrete deformations of the compressed area and tensile reinforcement, as well as the level of prestressing in the metal casing was carried out using dial indicators, and vertical displacements – by Aistov’s flexometer

Basic material and results

Findings

Conclusion