Strengthening of structural members is a common practice around the world that may arise due to deterioration of concrete with age or upgradation of design code. This paper aims to elucidate a technique used for strengthening of the reinforced concrete beam for flexural capacity by using externally welded steel angles and steel bars. For this motive, three beams were strengthened with external steel angles and three with external steel bars. The external strengthening steel elements were attached at the bottom of the beam with shear reinforcement. Control samples without external steel angles and steel bars for comparison purposes were also prepared. All reinforced concrete beams were first constructed using a concrete ratio of 1:2:4, and then external steel elements were added to existing flexural reinforcement by using a fillet weld with tee joints having thickness and length of 5/16" (7.9 mm) and 6" (152.4 mm), respectively. Fourth point loading criteria were used to investigate the flexural capacity of beams in positive bending. All beams were designed strong enough in shear, to resist the ultimate loads without shear failure. Test results indicated that beams strengthened with this technique have an average increase of 238% with steel angles and 106% with steel bars, in load-carrying capacity than control samples. Strengthened beams showed a uniform crack pattern. Moreover, the concrete cover made a good bond with existing concrete and was strong enough to withstand ultimate loads. Conclusively, the steel angles and steel bars can be used as an external strengthening material, to enhance the flexural capacity of reinforced concrete beams.

中文翻译：

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通过有效利用外部钢构件对现有钢筋混凝土梁进行抗弯加固和表征

结构构件的加固是世界各地的普遍做法，这可能是由于混凝土随时间老化或设计规范升级而引起的。本文旨在阐明一种用于通过使用外部焊接角钢和钢筋来增强钢筋混凝土梁的抗弯能力的技术。为了这个动机，三根梁用外角钢加固，三根用外钢筋加固。外部加强钢构件通过抗剪钢筋连接在梁的底部。还制备了没有外部角钢和钢筋的对照样品用于比较。所有钢筋混凝土梁首先使用1：2：4的混凝土比例建造，然后通过使用带三通的角焊缝将外部钢元件添加到现有的抗弯钢筋中，三通接头的厚度和长度分别为 5/16" (7.9 mm) 和 6" (152.4 mm)。第四点加载标准用于研究梁在正弯曲时的抗弯能力。所有梁的剪切强度都设计得足够强，可以抵抗极限载荷而不会发生剪切破坏。试验结果表明，采用这种技术加固的梁的承载能力比对照样品平均增加了238%的角钢和106%的钢筋。加强梁显示出均匀的裂纹图案。此外，混凝土保护层与现有混凝土的结合良好，强度足以承受极限载荷。最后，