Long- and short-term serviceability behavior of reinforced concrete beams: Mechanics models for deflections and crack widths

2017 ◽  
Vol 19 (2) ◽  
pp. 489-507 ◽  
Author(s):  
Phillip Visintin ◽  
Alexander B. Sturm ◽  
Deric J. Oehlers
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Short Term ◽  
Crack Widths

scholarly journals ANALYSIS OF METHODS FOR CALCULATING THE WIDTH OF NORMAL CRACKS IN REINFORCED CONCRETE STRUCTURES

2009 ◽  
Vol 1 (1) ◽  
pp. 23-39 ◽  
Author(s):  
Vidmantas Jokūbaitis ◽  
Linas Juknevičius
Keyword(s):  
Reinforced Concrete ◽  
Carrying Capacity ◽  
Crack Width ◽  
Concrete Beams ◽  
Experimental Tests ◽  
Reinforced Concrete Beams ◽  
Design Codes ◽  
Rc Beams ◽  
Reinforced Concrete Slabs ◽  
Crack Widths

The width of normal cracks at the level of tensile reinforcement was calculated according to various methods using the data obtained from experimental tests on reinforced concrete beams (without reinforcement pre-stress), pre-cast reinforced concrete slabs and ribbed roof slabs. Th e numerical results were compared to actual crack widths measured during the experimental tests. Also, the crack widths of pre-stressed reinforced concrete beams were calculated according to various methods and compared with each other. Th e following conclusions were reached based on the analysis of numerical and experimental results: 1) Design stresses in tensile reinforcement calculated according to [STR] and [EC] design codes are very similar, although the calculation of such stresses is more logical and simple according to [EC]. Design stresses calculated according to [RU] are greater due to the estimation of the plastic deformations of concrete in the compressive zone. Th e method proposed by Rozenbliumas (Розенблюмас 1966) estimates tensile concrete above the crack peak, and thus allows a more accurate calculation of stresses in tensile reinforcement (Fig 3). Therefore, the latter stresses in pre-stressed RC beams may be decreased by 10–12 %, when height hct ≠ 0 (Fig 1, c) and ratio M/MRd varies between 0,65 and 0,75; 2) The widths of normal cracks in conventional RC beams (subjected to load that corresponds approx. 70 % of their carrying capacity) calculated according to [STR] and [EC] design codes are almost equal to the experimentally obtained crack widths. When beams and slabs are loaded by approximately 52 % of their carrying capacity, design crack widths wk [EC] are approximately 12 % less than wk [STR], although the design crack width wk [RU] is signifi cantly greater. Here, ratio β in the beams and slabs is equal to 2 and 3.3 respectively. Th erefore, the design code [RU] ensures higher probability that the crack width will not reach the limit value (for environmental class XO and XC1) equal in all design codes mentioned in this article; 3) In case of loaded prestressed reinforced concrete beams, the calculated increases of crack widths wk [EC], wk [RU] and w [5] are greater if compared to wk [STR] (Fig 6). Th e increased reinforcement ratio ρ has more signifi cant infl uence on the increases of crack widths calculated according to other design codes if compared to wk [STR]. Tensile concrete above the crack peak has signifi cant infl uence on the design crack width when pre-stressed RC beams are lightly reinforced (ρ ≤ 0,008); 4) During the evaluation of the state of fl exural RC members, expression (5) could be used for calculating the crack width or a position of the neutral axis when the heights of the crack and the tensile zone above the crack are known (calculated or measured experimentally). Design crack widths w (5) are very similar to the experimentally obtained results.

scholarly journals Experimental Analysis of the Strengthening of Reinforced Concrete Beams in Shear Using Steel Plates

2018 ◽  
Vol 3 (4) ◽  
pp. 52 ◽  
Author(s):  
Marília Batti ◽  
Bruno Silva ◽  
Ângela Piccinini ◽  
Daiane Godinho ◽  
Elaine Antunes
Keyword(s):  
Reinforced Concrete ◽  
Bearing Capacity ◽  
Concrete Beams ◽  
Point Load ◽  
Reinforced Concrete Beams ◽  
Steel Plates ◽  
Short Term ◽  
Before And After ◽  
Underlying Causes ◽  
Structural Adhesive

In some situations, it is necessary to strengthen or rehabilitate a structure in the short term, but before doing so, a critical analysis of the underlying causes is required to find the best technique to solve the problem. The structural strengthening is used to increase an element’s ability to resist a stress when it no longer meets the original conditions or new necessities of use due to faults, deterioration, thermal variations, and lack of maintenance. The present article aims to evaluate the strengthening of reinforced concrete beams with 0.75 mm thick SAE 1020 steel plates bonded with epoxy-based structural adhesive. The steel plates were attached to the sheared area before and after the beams were taken to the breaking point load. According to the results, it was possible to conclude the effectiveness of the strengthening applied to healthy beams that had its bearing capacity increased up to 50%. The beam that was strengthened after the shear, with a fissure that was restored with epoxy-based structural adhesive, had its load bearing capacity increased by 49.2%. The beams with fissures that were filled with mortar had their bearing capacity decreased by 58.70% if compared with the reference beams, and thus they presented an unsatisfactory performance.

Deflection Calculation on Reinforced Concrete Beams Strengthened by Externally Prestressing Transverse Tensioning Method

2013 ◽  
Vol 671-674 ◽  
pp. 430-436
Author(s):  
Jin Jun Liu ◽  
Tian Wen Wang
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Large Error ◽  
Reinforced Concrete Beams ◽  
Secondary Effect ◽  
Test Results ◽  
Short Term ◽  
Secondary Load ◽  
Externally Prestressing ◽  
Good Agreement

Eight reinforced concrete beams (six externally reinforced and two contrast beams) were tested under primary or secondary load experiment. According to the test results, the existing specifications were applied to make calculations on short-term deflection which leaded to a large error. The secondary effect should be considered on calculating the deflection. Therefore, comparisons were made between the improved calculated value and test value on deflections of reinforced concrete beams strengthened by externally prestressed transverse tensioning method and they are in good agreement.

Experimental Studies of Reinforced Concrete and Fiber-Reinforced Concrete Beams with Short-Term and Long-Term Loads

2019 ◽  
Vol 968 ◽  
pp. 227-233 ◽  
Author(s):  
Stepan Neutov ◽  
Maryna Sydorchuk ◽  
Mykola Surianinov
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Concrete Beams ◽  
Experimental Studies ◽  
Fiber Reinforced Concrete ◽  
Reinforced Concrete Beams ◽  
Short Term ◽  
Ordinary Concrete ◽  
Fiber Concrete ◽  
Steel Fiber Concrete

Experimental studies of the stress-strain state of reinforced concrete and fiber-reinforced concrete beams under short-term and long-term loads were carried out. The tests were carried out on three series of beams of different types - from ordinary concrete, steel fiber concrete and combined section, when the lower zone of the beam with a height of0.5his made of steel fiber concrete, and the upper one is made of ordinary concrete. During short-term loading, the load was applied in steps with a 10-minute exposure at each step to failure or to a predetermined level of a continuously acting load. In the interval between the steps, the process of cracking was tracked. After reaching a given level of loading, the load was fixed and maintained unchanged with a spring cassette for 300 days. Deformations were measured using strain gauges and dial gauges. Deflections and relative deformations of the extreme upper and extreme lower fibers for three types of beams are determined. It has been established that stabilization of deflections in beams from steel fiber concrete occurs much earlier (100 days) than in beams made of ordinary concrete (175 days). Studies have shown that the beams of ordinary concrete in the process of long-acting load lowered the carrying capacity by 5.5%. The bearing capacity of steel concrete beams, in contrast, increased by 7.6%.

scholarly journals Experimental Study on Calculation Methods for Short-term Cracks in High-strength Reinforced Concrete Beams

2017 ◽  
Vol 11 (1) ◽  
pp. 187-194
Author(s):  
Ruliang Zheng ◽  
Degao Tang ◽  
Yulong Xue ◽  
Zhen Liao
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Concrete Beams ◽  
High Strength ◽  
Crack Spacing ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Calculation Methods ◽  
Short Term ◽  
Average Crack

High-strength steel has increasingly become widely used among various engineering practices, but the relevant provisions of the codes lag behind its development. Six sets of experiments on simple supported beams reinforced with HTB600 and HTB700 rebars subject to bending loading were conducted in this study to 1) investigate the conditions of crack development, 2) contrast the calculating modes of short-term crack width between Chinese and European concrete codes, and 3) analyze European applicability and precision pertaining to high-strength reinforcement of beams. According to the experiments and research, when the calculation formulae obtained from Chinese codes were used to calculate the average crack spacing of high-strength reinforced concrete beams, the error relative to that obtained in the experiment reached approximately 20%. Based on this, a revised formula for the calculation of average crack spacing is proposed in this article, and the results of these calculations align with the results obtained from the experiment. In addition, this study also demonstrates that the maximum cracking spacing calculated by adhering to Eurocode standards yielded no significant deviation as compared to the experimental results. However, owing to a difference in the crack width exceeding 20% being observed between the results obtained under Eurocode standards and the experimental results, the calculation methods need to be further improved for better applicability of high-strength reinforced rebars.

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