Design of Semilightweight Bridge Girders: Development-Length Considerations

2000 ◽  
Vol 1696 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Robert J. Peterman ◽  
Julio A. Ramirez ◽  
Jan Olek
Keyword(s):  
Shear Crack ◽  
Point Load ◽  
Critical Section ◽  
Tension Force ◽  
Transverse Reinforcement ◽  
Development Length ◽  
Bond Failure ◽  
Moment Capacity ◽  
Maximum Moment ◽  
Prestressed Reinforcement

In a recent study, 25 development-length tests were conducted on rectangular and T-shaped semilightweight beams having design compressive strengths of 48 MPa (7,000 psi) and 69 MPa (10,000 psi). In the rectangular beam tests, the design moment capacity was exceeded in every case. However, in the tests on T-shaped beams, bond failure occurred in some specimens immediately after the formation of a flexure-shear crack. Additional tests were then conducted on similar T-shaped beams having varying amounts of transverse reinforcement near the point load. These tests showed that bond failure could be prevented by increasing the transverse reinforcement near the point of maximum moment. The study showed that the shift in the tension force that occurs when flexural cracks turn diagonally may lead to bond failure if sufficient anchorage of the strand is not provided. Therefore, the investigators recommend that the current AASHTO requirements for strand development be enforced at a “critical section” located at a distance dp from the point of maximum moment toward the free end of the strand, where dp is the distance from the extreme compression fiber to the centroid of the prestressed reinforcement.

Bond Strength on the Interface between Concrete and Steel and Development Length of Reinforcing Bars in RC Structures

2011 ◽  
Vol 94-96 ◽  
pp. 456-459
Author(s):  
Wen Bin Sun ◽  
Wei Zhong He ◽  
Yang Jiang
Keyword(s):  
Concrete Surface ◽  
Transverse Reinforcement ◽  
Development Length ◽  
Reinforcing Bars ◽  
Bond Failure ◽  
Rc Structures ◽  
Analysis And Design ◽  
Reinforcing Bar ◽  
Extended Length ◽  
Current Design

For the analysis and design of RC structures, there is a fundamental assumption that the strain in an embedded reinforcing bar is the same as that in the surrounding concrete. Therefore, bond forces must be developed on the interface between concrete and steel, such as to prevent significant slip from occurring at the interface. An end anchorage may be considered reliable if the bar is embedded in to concrete a prescribed distance known as the development length of the bar. If in the beam the actual extended length of a bar is equal to or greater than this required development length, no premature bond failure will occur. Research has indicated that the development length was influenced by tensile strength of concrete, surface and diameter of bar, cover distance, bar spacing, transverse reinforcement, and other factors. Current design methods in different countries’ Codes, attentions are directed toward providing adequate length of embedment, which will ensure development of the full strength of the bar.

Application of acoustic emission monitoring for assessment of bond performance of corroded reinforced concrete beams

2016 ◽  
Vol 16 (6) ◽  
pp. 732-744 ◽  
Author(s):  
Ahmed A Abouhussien ◽  
Assem AA Hassan
Keyword(s):  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Signal Strength ◽  
Point Load ◽  
Reinforced Concrete Beams ◽  
Bond Failure ◽  
Acoustic Emission Monitoring ◽  
Bond Performance ◽  
Emission Monitoring

This article presents the results of an experimental investigation on the application of acoustic emission monitoring for the evaluation of bond behaviour of deteriorated reinforced concrete beams. Five reinforced concrete beam–anchorage specimens designed to undergo bond failure were exposed to corrosion at one of the anchorage zones by accelerated corrosion. Two additional beams without exposure to corrosion were included as reference specimens. The corroded beams were subjected to four variable periods of corrosion, leading to four levels of steel mass loss (5%, 10%, 20% and 30%). After these corrosion periods, all seven beams were tested to assess their bond performance using a four-point load setup. The beams were continuously monitored by attached acoustic emission sensors throughout the four-point load test until bond failure. The analysis of acquired acoustic emission signals from bond testing was performed to detect early stages of bond damage. Further analysis was executed on signal strength of acoustic emission signals, which used cumulative signal strength, historic index ( H( t)) and severity ( Sr) to characterize the bond degradation in all beams. This analysis allowed early identification of three stages of damage, namely, first crack, initial slip and anchorage cracking, before their visual observation, irrespective of corrosion level or sensor location. Higher corrosion levels yielded significant reduction in both bond strength and corresponding acoustic emission parameters. The results of acoustic emission parameters ( H( t) and Sr) enabled the development of a damage classification chart to identify different stages of bond deterioration.

“Apparent Net-Section-Collapse” Methodology for Circumferential Surface Flaws in Piping

2017 ◽  
Author(s):  
S. Kalyanam ◽  
G. Wilkowski ◽  
S. Pothana ◽  
Y. Hioe ◽  
C. Sallaberry ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Surface Crack ◽  
Steel Pipe ◽  
Constant Thickness ◽  
General Applicability ◽  
Moment Capacity ◽  
Thickness Change ◽  
Maximum Moment ◽  
Stainless Steel Pipe ◽  
Girth Welds

The Original Net-Section-Collapse (NSC) analysis was developed in the 1970s for prediction of the maximum (failure) moment for a pipe with a circumferential flaw, and is used widely for circumferentially surface-cracked pipe flaw assessments. A noticeable inaccuracy in the Original NSC analysis was that it predicts that under load-controlled loading the surface-cracked pipe will always have a higher moment capacity than a pipe with a through-wall crack (TWC) of the same length as the surface crack. A large number of past pipe tests show that deep surface cracks in pipes can break through the thickness and result in leaks; so the maximum moment of that surface-cracked pipe was below the maximum moment for the circumferential TWC pipe with the same length. In these cases the applied moment has to be increased for the resulting crack to grow as a TWC. Hence, load-controlled leak-before-break (LBB) fracture behavior has been experimentally observed although it is not predictable by the Original NSC analysis. Furthermore, the loads to develop the leak can be significantly less than the maximum loads predicted by the NSC analysis for the same size flaw. Since it is undesirable to have leakage in many applications, this deficiency in the Original NSC analysis was explored by conducting a matrix of pipe tests explicitly designed to show the experimental differences with the Original NSC equation for actual load-controlled LBB conditions. Circumferential surface-cracked pipe tests were conducted with flaws in the base metal of TP304 stainless steel pipe, as well as in the center of girth welds. Most of the pipe tests were conducted under pure bending, but a few selected surface-crack geometries were conducted with internal pressure. The Original NSC analysis for circumferential surface-cracked pipes under combined bending and axial tension were enhanced through the development of the “Apparent NSC” approach. This modification explained inconsistencies with the Original NSC that has been documented from recent pipe fracture tests conducted, and other pipe fracture data from many countries, as well as implemented in the current ASME Section XI flaw evaluation procedures. The data from the carefully planned circumferential surface-cracked pipe tests also showed that the toughness in the surface-cracked pipe decreases as the flaw depth increases. Additionally, an ovalization/thickness change aspect that increases the moment-carrying capacity for longer cracks was observed compared to the Original NSC equations that assume the pipe is perfectly circular with a constant thickness. The “Apparent NSC” modification accounts for toughness and ovalization/thickness changes and was also validated by stainless steel pipe test data from past EPRI/Battelle and JAERI pipe data from Japan on similar TP304 circumferentially surface-cracked pipe tests also at room temperature. Data from several other past programs with larger diameter pipes and different materials (and test temperatures) were also used to assess the general applicability of the “Apparent NSC” analysis.

Shear Strength of Members without Transverse Reinforcement Based on Development of Critical Shear Crack

2020 ◽  
Vol 117 (1) ◽  
Author(s):  
Francesco Cavagnis ◽  
João T. Simões ◽  
Miguel Fernández Ruiz ◽  
Aurelio Muttoni
Keyword(s):  
Shear Strength ◽  
Shear Crack ◽  
Transverse Reinforcement
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