Estimating fixed-end rotations of reinforced concrete members at yielding and ultimate

Strain-penetration of the longitudinal reinforcement of reinforced concrete (RC) members in the joints and/or footings results in fixed-end rotations at the member ends. Several experimental studies have shown that fixed-end rotations caused by strain-penetration contribute significantly (up to 50%) to the total displacement capacity of RC members. Hence, accurate determination of these fixed-end rotations at yielding and ultimate limit states becomes of primary importance when defining the structural response of RC members. The purpose of this study is to present the theoretical background and the assumptions behind the most common relationships found in the literature for determining strain-penetration induced fixed-end rotations at yielding and ultimate. Furthermore, new simple relationships are proposed on the basis of realistic and mechanically-based assumptions. Comparisons between the existing and proposed relationships demonstrate the limitations of the former. Finally, the proposed relationships are calibrated against experimental measurements of RC column specimens subjected to cyclic loading with recorded fixed-end rotations due to strain-penetration in the adjacent joints and/or footings

A combined local damage index for seismic assessment of existing RC structures

A new local damage index for existing reinforced concrete (RC) structures is introduced, wherein deterioration caused by all deformation mechanisms (flexure, shear, anchorage slip) is treated separately for each mechanism. Moreover, the additive character of damage arising from the three response mechanisms, as well as the increase in degradation rate caused by their interaction, are fully taken into consideration. The proposed local damage index is then applied, in conjunction with a finite element model developed previously by the authors, to assess seismic damage response of several RC column and frame test specimens with substandard detailing. It is concluded that in all cases and independently from the prevailing mode of failure, the new local damage index describes well the damage pattern of the analysed specimens

Damage Analysis of Reinforced Concrete Structures with Substandard Detailing

The goal of this study is to investigate seismic behaviour of existing R/C buildings designed and constructed in accordance with standards that do not meet current seismic code requirements. In these structures, not only flexure, but also shear and bond-slip deformation mechanisms need to be considered, both separately and in combination. To serve this goal, a finite element model is developed for inelastic seismic analysis of complete planar R/C frames. The proposed finite element is able to capture gradual spread of inelastic flexural and shear deformations as well as their interaction in the end regions of R/C members. Additionally, it is capable of predicting shear failures caused by degradation of shear strength in the plastic hinges of R/C elements, as well as pullout failures caused by inadequate anchorage of the reinforcement in the joint regions. The finite element is fully implemented in the general inelastic finite element code IDARC2D and it is verified against experimental results involving individual column and plane frame specimens with nonductile detailing. It is shown that, in all cases, satisfactory correlation is established between the model predictions and the experimental evidence. Finally, parametric studies are conducted to illustrate the significance of each deformation mechanism on the seismic response of the specimens under investigation. It is concluded, that all deformation mechanisms, as well as their interaction, should be taken into consideration in order to predict reliably seismic damage of R/C structures with substandard detailing

Effect of anchorage slip and inelastic shear on seismic response of reinforced concrete frames.

Reinforced Concrete structures located in regions of high seismic activity are expected to develop inelastic deformations in their critical regions. Therefore, inelastic dynamic analysis is required to obtain reliable predictions of structural behavior during an earthquake. Tests on reinforced concrete elements and subassemblages have shown that anchorage slip and inelastic shear deformations can be as significant as those due to inelastic flexure, in the critical regions. Hence, a proper seismic analysis should include inelastic deformations due to anchorage slip, shear and flexure. Flexural response has been researched extensively in the past. Research on the effects of anchorage slip and shear inelasticity is scarce in the literature. The effect of anchorage slip and inelastic shear on seismic response of moment-resisting reinforced concrete frames is investigated in this study. A hysteretic model for anchorage slip is developed in the first phase of the project. The model consists of a primary curve and a set of hysteretic rules. The primary curve is developed based on assuming inelastic strain distribution along the embedded length of reinforcing bars. Considerations are given for conditions existing at interior joints, exterior joints, and column-foundation interface. Hysteretic rules are derived based on observations from available experimental data. The model is verified against a large volume of experimental data conducted on single straight and hooked bars, as well as interior and exterior joints. In the second phase of the project, the hysteretic anchorage-slip model is implemented into the nonlinear dynamic analysis program Drain 2D. A recently derived hysteretic model for shear is also implemented into the program. Two major subroutines, SLIPM and SHEARM, are added in order to trace out nonlinearity in the anchorage-slip and shear models. The program is enhanced with calculations of ductility demand and energy dissipation factors. Related input and output features of the program are also enhanced. In the final phase of the project, the enhanced computer program is used to determine the seismic response of three reinforced concrete frames that were designed for this purpose. Emphasis is placed on determining effects of individual deformation components on ductility demands and overall deformation characteristics of the frames. The effect of interaction of the fundamental period of vibration of the structure and the frequency content of ground motion are also investigated. The study shows that anchorage slip reduces flexural ductility demand by up to 42%. The amount of reduction is shown to depend on the level of inelasticity experienced by the structure. Overall behavior of the structures is not affected significantly by anchorage slip. Inelastic shear is shown to have very little effect on the behavior of the frames investigated

Impact of Nasal Irrigation With Iodized Table Salt Solution on Mucociliary Clearance: Proof-of-Concept Randomized Control Trial

Introduction Saline nasal irrigation is a common recommendation shared between the majority of clinical guidelines for sinusitis and rhinitis in adults and children. Studies involving homemade saline have typically involved the use of noniodized salt. However, the literature does not contain any descriptions for the use of iodized table salt in homemade saline solutions. Objectives To study the usefulness of iodized salt in homemade saline and its impact on mucociliary clearance (MCC). Methods Only healthy volunteers were enrolled in this randomized controlled trial. The sinonasal outcome test (SNOT)-22 and rhinoscopy were used to rule out any clinical evidence of sinusitis or rhinitis in the enrolled subjects. The saccharine clearance time (SCT) was used to evaluate MCC at baseline. Each candidate received 2 different nasal wash solutions—one containing iodized salt and the other containing noniodized salt—on different days. Visual analog scale pain scores were recorded while using each type of nasal wash. The SCT was assessed after each wash. Results Thirty-eight healthy candidates (18 men and 20 women) were enrolled in the study. All subjects were in their 30s. The mean baseline SCT was 10.92 minutes. The use of the noniodized salt solution led to a nonsignificant change ( P = .139) in mean SCT (9.68 min). In contrast, a significant change ( P = .035) was observed in mean SCT after the use of the iodized salt solution (9.06 min). However, the mean postirrigation SCT was not significantly different between solutions ( P = .31). No significant differences were observed in pain/discomfort experience between solutions. Conclusion MCC improved with both solutions. Interestingly, the improvement was significant, when the iodized salt nasal irrigation solution was used. This finding contradicts the conventional recommendation against the use of iodized salt in nasal rinse solution. Moreover, this solution was well tolerated. Further studies regarding the long-term safety are recommended. </jats:sec

Validating parental reports of child dental visits against treatment received among children

Objective: This study aimed to examine the agreement between parent-reported dental visits and received dental treatment within the previous 12 months among primary school children in Riyadh, and to examine factors associated with over-reporting and under-reporting of dental visits. Methods: A stratified sample from 16 primary schools in Riyadh was selected. A total of 996 students aged 6-11 years were assessed for dental treatment at baseline and 12 months later. World Health Organization criteria for assessing oral health were used. Socioeconomic and behavioral data were also collected. Data included reported dental visits (RDVs) within the past 12 months. A variable indicating any dental treatment within the follow-up time (DTR). The difference between visits and treatments (DVS) was calculated (DVS= RDV- DTR), which included three categories: reported visits/received treatment; reported visits/no treatment; and no reported visits/received treatment. Results: Agreement between parent-reported dental visits and dental treatment within the previous 12 months was 55%, with nearly 8% under-reported dental visits. Children experiencing dental pain had higher odds of reporting dental visits with no treatment (OR = 2.11, 95%CI: 1.47-2.65). Baseline dental caries was significantly associated with under-reported dental visits (OR = 1.15, 95%CI: 1.07-1.23). Conclusion: The findings indicated under-reporting of dental visits by those with higher dental caries at baseline. While children could have visited a dentist but not received treatment, hence, some might have over-reported dental visits. The findings suggested that parental reports of child dental visits were relatively reliable. Keywords: Child, health care, dental health services, longitudinal studies, validation studies