STR-975: EFFECT OF SHEAR SPAN TO DEPTH RATIO ON SEISMIC PERFORMANCE OF REINFORCED MASONRY SHEAR WALLS

Over the past few decades there has been a substantial increase in the number of multi-story buildings constructed with reinforced masonry (RM). Similar to reinforced concrete (RC) buildings, shear walls are a popular lateral load resisting system in regions of high seismic activity due to its capability to provide lateral stiffness, strength and energy dissipation. One of the parameters that affects the inelastic behaviour and ductility of RM shear walls is the shear span to depth ratio, M/Vdv. This paper experimentally investigates the effect of M/Vdv on the seismic performance of RM shear walls that are dominated by diagonal shear failure. The experimental work involves two identical full-scale fully grouted rectangular RM shear walls, W-M/Vdv1.2 and W-M/Vdv1.8, tested under in-plane axial compressive stress and cyclic lateral excitations. Wall W-M/Vdv1.8 was subjected to a top moment so that M/Vdv was equal to 1.875, as compared to a value of 1.25 for wall W-M/Vdv1.2 that was tested without a top moment. Most of the existing design equations for nominal in-plane shear strength, Vn, for RM shear walls, including the current provisions of the Canadian Standards CSA S304-14, the Masonry Standards Joint Committee MSJC (2013), and the New Zealand code (2004) for masonry structures, limit the effect of the M/Vdv to an upper value of 1.0. The test results show a significant reduction of 25% in the shear strength when M/Vdv is increased, which means that limiting the effect of M/Vdv to an upper value of 1.0 is overestimating the Vn of RM shear walls at high values of M/Vdv. However, W-M/Vdv1.8 was able to achieve higher levels of displacement ductility. More results were analyzed and are presented in this paper according to force-based, displacement-based, and performance-based seismic design considerations

STR-976: EFFECT OF HORIZONTAL REINFORCEMENT ANCHORAGE END DETAIL ON SEISMIC PERFORMANCE OF REINFORCED MASONRY SHEAR WALLS

The most recent design codes for masonry structures necessitate the use of reinforced masonry (RM) shear walls in medium and high seismic areas. There are several factors that control the contribution of the horizontal reinforcement to the in-plane shear capacity of RM shear walls. One of these factors is its anchorage end detail. The current version of the Canadian Standards Association CSA S304-14 for design of masonry structures requires that the anchorage of the horizontal reinforcing bars in the plastic hinge region shall have a 90° or more standard hook at the ends of the wall. However, a 180° standard hook is required for ductile shear walls. On the other hand, some masonry design codes (e.g. New Zealand, NZS 4230:2004) permits a 90° anchorage hook for ductile walls. This paper discusses the results of three identical RM shear walls that were tested under in-plane axial compressive stress and cyclic lateral excitations. All the walls were dominated by shear failure before reaching their flexure capacity. Wall W-180° was constructed with a 180° hook while walls W-90° and W-Str had a 90° hook and straight bar. The test results show that a 180° hook is the most effective anchorage end detail in terms of lateral force capacity and ductility. However, wall W-Str reached a lateral resistance, Que, of 398 kN compared to 412 kN and 418 kN for walls W-90° and W-180°, respectively, with less than 5% difference. Moreover, wall W-180° achieved a high level of displacement ductility of 4.2 instead of 3.9 and 3.6 when using a 90° hook and straight bar at a drop in wall capacity to 80% of Que. More results are analyzed and presented in this paper according to force-based, displacement-based, and performance-based seismic design considerations

Global economic burden of unmet surgical need for appendicitis

Background: There is a substantial gap in provision of adequate surgical care in many low-and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods: Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results: Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion: For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Global variation in anastomosis and end colostomy formation following left-sided colorectal resection

Background End colostomy rates following colorectal resection vary across institutions in high-income settings, being influenced by patient, disease, surgeon and system factors. This study aimed to assess global variation in end colostomy rates after left-sided colorectal resection. Methods This study comprised an analysis of GlobalSurg-1 and -2 international, prospective, observational cohort studies (2014, 2016), including consecutive adult patients undergoing elective or emergency left-sided colorectal resection within discrete 2-week windows. Countries were grouped into high-, middle- and low-income tertiles according to the United Nations Human Development Index (HDI). Factors associated with colostomy formation versus primary anastomosis were explored using a multilevel, multivariable logistic regression model. Results In total, 1635 patients from 242 hospitals in 57 countries undergoing left-sided colorectal resection were included: 113 (6·9 per cent) from low-HDI, 254 (15·5 per cent) from middle-HDI and 1268 (77·6 per cent) from high-HDI countries. There was a higher proportion of patients with perforated disease (57·5, 40·9 and 35·4 per cent; P < 0·001) and subsequent use of end colostomy (52·2, 24·8 and 18·9 per cent; P < 0·001) in low- compared with middle- and high-HDI settings. The association with colostomy use in low-HDI settings persisted (odds ratio (OR) 3·20, 95 per cent c.i. 1·35 to 7·57; P = 0·008) after risk adjustment for malignant disease (OR 2·34, 1·65 to 3·32; P < 0·001), emergency surgery (OR 4·08, 2·73 to 6·10; P < 0·001), time to operation at least 48 h (OR 1·99, 1·28 to 3·09; P = 0·002) and disease perforation (OR 4·00, 2·81 to 5·69; P < 0·001). Conclusion Global differences existed in the proportion of patients receiving end stomas after left-sided colorectal resection based on income, which went beyond case mix alone

Predicting Compressive Strength of Blast Furnace Slag and Fly Ash Based Sustainable Concrete Using Machine Learning Techniques: An Application of Advanced Decision-Making Approaches

The utilization of waste industrial materials such as Blast Furnace Slag (BFS) and Fly Ash (F. Ash) will provide an effective alternative strategy for producing eco-friendly and sustainable concrete production. However, testing is a time-consuming process, and the use of soft machine learning (ML) techniques to predict concrete strength can help speed up the procedure. In this study, artificial neural networks (ANNs) and decision trees (DTs) were used for predicting the compressive strength of the concrete. A total of 1030 datasets with eight factors (OPC, F. Ash, BFS, water, days, SP, FA, and CA) were used as input variables for the prediction of concrete compressive strength (response) with the help of training and testing individual models. The reliability and accuracy of the developed models are evaluated in terms of statistical analysis such as R2, RMSE, MAD and SSE. Both models showed a strong correlation and high accuracy between predicted and actual Compressive Strength (CS) along with the eight factors. The DT model gave a significant relation to the CS with R2 values of 0.943 and 0.836, respectively. Hence, the ANNs and DT models can be utilized to predict and train the compressive strength of high-performance concrete and to achieve long-term sustainability. This study will help in the development of prediction models for composite materials for buildings

Ultra-high-performance concrete with Iron ore tailings and non-metallic and hybrid fibers-A comprehensive experimental study

This research discusses the behavior of ultra-high-performance concrete (UHPC) specimens made with dumped waste iron ore tailing (IOT) as a fine aggregate in the mix by 30% and 40% in volume fraction along with mono and hybrid fiber incorporation. Basalt fibers of 1%, 2%, and 3%, polypropylene fibers of 0.18%, 0.20%, and 0.22%, and glass fibers of 1%, 1.5%, and 2% of volume fractions were the non-metallic fibers used. Steel fibers as a metallic factor were kept 1% constant throughout the study. The water-to-binder ratio was maintained between 0.15 and 0.17 after sufficient trials. A high-range water reducer was utilized to improve the flowability of the mix. The experimental investigations confirmed that the SG2 mix with 1% steel and 1.5% glass fiber, and 30% IOT, exhibited improved tensile and impact strength compared to standard conventional concrete. This combination exposed an impact energy of 4.05 × 105 kJ for the first crack and 2.7 × 106 kJ for collapse. The energy taken by the specimen between the first crack and the collapse was about 2.3 × 106 kJ. The microstructure was analyzed using Scanning Electron Microscopy. The non–metallic fibers with dominant mechanical properties were thermogravimetrically analyzed

Utilization of waste marble powder as partial replacement of cement in engineered cementitious composite

AbstractThe current study focuses on the utilization of Marble Waste Powder (MWP) as a partial substitution of cement along with local sand instead of microsilica sand in Engineered Cementitious Composite (ECC). The aim was to reduce the environmental concerns of ECC by reducing the cement content without adversely affecting the desired properties. Four mixes were evaluated; the control mix which has no MWP and three test mixes having cement replacement with MWP by 10%, 15%, and 20% were used, respectively. The properties of ECC mixes were found in terms of compressive, tensile, and flexural characteristics. The trend of change in the basic properties of ECC with an increased percentage of MWP as partial substitution of cement was found along with the hypothesis test on the experimental data. From this study, it was concluded that the increased percentage of MWP reduces on the compressive strength of ECC. The maximum reduction in compressive strength of ECC was recorded as 49% with 20% replacement of cement with MWP, as compared to the control sample at 91 days of test age. The tensile strain of ECC increases with the increase in MWP content, while the tensile stress increases only with the increase of MWP content up to a specified limit. The ultimate load in the force–deflection curve first increases with the increase in MWP content up to a certain percentage, while upon further increase in MWP content from 15% to 20%, the ultimate load decreases. The study suggests that the properties do not vary significantly for the modified ECC samples containing MWP, especially the 10% and 15% MWP samples, and can be utilized instead of normal ECC, thus mitigating environmental concerns without compromising the ECC’s performance