Effect of geometrical properties on strength of externally prestressed steel-concrete composite beams

A parametric study was carried out to investigate the structural behaviour of composite steel-concrete T-beams under different prestressing conditions. The studied parameters include different cases of loading, tendon profiles, beam spans, initial prestressing levels and different dimensions of steel sections and concrete deck. The studied beams were modelled by the finite-element software Ansys. The effect of three geometrical parameters was investigated for three different tendon profiles. It was found that straight tendon profiles are more appropriate for beams under distributed loads, whereas a draped tendon profile is more convenient for beams under concentrated loads. In addition, the ratio of the tension flange area to the compression flange area is the most effective geometrical parameter on the ultimate resistance of the studied prestressed beams. For instance, increasing this ratio from 1 to 3 resulted in increasing the additional resistance of the beam due to prestressing from 15·4 to 46·1%. For composite beams, the presence of the concrete slab prevented the lateral-torsional buckling and accordingly minimised the effect of the span. Moreover, increasing the slab thickness-to-width ratio resulted in enhancing the average increase in beam strength from 13·5 to 19·9%

Effect of geometrical properties on strength of externally prestressed steel–concrete composite beams

A parametric study was carried out to investigate the structural behaviour of composite steel–concrete T-beams under different prestressing conditions. The studied parameters include different cases of loading, tendon profiles, beam spans, initial prestressing levels and different dimensions of steel sections and concrete deck. The studied beams were modelled by the finite-element software Ansys. The effect of three geometrical parameters was investigated for three different tendon profiles. It was found that straight tendon profiles are more appropriate for beams under distributed loads, whereas a draped tendon profile is more convenient for beams under concentrated loads. In addition, the ratio of the tension flange area to the compression flange area is the most effective geometrical parameter on the ultimate resistance of the studied prestressed beams. For instance, increasing this ratio from 1 to 3 resulted in increasing the additional resistance of the beam due to prestressing from 15·4 to 46·1%. For composite beams, the presence of the concrete slab prevented the lateral–torsional buckling and accordingly minimised the effect of the span. Moreover, increasing the slab thickness-to-width ratio resulted in enhancing the average increase in beam strength from 13·5 to 19·9%

Effect of geometrical properties on strength of externally prestressed steel–concrete composite beams

A parametric study was carried out to investigate the structural behaviour of composite steel-concrete T-beams under different prestressing conditions. The studied parameters include different cases of loading, tendon profiles, beam spans, initial prestressing levels and different dimensions of steel sections and concrete deck. The studied beams were modelled by the finite-element software Ansys. The effect of three geometrical parameters was investigated for three different tendon profiles. It was found that straight tendon profiles are more appropriate for beams under distributed loads, whereas a draped tendon profile is more convenient for beams under concentrated loads. In addition, the ratio of the tension flange area to the compression flange area is the most effective geometrical parameter on the ultimate resistance of the studied prestressed beams. For instance, increasing this ratio from 1 to 3 resulted in increasing the additional resistance of the beam due to prestressing from 15·4 to 46·1%. For composite beams, the presence of the concrete slab prevented the lateral-torsional buckling and accordingly minimised the effect of the span. Moreover, increasing the slab thickness-to-width ratio resulted in enhancing the average increase in beam strength from 13·5 to 19·9%

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

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