Blast And Ballistic Loading Of Structures

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Rational approach for predicting stress in beams with unbonded tendons

Aged structures and structures constructed based on outdated non-seismic design codes should be retrofitted to enhance their strength, ductility, and durability. This study evaluates the structural performance of reinforced concrete (RC) columns enhanced via polyurea or glass fiber reinforced polyurea (GFRPU) strengthening. Four RC column specimens, including a reference specimen (an unstrengthened column), were tested to evaluate the parameters of the strengthening materials and the strengthened area. The tests were carried out under a combined constant axial compressive load and quasi-static cyclic loading. The experimental results show that the composite strengthening provides lateral confinement to the columns and leads to enhanced ductility, shear-resistance capacity, and dissipated energy. The shear strength provided by the composites depends on the degree of lateral confinement achieved by the composite coating. The specimens finally failed through the development of diagonal tension cracks within the potential plastic hinge regions. The specimen treated with GFRPU strengthening showed greater strength and dissipated more energy than the specimen treated with polyurea strengthening. Furthermore, by modifying ATC-40, this study proposed an equation to estimate the shear capacity provided by the composites.

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Shear Strength of Reinforced Concrete Columns Retrofitted by Glass Fiber Reinforced Polyurea

Equilibrium of shell structures

Penetration behaviour of TBM disc cutter assisted by vertical precutting free surfaces at various depths and confining pressures

This paper studied reinforcing struts and ties in deep beams based on the Strut-and-Tie Model (STM) of ACI 318M-14. The study contained testing 9 simply supported specimens, divided into 3 groups. The difference between the groups was the loading type which was 2-concentrated forces, 1-concentrated force and uniformly distributed load. Each group contained three specimens; the first specimens in each group were conventional deep beams as references which had a length of 1400 mm, a height of 400 mm and a width of 150 mm. The second specimens were the same as references in dimensions, but with removing shoulders. In addition, only the paths of struts & ties of STM were reinforced in the second specimens as compression and tension members, respectively. The third specimens were the frames that took their dimensions from STM of ACI 318M-14. From the experimental work, it is found that the proposed frames were good alternatives for the references despite the small loss in ultimate capacity. However, these proposed frames already carried loads greater than the factored design loads of STM. In comparison with the references, these proposed frames provided 41-51% reduction in weight, 4-27% reduction in cost besides providing front side area about 46-55%.

Suggesting alternatives for reinforced concrete deep beams by reinforcing struts and ties

This laboratory research is concerned with the behavior of reinforced concrete deep beams, being exposed to high temperatures for one time or more. Two types of mixing water are used, namely, drinkable water (tap water) and non-drinkable water (raw water) brought from local wells in Baquba city, a situation which is currently under use in Iraq especially in large urban and nonurban engineering facilities. The specialized high temperature furnace is manufactured used in this study to heat twenty-four specimens. Later on after deep beams are casted, specimens are cooled down by two ways, gradually, by leaving them in the air for one day, and the fast way by gently putting them in water. This is to reflect the case of fire extinguish process with integrity of concrete. Testing of beams is carried out by loading each beam, using flexural machine, with two concentrated loads till failure. Test results show that using raw water in casting concrete (no heat exposure) leads to significant decrease in shear strength and an increase in deflection in comparison with using tap water. It is also observed that heat and then rapidly cooling causes a touchable strength decrease and deflection increase especially when raw water is used for concrete casting. Finally, it is worth to mention that the lowest percent reduction in loading strength recorded is that for specimens cast with non-drinkable water and exposed to cyclic temperatures, with rapid cooling at each time.

Effect of heating on simply supported reinforced concrete deep beams

This work aims at presenting detailed procedures companied by numerical examples for analyzing and designing reinforced concrete deep beams that subjected to non-central loadings based on Strut and Tie method (STM). The subjected loadings were moved from the center of the beam span towards the supports reaching the maximum non-centrality could be achieved (after which the beams became ‘not deep’ from ACI 318M-14 point of view). A total of three deep beams with three different types of loadings were taken into considerations; one concentrated force, two concentrated forces and uniformly distributed load. Every specimen had a cross section of 150  400 mm and a total length of 1000 mm. Generally, it was found that moving load from the span center towards one of the supports leads to worth notable decreases in the beam ultimate capacity. Therefore, in the case of one-concentrated force, the ultimate load capacity decreased by 30.2% when left shear span to effective depth ratio (a L /d) decreased from 1.3 to 0.65. While in the cases of two-concentrated forces or uniformly distributed loading, it was found that changing (a L /d) ratio from 1.02 to 0.37 led to decrease the deep beam ultimate capacity by 30.5%.

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Strut and Tie Modeling for RC Deep Beams under non-Central Loadings

Corbel strut and tie modeling – Experimental verification

A new perspective in the design of reinforced-concrete pile caps is proposed in this paper, where the conventional approach leading to a reinforcing mesh is replaced by modelling the cap as a strut-and-tie system, in agreement with the strut-and-tie model, STM proposed by several design codes, ACI 318 included. Twelve RC pile-cap specimens were designed and manufactured. In the first group of 4 specimens the caps rest on two piles (Group A, axis-to-axis distance 300 mm), while in the second and third groups the piles are three and four, respectively (Groups B and C, axis-to-axis distance 400 mm). In each group, the first and third specimens were designed according to the traditional sectional method (reference specimens, with constant depth and lateral shoulders), while the design of the second and fourth specimens was based on the strut-and-tie method (no lateral shoulders; no corners opposite to the piles). Needless to say, the nominal design load was the same within each group. The tests clearly show that cap design based on strut-and-tie systems brings in a sizable reduction in terms of reinforcement amount and cost, accompanied by a less pronounced but still sizable extra bearing capacity.

Khattab Saleem Abdul-Razzaq

Papers

Suggesting alternatives for reinforced concrete deep beams by reinforcing struts and ties

Effect of heating on simply supported reinforced concrete deep beams

Strut and Tie Modeling for RC Deep Beams under non-Central Loadings

Corbel strut and tie modeling – Experimental verification

Design-Oriented Testing and Modeling of Reinforced Concrete Pile Caps