Experimental study on repeatedly loaded foundation soil strengthened by wraparound geosynthetic reinforcement technique

In the recent past,the potential benefits of wraparound geosynthetic reinforcement technique for constructing the reinforced soil foundations have been reported.This paper presents the experimental study on the behaviour of model strip footing resting on sandy soil bed reinforced with geosynthetic in wraparound and planar forms under monotonic and repeated loadings.The geosynthetic layers were laid according to the reinforcement ratio to minimise the scale effect.It is found that for the same amount of reinforcement material,the wraparound reinforced model resulted in less settlement in comparison to planar reinforced models.The efficiency of wraparound reinforced model increased with the increase in load amplitude and the rate of total cumulative settlement substantially decreased with the increase in number of load cycles.The wraparound reinforced model has shown about 45% lower average total settlement in comparison to unreinforced model,while the double-layer reinforced model has about 41% lower average total settlement at the cost of approximately twice the material and 1.5 times the occupied land width ratio.Moreover,wraparound models have shown much greater stability in comparison to their counterpart models when subjected to incremental repeated loading.

Experimental and Theoretical Study on the Flexural Behavior of Recycled Concrete Beams Reinforced with GFRP Bars

This paper experimentally investigated the flexural behavior of reinforced recycled aggregate concrete(RAC)beams reinforced with glass fiber-reinforced polymer(GFRP)bars.A total of twelve beams were built and tested up to failure under four-point bending.The main parameters were reinforcement ratio(0.38%,0.60%,and 1.17%),recycled aggregate replacement ratio(R=0,50%,and 100%)and longitudinal reinforcement types(GFRP and steel).The flexural capacity,failure modes,flexibility deformation,reinforcement strains and crack distribution of the tested beams were investigated and compared with the calculation models of American code ACI 440.1-R-15,Canadian code CSA S806-12 and ISIS-M03-07.The tested results indicated that the reinforcement ratio has great influence on the ultimate load,crack width and deflection of GFRP-RAC beams,the recycled aggregate replacement ratio has little influence on it.However,it was found that the reinforcement ratio has no obvious influence on the cracking load which was only related to the recycled aggregate replacement ratio.The average cracking load decreased by 5%and 15%as the recycled aggregate replacement ratio increased from 0 to 50%and 100%.For the steel-RAC beams,the ultimate load was found to be about 1/2 of the ultimate load of GFRP-RAC beam under the same condition and the trend of strain,deflection and crack width were different from GFRP-RAC beams.This is due to the different material properties of GFRP bars and steel rebar.On the other hand,the calculation results showed that ACI 440.1-R-15 and CSA S806-12 underestimated the ultimate load of GFRP-RAC beams.Moreover,the deflection prediction of GFRP-RAC beams by CSA S806-12 is relatively accurate compared with ACI 440.1-R-15 and ISIS-M03-07.As for the prediction of crack width,the results of ACI 440.1-R-15 prediction were in good agreement with the experimental results at the ultimate load,with the average value of 1.09±0.28.

Punching of reinforced concrete slab without shear reinforcement: Standard models and new proposal

Reinforced concrete(RC)slabs are characterized by reduced construction time,versatility,and easier space partitioning.Their structural behavior is not straightforward and,specifically,punching shear strength is a current research topic.In this study an experimental database of 113 RC slabs without shear reinforcement under punching loads was compiled using data available in the literature.A sensitivity analysis of the parameters involved in the punching shear strength assessment was conducted,which highlighted the importance of the flexural reinforcement that are not typically considered for punching shear strength.After a discussion of the current international standards,a new proposed model for punching shear strength and rotation of RC slabs without shear reinforcement was discussed.It was based on a simplified load-rotation curve and new failure criteria that takes into account the flexural reinforcement effects.This experimental database was used to validate the approaches of the current international standards as well as the new proposed model.The latter proved to be a potentially useful design tool.

Flexural and longitudinal shear performance of precast lightweight steel-ultra-high performance concrete composite beam

In this study,the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete(UHPC)composite beams are investigated,where a cluster UHPC slab(CUS)and a normal UHPC slab(NUS)are connected to a steel beam using headed studs through discontinuous shear pockets and full-length shear pockets,respectively.Results show that the longitudinal shear force of the CUS is greater than that of the NUS,whereas the interfacial slip of the former is smaller.Owing to its better integrity,the CUS exhibits greater flexural stiffness and a higher ultimate bearing capacity than the NUS.To further optimize the design parameters of the CUS,a parametric study is conducted to investigate their effects on the flexural and longitudinal shear performances.The square shear pocket is shown to be more applicable for the CUS,as the optimal spacing between two shear pockets is 650 mm.Moreover,a design method for transverse reinforcement is proposed;the transverse reinforcement is used to withstand the splitting force caused by studs in the shear pocket and prevent the UHPC slab from cracking.According to calculation results,the transverse reinforcement can be canceled when the compressive strength of UHPC is 150 MPa and the volume fraction of steel fiber exceeds 2.0%.