In seismic areas, ductility is an important factor in the design of high strength concrete (HSC) members under flexure. In order to investigate this, here in this study, eight HSC beams with different percentages of  r & r’ were cast and incrementally loaded under bending. During the test, the strain on the concrete middle faces, the tension and compression bars, and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior, and especially the ductility of the HCS members are more deeply reviewed. Also a comparison between theoretical and experimental results is reported here.

With the technology development on the compressive strength of concrete over the years, the use of high strength concrete has proved most popular in terms of economy, superior strength, stiffness and durability due to many advantages it could offer. However, strength and ductility are inversely proportional. High strength concrete is a brittle material causing failure to be quite sudden and 'explosive' under loads. It is also known that true axial compression of structural concrete columns (axially compressed) rarely occurs in practice. The stress concentrations caused by the eccentric loading further reduce the strength and Ductility of high strength concrete. This paper presents results of testing eccentrically loaded Columns externally wrapped with different types of materials. The experimental results show That external reinforcement can enhance the properties of high strength concrete columns.      

High strength concrete (HSC) provides high strength but lower ductility compared to normal strength concrete. This low ductility limits the benefit of using HSC in building safe structures. This means that a designer should be aware of limiting the amount of tensile reinforcement to prevent the brittle failure of concrete. Therefore the full potential of the use of steel reinforcement cannot be achieved. This paper presents a method to prevent the brittle failure of concrete beams. Five beams made of HSC were cast and tested. The cross section of the beams was 200x300 mm, with a length of 4 m and a clear span of 3.6 m subjected to four-point loading, with emphasis placed on the midspan deflection. The first beam served as a reference beam. The remaining beams had different tensile reinforcement and the confinement shapes were changed to gauge their effectiveness in improving the strength and ductility of the beams. The compressive strength of the concrete was 85 MPa and the tensile strength of the steel was 500 MPa and for the stirrups was 250 MPa. Results of testing the five beams proved that placing helixes with the right diameter and pitch in the compression zone of reinforced concrete beams improve their strength and ductility.

HSC has great mechanical properties and durability and is one of technology developments in concrete. This type of concrete has high cohesion, compressive strength and low water to cement ratio and permeability which results to high durability. HSC is a cemental composite product that contains optimum amount of fines and with a water to cement ratio (W/C) less than 0.25.High performance concrete compared with normal concrete has a structure with discontinous pores that results to high performance and minimum water permeation to concrete. HSC's admixture contains water, silica fume, cement, fine sand, super plastisizer and rock powder like quartz that in this study are used of Iran’s local materials. In this study 10x10x10 cube specimens were made and evaluated. Compressive leads to failure were applied to concrete specimens. The purpose of this study is investigation of quartz powders increase in HSC. Results shows that concrete compressive strength with 11% quartz powder is the highest and increase in quartz powder lead to brittle pre failure and explossive failure of concrete specimens. Other considerations shows that increase of quartz powder leads to more crack on concrete and it is suggested to use fibers to prevent more crack in this type of concretes.

The use of unbounded tendons is common in prestressed concrete structures and evaluation of the stress increase in unbonded tendons at ultimate flexural strength of such structure has posed a great challenge over the years. Based on the bending experiment for two-span continuous post-tension beams with unbounded tendons and externally applied CFRP sheets, the monitoring of the stress increment of unbounded tendons is made in the loading process. For these aims, in this paper there are presented results of two continuous un-bonded post-tensioned I-beams were cast with high strength concrete (HSC) and monitored by electrical strain gauges. The beams are made of which are compared with the theory proposed by different codes. The results indicate that the ACI 318-2011 provides better estimates than AASHTO-2010 model whereas this model provides better estimates than BS 8110-97. Comparison of experimental ultimate tendon stress increase of strengthened and non-strengthened beams casted with HSC indicates that increase in tendon stress at an ultimate state in strengthened unbounded post-tensioned beam is lower than non-strengthened unbounded post-tension beam casted with HSC.

For the analysing purpose of the High Strength Concrete (HSC) box columns first, by two methods (i); by solving the governing differential equations of a thin-wall concrete section which act similar to an orthotropical plate and (ii), by the strain energy method the critical load of orthotropical plate was calculated. Then, by investigation, it was concluded that the local buckling is not an important aspect for the ratios of h/a> 0.06 ( the ratio of thickness to , the larger dimensions, of the section) and therefore the sections failure will be occurred while the load is reached io its ultimate capacity i.e.,prior to the local buckling.a simple and easy method was adapted to analyse and design the HSC box columns then, by use of this method and a computer program written (MATLAB Package)the interaction diagrams of such sections were plotted. Now, with availability of the setype of diagrams, the non-dimensional diagrams were plotted too. Based on the nondimentional diagrams it was concluded that, by availability of only one type of these diagrams, for example, the interaction diagrams for solid sections having HSC and applying the ratio of Ah/a (the ratio of area of box section to that of the solid section) to its interaction diagrams, the axial load and bending capacity of box sections can be determined quite easily.

The remarkable ability of stem cells to renew themselves and to give rise to specialized cell types has raised huge hope for their clinical application. However, our limited understanding of the mechanisms that regulate stem cells poses a substantial hurdle for their clinical use: Since we know relatively little about how stem cells function, it is not surprising that we also struggle in growing them in a cell culture dish; most likely an important requirement for stem cell-based therapies.I believe that one cause of this problem is the inadequacy of tools that we have available to study stem cells at the single cell level. That is to say, even after careful prospective isolation based on immunophenotype, individual stem cells of a well-defined population behave highly heterogeneous in culture: some cells divide rapidly and others more slowly; some self-renew while others begin to differentiate; some can give rise to more lineages than others, etc. Because of this inherent variability, population-based studies of stem cells are essentially ‘black boxes’ and often unable to accurately address key biological questions, such as defining the discrete development steps from a single stem cell to a complex population of specialized cells (lineage development), or elucidating the mechanisms that regulate symmetric versus asymmetric divisions of stem cells.In this talk I will highlight recent efforts in my lab to address this important problem by developing and applying microfluidic technology to sequentially capture single HSC after multiple divisions to assess their fate, and in particular the symmetry of division, by multigene single cell qRT-PCR.