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I don't like the all or nothing approach of the special confinement requirements in AS3600. I agree with the no special requirements under fc=50MPa and a confinement of 0.1*fc above 0.75*phi*Nuo. But I think it should have an intermediate confinement requirement between these two values of...

Hi I got a question/proposal similar to the one posted recently in thread744-371141 about the requirements of AS3600-2009 and trying to bring some simplification to them. I think it is sufficient to anchor at least V*/(Cot(theta_v)*phi) at the centre of bearing with a minimum of 30% of Ast...

What is everyone's approach to RC cores. I normally build up the core in RAPT and design for Axial Load and Bending. I change the tension controlled and compression controlled reduction factors down to 0.4 and 0.3 except when I provide compression ties to the vertical reo, then I keep the...

I know ETAB’s 2013 has many bugs, but has anyone had troubles with running a response spectrum analysis to AS1170.4? The analysis of my model is fine, mass, stiffness, natural frequencies all seem fine but when I perform a response spectrum analysis I am getting base shears around 4 to 5 times...

Hi I just wanted to ask this one here before I put it on the broader "other topics" posting. For fire separating walls in frame construction for town houses, who is responsible for the final sign-off for BCA compliance? Would that inspection be performed by the building certifier or other fire...

Hi I am providing a work method statement for a peno in a bonded PT slab where I need to cut thru a tendon for a 5' peno. It is bonded and I am guessing that once the tendon is severed that it will become de-stressed for a transmission length back towards the tendon anchorage. I have specified...

Hi Does anyone know the origins of why the development length has a 30% increase for walls built using slipform system and why it would be different than a conventionally formed wall? This is noted in AS3600 clause 13.1.2.2 Thanks

Hi I have requested mill certificates for the PT strands used on a project. The mill certificates came back from Tianjin stamped saying that they have been tested to and conform with Australian Standards. Should I be concerned with the quality of product used? I have heard stories from fellow...

Hi I have a temporary steel column (310UC158) that will need to be removed in the future. The column we be approximately 2,000kN (450kips) in compression and I am expecting the structure above to deform approximatley 2.0mm (1") when the column is removed. How would the column safely be removed...

Hi Guys I am using a wall as a deep beam and engaging the slabs as flanges. Is the theory the same for longterm deflection calculations for a deep beam as it is for a shallow flexural member (span/depth=2 ; span/thickness=40). I can find plenty of information regarding the flexural and shear...

Hi When transferring a large shear force across a vertical construction joint, is the ACI shear friction method an appropriate shear model for design. I have compared different scenarios using the shear model for beams and have found that a typical situation (0.25% flexural reo and Asv/s=4.52)...

Hi Guys I'm unsure here about what torsional stiffness to use for a slab using RAM Concept. The options are: 1. Two-way slab - (KMrs is set to 100%, when I perform the analysis the results give 11.4mm longterm deflection). 2. No torsion two-way slab - (KMrs = 0.1%, longterm deflection =...

Hi I have a column that for one reason or another has insufficient cover to the reinforcement. I am saying that it is non compliant because durability, fire rating and strength are compromised. The cover required is 1-1/2" and the as built cover is 1/2". They are not going to like it when I...

How are the reverse curvature radii of tendon profiles detailed on engineering drawings. I commonly design 70x19mm ducts with a reverse curvature radii of 2500mm but do not detail this with tendon profile points or cover it in the post-tensioning notes. Is it that a steel duct cannot be...

Hi guys What is everyone's opinion about moment transfer thru a slab-wall connection using either threaded reinforcement inserts (pull-out test certified to exceed 100% of the bar capacity) or proprietary cast-in pull-out reinforcement systems. I am happy when using cast-in U-bars or L-Bars...

Hi guys I am providing the design work for a residential renovation work where I need to excavate a 4' by 8' trench 9' deep. I am only 4' from the property boundary. My first thought was to use a prefabricated propriety trench box but because of site limitations it was requested to shore the...

Hi Guys Does anyone have any tricks for designing slender concrete columns where the Le/r ratio starts getting higher than 50. I am noticing a large fall away in strength for columns with high Le/r. Does anyone know how to reduce the effective length factor, I normally use a ke=0.85 for...

Hi I keep noticing on drawings that it says "Distribution Reinforcemet to be N12-300". That is 12mm bars at 300mm centres(1/2" bars at 12"c/c). But I cannot find anywhere else on the drawings or specifications where it says what distribution reinforcement is or where it goes. Is this...

Hi guys I have a question regarding crack control for flexure in prestressed slabs by limiting the increment in steel stress near the tension face. My code requirements limit this increment in steel stress for both bonded tendons and conventional reinforcement to 200MPa (29ksi). Is this to...

Hi guys Has anyone got any typical details for a concrete slab half joint. I know how to design corbels and nibs by strut-tie and detailing bearings but I just wanted to know if there is anything special that I need to look out for. The slab is rather large between permanent movement joints...