Sustainability Advantage of Post-tensioning in Buildings

We are pleased to announce that we will be presenting the technical session "Sustainability Advantage of Post-tensioning in Buildings" at the upcoming POST-TENSIONING INSTITUTE (PTI) Conference on May 3, 2010 in Fort Worth, Texas.  We hope to see you there.

Structural Engineering - at it's Exciting Best - then & now

Who should design - the Architect or the Engineer?

Albert Speer, Hitler’s Architect of the Third Reich, pointed out in his Autobiography that the Architect was the melding of Art and Science, expressed in the name, with Technician as part of the name.  Architecture at it’s best is Holistic in nature – a Unified Design.

On the flip side, within the Design Professional community, Architects and Engineers tend to see themselves as total opposites (right half brainers and left half brainers).  Whether they believe it or not, this perception is a choice that they have made individually for themselves.  I say that as an Architect and as a Structural Engineer. I am both and, fortunately, I do have both a right half and a left half to my brain, which I see as an advantage.

The reason that Architects tend to be generalists and Engineers tend to be specifists is primary due to the educational system that trains these disciplines.  Architectural Schools actually have classes, whose only purpose is to instill creativity in the students.  Engineering Schools focus on the math.

There is an old joke that says:

“The Architect is someone, who knows a little bit about a lot of things.  He goes on learning less and less about more and more, until he ends up knowing absolutely nothing about everything.

The Engineer is someone, who knows a great deal about a few things. He goes on learning more and more about less and less, until he ends up knowing absolutely everything about nothing.

The General Contractor is someone who starts out knowing absolutely everything about everything, but ends up knowing absolutely nothing about anything, due to the fact that he does business with Architects and Engineers, and

The Sub-Contractor is someone who starts out knowing absolutely nothing about anything, but he never learns anything, due to his persistence in doing business with Architects, Engineers and General Contractors.”

Well I can’t speak for the contractors, but for the Architect’s and Engineers it is an exaggeration of an underlying truth.  And it does not have to be that way, nor has it always been that way.

Structural Engineering is actually a very young profession.  I used to work for Structural Engineers with license numbers in the single digits – it is that young.

The great Architect, Julia Morgan, after graduating from the University of California in Architecture went on to graduate from the Ecole des Beaux-Arts in Paris.  This was an Engineering School.  Like other Architects of her time, she designed the Architecture, the Mechanical Engineering, the Electrical Engineering, the Structural Engineering and the performed the Construction Management.   The fact that she designed the steam heating system and the structural system of the Oakland YWCA, did not seem to negatively impact her ability to create the outstanding Architecture of that Beautiful National Historic Landmark. In fact, I believe it helped, since it allowed her designs to be holistic in nature – a unified design.

It was only over time that these disciplines became separate professions.

When I entered the profession of Structural Engineering in the 1970’s, the great achievements in Structural Engineering were Architectural, and Structural Engineering was an exciting field to enter.

Post-tensioned concrete, with it’s promise of long slender spans, was in it’s infancy. Buckminster Fuller was developing Geodesic Buildings and Tensegrity.  The most popular exhibit at the Spokane Worlds Fair was the American Pavilion – a tent structure.  Oakland California’s Oracle Arena was a ground breaking suspended roof structure, in which the whole building was a celebration of Structural Engineering.  At U.C. Berkeley, T.Y. Lin was experimenting on his dream of a Curved Suspension Bridge.  Thin Shell concrete roofs (domes, folded plates, etc., culminating in the 4 uprighted hyperpolic paraboloid thin concrete shells forming the roof soaring high above San Francisco’s Saint Mary’s Cathedral) was the most popular course in U.C. Berkeley’s Structural Engineering department.  During this period of time, so many great buildings were expressions of the Structure that support them.

On the flip side, it seemed like everyone was writing extremely innovative computer programs (i.e. POSTEN, SAP, HP calculator programs, etc.).

Structural Engineering was an Exciting field to enter. 

Structural Engineers tended to be more generalist than not, willing to try new things.  As an example, Structural Engineer Hugh O’Neil, after a long successful carrier building his Architecture/Structural Engineering practice, in his early 60’s decided to change gears and focus his talents on building a suite of the extremely powerful and innovative structural engineering computer software.  Late in life, he stepped out of his comfort zone, trying something completely new.

So - What happened?

Over the years, Structural Engineering’s focus shifted primarily to mathematics (i.e. strength vs ductility, asd vs lrfd, push over analysis, etc.). While Architects have Heroes (living and dead) who are ALL practicing Architects, designing outstanding buildings, Structural Engineers’ Heroes are almost always College Professors (researchers, who may never have actually designed a building). For many Structural Engineers, being a great Engineer meant being chairman of the SEAONC Seismology Committee.  With exceptionally few exceptions, there are no Structural Engineers that are idolized by fellow Structural Engineers for being Great Practicing Engineers.

This has had a demoralizing affect on Structural Engineers.  Many Structural Engineers have expressed resentment that Architects get the accolades and that the work of the Structural Engineers goes on un-noticed and un-recognized (underneath the skin of the Architect’s wall finish).  But that is certainly not the fault of the Architect.

Over the recent years, there have been major innovations in Structural Engineering, but most of them have occurred in the field of research or manufacturing and with structural materials that are normally hidden under the skin of the building.  Research is great and innovations in manufacturing make money for the inventors, but the effect on elevating the status of Structural Engineering or empowering pride in Structural Engineers is minimal.

Structural Engineers need to think beyond the calculations, beyond the normal ways of designing in every project they do and produce Structural Engineering that CELEBRATES the Building’s Structure, similar to the thin shells and tent structures of 40 years ago.  And we, as Structural Engineers, need to value and applaud these Structural Engineers by name.

To the credit of the Structural Engineers Association, they now present awards recognizing the achievements of practicing Structural Engineers.  It is a great start.

If you value yourself (the Practicing Structural Engineer), others will value you too.

The Structural Engineers of Skidmore Owings and Merrill have shown the way back with Oakland, California’s Christ the Light Cathedral, which is a celebration of the Best of Structural Engineering in Wood Frame.  The structural frame of this building is its soul.  It is what you see and are impressed by.  Bravo to SOM.

Structural Engineers usually tell the Architect what he can’t do.  In the case of Christ the Light Cathedral, clearly the Structural Engineer asked the Architect how he could help realize the Architect’s dream and most likely offered his own suggestions on how to make it better.  A true collaboration – A Holistic Design.

 As much as the Structural Engineer wants to create a Great Structural Design, as much as the Structural Engineer wants to be the equal partner with the Architect in making his dream your own, the Greater the Final Design will be.  It will naturally celebrate the building’s structure and embolden the whole profession.

Structural Engineering is an Exciting place to be – if you care to make it so.

Structural Engineering's Part in Sustainable/Green/LEED Design

Sustainable Design / Green Building / LEED are terms that are becoming a large part, & will become a much larger part, of our profession.  But what do these terms really mean?  What makes a Sustainable Design or a Green Building or a LEED certified project? And how does this affect Structural Engineering?

But first, why should we care?

On average, each American uses their weight in natural resources (food, fuel & materials) on every day.  If every person in the world were to live at our standard (which they are ALL trying to do), we would need 5 planet earths to sustain it.  In the mean time, at our present rate of consumption, we have increased the level of greenhouse gases to the extent that the polar ice caps are melting, we are experiencing violent storms like never before, we have wiped out half of our forests and have already faced the largest extinction of organisms and species since the dinosaurs.

To simply maintain what we have, we ALL need to be taking significant pro-active steps to reduce the impact that we have on our environment.  For us in the Building Design Professions, that means designing Sustainably.

For the sake of the conversation, let’s just use the word GREEN.  The ultimate GREEN building would be one that:

1.     Used very little energy to operate (i.e. My father built his house in 1952 with concrete block “thermal mass” exterior walls, white rock roof, with an attic fan connected to a thermostat to cool the house and a highly efficient regionally controlled radiant heating system).  In modern terms, this could be as simple as installing solar collectors on the roof;

2.     Used very little energy and natural resources to build;

3.     Used waste materials (i.e. flyash) and/or recycled (or recyclable) building materials that preferably came from local indigenous building materials (the cost to the environment in pollution to transport building materials from distant places is antithetical to GREEN).  If you are in the Pacific Northwest, building out of wood makes GREEN sense – it is local, renewable AND in many ways feeds the local lumber economy;

4.     Created little pollution in it’s construction and long term operation (this applies not just to the building, but also to the actual building materials. Manufacturing building materials creates pollution itself – although sometimes for the better good, i.e. the manufacture of the waste product sawdust into lumber, and sometimes not);

5.     Created little or no damage to the local environment (i.e. I remember reading an environmental impact report for a full valley that had been bulldozed to bare earth, that the construction of new housing in this valley would have no negative impact on the indigenous plant and animal life – Heck NO – the bulldozers killed them all already – there were none left to impact);

6.     Utilized the surrounding environment to reduce use of energy in construction and long term use (i.e. My father built his house under the shade of 4 mature walnut shade trees);

7.     Is designed in a way that the Building itself does not create pollution or negatively impact the environment (i.e. new large building projects are in many places that are now required to capture and pre-treat rain water on the site, prior to discharging the water to the Storm Sewer);

8.    Is designed in a manner that the waste products from construction (and demolition) are reduced and/or properly recycled; and

9.    Is designed in a manner that does not negatively impact the surrounding existing buildings or environment.

What a mouthful!!   Is all that possible?  Most likely not – but that is not the point of GREEN design.

Every action has a reaction – that Newton taught us. 

On a reality tv show, they build a shelter with indigenous palm throngs and cut bamboo and ultimately leave a mess that they set fire to at the end of the season – NOT VERY GREEN. 

In cutting lumber, milling lumber, shipping and installing lumber, energy is used and damage to the environment occurs.

It is pretty much a no- brainer to realize that an 80 story building, which requires a 60 foot deep hole in the ground & pilings extending another 40 feet into the ground (forever dedicating this site to this building) and massive amounts of building materials to construct (to the point that it is more expensive to demolish than to build) is on it’s face not GREEN.  In fact, on this basis, pretty much every modern building that we construct is not GREEN – in this Ultimate sense.

But then we can’t all just crawl into our thatch huts.

The whole point of GREEN design is to make intelligent decisions that reduce the impact of Architecture on the environment (in a positive manner) while at the same time increase the efficiency, useability and, in addition, the life span of such buildings.

Within the GREEN community, within Architecture & Mechanical/Electrical/Plumbing Engineering,  what is Sustainable Design is in many cases codified.  Plumbing systems that reduce the use of water, Electrical Systems that reduce the use of energy, Architectural building designs that provide shading, use low e glass, etc.

But for Structural Engineering, there is little specific to point to.  The use of Fly Ash (the waste product of burning coal) in concrete mixes is usually the first thing mentioned, and then the conversation often turns silent.

The Structural Engineer’s job in GREEN design is to:

A.     As much as possible, utilize renewable building materials in their designs;

B.     Recommend and design innovative new or already existing building materials and/or construction methods that meet the goals mentioned above;

C.     Sharpen the pencil and design efficiently.

In recent years, in virtually every building material, there have been great advances in new methods of building. 

Masonry - the use of structural brick instead of concrete block allows you to use less material in construction and cause less damage to the environment in manufacture.

Wood – economizing in material (i.e. using 2x6 studs at 24” o.c. instead of 2x4 studs at 16”) or utilizing new engineered materials (i.e. new glulam beams which have lvl’s as the outer ply’s) or designing with LRFD are just examples of ways to improve the building performance or reduce the use of resources.

Light Gauge Metal Framing – when used as bearing walls in multistory buildings, where concrete or conventional steel frame would otherwise be required, significant reductions of the use of steel are realized, since the partitions do double duty as the structural system.

Steel Frame – the use of tapered beams or girders, reducing the section of the steel to what is actually required, has been a proven method over the years for reducing the weight of the structure and improve building performance.  POSTEN Engineering Systems sells a great program “TaperSTEEL” for this Efficient Tapered Steel design.

Concrete – Post-tensioned Concrete has all but replaced conventionally reinforced concrete structures due to the significant savings of concrete and steel.  But designing with most post-tension programs is inherently inefficient.  These programs use a trial and error method to lead you after a lot of work to a “code compliant” design.  You may never get to an efficient design.  But even an inefficient post-tension design is better than a conventionally reinforced concrete design. 

On the other hand, POSTEN Multistory by POSTEN Engineering Systems Automatically designs (not just a code compliant design) a Highly Efficient Design.  Going further, POSTEN Engineering Systems, with it’s proprietary stress balancing algorithms, will Automatically design the most efficient design possible, and then tell you how much steel was saved in the process.  In addition, POSTEN Multistory will Automatically determine the thinnest section of concrete possible and Automatically design an Efficient design for that thinnest section.  Going for that Ultimate GREEN design, POSTEN Multistory is the only program in the world that will design a Multistory Post-tensioned Concrete Moment Frame Structure.

The opportunities for GREEN building structural design are endless. All it takes is a different Holistic approach to design and a willingness to do it.

Finite Element Analysis versus CONCRETE FRAME ANALYSIS - the cons and PROS

The popular trend in Structural Engineering these days (especially with the BIM’s introduction into the profession) is to use Finite Element Analysis software to design concrete structures, whether conventionally reinforced or post-tensioned.

Is this the be appropriate software to use, and

Can the results be trusted?

When Finite Element Analysis programs were originally developed over 30 years ago, no one presumed that finite element analysis should ever be considered for the design of concrete frame or shear wall structures (with the specific exception of analyzing the in plane and out of plane mohr circle shear forces in concrete thin shell roof structures – a very popular building type at the time). 

Finite Element Analysis was originally developed to analyze steel frame structures, trusses and the extremely difficult to analyze shear forces in concrete thin shell roofs.  For these structural types, Finite Element Analysis has always been a very powerful and appropriate tool.

As powerful as Finite Element Analysis has always been, Finite Element Analysis has significant limitations, which make it unsuitable for the design of reinforced concrete frame and shear wall structures.

1.     Finite Element Analysis programs presume that everything is co-linear and co-planar.  In reference to a concrete structure this means that to design a t-beam properly the slab should be modeled at a separate vertical grid elevation as the beam portion of the t-beam with rigid links installed between the slab to the beam for the full length of the spans (thousands of additional modeling decisions in a typical building) trying to force the beam and slab to bend together instead of apart;

2.     Finite Element Analysis programs presume that the bending of the beams and columns continues to the center of the beam/column joint.  While this is fine for steel construction, it is not fine in concrete structures, where the beam/column joints have real dimensions (i.e. 3 feet x 3 feet) and where the concrete is shearing – not bending.  There are ways to fool Finite Element Analysis Software into thinking that the bending stops at the face of the beam/column joint, but then the shear calculations may not be properly analyzed.  Some software performs this trick well while other programs do it poorly and again we are talking about thousands of additional modeling decisions;

3.      Finite Element Analysis programs presume that everything is perfectly elastic (i.e. nothing cracks – like concrete).  There are ways to fool the program into approximating a cracked condition, but this again requires many additional modeling decisions and special attention to detail;

4.     For approximately 20 years, no Finite Element Analysis program ever claimed to be able to analyze or design concrete shear walls. But then they all claimed that they could.  How do they do it?  They model the wall as a mesh.  The problem with this is that if you model a large mesh and then model a small mesh for the same wall, you will get different results.  At best, this is an approximation.  At worst, it is simply wrong, especially when the expectation of the program is accuracy;

5.     For years, these same Finite Element Analysis programs never claimed that they could design concrete floor slabs, and now they all do.  Same Method – Same Flawed Results; and

6.     If the section properties (shape of the slab or beam) of a beam or slab change as you cross the span, accurately modeling the shape of the changing section is virtually impossible in Finite Element Analysis.  You can make approximations or idealize (I hate that word) an approximate shape, but all this leads to questionable results and in some cases the program just won’t accept the input.

Most importantly, all of the thousands of rigid links, all of the tricks you need to use to fool the Finite Element Analysis program, all of the idealizations of the actual shape of the structure as something else, greatly increase the possibility of error and greatly increase the complexity of the output and overall reduces the reliability of the output.

This is why, back 30 years ago, when the National Science Foundation funded a project to create a Finite Element Analysis program, they also funded a project to produce a Multistory Concrete Frame Analysis program (originally called TABS in it’s 2 dimensional version and ETABS in it’s 3 dimensional version).

ETABS was developed by E.L. Wilson, J.P. Hollings and H.H. Dovey at the University of California at Berkeley as a public domain program under a grant by the National Science Foundation.

The current grandchildren of the original ETABS are the programs ETABS by Computer & Structures, Inc. and ezFRAME by POSTEN Engineering Systems.

The “Concrete Frame Analysis” program was designed specifically to deal with the Unique Characteristics of Concrete Frame and Shear Wall Structures that could not be addressed properly or accurately by Finite Element Analysis.  Those 6 items above, that Finite Element Analysis Software programs are not equipped to properly design, Concrete Frame Analysis programs are specifically designed to deal with, as they are supposed to be designed. 

It is for this reason, that we strongly believe that Finite Element Analysis software should NEVER be used to design concrete frame or shear wall structures.  For concrete frame or shear wall building analysis and design, Concrete Frame Analysis programs like ezFRAME (or ETABS) should be used.

Post-tensioned Moment Frame Buildings - the argument for

Traditionally Multistory Concrete Moment Frame Structures have been conventionally reinforced concrete. Originally this was because of the higher cost of Post-tensioned concrete (as a system) and the relatively low cost of concrete and mild steel. For years most post-tensioned concrete structures were single level concrete podium decks above parking in an apartment complex or in some multistory parking structures. (While there were many multistory post-tensioned concrete structures built in the very early formative years of post-tensioning, this form of construction fell out of favor for many years until the cost of concrete and steel skyrocketed to present levels compared to the post-tension installation cost.) But in both of these podium or parking structure cases, most often in the past, concrete or masonry shear walls were installed to resist horizontal wind or seismic forces. Again, the cost of concrete and mild steel was still low enough to justify a structural system (i.e. conventionally reinforced concrete) that uses a larger amount of steel and concrete.

Now, the cost of steel is very high and the environmental impacts of the manufacture of cement have been demonstrated to be significant.

So, now in the past few years we have seen an explosion of many new multistory post-tensioned concrete buildings. The construction of conventionally reinforced concrete multistory concrete buildings appears to have essentially disappeared.

But, most of these new post-tensioned buildings are still shear wall structures (Not Moment Frame). Why is that? - when the needs of saving materials, reducing the cost of construction and improving the use-ability of the building would indicate Moment Frames?

1. In many cases the design of the post-tensioning is being performed (or controlled) by the tendon installer, not the Structural Engineer or the Architect. The tendon installer has only one agenda and that is the post-tensioned slab. It is what they install and are responsible for. While the engineers that work for the tendon installers tend to be very knowledgeable about post-tensioned slabs, they may not have the appropriate knowledge for the design of the building as a whole. When the tendon installers design the post-tensioned slab, their priorities are not the impacts of the post-tensioned slab on the structure above or below. In their eyes, that is the responsibility of the Structural Engineer of record. In some cases this has led to the failure of the structure through bending of the exterior walls and columns from the lack of coordination between Tendon Installer and the Structural Engineer such that the Structural Engineer was not aware of the secondary moments being applied to the connection between the columns & walls and the floor slabs or the forces being applied to the columns and walls from the shrinkage of the slab. As a result, we have always recommended that the Structural Engineer perform his/her own design of the post-tensioned floor slabs.

This design by the tendon installer leaves only one option for the Structural Engineer of Record & (more importantly the Architect) and that is to design the structure as a Shear Wall Structure. To design the building as a Moment Frame requires that the columns be designed in concert with the design of the floor slabs. It must be a unified design by the Structural Engineer, not something piece mealed. In fact, in our opinion, in ALL situations the time to design the columns is when the slabs are being designed, not after and certainly not before.

In the case of the tendon installer designing the post-tensioned slabs, the Structural Engineer of Record is ultimately responsible for not just the design of the foundation, columns, walls & slab interface (that he/she is being paid for) but the design of the post-tensioned slabs (which he/she is NOT being paid for). If there is a failure in the slab, there will be just as many Attorney’s fingers pointing at the Structural Engineer than the tendon installer.

2. The statement “Shear wall structures is how everyone designs them”. As mentioned above, this is primarily because the tendon installer (who only designs the slab and only cares about the slab, and in many cases uses computer software that is incapable of designing anything but the slab) is putting the Structural Engineer and Architect in a position where a shear wall structure is the only option.

Aside from that, why would you NOT want to design a shear wall structure? The problems created by the existence of shear walls are related to the restrictions on the placement of the shear walls (typically toward the center of the building – avoiding the exterior corners) and the potential for cracks developing in the concrete or masonry wall or post-tensioned slab due to the forces applied to these connections (whether they’re shrinkage related at the exterior of the building or chord forces at the ends of the shear walls). There are many examples of large cracks occurring in the slabs and/or walls from these conditions (that may be compounded when masonry walls are installed in wet conditions).

3. On the flip side, while multistory post-tensioned concrete buildings have been permitted in high wind or moderate seismic regions, until ACI318-05, multistory post-tensioned concrete moment frame structures were not permitted in high seismic regions, like California. ACI318-05 now permits it’s use under certain conditions (i.e. the mild steel is required to essentially resist the full force of the earthquake). As a result, in high seismic regions, the reasons to use post-tensioning in a multistory moment frame structure would be to control deflections. However, in high wind areas battered by seasonal catastrophic wind storms or in some cases ocean wave surges, the survival of the building may depend on the construction NOT including shear walls, but moment frames instead.

In any regard, we believe that in so many cases, a multistory post-tensioned concrete moment frame structure would be the most appropriate design solution.

Here at POSTEN Engineering Systems, we produce POSTEN Multistory, the Only Software in the World that designs Multistory Post-tensioned Concrete Moment Frame Buildings (for Wind or Seismic Forces utilizing first or second order analysis – with P-delta effects).

Partially because of the much higher level of engineering required to perform this type of design in the first place, POSTEN Multistory is the Most Comprehensive, Powerful, Efficient – as well as Easy to Use Post-tensioned Concrete Design Software.

Additionally, POSTEN Multistory is the only Post-tensioned Concrete Design Software that produces Sustainable designs along with the documentation of material savings required in LEED projects.

LEED & Post-tensioned Concrete - A Perfect Match? - only with POSTEN Multistory

Background:

In a typical 150 ft. x 300 ft. Post-tensioned Concrete Slab, if you could reduce the thickness of the slab by 1”, you would reduce the CO2 pollution produced by the manufacture of cement by the same amount of CO2 produced by 4 automobiles in one year.

Imagine, if at the same time, you could reduce the amount of steel used in that thinner slab, Saving Resources and Energy Use - All the way around.

Imagine further that since that slab is thinner, how much more efficient the design is. Seismic and Wind forces reduce with a lower building height. Or the Architect can maximize the use of the building within the height limitations, set by zoning requirements.

Imagine that the building costs less to build; and

Imagine that Structural Engineering Design fees are also lower.

The Usual & Wrong Way:

For Structural Engineers to design Green, normally means Sharpening the Pencil, using newer more time consuming design methods, using very expensive software packages and, in some cases, new structural systems with limited or no performance background.

Design Services tend to be Costly,

Construction Costs may be high,

Testing and Inspections may be extensive.

With new untested systems Construction Liability may go up.

Adequate Documentation for LEED may be challenging.

AND YET

Sustainable Design produces more efficient buildings and does not have to cost more.

The POSTEN Multistory Way

Taking a Fresh Look at LEED & Believing that Sustainable Design can be done Economically.

We developed Innovative Design Procedures for Post-tensioned Concrete Design that:

Reduce Pollution (CO2 gases), Use of Resources & Energy Use from Construction;

Increase the Efficiency & Use-ability of the Building;

Enable the Architect’s Creativity;

Reduce the Cost of Construction; & Save on Design Fees.

For LEED projects, Documentation is Automatic.

We believe there are also additional Savings to be found in the upcoming Cap & Trade Legislation.

How Do We Do It?

To establish a base line, we produce a quick Conventionally Reinforced Concrete design using our program CONCRET.

Then, we produce a Post-tensioned Concrete Design with POSTEN, which is Efficient (as opposed to our competitors’ merely code compliant designs). Utilizing POSTEN’s proprietary “Slab Optimization” algorithms this run ALSO makes sure that the thinnest section of concrete slab possible is designed.

Then using POSTEN’s proprietary “Stress Balancing” algorithms, we then AUTOMATICALLY produce the Most Efficient Design Possible. This output also Automatically prints out how much steel is saved in the process.

At each stage, POSTEN Multistory produces Batched Tendon & Rebar Schedules, documenting the amount of steel used (i.e. saved) along the way.

All of this is done (including the documentation for LEED) in a FRACTION of the time that our competitors produce an inefficient, simply code compliant design.

Sustainable Design - the Challenge for the Structural Engineer

While Sustainable Design is fairly clear cut for the Mechanical/Electrical/Plumbing Engineer (simply selecting the appropriate MEP systems, which have typically demonstrated good performance) and while

Sustainable Design opens up wonderful opportunities of creativity and innovation to the Architect (basically allowing the Architect to practice in the way that he/she always dreamed of doing),

for the Structural Engineer it typically presents hard choices, increased work effort, use of often risky construction procedures, use of ("granted" innovative) new construction methods that lack a proven track record or significantly increase the cost of construction and/or (very importantly) significantly increases professional liability.

It doesn't have to be that way, but it most often is.

What is needed, is an Holistic Approach to Structural Engineering and Sustainable Design, looking at the process in a different way, understanding the materials and how they perform.

We presently have the tools necessary to save Energy and Resources in our Structural Designs with the present design methods and materials that currently exists.

In future blogs, I will discuss the opportunities and risks of Sustainable Structural Design using the different construction materials and how we at POSTEN Engineering Systems believe that we have accomplished Sustainable Design with Post-tensioned Concrete.

LEED & Post-tensioned Concrete - A Perfect Match

Welcome to my first blog.

In upcoming blogs, I will discuss the advantages of using Post-tensioned Concrete design to achieve Sustainable Designs and how to achieve that.