Thracian Cult Complex, Starosel

From landing in Sofia, to Plovdiv, and then back to Sofia, we have witnessed and experienced many different and wonderful sites in Bulgaria. On our way from Plovdiv to Sofia we took a one night rest in the town of Starosel, but not before spending some time at our next site, The Thracian Cult Complex of Starosel!

This ancient cult complex is the 2000 largest of its time, which dates back to about five to four centuries before Christ. Along the southwest portion of the complex there is a break on the wall where the Thracians created a winery. The winery has a capacity of 6kL. That’s a lot of wine but if you think back, the Thracians were well known for their heavy drinking habits.

The temple itself consists of two chambers: the outside of the temple is made up of mostly granite, while the inside chamber is made of volcanic tuff. It’s important to note that material for the temple was not local. The quarry for the stones is about 30km from the temple. Moving such heavy stones must have not been an easy task back then. By itself, the stone door to the inside chamber of the temple weighs 750kg. It was carved to have a steep framing and a locking mechanism. The stones were all mostly joined with the use of iron and lead. Archeologists found the Cult Complex as is except for the copula inside which was restored.

Leading into the inside chamber are three steps. Each step is meant to symbolize the unity between the earth, the sky, and the underworld. Just like in Mt. Perperikon, the steps were believed to be profusely high so those going inside would bow on their way up. The door framing consists of oval shapes all around to symbolize the beginning of life.

Inside the copula of the temple forms a perfect circle, 5.4m in diameter. Some of the stones were painted blue, red, and black used again to symbolize the sky, the earth, and the underworld, respectively. In total there are ten pilaster columns around the circumference of the copula, though the Thracians put them in only for aesthetic reasons. The recent renovations were done on 14 of the 17 total rows leading up to the center stone, otherwise known as the keystone. The retaining walls outside the whole complex were covered.

Historians believe that the copula was opened during the solstice, and astronomers have confirmed that placing yourself in the with the top open would shower you with the sun during the summer solstice. During the winter solstice the sun rays would shine starting from the entrance and end in the middle of the temple. Unlike other Thracian sites, the Cult Complex was specifically a temple for rituals most likely for the sun goddess, which represented fertility. Since Thracians believed that life started after death, rituals would be held at the temple when their leaders died. At that time though the Thracians would burn their dead unlike in Mt. Perperikon where we saw tombs.

We walked around the perimeter of the complex where we found the winery. Looking out into the valley you notice several hills all around. History says that when the Thracians would flee they would cover their temples with earth to make them seem like natural hills. Archeologists believe that all the surrounding hills around the complex have the high possibility of being more ritual temples.

(P.S. – Pictures to come!)

Mt. Perperikon

Hi there. My name is Michael Mondragon and I am a senior at Syracuse University in the civil engineering program. As you have probably read from my previous classmates, we are on an experiential trip in Bulgaria. We visited a total of 10 different sites, both current and historical. One of those historical sites was hiking our way up Mt. Perperikon.

After a long two hour drive through many twists and turns, we finally arrived at our starting point. We had with us a guide that gave us important historic information along the way.

The first fun fact was about the mountain itself. It used to appear similar to the adjacent mountains, with trees, shrubs, and fauna all around it. Millennia ago it was found by the “Stone People”, which due to their animistic beliefs chose the mountain as a holy ground to carve out the faces of animals in the stones. Mt. Perperikon is made of a soft, brittle stone. Knowing this the “Stone People” were ingenious enough to use granite, a stronger stone, as a carving tool. Along the path where the carvings were located they also carved out a set of stairs from a small opening. Soon after carving out the mountain, the “Stone People” seem to have just vanished.

For years people had known about the mountain, but never had been anyone to officially explore it. The story goes that Prof. Nickolay Ovcharov, an archaeologist from Bulgaria, travelled by horseback through the many villages surrounding the mountain to record the various stories the people had about the mountain. Ovcharov discovery of the archeological site within the mountain is what has led current generations to uncover the surrounding area of the mountain. He is know as the Bulgarian Indiana Jones.

Roughly about 2000 years after the “Stone People” vanished, the Thracians came upon the face of the mountain. Witnessing the massive animal carvings on the mountain, the Thracians saw it as a sign from the gods to make the mountain their new home. The opening was widened by the Thracians, and the steps were made wide and high enough so when people were to climb the stairs it would appear as if they were bowing along the way.

Hiking further up the mountain we found remains of where doors used to be, ancient drainage systems, the temple of Dionysus, rooms in houses, and tombs. The Thracians believed in celebrating the dead rather than the living. They knew that life was hard, so at birth they would cry and at death they would drink to celebrate a person being put out of their misery of the world. Speaking of drinking, the Thracians were know to be heavy drinkers, hence their worship of Dionysus, the god of wine. Along the mountain path we encountered what used to be their wine storing area.

Finally, after a long hike up the mountain we had reached the top. From there we got a great view of the surrounding valley and nearby towns. Mt. Perperikon wasn’t just the home to the Thracians. Along the years it has belonged to those who conquer the land. The timeline consists of Thracian, Greek, Persian, Roman, Byzantine, Bulgarians, Ottoman, Turks, Soviet Union, and finally returning to the Bulgarians.

Our last stop before making our way back down was climbing inside the tower for a final group picture!

(P.S. – Pictures to come!)

Oil Depot Renovation Project

Hello all, this is Arthur again.  We went to the oil depot. The owner of the depot is a successful engineer and great business man. Due to the recent market competition, the owner of want to recover one of the old station they abandoned for three years and renovate the systems. It was started in January and has most of the work. We get a chance to take an adventure going into one of the new tanks almost finished.

Differed from most infrastructures, the petroleum tanks do not have a foundation. The tank was sitting on a solid concrete platform. Between the concrete and tank, there is a layer of sand. So when the tank was full of petroleum or expand during summer, the bottom of the tank will bend without damage of the tank. And the bottom of the tank will The tank build from pieces of 5 cm thick iron plates. Due to the nature of the thermal expansion, they would expand under long time sun exposure and shrink during the winter. During the summer, they will cool the tank using water spray from outside of the tank. The water stored in a reservoir and supplied from the blue water line. The tank is different in the States which we would have to use concrete double walls with a positive separation to prevent any environmental hazard.


The Orange( red ) line connected to the tank is for emergency fire extinguishers by spray foams. Although there is never a fire accident happened on the site, the owner still needs to upgrade the lightning system. The grounding line from the Lightning system would be the only connection between the tank and soil.

During the 1970s oil crisis, the former owner of the station come up several irrational solutions to deal with it. One of those solutions is by adding more water into the tank to dilute the petroleum. These unethical methods only bring a short term profit, since then the tank was oxidized critically because of the water. Therefore part of the renovation is to clean up the rust and apply a new layer of Epoxy inside of the tank. Epoxy provides a great isolation metal coating.


The owner of the oil depot showed us a critical section been recovered. (See the wrinkle on the tank) The specific heat of the iron is about one tenth of the water. These iron tanks naturally expand after long exposure to the sun. Also, it would shrink during the winter. The iron plates fatigued after years and part of the tank failed and bent inward permanently. What they did is put on three support beam to force it rebound and prevent further damage.


The owner always put the customer as his priority. He paid million dollars to renovation. The petroleum supply is fully computer controlled the unmanned system to shorten the time and precisely control the supply. That would bring up the efficiency of the petroleum distribution lines.  Besides, they also restart the petroleum recycling system. It is a machine which would filter the gas from the fuel tanker to capture any leftover petroleum from the gas stage. Although the owner has to pay more than what would he gain from recovered gas, he still willing to do so in the matter of sustainable development. He also utilizes geothermal bump in the new office.

Single Family Houses, Marinski Ltd.

Hi, this is Arthur again. We went to a privately owned site in an upscale neighborhood on Tuesday. The whole project actually contains two individual houses. One of them just finished up with the foundation. The other one is preparing for pouring the beam on the second floor. In this blog, I will continue to compare the different methods being used for the construction management and engineering in practice within different countries.


First, I want to introduce the owner of the company, Marinski, and talk about what he does differently in the field of construction management (CM) from the States and China. Marinski has a high criterion of his project, dedicate in the projects he does and takes care of his employees. He would do those projects he likes. He loves small size crew of 60 including the construction workers and only takes few projects at same time.  He trains each worker by himself and keeps them as full-time employees. He offers them a one-month break during the new year on top of their annual vacation.  Similar to the States, nobody works during the weekends. It’s different in China, construction worker usually has to work every day except few days’ vacation for the Chinese New Year. Employees in Marinski Ltd. get paid well. They get paid for each stage they finished as an incentive. We would never have that in the States. Marinski also invented his own management software to tracking the materials and equipment in the warehouse. Bulgaria does not yet have a reliable CM software, such as the Procore we often use in the States.

In the construction site, safety is always the first concern. However, in the Marinski Ltd, they only had one accident in the past ten years. One the worker got into a car accident on the way back home. In Bulgaria, the company takes all the responsibilities for anything happens to the employees during the transportation to the work and back home. The company also provides steel-toe shoes and hard hats, as well as daily safety instructions. When the temperature rises up to 35c any exterior constructions has to stop. Unlike in the States, we would continue the construction but offer more breaks during the work. However, the staff work with the concrete did not have their mask on, which is required in the States. Also, they did not have the protect from the height, which is required in China. We would have a decorated wall covered the construction site, and cover the building with a special polymer net.  Not only for the protection of the construction workers falling down, but also prevent anything drops from the height to hit anyone else.

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Now, I will introduce the project we visited. The owner of the house want wants the Marinski Ltd to help him building two additional houses for his child on his land. Similar to the most Europian and Asian Country, it is really common in Bulgaria, that parents would take care of their children’s houses and they usually live close to the family, which is not typical in the States. The project involves massive concrete and brickworks, which differ from the typical wooden structure from the northern America. One of the reasons is the typical timber produced in Bulgaria is too soft to support the loads.


One interesting feature is that the project was enclosed by planks with dozens of nails on it.  Those nails were not placed randomly. They represent the ground level and the orientation of the columns. Those magic nails were placed by geotechnical engineer and surveyor after excavation. They would connect each two pairs of nails by orange wire, and each cross of two wires are the center of a column. Therefore, the positioning and leveling of the foundation and columns are easily done. In China, survey usually would come after excavation and label the center of the piles. The contractor would trust the drillers do the work, most of the time the error is negligible. In the States, Caterpillar invented Terrian™ and ACCUGRADE™ systems for drilling and excavation.  It using GPS, GNSS, laser and ATS technologies to precisely control the process and minimize the degree of accuracy, meanwhile increases in productivity up to 40 percent.

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Addition to the magic nail they used, they also have some magic joint connect the steel forms for the foundation. There are four joint inserted between two feet long steel plates and joined by huge bolts. Therefor the form would firmly connected and minimize any displacement or potential failure during the vibration process. The joint will leave inside of the concrete, and the workers will bend it to the side and cover with another layer of stucco.

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EU has very strict regulations on the new buildings under constructions. For the exterior walls, the minimum width is 35 cm which is equivalent to 14 inches. And the interior wall has to be wider than 15 cm. Marinski recommended to his client use thicker bricks for the interior too for the best thermal insulation. The concrete they used is C20_25, which has a bearing capacity of 3600 Psi. That is similar to what we use in the States.


Overall, the Marinski Ltd does a great job in the construction. Especially, on the safety and some unique construction methods they used are practical in the States and China, such as the magic nail. I would like to implement those into my future career

Starosel Winery


                Rachael back again!  Today’s adventures led us to a winery…. so that begs the question: Does this post belong here or the food page?  Read on to find out why this post is here and not on the food page!

              When in the wine business, you must be prepared to invest a small fortune in land, facilities and equipment before seeing a return.  At the Starosel Winery, they thought ahead and solved a very troublesome problem in a very unique fashion.  In one of the two large fermenting rooms on site, they installed a removable roof structure.  This will allow for them to remove the roof when they need to remove/ replace any of the very large fermenting vats.  They designed a reinforced concrete structure as the facility and literally placed a wooden, truss frame roof on top of concrete pillars.  They secure the roof to the concrete columns with removable bolts.  And since wood is a relatively lightweight material, there is no problem removing it when they need to get machines in to access the large vats.DSC_0859 

                There was not really anything spectacular about the actual design of the wood frames and the trusses; where the ingenuity and beauty of the work is through its purpose.  Many people would build the bones of the structure, install the equipment and then install the roof, never thinking ahead of how the client’s needs might change throughout the course of the life of the building.  However, whoever designed this was thinking ahead and foresaw a problem if they ever needed to replace a vat due to defect or even age and wear and tear.  As engineers, our clients may not always be inclined to think ahead and it is part of our responsibility to think of all possible issues they may have and make suggestions on how to build them a structure that fits their present and future needs.DSC_0861 

                I am not entirely sure the cost of removable roof and if it was more expensive to do this way as opposed to an attached roof, I am not sure how much more expensive it was.  However, in my opinion it was well worth the money because it saved them from major headaches down the road. 


Gerbera Ltd. ~ High Rise Construction

              Rachael here!  Today we met with a man that could be considered a developer.  He buys land and builds mixed use high rise buildings under the business of Gerbera Ltd.  They usually contain commercial stores at the ground level with basements for the stores use and condos on the remaining floors.  The number of floors ranges, we saw the construction of a twelve story mixed use high rise.  Once he is done building the structures, he will sell each individual space to a company or family, however he fronts all the money himself first.  In this way, he is essentially the owner and sells his property.  At the beginning of his business, when he did not have such capital, he would have the eventual owners pay in increments beginning at the design phase all the way through to the signing of ACT 16 (certificate of occupancy). 

                He has a unique way of organizing and operating his business.  First, all the construction crew members are his own employees and he groups them into specific jobs.  There will be a crew that does all the ground zero work (up until the ground level), another group that does floor slabs, another that does stucco, etc.  And he will not pay them until 100% of the work in that building is completed.  In handling it this way, he has found that the groups push one another to work efficiently and to stay on schedule because if one group is going slow, then the other group cannot start their job and therefore they cannot get paid.  He also keep different projects at different construction phases.  One building will be at the ground zero phase, another at the floor slab phase, another at the stucco phase, etc.  This allows for there to always be at least one complete team working at all times.  Usually they start one building and then the ground zero crew starts another and so on.  There is one crane that is set on railroad tracks and is used as the crane for all the different buildings in the lot.  In this fashion it is very efficient that the crane does not have to be repositioned for every building.  He has about 20 high rise structures being constructed at one time.  The only job that he contracts out is the roofing work because that is a very delicate and involved process.  DSC_0621

                Since it is high rise building, the process of construction can take a very long time.  There is foundation work, column work, floor slabs and a great deal more area to construct.  Gerbera Ltd has come up with an ingenious way to save time.  They call it a drawer system.  It is where they frame out a floor slab, pour the slab, wait the 11 days to get early strength, then slid the forms out with a crane and place the forms (still intact and constructed) on the next story.  They entire process takes about 14 days and therefore they are able to pour two stories a month.  This is possible because they make each floor a beamless slab and if they do need a beam, they invert it.  This requires more reinforcement but it saves time so the cost more than likely balances out.  They have no way of making the columns more efficient; they must have two columns that run the entire height of the structure in both directions to help brace the system since it is not a steel braced structure.  DSC_0619

                Another cool feature of the buildings is that they keep a 20 cm gap between each and fill it in with light weight foam to protect against earthquakes.  Therefore, each building’s foundation is independent from the buildings adjacent and in the event of an earthquake, all the buildings would move in the same direction but they would be independent from each other. 

                We also visited a concrete plant and were able to see the operating room and stockpiles of materials.  This particular plant had 10 recipes that varied for use like foundation, walls, high strength, etc.   They are also able to create a custom recipe based on client request and in that event they would make a sample batch and test it before sending any concrete to the site.  They have their own testing facility at the plant and they make cubes (not cylinders like the US) and cure them in a lime bath.  They also do breaks at 7, 14 and 28 days.  They also test once daily each class of concrete they make.  The density of their concrete is usually 2.3 ton/cubic meter.  Their machines can mix 3.5 cubic meters of concrete at a time, the trucks can carry between 7.5-9 cubic meters and they maximum productivity of the plant is 110 cubic meters per hour.  They also source the stone and sand from two different quarries just in case there are any problems with the materials from one quarry.DSC_0628

                The operation of Gerbera Ltd was very different than the operation of Marinski and it was very interesting to see both.  But then again, they specialize in two different kinds of structures, high rises and low rises so naturally there will be some differences.         

Ancient Roman Structures, Plovdiv.

Hi, I am Arthur, Qiming Wang, senior Civil Engineering student at Syracuse University. It is my great honor to travel with professors and peers from SU and Utica College. We are now in Plovdiv about 3-hours drive east from Sofia . We enjoyed the one-day tour in two historical sites from Philippopolis. We were interested in how the stairs are evolved over time. I was amazed by the technics used by ancient Romans in building and infrastructure.


The first site we visited is the Ancient stadium of Philippopolis, also known as the Ancient Roman Stadium. The stadium was built with marble blocks from 2nd Century AD. It could seat up to 30,000 spectators almost the 2/3 capacity of the Yankee Stadium. The dimension is 240 meter (820 ft) long by 50 meters (164 ft) wide, have an area more than two of American football court.
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The other site we visited is the Theatre from Emperor Trajan in a shape of a semicircle. It is so spectacular although it was seriously damaged and only partly recovered. The stages, scaenae, have three floors supported by ionic columns, with a pediment with incredible sculptures. The stand, cavea, has been restored with about 3500 seats, which is nearly half of the original capacity. There is an annual summer concert host in the theater, we are going to see in the next few days.


Also we passed by Hisar Kapiya, an arch represent the stonework and brickwork of ancient Philippopolis. It was founded from Roman Age and be destroyed and reconstructed several times.  Arch are wildly used not only as a architectural element but also structure stiff  to transfer tremendous loading. The smaller entrance for the stadium on the north has been recovered. It is a small tunnel supported by a barrel vault. A barrel vault is an extended arch with multi keystone on the top, which we call the crown. The crown transfers the weight to rest of the vault- haunch, then transfer to the buttress on the side.

Roman Stadium-Barrel Vault

The masonry structured used a lot of Mortise and Tenon Joints. The stones are crafted in multi-faceted, with dent and protuberances. It has been wide used crossed the world. Traditional Chinese timber architectures often use Mortise and Tenon joints to make the structure support. Ancient Romans developed the melting iron and locking method to reinforced the marble structures. They drilled a hole through two stones pour melted iron into it to provide extra support and connection. Later on, they discovered that lead cover would help to keep the iron from rust.


We tape measure the stairs from both stadium and theater, and contemporary stairs. We found things are evolved dramatically. The average rise of the stairs in the stadium was 20.150cm (7.93 inches). It is almost one inch longer than the US stander 7 in. The run of the stairs varies from 15.5 cm to 56 cm. The rise and run of the theater are close to the modern system.

Tape Measure of the Stadium

  Tape Measure - Theater

Wise Romans implement drainage system on the street. The street of Philippopolis have concave dihedral pavement, and a narrow gutter run through the mid. Precipitations will be collected by the gutter from the sloped pavement, and run down the hill.


Roman Stadium - cavea

Roman Stadium- View from South, Portrait

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