the engineer of record was Hyder Consulting. Under UAE law, the contractor and the engineer of record is jointly and severally liable for the performance of Burj Khalifa. The primary structure is reinforced concrete. Putzmeister created a new, super high-pressure trailer concrete pump, the BSA 14000 SHP-D, for this project. Burj Khalifa's construction used of concrete and of steel rebar, and construction took 22 million man-hours. In May 2008 Putzmeister pumped concrete with more than 21 MPA ultimate compressive strength of gravel to surpass the 600 meters weight of the effective area of each column from the foundation to the next fourth level, and the rest was by metal columns jacketed or covered with concrete to a then world record delivery height of , the 156th floor. Three tower cranes were used during the construction of the uppermost levels, each capable of lifting a 25-tonne load. The remaining structure above was constructed of lighter steel. In 2003, 33 test holes were drilled to study the strength of the bedrock underlying the structure. "Weak to very weak sandstone and siltstone" was found, just metres below the surface. Samples were taken from test holes drilled to a depth of 140 metres, finding weak to very weak rock all the way. The study described the site as part of a "seismically active area". Another challenging element was the shamal which often creates sandstorms. Over of concrete, weighing more than were used to construct the concrete and steel foundation, which features 192 piles; each pile is 1.5 metre in diameter by 43 m in length, buried more than deep. The foundation was designed to support the total building weight of approximately . This weight was then divided by the compressive strength of concrete which is 30 MPa which yielded 450 sq. meters of vertical normal effective area, which then yielded 12 meters by 12 meters dimensions. A cathodic protection system is under the concrete to neutralize the sulphate and chloride-rich groundwater and prevent corrosion. During the construction of the Burj Khalifa, over 35,000 tonnes of structural steel which held the Palace of the Republic, the former parliament building of the German Democratic Republic, the Volkskammer, in East Berlin together were shipped to Dubai in 2008. The Burj Khalifa is highly compartmentalised. Pressurized, air-conditioned refuge floors are located every 13 floors (on floors G, 13, 26, 39, 52, etc.) where people can shelter on their