1. KINGDOM OF SAUDI ARABIA Arriyadh Development Authority RIYAD المملكة العربية السعودية اله ـ ي ـــ ئ ـ ة العلي ــ ا لتطوي ـ ر مدينة الري ـ اض ASSOCIATED CONSULTING ENGINEERS
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4. Prince Turkey Underpass Takhassussi Underpass King Fahd Tunnel Olaya Tunnel Prince Ahmad Intersection King Abdul Aziz Underpass
7. Top-Down Construction Methodology The “Top-Down” construction approach was primarily devised for existing structures short of space (parking, offices, utilities etc..) such as the existing building may remain in place and its activities uninterrupted while the additional construction works and expansion is happening beneath it. Later it was adopted to other construction industries such as highways, bridges, and even new buildings where significant benefits may be achieved by adding the ability to proceed with construction in both directions at the same time, starting at the ground surface. In existing buildings or structures, where appreciable loads are present on the existing foundations, micropiles will be required to retain the sides of the excavation and to transfer the vertical loads onto a new bearing stratum taking into consideration differential settlement and its effects on the structure. Normally such works are very sensitive and require high technicity and expertise.
8. Design principle Step One: Drill the 60 cm piles, 150 cm on centers, install the piles reinforcement cage, and cast concrete up to the bottom level of the (60x146) pile cap.
9. Step Two: Install the reinforcement cage of the (60x146) pile cap. Design principle
10. Step Three: Cast 20 cm of the 146 cm depth of the pile cap to provide seating for the pre-cast pre-stressed beams. Design principle
11. Step Four: Place the (60x100) pre-cast pre-stressed beams, seated 3 cm on the 20 cm cast portion of the pile cap. One beam is placed every 150 cm, i.e. one per pile. Design principle
12. Step Five: Lay the 6 cm pré-dalle seated 3 cm on the top of the pre-cast pre-stressed beams. Design principle
13. Step Six: Place the reinforcement of the 20 cm topping slab, anchored in the pile cap reinforcement cage. Design principle
14. Step Seven: Cast the topping slab along with the pile cap. Design principle