The Mudeirej Bridge is the highest overpass in the Middle East. It is located in Hammana and constitutes a vital link between Mount Lebanon and the Bekaa Valley. Unfortunately, during the summer war of 2006, the bridge was severely damaged by the bombardment (especially the southern section).

MAN Enterprise accepted the challenge of participating in the reconstruction works of the Mudeirej Bridge, in particular the demolition works and the reconstruction of the damaged foundation and vertical structures. MAN Enterprise exceeded expectations with the project, and a new achievement was added to its outstanding record in the construction industry. Several special construction techniques were implemented during the reconstruction works such as:

COLD WEATHER CONCRETING: Cold weather concreting is the process in which concrete works must be carried out during cold and freezing weather conditions. Specifications of the Mudeirej Bridge stated that cold weather concreting should be considered when the air temperature is below two degrees Celsius (2º C). Pouring and casting concrete required special techniques and methods to prevent damage to the concrete due to early freezing. We had to insure that the concrete developed the required strength for sage removal of forms, maintained curing conditions that yielded normal strength, and limited rapid temperature changes before the concrete reached sufficient strength. The applied method for cold weather concreting for the Mudeirej Bridge Restoration Project consisted of: • Removal of snow, ice, and frost from all spaces intended to fill with concrete using hot-air or basic mechanical methods. • Insulation of formwork in order to prevent early-age freezing by covering / insulating newly poured concrete by tightly wrapping the insulating miothane blanket (geofrost) around the formwork and the hollow section of the pier to ensure that the temperature of the concrete does not drop below 10º C. • Maintaining concrete and frequently checking the temperature to make sure it is within the acceptable margins. • Stripping of forms after the concrete has reached the required strength, should be carried out slowly and carefully to ensure the corners stay intact and crack-free.

• Protection of the concrete after stripping the relevant forms with insulating blanket to maintain concrete temperature by tightly wrapping the blankets around the concrete section and being fixed in place by heavy duty ropes and plastic straps. This insulation process should remain for a period of 7 days after the concrete has been placed for the subject element.

IMPLOSION: After a detailed study, the decision to partially demolish the south part of the bridge was taken due to the unrepairable damage. Since it was crucial not to cause any physical damage to the northern part of the bridge and the remaining areas of the southern part in the demolition process, and as time was a major concern in the restoration process due to the huge importance of the bridge, the most convenient method chosen for demolition was implosion. Implosion is a controlled demolition method performed by strategically placing explosives on critical supports of any given structure and distantly detonating it in a way so that the structure can no longer withstand the force of gravity. Many critical studies and surveys were performed, including but not limited to: structural studies, load, primary structural motion, load ratios (which conclude the amount of explosives needed for every cubic meter of reinforced concrete), predicting drop and debris areas, and the key location of which the explosives should be placed. Once all the studies were performed, the following steps took place: pre-weakening of the structure, drilling holes with the appropriate dimensions into the key areas, placing explosive charges, making necessary connections, and wrapping the targeted piers with a geotextile fabric and close-mesh metal fence.

FRP (FIBER REINFORCEMENT POLYMER): The fiber wrapping (FRP System) technique was applied to repair some of the damaged piers. The methodology of work related to this repair system can be summarized as follows: Preparatory Works: - The concrete surface of the pier was sandblasted to remove the paint and all damaged areas were chipped to eliminate unsound concrete and loose particles. - The cracks were injected and the walls were filled with the relevant marban and grout. - A surface preparation was conducted in order to remove protrusions, sharp corners, irregularities, laitance and/or dust from the concrete surface. Application Works: - A surface primer was applied on the pier surface which received the FRP fabric. - A sufficient workable quantity of resin was applied on the FRP fabric and spread evenly until the reinforcement was fully covered and saturated thoroughly with resin. Subsequently, the fabric was fixed by using a roller.

- The same procedure was applied for the installation of the consequent FRP layer(s). The number of FRP layers to be applied at the various levels of the pier was determined by the study / calculations of the specialist. - The final FRP layer was protected by a protective coating.

Walid Khalife - Contract Manager NB: The FRP works should be supervised by persons certified by the FRP manufacturer. In addition, the FRP system cannot be applied in rainy or snowy conditions or if the ambient temperature is below 4°C.