About The Bridge
At the time of its opening in 1993, the Mezcala bridge was the highest bridge in Mexico and the second highest cable stayed bridge in the world. The Mezcala is also the largest and highest of many spectacular bridges on the incredible México City-Acapulco Highway. Built to connect Mexico City to the vacation and resort town of Acapulco on the Pacific Ocean, the 163 mile (263 km) long highway was one of Mexico’s first major toll roads and was a forerunner to the even more spectacular Durango-Mazatlán highway scheduled to open in 2012.
One of the first double span cable stayed bridges ever built, the Puente Mezcala consists of three tall towers that support two uneven spans of 1,020 feet (311 mtrs) and 984 feet (300 mtrs). The central tower of Mezcala is notable for being the tallest bridge structure in North America. Rising 774 feet (236 mtrs) from the surface of the foundation to the top of the tower, pier 3 is 28 feet (8.5 mtrs) taller than the Golden Gate bridge! During construction, the road deck was initially cantilevered out from both sides of pier 3. As the two central spans grew in size, the stability of pier 3 was ensured by tying the two sides of the deck down to the ground with thick anchor cables. Bridge sections for tower 3 were raised 500 feet (152 mtrs) from the floor of the valley while deck sections for towers 2 and 4 were launched out from the side of the canyon.
The Mezcala bridge a strategic structure for the implementation of a continuous and real-time monitoring system in order to guarantee the safety of users and understand structural integrity over time. To achieve the proposed objectives ChM4 Inc. was contracted to setup the passive optical FBG system as a kit install by IMT and its subcontractors. From the previous installation of the Papaloapan Bridge and ChM4 training provided to IMT we provided design assistance building all hardware, ordering of all necessary components and optical sensor selection types to install the system. We reviewed IMT drawings to consult optical cable runs, optical equipment/interrogators composed of optical fiber FBG strain gauges, 3 axis accelerometers, single axis accelerometers, tilts, displacement sensors, 2 video cameras, and a weather station. The sensor equipment was continuous real-time remote monitoring to receive data at a remote command and control center at IMT. The installed sensors generated statistical distributions of the live loads present in the bridge, trend lines, to calibrate mathematical models. IMT will make prognosis of structural integrity through Monte-Carlo simulation and calculate reliability indices of the Bridge. MCH Engineering coordinated the relationships with IMT as with past projects in Mexico region.
SHMS Optical Sensors and analog Hybrid System Supplied as a Kit for Installation
Equipment and Sensors (1) Luna Interrogator, (2) optical multiplexer 16 channel, Luna optical sensors (10) os3600 strain sensors with onboard temperature compensation mounted to concrete pylons, (38) os3150 strain sensors and (10) os3155 to monitor various areas of the steel structure, (13) 0s4350 temperature absolute sensors for environmental purposes, (1) os5100 optical displacement sensors to monitor expansion joint, (30) os7100 accelerometers for stay cable signature sampling, bridge deck and pylon signatures, (16) FBG Korea tilt sensors for bridge deck and pylons.
Total SHM FBG optical gratings 155
A NOMIS analog data logger and 3D Seismograph Accelerometer was used to understand how seismic activity effects the bridge structure in this region of Mexico exhibiting seismic activity over several years.
Analog to Fiber A/D to carry weather information to the main control panel with (1) Weatherhawk ultrasonic weather stations at the top of pylon. The environment and weather plays a roll when looking at a bridge structure and loading on the bridge deck, stay cable and pylons wind direction and speed is vital to understand sensor data.
All control panels prebuilt for optical sensors and Security Cameras for traffic monitoring:
ChM4 designed the control panel, optical camera panels with A/D converters to integrate with the optical trunk line using two Bosch cameras to monitor traffic and security due to the bridges remote location. Should a problem occur the camera would allow a visual inspection incase of SHM warnings or vandalism before dispatching personal.
ChM4 used structural health monitoring drawings by IMT for consulting of FBG optical sensors, smart camera system, siemic system and control panels location.