Bridges: Rio Puerco

Case study: SOFO, ADAM System

Prestress losses monitoring
Whole lifespan monitoring
Automatic operation
Deformation monitoring
Temperature monitoring

Project Description

Summary: Deformation monitoring of 4 prefabricated girders during construction, bridge erection, slab pouring and in the long term. Prestress loss monitoring. Automatic operation

Clients: Federal Highway Administration

Place: New Mexico (USA)

Period: 2000 - N/A

Installation: University of New Mexico Las Cruces

Structure's short description: Rio Puerco bridge is situated on national highway 40, near Albuquerque, New Mexico (see Figure 1). It consists of three spans, four girders in each span. Girders are precast prestressed I-beams, approximately 30 m long. They support on-site cast monolithic concrete deck (see Figure 2). The girders were fabricated in open-air plant. The workforms of four girders, with the rebar cages and strands, were aligned, the strands put in tension and the concrete was cast. The girders were then steam cured at temperature in range of 60?C to 90?C. Three days after the pouring, the strands were cut and prestressing force were introduced into the girders. Approximately three months later, the girders were transported on site and the deck was poured.

Aim of monitoring: The main aim of the project has been to monitor prestress losses over the whole life of the bridge, including the early age of girders. For this purpose, four girders were equipped with SOFO sensors and thermocouples as shown in Figure 3. Each girder has contained 10 SOFO sensors and 6 thermocouples. This configuration of sensors allows monitoring of deformation and curvature, and determination of thermal influences. Using appropriate algorithms it is possible to determinate prestress losses in girders. Only four girders are selected due to symmetry of the bridge (see Figure 2). All sensors were installed before the pouring. Details from installation phases are presented in Figure 4.

Number of sensor: 64

Main Results: Measurements started immediately after the pouring. In this way the early and very early age deformation were recorded during the first three days. The deformation is later recorded during the prestress phase, after each strand was cut. Thus, real initial strain state of girders was stored. Followed the period of continuous monitoring before transportation on-site, during transportation and during the pouring of the deck. In present, long-term monitoring is carried on. The results helped comparison with different theoretical models and confirmed very good condition of the bridge after construction.

Schema of bridge and monitored girders

Position of SOFO sensors and thermocouples in girder

Details from installation phase

Part of results obtained form monitoring related to pre-stressing losses

Bibliography:

Monitoring Of A Smart Bridge With Embedded Sensors During Manufacturing, Construction And Service , Rola L. Idriss, Third International Conference on Health Monitoring, Stanford California, September, 2001

Monitoring Of A High Performance Prestressed Concrete Bridge With Embedded Optical Fiber Sensors During Fabrication, Construction And Service , Rola L. Idriss, Structural Faults and Repair Conference, London, England, July 2001, 2001

Prestress Losses In High Performance Concrete Beams- Actual Versus Predicted , Rola L. Idriss, Amor Solano, Transportation Research Record No. 1813, Construction 2002,, paper No. 02-3087, pp.218-228, 2002

Continuous monitoring of concrete bridges during construction and service as a tool for data-driven Bridge Health Monitoring , D. Inaudi, B. Glisic, IABMAS'06 The Third Int'l Conference on Bridge Maintenance, Safety and Management, 16 - 19 July, Porto, Portugal, 2006