The Structural and Geotechnical Engineering

Testing of Bridge Deck in Structures Lab

faculty in the Department of Civil, Environmental & Architectural Engineering has been actively involved in Earthquake Engineering education and research for a number of years. There are 9 faculty members in the Structural Engineering and Structural Mechanics group and 7 in Geotechical Engineering. Most of the faculty members are involved in both experimental and theoretical research, with distinct reputations and achievements in the areas of pseudodynamic testing, experimental evaluation and finite element analysis of concrete and masonry structures, constitutive modeling of cementitious materials and geomaterials, centrifuge testing, soil dynamics, soil-structure interaction, fracture of concrete dams, structural reliability, and risk analysis. Current research activities in the Earthquake Engineering area include:

• Modeling of the shear and bond-slip behavior of RC members using beam-column elements.

• Modeling of the behavior of RC structures retrofitted with FRP wraps.

• Dowell effect under seismic excitation.

• Dynamic response of cracked concrete dams.

• Centrifuge testing of concrete dams and earth structures.

• Soil-dynamics and soil-foundation interaction.

• Finite element analysis of RC structures with various crack models.

• Simulation of the earthquake response of RC structures using parallel computing.

• Development of a fast hybrid test system under the NSF-sponsored NEES program.

Structures and Materials Laboratories

The Structures Laboratory of the Department has servo-hydraulic testing apparatus for Earthquake Engineering research. The strong floor area in the laboratory is 40 ft. by 70 ft. The strong floor is 2-ft. thick with 3-in. diameter holes spaced at a center-to-center distance of 3 ft. in each direction for anchoring structural specimens. The testing bay has a vertical clearance of about 20 ft. There is a unique direct shear machine in the laboratory for testing rock joints, concrete crack interfaces, and masonry mortar joints. The machine can apply a maximum vertical force of 165 kips with a servo-controlled hydraulic actuator and a maximum horizontal shear force of 35 kips for cyclic shear reversals.

Under the NEES program of the NSF, the laboratory is going to acquire some high-performance, high-speed actuators and a digital control system to develop a Fast Hybrid Test System that combines model-based simulation with physical experiments.

The Materials Laboratory that is adjacent to the Structures Laboratory has three MTS load frames. One of load frame has 1000-kip load capacity and is equipped with hydraulic tension grips. In addition, this machine has two additional horizontal actuators, each with a capacity 130 kips in tension and 165 kips in compression, for bi-axial testing. Each of the actuators can be controlled separately by an analog controller. The second load frame has a load capacity of 110 kips. The third load frame has a load capacity of 110 kips and is equipped with hydraulic tension grips and an environmental chamber. The grips have temperature regulated extension rods that are designed for use with high and low temperatures. The hydraulic piston in the load frame is controlled by a digital controller. The temperature in the environmental chamber can be controlled between –40° C and 177° C with a control accuracy of ±1° C. The humidity range is between 10 and 95% relative humidity.

Geotechnical Centrifuges

There are two geotechnical centrifuges in the Department. The larger of the two has a 400-g-ton capacity. It has an unsymmetrical rotor arm, with a swing platform on one end to carry a payload and a fixed counterweight compartment on the other end. In the fully extended position, the top of the swing platform is at a radius of 18 ft. It is capable of accelerating a 4000 lb payload to a maximum of 200 g in about 17 minutes.

A servo-controlled electro-hydraulic shake table can be mounted on the swing platform of the centrifuge, which could be operated in-flight to simulate a desired earthquake-like motion. The system components consist of a servo-valve combination, a hydraulic power supply system, a linear actuator, a LVDT, linear bearings, and bearing mounts. The shake table is mounted on the centrifuge platform in such a way that a model container is shaken along its longitudinal axis, thus minimizing the adverse effects of the variation in g-level along the width of the container. The shake table follows a correction algorithm, which helps in generating any desired motion ranging from sinusoidal to random, real earthquake-like. Other accessories of the centrifuge include several containers suitable for static, dynamic, as well as seismic testing including a laminar container. A typical instrumentation package includes AC and DC LVDTs to measure displacements, pore pressure transducers, accelerometers, strain gages, earth pressure transducers, and load cells. A total of up to about 50 transducers can be used in a single experiment depending on the size of the model and the type of the experiment.

Master’s Program

There are two degree plans for the M.S. Degree:

Plan I consists of 30 semester hours, which include 6 thesis hours for writing a Master Thesis. The faculty requires Plan I for those students who anticipate receiving financial support in the form of Research Assistantships. This plan is recommended for all M.S. students as it entails a significant research experience.

Plan II consists of 30 semester hours and has two versions:
Plan II/A includes 3 master report hours for writing a Master Report.
Plan II/B consists of 30 hours of coursework only.

M.S. students in the Structures area are required to take at least two courses in each of the Structural Mechanics and Structural Engineering areas. All M.S. candidates are required to pass a Final Comprehensive Examination administered by an Examining Committee. The Final Comprehensive Examination shall be written, or oral, or both. For Plan I students, this examination consists of a public defense of the thesis.

Doctoral Program

The curriculum for the doctoral program is customized to the background and experience of each individual doctoral student. The doctoral student is required to pass a Preliminary Examination within one academic year of the beginning of his/her doctoral program, and a Comprehensive Examination after all course work has essentially been completed. In addition, the doctoral candidate must defend his/her dissertation successfully and publicly in the “Thesis Defense” at the final stage of his/her doctoral program. The minimum requirements for the doctorate are 30 semester hours of graduate level coursework, as many as 18 hours of which may be transferred from M.S. work at CU-Boulder. In addition to the coursework, the doctoral program requires completion of 30 thesis hours of research towards the doctoral degree.

Graduate Course Work

Students in the Structural Engineering and Geotechnical Engineering Programs can have an emphasis in Earthquake Engineering. In addition to the basic structural engineering, structural mechanics, and geotechnical engineering courses, students interested in Earthquake Engineering have a number of pertinent courses to choose from, such as Introduction to Structural Dynamics, Dynamics of Soils and Foundations, Earthquake Engineering, and Structural Reliability. There is also an array of advanced courses on geo-mechanics, construction materials, computational mechanics, fracture mechanics, and structural optimization to strengthen students’ background for research and engineering practice.