Research and Specialties

In this section, the summary of research and specialties including consulting services are given.

Research Interests

• Nonlinear Finite Element Analysis of Reinforced Concrete Structure

• Strut-and-Tie Model

• Computational Mechanics and Methods

• Topology Optimization

• Probabilistic Methods and Reliability Analysis

• Validation of Nonlinear Computational Tools in Reinforced Concrete Structures

• Structural Health Monitoring

• Earthquake Engineering

• Finite Element Calibration and Updating

• Corrosion Protection Solution

Selected Research Projects

1) "Design and Analysis of Complex D-Regions in Reinforced Concrete Structures (PhD Thesis)": 2005-2009 (Dissertation Link)

This research project is supported by Royal Thai Scholarship Program

Discontinuity or D-Regions are those portions of a structure for which there is a particularly complex state of stress. These include joints, squat walls with openings, deep beams, footings and other portions of structures for which the engineering beam theory assumption of plane-sections remaining plane does not apply. While building codes of practice provide reasonable guidance for the design and strength evaluation of the more slender portions of concrete structures, they provide limited or no design guidance for D-Regions and when they do they are often inaccurate. The PhD research builds upon Master’s research at the University of New South Wales in Australia in which the use of topology optimization for shape selection of the strut-and-tie approach for the design and strength evaluation of D-Regions. At the University of Illinois, working on improving several aspect of the strut-and-tie design method for D-Regions leading to performance based design approach can be described below:

Improving Provisions in Codes of Practice

Provisions for the design of D-Regions by the strut-and-tie method have recently been incorporated into several national design codes of practice. These provisions consist of rules for evaluating the dimensions and stress limits in struts, ties, and the joints (nodes) that connect them. There are substantial differences in the rules employed in these different codes of practice due to uncertainty in what the dimensions and stress limits should be for the broad range of structural concrete components that can be designed using a strut-and-tie philosophy. The task is to examine and compare these provisions versus experimental test data and the predictions of non-linear analysis methods in order to develop improved rules for evaluating the dimensions and setting stress limits for struts and nodes.

Development of Guidelines in Selecting Shape of Strut-and-Tie Model (STM) for Design of Complex D-regions

One of the tasks in design of D-regions by using STM is that the designers are allowed to freely select the shape of STM to idealize the load transfer mechanism. However, not all of the shapes of STM result in the safe and efficient D-regions design, rather than may result in the poor performance or premature failure totally different from the design assumption. With this reason, this task is to work on introducing and verifying the techniques e.g. topology optimization method whether it can be used as a tool to assist designers in selecting the STM shape for good performance D-regions design or not.

Development of Automated Analysis Methods

There has been some resistance in the structural engineering design community to use the strut-and-tie method due to uncertainty in the accuracy of this method for predicting capacity and in the performance (condition) of members designed by this method under service (everyday) loadings. To address this concern, this task is to develop an automated means of checking a strut and tie design that we refer to as a CAST2FEM framework. CAST2FEM will enable a non-linear finite element analysis of a designed discontinuity region to be completed purely based on a drawing of the completed D-Region that was designed using the strut-and-tie method.

2)"Automated Nonlinear Finite element Analysis ": 2005-Present

This research project is supported by NSF CMS CAREER 0092668, Precast/Prestressed

Concrete Institute, and Royal Thai Scholarship Program

The last three decades have seen the development and advance of non-linear finite element analysis tools for predicting the complete response of reinforced and prestressed concrete structures to static and dynamic loadings. These tools employ a large variety of constitutive relationships, behavioral models, failure theories, and solutions methods. These tools have enabled their dominant users, researchers, to examine the impact of different modeling assumptions on behavior. Unfortunately, these tools do not provide practicing structural engineers with what they need, which is a unique prediction of response with quantified levels of uncertainty as is provided by design code provisions. In addition, the time required to model a structure is prohibitive for design practice. Through this research, an automated procedure is being developed for the non-linear analysis of structural concrete in which the finite element model is generated from overall geometry and material properties and in which the impact of different modeling selections on response is quantified.

3)"Strengthening of Structural Concrete Using Optimal Strut-and-Tie models Generated by A new approach on Performance-Based Optimization(PBO) Techniques": 2003-Present

This research project is supported by Royal Thai Scholarship Program

In this research, a new approach on Performance-Based Topology Optimization was proposed by extending the original scheme entitled “Performance-Based Optimization (PBO), previously proposed by Dr. Qing Quan Liang, to include a novel formulation that reduces the mesh sensitivity and dependency. The mesh dependence reduction scheme leads to the improved and unique solution of topology optimization when the domain of the problem is discretized into different mesh refinement level. Subsequently, the proposed topology optimization was applied to obtain the optimal STM shape for designing and strengthening the structural concrete D-Regions by using STM approach.

4) Study on Upgrading Long-Span Box-Girder Bridges for Logistic Routes (Investigators: Dr. Rajwanlop Kumpoopong and Dr. Sukit Yindeesuk, To be completed: November 14, 2012).

5) Field and Laboratory Investigations of DOH Bridges subjected to Traffic and Earthquake Excitations for Enhancing Design and Strengthening (Investigators: Dr. Rajwanlop Kumpoopong and Dr. Sukit Yindeesuk, To be started: December 2012)

6) An In-Situ Investigation of Thermal and Live Load Stresses in Tinsulanonda Bridge for Performance Evaluation after 27 Years of Service (Investigators: Dr. Rajwanlop Kumpoopong, Dr. Sukit Yindeesuk, and Mr. Pornchai Silarom, Proposal for December 2013).

7) Seismic Retrofitting of Substructures of Existing DOH Short-Span Bridges (Investigators: Dr. Sukit Yindeesuk and Dr. Rajwanlop Kumpoopong, Proposal for December 2013).