An experimental study of damage characteristics of reinforced concrete beams | |
| Author | Nantawat Khomwan |
| Call Number | AIT Thesis no. ST-99-31 |
| Subject(s) | Earthquake resistant design Concrete beams |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | In the current seismic design practice, the building and its components are expected to sustain the expected maximum seismic loading without collapse although it may undergo some structural as well as nonstructural damages. It is therefore very important to control these damages to an acceptable level. However, one major factor that has hindered the damage controlling of reinforced concrete members is the lack of understanding of damage mechanisms and reliable method for assessing the damage. To solve this problem, extensive experimental studies are essentially needed. These research studies focus on the experimental identification of damage characteristics and three energy based damage models namely, Park and Ang, Chai et al. and Rajaram and Usami models. Experiments are conducted on 15 reinforced concrete cantilever beams of identical shape and size using quasi-statics testing method. These specimens are subjected to various displacement histories which include monotonic and cyclic tests. In order to understand the effect on the overall damage characteristics of the specimens with the change in design method, the specimens are designed according to capacity design method and ACI method. One major difference of these two design methods for reinforced concrete beam design is shear design concepts. Capacity design method specifies that, in plastic hinge zone, only shear reinforcement (Vs) resists the entire shear. Concrete shear resistance (Ve) is neglected due to ineffectiveness of interlocking across wide cracks. In contrast, ACI method includes both contributions from concrete (Ve) and shear reinforcement (Vs). From these concepts, the specimens are divided into three groups with varying shear reinforcement spacing. Five specimens are provided with small shear reinforcement spacing according to the capacity design method and five specimens of the large spacing are designed according to ACI method. In addition, five specimens are also provided with moderate shear reinforcement spacing to observe the tendency of beams behavior. Other parameters of all specimens remain unchanged. To establish comprehensive experimental studies, many strain gauges are installed to check internal response mechanisms in the inelastic range. Test results show that, during the increase of shear reinforcement strain, concrete gradually loses its shear strength while shear reinforcement contributes to resist more shear force. It can confirm that the contribution of concrete shear resistance (Ve) is ineffective in plastic hinge zone, therefore, shear reinforcement should be provided for resist entire shear force. The results also clearly demonstrate that shear reinforcement is an important component to improve the ductile performance and reduce the rate of strength degradation of reinforced concrete beams. The comparisons of damage models show that the Park-Ang model works well for damage assessment of reinforced concrete beams. The values of fJ for samples with the same shear reinforcement details (but different displacement time histories) are very close to each other. The results suggest that the strength degradation parameter (/3) is path independent. |
| Year | 1999 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Pennung Warnitchai |
| Examination Committee(s) | Kishi, Toshiharu;Pichai Nimityongskul; |
| Scholarship Donor(s) | Asian Institute of Technology Partial Scholarship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1999 |