In recent years, the Performance Based Design has become the main trend of international engineering design codes. To follow up this trend, the Public Construction Commission of Taiwan initiated a study in 2009 to set up the guidelines of the codes of performance based design for domestic public constructions. Under the framework of the guidelines, the Ministry of Transportation and Communications of Taiwan has been starting to draft the seismic performance based design code for highway bridges since 2011. This paper introduces the basic framework of the performance based design codes in Taiwan, and briefly introduces the procedures of foundation design in the drafted seismic performance based design code for highway bridges.
In general, a complete deep excavation design includes design items such as retaining wall, bracing system, dewatering system, instrumentation, and adjacent building protection system. By all means, excavation design is to follow the requirements as outlined in Chapter 8 of the "Design Code for Building Foundation" published in 2001. Since then, we have witnessed a major improvement on the practice of deep excavation. Among others, the widespread application of numerical tools, extensive use of buttress walls and cross walls, and a stringent requirement on wall deformation all contribute in shaping a new era of deep excavation. One thing remains unchanged, i.e., the design must follow the code, even if there is a gap between the current practice and design code.
This paper discusses the gap between current deep excavation practice and design code. In general, the design code serves the design needs just well. It appears that the only confusion in using the code is related to the calculation of penetration depth for retaining wall embedded in soft clay. Design case is provided in this paper to exemplify this situation. An approach to resolve this confusion is also proposed, though it has to be emphasized that any approach must comply with the current design code.
The Guidelines for Ground Anchor Design and Construction, which was first published by the Chinese Institute of Civil and Hydraulic Engineering in 1993, is reviewed after being practiced for nearly two decades. Problems encountered in the design aspect of anchors include the different factors of safety applied to different components of anchor, the misuse of factor of safety to determine the maximum pullout load for anchor tests, and the misunderstanding on designing the dimension of anchor. These problems are addressed and tried to clarify in this paper. Among the problems associated with the ground anchors in Taiwan, corrosion definitely is the most significant one. This corrosion problem is closely related to the design, construction and maintenance practice of anchors. Based on the findings from the failed anchored slope and the exposed anchor components, it is able to identify the likely corrosion portions of anchor and find out the reasons as well. An anchor tendon assembly is proposed herein to sustain the anchors against the negative effects from the weather, geologic, and workmanship conditions in Taiwan. Since this anchor assembly is inexpensive to make and can be easily modified from the current practice, it is highly recommended to be used in the future anchor construction.
Due to the plate tectonic action, the mountainous area covers more than 70% of Taiwan area. To install the transportation system, the construction in the mountain area and design of highway slope are required. Investigation of slope, stability analysis and design are important issues for most highway projects. However, due to the high variability in distribution and investigation of geotechnical parameters, it is important to consider reliability and risks involved in the slope design, and to categorize the design according to serviceability and life cycle of engineering facilities, which was seldom considered in the current design codes. In this study, the related international design codes are reviewed, and modifications of current practice are proposed to take into account the variability of geotechnical parameters and serviceability of engineering facilities. Moreover, the analysis methods are not enforced in design codes when the serviceability limit states are specified. This approach provides more flexibility for engineers and owners toward efficient and safe design.
Based on the study of subject projects, a geological investigation and a complete assessment of analysis process should be extended to the construction phase of excavation project at the high ground water or complicated geological areas. The specifications should be also included in the design guidelines and implemented as well. The study reveals that the proper design specifications should also adopt other foreign design guidelines in addition to these referred factors due to extreme climate patterns in Taiwan. Updated guidelines should include considerations on loading reoccurrence period, importance of life safety and property security, and the complete site information to suit the rapidly changing weather and international design standards. Currently, disaster remediation projects are conducted based on standard operation procedures only. Update of the specifications are strongly recommended and to be implemented for better results. In addition, there is no any other available hillside building design code. It is highly suggested to speed up establishment of the Code to protect public facilities and civilians’ lives and properties.
In Taiwan, the history of construction of earth dams has been over than sixty years. No official design guidelines were published to be directly followed, so engineers frequently adopted the guidelines from the United States or Japan. This paper reviewed those guidelines, including these subjects: geology investigation, design earthquake, dam height, dam body safety, stability of foundations, abutments and slopes around the reservoir, and monitoring system. Referring the latest technology and building experiences of earth dams, some revised opinions and suggestions were proposed. This may provide a direction for the “Hydraulic structures design criteria”.
To prevent economic barrier, including civil engineering among countries, the limit state design concept, which takes account both safety and economic interest, has currently become a dominating design approach over the allowable stress method not only in structure engineering but also gradually in geotechnical engineering. Eurocode is one of the design codes developed based on limit states, including the ultimate limit state and the serviceability limit state. Considering the difference between geotechnical and structure engineering, there is a chapter concerning with geotechnical engineering, Eurocode 7. Eurocode 7 includes two parts, one for the general rule of geotechnical engineering design, and the other for ground investigation and test. This paper is going to brief the Eurocode 7 and the local practice in Taiwan which involved in site investigation and test; besides, further recommendation for geotechnical code developments of site investigation will be discussed as well.