Seismic performance of the wall foundation joint in concrete reservoirs

Abstract

Works Consultancy Services Ltd (WORKS) submitted a proposal to the Earthquake and War Damage Commission (EQC) to investigate aspects of precast concrete reservoir design. The proposal was prompted by an apparent weakness in the wall/foundation joint of some existing structures identified by WORKS through its extensive background and experience in reservoir design and strengthening.  QC accepted the proposal and commissioned WORKS to undertake the study.

WORKS first identified the need to provide for shear restraint at the wall/foundation interface under seismic loading in a study (reference 1) undertaken in 1974/75. The findings of that work along with code recommendations were presented in a paper (reference 2) at the 1975 Technical Conference of the New Zealand Concrete Association (then called NZ Prestressed Concrete Institute). Subsequently these provisions were included in DZ 3106:1976, the draft code of practice for the design of concrete structures for the storage of liquids and more recently in the latest version of that code, NZS 3106:1986.

While the concept of seismic shear restraint was sufficiently recognised and accepted to justify code inclusion, there remained an element of scepticism within the engineering profession as to the theoretical validity of the concepts involved. The purpose of this study is to provide sufficient theoretical evidence to allay this scepticism and to produce design guidelines and recommendations which will improve the seismic safety and integrity of both new and existing concrete reservoirs.