SUMMARY

Tunnel-form structural systems (i.e., box systems), having a load-carrying mechanism composed of reinforced concrete (RC) shear walls and slabs only, have been prevailingly utilized in the construction of multistory residential units. The superiority of tunnel-form buildings over their conventional counterparts stems from the enhanced earthquake resistance they provide, and the considerable speed and economy of their construction. During recent earthquakes in Turkey, they exhibited better seismic performance in contrast to the damaged condition of a number of RC frames and dual systems (i.e., RC frames with shear wall configurations). Thus the tunnel-form system has become a primary construction technique in many seismically active regions. In this paper, the strengths and weaknesses of tunnel-form buildings are addressed in terms of design considerations and construction applications. The impacts of shear wall reinforcement ratio and its detailing on system ductility, loadcarrying capacity and failure mechanism under seismic forces are evaluated at section and global system levels. Influences of tension/compression coupling and wall openings on the response are also discussed. Threedimensional nonlinear finite element models, verified through comparisons with experimental results, were used for numerical assessments. Findings from this projection provide useful information on adequate vertical reinforcement ratio and boundary reinforcement to achieve enhanced performance of tunnel-form buildings under seismic actions. Copyright © ۲۰۰۷ John Wiley & Sons, Ltd.

INTRODUCTION

A recent trend in the building industry in Turkey, as well as in many countries with increasing city populations, is toward utilizing the tunnel-form (shear wall dominant) construction system for development of multistory residential units. This has been driven basically by the need to construct earthquakeresistant multistory reinforced concrete (RC) buildings with considerable ease, speed and economy. The tunnel-form system is an industrialized construction technique in which structural walls and slabs are cast (in situ) simultaneously using steel forms composed of vertical and horizontal panels set at right angles. Figure 1 portrays the typical tunnel-form building construction and special formwork system. To expedite the construction, non-structural components such as facade walls, stairs and chimneys are commonly produced as prefabricated elements. Tunnel-form buildings generally have a symmetrical configuration in horizontal and vertical planes (see Figure 1) that enables continuous flow of construction and better quality assurance.