۱- Introduction

۲- Design of the studied buildings

۳- Nonlinear modeling

۴- The ground motions

۵- Numerical results

۶-Conclusions

References

Abstract

The problem of seismic impact between torsionally coupled multi story moment frame buildings is investigated in this paper. Five pairs of adjacent structures spaced at various separation distances are considered. The buildings are 4–۱۰ stories in height. Although a common plan being symmetric with regard to lateral stiffness is considered, a mass eccentricity variable from zero to 30% of the plan dimension is assumed. By three-dimensional modeling of the nonlinear torsional buildings having common story elevations, the seismic pounding happen anywhere along the adjacent buildings edges. Effect of impact and torsional eccentricity are studied by comparison of nonlinear dynamic responses of buildings at different clear distances under 11 consistent earthquakes. The responses include pounding forces at stories, story drifts, story shears and plastic hinge rotations. It is shown that how pounding incidents increase for larger eccentricities and how pounding occurs even at the clear distances prescribed by seismic design codes. The combined effect of torsional eccentricity and pounding results in amplifying the nonlinear response of structure especially for the peripheral frames.

Introduction

The seismic pounding can happen between closely spaced adjacent structures during large earthquakes. In such an event, the impact force is applied as a shock on a dynamical system. Such a shock force can alter totally the design responses, as anticipated, for the system under study. Moreover, the local damage sustained by the structural elements under direct impact force, can result in local or global failure in extreme cases. Because of complexity and existence of many uncertainties in modeling and estimation of pounding, both as an event and as an extra force, it has been the tradition of building codes to set a rule to distance the buildings at an amount to practically eradicate the possibility of impact. Some researchers focused on the adequacy of these prescribed separation distances and possibility of estimating the safe separation distance to avoid pounding. Penzien [1], Lin [2], Jeng et al. [3], Hong et al. [4], Yu et al. [5] and Lopez-Garcia and Soong [6] employed different methods to estimate the required separation distance to avoid seismic pounding between adjacent buildings. Hao and shen [7] utilized the random vibration procedure to estimate the minimum required separation distance to preclude earthquake-induced pounding between adjacent asymmetric structures. Barros and Khatami [8] investigated the influence of separation distance on pounding between adjacent buildings under near-fault earthquake excitation. An appropriate model is necessary to simulate pounding effects between adjacent structures and several linear and non-linear models have been proposed so far for the same purpose. Jankowski [9] developed a non-linear viscoelastic model of pounding force to simulate the structural pounding during earthquake. The results showed that their model possessed a better accuracy compared to other linear models but it required more experimental studies to assess the range of the model’s parameters for different pounding conditions. Mate et al. [10] studied various pounding elements in the problem of impact of adjacent buildings. They showed that the elements composed of nonlinear springs developed smaller impact forces compared with the linear impact elements.