Minimum Design Loads for Buildings and Other Structures provides requirements for general structural design and includes means for determining dead, live, soil, flood, wind, snow, rain, atmospheric ice, and earthquake loads, as well as their combinations, which are suitable for inclusion in building codes and other documents. This Standard, a revision of ASCE/SEI 7-05, offers a complete update and reorganization of the wind load provisions, expanding them from one chapter into six. The Standard contains new ultimate event wind maps with corresponding reductions in load factors, so that the loads are not affected, and updates the seismic loads with new risk-targeted seismic maps. The snow, live, and atmospheric icing provisions are updated as well. In addition, the Standard includes a detailed Commentary with explanatory and supplementary information designed to assist building code committees and regulatory authorities. Standard ASCE/SEI 7 is an integral part of building codes in the United States. Many of the load provisions are substantially adopted by reference in the International Building Code and the NFPA 5000 Building Construction and Safety Code. Structural engineers, architects, and those engaged in preparing and administering local building codes will find this Standard an essential reference in their practice. Note: New orders are fulfilled from the second printing, which incorporates the errata to the first printing.

Minimum Design Loads for Buildings and Other Structures

Influence of seismic orientation on the statistical distribution of nonlinear seismic response of the stiffness-eccentric structure

Evaluation of seismic torsional response of ductile RC buildings with soft first story

Several design codes consider the non-linear response of a building by using one of the most important seismic parameters, called the response reduction factor (R). The lack of a detailed description of the R factor selection creates the need for a deeper study. This paper emphasises a methodology for the selection of a proper R factor based on resilience aspects. Unsymmetrical/irregular buildings have become the most common in recent times due to aesthetic purposes. However, because of the complexity due to the torsional effect, the selection of the R factor is even more difficult for this type of building. Therefore, a high-rise G+10-storey L-shaped building is herein considered. The building has re-entrant corners based on the structural/plan arrangement. Different R factors were used in the building design, considering buildings subjected to both unidirectional and bidirectional seismic loading scenarios. The building response with respect to various R factors (R equal to 3, 4, 5 and 6) in terms of its performance level, functionality, damage ratio and resilience was assessed at two design levels, i.e., design basic earthquake (DBE) and maximum considered earthquake (MCE). The study concludes that, considering the above criteria along with the resilience aspect, a maximum R factor up to 4 can be recommended for unidirectional loading, whereas for bidirectional loading, the maximum recommended R factor is 3.

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Accounting for Resilience in the Selection of R Factors for a RC Unsymmetrical Building

During an earthquake, structures are generally excited to multiple ground motion components: two orthogonal horizontal components and one vertical component. However, the interaction of the deformations along two principal orthogonal directions in the presence of various levels of axial force in columns in post elastic range can be successfully captured if nonlinear dynamic analysis can be carried out using the bidirectional hysteresis model. On the other hand, the seismic codes prescribed simple combination rules to capture this effect in an equivalent sense even without consideration of axial force in columns. Though these rules may be valid in the elastic range, they may not be applicable in the post-elastic range as mentioned in a few seismic codes. Surprisingly, these codes did not specify any user-friendly provision needed by design offices. Hence, the applicability and efficacy of these rules in the post-elastic range is needed to be compared with that obtained from detailed nonlinear tine history analysis under orthogonal pair of bidirectional ground motions obtained from a number of chosen seismic acceleration data for performance-based design. In this study, idealized low-rise buildings with small, medium, and long periods were investigated, considering the presence of axial force in columns. Most of the current design codes and standards suggest that the addition of response of 30% of ground motion in other direction if added to the response of unidirectional ground motion in the considered direction of analysis or the resultant responses obtained by square root of sum of square from the unidirectional analyses carried out separately in both principal directions (referred as SRSS response) may predict the response with reasonable accuracy. The results obtained from the current study makes an attempt to exhibit the trends of post elastic range response for the structures. Further, it shows that seismic codes options significantly underestimate the post-elastic range seismic demand though they are proved to be adequate to predict elastic range response. This paper may prove helpful in improving code provisions.

Effect of bidirectional ground shaking on structures in the elastic and post-elastic range: Adequacy of design provisions

Inelastic seismic behavior of asymmetric structures under bidirectional ground motion: An effort to incorporate the effect of bidirectional interaction in load resisting elements

The structures are generally designed through dual design philosophy or more broadly known as performance-based design. In this philosophy, the strength is limited to minimize the cost relying on damage-absorbing capacity or ductility capacity of structural members. Still lack of understanding of many issues of nonlinear behavior of structural member makes this method an interesting topic for further research. Base isolation technique is not possible to adopt many a times due to financial limitation. However, this technique may be made more economic and practically implementable through further research. Further, design methodology can also be simplified. Thus, possibly such methodology can be used for an identified class of buildings through further research in this direction. Example case studies presented in the paper for both structures on base isolator and those designed by dual design philosophy clearly indicate intuitively understandable findings. Finally, the paper provides a qualitative insight for economically viable use of base isolation system. It also shows the possibilities of how inelastic excursion-based dual design philosophy can be simultaneously used along with base isolation for reducing the cost further.

Ahsaan Hussain

Papers

Inelastic seismic behavior of asymmetric structures under bidirectional ground motion: An effort to incorporate the effect of bidirectional interaction in load resisting elements

Effect of bidirectional ground shaking on structures in the elastic and post-elastic range: Adequacy of design provisions

Base Isolation Versus Dual Design Philosophy for Seismic Design of Buildings: Preliminary Case Study

Behavior of vertically irregular structures near mines: Comparison of responses under seismic and mine blast-induced ground motion