Earthquake resistant structures

About: Earthquake resistant structures is a research topic. Over the lifetime, 1126 publications have been published within this topic receiving 27467 citations.

Ductile Seismic Retrofit of Steel Deck-Truss Bridges. I: Strategy and Modeling

Abstract: Most deck-truss bridges have been designed and constructed without seismic resistance considerations; as a result, their members, connections, and frequently their substructure are not sized and detailed to provide the ductile response needed during major earthquakes. A ductile seismic retrofit solution proposed here consists of converting the deck slab into a composite slab and replacing the end cross-frames and the lower lateral braced panels adjacent to the supports by special ductile diaphragms, thus creating ductile fuses to protect the remaining superstructure an substructure. This paper illustrates the typical seismic vulnerability of such bridges, presents a model governing transverse seismic response of retrofitted deck-trusses, and a methodology to determine overall stiffness and strength of such ductile panels based on developed seismic performance goals. The results of computer simulations for a retrofitted deck-truss subjected to severe ground excitation validates the proposed methodology and the global modeling. It is concluded that the proposed ductile retrofit solution can significantly enhance seismic performance of deck-trusses.

Performance of precast/prestressed building structures during northridge earthquake

Abstract: Observations are reported of the performance in the January 17, 1994 Northridge, California, earthquake of buildings in which precast/prestressed concrete components were utilized. Ground motions recorded during the earthquake are discussed in relation to fault movements, observed responses at building sites, and prevailing building code design requirements. The results of field observations of parking garages, cladding for buildings and foundations for residences are reviewed. For garages, the performance of structures utilizing primarily precast/prestressed concrete components is compared with garages utilizing other materials. It is concluded that, with the exception of buildings in the immediate vicinity of the epicenter, engineered structures, including those with precast/prestressed concrete components, generally performed well. Parking garages, particularly those with large plan areas, did not perform as well as other types of buildings. The greatest damage was in collector elements funneling lateral forces to the vertical elements of the lateral load resisting system and in the columns of gravity load carrying systems that were not intended to be part of seismic resisting system. No damage was observed to cladding due either to inadequacies of the precast components or their connections to the building's structural system.

Seismic Panel Zone Design Effect on Elastic Story Drift in Steel Frames

Abstract: A substantial change in seismic design requirements for column panel zones (PZs) in steel moment-resisting frames (MRFs) for buildings was implemented recently in several codes for building construction. Previously, it was implied that PZs had to develop the full flexural plastic strength of the beams framing a joint without yielding. In the newer seismic steel codes the concept of allowing panel zones to yield prior to or simultaneously with beams has been adopted. This change is based on increasing evidence that PZs can safely sustain cyclic strain reversals and thereby provide some of the needed ductility for a frame. After discussing the basis and the nature of these new provisions, their effect on elastic story drift is illustrated in two examples. A simple approximate method is developed for determining elastic story drift due to PZ deformations. This method can be conveniently used with conventional computer frame-analysis programs without introducing additional degrees of freedom into the system.

Seismic performance and retrofit of steel pile to concrete cap connections

Abstract: This paper looks at the seismic-performance of steel pile-to-pile cap connections representative of construction practice in the eastern U.S. Two perspectives are considered. The first is the seismic vulnerability of existing pile cap connections, where the embedment depth of the pile inside the cap beam is small. An initial experimental study, therefore, was conducted for testing 2 specimens that represented existing exterior connections under cyclic lateral loading. The second perspective is the seismic design requirements for strong cap beam-to-pile connections. Hence, a theory assuming a linear distribution of stresses along the connection embedment depth was developed, and comparisons with a finite element model were performed. A second experimental program was conducted to evaluate the performance of specimens retrofitted in accordance with the theoretical model developed in this study. Results of the second experimental study validated the proposed retrofit strategy.

Modeling earthquake response of concrete masonry building structures

Abstract: The paper discusses considerations involved with modeling concrete masonry building structures at one-qurater scale and reports on tests carried out to evaluate mechanical properties of reduced-scale masonry materials. Procedures used to design and test two different 3-story building structures to failure on a shaking table are also presented. Samples of dynamic response are presented to demonstrate the relevance of using a scale model of earthquake engineering research.