Ronald O. Hamburger

Bio: Ronald O. Hamburger is an academic researcher. The author has contributed to research in topics: Earthquake engineering & Earthquake resistant structures. The author has an hindex of 1, co-authored 1 publications receiving 399 citations.

Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications, ANSI/AISC 358-05

Abstract: Building code provisions for the seismic resistant design of structures incorporate two basic types of requirements. The first of these is very similar to the code requirements for most other types of loading and comprises specification of minimum permissible strength and structural stiffness. The second is unique to design for seismic resistance and consists of prescriptive criteria on the detailing practice for the structural elements. While strength and stiffness requirements have been part of building codes for nearly 100 years, these detailing practice requirements, which include such things as prescription of the volumetric ratio and spacing of reinforcing in concrete structures, and permissible width/thickness ratios for elements of members in steel structures are a recent addition to the code. They were first introduced into the codes in the late 1960s and primarily affected the design of reinforced concrete structures. However, as researchers have continued to understand the importance of detailing to seismic performance and actual earthquakes have made clear to the profession that poor detailing practice directly leads to adverse structural behavior, the volume and complexity of these detailing requirements has steadily increased. Extensive detailing requirements for reinforced concrete structures were introduced into the building codes following the 1971 San Fernando earthquake. Requirements for timber and masonry structures were also added throughout the 1970s and 1980s as relatively modest earthquakes, such as the 1979 Imperial Valley, California; 1983 Coalinga, California and 1984 Morgan Hill, California earthquakes indicated problems associated with improperly detailed structures of this construction type. However, relatively few requirements for detailing of steel structures were placed in the codes during this period, largely because there were few examples of poor performance of steel structures. This began to change with the 1985 Mexico City, Mexico earthquake in which several large steel buildings in the lake bed region of Mexico City collapsed. Additional requirements for detailing of steel structures were introduced following the 1987 Whittier Narrows, California earthquake. Most of these requirements pertained to the detailing of braced steel frames. The 1994 Northridge, California earthquake resulted in the introduction of extensive code detailing requirements for moment-resisting steel frames. Immediately following the earthquake, brittle fractures were discovered in the beam to column connections of several buildings in the San Fernando Valley (Figures 1, 2). This damage was

Average spectral acceleration as an intensity measure for collapse risk assessment

Abstract: This paper investigates the performance of spectral acceleration averaged over a period range (Saavg) as an intensity measure (IM) for estimating the collapse risk of structures subjected to earthquake loading. The performance of Saavg is evaluated using the following criteria: efficiency, sufficiency, the availability or ease of developing probabilistic seismic hazard information in terms of the IM and the variability of collapse risk estimates produced by the IM. Comparisons are also made between Saavg and the more traditional IM: spectral acceleration at the first-mode period of the structure (Sa(T1)). Though most previous studies have evaluated IMs using a relatively limited set of structures, this paper considers nearly 700 moment-resisting frame and shear wall structures of various heights to compare the efficiency and sufficiency of the IMs. The collapse risk estimates produced by Saavg and Sa(T1) are also compared, and the variability of the risk estimates is evaluated when different ground motion sets are used to assess the structural response. The results of this paper suggest that Saavg, when computed using an appropriate period range, is generally more efficient, more likely to be sufficient and provides more stable collapse risk estimates than Sa(T1). © 2015 John Wiley & Sons, Ltd.

An efficient method for estimating the collapse risk of structures in seismic regions

Abstract: SUMMARY Assessing the probability of collapse is a computationally demanding component of performance-based earthquake engineering. This paper examines various aspects involved in the computation of the mean annual frequency of collapse (λc) and proposes an efficient method for estimating the sidesway collapse risk of structures in seismic regions. By deaggregating the mean annual frequency of collapse, it is shown that the mean annual frequency of collapse is typically dominated by earthquake ground motion intensities corresponding to the lower half of the collapse fragility curve. Uncertainty in the collapse fragility curve and mean annual frequency of collapse as a function of the number of ground motions used in calculations is also quantified, and it is shown that using a small number of ground motions can lead to unreliable estimates of a structure's collapse risk. The proposed method is shown to significantly reduce the computational effort and uncertainty in the estimate. Copyright © 2012 John Wiley & Sons, Ltd.

Effect of gravity framing on the overstrength and collapse capacity of steel frame buildings with perimeter special moment frames

Abstract: This paper investigates the effect of the gravity framing system on the overstrength and collapse risk of steel frame buildings with perimeter special moment frames (SMFs) designed in North America A nonlinear analytical model that simulates the pinched hysteretic response of typical shear tab connections is calibrated with past experimental data The proposed modeling approach is implemented into nonlinear analytical models of archetype steel buildings with different heights It is found that when the gravity framing is considered as part of the analytical model, the overall base shear strength of steel frame buildings with perimeter SMFs could be 50% larger than that of the bare SMFs This is attributed to the gravity framing as well as the composite action provided by the concrete slab The same analytical models (i) achieve a static overstrength factor, Ωs larger than 30 and (ii) pass the collapse risk evaluation criteria by FEMA P695 regardless of the assigned total system uncertainty However, when more precise collapse metrics are considered for collapse risk assessment of steel frame buildings with perimeter SMFs, a tolerable probability of collapse is only achieved in a return period of 50years when the perimeter SMFs of mid-rise steel buildings are designed with a strong-column/weak-beam ratio larger than 15 The concept of the dynamic overstrength, Ωd is introduced that captures the inelastic force redistribution due to dynamic loading Steel frame buildings with perimeter SMFs achieve a Ωd>3 regardless if the gravity framing is considered as part of the nonlinear analytical model representation © 2014 John Wiley & Sons, Ltd

Special Perforated Steel Plate Shear Walls with Reduced Beam Section Anchor Beams. I: Experimental Investigation

Abstract: This paper presents results of an experimental investigation of specially detailed ductile perforated steel plate shear walls SPSWs designed to accommodate utility passage, and having anchor beams with reduced beam sections connections. Single-story, single-bay SPSW frames are subjected to quasi-static cyclic loading up to their maximum strength and displacement capacity. The tested specimens also had low yield strength steel infill panels. Two specimens make allowances for penetration of the panel by utilities. The first, having multiple holes specially laid out in the steel panel, also has the characteristic of reduced panel strength and stiffness compared to the corresponding SPSW having a solid panel. The second such specimen utilizes quarter-circle cutouts in the panel corners, which are reinforced to transfer the panel forces to the adjacent framing. A SPSW with solid panel is also tested for reference purposes. All specimens resisted an imposed input history of increasing displacements to a minimum drift of 3%. The perforated panel reduced the elastic stiffness and overall strength of the specimen by 15% as compared with the solid panel specimen.

Modeling of the composite action in fully restrained beam‐to‐column connections: implications in the seismic design and collapse capacity of steel special moment frames

Abstract: SUMMARY: This paper investigates the effect of the composite action on the seismic performance of steel special moment frames (SMFs) through collapse. A rational approach is first proposed to model the hysteretic behavior of fully restrained composite beam-to-column connections, with reduced beam sections. Using the proposed modeling recommendations, a system-level analytical study is performed on archetype steel buildings that utilize perimeter steel SMFs, with different heights, designed in the West-Coast of the USA. It is shown that in average, the composite action may enhance the seismic performance of steel SMFs. However, bottom story collapse mechanisms may be triggered leading to rapid deterioration of the global strength of steel SMFs. Because of composite action, excessive panel zone shear distortion is also observed in interior joints of steel SMFs designed with strong-column/weak-beam ratios larger than 1.0. It is demonstrated that when steel SMFs are designed with strong-column/weak-beam ratios larger than 1.5, (i) bottom story collapse mechanisms are typically avoided; (ii) a tolerable probability of collapse is achieved in a return period of 50years; and (iii) controlled panel zone yielding is achieved while reducing the required number of welded doubler plates in interior beam-to-column joints. © 2014 John Wiley & Sons, Ltd.