Journal of Structural Engineering

Precast concrete facilitates a construction method using durable and rapidly erectable prefabricated members to create cost-effective and high-quality structures. In this method, the connections between the precast members as well as between the members and the foundation require special attention to ensure good seismic performance. Extensive research conducted since the 1980s has led to new precast concrete structural systems, designs, details, and techniques that are particularly suited for use in regions of high seismic hazard. This paper reviews the state of the art of these advances, including code developments and practical applications, related to four different systems: (1) moment frames; (2) structural walls; (3) floor diaphragms; and (4) bridges. It is concluded from this review that the widespread use of precast concrete in seismic regions is feasible today and that the jointed connection innovation introduced through precast research leads to improved seismic performance of building and bridge structures.

This state-of-the-art review provides an overview of the evolution of seismic design requirements for main steel building seismic force–resisting systems, as driven by new developments, the 1994 Northridge, California, earthquake, and changes in earthquake engineering practice in the United States. Important aspects of these systems in terms of ductility design and capacity design are highlighted. Recent developments in practice related to innovative systems are touched upon. The work presented here is intended to provide the reader with an appreciation of why the current seismic design requirements for steel structures are as framed, highlighting in the process several unresolved issues and inconsistencies that will require attention in future research. Implications of the Christchurch, New Zealand, rebuilding after the 2010–2011 earthquakes there for future U.S. seismic code development are also presented.

Cast-in-place headed anchors with different head sizes embedded in plain and reinforced concrete members of various thicknesses were subjected to pullout tests. The influence of member thickness, anchor-head size, and orthogonal surface reinforcement on the tensile capacity and performance of anchor bolts was evaluated. The member thickness varied from 1.5 to 3.0 times the anchor embedment depth, and headed anchors with small, medium, and large heads were tested. The experimental results of the study showed that increasing member thickness and/or use of orthogonal surface reinforcement lead to increased anchorage capacity and ductility, whereas the anchorage stiffness decreases slightly. In contrast to anchorage ductility, tensile breakout resistance and anchorage stiffness increased significantly with increasing size of the anchor head. The experimental results corresponded closely to the results of a previous numerical study that suggested a modified model incorporating several modification factors for improving the predictive capability of the concrete capacity (CC) method. In the present study, these factors yielded improved prediction of the tensile breakout capacity of the tested headed anchors.

This paper presents the results of a set of experiments performed on four large-scale exterior wide beam–column connections. The beam and column geometry and reinforcement detailing are identical for all four specimens, but the spandrel beam sizes and reinforcement ratios are different in each specimen. The specimens are tested under a combination of a constant axial force and quasi-static reversed cyclic lateral displacements. Detailed strain measurements, crack patterns, and data analysis indicate that the strength and stiffness of the spandrel beams could significantly change the expected response of wide beam–column connections. According to the results of the tests, the specimen with no reinforcement in its spandrel beam failed in brittle torsion with a significant reduction of strength and ductility compared to the expected capacities of the connection. Comparison of the test results indicates that the joint shear capacity of the specimen having a conventional deep spandrel beam did not significantly improve over the same specimen having a shallow spandrel beam. However, the results confirm that a well-reinforced wide spandrel beam substantially enhances both the joint shear capacity and the spandrel beam torsional strength of the connection. Design proposals, accounting for the joint shear and spandrel beam torsion, are recommended.

The roof is the part that experiences the largest wind load and is usually the most vulnerable part of a house. However, data on how the wind loads are transferred through the roof structure are scarce. The fluctuating nature and variable spatial distribution of wind loads combined with the structural response can cause significant challenges for assessing the distribution or sharing of loads in a roof. Such studies are required to obtain more reliable estimates on vulnerability assessment to windstorms. This paper describes the transmission of wind loads from the pressure on the cladding through the cladding-to-batten connections to the batten-to-truss connections on a roofing system typical of that in many contemporary houses constructed in cyclonic regions of Australia. The study found that the use of normal design practices can significantly underestimate connection loads when highly correlated large-scale wind pressures act on these roof systems.

This study proposes a framework for the probabilistic prediction of building portfolio functionality loss (BPFL) in a community following an earthquake hazard. Building functionality is jointly affected by both the structural integrity of the building itself and the availability of critical utilities. To this end, the framework incorporates three analyses for a given earthquake scenario: (1) evaluation of the spatial distribution of physical damages to both buildings and utility infrastructure; (2) computation of utility disruptions deriving from the cascading failures occurring in interdependent utility networks; and (3) by integrating the results from the first two analyses, making a probabilistic prediction of the postevent functionality loss of building portfolios at the community scale. The framework couples the functionality analyses of physical systems of distinct topologies and hazard response characteristics in a consistent spatial scale, providing a rich array of information for community hazard mitigation and resilience planning. An implementation of the BPFL framework is illustrated using the residential building portfolio in Shelby County, Tennessee, subjected to an earthquake hazard.

The collapse behavior of individual deep columns subjected to realistic loading and boundary conditions is investigated in this study. Loading protocols that are representative of seismic demands on first-story columns are developed through simulations of complete frames subjected to collapse-inducing seismic loading. A set of deep columns that cover a wide range of both global and local slenderness ratios representative of commercially available deep sections is used to investigate and codify the effects of three key parameters: level of axial loading, global slenderness ($L/r_y$), and web slenderness ($h/t_w$). Current design recommendations are critiqued and modified provisions that incorporate the influential parameters identified in this study are proposed for designing highly ductile members for seismic applications. The new provisions are proposed in a format that can facilitate adoption into future specifications.

This investigation was focused on developing an approximate approach for properly orienting ground motion inputs to achieve the maximum displacement demands on electricity transmission towers in the near-fault regions. The approximate approach is based on the fundamentals of dynamics of structures and inspired by the classic response spectrum analysis (RSA) method. To validate the approximate approach, a prototype was identified and analyzed using two computer models with and without consideration of the interaction between the transmission towers and transmission lines. The parametric response history analyses (RHAs) using a set of pulse-type near-fault ground motion records were performed on both computer models to generate the reference data for assessing the adequacy of the approximate approach. Result comparisons show that the approximate approach remains valid for both computer models and can be used for future designs. Moreover, the analysis results demonstrate that the fault-normal (FN) direction cannot be used as a surrogate for the orientation of the ground motion components causing the maximum displacement demands on electricity transmission towers in the near-fault regions. Further, the analysis results from one computer model were used to illustrate the limitations of the current analysis strategy used in designs.

This paper presents an experimental study carried out on eight full-scale uncorroded and corroded reinforced concrete short columns subjected to the simulated seismic loading to investigate effects of corrosion on the seismic performance of short columns that failed in shear. The key variables are the corrosion level of reinforcement and the applied axial force ratio. The seismic behavior of test specimens was evaluated in terms of crack pattern, hysteretic response, shear strength, displacement ductility, drift capacity, and energy dissipation capacity. The experimental results highlighted that the corroded columns suffered a significant degradation of shear strength and deformation capacity as compared with uncorroded columns, especially when they are highly corroded and under high axial load ratio. Methods were proposed to estimate the shear strength of corroded short columns that failed in shear that consider the contribution reductions to the shear strength of transverse reinforcement and concrete due to corrosion. Among these methods, the shear strength of corroded RC short columns estimated based on both the average corrosion mass loss and average residual cross-sectional area was not conservative as compared with the test results. The shear strength of corroded short columns estimated using the minimum residual cross-sectional area of transverse reinforcement, however, showed good and reliable agreement with the test results in this study.

The component and cladding wind load provisions for low-sloped roofs on low-rise buildings in ASCE 7-10 were examined using measured pressure data from an aerodynamic database. It was found that both the design pressure coefficients and size of the roof zones in ASCE 7-10 are much smaller in magnitude than indicated by the data. The data indicate that building height is the most significant parameter affecting the size of the roof zones, while plan dimensions have a limited impact on this class of buildings. Recommendations for revised roof zones are developed, which include a modification to the shape of the corner zone, the addition of a new interior zone far from the roof edges, and a zone size definition that depends only on building height. However, even with increased roof zone sizes, the measured data indicate that the design pressure coefficients must also be increased in the corners and edges.

The rivet-fastened rectangular hollow flange channel beam (RHFCB) is a new cold-formed steel section and is considered to be a substitute for welded hollow flange channel beams. This monosymmetric channel section is made from two torsionally rigid rectangular hollow flanges connected to a web plate using rivets at intermittent spacing. This fabrication process allows great flexibility in selecting different combinations of web and flange element sizes to attain optimum design capacities. Although the shear behavior of the commonly used lipped channel beam (LCB) and welded hollow flange beam (HFB) sections, with and without web openings, has been investigated previously, the shear strength and behavior of rivet-fastened RHFCBs with web openings have not been investigated yet. Therefore a series of shear tests was conducted to investigate the shear behavior and strength of rivet-fastened RHFCBs with circular web openings. Simply supported test specimens with aspect ratios of 1.0 and 1.5 were loaded at midspan until failure. The shear capacities determined from the tests were compared with those predicted by current cold-formed steel design standards. The results revealed that the existing design equations were not able to accurately predict the shear capacities of rivet-fastened RHFCBs with circular web openings. This is mainly due to the shear buckling capacity improvements provided by the rectangular hollow flanges and associated postbuckling strength. Hence the shear strength capacity results were used to propose improved design equations for rivet-fastened RHFCBs with circular web openings. This paper presents the details of the shear tests, observations, design capacity comparison, and proposed design equations.

This study conducts shake table studies and analysis of a large-scale novel posttensioned (PT) precast bridge column connected to a precast footing with a pocket connection. The primary objective is to develop a resilient square precast bridge column with minimal residual lateral displacement and plastic hinge damage when subjected to strong earthquakes. Another objective is to evaluate a column-footing pocket connection. The column is posttensioned with unbonded carbon fiber–reinforced polymer (CFRP) tendons to eliminate permanent drifts. To mitigate seismic damage, ultra-high performance concrete (UHPC) is used in the plastic hinge zone of the column. The column model is subjected to the 1994 Northridge-Rinaldi earthquake record with increasing amplitudes until failure. Experimental results show that the drift ratio and displacement ductility capacity of the column are 6.9 and 13.8%, respectively, and the residual displacement is negligible. Furthermore, the pocket connection is effective in forming the plastic hinge in the column with no connection damage. Another finding of the study is that available fiber element models lead to close correlation between the measured and calculated responses.

Under normal in-service conditions, beams and slabs in reinforced concrete structures are usually cracked. Concrete cracking and steel-concrete bond damage lead to an irreversible reduction in the overall stiffness, thereby affecting the serviceability of reinforced concrete structures. The method proposed in this paper aims to assess both the steel-concrete bond damage and the bending stiffness of existing structures based on the cracking pattern observed in situ including the location of bending cracks, their spacing, and their width. The time-dependent effects of creep and shrinkage are also considered. Short-term and long-term experimental results obtained from tests on five reinforced concrete beams are used to evaluate the effectiveness of the method. For each beam, the cracking pattern and the width of cracks measured immediately after first loading and after a 6-month period of sustained loading are used to assess the immediate and time-dependent instantaneous stiffness of the beams. The stiffness and the load-deflection response determined using the proposed method are shown to agree well with experimental observations.

This paper summarizes results of a comprehensive computational study on the time-dependent or creep behavior of flush endplate beam-column connections subjected to elevated temperatures due to fire. Using a connection prototype that was previously studied experimentally, creep connection tests were simulated in a finite-element software package to establish the response of flush endplate connections as a function of time. The effect of important design parameters such as shear-to-axial load ratio, endplate thickness, and bolt size on the time-dependent response of flush endplate connections was also investigated in creep connection simulations. Results of creep connection simulations were further used to develop a methodology to quantify the effect of thermal creep of structural steel on the behavior of flush endplate connections in fire. In this methodology, time effects on the strength and rotational capacity of flush endplate connections are explicitly presented in the form of isochronous force-rotation curves. Results from this study clearly indicate that the strength and deformation capacity of flush endplate connections are highly time dependent for temperatures, stresses, and time durations expected in building fires and that ignoring the effect of thermal creep of steel may lead to unsafe predictions of the response of steel connections exposed to fire temperatures.