Abstracts:This paper deals with the shear behavior of steel stud connectors between a concrete slab and steel beam under static and impact loading. An experimental program involving four static and nine impact pushout tests was designed and carried out according to the descriptions in related specification. The failure modes and the time history of impact load and slippage displacement as well as the shear strength of stud connectors are presented and investigated. It is found from static tests that the shear capacity of stud connectors reasonably met the corresponding requirements in a related specification, while the dynamic shear capacities of the connectors were improved by 33–63% compared with the static results. Based on the dynamic responses, the shear mechanism of the steel stud shear connectors under impact loading is also examined, and the failure process can be divided into three typical stages. Furthermore, based on the equations given in some existing guidelines, a design proposal is developed to accurately predict the shear capacity of stud connectors under impact loading, where the strain-rate effect is considered according to the recommendations given in a published report for the concrete strength and in a published journal paper for the steel strength under impact loading. The testing results can provide essential data for future analytical and design-oriented study of composite beam with shear stud connectors under extreme loading conditions.

Abstracts:This paper presents a new structural identification (St-Id) framework along with a damage indicator, displacement unit influence surface using computer vision–based measurements for bridge health monitoring. Unit influence surface (UIS) of a certain response (e.g., displacement, strain) at a measurement location on a beam-type or plate-type structure (e.g., single-span or multispan bridge with its deck) is defined as a response function of the unit load with respect to the any given location of the unit load on that structure. The novel aspect of this paper is a framework integrating vehicle load (input) modeling using computer vision and the development of a new damage indicator, UIS, using image-based structural identification. This framework is demonstrated on the large-scale bridge model in the University of Central Florida Structures Laboratory for verification and validation. The UIS damage indicators successfully identified the simulated damage on the bridge model, including damage detection and damage localization.

Abstracts:The objective of the present study is to contribute to the understanding of the seismic behavior and performance of reinforced concrete flexure-dominated walls when their boundaries are subjected to high compression. Typical structural wall specimens that conform to the current Japanese design code were investigated experimentally and analytically. The specimens failed in a brittle manner, with concrete crushing over a length of approximately 2.5 times the wall thickness, which was much shorter than that in the tensile plastic region. A model for the bending analysis considering such nonuniform hinge length was proposed to evaluate the structural performance of flexure-dominated walls. The analytical results simulated the experimental behavior well and clarified the bending-compression failure mechanism: the lateral strength deterioration was triggered by a loss of compressive resistance within the neutral axis depth and was then accelerated by a rapid increase of the neutral axis depth. On the basis of these findings, simplified formulas are presented for the evaluation of the ultimate deformations at the bending-compression failure for flexure-dominated walls.

Abstracts:Wind pressures acting on a cubic building with openings exposed to stationary tornadolike vortices were studied experimentally. The effects of opening ratio, single central opening azimuth, and radial distance between the building model and tornadolike vortex on external and internal wind pressure distributions were the focus of this study. Particular attention was paid to the difference between tornado-induced wind pressure coefficients and those obtained in conventional boundary-layer wind flow, American design code, and Chinese design code. The results indicate that the measured wind pressures on the model are due to the combined effects of pressure drop accompanying a tornado and flow-structure aerodynamic interaction. Both the opening ratio and large single opening azimuth influence the internal wind pressure and vertical wind force on roof structure. The low-rise building model experiences maximum wind forces when it is located at the tornado core radius. Additionally, owing to the high negative pressure drop accompanying a tornado, tornado-induced wind pressure coefficients exceed the provisions of American design code and Chinese design code by large factors.

Abstracts:Seismic damage affecting industrial-process components can cause severe disruption, leading to not-negligible profit reduction associated with business interruption. Hence, the implementation of a proper seismic risk mitigation strategy is often required, accounting for financial issues as well. This study presents a novel probabilistic seismic risk assessment framework able to quantify business-interruption losses on the basis of a company’s balance-sheet data. The framework contains a financial module that uses a profitability index (PI) for identifying the most profitable seismic retrofit strategy to be implemented, given a reference time window and available budget. Application of the framework to a typical Italian cheese factory is also illustrated. Results show how business-interruption losses are comparable with direct costs for the rehabilitation of seismically damaged components. Additionally, it is demonstrated that PI can be considered a suitable financial indicator, and evaluating the contemporary benefit has a primary importance when a retrofit strategy is applied to more components.

Abstracts:This paper describes the experimental performance of D-region reinforced concrete bent specimens affected by varying levels of alkali-silica reaction (ASR) from none to mid-to-late stages, as determined from petrography analysis and from the presence and extent of concrete expansion and cracking. It also describes the analytical methodology employed. It is shown that specimens showing varying degrees of ASR compared with the control specimen without ASR had slightly greater stiffness, strength, and ductility, with no evident detrimental effects on structural response. The apparent improved behavior can be explained as a result of the activation of the specimen’s reinforcing steel due to concrete expansion primarily from ASR, which effectively prestresses and confines the core concrete. Analytically, conventional code-based methods, including sectional analysis and strut-and-tie modeling (STM), underestimate the strength capacity of the specimens when tested to failure.

Abstracts:Experiments on deformed reinforcing bar anchorages developed in strain-resilient cementitious composites (SRCCs) with high tensile deformation capacity illustrate that the bar-matrix assembly may respond in a ductile manner marked by pullout failure with no cover splitting—even in the absence of external confinement. This ductile bond-slip response is owing to the extremely high tensile fracture energy of the matrix, which is attributed to the reinforcing action of the dispersed microfibers in the cementitious matrix. This enhances the associated bond-slip law with higher strength and a slowly descending branch, very similar in form to the response curve of confined anchorages that demonstrate ductile, resilient response. To understand and model the structural response of an elastic bar anchorage in a SRCC matrix, the analytical solution of the field equations that govern the bond problem are established with reference to the entire range of the bond-slip law up to large levels of slip, including the postpeak descending branch, which quantifies the fracture energy of the matrix. The accuracy of the mathematical solution is verified through correlation with laboratory evidence, benchmark finite-element analysis examples, and numerical solutions of the discretized problem. The mathematical solution is used in order to conduct a parametric investigation that accounts both for the bond toughness and the anchorage geometry, to illustrate their significance as prerequisite for development of high-strength reinforcement.

Abstracts:Reducing the potential impacts from a future disaster can be accomplished through decreasing the hazard exposure and reducing the community’s vulnerability. Moreover, communities have both physical and social vulnerabilities that deserve attention; however, most engineering studies focus on assessing and mitigating the physical infrastructure without fully considering the social infrastructure. This paper offers a more holistic examination of vulnerability. Specifically, a two-stage analytical approach is presented that treats both an earthquake and a community’s socioeconomic and demographic makeup as hazards. The first stage addresses the physical vulnerability of a community through retrofitting the residential building stock using an inventory of woodframe building archetypes. The second stage incorporates the social characteristics of a community through modeling six social vulnerability variables. A social disaster factor (SDF) is introduced to offer a quantifiable approach for understanding the intersections between physical and social vulnerabilities. Case studies are presented for three communities: a middle-class ZIP code, the poorest ZIP code, and the wealthiest ZIP code, all in Los Angeles County, California. The SDF is computed and compared for the case studies during both stages of the analysis. The analyses demonstrate that when only physical vulnerabilities are modeled, one might incorrectly conclude that the impacts of the event are virtually eliminated. However, when social vulnerabilities are modeled as a hazard alongside the physical vulnerabilities, the projected impacts of the disaster are severe, especially for the most vulnerable populations, in terms of injuries, fatalities, posttraumatic stress disorder diagnoses, and number of dislocated households. In the combined model, these impacts run along racial and economic fault lines, with the most marginalized communities experiencing the most extreme projected losses. These results may have implications for both theory and practice.

Abstracts:Small-amplitude cyclic vertical motions of timber floors perceived as unacceptable by humans are commonly the result of walking impact forces. Contemporary vibration serviceability guidelines mainly require prediction of static displacement and modal frequencies of floors. This study used an advanced finite-element (FE) analysis approach to model glulam beam-and-deck floor systems. This permits prediction of static displacement and modal response characteristics that closely match values determined by testing full-scale floor. The verified modeling method is used to show how variations in floor details such as span and floor width affect the vibration behaviors of these floors. This shows that changing the floor width has little effect on the fundamental frequency and midspan deflection of a floor, but higher-order modal frequencies are strongly affected. Although fundamental frequency of floors is not highly sensitive to the flexural rigidities of decking layers, higher-order modes are strongly affected. The broad conclusion is that reliable prediction of parameters engineers used to predict vibration serviceability of such floors depends on the use of appropriate models. Appropriate models are ones that incorporate deep system effects on motions stemming from the layered nature of beam-and-deck element floors and depths of glulam elements used as the beams.

Abstracts:The current study proposes a simple and mechanically sound analytical approach for crack analysis of reinforced concrete (RC) flexural members at the stage of stabilized cracking. The philosophy behind the proposed methodology is to establish mean spacing between the primary cracks through the compatibility of the stress transfer and mean strain approaches. The governing parameters of crack spacing are obtained by equating mean strains of the tension reinforcement defined by these approaches. The model assumes that a single RC block of a length of mean crack spacing represents the averaged deformation behavior of the cracked member. Based on the experimental evidence, reinforcement strain within the block is characterized by a strain profile consisting of straight lines representing zones with different bond characteristics. It was shown that crack spacing is mostly governed by four geometrical parameters given in the order of significance: section height, reinforcement ratio, bar diameter, and cover. A limited comparative analysis has demonstrated that the predictions of mean crack spacing by the proposed model agree well with the tests. Considerations are given to extend the proposed methodology to the analysis of maximum crack width.