While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes.

Horizontal wood diaphragm systems, whether decked with conventional or mass timber panels, transfer wind and seismic loads to vertical elements of the lateral force-resisting system, in flexible, rigid, or semirigid ways. Characterizing and calculating the resulting diaphragm deflections will help determine the distribution of forces to critically loaded components and a significant portion of lateral building translations and rotations. Deflection equations for sheathed wood structural panel (WSP) diaphragms are well established in US design standards in a four-term expression that models flexural, shear, and fastener-slip deformations, but similar equations for cross-laminated timber (CLT) diaphragms have yet to unfold, despite growing industry consensus that CLT panels make efficient slabs and decks. Building code standards require CLT diaphragm deflections be computed using the principles of engineering mechanics. The current three-term and four-term deflection equations for WSP diaphragms are based on various assumptions that are often outpaced by current design practices. This is the second of two companion papers, in which the first paper provides the full generalized derivation of the current four-term WSP diaphragm deflection expression with a mechanics-based expansion to unify both potential WSP and CLT applications. This second paper builds on the first paper by expanding the generalized equation with implementation insights unique to WSP and CLT diaphragms. The various challenges of calculating diaphragm deflections associated with the current design practices are discussed with suggestions to assist in implementation.

Horizontal wood diaphragm systems, whether decked with conventional or mass timber panels, transfer wind and seismic loads to vertical elements of a lateral force-resisting system (LFRS), in flexible, rigid, or semirigid fashion. Characterizing and calculating the resulting diaphragm deflections determines the distribution of forces to critically loaded components and a significant portion of lateral building translations and rotations. Deflection equations for sheathed wood structural panel (WSP) diaphragms are well established in US design standards in a four-term expression that models flexural, shear, and fastener-slip deformations, and its full derivation using principles of mechanics is provided herein. Derivations of similar equations for cross-laminated timber (CLT) diaphragms have yet to unfold, despite growing industry consensus that CLT panels make efficient slabs and decks. In this first of two companion papers, the corrected full derivation of the current four-term WSP diaphragm deflection expression is provided and assessed, and two ways to quantify the cumulative contribution of fastener slip are presented to expand its usage to a wider variety of WSP and CLT configurations in current use. Building on this generalized mechanics-based derivation, the authors are able to propose and assess in the companion paper a unified diaphragm deflection model to compute both WSP and CLT diaphragm deflections as implemented under current practice and guide further development.

This paper presents the behavior of floor diaphragms of a shake-table experiment of a full-scale 2-story mass-timber building structure. The structure consists of glued-laminated timber beams and columns, and floors and walls were designed and built making use of cross-laminated timber panels. Two different floor systems were designed, where the roof consists of a topped cross-laminated timber (CLT)-concrete composite system, and the floor level consists of untopped CLT panels connected with plywood single-surface splines. The CLT floor systems were designed to remain essentially elastic over the whole series of shake-table tests, which included testing of three lateral force-resisting systems tested at three different seismic intensity levels (service level, design basis, and maximum considered earthquake) for a total of 34 shake-table earthquake tests. Results from the testing indicate that CLT diaphragms designed to remain essentially elastic based on basic principles of structural mechanics and existing test data can achieve desired seismic performance objectives. In addition, sources of overstrength in certain elements of the diaphragm need to be explicitly considered for a holistic diaphragm design. (C) 2021 American Society of Civil Engineers.

To simplify system development and software integration, specialized software platforms are now employed in various unmanned vehicles, including unmanned air vehicles (UAVs), mobile ground robotics and underwater vehicles. The "software platform" provides a software framework and supporting tools in an integrated development environment. This paper describes some examples of the use of software platforms in the development of unmanned vehicles and common characterists of the software platforms.

Specialized platforms have recently been employed in various autonomous systems, such as unmanned vehicles and mobile robotics, to address system development and integration challenges. This paper describes the key elements of platforms and their use in the development of autonomous systems. A software platform includes both a architectural framework and supporting tools. Software frameworks for autonomous systems typically combine hierarchical component architectures with domain-specific behavioral patterns. They can also provide many pre-written components that partially implement the solution. This provides an infrastructure to effectively construct the layered control of autonomous systems. Software platforms can be used to integrate low-level device drivers, hand-written or custom code, telemetry and communication software, and model-based intelligence in a robust manner. With the progress of modelbased development and automated generation of production quality code, platforms become increasingly valuable to system architects.

System development and integration is a major challenge for unmanned vehicles. Different tools, modeling abstractions and engineering skills are utilized at various stages of a typical unmanned vehicle development project. These may range from writing low-level device drivers in C/C++ to building physical simulation models and control algorithms with tools such as MATLAB ® and Simulink ® to developing HMIs (human machine interfaces) in a high-level language such as Java™. All these must be finally integrated into a coherent, documented, tested system. This process often breaks down, especially since ad hoc designs provide too little structure to help the process. Recently, new software platforms technology is emerging to address these needs. A platform includes both a architectural framework and supporting tools. It also provides many pre-written components that partially implement the solution. The most effective frameworks are tailored to a specific problem domain. This paper describes the characteristics, capabilities and benefits of frameworks and gives examples of their use in some current unmanned vehicle projects. Some major benefits include component sharing and reuse, system integration, and rapid prototyping.

The structural engineering community has been developing performance-based earthquake engineering methodologies. Structural control can provide an additional method to meet desired performance objectives. One approach is the development of probabilistic seismic demand curves, so that the probability that any damage measure exceeds a pre-determined allowable limit can be determined. Cornell developed a procedure that couples conventional Probabilistic Seismic Hazard Analysis with nonlinear dynamic structural analyses in order to determine the annual probability of exceedance of a given parameter, resulting in the Probabilistic Seismic Demand Analysis. These concepts are then extended to the analysis of controlled structural response, referred to as Probabilistic Seismic Control Analysis. This research then evaluates the performance of various control systems under seismic excitations. It focuses on the SAC Phase II structures for the Los Angeles region, and three types of possible controllers: (1) base isolation system; (2) linear viscous brace dampers; (3) and active tendon braces. such as the peak bearing displacement for the isolation system. As a result, fewer control analyses may be required to estimate the expected structural behavior. The resulting annual hazard curves can be used to evaluate the effect of different control parameters as well as provide a basis for comparison between different control strategies.

A preliminary study is presented which addresses the role of active control technology in the improvement of structural performance during earthquakes. Performance-based evaluation of control methods is an important step in relating the bene ts of these non-traditional structural solutions to the earthquake engineering community. A nonlinear model of a steel moment frame is developed and integrated with an active control system. The nonlinear model is a strong-column-weak-girder system, with lumped plasticity model described by the smooth-varying Bouc-Wen hysteretic model. The steel moment resisting frame with tendon actuator in the rst story is subjected to four di erent earthquakes and varying control e ort. The results from the control simulations are then presented. Research Assistant; Dept. of Civil Engineering, Stanford Univ., Stanford, CA 94305-4020. Associate Professor; Dept. of Civil Engineering, Stanford Univ., Stanford, CA 94305-4020.

1 Dept. of Civil Engineering, Texas A&M University, College Station TX, 77843-3126; lbarroso@civilmail.tamu.edu 2 Dept. of Civil and Environmental Engineering, Stanford University, Stanford CA, 94305-4020; breneman@stanford.edu 3 Dept. of Civil and Environmental Engineering, Stanford University, Stanford CA, 94305-4020; smith@gofannon.stanford.edu COMPARISON OF STORY DRIFT DEMANDS OF VARIOUS CONTROL STRATEGIES FOR THE SEISMIC RESISTANCE OF STEEL MOMENT FRAMES

This study develops an active control methodology for the AMD benchmark problem of Spencer, et al. (1997) based on dynamic output feedback controllers designed using an H1 based approach. Kalman lter estimators of the states of a reduced order model of the benchmark structure are coupled to static state feedback controller gains to develop the dynamic feedback controllers. A method is outlined for designing H1 feedback controller gains, and a comparison is made between the e ectiveness of H1 static output feedback and the dynamic acceleration feedback controllers. The results quantify the performance increase obtained with the additional complexity of the dynamic output feedback controllers compared to the static acceleration feedback controllers. Introduction For the AMD benchmark problem of Spencer, et al. (1997), controllers are designed using two H1 based approaches: one approach uses direct static output feedback of sensor measurements, and the second approach uses a dynamic output feedback controller that consists of static state feedback controller gains with a Kalman lter state estimator. The controllers considered in this study are designed by a continuous-time H1 controller approach, then discretized for simulation with the benchmark model. The controllers are developed from a state space design model of the form: _ x(t) = Ax(t) +Buu(t) +Bww(t) (1) z(t) = Czx(t) +Dzuu(t) +Dzww(t) (2) y(t) = Cyx(t) +Dyuu(t) +Dyww(t) (3) where x(t) is the state vector, u(t) is the vector of control inputs, w(t) is the vector of disturbance inputs, y(t) is the vector of sensor measurements, z(t) is the vector of regulated outputs, and A, Bu, Bw, Cz, Dzu, Dzw, Cy, Dyu, and Dyw are matrices of Assistant Professor, Stanford University, Dept. of Civil Engineering, Stanford, CA 94305. Research Assistant, Stanford University, Dept. of Civil Engineering, Stanford, CA 94305.

There are several key issues to be considered in the design of active control systems for civil structures, including robustness to perturbations of the structural parameters; stability in the presence of nonlinear actuator saturation eeects; and the use of output feedback methods when it is not possible, or practical, to obtain the full state of the system. This research presents a design algorithm to create robust H 1 static output feedback controllers, for seismically excited civil structures, which account for all these eeects in a single design. Robust, static acceleration feedback H 1 controllers are created for a ve story structure with a bounded, structural parameter uncertainty model. A non-convex optimization problem is formulated and solved using an iterative solution method to obtain the desired control gains. A primary advantage of this method is that an intuitive, feasible starting point is available using the open loop (uncontrolled) system and the worst case attenuation constant for the uncertain system. Simulation results using seismic excita-tions show the controllers obtained using this design method to be eeective with minimal control eeort.

Control of external acoustic radiation from vibrating structures typically has employed models of simple systems which make the creation of controllers straightforward. This research proposes a method of creating robust H1 static output feedback controllers for arbitrarily complex uid structure systems. Fluid structure systems are shown to be easily modeled as linear time invariant systems for the external acoustic control problem using newly developed far eld boundary conditions. The models created contain the uid, structure, and their interaction boundary as a single system model to be controlled. Robust H1 output feedback controllers are formulated and the resulting non-convex optimal equations are reduced to an iterative convex optimization algorithm.

A comprehensive computer program that analyzes bridge piers including the pier structure, nonlinear piles, and nonlinear soil interaction is discussed. The program, LPGSTAN (laterally loaded pile group and structural analysis), includes pile group effects, missing and battered piles, and bridge connection effects. The program is unique in that the analysis models are defined by using the designer specifications such as pile spacing, number of columns, and soil layer information. All model definition and result review are performed in a graphical environment. The program has not been tested by comparisons with data in the literature on pile group tests and an extensive series of centrifuge tests performed at the University of Florida. The program is in use at the Florida Department of Transportation and consulting firms throughout Florida. An overview of the program's assumptions, modeling, and capabilities is given.