Practice Periodical on Structural Design and Construction

Every year, construction activities expose millions of acres of soil to the elements of wind, rain, and snow. This greatly increases the potential for erosion; and therefore, the need for efficient erosion and sediment control practices is a high priority. In this research, the performance of a silt fence system with tiebacks (a.k.a., “j-hooks”) was investigated to determine its effectiveness as a sediment control technology at highway construction sites over multiple rainfall events. The data presented provide a qualitative perspective showing sediment migration over time along with the occurrence or lack of failures among two silt fence systems tested. The results from this field test exhibit that silt fence tieback systems are more effective in containing eroded sediment from construction sites and also reduce the risk of silt fence system failures than traditional linear silt fence systems.

Ductility is a fundamental component in the design of robust structures. For timber structures, the unfavorable material characteristics pose particular problems to its realization. Two approaches for improving the post-elastic behavior of glued-laminated timber beams have been investigated by testing and numerical analysis. The first is based on forming mixed beams with suitably assembled lamellae of different strength class; in the second, steel reinforcement is used. Satisfactory results have been obtained mixing laminations of different grade, whether from a single species or from different species, as long as the strengths of the lamellae are well differentiated. Steel-reinforced timber beams require taking special provisions in order to develop a ductile bending behavior, because material irregularities induce brittle failure of wood in tension before the steel bars may yield. Positive results were obtained, specifically preventing local failure modes, by releasing tension stresses in wood, by inserting small-diameter steel screws, or with a suitably balanced distribution of steel area. Steel reinforcement seemed once more capable of providing a simple and reliable solution.

The study evaluates an alternative to traditional wood-framed shear wall construction, an innovative use of a water and seismic damage resistant, wood-concrete-composite (WCC). The WCC design consisted of a thin layer of engineered cementitious composite (ECC) cast in a traditional wood frame. Structural performance and damage sustained during lateral loading and cost were evaluated, and compared to a traditional wood frame with OSB sheathing. Monotonic tests of WCC walls show that the average maximum load was $47.5\mathrm{kN}$ $\left(\mathrm{10,700}\mathrm{lb}\right)$ , average elastic shear stiffness was $1.78\mathrm{kN}∕\mathrm{mm}$ $(\mathrm{10,200}\mathrm{lb}∕\mathrm{in.})$ and average energy absorbed was $\mathrm{4,810}\mathrm{J}$ $\left(\mathrm{42,600}\mathrm{lb}\text{-}\mathrm{in.}\right)$ . Tests show WCC is comparable with or superior to the OSB wall in shear strength and stiffness, energy absorption and ductility. During lateral loading the WCC appeared to sustain less damage than the OSB wall. Panelized construction of the WCC may increase cost but yield benefits such as decreased construction time and greater durability. WCC appears to be a viable shear wall system that should be refined and tested for building code compliance.

A unique structural problem and solution is presented on the analysis and design of a continuous structural concrete slab track on grade. Rails embedded into the structural concrete with an elastomeric grout system act as part of the overall load resisting system. To successfully and effectively design the concrete slab track the interaction between the rail, elastomeric grout, concrete, reinforcement and the soil subgrade must be accurately be predicted. The classical theory of beams on an elastic foundation is used to predict the response of the floating rail system.

Measurement of force on 1:100 scaled model representing a typical two-story building with a flat roof configuration adopted by a low-income group community was carried out. The models of buildings having a parapet were tested in isolation and located in a rectangular array of $5\times 4$ building clusters under simulated terrain conditions. Three groups of building clusters having clear spacings of 60, 90, and $220\mathrm{mm}$ in the direction of wind were considered. The effect of wind angle on building clusters was studied between yaw angles from $-45°$ to $+45°$ at equal intervals of 15°. Mean and root-mean-square force coefficients for the panels were evaluated using quasi-static and pseudosteady approximations. The factors of shielding and enhancement were computed depending on the location of the building. Test results were further compared and validated with the values obtained from similar studies reported in literature.