Practice Periodical on Structural Design and Construction

Imagine how much time and expense could be saved if virtual experiments were done prior to actual testing in order to have some confidence in the chosen parameters. Structural tension connection strength is often expressed as efficiency, the test failure load divided by the failure load for the gross area of the connected member. Experimentally this is done by testing a connection to failure and also testing a tension coupon to find ultimate strength. Finite element studies are often used to predict relative structural failure loads, but actual failure load depends upon the failure criterion. This paper presents an analytic procedure that may aid in the development and interpretation of full-scale tests. This is especially important in an experimental program for steel connections due to the cost involved in the testing of a single connection and the need to find results for varying geometries. Finite-element results are compared to experimentally found efficiencies of some welded steel connections for plates and angles. Some observations are made about the effect of eccentricity on welded tension connections.

Traditional methods of underground utility installation and replacement generally employ conventional open cut methods. These trenching methods in most urbanized settings typically create road closures, traffic delays, unnecessary detours, loss of access to homes and business, unsightliness, noise, and general disruption. Faced with population growth and an aging underground utility system, China has looked to emerging technologies to assist in providing sustainable solutions to addressing this situation. Three trenchless construction methods that have currently been adopted in China are horizontal directional drilling (HDD), pipe bursting, and pipe ramming. HDD is a technique that enables the installation of conduits and pipelines with minimum need for open-cut surface excavation. Pipe bursting is an accepted method for trenchless pipe replacement where an existing sewer or utility pipeline is replaced with a totally new structural pipe of equal or greater inside diameter. Pipe ramming is an established technology that provides a cost efficient alternative for placing steel casings under roads, railroads, finished landscapes, and structures. This paper describes each of the three trenchless construction methods and discusses several applications for sustaining underground utility networks through case histories of successful projects in China.

Foundation construction adjacent to landmark structures can present numerous challenges for the geotechnical engineer and contractor, including difficult geology, unexpected subsurface conditions, limited access, and massive and relatively heavily loaded foundation elements, in addition to being sensitive to their historic fabric. This paper presents two case histories where underpinning was successfully executed in two different geologic settings and utilized various techniques.

Visiting an earthquake damaged town is like visiting a gigantic structural testing laboratory. A carefully conducted forensic engineering can reveal much insight on the nature of earthquakes and the fundamental principles of seismic design. The earthquake devastated area is sufficient proof that earthquakes release a tremendous amount of energy. This energy propagates in all directions and enters a structure as ground motion which has displacement, velocity, and acceleration components. The seismic energy which is introduced into the structure must be dissipated within the structure. Energy dissipation shows itself mainly as inelastic behavior of the structural system. The structure must be damaged to dissipate energy. If seismic energy is dissipated at locations which make the structure unable to satisfy equilibrium of forces, collapse is inevitable. An earthquake resistant structure should dissipate seismic energy as damage in the structural system, but collapse should not occur. What is more, after the earthquake, damage should be economically feasible to repair. Observations reveal that beam-column joints and column ends are wrong locations to dissipate seismic energy. Shear failures and anchorage failures of reinforcing bars are wrong types of damage which dissipate very little energy and lead to collapse. Short columns and soft or weak stories must be strictly avoided. Longitudinal and transverse reinforcement should be well detailed and anchored. A successfully designed and constructed building should contain shear walls conforming to the year 2000 requirements of the ACI. In the wide earthquake devastated area, observations reveal that no buildings have collapsed which contain shear walls as part of the structural system. Shear walls are the seismic collapse insurance of a building. A successfully designed and constructed building should not sway out of control, should dissipate seismic energy by flexural plastification at bottom of shear walls and ends of beams. The occurrence of shear failure before flexural failure should never be permitted.

The down-aisle lateral load-resisting systems of pallet-type steel storage racks are typically moment frames utilizing special beam-to-column moment-resisting connections. Both the stability and seismic response of racks are strongly influenced by the rotational stiffness developed by the beam-to-column connectors. The behavior of these connectors is poorly known, and consequently there is significant uncertainty as to proper values of connector stiffness and strength to use in design. This paper presents the results of down-aisle shake table tests performed on steel pallet-type storage racks fabricated from hot-rolled sections and incorporating four different bolted beam-to-column connectors. The main objectives of the tests were to determine appropriate static load connector rotational stiffness values from measured dynamic characteristics of storage racks under low amplitude vibrations, and to evaluate their response under quasi-static conditions as well as under strong earthquake ground motions. The experimental results suggest an initial static stiffness which degrades and recovers with small motions typical of in service conditions. This result may explain the poor repeatability of some testing protocols. For seismic motions, all rack specimens were able to undergo large inelastic deformations without compromising their load carrying capacity.

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures provides the means to recycle the existing roadway and use that material, in a limited amount, in the construction of new pavements. This is an environmentally friendly method to recycle the existing pavement and provide a new pavement surface. While this is a most economical means of pavement rehabilitation, the life of the overlay is generally 10 to 20 years before rehabilitation is pursued. As a new overlay is placed, the previous overlay is milled, creating RAP. The amount of available RAP material in the U.S. is considerable and continually increasing, and the use of RAP as a component in new mixes is strongly supported by the asphalt industry. However, currently, there seems to be no method to control the quantity of RAP in an asphalt mix. This is due to the differences in plant readout units that vary based on plant types and contractor practices. As part of a larger research project to devise a test that can identify the presence and quantity of RAP in hot-mix asphalt pavements, this paper presents the state of the art research conducted on RAP and RAP detection. The paper also presents the results of a survey conducted to investigate the availability of a RAP detection and quantity determination method used by the various states. It was concluded that at the current time, there is no specific test available that would accurately determine the presence and quantity of RAP in hot-mix asphalt.