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The Task Committee on Structural Connections decided to survey the current state of research and research needs in the general area of structural connections in metal. The information was gathered from responses to a short questionnaire published in the July 1973 Newsletter of the Structural Division. Responses were received covering 13 projects either recently completed or currently underway. The projects fall into six broad categories: 1) fatigue behavior of connections, 2) fastener characteristics, 3) seismically loaded connections, 4) end plate connections, 5) beam-to-column connections, and 6) general analysis.

Analytical studies of the elastic and inelastic response of reinforced concrete frames subjected to earthquake motion are presented. The effect of stiffness degradation on the seismic response and in particular on ductility demand is examined. Several single-story frames are analyzed; stiffness degradation significantly increases ductility demand in short period systems. Studies of multistory frames are also presented; stiffness degradation again increases ductility demand but the effect is pronounced only in the upper stories. The bending moments and forces induced in an inelastic multistory frame are smaller than those in a purely elastic frame. However, if the columns are designed to remain elastic while the girders yield, the reduction in the column moments and axial forces is not as large as that in the girder moments.

The earthquake damage experienced by electric power systems is briefly reviewed. Low cost methods for improving the seismic response of five categories of equipment damage are discussed. Securing substation transformers prevent catastrophic losses due to transformers falling from elevated pedestals, and the failure of lighting arrestors, bushings and control cables due to lack of slack in interconnections. Securing substation and power station batteries to their racks and the racks to their foundation prevents the serious consequences of their loss. Securing computers can prevent damage and disruption due to their loss. Properly supporting ceilings in control rooms can prevent damage and disruption caused by restriction in their operation. While securing circuit breakers may reduce damage, improved design, materials or installation methods may be required.

A method is presented to obtain seismic design response of linearly behaving structures with nonproportional damping characteristics. For such systems, time history analyses are usually performed to obtain accurate seismic response. To obtain design response, such procedures can become expensive and cumbersome as an ensemble of time histories may have to be considered as seismic input. Other procedures have been developed to ascertain appropriate values of modal dampings so that modal analysis approach and thus commonly adopted square-root-of-the-sum-of-the-sqaures (SRSS) procedures can be used. The approach presented here considers nonproportional damping effects exactly in analytical sense. It uses state-vector formulation and is based on random virbration priciples. The approach is similar to conventional SRSS approach and thus ground response spectrum can be directly used to obtain designd respose.

A methodology for the computation of probability of seismically induced liquefaction of saturated cohesionless soils is presented. Using available information on soil strength and expected earthquake ground motion, a Monte Carlo technique is used to predict the probability of liquefaction. Using site earthquake recurrence information, the probability of an earthquake causing liquefaction may be determined. A criteria is proposed for the selection of a bridge site to limit damage from liquefaction.

Input excitations of certain intensity that maximize the structural response have been an interesting subject of several investigations since the early 1970s. The basis of this lies in a worst case type of analysis that can be conservatively used in defining the seismic input. Such an approach may complement currently used procedures which are based primarily on design spectra. However, when maximizing inputs are considered in seismic assessments, inelastic behavior should be anticipated. This paper presents some seismic inputs that may be used for nonlinear structures. They are generated from recorded earthquakes and produce maximum nonlinear response.

Solutions are presented for modal analysis of hydrodynamic pressures generated by the three translational seismic components — longitudinal, vertical, and transverse — on a dam limiting a semicircular cylindrical reservoir. The main purpose is to show the influence of the cross-sectional shape of the reservoir in the hydrodynamic responses. Results are compared with those for rectangular cross section. Responses are found to be systematically smaller with semicircular cross section for a given cross-sectional area and depth. It is concluded that, for design purposes, the fundamental mode adequately approximates the response for various excitations of practical interest.

The desirability of installing seismic instruments on and near major dams is explained. Two types of instruments are required: (1) Strong-motion accelerographs for recording potentially destructive ground shaking and resulting dam vibrations; and (2) sensitive seismographs for determining the local seismicity. A minimum of two strong-motion accelerographs should be installed on the dam and a minimum of two should be installed in the immediate vicinity of the dam. Each accelerograph should record three components of motion, should have a natural frequency of approx. 20 Hz, a recording speed of approx 1 cm/s. The sensitive seismographs are intended to record the local seismicity in the vicinity of the dam site before construction, and to detect any changes in seismicity during reservoir filling. A minimum of three seismographs is recommended for installation in the vicinity of the dam site. A vertical-component seismometer (1 Hz - 5 Hz) with visual recorder and approx l0,000 magnification at 1 Hz is recommended.

The performance of dynamic seismic analysis from an economic viewpoint is presented. Dynamic models are discussed and several illustrations of economically developed models are presented. Economic considerations in selecting a computer code are also discussed.

Inelastic responses of four irregular multistory reinforced concrete framewall structures to strong base motions are analyzed using response spectrum methods, which account explicitly for effects o...

The behaviour of energy-absorbing friction joints in vertical connections was studied using a model on a shaking table. By varying the slip force in the joints it was shown that there is an optimum value that maximizes the energy dissipation and minimizes the stress for a given seismic intensity.Results given by nonlinear time history dynamic analysis are compared with values from the tests. A proposed approximate method for the calculation of the optimum slip force is given that agrees well with the other values obtained. Keywords: seismic response, tall buildings, friction joints, energy dissipation, earthquake resistant structures, model tests, dynamic analysis.

Acceleration floor spectra curves are commonly used as seismic design inputs for light equipment and other secondary systems. Earlier the writer had presented a method for generation of floor spectra directly from prescribed ground spectra. Further complementary developments in this method are made. These are: (1)The development of the method for generation of floor spectra at structural frequencies (an important resonance case); and (2)evaluation of nonstationarity of earthquake motions on floor spectra curves. Also, some approximations made in earlier work are further evaluated. As a result of these developments and evaluations, a comprehensive procedure based on stochastic principles is presented in the paper for definition of seismic design inputs for secondary systems. This procedure avoids the use of often used and recently criticized spectrum-consistent time history as seismic input for generation of floor spectra curves.

The methods used to provide horizontal and vertical control for the reconnaissance of an Antarctic ice cap are discussed and evaluated. Primary horizontal control was established by the line of position method. Primary vertical control was established from seismic measurements of the Ross Ice Shelf. Secondary horizontal control was established by angle and odometer traverse. Secondary vertical control was established by barometric leveling.

Data on use of refraction seismic and electrical resistivity geophysical methods, throughout United States, are given; examples of application of these methods to variety of subsurface problems pertinent to highway design and maintenance; studies of landslide conditions and tests made over water-covered areas.

Nuclear power stations, due to the consideration of insuring public safety, must be designed to withstand the effects of postulated strong motion earthquakes. A few of the many aspects of a complete seismic analysis are discussed. The loadings on the structures are determined by a dynamic analysis. The mathematical bases for the two most common methods of analysis, the response spectrum method and the time-history method, are presented. A description of an analytical model which includes the torsional response is given. There are a large number of component structures and items of equipment which cannot be included individually in the dynamic analysis of the building structures. A discussion of current methods for determining the dynamic response of these components and a suggested solution of the problem is presented. A discussion of the analysis of piping systems and soil-structure interaction is given.

The arithmetical steps in the computation of the spectrum are extremely lengthy. A mechanical analyzer was developed by the author at Columbia University, in New York, N. Y., to avoid this numerica...

The seismic response of earth banks is studied by the finite element method. The effects of the division and extent of the section of the bank used in the analysis are examined. The appropriate extent of the bank to be included in the analysis is ascertained by studying several sections of varying extents and observing the influence of the boundaries on the response values. The effects of the division of the bank are examined by increasing the number of divisions and observing the influence on the response values. Based on these results, criteria for the appropriate division and extent of earth banks on either rigid or flexible foundations are proposed. An independent check on the results is provided by the fact that the response values of the parts of the bank well behind the crest and well beyond the toe of the slope approach those of corresponding semi-infinite layers.

THE PAPER SUMMARIZES MAJOR CONCLUSIONS FROM A TWO-YEAR STUDY OF THE INFORMATION CURRENTLY AVAILABLE TO THE PRACTICING CIVIL ENGINEER TO AID HIM IN ANSWERING THE QUESTION, HOW SHOULD EARTH DAMS BE DESIGNED DIFFERENTLY IN REGIONS OF EARTHQUAKE ACTIVITY{ EMPHASIS IS PLACED ON SOME OF THE MAIN DESIGN PROBLEMS WHICH ARE NOT SUBJECT TO ANALYTICAL TREATMENT, SUCH AS, THE DEGREE OF CONSERVATISM JUSTIFIED, THE IMPORTANCE OF ZONING AND TRANSITIONS; DESIGN DETAILS FOR THE TOP OF THE DAM, THE INFLUENCE OF THE PROPERTIES OF THE CORE MATERIAL, THE EVALUATION OF THE SEISMICITY OF THE SITE, AND THE INFLUENCE OF THE SPILLWAY DESIGN ON THE SAFETY OF THE DAM AGAINST THE EARTHQUAKE HAZARD. INTERVIEWS WERE HELD WITH EXPERTS IN THE FIELDS OF SEISMOLOGY, GEOLOGY, EARTHQUAKE ENGINEERING, SOIL MECHANICS AND DAM ENGINEERING. /ASCE/

A practical method is presented to obtain synthetic motions that closely match a reasonable specified deisgn spectrum for a seismic design of important earthquake-resistant structures and equipment. The principle of this method is to modify existing motions. For this purpose, a spectrum-suppressing technique and a spectrum-raising technique are developed. Examples are then given to illustrate their applicability to actual structure design.

The earthquake design of a 37-story steel building is described. The structural solution is a flexible perimetral tube which resists the seismic effects and conforms to the side-sway limitation imposed by the Venezuelan seismic code. The spatial properties of the perimetral tube were taken into account and analyzed by a mathematical model representing a plane frame image of the three-dimensional structure. The mathematical model is able to evaluate the shear transferred at each floor level to the frames perpendicular to the action, across the corners of the building. An adjustment of the dynamic response of the building in relation to the minimum base shear design imposed by the code was made because no representative earthquake response spectrum has been recorded in Caracas. In order to evaluate the influence of axial deformations and the importance of shear transfer at the corners, comparative analyses with and without shear transfer at the corners and with and without axial deformation of members were made and reviewed.

Damage to continuous framing caused by the lateral forces resulting from seismic tremors or cyclonic winds can be catastrophically severe. Cross sections forced early into plastic hinging may enter a failing stage prior to the development of ductile properties of remaining sections, or the formation of a collapse mechanism may occur with uncontrolled increases in strain at hinging sections. Analog computer studies are presented which lead to the conclusion that increases in strains should be accompanied by stress increases in order to minimize structural damage. Inhibiting the development of purely plastic conditions would also reduce the vulnerability of continuous framing to off center shifts of the axis of oscillation and the crawling effect of distortions in one direction. Steel without a yield plateau, low steel ratios, and confined compression reinforcement in all sections of a frame would reduce the susceptibility of a reinforced concrete framework to severe damage from severe natural phenomena such as earthquakes and cyclonic winds.

This note presents an investigation into the susceptibility of a silty clay of medium sensitivity to earthquake-induced creep. Using undisturbed samples of estuarine clay representative of the upper member of the youngest deposit underlying the body and margin of San Francisco Bay, a series of experiments was performed to determine the undrained compressive strength of the samples after seismic loading. Results are presented and conclusions described.

A report is presented on the investigation of more than 1,000 existing dams in California. Deficiencies at over 100 reservoirs are examined and remedial measures are investigated. Many defects in old dams are attributed either to adverse geological conditions or outmoded engineering practices, often combined with poor maintenance. The strengths and weaknesses of various types of dams are compared. Seismology and geology in California are considered in relation to construction and maintenance of dams and reservoirs. Problems in spillways and outlets and in reservoir margins are described. The requirements for programs to safeguard dams are examined.

Future housing in developing countries will be provided mainly in medium rise, four to six stories, bearing wall masonry buildings. This paper reports on the rationality behind this political decision and the technological processes that make it possible.

Uni-axial seismic tests were performed on /sup 1///sub 5/-scale and /sup 1///sub 2/-scale two-dimensional models of the HTGR core consisting of 73 graphite elements in a hexagonal array. Core displacement and velocity, boundary support force, and in-core element force were measured. The test rigs were excited in two directions: across-the-flats of an element and across-the-corners. Results from the two models were compared on a normalized scale basis to check the scaling laws.

An in situ geophysical investigation consisting of surface refraction, surface vibratory, downhole and crosshole seismic tests was performed at the man-made water retaining structures at Folsom Dam and Reservoir Project, located on the American River approximately 23 miles northeast of Sacramento, CA. More specifically the investigation was performed at Dike 5, the Right and Left Wing Dams, and at Mormon Island Auxillary Dam. The investigation was conducted to obtain compression-, shear-, and Rayleigh-wave (P-, S-, and R- wave) velocities as a function of depth within the dike and dams and their underlying foundations for input to the seismic stability analysis of these earthen retaining structures.

Description of 46,000 kw project given; methods used in excavating and concreting underground powerhouse; model studies made for design of tailrace surge chamber and particular attention given to question of moisture, temperature and lighting in powerhouse; seismic forces considered in design.

Results obtained from analysis of deflection, strain, temperature and other measurements on nine Italian arch dams; important way in which temperature changes influence arch dam behavior; results of testing for foundation modulus by seismic methods before, during and after construction of dams.

The thickness and extent of the sediment cover in the Patuxent Estuary has been determined using a high-frequency, high-spatial resolution, shallow penetration, continuous seismic profiling system. From these data, an isopachous map was prepared The isopachous map provides the subbottom information required to determine optimum locations for placing test equipment on the river bottom Mud filled depressions, acoustically transparent to 12-kHz sound pulses, occur mainly to the north of Half Pone Point, and east of the present channel Based on the identification of first subbottom reflectors, these depressions are as much as 16 feet thick The dominance of the thicker deposits east of the channel and evidence of a submerged terrace indicates that either the channel has migrated to the west, or that the channel of the Patuxent River at this location was larger in the past and has subsequently filled in much of the material in the eastern edge Maximum penetration at the scarp of the submerged terrace was 36 feet beneath the water-sediment interface This study demonstrates the use of seismic profiling techniques for collecting and presenting data required for coastal engineering applications.

In a previous paper by the same authors the values of the shear-wave velocity in natural soils found from laboratory tests were compared with wave velocities measured in situ. Dynamic free-vibration torsion tests were carried out in the laboratory on undisturbed 150 × 75 mm soil samples. Downhole seismic tests were performed at the site to measure the velocity of propagation of low strain shear waves from a surface wave source. Differences between laboratory and field values of the shear-wave velocity were considered to be due to sample disturbance. Further work has established that, provided system compliance in the laboratory apparatus is allowed for, laboratory and field values agree reasonably well. The test results are analysed again with account being taken of the stiffness of the laboratory apparatus.