Jayne, Clapp and Francis. The opinion of the court was delivered by Francis, J.A.D.
Respondent sought a recovery on account of damage claimed to have been suffered by its motion picture theatre as the result of an explosion in appellant's plant. After a lengthy trial, the jury awarded a substantial verdict. Reversal of the consequent judgment is now sought because of a number of alleged trial errors.
The Baker Theater, owned by respondent, is located at 39-41 West Blackwell Street, Dover, N.J. This is 4 to 4 1/2 miles east of the Hercules Powder Company plant in Kenvil where nitroglycerin is manufactured. It was built in 1905 and has a seating capacity of 1,435 persons.
The original roof construction consisted of a series of five wooden trusses, each with a 60-foot span, extending from sidewall to sidewall. Between the upper chords of the
trusses were rafters on which wooden sheathing and roofing had been installed. Ceiling joists were attached to the bottom chords. Metal lath was fastened to the bottom of the ceiling joists and a plaster ceiling was affixed to the lath.
In 1924 the front of the theatre was rebuilt and at this time the wooden truss located in that part of the building was replaced with one of steel. The remaining four wooden ones were not disturbed.
In 1941 the trusses were inspected. They were basically in good sound condition; there was no dry rot, no visible deterioration of the wood, and there were no termites. However, there was a slight localized deflection of one of them. Re-examination in 1942 showed the same condition and it was then corrected.
A further inspection in 1945 disclosed that no appreciable change had taken place since the 1942 repairs.
On June 21, 1948 an explosion of a total of 30,900 pounds of nitroglycerin took place at appellant's plant. Appellant offered proof to the effect that there were three separate explosions, one of 7,000 pounds of nitroglycerin, the second of 12,500 pounds, separated from the first by "just about a minute," and the third of 11,400 pounds, "about a second" later. However, witnesses for the respondent spoke of hearing and feeling one explosion.
The blast was a severe one. It cracked walls and ceilings of some private dwellings and a stairway in one of them. A church stands next door to the theater. There is evidence that the four-foot thick walls of its stone tower were split as well as its vestibule floor. One witness, who was working on a machine in a nearby factory, said the building shook. The manager of the theater was thrown out of his office chair by the concussion.
In the afternoon of June 25, the porter of the theater found pieces of plaster in the balcony, which he observed had fallen from the ceiling at the point where it joins the wall on the right side of the theater. He noticed also that the ceiling was "broke all the way along on both sides." The manager was notified and engineers were called in to inspect
the condition. As a result, on June 27 the theater was closed for repairs.
One of these engineering experts, Ruderman, is the person who made the inspections in 1941 and 1942. Following the explosion he studied the damage on June 28 and 29. At this time he discovered that the bottom chords of two of the trusses were definitely ruptured. They had cracks in them, which were variously described as "fresh," "new," "recent," "less than a month old," "one week, two weeks, maybe, definitely not three" weeks old. The ruptures appeared in the bottom chord at about its intersection with the top chord at each end of the truss. The breaks consisted of vertical cracks and there was a sagging of two or three inches at these points.
He could not tell the full extent of the damage because the cracks extended into the interior of the wooden trusses, so the minimum extent of the damage was observable from the outside. In any event, the injury to the bottom chords of the two trusses was "quite severe" and he would not want to put "any load on" or "any faith" in them. In his judgment the building was unsafe for occupancy.
According to Ruderman, a force or forces suddenly applied would produce the fractures he observed. They would result from "a sudden shock"; "it would have to be a very large, suddenly applied, recent force." It was the kind of damage that could be produced "by a force such as a lifting of the truss and the dropping of it."
An additional important factor came into the case through this witness. Aside from the fractures referred to there was nothing particularly wrong with the trusses. The condition was the same as it had been in 1942 when the local deflection of the one truss was neutralized. There was "absolutely no evidence of any deterioration in the structure of the wood, anything like rot, fungus or borers." And the new cracks had no relationship whatever with the 1942 bowing of the truss.
Dr. Hans Bleich, a professor of engineering at an eastern university, who exhibited substantial qualifications in the
field of effects of explosives on structures, also testified for respondent.
After perusing a topographical map of the area between the explosives plant in Kenvil and Dover, he expressed the opinion that the terrain was such as to cause the effect of the explosion in Dover to be increased rather than decreased -- that is, "larger than average." The reason is that a hill intervening between an explosion and a target will have a shielding effect, but a target located in a valley or on the side of a hill in a valley will suffer a heavier impact. However, he did not believe that here the terrain was a paramount consideration.
In explaining the effect of force generated by such a large amount of explosives, he said that the force travels from the explosion to the target (which was his way of referring to the object or structure damaged) at approximately the speed of sound. At the explosion a heavy pressure is generated which expands in waves in all directions. At the target the air presses against the building and then tries to pull away from it. "The principal effect of an explosion of this magnitude and at this distance is a pressure effect on the target, on the building, like someone taking a ball and squeezing it in his hands."
He had computed the force produced at the target under the conditions presented and with the explosions in the two or three steps described. The result of the computation was not given on direct examination, but the statement was made that the force would be sufficient to do some damage to an old, weak structure. Inquiry on cross-examination revealed that the peak pressure would amount to ten pounds per square foot at the height of the roof of the theater, and on redirect examination it was said that a load of approximately ten pounds per square foot would be damaging to the structure under consideration.
In discussing the strength of the trusses, the witnesses for both parties spoke of dead load and live load. The dead load is the weight of the roof on the trusses and a live load
would be any outside load added thereto, such as snow, for example.
Types of live loads were distinguished. A live load of ten pounds per square foot of an impact nature, such as an explosive force, may have up to twice the effect of a uniformly applied live load. If a person were to stand on a board, the ends of which rested on supports, his weight would be a live load. But if such person jumped from a height on to the board, his weight would be a live load of impact force. It would be the equivalent of increasing the static load up to twice the weight.
In answer to a rather long hypothetical question containing an outline of the material facts adduced in support of respondent's theory of the case, and which also asked Dr. Bleich to assume that the described damage to the trusses "in the opinion of the qualified licensed professional engineer who examined the same was caused by a recent, very large, severe, suddenly applied outside force or shock * * *," the conclusion was given that "there was a causal connection between this explosion of 30,000 pounds approximately in the defendant's plants and the damage done to the structures; * * *."
Another engineering expert who had examined the trusses on July 1, 1948 also said they showed recent fractures which were less than a month old. The damage, in his judgment, was caused by a recent overloading beyond their strength. And a suddenly applied live load of ten pounds per square foot in all probability would have caused the trusses to fail and would have caused the failure he observed.
There was additional expert testimony to the effect that these trusses "were weak in their end connections" against their normal dead load and "particularly weak in shear against an impact load" judged by "today's design." But it was said also that as designed and in their condition in 1948 they were proper for the regular loads to be carried. There were other methods of using wooden trusses; each method had its advantages and disadvantages. And one of the disadvantages of the method employed in respondent's theater
is that under impact forces the trusses "will go faster." And one of the experts said that on the basis of actual computations he made, a load of ten pounds applied to the roof as an impact force ...